JPS62299822A - Electrochromic display element - Google Patents

Abstract

PURPOSE:To improve a repeating life, response speed and contrast by forming the boundary face between a color forming layer and electrolyte layer as a rough surface having very small ruggedness. CONSTITUTION:The boundary face between the color forming layer and the electrolyte layer is formed as the rough surface having the very small ruggedness. Such rough surface is formed by treating the surface of the color forming layer formed on transparent display electrodes by the bombardment action generated by the plasma of a gaseous halogen compd. The halogen compd. to be used is the compd. contg. any of carbon, nitrogen or sulfur alone or in combination. The halogen is constituted of fluorine or chlorine. An org. electrochromic material to constitute the color forming layer may be either an org. compd. or org. and inorg. or org. metal compd. and is preferably a phthalocyanine compd.

Description

[Detailed Description of the Invention] 3. Detailed Description of the Invention The present invention relates to an electrochromic display element, specifically an electrochromic display element in which the electrochromic material (referred to as EC material) of the coloring layer is an organic compound. (EC
D).

Transition metals are well known as inorganic compounds exhibiting conventional Fukyo EC properties, and research and development of WO1-based ECDs has been particularly active. However, EC materials of transition metal oxides generally exhibit only a single color, and the color tone is not necessarily clear, and furthermore, there are problems such as it is difficult to produce full color. Therefore,
Recently, organic compound EC materials that are easy to design in color have been attracting attention.

When organic compound EC materials are classified based on their color development mechanism, they are divided into reversible electrodeposition type and ion implantation type.

The EC materials that belong to the former category include bioloden-based materials.

There are anthraquinone-based pigments, and among the latter, tetrathiafulvalene-based (TTF) and rare earth sifthalodianine-based pigments are known. It is known that a vapor-deposited film of rare earth elements such as lutetium cyrusyanine changes from red to orange to green to blue to violet in the range of ±1.5 V depending on the applied voltage (for example, (Japanese Unexamined Patent Publication No. 58-57113). Since multiple colors can be achieved with one type of EC material in this way, there are great expectations for its practical application (commercialization).

However, there are many problems that need to be solved for practical use, especially ■ short repetition life, ■ slow response speed, ■
Problems such as low contrast have been pointed out.

■In terms of repeat life, EC layer, electrode and electrolysis 1! Deterioration occurs for each IN, and the waiting time is approximately 107 times at a practical level. If 10' times is achieved, the applications will expand, so 108 times is currently the goal. Regarding the deterioration of the EC layer, it has become clear that as alkali metal ions in the electrolyte layer (regardless of liquid or solid) repeatedly enter and leave the EC layer, they are captured and accumulated in the EC layer, causing this deterioration. There is. As a result, the conventional method has a limit of 10' times, and no effective solution seems to have been found yet.

■As for the slow response speed, it is known that WiEC materials can achieve up to several tens of pupils sec (5O-100InlIcc for the ECD in the above publication), but it is practical for a wide range of applications. 1. IOa + qec is the issue, and if you want to display a video,
Strict conditions are imposed: 5 m5 ec or less (practical level is approximately 3 m5 ec or less).

(2) Regarding low contrast, the color density can be increased by increasing the applied voltage, but it is not appropriate to increase the voltage too much because it shortens the repeat life and causes deterioration of the display electrode. EC membrane po
Another solution is to increase the porosity, and for this purpose it is effective to increase the deposition pressure. However, there is a limit to this as the mechanical strength is reduced. Therefore, when an electrolyte layer is provided, chemical changes such as elution and deposition are significant.

- In view of the problems described in F, the present invention is not repeatable.

The purpose is to improve response speed and contrast.

More specifically, we aim to achieve a repeat life of approximately 108 times, as well as a response speed of 10nse.
The aim is to be able to achieve the following.

In order to achieve the above object, the present invention provides a transparent display electrode with at least a coloring layer made of an organic electrochromic material, a liquid or solid electrolyte layer, and a counter electrode. In an electrochromic display element, in which the coloring layer changes color and disappears when a predetermined DC voltage is applied between the two electrodes, the interface between the coloring layer and the electrolyte layer is Its basic feature is that it has a rough surface with unevenness.

Preferably, the rough surface having minute irregularities is treated by bombarding the surface of the coloring layer formed on the transparent display electrode with plasma of a halogen compound gas.

Also preferably, the halogen compound is carbon.

A compound containing either nitrogen or sulfur, either singly or in combination. More preferably, the halogen of the halogen compound is composed of a heptad or chlorine. This halogen compound gas is used for RIE (reactive ion etching), for example CF4. NF,,SF,,CC
J', gas is most preferred.

In addition to these, inert gases such as Hz-1]e, NztcI12N, and A' can also be applied depending on the conditions (conditions such as length of action time, etc.).

The organic electrochromic material constituting the coloring layer in the present invention may be an organic compound, an organic and an inorganic compound, or an organometallic compound, and is preferably a 7-thalocyanine compound.

As an electrochromic material of a 7-talocyanine compound, any of the 7-allocyanine and its derivatives, which are known per se, can be used. Specifically, those with a central metal of copper, silver, beryllium, magnesium, calcium, gallium,
Zinc, cadmium, barium, mercury, aluminum, indium, lanthanum, neodymium, samarium, europium, gadolinium, dysprosium, holmium, sodium, lithium, ytterbium, lutetium, titanium, tin, hafnium, lead, thorium, vanadium, antimony, chromium, These include molybdenum, uranium, manganese, iron, cobalt, nickel, rhodium, palladium, osmium, and platinum. Furthermore, the central nucleus of the 7-thalocyanine may not be a metal atom, but a handicapped metal having a valence of 3 or more. Furthermore, metal-free 7-talocyanine derivatives such as copper-4-7 mino-7-talocyanine, iron polyhalo-7-talocyanine, cobalt hexaphenyl-7-talocyanine, tetraazo-7-talocyanine, tetramethyl-7-talocyanine, and dialkylamino-7-talocyanine can be used. These can be used alone or in combination.

A 7-talocyanine derivative in which the hydrogen atom of the benzene nucleus in the 7-talocyanine molecule is substituted with at least one electron-withdrawing group selected from the group consisting of a nitro group, a cyano group, a halogen atom, a sulfone group, and a carboxyl group; and at least one unsubstituted 7 talocyanine compound selected from the 7 talocyanine compounds described above, and a 7 talocyanine-based material composition obtained by mixing them with an inorganic acid capable of forming a salt, and precipitating the mixture with water or a basic substance. You can also use In this case, the electron-withdrawing group-substituted 7-talocyanine derivative can be any one in which the number of substituents in the molecule is from 1 to 16, and the electron-withdrawing group-substituted 7-talocyanine derivative and other unsubstituted The composition ratio with the 7-talocyanine compound is such that the number of substituents of the former is 0.00 to 2, preferably 0.002 to 1 per molecule of 7-talocyanine in the composition. good. 7 used in producing the 7 talocyanine-based electrochromic material composition.
Inorganic acids that can form salts with talocyanine compounds include:
Examples include sulfuric acid, orthophosphoric acid, chlorosulfonic acid, hydrochloric acid, hydroiodic acid, heptathonic acid, and hydrobromic acid.

Among the electrochromic materials, those particularly suitable for achieving the object of the present invention include metal-free 7-thalocyanine, copper 7-thalocyanine and derivatives thereof, such as nuclear electron-withdrawing group-substituted derivatives, and rare earth sifthalocyanines. It will be done.

The coloring layer may be formed using these electrochromic materials by any of coating, vacuum deposition, and sputtering. The most preferred method is
Plasma polymerization is carried out under specific conditions while introducing a carrier gas.

In the case of plasma polymerization, the carrier gas is oxygen gas, nitrogen gas, hydrogen gas, or chlorine gas.

Selected from the group consisting of inert gas such as argon, halogenated carbon gas, and halogen compound gas. Ha=8- For halogenated carbon gas, CC1,, CF,, C2F6.
Gases such as C1F a = C4F a can be used.

Further, as the halogen compound gas, sulfur halide gas such as SF6 gas, nitrogen nitrogen gas such as NF3w gas can be used, and gases having the general formula CIF mX n (X is a halogen element other than fluorine F), such as CF
3 Ci'-CF2Cf2, C2Fs
C1+ CF 3 B r lCF 4+C12, CF
, +I2 can be used (in addition, +I2 means mixed). In addition to these, CHF3゜CCI F3
, CB r F 3 , B C1, , SiCl, etc. may be used.

The apparatus used for the plasma polymerization is preferably a capacitively coupled apparatus, particularly an apparatus equipped with parallel plate electrodes. Furthermore, depending on the conditions, an inductively coupled device can be used.

The plasma polymerization conditions are such that the degree of vacuum for generating glow discharge is, for example, a gas pressure of 0.01 to 3.0 Torr, and the frequency of the alternating electric field is particularly selected from one frequency in a low frequency range of IKHz to 3 MHz. Preferably 5KHz~5
The frequency shall be 00K1-Iz. The lower limit value is determined by the uniformity of film formation and color development caused by uneven discharge during plasma polymerization, and the upper limit value is determined by the ability of ions to follow an alternating electric field, that is, the quality of the formation of a fine network structure due to the bombardment effect of ions. Response speed of the coloring layer as a forming film 2
There are restrictions on the quality of color development. Further, the temperature of the substrate on which the coloring layer is formed may remain at room temperature. Although the substrate may be heated and controlled to a predetermined temperature or temperature range, the substrate temperature increases due to the energy of the plasma itself. The substrate temperature is maintained within a generally constant temperature range depending on the input power for plasma generation. If the substrate temperature becomes too high, it is better to cool it down.

Shima Example 7 The present invention will be specifically described below with reference to an example based on the accompanying drawings.

FIG. 1 shows a schematic cross section of a parallel plate type plasma polymerization apparatus, in which (1) is a belt jar airtightly installed on a metal base plate (2). Parallel plate electrodes consisting of an upper electrode (3) and a lower electrode (4) are provided in this Pelger (1). A glass substrate formed with a transparent electrode such as ITO, that is, a Nesa glass substrate (5) is fixed to the L part electrode (3). The 7-talocyanine-based EC material (6) to be formed into a thin film on the substrate (5) is sublimated by heating with the temperature controller (7), vaporized into a monomer state, and passed through the valve (v2) to the Pelger ( 1) be introduced within.

A carrier gas such as CF, ys (8) is introduced into the Pelger (1) via the valve (Vl) together with the introduction of the ECC material soot.

The pressure inside the belt jar (1) is reduced by opening the valve (v3) and using the vacuum pump (9). The EC material discharged by this reduced pressure is deposited in a cooler (cold trap) (10). The degree of vacuum is measured with a vacuum gauge (not shown).
Gas pressure for glow discharge, for example about 0.05 to 2.0
Torr is maintained. The alternating electric field to be formed in the parallel plate electrodes (3) and (4) is generated by the matching box (11
) is applied by a low frequency power source (12). Note that this low frequency power source (12) uses a variable frequency power source. In the example, the discharge frequency IK is 50, IM,
Each case of 3M, 5Ml-[z was tried, and 13 as a comparative example.
．． We tried cases of 56 MHz and 500 Hz.

Typical embodiment conditions include power of 40-80W.

The discharge frequency is 50 KHz, the carrier gas is CF4 gas and the flow rate is 40 to 60 scc11, the substrate (5) is unheated at room temperature,
The gas pressure was 0.1 to 0.3 Torr. The 7-talocyanine-based EC material (6) is lutetium di7-lycyanine. Note that the ITO film of the substrate (5) is lowered to the ground potential.

Lutetium siphthalodianine (6) is heated and sublimated and introduced into the Perger (1) in a monomer state, and CF and ys (8) are also introduced. parallel plate electrode (3),
(4) A low frequency power source of 50 KHz is applied. Between the parallel parallel electrodes (3) and (4), large molecules are ionized by free electrons in the gas accelerated by the electric field, and conductive plasma gas is generated. Electrons, ions, radicals, and various excited species exist in plasma gas. However, since this system is in a low-temperature plasma state, chemical species are relatively not subject to thermal destruction, and additive chemical reactions proceed from radical species and excited species. Since the discharge frequency is selected to be a low frequency of 50 KHz, various ion species including CF ions among the various species generated in the plasma are transferred between the upper electrode (3) and the F section electrode (4). Move alternately. This migrating ionic species attacks the thin film that is being plasma polymerized on the substrate (4). The polymeric film is deposited in the presence of ion bombardment. This has a great influence on the membrane structure. That is, while maintaining the strong polymerizability of three-dimensional crosslinking, the film itself becomes a fine network structure by increasing the temperature and pressure in the microscopic areas by ion bombardment.

On the other hand, the discharge frequency is less than i K H7 (501
In the case of a lower frequency (1z to IKHz), if the film is formed by glow discharge in the same way, the charge of the ion species generated in the plasma will be charged up on the film or near the electrode, and the DC electric field will increase. An ion sheath (electric field entering the sheath) is formed, which causes an abnormal discharge or stops a sustained discharge.

That is, it is rarely formed as a film. This has been confirmed in the case of 500Hz.

On the other hand, when the discharge frequency is 3 MHz or more, the ion species in the plasma can hardly follow changes in the alternating electric field, and there is no effect of ion bombardment and charged particle bombardment. This plasma polymerized film has an extremely dense structure.

Figure 2 shows E with an EC layer created at each discharge frequency.
It shows a common cross-sectional structure of CDs (comparative examples to the examples described later). (21) is a glass substrate.

(22) is an ITO electrode, (23) is a coloring layer formed by the above plasma polymerization, (24) is an electrolyte layer, and (26) is an opposing IT
An O electrode, (25) a glass substrate, and (27) a spacer.

Examples of the electrolytic solution constituting the electrolytic solution layer (24) include:
K C1r N a CII O4-K C104-L
i C104, K 2S 041Na2SOoLi2
An aqueous solution such as SO can be used.

In this example, a 1 molar aqueous solution of L:C10- was used.

The thickness of the coloring layer (23) is 0.1 to 10 μm, preferably 1 to 7 μm. If the ring is thinner than 1 μm, sufficient contrast cannot be obtained during color development, and if it is thicker than 7 μm, the color change becomes considerably dull. Within the above preferred range, sufficient contrast can be obtained and the color change upon application of bias will also be sharp. The thickness of the ITO electrodes (22) and (26) is 0.03 to 0.5 μm, preferably 0.05 to 0.1 μm. The minimum film thickness that effectively functions as an electrode is about 0.05 μm.

E CD (20) of a preferable comparative example (discharge frequency 50Kllz) configured as described above has a color forming layer (
No. 23) exhibited green color, and when a DC voltage of -2V to +2V was applied, the color changed continuously from blue to red, showing good EC properties. Response speed is approximately 10+sec, number of repetitions is 10
7 to 108 times, operating temperature range is -30 to +80℃, E
All items of C characteristics are generally good. In particular, response speed 1 color development is improved because of the color development layer (23) as mentioned above.
has a fine network structure, and electrolyte ions (
This is because the structure has many fine bores through which Li') can pass through, and the contact area has increased considerably.

The sample name (
Al~A5. A6) is shown in FIG. 3.

In contrast to these comparative examples, at a discharge frequency of 500 Hz, film formation could not be achieved due to abnormal discharge or discharge stop during film formation as described above. Therefore, we switched to a vacuum evaporation method and formed a film.
An ECD (20) having a structure similar to that of the comparative example was created and used as a conventional example. As a result, when a DC voltage of -2v to +2■ was applied, a change in color from blue to red was observed, but the color development was weak;
Also, the contrast is dull and the response speed is 50 to 100 V.
The number of asecs repetitions was 106-107. The ECC characteristics () of this conventional example are also shown in Figure tl&3.

Vacuum evaporation group produces crystals while forming an island structure on the substrate,
Since voids exist between crystal grains, electrolyte ions diffuse there and become electrochemically active. On the other hand, plasma polymerized membranes are generally electrochemically inert because they have a strong and dense membrane structure due to polymerization based on cross-linking reactions. The formation of the bore allowed the intrusion of electrolyte ions.

When electricity is applied to the ECD, Joule heat is generated, and this energy promotes the chemical reaction (color development +11:), but the chemical reaction at the interface between the solid phase and the liquid phase becomes more intense, so the ionic species (including exudation of EC substances in response to
It becomes a stable compound and is fixed and deposited on the interface (vacuum evaporation deteriorates color development and response speed), but plasma polymerization maintains chemical stability because the film itself is dense and strong. Therefore, the comparative example had improved color development and a longer cycle life than the conventional example.

Next, the present invention will be explained in detail.

A substrate (35) in which a lutetium-shiftalodianine EC layer (23) is formed on Nesa glass substrates (21 and 22) by plasma polymerization (discharge frequency 50 Kllz) is fixed to the upper electrode (3) of the same device as in FIG. RF power supply (12
) frequency is set to 13.56MHz, and the supplied power is set to 5.
It is assumed to be 0W. Instead of the carrier gas (8), N F 3 N gas is supplied into the Pelger (1). Substrate (3
5) is not heated (room temperature) and the pressure inside Hernoya (1) is 0.
．． Maintain at 2 Torr. Parallel plate electrode (3), (
4) In between, NF.

A gas plasma is generated that moves violently between the electrodes. Substrate (35) or EC layer (23)
surface receives plasma bombardment. Approximately 20
Lasted for minutes.

Innumerable minute irregularities are formed on the surface of EC/1 (23) by plasma bombardment. It is thought that ion bombardment is concentrated in areas where the bonds between carbons are weak, resulting in the formation of sharply cut uneven surfaces from the surface. , E
The surface of the C layer (23) becomes a rough surface (36) as schematically shown in FIG.

Note that the gas for roughening the surface of the EC layer as described above is CF4-8FstCCI! 4 etc. may be sufficient.

Alternatively, an inert gas such as H2, He-N2, Cl2-Ar may be used. However, it is thought that gases with components with small atomic numbers have a small surface roughening effect in the plasma, and if this is used, it will take time. Here, it is also possible to use 02 gas, but if it is an inorganic coloring layer such as WO3, it is expected to have some effect, but in the case of an organic coloring layer, oxygen plasma may be used to iodine (ashing). ) resulting in C
It becomes o2w and breaks down. Furthermore, even if conditions are restricted to prevent decomposition and the roughening is limited to a weak level, the vicinity of the surface will be chemically altered, and the EC properties, especially the coloring properties, will be adversely reduced, causing the 02 gas to deteriorate. cannot be used.

In FIG. 4, (21) to (27) are similar to those in FIG. 2, and have the same film thickness. Electrolyte layer (24
) is a similar 1 molar aqueous solution of l-1iC104.

The surface (36) of the i>c layer (23) in contact with this electrolytic solution has increased several times compared to FIG. 2 due to surface roughening. Therefore, the reaction speed upon voltage application is significantly improved.

In this example, E CD (30) has a DC voltage of -2v~
When +2V was applied in a variable and continuous manner, the color changed continuously from blue to red, and the color development was clear and the color change due to voltage variation was also sensitive. Response speed is 2-3m5ec, number of repetitions is 8.4X10? We have obtained good results twice. The EC characteristics of Examples, Comparative Examples, and Conventional Examples are summarized in the following table.

Table 1゜It should be noted that the effect of surface roughening is that when the discharge frequency was 1.3.56 MHz (Fig. 3, sample 6) created as a comparative example, EC properties were almost not observed in the structure shown in Fig. 2. Whereas there is no
It has been found that by forming the surface roughening structure shown in FIG. 4, a certain level of color development is exhibited, although it is not practical, and this proves the effectiveness of surface roughening.

In addition, in the second embodiment, the substrates (5) and (35) were installed on the -L part electrode (3) of the parallel plate electrode, but in any case, they could be installed on the lower electrode (4). good.

No difference in effectiveness was observed.

Further, in the above embodiment, the electrolyte layer (24) is a liquid, but it may be a solid. The solid includes a mixture of porous material 20 and a liquid substance. Liquids also include those in the form of sol. Furthermore, if the electrolyte layer is solid, instead of roughening the surface of the coloring layer, the surface of the electrolyte layer (interface with the coloring layer) may be roughened, and the coloring layer may be formed on top of this. good.

In the examples, a preferred example was shown in which the coloring layer (23) was formed by plasma polymerization, but the effect of surface roughening is of course not limited to coloring layers formed by plasma polymerization.

A coloring layer formed by a coating method or a vacuum evaporation method, or a coloring layer formed by a sputtering method is equally effective.

4. According to the present invention, the interface between the coloring layer and the electrolyte layer is roughened to increase the contact area between the two, which not only improves the repeat life and contrast, but also greatly improves the EC response speed. You can make it 1 d.

[Brief explanation of the drawing]

Figure 1 is a schematic cross-sectional view of the plasma polymerization apparatus, Figure 2 is a schematic cross-sectional structure diagram of EC, D as a comparative example, and Figure 3 is a table summarizing the EC characteristics of the comparative example and conventional example. FIG. 4 is a schematic cross-sectional structural diagram of an embodiment of the present invention. 5... Nesa glass substrate, 35... EC layer forming Nesa glass substrate, 8... CF, gas, 13... NFs*, 22.26... Electrode, 23... Coloring layer, 24...・
- Electrolyte layer, 30... Electrochromic display element, 36... Rough surface.

Claims (4)

[Claims] (1) At least a coloring layer made of an organic electrochromic material, a liquid or solid electrolyte layer, and a counter electrode are stacked in this order on a transparent display electrode,
An electrochromic display element in which the coloring layer changes color and disappears when a predetermined DC voltage is applied between the two electrodes, characterized in that the interface between the coloring layer and the electrolyte layer is a rough surface with minute irregularities. An electrochromic display element. (2) The rough surface having minute irregularities is obtained by treating the surface of the coloring layer formed on the transparent display electrode with a bombardment effect using plasma of a halogen compound gas. ) The electrochromic display element described in item 2. (3) The electrochromic display element according to claim (2), wherein the halogen compound is a compound containing carbon, nitrogen, or sulfur singly or in combination. (4) The electrochromic display element according to claim (2) or (3), wherein the halogen of the halogen compound is fluorine or chlorine.