JP2623595B2 - Electrochromic device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention shows an electrochromic phenomenon between a transparent electrode provided on a transparent substrate such as glass and a counter electrode plate provided opposite to the transparent electrode. The present invention relates to an electrochromic device having a color developing section suitable for, for example, a display device.

2. Description of the Related Art Electro-chromic display devices (hereinafter referred to as ECs) using liquid electrolytes such as sulfuric acid and lithium perchlorate / propylene carbonate.
Although abbreviated as D, it is not particularly limited to display devices, and since this type of device is also used for optical shutters and active color films, etc.
D) requires complete liquid sealing, and there is a risk of leakage or freezing of the electrolyte. An all-solid-state ECD using a solid electrolyte has a wider operating temperature range, is highly reliable, can be easily driven in a matrix, and is expected to be a practical display device in the future.

The solid electrolytes used in all-solid-state ECDs are roughly classified into those using metal ion conductors or their dispersion in resin, those using ferroelectric films, and those using polymer solid electrolytes. There are various types, and in particular, polymer-based solid electrolytes have been attracting attention and studied since they have excellent moldability.

An all-solid-state ECD has already been developed using Nafion (registered trademark: polymer ion exchange resin of perfluorosulfonic acid developed by Du Pont) as an electrolyte layer. But Nafio
n cannot be formed into a thin film (250 μm), and H ⁺ is adsorbed by a polymer, and it takes time for H ⁺ to move.
One second is bad. It was also reported that an all-solid ECD was formed using a material obtained by mixing and pressing an electrolyte with a Teflon powder and a white pigment (composite polymer type solid electrolyte), and the contrast and response speed equivalent to those of a liquid type were obtained. ing.

On the other hand, ECD using a polymer composite solid electrolyte in which an inorganic salt and / or a plasticizer is dispersed in a polymer is also being studied. The addition of the plasticizer greatly facilitates the transfer of ions and effectively works as a solid electrolyte. The all-solid-state ECD using this type of electrolyte has almost no change in response characteristics (for example, 0.2 seconds), contrast, and other operating characteristics, and has excellent moldability. It can be used. Specifically, ECD using this polymer composite type solid electrolyte is disclosed in JP-A-58-4.
Japanese Patent Application Laid-Open No. 0531 and Japanese Patent Application Laid-Open No. Sho 59-135431 have been proposed. In both cases, the contrast, the responsiveness, and the repetition life are improved.

However, all of above ECD, the coloring layer show coloration, this e ^- contact or H ⁺ or a so-called two-layer structure and the electrolyte layer is separated implanting ions, with a color layer and the electrolyte layer It is pointed out that the ion implantation efficiency is relatively low due to the limited area, and the contrast during operation is limited.

On the other hand, while trying to improve the operating characteristics of ECD,
From the viewpoint of practicality, in consideration of production problems, that is, easiness of production, possibility of mass production, and economical efficiency such as cost, an organic solid electrolyte film is disclosed in Japanese Patent Application Laid-Open No. 58-30731. Although an example using the same has been proposed, the practical use of the two-layer structure is delayed because the process is inevitably complicated and the cost is increased.

A main object of the present invention is to provide an ECD having a single-layer color-developing portion, which has a high ion mobility and a long life, which is different from the conventional one.

It is another object of the present invention to provide an ECD which is excellent not only in chemical properties but also in physical properties and also in environmental resistance such as heat resistance and moisture resistance.

Another object of the present invention is to make it possible to simplify the steps of ECD production.

SUMMARY OF THE INVENTION To achieve the above object, the present invention comprises a transparent electrode provided on a transparent substrate, and a color-forming portion exhibiting an electrochromic phenomenon between a counter electrode provided opposite to the transparent electrode. In the electrochromic device, the color-forming portion comprises a solid electrolyte and a plasma polymerized film using an organic compound as a raw material, and the solid electrolyte is a compound having a composition of an alkali metal and an element having a large electronegativity, and the plasma polymerization In the structure of carbon constituting the film, the ratio of the number of carbons having an unsaturated bond to the number of carbons having a saturated bond is basically 1: 1.4 to 1: 0.25. element is large, F, O, N, Cl, and the like organic polar group configured to include S or these, attract alkali metal ions such Li ^+, Na ^+, K ^+, etc. electrostatically Than it is. The element having a high electronegativity may be one that forms a group in the plasma polymerized film (for example, oxygen of an ether group).

In the ECD with the above structure, the EC coloring part, the transparent electrode, and other electrodes can both be formed in a vacuum system, so that the ECD can be manufactured in the same equipment system, and the manufacturing equipment systems are dispersed into multiple units like liquid systems. In addition, the number of complicated steps is not reduced (for example, a step of sealing an electrolytic solution).

Examples Hereinafter, the present invention will be specifically described based on examples.

FIG. 1 shows an outline of an ECD manufacturing apparatus according to one embodiment. In the figure, (1) is a base plate, a bell jar (2) is provided on this base plate (1) in an airtight manner, and the air in the bell jar (2) is exhausted by a vacuum pump (not shown). Measure.

Substrate holder (4) on which ECD substrate (3) is placed
Has a structure in which the support rod (4a) is slidably fitted to the base plate (1) and can move up and down, so that the vertical position of the substrate (3) can be changed. The substrate holder (4) is equipped with a heater (5) for heating the substrate, and operates a temperature control external control circuit to keep the temperature of the substrate (3) constant when necessary. Can be. A temperature sensor for detecting the temperature of the substrate (3) is provided at a predetermined position of the substrate holder (4). Furthermore, in consideration of the case where the substrate (3) needs to be cooled, a water cooling device (not shown) is attached to the substrate holder (4).

A high-frequency coil (7) connected to an RF power supply (6) is provided at the upper small-diameter portion of the bell jar (2), and the high-frequency coil (7) turns the introduced gas into plasma by electromagnetic induction. The high-frequency coil (7) is provided with a pipe through which cooling water circulates.

Gas inlet (8) opened at the top of the bell jar (2)
, A carrier gas is introduced. Three gas inlets (9), (10), and (11) opened below the high-frequency coil (7)
, A source gas of a film material to be formed on the substrate (3) is introduced. This source may be a gas, liquid, or solid (so-called monomeric material or hydrocarbons in the methane series). In the case of liquid or solid, the temperature is adjusted with a temperature controller and vaporized under reduced pressure to obtain a gaseous state. It is sufficient to introduce it. In this example, the first and second source gas inlets (9) and (10)
A main component gas of the formed film can be introduced, and a Brent gas is introduced into the third source gas inlet (11). Of course, a monomer gas containing oxygen may be introduced from this inlet. The third gas inlet (11) has a bell jar (1) as shown in FIG.
Although it is shown as though it is located at the center of the drawing, this is for convenience of explanation, and is actually opened in a direction perpendicular to the paper surface. When the gas is introduced from such a direction, the gas can be mixed well and unevenness is less likely to occur. Also, as described above, the three source gas inlets (9), (10), (11)
Is provided so that the distance between the discharge electrode, that is, the high-frequency coil (7), and the introduction portion of the source gas can be varied, thereby controlling the lifetime of free radicals, active species, and ions, and producing a film. (Film quality). That is, the type of species deposited on the substrate can be selected, thereby changing the composition and structure of the film,
The properties of the film can be changed. For the same purpose, the substrate holder (4) is configured to be vertically movable so that the number of radicals reaching the substrate (3) can be varied. Therefore, a combination of the two suggests a preferable possibility that the film quality can be optimized.

In the bell jar (2), between the substrate holder (4) and the third gas inlet (11) located at the bottom, a metal cylinder is provided parallel to the substrate holder (4) and at a predetermined interval. Plate mesh electrodes (12) and (13) are provided. The upper mesh electrode (12) can apply a DC voltage + Vb, and the lower mesh (13) can apply a ground potential or a -Vb DC voltage. This mesh electrode (12), (13)
Works as a grid that captures and collects electrons and charged particles in the plasma, eliminating plasma bombardment.
In addition, other than the mesh electrode, for example, a conductive filter having a large number of fine holes may be used as the grid. However, it is most preferable to use a mesh electrode to prevent clogging. Further, the number of mesh electrodes is not limited to two (12) and (13) having opposite polarities as shown in the figure, and more than two mesh electrodes may be provided for collection efficiency and collection control. Further, the size of the mesh of the mesh electrode is preferably within 8 mm square, and more preferably 1 to 4 mm square. If the size is larger than 8 mm square, there is a disadvantage that electrons and charged particles leak from the mesh openings, and the effect of allowing only radicals (neutral species) to reach the substrate (3) is reduced by half. Conversely, 1m
When the angle is smaller than the m-angle, charged particles adhere to the mesh holes, reduce the number of radicals reaching the substrate (3), and extremely lower the deposition rate.

 Next, a production example will be described.

Example [1] The plasma conditions were a pressure of 0.9 Torr (absolute pressure; measured with a diaphragm type vacuum gauge), an RF fraction of 13.56 MHz, and a power of 80 W.
Ar gas is introduced into the carrier gas inlet (8) at a rate of 40 sccm. From the raw material gas inlet (9), lithium tertiary butyrate (LiOtC ₄ H ₉ : boiling point 110 ° C./0.1
(Torr) with a vaporizer (not shown) and into the chamber.
Introduce at a rate of 10 sccm. About 50 sccm of 1,3-butadiene monomer is introduced into the inlet (10). The inlet (11) is filled with 100% O ₂ gas as a blending gas.
Supply 1.5sccm. The gas for blending is N ₂ O instead of O _2.
May be. The voltage application switch is turned on, and a bias of + Vb−Vb is applied to the mesh voltages (12) and (13) at the same time.

The substrate (3) is formed by forming a conductive transparent film ITO on glass, that is, Nesa glass. The temperature of the substrate (3) is kept at about 65 ° C. Here, the above-mentioned heater (5) and water cooling device were not operated. Room temperature (~ 30
C), it can be heated to about 65 ° C by the energy of the plasma. Of course, if the substrate (3) becomes abnormally high due to the voltage applied to the plasma generation, the water cooling device is operated to lower the temperature.

In this manner, a polymer polymer film having an ether group was deposited on the Nesa glass (3) at a film forming rate of about 1.7 μm / h. In this embodiment, the thickness is about 12 μm. An analysis of the thus obtained plasma polymerization revealed that the ratio n ₁ : n ₂ of the number of unsaturated bonds (n ₁ ) to the number of saturated bonds (n ₂ ) in the carbon in the film was 1: 0.53. Met.

In FIG. 1, the introduced Ar gas is a discharge electrode (7).
Is converted into plasma. The Ar plasma (14) excites lithium tertiary butyrate gas, 1,3-butadiene gas, and O ₂ by its excitation energy, and turns into plasma. This plasma gas (15) contains radicals, ions, active atoms, molecules and electrons. Negative ions and electrons are captured and collected by the positively biased mesh electrode (12). Furthermore, positive ions are trapped by the mesh electrode (13) having a negative bias, and only neutral radicals, neutral active atoms and molecules pass through both mesh electrodes.

The normal system without the mesh electrode (the configuration shown in Fig. 1) is certainly a system in which the substrate and the plasma part are separated, and deposits as much as possible without damaging the characteristics of the raw material without destroying the structure of the raw material gas. Although it is possible, it is necessary to increase the power to a certain extent in order to maintain an appropriate deposition rate. However, in this case, the plasma portion spreads to the vicinity of the substrate and causes plasma damage. When the applied power is increased, the deposition rate is increased, but the decomposition proceeds due to plasma damage, and the film quality is deteriorated in proportion to this. For example, there are adverse effects such as the inability of the alkali metal ion Li ⁺ to enter well, and the excessive progress of the crosslinking to lead to Li ⁺ . However, by using both mesh electrodes described above, the species that cause plasma damage are almost completely removed, and only neutral radicals and other neutral excited species contribute to the deposition, which is industrially feasible. A thin film having a desired function can be formed while maintaining the position rate.

Prototype gas inlets (9) and (10) were prototyped, but the inlet (10) near the end of the Ar plasma
The film quality was better when lithium tertiary butyrate and a raw material gas of 1,3-butadiene were mixed and introduced. It has been found that it is better to excite the raw material gas indirectly with Ar plasma instead of directly converting it into plasma, and to make the excitation gentle. It is thought that mild radical polymerization, that is, diffusion of radicals (neutral species) plays a central role and deposits on the substrate. Even if bombardment of charged particles, electrons, etc. is small, it is extremely small. It is considered that the film quality is improved as an EC coloring portion. In addition,
Although only the source gas is introduced into the inlet (10), a mixed gas obtained by further adding O ₂ gas to the source gas may be used.
Further, depending on the selection of conditions, all of the above-mentioned mixed gas may be introduced into the gas inlet for blending (11). In addition, in this embodiment, the inlet (9) and the inlet (1
The distance between 0) was about 2 cm.

FIG. 2 shows a schematic cross-sectional structure of the embodiment. (21) is a glass substrate as a transparent substrate, and (22) is a glass substrate as a transparent electrode.
An ITO film, (23) is a single-phase color-developing part exhibiting EC properties according to the above-mentioned fabrication, (24) is a counter electrode formed opposite to a transparent electrode, and here is a transparent ITO film as in (22). It is. The plasma polymerized film of the coloring portion (23) is formed on a Nesa glass, that is, a glass substrate (21) on which an ITO film (22) is formed. ITO film (2
2) is In ₂ O ₃ − by vacuum evaporation or sputtering.
SnO ₂ is provided in a thickness of 0.1 to 0.5 μm. After forming the layer (23) of the color forming portion, ITO, that is, In ₂ O ₃ —SnO ₂ is formed thereon with a thickness of 0.1 to 0.5 μm by sputtering deposition,
ECD (20) was completed.

When about 2.2 V was applied to the ECD (20) of Example 1 by the DC power supply (30) capable of switching the polarity of the applied voltage, good color development was exhibited. The response speed was several msec, the repetition life was 5 × 10 ⁷ times or more, and the operating temperature range was -30 to 85 ° C.

Example [2] Example [2] was prepared in the same manner as in Example [1].
The difference is in the configuration of the color-forming section (23).
The source gas was substituted without introducing O ₂ gas. Lithium methacrylate monomer (Li-MA monomer) and acetylene gas were used. According to the carbon analysis of the formed plasma-polymerized film, the number of carbons having an unsaturated bond (n ₁ ) and the number of carbons having only a saturated bond without this (n ₂ ) among the carbons in the film are shown.
The ratio n ₁ : n ₂ was 1: 0.9. In addition, Example [2] also showed almost the same EC characteristics as Example [1].

Example [3] Example [3] was prepared in the same manner as in Example [1].
The difference is in the configuration of the color forming section (23), in which only the source gas was substituted in the apparatus system of FIG. 1 (O ₂ gas was introduced similarly). As a raw material gas, a lithium acrylate monomer (Li-A monomer) and a styrene monomer were used.
Ratio of the number of carbon atoms having an unsaturated bond (n ₁ ) to the number of carbon atoms having a saturated bond (n ₂ ) in the formed plasma polymerized film n ₁ : n
₂ was 1: 0.71. Example [3] also showed the same preferable EC characteristics as Example [1].

By the way, in the same manner as in Examples [1], [2], and [3], the relative amounts of the source gases were changed, and 3 to 4 production examples and comparative examples were prepared for each example. ,
The ratio of n ₁ : n ₂ was 1: 1.4 or more, that is, the plasma polymerized film containing a large amount of n ₂ did not have good EC properties. That is, the second
Even in the configuration shown in the figure, the function of the EC film is significantly reduced, the contrast of color development is weak, and the color of the film itself is close to brown from the beginning (low transparency). It does not recover even if a reverse bias is applied.

When n ₁ : n ₂ = 1: 0.25 or less, that is, n ₂
In a plasma polymerized film having too little, when exposed to the atmosphere, the change with time was large, and it was judged that the film was not practically usable. This is considered to be due to the susceptibility to adsorption of atmospheric moisture and O ₂ gas. In this regard, it is preferable to provide an air-neutral protective film, and the restriction on the ratio can be improved.

Comparative Example As a comparative example, an ECD (solid-phase-liquid) in the case of using an electrolyte layer obtained by adding propylene carbonate to a 1 mol electrolyte of lithium chlorate (LiClO ₄ ) on a tungsten oxide deposited film (color-forming layer) was used. Phase type, electrodes are ITO). When a DC voltage of 2 V is applied to this ECD, the response speed is 2se
c, The repetition life is less than 10 ⁶ times, color deposition is severe, and the operating temperature range is -20 to 70 ° C. Compared with this comparative example, at least the response speed is improved by 2 digits or more and the repetition life is significantly improved by 1 to 2 digits or more.

The reason that conventional ECDs are not widely used is that there are still difficulties in response speed and repeated life. This is because, when the EC coloring layer and the electrolyte layer have a two-layer structure of a liquid layer and a solid layer, the coloring reaction rate at the contact surface between the EC layer and the ion implantation part and the ion mobility in the electrolyte layer are low, and This is because the chemical reaction due to Joule heat at the time of energization is promoted, causing color deposition in the EC layer and deteriorating the color development. Example [1]
By forming the coloring layer as a polymer layer formed by plasma polymerization as in the above, ion mobility and reaction rate are improved, and chemical deposition due to energization can be effectively prevented.

That is, an element having a large electronegativity (eg, O, including an ether group element having a polar group structure) as in Example [1] is electrostatically charged with an alkali metal ion (eg, L
i ⁺ ) is attracted and more positive and negative ions (eg, Li ⁺ and ClO) than are present in a normal electrolyte (eg, LiClO ₄ ).
₄ ^-) electrostatic attraction easily move weakened the. further,
This alkali metal can be more efficiently incorporated into the polymer by plasma polymerization. Further, the film deposited by the inductive type plasma polymerization apparatus has a lower degree of crosslinking than that of the film formed by the capacitive coupling type apparatus, the structure itself has a somewhat flexible network structure, and the density of the presence of the alkali metal increases.

In addition, ions and e ^- are attracted by a voltage toward hydrocarbons to generate color, but the probability is considerably high in the form of highly dispersed electrolyte, so the color reaction is strengthened,
As a result, it can be understood that the reaction rate is increased (there are many points that are still unknown in theory). In the embodiment, the inductive coupling type device as shown in FIG. 1 is used, but this does not prevent the use of the capacitive coupling type device. However, in the case of the latter, it is necessary to devise radical neutral species diffused smoothly to guide the radical neutral species to the substrate, for example, to electrically float the substrate.

In addition, Joule's heat due to energization is a chemical reaction (coloring reaction).
However, as seen in the conventional example, the chemical reaction at the interface between the solid phase and the liquid phase becomes intense, so that the ionic species chemically react to become a stable compound, which is immobilized on the interface. Although the coloring property is deteriorated, the chemical deposition reaction is considered to be smaller in the example than in the comparative example, so it is inferred that the deposition is suppressed even under generation of Joule heat.

The ECD of the embodiment can be easily thinned. That is, in the case of a normal polymer, for example, in the case of coating by a dip spray method or the like, a binder is required to considerably lower the viscosity or to dilute the film in order to obtain a film thickness of several hundreds to several micrometers. As a result, the solvent component and the binder are increased, and the absolute amounts of the polar group and the alkali metal are reduced, so that it is difficult to form a thin film. According to the plasma polymerization method, the raw material can be plasma-polymerized as it is, and the thickness can be easily controlled because the thickness can be controlled simply by time.

Further, unlike a physicochemical vapor-deposited film, the plasma-polymerized film is based on a chemical bond, so the film itself is strong and generally has moisture resistance, heat resistance, oxidation resistance, and gas resistance. It has the advantage of being rich in environment and less affected by the environment.

In the above embodiment, in particular the EC illustrated in section in FIG.
D is a transmission type, but a reflection type in which, for example, a white background material is inserted between a display electrode and a counter electrode can be similarly applied without departing from the gist of the present invention.

Effects of the Invention As described above, according to the present invention, a single-layer thin film formed by plasma polymerization using a compound containing an alkali metal and an element having a large electronegativity and an organic compound as a raw material is used as a coloring part of an ECD. In addition to improving ion mobility, it is possible to effectively prevent color deposition at the interface of the EC layer as in the past, and to provide a practical, general-purpose excellent ECD with a high response speed, high contrast, and a long repetition life. Can be provided.

[Brief description of the drawings]

FIG. 1 is a diagram showing an outline of an apparatus for manufacturing an electrochromic device according to one embodiment of the present invention, and FIG. 2 is a schematic sectional view of the electrochromic device according to one embodiment. 2 ... bell jar, 3 ... board, 4 ... board holder,
7… High frequency coil, 9,10,11… Inlet for raw material gas, 1
2,13, ... mesh electrode, 23 ... single layer colored part by plasma polymerization.

Claims (2)

(57) [Claims] 1. An electrochromic device comprising a color-forming portion exhibiting an electrochromic phenomenon between a transparent electrode provided on a transparent substrate and a counter electrode provided opposite to the transparent electrode, wherein the color-forming portion is provided. A solid electrolyte and a plasma polymerized film made of an organic compound as raw materials, wherein the solid electrolyte is a compound having a composition of an alkali metal and an element having a large electronegativity,
An electrochromic device, wherein the ratio of the number of carbons having unsaturated bonds to the number of carbons having saturated bonds is 1: 1.4 to 1: 0.25 in the structure of carbon constituting the plasma polymerized film. 2. The element having a high electronegativity is fluorine,
2. The electrochromic device according to claim 1, wherein said electrochromic device is oxygen, nitrogen, chlorine, sulfur or an organic polar group containing these.