JPS63108324A - Electrochromic display element - Google Patents

Abstract

PURPOSE:To improve the initial response characteristic and to display the improved response characteristic stably for over a long time by using a lithium salt together with other specified material in combination as the electrolyte. CONSTITUTION:When a nonaqueous soln. contg. a lithium salt and a small amt. of water is used as a liquid electrolyte, other electrolyte than the lithium salt is further added to the liquid electrolyte. Namely, a tert. alkyl ammonium salt is added together with the lithium salt as an electrolyte to a nonaqueous solvent contg. a small amt. of water, as liquid electrolyte and dissolved. By using such liquid electrolyte, the initial response characteristic of the electrochromic display element is improved and the improved response characteristic is displayed stably for over a long time.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention is an electrochromic material that displays characters, patterns, etc. by color change of a reactant between an electrochromic material of a display electrode and a counter electrode material of a counter electrode through an electrolytic solution. This invention relates to a chromic display element.

[Conventional technology]

A typical example of this type of display element is, for example, a display device in which an electrochromic material layer is provided on the inner surface of a light-transmitting display substrate via a transparent display electrode, and the display is divided into segments constituting a required pattern. a counter electrode material layer is provided on the inner surface of the opposite substrate via a counter electrode to serve as a counter electrode;
It is known that an electrolytic solution is sealed between the two electrodes of side substrates that are placed opposite to each other with a spacer interposed therebetween.

In such a display element, by applying a voltage to the display electrodes corresponding to the required segments using the above-mentioned counter electrode as a common electrode, color change of the reactant through the electrolyte between the electrochromic substance and the counter electrode substance is performed. , the required display is made on the surface of the display side substrate. For example, in the case of blue display, tungsten oxide (W O3) is generally used as the electrochromic substance, but the color change in this case occurs when a lithium salt dissolved in a non-aqueous solvent is used as the electrolyte. , is based on the following reaction.

WO3+nLi'″+ne-:Li　nWo.

(Transparent) (Blue) By the way, in display elements using tungsten oxide as an electrochromic substance as described above and a lithium salt dissolved in a non-aqueous solvent as an electrolyte, the amount of electricity injected is high and the response characteristics are In order to obtain an excellent electrolyte, water is generally added to the electrolyte and an activated carbon material such as activated carbon fiber is used as a counter electrode material. In particular, the water mentioned above dissociates in the electrolytic solution to produce Ho, and this H+ functions in the same way as Li0 in the above formula.

It is something that

[Problem that the invention seeks to solve]

However, conventional electrochromic display elements using such activated carbon materials as counter electrode materials have the advantage that desired response characteristics can be obtained by increasing the amount of water added to the electrolyte. There was a problem in that the amount of injected electricity decreased significantly during storage, making it difficult to maintain the initial response characteristics stably over a long period of time.

Therefore, the present invention has a high amount of injected electricity and a small drop in this amount of electricity during storage, that is, it has excellent initial response characteristics and can stably exhibit this response characteristic over a long period of time. The object of the present invention is to provide an electrochromic display element with excellent storage stability.

[Means for solving problems]

As a result of intensive studies to achieve the above object, the inventor used a counter electrode material made of an activated carbon material for an electrochromic material made of tungsten oxide, and added lithium salt and a small amount of water to a non-aqueous solvent as an electrolyte. When using an electrolyte containing a lithium salt, it is possible to improve the initial response characteristics by further adding an electrolyte other than the lithium salt to the electrolyte, that is, by using a lithium salt and a specific substance other than the lithium salt together as an electrolyte. The present invention was completed based on the knowledge that an electrochromic display element with excellent storage stability that can exhibit excellent response characteristics stably over a long period of time can be obtained.

That is, in this invention, a pair of substrates which are transparent at least on the display side are disposed facing each other, and an electrochromic material layer of a predetermined pattern made of a tungsten oxide thin film is provided on the inner surface of the display side substrate via a display electrode. An electrochromic display element in which a display electrode is formed, a counter electrode is formed by providing a counter electrode material layer made of an activated carbon material on the inner surface of a counter substrate via a counter electrode, and an electrolyte is sealed between these two electrodes. The electrochromic display element is characterized in that the electrolytic solution is made by dissolving a tertiary alkyl ammonium salt together with a lithium salt in a non-aqueous solvent, and adding a small amount of water to the electrolyte. be.

[Structure and operation of the invention]

In this invention, as described above, the initial amount of electricity injected can be increased by adding and dissolving a tertiary alkyl ammonium salt together with a lithium salt as an electrolyte in a non-aqueous solvent to which a small amount of water has been added. At the same time, it is possible to maintain this amount of electricity stably for a long period of time. The reason for this is not necessarily clear at present, but according to the inventor's speculation, it is thought to be as follows.

That is, in a conventional electrochromic display element using an electrolytic solution in which lithium salt and water are added to a non-aqueous solvent, anion (for example, lithium) constituting the lithium salt is added to the active carbon material as a counter electrode material. Salt is L
iCj! In the case of O, C104-), H' produced by the dissociation of water is likely to be adsorbed (and as a result of this adsorption gradually progressing during storage, the concentration of OH- in the electrolyte becomes relatively gradual). A phenomenon occurs in which the H″ concentration in the electrolyte becomes higher and the H″ concentration in the electrolyte becomes lower.
When the temperature decreases, tungsten oxide as an electrochromic substance becomes more easily dissolved in the electrolytic solution, or becomes more likely to change into a substance that cannot function as an electrochromic substance, such as l, iz W Oa. Due to these causes, and also due to the direct cause of the decrease in the H0 concentration in the electrolytic solution itself, it is thought that the amount of electricity injected after storage will decrease significantly.

On the other hand, when a lithium salt and a tertiary alkyl ammonium salt are used together as an electrolyte as in the present invention, the tertiary alkyl ammonium ion (for example, the tertiary alkyl ammonium salt) constituting the latter salt is C
z Hs ) 3 HNCIlO4, (Cz H
s) Since 3HN") is a larger cation than H", it and anion, such as the above C10,-
In other words, the use of the tertiary alkyl ammonium salt suppresses the adsorption of H onto the activated carbon material, and as a result, unlike the conventional method described above, It is thought that the phenomenon that the H'' concentration in the electrolytic solution decreases is suppressed, and a significant decrease in the amount of injected electricity is no longer observed.

It should be noted that the phenomenon that the decrease in H'' concentration in the electrolytic solution is suppressed by the use of a tertiary alkyl ammonium salt can be easily inferred from the following test results conducted by this inventor. That is, Four types of solutions A are prepared by dissolving a predetermined amount of a predetermined electrolyte in 100% pure water without using a non-aqueous solvent.

Prepare B, C, and D, and add 300 c to 100 ml of each solution.
An activated carbon fiber cloth (trade name: CH-20, manufactured by Kuraray Co., Ltd.) having a size of d (length x width area) was immersed in the solution, and the pH of the solution was measured over time. The results were as shown in Table 1 below. The electrolytes used were 0.1 mole glue and LClOa for solution A, and 0.1 moBv (7
) L i CI Oa and (Cz
Hs ) 3 HN CI Oa, 0 in solution C.
03 moles of (C3Hff) 3 HN Ce 04
, in solution 0.1 mol of (Cz Hs)3 HNC
IIOa.

Table 1 As is clear from the results in Table 1 above, solution A using only lithium salt as an electrolyte has a large increase in pH over time, that is, a large decrease in the H"fi degree in the solution. On the other hand, solution B, which used both a lithium salt and a tertiary alkyl ammonium salt as an electrolyte, showed a remarkable increase in P is suppressed.And,
From this test result, it can be easily predicted that the same phenomenon described above will occur in an electrolytic solution prepared by adding water to a non-aqueous solvent.

As described above, in this invention, by using a tertiary alkyl ammonium salt together with a lithium salt as an electrolyte, a decrease in the oral H'' concentration of the electrolyte is suppressed, and the initial amount of electricity injected can be maintained over a long period of time. This has the effect of stably holding the electrolyte, but it also has the advantage that the initial amount of electricity injected can be increased even if the amount of water added to the electrolyte is smaller than before, which also improves the storage stability mentioned above. gives even more favorable results.

The reason why the initial amount of electricity injected can be high even if the amount of water added is small is that the use of tertiary alkyl ammonium salt suppresses the adsorption of H onto the activated carbon material, making the ionization effect of water effective. This is thought to be due to the fact that the above-mentioned salt itself has excellent electrical conductivity, but the details are not clear at present.

On the other hand, as is clear from the above, this invention is characterized by the combined use of a lithium salt and a tertiary alkyl ammonium salt as an electrolyte.
Using only a tertiary alkyl ammonium salt as an electrolyte yields favorable results in terms of storage stability, as suggested by the test results for solutions C and D in Table 1, but the initial injection You will not be satisfied with the amount of electricity.

According to the inventor's experimental studies, when lithium salt and tertiary alkyl ammonium salt are used together in a specific ratio,
It has been confirmed for the first time that when a tertiary alkylammonium salt is used alone, a synergistic effect can be obtained in that the initial amount of electricity injected can be made higher than when a lithium salt is used alone. That is, when the proportion of lithium salt in the total amount of both temperatures is in the range of 50 to 70 mol %, the largest amount of injected electricity is obtained, and as the above range is exceeded, the amount of injected electricity gradually decreases. However, it was confirmed that if the above ratio is within the range of 30 to 90 mol %, the amount of electricity injected can be expected to be improved more than in the case of using lithium salt alone.

Such a synergistic effect is thought to be based on the excellent electrical conductivity of the tertiary alkyl ammonium salt mentioned above and the excellent ionization effect of lithium salt, but the detailed reason for this is not yet clear at present. It cannot be said that this has been done.

In this invention, the tertiary alkyl ammonium salt used to obtain the above-mentioned effect may be (Cz Hs) x HN C104 or (C3H?) x HNCfO4 (CH: l)
3 HN C104 can be mentioned as the most representative example, but various other salts having an alkyl group having up to 4 carbon atoms can be used. Those in which the number of carbon atoms in the alkyl group exceeds 4 are chemically unstable and are therefore not preferred. In addition, as the lithium salt used in combination with this, the above-mentioned LiC
l0a is the most suitable, others LiBF4, LiPF
A wide variety of known salts such as H can be used.

Non-aqueous solvents for dissolving such electrolytes include:
Any of the usual solvents used in electrochromic devices can be used, and specific examples include propylene carbonate, acetonitrile, γ-butyrolactone, and dimethoxyethane.

In this invention, an electrolyte is prepared by dissolving the electrolyte in the non-aqueous solvent and adding a small amount of water thereto. The total amount with the tertiary alkylammonium salt is preferably 0.3 to 1.5 mol, preferably 0.5 to 1.0 mol, based on the nonaqueous solvent 1). In addition, the ratio of the above-mentioned combination of both temperatures is determined by the balance between the initial amount of electricity injected and the storage characteristics, but normally, as mentioned above, the proportion of lithium salt in the total amount of both temperatures is 30%. It is preferable to set the amount to 90 mol%, preferably 40 to 80 mol%, most preferably 50 to 70 mol%.

The amount of water added is determined in consideration of the initial amount of electricity injected and the storage characteristics, as in the case of the combination ratio of both temperatures mentioned above.
The amount may be smaller than in the past, and is generally 1% by weight or less, preferably 0.5% by weight or less, most preferably 0.2% by weight or less based on the non-aqueous solvent.

The electrochromic display element of the present invention is characterized by using the above-mentioned specific electrolyte,
The other configurations of this element may be the same as those of conventional elements. Hereinafter, an example of the electrochromic display element of the present invention, including the other configurations mentioned above, will be described with reference to the drawings.

In the figure, l is a light-transmitting display-side substrate, and an electrochromic material layer 3 is provided on the inner surface of this substrate 1 via a transparent display electrode 2, and the display is divided into segments constituting a required pattern. Pole 4 is formed. Reference numeral 5 denotes a counter substrate, and a counter electrode material layer 7 made of an activated carbon material is provided on the inner surface of the substrate 5 via a counter electrode 6 to form a counter electrode 8. The side substrates 1.5 are arranged to face each other with a spacer 9 made of synthetic resin, glass, etc. interposed therebetween, and an electrolytic solution 10 having the above-described specific structure is sealed inside the side substrate 1.5, that is, between the two electrodes 4.8.

Although a light-transmitting material such as glass is generally used as the above-mentioned both-side substrates 1.5, the opposite-side substrate 5 may be non-light-transmitting. Further, the display electrode 2 is made of indium-
It is made of a transparent conductive material such as tin composite oxide (hereinafter referred to as ITO), and is usually made of 1,000~ It is formed to a thickness of about 3,000 people. Furthermore, the counter electrode 6 is made of gold.

Precious metals such as platinum, alloys of these metals with other metals, or materials similar to those for the display electrode 2 are used, and in addition to the same thin film forming techniques described above, in the case of metals, the opposing electrodes are formed by pressing or bonding foil-like materials. Usually 1 on the inner surface of the side board 5
It is formed to a thickness of about ,000 to 3,000 people.

The electrochromic material layer 3 is made of tungsten oxide (W
O3) It is made of a thin film and is formed on the display electrode 2 by the same thin film forming technique as described above to a thickness of usually about 3.000 to 1.000 mm. Further, the counter electrode material layer 7 made of an activated carbon material is usually formed by pasting an activated carbon fiber cloth with a thickness of about OO to 500 μm on the counter electrode 6 using an electrically sensitive adhesive. There is no limitation, and any method may be used as long as activated carbon is used as a counter electrode material.

In addition, 1). 12 is a lead terminal on the display electrode side and the counter electrode side fixed to the side edge of the display side substrate 1; 13 is a conductive layer made of a material such as conductive paste or metal foil that constitutes the external lead-out portion of the counter electrode 6; , 14 is an insulating layer made of 5iOz or the like for protecting the display electrode 2, and 15 is a background material that hides the counter electrode 8 and uses its own color tone as the background of the display.The pigment that develops the color tone is made of polytetra It is composed of a sheet-like molded product impregnated with an electrolytic solution dispersed in a binder component such as fluoroethylene, or a gel body of a pigment and an electrolytic solution.

〔Effect of the invention〕

As described above, according to the present invention, a counter electrode material made of an activated carbon material is used for an electrochromic material made of tungsten oxide, and a non-aqueous solvent containing lithium salt and a small amount of water is used as the electrolyte. If you do,
By adding and dissolving a tertiary alkyl ammonium salt together with a lithium salt in the electrolytic solution, it has excellent initial response characteristics and storage stability that allows these response characteristics to be stably exhibited over a long period of time. The effect of providing an excellent electrochromic display element is obtained.

〔Example〕

Hereinafter, the present invention will be specifically explained with reference to Examples.

Example 1 ITO with a thickness of 2.500λ was placed on one side of the display side substrate made of transparent glass with a length of 50 mm, a width of 165 mm, and a thickness of 1.1 mm.
A display electrode with a predetermined pattern consisting of a display electrode with a thickness s, o
8 for numerical display made of thin tungsten oxide film
An electrochromic material layer with a letter-shaped pattern (consisting of 7 segments) is formed by a thin vacuum deposition method, and a layer with a thickness of 5.0 mm is formed on the exposed surface of the substrate and display electrode.
A SiO2 insulating film of 0.000000000000 was provided to serve as a display electrode.

On the other hand, one side of the opposite substrate, which is made of transparent glass with 45 vertical layers, *160 m square, and 1.1 mm thick, is coated on the entire surface of the opposite substrate with a thickness of 2.1 mm thick.
A counter electrode made of 500 ITO was formed by vacuum evaporation, and activated carbon fiber cloth (trade name: CH20, manufactured by Kuraray Co., Ltd.) was pasted thereon via carbon paste (trade name, PR-10, manufactured by Tokurikisha Co., Ltd.). They were combined and heat-treated at 180° C. for 2 hours to form a counter electrode material layer to serve as a counter electrode.

Then, the above-mentioned side substrate was placed in such a way that the display electrode and the counter electrode faced each other, and between the two electrodes was formed a sheet-like molded mixture of titanium dioxide pigment and polytetrafluoroethylene powder (trade name: Boaron, manufactured by Sumitomo Denki Kogyo Co., Ltd.). ) are interposed, and rectangular annular spacers made of polyester resin with a thickness of 1.0 mm are interposed on the periphery, and are placed facing each other, tightly sealed with an epoxy resin adhesive, and inside 0.7 mol/l LiCj in propylene carbonate! On
and 0.3 mol/l (Cg ) Is ) z HNCI
Approximately 6 ml of an electrolytic solution prepared by dissolving Oa and adding 0.1% by weight of pure water was sealed. Next, lead terminals were attached and a conductive layer was formed by applying silver paste, thereby producing an electrochromic display element having the configuration shown in the drawings.

Example 2 An electrochromic display element was produced in the same manner as in Example 1, except that the amount of water added to the electrolytic solution was 1% by weight.

Example 3 As an electrolytic solution, propylene carbonate was mixed with 0.5 mol/
1 LiCj! On and 0.5 mol/E (CSH7)
3 HN Cj! Example 1 except that a solution obtained by dissolving Oa and adding 0.1% by weight of pure water was used.
An electrochromic display element was produced in the same manner as described above.

Example 4 An electrochromic display element was produced in the same manner as in Example 3, except that the amount of water added to the electrolytic solution was limited to 1% by weight.

Comparative Example 1 As an electrolyte, 1.0 mole/propylene carbonate was added to the electrolyte.
An electrochromic display element was produced in the same manner as in Example 1, except that LiCl0a of II was dissolved and 0.1% by weight of pure water was added.

Comparative Example 2 An electrochromic display element was produced in the same manner as Comparative Example 1 except that the amount of water added to the electrolytic solution was 1% by weight.

For each element obtained in Examples 1 to 4 and Comparative Examples 1 and 2 above, the initial injected electricity when a main square wave AC voltage of 1°2 V for 0.6 seconds was applied between the display electrode and the opposing electrode. The amount was measured. In addition, the amount of electricity injected after being left in a constant temperature room at 45° C. for a predetermined number of days was measured in the same manner as described above, and the retention rate of the amount of injected electricity after being left was examined with the initial amount of electricity injected as 100%. These results were as shown in Table 2 below.

Table 2 As is clear from the results in Table 2 above, the electrochromic devices according to Examples 1 to 4 of the present invention had an initial amount of injected electricity that could not be achieved with the same device of conventional comparative example 1.2. It satisfies both the amount of electricity injected after storage and the amount of electricity injected after storage, indicating that it has excellent initial response characteristics and can stably maintain these response characteristics over a long period of time.

[Brief explanation of the drawing]

The drawing is a sectional view showing an example of an electrochromic display element of the present invention. DESCRIPTION OF SYMBOLS 1... Display side substrate, 2... Display electrode 1.3... Electrochromic material layer, 4... Display electrode, 5...
Opposing substrate, 6... Opposing i scratch, 7... Counter electrode material layer,
8... Counter electrode, 10... Electrolyte

Claims (5)

[Claims] (1) A display electrode is formed by disposing a pair of substrates whose display side is transparent at least and facing each other, and providing a predetermined pattern of an electrochromic material layer made of a tungsten oxide thin film on the inner surface of the display side substrate via a display electrode. In an electrochromic display element in which a counter electrode is formed by providing a counter electrode material layer made of an activated carbon material on the inner surface of a counter substrate via a counter electrode, and an electrolyte is sealed between these two electrodes, the above-mentioned method is used. An electrochromic display element characterized in that the electrolytic solution is made by dissolving a tertiary alkyl ammonium salt together with a lithium salt in a nonaqueous solvent, and adding a small amount of water to the electrolyte. (2) Lithium salt is LiClO_4, tertiary alkyl ammonium salt is (CH_3)_3HNClO_4, (C
_2H_5), HNClO_4 or (C_3H_7)
The electrochromic display element according to claim (1), which is _3HNClO_4. (3) Claim (1) or (2), wherein the total number of moles of the lithium salt and the tertiary alkylammonium salt is 0.3 to 1.5 moles per liter of nonaqueous solvent. The electrochromic display element described above. (4) The proportion of lithium salt in the total amount of lithium salt and tertiary alkylammonium salt is 30 to 90 mol%
An electrochromic display element according to any one of claims (1) to (3). (5) The electrochromic display element according to any one of claims (1) to (4), wherein the amount of water is 1% by weight or less based on the non-aqueous solvent.