Ion conductive material

Details Ion conductive material Ion conductive material

2000-10-13

2003-02-04

Kopec, Mark (Department: 1751)

Compositions

Electrically conductive or emissive compositions

C252S501100, C252S062200, C252S589000, C428S690000, C359S270000, C359S273000

Reexamination Certificate

active

06514431

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to ion conductive materials and more particularly to ion conductive materials having excellent ultraviolet absorptivity and enhanced electric conductivity. This invention also relates to an electrochromic device provided with a layer containing such ion conductive materials.
2. Description of the Prior Art
Recently, electrochemical devices using ion conductive materials such as polymeric solid electrolytes have been vigorously developed. Particularly in the electrochromic device field, a problem has been pointed out that the chromogenic layers are deteriorated with ultraviolet radiation. Such deterioration caused by ultraviolet radiation can be suppressed by arranging an ultraviolet absorbing layer in an electrochromic device. However, the arrangement of such an layer will increase the number of steps for producing the device and thus will be disadvantageous in terms of productivity.
In view of the current situations, the present invention is intended to provide an ion conductive material with excellent ion conductivity and an electrochromic device having an ion conductive layer containing the ion conductive material.
BRIEF SUMMARY OF THE INVENTION
After intensive research and efforts made to solve the above-described technical problems, it has been found that an ion conductive material having the structure described below can overcome these problems.
According to one embodiment of the present invention, there is provided an ion conductive material comprising a mixture of a solvent, a supporting electrolyte and an ultraviolet absorber and having an ion conductivity at 25° C. of 1×10
−7
or greater, the ultraviolet absorber being contained in the mixture in such an amount that the transmissivity of electromagnetic rays having a wavelength from 300 to 360 nm which transmit or penetrate through a 0.2 mm-thickness layer of the mixture can be maintained 0.1% or below.
According to the other embodiment of the present invention, there is provided an ion conductive material which is a solid ion conductive material obtained by solidifying a mixture of a solvent, a supporting electrolyte, a polymerizable monomer, and an ultraviolet absorber by polymerization of the monomer and has an ion conductivity at 25° C. of 1×10
−7
or greater; the ultraviolet absorber being contained in the mixture in such an amount that the transmissivity of electromagnetic rays having a wavelength from 300 to 360 nm which transmit or penetrate through a 0.2 mm-thickness layer of the mixture can be maintained 0.1% or below.
Furthermore, an electrochromic device according to the present invention is characterized in that an ion conductive layer formed by the above ion conductive- or solid ion conductive- material, and an electrochromic layer are disposed between two opposed electrically conductive substrates disposed in an opposing relation to each other and having on their inner surfaces an electrode layer.
DETAILED DESCRIPTION OF THE INVENTION
A first ion conductive material according to the present invention is comprised of a mixture containing a solvent, a supporting electrolyte, and an ultraviolet absorber as essential components, and has an ion conductivity at 25° C. of 1×10
−7
S/cm or greater, preferably 1×10
−6
S/cm or greater, more preferably 1×10
−5
S/cm or greater. An ion conductivity which deviates from this range would lead to insufficient responding performance of an electrochromic device.
The term “ion conductivity” used herein is a value calculated by analyzing Cole-Cole plot derived in accordance with a complex impedance method.
An ion conductive material with an ion conductivity within the aforesaid range may be made of a mixture containing a solvent, a supporting electrolyte, and an ultraviolet absorber. Solvents used herein may be conventional ones generally used in electrochemical cells or batteries, and any types of such solvents are applicable as long as they can dissolve a supporting electrolyte described later. Specific examples of the solvents are water, acetic anhydride, methanol, ethanol, tetrahydrofuran, propylenecarbonate, nitromethane, acetnitrile, dimethylformamide, dimethylsulfoxide, hexamethylphosamide, ethylenecarbonate, dimethoxyethane, &ggr;-butyrolactone, &ggr;-valerolactone, sulforan, dimethoxyethane, propionnitrile, glutaronitrile, adiponitrile, methoxyacetonitrile, dimethylacetoamide, methylpyrrolidinone, dimethylsulfoxide, dioxolane, sulforan, trimethylphosphate and polyethylene glycol. Among these solvents, the preferred are propylenecarbonate, ethylenecarbonate, dimethylsulfoxide, dimethoxyethane, acetnitrile, &ggr;-butyrolactone, sulforan, dioxolane, dimethylformamide, dimethoxyethane, tetrahydrofuran, adiponitrile, methoxyacetonitrile, dimethylacetoamide, methylpyrrolidinone, dimethylsulfoxide, trimethylphosphate, and polyethylene glycol. These solvents may be used singly or in combination.
Supporting electrolytes used herein may be conventional ones used in electrochemical experiments or batteries, such as salts, acids, and alkalis. No particular limitation is imposed on salts used for the supporting electrolyte, which may be inorganic ion salts such as alkali metal salts and alkaline earth metal salts, quaternary ammonium salts, and cyclic quaternary ammonium salts. Specific examples of such salts are alkali metal salts of lithium, sodium or potassium such as LiClO
4
, LiSCN, LiBF
4
, LiAsF
6
, LiCF
3
SO
3
, LiPF
6
, LiI, NaI, NaSCN, NaClO
4
, NaBF
4
, NaAsF
6
, KSCN and KCl; quaternary ammonium salts or cyclic quaternary ammonium salts such as (CH
3
)
4
NBF
4
, (C
2
H
5
)
4
NBF
4
, (n-C
4
H
9
)
4
NBF
4
, (C
2
H
5
)
4
NBr, (C
2
H
5
)
4
NClO
4
and (n-C
4
H
9
)
4
NClO
4
and mixtures thereof. Among these, LiClO
4
, LiBF
4
, and LiI are preferably used.
No particular limitation is imposed on acids. Any inorganic acids and organic acids may be used. Specific examples are sulfuric acid, hydrochloric acid, phosphoric acid, sulfonic acid, and carboxylic acid.
No particular limitation is imposed on alkalis as well. Sodium hydroxide, potassium hydroxide, and lithium hydroxide may be used.
No particular limitation is imposed on the content of such a supporting electrolyte in a mixture forming an inventive ion conductive material. The lower limit of the supporting electrolyte content is usually 0.01 M, preferably 0.1 M, and more preferably 0.2 M, based on the above-described solvent. The upper limit of the supporting electrolyte content is usually 20 M, preferably 10 M, and more preferably 5 M.
Eligible ultraviolet absorbers which are essential for the inventive ion conductive material may be conventionally known absorbers, such as benzotriazole-, benzophenone-, triazine-, salicylate-, cyanoacrylate-, and oxalic anilide-based compounds. Particularly preferred ultraviolet absorbers for the present invention are as follows:
Benzotriazole-based compounds represented by formula (1)
In formula (1), R
1
is hydrogen, a halogen atom or an alkyl group having 1 to 10, preferably 1 to 6 carbon atoms. Specific examples of the halogen atom are fluorine, chlorine, bromine and iodine. Specific examples of the alkyl group are methyl, ethyl, propyl, i-propyl, butyl, t-butyl and cyclohexyl groups. Preferred for R
1
are hydrogen and chlorine. R
1
is usually substituted at the 4- or 5-position of the benzotriazole ring but the halogen atom and the alkyl group are usually located at the 5-position.
R
2
is hydrogen or a hydrocarbon group having 1 to 10, preferably 1 to 8 carbon atoms. Examples of the hydrocarbon groups may be alkyl, cycloalkyl, aryl, and aralkyl groups More specific examples are methyl, ethyl, propyl, i-propyl, butyl, t-butyl, t-pentyl, cyclohexyl, and 1,1-dimethylbenzyl groups. The particularly preferred are t-butyl and 1,1-dimethylbenzyl groups.
R
3
is a hydrocarbon group having 4 to 10, preferably 4 to 8 carbon atoms, a carboxyl-substituted alkyl group having 2 to 10, preferably 2 to 4 carbon atoms and represented by —R—COOH wherein R

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