Measuring and testing – Gas analysis – Moisture content or vapor pressure
Reexamination Certificate
2002-03-13
2003-09-09
Lefkowitz, Edward (Department: 2855)
Measuring and testing
Gas analysis
Moisture content or vapor pressure
C073S029010, C338S035000, C324S664000
Reexamination Certificate
active
06615659
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
This invention relates to a humidity sensor device for detecting and determining moisture in the surrounding atmosphere and a method for preparing the same.
2. Background Art
Known humidity sensors designed to detect humidity through changes of electrical properties, typically electric resistance include those using electrolytes such as lithium chloride, metal oxides, and organic polymers as the humidity sensitive material.
However, the humidity sensors using electrolytes such as lithium chloride can measure only a narrow range of humidity and are less resistant to water in that their performance can be altered by dew condensation and wetting. The humidity sensors using metal oxides are resistant to water, but low sensitive. Because of the lack of long-term stability when used alone, they undesirably require a heat cleaning circuit which would add to the operating cost and make the sensor structure complex.
Among the humidity sensitive materials, organic polymers, especially polymeric electrolytes having quaternary ammonium salt have been widely used in commercial and industrial applications and so appreciated.
For example, Japanese Patent Publication (JP-B) No. 61-54176 discloses a humidity sensitive material comprising aggregates of latex particles formed of a copolymer between a hydrophobic monomer and an ionic or non-ionic hydrophilic monomer and having a hydrophilic surface layer. There are exemplified some cationic compounds having primary to quaternary ammonium salts.
JP-B 62-7976 discloses a humidity sensitive material in the form of a polymer which is obtained by polymerizing a compound containing 2-hydroxy-3-methacryloxypropyl-trimethylammonium chloride to a degree of polymerization of 1,000 to 10,000.
JP-B 2-24465 discloses the use as a humidity sensitive polymeric thin film of a thin film of an ionene polymer having the structural formula:
—(N
+
(R
1
)(R
2
)X
−
-A-N
+
(R
3
)(R
4
)X
−
—B)
n
—
wherein R
1
to R
4
are alkyl, X
−
is a halide ion, A and B each are —(CH
2
)
m
— wherein m≧2, or a thin film of a mixture of the polymer with another polymer such as polyvinyl pyrrolidone for the purposes of improving substrate adhesion and water resistance.
Humidity sensors using the polymeric electrolytes exemplified above as the humidity sensitive material, however, are still low in water resistance in that the polymeric electrolytes can be partially leached in a high humidity region, especially in a dew condensing atmosphere. They also suffer from a hysteresis phenomenon that they produce different outputs at the same humidity depending on whether the humidity is increasing or decreasing. In a low humidity region having a relative humidity (RH) of less than 10%, they have so high resistance values that practical humidity measurement is impossible.
JP-A 7-318526 discloses that water resistance is improved by introducing an unsaturated bond into the ionene polymer at either end and crosslinking with ultraviolet radiation. In this case, a very thin film provides satisfactory properties and water resistance. However, the small thickness means so small an absolute amount of the polymer that the film is vulnerable to a gas which is dissolved in water to form ions (e.g., Cl
2
, NOx, SOx). The problem is serious particularly in a commercial application.
The conductivity of a film having a thickness above a certain level is not substantially altered even when gas-origin ions are created in the surface layer. The polymer layer obtained by the above crosslinking method, however, undergoes substantial swell upon absorption of water, giving rise to serious problems of crack generation and separation from the substrate. Under such circumstances, the film must be used at a thickness of no more than 1 &mgr;m.
SUMMARY OF THE INVENTION
A primary object of the present invention is to provide a humidity sensor device having a humidity sensitive thin film which is resistant to water, maintains effective, stable performance over a long time even in a dew condensing atmosphere, is resistant to solvents and less vulnerable to gases such as nitrogen oxides, sulfur oxide and chlorine, and produces accurate outputs in a stable manner over a wide humidity region, especially in a low humidity region; and a method for preparing the same. Another object is to provide a simple method for preparing such a humidity sensor device having improved properties as mentioned above.
These and other objects are achieved by the present invention which is defined below as (1) to (38).
(1) A humidity sensor device comprising an insulating substrate, a pair of opposed electrodes disposed on the substrate to define a gap therebetween, and a humidity sensitive thin film lying on the gap,
said humidity sensitive thin film comprising a copolymer of at least one monomer of the following formula (1) with at least one monomer of the following formula (2):
wherein A
11
is a divalent group, each of R
11
, R
12
, R
13
and R
14
which may be the same or different is an alkyl group, each of Y
11
and Y
12
which may be the same or different is a monovalent group terminated with an ethylenically unsaturated reactive group, any two or more of R
11
to R
14
, Y
11
, Y
12
, A
11
and portions thereof adjoining the nitrogen (N) atom may bond together to form a ring with the nitrogen (N) atom, and each of X
11
−
and X
12
−
which may be the same or different is an anion,
wherein each of A and B is a divalent group, each of Y
1
, Y
2
, Y
3
, Y
4
, Y
5
and Y
6
which may be the same or different is a monovalent group, at least one of Y's is a group terminated with an ethylenically unsaturated reactive group, any two or more of Y
1
, Y
2
, Y
3
, Y
4
, Y
5
, A and portions thereof adjoining the nitrogen (N) atom or any two or more of Y
4
, Y
5
, Y
6
, B and portions thereof adjoining the nitrogen (N) atom may bond together to form a ring with the nitrogen (N) atom, each of X
1
−
and X
2
−
which may be the same or different is an anion, and n is a number of 2 to 5,000.
(2) The humidity sensor device of above (1) wherein the anions represented by X
11
−
and X
12
−
in formula (2) and the anions represented by X
11
−
and X
12
−
in formula (1) are halide ions.
(3) The humidity sensor device of above (2) wherein chloride ions or bromide ions are contained as the halide ions.
(4) The humidity sensor device of above (1) wherein the divalent groups represented by A and B in formula (2) and the divalent group represented by A
11
in formula (1) each are an alkylene, alkenylene or arylene group or a mixture thereof.
(5) The humidity sensor device of above (1) wherein the monovalent groups represented by Y
11
and Y
12
in formula (1) each are an alkylene acrylate or methacrylate group or alkylene acrylate or methacrylate amide group.
(6) The humidity sensor device of above (1) wherein the monomer of formula (1) is a difunctional monomer obtained by reacting a dialkylaminoethyl acrylate or methacrylate or a dialkylaminoethyl acrylate or methacrylate amide with a dihalogen compound.
(7) The humidity sensor device of above (1) wherein the monomer of formula (1) is obtained by reacting an acrylic unsaturated compound having a dialkylamino group with a dihalogen compound of the divalent group represented by A
11
in formula (1).
(8) The humidity sensor device of above (1) wherein the copolymer further includes an acrylic monomer having an alkoxysilyl group.
(9) The humidity sensor device of above (1) wherein the insulating substrate is an insulating substrate from which contaminants and/or oxides on its uppermost surface layer have been removed by physical means.
(10) A method for preparing a humidity sensor device comprising an insulating substrate, a pair of opposed electrodes disposed on the substrate to define a gap therebetween, and a humidity sensitive thin film lying on the gap, said method comprising the steps of coating a coating solution containing a monomer of the following formula (1) and a monomer o
Namba Kenryo
Shibue Akira
Cygan Michael
Lefkowitz Edward
TDK Corporation
LandOfFree
Humidity sensor and method for manufacturing the same does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Humidity sensor and method for manufacturing the same, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Humidity sensor and method for manufacturing the same will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3043562