JPH06160327A - Humidity sensor element and manufacture thereof - Google Patents

Abstract

PURPOSE:To furnish a humidity sensor element for detecting and determining moisture in atmosphere, excellent in water resistance and having a stable output characteristic in a wide range of humidity, and a manufacture thereof. CONSTITUTION:A pair of electrodes 4 having a gap 5 are provided on an insulating base 2, a humidity-sensitive thin film 3 is provided on this gap and further a water-repellent film is provided as occasion demands. This humidity-sensitive thin film 3 has a constitution wherein a crosslinking monomer constituent of a copolymer of a conductive monomer constituent of 60mol% or more and the crosslinking monomer constituent containing at least one of an N-methylol group or an N-methylol part being a derivative thereof and active hydrogen is self-crosslinked or crosslinked by a crosslinking agent.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a humidity sensor element for detecting and quantifying water in an atmosphere and a method for manufacturing the humidity sensor element.

[0002]

2. Description of the Related Art Hitherto, various principles of humidity sensor elements have been used, but they have their respective drawbacks, and efforts are being made to improve them. Among them, the one using the polymer electrolyte membrane is particularly poor in water resistance such as a part of the polymer electrolyte being eluted in a high humidity region, especially in a dew condensation atmosphere, or when the humidity is increased or decreased. There is no humidity sensor element that can obtain stable output characteristics over a wide humidity range, such as showing different output values even at the same humidity and exhibiting large hysteresis particularly in a low humidity region.

There have been many attempts to improve such drawbacks. For example, in Japanese Patent Publication No. 24465/1990, a polyelectrolyte has a cationic ammonium group in the main chain portion of a linear chain structure, By mixing polyvinylpyrrolidone, polyvinyl alcohol, etc. for the purpose of improving the adhesiveness and water resistance to the substrate as necessary,
It has been proposed that a good response can be obtained without increasing the hysteresis, and the adhesion to the substrate and the water resistance can be improved. However, this proposal is insufficient in water resistance, and deterioration of output characteristics is observed after long-term use in a dew condensation atmosphere.

Further, in JP-A-2-253148, as an improvement by a method of crosslinking the used polyelectrolyte, a cross-linking reaction between a hydroxyl group and a dicyano compound of a cationic polymer having a quaternary ammonium salt group and a hydroxyl group is carried out. We have proposed a moisture-sensitive element with a polymer moisture-sensitive film formed in an interpenetrating network with the obtained polymer and a thermosetting resin. It is said that a humidity sensor element can be obtained. However, the cationic polymer (2-hydroxy-3-methacryloxypropyltrimethylammonium chloride polymer) used here has many hydroxyl groups as cross-linking points, so that it is difficult to control the degree of cross-linking and the degree of cross-linking is When it is too high, the moisture-sensitive film is exposed to high humidity for a long time to swell, and then repeatedly dried, whereby cracks occur in the moisture-sensitive film and the durability tends to deteriorate.

Therefore, in order to control the degree of cross-linking, the proposal further uses, for example, methoxymethylmelamine, which are cross-linked with diisocyanates. However, the isocyanate group has a strong hygroscopic property, and deterioration due to moisture absorption is rapid, so that process control is difficult, and the hydrophobicity of the moisture-sensitive thin film is increased, which deteriorates the moisture-sensitive property, which is not preferable. Further, it is known that when crosslinked with diisocyanate, it is generally colored and the time-dependent characteristics deteriorate.

[0006]

The main object of the present invention is to provide a moisture-sensitive thin film having excellent water resistance, stable operation for a long period of time even in a dew condensation atmosphere, and stable and excellent output characteristics in a wide humidity range. It is to provide a humidity sensor element having.

[0007]

Such an object is achieved by the following constitutions (1) to (11). (1) A pair of electrodes are provided on an insulating substrate so as to face each other with a gap, and a moisture-sensitive thin film is provided on the gap. The moisture-sensitive thin film contains a conductive monomer component, an N-methylol group, or Self-crosslinking of the above-mentioned crosslinkable monomer component of a polymer with a crosslinkable monomer component containing at least one of an N-methylol moiety and active hydrogen, which is a derivative thereof, by reacting the N-methylol moiety with active hydrogen. A humidity sensor element which is or is crosslinked with a crosslinking agent. (2) The conductive monomer component undergoes a cyclopolymerization reaction to form a cyclopolymerized portion in the main chain portion of the polymer (1).
Humidity sensor element. (3) The humidity sensor element according to (1) or (2) above, wherein the conductive monomer component is cyclopolymerized to form a quaternary ammonium salt group in the main chain of the polymer. (4) The monomer forming the conductive monomer component is
The humidity sensor element according to (2) or (3) above, which is a diallylammonium compound. (5) The monomer forming the conductive monomer component is
The humidity sensor element according to (2) above, which has at least one of a heptadiene skeleton, a diacrylamide skeleton and a dimethacrylamide skeleton. (6) The humidity sensor element according to (1) or (5) above, wherein the conductive monomer component is polymerized to have a quaternary ammonium salt group on a side chain of the polymer. (7) The conductive monomer component is 60 mol% of the polymer
The humidity sensor element according to any one of the above (1) to (6). (8) The moisture-sensitive thin film is formed by using an aqueous solution containing a polymer of the conductive monomer component and the crosslinkable monomer component, or using an aqueous solution containing a crosslinking agent in addition to the polymer. Viscosity (1)-
The humidity sensor element according to any one of (7). (9) The above (1), wherein a water-repellent coating is provided on the moisture-sensitive thin film.
The humidity sensor element according to any one of to (8). (10) An aqueous solution containing a polymer of a conductive monomer component and a crosslinkable monomer component on a pair of electrodes provided on an insulating substrate, or an aqueous solution containing a crosslinker in addition thereto, having a Newtonian viscosity. A method for producing a humidity sensor element, which comprises applying an aqueous solution having the above formula, and then self-crosslinking the copolymer, or crosslinking the copolymer with the crosslinking agent to form a moisture-sensitive thin film. (11) The method for manufacturing a humidity sensor element according to the above (10), in which the hysteresis in the low humidity region of the moisture sensitive thin film is reduced.

[0008]

In the present invention, the moisture sensitive thin film of the conductive polymer is formed so as to cover the pair of electrodes provided on the insulating substrate. This moisture-sensitive thin film is a polymer, particularly a copolymer, having a conductive monomer component and a crosslinkable monomer component, and if necessary, a crosslinking agent is added, and if necessary, a water-repellent film is formed on the surface of the moisture-sensitive thin film. Is obtained and then crosslinked. The above-mentioned copolymer used in the moisture-sensitive thin film exhibits ion conductivity by dissociation of a conductive portion contained in the molecule, for example, a counter ion of a quaternary ammonium salt group by water in the atmosphere.
The degree of dissociation changes depending on the amount of water in the atmosphere, and this is used to detect humidity. Further, since the moisture-sensitive thin film is crosslinked by using the crosslinkable monomer component in the copolymer, it has excellent water resistance. As the conductive monomer component, for example, by selecting a compound that undergoes a cyclopolymerization reaction, a moisture-sensitive thin film solution containing a copolymer with the crosslinkable monomer component and, if necessary, a crosslinking agent, has a Newtonian viscosity. The humidity sensor element formed from this aqueous solution has a characteristic that it exhibits almost no hysteresis in a low humidity region.

Further, by controlling the content of the crosslinkable monomer component among the monomer components forming the copolymer, the degree of crosslinking relating to the water resistance of the moisture-sensitive thin film can be easily controlled. The water resistance can be improved without impairing the wet characteristics.

Regarding the use of the conductive monomer component of the present invention which is cyclopolymerized to form a main chain portion in a humidity sensor element, JP-A-58-97651 discloses a diallylamine derivative or 4- (4-pyridyl). There is a proposal that a copolymer such as a -1,6-heptadiene derivative is used as a high molecular weight polycation and that crosslinking is preferable in order to improve water resistance. However, in this proposal, a copolymer of the derivative and the crosslinkable monomer component has not been proposed,
Furthermore, there is no suggestion of using the crosslinkable monomer component of the copolymer as a crosslinking component.

[0011]

Specific Structure The specific structure of the present invention will be described in detail below.

In the humidity sensor element of the present invention, an aqueous solution of a copolymer of a conductive monomer component and a crosslinkable monomer component is applied onto a pair of comb-shaped electrodes provided on an insulating substrate, and a crosslinking agent is added if necessary. It is obtained by adding and adding a water-repellent film and then performing a predetermined crosslinking treatment by heating.

[Conductive monomer component] The conductive monomer component used in the present invention may have various hydrophilic groups, but is particularly preferably one formed from a cationic monomer. As the cationic monomer, those having a quaternary ammonium base are preferable, and those represented by Chemical formula 1 are particularly preferable.

[0014]

[Chemical 1]

In the chemical formula 1, A is an acryloyloxy group, a methacryloyloxy group, an acryloylimino group,
It represents an ethylenic group such as methacryloylino group, vinyl group, allyl group, diallylmethyl group, allyloxy group, diacryloylyomino group or dimethacryloylyomino group. B is a C ₂ -C ₇ alkylene, arylene such as phenylene, or a part of them substituted with a hydroxyl group or a combination thereof, and a linking group such as a bond with another linking group or a simple bond. Represents R ₁ has 1 to 10 carbon atoms (hereinafter C _{1 to} C ₁₀ )
Represents an alkyl group or an aryl group of R ₂ and R
₃ represents a C _{1 to} C ₁₀ alkyl group, respectively. Further, R ₁ , R ₁ , R ₂ and B may be bonded to each other to form a 5- or 6-membered ring, particularly an aromatic ring. Further, as the counter anion (X) of the quaternary ammonium base, halogen ions such as chloride ion, bromine ion and iodine ion, various acid anions such as sulfate ion, perchlorate ion, phosphate ion and nitrate ion can be used. Of these, chlorine ion, bromine ion, iodine ion and the like are preferable.

(Cyclic Polymerization Main Chain Ammonium Salt Type) Among the conductive monomer components represented by Chemical formula 1, those which are cyclopolymerized by a copolymerization reaction and further have a quaternary ammonium salt group in the main chain portion are preferable. An example thereof is shown in Chemical formula 2.

[0017]

[Chemical 2]

In the chemical formula 2, two Rs may be the same or different and each represents a C ₁ -C ₅ alkyl group such as a methyl group. Further, as the counter anion (X) of the quaternary ammonium base, halogen ions such as chlorine ion, bromine ion, iodine ion, sulfate ion, perchlorate ion,
Various acid anions such as phosphate ion and nitrate ion can be used, and among these, chloride ion, bromine ion, iodine ion and the like are preferable.

Specific examples of these are shown below. However, the present invention is not limited to the following compounds.

[0020]

[Chemical 3]

[0021]

[Chemical 4]

In the chemical formulas 3 and 4, the counter anion (X) of the quaternary ammonium salt group is a halogen ion such as chlorine ion, bromine ion, iodine ion, sulfate ion,
Various acid anions such as perchlorate ion, phosphate ion and nitrate ion can be used, and among these, chloride ion, bromine ion, iodine ion and the like are preferable.

(Cyclopolymerization side chain ammonium salt type)
Among the conductive monomer components represented by Chemical formula 1, those which are cyclopolymerized by a copolymerization reaction and have a quaternary ammonium salt group in a side chain can be preferably used. For example, those shown in Chemical formulas 5 and 6 are given.

[0024]

[Chemical 5]

In Chemical formula 5, R ₄ represents the residue shown in Chemical formula 7.

[0026]

[Chemical 6]

In the chemical formula 6, R represents H or CH ₃ , and R ₄ represents the residue shown in the chemical formula 7.

[0028]

[Chemical 7]

In the chemical formula 7, B, R ₁ , R ₂ and R ₃
Are synonymous with B, R ₁ , R ₂ and R ₃ in Chemical formula ₁ , respectively. As the counter anion (X) of the quaternary ammonium base, halogen ions such as chlorine ion, bromine ion and iodine ion, various acid anions such as sulfate ion, perchlorate ion, phosphate ion and nitrate ion can be used. Of these, chlorine ion, bromine ion, iodine ion and the like are preferable.

Specific examples of chemical formula 5 are shown in chemical formulas 8 and 9, and specific examples of chemical formula 6 are shown in chemical formulas 10 and 11. However, the present invention is not limited to the following compounds.

[0031]

[Chemical 8]

[0032]

[Chemical 9]

[0033]

[Chemical 10]

[0034]

[Chemical 11]

In the chemical formulas 8 to 11, the counter anion (X) of the quaternary ammonium base is a halogen ion such as chlorine ion, bromine ion, iodine ion, sulfate ion, perchlorate ion, phosphate ion and nitrate ion. The various acid anions can be used, and of these, chloride ion, bromine ion, iodine ion and the like are preferable.

(Other Side Chain Quaternary Ammonium Salt Type) In the present invention, the side chain is not cyclopolymerized and has an acryloyl group, a methacryloyl group, an allyl group, a vinyl group or the like as the component A shown in Chemical formula 1. Those having a quaternary ammonium salt group can also be used as the conductive monomer component.

Specific examples of these are shown below. However, the present invention is not limited to the following compounds.

[0038]

[Chemical 12]

[0039]

[Chemical 13]

[0040]

[Chemical 14]

[0041]

[Chemical 15]

[0042]

[Chemical 16]

[0043]

[Chemical 17]

[0044]

[Chemical 18]

[0045]

[Chemical 19]

[0046]

[Chemical 20]

[0047]

[Chemical 21]

[0048]

[Chemical formula 22]

[0049]

[Chemical formula 23]

[0050]

[Chemical formula 24]

[0051]

[Chemical 25]

In Chemical formulas 12 to 25, R is H or C
Represents H ₃ . Further, as the counter anion (X) of the quaternary ammonium base, halogen ions such as chlorine ion, bromine ion and iodine ion, various acid anions such as sulfate ion, perchlorate ion, phosphate ion and nitrate ion can be used. Of these, chlorine ion, bromine ion, iodine ion and the like are preferable. Further, in the chemical formulas 23 to 25, the structural formulas shown show the vinyl group bonded to the 4-position of the 6-membered ring.
Any of the 4th place may be used.

[Crosslinkable Monomer Component] (Containing Active Hydrogen) Among the constituent components of the copolymer, as the monomer for forming the crosslinkable monomer component, the skeleton component is acryloyl or methacryloyl-based (hereinafter,
(Meth) acryloyl) is preferable, and those having a group having active hydrogen are further contained. As the group having active hydrogen, various groups such as hydroxy, amido, carboxy, sulfo, amino and the like can be used, and in particular, —OH or —NH ₂ or —NHR ′ (R ′ is C _{1 to} C ₅ alkyl. Groups) are preferred. More specifically (meth) acrylamide _{(CH 2 = CR-CONH 2} ): or an alkyl-substituted bodies of the _{C 1 ~C 5 (CH 2 =} CR-CON
HR ′), optionally further substituted with OH or NH ₂ or the like: or (meth) acrylic acid C _1-
A C ₅ alkyl ester (CH ₂ ═CRCOOR ′) substituted with OH, NH ₂ or the like is preferable. In these cases, it is preferable that about 1 to ₂ OH and NH ₂ are present. Furthermore, these monomers are
It may have a primary ammonium base, and these will also be used as a conductive monomer component. These crosslinkable monomer components are crosslinked by forming a copolymer with the conductive monomer component and then adding a crosslinking agent described later. Specific examples of these are shown below. However, the present invention is not limited to the following compounds.

[0054]

[Chemical formula 26]

[0055]

[Chemical 27]

[0056]

[Chemical 28]

[0057]

[Chemical 29]

[0058]

[Chemical 30]

[0059]

[Chemical 31]

[0060]

[Chemical 32]

[0061]

[Chemical 33]

[0062]

[Chemical 34]

[0063]

[Chemical 35]

[0064]

[Chemical 36]

In Chemical formula 26 to Chemical formula 36, R is H or C
Represents H ₃ . Further, as the counter anion (X) of the quaternary ammonium base, halogen ions such as chlorine ion, bromine ion and iodine ion, various acid anions such as sulfate ion, perchlorate ion, phosphate ion and nitrate ion can be used. Of these, chlorine ion, bromine ion, iodine ion and the like are preferable.

(Self-crosslinking type) In addition to the above, in the present invention, the monomer for forming the crosslinkable monomer component is acrylamide or methacrylamide, and the amide group thereof is methylol (-CH ₂ OH) or its A compound having a C _{1 to} C ₅ alkyl ether derivative can also be used. These crosslinkable monomer components, after forming a copolymer with the conductive monomer component,
It self-crosslinks by the crosslinking treatment described below. Alternatively, it can be cross-linked with another cross-linking agent if necessary. Specific examples of these are shown below. However, the present invention is not limited to the following compounds.

[0067]

[Chemical 37]

[0068]

[Chemical 38]

[0069]

[Chemical Formula 39]

[0070]

[Chemical 40]

[0071]

[Chemical 41]

In Chemical formula 37 to Chemical formula 41, R is H or C
Represents H ₃ .

[Crosslinking Agent] As a crosslinking agent for crosslinking the above-mentioned crosslinkable monomer component, N-methylol melamine, alkoxymethylated melamine having about 1 to 5 carbon atoms or a melamine molecule having a degree of polymerization of 2 to 2 is used. An initial condensate having about 100, further an N-methylolated urea, an alkoxymethylated urea having about 1 to 5 carbon atoms, or an initial condensate having a degree of polymerization of the urea molecule of about 2 to 300 is used. In this case, N-methylol or N-
Alkoxymethyl moieties are present in the molecule in the range of about 2 to 200. Further, a polymer obtained by polymerizing a monomer compound which is acrylamide or methacrylamide and has methylol (—CH ₂ OH) or its C _{1 to} C ₅ alkyl ether derivative bonded to the N position thereof can also be used. A polymer compound having an average molecular weight (Mw) of about 10,000 to 3,000,000 can be used.

Further, as the cross-linking agent, the conductive monomer component and, among the cross-linkable monomer components, methylol (—CH ₂ OH) of acrylamide or methacrylamide or its C ₁ -C ₅ alkyl ether can be used. A copolymer with a derivative having a copolymerization content ratio of the conductive monomer of 60 mol% or less and an average molecular weight (Mw) of about 10,000 to 3,000,000 is also included. In this case, two or more kinds of copolymers having a self-crosslinking type crosslinkable monomer component are crosslinked with each other.

[Copolymerization] (Content of Conductive Monomer Component) A moisture-sensitive thin film is formed on an insulating substrate by using these constituents. First, the conductive monomer component and the crosslinkable monomer component are separated from each other. Copolymerize. In the present invention, the content of the conductive monomer component,
The content in the copolymer is 60 mol% or more, preferably 70 mol% or more. If the amount of the conductive monomer component is too small, the output particularly in the low humidity region remarkably decreases, which is not preferable.

Further, in the present invention, a suitable one kind of the conductive monomer and the crosslinkable monomer may be copolymerized, and, for example, a single or a plurality of kinds of conductive monomer components and a single or a plurality of kinds. Any kind of cross-linkable monomer component may be optionally combined and copolymerized. It is also possible to use a copolymerized compound having the properties of both a conductive monomer component and a crosslinkable monomer component, in which case there will be a large amount of quaternary ammonium salt group, and when used as a humidity sensor element. High output can be obtained.

The copolymerization reaction of the conductive monomer component and the crosslinkable monomer component is usually carried out by radical polymerization. In order to start this reaction, a reaction initiator of about 0.5 to 3 wt% is added, but the reaction initiator used in the present invention is not particularly limited, and a thermal radical initiator or a photoradical initiator usually used. Agents can be used.

A peroxide radical initiator or an azo radical initiator can be used as the thermal radical initiator, and a Michler's ketone initiator, a thioxanthone initiator, a benzophenone initiator or an acetophenone initiator can be used as the photo radical initiator. Any initiator etc. can be used,
Preferably ammonium persulfate, potassium persulfate, tert
-Butyl hydroperoxide may be used.

Addition of this reaction initiator, preferably under an atmosphere of an inert gas such as nitrogen, the optimum conditions are selected for the conductive monomer component and the crosslinkable monomer component to be used, and polymerization is carried out by heating or light in a usual manner. All you have to do is react. The optimum conditions in this case are peculiar to the conductive monomer component, the crosslinkable monomer component, the radical initiator, etc. used, for example, the conditions specified by the manufacturer who produced each, or the conditions obtained by experiments. .

The average molecular weight (Mw) of the copolymer thus obtained is preferably about 10,000 to 5,000,000. If the molecular weight is too large, a moisture-sensitive thin film solution becomes a gel-like solution and it becomes difficult to form a uniform moisture-sensitive thin film. On the other hand, if it is too small, the water resistance decreases, which is not preferable.

[Preparation of Moisture-Sensitive Thin Film] (Addition of Crosslinking Agent) A moisture-sensitive thin film solution is prepared by using the copolymer thus obtained alone or by combining a plurality of different copolymers. Then, in order to enhance water resistance, it is preferable to perform a crosslinking treatment on the above-mentioned crosslinking monomer component portion of the copolymer. Therefore, when a compound that is crosslinked by the addition of a crosslinking agent is used as the crosslinkable monomer component, the crosslinkable monomer component of the copolymer is 0.2 to
2 to 6 per about 6 meq / g per reactive group of the cross-linking agent
About 30 meq / g is mixed at a ratio of about 20 to 60 wt% to prepare a moisture sensitive thin film solution.

When the self-crosslinkable compound is used as the crosslinkable monomer component, the copolymer may be used as a moisture-sensitive thin film solution without adding the crosslinking agent, and the crosslinking agent may be added as described above. You may. In this case, the addition of the crosslinking agent can be expected to further improve the water resistance of the humidity sensor element.

[Newtonian Viscosity] Among the moisture-sensitive thin film solutions thus prepared, a solution prepared from a copolymer using a conductive monomer component accompanied by a cyclopolymerization reaction exhibits Newtonian viscosity. The humidity sensor element formed using the moisture-sensitive thin film solution shown has extremely small hysteresis in the low humidity region. Therefore, by using the moisture-sensitive thin film solution exhibiting Newtonian viscosity, it is possible to manufacture a humidity sensor element having excellent characteristics over a wide humidity range. Further, the moisture-sensitive thin film solution prepared by using a conductive monomer component that does not accompany the cyclopolymerization reaction in the copolymer exhibits non-Newtonian viscosity, and the humidity sensor element produced by using this moisture-sensitive thin film solution is There is a slight hysteresis in the low humidity region. However, since it has high water resistance, which is a feature of the present invention, it can be used as an excellent humidity sensor element for use in a high humidity region.

Further, in the present invention, a moisture-sensitive thin film solution is prepared by mixing copolymers obtained by using a conductive monomer component accompanied by a cyclopolymerization reaction and having Newtonian viscosity when forming a moisture-sensitive thin film solution. Even if the copolymer having the Newtonian viscosity and the conductive monomer components not accompanied by the cyclopolymerization are used alone or in combination, a copolymer exhibiting a non-Newtonian viscosity in a moisture-sensitive thin film solution is obtained. May be mixed to prepare a moisture-sensitive thin film solution, or the above-mentioned copolymers having non-Newtonian viscosity may be mixed to prepare a moisture-sensitive thin film solution. In this case, the humidity sensor element manufactured using the moisture-sensitive thin film solution made of the above-mentioned Newtonian copolymer does not show hysteresis.

In the present invention, having Newtonian viscosity means that when the viscosity of an aqueous solution is measured using a B type viscometer,
Viscometer It means that the viscosity does not change substantially even when the rotational speed of the rotor is changed. Furthermore, when the viscosity of a 1 wt% aqueous solution of the same sample is measured by changing the rotation speed of the B-type viscometer to 12 rpm, 30 rpm, and 60 rpm, the change in the measured value at each rotation speed is not substantially changed. Is ±
It shall be within 10%.

[Substrate] Using the moisture-sensitive thin film solution thus obtained, a humidity sensor element 1 as shown as an example in FIG. 1 is formed. As the insulating substrate 2 used in the present invention, any material may be used as long as it has good adhesiveness to the moisture sensitive thin film 3 and has electrical insulating properties, such as glass, plastic, ceramic or insulating coating. A metal or the like is used.

The electrode 4 is not particularly limited as long as it is a commonly used one, and for example, a low resistance paste made of Au or RuO ₂ can be used. The electrode terminals 6 may be of any type as long as they are compatible with the solder. For example, Ag-Pd alloy or the like may be used, and these may be printed by a usual method and sintered at a high temperature. Furthermore, for example, when Au is used for the electrode 4, Au during the soldering process is used.
A resist film 9 made of resist or glass is preferably provided to prevent diffusion. There is no limitation on the thickness and shape of the resist film 9 as long as it has an effect of preventing Au diffusion during the soldering process.

[Film Formation] Examples of methods for forming a moisture-sensitive thin film on an insulating substrate from the moisture-sensitive thin film solution of the present invention include dipping, brush coating, gravure printing, screen printing and spinner coating. Various methods such as a method can be used, and the method may be selected depending on the process, application and type of product.

(Film Thickness) The dry thickness of the moisture-sensitive thin film of the present invention is preferably about 1 to 10 μm, more preferably about 2 to 5 μm. If the film thickness is too thick, the reaction speed of the electric resistance value of the film with respect to humidity, that is, the response becomes slow, and if the film thickness is too thin, the output particularly in the low humidity region decreases, and the water resistance also decreases. It is not preferable.

(Water-repellent coating) It is preferable to form a water-repellent coating on the surface of the moisture-sensitive thin film of the humidity sensor element of the present invention. By forming the water repellent film, peeling between the substrate and the sensor film and peeling between the films due to continuous use are prevented. For this reason, the sensor becomes more durable and the reliability of moisture detection and quantitative determination is further improved.

The water-repellent coating has a contact angle with water of 90 ° or more, particularly 90 to 130 °, and it is preferable to prevent the influence on the water droplets to be attached. At the same time, it is necessary to secure sufficient water permeation.
It is preferable to regulate to less than or equal to μm, particularly 0.1 to 2 μm.

As a material for forming such a water-repellent coating, a hydrophobic polymer, for example, a fluoropolymer such as polytetrafluoroethylene; an olefin polymer such as polyethylene or polypropylene; a silicone polymer or the like is preferably used. It There is no limitation on the method for forming the protective film of such a water-repellent coating, but it may be formed by a dipping method or the like as in the method for forming the moisture-sensitive thin film.

[Crosslinking Treatment] The moisture-sensitive thin film thus coated on the insulating substrate having the electrode and optionally having a water-repellent coating on its surface is subjected to a crosslinking treatment at about 120 to 220 ° C., preferably 120. It may be carried out by heating at about 180 ° C. for about 10 minutes to 5 hours. At this time, heat treatment is preferably performed in an inert gas such as a nitrogen atmosphere to prevent thermal oxidation.

[0094]

EXAMPLES The present invention will be described in more detail below by showing specific examples of the present invention. Example 1 43.1 g of diallyldimethylammonium chloride (60% aqueous solution) as a conductive monomer and 2.84 g of acrylamide as a crosslinkable monomer were distilled water 97.5.
g, and tert-butyl hydroperoxide 0.
3 g was added, and the copolymerization reaction was carried out under nitrogen atmosphere with stirring at 75 ° C. for 24 hours. After completion of the reaction, the mixture was cooled and distilled water was added to obtain a solution having a solid content concentration of 1 wt% (copolymerization molar ratio conductive monomer component: crosslinkable monomer component = about 8).
0:20 and below are the same).

As the cross-linking agent, an 80% aqueous solution of trimethoxymethylmelamine diluted with distilled water to 1 wt% was used as the cross-linking agent solution.

A mixture of the 1 wt% copolymer solution and the 1 wt% crosslinking agent solution in a weight ratio of 2: 1 was used as a moisture-sensitive thin film solution, which was applied onto the porous ceramic substrate 2 shown in FIG. 1 by dipping. The moisture sensitive thin film 3 was formed by drying at 70 to 80 ° C. for 5 minutes. Next, amorphous Teflon (Teflon AF2400: manufactured by DuPont) is dissolved in saturated fluorocarbon (Fluorinert FC43: manufactured by Sumitomo 3M) to obtain 0.2.
A 5 wt% solution was used to apply and impregnate the formed moisture-sensitive thin film by dipping, followed by drying at 70 to 80 ° C for 5 minutes to form a water-repellent film, and then at 180 ° C for 2 minutes.
A time-crosslinking treatment was performed to obtain a humidity sensor element.

The humidity sensor element thus obtained was subjected to measurement of output characteristics and water resistance test. Regarding output characteristics, a humidity sensor element is incorporated in the circuit described in Japanese Patent Application Laid-Open No. 2-123843, and a shunt type humidity generator (model S
RH-1, manufactured by Shinei Co., Ltd.). The humidity sensor element incorporated in the circuit is placed in the shunt humidity generator, and the relative humidity at 25 ° C. is changed from the low humidity side to the high humidity side, continuously from the high humidity side to the low humidity side, and is 0 to 95%. The output voltage at each set value was measured by providing 9 to 11 kinds of set values in the range and changing the set value stepwise. However, each output value was a read value after being kept at each set humidity for 15 minutes. The obtained results are shown in FIG.

In the water resistance test, a humidity sensor element was incorporated in the circuit, and first, the humidity sensor device was left standing in the shunt type humidity generator kept at a constant humidity for 15 minutes, and the output voltage was measured. Then, after immersing the humidity sensor element in distilled water for 15 minutes,
The product was taken out and dried at 70 ° C. for 5 minutes, kept at constant humidity for 15 minutes in the same manner as above, and the output voltage was measured. The change in the output characteristics of the humidity sensor element was measured by repeating this immersion in distilled water and measurement of the output voltage after leaving it at a constant humidity.
Set values for constant humidity are 94% (a), 58% (b), 48
% (C), 26% (d) and 12% (e). The obtained results are shown in FIG. Each of a to e in the figure indicates the set value of the humidity.

Example 2 43.1 g of diallyldimethylammonium chloride (60% aqueous solution) as a conductive monomer, and 4.64 g of 2-hydroxyethyl acrylate as a crosslinkable monomer.
And are dissolved in 104.7 g of distilled water, 0.3 g of tert-butyl hydroperoxide is added, and the mixture is placed in a nitrogen atmosphere at 75
The copolymerization reaction was carried out while stirring at 24 ° C. for 24 hours. After completion of the reaction, the mixture was cooled and distilled water was added to obtain a solution having a solid content concentration of 1 wt% (copolymerization molar ratio of about 80:20). A humidity sensor element was obtained in the same manner as in Example 1 except that this was used as a copolymer solution.

The output characteristics and water resistance of the humidity sensor element thus obtained were measured in the same manner as in Example 1. The obtained output characteristic measurement results are shown in FIG. 3, and the water resistance measurement results are shown in FIG.

Example 3 43.1 g of diallyldimethylammonium chloride (60% aqueous solution) as a conductive monomer and 3.64 g of N-methylolacrylamide as a crosslinkable monomer were dissolved in 100.7 g of distilled water to prepare ammonium persulfate (0.1%).
Add 3 g and under nitrogen atmosphere at 25 ° C. for 5 hours, then 6
The copolymerization reaction was carried out while stirring at 0 ° C for 8 hours. After completion of the reaction, the mixture was cooled and distilled water was added to obtain a solution having a solid content concentration of 1 wt% (copolymerization molar ratio of about 80:20). A humidity sensor element was obtained in the same manner as in Example 1 except that this was used as a copolymer solution.

The output characteristics and water resistance of the humidity sensor element thus obtained were measured in the same manner as in Example 1. The obtained output characteristic measurement results are shown in FIG. 4, and the water resistance measurement results are shown in FIG.

Example 4 43.1 g of diallyldimethylammonium chloride (60% aqueous solution) as a conductive monomer, and 6.29 g of N-butoxymethylacrylamide as a crosslinkable monomer.
Was dissolved in 111.3 g of distilled water, 0.3 g of ammonium persulfate was added, and a copolymerization reaction was carried out under a nitrogen atmosphere while stirring at 25 ° C. for 5 hours and further at 60 ° C. for 8 hours. After the reaction is complete, cool and add distilled water to obtain a solid content of 1 wt.
% Solution was obtained (copolymerization molar ratio about 80:20). A humidity sensor element was obtained in the same manner as in Example 1 except that this was used as a copolymer solution.

The output characteristics and water resistance of the thus obtained humidity sensor element were measured in the same manner as in Example 1. The obtained output characteristic measurement results are shown in FIG. 5, and the water resistance measurement results are shown in FIG. 17, respectively.

Example 5 26.9 g of diallyldimethylammonium chloride (60% aqueous solution) as a conductive monomer and 23.8 g of 2-hydroxy-3-methacryloyloxypropyltrimethylammonium chloride as a crosslinkable monomer were dissolved in 149 g of distilled water. Then, add 0.3 g of tert-butyl hydroperoxide, and under a nitrogen atmosphere at 75 ° C for 2
The copolymerization reaction was carried out while stirring for 4 hours. After completion of the reaction, the mixture was cooled and distilled water was added to obtain a solution having a solid content concentration of 1 wt% (copolymerization molar ratio of about 50:50). A humidity sensor element was obtained in the same manner as in Example 1 except that this was used as a copolymer solution. However, 2-hydroxy-3-methacryloyloxypropyltrimethylammonium chloride added as a crosslinkable monomer in this example has a quaternary ammonium salt group and can be considered as a conductive monomer component.

The output characteristics and water resistance of the humidity sensor element thus obtained were measured in the same manner as in Example 1. The obtained output characteristic measurement results are shown in FIG. 6, and the water resistance measurement results are shown in FIG.

Example 6 A copolymer of 2-methacryloxyethyltrimethylammonium chloride, which is commercially available as a polymer flocculant, and acrylamide (copolymerization molar ratio 80:20) was dissolved in distilled water to obtain a solid content concentration of 1 wt. % Copolymer solution was prepared. Using this, a humidity sensor element was obtained in the same manner as in Example 1. A humidity sensor element was obtained in the same manner as in Example 1 except that this was used as a copolymer solution.

The output characteristics and water resistance of the humidity sensor element thus obtained were measured in the same manner as in Example 1. The obtained output characteristic measurement results are shown in FIG. 7, and the water resistance measurement results are shown in FIG.

Example 7 2-Methacryloxyethyltrimethylammonium chloride (80% aqueous solution) as a conductive monomer 41.
5 g and 4.64 g of 2-hydroxyethyl acrylate as a crosslinkable monomer were dissolved in 143.2 g of distilled water, and 0.4 g of potassium persulfate was added to the solution under a nitrogen atmosphere.
The copolymerization reaction was carried out while stirring at 5 ° C for 1 hour and further at 60 ° C for 5 hours. After completion of the reaction, the mixture was cooled and distilled water was added to obtain a solution having a solid content concentration of 1 wt% (copolymerization molar ratio of about 8).
0:20). Other than using this as a copolymer solution,
A humidity sensor element was obtained in the same manner as in Example 1.

The output characteristics and water resistance of the humidity sensor element thus obtained were measured in the same manner as in Example 1. The obtained output characteristic measurement results are shown in FIG. 8, and the water resistance measurement results are shown in FIG. 20, respectively.

Example 8 2-methacryloxyethyltrimethylammonium chloride (80% aqueous solution) as a conductive monomer 41.
5 g and 3.64 g of N-methylol acrylamide as a cross-linkable monomer were dissolved in 139.1 g of distilled water, 0.4 g of potassium persulfate was added, and the mixture was added at 25 ° C. under a nitrogen atmosphere.
The copolymerization reaction was carried out while stirring for 1 hour and further at 60 ° C. for 5 hours. After completion of the reaction, the mixture was cooled and distilled water was added to obtain a solution having a solid content concentration of 1 wt% (copolymerization molar ratio of about 80: 2).
0). A humidity sensor element was obtained in the same manner as in Example 1 except that this was used as a copolymer solution.

The output characteristics and water resistance of the humidity sensor element thus obtained were measured in the same manner as in Example 1. The measurement results of the obtained output characteristics are shown in FIG. 9, and the measurement results of water resistance are shown in FIG. 21, respectively.

Example 9 1 wt% copolymer solution of Example 5 and 2 as a cross-linking agent solution
-Methacryloxyethyl trimethyl ammonium chloride and N-methylol acrylamide were dissolved at a copolymer molar ratio of 50:50 to synthesize a copolymer under the same conditions as in Example 7, which was distilled water. Dissolves in
A 1 wt% solution was mixed at a weight ratio of 1: 1 to form a moisture-sensitive thin film solution, which was coated on an insulating substrate, formed with a water-repellent film, and crosslinked in the same manner as in Example 1 to obtain a humidity sensor. The device was obtained.

The output characteristics and water resistance of the humidity sensor element thus obtained were measured in the same manner as in Example 1. The obtained output characteristic measurement results are shown in FIG. 10, and the water resistance measurement results are shown in FIG. 22, respectively.

Example 10 A 1 wt% copolymer solution of Example 1, a diallyldimethylammonium chloride as a crosslinking agent solution, and N-methylolacrylamide were dissolved in a copolymer molar ratio of 50:50. A copolymer was synthesized under the same conditions as in Example 3 and dissolved in distilled water to prepare a 1 wt% solution, which was mixed at a weight ratio of 1: 1 to prepare a moisture-sensitive thin film solution. A humidity sensor element was obtained by performing coating on an insulating substrate, forming a water-repellent coating, and crosslinking treatment in the same manner as in.

The output characteristics and water resistance of the thus obtained humidity sensor element were measured in the same manner as in Example 1. The obtained output characteristic measurement results are shown in FIG. 11, and the water resistance measurement results are shown in FIG. 23.

Example 11 A 1 wt% copolymer solution obtained in Example 5 and a 1 wt% solution of the crosslinking agent obtained in Example 9 were mixed at a weight ratio of 1: 1 to obtain a moisture-sensitive thin film. As a solution, a humidity sensor element was obtained by performing coating on an insulating substrate, forming a water-repellent coating, and crosslinking treatment in the same manner as in Example 1.

The output characteristics and water resistance of the humidity sensor element thus obtained were measured in the same manner as in Example 1. FIG. 12 shows the measurement results of the obtained output characteristics, and FIG. 24 shows the measurement results of water resistance.

Comparative Example 1 Among the humidity sensor elements described in JP-B-2-24465, those of the first invention were used to measure the output characteristics and water resistance in the same manner as in Example 1. The obtained output characteristic measurement results are shown in FIG. 13, and the water resistance measurement results are shown in FIG. 25.

<Results of Output Characteristics Measurement> The results of the output characteristics of Examples 1 to 4 and 10 using a compound forming a copolymer having a cyclic structure in the main chain as the conductive monomer are shown in FIG.
3, 4, 5 and 11. As is clear from these figures, no hysteresis was observed in the low humidity region,
Further, good output can be obtained from the high humidity region to the low humidity region.

Examples 5 to 10 using a compound forming a copolymer having no cyclic structure in the main chain as the conductive monomer
The results of the output characteristics of 9 and 11 are shown in FIGS.
It was shown to. In these figures, there is a slight hysteresis in the low humidity region.

The results of Comparative Example 1 are shown in FIG. Although no hysteresis is observed, it can be seen that no output change can be obtained in the low humidity region, particularly 10% or less.

<Measurement Result of Water Resistance Test> Regarding the measurement result of the water resistance test, the results of Examples 1 to 11 are shown in FIGS. 14 to 24, and the result of Comparative Example 1 is shown in FIG. The measurement results of the humidity sensor element of the present invention and the results of Comparative Example 1 clearly show that the humidity sensor element of the present invention has excellent water resistance.

[0124]

According to the humidity sensor element of the present invention and the method of manufacturing the same, the humidity sensor element formed of a moisture-sensitive thin film solution which is excellent in water resistance, operates stably for a long time even in a dew condensation atmosphere, and has Newtonian viscosity. Has extremely small hysteresis. Therefore, it is possible to provide a humidity sensor element having stable and excellent output characteristics in a wide humidity range.

[Brief description of drawings]

FIG. 1 is a plan view showing one configuration example of a humidity sensor element of the present invention.

FIG. 2 is a graph showing output characteristic measurement results of the humidity sensor element obtained in Example 1.

FIG. 3 is a graph showing output characteristic measurement results of the humidity sensor element obtained in Example 2.

FIG. 4 is a graph showing the output characteristic measurement results of the humidity sensor element obtained in Example 3.

FIG. 5 is a graph showing output characteristic measurement results of the humidity sensor element obtained in Example 4.

FIG. 6 is a graph showing the output characteristic measurement results of the humidity sensor element obtained in Example 5.

FIG. 7 is a graph showing measurement results of output characteristics of the humidity sensor element obtained in Example 6.

FIG. 8 is a graph showing the output characteristic measurement results of the humidity sensor element obtained in Example 7.

FIG. 9 is a graph showing the output characteristic measurement results of the humidity sensor element obtained in Example 8.

FIG. 10 is a graph showing the output characteristic measurement results of the humidity sensor element obtained in Example 9.

FIG. 11 is a graph showing the output characteristic measurement results of the humidity sensor element obtained in Example 10.

FIG. 12 is a graph showing the output characteristic measurement results of the humidity sensor element obtained in Example 11.

FIG. 13 is a graph showing the output characteristic measurement results of the humidity sensor element of Comparative Example 1.

FIG. 14 is a graph showing measurement results of a water resistance test of the humidity sensor element obtained in Example 1.

FIG. 15 is a graph showing measurement results of a water resistance test of the humidity sensor element obtained in Example 2.

16 is a graph showing the measurement results of a water resistance test of the humidity sensor element obtained in Example 3. FIG.

FIG. 17 is a graph showing the measurement results of the water resistance test of the humidity sensor element obtained in Example 4.

FIG. 18 is a graph showing measurement results of a water resistance test of the humidity sensor element obtained in Example 5.

FIG. 19 is a graph showing measurement results of a water resistance test of the humidity sensor element obtained in Example 6.

20 is a graph showing measurement results of a water resistance test of the humidity sensor element obtained in Example 7. FIG.

FIG. 21 is a graph showing measurement results of a water resistance test of the humidity sensor element obtained in Example 8.

22 is a graph showing measurement results of a water resistance test of the humidity sensor element obtained in Example 9. FIG.

23 is a graph showing measurement results of a water resistance test of the humidity sensor element obtained in Example 10. FIG.

FIG. 24 is a graph showing measurement results of a water resistance test of the humidity sensor element obtained in Example 11.

FIG. 25 is a graph showing measurement results of a water resistance test of the humidity sensor element of Comparative Example 1.

[Explanation of symbols]

 1 Humidity Sensor Element 2 Insulating Substrate 3 Moisture Sensitive Thin Film 4 Electrode 5 Gap 6 Electrode Terminal 7 Lead Wire 8 Solder 9 Resist Film

[Procedure amendment]

[Submission date] May 7, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0015

[Correction method] Change

[Correction content]

In the chemical formula 1, A is an acryloyloxy group, a methacryloyloxy group, an acryloylimino group,
It represents an ethylenic group such as methacryloylino group, vinyl group, allyl group, diallylmethyl group, allyloxy group, diacryloylyomino group or dimethacryloylyomino group. B is alkylene of C ₂ -C _7, arylene or or those with some of them was replaced hydroxyl group and the combination thereof, further linking group or a single bond, such as those of other linking groups they are attached a phenylene Represents R ₁ has ₁ to 10 carbon atoms (hereinafter C ₁ to
Represents an alkyl group or an allyl group C _{10), R 2} and _{R 3} each represents an alkyl group of _C 1 _{-C 10.} Further, R ₁ , R ₁ , R ₂ and B may be bonded to each other to form a 5- or 6-membered ring, particularly an aromatic ring. Further, a counter anion (X) of quaternary ammonium salt group
As the halogen ion such as chlorine ion, bromine ion and iodine ion, various ion anions such as sulfate ion, perchlorate ion, phosphate ion and nitrate ion can be used,
Of these, chlorine ion, bromine ion, iodine ion and the like are preferable.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0076

[Correction method] Change

[Correction content]

Further, in the present invention, a suitable one kind of the conductive monomer and the crosslinkable monomer may be copolymerized, and, for example, a single or a plurality of kinds of conductive monomer components and a single or a plurality of kinds. Any kind of cross-linkable monomer component may be optionally combined and copolymerized. Further, it is also possible to use a product obtained by copolymerizing a compound having the properties of both a conductive monomer component and a crosslinkable monomer component. In that case, the amount of quaternary ammonium base increases, which is high when used as a humidity sensor element. Output is obtained.

Claims (11)

[Claims] 1. A pair of electrodes are provided on an insulating substrate so as to face each other with a gap therebetween, and a moisture sensitive thin film is provided on the gap. The moisture sensitive thin film comprises a conductive monomer component and N-methylol. A crosslinkable monomer component of a polymer with a crosslinkable monomer component containing at least one of an N-methylol moiety which is a group or a derivative thereof and active hydrogen,
A humidity sensor element which is self-crosslinked or crosslinked with a crosslinking agent by a reaction between an N-methylol moiety and active hydrogen. 2. The humidity sensor element according to claim 1, wherein the conductive monomer component undergoes a cyclopolymerization reaction to form a cyclopolymerized portion in a main chain portion of the polymer. 3. The humidity sensor element according to claim 1, wherein the conductive monomer component is cyclopolymerized to form a quaternary ammonium salt group in the main chain of the polymer. 4. The monomer forming the conductive monomer component is a diallylammonium-based compound.
Or the humidity sensor element of 3. 5. The humidity sensor element according to claim 2, wherein the monomer forming the conductive monomer component has at least one of a heptadiene skeleton, a diacrylamide skeleton and a dimethacrylamide skeleton. 6. The humidity sensor element according to claim 1, wherein the conductive monomer component is polymerized to have a quaternary ammonium salt group on a side chain of the polymer. 7. The humidity sensor element according to claim 1, wherein the conductive monomer component is 60 mol% or more of the polymer. 8. The moisture-sensitive thin film contains a polymer of the conductive monomer component and the crosslinkable monomer component,
Alternatively, it is formed by using an aqueous solution containing a cross-linking agent in addition thereto, and the aqueous solution exhibits Newtonian viscosity.
A humidity sensor element according to any one of to 7. 9. The humidity sensor element according to claim 1, further comprising a water-repellent coating on the moisture-sensitive thin film. 10. A pair of electrodes provided on an insulating substrate,
An aqueous solution containing a polymer of a conductive monomer component and a crosslinkable monomer component, or an aqueous solution containing a crosslinking agent in addition to this, after applying an aqueous solution having Newtonian viscosity, self-crosslinking the copolymer Or a method for manufacturing a humidity sensor element, which comprises forming a moisture-sensitive thin film by crosslinking with the crosslinking agent. 11. The method for manufacturing a humidity sensor element according to claim 10, wherein hysteresis in the low humidity region of the moisture sensitive thin film is reduced.