JPS63243857A - Temperature sensor-incorporated type humidity sensing element - Google Patents

Abstract

PURPOSE:To eliminate the need for temperature compensation and to improve the water resistance of a humidity sensing part by coating two conductive comb-line electrode parts with a humidity sensing film and a vapor permeable protection film and further forming a humidity shield film on only one electrode part. CONSTITUTION:Interdigital electrodes 3, 4, and 5 where two comb-line electrode parts 1 and 2 are formed provided on an insulating substrate. Those comb-line electrode parts 1 and 2 are masked and then the surfaces are coated with the humidity sensing films 6 and 7 consisting of plasma polymer films of a mixture of a nitrogen-containing organic silicate compound with superior humidity sensing characteristics and silane halide. Then the humidity sensing films 6 and 7 are coated sufficiently with room-temperature curing type silicone rubber to form the vapor-permeable protection films 8 and 9. Further, only the protection film of one comb-line electrode part 1 is coated completely with epoxy resin, polyethylene, polytetrafluoroetylene, etc., to form the humidity shield film 10 as a temperature detection part, and the other is used as a humidity detection part as it is.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a humidity sensing element with a built-in temperature sensor.

More specifically, the present invention relates to a humidity sensing element with a built-in temperature sensor that has a simplified temperature compensation circuit.

[Conventional technology]

Hitherto, humidity sensors using various moisture-sensitive materials such as polymer materials and metal oxides have been developed as a means of detecting humidity. It is roughly divided into two types of change.

The former variable resistance type moisture sensing element changes the ion mobility of alkali metal ions, etc. contained in the humidity sensitive material depending on the partial pressure of water vapor in the atmosphere.

This is detected as a resistance change in the moisture sensitive material. The polymer material used here is generally called a polymer electrolyte membrane, and sodium polystyrene sulfonate is mainly used, but these polymer electrolyte membranes cannot be used in environments with high humidity and large temperature changes. For example, in environments where dew condensation is likely to occur, it is likely to dissolve in water and cause deterioration of properties.

There were problems with reliability.

Furthermore, in general, a humidity sensing element using a polymer electrolyte membrane causes a resistance change not only due to changes in humidity, but also due to temperature. For this reason, the relative humidity should be set to, for example, O~1
When outputting with a linear relationship of 0 V, the temperature is detected at the same time using a thermistor or the like, and the resistance change due to temperature of the humidity sensing element is compensated for on the circuit. However, such a circuit is complicated, and inexpensive thermistors have the disadvantage that the humidity coefficient varies widely and the circuit is difficult to adjust.

[Problem that the invention seeks to solve]

Therefore, as a result of various studies in order to simplify the temperature compensation circuit in a resistance change detection type humidity sensing element, the present inventor provided two sets of conductive comb-shaped electrodes on an insulating substrate, and the temperature It has been found that this problem can be effectively solved by providing the necessary coatings to the conductive comb-shaped electrode portions to serve as the sensing portion and the humidity sensing portion.

[Means for solving problems]

Therefore, the present invention relates to a humidity sensing element with a built-in temperature sensor, and this humidity sensing element with a built-in temperature sensor has two sets of conductive comb-shaped electrode parts provided on an insulating substrate, and these conductive comb-shaped electrode parts. After sequentially covering the substrate with a moisture-sensitive film and a water vapor permeable protective film, a humidity-blocking film is further formed on only one of them to form a temperature sensing portion, and the other is directly configured as a humidity sensing portion.

The two sets of conductive comb-shaped electrode portions formed on an insulating substrate such as glass, quartz, alumina, etc. can be provided independently, but preferably two sets are provided as shown in FIG. One comb-shaped electrode 3 on which comb layer groups 1.2 are formed, and two comb-shaped shapes W4. which engage with these comb layer groups. It is formed from s.

When forming conductive comb-shaped electrodes on an insulating substrate, first, a corrosion-resistant metal such as stainless steel, Hastelloy C, Inconel, Monel, or gold, or an electrode forming material metal such as silver or aluminum is sputtered onto the insulating substrate. Approximately 0.1~
A thin film with a thickness of about 0.5 μm is formed, and then a photoresist and a pattern are formed thereon.

For example, in the case of aluminum, a photoresist pattern is formed on the metal thin film of the electrode forming material thus formed by applying a well-known photolithography process. That is, a photoresist coating is applied to a metal thin film, a glass dry plate on which a negative or positive image of a comb-shaped electrode pattern is printed is placed on top of the photoresist coating, and the photoresist is printed by light irradiation and developed. After this, wet chemical etching is performed, and the etching solution is phosphoric acid-sulfuric acid-chromic anhydride-water (weight ratio 65:15:5).
:15) Mixed liquid, Bl(F (hydrofluoric acid), ferric chloride aqueous solution, nitric acid, phosphoric acid-nitric acid mixed liquid, etc.) are used.

After the two sets of conductive comb-shaped electrodes formed on the insulating substrate are subjected to necessary masking, the surface is further coated with a mixture of a nitrogen-containing organosilicon compound and a halogenated silane having excellent moisture-sensitive properties. Alternatively, it is covered with a plasma polymerized film 6.7 of a mixture of an organic amine compound and a halogenated hydrocarbon or halogenated silane.

As the nitrogen-containing organosilicon compound, for example, a compound represented by the following general formula is used.

R,5i-NRt R,N-3iR2-NR.

(R,N)3-5iR (wherein, R is a hydrogen atom, methyl group, ethyl group, vinyl group, or acetylene group, R2 or R3 are the same or different R groups, and at least 2 Specific examples of such compounds include groups other than hydrogen atoms, such as trimethylsilyldimethylamine 5
Triethylsilazane, hexamethyldisilazane, hexamethylcyclotrisilazane, bis(dimethylamino)
Methylvinylsilane, bis(trimethylsilyl)acetamide, tris(dimethylamino)silane, tris(dimethylamino)methylsilane, tris(methylamino)
Methylsilane, tris(methylamino)ethylsilane,
N,N-dimethylamino-N'-methylamino-N'-
Examples include dithylaminosilane, and preferably trimethylsilyldimethylamine, bis(dimethylamino)methylvinylsilane, or bis(dimethylamino)dimethylsilane is used.

As the organic amine compound, primary to tertiary amino compounds can be used, but preferably secondary to tertiary amino compounds substituted with an alkyl group, such as n-butylamine, sec-butylamine, isopropylamine, dimethylethylamine, diethylamine. , substituted monoamino compounds such as dimethylallylamine, N,N-dimethyl-1,3-propanediamine, N,N.

Substituted diamino compounds such as N',N'-tetramethylethylenediamine, and also pentamethyleneimine,
Cycloalkyl-substituted monoamino compounds such as hexamethyleneimine and cycloalkyl-substituted diamino compounds such as N,N'-dimethylpiperazine are used, and in addition to these, dimethylpyrazole and the like can also be used.

As the halogenated hydrocarbon, preferably an alkyl halide is used, and the halogen substituent may be one or more. Specifically, methylene bromide, methane bromide, methane tribromide, ethylene bromide, ethylene dibromide, propane bromide, propane dibromide, butane bromide, butane dibromide, methylene chloride, bromide Methylene chloride, ethyl iodide, etc. are used. Further, the hydrocarbon group to be halogenated may be a chain unsaturated bond or an aromatic nucleus.

As the halogenated silane, general formula 5iXLX2X,
X4 (where X-X4 is a halogen atom, a hydrogen atom,
A lower alkyl group, a lower alkenyl group, or a lower alkynyl group, of which 1 to 3 are halogen atoms, is used, and a lower alkyl-substituted halogenated silane is preferably used. Some examples of such halogenated silanes are as follows.

CH,5LC13 C) I3SiH2Br%CH35iHBr.

(CH3)25jBr2 Plasma polymerization is carried out using a nitrogen-containing organosilicon compound or an organic amine compound at a pressure of several meters to several Torr, or a halogenated silane, halogen, or This is carried out by using hydrocarbons at a pressure of several meters to several Torr and supplying the mixture with electric power of several to several 100 volts of discharge output.

Specifically, for example, when the discharge output is 10 Torr, the nitrogen-containing organosilicon compound is used in a ratio of about 0.15 to 0.08 Torr and the halogenated silane is used in a ratio of about 0.06 to 0.01 Torr. Or, for example, if the discharge output is 2011
! In this case, the organic amine compound is approximately 0.04 to 0.2 To
rr, the halogenated hydrocarbon or halogenated silane is about o, oos to 0. It is used at a rate of ITorr. If the proportion of halogenated silane or halogenated hydrocarbon is too small, the halogen content in the plasma polymerized film will decrease and the moisture sensitivity will deteriorate, while if this proportion is too large, the relative Since the nitrogen content is reduced and the polymer film is also hardened, the moisture sensitivity properties are also reduced.

Next, in order to sufficiently cover these moisture-sensitive films, after masking the exposed area slightly larger than before, a room-temperature curable (RTV) silicone rubber is coated using a spatula, and water vapor is applied thereto. Permeable protective films 8 and 9 are formed. The curing of silicone rubber is, for example, 30°C, 5°C.
This is carried out under conditions of 0% RH for 12 days, and a protective film is formed with a thickness of about 30 μm. Although this protective film is permeable to water vapor, it does not allow liquid water to pass through, so it improves water resistance without degrading moisture sensitivity.

Finally, after adjusting the conditions in a constant temperature and humidity chamber at 30°C and 40% RH, only the protective film of one comb-shaped electrode part (the part formed by numbers 1 and 4) is coated with epoxy resin, polyethylene, or polyester. It is completely coated with tetrafluoroethylene or the like to form a humidity barrier film 10. The comb-shaped electrode portion on which the humidity shielding film is formed is defined as a temperature sensing portion A that is not sensitive to humidity and is sensitive only to temperature, and the comb-shaped electrode portion on which no humidity barrier film is formed is defined as a humidity sensing portion B.

[Effect]

The electrical characteristics of the variable resistance 6m element of the present invention constructed in this way are measured by terminals II and 12 and terminals 11 and 13.

For example, an Au/Cr electrode (film thickness: 1,000 to 1,500) having a comb-shaped part with a line width of 400 μm and a line spacing of 200 μm is formed on a glass substrate using a photolithography method.
The two sets of conductive comb-shaped electrodes were formed in the shape shown in FIG.
A plasma polymerized film with a thickness of 0.3 μm was formed using masking under the conditions of a discharge output of 20111 and a discharge time of 30 minutes using a mixed gas of For the product formed with a thickness of 30 μm, after adjusting the conditions in a constant temperature and humidity chamber at 30°C and 40% RH, the resistance value with respect to relative humidity was measured at terminal 11-
When measuring between 12 and 12, the results shown in the graph of FIG. 2 were obtained.

Regarding the temperature sensing part A, this humidity sensing element is sealed with an epoxy resin humidity barrier film in an atmosphere of 30 ° C. and 40% RH.
When the resistance is measured between terminals 11 and 12, the resistance value is I
A temperature sensing portion A is formed therein, which is fixed at MΩ and exhibits a temperature-sensitive characteristic of the humidity sensing portion B, that is, a coefficient B, which is approximately constant from 6500 to 7500 with respect to temperature changes.

Generally, a humidity sensing element has temperature characteristics, and its B coefficient is larger than that of a commercially available thermistor (B = 2000 to 5000). complex compensation is being carried out.

Looking at the output at ■-■ in this circuit, as shown in the graph of Figure 4, the resistance value changes logarithmically and linearly depending on the relative humidity; The influence of temperature is still clearly visible.

On the other hand, in the humidity sensing element with a built-in temperature sensor according to the present invention, the circuit is simplified as shown in FIG. 5, and the resistor R in FIG. 3 is replaced with a temperature sensor, and the output at As shown in the graph result in FIG. 6, it is not affected by temperature, and therefore temperature compensation can be easily performed.

Furthermore, in order to measure the water resistance of the humidity sensing part B, a test was conducted in which it was immersed in water at room temperature for 5 days, and the humidity sensitivity characteristic value was within ±2% RH of the initial value.

〔Effect of the invention〕

In the humidity sensing element with a built-in temperature sensor according to the present invention, since the temperature sensing part and the humidity sensing part are made of the same material, the temperature coefficients are equal, and a temperature compensation circuit is not required. Moreover, the water resistance of the moisture sensitive part is also good.

[Brief explanation of drawings]

FIG. 1 is a plan view of one embodiment of a humidity sensing element with a built-in temperature sensor according to the present invention. FIG. 2 is a graph showing the relationship between relative humidity and resistance of a humidity sensing element without a humidity barrier film. FIG. 3 shows an example of a humidity output circuit using a conventional temperature sensing element, and FIG. 5 shows an example of a humidity output circuit using a temperature sensing element according to the present invention. FIG. 4 is a graph showing the relationship between relative humidity and AC voltage in the circuit when the humidity output circuit shown in FIG. 3 and FIG. 6 are used, respectively. (Explanation of symbols) 1.2... Kushi layer group

Claims (5)

[Claims] 1. Two sets of conductive comb-shaped electrode portions are provided on an insulating substrate, and after these conductive comb-shaped electrode portions are sequentially coated with a moisture-sensitive film and a water vapor permeable protective film, only one of them is further covered with a humidity-blocking film. A humidity sensing element with a built-in temperature sensor, with one formed as a temperature sensing part and the other as a humidity sensing part. 2. Two sets of conductive comb-shaped electrode parts are formed from one conductive comb-shaped electrode with comb-shaped groups formed at two places and two conductive comb-shaped electrodes that mesh with these comb-shaped groups. A humidity sensing element with a built-in temperature sensor according to claim 1. 3. Claim 1, wherein the moisture-sensitive membrane is a plasma polymerized membrane.
Moisture sensing element with a built-in temperature sensor as described in . 4. 2. The temperature sensor built-in moisture sensing element according to claim 1, wherein the water vapor permeable protective film is a cured film of room temperature curing silicone rubber. 5. The temperature sensor built-in humidity sensing element according to claim 1, wherein the humidity blocking film is an epoxy resin film.