JPS6288951A - Moisture sensitive element and its production - Google Patents

Abstract

PURPOSE:To obtain a moisture sensitive element having high reproducibility without being affected by the temp. of using environment in a wide humidity region by coating a polymer of methacrylate monomer across comb-shaped electrodes on an insulating substrate then heating and crosslinking the same by a resin. CONSTITUTION:A conductive film is formed on the glass substrate 1 having high purity and after the comb tooth-shaped counter electrodes 2, 2 are formed thereon, a moisture sensitive liquid consisting of an org. high-polymer material is coated thereon across the opposed parts thereon. The moisture sensitive liquid is formed by heating the polymerizing the methacrylate monomer having >=1 hydroxyl groups to form a polymer and adding a melamine resin as a crosslinking agent thereto. Said liquid has a thermosetting property. Such moisture sensitive liquid is heated to accelerate the curing reaction by the melamine resin by which the moisture sensitive film 3 is obtd. Lead wires 4, 4 are provided to the exposed parts of the electrodes 2, 2 and the moisture sensitive element is thus obtd.

Description

[Detailed description of the invention] <Industrial field of application> This relates to a moisture-sensitive element that detects the thickness of 01111 + Torai 6 volumes (Pi-7. -■γ width n!) .

BACKGROUND ART Conventionally, there are two types of humidity sensing elements for measuring humidity in an atmosphere: a variable resistance type and a variable capacitance type, of which the variable resistance type is most commonly used. In general, devices using this method become unable to measure in the low humidity region, that is, when the relative humidity RH is around 0 to 10 (%), or even if it is possible to measure, the auxiliary circuit of the humidity element is very complicated and is prone to failure. In addition, it has disadvantages such as an increase in cost due to the complexity of the circuit, and there is an aspect that it cannot necessarily be adapted to all purposes and conditions.

In addition to the above examples, there is also a so-called capacitive type moisture sensing element whose electrostatic capacity changes depending on the influence of humidity.

This capacitive humidity sensing element utilizes the hygroscopicity of inorganic materials such as alumina, but although it shows good performance in low humidity regions, it has very poor response in high humidity regions, and suffers from poor reproducibility. It has the disadvantage that it exhibits significant hysteresis and cannot accurately respond to changes in humidity.

In order to cope with such a situation, there is a device that uses a moisture-sensitive film as a grown polymer film, but with this moisture-sensitive element, the moisture-sensitive film cannot be held in close contact with the entire surface, so the peripheral part is placed on a holding base. At the same time, a conductive electrode film is provided on the opposite surface of the moisture-sensitive film, and a lead wire is provided to this film to extract the moisture (1 change).

However, since this type of moisture-sensitive element has hygroscopic properties, it expands and contracts due to the influence of humidity, that is, absorption of moisture, which causes loosening and wavy distortion deformation in the parts that do not support the film, resulting in poor flatness. At the same time, there is a problem that sensitivity cannot be maintained uniformly due to a large change in air permeability.At the same time, due to the structural constraints of supporting the periphery of the moisture-sensitive membrane, it is necessary to make the moisture-sensitive membrane thinner. I was unable to improve responsiveness due to difficulty and difficulty in doing so.

In addition, there is a capacitive humidity-sensitive element that uses a grown polymer film as a moisture-sensitive film, and its structure is such that two electrode plates are placed in close contact with each other on a support base, and both electrode plates are placed on top of the support base. That's one of the best! '
A Li molecular film was coated, and a single surface electrode plate having water permeability and conductivity was uniformly provided on the grown polymer film 1, and two surface electrode plates provided on the support base 2 were disposed on the grown polymer film 1. There is a method in which two series capacitors are formed by attaching lead wires to each electrode plate.

However, in the case of a series capacitance type moisture sensing element as mentioned above, the former exists (and although the thickness of the element itself can be made somewhat thinner than that of a moisture sensing element using a polymer/film as a moisture sensing film, it is still It is far from ideal (less than 1 micron) thinning, and if we try to make it even thinner with this structure, there is a risk of short-circuiting between the two electrode plates that sandwich the grown polymer film, so we cannot hope for further thinning. ,
Therefore, sufficient responsiveness cannot be obtained.

A common drawback of the moisture-sensitive elements using the above-mentioned two examples of grown polymer films as moisture-sensitive films is that they are stacked in a sandwich-like manner.
Since it is molded, it is necessary to allow moisture to pass through the surface electrode, and in order to obtain good electrical characteristics,
Moisture permeation is poor and responsiveness is reduced.

<Problems to be Solved by the Invention> In the conventional humidity sensing elements described above, the variable resistance type element has poor response in a low humidity region, and the non-resistance variable capacitance type element has poor response in a high humidity region. Bad sex.

Furthermore, in devices using polymer membranes, the moisture-sensitive membrane undergoes physical changes (irreversible) due to the influence of humidity and temperature itself, which causes performance to deteriorate. The humidity characteristics varied and showed hysteresis, which was not ideal.

Therefore, the present invention addresses the deficiencies 7α of the conventional humidity sensing element and provides a thin humidity sensing element that has a wide humidity range and has high reproducibility that is not affected by the temperature of the atmosphere in which it is used.

Means for resolving these problems: After applying a polymer of methacrylate monomer having hydroxyl groups between the comb-shaped opposed electrodes formed on the insulating substrate, a thermosetting synthetic resin was applied with a trowel. It is cross-linked by heating.

<Example> Hereinafter, the present invention will be explained in detail based on the example shown in the drawings.A high-purity insulating material, polymerizable glass material, for example, is made of an insulating material with a thickness of about 0.615 m + i and a width of 8 x 5.08 + 11.
An area of 1112 was polished and used as a substrate 1, and a metal such as silver A11s, platinum Pt, or chromium Cr was deposited on the surface to a thickness of about 1 μII+ by vacuum evaporation.
A conductive film is formed, and then a predetermined comb-shaped masking etc. is performed on the film, and then by an etching method,
+l approx. 2μ"n, opposing electrodes with a gap of 1μIll or less 2.2
form.

Then, a moisture-sensitive liquid made of a high polymer film that is physically stable against temperature, humidity, etc. is applied to the upper surface of the opposite part of the counter electrode 2.2 using a spinner method (centrifugal method). Or apply by dipping method.

Here, the composition of the moisture sensitive liquid is a methacrylate monomer having one or more hydroxyl groups, that is, 2-hydroxy.
Ethyl methacrylate moamer or 2-hydroxy
Propyl methacrylate tomo/7-'i-jJL!
[I is combined to form a homopolymer (liquid), and by further adding melanin 4J (I + old liquid) as a cross-linking agent to the homopolymer, a liquid moisture-sensitive liquid having thermosetting properties is obtained.

The moisture sensitive liquid applied on the counter electrodes 2, 2 has a concentration of 120
By heating at a temperature of ℃ to 150℃ for about 30 to 60 minutes, a curing reaction progresses due to the action of the melanin resin in the moisture-sensitive liquid, resulting in a physically and chemically stable thickness of about 1 μm.
The following moisture sensitive film 3 is obtained.

Here, IJ-domain wires 4 are connected to the exposed portions of the counter electrodes 2, 2, respectively.
, 4 constitutes the moisture sensing element intended by the present invention.

The relative humidity and capacitance change of the humidity sensing element obtained as described above are shown in Figures 3 to 5, and the rate of capacitance change is approximately constant in both low humidity and high humidity regions. This clearly shows that the responsiveness is uniform.

In Figure f54, even when the same measurement was made after 1 hour after immersing the moisture sensitive element in water, almost no effect was seen, and the rate of change in capacity after being left for 100 hours at a relative humidity of 99% was as shown in Figure 3. It was found that the device is very stable even under abnormal humidity and temperature without much difference from the standard state of can get.

<Effects of the Invention> Due to the structure of the present invention as described above, the moisture sensitive film is completely adhered to the electrode or the substrate, so it is structurally stable and robust, and moisture is absorbed by the organic polymer film. Since the moisture is directly detected using a moisture-sensitive membrane, the moisture permeation rate is not affected by the temperature increase as in the conventional method, and the moisture permeation rate is not affected by the temperature increase, but the moisture is always in contact with the atmosphere under the same conditions, resulting in excellent responsiveness.

Furthermore, the hysteresis effect is extremely small and the reproducibility is good, and the capacitance ratio is stable with almost no deformation even in high temperature and high humidity regions and even when left in the same atmosphere for a long time.

Furthermore, since the counter electrode is formed in a comb-like shape with small gaps, a sufficient moisture-sensitive surface can be formed, which has the effect of further improving sensitivity.

In addition, since it differs from the conventional sandwich structure, it can be easily made thinner, making it an ideal moisture-sensitive element with excellent durability and reliability.

[Brief explanation of drawings]

Fig. f51 is a partially cutaway plan view of the moisture sensing element of the present invention, Fig. 2 is a sectional view taken along line A-A of the same as above, Fig. 3 is a relative humidity vs. capacitance change rate characteristic diagram, and Fig. 4 is a diagram showing the humidity sensing element under water at room temperature. FIG. 5 is a characteristic diagram of relative humidity versus capacity change rate after soaking for 9 hours. FIG.

Claims (2)

[Claims] 1. Two conductive comb-shaped electrodes are formed on the surface of an insulating substrate to face each other in an interlocking state, and a methacrylate monomer having one or more hydroxyl groups is formed across the opposing parts of the two electrodes. 1. A moisture-sensitive element obtained by applying a moisture-sensitive liquid and crosslinking the liquid with a thermosetting resin. 2. After forming a metal film on an insulating substrate, the metal film is extracted in a comb-like shape by an etching method to form a counter electrode, and a moisture-sensitive liquid made of a polymer of a methacrylate monomer having a hydroxyl group is placed on the counter electrode. Apply 1
A method for manufacturing a moisture-sensitive element, comprising forming a moisture-sensitive film by heating at a temperature of 20°C to 150°C for 30 to 60 minutes.