JPS60200152A - Humidity-sensitive element - Google Patents

Abstract

PURPOSE:To obtain a freely deformable humidity-sensitive element having high accuracy and excellent durability, by mounting flexible porous electrodes for detecting electric resistance or capacity to both surfaces of an air permeable porous film or sheet having humidity sensitivity and flexibility. CONSTITUTION:(Nonwoven) fabrics made of carbon fibers are adhered to both surfaces of a high-molecular film, sheet or (nonwoven) fabric made of polyester or polystyrene having pores piercing from the front surface thereof to the back surface thereof by a hot melt adhesive (Diamide D1020 manufactured by Daiseru Chemical Industry K.K.) to form a flexible porous electrode. Subsequently, the whole of the electrode is impregnated with an aqueous solution containing a copolymer of a monomer having a SO3H group and glycidyl methacrylate and a curing agent such as triethylenetetramine while the impregnated one is crosslinked and bonded under heating to obtain a humidity-sensitive element. In another method, gold is vapor deposited to both surfaces of the aforementioned flexible porous film and, thereafter, the humidity-sensitive coating solution is applied thereto as mentioned above to form the humidity-sensitive element. By these methods, the freely deformable element easy to handle and free fo delamination of an electrode is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a moisture sensing element that is flexible, can be deformed into any shape, and is lightweight.

In recent years, there has been an increasing demand for moisture-sensitive devices that are highly accurate, easy to handle, and have excellent durability.

In particular, the above requirements have become more urgent as a trend toward use in household products, barley cutters, etc. has emerged.6 Moisture-sensing elements as shown below have been developed and commercially available. For example, (1) moisture-sensitive ceramics, (g) electrically insulating end plates coated with moisture-sensitive metal oxides, organic polymers, or conductive particles and binders, or (ii)
i) Moisture-sensitive semiconductors, etc. However, (1) above
The moisture-sensitive elements shown in (i+i) are all rigid and cannot be bent and have to be reduced in size in order to be installed in a narrow space, which requires an electric resistance or an electric capacitance. There are disadvantages such as making it difficult to measure.

In addition, if soldering or conductive adhesive is used to connect the electrodes and lead wires or the lead wires and humidity detection, amplification, and display circuits, the sensor is rigid and heavy, so if there is severe vibration, Another drawback is that failures such as wire breakage and disconnection are more likely to occur.

Additionally, a screen printing machine is used to produce the moisture-sensitive element.
High S! Special equipment is required, such as an electric furnace for firing and a special cutting machine for cutting ceramics, etc., which reduces productivity and
The uniformity of the product was also not sufficient.

The present inventor has completed the present invention as a result of repeated studies in order to overcome the drawbacks of conventional products such as the above-mentioned product. 1e
According to the present invention, a moisture-sensitive and flexible film or sheet-like porous body;
A moisture sensing element is provided, characterized in that it has a flexible porous electrode for measuring drowsiness resistance or capacitance.

Since the moisture sensing element of the present invention has a flexible groove, it can take any shape, and can also be bent when the space in which it should be installed is limited. In addition, since the moisture sensing element of the present invention is made of porous film, woven fabric, knitted fabric, or 4 non-woven fabric, it is lightweight and absorbs vibrations, and even when used in equipment with a lot of vibration (for example, a car), it can be used without causing vibrations. Accidents such as wire breakage or disconnection at connections are extremely rare. A further advantage of the present invention is that it does not use a substrate such as a ceramic or glass, and instead uses a porous film.
Since woven fabrics, knitted fabrics, or non-woven fabrics are used, mass production is easy, and expensive manufacturing equipment is not required, so moisture-sensitive elements of uniform quality can be provided at low cost.

The moisture-sensitive and flexible film or sheet-like porous body of the present invention includes, for example, (A) a film in which the pores penetrate from the front surface to the back surface; Porous plastic film with insulation properties, such as polystyrene, styrene copolymer, polyvinyl chloride, vinyl chloride copolymer, polyacrylonitrile, acrylonitrile copolymer, polycarbonate, polyamide, polyester, polyimide, polyamideimide , a porous film primary sheet made of a polymeric material such as polyphenylene oxide, polyetherketone, polysulfone, or a woven fabric made of ultrafine polymeric materials as described above;
Polymerizable unsaturated sulfonic acids or carboxylic acids, such as vinyl sulfonic acid, styrene sulfonic acid, allyl sulfonic acid, acrylic acid, methacrylic acid, or their salts, are added to at least the pore wall portion of the knitted or nonwoven fabric. rt, or sulfonate the polymer', a porous film or film, or a woven, knitted or non-woven fabric J-, using, for example, concentrated sulfuric acid, oleum, chlorosulfonic acid, etc. (B) Water-soluble polymeric substances such as acrylic acid, methacrylic acid, ethylene sulfonic acid, and styrene sulfonic acid. , a porous film made of a copolymer containing a hydrophilic functional group-containing monomer unit such as acrylic acid, by introducing cross-linking bonds by a method known per se; (C) from the above polymeric substance; After impregnating a porous film or sheet or a woven fabric, knitted fabric, or nonwoven fabric made of fibers of the upper and lower molecular members with the polymer or copolymer containing the above-mentioned hydrophilic group-containing monomer, by a method known per se. Those made unsaponifiable by introducing cross-linking bonds can be used.

The amount of the hydrophilic functional groups in these porous films or sheets is sufficient to impart moisture sensitivity to the porous material, generally at least 0.1 meq/l.
, preferably 0.2 to Z Omet q/f. Furthermore, when the porous body is made of the above-mentioned porous film, the porosity of the porous film is generally 5 to 5.
It is desirable that it be within the range of 90%, preferably 10 to 80%. Here, the term "porosity" refers to the ratio of the lateral area of pores to the total volume by the substitution method. On the other hand, the porous body is a textile,
When made of a fabric such as a knitted fabric or a non-woven fabric, the porous body generally has a density of 5 to 200 y/m", preferably 10 to 10
It is desirable to have a basis weight within the range of 0 f /m2.

The thickness of these films or sheet-like porous bodies can vary depending on the humidity range to be detected, the purpose of use, and the specifications of the electronic circuit for humidity detection, but is generally 0.01 to 3.
A suitable range is preferably 0.02 to 10%.

As the flexible porous electrode to be attached to the moisture-sensitive porous body described above, conductive woven fabrics, knitted fabrics, or nonwoven fabrics mainly composed of carbon fibers are preferably used. The specifications of the fabric made from Joki Back Soft Fiber are the purpose and conditions of use of the moisture sensing element,
Although it varies depending on the manufacturing method, the type of moisture-sensitive porous material, etc., the basis weight is generally 527 cm or more, preferably 10 to 5.
017m" with a thickness of 0.1 to 3 mm, preferably 0.15
Those within the range of ~2 groups are preferably used.

Other electrodes that can be used to detect changes in electrical resistance of the moisture-sensitive porous body include a conductive metal thin film attached to the surface of the porous body, such as plasma coating, ion splattering, etc. It can be formed on the surface of the porous body. The metal that can be used as the electrode varies depending on the usage conditions of the moisture-sensitive element, but generally gold, platinum, palladium, tantalum, tungsten, etc., which have excellent conductivity and corrosion resistance, can be used.

The moisture-sensitive element of the present invention obtained in this manner is flexible, lightweight, does not cause failure due to vibration or impact, is easy to manufacture, and can be obtained at low cost with uniform performance. , fields in which humidity sensors have not been used in the past due to durability and price, or have been used only in a limited number of fields, such as home air conditioners such as near conditioners, humidifiers, and dehumidifiers; automobiles; It is very useful and can be widely used as a humidity sensing element for transportation equipment such as trains and airplanes; and for any other industrial or household equipment that detects and controls humidity.

Next, the present invention will be explained in more detail by giving examples.

Example 1 Carbon fibers with a thickness of 15 μm and a fabric weight of 40 f were placed on both sides of polyethylene terephthalate spunbond with a fabric weight of 70 t/cm, a single fiber thickness of 3 denier, and a thickness of 0.3 tone.
/vt”, carbon fiber paper with a thickness of 0.2rt!n and a non-woven hot melt adhesive (Diamid D
1020, manufactured by Daicel Chemical Industries, Ltd.), and a copolymer of methacrylic sulfonic acid and glycidyl methacrylate (sulfonic acid group content: 1. F3 m
gq/l, epoxy equivalent: 1500) After impregnating with an aqueous solution consisting of 1 part of triethylenetetramine and 90 parts of water, the mixture was squeezed to a liquid ratio of 1:1 and heat treated at 130°C for 1 hour. A cross-linking bond was introduced by reacting the epoxy group of the compound with triethylenetetramine. This was cut to a size of 1.5 cm XICrn, and the relative humidity-schisis resistance characteristics were measured. The results are shown in the curve <A) in the attached Figure 1.

Example 2 Fabric weight 100? /m2, monofilament thickness 2 denier, thickness 0.35 ram polypropylene non-woven fabric is ion coated with gold on both sides, with in-plane electrical resistance of 500 Ω/m2 and inter-plane electrical resistance of 2-5 MΩ. I got non-woven fabric. In addition, a copolymer of sodium styrene sulfonate and grindyl methacrylate with an average molecular weight of 1800 (sulfonic acid group content: Z, 5 meq/2, Evo 1,000 bonds: 1
000) water 7 boldly glycerin 20 P, Ii R
After impregnation with an aqueous solution containing
''C for 2 hours to react the epoxy groups in glycidyl methacrylate with glycerin to introduce crosslinks. This was cut into a size of 1 crn x 1 crn, and the humidity-electrical resistance characteristics were measured. The results are expressed as the curve in Figure 1 (
B) Shown in ゛.

Example 3 To a mixed monomer of styrene:divinylbenzene = 97:s <heavy ratio), 1 tbsp of benzophenone and 80% of colloidal silica (Aerosil R972, manufactured by Nippon Aerosil Co., Ltd.) were added, and the mixture was irradiated with ultraviolet rays in a nitrogen stream. After cutting the cross-linked polystyrene into 0.25-thick pieces, 10%
Treated in sodium hydroxide watercolor solution at 50°C for 1 hour,
Colloidal silica was dissolved and removed. This porous polystyrene was subjected to riJ for 1 hour at 80'C in 98% sulfuric acid.
] Sulfonated, sulfonic acid group content 1.3 me
q/? of polystyrene sulfonic acid was obtained. Platinum was attached to both sides of this porous film by ion/4' tuttering. 1 cm X l− from the obtained film
A humidity sensing element was made and its humidity-capacitance characteristics were measured. The results are shown in curve (C) of FIG.

Example 4 150 PHR of common salt with an average particle size of 3 μm was added to a solution of polyvinyl chloride (average degree of polymerization: 350) in 5-cyclohexanone, and the mixture was cast onto a glass plate and dried to form a film with a thickness of 0.3. After the preparation, salt was extracted with 60°C warm water to obtain a porous film. This porous film was immersed for 30 minutes in a 1% benzene-methanol mixture of azobisisobutyldinitrile (methanol/methanol = 7/3) for 30 minutes, and then soaked in a 5% sodium acrylate water bath solution. 7.
The graft reaction was carried out at 0°C for 5 hours. After washing and drying the obtained film, a 1 crn×2 cIn moisture sensitive element was prepared and the humidity-electrical response characteristics were measured. The results are expressed as the curve in Figure 2 (
J) Shown in ).

[Brief explanation of the drawing]

Figure 1 shows the humidity-electrical resistance characteristic curves of the humidity sensing elements obtained in Examples 1 and 2, and Figure 2 shows the humidity layer-air capacity characteristics of the humidity sensing elements obtained in Examples 3 and 4. It is a curve. I vs. j1 degree 1%) 18f1 degree L (%)

Claims (1)

[Claims] 1. A film or sheet-like porous body having moisture sensitivity and flexibility, and an oJ flexible porous electrode for detecting electrical resistance or capacitance on both sides of the porous body. A moisture-sensitive confectionery featuring 2. The moisture-sensitive element according to claim 1, wherein the film or sheet-like porous body is a moisture-sensitive multi-→'L film, woven fabric, knitted fabric, or non-woven fabric. 3. The moisture sensing element according to claim 1, wherein the flexible porous electrode is a woven fabric, knitted fabric, or nonwoven fabric made of carbon fiber. 4. The moisture-sensitive element according to claim 1, wherein the flexible porous electrode is a conductive thin film attached to the surface of a film or sheet-like porous body.