KR20030078466A - humidity sensing materials and manufacturing method for humidity sensing film using the same - Google Patents

Abstract

PURPOSE: A humidity-reducing material for a poly(vinyl alcohol)-based hygroscope and a method for preparing a humidity-reducing film by using the humidity-reducing material are provided, to improve the resistance to moisture without deterioration of the humidity sensing power of a hydrophilic organic polymer material. CONSTITUTION: The humidity-reducing material comprises a crosslinked product obtained by crosslinking poly(vinyl alcohol) with any one selected from the group consisting of sodium m-benzene disulfonate, sodium p-styrenesulfonate and poly(acrylic acid), in the presence of an alkaline earth metal or transition metal chloride or its hydrate. Preferably the alkaline earth metal or transition metal chloride or its hydrate is selected from the group consisting of FeCl2, LiCl, NaCl, KCl, MgCl2, CuCl2, CoCl2 and their hydrates.

Description

Humidity sensing materials and manufacturing method for humidity sensing film using the same

The present invention relates to a moisture sensitive material and a method for producing a moisture sensitive film using the same, and more particularly, to a moisture sensitive material having excellent durability against moisture and a method for producing a moisture sensitive film using the same.

In order to maintain proper humidity in industrial processes or to make the living environment more comfortable, automated humidity control systems have been developed for controlling the humidity of the surrounding environment.

The humidity sensor, which is the core of the automated humidity control system, has a built-in moisture sensitive membrane. Conventionally, ceramic materials containing metal oxides have been mainly studied as a material for manufacturing the moisture-sensitive film. Ceramic humidity sensor is based on the principle that moisture is adsorbed and desorbed on the ceramic surface according to the change of ambient humidity, and the characteristic value of ceramics is changed accordingly. Detecting

However, there are many problems with the humidity sensor using the ceramic material. Specifically, the humidity sensor requires periodic reproducibility, but in the case of the humidity sensor using ceramics, there is a problem in that chemically stable hydroxides are formed on the surface of the sensor when exposed to the external environment for a long time, so that the sensor does not return to its original state. In addition, the ceramic material must be regularly heat treated to remove the moisture adsorbed in the pores, it is difficult to remove when the dirt is adsorbed in the pores, it is difficult to expect reproducibility as a sensor.

Therefore, in recent years, much attention has been paid to the development of a humidity sensor using a hydrophilic organic polymer having excellent affinity for moisture, which is low in polymer value, the manufacturing process is easily processed at low temperature, and it is difficult to manufacture the sensor in the form of a film. This is because it can be widely used commercially because it is excellent in various aspects as well as electrical properties compared to the humidity sensor using a ceramic. In addition, the organic polymer is excellent in that it can change the physical properties of the sensor by appropriately adjusting the chemical elements necessary for the manufacturing of the humidity sensor.

Among the humidity sensors using polymers, the electrical resistance organic polymer film humidity sensor is applied to the electrode formed on the alumina substrate by applying an electrolyte polymer film as a moisture sensitive film. When the humidity in the air changes, the impedance of the polymer film as the moisture sensitive film is changed. Humidity sensor to detect.

The electrical resistance humidity sensor using an electrolyte polymer membrane as such a moisture-sensitive material exhibits electrical conductivity after dissociation of the electrolyte polymer membrane after absorbing the surrounding moisture, so that impedance between relative humidity 0 to 100% RH (relative humidity) is high. Change continuously. Therefore, there is an advantage that can accurately measure the relative humidity.

Among polymer materials, PVA (polyvinyl alcohol) is a typical general-purpose hydrophilic polymer which is insensitive to moisture because it is inexpensive and has a -OH group between carbon atoms in chemical structure. The PVA has a high affinity for water molecules, so the electrical properties of the sensor change due to the adsorption and desorption of water molecules, but because of its high solubility in water, it is easily attacked by moisture when applied to a humidity sensor in the form of a film. The disadvantages are poor durability and very high impedance (CAFinch, polyvinyl alcohol-developments, Wiley New York 1992).

Sakai et al. (Y.Sakai, Y.Sadaoka, M.Matsuguchi, Sensors and Actuators B, 1995, 35, 85-90) are humidity sensors that have several grafted-polymers to improve the stability and persistence of polymers. ) Was synthesized. Although the material produced by this copolymerization method had an effect of having an insoluble characteristic in water to some extent, this method also had a problem in water sensing physical properties and was not a breakthrough method.

The present invention has been made to solve the above problems, the present invention is to provide a humidity sensor for the humidity sensor improved moisture resistance while maintaining the humidity sensing properties and processability of the hydrophilic organic polymer material.

Another object of the present invention is to provide a method of manufacturing a humidity sensor moisture-sensitive film having improved durability against moisture while maintaining the humidity sensing properties and processability of the organic polymer material.

1 is a graph showing the characteristics of the impedance according to the humidity in the humidity sensor for each moisture-sensitive material according to the present invention.

2 is a plan view showing a configuration example of a humidity sensor according to the present invention;

Explanation of symbols on the main parts of the drawings

10 humidity sensor 12 insulation board

14a, 14b: electrode 16: gap

18: moisture sensitive film

In order to achieve the above object, the polyvinyl alcohol (PVA) humidity sensor for the humidity sensor according to the present invention is the alkaline earth metal or transition metal of the chloride or metal chloride hydrate of the PVA and m-benzene disulfonic acid (MBDS) Sodium salt, sodium salt of p-styrenesulfonic acid (PSSA) and polyacrylic acid (PA) is selected from the group consisting of crosslinked crosslinked product.

According to the above configuration, there is an advantage that the resistance to moisture is also improved while maintaining the humidity sensing properties and processability of the organic polymer material. Since the selected additives are suitably added to the hydrophilic polymer PVA, moisture absorbs and desorbs on the material surface, and the conductivity is better. In other words, when moisture is chemisorbed on the surface of the moisture-sensitive material, the conduction ions or electrons of the material become more free and the resistance of the humidity sensor is reduced.

Examples of the chloride or metal chloride hydrate of the alkaline earth metal or transition metal include FeCl ₂ , LiCl, NaCl, KCl, MgCl ₂ , CuCl ₂ , CoCl ₂ or metal chlorides thereof, among which FeCl ₂ .4H ₂ O is Most preferred.

PVA-based humidity sensor manufacturing method of the humidity sensor according to the present invention includes the following steps. First, 0.1-10 mg of PVA is added to 5-15 ml of water, inflated at room temperature and 90 ° C. for 5 to 24 hours, and then dissolved PVA the next day (first step). MBDS, PSSA or PA dissolved in 1-3 ml of water is then added to the PVA solution (second step). A minimum amount of dilute acid is used to dissolve an alkaline earth or transition metal chloride or metal chloride hydrate, followed by dry evaporation to form a solution of 1-50 mg (step 3). The mixture of step 3 is dissolved in 1-20 ml of water and mixed with the PVA mixture formed in step 2 (step 4). Then, the mixture of the fourth step is heated to remove the gas, coated on the electrode substrate for humidity sensor, and cured to obtain a moisture-sensitive film according to the present invention (step 5).

In the second step, 100 mg-1 g of MBDS is dissolved, and preferably 400-600 mg are added. Also, in the case of PSSA, 200 mg-800 mg are dissolved, preferably 400-600 mg are added. In the case of PA, 500 mg-1.60 g are dissolved, and preferably 900 mg-1.20 g is added.

The chloride or metal chloride hydrate of the alkaline earth metal or transition metal is selected from FeCl ₂ , LiCl, NaCl, KCl, MgCl ₂ , CuCl ₂ , CoCl ₂ and metal chlorides thereof, and FeCl ₂ .4H ₂ O is preferred. The FeCl ₂ .4H ₂ O is used 60-600mg (optimum amount 150mg) when MBDS or PSSA is added in the second step, 100-450mg (optimum amount 250-300mg) is used when PA is added.

In the third step, the acid can be selected from HCl, HNO ₃ and H ₂ SO ₄ , the amount is 0.1-100 g.

The moisture-sensitive material according to the present invention obtained as described above is coated on the alumina substrate on which the electrode is formed of gold or silver by a conventional method by a conventional coating method such as painting, dipping or spin coating. The coated solution is then cured in a 100-200 ° C. dryer for 10-180 minutes, preferably at 140-160 ° C. for 2-3 hours.

The characteristic of the impedance according to the humidity in the humidity sensor for each moisture sensitive material according to the present invention of the above characteristics is shown in FIG.

The humidity sensor of the present invention is not particularly limited as long as the humidity sensor has the above-described moisture-sensitive film on the insulating substrate provided with the electrode. 2 is a plan view showing a configuration example of an electrode substrate of the humidity sensor according to the present invention.

As shown in FIG. 2, the humidity sensor 10 has a pair of comb-shaped electrodes 14a and 14b on the insulating substrate 12, and the pair of comb-shaped electrodes 14a and 14b are constant. It is arranged on the insulating substrate 12 to be engaged by the gap 16 of distance. A moisture sensitive film 18 is provided on the insulating substrate 12 and the electrodes 14a and 14b as shown.

The material and size of the insulating substrate 12 are not particularly limited as long as they are commonly used. The insulating substrate 12 may be an alumina substrate having a size of 7.5 X 7.5 mm and a thickness of 0.25 to 0.42 mm.

The materials and sizes of the electrodes 14a and 14b are also not particularly limited as long as they are commonly used. The electrodes 14a and 14b may be formed of gold or silver that are electrically conductive, and may be formed by a conventional method such as screen printing or photolithography. The electrode 14a and 14b may be 0.2 mm in order to maximize the contact area with the moisture sensitive film 18. It is preferable to cross | intersect each other and to form five or more at intervals, and each width can be 0.2-0.3 mm.

When power is applied between the two electrodes 14a and 14b in the above-described configuration, the output voltage is changed by resistance and impedance change according to the humidity of the humidity sensitive film 18 so that humidity is detected.

Although only the PVA system is mentioned above, the present invention may also be applied to hydrophilic organic polymer materials such as PEG and PEO.

Specific examples of the moisture-sensitive material according to the present invention and a method of manufacturing the moisture-sensitive film using the same are as follows, but the present invention is not limited thereto.

Example 1

PVA 1g in 10ml of water and inflated at room temperature for 24 hours. The next day, when PVA is completely dissolved, add 400-600 mg of MBDS dissolved in 2 ml of water. Then _, 100-200 mg of FeCl ₂ 4H ₂ O is independently dissolved in 10 mg of dilute HCl, followed by drying to evaporate the solution. The mixture is dissolved in 2 ml of water, mixed with the PVA mixed solution prepared above, and mixed thoroughly. Then, some heat is added to the mixed solution to remove the gas. Then, an electrode formed of gold or silver on an alumina substrate (size 7.5 mm X 7.2 mm X 0.381 mm) is coated in the mixed solution. Finally, the coated solution is cured in an oven at 150-160 ° C. for 2-3 hours.

Example 2

A solution containing 1 g of PVA was added to 10 ml of water, followed by mixing by adding a solution of 400-600 mg of PSSA in 2 ml of water. It then is added and mixed well with a FeCl ₂ .4H ₂ O 150mg solution the same method as in Example 1. The solution is coated on the alumina substrate on which the gold electrode or silver electrode is formed with the mixed solution and cured at 130-145 ° C. for 2-3 hours in an oven.

Example 3

Make a solution containing 1 g of PVA in 10 ml of water, and mix by adding a solution of 900 mg-1.20 g of PA in 2 ml of water. Then, Example 1, FeCl ₂ .4H ₂ O 250 prepared as in - the addition in the same way to 300mg solution and then mixed well. The solution is coated on the alumina substrate on which the gold electrode or the silver electrode is formed with the mixed solution and cured at 140-160 ° C. for 2-3 hours in an oven.

The humidity sensor for moisture sensor according to the present invention configured as described above can achieve the effect of improving the durability against moisture while maintaining the humidity sensing properties and processability of the hydrophilic organic polymer material.

In addition, according to the method for manufacturing a moisture sensitive film according to the present invention, it is possible to achieve an effect of easily obtaining a moisture sensitive moisture sensitive film for humidity sensor while maintaining the humidity sensing properties and processability of the hydrophilic organic polymer material. . In addition, the humidity sensor to which the moisture sensitive film is applied has improved humidity sensing characteristics and excellent reproducibility.

Claims (10)

In the moisture-sensitive material for polyvinyl alcohol (PVA) humidity sensor, Selected from the group consisting of sodium salts of PVA and m-benzenedisulfonic acid (MBDS), sodium salts of p-styrenesulfonic acid (PSSA) and polyacrylic acid (PA) in the presence of chlorides or metal chlorides of alkaline earth or transition metals Humidity sensor for humidity sensor, characterized in that it comprises a crosslinked by crosslinking with one. The humidity sensor according to claim 1, wherein the chloride or metal chloride of the alkaline earth metal or transition metal is selected from FeCl ₂ , LiCl, NaCl, KCl, MgCl ₂ , CuCl ₂ , CoCl ₂ and metal chlorides thereof. Moisturizing Materials. In the manufacturing method of the moisture-sensitive film for polyvinyl alcohol-based humidity sensor, 0.1-10 mg of PVA in 5-15 ml of water, incubated at room temperature-90 ° C. for 5-24 hours, and then dissolving PVA; A second step of adding one selected from the group consisting of sodium salt of m-benzene disulfonic acid (MBDS), sodium salt of p-styrenesulfonic acid (PSSA) and polyacrylic acid (PA) dissolved in 1-2 ml of water to the PVA solution step; A third step of dissolving an alkaline earth metal or transition metal chloride or metal chloride hydrate using dilute acid and then evaporating it; A fourth step of dissolving the mixture in 1-20 ml of water and mixing with the PVA mixture; And And heating the mixture to remove the gas and coating and curing the electrode substrate for a humidity sensor, followed by curing. 5. 4. The method of claim 3, wherein in the second step, 100 mg-1000 mg of MBDS is dissolved. The method of claim 3, wherein in the second step, PSSA 200mg-800mg is dissolved. 4. The method of claim 3, wherein in the second step, PA 500 mg-1600 mg are dissolved. The humidity of claim 3, wherein the chloride of the alkaline earth metal or the transition metal or metal chloride thereof is selected from FeCl ₂ , LiCl, NaCl, KCl, MgCl ₂ , CuCl ₂ , CoCl ₂ and metal chlorides thereof. The manufacturing method of the humidity sensitive film for sensors. Claim 3 or 8. The method of claim 7 wherein the alkaline earth metal chloride or a metal chloride or a hydrate of a transition metal is FeCl ₂ .4H ₂ O in a humidity sensor humidity-sensitive film production method according to claim one. 8. The method of claim 3, wherein the acid is selected from HCl, HNO _3, and H ₂ SO ₄ in the third step. 9. The process of any one of claims 3 to 7, wherein in the fifth step, the coating and curing of the mixture on the electrode substrate for humidity sensor is performed on the alumina substrate on which the gold electrode or the silver electrode is formed. Coating and curing method for the humidity sensor for humidity sensor, characterized in that the curing for 2 to 3 hours at 140-160 ℃ in the oven.