JPS59172228A - Method of producing moisture detecting element - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method of manufacturing a humidity sensing element, particularly a variable capacitance type humidity sensing element.

Configurations of conventional examples and their problems Currently, various devices are known that can detect humidity and output it in the form of an electrical signal.Among them, humidity detection devices that use capacitance changes are accuracy, sensitivity, responsiveness, hysteresis, aging, chemical resistance,
It is excellent in terms of measurement range, Ii1 thermal properties, etc.

Next, the basic configuration of an example of this humidity detection element is shown in FIG. In the figure, 1 is a valve metal such as Kuntal, and the surface of this metal base 1 is coated with a dielectric anodic oxide film 2.
A dielectric anode 3 is formed, and a semiconductive metal oxide layer 3 such as manganese dioxide is formed on the oxide film 2. On this semiconductive metal oxide layer 3, an electrode 4 facing the metal base 1 is provided. For example, as a counter electrode, first, carbon particles of 10ρ7 to several hundred μ2 are attached to a metal oxide.
A silver paint layer is then formed. However, all of the above-mentioned constituent materials contain water, and adsorption and desorption of water vapor does not proceed smoothly, resulting in a hysteresis phenomenon. This also contributes to the apparent change over time. Furthermore, the silver bay 71- which has been used conventionally is a type containing 1.0% of fluororesin or epoxy resin and dispersed in silver paint in an organic solvent, and has water repellency, but does not contain an organic binder. Disadvantages include poor weather resistance, natural oxidation of silver, and silver migration under high temperature and high humidity conditions. This also becomes a factor that causes the element to change over time.

Purpose of the Invention The present invention provides a humidity sensing element which reduces the hysteresis phenomenon that occurs when moisture once absorbed by the constituent material itself is retained within a month, as described in item 1, and which exhibits small changes over time due to environmental changes. The purpose is to provide a method for manufacturing.

Structure of the Invention In order to achieve the above object, the present invention uses an organosilicon compound having water repellency to a thermally decomposable metal salt solution when forming a semiconductive metal oxide layer constituting a humidity sensing element. is dispersed to impart water repellency to the semiconductive metal oxide layer after thermal decomposition, as well as to prevent migration of silver paint that tends to occur under high temperature and humidity conditions. A highly reliable humidity sensing element can be manufactured by curing the silver paint at high temperature, immersing it in an organosilicon compound that forms a film, and baking it to prevent natural oxidation of the silver paint.

Description of Examples Example 1 The fact that the humidity detection element of the present invention has a lower water absorption rate than conventional elements will be explained using a specific example.

51 Lee-2) A part of a metal substrate made of tantalum with a diameter of 8 yym and a length of 15 mm was subjected to constant voltage chemical conversion at 40 V in a 50% phosphoric acid solution to form a tantalum oxide film, which was further coated with a specific gravity of 1. ．．
○wt, 0.0001wt% of a polymer of an organosilicon compound was added to a manganese nitrate solution of No. 10.

0,○o1wj%, 0,01 wt%, 0,1 w
t%, 1wt%.

After being immersed in a solution containing Swt% and 10wt% (all percentages are by weight), it was thermally decomposed at 2°C for 20 minutes to form a manganese dioxide layer. Figure 2 shows the hygroscopicity of the elements fabricated using solutions containing the above-mentioned organosilicon compounds at various concentrations when left at a constant temperature and humidity of 50'C and relative humidity of 90% FtH. It is shown using the weight increase rate. In the figure, 0wt%, that is, the conventional element, B
is 0.0001wt%, C is 0.001wt%, D is 0
．． 01 wt%, E is 0.1 wt%, F is 1 wt%, G
shows the results at 5 wt% and H at 10 wt%. From the human curve, it can be seen that the manganese dioxide layer formed by thermal decomposition on the anodic oxide film is porous and easily absorbs moisture. It can also be seen that as the content of the organosilicon compound increases, the amount of water absorption decreases significantly. After forming a manganese dioxide layer under the conditions of A-H and further forming a carbon layer using colloidal carbon, a silver paint layer is formed. Table 1 shows the initial characteristics of the device thus manufactured.

Table 1 From Table 1, the amount of organosilicon compound, which is a foreign substance, added to the solid electrolyte of manganese dioxide is 7. This would impair the characteristics of the product, which is not a good idea. However, if the concentration is too low, the water repellency will not be sufficient and the effect will be weak. Therefore t
In order to make anδ small and have remarkable water repellency,
．． It is necessary to set the concentration to about 0.001 wt% to 6 Wt. The initial characteristics are fixed at 60 RH.

Next, the moisture resistance of the elements produced under conditions A to G in Section 2 will be described. A to G at 60℃, relative humidity 90tI
) The output capacity values after being left in a constant temperature and humidity chamber at RH for 1000 hours were measured in a 60% RH atmosphere and compared with the initial values, and the results are shown in Table 2. From the table, it can be seen that the change in characteristics is smaller compared to the conventional example A. This corresponds to the amount of water absorbed by the manganese dioxide layer shown in FIG. 2, and is thought to be due to the fact that without water repellency, once moisture is included at high temperatures, it becomes difficult to desorb. As described above, by the method of the present invention, a temperature sensing element that is resistant to long-term high humidity can be manufactured.

Table 2 Example 2 A part of a metal substrate made of scrap tantalum with a diameter of 0.8 mm and a length of 15 ff was subjected to constant voltage chemical conversion at 40 V in a 50% phosphoric acid solution to form a tantalum oxide film. After immersing a polymer of an organosilicon compound in a manganese nitrate solution with a specific gravity of 1.10 and an o-oiwt% diaphragm solution,
Pyrolyzed at 0℃ for 20 minutes to produce manganese dioxide P? Form Jk. Thereafter, the carbon layer is immersed in colloidal carbon, and the carbon layer is further immersed in silver paint and fired at 100° C. to form a silver paint layer. An organosilicon polymer film that dries at room temperature is formed on the silver oxide. This membrane is water vapor permeable but highly water repellent. The temperature sensing element manufactured by the method of the present invention and the diameter method, that is, the manufacturing method described above, lacks an organosilicon compound in manganese nitrate,
In addition, the changes over time are compared with a device that also lacks an organosilicon film on silver baymeth. The fluctuation range from the initial characteristics of the device manufactured by the manufacturing method of the present invention and the device manufactured by the conventional manufacturing method after being left outdoors for 5000 hours is shown as the average value of 60 devices for each device. Characteristic measurements were performed at a relative humidity of 60% RH. Furthermore, Table 3 also shows the range of characteristic fluctuations after being left in an atmosphere of 901% RH at 50°C for 1000 hours and after being left in an atmosphere of 10% RH at 66°C for 1000 hours. Table 3 clearly shows that the elements manufactured by the manufacturing method of the present invention have better weather resistance, especially in high humidity and low humidity atmospheres.

1.

Table 3 Effects of the Invention By the method of the present invention, it is possible to reduce the water absorption rate of the manganese dioxide layer and to make it water repellent, to reduce the hysteresis phenomenon, and to produce an element that is resistant to high humidity. A film of organosilicon polymer can be formed on the exposed cathode surface to improve the weather resistance of the device.
It is possible to manufacture a highly reliable humidity detection element with little change over time, which brings great benefits to industry.

[Brief explanation of the drawing]

11 bae. Fig. 1 is a basic configuration diagram of a conventional humidity detection element, and Fig. 2 is a diagram showing the content concentration and water absorption rate of organosilicon compounds in manganese nitrate versus elapsed time. DESCRIPTION OF SYMBOLS 1... Valve metal, 2... Dielectric anodic oxide film, 3... Semiconductive metal oxide layer, 4...
...Counter electrode. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2

Claims (4)

[Claims] (1) After forming a dielectric anodic oxide film on a metal substrate by an anodizing method, it is immersed in a pyrolyzable metal salt solution in which a polymer of an organosilicon compound is dispersed or dissolved, and then thermally decomposed. 1. A method for manufacturing a humidity sensing element, comprising: forming a solid electrolyte made of a semiconductive metal oxide; and providing a cathode conductive layer such as a carbon layer or a silver paint layer on the solid electrolyte layer. (2) The method for manufacturing a humidity detection element according to claim 1, wherein the cathode conductive layer has a coating made of a polymer of a water vapor permeable organosilicon compound thereon. (3) The humidity sensing element according to claim 1, characterized in that a polymer of an organosilicon compound is added in an amount of 0.0001 to Swt% (polymerization percentage) to the thermally decomposable metal salt solution. manufacturing method. (4) The polymer of the organosilicon compound can be hardened and formed by heat treatment at 130"C or less, and is physically and chemically stable in the usage environment of the humidity sensing element. 2. Method for manufacturing the humidity sensing element described in .