JPS58129241A - Manufacture of ceramic humidity sensor - Google Patents

Abstract

PURPOSE:To obtain a humidity sensor of desired thickness having superior in response characteristics, by coating a base with a mixture of a burnt metal oxide powder and a binder and drying it to form a thin film sheet, laminating plural sheets of this film, pressing them into one body, heat treating it, and attaching electrodes to it. CONSTITUTION:Metal oxide, such as TiO2 type or Li2O-MgO-V2O5 type, is calcined at 700-750 deg.C, the calcined product is pulverized, and a ceramic binder is added to form a liquid preparation like paste. A glycerin film formed thinly on a glass plate is coated with this preparation in uniform thickness, and dried. A self-supporting about 100mum thin film sheet is obtained by immersing this dried film into pure water and dissolving the glycerin film. This sheet is again dried and cut into a prescribed size, and plural sheets, such as 3'5, of the cut sheets are laminated and pressed into one body. Then, it is heat treated at about 800 deg.C to form a burnt product 1. A humidity sensor is formed by attaching 2 lattices of electrodes 2, 3 to both sides of this product 1 respectively, and connecting conductors 4, 5 with electrodes 2, 3, thus permitting the humidity sensor high in strength and superior in hysteresis characteristics of humidity- resistivity relationship, etc. to be obtained with high yield.

Description

Detailed Description of the Invention The present invention relates to a moisture-sensitive element made of a sintered body of a metal oxide, and in particular, to a ceramic element having a thin and uniform body thickness to improve response characteristics and hysteresis characteristics. The present invention relates to a method of manufacturing a moisture-sensitive element.

General humidity-sensing elements for detecting humidity are known, for example, highly porous ceramic sensors made of fired metal oxides, and the resistance that occurs due to the adsorption and desorption of moisture in the porous portion inside the sintered body is known. Changes in value are detected from the electrode body. mosquito! For example, the ceramic humidity sensing element is M qCrz On
Th Ox series, ZnO series, Tie, etc.

It is made by sintering metal oxides known as Li, O-MqO-V+O, thread, etc. into a porous heptadramic structure, and its structure is made by press-molding the raw metal oxide powder into a single plate of a predetermined shape. There are so-called free-standing types in which electrodes are formed on the front and back sides of a sintered body that has been fired, and comb-shaped electrodes are formed on a sintered body that has been fired by coating a metal oxide film on a ceramic substrate. A so-called substrate type type is known.

By the way, the former self-supporting type is generally one in which, prior to press molding, the metal oxide powder as a material is granulated to a uniform particle size that is easy to mold, and this granulated powder is press molded using a mold, etc. However, it is difficult to press homogeneously, and if the VCC is particularly thin (for example, less than 0.5 tranl) and becomes rancid, it may be damaged during pressing or deformed during firing. For this reason, the sintered body has a thickness of 1ν, and the response characteristics become richer, resulting in a disadvantage that the humidity characteristics have thicker hysteresis. On the other hand, with the r+H block plate shape, the desired thickness can be obtained relatively easily using printing methods, but there are problems such as burning of foreign substances, diffusion into the ζ body, dust, etc. The drawback was that it was difficult to obtain products with uniform quality characteristics.

4: The invention has been proposed in view of the following, and is to manufacture a self-supporting ceramic moisture-sensitive element that can be easily formed into a sintered body with a desired thin wall thickness and has good response characteristics and hysteresis characteristics. provide a method.

4: In the method for manufacturing a ceramic moisture-sensitive element according to the invention, first, a free-standing 1171 film sheet of a thin, homogeneous metal oxide film is created. Then, a plurality of these thin film sheets are laminated and press-formed into one piece, and then fired.
Since metal oxide powder is not press-formed with one layer of gold as in the past, it is pressed homogeneously, and the deformable element due to damage during molding or warping during firing is a thin plate-shaped sintered body with a predetermined wall thickness. The hysteresis characteristics are much better than conventional press-formed products.

Embodiments of the present invention will be described in detail below in comparison with conventional examples.

Figures 1 and 2 show a self-supporting ceramic humidity sensing element obtained by the method of the present invention. It is a sintered body made of ceramic. 2 and 8 are electrodes printed in a grid pattern on the north and lower surface of the sintered body 1, and electrode leads 4,
5 is connected. The humidity sensing part 1 used in such a humidity sensing element can be made of a suitable metal oxide whose electrical resistance value changes linearly and widely depending on changes in humidity, such as Ti1t-based Li, O, etc.
A sintered body of a M f OV20S-based composite metal oxide was used. That is, first T10. system oxide and Li, O-Mg
Prepare appropriate amount of 0-V, O, type oxide and heat to 700-750℃
Calculate it. After pulverizing the calcined mixed material in a mortar, several percent of a ceramic binder (for example, B-γ) is added and kneaded into a paste-like mixture.

Spread this paste-like mixture onto 11 glass plates in a thin layer/
A film of approximately 100 μm in thickness is uniformly coated on one can of chrycerin film using a doctor blade method, and dried in a cup. After drying, it is immersed in pure water to dissolve the chrycerin to obtain a thin free-standing thin film of metal oxide about 100 μm in thickness. Next, after drying this /4 III sheet in a Shikoku oven, it is cut into a predetermined shape (l). Then, to obtain mechanical strength, 0! several sheets (3 to 5 sheets) are stacked to give approximately 200 Kt / ctd(7) 7'Res II:
Then press it all together. Thereafter, it is fired at a firing temperature of about 800°C to obtain a sintered body l of ceramicized metal oxide. Next, V-shaped electrodes are printed on the front and back sides of the sintered body 1 and baked at approximately 600°C to form electrodes 2°8, and electrode leads 4
, 6 to complete the PeX wet element. The sintered body of the moisture sensitive part l of the moisture sensitive element E thus obtained has a wall thickness of 0.1 ttMl to 0.8 ml and provides mechanical strength during use of the device. It is. The sintered body 1 is made by laminating a plurality of thin film sheets of metal oxide obtained by uniformly applying a paste-like mixture using a doctor blade method to a predetermined thickness. Since it is formed by pressing it in one piece, it has a uniform wall thickness, and unlike conventional products, it does not break during press molding or deform during firing. Further, the thickness can be arbitrarily set by changing the number of laminated thin film sheets used.

Figure 3 shows the humidity at room temperature of a moisture-sensitive element obtained by the method of the present invention when 8 unfired thin film sheets were laminated to form a thin film with a bulk thickness of 0.2 tts l after firing. -The resistance value characteristics clearly show several times the hysteresis characteristics on the humid side compared to the humidity-resistance characteristics of a moisture-sensitive element with a bulk thickness of 0.4 rmt obtained by conventional press molding as shown in Figure 4. has been done.

As described above, according to the method of the present invention, it is possible to improve the hysteresis of the humidity-resistance value characteristics, and to produce a self-supporting ceramic "J" with excellent quality characteristics that does not cause breakage during press molding or warpage during firing, etc. We can provide humidity sensors.

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[Brief explanation of drawings]

Fig. 1 is a city view of a free-standing ceramic ivy moisture sensitive element f obtained by the method of the present invention, Fig. 2 is a partial cross-sectional view along the TI-TI line in Fig. tAlso, the humidity-resistance value characteristic curve of the humidity-sensitive element. FIG. 4 is the humidity-low+111 linear characteristic curve of the humidity-sensitive element obtained by press-molding rI11 bundles. 7-

Claims (1)

[Claims] A step of coating a mixture of fired metal oxide powder, ceramic, and binder on a flat substrate to form a thin IIQ sheet of metal oxide on the substrate, drying the thin film sheet on the substrate, A step of obtaining a thin film sheet of a metal oxide by peeling it off, a step of laminating a plurality of the peeled thin film sheets and pressing them together, ]11 (a step of firing the thin film sheets pressed together, and a step of forming an electrode on the fired thin film sheet.