JPS58200503A - Moisture sensitive 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 The present invention relates to a humidity sensing element that uses a winter moisture sensitive substance whose electrical resistance changes depending on humidity.

Conventionally, moisture-sensitive elements using lithium chloride as a moisture-sensitive substance have been widely used, but in recent years, moisture-sensitive elements using metal oxides have been developed.

This metal oxide-based humidity sensing element is superior to the lithium chloride-based humidity sensing element in terms of deterioration of characteristics over time and the size of the applicable relative humidity range. However, during humidity cycling, a stable metal hydroxide layer is formed on the surface of the humidity-sensitive resistor layer, resulting in a decrease in sensitivity, so it is necessary to perform periodic heating cleaning. For this reason, such metal oxide-based moisture sensing elements are equipped with an indirect heater, but this complicates the structure, leaving major problems in terms of mass production and manufacturing cost. Additionally, it has been frequently experienced that the adhesion between the substrate and the humidity-sensitive resistor layer accelerates during temperature and humidity cycles, and cracks occur in the humidity-sensitive resistor layer, so it is desirable to improve the characteristics in this regard. ing.

The present invention improves the above-mentioned drawbacks, has high sensitivity and stable moisture sensitivity performance over a wide range of relative humidity, and
It is an object of the present invention to provide a moisture-sensitive element that has good adhesion between an insulating substrate and a humidity-sensitive resistor layer, is mass-producible, and can be manufactured at a low price.

That is, in the present invention, the moisture-sensitive resistor layer formed between a pair of opposing electrodes formed on an insulating substrate contains at least one compound powder selected from LiP'bNbO4 and LiPbTa○4. It is made of a sintered body of the composition.

The above composition comprises the above compound powder and v, o, vN
.

VC, FeV2O5, IVtuVzO@Natotsubein I
' It consists of components (1) and (1) and vehicle, and in that case, the compounding ratio of the compound powder is appropriately selected within the range of 98 to 60 V%. The reason for this is that if the blending ratio of the compound powder is less than 60%, the formation of pores in the moisture sensitive membrane will deteriorate, and if it is more than 98%, the adhesion to the main board will deteriorate significantly. Because it does. In addition, it can also be used as a binder.
It is desirable to use the amount within the range of 5 to 30 mo/L/%, and the vehicle is made of, for example, ethyl cellulose, an acrylic resin, butyl carpitol acetate, terpineol, and the like.

Further, a composition containing the above compound powder is prepared by adding 5 to 30 mol% of V, O, to the above compound powder, adding the above vehicle to the mixed powder, and mixing thoroughly with a roller or Beaufrem mill. The thus obtained dark blue ribbon hQ is a paste-like material having an appropriate viscosity.Next, the moisture-sensitive element according to the present invention has high sensitivity and excellent linearity over a wide range of relative humidity, and its There is little deterioration of the characteristics over time, and it still shows very stable characteristics when left in a high humidity atmosphere, and has good atmosphere resistance, so there is no need to install an indirect heater as in the case of conventional products. . In addition, since this device can be produced using thick film technology, it is suitable for mass production and cost reduction, and has the advantage of high industrial utility value.

Next, the specific structure of the moisture sensitive element of the present invention will be explained with reference to the drawings.

FIG. 1 shows an example of the moisture-sensitive element of the present invention, in which U represents an insulating substrate made of ceramic or the like, and ν and mouth represent a pair of electrodes facing each other and each having a comb shape. The bottom of the moisture-sensitive resistor layer, which is made of a sintered body of the composition described above, is coated over the main parts of the electrode base except for the lead-out parts 12b and 13b, respectively. The positive and negative electrodes connect the top of the electrode and the mouth to the external lead U and back, respectively. Figure 2 shows
2-2' cross section of FIG. 1 is shown.

Such a moisture sensitive element is manufactured, for example, by the following method. First, using an insulating substrate U on which electrodes and wires have been provided in advance, comb-shaped electrodes and wires are formed on the surface by screen printing, and the
The electrode is fired at about 950°C. Next, using the paste-like composition described above, screen printing is performed to a uniform thickness so as to completely cover the top of the electrode, the main part of the field, and the top of the field to form a coating layer, and then the insulating substrate is coated. In order to increase the adhesion between U and the moisture-sensitive resistor layer 14, for example, 9
Calcinate at a suitable temperature of 00 to 1200°C.

In the cooling process after firing, the moisture-sensitive resistor layer 14 hardens and becomes a film that has good adhesion to the insulating substrate H and has an appropriate pore distribution. After this cooling, the external lead 17 and the sleeve are attached, and then load aging is performed under high temperature and high humidity to stabilize the characteristics.

In addition, in the above-mentioned example of the humidity sensing device having the structure shown in FIGS. 1 and 2 and its manufacturing operation,
Although a structure has been described in which the humidity-sensitive resistor layer 14 is formed in the order in which the humidity-sensitive resistor layer 14 is formed, the humidity-sensitive element of the present invention has a configuration in which the formation order of both layers is reversed and a pair of electrodes are formed under the humidity-sensitive resistor layer. It also includes a counter electrode in which a humidity-sensitive resistor layer is sandwiched between electrodes.

Next, this invention will be explained in detail.

10s powder and 10s powder are mixed in a BoyvMiμ, and to this mixture is added a vehicle consisting of ethyl cellulose, buty-carpi)-ru acetate and TVneo-μ,
A paste-like composition of uniform viscosity was prepared in an agate mortar.

Next, this composition is applied to the configurations shown in FIGS. 1 and 2, where the electrodes ν and the fields are j, tt! The electrodes, electrodes 16, and 16 are Ag-pCI-electrodes, which are screen printed on an alumina insulating substrate to a film thickness of 30 to 100 μm, and heated in air at about 450'C to remove the peak μ component. After volatilization, it was sintered at 950°C, and after cooling, it was aged under electric current at 60°C and 19Q%RH to obtain a moisture-sensitive element according to a conventional method.

Table 2 below shows the electrical resistance between the electrodes of the humidity sensing element obtained in the above example, measured at 25° C. while varying the relative humidity of the measurement atmosphere.

Table 1 Table " 2 Figure 3 shows the relationship between relative humidity and resistance value shown in Table 2 as a line diagram. For comparison, Figure 3 shows the relationship between the relative humidity and the resistance value shown in Table 2. The characteristics of the moisture-sensitive resistance element are also listed.

As is clear from FIG. 3, each element of the above example has higher sensitivity and superior linearity over a wide range of relative humidity than conventional ones, and is particularly resistant to being left in a high-temperature atmosphere. It also shows very stable characteristics.

Furthermore, as is clear from the above, this element is easily produced using thick film technology.

[Brief explanation of the drawing]

Fig. 1 is a plan view showing an example of the humidity sensing element of the present invention, Fig. 2 is a sectional view taken along line 2-2' in Fig. 1, and Fig. 3 is a characteristic diagram showing the relationship between relative humidity and electrical resistance value. . U...Insulating substrate, 12. L (...pair of electrodes facing each other, 14...moisture-sensitive resistor layer. Patent applicant: Tateishi Electric Co., Ltd.

Claims (1)

[Claims] (1) A pair of electrodes facing each other and a humidity-sensitive resistor layer extending between these electrodes are formed on an insulating substrate. 1. A moisture-sensitive element characterized in that the humidity-sensitive resistor layer is made of a sintered body of a composition containing powder of at least four kinds of compounds selected from LiPbN'bO4 and LiP'bTaO.