JP3331507B2 - Pyroelectric infrared sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pyroelectric infrared detecting element such as a pyroelectric ceramic plate having electrodes for polarization and detection, and to transmit the pyroelectric infrared detecting element to infrared rays. The present invention relates to a pyroelectric infrared sensor having a sealed structure sealed in a possible case.

[0002]

2. Description of the Related Art Conventionally, a pyroelectric infrared sensor has a filter capable of transmitting infrared rays through a light-receiving surface of a pyroelectric infrared detecting element (pyroelectric body) such as a pyroelectric ceramic plate having electrodes formed thereon. There is a sealed structure in which the pyroelectric body is sealed in a case.

In general, a pyroelectric infrared sensor generates a temperature change in a pyroelectric body by converting infrared light absorbed by the pyroelectric body through a filter into thermal energy, and thereby the spontaneous polarization of the pyroelectric body is reduced. The device belongs to a device utilizing a phenomenon in which a voltage is induced on the surface of a pyroelectric body by changing (called a pyroelectric effect). It is desired that the pyroelectric body has a large pyroelectric coefficient indicating a change in surface charge with respect to a temperature change. As such a pyroelectric material having a large pyroelectric coefficient, LiTa
Single crystal such as O ₃ , PbTiO ₃ , PZT ceramic,
And those of polymer-based, such as PVF _2. In general, in a pyroelectric infrared sensor, it is necessary to reduce the heat capacity by reducing the thickness of the pyroelectric body in order to improve sensitivity and responsiveness. Pyroelectrics have been put to practical use.

However, in the pyroelectric infrared sensor, when the thickness of the pyroelectric body is reduced, the mechanical strength of the pyroelectric body is reduced and handling becomes difficult, and when the pyroelectric body is subjected to external vibration, the pyroelectric body vibrates. Noise is generated, the S / N ratio is degraded, and the basic performance as an infrared sensor is easily reduced.

Therefore, as disclosed in Japanese Patent Publication No. 58-2366, a pyroelectric body for a pyroelectric infrared sensor which solves such a problem has been proposed. FIG. 3 is a perspective view showing a basic configuration of the pyroelectric body.
In this pyroelectric body, a comb-shaped counter electrode 33 is provided on the front surface (light receiving surface) and the back surface of the pyroelectric plate 32 at a distance of 100 μm or less with respect to the incident direction of the infrared light 31. The comb-shaped counter electrode 33 of the pyroelectric plate 32 has a front surface used as a light receiving electrode and a back surface used as a ground electrode. Incidentally, the pyroelectric plate 32 is fixed to a mount table, and a lead wire is connected to a predetermined portion of each electrode.

As described above, if the pyroelectric body is formed such that the comb-shaped counter electrode 32 is formed on the light receiving surface of the pyroelectric plate 32 at a predetermined distance, the pyroelectric body can be formed without reducing the thickness of the pyroelectric body. The above-mentioned disadvantages of the electric infrared sensor can be solved.

[0007]

However, when a pyroelectric infrared sensor is constructed using the pyroelectric body shown in FIG. 3, the infrared ray 31 is actually absorbed before the infrared ray is absorbed by the pyroelectric plate 32 itself. Since considerable infrared rays are absorbed by the comb-shaped counter electrode 33 formed on the surface of the pyroelectric plate 32, the output voltage due to the polarization change of the pyroelectric plate 32 becomes extremely small.

When the comb-shaped counter electrodes 32 are formed at a distance of 100 μm or less, these electrode patterns must be formed with high precision. The distance varies,
The insulation resistance also varies. As a result, various problems such as an increase in variation in sensitivity of the infrared sensor and a decrease in the yield in the manufacturing process are caused.

Therefore, at present, reexamination of the basic structure of the pyroelectric body in which electrodes are formed on the pyroelectric plate, that is, the basic structure of the pyroelectric infrared detecting element is considered.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and its technical problem is that electrical insulation between electrode patterns can be ensured with high reliability and a sufficiently large output voltage can be obtained. Another object of the present invention is to provide a pyroelectric infrared detecting element which can be easily manufactured and a pyroelectric infrared sensor using the same.

[0011]

According to the present invention, there is provided a first pyroelectric thin plate having a first comb-shaped electrode formed with a predetermined pitch and line width in one direction on one surface serving as a light receiving surface for infrared rays. A second comb-shaped electrode having a predetermined pitch and a line width in a direction opposite to one direction of a surface serving as a light receiving surface for infrared rays and having a comb portion which is shifted by a half pitch from the comb portion of the first comb-shaped electrode; Thus, a pyroelectric infrared detecting element including a laminated portion obtained by laminating the obtained second pyroelectric thin plates such that the directions of the light receiving surfaces are separated and alternately arranged is obtained.

According to the present invention, in the pyroelectric infrared detecting element, the predetermined pitch and the line width are such that the pitch is 1 mm or less and the line width is 0.5 mm or less. A detection element is obtained.

Further, the uppermost light receiving surface of any one of the pyroelectric infrared detecting elements is sealed with a filter capable of transmitting infrared light, and the pyroelectric infrared detecting element is sealed in a case. Thus, a pyroelectric infrared sensor having a sealed structure can be obtained.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

First, the basic configuration of a pyroelectric infrared detecting element used in the pyroelectric infrared sensor of the present invention will be described with reference to FIGS. 1 and 2A and 2B.

In this pyroelectric infrared detecting element, a first pyroelectric ceramic thin plate as a first pyroelectric thin plate on which a first comb-shaped electrode 13 is formed, and a second comb-shaped electrode 14 are formed. A pyroelectric ceramic 12 including a laminated portion in which the respective light receiving surfaces are spaced apart and alternately aligned with a second pyroelectric ceramic thin plate as a second pyroelectric thin plate.
Is configured as

The first pyroelectric ceramic thin plate has one surface, which is a light receiving surface for infrared rays 11, as shown in FIG.
As shown in FIG. 5, the comb-shaped electrode pattern 21 is formed so that the first comb-shaped electrode 13 is obtained at a predetermined pitch P and a line width D. Further, the second pyroelectric ceramic thin plate has a predetermined pitch P and a predetermined line width D in the other direction opposite to the one direction of one surface serving as a light receiving surface for the infrared rays 11 as shown in FIG. And the comb portion of the first comb-shaped electrode 13 is a half pitch P
A comb-shaped electrode pattern 22 is formed so as to obtain a second comb-shaped electrode 14 having a comb portion shifted by / 2.

That is, in the pyroelectric ceramic 12, as shown in FIG. 1, the first and second comb-shaped electrodes 1 are formed in a laminated portion where the first and second pyroelectric ceramic thin plates are laminated.
Since the first and second comb electrodes 3 and 14 are positioned so as to intersect with each other three-dimensionally, the first comb-shaped electrode 13 located on the front surface side with respect to the incident direction of the infrared rays 11 serves as a detection surface electrode for the infrared rays 11 in the incident direction of the infrared rays 11. On the other hand, the second comb-shaped electrode 14 located inside is used as an internal electrode for polarization.

Incidentally, the first comb-shaped electrode 13 formed on the first pyroelectric ceramic thin plate and the second comb-shaped electrode 14 formed on the second pyroelectric ceramic thin plate both have a pitch of 1 mm. And the line width is 0.5 mm or less. Here, the first and second comb-shaped electrodes 13, 1
The reason why the pitch of No. 4 is 1 mm or less is that the pitch is 1 mm
If it is larger, the voltage output becomes smaller due to a temperature change when the infrared rays 11 are incident, the capacitance of the pyroelectric infrared sensor becomes smaller, and the influence of the stray capacitance becomes a problem. Therefore, the pitch must be 1 mm or less in order to secure a capacitance that avoids the influence of the stray capacitance. Also, the first and second comb-shaped electrodes 13,
The reason for setting the line width of 0.5 to 0.5 mm or less is that the line width is 0.1 mm or less.
If the width is larger than 5 mm, the area of the surface electrode portion that absorbs the infrared rays 11 becomes too large and the output voltage is lowered, and the line width needs to be 0.5 mm or less.

Further, the thickness of each of the first and second pyroelectric ceramic thin plates is set to 0. 0 in consideration of the labor and cost of production.
Those having a size of about 2 to 1.0 [mm] are used. If the thickness of these pyroelectric ceramic thin plates is more than 1 mm, the material cost increases, which is disadvantageous in cost.

The first and second comb-shaped electrodes 13 and 14 in the laminated portion are formed by printing electrodes on the first and second pyroelectric ceramic thin plates (ceramic green sheets) and forming each of the pyroelectric ceramic thin plates (described above). (Including pyroelectric ceramic thin plates other than the first and second pyroelectric ceramic thin plates), and a sintering process.
It can be formed at the same time. The distance from the second comb-shaped electrode (polarizing internal electrode) 14 to the surface of the first pyroelectric ceramic thin plate is set to 0.02 to 0.2 [mm] by selecting the thickness of the ceramic green sheet. It can be adjusted in the range of the degree. Furthermore, land external electrodes for lead attachment are respectively connected to the exposed portions of the pyroelectric ceramic 12 on the side surfaces facing each other.

Incidentally, such a pyroelectric ceramic 12
When the pyroelectric infrared sensor is configured by using, the light receiving surface of the first pyroelectric ceramic thin plate on which the first comb-shaped electrode 13 is formed is sealed with a filter capable of transmitting infrared light,
The pyroelectric ceramic 12 may be sealed in a case to form a sealed structure.

In the case of the pyroelectric infrared sensor thus obtained, the first and second comb electrodes 13 and 14 have a structure in which two three-dimensionally crossed electrode groups having different polarization directions are connected in series. Since a structure is provided in which one direction is shielded from the infrared rays 11, it is possible to cancel a voltage generated due to a sudden temperature change or disturbance vibration.

Next, a method of manufacturing the pyroelectric infrared sensor will be specifically described. First, lead zirconate titanate (PZ) was used as the first and second pyroelectric ceramic sheet materials.
T) Two green sheets having a thickness of 0.1 mm were prepared using a calcined powder of a T) -based ceramic. Subsequently, using a silver-palladium-based electrode paste on these green sheets, as shown in FIGS. 2A and 2B having a width of 0.2 mm, a length of 3 mm, a pitch of 1.0 mm, and eight comb teeth. The comb-shaped electrode patterns 21 and 22 were printed to obtain first and second pyroelectric ceramic thin plates.

Eight green sheets on which no electrodes are formed by printing are laminated, and the second pyroelectric ceramic thin plate and the first pyroelectric ceramic thin plate are laminated on the laminated body in this order. After that, a thermocompression bonding was performed to obtain a laminated thermocompression bonded body. Thereafter, the laminated thermocompression bonded body was
The pyroelectric ceramic 12 was obtained by baking in the air at a temperature of 2 ° C. for 2 hours.

Subsequently, a portion of the pyroelectric ceramic 12 exposed on the side surface facing each other, that is, an exposed portion of the second comb-shaped electrode (polarizing internal electrode) 14 and a first comb-shaped electrode (detection surface electrode) And 13) exposed lead external electrodes were respectively connected to the exposed portions.

After that, the first comb-shaped electrode (detection surface electrode) 13 of the pyroelectric ceramic 12 is sealed in a metal case with an infrared filter capable of transmitting infrared rays 11, and the pyroelectric ceramic 12 is sealed. An electronic infrared sensor was created.

Therefore, the pyroelectric infrared sensor of this embodiment and the pyroelectric infrared sensor of the comparative example constituted by using the pyroelectric infrared detecting element shown in FIG. 3 were each separated from the heat source at 40 ° C. by 3 m. The device was installed at a distance, the output voltage (mV) was measured at a chopper frequency of 5 Hz, and the production yield (%) of the pyroelectric infrared sensor in the production process was examined. The results are shown in Table 1. .

[0029]

[Table 1]

From Table 1, it can be seen that the pyroelectric infrared sensor of the embodiment can obtain an output voltage approximately 1.6 times higher than that of the pyroelectric infrared sensor of the comparative example, and the manufacturing yield of the comparative example is also high. It can be seen that the result is far superior to the pyroelectric infrared sensor.

In the embodiment, the case where the laminated portion of the pyroelectric ceramic 12 is formed by laminating the first pyroelectric ceramic thin plate on the second pyroelectric ceramic thin plate has been described.
This stacking order may be reversed. Further, this laminated portion is not limited to the case where each of the first and second pyroelectric ceramic thin plates is laminated, but may be constituted by a plurality of sheets. The present invention is not limited to the embodiments, since the light receiving surfaces may be stacked so that the directions of the respective light receiving surfaces are separated and alternately arranged.

[0032]

As described above, according to the present invention, a comb-shaped electrode has a structure in which two three-dimensionally crossed electrodes having different polarization directions are connected in series, and one direction is shielded from infrared rays. The use of a pyroelectric infrared detector that includes a layered structure with a simple structure prevents the amount of infrared light absorbed by the light-receiving surface from being excessively absorbed, resulting in reliable electrical insulation between the electrode patterns. While being secured high,
It is possible to obtain a pyroelectric infrared sensor that has a sufficiently large output voltage and is excellent in manufacturing yield and can be easily manufactured.

[Brief description of the drawings]

FIG. 1 is a side sectional view showing a basic configuration of a pyroelectric infrared detecting element (pyroelectric ceramic) used in a pyroelectric infrared sensor of the present invention.

FIG. 2 shows an electrode pattern of each part constituting the pyroelectric infrared detecting element (pyroelectric ceramic) shown in FIG. 1, wherein (a) shows a first pyroelectric ceramic thin plate formed on a first pyroelectric ceramic thin plate; 1 shows a pattern of a comb-shaped electrode, and (b) shows a pattern of a second comb-shaped electrode formed on a second pyroelectric ceramic thin plate.

FIG. 3 is a perspective view showing a basic configuration of a pyroelectric infrared detecting element (pyroelectric body) used in a conventional pyroelectric infrared sensor.

[Explanation of symbols]

 11, 31 Infrared ray 12 Pyroelectric ceramic 13, 14 Comb electrode 21, 22 Comb electrode pattern 32 Pyroelectric plate 33 Comb counter electrode

Claims (3)

(57) [Claims] 1. A first pyroelectric thin plate having a first comb-shaped electrode formed at a predetermined pitch and a line width in one direction on one surface serving as a light receiving surface for infrared light, and one surface serving as a light receiving surface for infrared light. A second pyroelectric element in which a second comb-shaped electrode having a comb portion in the other direction opposite to one direction and having a predetermined pitch and a line width and being shifted by a half pitch from the comb portion of the first comb-shaped electrode is formed; A pyroelectric infrared detecting element, comprising: a laminated portion in which a light-receiving surface is spaced apart from a conductive thin plate so as to be alternately aligned. 2. The pyroelectric infrared detecting element according to claim 1, wherein the predetermined pitch and the line width are such that the pitch is 1 m.
m or less, and the line width is 0.5 mm or less. 3. The pyroelectric infrared detecting element according to claim 1, wherein the light receiving surface positioned at the uppermost position is sealed with a filter capable of transmitting infrared light, and the pyroelectric infrared detecting element is enclosed in a case. A pyroelectric infrared sensor characterized by being enclosed and sealed.