JPS6145937A - Structure of infrared sensor - Google Patents

Abstract

PURPOSE:To obtain high sensitivity by connecting plural pyroelectric elements which has electrodes on both surfaces and are a single-domain processing in series as electric circuits. CONSTITUTION:Plural pyroelectric elements which have electrodes 1-4 and 1'-4' on both surface and are processed with the single-domain treatment are connected in series as electric circuits. Further, the polarities of the respective pyroelectric elements are set in the same direction along the series circuit. Then, outputs of those series-connected pyroelectric elements are outputted through an FET20.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to the structure of a highly sensitive infrared sensor composed of a plurality of pyroelectric elements.

[Prior art 1 Lead titanate/lead zirconate (hereinafter PZT) is used as a pyroelectric element.
), lithium tantalate (hereinafter referred to as Li2Tag), triglycine sulfate (hereinafter referred to as TGS), etc., ceramics or single crystals of materials with a large pyroelectric effect are made into a thin layer, and an electrode is attached to this to perform single-domain processing. That which has been subjected to this is the common knowledge.

Furthermore, recently, stretched vinylidene fluoride films and particle-dispersed composite sheets in which powder particles of a material with a large pyroelectric effect are dispersed in a resin are also known.

When these electrode surfaces are irradiated with infrared rays, charges are induced on the electrode surfaces due to the pyroelectric effect, and the amount of charge is converted into a voltage by a suitable electric circuit such as a field effect transistor (hereinafter referred to as FET) and output.

That is, when receiving infrared rays with a certain energy density,
It can be said that the more sensitive an infrared sensor can be, the more output it can produce by converting it into voltage.

Conventionally, in order to improve the sensitivity of such infrared sensors, improvements have been made to the materials, and efforts have been made to increase the effective light-receiving area by changing the shape and making the film as thin as possible to reduce the heat capacity. There was a limit to how high the sensitivity could be achieved within the range of use.

[Objective of the Invention 1] The object of the present invention is to provide an infrared sensor with high sensitivity, which could not be obtained with a single element, by using a plurality of pyroelectric elements in combination.

[Configuration 1 of the Invention The present invention consists of a plurality of pyroelectric elements having electrodes on both sides and subjected to single-domain processing, each element being connected in series as an electric circuit, and each element having a This is an infrared sensor structure characterized in that polarities are arranged in the same direction along a series circuit.

In the present invention, the electrodes include gold, silver, copper, nickel, chromium,
It is preferable to use aluminum or other metals deposited by sputtering or ion blasting, but the material is not limited to these.

Methods such as printing, vapor deposition, and plating can be selected.

The electrode film used as the light-receiving surface may be further subjected to treatment such as blackening treatment to improve infrared absorption efficiency.

Single domain processing is achieved by applying an electric field of the required strength between the electrodes of each element.

The pyroelectric element in the present invention refers to the conventionally used P
It may be a thin layer of ceramics or single crystals such as ZT, Li2Tag3, or TGS, or may be a stretched vinylidene fluoride film or a pyroelectric particle-dispersed composite sheet.

A pyroelectric particle dispersed composite sheet is a composite material sheet in which fine particles of pyroelectric ceramic are dispersed in a binder such as a synthetic resin.

Each element has a polarity after being subjected to single domain processing.

That is, during this process, the electrodes on the (+) side and the electrodes on the (-) side are determined.

The most important point in the present invention is that the (+) side electrode of one element is connected to the (-) side electrode of the next element to be connected.
The +) side electrode is further connected in series with the (-) Lull electrode of the next element.

Although the number of constituent elements may be any number greater than or equal to two, the structure of an infrared sensor according to the present invention composed of four elements will be selected as an example and illustrated.

FIG. 1(A) is a side view showing a structure in which four elements are randomly arranged on the front and back, inside and outside, facing the infrared ray source (upper part of the figure).

The polarization direction of each element is indicated by an arrow.

The numbers assigned to the electrodes on both sides also serve as the device numbers, meaning that they were polarized by an electric field with the side with a ``'' in the number being positive and the side with a number without a `` being negative.

In this figure, 1, 2, 3 and 4 are the light receiving surfaces.

The connections are PET, 1.1' and 2, and 3.3' and 4.4'.
This indicates that the polarization direction of each element is aligned along the series circuit.

The same connection is used in FIG. 1(B).

In (A), each element is an independent individual sensor, but in (B), each element is integrated within a single sheet.

In FIG. 1(C), the polarization directions of adjacent elements are opposite to each other, and therefore, the coupling between adjacent elements is established by connecting the surfaces on the same side of the sheet.

That is, FET and 1゛, 1 and 2゛, 2 and 31.3 and 4゛,
4 and ground, and the polarization direction of each element is also aligned along the series circuit, and the structure does not require connection from the A side to the 8th side.

FIG. 1 (D) is an application example of (C).

That is, it has a structure in which adjacent elements are provided with a common electrode 11'', and is functionally the same as (C).

This is an example of a highly practical structure that is extremely effective in utilizing printed wiring technology.

FIG. 2 is a diagram of each structure shown in FIG. 1 viewed from the infrared source side.

(A), (B), (C) and (D) each correspond to FIG.

The infrared sensor with the structure shown in Figures 1 and 2 is F
Connecting to an appropriate electrical circuit, including ET, is handled in the same way as a single element.

It goes without saying that the present invention is applicable to cases where the number of elements is any plurality other than four.

[Effects of the Invention] According to the present invention, the sensitivity is increased compared to a conventional infrared sensor using a single element.

In particular, in the case of an element with low internal resistance, if it is composed of n (>2) elements, a sensitivity close to 0 times that of a single element can be obtained.

The effect of increasing sensitivity will be shown in Examples described later.

Also, an infrared sensor constructed according to the invention has a faster response time than one with a single element.

This is because according to the present invention, the total capacitance of a group of devices integrated in series is reduced compared to that of a single device.

In the present invention, if a plurality of elements are arranged in a sheet, it is convenient because they can be handled as one sheet.

Furthermore, if the polarization directions of the adjacently connected elements are opposite to each other, the structure is such that the electrodes facing the same side of the sheet are connected, which is a structure suitable for printed wiring.

[Example 1 Example 1 Element; Modified lead titanate ceramic N200 (manufactured by Tohoku Metal Industries)? , 5X7, 5XO, 5 (mm)
Silver electrode baking, single area processing chip, surface black ink painting.

Measurement: A flame with a length of 3 cm was lit using a commercially available candle, and the element was placed at a distance of 20c+n so that it could receive light. Average irradiation energy density (40 mW/can2) The shutter was closed, and the output when the shutter was opened was determined. (However, to reduce noise during output, cut off below 1.12Hz.

Results: Shown in Table 1.

Example 2 Element; PZT powder (particle size 5 to 10 μm), mixed epoxy resin sheet 25×20×0.10 (m+n) double-sided copper clad plate (25 μm thick copper) 1 single domain treatment, etching on both sides to form 4×4 (+nm) A pattern is created in which 12 pairs of electrodes are opposed to each other.

A small hole is made in the gap between adjacent elements and a conductive wire is passed through the gap, and the positive and negative electrodes of each element in the polarization direction are successively connected.

Measurement: The element was installed at a distance of 42 ctn from the tongue lamp and the irradiation energy density was 7i4,8+nV.
/Cl112. Light was received through an 8Hz chopper.

Results: Shown in Table 2.

Example 3 Element; C particle size 5 obtained by crushing and classifying N200
0~70μm) Parallel dispersion of powder particles polyimide resin composite sheet 7X5oxo, 5X5 on both sides of o4(m+n)
A pattern of 8 pairs of silver-deposited electrodes (mm) facing each other was created, and single-domain processing was performed to form 8 elements. At this time, adjacent elements are processed so that the directions of polarization are opposite to each other. Next, the electrodes are connected in series by silver vapor deposition.

That is, on one side of the sheet, the first and second, the third and fourth,
Silver vapor deposition is applied to connect the fifth and sixth electrodes, and the seventh and eighth electrodes, and on the other side, the second and third electrodes, the fourth and fifth electrodes are connected, and the sixth and seventh electrodes are connected. 1 is connected to ground, and 8th is connected to FET.

Measurement: Conducted under the same conditions as Example 2.

Results: Shown in Table 3.

Example 4 Element: The same element as in Example 3 was used.

Measurement: The element was installed at a distance of 31 cm from the tungsten lamp, the shutter was closed, and then the shutter was opened to determine the output.

Results: Shown in Table 4.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a side view of the structure of the present invention, (A)
shows an example in which the elements are separated and connected in series. (B) shows an example in which elements are formed in the same sheet and connected in series. (C) shows an example in which the polarities of adjacent elements are opposite to each other. (D) shows an example in which a large electrode is used to connect two electrodes to be connected. FIG. 2 is a diagram of the structure of the present invention viewed from the infrared source side. (A) to (D) correspond to those in FIG. 1, respectively. The accompanying numbers 1 to 4 are the surface on the cathode side during polarization, 1゛ to 4゛ are the surface on the anode side, 11 is the electrode shared by the element, 22 is the sheet, 3
3 is a lead wire connecting the electrodes, 44 is a contact point of the lead wire to the front electrode, 55 is a contact point of the lead wire to the back electrode, 66 is a lead wire passing through a through hole in the pyroelectric sheet, and 10 is a lead wire of the element. Arrows indicate polarity direction, 20 indicates FET, and 30 indicates ground. Applicant Sumitomo Bakelite Co., Ltd. Figure 1

Claims (3)

[Claims] (1) Consisting of a plurality of pyroelectric elements having electrodes on both sides and subjected to single-domain processing, some or all of the elements are connected in series as an electric circuit, and each An infrared sensor structure characterized in that the polarization directions of the elements are arranged in the same direction along a series circuit. (2) The structure of the infrared sensor according to claim 1, wherein a plurality or all of the elements are constructed in one sheet. (3) The structure of an infrared sensor according to claims 1 and 2, wherein the polarization directions of adjacent elements are opposite to each other when connected in series.