JPS6314457B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a planar pyroelectric element for a pyroelectric thermal image pickup tube and a method for manufacturing the same, and the present invention relates to a planar pyroelectric element with high resolution and high sensitivity, and a planar pyroelectric element that can be manufactured with high yield. The purpose is to provide a method for

Conventionally, in order to obtain a temperature distribution image of a two-dimensional surface of an object using infrared rays, two methods have been used: a combination of a point-like infrared detector and two-dimensional mechanical scanning of an optical system, and a combination of a two-dimensional infrared detection surface and electron beam scanning. combination,
That is, there was a camera tube type one. In the former combination, a single point detector measures many pixels sequentially in time to obtain a temperature distribution image on a two-dimensional surface. _{1- xCd} The drawback is that it is large and expensive. On the other hand, in the latter type of image pickup tube, each pixel is detected by one element of the planar detector, so the detector may have a slightly longer time constant, so cooling is not required, and the device is compact. It has the advantage of being lightweight and low cost. In recent years, pyroelectric infrared detectors have been put into practical use as planar elements, replacing thermistors with low sensitivity, and devices with high sensitivity and excellent time constants are being developed, but they still have many problems.

The physical properties required of the pyroelectric materials used in these materials include a large pyroelectric coefficient P _T (coul/cm ² °C), a high Curie temperature T _C 5 (°C), and an electrical resistivity ρ (Ω・cm) is small, and thermal conductivity K (W/cm°C) and thermal diffusion coefficient χ (cm ² /S) are small. In addition, what is required when producing an image pickup tube is that it has excellent stability in vacuum, workability, heat resistance, operability, and the like. The reason why a large pyroelectric coefficient P _T is necessary is to increase the pyroelectric current j _T obtained by the surface charge induced in response to a temperature change of the detection element. Also, the reason why a high Curie temperature T _C is necessary is that the Curie temperature
This is because if a pyroelectric material with a low T _C of, for example, 100° C. or less is used, it will not lose its pyroelectric effect and will no longer function as an element if the surrounding temperature rises. The reason why a low electrical resistivity ρ is necessary is to prevent negative charges from being accumulated on the planar pyroelectric device due to electron beam scanning when the planar pyroelectric device is used as a target for an infrared imaging tube. The reason why it is necessary that both the thermal conductivity K and the thermal diffusion coefficient χ are small is from the viewpoint of sensitivity such as spatial resolution and excessive resolution. Regarding processability, these planar pyroelectric elements have thin films to reduce the heat capacity of the detection element on the surface against external thermal stimuli and infrared rays, and to increase response speed and sensitivity for temperature rise and fall. However, due to strength issues, the thickness must be approximately several tens of micrometers, so it must be easy to make it thin.

Conventionally, TGS was used as this pyroelectric infrared detection element.
(triglycine sulfate), PVF ₂ (polyvinylidene fluoride), single crystal PbTiO ₃ (lead titanate) PZT, Pb ₅ Ge ₃ O ₁₁ (lead germanate), etc. have been reported.

Considering these items for each typical pyroelectric material, TGS is the Curie temperature T _C
(T _C = 49℃), has deliquescent properties, and has a
Because it decomposes at 150°C, it is difficult to incorporate it into image pickup tubes, etc. It is a tetragonal ferroelectric material.
PbTiO ₃ has a high Curie temperature T _C (=470℃) and a large pyroelectric coefficient P _T (P _T =6×10 ^-8 coul/
cm ² °C), and has relatively good sensitivity, but has the disadvantage of poor spatial resolution due to the large thermal diffusion coefficient χ (χ = 9.9×10 ^-3 cm ² /S). However, by forming grooves on the surface of the element, the thermal diffusion coefficient can be effectively reduced. However, since it is necessary to process from a single crystal to a thin body, a large amount of time and material loss occur, leading to an increase in costs. PVF ₂ has a slightly lower Curie temperature T _C of 120°C, but since it is an organic substance, it is easy to process into thin films and has a small thermal diffusion coefficient, but its sensitivity is not very good (P _T = 0.24
×10 ^-8 coul/cm ² ℃). In addition, lead germanate (Pb ₅ Ge ₃ O ₁₁ ) has T _C = 178℃, P _T = 0.5×
10 ^-8 coul/cm ² ℃), and is a hexagonal crystal that is practically the second material for infrared detection elements after PbTiO ₃ .
However, this has a large electrical resistivity ρ (ρ=3
×10 ¹² Ωcm). In the end, there was a problem in that it was not possible to obtain a product that satisfied all the requirements such as physical properties and thinning of the material.

The present invention solves this problem by locally applying thermal energy to an amorphous thin body mainly composed of ferroelectric material to crystallize it into a dot matrix shape. To provide a highly sensitive planar pyroelectric element and a method for manufacturing the same, by arranging the crystallized parts and orienting the C-axis direction of each crystallized crystal in a direction perpendicular to the ribbon surface. It is.

Hereinafter, the configuration of the present invention will be explained in detail using FIGS. 1 and 2.

FIG. 1 is a schematic cross-sectional view of a ribbon manufacturing apparatus used to carry out the manufacturing method of the present invention, and FIG. 2 is a perspective view showing an example of the planar pyroelectric element of the present invention.

In the figure, 1 is a quartz tube containing a sample 3 heated and melted by a heater 2 .

A diameter of 0.5 mm is provided at the bottom of the quartz tube 1 by pressurizing with an inert gas such as Ar gas or _N2 gas.
A pair of stainless steel rollers 5 with a diameter of 50 to 200 mm rotate in close proximity to each other and in opposite directions at 500 to 4000 rpm.
An amorphous ribbon 6 having a thickness of 10 to 50 μm was obtained by ejecting the mixture into the gap, rapidly cooling and solidifying it.

In addition, as sample 3, for example, as a ferroelectric material,
Methods for producing ordinary ceramics from pyroelectric materials mainly composed of Pb ₅ Ge ₃ O ₁₁ , PZT barium titanate PbTiO _{3 ,} etc., namely, blending, mixing, drying, calcining, pulverizing, and drying of starting materials. A sintered body created through a series of steps of grain molding and final firing was used. This amorphous thin body 6 was irradiated with a laser beam having a diameter of 1 to 2 μm, and only the irradiated portion was heated and crystallized. By performing this light irradiation two-dimensionally at regular intervals, crystallized portions 8 and amorphous portions 7 were formed like the eyes of the base.

The C-axis direction of the crystal of the crystallized portion 3 thus formed was oriented in a direction perpendicular to the ribbon surface, as shown by arrow 9.

Next, examples of the present invention will be described.

Example 1 Polycrystal made using ceramics synthesis method
30g of PbTiO ₃ was heated to 1200°C using the equipment shown in Figure 1.
melted in a quartz tube with 0.3Kg/ ^cm2 Ar gas,
A thin amorphous film 6 with a thickness of 20 μm is sprayed into the gap between a stainless steel roller 5 with a diameter of 100 mm rotating at 1000 rpm.
I got it.

A piece with an area of 3 cm x 5 cm was made from this thin strip. A ruby laser light pulse (1msec) with an output of 1W focused to a diameter of 1.5μm is applied to this amorphous ribbon.
was irradiated to form crystallized portions 8 with a diameter of .mu.m at 7.0 .mu.m intervals in the shape of a dot matrix, thereby producing a planar pyroelectric element. We also measured its characteristics. As a result, the temperature resolution is approximately 0.5℃, compared to conventional single crystal films.
Compared to the resolution of 1 to 2° C. using PbTiO ₃ , a device with significantly improved characteristics was obtained.

Example 2 5 mol% of SiO ₂ to facilitate amorphization
Added Pb ₅ Ge ₃ O ₁₁ to make polycrystals, of which 50
g was melted at 1000℃ in the same manner as in Example 1 to give 0.4Kg/cm ²
Ar gas was ejected onto a stainless steel roller 5 with a diameter of 100 mm rotating at 800 rpm to obtain an amorphous thin body with a thickness of 15 μm. Thereafter, as in Example 1, the crystallized portions 8 with a diameter of 6.0 μm are arranged at 8.0 μm intervals in a dot matrix shape, and the crystals are oriented so that the C axis is perpendicular to the surface of the ribbon. and created a planar pyroelectric element. As a result of measuring its characteristics, the temperature resolution was approximately 0.3℃, which showed excellent characteristics.

As described above, according to the present invention, since the dot-shaped crystallized portion and the surrounding amorphous portion can be made to exist on the same plane, Compare the charge with that of a crystal
It is possible to quickly cause leakage to the amorphous portion, which has an electrical resistivity ρ that is 10 ⁵ to 10 ⁶ times smaller. Therefore, for example, Pb ₅ Ge ₃ O ₁₁ has a large electric resistance value, so it solves the conventional drawback of charging up, and furthermore, in the process of crystallizing from an amorphous body,
Since the C-axis is aligned perpendicular to the film surface, the crystal direction with the highest pyroelectric coefficient can be used (pyroelectric effects are not observed in other crystal directions), providing a planar pyroelectric element with high sensitivity and high resolution. can do.

In addition, according to the present invention, by using the liquid ultra-quenching technique, a thin body with a thickness of several tens of micrometers can be easily obtained, and conventionally, when producing a thin body from a single crystal, it is possible to obtain a thin body with a thickness of several tens of μm. It is possible to provide a method that can greatly reduce the amount of time, difficulty in processing, and material loss, and easily manufacture the above-mentioned high-sensitivity, high-resolution planar pyroelectric element at a high yield.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view of a ribbon manufacturing apparatus used to carry out the manufacturing method of the present invention, and FIG. 2 is a perspective view showing an example of the planar pyroelectric element of the present invention. 1... Quartz tube, 2... Heater, 3... Melted sample, 4... Nozzle hole, 5... Stainless steel roller, 6... Amorphous ribbon, 7... Amorphous body part,
8... Crystallized portion, 9... C-axis orientation direction.

Claims (1)

[Scope of Claims] 1. A crystalline ferroelectric material that has a dot matrix-like pyroelectric effect in a thin ribbon made of an amorphous ferroelectric material, and the C-axis direction is perpendicular to the surface of the ribbon. A planar pyroelectric element characterized by having: 2 Form an amorphous ribbon of ferroelectric material that has a pyroelectric effect, and locally heat the amorphous ribbon in a dot matrix shape using a laser beam to crystallize it. 1. A method for manufacturing a planar pyroelectric element, characterized in that a crystalline ferroelectric material in which the C-axis of the crystal is aligned in a direction perpendicular to the surface of a ribbon is formed in a dot matrix shape.