JPS6011444B2 - Organic temperature sensor composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an organic temperature sensor composition using a conductive organic substance, particularly for flexible linear, strip or planar temperature sensors (hereinafter collectively referred to as planar temperature sensors). The present invention relates to an organic temperature sensor composition suitable as an organic temperature sensor composition.

Organic substances with electrical conductivity were previously only a subject of academic interest, but advances in organic synthesis methods have led to the synthesis of compounds with new physical properties, and technology to control these properties using solid-state chemistry methods is now available. Due to its development, it is now attracting attention from an engineering perspective. Among conductive organic substances, ionic radical salts made of a combination of 7, 7, 8, 8 tetracyanoquinodimethane (hereinafter referred to as TCNQ) and appropriate cation molecules are known to have excellent conductivity. Proposals have been made for heat-sensitive elements, time-limiting elements, capacitors, etc. that utilize these TCN law salts. The present invention relates to an organic temperature sensor using the above-mentioned TCN law salt, and more particularly to a planar temperature sensor suitable for detecting the temperature of a non-point portion such as a linear, planar, or tubular portion.

Conventionally, a temperature sensor using an inorganic oxide (generally called a thermistor) has been widely used as a temperature sensor for detecting the temperature at a certain point.

Since temperature sensors using inorganic oxides have excellent safety and reliability, the practical application of other temperature sensors, especially temperature sensors using organic substances, has been delayed. However, today there is an increasing demand for accurately detecting the temperature of objects that are tubular, planar, or complex in shape, rather than detecting the temperature of a point.

To detect the temperature of such an object, a flexible linear, strip, or planar temperature sensor is required. However, the above-mentioned inorganic oxides are difficult to process into linear, band-like, or planar shapes, and they also lack flexibility, making them unsuitable for use as planar temperature sensors, and they do not have the characteristics generally required for temperature sensors. If there is something that satisfies the requirements, organic materials with good moldability and flexibility are suitable. By the way, a temperature sensor is required to have the following characteristics.

■ Temperature dependence of resistance value, that is, large B constant.

■ The resistance value to be detected is appropriate.

■ Must have excellent heat resistance and moisture resistance. Furthermore, as a linear or planar temperature sensor.

■ Requires flexibility and mechanical strength.

As mentioned above, TCN's conductivity varies depending on the type of cation molecule, but has a wide range of conductivity ranging from 10-3 to 10-100. ), it can be applied as a temperature sensor material.

Applications have already been filed by the same applicant regarding several TCNQ salts that are promising as heat-sensitive materials. For example, in Japanese Patent Application Laid-open No. 51-45685, (N-n.propylpyridinium)ten(TCNQ)-(TCNQ)m(
However, 0.8 mmSI. 5) as a heat-sensitive material, and in addition to this, for example, Japanese Patent Application Laid-open No. 52-151886 describes (N-n.butylpyridinium)-(TCNQ)-(TCNQ)m( However, 0.
6 mm mi 1.1), and (N-n propylthiazolium) ten (TCNQ) in Hakama Seki Sho 52-151888 publication.
- (TCNQ) m (however, 0.8 mm - 1.2), and (N-n.butylthiazolium) ten (TCNQ) - (TCNQ) m (however, 0.7mmSI.2), and (Nn Propylisothiazolium) ten (T
CNQ)-(TCNQ)m (0.8<mSI.5
) are used as heat-sensitive materials, respectively.

Also, in Tokukan Sho 52-152160 (N-n.
propylpyridinium) rX (N-butylpyridinium)
0) "In the specification of Japanese Patent Application No. 52-57293, (N-n.
propylpyridinium), -x(N-n.propylthiazolium)X(TCNQ)2 (where 0<x<0.6)
Inventions have been described in which Sono's solutions such as the following are used as heat-sensitive materials.

All of these TCN law salts have a unique phase transition accompanied by a change in conductivity, and some materials have a large B constant. Therefore, these materials can be applied as unique thermal fuses and as temperature sensors. Furthermore, ``Metal TCNQ salts such as NaTCNQ and N-alkyl quinolinium (TCNQ) x salts have relatively excellent thermal stability, so they can be used as temperature sensors using the LB constant. Since it is a powder material, many efforts must be made to give it moldability, coagulability, and film properties.The simplest method for this purpose and suitable for mass production is polyester, polyimide L. There is a method of forming elements on a flexible polymer substrate such as by screen printing, doctor blade method, gravure printing, etc.A flexible substrate is used as an insulator and can be easily bent freely. In order to take advantage of the characteristics of the flexible substrate and form an element by the above method, the following conditions must be satisfied.
■ The formed film must firmly adhere to both the plastic substrate and the electrode. ■The film formed is TCN
It is necessary to reproduce well the characteristics of regular salt, ■ the film must be uniform and resistant to bending, etc. In order to satisfy these conditions, it is important to use a polymeric material that functions as a film-forming material and an adhesive. A patent application has been filed by the same applicant regarding such polymer materials.
Vinyl acetate copolymers (hereinafter abbreviated as EVA), polystyrene, polyvinyl butyral, and the like have excellent properties as such polymeric materials. However, although the film prepared in this manner is relatively stable as a film consisting only of a binder and a TCN salt, it has the following drawbacks. ■ The thermal stability of the film is
For example, (N1n Propylpyridinium) ten (TC
When NQ)-(TCNQ)m salt is used, even if it is stable, the resistivity value will double after 500 hours and the thermal stability cannot be said to be sufficient. ■ TCNQ in the film
The amount of salt is 50-90%, and considering the current high price of TCNQ, the amount of TC used for practical use is
The amount of salt in NQ must be reduced. Therefore, the purpose of the present invention is to improve the above-mentioned drawbacks of a film consisting only of TCN salt and a binder polymer, and to create a film that is more thermally stable and requires less amount of TCN salt. The present invention aims to provide a planar temperature sensor composition that provides the following properties. In order to specifically explain the background, purpose, etc. of the present invention described above, FIGS. 1 and 2 show the structure of a flexible planar temperature sensor constructed using the composition of the present invention.

FIG. 1 is a plan view, and FIG. 2 is a sectional view. In the figure,
1 is a flexible substrate, and 2 is a pair of electrodes, which are formed in close contact with the substrate 1. Reference numeral 3 denotes a heat-sensitive body film mainly composed of the above-mentioned conductive organic substance, and the electrode 2 and the substrate 1 are connected between the electrodes 2 and 3.
It is formed in close contact with the

Reference numeral 4 denotes an exterior material film, which is disposed in close contact with the electrode 2, the V heat-sensitive body film 3, and the substrate 1, except for a part 20 of the electrode for taking out lead wires.

As the substrate 1, a flexible substrate of 15 to 500 microns made of polyethylene, polyvinyl chloride, polyester, polyimide, polycarbonate, or the like is selected depending on the purpose. Furthermore, a flexible carbon film having an insulator on the surface, a metal foil such as steel or aluminum, etc. can be used similarly. The electrode 2 is formed by adhering steel foil to the substrate 1 with adhesive, or by screen printing on the substrate 1 using a paste of silver, copper, carbon, etc., and is formed in close contact with the substrate 1. be done. The thermosensitive body film 3 is made by dispersing conductive organic powder in a polymeric binder. A paste made using an appropriate solvent is processed by screen printing, doctor blade method, gravure printing, spray method, wire bar method, etc. formed on a substrate by a method. When a film is formed by these methods, the film thickness is between 2 and 100 microns, considering the particle size of the conductive organic substance, the thickness of the film, or the reproducibility of the resistance value. Binders used in the heat-receptor film include polyvinyl petyral, polyvinyl formal, polyvinylpyrrolidone, polyvinylpyridine, polyvinyl acetate, polystyrene, (ethylene/vinyl acetate) copolymer, (ethylene-vinyl alcohol) copolymer. Copolymer, (vinyl chloride-pinyl acetate) copolymer, etc. can be used. The exterior material 4 protects the heat sensitive body film 3 from the outside air and provides insulation at the same time.It is made by dissolving the same polymer as the polymer binder mentioned above in a solvent and applying it by spraying, brushing, doctor blade, etc.
It is applied to a thickness of 5 to 20 microns by dipping or the like. Further, insulating powder may be added as a filler to this exterior coating, if necessary. Next, the cause of the deterioration of the resistance value of the film formed in this manner will be described.

Infrared spectra of a film sample made of (N-propylpyridinium)-(TCNQ)-(TCNQ)m ethylene/acetic acid bicopolymer whose resistance value has already deteriorated.
The results of analysis using visible spectra and elemental analysis revealed the following. ■ At temperatures below 80°C, there is almost no deterioration due to decomposition and sublimation of TCN salt, and the deterioration in resistance value is mainly due to changes in the contact state of particles. ■100
At temperatures above ℃, the contact conditions change and TCNQ salt decomposes.
Deterioration due to sublimation is added. Therefore, it is conceivable that a stable film can be obtained if measures are taken to prevent thermal movement of particles and prevent changes in the contact state at temperatures below 80°C. For this purpose, it is sufficient to add some kind of additive to fix the particles. Based on this idea, we attempted to create a thermally stable film by adding powder made of inorganic oxide to the composition. The present invention will be described in detail with reference to examples below.
Q) m 6 EVA (vinyl acetate 45) as the polymer binder
%) 4 parts, make a paste using dichlorobenzene as a solvent, and add 3$ of a suitable powdered inorganic oxide.
After blending, the viscosity was adjusted using a solvent and then printed using a doctor blade method (200 openings between the substrate and the blade).

After printing, dry for 1 hour at 100 pm, then dry at 140°C for 30 pm.
Heat treatment was performed for 1 minute. The substrate is polyester and the electrodes are copper. The thermal stability of the film thus prepared at 80 oo is shown in FIG. It can be seen that the thermal stability of the films is significantly improved in all cases compared to the case where no inorganic oxide is added. In particular, it has been found that magnesium oxide (M-mosquito) has an excellent heat stabilizing effect. Example 2 A paste consisting of TCNQ salt and EVA was prepared in the same manner as in Example 1, an appropriate amount of powdered magnesium oxide was added, and the amount of magnesium oxide that could be added was examined.

The results are shown in FIG. When the amount of Mg○ added exceeds 10% of the TCNQ salt, the effect of improving the thermal stability of the film begins to appear, and conversely, in the case of a film containing three times the amount of TCNQ salt, the thermal stability decreases seriously. , it can be seen that when 5 times the amount is added, the thermal stability is lost. It is conceivable that such an addition limit amount changes if the amounts and ratios of the TCN■ salt and the polymer binder are different.

In fact, considering only from the viewpoint of film properties, it is possible to add more magnesium oxide as the amount of polymer/indider increases. To determine the limit amount of addition in such cases,
Regarding the thermal stability of the film, we must consider three points: ■ reproducibility of resistance-temperature characteristics, and ■ film properties. Based on these requirements, we conducted experiments to determine the limit amount of addition when the ratio of TCNQ salt and EVA binder is different. The results are shown in Table 1. The minimum value of the effective addition range in Table 1 is the point at which the thermal stabilizing effect begins to appear in the film.

The maximum value for a system with a TCNQ salt/EVA ratio of 80/20 is determined from the viewpoint of film properties, and the maximum value for a system with a TCNQ salt/EVA ratio of 40/60 is determined from the viewpoint of reproducibility of resistance-temperature characteristics. It can be fully expected that such an additive effect is also effective when a polymer binder other than EVA is used.

Next, we will discuss such an example. Example 3 A paste consisting of 6 parts of TCN salt and polystyrene (4 parts) was prepared in the same manner as in Example 1, and various inorganic oxides (3 parts) were added to improve the thermal stability of the film. Examined.

The results are shown in FIG. Even when the polymer binder is polystyrene, the printed film shows a remarkable improvement in thermal stability by adding an inorganic oxide, and this effect is also similar to that of EVA.
It can be seen that it is almost the same as in the case of . In the above example, T
(N-propylpyridinium)-(TCNQ)-(TCNQ)m salt, which exhibits a phase transition, was used as the CN law salt, but such a technique cannot be applied to the T
It goes without saying that it is also effective against CN gong salt.

Also, other TCNQ salts, such as Na(TCNQ),
K (TCNQ), Li (TCNQ), Cu (TCNQ)
, NMP (TCNQ), and other TCN rule salts can be commonly applied to all cases where conduction when a film is created is mainly due to contact with TCN nail salt particles. Example 4 A paste was prepared using 6 parts of Na (TCNQ) finely powdered by reprecipitation method as a TCN rule salt, 4 parts of EVA (vinyl acetate 45%) as a polymer binder, and chlormephthalene as a solvent. Three sparse portions of appropriate inorganic oxides were added and blended, and printed by screen printing.

The thermal stability of the prepared film at 95 qo is shown in FIG. As described above, even when the TCNQ salt is Na(TCNQ), the thermal stability of the printed film is significantly improved by the addition of an inorganic oxide.

In the case of salts that do not exhibit such a phase transition, the requirements for the limit amount to be added are not as strict as in the case of TCN salts that exhibit a phase transition, from the viewpoint of reproducibility of resistance-temperature characteristics, but the thermal stability of the film and Due to the two requirements that the resistance value be appropriate, it is not preferable that the upper limit of the amount added exceeds 3 times the amount of TCN salt. As described above, the present invention provides an improved thermosensitive composition that improves the thermal stability of the printed film, which is the most important property when used as a planar temperature sensor for TCN treated salts.

[Brief explanation of the drawing]

FIG. 1 is a plan view of a flexible planar temperature sensor using the composition of the present invention, FIG. 2 is a cross-sectional view thereof, and FIG. 3 is a (N
-n-propylpyridinium) (TCNQ) - (TC
Figure 4 shows the thermal stability characteristics of the film at 80:00 when an inorganic oxide is added to the printed film consisting of NQ)m and EVA.
80 when various amounts of magnesium oxide were added to printed films consisting of CNQ)-(TCNQ)m and EVA.
Figure 5 shows the thermal stability characteristics of the film at oC.
n-propylpyridinium) ten (TCNQ)-(TCN
Figure 6 shows the thermal stability characteristics of a printed film made of Na (TCNQ) and EVA when an inorganic oxide is added to a printed film made of Na (TCNQ) and EVA. It is a figure which shows the thermal stability characteristic of the film|membrane at 95:00 when added. 1...Flexible substrate, 2...Electrode, 3
...Thermosensitive body film, 4...Exterior film. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6

Claims (1)

[Scope of Claims] 1. An organic temperature sensor composition comprising at least 7,7,8,8-tetracyanoquinodimethane salt, a polymer binder, and magnesium oxide. 2. The organic temperature sensor according to claim 1, wherein the amount of magnesium oxide added is 0.1 to 3.0 times that of 7.7.8.8.tetracyanoquinodimethane salt. Composition.