JPS6046521B2 - 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 use in flexible linear, strip or planar temperature sensors (hereinafter collectively referred to as planar temperature sensors). The present invention relates to suitable organic temperature sensor compositions.

Organic substances with electrical conductivity have traditionally been merely 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 has become 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 thione molecules are particularly famous for their excellent conductivity. , heat-sensitive elements, time-limiting elements, capacitors, etc. using these TCNQ salts have been proposed. The present invention relates to an organic temperature sensor using the above-mentioned TCNQ salt, and 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 tubular, planar, or complex-shaped objects, 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 have poor flexibility, making them unsuitable for use as planar temperature sensors and lacking the characteristics generally required for temperature sensors. If there is a material that satisfies the requirements, organic materials with good moldability and flexibility are suitable. By the way, does the temperature sensor have the following characteristics? required.

1.The temperature dependence of resistance value, that is, the B constant is large.

2. The resistance value to be detected is appropriate. 3 heat resistance,
Must have excellent moisture resistance.

Furthermore, as a linear or planar temperature sensor, it must have 4 flexibility and mechanical strength.

is required.

The TCNQ salt mentioned above has a wide range of conductivity ranging from 10-3 to 1010 Ω·o and an activation energy value (-0.
1 eV to +1.011-V), 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, JP-A No. 51-45685 discloses an invention in which (N-n propylpyridium) + (TCNQ) - (TCNQ) (0.8〈m×1.5) is used as a heat-sensitive material. In addition to this, for example, JP-A-5
No. 2-151886 discloses (N-n.butylpyridinium)+(TCNQ)-(TCNQ). n (but 0.
6cm×1.1), and (N1n・propylthiazolium) + (TCNQ) in Japanese Patent Application Laid-open No. 52-151888.
- (TCNQ) m (0.8 cm × 1.2), and (N-n.butylthiazolium) + (TCNQ) - (TCNQ) m (however, 0.7 cm x 1.2), and (N-n Propylisothiazolium) + (TC
NQ) one (TCNQ) m (however, 0.8 cm × 1.5)
An invention is described in which each of these is used as a heat-sensitive material. Also, in Japanese Patent Application Laid-open No. 52-15216, (N-n
●Propylpyridinium), -x (N-n・butylpyridinium) x (TCNQ)2 (here 0.15 x x 0
．． 90), Japanese Patent Application No. 52-57293 describes (Nn.propylpyridinium), -x(Nn.propylthiazolium) x (TCNQ)2 (where O<X<0.6). The invention describes the use of various solid solutions as heat-sensitive materials. All of these TCNQ salts have unique phase transitions accompanied by changes in conductivity, and some materials have large flux constants. Therefore, these materials can be applied as special thermal fuses and as temperature sensors. Also, metal TC such as NaTCNQ
NQ salt and N-alkyl◆quinolium (TCNQ). Since salt has relatively good thermal stability, it can be considered to be used as a temperature sensor using the B constant. However, since these are all crystalline or powdered materials, they have poor moldability.
Many efforts must be made to impart flexibility and film properties. The simplest and most suitable method for mass production is to form elements on a flexible polymer substrate such as polyester or polyimide by screen printing, doctor blade, gravure printing, etc. There is a way. Flexible substrates are used as insulators and can be bent easily and freely, but in order to take advantage of these characteristics of flexible substrates and form elements using the above method, the following conditions must be met. There must be.

1. The formed film should firmly adhere to both the plastic substrate and the electrode, and 2. The formed film should be TCN.
It is necessary to reproduce well the characteristics of Q, and the three coatings must be uniform and resistant to bending, etc.

In order to satisfy these conditions, it is important to use a polymeric material that can be used as a film-forming material or adhesive. A patent application has been filed by the same applicant regarding such a polymer material, and the (ethylene/vinyl acetate) copolymer (hereinafter referred to as E
VA), polystyrene, polyvinyl butyral, etc. have excellent properties as such polymeric materials. However, although the film prepared in this manner is the most stable of films consisting only of a binder and TCNQ salt, it still has the following drawbacks. Regarding the thermal stability of a film, for example, when using (N-n●propylpyridinium)+(TCNQ)-(TCNQ)m salt, even if it is stable, the specific resistance value doubles after 50 cycles at 80℃. However, it cannot be said that the thermal stability is sufficient.

2 The amount of TCNQ salt in the film is 50 to 90%,
Considering the current high price of TCNQ, the amount of TCNQ salt used must be reduced for practical use.

Therefore, the purpose of the present invention is to improve the above-mentioned drawbacks of a film consisting only of TCNQ salt and a binder polymer, and to create a film that is more thermally stable and requires less amount of TCNQ 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. Figure 1 is a plan view, and Figure 2 is a cross-sectional view.
1 is a flexible substrate, and 2 is a pair of electrodes formed in close contact with the substrate 1. Reference numeral 3 denotes a heat sensitive film mainly composed of the above-mentioned conductive organic substance, which is formed between the electrodes 2 in close contact with the electrodes 2 and the substrate 1.

Reference numeral 4 denotes an exterior material film, which is disposed in close contact with the electrode 2, the 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, etc. is selected depending on the purpose. Furthermore, a flexible carbon film having an insulator on the surface, a metal foil such as copper or aluminum, etc. can be used similarly. Electrode 2 is made of copper foil and adhesive attached to substrate 1, or made of silver,
It is formed by screen printing on the substrate 1 using a paste of copper, carbon, etc., and is formed in close contact with the substrate 1. The thermosensitive body film 3 is made by dispersing conductive organic powder in a polymer binder, and a paste made using an appropriate solvent is processed by screen printing, doctor blade method, gravure printing, spray method, wire purring 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, taking into account the particle size of the conductive organic substance, the thickness of the film, or the reproducibility of the resistance value. Binders used in the thermosensitive body film include polyvinyl butyral, polyvinyl formal, polyvinylpyrrolidone, polyvinylpyridine, polyvinyl acetate, polystyrene, (ethylene-vinyl acetate) copolymer, (ethylene-vinyl alcohol) copolymer, (vinyl chloride-vinyl 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 blading, dipping, etc. The coating was applied to a thickness of 5 to 20 microns. Insulating powder may also be added to this exterior coating as a filler, if necessary.
In order to improve the thermal stability of the film, we first investigated the cause of the resistance value deterioration of the film.

(N-n Propylpyridinium)+(TCNQ)-(TCNQ) whose resistance value has already deteriorated? 9 Infrared spectra of film samples made of ethylene/vinyl acetate copolymer;
As a result of analysis using visible spectrum and elemental analysis methods, the following was clarified. At temperatures below 180°C, there is almost no deterioration due to decomposition and sublimation of the TCNQ salt, and the deterioration in resistance value is mainly due to changes in the contact state of particles.

At temperatures above 2100°C, the contact state changes and deterioration occurs due to decomposition and sublimation of the TCNQ salt.

Therefore, it is conceivable that a stable film can be obtained at temperatures below 80° C. by preventing thermal movement of particles and preventing changes in the contact state. 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 below with reference to Examples. [Example 1] TCNQ was pulverized by reprecipitation method (N-
n.propylpyridinium)+(TCNQ)-(TCN
Q). ．． 60 parts, EVA (vinyl acetate 4
After creating a paste using dichlorobenzene as a solvent, blending with 30 parts of ZnO, TiO2 or CaO powder, and adjusting the viscosity with the solvent, the doctor blade method is applied. (Opening 200 μm between the substrate and the substrate).

After printing, dry at 100°C for 1 hour, then dry at 140°C for 30 minutes.
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°C is shown in Figure 3. It can be seen that the thermal stability of the film is improved compared to the case without additives. [Example 2] A film was prepared in the same manner as in Example 1 except that the polymer binder in Example 1 was replaced with polystyrene instead of EVA, and its thermal stability was examined.

The results are shown in FIG. It can be seen that even when the polymer binder is polystyrene, the printed film exhibits a remarkable improvement in thermal stability by adding an inorganic oxide, and the effect of the addition is almost the same as in the case of EVA. In the above embodiment, TC
(N-n●propylpyridinium)+(TCNQ)-(TCNQ)m salt, which exhibits a phase transition, was used as the NQ salt;
Of course, it is also effective against NQ salt.

Also, other TCNQ salts, such as Na(TCNQ),
K (TCNQ), L1 (TCNQ), Cu (TCNQ)
Even in the case of TCNQ salts such as , NMP (TCNQ), the conduction when a film is created is mainly TCNQ? It can be commonly applied to all cases due to contact of particles. [Example 3] Using (1) part of Na (TCNQ) finely powdered by reprecipitation method as TCNQ salt, EVA (45% vinyl acetate) as a polymer binder, and chlormephthalene as a solvent. A paste was prepared, and an appropriate inorganic oxide and component were added, blended, and printed using a screen printing method.

The thermal stability of the produced film at 95°C is shown in Figure 5.
As described above, even when the TCNQ salt is a metal salt such as Na(TCNQ), the thermal stability of the printed film can be significantly improved by adding an inorganic oxide. Next, Example [,2
, 3, TiO2, CaO
, the effective addition amount of ZnO was investigated.

The minimum value of the effective addition amount is the point at which the thermal stability effect begins to appear due to addition, and the maximum value is the point at which stability becomes worse due to addition than in the case of no addition. As described above, the present invention provides an improved thermosensitive material composition that improves the thermal stability of the printed film, which is the most important property when using TCNQ salt as a planar temperature sensor. .

[Brief explanation of the drawing]

FIG. 1 is a plan view of a flexible planar sensor using the temperature sensor composition of the present invention, FIG. 2 is a cross-sectional view of the same, and FIG. 3 is (N-n.propylpyridinium)+(TCNQ)-
Figure 4 is a diagram showing the thermal stability characteristics of a signet ring film composed of (TCNQ)m and EVA at 80°C when an inorganic oxide is added to the film.
Figure 5 shows the thermal stability characteristics of a printed film made of TCNQ)-(TCNQ)m and polystyrene at 80°C when an inorganic oxide is added.
9 when an inorganic oxide is added to a printed film made of VA
FIG. 2 is a diagram showing the thermal stability properties of the film at 5°C. 1...Flexible substrate, 2...Electrode,
3... Heat sensitive body film, 4... Exterior film.

Claims (1)

[Claims] 1. An organic temperature sensor composition comprising a 7,7,8,8-tetracyanoquinodimethane salt and a polymer binder,
An organic temperature sensor composition characterized by adding powder of ZnO, TiO_2 or CaO. 2. The organic temperature sensor composition according to claim 1, wherein the ZnO powder is added in an amount of 0.1 to 2.5 times the amount of 7,7,8,8-tetracyanoquinodimethane salt. 3. The organic temperature sensor composition according to claim 1, wherein the TiO_2 powder is added in an amount of 0.05 to 2.5 times the amount of 7,7,8,8-tetracyanoquinodimethane salt. 4. The organic temperature sensor composition according to claim 1, wherein the CaO powder is added in an amount of 0.1 to 2.0 times the amount of 7,7,8,8-tetracyanoquinodimethane salt.