JPH10183039A - Printing ink for self-temperature-controlling heater - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a printing ink which realizes an ideal PTC print heater which has excellent PTC characteristics, easily controllable film thickness, and a film print film. SOLUTION: A vinyl acetate-ethylene copolymer having a vinyl acetate content of 12-35wt.% as the base polymer is compounded with 3-70wt.% at least one kind of conductive particles [such as carbon particles (e.g. particles of graphite, carbon black, carbon whiskers, or carbon fibers), metal particles (e.g. particles of a metal power or metal foils), or surface-treated particles made electrically conductive by forming carbon or metal thin films on the surfaces of minute chips of potassium titanate or mica by CVD, PVD, or chemical plating] for imparting electrical conductivity to the resultant compsn., finely graded glassy carbon in an amt. of 5-70wt.% of the conductive particles and a phenol- modified terpene resin in an amt. of 5-40wt.% of the conductive particles.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink for producing a self-regulating surface heating element having excellent characteristics by printing. It has been found that not only a sheet heating element having excellent properties can be obtained by the completion of this ink, but also an excellent advantage in the process control of print manufacturing can be achieved. At present, sheet heating elements using this ink are
Not only floor heating, but also snow melting in roofs and parking lots, anti-fog in car mirrors, and as an unusual example, production of dried flowers (JP-A-8-305694).

[0002]

2. Description of the Related Art A system in which conductive particles such as carbon are dispersed in a polymer becomes conductive when the carbon filling concentration exceeds a certain threshold value (called a percolation threshold value). Can be used. Certain of these systems exhibit the property that their electrical resistance increases sharply above a certain temperature. A heating element having this property is usually called a PTC heating element because of its similarity to barium titanate ceramics, or a self-temperature control heating element because of its function. Various techniques have been disclosed for these self-temperature-regulating heating elements, but in principle they can be divided into the following two.

The first principle is that a self-regulating heating element based on a polyethylene glycol-graphite system (JP-A-3-7447)
2, JP-A-3-74473, JP-A-3-42681, etc.), and the electrical conduction in this system is explained by hopping conduction between trapping levels in a thin polyethylene glycol layer interposed between graphite particles, The mechanism of regulation is explained by the change in trap depth at the switching temperature. Details
(T. Kimura and S. Yasuda, Polymer, 37, 2981 (1996))
Please refer to. However, up to now, nothing working on this principle is known other than this polyethylene glycol-graphite system. Therefore, except for the polyethylene glycol-graphite system, all work according to the following second principle.

[0004] The second principle is the thermal expansion of a polymer containing conductive particles. At a low temperature, the particle concentration is set such that the particles come into direct contact with each other to form a conductive path between the electrodes. When an electric current is passed through this, the temperature of the system rises due to Joule heat and the polymer thermally expands. Accordingly, a gap is generated between the particles in contact with each other, and current does not flow. This is the principle of self-temperature control of all systems except the polyethylene glycol-graphite system.

[0005] The technique of the self-regulating heating element by thermal expansion is described in detail in Japanese Patent Application Laid-Open No. 51-76647. Although the polymers used are almost completely covered in the above-mentioned JP-A-51-76647, other polycyanurate compounds (JP-A-5-3
07993), cellulose (JP-A-58-71584), polyvinylidene fluoride (JP-A-58-71585) and the like. Although carbon black and graphite are used as the conductive particles, whiskers, conductive capsules, and the like are also disclosed (JP-A-6-3157827).

[0006] In some of the techniques disclosed so far, the range of the particle size of the conductive particles to be used is indicated. The basis for limiting the range is based on the electrical characteristics and workability of the obtained heating element. It is understood that it is determined in view of the above. It is not disclosed that the range of the particle diameter is determined from other new technical viewpoints.

As for the polymer to be used, it is desirable that the polymer does not have a very large coefficient of thermal expansion up to the switching temperature and exhibits a large coefficient of thermal expansion up to the switching temperature. To achieve this, it is essential to use a polymer with high crystallinity.
The crystalline polymer exhibits a sharp change in density, that is, a change in thermal expansion at the melting point.

[0008] Next, as a method of manufacturing a sheet heating element, a method of melt-mixing a polymer and conductive particles and molding with an extruder or the like is generally used. (JP-A-6-96843, JP-A-58-71584,
JP-A-63-66035 and JP-A-63-66036). In the molding method using an extruder or the like, the resistance value jumps by several digits at the switching temperature, but the result of the above-described printing method shows that the resistance value change at the switching temperature is several times.

[0009]

The production of a heating element by a printing method has various advantages as compared with the molding of an extruder or the like. First, in the case of producing a planar heating element having an irregular shape, the molding method is disadvantageous. For example, when a permanent hair set dryer is made of a sheet heating element, the completed heating element becomes hemispherical, so that the sheet heating element in which the hemisphere is developed into a plane must be made. In such a case, the printing method is advantageous. Other anti-fog heaters in automotive mirrors also require a nearly elliptical shape and a non-trivial electrode configuration, so the printing method works well. By using the printing method, it is possible to print directly on an object, a part, or the like to be heated. For example, a floor panel or the like on which a PTC heater is already printed is possible, and construction and electrical work can be performed simultaneously as one process. A method other than printing requires an operation of separately incorporating a completed heater.

[0010] Despite the usefulness of the printing method described above, PTC print heaters manufactured by printing are unfortunately PTC print heaters.
Poor properties. In the case of a molding method such as an extruder, although the resistance value increases by several orders of magnitude at the switching temperature, the increase in the resistance value is generally low in the printing method, and in the disclosed results, the increase is only about several times. ing. Therefore, enhancement of PTC characteristics is indispensable for manufacturing a print heater that is rich in constant temperature, energy saving and safety by the printing method.

[0011] The next problem is that the obtained ink makes it possible to print a PTC print heater by printing.
Even if the characteristics are obtained, there may be some problems in controlling the film thickness of printing. This can be solved in principle by customizing the polymer, but another solution is needed in view of the real economics. Therefore, production of an ink capable of controlling a printed film thickness is also one of the issues.

Finally, an excellent PT whose film thickness can be easily controlled.
As a problem after the ink giving the C characteristic is completed, there is a problem of the strength of the printed film. In many cases, a printed film having high strength is desired depending on the use conditions. Excellent PTC characteristics, easy film thickness control during manufacturing, and the final solid printed film will result in an ideal PTC print heater.

[0013]

That is, a copolymer of vinyl acetate and polyethylene (hereinafter abbreviated as EVA), wherein the vinyl acetate content in the copolymer is 12% by weight or more and 35% or more.
A printing ink for a self-regulating heater using a polymer having a weight percent or less as a base polymer provides the ideal PTC print heater. Obtaining inherently excellent PTC properties and producing inks are at odds with one requiring a crystalline polymer and the other requiring an amorphous polymer. By using an EVA that has both crystalline polyethylene and amorphous polyvinyl acetate at the same time, and selecting a vinyl acetate content that makes use of both properties, an excellent PTC with these contradictory properties This enables a print heater ink having characteristics.

[0014] The above-mentioned base polymer is coated with carbon fine particles such as graphite, carbon black, carbon whiskers, and carbon fibers, metal fine particles such as metal powder and metal foil, or potassium titanate or mica fine particles on the surface of CV.
Self-temperature control by containing 3 to 70% by weight of one or more conductive particles such as surface-treated fine particles that have been made conductive by forming a carbon or metal thin film by D, PVD or chemical plating Conductivity was imparted to the printing ink for the heater.

Until now, there has been no other method of controlling the print film of the print heater than to finely control the viscosity of the ink. Therefore, the film thickness is controlled and an arbitrary film thickness is obtained by adding 5 to 70% by weight of finely divided glassy carbon to the conductive particles of each ink.

EVA has a somewhat weak printed film in nature.
Even if an ink having excellent PTC characteristics and easily controllable film thickness is obtained, it may not be possible to use the ink due to insufficient film strength in some cases. In the present invention, the strength of the printed film is enhanced by adding 5 to 40% by weight of a phenol-modified terpene resin to the EVA ink.

[0017]

First, the cause of the poor PTC characteristics of a print heater manufactured by a conventional printing method will be clarified. First of all, PT based on thermal expansion
In order for the C characteristic to be exhibited, a sharp change in the density of the base polymer at the switching temperature is required, and therefore, the polymer needs to have high crystallinity. For example, a system in which carbon is dispersed in polyethylene shows excellent PTC characteristics, whereas a polybutadiene-carbon system
No PTC properties are exhibited. This is because the former shows a high degree of crystallinity, while the latter is almost amorphous. Therefore, it is essential to use a crystalline polymer in order to realize high PTC characteristics.

However, when a printing method is used, an ink must be produced using a mixture of a polymer and conductive particles. Generally, an amorphous polymer has higher solubility in a solvent, and in the case of crystallinity, there is a problem in solubility in a solvent. For example, polyethylene is a polymer that provides excellent PTC properties as a base polymer for PTC heating elements. However, the solvent that dissolves polyethylene is limited, and a polyethylene-carbon based printing ink is practically impossible.

Even if a good solvent exists for the crystalline polymer, there is a problem in the coating film after printing. In the case of an amorphous polymer, there is no problem in the film formability after printing, but in the case of a crystalline polymer, a clean film is often not obtained. Therefore, an amorphous polymer rich in crystallinity and unavoidable in the printing method is used. As a result, only low PTC characteristics can be obtained. Therefore, in order to manufacture a print heater having excellent PTC characteristics by a printing method, it is necessary to simultaneously have two contradictory elements.
That is, a crystalline polymer is desirable for excellent PTC properties, and an amorphous polymer is desirable for printing.

As a method for simultaneously realizing these two contradictory properties, an ethylene-vinyl acetate copolymer (EVA) having a highly crystalline polyethylene portion and an amorphous polyvinyl acetate portion in one molecule is used. ) Was selected from among those that served the purpose. Even if you say EVA, in the case of EVA with high vinyl acetate content, the amorphous part is strongly reflected and high PTC characteristics cannot be obtained. Conversely, when the vinyl acetate content is low, the solubility in a solvent is reduced, and a printing ink cannot be produced. Therefore, the vinyl acetate content in the EVA should be in the range 12-35% by weight, preferably 17-30% by weight.

EVA as a polymer for PTC heating elements has already been disclosed previously. However, this is EVA
Merely shows the potential as a polymer constituting a PTC heating element, but does not disclose an ink manufacturing technique for a PTC print heater. In fact, a good PT as described below
For the manufacture of print heaters with C characteristics, the types of EVA are limited, and EVA cannot be anything.

As shown in the examples below, we have excellent
We clarified what the concentration of vinyl acetate in EVA should be for the production of print heaters with PTC characteristics, and completed the invention of print heater printing inks with excellent PTC characteristics. As a result, as a print heater ink that fully demonstrates PTC characteristics, the vinyl acetate concentration is 35% by weight or less.
It was concluded that preferably 30% by weight or less.

On the other hand, from the viewpoint of the solubility of EVA in a solvent, the solubility or swelling of an EVA having various vinyl acetate contents in a solvent (tetralin) was determined. If the polymer is completely dissolved in the solvent, it can be made into an ink in principle. Also, even if it could not be dissolved within the allowed time, it was found that if it swelled enough, it could be made into an ink, and the conditions for making the ink were that the vinyl acetate content in the EVA was 12% by weight or more, It has been found that the content is preferably 17% by weight or more.

The following is a technique relating to film thickness control. The film thickness after printing depends of course on the polymer used. The molecular weight of the polymer, the degree of swelling in a solvent, and the like are factors that determine the film thickness. When the polymer is specified, the viscosity of the ink is a factor that controls the film thickness after printing. Then, if controlling the viscosity solves the problem, it may not actually be the case. Ink naturally contains not only polymer but also carbon and the like, and the malleability of the ink itself is actually an important item for printing. Therefore, the required viscosity is often difficult to implement in practice.

The present invention is to use the conductive particles which are classified for controlling the film thickness after printing. Spherical carbon having a particle size of 5 to 20 μm is sized and the particles are aligned with an accuracy of ± 1 μm, and 5 to 70% by weight of the conductive particles is added. Since the ink obtained by adding the carbon has particles in the print film forming only the first layer, the particle diameter of the carbon determines the film thickness after printing. This is shown conceptually in FIG. At present, such carbon is available as glassy carbon. Since this carbon alone has slightly lower conductivity, it is necessary to simultaneously add small carbon of a highly conductive particle type.

Generally, a print heater is 10 to 20 μm.
A film thickness of the order of magnitude is desirable. However, depending on the polymer, a great deal of labor such as viscosity adjustment or the like may be required to obtain this thickness. However, by using the carbon having the separated particle size, these efforts can be easily reduced. The carbon concentration for controlling the film thickness varies somewhat depending on the viscosity of the ink, but is about 5 to 70% by weight. However, the carbon concentration for controlling the film thickness is not so strict. An almost constant film thickness can be obtained whether it is more or less than the optimum value. Actually, the carbon concentration for film thickness control is determined not from the viewpoint of film thickness control but from the viewpoint of resistance value control. In fact, if the fine particles of carbon used for the conductive reinforcement are selected widely from graphite to carbon black, the range of the carbon concentration for controlling the film thickness that can be obtained is considerably widened.

If a constant film thickness is to be obtained by a printing method without using such a film thickness control carbon, the viscosity of the ink must be strictly controlled. Often, inks with the required viscosity may be virtually impossible. Therefore, the thickness can be controlled very easily by adding the carbon having the sorted particle size for the thickness control according to the present invention (see FIG. 1).

As described above, the invention of a print heater exhibiting excellent PTC characteristics by using EVA having a limited vinyl acetate concentration range and adding carbon for controlling the film thickness has been attained. The last remaining problem is the strength of the printed film.
Depending on the type of use of the print heater, the strength of the print film may not always be satisfactory. Compared with PE, the film strength of EVA certainly decreases considerably depending on the vinyl acetate concentration. Therefore, as long as EVA is used, a decrease in film strength cannot be avoided. However, it has been found that the addition of the phenol-modified terpene resin increases the strength of the printed film. It was found that adding the phenol-modified terpene resin at a concentration of 5 to 40% by weight based on EVA can contribute to an increase in film strength.

[0029]

EXAMPLE An example in which the relationship between PTC characteristics and the content of vinyl acetate in EVA was first determined will be described. Example 1 EVA having a vinyl acetate content shown in Table 1 was prepared. Melt and mix graphite (Japanese graphite, J-SP) into 68 parts of each EVA, press between Teflon plates and press, mold to 2 mm thickness, 20 x 20 mm, provide electrodes with silver paste on both sides, temperature and The relationship of volume resistance was determined.

[0030]

[Table 1]

FIG. 2 shows the results. In the figure, a) shows the case of EVA having a vinyl acetate content of 41.9% by weight.
The vinyl acetate concentration decreases in the order of c), and g) and h) are for polyethylene. It can be seen that as the vinyl acetate content decreases, the PTC characteristics improve and the maximum resistance temperature shifts to the higher temperature side. When the vinyl acetate content of a) is 41.9% by weight, the ratio of the maximum resistance to the resistance value at 20 ° C. is only 14.5, whereas
As the vinyl acetate content decreases, this ratio increases by three orders of magnitude.
The ratio of the maximum resistance to the resistance at 20 ° C. is plotted in FIG. 3 with respect to the vinyl acetate content in the sample. Although there was some variation in the experimental results, it was excellent as can be seen from FIG.
It can be seen that to achieve PTC, the vinyl acetate content should be less than 35% by weight, preferably less than 30% by weight.

Example 2 For each 30 g of the polymer shown in Table 1, sample numbers 1 to 3
(Vinyl acetate content 41.9 to 25.0% by weight), 200 g of tetralin (solvent);
After stirring for 24 hours at room temperature,
The solvent was filtered to determine the weight of the polymer swollen with tetralin, and the degree of swelling was evaluated by the following equation. Swelling degree (%) = (Polymer weight after swelling−Polymer weight before swelling) / Polymer weight before swelling × 100

In the case of sample No. 1 (vinyl acetate content: 41.9% by weight), the sample was completely dissolved. FIG. 4 shows the relationship between the degree of swelling and the vinyl acetate content of the other samples determined by the above equation. The swelling degree of sample Nos. 2 and 3 exceeded 400%, and it was possible to form an ink at room temperature by adding carbon to the swollen polymer, kneading the mixture, and gradually adding tetralin while stirring. . Other samples could not be inked at room temperature.

Then, for sample Nos. 4 to 8, 200 g of tetralin was added to 30 g of the polymer in the same manner.
Stirred at 10 ° C. for 1 hour. Sample No. 4 (vinyl acetate content 17.
(8% by weight), it was almost completely dissolved in tetralin, and after cooling, carbon was added and kneaded, and tetralin was added to form an ink. In the case of Sample Nos. 5 and 6, although they swelled greatly at 110 ° C., they solidified firmly when cooled, making it impossible to form an ink. Sample numbers 7 and 8 hardly swelled as a matter of course. From these results
It is concluded that for inking EVA, the lower limit of vinyl acetate content in EVA is approximately 12% by weight, preferably 17% by weight.

Example 3 59 parts of EVA having a vinyl acetate content of 25% by weight and 41 parts of graphite (J-SP) were mixed in a planetary mixer at 120 ° C. in a vacuum, and tetralin was added little by little to the same amount as the composition. In addition, ink was made. The viscosity of the ink was adjusted to 5000 cp. Thickness 100
A μm PET film was used as a printing material, and silver paint (Dotite D-51, Fujikura Kasei) was printed to form electrodes.
Print on this with the above-mentioned ink, distance between electrodes 60 mm, length 25
A heating element of mm was created. The printing of the electrodes and the heater was all performed by screen printing. After printing in an infrared drying oven 10
Dry at 0 ° C. for 3 hours. The thickness of the printed layer after drying was 17 μm. The sheet heating element was insulated with foamed polyethylene having an upper part of 20 mm and a lower part of 100 mm, and a current of 100 V was applied. As shown in FIG. 5, the heating element rises to near the saturation temperature in 5 minutes and reaches almost the saturation temperature in 10 minutes. Achieving the target temperature quickly in such a short time reflects excellent PTC characteristics (the ratio of the local maximum resistance to the room temperature resistance is three digits or more).

Embodiment 4 The following example relates to an anti-fog heater for a door mirror of an automobile. In the case of a car, the power supply is 12V, and the mirror during running is cooled. Therefore, the purpose cannot be sufficiently achieved unless the calorific value is increased more than the normal condition, so that the distance between the electrodes needs to be considerably reduced. FIG. 6 shows an electrode configuration diagram of this heater.

The ink used in Example 3 was further diluted with tetralin to have a viscosity of 3500 cp. It has been empirically found that it is better to lower the viscosity somewhat because the electrode pattern is fine. Printing and drying were performed in the same manner as in Example 3. The printed film thickness after drying was 13 μm. In the example of FIG. 6, the collecting electrodes 2a and 2b on both sides in the longitudinal direction of the PET film 1 having a size of 70 × 140 mm, and the comb-shaped electrodes 3a and 3b are alternately formed therefrom.
Printed at 1.5 mm width and 6 mm intervals. A 100 mm styrene foam was placed on the lower part of the heater, and nothing was placed on the upper part except for the temperature measurement sensor. DC 12 V was applied, and the relationship between the energizing time and the heat generation temperature was determined. In this case, since the upper portion of the heater is completely open, the saturation temperature is somewhat lower than in the case of the third embodiment. Since the heat generation temperature is determined by the balance between the energy input speed and the energy loss speed due to natural cooling, it is a problem that cannot be avoided under a large heat loss condition in which one side is in a free state. However, if the initial resistance before energization is made sufficiently low, a considerable improvement can be obtained, but the fact that a large current flows at the moment when the switch is turned on is generally not preferred due to the problem of a spare battery. Therefore, under the condition of a large cooling rate such as outside of a running car, it is practical not to reduce the initial resistance but rather to increase the heat generation temperature somewhat.

Example 5 This relates to a heater for a permanent dryer. The dryer is of a so-called shell type, and the heater incorporated therein is almost a hemispherical type. Therefore, the planar heating element must be molded in a shape of a developed plane view of a spherical surface.
FIG. 8 shows an electrode configuration diagram of this heater.

The ink was manufactured as follows. 54 parts of EVA with 25% by weight of vinyl acetate and soil graphite (Nippon Graphite ASP) 46
Mix the parts in a vacuum at 117 ° C with a planetary mixer,
Tetralin was gradually added to this composition to form an ink. The viscosity of the ink was adjusted to 4800 cp. Next, thickness 150μ
After printing and drying the collective electrodes 2a and 2b and the comb-like electrodes 3a and 3b on a PET film 1 of 300 mm x 300 mm as shown in FIG. FIG. 9 shows the relationship between the power-on time and the heat generation temperature. In this example, the initial resistance at room temperature is designed to be higher, and is designed to be about 43 ° C. when used in a dryer.

Example 6 39 parts of EVA having a vinyl acetate content of 25% by weight and 41 parts of graphite (J-SP) were mixed in a planetary mixer at 120 ° C. in a vacuum, and tetralin was added little by little to the composition. Viscosity 2000
~ 6000cp of ink was produced. Using these, 100μm
After printing on PET fabric and drying, the relationship between the thickness of the printed film and the viscosity of the ink was determined and is shown in FIG. FIG. 10 shows that the film thickness changed from approximately 10 μm to 20 μm as the ink viscosity increased.

As a thickness controlling carbon, Univex micro-sphere-shaped glassy carbon (Unitika) is sized to obtain a particle size of 1
7 ± 1 μm was prepared. Next, 39 parts of EVA having a vinyl acetate content of 25% by weight, 32.8 parts of graphite (J-SP), and 8.2 parts of the above-mentioned glassy carbon were mixed in a planetary mixer at 120 ° C. in a vacuum. As described above, tetralin was gradually added to this composition to produce an ink having an ink viscosity of 2000 to 6000 cp. Printing on 100μm PET fabric using these, to determine the relationship between the thickness of the printed film after drying and the viscosity of the ink,
As shown in FIG. As can be seen from FIGS. 10 and 11, when carbon for adjusting the film thickness is not added, the film thickness strongly depends on the viscosity of the ink. However, when the classified glassy carbon is added, the film thickness is not much affected by the viscosity of the ink. In other words, in order to obtain a constant film thickness, if there is no thickness control carbon, the viscosity of the ink must be finely controlled, but glassy carbon whose particle size has been sieved to a value close to the target film thickness is added. By doing so, a constant film thickness can be obtained without paying much attention to the ink viscosity.

Example 7 This is an example in which the strength of the printed film can be increased by adding an additive to the ink. Here, 59 parts of EVA having a vinyl acetate content of 25% by weight and 41 parts of graphite (J-SP) were mixed in a vacuum at 120 ° C with a planetary mixer, and tetralin was gradually added to this composition to form an ink. 6000
Adjusted to cp. This was printed on a 150 μm thick PET film and dried. The strength of this film corresponded to a pencil hardness of approximately 2B. On the other hand, EVA59 with a vinyl acetate content of 25% by weight
Parts, 16.4 parts of a phenol-modified terpene resin (Hercury Co., Picofin T-125) and 41 parts of graphite (J-SP) were mixed in a planetary mixer at 120 ° C. in a vacuum, and tetralin was gradually added to the composition. Make ink and increase viscosity to 6000cp
Was adjusted. This was printed on a 150 μm thick PET film and dried. This film has increased strength and pencil hardness of 2H
Was equivalent to Comparing the two films, the film to which the phenol-modified terpene resin was added had a smooth and glossy surface. It can be seen that the film density increased and the strength improved.

[0043]

According to the conventional print heater, a polymer having a large number of amorphous portions had to be used, and as a result, the ratio of the maximum resistance to the resistance at room temperature is only several times the PTC characteristic. Only known. Therefore, EVA, which has both crystalline polyethylene, which is an essential element of PTC characteristics, and amorphous polyvinyl acetate, which is an essential element for printing inks, has PTC characteristics and ink-forming and printing characteristics. By selecting the vinyl acetate content so that it has the same function, it became possible to manufacture ink for print heaters with high performance PTC characteristics.

Conventionally, there has been no method for controlling the thickness of the print heater other than controlling the viscosity of the ink. This was a very severe condition for process control. However, the thickness can be easily controlled by adding the classified glassy carbon for controlling the thickness. This not only eliminates the need for strict control of the viscosity of the ink, but also allows the selection of a free thickness in units of ± 1 μm.

The use of EVA having a selected vinyl acetate content makes it possible to produce a print heater having excellent PTC characteristics. In addition, by adding a glassy carbon particle for controlling the thickness, the thickness of the printed film can be reduced. Control becomes easy, and an arbitrary thickness can be selected. But EV
The A film has essentially low film strength. In this regard, by adding a phenol-modified terpene resin, the film strength was sufficiently enhanced.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of film pressure control using particles.

FIG. 2 is a graph showing the relationship between temperature and resistance of graphite-various polymer compositions.

FIG. 3 is a graph showing the relationship between the ratio of the maximum resistance to the resistance value at 20 ° C. and the concentration of vinyl acetate.

FIG. 4 is a graph showing the relationship between the content of vinyl acetate in EVA and the degree of swelling with respect to tetralin.

FIG. 5 is a diagram illustrating a relationship between a current-carrying time and a heat-generation temperature of a sheet heating element according to a third embodiment.

FIG. 6 is an electrode configuration diagram of an anti-fog heater of a door mirror of an automobile.

FIG. 7 is a diagram illustrating a relationship between a heating time and a heating time in Example 4.

FIG. 8 is a configuration diagram of a heater for a permanent dryer.

FIG. 9 is a diagram illustrating a relationship between an energization time and a heat generation temperature in a fifth embodiment.

FIG. 10 is a diagram illustrating a relationship between ink viscosity and a printing film.

FIG. 11 is a graph showing the relationship between the viscosity and the film pressure of ink to which fine-grained glassy carbon is added in Example 6.

[Explanation of symbols]

 1 PET film 2 Collective electrode 3 Comb electrode

Claims (4)

[Claims] 1. A copolymer of vinyl acetate and polyethylene.
(EVA) A printing ink for a self-temperature-regulating heater, comprising a polymer having a vinyl acetate content of 12% by weight or more and 35% by weight or less in the copolymer as a base polymer. 2. A copolymer of vinyl acetate and polyethylene.
(EVA), wherein a polymer having a vinyl acetate content of 12% by weight or more and 35% by weight or less in the copolymer is defined as a base polymer, and a polymer such as graphite, carbon black, carbon whisker, carbon fiber, etc. Conductivity such as fine particles, metal powder, metal fine particles such as metal foil, or surface-treated fine particles that have been made conductive by forming a carbon or metal thin film on the surface of potassium titanate or mica fine pieces by CVD, PVD or chemical plating One or more of the conductive particles
Printing ink for self-temperature control heater containing 70% by weight. 3. The printing ink for a self-temperature-regulating heater according to claim 2, further comprising 5 to 70% by weight of the classified glassy carbon based on the conductive particles in the ink. 4. The printing for a self-temperature controlling heater according to claim 2, wherein the phenol-modified terpene resin is contained in an amount of 5 to 40% by weight based on a copolymer of vinyl acetate and polyethylene (EVA) in the ink. ink.