JPH11310739A - Conductive ink composition and flat heating element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a conductive ink composition which can form a coating film having a low volume resistivity and good PTC characteristics and has suitability for coating or printing and to provide a flat heating element prepared by using the same. SOLUTION: There are provided a conductive ink composition containing a solvent, a crystalline polymer particles, an amorphous polymer, and a conductive substance, wherein the crystalline polymer is one dispersible in the solvent at ordinary temperature and compatible with the solvent at a temperature of 40-140 deg.C and having a mean particle diameter of 0.2-100 μm, the amorphous polymer is one soluble in the solvent at ordinary temperature, and the weight ratio of the crystalline polymer particles to the amorphous polymer is 50:40 to 95:5 and a flat heating element prepared by using the same.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive ink composition and a sheet heating element using the same, and more particularly to a conductive ink composition having low volume resistivity, good PTC characteristics, and excellent flexibility and mechanical strength. The present invention relates to a conductive ink composition which can form an excellent coating film, can be easily produced, and has properties suitable for application or printing, and a sheet heating element using the same.

[0002]

2. Description of the Related Art A planar heating element is obtained by printing or applying a conductive ink composition on a substrate to form a coating film having an arbitrary thickness and shape. It is used as a small shape and small heating element. As a conductive ink composition used for the sheet heating element, a base polymer such as a crystalline polymer or an amorphous polymer and a conductive material such as carbon black, metal powder, and graphite are dispersed in a solvent. Are used.

A conductive ink composition using a crystalline polymer such as polyethylene as a base polymer is an excellent conductive ink composition capable of forming a coating film exhibiting a steep PTC characteristic with a rise in temperature. The PTC characteristic is manifested when the chain of the conductive substance is broken by the volume expansion of the crystalline polymer due to a temperature change, and the resistance increases accordingly. For this reason, a conductive ink composition using a crystalline polymer exhibiting a steep PTC characteristic is used in a planar heating element obtained by applying or printing the same, for example, when the ambient temperature rises. This has the advantage that thermal runaway due to temperature rise can be prevented and burnout can be suppressed.

However, the conductive ink composition using the crystalline polymer cannot obtain properties suitable for coating or printing because the base polymer does not dissolve in a solvent. Productivity decreases,
In addition, there is a problem that gelation easily occurs during low-temperature storage. Furthermore, the coating film obtained by printing or coating this on a substrate has insufficient mechanical strength and flexibility,
Had been a problem.

[0005] There is also a conductive ink composition using a non-crystalline polymer such as ethylene-propylene rubber as a base polymer. Since the base polymer is dissolved in the solvent, the conductive ink composition has properties suitable for application or printing, and has excellent workability during application or printing. However, since the conductive ink composition using this non-crystalline polymer has a moderate thermal expansion due to a temperature rise, the PTC property of a coating film obtained using the same is also moderate. For this reason, for example, when the ambient temperature rises, or when the sheet heating element is unexpectedly exposed to adiabatic conditions, the heat generation temperature may rise and cause burnout due to thermal runaway, which is a problem. Was. Therefore, it is necessary to provide an overheating prevention mechanism or the like corresponding to the use environment in the sheet heating element using this, which has been a problem.

Further, a conductive ink composition using both a crystalline polymer and a non-crystalline polymer as a base polymer has been proposed. Specifically, non-crystalline polymers such as natural rubber and synthetic rubber, crystalline polymer particles such as polyethylene and polyester incompatible with the non-crystalline polymers, conductive carbon black, graphite and inorganic fillers Have been proposed. This conductive ink composition has both the advantages of the crystalline polymer particles and the advantages of the non-crystalline polymer, and in particular, exhibits excellent stability with a small decrease in resistance even in an extremely cold environment. It is a thing.

[0007]

However, in this conductive ink composition, since the volume resistivity of a coating film obtained by printing or coating the conductive ink composition on a substrate is high, it is necessary to obtain a desired calorific value. There is an inconvenience that it is necessary to make the electrode interval as narrow as about 1 mm, which has been a problem.

Accordingly, the present invention solves such a problem and has the advantage of forming a coating film having good PTC characteristics of crystalline polymer particles, and the property suitable for coating or printing of a non-crystalline polymer. It is another object of the present invention to provide a conductive ink composition which has an advantage of having a low viscosity and has a low volume resistivity. It is another object of the present invention to provide a planar heating element using the conductive ink composition.

[0009]

The object of the present invention is to provide a solvent containing a solvent, crystalline polymer particles, an amorphous polymer, and a conductive material, wherein the crystalline polymer particles are dispersed in a solvent at room temperature. ,
It is compatible with the solvent at a temperature of 40 to 140 ° C. and has an average particle diameter of 0.2 to 100 μm, and the amorphous polymer is soluble in the solvent at room temperature. Further, the problem can be solved by a conductive ink composition in which the weight ratio between the crystalline polymer particles and the non-crystalline polymer is 60:40 to 95: 5. Also, the problem is:
The problem can be solved by using a sheet heating element using the conductive ink composition.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
As the crystalline polymer particles used in the conductive ink composition of the present invention, those having an average particle diameter of 0.2 to 100 μm, preferably 1 to 50 μm are used. When the average particle diameter is less than 0.2 μm, the viscosity of the ink increases, and the ink becomes unsuitable for coating or printing, and the productivity of the sheet heating element using the ink decreases, which is not preferable. In addition, when the particles having an average particle diameter exceeding 100 μm are used, problems such as pinholes are likely to occur in a coating film obtained by using the particles, which is not preferable.

As the crystalline polymer particles, those which are compatible with the solvent at a temperature of 40 to 140 ° C. are preferably used. It is not preferable to use a solvent that is compatible with the solvent at a temperature of less than 40 ° C., because the workability in preparing the conductive ink composition deteriorates. On the other hand, when a conductive ink composition which is compatible with a solvent at a temperature exceeding 140 ° C. is used, the dispersed state of the crystalline polymer particles and the non-crystalline polymer when the coated or printed conductive ink composition is dried. Is not preferable because the volume resistivity of a coating film obtained using the same becomes high.

As the crystalline polymer particles, for example, polyamide, polyester, low molecular weight polyethylene, polypropylene, trans-polybutadiene, polyoxymethylene, polystyrene, polyoxyethylene, polyoxypropylene, polyvinyl chloride and the like are used. Specifically, for example, a crystalline polyamide (trade name: polyamide S)
-1962, melting point 117 ° C, manufactured by Sanyo Chemical Industries, crystalline polyester (trade name: Aronmelt PES-110, manufactured by Toa Gosei Chemical) and the like are preferably used.

As the non-crystalline polymer used here, any one can be used as long as it has a crystallinity of 5% or less and is soluble in a solvent at room temperature. Copolymer of ethylene and vinyl acetate, acrylic acid, acrylic acid ester, maleic acid, etc., polyester,
Natural rubber, various synthetic rubbers such as isoprene rubber, nitrile rubber, and ethylene propylene rubber, and alkyl acrylate polymers are used. Specifically, for example,
Saturated polyester (trade name: Byron 200, manufactured by Toyobo) or the like is preferably used.

Further, as the conductive substance, conductive carbon black, graphite, metal powder and the like are used. The conductive carbon black here has a small structure and a relatively large particle size of about 30 to 150 μm, for example, HAF, SRF, GPF,
Those classified by type names such as FEF and FT are used. As the graphite, flakes of natural graphite and artificial graphite, clay lumps and the like are used.

The solvent is preferably one that can dissolve the non-crystalline polymer well and stably disperse the crystalline polymer particles. Specifically, for example, hydrocarbon solvents such as toluene, xylene, mineral spirit, solvent naphtha, and tetralin; polyhydric alcohol derivative solvents such as butyl cellosolve, cellosolve acetate, butyl carbitol, and carbitol acetate;
Ester solvents such as -butyl, methoxybutyl acetate and γ-butyrolactone are preferably used.

The preparation of such a conductive ink composition comprises:
This is performed by adding and dispersing crystalline polymer particles, an amorphous polymer, and a conductive substance in a solvent.
These operations are performed using a wet dispersion device, for example, a Dyno mill or a three-roll mill. Further, the degree of dispersion of the conductive ink composition is confirmed using a particle gauge or the like. In some cases, it is preferable to add the crystalline polymer particles to the solvent after using such a dispersing device.

In this preparation, the weight ratio of the crystalline polymer particles to the non-crystalline polymer in the solvent is from 60:40 to 9
5: 5 is preferred. If the weight ratio is less than 60:40, good PTC characteristics cannot be obtained, which is not preferable. If the ratio exceeds 95: 5, properties suitable for application or printing cannot be obtained, and the mechanical strength and flexibility of a coating film obtained by printing or applying the composition on a substrate are insufficient. Is not preferred.

The amount of the conductive substance added to the solvent is in the range of 5 to 80 parts by weight based on 100 parts by weight of the combination of the crystalline polymer particles and the non-crystalline polymer. Is preferred. Further, the amount of the solvent used here is not particularly limited, but is 80 to 400 parts by weight per 100 parts by weight of the combination of the crystalline polymer particles and the non-crystalline polymer.
It is preferably about parts by weight.

In such a conductive ink composition, crystalline polymer particles are dispersed in a solvent at room temperature,
At a temperature of, it is compatible with the solvent, so that the dispersion state of the crystalline polymer particles and the non-crystalline polymer at the time of forming the coating film becomes good, so that the volume resistivity is low and a good PT
A coating film having C characteristics can be formed.

Since the crystalline polymer particles are crystalline polymer particles having an average particle diameter of 0.2 to 100 μm, the crystalline polymer particles have properties suitable for coating or printing. In this case, the printing or coating operation becomes easy, and the productivity can be improved. In addition, the coating film obtained by using this hardly causes defects such as pinholes, and a good coating film can be obtained.

Further, since the weight ratio between the crystalline polymer particles and the non-crystalline polymer is 60:40 to 95: 5, the advantages of the crystalline polymer particles and the non-crystalline polymer can be further exploited. And a conductive ink composition capable of forming a coating film having excellent flexibility and mechanical strength.

The sheet heating element of the present invention is a sheet heating element using the conductive ink composition. This planar heating element
A coating film comprising the conductive ink composition is formed on a substrate provided with a conductive layer.

As the substrate used here, a resin film of polyethylene terephthalate (PET), polyimide, polyvinyl chloride, or the like having a thickness of about 10 to 100 μm is generally used. Sometimes, a material having a high heat-resistant temperature is desirable.

The electrodes provided on the substrate include an electrode formed by screen-printing an ink-like composition containing conductive particles such as silver, copper, and carbon on the substrate in a predetermined pattern. Through an adhesive, a metal foil such as a copper foil, an aluminum foil, and a silver foil having a thickness of about 10 to 50 μm, preferably a silver foil is bonded, and an etching process is performed thereon, and a fine pattern such as a comb shape or a zigzag shape is formed. And an electrode formed by forming a desired pattern such as a simple pattern.

In order to manufacture such a planar heating element, a conductive ink composition is applied or printed on a substrate provided with a conductive layer to form a coating film. This coating or printing can be performed by using any method capable of obtaining a coating film having a uniform thickness, and is preferably performed by, for example, screen printing, a method using a knife coater or a gravure coater. During this production,
The used conductive ink composition is dried at a temperature of about 80 to 150 ° C. for about 1 to 30 minutes using a heater or a furnace to form a coating film having a thickness of about 10 to 50 μm.

Since such a sheet heating element uses the conductive ink composition, it is excellent in workability in printing or coating the conductive ink composition and can be easily manufactured. Becomes In addition, the sheet heating element has low volume resistivity, good PTC characteristics, and excellent flexibility and mechanical strength.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to embodiments. (Preliminary test) Crystalline polyamide (trade name: polyamide S-1962, melting point 117) in carbitol acetate
° C, manufactured by Sanyo Chemical Co., Ltd., crystalline polyester (trade name: Aronmelt PES-110, manufactured by Toagosei Chemical), high-density polyethylene (trade name: HIZEX 2100J, melting point: 1)
(27 ° C., manufactured by Mitsui Chemicals, Inc.) at a concentration of 35 wt% to prepare dispersions. The dispersions thus obtained were each heated, and the state was observed.

As a result, in the dispersion using the crystalline polyamide and the crystalline polyester, it is apparent that the crystalline polyamide and the crystalline polyester in the solvent are dissolved at a temperature of 90 ° C. to form a transparent solution. Was. On the other hand, in the dispersion using the high-density polyethylene, it became clear that the high-density polyethylene in the solvent did not dissolve even when heated to 140 ° C.

(Examples 1 to 5, Comparative Examples 1 to 4) Crystals similar to those used in the preliminary test were ground in 200 parts by weight of carbitol acetate to the average particle size shown in Table 1. Polymer particles selected from crystalline polyamide, crystalline polyester, and high-density polyethylene, and a non-crystalline polymer copolymerized polyester (trade name: Byron 20)
0, manufactured by Toyobo Co., Ltd.) and 25 parts by weight of carbon black (trade name: Denka Black, manufactured by Denki Kagaku Kogyo Kogyo Co., Ltd.) were added, and the mixture was stirred and kneaded with a three-roll mill. An ink composition was prepared.

This conductive ink composition was applied on a substrate made of polyethylene terephthalate on which a silver electrode pattern having a spacing of 50 mm was previously provided, in an area of 10 × 60 mm ² and a thickness of 20 ± 3 μm. After drying for a minute, a coating film was formed to prepare a sheet heating element.

The following items were measured and evaluated for each of the sheet heating elements of Examples 1 to 5 and Comparative Examples 1 to 4 obtained as described above. [Volume resistivity] The volume resistivity at room temperature (20 ° C) was measured. [PTC resistance change magnification] The volume resistivity at a temperature of 20 to 150 ° C was measured. Next, the ratio of the maximum value of the volume resistivity obtained in the temperature range of 20 to 150 ° C. to the volume resistivity at room temperature (20 ° C.) (the PTC resistance change magnification) was determined. [Presence / Absence of Pinhole] The presence / absence of a pinhole of the sheet heating element was visually examined. [Resistance change due to winding] Sheet heating element and outer diameter 1
The electrical resistance value of the sheet heating element wound around the 0 mm rod halfway was measured, and the flexibility and mechanical strength of the sheet heating element were examined. If the electric resistance value in the state of being wound around the rod is within ± 20% of the rate of change of the electric resistance value in the state of not being wound, the resistance is determined to be “nothing” by the winding,
Good flexibility and mechanical properties. Table 1 shows the results.

[0032]

[Table 1]

From Table 1, it was found that Examples 1 to 5 had a high PTC resistance change ratio, had no pinholes, and were excellent in flexibility and mechanical strength. On the other hand, in Comparative Example 1 using crystalline polymer particles having a large average particle diameter, pinholes occurred. In Comparative Example 2 in which the number of the crystalline polymer particles was less than the preferred range, the result was that a sufficient PTC resistance change magnification was not obtained. On the contrary, in Comparative Example 3 in which the number of the crystalline polymer particles was large, the resistance was increased by winding. And resulted in poor flexibility and mechanical properties. Furthermore, Comparative Example 4 using high-density polyethylene as the crystalline polymer particles did not provide a sufficient PTC resistance change magnification.

[0034]

As described above, in the conductive ink composition of the present invention, the crystalline polymer particles are dispersed in a solvent at normal temperature and are compatible with the solvent at a temperature of 40 to 140 ° C. Since the dispersion state of the crystalline polymer particles and the non-crystalline polymer at the time of forming the coating film is improved, the conductivity is low so that the coating film having a low volume resistivity and good PTC characteristics can be formed. It can be an ink composition.

Furthermore, by making the crystalline polymer particles into crystalline polymer particles having an average particle diameter of 0.2 to 100 μ,
The conductive ink composition has properties suitable for application or printing, and can be used to produce a conductive ink composition that is easy to print or apply when producing a sheet heating element. Also,
A coating film obtained by using this is less likely to cause problems such as pinholes, and can be a conductive ink composition from which a good coating film can be obtained.

Further, by setting the weight ratio between the crystalline polymer particles and the non-crystalline polymer to be 60:40 to 95: 5, the advantages of the crystalline polymer particles and the non-crystalline polymer can be further enhanced. A conductive ink composition that can be utilized and can form a coating film having excellent flexibility and mechanical strength can be obtained.

Since the sheet heating element of the present invention uses the above-described conductive ink composition, it has excellent workability in printing or applying the conductive ink composition, and can be easily manufactured. In addition, a sheet heating element having excellent flexibility and mechanical strength can be obtained. Further, a planar heating element having low volume resistivity and good PTC characteristics can be obtained. Therefore, it is not necessary to use the sheet heating element to reduce the electrode interval.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Nobutada Hyakutake 5-3-1-1, Sakurada, Washinomiya-cho, Kita-Katsushika-gun, Saitama Prefecture Fujikura Kasei Co., Ltd.

Claims (2)

[Claims] 1. A solvent, comprising crystalline polymer particles, a non-crystalline polymer, and a conductive material, wherein said crystalline polymer particles are dispersed in a solvent at room temperature, and
It is compatible with a solvent at a temperature of ~ 140 ° C, and has an average particle size of 0.2 to 100 µm. The non-crystalline polymer dissolves in a solvent at room temperature, A conductive ink composition, wherein the weight ratio between the polymer particles and the non-crystalline polymer is 60:40 to 95: 5. 2. A sheet heating element using the conductive ink composition according to claim 1.