JPH08330054A - Flat heater element and manufacture thereof - Google Patents

Abstract

PURPOSE: To provide a thin and flexible flat heater element excellent in homogeneity and durability by weaving a composite yarn mixedly twisted with a metal single yarn and a cotton single yarn into the substrate fabric of electrode sections continued from the substrate fabric of a heating section woven with a cotton yarn. CONSTITUTION: Electrode sections are formed at both end sections, and a heater section is formed between them on a substrate fabric to form a flat heater element. The substrate fabric of the heater section is woven with a cotton yarn. The substrate fabric of the electrode sections is woven with a composite yarn mixedly twisted with a metal single yarn and a cotton single yarn into the substrate fabric continued from the substrate fabric of the heater section, and it is formed to nearly the same thickness and flexibility as those of the substrate fabric of the heater section. The whole substrate fabric separately woven into the electrode sections at both ends and the heater section in the middle is coated with a conductive paint, and power connecting lines are provided on the electrode sections to form a flat heater element. The flat heater element is sealed in a soft vinyl chloride sheet with a heat sealer as required.

Description

Detailed Description of the Invention

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improved sheet heating element, and more specifically, it is thin, flexible and pliable with high durability and excellent bondability between an electrode section and a heating section. With respect to a planar heating element, in particular, even if the surface of the planar heating element is subjected to non-uniform and / or repetitive load on the surface of the planar heating element, electric power is applied to the entire surface of the heating element for a long period of time. The present invention relates to a sheet heating element that can be evenly distributed over the entire surface.

[0002]

2. Description of the Related Art Various sheet heating elements including an electrode portion and a heating portion having a conductive coating material obtained by uniformly dispersing a conductive material in a binder as a heating element have been proposed. For example, Japanese Patent Application Laid-Open No. 63-184670 discloses a snow melting sheet having a flexible sheet heating element and a flexible heat insulator integrally provided on one surface of the sheet heating element. In JP-A-62-21948, a synthetic resin material having flexibility, stretchability and flexibility after fixation is used as a binder, and a conductivity-imparting substance is mixed with the binder. Using the composition described above, a thin film designed to generate heat appropriately is formed on the surface of a knitted woven fabric, a non-woven fabric, or the like to form a heating portion, and then the same kind of binder as described above is used at both ends of the heating portion. A flexible sheet heating element is described in which a conductive thin film is used to form a strip-shaped thin film designed to be capable of supplying an appropriate amount of electric power.

Such flexible sheet heating elements are used for melting snow on roofs and roads, for blankets and carpets, for agriculture, for heating homes, for defrosting home appliances, for defrosting mirrors, and for improving blood circulation. For treatment, for fixing toner images on copiers and printers,
Alternatively, it is widely used for cooking, etc., and the material, structure, and heat resistant temperature of the electrode part and the heat generating part vary depending on the application and purpose of use, but in any case, it has excellent refraction resistance,
There is a constant need for flexible planar heating elements that have high heat generation efficiency, uniform temperature distribution, and can be used reliably for a long period of time even under harsh conditions. Efforts have been made. In particular, since the electrode part and the heat generating part have different roles, many techniques have been proposed for each, and many proposals have also been made for the bonding relationship between the two.

That is, the electrode portion is coated with a conductive paste in some cases (Japanese Patent Laid-Open No. 50-1 / 1975).
No. 04445, JP-A-57-113579,
JP-A-57-113576, JP-A-57-501
No. 308, Japanese Utility Model Application Laid-Open No. 64-2390, etc.), and in some cases, an electrode portion in which a belt-shaped metal is attached to, or sewn on, or screwed to a base fabric (Japanese Patent Laid-Open No. 55-55).
-144682, JP-A-55-146892, JP-A-57-143285, and JP-A-58-5.
No. 986, etc.) has been proposed. Regarding the manufacturing method, Japanese Patent Laid-Open No. 47-44427 discloses a method for producing a paper pulp of mixed paper after applying a conductive paint to both sides of the sheet-like heating element made of the mixed paper with carbon fiber to be the electrode part. By heating and pressurizing until carbonized to integrally form an electrode portion, a method for producing a planar heating element that does not require the use of a copper tape is described, and JP-A-55-144682 discloses. An electrode is formed by placing a shielding plate for a plastic heating element pattern on a metal layer vapor-deposited on a nylon sheet, and irradiating a laser beam to vaporize the metal vapor deposition agent in the metal region leaving the heating element pattern portion. Although making a pattern is described, generally, the former type is considerably less durable and the latter type is less flexible.

Therefore, it has been proposed that the metal yarn is a warp or weft and the other fiber is braided as a weft or a warp, or both the warp and the weft are braided as a metal yarn. For example, JP-A-47-19169 describes the advantage of electrodes which consist of a fine-grained copper woven fabric and which are well adhered to the heating conductor layer and thereby give a very low contact resistance. JP-A-48-5451
No. 9 discloses that a tape is formed by using a conductive wire as a warp thread, a glass thread as a weft thread, and roughening the warp and weft intervals. The tape is brought into contact with a predetermined position of a surface plate of a glass cloth coated with graft carbon. It is described that the metallicon is thermally sprayed and the tape is fixed to the planar plate to form the surface heating plate electrode.

In Japanese Utility Model Laid-Open No. 62-66195, electrode wires attached to both sides of the resistance heating layer in the longitudinal direction in close contact with the resistance heating layer are braided copper foil or ultrafine copper wire having flexibility. Since it is formed of a copper braided wire, the tensile force acting on the electrode wire during the transportation of the carbon heater, the laying work, or the use of the electrode wire makes it relatively easy to break the wire, and the resistance will be applied without knowing this. It is described that a metal protector is provided on the copper braided wire in order to avoid the risk that an overcurrent flows in the heat generating layer and the resistance heat generating layer locally generates abnormal heat. Japanese Utility Model Laid-Open No. 62-66196 discloses a reinforcing wire in a copper braided wire in order to supplement the mechanical strength in the case of a copper braided wire using an ultrafine copper wire in consideration of flexibility, workability and thinness. It is described to weave.

In Japanese Utility Model Laid-Open No. 62-66197, an extra-fine copper wire used in consideration of flexibility, workability and thinness is cut to cut off a current path, so that an excessive current flows to other portions. It is described that a bypass wire is provided in advance between the copper braided wires in order to prevent local concentration and local overheating. Japanese Utility Model Application Laid-Open No. 62-77894 describes that the electrode wire is connected by a braided wire made of fine copper wire so that it can be bent without deteriorating the characteristics of the planar heating element. In Japanese Utility Model Publication No. 62-92591,
In a carbon heater in which the above-mentioned power supply line is provided at both longitudinal edges of an insulating sheet provided with a resistance heating layer formed by mixing carbon into rubber or plastic, the power supply line is provided inside the power supply line. It is described that a power sub-supply line for wrapping and for arbitrarily adjusting the heat generation amount of the resistance heat generation layer is provided.

In Japanese Utility Model Laid-Open No. 62-178492, an electrode wire, for example, a twisted wire in which 5 to 8 thin metal wires are twisted on both edges of a woven cloth for impregnating planar heating element such as cotton cloth, is disclosed. Of 12
Using standard electrode wire, weave in warp or weft and satin weave, apply conductive paint such as carbon paint to the whole surface, and apply an insulating sheet on it to make a sheet heating element. It is also described that the electrode wire is a braided wire, and a plurality of pieces are made of Venetian weave, and the electrode wire 2 is woven on both sides of the woven cloth in the warp direction. Japanese Utility Model Laid-Open No. 63-139788 discloses a conductive sheet in which a vinyl chloride film is attached to one side by applying a conductive adhesive to a woven cloth of a coarse woven structure in which a plurality of wire wires such as copper wires are interwoven. It is described that the cloth sides are laminated facing each other to form the electrode portion of the sheet heating element.

In Japanese Patent Laid-Open No. 63-168990, conductive yarns for heating elements are arranged alternately or every several yarns with respect to the insulating yarns, and a tape-shaped temperature sensor is sandwiched between the insulating yarns.
And a plurality of warp yarns arranged at wide intervals, and a large number of insulating yarns woven into the warp yarns, and an electrode formed by weaving a plurality of dielectric yarns side by side into the warp yarns, A warp group formed by arranging the electrodes in two rows closely spaced from each other at both ends of the warp group, or two rows having one end closely spaced and the other end arranged in a single row; It is described to be composed of. Japanese Utility Model Application Laid-Open No. Sho 64-2390 discloses a thread and polyester, polyamide, aromatic polyamide or the like which are formed by vapor-depositing a conductive member such as nickel, copper or zinc in advance, or by vapor-depositing a conductive member or chemical plating on a fabric. It is described that an organic fiber yarn as a raw material is used as various woven fabric structures such as satin, twill and plain weave to prepare an electrode part. Actual Kaihei 2-
JP-A-140790 discloses that in a planar heating element in which an electrode is arranged on a heating element layer, the electrode is formed by a thread-shaped electrode made of a metal thread-shaped conductor or a cloth-shaped electrode made of a cloth-shaped conductor. A planar heating element is described.

Japanese Unexamined Patent Publication (Kokai) No. 63-6767 describes that in a sheet heating element obtained by paper-making a fibrous heating element, the fibrous heating elements are oriented in alternating directions with respect to the electrode wires. Has been done. Japanese Unexamined Patent Publication (Kokai) No. 5-283151 discloses a sheet heating method in which sheet-like carbon fiber is post-processed to eliminate the occurrence of sheet breakage due to insufficient tear strength in the steps of heater production and unit production. In order to improve the production efficiency in processing, the sheet heating element of the sheet heating element is composed of two or more layers, and a reinforcing net is inserted between any one of the layers, and the reinforcing net is located between the upper and lower paper layers. It is described that each layer is blended with a hot-melt binder fiber and other synthetic fibers, inorganic fibers, and cellulose fibers so that the adhesion will be good.

From these prior arts, the biggest problem in the electrode portion of the planar heating element is the familiarity of how to secure the electrical contact between the electrode portion and the heating portion, and how stable the electrical contact is maintained. It has excellent durability, electrical contact failure caused by shuttle driving tension fluctuation during fabric forming processing, difference in thermal expansion at the time of temperature rise, excessive bending of heat generating part, or change of applied pressure from the outside. It is understood that how to prevent the occurrence of electrical contact failure due to the problem is an important and difficult problem to solve. In fact, an electrode made of a plate-shaped metal or an electrode portion formed by braiding metal threads as warp threads and / or weft threads has insufficient strength and lacks flexibility, and such problems cannot be solved.

On the other hand, as the heat generating portion of the flexible sheet heating element, (1) a heat generating circuit is formed on a corrosion-resistant aluminum alloy foil or copper foil by etching, or a conductive paint is applied or metal is vapor-deposited. A heat-resistant plastic film laminated to form a heat-generating circuit, and (2) a heat-resistant resin film or the like as a substrate, and a heat-generating wire formed by coating a thin metal resistance wire or a heat-resistant fiber with a conductive paint Attached by a method such as sewing or weaving and optionally adhering another film on them, (3) Heat resistant plastic film or woven fabric such as glass woven fabric is used as a substrate and carbon powder type conductive agent is attached , Which is laminated with insulation coating,
(4) Various materials such as one in which carbon fibers are embedded in a heat resistant resin, one in which a woven cloth having carbon fibers is formed, and the like are mentioned. Each of them has advantages and disadvantages, but like the case of the electrode, There is no commercially available product that satisfies various requirements such as durability, uniform heating property, and bending resistance.

In particular, the electrode part and the heat generating part often differ in required material characteristics, structure, flexibility and strength due to the difference in their roles. However, there is a drawback in that, if the material is not firmly joined to the steel sheet and is bent, fatigue embrittlement of the material occurs at this portion, and electrical contact failure or breakage easily occurs.

For example, as shown in FIG. 1, in order to make the electrode part have a sufficient function, a thick, thick, and tough material is adopted, while a heat generating part is made of a thinner base material. When a step is created at the joint between the electrode part and the heat generating part and the conductive paint is impregnated and applied in this state, the step of the conductive paint is created in the step, and if this is dried as it is, the conductive paint The part of the outline becomes hard and brittle, and when the sheet heating element is bent, deterioration and breakage occur from this part. More importantly, in the tamari part, heating, sparking,
It is a cause of fire.

In addition, since metal is generally high in rigidity and the surface is slippery, even when a filament metal and other, for example, synthetic yarn are plain woven, as shown in FIG. 2, a slight eccentric force is applied. "Misalignment" is likely to occur and the texture is apt to be deformed, and when the core of the synthetic fiber bundle is circled, "misalignment" or disconnection is likely to occur as shown in FIG.

[0016]

SUMMARY OF THE INVENTION The object of the present invention is to improve the problems in the prior art as described above, to provide excellent bonding between the electrode portion and the heat generating portion, and to provide a thin and flexible material having high durability. , A flexible sheet heating element, particularly, an improved electrode section, and the entire surface of the sheet heating element even under a condition where a non-uniform and / or repeated load is applied to the surface of the sheet heating element. Another object of the present invention is to provide a sheet heating element in which electric power can be evenly distributed over a long period of time.

[0017]

SUMMARY OF THE INVENTION The object of the present invention is to provide a planar heating element having strip-shaped electrode parts at both ends and a heating part between the electrode parts, and the electrode part and the heat generating part. Part is formed on one base fabric, the base fabric of the heat generating part is braided with a cotton thread, and the base fabric of the electrode part is a cotton yarn continuous from the base fabric of the heat generating part to a metal. Weaving a composite yarn made by mixing and twisting single composite yarn and cotton single composite yarn,
In addition, the planar heating element is characterized in that it has substantially the same thickness and approximately the same flexibility as the base fabric of the heating section. Further, in the sheet heating element of the present invention, in the method for manufacturing a sheet heating element comprising strip-shaped electrode portions attached to both ends and a heating portion attached between the two electrode portions, the electrode portion and the heating portion are provided. Is formed on one base cloth, and the base cloth of the heat generating portion is braided with cotton yarn, and the base cloth of the electrode portion is a continuous cotton thread from the base cloth of the heat generating portion to a metal single yarn and a cotton single yarn. A process of weaving a composite yarn obtained by mixing and twisting a composite yarn, and braiding so as to have substantially the same thickness and approximately the same flexibility as the base fabric of the heat generating portion, and the entire surface of the base fabric. It is manufactured by including a step of coating with a conductive paint and a step of attaching a power source connecting wire to the electrode portion.

The inventors of the present invention are composed of a thin, flexible, and flexible sheet heating element having excellent bonding property between the electrode portion and the heat generating portion and having high durability, and particularly, an improved electrode portion. , Long-term research on a sheet heating element in which electric power can be evenly distributed over the entire surface of the sheet heating element for a long period of time even under the condition that a non-uniform and / or repeated load is applied on the surface of the sheet heating element. And some of the results have already been announced (Shinkaihei 3-8
No. 4584), thereafter, all the factors that can affect the performance of the planar heating element, particularly durability and reliability, such as the structure, material, and manufacturing method of the electrode portion of the planar heating element, are fundamentally studied. The present invention has now been arrived at through examination.

That is, when the electrode portion and the heat generating portion have different required material characteristics, structure, flexibility and strength due to the difference in their roles, the two having different properties are firmly bonded to each other at the joint portion. If not bent and bent, the material is subject to fatigue embrittlement at this portion, and there is a drawback that electrical contact failure or breakage easily occurs. Such a problem is not compensated by the application of the conductive paint, but more fundamentally, it is solved in the base fabric of the sheet heating element, which imposes an excessive burden on the application process of the conductive paint. Without making it possible, we eagerly studied from the standpoint of trying to solve the problem.

When a warp (or weft) made of a metal thread or a strip-shaped metal is braided with the other weft (or warp) to fabricate an electrode portion for a sheet heating element, Bonding with the heat generating part, durability is not enough, lacking in refractive strength, lacking physical strength, and easily generating an uneven heat generating surface. This is because the metal yarn has high rigidity and is hard to blend with other fibers. Because it does not expand or contract so much and it is slippery, it is partly because the structure of the braided fabric itself is easily distorted during the coating and other treatment of the conductive paint and the laying work and use after completion. However, even if it is a twisted yarn of a metal yarn and a yarn made of another material, if the other material is a synthetic fiber other than cotton or a synthetic fiber, it is more difficult to achieve the intended purpose. It is rather possible to add a surface active agent or use conductive particles with an extremely small particle size. PTC characteristics in section (described later)
In case of using a cotton thread as a core and arranging a metal thread around it, even if a cotton thread is used, the intended purpose cannot be achieved. However, the planar heating element and the method for producing the same according to the present invention have been completed based on many findings such as the difference in the results depending on the thickness and the number of twists of the two. Hereinafter, the present invention will be described in detail.

As described above, the sheet heating element of the present invention has strip-shaped electrode portions provided at both ends on the integrated base cloth and the heat generating portions between the electrode portions, and the base cloth is formed. Is of a type in which a conductive paint is coated on the entire surface. In the sheet heating element of the present invention, cotton yarn is used as the material of the base cloth. The present inventors have studied various materials,
It was found that the cotton material not only has high heat resistance as compared with a polymer material such as a thermoplastic polymer material, but is also easily compatible with other metal threads, for example. The heat resistance as referred to herein means not only the combustion resistance but also a change in various physical resistance such as expansion and contraction due to heating as described below.

Since the conventional sheet heating element does not use a cotton material for some reason as a base cloth and the like, it is difficult to fit in with the metal thread, and it itself deteriorates with time, which causes a temperature rise. It may cause a burn or a fire to the user. This is because the heating layer is planar, so if a part of it deteriorates due to some kind of stimulus, the electric resistance value of that part rises, the current that should pass therethrough diverges to the other part, and that current flows in. The result is that the calorific value is increased. Then, as the deteriorated portion increases, the current flowing into the normal portion increases and raises the temperature, and when the temperature reaches the ignition point of the polymer material, combustion occurs. Such abnormal heat generation is mainly due to deterioration over time of the polymer material used for the planar heating element. According to Kirichhoff's steady-state current rule, the larger the number of other bypass paths, the smaller the amount of excess current shared by each path, and therefore the deterioration over time tends to accelerate. Conventionally, a thermoplastic material is used as a polymer material for both the base cloth and the binder in order to impart flexibility to the sheet heating element. Therefore, because of its viscoelasticity, especially viscosity,
If an external force is continuously applied for a long period of time, it deforms and, as a result, the ohmic contact state between the conductive materials in the conductive coating material is physically broken. This leads to localized overheating of the sheet heating element. Such deformation is significantly promoted when an external force is continuously applied under heating.

When the structure of the thermoplastic polymer used as the binder is heated to the glass transition point (Tg) at which its structure changes from the spherulite state to the amorphous state, the volume thereof expands rapidly and is contained therein. The characteristic that physically breaks the ohmic contact between the conductive material particles, that is, the positive temperature characteristic of the resistance in the planar heating element (so-called PTC characteristic; that is, the resistance (Rt) at a certain heating temperature (T)). And the resistance at room temperature (Ro), {Rt >> Ro / e
xp (-ΔE / kT) (where ΔE is the enthalpy change, k
Is a Boltzmann constant)}, and in practice, [Rt >> Ro {(1 + α (T-To)} (where α is the temperature resistance coefficient of a normal metal, that is, about 4.0 × 10 ^-2). / C)] is desired, and a material that easily deteriorates with time is desired, such as the characteristics that are satisfied. It may be improved or imparted with flame retardancy, but none of these can be a fundamental solution.

In the sheet heating element of the present invention, as described above, the base cloth is prepared in advance so that the base cloth itself having the electrode part and the heat generating part has substantially uniform physical characteristics. The electrical characteristics of the two parts are different from each other, and exhibit different desired properties. That is, the planar heating element of the present invention is specifically a planar heating element having strip-shaped electrode portions at both ends and a heating portion between the electrode portions, wherein the electrode portion and the heating portion are It is formed on one base fabric, the base fabric of the heat generating part is braided with cotton yarn, and the base fabric of the electrode part is a continuous metal yarn from a cotton yarn continuous from the base fabric of the heat generating part. A composite yarn obtained by mixing and twisting a cotton single yarn and a cotton single yarn is woven, and the base fabric in the electrode portion is formed by mixing and twisting the metal single yarn and the cotton single yarn in the heat generating portion. It is characterized in that it has approximately the same thickness and approximately the same flexibility as the base fabric after the composite yarn is woven,
The point to be noted here is to use a composite yarn obtained by mixing and twisting a metal single composite yarn and a cotton single composite yarn as the conductive yarn, and when the metal single composite yarn is used instead of the composite yarn, The metal single-plied yarn is different from the cotton single-plied yarn or the cotton yarn in the electrical property as well as in the physical property. In particular,
Both materials have different densities and elasticity. Thus, the mixed yarn in which the single metal composite yarn is twisted without any adjustment or adjustment causes problems such as the slipperiness described above, and tends to become bulky due to the spring (elasticity) force of the metal. . It also tends to be denser. Such difficulties are overcome in the present invention.

In the present invention, the base cloth of the electrode section and the heat generating section is basically braided with cotton yarn, and the electrode section of the base cloth has a plurality of metal single-bonded threads and a single cotton composite thread. The necessary number of composite yarns obtained by mixing and twisting a plurality of the above are woven as warp yarns or weft yarns to form an electrode portion. This base fabric is made of a woven fabric having a yarn thickness of 10 to 50, a warp density and a weft density of 50 to 200 per inch, and a design point of 50 to 5000 points per square inch. When a yarn with a smaller yarn count (thicker yarn) is used, unevenness occurs in the weave, and this unevenness causes the conductive paint to be applied thicker than necessary and unevenly. If it is larger (the thread is thin), the physical strength such as refraction resistance is lacked, and the sheet heating element or the like in which the amount of the conductive material and the binder attached is too small is produced. The weaving density of the threads is preferably about 30 to 80 threads per inch for both the warp threads and the weft threads, but it varies depending on the thickness of the threads used. That is, by selecting the thickness and density of the yarn so that the coating amount is 80 to 130 g per square meter, and the conductive paint is present on the heating surface side and does not reach a large amount on the back non-heating surface, The portion and the electrode portion may have approximately the same thickness and approximately the same flexibility.

Further, when compared with the same thickness and the same density,
Since the woven cloth having a smaller number of texture points is more flexible, the sheet heating element manufactured using the woven cloth has excellent flexibility.
Therefore, when classified by the Mihara structure, a satin weave, a twill weave, or the like can provide a planar heating element having higher flexibility than a plain weave, but in the present invention, a plain weave has sufficient flexibility. Can be obtained. On the other hand, when the single metal wire or the metal yarn as shown in FIG. 3 is adopted, not only the flexibility is lacked but also the warp yarn and the warp yarn constituting the base fabric are deviated.

Further, for example, when the conductive paint is applied, the conductive paint is sufficiently provided on the front and back sides of the base fabric, and the conductive paint does not melt through (to be described later) on the back surface side. In addition, the weaving mode of the warp exposed on both the front and back surfaces of the base fabric can be adjusted. In the invention, in the process of manufacturing such a base cloth, a composite yarn formed by mixing and twisting a plurality of metal single-bonded yarns and a plurality of cotton single-bonded yarns is required as a warp or a weft in the strip-shaped electrode portion. Weave in a certain number. The weaving width, that is, the width of the strip-shaped electrode part, is the distance between both electrodes, the thickness of the heat generating part (heat generation amount per square meter)
However, if the base fabric is plain weave, it is usually about 3 mm.
To about 30 mm, desirably about 5 mm to about 25 mm, preferably 7 mm to about 15 mm, and the required number of weaves is 2 to 20, preferably 7 to 15.

As described above, the present invention has a great advantage in using a specific composite yarn. Here, the inventors of the present invention have referred to as “sliding” in the composite yarn for electrodes, which is made of a metal yarn spirally wound around the core of a conventional synthetic fiber as shown in FIG.
And as a means for avoiding wire breakage, a cotton thread is used instead of the synthetic fiber thread, and both the metal thread and the cotton thread are spirally wound around one side so that they have substantially the same rigidity. We have found that both use twisted ones, as illustrated in FIG. In addition, in order to achieve rigidity and such mutual twisting of both different materials, and to obtain good conductivity, in the case of copper threads and aluminum threads, a cotton thread of approximately the same thickness and a number ratio are used. 3 to 9: within 1 to 3 is the limit, and in the case of copper wire and stainless wire, 1 to 8
Book: 1 to 3, the best result is achieved, for example, in the case of a copper wire, 6 single copper composite yarns having a diameter of 0.007 mm and 2 cotton single composite yarns of 20 count. I found out.

In the inside of the composite yarn, the metal single composite yarn and the cotton single composite yarn are twisted together to have a structure of a gentle spiral three-dimensional structure. The metal single composite yarn in this gentle three-dimensional structure is a partner. It is woven into the base fabric without being distorted so much by being supported by the cotton union yarn. On the other hand, the cotton single-bonded yarn is highly compatible with the conductive paint. Thus, the conductive coating is allowed to penetrate into the internal structure of the composite thread, and after drying, the conductive coating is firmly held in the composite thread structure with a gap to secure more current paths between both electrodes, and Retains its flexibility. Furthermore, when a non-uniform and / or repetitive load is applied to the surface of the electrode portion, it is less likely that the metal single bond system will be disconnected. Therefore, the conductive paint in the sheet heating element of the present invention is disposed inside and on the outer periphery of the material itself of the base cloth of the heat generating portion and the base cloth in which the composite yarn of the electrode portion is woven, and is firmly held. Therefore, it is not always the case that a uniform layer having no holes is formed so as to fill the voids (mesh) of the base fabric. That is, it is different from the planar heating element obtained by uniformly coating the entire surface of a resin film, for example, a polyimide film with a conductive paint. Of course, in many cases, a conductive coating material is applied enough to completely fill the voids (mesh portion) of the base fabric, and as a result, a sheet heating element often appears as if a conductive layer with a uniform thickness is provided. However, the internal organization is different. This makes it possible to avoid the inconvenience of melt-through that tends to occur when laminating the protective sheet, which will be described later.

In the composite yarn used in the present invention, in order to secure the flexibility of the portion which becomes the electrode portion and the required strength, the cotton single composite yarn having a small number of counts and the metal single composite yarn are twisted with a small inter-inch twist. Those twisted by the number are preferable. For example, specifically, as the composite yarn, a twisted yarn composed of 3 to 9 single copper and / or aluminum single composite yarns having a diameter of 0.001 to 0.1 mm and 1 to 3 single cotton single composite yarns of 10 to 50 count. Or 0.001
One 0.1 mm diameter steel and / or stainless steel single yarn
Twisted yarns composed of 8 yarns and 1 to 3 cotton union yarns of 10 to 50 count can be used. Between the number of twists per inch (T1) and the count (N1) of the cotton single-bonded yarn, T1 ≦ K1√N1 (however, K1
Is a twist coefficient, which is 1.5 to 5.0), and T2 ≦ K between the number of twists per inch T2 of the composite yarn and the count N2.
2√N2 (However, K2 is the twist coefficient, 0.01-3.0
Is more preferably used. Thicker composite threads or thinner composite threads make the thickness of the base fabric of the electrode portion significantly different from the thickness of the heat generating portion. Thus, it becomes difficult to apply a desired amount of the conductive coating material to the planar heating element, and when the base material is coated with the conductive coating material, a lump of the conductive coating material occurs at the boundary between the electrode portion and the heat generating portion. .
This causes local heat generation. Further, when the number of twists between inches is larger, not only the flexibility of the portion which becomes the electrode portion cannot be secured, but also the conductive coating does not sufficiently penetrate into the base fabric.

In the present invention, a commercially available conductive paint (a commercially available product, for example, a Fuji paste manufactured by Fujikura Kasei, a silver paste having a viscosity of 250 centipoise (normal temperature) such as FA303) can be used. It is also possible to use a conductive paint prepared by itself.

Here, as the conductive material, carbon black, graphite; metal particles such as copper powder and stainless powder; conductive fibers such as carbon short fiber, stainless short fiber and brass short fiber; tin oxide, zinc oxide, etc. Examples of the metal oxide particles include conductive whiskers, and among them, carbon black is preferable. In the case of conductive particles, the particle size is preferably 15 to 60 μm. Larger conductive particles make it difficult to apply the desired amount and uniform application of the conductive paint, and smaller conductive particles hinder the so-called PTC characteristics of the conductive paint. The preferred carbon black is usually about 20 Ω / c
It has a surface resistance of less than or equal to m and a surface area per gram of less than or equal to 10 m ² .

As the binder, polycarbonate (bisphenol A type, bisphenol Z type), methacrylic acid resin, polyvinyl chloride, polyvinyl acetate resin, polystyrene resin, polyurethane resin, vinyl chloride-ethylene copolymer, phenol resin, acrylic resin Resin, polyester resin, epoxy resin, vinyl chloride-
Vinyl acetate copolymer, vinyl chloride-ethylene copolymer,
Vinyl chloride-propylene copolymer, vinyl chloride-styrene copolymer, vinyl chloride-butadiene copolymer, polyvinylidene chloride resin, vinylidene chloride copolymer, vinyl chloride-acrylic acid ester copolymer, vinyl chloride-maleic acid Ester copolymer, vinyl chloride-methacrylic acid ester copolymer, vinyl chloride-acrylonitrile copolymer, vinyl chloride-vinylidene chloride-vinyl acetate terpolymer, polyvinyl butyral resin, polyvinylcarbazole resin, silicone resin, silicon modification Resins and the like can be used, and these can be kneaded and used. In particular, polyvinyl chloride and vinyl chloride-ethylene copolymer can be preferably used. These binder resins can be preferably kneaded and used in an amount ratio such that the binder resin has a Tg (glass transition point) in consideration of the upper limit heat generation temperature of the sheet heating element.

The conductive coating material is composed of 10 to 1000 parts by weight of the conductive material with respect to 100 parts by weight of the binder, for example, preferably 30 to 70 parts by weight of carbon black with respect to 100 parts by weight of the normal plastic resin, N, N'-dimethyl. Formamide, acetone, methyl ethyl ketone, xylene, chloroform, 1,2-dichloroethane, dichloromethane, monochlorobenzene, tetrahydrofuran, dioxane,
It is prepared by mixing in an appropriate amount of a solvent such as methanol, ethanol, isopropanol, ethyl acetate, butyl acetate, dimethyl sulfoxide, trichlene. However, before mixing in a solvent, a conductive material such as carbon black,
Mixer for graphite, metal particles, metal plated particles, etc. with binder and Henschel mixer, Banbury mixer, etc.
It is preferable to knead with a kneader, an extruder, a roll mill, a kneader, an intermix, or the like. And a solvent can be used in this kneading process, and necessary plasticizers, for example, dibutyl phosphate, dioctyl phosphate, phosphate plasticizers such as diheptyl phosphate,
Phthalates such as dibutyl phthalate, dioctyl phthalate, diheptyl phthalate, glycol oligomers, polyesters such as trimellitic acid ester, phenylsulfonic acid alkylamide, 2-ethylhexanol alkyl ester, dihexyl adipate, dioctyl adipate, polyethylene Flexibility can be imparted by adding a plasticizer such as glycol monoalkyl ether adipate.

With respect to this plasticizer, in the conventional sheet heating element, in order to be used for bending, a binder, for example, a large amount of plasticizer such as 80 parts by weight per 100 parts by weight of the soft polyvinyl chloride resin is generally used. However, if the heating element is used at a high temperature for a long period of time, the plasticizer in the conductive paint migrates to the binder and the binder swells, resulting in a decrease in conductivity and a decrease in adhesive strength with the underlying fabric. However, there was a problem in maintaining the stable performance of the sheet heating element. If the content of the plasticizer is reduced, the above-mentioned problems are solved, but the flexibility is lowered thereby, and there is a new problem that the coating film of the conductive paint is broken by repeated fatigue due to bending, which is a win. Further, the use of a large amount of plasticizer often makes temperature control difficult, such as impairing the preferable PTC characteristics of the coating film of the conductive paint. On the contrary,
In the case of the sheet heating element of the present invention, the addition amount of the plasticizer can be extremely small. For example, in polyvinyl chloride resin, vinyl chloride 100
1 to 5 parts by weight is sufficient per part by weight, and therefore, a planar heating element which does not change in flexibility and does not change in resistance value even after long-term use is provided. For the same reason, it is possible to avoid adding a large amount of plasticizer, and thus it is possible to produce a desired planar heating element without impairing the preferable PTC characteristics.

The prepared conductive paint has a temperature of 1000 to 1 at room temperature.
It has a viscosity of 0000 cp and is applied to a base fabric in which a composite thread is woven in a portion which will be an electrode portion. The coating is performed by a roll coater method, a rubber doctor method, a wire bar coater method, an air knife coater method, a dip coater method, a screen printing method (a printing method), for example, a silk screen printing method, a gravure printing method, a spray method, a gun spray method, a rotary centrifugal method. It can be carried out by a conventionally known method such as a plate method (shaking off method) or a combination of these methods.

The amount and thickness of the conductive paint applied depend on the desired output of the sheet heating element and the distance between both electrodes of the sheet heating element (the amount of current between the two electrodes of the sheet heating element is Is inversely proportional to the distance and proportional to the square of the coating thickness of the sheet heating element), but is not more than about 700 μm, preferably about 500 from the viewpoint of flexibility.
μm to about 30 μm, that is, 2 g / m ² to 2 in dry weight
It is 00 g / m ² . When the thickness exceeds about 700 μm, problems arise in terms of heat generation amount (temperature), flexibility, and refraction resistance strength. Further, it is not appropriate to make the thickness as thin as about 20 μm as in the case of a planar heating element in which a conductive film is simply uniformly coated on a resin film such as a polyimide film. The conductive paint applied is 100 ° C-210
5 minutes to 60 ° C., preferably 160 ° C. to 180 ° C.
It is dried and heat-treated for a minute, preferably 10 to 20 minutes.

A film or sheet such as a polyvinyl chloride resin film, a polyimide film, a polyamide resin film, or a polyester resin film may be formed on one or both surfaces of the electrode portion and the heat generating portion coated with the conductive coating, if necessary. Insulating layer can be provided. For example, a polyvinyl chloride resin sheet can be laminated at a temperature of about 180 ° C.

As described above, the sheet heating element of the present invention can avoid the adverse effects of "melt-through" of the laminate sheet resin, which are likely to accompany this difference in the laminating process. Melt-through is a term probably used only by the present inventors for a certain trouble phenomenon experienced by the present inventors, and is not a scientific term,
Nor is it a commonly used idiom. The melt-through phenomenon is a troublesome phenomenon that often occurs when a protective sheet is laminated on a base fabric for a surface heating element, which is coated with a conductive paint and dried. That is, the sheet heating element on which the conductive paint is arranged is brought into close contact with the thermoplastic resin sheet to be laminated and heated under pressure. At this time, when the thermoplastic resin sheet to be laminated is in an overheated state and melted when pressure-bonded to the base cloth with excessively strong pressure, the thermoplastic resin sheet material is present especially in the mesh hole portion of the base cloth. The more the conductive material is pushed away to reach the back side of the base fabric, the more the hole portion is occupied. The amount of resin in the thermoplastic resin sheet material is often higher than the amount of the conductive coating material present, and therefore this melt-through often occurs locally and may cause local interruption of power supply. However, in the sheet heating element of the present invention, the conductive cloth is permeated and fixed to the weaving yarn itself which forms the base cloth, and as a result, even if such a local current interruption occurs, the base cloth is Through the constituent weaving yarns, it is possible to maintain a uniform energized state over the entire surface.

The planar heating element of the present invention produced in this manner is flexible and has a heat generation temperature of about 0 to 15 ° C. for melting snow and frost in cold regions, for plant cultivation. As a fever temperature of about 15 to 30 ° C., as a fever temperature of about 25 to 45 ° C. for bedding at home, and for use on the human body such as an isothermal heat treatment device. 80 to 1 for exhibiting a heat generation temperature of about 40 to 60 ° C and for sterilizing boiling water
It can be used as a material having a heat generation temperature of about 10 ° C. and a material having a heat generation temperature of about 100 to 250 ° C. for cooking. Hereinafter, the present invention will be described in more detail by way of examples with reference to the drawings. This example is intended to illustrate the present invention and not to limit the present invention. In the examples, "parts" means "parts by weight" unless otherwise specified.

[0041]

[Examples] <Composite yarn (metal-cotton blended yarn)> 6 copper single yarns (single fiber diameter = 0.07mm) 6 cotton single yarns (20th count, number of twists = 1.75) 2 Were twisted so that the number of twists was 0.725, and a composite yarn as illustrated in FIG. 4 was prepared. In addition, FIG. 4 shows a single copper compound yarn 1
Represents a twisted yarn consisting of a book and two single cotton yarns.

<Base fabric> As the warp yarn, the twist coefficient is 2.5.
With a very low twist cotton yarn, the density per inch is 80
Using a book, 12 composite yarns were arranged in a portion which becomes a strip-shaped electrode portion having a width of ⅔ inch from a position inside ⅔ inch from both ends of the base fabric to form a base fabric for the electrode portion. . As the weft yarn, use the same cotton yarn as the warp yarn and have a density of 80 per inch.
It was a book. The warp yarn and the weft yarn were woven into a plain weave to prepare a base fabric for the sheet heating element.

<Electrically conductive coating> Polyvinyl chloride resin 43 parts Graphite 5 parts Carbon black 20 parts Methyl ethyl ketone 31 parts DOP 1 part A raw material consisting of 30 parts was previously mixed with a ball mill for 30 minutes, and then stirred with a mixer for 2 hours to give a viscosity of about A uniform conductive paint of 5000 cp (normal temperature) was prepared.

<Planar heating element> The above-prepared conductive coating material was applied to the above-mentioned base cloth using a rubber knife doctor so that the dry weight was 100 g / m ^2, and 170 ° C.
Was dried and heat-treated for 7 minutes in the electrothermal drying furnace, and a lead cord was attached to the electrode portion of the taken out base cloth to obtain a sheet heating element of the present invention.

<Exterior> The above sheet heating element has a degree of polymerization of 15
A vinyl chloride resin sheet having a thickness of 0.4 mm and containing 35 parts of a trimellitic acid ester as a plasticizer per 100 parts of a soft polyvinyl chloride resin of 00 was sealed with a heat sealer heated to 170 ° C. The final product was obtained.

[0046]

[Comparative example]

 <Metal thread> Copper wire (diameter = 0.5 mm)

<Base fabric> As a warp yarn, the twist coefficient is 2.5.
With a very low twist cotton yarn, the density per inch is 80
Using a book, 12 pieces of the metal threads are arranged in a portion which becomes a strip-shaped electrode portion having a width of ⅔ inch from a position located ⅔ inch from both ends of the base fabric to form a base cloth for the electrode portion. . As the weft yarn, use the same cotton yarn as the warp yarn and have a density of 80 per inch.
It was a book. The warp yarn and the weft yarn were woven into a plain weave to prepare a base fabric for the sheet heating element.

<Conductive Paint> Polyvinyl chloride resin 43 parts Graphite 5 parts Carbon black 20 parts Methyl ethyl ketone 31 parts DOP 1 part A raw material consisting of 30 parts was previously mixed with a ball mill for 30 minutes, and then stirred with a mixer for 2 hours to give a viscosity of about A uniform conductive paint of 5000 cp (normal temperature) was prepared.

<Flat heating element> The above-prepared conductive coating material was applied to the above-mentioned base cloth using a rubber knife doctor so that the dry weight was 100 g / m ^2, and 170 ° C.
Was dried and heat-treated for 7 minutes in the electrothermal drying furnace, and a lead cord was attached to the electrode portion of the taken out base cloth to obtain a sheet heating element of the present invention.

<Exterior> The above sheet heating element has a degree of polymerization of 15
A vinyl chloride resin sheet having a thickness of 0.4 mm and containing 35 parts of a trimellitic acid ester as a plasticizer per 100 parts of a soft polyvinyl chloride resin of 00 was sealed with a heat sealer heated to 170 ° C. The final product was obtained.

[0051]

[Performance test] The above-mentioned sheet heating element was subjected to various performance tests.
The results were extremely excellent as follows. (Refraction Resistance Test-Part 1-) As shown in FIG.
Firmly strain the 4th piano wire, 125mm x 15
The 0 mm-sized sheet heating element of the present example and the conventional sheet heating element shown in the comparative example were repeatedly refracted in a state of being in contact with the piano wire, and then the electric resistance value between the electrodes was measured. , And compared their durability. The results were as follows.

[0052]

[Table 1]

(Refraction Resistance Test-Part 2-) The sheet heating element of this example was subjected to JIS-P81 using a MIT refraction resistance tester.
A refraction resistance test was conducted by the method of 15 at -5 ° C or lower. As a result, it was found that it can withstand bending more than 5000 times. On the other hand, the thickness of cotton thread is 20th and the density is 8 per inch.
When 0 plain weave cotton cloth was used, cracking occurred in the vinyl chloride film after 1000 cycles. Further, the dynamic viscoelasticity of these two kinds of sheet heating elements was measured, and the storage elastic modulus was −5 ° C. when a plain weave cotton cloth having a yarn count of 20 and a density of 50 yarns per inch was used. It was 8 × 10 ⁹ while the thickness of cotton thread was 20th and the density was 8 per inch.
It was found that when 0 plain weave cotton cloth was used, it was as high as 8 × 10 ¹⁰ at -5 ° C.

[0054]

[Heat generation characteristics and power efficiency test]

Experimental Outline The heat generation characteristics and power efficiency of the sheet heating element of the present invention were tested. This test assumes that the planar heating element of the present invention is used outdoors, and assumes future use of the heat generation characteristics and power efficiency under the condition of being buried under the road under particularly severe usage conditions. I went for the basics.

(1) Specimen A planar heating element having a length of 40 and a width of 40 cm and an output of 40 W and a linear heating element are embedded in a heat insulating material (styrofoam) with one surface exposed. It was used as a specimen. The sectional view is shown in FIG. The electric heater used for the linear heating element has a total length of 2.25 m and an electric resistance of 0.08.
It is 325Ω. The layout of the electric heater is shown in FIG.

(2) Test conditions Ambient temperature: The specimen was placed in a temperature-controlled room maintained at -10 ° C. Supply power amount (P): Adjusted by a variable resistor, supply voltage (E ₀ ) is 1.82 V, supply current (I ₀ ) is 21.98 A.
And the power supply amount was set to 40W. The design output of the heating element is 250 W / m ² .

(3) Measurement After the specimen was placed in a temperature-controlled room for 12 hours for curing, the voltage was adjusted with a variable resistor so that the heating element was 40 W (250 w / m ² ), and the elapsed time after input The ambient temperature, the temperature of the heating element, and the electric output of the heating element were measured and recorded. 3181 Digital Power HiTester (manufactured by Hioki Electric Co., Ltd.), UCAM10
A (manufactured by Kyowa Denki Co., Ltd.). The layout and wiring of the measuring instrument and recorder are shown in FIG.

(4) Measurement Results Table 2 shows the measurement results. The results of Table 2 are shown in FIGS.
Is shown in the graph.

[0059]

[Table 2]

Further, these test results are summarized in Table 3 as data of the planar heating element and the linear heating element at the time when 400 minutes have elapsed.

[0061]

[Table 3] The temperature difference between the pavement surface temperature and the interface between the heating element and the dense-grained ascon was as follows. Sheet heating element 16.9−8.9 = 8.0 ° C. Linear heating element 2.9 − (− 0.3) = 3.2 ° C.

Based on these results, the thermal efficiency due to the difference in the heating element was examined. That is, the energy (W) absorbed by the sample is expressed by the following equation. W = CMΔt (W: absorbed energy (cal), C: specific heat of the specimen (cal / g · ° C), M: weight of the specimen (g), Δt: elevated temperature (° C)) And the thermal efficiency (η) is expressed by the following equation.

[0063] (W1 is work done outside, J is work of heat, Q
Represents the amount of heat from the heat source.) The ratio of the thermal efficiency (η ₁ ) of the planar heating element to the thermal efficiency (η ₂ ) of the linear heating element is the temperature ratio, assuming that weight, specific heat and work are the same. It can be replaced, that is, the ratio of the two is calculated as follows.

[0064] As a result, it was found that the planar heating element of the present invention is surprisingly excellent in that the thermal efficiency is reduced by about 58% as compared with the linear heating element. Further, in the planar heating element of the present invention, the surface temperature and the temperature difference between the ascon are large, and the amount of heat stored in the ascon is larger than that of the linear heating element. This is one of the great advantages in consideration of the actual conditions of road freezing in winter and the temperature difference change between day and night in cold regions, that is, the slow heat transfer rate and large heat capacity on paved roads. it can.

[0065]

As described above in detail and concretely,
According to the present invention, it withstands long-term use under severe usage conditions,
An effect is provided that a flexible planar heating element that has excellent thermal efficiency and that exhibits particularly remarkable convenience under realistic usage conditions such as snow melting and ice melting, and a method for manufacturing the same are provided.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a summary of a conductive coating material in a conventional sheet heating element.

FIG. 2 is a diagram showing an example of a material forming a conventional sheet heating element.

FIG. 3 is a diagram illustrating an example of a base fabric of a conventional sheet heating element.

FIG. 4 is a diagram illustrating an example of a composite yarn forming the sheet heating element of the present invention.

FIG. 5 is a diagram showing a durability test method for the sheet heating element of the present invention.

FIG. 6 is a view showing a heat generation characteristic of the sheet heating element of the present invention and a test piece for a power efficiency test.

FIG. 7 is a diagram showing the heat generation characteristics of the planar heating element of the present invention and the arrangement of electric heaters of linear heating elements compared in a power efficiency test.

FIG. 8 is a diagram showing the arrangement and wiring of a measuring device and a recorder used in a heat generation characteristic and power efficiency test of the planar heating element of the present invention.

FIG. 9 is a graph showing the performance of the sheet heating element of the present invention.

FIG. 10 is a graph showing the performance of the sheet heating element of the present invention.

FIG. 11 is a graph showing the performance of the sheet heating element of the present invention.

FIG. 12 is a graph showing the performance of the sheet heating element of the present invention.

Claims (6)

[Claims] 1. A planar heating element having strip-shaped electrode parts at both ends and a heating part between the electrode parts, wherein the electrode part and the heating part are formed on one base cloth. And
The base fabric of the heat generating part is braided with cotton yarn, and the base fabric of the electrode part is a composite yarn obtained by mixing and twisting a metal single yarn and a cotton single yarn with a cotton yarn continuous from the base fabric of the heat generating part. And a base fabric in the electrode portion, and a base fabric after the composite yarn formed by mixing and twisting the metal single yarn and the cotton single yarn in the heat generating portion is woven. A planar heating element having substantially the same thickness and substantially the same flexibility. 2. The composite yarn has a diameter of 0.001 to 0.
The sheet heating element according to claim 1, which is a twisted yarn composed of 3 to 9 single-mm composite yarns of 1 mm of copper and / or aluminum and 1 to 3 single cotton composite yarns of 10 to 50 count. . 3. The composite yarn has a diameter of 0.001 to 0.
The sheet-like heat generation according to claim 1, which is a twisted yarn consisting of 1 to 8 single-mm composite yarns of 1 mm steel and / or stainless steel and 1 to 3 cotton single-composite yarns of 10 to 50 count. body. 4. T1 ≦ K1√N1 (where K1 is a twist coefficient and is 1.5 to 5.0) between the number of twists T1 between inches T1 and the count N1 of the single cotton composite yarn. There is a relationship between the number of twists per inch T2 of the composite yarn and the number N2, and T2 ≦
K2√N2 (where K2 is the twisting coefficient, 0.01-
3.0).
The sheet heating element according to claim 2, claim 2 or claim 3. 5. A method for manufacturing a planar heating element comprising strip-shaped electrode portions attached to both end portions and a heat generating portion attached between both electrode portions, wherein the electrode portion and the heat generating portion are formed as one sheet. It is formed on a base fabric, the base fabric of the heat generating portion is braided with cotton yarn, and the base fabric of the electrode portion is a continuous metal yarn from the base fabric of the heat generating portion made of a metal single yarn and a cotton single yarn. An electrode part and a heat generating part are formed on one base cloth by weaving a mixed yarn formed by mixing and twisting and braiding so as to have substantially the same thickness and substantially the same flexibility as the base cloth of the heat generating part. 2. The surface according to claim 1, further comprising: a step of weaving separately from each other, a step of covering the entire surface of the base cloth with a conductive paint, and a step of attaching a power source connecting wire to an electrode part. Of producing a heating element. 6. The surface according to claim 5, further comprising a step of enclosing a sheet heating element in a soft vinyl chloride sheet with a heat sealer after the step of attaching a power source connecting wire to the electrode portion. Of producing a heating element. [0001]