JP5217411B2 - Polymer heating element - Google Patents

Description

  The present invention relates to a polymer heating element using Joule heat of a polymer resistor, and more particularly to a polymer heating element that has long-term reliability and can be produced at low cost.

  2. Description of the Related Art Conventionally, as a heat generating portion of a planar heating element, one obtained by dispersing a conductive material such as carbon black, metal powder, or graphite in a resin is known. In particular, in the case of using a PTC heating element (which means an abbreviation of English Positive Temperature Coefficient, which means a positive resistance temperature characteristic) by a combination of a conductive material and a resin, a temperature control circuit is provided. Is known as a device that has advantages such as eliminating the need for components and reducing the number of components.

  As shown in FIG. 4, these structures are obtained by printing or applying a conductive ink composition on a base material 22 having a function as a housing structure such as a ceramic or an insulating metal plate. 23, and a resistor 24 obtained by printing or applying a resistor ink composition at a position to which power is supplied, thereby providing a heating element 21.

Conventionally, examples in which a polymer resistor is formed by printing and used as a heating element include a door mirror of an automobile, a mirror of a wash basin, a floor heater, etc. for dew / frost removal (for example, Patent Document 1). reference).
JP 2002-371699 A

  In the conventional configuration, the specific resistance of the resistor composition to be used is usually 1000 Ω · cm or more, so that power is supplied very close like a comb electrode. In general, the comb-shaped electrode is made of silver paste, and is formed by printing and drying. Therefore, the amount of the comb-shaped electrode increases, so that the comb electrode is expensive.

  In the case where a polymer resistor is manufactured as an ink, the heat generating portion can be formed in a thin film of about several tens of micrometers by adjusting the coating amount, and therefore it is easy to exhibit flexibility as a polymer heating element. However, as the surface on which the ink-like polymer resistor is applied, it is necessary to use an electrically insulating base material such as a polyester film having a smooth and non-impregnated surface, which results in a loss of flexibility. It was. Further, since it is necessary to use a large amount of expensive conductive paste as a comb-shaped electrode as a power feeding portion of the polymer heating element, there is a disadvantage that the cost is high.

  On the other hand, the resistor used for extrusion molding is thicker in millimeters than the one used for the ink, lacks flexibility, and has a configuration in which the electrode cables are close to each other, so it cannot be said to be a planar heating element. There are thin-wall molding methods such as T-die extrusion and calendering, but no polymer resistor suitable for these methods has been proposed.

  In view of the above-mentioned problems of the conventional technology, the problem to be solved by the present invention is that when a polymer resistor showing a low resistance capable of being thin-walled is provided, a planar heating element when mounted on a device with flexibility. An object of the present invention is to provide a polymer heating element that improves the feeling of use and reliability and reduces costs.

The polymer heating element of the present invention for solving the conventional problems includes an electrically insulating substrate, an electrode made of at least a pair of metal strands disposed on the electrically insulating substrate, and the electric A polymer resistor disposed on an insulating substrate and having a PTC characteristic that does not directly contact the pair of electrodes, and a conductive layer that contacts both the electrode and the polymer resistor It is.

  In the present invention, a polymer resistor having a low resistance is basically formed in a thin film. However, this configuration eliminates the need for a comb-shaped configuration between the electrodes that feed the polymer resistor, and thus wide. Electrodes can be arranged at intervals, and the amount of electrodes used can be reduced, and it is not necessary to pattern the polymer resistor, so that a low-cost planar heating element can be provided.

  As a material that performs the same function as the conductive layer, there is a conductive coating material. In the present invention, the electrode and the conductive layer, and the conductive layer and the polymer resistor may be in a bonded state, The state of covering of the electrode itself is not limited. As a result, the electrode portion may be entirely covered with the conductive layer, or may be in a state where only a part is covered.

  According to the present invention, it is possible to provide a planar heating element having a thin film and a low resistance, a high flexibility, a feeling of use and a high reliability, and a reduction in cost can be promoted.

The first invention includes an electrically insulating substrate, an electrode made of at least a pair of metal strands disposed on the electrically insulating substrate, the electrically insulating substrate, and the pair Comb-shaped structure between electrodes for supplying power to the resistor composition, comprising a polymer resistor having a PTC characteristic that is not in direct contact with the electrode and a conductive layer in contact with both the electrode and the polymer resistor no longer need to be, it is possible to arrange the electrodes in a wide interval, while reducing the amount of electrode, there is no need to pattern the polymer resistor, provides a planar heating element of a low-cost it can.

  In addition, a complicated construction method is not required, and the polymer resistor or conductive layer obtained by a T-die or a calender roll method can be easily manufactured by bonding together with an electrode to an electrically insulating base material by heat fusion or the like.

  Furthermore, the conductive layer provided between the electrode made of a stranded wire and the polymer resistor plays a role of mediating the adhesion between the electrode and the polymer resistor, and the durability with respect to flexibility and bendability can be improved. Even when an electrode made of a stranded wire is disconnected, the presence of the conductive layer can suppress the occurrence of sparks, thereby improving safety.

  The second invention is the first polymer heating element, wherein the conductive layer is carbon black, graphite, carbon nanotube, carbon fiber, conductive ceramic fiber, conductive whisker, metal fiber, conductive inorganic oxide, conductive polymer Since it contains a conductor selected from at least one kind of fiber and the raw material for the conductor can be obtained relatively inexpensively and stably, it is possible to provide a high-quality and low-cost polymer heating element.

  In the third invention, particularly in the second polymer heating element, the conductive ceramic fiber contains at least one element of carbon, silicon, titanium, and tungsten, and is chemically and mechanically stable. A polymer heating element can be produced relatively easily, and a highly reliable polymer heating element can be obtained.

  In addition, these conductive ceramic fibers are a material that does not easily burn, and show flame retardancy and non-flammability against external ignition.

  In the fourth invention, particularly in the polymer heating element of any one of the first to third inventions, the specific resistance of the conductive layer is 0.01 to 500 Ω · cm, and the heat loss in the conductive layer is small. An electrically stable polymer heating element can be produced. In order to make it smaller than 0.01 Ω · cm, it is necessary to increase the ratio of the conductor. However, in this case, the resin ratio as the binder is decreased, so that the adhesion with the metal is decreased. On the other hand, if it exceeds 500 Ω · cm, the resistance value of the conductive layer becomes larger than that of the polymer resistor when a voltage is applied, and only the conductive layer generates heat, and a planar heating element cannot be obtained.

  According to a fifth aspect of the present invention, in the polymer heating element of any one of the first to fourth aspects of the invention, the conductive layer contains at least one flame retardant of a phosphorus type, a nitrogen type, or a silicone type. Even when heated from above, even if the electrode wire is disconnected and the temperature rises locally, an optimum polymer heating element capable of suppressing smoke and ignition can be provided.

  According to a sixth invention, in particular, in the polymer heating element of any one of the first to fifth inventions, the electrode has a stranded wire structure obtained from a thin metal wire of a silver-copper alloy, and is excellent in flexibility and flexibility. Therefore, a polymer heating element having good heat generation characteristics can be provided over a long period of time.

  According to a seventh invention, in particular, in the polymer heating element according to any one of the first to sixth inventions, the electrically insulating substrate, the electrode, the polymer resistor, and the conductive layer have flexibility, and the human body It is possible to provide a polymer heating element that can also be used as a device that is brought into direct contact with the above.

  In the eighth invention, in particular, in the polymer heating element of any one of the first to seventh inventions, the electrically insulating substrate is made of at least one of a resin film, a woven fabric, and a non-woven fabric, and is flexible and comfortable. Thus, a polymer heating element excellent in long-term reliability can be obtained.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Embodiment 1)
In FIG. 1, the polymer heating element 1 includes a pair of electrodes 3, 3 ′, a polymer resistor 4, and conductive layers 5, 5 ′ on an electrically insulating substrate 2.

  The electrically insulating substrate 2 is, for example, a needle punch type made of polyester fiber, and a nonwoven fabric impregnated with a flame retardant can be used.

  The pair of electrodes 3 and 3 ′ were obtained by twisting 15 silver-copper alloy wires having a wire diameter of 0.06 mm, and were heat-bonded at predetermined positions on the nonwoven fabric.

  Similarly, the polymer resistor 4 is disposed by thermal fusion so as not to directly contact the electrodes 3 and 3 ′, and then the conductive layers 5 and 5 for contacting the electrodes 3 and 3 ′ and the polymer resistor 4. The polymer heating element 1 was obtained by thermally fusing '.

  A lead wire for supplying power to the electrodes 3 and 3 'is omitted.

  At this time, the polymer resistor 4 was prepared by preparing a kneaded material according to the following materials and procedures and then processing it into a film by calendering.

Polymer Resistor 4 includes, as a crystalline resin, 30 parts of ethylene / methyl methacrylate copolymer (trade name “ACRIFT CM5021”, melting point 67 ° C., manufactured by Sumitomo Chemical Co., Ltd.), ethylene / methacrylate copolymer 30 parts of a polymer (trade name “Nucleel N1560”, melting point 90 ° C., manufactured by Mitsui DuPont Polychemical Co., Ltd.) and a metal coordination product of ethylene / methacrylic acid copolymer (trade name “Himiran 1702”, melting point 90 And 40 parts of Mitsui DuPont Polychemica Co., Ltd.).

  35% by weight of this crystalline resin, 2% by weight of a reactive resin (trade name “Bond First 7B”, manufactured by Sumitomo Chemical Co., Ltd.), and carbon black (trade name “Printex L” as two types of conductors) Primary particle size 21 nm, 25% by weight (Gusa), graphite (trade name “GR15”, scaly graphite, Nippon Graphite Co., Ltd.) 18% by weight, flame retardant (trade name “Reophos RDP”, phosphorus A kneaded material A was prepared with 20% by weight of an acid ester liquid flame retardant, manufactured by Ajinomoto Co., Inc.

  Next, as the elastomer, styrene thermoplastic elastomer (trade name “Tuftec M1943”), 40% by weight, manufactured by Asahi Kasei Engineering Co., Ltd., carbon black (trade name “# 10B”, primary particle diameter 75 nm, Mitsubishi Chemical) Co., Ltd.) 45% by weight, tungsten carbide (Izawa Metal Co., Ltd.) 13% by weight, and a mixture of an alkyl methacrylate / alkyl acrylate copolymer and a tetrafluoroethylene copolymer as a melt tension improver. A kneaded product B was prepared from 2% by weight (trade name “METABBRENE A3000”, manufactured by Mitsubishi Rayon Co., Ltd.).

  Then, an equal amount of the kneaded material A and the kneaded material B, 2% by weight of modified silicone oil as a release agent, and 2% by weight of an alkyl methacrylate / alkyl acrylate copolymer as a fluidity imparting agent are kneaded. Thus, a polymer resistor 4 was produced.

  The conductive layers 5 and 5 ′ are made of 35% by weight of crystalline resin used for forming the polymer resistor 4 as a binder and conductive whisker (trade name “FTL-110”, acicular oxidation as a conductor). Titanium, manufactured by Ishihara Sangyo Co., Ltd.) 35% by weight, carbon black (trade name “Printex L”, primary particle diameter 21 nm, manufactured by Gusa) 20% by weight, flame retardant (trade name “Reophos RDP”, phosphoric acid A kneaded material was obtained from 10% by weight of an ester-based liquid flame retardant, manufactured by Ajinomoto Co., Inc., and a film having a thickness of 100 μm was prepared. The specific resistance was 20 Ω · cm.

  As shown in FIGS. 2 and 3, the polymer heating element 1 is used as a seat heating heater by attaching the base member 2 side to the seat portion 8 and the backrest 9 that are the seat device 7 of the automobile. Is.

  Ear portions (extension portions of the base material 2) are provided to be suspended at the central portion and the peripheral portion in order to correspond to the suspended portions (not shown) of the seat portion 8 and the backrest 9, but are omitted here. Yes.

  In addition, the seat 8 and the backrest 9 on which the planar heating element 1 is mounted are generally deformed when a load is applied by a human body seated on the seat, such as a urethane pad that is restored when the load is no longer applied. The seat base 10 and the seat skin 11 are provided, and therefore, the polymer resistor 4 side is disposed on the seat base 10 of the seat 8 and the backrest 9 and the base 2 side is disposed on the seat skin 11. The thin sheet heating element 1 must be similarly deformed corresponding to the deformation of the seat 8 and the backrest 9 described above.

  For this purpose, it is needless to say that various heat generation pattern designs and the arrangement shapes of the electrodes 3 and 3 ′ and the conductive layers 5 and 5 ′ need to be changed.

The electrodes 3 and 3 ′ are arranged so that a wide pair (electrically positive side and negative side) is arranged along the outer side in the longitudinal direction of the planar heating element 1 so as to be opposed to each other, and come into contact therewith. A current flows through the polymer resistor 4 through the disposed conductive layers 5 and 5 ', and heat is generated.

  In the present embodiment, the polymer resistor 4 has PTC characteristics, and when the temperature rises, the resistance value rises, and has a self-temperature adjusting function so as to reach a predetermined temperature, and temperature control is unnecessary. It has a function as the highly safe planar heating element 1.

  In addition, as a car seat heater incorporated in an automobile seat, a seating feeling and flame retardancy can be satisfied.

  The seating feeling can be satisfied by the fact that there is no squeaking like paper and an elongation characteristic equivalent to that of the seat skin material, that is, a load of 7 kgf or less for 5% elongation.

  Further, as a planar heating element having PTC characteristics, quick heat and energy saving can be exhibited as compared with a conventional heating element using a tubing heater. A tube heater that uses a heating element requires a temperature controller and controls the heat generation temperature by controlling energization by ON-OFF control.

  Since the heater wire temperature at the time of ON rises to about 80 ° C., it is necessary to dispose it at a certain distance from the seat skin material. On the other hand, in the planar heating element of this embodiment, the heating temperature is high. Since it is self-controlled in the range of 40 ° C. to 50 ° C., it can be arranged close to the seat skin material. Since the heat generation temperature is low and it is in the vicinity of the seat, it is possible to realize energy saving by being able to reduce heat loss and heat dissipation loss to the outside.

  In addition, flame retardancy can be realized by using a flame retardant nonwoven fabric for the electrical insulating base material 2 and blending a flame retardant with the polymer resistor 4 and the conductive layers 5 and 5 ′.

  Flame retardancy is the automotive interior material flame retardant standard FMVSS302 (single fire extinguishing as well as nonflammability due to horizontal ignition, or if the burning rate between marked lines is 80 mm / min or less It was confirmed that it can be met if the amount of the flame retardant is at least 10% by weight.

  The polymer heating element 1 obtained in this embodiment was subjected to an 80 ° C. oven standing test, a 150 ° C. oven standing test, and a −20 ° C. and 50 ° C. heat cycle test. As a result, the resistance value change rate was within 30% of the initial value after 500 hours, 200 hours and 200 times, respectively. The reason for this was considered to be that the crystalline resin itself and the bonding between the crystalline resin and the conductor were attempted by a crosslinking reaction with the reactive resin.

  In this embodiment, a combination of a plurality of conductors and a sea-island configuration are applied in order to exhibit excellent PTC characteristics. The details of the mechanism are currently unknown, but are presumed as follows.

  First, in order to obtain a resistor composition having PTC characteristics, it is necessary to select a crystalline resin to be used whose melting point is in the vicinity of the exothermic saturation temperature.

  The conductor is required to achieve a predetermined resistance value with the smallest possible addition amount, but such a conductor is generally called conductive carbon black, and has a primary particle diameter of about 20 nm or less and a structure. (It is an aggregate of primary particles such as a bunch of coral, which is correlated with oil absorption.) On the other hand, such conductive carbon black exhibits PTC characteristics. It had the disadvantage of being difficult to do.

  This is because the structure of conductive carbon black is developed, and the conductive path of the structure is not easily cut even by the change in specific volume due to the temperature of the crystalline resin (which is said to be the main cause of the PTC characteristics). It is said.

  On the other hand, the inventors have obtained as knowledge that carbon black having a large primary particle diameter has excellent PTC characteristics.

  In addition, a conductor such as graphite has a particle size larger than that of carbon black and has a layered structure such as a scale, and has a large particle size such as metal or ceramic, and has excellent amorphous conductivity. (Has a small volume resistivity)

  By combining these conductors, the thickness is about 100 microns or less, the sheet resistance is 400Ω □ or less, and the specific resistance is 3Ω · cm or less. In addition to having a resistance, the ratio of the resistance value at 50 ° C. to the resistance value at 20 ° C. which is one index of the PTC characteristic is 1.5 or more, and the ratio of the resistance value at 80 ° C. to the resistance value at 20 ° C. is 5 or more The resistor composition could be obtained.

  Although the details of the mechanism that was able to demonstrate excellent PTC characteristics while being low resistance are unknown, the formation of a new conductive path by combining a crystalline resin and a plurality of conductors, and the flame retardant made liquid This is considered to be due to the fact that the large thermal expansion coefficient of the liquid could be used.

  It goes without saying that waxes such as montanic acid partly saponified esters, and plasticizers and dispersants such as other waxes may be used as necessary.

  Further, although the conductor is formed using a whisker shape, it may be spherical or other rug shape.

  Further, in the present embodiment, the polymer resistor 4 and the electrodes 3 and 3 ′ are shown so as not to overlap each other in the same plane. However, the polymer resistor 4 and the electrodes 3 and 3 ′ are stacked as long as they are in contact with each other through the conductive layers 5 and 5 ′. The arrangement may be different.

  As described above, the planar heating element according to the present invention has high flexibility and high reliability, and can be used as a heating element for heating a vehicle seat device, a handle device, and other parts.

(A) The top view which shows the structure of the polymer heating element in this Embodiment 1, (b) is XY sectional drawing of (a). 1 is a perspective side view showing a seat of an automobile to which a polymer heating element is mounted in Embodiment 1 of the present invention. A perspective front view of the seat shown in FIG. (A) is a top view which shows the conventional heat generating body, (b) is XY sectional drawing of (a).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Polymer heating element 2 Electrically insulating base material 3,3 'Electrode 4 Polymer resistor 5,5' Conductive layer

Claims (8)

An electrically insulating substrate, an electrode composed of at least a pair of metal strands disposed on the electrically insulating substrate, and disposed on the electrically insulating substrate and in direct contact with the pair of electrodes A polymer heating element formed from a polymer resistor having non-PTC characteristics and a conductive layer in contact with both the electrode and the polymer resistor. The conductive layer contains a conductor selected from at least one of carbon black, graphite, carbon nanotube, carbon fiber, conductive ceramic fiber, conductive whisker, metal fiber, conductive inorganic oxide, and conductive polymer fiber. Polymer heating element. The polymer heating element according to claim 2, wherein the conductive ceramic fiber contains at least one element of carbon, silicon, titanium, and tungsten. The polymer heating element according to claim 1, wherein the conductive layer has a specific resistance of 0.01 to 500 Ω · cm. The polymer heating element according to any one of claims 1 to 4, wherein the conductive layer contains at least one flame retardant of phosphorous, nitrogen, and silicone. The polymer heating element according to claim 1, wherein the electrode has a stranded wire structure obtained from a thin metal wire of silver-copper alloy. The polymer heating element according to claim 1, wherein the electrically insulating substrate, the electrode, the polymer resistor, and the conductive layer have flexibility. The polymer heating element according to claim 1, wherein the electrically insulating substrate comprises at least one of a resin film, a woven fabric, and a nonwoven fabric.