MXPA98009261A - Electrical device containing a composition of positive temperature coefficient resistor and method for manufacturing the disposit - Google Patents

Abstract

A positive temperature coefficient resistor (CTP) composition, which comprises: (a) from about 3 percent to about 75 weight percent of a binder resin, (b) from about 2 percent to about 70 percent by weight of a semicrystalline polymer activatable by temperature, which is a thermoplastic elastomer (ETP) that melts on a relatively narrow temperature scale, to change from a crystalline state to an amorphous state, (c) of about 20 percent to about 80 weight percent of an electrically conductive material in a finely-selected form by selecting from the group consisting of silver, graphite, graphite / carbon, nickel, copper, silver-coated copper, and aluminum , (d) from about 0.01 percent to about 80 percent by weight of a solvent material for the composition

Description

ELECTRICAL DEVICE CONTAINING A COMPOSITION OF POSITIVE TEMPERATURE COEFFICIENT RESISTOR AND METHOD TO MANUFACTURE THE DEVICE BACKGROUND OF THE INVENTION This invention relates broadly to electrical devices that contain or include a new positive temperature coefficient resistor (RCTP) composition, and to the method for manufacturing these devices, as well as to the method for preparing these coefficient resistor compositions. of positive temperature. These compositions are highly useful for screen printing, for the preparation of printed circuits, and for the preparation of numerous different types of electrical devices, as will be descr hereinafter. The prior art is indicated in the following patents of the United States of America: Shafe et al., No. 5,093,036; Sherman et al., No. 4,910,389; Kim et al, No. 5,556,576; and Tsuboka a et al. No. 5,374,379. These prior patents involve mixing carbon / graphite with a semicrystalline polymer, which is dissolved in a strong solvent or extruded; or insert graphite on a semicrystalline polymer. The disadvantages of the dissolution approach are that the polymer has bad Physical properties, and strong solvents can not be used in screen printing, due to the fact that they will attack the screen emulsion. SUMMARY OF THE INVENTION From a compositional point of view, the inventive discovery of the present invention involves a positive temperature coefficient (CTP) resistor composition, which comprises: (a) from about 3 percent to about 75 percent by weight of a binder resin, (b) from about 2 percent to about 70 percent by weight of a semicrystalline temperature-activatable polymer, which is a thermoplastic elastomer (ETP) that is melted on a scale of relatively narrow temperature, to change from a crystalline state to an amorphous state, (c) from about 10 percent to about 80 weight percent of an electrically conductive material in a finely particulate form selected from the group consisting of silver, graphite, graphite / carbon, nickel, copper, silver coated with copper and aluminum, (d) from about 0.01 percent to about 80 percent by weight of a solvent material for the composition. In another aspect, the invention involves an electrical device from a resistor composition of positive temperature coefficient, comprised of: (a) about 3 percent to about 75 weight percent of a binder resin, (b) from about 2 percent to about 70 weight percent of a temperature-activatable semicrystalline polymer, which is a thermoplastic elastomer ( ETP) that melts on a relatively narrow temperature scale, to change from a crystalline state to an amorphous state, (c) from about 10 percent to about 80 percent by weight of an electrically conductive material in a finely formed form particulate selected from the group consisting of silver, graphite, graphite / carbon, nickel, copper, silver coated with copper and aluminum, (d) from about 0.01 percent to about 80 percent by weight of a solvent material for the composition, and wherein the positive temperature coefficient resistor composition is applied to at least one substrate surface inside the device electrical, and this device includes at least one electrical circuit to conduct electricity inside the device. From one aspect of the method, the invention involves a method for manufacturing an electrical device, which comprises the steps of: (1) providing a resistor composition of positive temperature coefficient, comprised of: (a) of about 3 percent to about 75 weight percent of a binder resin, (b) of about 2 percent to about 70 weight percent of a semicrystalline temperature-activatable polymer, which is a thermoplastic elastomer (ETP) that melts on a relatively narrow temperature scale, to change from a crystalline state to a state amorphous, (c) from about 10 percent to about 80 weight percent of an electrically conductive material in a finely particulate form selected from the group consisting of silver, graphite, graphite / carbon, nickel, copper, silver coated with copper and aluminum, (d) from about 0.01 percent to about 80 percent by weight of a solvent material for the composition, and (2) applying the resistive composition of positive temperature coefficient to a substrate, the which is a part of the electrical device mentioned. Brief Description of the Drawings Figures 1 to 4 illustrate graphic representations of the thermal cycle of the positive temperature coefficient resistor compositions according to the invention. Figure 5 illustrates a graphic representation of the thermal cycle of the positive temperature coefficient ink composition of Example 3, according to the invention. Figure 6 illustrates a graphic representation of the thermal cycle of the positive temperature coefficient ink composition of Example 6, according to the invention. Figure 7 illustrates a graph comparing the positive temperature coefficient ink product of Example 9 with a commercially available positive temperature coefficient ink. Figure 8 illustrates an electrical device prepared in accordance with the invention. DESCRIPTION OF THE PREFERRED EMBODIMENTS AND BEST MODE OF THE INVENTION The present invention involves a new unique concept for mixing an insoluble semicrystalline polymer in a thick polymer film (PPG) system. The thick polymer film systems employed in this invention, for example, contain silver, nickel, or carbon / graphite. It has also been discovered that other conductive fillers, such as copper, copper coated with silver, aluminum, or the like, can be used. The conductive fillers are used in a finely divided form or in particles. The preferred temperature-activated semicrystalline polymers that can be used in this invention are available from Landec Corporation (Menlo Park, California) under the trade name of IntelimerR, although other semicrystalline polymers can also be used, as will be described later herein. These semicrystalline polymers exhibit significant volume increases by means of phase transitions at certain temperatures, and also use a special side-chain technology, which makes it possible for these polymers to have a unique "deactivated-activated" control capability, ie, a "temperature switch". These polymers are crystalline below the "temperature switch," and amorphous above it. Although the operation of the present invention is not fully understood, it has been found that the electrical resistivity of the positive temperature coefficient composition (CTP) increases significantly over this transition, and then it returns to its original value upon cooling. In order to ensure that any large particles of the semicrystalline polymer are broken, the mixtures prepared in accordance with this invention were roller milled, or heated, such that the polymer will liquefy to form an emulsion, and then solidify at cool down, into finer particles. The polymers used in this invention and in the following examples exhibit an acute melting point / flux between about 30 ° C and about 95 ° C, and preferably between about 60 ° C and about 75 ° C, the best results being obtained using polymers with a trigger point between approximately 63 ° C and 68 ° C. The term "temperature-activated semicrystalline polymers", as used herein, means a thermoplastic elastomer polymer (ETP), which melts on a relatively narrow and precise temperature scale, thereby changing from a crystalline state to an amorphous state These polymers are more specifically defined as a thermoplastic elastomer (ETP) comprising polymeric molecules, which comprise: (i) at least two polymeric blocks A, (a) each of the crystalline A blocks being, and having a melting point P, and (b) comprising at least one of the A blocks, a side chain comprising crystallizable fractions that make the block crystalline; and (ii) at least one polymer block B, which (a) is bonded to at least two A blocks, (b) is amorphous at temperatures at which the thermoplastic elastomer exhibits an elastomeric behavior, (c) have a point of glass transition Tqs which is less than (T-10) "C, and (d) is selected from the group consisting of polyethers, polyacrylates, polyamides, polyurethanes, and polysiloxanes.These polymers are also more specifically described in Bitler and co-workers, U.S. Patent Number 5,665,822 (the disclosure of which is incorporated herein by reference), and these polymers are commercially available from Landec Corporation, Menlo Park, California. In order to further illustrate the present invention, the following examples are provided. However, it should be understood that the examples are included for illustrative purposes, and are not intended to limit the scope of the invention as described herein. Example 1 (052A) 70 parts by weight of ELECTRODAGR 440A - this is a highly conductive thick polymer film material, which can be printed on the screen. Contains graphite * conductor dispersed in a vinyl polymer. The 440A is available in Acheson Colloids Co, Port Huron, Michigan, E.U.A. 30 parts by weight of semicrystalline polymer Landec Intelimer R 1000 Series. Procedure: the materials were mixed together in a Cowles mixer, DBE solvent was added, and then ground with rollers until the polymer dispersed. Additional solvent was added to obtain a viscosity that could be printed on the screen. [IntelimerR is a registered trademark of Landec Corporation]. Example 2 (059) 70 parts by weight of ELECTRODAGR 440A 30 parts by weight of Landec Intelimer® 1000 Series polymer. Procedure: the materials were mixed together, they were heated in an oven at 107 ° C, and mixed for 5 minutes. After cooling to room temperature, solvent was added to obtain a viscosity that could be milled with rollers, and then the mixture was milled with rollers. Solvent was added to obtain a viscosity that could be printed on the screen. Example 3 (058) 87.5 parts by weight of ELECTRODAGR 28RF129 - thick thermoset polymeric film filled with silver. ELECTRODAGR 28RF129 is available from Acheson Colloids Co. It is made from a modified phenolic polymer (approximately 30 to 35 percent by weight), approximately 65 percent by weight silver particles, and a small amount of control substance from flow. 12.5 parts by weight of polymer Landec IntelimerR Series 1000. Procedure: the materials were mixed together, heated in an oven at 107 ° C, and mixed for 5 minutes. After cooling to room temperature, solvent was added to obtain a viscosity that could be milled with rollers, and then the mixture was milled with rollers. Solvent was added to obtain a viscosity that could be printed on the screen. Example 4 (059A) 87.5 parts by weight of a film ink nickel-based coarse polymer, Product Number SS-24711, available from Acheson Colloids Co. See the following Example 5. 12.5 parts by weight of Landec Intelimer® 1000 Series polymer. Procedure: the materials were mixed together, they were heated in an oven at 107 ° C, mixed for 5 minutes. After cooling to room temperature, solvent was added to obtain a viscosity that could be milled with rollers, and then the mixture was milled with rollers. Solvent was added to obtain a viscosity that could be printed on the screen. Example 5 Thick Polymer Film Ink (SS-24711 used in Example 4) Polyester resin (30 percent solids in solvent) (thermoplastic binder) 38.5 Carbitol Acetate 8.6 Bentona Thickener (Rheological Additive) 1.8 Colloidal silica 3.1 Nickel flakes (in the form of finely divided particles) 48.0 100.0 parts by weight The compositions of Examples 1 to 4 mentioned above were printed on the screen on Kapton or Mylar, and then cured at 150 ° C for 30 minutes. The type of substrate and the curing conditions were not critical for the purposes of this test. Then volt meter probes were attached to the ends of the printed strips, which had dimensions of 1.27 centimeters by 13.97 centimeters; and these strips were then placed on a hot plate, and changes in resistance at different temperatures were recorded. Results The following tables show the initial ambient temperature, and the resistivities at high temperature, as well as the percentage changes. As a comparison, the initial point-to-point resistance of the Acheson ELECTRODAGR 440A Product is 399 ohms, and the resistance at 121 ° C is 464 ohms (change of 16.29 percent). With the Acheson Product No. 28Rfl29 (commercially available from Acheson Colloids Co.), the point-to-point strength is 1.46, and the resistance at 121 ° C is 1.72 (17.8 percent change). Table of Results Example 4: 059A (SS24711-87.5 percent; Landec- 12.5 percent) Temperature 22.2 ° C 121 ° C% change Resistance 3,390 840,000 24,678 Ohms / 645.16 μ2 491 106,909 24,704 Example 2: 059 (440A-70 percent; Landec- 30 percent) Temperature 22.2 ° C 121 ° C% change Resistance 9,877 24,055 143 Ohms / 645.16 μ2 1,795 4,373 143 Controls (440A, 28RF129) 22.2 ° C 121 ° C% change 28RF129 1.46 1.27 17.8 440A 399 464 16.29 The reversibility of resistivity was also determined, cyclizing each impression between room temperature and 121 ° C. As shown in the graphs of Figures 1 to 5, graphite-based materials after the first cycle exhibited more than one ability to quickly return to the original strength. The silver-nickel-based systems exhibited more than one delay to return to the original resistance. In actual practice, all of these materials could be coated with a protective coating, such as an ultraviolet curable dielectric coating material. Additional Description of the Development of the Composition of Positive Temperature Coefficient The graphite positive temperature coefficient ink of Example 2 showed defined change properties and a good chance of repetition / recovery, and had an elevation of 75 to 100 percent in strength over its activation. It was also observed with the composition of Example 2, that there was a moderate degree of inclination (natural positive temperature coefficient of the ink) within the activated low strength, non-activated, and high strength regions. The nickel ink composition of Example 4 showed a very large positive temperature coefficient effect; however, it had a high hysteresis, requiring several hours or even days to recover to the original resistance value. Also, the degree of hysteresis depended on the highest exposure temperature, as well as the heating and cooling rates. For the purposes of providing a further improvement in the response of the positive temperature coefficient inks, it was decided to modify the binder resins and the conductive pigments, in order to maximize the effect that is seen from the expansion of the Landec polymers (by example, Landec thermoplastic elastomer polymers) on activation. It was thought that the use of a highly flexible binder would give Landec polymers greater freedom of expansion. It is believed that this allows a greater separation of the conductive pigments, which results in greater increases in strength. The flexible resin also allows the pigments to return more easily to their original position when cooling and shrinking the elastomer polymers thermoplastic, and therefore reduce the hysteresis seen with the previous inks. Furthermore, it is believed that the use of a highly flexible binder, better stabilizes the Landec polymers, and decreases the tendency of the non-miscible Landec resin to migrate away from the base binder resin, and to self-coalesce. In total, it is believed that the effect of positive temperature coefficient is maximized through the use of an elastomeric resin material, to encapsulate essentially the Landec polymer and the conductive pigments in a free-expanding and freely contracting dough. Flexible Elastomer Binding Resins The concept of this invention of using a highly flexible resin (or flexible elastic binder resin) as the binder for the positive temperature coefficient ink is applicable to a wide range of materials, from simple solvent-based thermoplastics. , to reactive elastomeric systems (thermosetting, urethanes, acrylates curated by ultraviolet or thermally, etc.). For this development, it was preferred to use thermoplastic resins; however, it was also widely considered that urethane resins or reactive acrylate resins would also be useful (ie, thermosettable resins). In the latter examples of this disclosure, the Landec polymers are used at lower levels than those used in Examples 1 to 4. The compositions of the Examples 1 to 4 were prepared by adding Landec polymers to pre-prepared formulations. In this approach, a high level of Landec polymer was required for proper temperature performance, with most systems requiring about 10 to 20 percent (by weight) of Landec polymers, to achieve reliable "switching". However, the high level of Landec polymer matched or exceeded the amount of the binder polymer in the ink, which often resulted in inappropriate cohesion and remarkable migration and coalescence of the fused Landec polymer. It was considered that a flexible resin would improve the commutation properties sufficiently so that the level of Landec polymer could be substantially reduced. This also has the benefit of reducing the emigration tendency, due to the reduced amount of Landec polymer present in the system. Along with the reduction of the Landec, a new ink composition with a reduced pigment level was formulated, to maximize the influence of the Landec polymer, while maintaining a relatively high binder content to have good film properties. Additional tests were performed using different thermoplastic binder resins having suitable elastomeric type properties. The Requesters examined the fusion performance of different resins together with its film properties when drying from solvent solutions. The best results were obtained with the flexible urethane resins of B.F. Goodrich Co. sold under its trade name EstaneR. As a result of this study, it was discovered that the Estañe 5703, in particular, produces a film with extremely good flexibility and hardness. This resin was able to produce a suitably elastomeric film upon drying from a "cut" of resin in methyl ethyl ketone with approximately 20 percent solids, or was able to produce a film with similar properties and good uniformity, when the dried resin granules were They were raised to reflux temperatures, and melted to obtain a resinous sheet (or emptied into a thicker crockery). Other urethanes, such as Estane 5706, 5712, and 5715P, were examined together with CA239 urethane from Morthane Co., and were considered to be functional in this invention. The first step in the preparation of the ink, was to prepare cuts of Estañe 5703 resin in slow evaporation solvents suitable for use in screen printing. It was found that resin 5703 had an unsatisfactory solubility in many of the commonly used screen printing solvents, with the lowest useful viscosities being achieved in gamma-butyrolactone (BLO) and N-ethylpyrrolidone (NMP) from ISP Co., and Acetate Ether Diethylene Glycol Monoethyl (Carbitol Acetate) and Diacetone Alcohol from Ashland Co. The lower viscosity resin cut was achieved using Diacetone Alcohol ("DiAcOH"). Example 6 A resin cut of 25 percent of Tin 5703 in Diacetone Alcohol, and a nickel-based ink was formulated using CHT type Nova et flakes, and 65 ° C Intelimer Landec polymer. The proportions of the Landec / binder pigment (proportion of the pigment to the binder) were set at 0.75, while the proportion of the nickel pigment to the binder was 2.5. This represented lower proportions of pigment to binder for both elements, compared to the nickel ink of Example 4. The non-volatile solids of the ink were 55 percent in the following formulation: Ink Product No. 76055: Tin 5703 12.94 (high flexibility binder material). Diacetone alcohol 45.00 (solvent) Nickel type CHT 32.35 (Finely divided nickel particles) Landec polymer 65 ° C 9.71 (Intelimer Polymer) 100.00% by weight The ingredients were mixed manually until they were uniform, and then they were passed over a three-roll mill for two passes. At that point, some apparent drying was seen on the mill, and it was noted that the diacetone alcohol would probably be too fast for many screen printing applications. The amount of drying was also questionable, possibly due to an incompatibility of the Landec polymer and this particular ink composition. In accordance with the above, there was a certain amount of dehydration of the Landec polymer. The ink seemed to dry prematurely, even though it was not like that. The ink composition of Example 6 was compared to a commercially available 65-70"C positive temperature coefficient ink (i.e., a prior art positive temperature coefficient ink known as Raychem SRM ink, from Raychem Corp. of Menlo Park, California) printed on an etched copper substrate Due to the presence in some circumstances of unsatisfactory screen printing performance and drying behavior with previous Landec-based tapes of the Requesters, it was decided to spread a wet film of the ink of Example 6 on an etched copper substrate, instead of printing it on the screen, a pattern of 5.08 centimeters x 10.16 centimeters, of approximately 127 microns, was spread thick, over the etched copper, and dried for 10 minutes at 107 ° C. Due to the shape of the pattern and the substrate, the normalized resistivity was not calculated. Instead, the resistance was measured from point to point as the circuit was heated from minus 20 ° C to 100 ° C; and the effect of the positive temperature coefficient was observed through the relative change of the entire resistance of the circuit. Example 6 was compared against the ink of Example 2 of the Applicant, and the commercial positive temperature coefficient ink (Ráychem) was applied to the same substrate. It was observed that the behavior of the positive temperature coefficient of the ink of Example 6 occurs rapidly close to the "switching" activation temperature of the Landec polymer, i.e. about 65"C. Upon activation, a large change was seen in the The resistance, the resistance remaining above the relatively constant activation temperature, The performance of the ink of Example 6 was found to have a performance markedly superior to that of the commercial positive temperature coefficient ink (Raychem) .The ink of Example 6 it provided much greater changes in strength and a much sharper transition point on the activation curve.The ink of Example 2 gave an increase of approximately 100 percent in the resistance, changing from 30-35 ohms to 65-70 ohms , while the commercial positive temperature coefficient ink (Raychem) produced an increase of 1, 300 percent, changing from less than 25 ohms to 350 ohms. However, it was found that the ink of Example 6 changed from less than 10 ohms to more than 2.5 Megaohms, an increase of 25,000,000 percent an extremely significant and unexpected technical advance. [A Megaohm equals 1 million ohms]. To study the long-term properties, the test was repeated with the ink of Example 6, repeatedly cycling the print from -20 ° C to 100 ° C, and graphing the resulting resistance (see the graph of Figure 6). The test was continued for 30 complete cycles, at which time the material exhibited excellent stability essentially without hysteresis, while retaining acute activation of "on-off". The print showed a slightly higher "activated" resistance of approximately 3.5 Megaohms in the first cycle, then dropped to, and remained at approximately, 2.5 Megaohms for the remainder of the test. The overall change for the ink system of Example 6 was at least an increase of 25,000,000 percent in the resistance when heating and activating the ink system of positive temperature coefficient. Following the thermal cycle, it was observed that the printing surface had taken a slightly irregular surface, as would be seen if the wet printing layer had contained a small amount of water. bubbles. The wet and initially dry printing surface did not show this appearance. Cycled printing continued to show good adhesion and cohesion in light of the naturally soft surface to the Tin. With the success of the formulation of Example 6, an additional examination of the screen printing characteristics was made. The approach was to change the ink system to an even better solvent for the screen printing application, and also, to improve the compatibility of the thermoplastic elastomer polymer (for example, the Landec Intelimer polymer). From the above solvency work, it was determined that another solvent suitable for use with the given Estane 5703 polymer was Diethylene Glycol Monoethyl Ether Acetate [Carbitol Acetate]. This solvent had previously been used with coarse polymer film inks, and was found to provide much longer screen residence times, and ease of handling, compared to faster Diacetone Alcohol ("DiAcOH"). However, the viscosity of Tin 5703 in Diethylene Glycol Monoethyl Ether Acetate ("Acetate DE") is slightly higher than that of diacetone alcohol, which required a lower solids ink for final use. Example 7 A resin cut of 20 percent of Tin 5703 in acetate, and a nickel-based ink was prepared using nickel flakes Novamet type CHT and polymer Landec Intelimer 65 ° C. The proportion of the Landec pigment to the binder remained at 0.75, while the proportion of the nickel pigment to the binder was 2.5. The solids in this version were 51.5 percent, compared to the previous 55 percent of Example 6. Ink Product No. 76056: Tin 5703 12.12 (Carbitol) Acetate DE 48.49 (Solvent) Nickel flakes Novamet type CHT 30.30 Polymer Landec of 65 ° C 9.09 100.00% by weight The ingredients were mixed manually until they were uniform, and they were observed to have a "hazy" hue.

The material was passed over a 3-roll mill for two passes, without significant drying, and the ink maintained a somewhat paste-like character. Experiments were conducted to print the ink of the Example 7 with a screen of 100 mesh polyester, using an open pattern of 6.35 centimeters x 15.24 centimeters, but did not provide a printing behavior as good as desired. The dry ink seemed to be a little rich in resin, without depositing enough nickel pigment through the screen. Then an additional impression was made with samples containing extra solvent, Modaflow [an acrylic flow substance; available from Monsanto Chemical Co.] or Care 16 (substance of silicone oil flow). Care 16 silicone showed an improvement in terms of printing softness, and higher film density. (See the following example) Example 8 In this example, a formulation was prepared with Care 16 (silicone oil flow substance), and the pigment content was raised for the purposes of increasing the density of the pigment and filling the printed pattern. The proportion of the Landec pigment to the binder was raised to 0.8, and the proportion of the nickel pigment to the binder to 3.5. The solids in this version were at 55 percent. Ink Product No. 76057: Tin 5703 10.28 Acetate DE (solvent) 45.00 Nickel type CHT 36.00 Polymer Landec 54 ° C 8.22 Care 16 0.50 (Silica flow substance 100.00% by weight cona) [Available from Nazdar Co. ] The ink was prepared and ground as in the Examples 6 and 7, the final ink having an appearance similar to previous systems. The ink was printed using a 100 mesh polyester screen, with an open pattern of 6.35 centimeters x 15.24 centimeters. The printing surface was improved with the addition of silicone, now giving a much smoother appearance, although the printing was still a little insufficient in pigment content. The CHT nickel flakes used were much finer than the Novamet HCA-1 that applicants used in other conductive thick film inks. Circuits were also made with additional printing layers. Example 9 A larger amount of the finely divided HCA-1 nickel was added to the wet ink (from Example 8), for the purpose of filling the voids, and to serve as a bridge to connect the smaller CHT particles. The nickel was added and ground as in Examples 6 to 8, followed by the addition of DE acetate, to maintain 55 percent solids. This resulted in the following formulation: Ink product No. 76058: Tin 5703 7.75 Acetate DE (solvent) 45.00 Nickel type CHT 27.12 Nickel HCA-1 13.56 (finely divided nickel) Landec Polymer 65 ° C 6.19 Care 16 0.38 100.00% by weight The previous ink was printed on the screen, and dried as before (ie, see Examples 7 and 8), and produced good print quality . A good conductive impression was achieved with three full printing passes. Then tests were performed on a complete ink pack of positive temperature coefficient printed on the screen. The ink of Example 9 was printed in two different configurations for the test. The first method was to manually spread the ink down on the etched copper panel, to be compared with the commercial positive temperature coefficient ink (Raychem), as was done previously. This method produced a smooth impression on the copper, with no apparent bubbles, and none of the surface brilliance associated with the earlier resin-rich systems. A single thermal cycle was performed with this system, the test being conducted together with the commercial ink (Raychem) as the control. The response of the ink of Example 9 was once again only better than that of the commercial ink, giving a much greater change in overall strength, and a more defined activation profile (see the graph of Figure 7). The ink of Example 9 remained essentially in one constant resistance until activation, at which time, responded quickly with very little delay in the resistance rise. The initial resistance of the circuit was 5 ohms, rising to more than 8,000 ohms over the initial activation. The additional heating resulted in a slightly different profile, once again rising to 8,000 ohms with the maximum heating. The test circuit always remained above 1,700 ohms when it was activated, although in this construction, it appeared to have a positive temperature coefficient resistor defined above the trigger point. The commercial positive temperature coefficient (Raychem) comparative ink gave its expected performance, without an acute activation profile being seen with the inks of this invention. The second test method was for a real screen printed construction, printing three separate additive layers of the ink of Example 9, and then applying a highly conductive interdigitated bus bar using Acheson Colloids Co. 725A thick polymeric film ink (this ink is available under the trade name ELECTRODAGr 725a in Acheson Colloids Co.). The separation of the legs of the bus bar was 1,016 centimeters across the width of the positive temperature coefficient ink pattern of 6.35 centimeters by 15.24 centimeters. Three temperature coefficient circuits were built positive in this way, and thermally cycled through 8 complete cycles of -20 ° C to 100 ° C. Initial resistance of all circuits was less than 50 ohms. Upon activation, the three circuits rose drastically in resistance to more than 50 Megaohms, and often exceeded the maximum value of 120 Megaohms of the instrument, as it raised the temperature above the activation temperature of 65 ° C. All test circuits returned to less than 100 ohms when cooled for the duration of the cycle test. The above tests establish the significant technical progress and the unexpected results achieved with the products of this invention. Figure 8 illustrates an electrical device (in a schematic form) made in accordance with the invention. The device of Figure 8 includes a rearview mirror 1 which includes an ink-conducting coating of positive temperature coefficient 2 on the rear side of the mirror, the ink coating being formulated in accordance with the invention. Connections of the electrical circuit are made with the coating 2 by using the connector leads designated 3 and 4 (ie, providing a heating technique of the rear side of an automotive exterior rearview mirror for demisting purposes). As will be appreciated after reading the disclosure of the previous invention, the coefficient ink of positive temperature or the coating materials according to this invention, could also be used in applications such as refrigerator door heaters, de-icing heaters, baby bottle warmers, for the protection of rechargeable batteries, for thermistors (detection of preset temperatures), for printed fuses and resettable fuses, for process heaters, for printed circuits, and many more of these applications. The binder resin used in the invention should be present in the resistor composition of positive temperature coefficient within the broad range of about 3 percent to about 75 percent by weight of the composition, and preferably within the scale from about 4 percent to about 60 percent by weight, the best results being obtained when the binder resin is present within the range of about 5 percent to 10 percent by weight of the composition. The binder resin is preferably a thermoplastic binder resin selected from the group consisting of a urethane resin, a vinyl resin, and an acrylic resin, a phenoxy resin, or a polyester resin. However, said widely, the binder resin can also be selected from the same groups of resins mentioned, but which is of the type thermoforbable The temperature-activatable semicrystalline polymer, which is a thermoplastic elastomer (ETP), should be widely present in the resistor composition of positive temperature coefficient within the range of about 2 percent to 70 percent by weight, and preferably within the range of about 4 percent to about 45 percent by weight, the best results being obtained when this polymer is present within the range of about 6 percent to about 10 percent by weight of the composition . This semi-crystalline temperature-activatable polymer is a polymer different from that used for the binder resin, and is mutually exclusive with respect thereto. The electrically conductive material in a form of fine particles should be widely present in the resistive composition of positive temperature coefficient, within the range of about 10 percent to 80 percent by weight, and preferably within the scale from about 20 percent to about 70 percent by weight, the best results being obtained when this conductive material is present within the range of about 25 percent to about 45 percent by weight of the composition. The solvent material used in connection with the Resistor composition, and / or with the applied ink coatings made with this resistor composition, should be widely present within the range of about 0.01 percent to about 80 percent by weight of the composition, and preferably within of the scale from about 0.5 percent to about 75 percent by weight, the most preferred results being obtained when the solvent is present within the range of about 8 percent to about 50 percent by weight of the composition, and the best results being obtained with 30 percent to 50 percent by weight of the composition. It should also be understood that, when the positive temperature coefficient resistor composition is applied as a coating or as an ink to a substrate, for the purposes of forming an electrical device, the solvent may only be present in trace amounts within the applied or coating applied ink; and in accordance with the foregoing, the lower limit of 0.01 weight percent means that it includes only trace amounts of this solvent, which would remain in the composition after it was applied as a coating or as an ink to some substrate. The substrates on which the resistor composition is applied or used may be of a flexible, semi-flexible, or rigid form. The additive materials that are used in the Composition of the invention are present anywhere from about 0 to about 15 weight percent of the positive temperature coefficient resistor composition, and are preferably present within the range of about 0.01 percent to about 12 weight percent of the composition, still improved results being obtained when this additive material or materials are present within the range of about 1 percent to about 10 percent by weight of the composition. The additive materials useful in the invention are selected from at least one member of the group consisting of a flow substance, a dispersion substance, a wetting substance, a viscosity control substance, or a rheological substance. Although it will be seen that the preferred embodiments of the invention, disclosed above, are well calculated to satisfy the objects, benefits, and advantages of the invention, it will be appreciated that the invention is amenable to modification, variation, and change, without departing from of the appropriate scope or the fair meaning of the appended claims.

Claims (21)

1. NOVELTY OF THE INVENTION Having described the foregoing invention, it is considered as a novelty, and therefore, the content of the following is claimed as property: CLAIMS 1. A resistor composition of positive temperature coefficient (CTP), comprised of (a) an electrically conductive material in finely particulate form, selected from the group consisting of silver, graphite, graphite / carbon, nickel, copper, silver coated with copper, and aluminum; this conductive material being dispersed in a thick polymer film (PPG) system; (b) a semicrystalline polymer that exhibits significant increases in volume by means of phase transitions at elevated temperatures; This semicrystalline polymer is dispersed in the thick polymer film (PPG) system. The invention according to claim 1, characterized in that, the percentage by weight, part (a) is from about 60 percent to about 90 percent of the composition; part (b) is from about 10 percent to about 40 percent of the composition. 3. The invention according to claim 2, characterized in that: the semicrystalline polymer is a polymer of thermoplastic elastomer (ETP), which melts on a relatively narrow and precise temperature scale, to change in this way from a crystalline state to an amorphous state. 4. A positive temperature coefficient resistor (CTP) composition, which comprises: (a) from about 3 percent to about 75 weight percent of a binder resin, (b) of about 2 percent to about 70 weight percent of a semicrystalline temperature-activatable polymer, which is a thermoplastic elastomer (ETP) that melts on a relatively narrow temperature scale, to change from a crystalline state to an amorphous state, (c) from about 10 percent to about 80 weight percent of an electrically conductive material in a finely particulate form selected from the group consisting of silver, graphite, graphite / carbon, nickel, copper, silver coated with copper and aluminum , (d) from about 0.01 percent to about 80 percent by weight of a solvent material for the composition. 5. The invention according to claim 4, characterized in that, the percentage by weight: part (a) is from about 4 percent to about 60 percent; part (b) is from about 4 percent to about 45 percent; part (c) is approximately 20 percent, approximately 70 percent; part (d) is from about 0.5 percent to about 75 percent. 6. The invention according to claim 4, characterized in that, the percentage by weight: part (a) is from about 5 percent to about 10 percent; part (b) is from about 6 percent to about 10 percent; part (c) is from about 25 percent, to about 45 percent; part (d) is from about 30 percent to about 50 percent. The invention according to claim 4, characterized in that, the weight percentage, this composition also includes: from zero to about 15 weight percent of an additive material selected from at least one member of the group consisting of a flow control substance, a dispersion substance, a wetting substance, a viscosity control substance, and a rheological substance. The invention according to claim 4, characterized in that, the weight percentage of the composition also includes: from about 0.01 percent to about 12 percent by weight of an additive material selected from when less a member of the group consisting of a flow control substance, a dispersion substance, a wetting substance, a viscosity control substance, and a rheological substance. The invention according to claim 6, characterized in that, the weight percentage of the composition also includes: from about 0.001 percent to about 12 percent by weight of an additive material selected from when minus one member of the group consisting of a flow control substance, a dispersion substance, a wetting substance, a viscosity control substance, and a rheological substance. 10. An electrical device made of a resistor composition of positive temperature coefficient, comprised of: (a) from about 3 percent to about 75 percent by weight of a binder resin, (b) about 2 percent by weight one hundred to about 70 weight percent of a semicrystalline temperature-activatable polymer, which is a thermoplastic elastomer (ETP) that melts on a relatively narrow temperature scale, to change from a crystalline state to an amorphous state, (c) ) from about 10 percent to about 80 percent by weight of an electrically conductive material in a finely particulate form selected from the group consisting of silver, graphite, graphite / carbon, nickel, copper, silver coated with copper and aluminum, (d) from about 0.01 percent to about 80 percent by weight of a material solvent for the composition, and wherein the positive temperature coefficient resistor composition is applied to at least one substrate surface inside the electrical device, and this device includes at least one electrical circuit to conduct electricity into the device. The invention according to claim 10, characterized in that, the percentage by weight: part (a) is from about 4 percent to about 60 percent; part (b) is from about 4 percent to about 45 percent; part (c) is from about 20 percent, to about 70 percent; part (d) is from about 0.5 percent to about 75 percent. 12. The invention according to claim 10, characterized in that, the percentage by weight: part (a) is from about 5 percent to about 10 percent; part (b) is from about 6 percent to about 10 percent; part (c) is approximately 25 percent, approximately 45 percent; part (d) is from about 30 percent to about 50 percent. 13. The invention according to claim 10, characterized in that, this composition also includes: from zero to about 15 weight percent of an additive material selected from at least one member of the group consisting of a flow control substance, a dispersion substance, a wetting substance, a viscosity control substance, and a rheological substance. The invention according to claim 10, characterized in that, this composition also includes: from about 0.01 percent to about 12 percent by weight of an additive material selected from at least one member of the group which consists of a flow control substance, a dispersion substance, a wetting substance, a viscosity control substance, and a rheological substance. 15. The invention according to claim 12, characterized in that, this composition also includes: from about 0.01 percent to about 12 percent by weight of an additive material selected from at least one member of the group which consists of a substance of flow control, a substance of dispersion, a wetting substance, a viscosity control substance, and a rheological substance. 16. A method for manufacturing an electrical device, which comprises the steps of: (1) providing a resistor composition of positive temperature coefficient, comprised of: (a) from about 3 percent to about 75 percent in weight of a binder resin, (b) from about 2 percent to about 70 percent by weight of a semicrystalline temperature-activatable polymer, which is a thermoplastic elastomer (ETP) that melts on a relatively narrow temperature scale , to change from a crystalline state to an amorphous state, (c) from about 10 percent to about 80 weight percent of an electrically conductive material in a finely particulate form selected from the group consisting of silver, graphite , graphite / carbon, nickel, copper, silver coated with copper and aluminum, (d) from about 0.01 percent to about 80 percent by weight of a solvent material for the composition, and (2) applying the resistive composition of positive temperature coefficient to a substrate, which is a part of the electrical device mentioned. 17. The invention in accordance with the claim in claim 16, characterized in that, the percentage in weight: part (a) is from about 4 percent to about 60 percent; part (b) is from about 4 percent to about 45 percent; part (c) is from about 20 percent, to about 70 percent; part (d) is from about 0.5 percent to about 75 percent. 18. The invention according to claim 16, characterized in that the percentage by weight: part (a) is from about 5 percent to about 10 percent; part (b) is from about 6 percent to about 10 percent; part (c) is from about 25 percent, to about 45 percent; part (d) is from about 30 percent to about 50 percent. 19. The invention according to claim 16, characterized in that, this composition also includes: from zero to about 15 weight percent of an additive material selected from at least one member of the group consisting of a flow control substance, a dispersion substance, a wetting substance, a viscosity control substance, and a rheological substance. 20. The invention in accordance with the claims made in Claim 16, characterized in that, this composition also includes: from about 0.01 percent to about 12 percent by weight of an additive material selected from at least one member of the group consisting of a flow control substance, a dispersion substance, a wetting substance, a viscosity control substance, and a rheological substance. The invention according to claim 18, characterized in that, this composition also includes: from about 0.01 percent to about 12 percent by weight of an additive material selected from at least one member of the group which consists of a flow control substance, a dispersion substance, a wetting substance, a viscosity control substance, and a rheological substance.