The use of conductor compositions in electronic circuits

The present invention relates to a zinc-containing conductor composition. These compositions are particularly useful, for example, in automotive glazing, especially in the manufacture of anti-fog elements for heated windows in automotive backlights.

The use of thick-film conductors as components in hybrid ultra-small electronic circuits is well known in the electronics field. Compositions for the manufacture of such parts usually take the form of a paste-like solid-liquid dispersion system in which the solid phase contains finely divided particles of a noble metal or noble metal alloy or a mixture thereof and an inorganic binder. The liquid vehicle for the dispersion system is typically an organic liquid medium, but may be an aqueous liquid medium. Small amounts of additives (generally less than about 3% by weight of the composition) may be added to modify the properties of the composition, which are contaminants, rheology modifiers, adhesion enhancers and sinterings. Contains modifiers.

The metal used in the preparation of the thick film conductor composition is typically selected from silver, gold, platinum and palladium. The metal can be used either isolated or as a mixture that forms an alloy upon firing. Common metal mixtures include platinum / gold, palladium / silver, platinum / silver, platinum / palladium / gold and platinum / palladium / silver. The most common systems used in the production of heating elements are silver and silver / palladium. Inorganic binders are typically glass-forming materials such as glass or lead silicate, which serve as both binders within and between the composition and the substrate on which the composition is coated. .. Due to environmental concerns, the use of lead-containing binders has become less common, and lead-free binders such as zinc borosilicate or bismuth borosilicate are now often used. The role of the organic medium is to disperse the microparticle constituents and to facilitate the transfer of the composition onto the substrate.

The consistency and rheology of the composition is tailored to the individual method of application, which may include screen printing, brushing, dipping, extrusion, spraying and the like. Typically, screen printing is used to apply the composition. The paste is usually applied to an inert substrate such as alumina, glass, ceramic, enamel, enamel coated glass or metal substrate to form a patterned layer. The thick conductor layer is usually dried and then usually fired at temperatures between about 600 ° C and 900 ° C to volatilize or burn the liquid vehicle and sinter or melt the inorganic binder and metal constituents. Let me. Direct wet firing, i.e. firing in which the thick film layer is not dried prior to firing, has also been used to produce patterned layers.

Of course, it is necessary to connect the conductive pattern to other components of the electronic circuit, such as power supplies, resistors and capacitors networks, resistors, trim potentiometers, chip resistors and chip carriers. This is generally achieved by using metal chips that typically contain copper, either directly adjacent to the conductive layer or soldered to the top surface of the layer. When the chip is soldered to the top surface of the conductive layer, the bond is either directly onto the conductive pattern itself or onto a solderable composition (overprint) that is overprinted onto the pattern. Either. Overprints are generally areas of the conductive pattern in which the metal chips are soldered together and are applied only in what is commonly referred to as the "clip area". The ability to solder onto the conductive layer is an important parameter in the manufacture of heating elements as it removes the requirement for overprinting. However, the inorganic binder, which is important for binding the paste onto the substrate, can prevent solder wetting and result in unsatisfactory adhesion of the soldered metal chips to the conductive layer. It is often difficult to meet the requirements of high substrate adhesion and high solderability (or adhesion of metal chips to conductive patterns) at the same time. The US Patent Gazette (Patent Document 1) provides a solution to this problem by incorporating crystalline materials from the feldspar family into the composition.

An important application of patterned conductive layers is in the automotive industry, especially with defrosting and defrosting by a conductive grid that is permanently attached to the window and can generate heat when powered by a power source. / Or in the manufacture of windows that can prevent fogging. In order for the windows to defrost quickly, the circuit must be able to supply a large amount of power from a low voltage power source, typically 12 volts. For such power supplies, the perfection requirement of the conductive pattern is generally in the range of about 2 to about 5 μΩcm (5 mΩ / Y at 10 μm after firing). This requirement is easily met by conductors containing precious metals, especially silver, which are the most commonly used materials for this application.

For certain applications, conductive compositions with higher intrinsic resistance are required. In particular, as the automotive industry is expected to adopt the use of 42 and 48 volt power supplies in the near future, it is expected that the resistance requirements for window heating elements in automobiles will soon need to be changed. As a result, the conductive compositions used to make window heating elements have higher intrinsic resistance values, typically greater than about 10 μΩcm, preferably greater than about 12 μΩcm, especially about 20 to about 70 μΩcm. It will be necessary to show the intrinsic resistance value in the range of.

A number of different materials may be added to adjust the specific resistance of the conductive composition. As disclosed in US Patent Gazette (Patent Document 2) and US Patent Gazette (Patent Document 3), metal resinates such as rhodium and manganese resinates have been used to increase intrinsic resistance, for example. In addition, increased content of noble metals, especially platinum group metals such as platinum and palladium, have also been used to increase specific intrinsic resistance. Silver / palladium and silver / platinum compositions can achieve intrinsic resistance values from about 2 μΩcm (values for compositions containing only silver and binder) to about 100 μΩcm (for 70:30 Pd: Ag blends). However, systems containing platinum and / or palladium are significantly more expensive and their use is prohibited in applications that require large surface area coverage, such as window heating elements used in the automotive industry. Will. In addition, certain metal blends contain high amounts of silver (and typically small amounts of filler), such as compositions containing high palladium levels, to achieve sufficient solder adhesion. Overprinting of the composition is generally required. Conventional conductive compositions, typically operating with an intrinsic resistance value of 2-5 μΩ cm and consisting primarily of silver, can be overprinted as acceptable levels of solder adhesion can be achieved by adjusting the level of the inorganic binder. do not need.<patcit num="1"><text>U.S. Pat. No. 5,518,663</text></patcit><patcit num="2"><text>U.S. Pat. No. 5,162,062</text></patcit><patcit num="3"><text>U.S. Pat. No. 5,378,408</text></patcit><patcit num="4"><text>U.S. Pat. No. 3,583,931</text></patcit><patcit num="5"><text>U.S. Pat. No. 5,378,406</text></patcit>

<p> Another lower cost approach to achieving high intrinsic resistance involves blending large amounts of filler into the silver-containing conductive composition to block the conductive path. Fillers are typically inorganic materials, commonly used are glass (which may be the same as or different from that used for binders) and alumina (or other metal oxides). .. However, such an approach tends to result in loss of solder acceptance and solder adhesion. For example, sufficient solder adhesion can be maintained up to the level of only about 10% by weight alumina in the composition, but this level is generally too low for an easily perceptible increase in intrinsic resistance. For glass-type fillers, solder adhesive loss occurs at even lower levels, again this level is too low for an easily perceptible increase in intrinsic resistance. Moreover, this problem cannot usually be ameliorated by the use of silver overprints due to the interlaminar transition of the glass during firing, specifically the transition from the conductive coating to the overprint.</p><p> A further favorable property of the conductor composition is its chemical durability and resilience to exposure to changing environmental conditions such as temperature, humidity, acids and salts. Compositions containing large amounts of glass fillers, especially lead-free glass fillers, are often relatively unstable to such factors.</p><p> An additional consideration is that it is desirable that the resistance of the coating composition be substantially independent of the firing temperature used in the production of the patterned conductive layer. For example, in the case of application of a conductive composition to a glass substrate, the behavior of the composition during sintering and melting should remain substantially constant between temperatures of about 620 and 680 ° C. .. Nevertheless, a change in resistance of up to about 10% between these two temperatures, which corresponds to the behavior of the sterling silver composition, is generally acceptable. The use of large amounts of filler to sufficiently increase the intrinsic resistance generally results in compositions that do not meet this requirement.</p><p> Further additional considerations are that the relationship between the intrinsic resistance and the amount of intrinsic resistance modifier added to the composition is relatively predictable and / or substantially within the desired intrinsic resistance target range. It is desirable to be primary. The intrinsic resistance of a composition containing a large amount of packing material generally increases almost in the primary wind until the critical concentration is reached. At this critical concentration, the intrinsic resistance increases very rapidly, often by an order of magnitude, when the level of the intrinsic resistance modifier increases by only a fraction of the weight percent. As a result, it is difficult to target specific values of intrinsic resistance for such compositions.</p><p> It is an object of the present invention to provide a higher intrinsic resistance conductive composition that is not impaired by the above inconveniences. In particular, it is an object of the present invention to provide an economical conductive coating composition that has increased intrinsic resistance but at the same time exhibits good solderability.</p>

<p> According to the present invention, a composition comprising (a) a conductive material, (b) one or more inorganic binders, and (c) finely divided particles of zinc, which is conductive on a substrate. For the purpose of increasing the intrinsic resistance of the pattern, the use of compositions in which the constituents (a), (b) and (c) are dispersed in a liquid vehicle, preferably an organic medium, is provided.</p><p> According to a further embodiment of the invention, (a) conductive materials and (b) one or more dispersed in a liquid vehicle for the purpose of increasing the intrinsic resistance of the conductive pattern produced from the composition. The use of finely divided particles of zinc in the composition further comprising finely divided particles of the seed inorganic binder is provided.</p><p> According to a further embodiment of the invention, a conductive material made from a composition comprising (a) a conductive material dispersed in a liquid vehicle and (b) finely divided particles of one or more inorganic binders. A method of increasing the intrinsic resistance of a pattern is provided that comprises (c) incorporating finely divided particles of zinc into the composition.</p><p> According to a further embodiment of the present invention, a method for producing a conductive pattern, which comprises (a) conductive particles, (b) one or more inorganic binders, and (c) finely divided particles of zinc. A step of applying a composition containing the constituents (a), (b) and (c) to a liquid vehicle, preferably dispersed in an organic medium, and firing the coated substrate. , A method comprising a step of achieving sintering of finely divided particles into a substrate is provided. Preferably, the method is a screen printing method.</p><p> According to a further embodiment of the invention, a substrate, typically a hard substrate such as glass (including tempered and laminated glass), enamel, enamel coated glass, ceramics, alumina or metal substrates. Provided are (a) conductive materials, (b) one or more inorganic binders, and (c) substrates having a conductive pattern on one or more surfaces thereof, including zinc. ..</p>

The compositions described herein are suitable for use, for example, as a paste composition for forming a thick film conductive pattern on a substrate by a screen printing method. These compositions are particularly useful for use in the automotive industry as parts in the manufacture of windows that can be defrosted and / or prevented from fogging by a conductive grid attached to the window.

The composition preferably exhibits a value of intrinsic resistance greater than about 10 μΩcm, preferably greater than about 12 μΩcm, preferably in the range of about 20 to about 70 μΩcm, more preferably in the range of about 20 to about 50 μΩcm. Thus, as used herein, the term "increasing the intrinsic resistance" is more preferably greater than about 10 μΩcm, preferably greater than about 12 μΩcm, preferably in the range of about 20 to about 70 μΩcm. Means that the value of the intrinsic resistance in the range of about 20 to about 50 μΩcm is preferably increased. In one embodiment, the intrinsic resistance is in the range of about 30 to about 40 μΩcm.

As used herein, the term "finely chopped" is intended to mean that the particles are fine enough to pass through a 400 mesh sieve (US standard sieve scale). It is preferred that at least 50%, preferably at least 90%, more preferably substantially all of the particles are in the size range of 0.01-20 μm. Preferably, the maximum size of substantially all particles is about 10 μm or less, preferably about 5 μm or less.

Preferably, the constituents are present in such an amount that the total amount of the constituents (a), (b) and (c) is about 50 to about 95% by weight of the composition, and the liquid vehicle is about 5 to about 5 to about 5 to about 5 to about 5% by weight of the composition. It is present in an amount of about 50% by weight. In a preferred embodiment, the total amount of the constituents (a), (b) and (c) is in the range of about 60 to about 90% by weight, preferably about 70 to about 85% by weight of the composition.

Formulations (a), (b) and (c) generally include substantially all of the solid phase materials used to prepare the compositions used in the present invention.

Preferably, component (a) is about 30 to about 99.4% by weight, preferably about 50 to about 98% by weight, more preferably about 60 to about 90% by weight, and more of the total solids present in the composition. It is preferably present in an amount of about 60 to about 75% by weight.

The component (b) is preferably present in an amount of about 0.5 to about 40% by weight, preferably about 1 to about 25% by weight, preferably about 2 to about 15% by weight of the total solid content present in the composition. To do.

Preferably, the component (c) is in an amount of about 1 to about 30% by weight, preferably about 2 to about 20% by weight, more preferably about 10 to about 20% by weight of the total solids present in the composition. Exists.

The conductive particles of component (a) can be in any form suitable for the production of the compositions used in the present invention. For example, the conductive metal particles may be in the form of either metal powder or metal flakes or a blend thereof. In one embodiment of the invention, the metal particles are a blend of powder and flakes. The particle size of the metal powder or flakes is not meticulously critical on its own in terms of technical efficacy. However, particle size affects the sintering properties of metals, as large particles sinter at a lower rate than smaller particles. Blends of powders and / or flakes of different sizes and / or proportions can be used to match the sintering properties of the conductor formulation during firing, as is well known in the art. However, the metal particles should be of suitable size for the application method, which is usually screen printing. Therefore, metal particles are generally about 20 μm or less in size, preferably less than about 10 μm. The minimum particle size is usually about 0.1 μm.

The preferred metal for the conductive component (a) of the conductor composition is silver. Silver particles larger than about 1.0 μm give the composition greater coloration. The composition preferably contains at least 50% by weight silver particles larger than 1.0 μm. Silver is usually of high purity, typically greater than 99%. However, less pure materials can be used, depending on the electrical requirements of the conductive layer or pattern. In one embodiment of the invention, component (a) comprises a mixture of silver and nickel and / or a suitable derivative. A preferred nickel derivative suitable for use in this embodiment of the invention is nickel boride (Ni).₃B). Typically, the Ag: Ni ratio is about 1: 1 to about 25: 1, preferably at least about 1.5: 1, and more preferably about 1.5: 1 to about 3: 1. References to the conductive component (a) and its relative amounts herein refer to the component (c), even if the particles of the component (c) are conductive in their own right. It will be appreciated by those skilled in the art that it does not include references to or its relative quantities. Similarly, references to constituent (c) particles and their relative quantities refer to constituent (a) conductive particles and their relatives, even if the constituent (c) particles are themselves conductive. Does not include reference to quantity.

The constituents (c) in the compositions used in the present invention are substantially in the following forms: (i) zinc metal particles, (ii) particles of zinc-containing alloys, and (iii) substantially on metals under the action of heat. Includes one or more zinc derivatives of zinc that are converted to.

Preferably, the particles of component (c) are metallic zinc particles and / or particles of a zinc-containing alloy. More preferably, the particles of the component (c) are metallic zinc particles.

The particle size should generally be no more than about 20 μm, preferably less than 10 μm. The minimum particle size is usually about 0.1 μm. The particles may be spherical or spheroidal or irregular in shape, in the form of flakes or powders, or other suitable morphology.

The use of component (c) as an additive uses a large amount of filler to increase (i) high intrinsic resistance, and (ii) high solder adhesion, preferably (iii) intrinsic resistance. Provided are compositions that increase the concentration of additives with respect to the composition and show a more uniform increase in intrinsic resistance, and preferably (iv) a lower change in resistance at calcination temperature. In addition, zinc is a relatively inexpensive material and is an economical way to increase intrinsic resistance.

Inorganic binders suitable for use in the present invention bond metals to substrates such as glass (including tempered glass and laminated glass), enamel, enamel coated glass, ceramics, alumina or metal substrates during sintering. It is a useful material to do. Inorganic binders, also known as frit, contain finely divided particles and are important constituents in the compositions described herein. The softening point and viscosity of the frit during firing are important factors as well as the wetting properties of the metal powder / flakes and substrate. The particle size of the frit is not meticulously critical and the frit useful in the present invention typically has an average particle size of about 0.5 to about 4.5 μm, preferably about 1 to about 3 μm.

The composition can be fired at the desired temperature (typically 300-700 ° C, especially 580-680 ° C) to achieve proper sintering, wetting and adhesion to the substrate, especially the glass substrate. To be possible, the inorganic binder is preferably a frit with a softening point between about 350 ° C and 620 ° C. It is known that a mixture of high and low melting point frits can be used to control the sintering properties of conductive particles. In particular, it is believed that the high temperature frit dissolves in the lower melting point frit and together they slow down the sintering rate of the conductive particles compared to a paste containing only the low melting point frit. This control of sintering properties is particularly advantageous when the composition is printed on decorative enamel and fired. (Decorative enamel is usually a paste consisting of one or more pigment oxides and emulsions and glass frit dispersed in an organic medium.) High melting point frit has a softening point above 500 ° C. The low melting point frit is considered to have a softening point below 500 ° C. The difference in melting temperature between the high and low melting point frits should be at least 100 ° C, preferably at least 150 ° C. Mixtures of three or more frits with different melting temperatures can also be used. When mixtures of high and low melting point frits are used in the present invention, they are usually used in a weight ratio of 4: 1 to 1: 4.

As used herein, the term "softening point" means the softening temperature obtained by the fiber elongation method of ASTM C338-57.

Suitable binders are lead borate, lead silicate, lead borate, cadmium borate, lead cadmium borate, zinc borosilicate, sodium cadmium borosilicate, bismuth silicate, bismuth borosilicate, bismuth silicate and borosilicate. Contains bismuth lead. Typically, any glass having a high content of bismuth oxide, preferably at least 50% by weight, more preferably at least 70% by weight, is preferred. Lead oxide as the exfoliation phase may also be added if desired. However, due to environmental considerations, lead-free binders are preferred. Examples of glass compositions (compositions A through I) are shown in Table 1 below, with oxide constituents shown in weight percent.

<tables num="1"><img file="JP4163003B2_D0001.tif" /></tables>

Glass binders are made by conventional glass manufacturing techniques with the desired constituents (or precursors thereof, eg B).₂O₃About H₃BO₃) Are mixed in the desired proportions and the mixture is heated to form a melt. As is well known in the art, heating is carried out for a period of time to a peak temperature at which the melt is completely liquid and further gas generation ends. Peak temperatures are generally in the range of 1100-1500 ° C, usually 1200-1400 ° C. The melt is then quenched by cooling it, typically by pouring it onto a cold belt or into cold running water. Particle milling can then be accomplished by milling as desired.

Other transition metal oxides may also be used as part of the inorganic binder, as is well known to those of skill in the art. Oxides or precursors of zinc, cobalt, copper, nickel, manganese and iron are commonly used, especially with substrates other than glass substrates such as alumina substrates. These additives are known to improve soldering adhesion.

Inorganic binders also have the general formula (M)_XM'_2-X) M ₂O_7-Z(In the formula, M is selected from at least one of the rare earth metals having atomic numbers Pb, Bi, Cd, Cu, Ir, Ag, Y and 57-71 and mixtures thereof, and M'is Pb, Bi. And selected from their mixtures, M "is selected from Ru, Ir, Rh and mixtures thereof, with X = 0 to 0.5 and Z = 0 to 1). The paste can be contained up to approximately 4 parts by weight.

The yellow-green stone material is described in detail in the US Patent Gazette (Patent Document 4), the disclosure of which is incorporated herein by reference. The yellow-green stone material acts as an adhesion promoter for the compositions of the present invention. Copper bismuth lutenate (Cu_0.5Bi_1.5Ru₂O_6.75) Is preferable.

Traditionally, conductive compositions have been based on lead frit. Binders that can be used to achieve the desired softening and flow properties while simultaneously meeting wettability, thermal expansion, cosmetic and performance requirements by removing lead from the glass composition to comply with current toxicity and environmental regulations. Types may be limited. The disclosure is incorporated herein by reference (Patent Document 5), all of which may be used in the compositions described herein.₂O₃, Al₂O₃, SiO₂, CaO, ZnO and B₂O₃Describes a series of low toxicity, lead-free glasses based on.

In a preferred embodiment of the invention, the frit is composition I of Table 1 herein.

The components (a)-(c) of the compositions described above herein are usually dispersed in a liquid vehicle to form a semi-fluid paste that can be printed into the desired circuit pattern. To do. The liquid vehicle may be an organic medium or an aqueous vehicle. Preferably the liquid vehicle is an organic medium. Any preferably inert liquid can be used as the organic medium. Liquid vehicles have acceptable wettability between solids and substrates, relatively stable dispersion of particles in the paste, good printing performance, sufficient dry film strength to withstand rough handling, and good firing properties. Should be provided. Various organic liquids with or without thickeners, stabilizers and / or other common additives are suitable for use in the preparation of the compositions of the present invention. Typical organic liquids that can be used are alcohols (including glycols), acetates, propionates and phthalates, such as esters of such alcohols such as dibutyl phthalate, pine oils, terpineols. A solution of a resin such as terpen, a lower alcohol polymethacrylate, or a solution of ethyl cellulose in a solvent such as pine oil and monobutyl ether of diethylene glycol. The vehicle can also contain a volatile liquid to facilitate fast setting after application to the substrate.

Preferred organic media are, for example, dibutyl phthalate or monobutyl ether of diethylene glycol (butyl carbitol).^TMIt is based on a thickener combination consisting of ethyl cellulose (typically in a 1: 9 ratio) in terpineol, optionally combined with (sold as). A further preferred organic medium is based on an ethyl cellulose resin and a solvent mixture of alpha-, beta- and gamma-terpineols (typically 85-92% alpha-terpineols containing 8-15% beta and gamma-terpineols). ing.

The ratio of liquid vehicle to solid content in the dispersion system can vary considerably and is determined by the final desired formulation viscosity, which in turn is determined by the printing requirements of the system. Generally, in order to achieve good coverage, the dispersion is about 50 to about 95% by weight, preferably about 60 to about 90% by weight solids, and about 5 to about 50% by weight, as described above. Preferably it will contain from about 10 to about 40% by weight liquid vehicle.

The composition is a further addition known in the art, such as colorants and contaminants, rheology modifiers, adhesion enhancers, antisinters, green-state modifiers, surfactants and the like. It may further contain objects.

In the preparation of the composition, the granular inorganic solids are mixed with the liquid vehicle and dispersed in a suitable device such as a 3-roll mill or power mixer according to the prior art well known in the art to form a suspension. The resulting composition is generally about 10-500 Pa · s at a shear rate of 4 / sec, as measured, for example, on a Brookfield HBT viscometer using a # 5 spindle at 10 rpm and 25 ° C. It has a viscosity in the range of, preferably in the range of about 10 to 200 Pa · s, more preferably in the range of about 15 to 100 Pa · s. The general procedure for preparing the compositions used in the present invention is described below.

Weigh the ingredients of the paste together in a container. The components are then vigorously mixed with a mechanical mixer to form a uniform blend, which is then passed through a disperser such as a 3-roll mill to achieve good dispersion of the particles, eg, a rheology by screen printing. It produces a paste-like composition with a consistency and rheology suitable for application on the material. A Hegman instrument is used to measure the dispersion of particles in the paste. The instrument consists of channels in a steel block that are 25 μm (1 mil) deep at one end and slope to zero depth at the other end. A blade is used to pull the paste down along the length of its channel. If the diameter of the agglomerates is larger than the channel depth, scratches will appear in the channel. A satisfactory dispersion will typically give a fourth scratch point of 10-18 μm. The point where half of the channels are not covered with a well-dispersed paste is typically between 3 and 8 μm. A fourth scratch measurement of&gt; 20 μm and a half-channel measurement of&gt; 10 μm suggest an unsatisfactory dispersed suspension.

The composition is then applied to the substrate to a wet thickness of about 20-60 μm, preferably about 35-50 μm, typically by screen printing, using prior art known in the art. The composition can be printed on the substrate by using either an automatic printer or a manual printer in the conventional manner. Preferably, automatic screen printing techniques are used with 200-325 mesh screens per inch. The printed pattern is optionally dried below 200 ° C., preferably at about 150 ° C., for about 30 seconds to about 15 minutes before firing. Firing to achieve sintering of both the inorganic binder and the finely chopped metal particles allows the vehicle to burn out at about 200-500 ° C and lasts about 30 seconds-about 15 minutes at about 500-1000 °. C, preferably a period of maximum temperature of about 600-850 ° C, is preferably carried out in a well-ventilated conveyor belt furnace with a subsequent temperature profile. This is followed by a cooling cycle, an arbitrarily controlled cooling cycle, to prevent substrate breakage that can result from oversintering, unwanted chemical reactions at intermediate temperatures or premature cooling. Alumina substrates are particularly vulnerable to breakage resulting from excessive cooling. The entire firing procedure is about 1 to 25 minutes to reach the firing temperature, about 10 seconds to about 10 minutes at the firing temperature, and about 5 seconds to about 25 minutes for cooling, preferably about 2 to. It will last for a period of 60 minutes. For the production of tempered glass substrates, the entire firing procedure is controlled over a period of typically approximately 2-5 minutes, with approximately 1-4 minutes to reach the firing temperature and subsequent rapid cooling. Cooling cycle is commonly used.

The typical thickness of the thick film after firing is about 3 μm to about 40 μm, preferably about 8 μm to about 20 μm.

The compositions described herein are primarily intended for use in automotive glazing, especially in the manufacture of heating elements in windows such as defrosting or anti-fog elements in automotive backlights. The composition may also be used to incorporate other conductive features such as printed antennas or antennas into the window. However, the coating composition can be used in a variety of other applications, generally including printed circuits and heating elements. For example, the composition may be used as a bottom plate in a hot water heater. Within the electronics and electrical industries, there is a general demand for lower cost heating elements, especially screen printable heating elements.

The compositions described herein were evaluated using the following procedure.

(Test procedure) (Adhesive) Copper chips (obtained from Quality Product Gen. Eng., Wickwar, UK), 70/27/3 Pb Using a / Sn / Ag solder alloy, solder was applied to a fired conductive pattern on a glass substrate (dimensions 10.2 cm × 5.1 cm × 3 mm) at an iron soldering temperature of 350 to 380 ° C. ALPHA 615-25® (Alpha Metals, Croydon, UK) A small amount of slightly active rosin flux, such as Limited, Croydon, UK)), may be used to increase solder wetting and hold the solder and clip in place during assembly of the part, in which case the flux will be. , May be soldered using a shallow tray containing a thin film of new flux. The adhesive strength was measured with a Chattillon (registered trademark) tensile tester model USTM at a tensile speed of 0.75 ± 0.1 inch / min (1.91 ± 0.25 cm / min), and the tensile strength was recorded by adhesive fracture. The average value of adhesive fracture over 8 samples was calculated. The adhesive strength should be preferably greater than 10 kg, more preferably greater than 15 kg, and even more preferably greater than 20 kg. The main methods of bonding adhesion are as follows. (a) The clip separates from the conductive pattern (ie, unsatisfactory soldering). (b) The conductive pattern separates from the substrate (ie, unsatisfactory substrate adhesion). (c) Glass pullout / breakage (ie, the bond strength between the clip and the conductive layer and between the conductive layer and the equipment is greater than the strength of the substrate). (d) Destruction in solder

(Resistance and Intrinsic Resistance) The resistance of the conductive pattern fixed on a glass substrate (dimensions 10.2 cm x 5.1 cm x 3 mm) is Genrad calibrated for use between 1 and 900 Ω or equivalent. Model (GenRad Model) 1657 Measured using an RLC bridge. The thickness of the conductive layer can be determined by an isowave analyzer (eg, TALYSURF, a contact measuring device that analyzes the surface of the substrate in two dimensions using a spring-loaded stylus; any change in height. Use a thickness measuring device such as (the stylus is deflected and then this change is recorded on a recorder such as a chart recorder and the difference between the baseline and the average height indicates the print thickness). To measure. The resistance of the pattern is measured by placing the probe tip at the point where the conductive track meets the solder pad. The body-specific resistance (thickness standardization) of a layer is determined by dividing the measured resistance for the pattern by the number of squares there, where the number of squares is the length of the conductive track divided by the width of the track. Is. The intrinsic resistance value is obtained as mΩ / Y at a standardized thickness (10 μm herein) and is given here in μΩcm units.

(Particle size) The particle size in the composition is measured according to ASTM D1210-79 using a large Hegman type grain fineness meter.

(Chemical durability) A 1% glacial acetic acid solution in deionized water is used in this test. A glass substrate (50 x 100 mm) having a fired conductive pattern is placed on it in a plastic container half-filled with the test solution. The container is then sealed and left at ambient temperature. After 96, 168 and 336 hours, the test substrate is removed, dried and then analyzed by lift test. Lift test is 0.75 inch (19.1 mm) wide masking tape (Nice day)^TM) Is affixed onto the substrate and then sharply removed after approximately 1/2 second. The results of the lift test are shown as an approximate percentage of the film area removed by the tape.

The present invention will now be described with respect to the following examples. The examples are not intended to be limiting and it will be appreciated that detailed modifications can be made without departing from the scope of the invention.

(Examples 1 to 4) Conductive patterns were prepared using the method described earlier in this specification. The zinc particles used were sub-100 mesh spheroidal particles. The silver particles are 50% spherical silver particles (0.80 to 1.40m).²g^-1Surface area) and 50% flake silver particles (0.60 ~ 0.90m)²g^-1Was a mixture with (surface area). The glass used was Composition I in Table 1 herein. The liquid vehicle is diethylene glycol monobutyl ether (butyl carbitol).^TMIt was ethyl cellulose (in a 1: 9 ratio) in terpineol mixed with (sold as). The substrate was a float glass (non-tempered) substrate. The thickness of the fired film was 8 to 20 μm. Unless otherwise stated, the sample passed a peak temperature of approximately 72 seconds and all parts were fired through a belt furnace with a peak firing temperature of 660 ° C. The total transit time from the inlet to the outlet of the furnace was approximately 21 minutes.

The inherent resistance and solder adhesion of the pattern were measured as a function of composition according to the above procedure. The results are shown in Table 2 below.

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The data demonstrate that zinc-containing compositions allow the preparation of conductive patterns that exhibit increased intrinsic resistance but maintain solder adhesion. The present invention includes the inventions described in (1) to (26) below. Use of a composition comprising (1) (a) a conductive material, (b) one or more inorganic binders, and (c) finely divided particles of zinc, constituents (a), ( The fact that b) and (c) are dispersed in the liquid vehicle when the conductive pattern is produced on the substrate for the purpose of increasing the intrinsic resistance while maintaining the solder adhesion of the conductive pattern. Use of characteristic compositions. (2) A method of increasing the intrinsic resistance while maintaining the solder adhesiveness of the conductive pattern. In the production of the conductive pattern, (a) a conductive material, (b) one or more kinds of inorganic binders. , And (c) utilizing a composition comprising finely divided particles of zinc, characterized in that the constituents (a), (b) and (c) are dispersed in a liquid vehicle. Method. (3) The use according to (1) above, wherein the liquid vehicle is an organic medium. (Four) The use according to (1) above, wherein the component (c) contains metallic zinc particles. (5) The use according to (1) above, wherein the component (c) contains zinc-containing alloy particles. (6) The use according to (1) above, wherein the conductive particles are silver particles. (7) The use according to (1) above, characterized in that substantially all particles are in the range of 0.01 to 20 μm. (8) The use according to (1) above, wherein the total amount of the constituents (a), (b) and (c) is about 50 to about 95% by weight of the composition. (9) The use according to (1) above, wherein the constituent component (a) is present in an amount of about 50 to about 98% by weight of the total solid content present in the composition. (10) The use according to (1) above, wherein the constituent component (b) is present in an amount of about 2 to 15% by weight of the total solid content present in the composition. (11) The use according to (1) above, wherein the constituent component (c) is present in an amount of about 2 to 15% by weight of the total solid content present in the composition. (12) The production of the conductive pattern is a composition comprising (a) a conductive material, (b) one or more inorganic binders, and (c) finely divided particles of zinc, said component (a). ), (B) and (c) are dispersed in a liquid vehicle. The step of applying the composition to the base material, and firing the coated base material to sinter the finely divided particles into the base material. The use according to any one of (1) above or (3) to (11) above, which comprises a step of achieving the above. (13) The use according to (12) above, wherein the manufacture comprises a screen printing method. (14) Use in a composition of finely divided particles of zinc, dispersed in a liquid vehicle for the purpose of increasing the intrinsic resistance of the conductive pattern produced from the composition (14). Use of compositions characterized by a) further comprising a conductive material and (b) finely divided particles of one or more inorganic binders. (15) By a method of increasing the intrinsic resistance of a conductive pattern produced from a composition comprising (a) a conductive material dispersed in a liquid vehicle and (b) finely divided particles of one or more inorganic binders. A method, wherein the method comprises (c) incorporating finely divided particles of zinc into the composition. (16) The method according to (2) above, wherein the liquid vehicle is an organic medium. (17) The method according to (2) above, wherein the constituent component (c) contains metallic zinc particles. (18) The method according to (2) above, wherein the constituent component (c) contains particles of a zinc-containing alloy. (19) The method according to (2) above, wherein the conductive particles are silver particles. (20) The method according to (2) above, wherein substantially all particles are in the range of 0.01 to 20 μm. (21) The method according to (2) above, wherein the total amount of the constituents (a), (b) and (c) is about 50 to about 95% by weight of the composition. (22) The method according to (2) above, wherein the constituent component (a) is present in an amount of about 50 to about 98% by weight of the total solid content present in the composition. (twenty three) The method according to (2) above, wherein the component (b) is present in an amount of about 2 to 15% by weight of the total solid content present in the composition. (24) The method according to (2) above, wherein the constituent component (c) is present in an amount of about 2 to 15% by weight of the total solid content present in the composition. (25) The production of the conductive pattern is a composition comprising (a) a conductive material, (b) one or more inorganic binders, and (c) finely divided particles of zinc. A step of applying a composition in which the constituents (a), (b) and (c) are dispersed in a liquid vehicle to a base material, and a base of finely divided particles by firing the coated base material. The method according to any one of (2) above or (16) to (24) above, which comprises a step of achieving sintering into a material. (26) The method according to (25) above, wherein the production comprises a screen printing method.