FR2496386A1 - METHOD FOR FORMING A CONDUCTIVE COATING ON A SUBSTRATE AND METHOD FOR FORMING A CIRCUIT BOARD - Google Patents

Abstract

THE INVENTION RELATES TO A PROCESS FOR FORMING A CONDUCTIVE COATING ON A SUBSTRATE. ACCORDING TO THE INVENTION, AN ELECTRICALLY CONDUCTIVE MATERIAL IS APPLIED TO THE SURFACE OF A COMPOSITION OF UNHARDENED OR PARTLY HARDENED ORGANIC RESIN, HAVING A STICKY SURFACE, THIS COMPOSITION BEING PATTERNED LIKE A CIRCUIT ON A SUBSTRATE, AND THEN THE COMPOSITION IS HARDENED TO KEEP THE ELECTRICALLY CONDUCTIVE MATERIAL ON THE SURFACE BY THERMAL OR UV RADIATION AND THE ELECTRICALLY CONDUCTIVE MATERIAL IS REMOVED IN THE FREE STATE. THE INVENTION APPLIES IN PARTICULAR TO PRINTED CIRCUITS.

Description

The present invention relates to a method

  to form a conductive coating on a substrate.

  The present invention also relates to a method for forming conductive coatings on substrates to form circuit boards. Conductive coatings are known in the art.

  U.S. Patent No. 3,412,043 teaches a composition of

  The resinous and electrically conductive composition consists essentially of silver flakes, a resinous resin and finally an inert load subdivided at specified weight ratios. In this case, the resinous binder is an epoxy resin system which is cured by the addition of an amine curative at slightly elevated temperatures.

high.

  U.S. Patent No. 3,746,622 teaches revolu-

  electrically conducting elements comprising certain epoxy resins, particles of a hard or hard polymer

  having carboxy, hydroxy, amino or iso substituents

  cyanates that co-harden with the epoxy resin, and finally

  subdivided particles of a metal and a hardening agent

  epoxy resin. Curing is achieved by heating the composition to temperatures of 1250 ° C or higher. U.S. Patent No. 3,968,056 discloses a radiation curable ink comprising a particulate electrically conductive metal-containing material in combination with an organic resin binder that is converted to a conductive coating on the surface of a substrate by exposure to actinic or ionizing radiation. RE 30274 teaches a circuit board for activating high voltage flash lamps, which board comprises a thermoplastic and non-conductive substrate having an electrically conductive coating in a pattern on one of its surfaces and defining an electrical circuit for the lamps. flash, said coating comprising a UV curable organic resin matrix and an electrically conductive and particulate material selected from the group consisting of an electrically conductive and particulate metal and an electrically conductive and particulate metal-containing material, including mixtures thereof with not more than about 15% by weight of the electrically conductive and particulate material having an aspect ratio of diameter to

  the thickness of a value greater than 20.

  In all the above compositions according to the prior art used to form conductive coatings, it should be noted that an electrically conductive material is mixed in and with an organic resin, which mixture is then exposed to either heat or radiation. UV or ionizing. Such a system has a disadvantage because, because the organic resin is non-conductive but must necessarily act as a matrix for the electrically conductive material and adhere to the substrate in a desired pattern, it is necessary to use large amounts of an electrically conductive material such as flakes or pearls of silver, in order to obtain a commercially acceptable conductivity. Indeed, as the silver flakes or beads are scattered throughout the organic resin and not just in a linear conductive line, it is necessary to use an excessive amount of silver flakes or beads which represents the

  expensive of the electrically conductive composition.

  The use of large quantities of a material

  electrically conductive mixture with the hard resin

  This resultant mixture results in a mixture so thick and so high in viscosity that the screen printing of the circuit

  desired is extremely difficult, if not impossible.

  On the other hand, if the quantity of

  When the conductive agent mixed with the curable resin is reduced to allow the printing on the screen, the conductance obtained in the hardened mixture is often not

commercially acceptable.

  The present invention provides a method of forming a conductive coating on a substrate that requires less electrically conductive material to achieve the same conductivity. Another object of the present invention is a method wherein a conductive coating may be formed on a substrate using screen printing. Another subject of the present invention is a process for forming a conductive coating of a substrate by a photo-image. Other objects will become

  better apparent from reading the description which follows.

  The present invention relates to a method of forming a conductive coating on a substrate which comprises (1) applying an electrically

  conductor on the surface of an organic resin composition

  wherein the composition is patterned in a pattern on a substrate and then in any order (2) curing said composition to secure the electrically conductive material in position on said surface either through a surface on a substrate; UV radiation, preferably, but not necessarily, in an inert atmosphere or by heat and (3) remove any electrically

driver in the free state.

  The electrically conductive material used herein may be in the form of particles, spheres, beads, powder, fibers, flakes, or mixtures thereof. In addition to noble metals and noble metal-coated substrates that can be used as electrically conductive material in this case, the use of other metals such as copper, aluminum, iron, nickel and zinc is also considered. Silver-coated glass spheres, sometimes called "pearls", which have an average diameter of the order of 6 to 125, b, can also be used. These materials are made of glass spheres commonly used as a reflective filler and are marketed. In addition, glass fibers coated with silver, copper or nickel as indicated in French Patent No. 1 531 272 can also be used. An electrically conductive material used herein also contains carbon black and graphite. In the process according to the invention, the quantity of the electrically conductive material necessary for the

  conductance is independent of the thickness of the composi-

  organic resin used. Indeed, as the electrically conductive material is applied only to the upper surface of the organic resin, it is not important that the resin has a thickness of 0.0127 mm or 0.508 mm. Usable thicknesses of resin can range from about 0.00127 mm to 0.508 mm or

better between 0.0127 mm and 0.0508 mm.

  The electrically conductive material used

  here can be used in various dimensions depending on its shape.

  For best results, the major dimension of the electrically conductive material should not exceed about 75 / LA. However, since the electrically conductive material in the present system is not subject to screen printing, which limits its major dimension, even larger particles, flakes or beads having a major dimension of 100 ", More preferably, the electrically conductive material has a major dimension of between 10 and 10. The organic resin composition used herein for use as a surface matrix for the electrically conductive material is a solvent free, curable liquid organic resin. heat and / or aux, reactive and which contains at least two carbon-carbon olefinic double bonds per molecule.The resin is added in combination with a photoinitiator thereof, and in the case of thermal curing, a thermal initiator If high energy ionizing radiation replaces UV radiation, no photoinitiator

necessary in the composition.

  The solvent-free, curable and reactive liquid organic resins usable herein include, but are not limited to, at least one ethylenically unsaturated member of the group consisting of: (a) an ethylenically unsaturated monomer, oligomer or liquid prepolymer of formula I (CH 2 = CCO- R1 is R or R3, R1 is an organic moiety and n is 2 to 4;

  (b) a polythiol in combination with (a)

  above, and (c) a polythiol in combination with an ethylenically unsaturated liquid monomer, oligomer or prepolymer of the formula

(CH2 = C-CH2) R3

  R2 R2 is H or CH3, R3 is an organic moiety and

  n is at least 2, and mixtures thereof.

  Although the above organic resins are themselves useful for forming useful products, they can also be used in combination with traditional copolymerizable monomeric compounds or reactive diluents. The mixing of the composition according to the invention with other monomers is usually used to control the viscosity and other variables of application such as the cure rate as well as the final properties of the film or coating such as hardness and flexibility. These reactive diluents encode with the organ of the ethylenically unsaturated group upon exposure to UV radiation and

  heat. Examples of compound compounds are

  conventional polymerizable materials useful as reactive diluents, without limitation, monofunctional acrylic esters, monofunctional methacrylic esters, styrene, vinyltoluene, acrylonitrile, methacrylonitrile, vinyl acetate, vinylpyrrolidone, vinyl chloride, vinylidene chroride, butadiene, isoprene,

  chloroprene, divinylbenzene, di (vinylphenyl) -

  carbonate, diallyl phthalate, diallyl carbonate, di (allylphenyl) carbonate, diallyl fumarate, triallyl isocyanurate, triallyl cyanurate, diallyl chlorendate, maleate

  diallyl and unsaturated polyesters and mixtures thereof.

  The term "unsaturated polyesters" means here the usual polycondensation products which consist of residues linked in the manner of polyvalent and in particular divalent alcohol esters, as well as possibly also residues of monovalent alcohols and / or monovalent carboxylic acids. ,

  residues to contain at least partial groups

  unsaturated. Mention may be made, as examples of acids, of maleic acid, fumaric acid, itaconic acid, mesaconic acid, citraconic acid, succinic acid, glutaric acid, adipic acid, acid

  phthalic acid, tetrachlorophthalic acid, hexa

  chloroendomethylenetetrahydrophthalic acid, tri-

  mellitic acid, benzoic acid, the fatty acid of

  flax and ricinoleic fatty acid, and mixtures thereof.

  Examples of alcohols are ethylene glycol, diethylene glycol, propane, butane and hexane diols, trimethylolpropane, pentaerythritol,

  butanol and tetrahydrofurfuryl alcohol.

  The reactive diluents can be added to the system in amounts of up to 90% by weight of the organic resin, and preferably between 20 and 50% by weight

on the same-base.

  The thermal initiators used here are

  selected from substituted or unsubstituted pinacols.

  The substituted or unsubstituted pinacols usable here as a thermal initiator have the general formula

R1 R3

R2-C - C-R4

I i

X Y

  R1 and R3 are identical or different substituted or unsubstituted aromatic radicals, R2 and R4 are substituted or unsubstituted aliphatic or aromatic radicals and X and Y may be identical

  or different are alkoxy or aryloxy hydroxyls.

  The preferred pinacols are those where R1, R2, R3 and R4 are aromatic radicals, in particular the

  phenyl radical and X and Y are hydroxyl.

  An example of this class of

  compounds, without limitation, benzopinacol, 4,4'-

  dichlorobenzopinacol, 4,4'-dibromobenzopinacol,

  4,4'-diiodobenzopinacol, 4,4 ', 4 ", 4"' - tetrachloro-

  benzopinacol, 2,4-2 ', 4'-tetrachlorobenzopinacol, 4,4'dimethylbenzopinacol, 3,3'-dimethylbenzopinacol,

  2,2'-dimethylbenzopinacol, 3,4-3 ', 4'-tetramethyl-

  benzopinacol, 4,4'-dimethoxybenzopinacol, 4,4 ', 4 ", 4" tetramethoxybenzopinacol, 4,4'-diphenylbenzopinacol,

  4,4'-dichloro-4 ", 4" '- dimethylbenzopinacol, 4,4'-

  dimethyl-41 ", 4" '- diphenylbenzopinacol, xanthonpinacol,

  fluorenonepinacol, acetophenonepinacol, 4,4'-

  dimethylacetophenone pinacol, 4,4'-dichloroacetoacetate

  phenonepinacol, 1,1,2-triphenylpropane-1,2-diol,

  1,2,3,4-tetraphenyl-butane-2,3-diol, 1,2-diphenyl-

  cyclobutane-1,2-diol, propiophenone-pinacol,

  4,4'-dimethylpropiophenone pinacol, 2,2'-ethyl-3,3'-

  dimethoxypropiophenone-pinacol, and 1,1,1,4,4,4-

  hexafluoro-2,3-diphenyl-butane-2,3-diol.

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  As other compounds according to the invention may be mentioned: benzopinacolmono-methyl ether, benzopinacol-mono-phenyl ether, benzopinacol monoisopropyl ether, benzopinacol monoisobutyl ether, benzopinacol mono (diethoxy methyl) ether and the like. The pinacol is added to the composition in amounts of between 0.01 and 10% and preferably between 0.1 and 5% by weight based on the weight of the

organic resin.

  The thermal initiator can be added to the system in a variety of ways. Indeed, the thermal initiator, in itself, can be mixed with the resin

  organic. In addition, it can be mixed with a photo-

  initiator and added to the organic resin. Otherwise,

  the thermal initiator can be dissolved or suspended

  in well known and marketed solvents such as dibutyl phthalate; ketones such as acetone and methyl ethyl ketone or chlorinated hydrocarbons such as

  methylene chloride, and then be added to the system.

  In the practice of this invention,

  It is sometimes desirable to add a polythiol to the composition prior to curing. This is particularly true if the ethylenic unsaturation in the organic resin (sometimes hereinafter referred to as polyene) is an allyl group. In this case, during the curing step, the polythiol is added through the double bond of the allyl group resulting in solid materials and cured in a commercially acceptable time period. In the case where the ethylenic unsaturation in the polyene is an acrylic or methacrylic group, the addition of a polythiol to the system results in a fully cured resin and prevents the presence of a sticky surface due to the inhibition of

hardening by air.

  In the present case, the term polythiols indicates simple or complex organic compounds having a multiplicity of pendant -SH functional groups or

  placed at the end of each molecule.

  On average, the polythiols must contain two -SH / molecule groups or more and they usually have a viscosity slightly greater than 0 to 20 million centipoise (cps) at 70 C, measured by a Brookfield viscometer. In the term "polythiols" as used herein are also incorporated materials which, in the presence of an inert solvent, an aqueous dispersion or a plasticizer, fall within the viscosity range indicated above at 70.degree. C. The polythiols that can be used in

  The present invention usually has molecular weights

  between 94 and 20,000 and preferably between

and 10,000.

  The polythiols usable in the present invention may be represented by the general formula: R 8 - (SH) n is at least 2 and R is a polyvalent organic moiety free of carbon-carbon reactive unsaturation. Thus, R8 may contain cyclic groups and minor amounts of heteroatoms such as

  N, S, P or O, but mainly contains carbon-

  hydrogen, carbon-oxygen or silicon-oxygen containing chain bonds without any unsaturation

carbon-reactive carbon.

  A class of polythiols which can be used with the polyenes in the present invention to obtain essentially odorless polythioether products, is composed of the esters of the thiol-containing acids of the general formula HS-R 9 -COOH, where R 9 is an organic moiety which does not contain Reactive carbon-carbon "unsaturation" with polyhydroxy compounds of the general structure R10- (OH) n, where R10 is an organic moiety not containing carbon-carbon "reactive" unsaturation and is 2 or more. These components will react under appropriate conditions to give a polythiol having the general structure R 10 (O -C -R 9 -SH) n R and R 10 are organic moieties not containing carbon-carbon "reactive" unsaturation and n is 2

or more.

  Certain polythiols such as aliphatic polythiol monomers (ethanedithiol, hexamethylene dithiol, decamethylene dithiol, tolylene-2,4-dithiol, and others) and certain polymeric polythiols such as a thiol-terminated ethylcyclohexyl dimercaptan polymer and the like and polythiols which are advantageously and usually synthesized on a commercial basis, although having unpleasant odors, are usable in the present invention but many end products are not widely accepted from a practical and commercial point of view. Examples of preferred polythiol compounds within the scope of the invention for their relatively low level of odor are:

  without limitation, esters of thioglyco-

  (HS-CH2COOH), alpha-mercaptopropionic acid (HS-CH (CH3) -COOH) and beta-mercaptopropionic acid (HS-CH2CH2COCH) with polyhydroxy compounds such as

  glycols, triols, tetraols, pentaols, hexaols and others.

  Specific examples of the preferred polythiols include, but are not limited to, ethylene glycol bis (thioglycolate), ethylene glycol bis (betamercaptopropionate),

  trimethylolpropane tris (thioglycolate), tris (beta)

  mercaptopropionate) of trimethylolpropane, tetrakis

  pentaerythritol (thioglycolate) and tetrakis (beta

  mercaptopropionate) pentaerythritol, all of which are commercially

  cialised. A specific example of a preferred polymeric polythiol is polypropylene ether bis (betamercaptopropionate) which is prepared from polypropylene ether glycol (such as Pluracol P2010, Wyandotte Chemical Corp.) and betamercaptopropionic acid.

by esterification.

  In addition, the polythiols useful herein to provide solid and cured polythioether products with the polyene in the presence of a free radical generator include the mercaptoester derivatives of styrene-allyl alcohol copolymers disclosed in US Patent No. 3,904,499 and isocyanurate-containing polythiols disclosed in US Patent No. 3,676,440 and thiol-terminated liquid polymers made in accordance with US Pat. No. 3,258,495, all incorporated herein by reference. An example of the last type of thiol-terminated liquid polymer, CAPCURE 3-800, marketed by Diamond Shamrock Chemical, is exemplified.

Company.

  Preferred polythiol compounds are

  low mercaptan-like odor initially, and after the reaction they give polythioether end

  smell, which are useful for fixing the electrical material-

driver in position.

  In the case of a polythiol in combination with allyl polyenes, the molar ratio of the groups

  thiol / ene for the preparation of the hardened composition

  sand is between 0.2 / 1 and about 2/1 and better

  between about 0.75 / 1 and about 1.5 / 1 group-ratio.

  In the case of a polythiol in combination with acrylic components, the molar ratio of the groups

  thiol / ene for the preparation of the hardened composition

  sand is between 0.01 / 1 and about 1/1 and

  between about 0.02 / 1 and about 0.5 / 1 ratio

of group.

  Before curing, the polyene and polythiol components are mixed in an appropriate manner to

  to form a liquid and homogeneous curable mixture.

  Thus, the polyene and polythiol reactants can be mixed without the use of a solvent at room temperature or at slightly elevated temperatures of up to about 40 ° C. when one of the components is a solid, or, if desired, the reactants. can be dissolved in a suitable solvent and then the solvent can be removed by suitable means such as evaporation. The compositions according to the present invention may, if desired, contain additives such as antioxidants, inhibitors, fillers, antistatic agents, flame retardants, thickeners, thixotropic agents, surfactants and the like. active agents, viscosity modifiers, plasticizers, adhesive agents and the like in the context of the invention. Such additives are usually premixed with the ethylenically unsaturated compounds before or during the mixing step. Usable fillers that can be added to the system to reduce the price include natural and synthetic resins, glass fibers, wood flour, clay, silica, alumina, carbonates, oxides, hydroxides, silicates, glass flakes, borates, phosphates, diatomite, talc, kaolin, barium sulphate, calcium sulphate, calcium carbonate and the like. The above additives may be present in amounts of up to 500 parts or more per 100 parts of the organic resin,

  by weight, and preferably about 0.005 to about 300 parts

on the same basis.

  In addition, conventional UV stabilizers

  and antioxidants such as hydroquinone, tert-butyl hydroquinone, tert-butyl catechol,

  p-benzoquinone, 2,5-diphenylbenzoquinone, 2,6-di-

  tert-butyl-p-cresol and others, are added to the system in customary amounts of between 0.001 and 2.0% by weight.

weight of the organic resin.

  It is preferably necessary to add photoinitiators in order to initiate the reaction of ultraviolet rays. One class of photoinitiators comprises the aldehyde and ketone carbonyl compounds having at least one aromatic ring which is attached directly to the group -C. Among the various photoinitiators of this type, without limitation, benzophenone, acetophenone, o-methoxy-benzophenone, acenaphthene-quinone, methyl ethyl ketone, valerophenone, hexanophenone, alpha-phenylbutyrophenone, pmorpholinopropiophenone dibenzosuberone, 4-morpholino-benzophenone, 4'-morpholino deoxybenzolene, p-diacetylbenzene, 4-aminobenzophenone, 4'-methoxyacetophenone, benzaldehyde, alphatetralone, 9-acetylphenanthrene,

  2-acetylphenanthrene, 10-thioxanthenone, 3-acetyl-

  phenanthrene, 3-acetylindone, 9-fluorenone,

  1-indanone, 1,3,5-triacetylbenzene, thioxanthene-9-

  one, xanthrene-9-one, 7-H-benzodu anthracene-7-one, 1-naphthaldehyde, 4,4'-bis (dimethylamino) -benzophenone, fluoren-9-one, 1'-acetonaphthon , 2'-acetonaphthon, 2,3 butanedione, acetonaphthon, la-benz La3 anthracene 7,12 dione, and the like. As another class of photoinitiators, mention may be made of benzol ethers, for example benzol methyl ether, benzoin ethyl ether, benzoin isopropyl ether and isobutyl.

  benzoyl ether and 2,2-dimethoxy-2-phenylacetophenone.

  A third class of photoinitiators is represented by benzyl dimethyl ketal. Other photoinitiators usable herein include triphenylphosphine and tri-o-tolylphosphine. The photoinitiator or its mixtures are usually added in an amount between

  0.0005 and 30% by weight of the organic resin.

  The type of radiation useful here for curing, ultraviolet light and other forms of actinic radiation which are normally found in radiation emitted by the sun or artificial sources such as sun lamps of the RS type may be mentioned. , carbon arc lamps, xenon arc lamps, mercury vapor lamps, tungsten halide lamps, and the like. Ultraviolet radiation can be used very effectively if the photocurable composition contains a suitable photoinitiator. The curing times can be adjusted to be very short and therefore economically viable by a good choice of ultraviolet light source, photoinitiator and concentration, temperature and molecular weight as well as the functionality of the groups. reagents of the organic resin. Hardening times of the order of one second to

  minutes are usable according to the variables above.

  When using UV radiation, an intensity of 0.0004 to 60.0 watts / cm2 is usually employed

  in the region of 200-400 nanometers.

  As previously indicated, the uncured or partially cured organic resin to which the electrically conductive material is added may be formed by screen printing or photo-imaging. In the printing process on the screen, the organic resin

  mixed with the photoinitiator (and possibly

  initiator if heat is to be used for the final hardening) is scraped through a screen into a desired circuit pattern. In the case where the ethylenic unsaturation in the organic resin is a group

  acrylic or methacrylic, the direct exposure sub-

  sequence with UV radiation results in a surface

  sticky and uncured on the resin, due to the inhibition of

  curing by air. The electrically conductive material is sprinkled, sprinkled or sprayed on this

  sticky surface and the surface is hardened

  the UV light from the apex, from below (if the substrate is transparent to ultraviolet rays) or from both sides in an inert atmosphere, or from heat, for example in a conventional heating furnace (air) at a temperature of 50-250 ° C if a thermal initiator has been added to the system. In other cases, where the air does not affect the hardening of the organic resin due to the presence of a polythiol which is mixed therein, the organic resin is printed on the screen in the manner of a circuit, sprayed, sprinkled or sprayed with electrically conductive material and then it is

Z496386

  subjected to ultraviolet radiation in air from the top or bottom through a UV-transparent substrate or both. In addition, instead of using UV radiation for the final cure, a thermal initiator can be mixed with the formula

  of origin, and after adding the electrical material-

  conductive material, on the surface of uncured or partially hardened resin, heat may be

  harden the organic resin and fix the electrical material

  conductive in position on its surface.

  In the case of the photo-image, the non-conductive substrate is completely coated with a thin coating (up to 0.127 mm) of the organic resin mixed with the photoinitiator and optionally the thermal initiator. The coating is then exposed to ultraviolet radiation through a slide whose image is positive with respect to the desired circuit. In the case where the organic resin employed is not inhibited by air,

  a sticky surface is avoided throughout the exposed area.

  The slide is removed and the electrically conductive material is sprayed, sprinkled or sprinkled onto the uncured and unexposed portion of the organic resin, i.e. the desired circuit patterned by the slide. The thus coated substrate is then exposed directly to ultraviolet radiation in air from above or below or both to harden the circuit pattern and secure the electrically conductive material. This last step can also be accomplished, if a thermal initiator is added to the system, exposing the heat-coated substrate to a temperature of between 50 and 2500 ° C. for a time sufficient to cause the organic resin to cure in the circuit pattern. in order to fix

  position the electrically conductive material. In use

  the photo-image process in the event that the unsaturation

  If the ethylenic resin in the organic resin is an acrylic or methacrylic group, it is necessary to carry out the photo-image step using UV radiation through a slide in an inert atmosphere, for example nitrogen. In this way, the parts exposed to ultraviolet radiation will completely harden and there will be no sticky surface. The unexposed part

  the circuit pattern on the slide will remain uncured.

  The electrically conductive material is then applied to the pattern of the uncured circuit on the coated substrate and then the pattern is re-exposed from the top, bottom or both to the UV radiation in an inert atmosphere. In addition, this second curing step can be performed when a thermal initiator is added to the system, exposing the uncured organic resin with the electrically conductive materials over heat at a temperature of 50-250 ° C for one hour.

  sufficient time to cure the uncured organic resin.

  In all the above processes, the free particles of the electrically conductive material which, upon application, fall or reside on the substrate or cured coating on the substrate, can be easily

  removed before the electrically conductive

  be fixed in the desired circuit by hardening.

  final stage or after the final hardening step. This removal before final curing can easily be accomplished by conventional means, for example by brushing excess electrically conductive material, typing

  substrate at one end or using a spray

  air. After final curing, in addition to the methods available before final curing, it is possible to use a jet or spray of water or detergent in water or a bath. The electrically conductive material thus removed can then be reused in the

  system after reprocessing to remove the oxides.

  The heating step using a thermal initiator to cure the organic resin and to fix the electrically conductive material in position is usually carried out for 1 to 10 minutes at a temperature of 50 to 250 C, preferably 80 to 175WC, which is sufficient to completely cure the composition to obtain a solid product. In addition to traditional sources of heat such as a heating oven that can be used for the heating stage to harden

  the organic resin, it is also possible to use a

  such as infrared, a microwave or a radial frequency to produce the required temperature in

  the organic resin for hardening.

  The following examples will help explain

  the present invention without particularly limiting it.

  Unless otherwise noted, all

  parts and percentages are by weight.

EXAMPLE 1

  Preparation of an oligomer of urethane triacrylate with diacrylate as diluent

  To a mixture of 30.035 parts methylene-

  bis (cyclohexylisocyanate) containing 0.0275 parts of stannous octoate and 0.506 parts of triphenyl phosphite,

  15.231 parts of hydroxypropyl acrylate were added.

  After 2 hours at 50 ° C, 0.020 part of monomethyl ether was added. of hydroquinone, 0.0275 parts of stannous octoate and 24.5 parts of hexanediol diacrylate, followed by 29.562 parts of PLURACOL.TP-740 (triol of

  730 molecular weight obtained by reaction of trimethylol

  propane with propylene oxide). After an hour

  at 80 ° C, the isocyanate content reached 0. The oligo-

  resulting urethane triacrylate mother and diluent diacrylate will be hereinafter referred to as prepolymer A.

EXAMPLE 2

  An on-screen photocurable organic resin composition was prepared by mixing the following components:

TABLE I

  Components Weight parts Prepolymer A of Example 1 40.4 Hexanediol diacrylate 25.9 Trimethylolpropane triacrylate 26.5 Diethoxyacetophenone 1.0 Benzophenone 2.0 Cab-o-sil 4.0 Phosphorous acid 0.2 Formula above will be hereinafter called photocomposition A.

EXAMPLE 3

  In a 5 liter round-bottomed flask equipped with stirrer, thermometer, Graham condenser (coil) and a drip funnel, 1.164 g of redistilled diallylamine, commercially available, was added. . The flask was rinsed with nitrogen and kept under nitrogen blanket during the reaction. The flask was heated to 80 ° C. with stirring and 1.940 g of bisphenol A diglycidyl ether epoxy resin, marketed by Shell Chemical Co under the trade name "EPON 828", was added slowly to the reaction vessel. dribble funnel over a period of 2 hours while the flask was maintained at a temperature of 80-90 C. After completing the addition, stirring and heating at 80-90 was continued. C for 4 hours. Diallylamine (194 g) in excess was

  vacuum extracted at 90 ° C. and 1.333-13.33 × 102 N / m 2.

  The epoxy tetraene produced, that is to say

OH CH3 OH

  (CH2 = CHCH2) 2 NCH2CHCH C H2CHCH2N (CH2CH = CH2) 2

  CH3 obtained reached 2,910 g and will be hereinafter called prepolymer B.

EXAMPLE 4

  An on-screen photocurable organic resin composition was prepared by mixing the following components:

TABLE II

  Components Weight parts Prepolymer B of Example 3 39.4 Triallyl cyanurate 19.5 2,2-dimethoxy-2-phenylacetophenone 2.0

  Pentaerythritol tetrakis (beta-mercapto

  propionate) 39.4 Benzopinacol 1.0 FC-430 (coating additive - 3M Corp.) 0.24 Triphenylphosphine 0.20 Stabilizers pyrogallol 0.10 phosphorous acid '0.02 The above formula will be referred to hereinafter as photocomposition B.

EXAMPLE 5

  To 10 parts of photocomposition A of Example 2 was added 0.1 part of benzopinacol. This mixture will be called hereinafter photocomposition C.

EXAMPLE E6

  The photocomposition A of Example 2 was printed on the screen in an in-line circuit pattern (0.64 cm x 10.16 cm) on a Mylar substrate through a nylon screen having 55 mesh per centimeter. . The coated substrate was exposed to UV radiation from an Addalux mercury pressure lamp (56 mW / cm) for 2 minutes in air. The thus-exposed composition adhered to the Mylar substrate but had a sticky upper surface and partially cured. Money in the form of a silver flake (mesh -128) was sprayed onto the tacky surface of the composition. The excess silver was removed from the substrate by brushing and the silver-coated sticky composition was re-exposed to the lamp

  Addalux for 2 minutes in a nitrogen atmosphere.

  A fully cured solid composition 0.107 ± 0.005 mm thick was obtained with the silver fixed in a position embedded on its surface. The resulting conductive silver coating weighed 0.099 g and had a resistivity

specific of 1.43 x 10 2 ohm-cm.

  This example has been repeated. The resulting conductive silver coating weighed 0.103 g and had a resistivity

specific of 1.88 x 10-2 ohms / cm.

EXAMPLE 7

  Photocomposition A of Example 2 was printed on the screen in an in-line circuit pattern (0.64 cm x 10.16 cm) on a Mylar substrate through a nylon screen having 55 mesh per centimeter. The coated substrate was exposed to UV radiation from an Addalux mercury pressure lamp (56 mW / cm 2) for 2 minutes in air. The thus-exposed composition adhered to the Mylar substrate but had a sticky and partially cured upper surface. Silver in the form of silver-coated glass beads (8% silver by weight) was sprayed onto the sticky surface of the composition. The excess silver beads were removed from the substrate by brushing and the glass-beaded adhesive composition was re-exposed to the Addalux lamp for 2 minutes under a nitrogen atmosphere. A solid and fully cured composition was obtained (0.124 + 0.005 mm thick)

  with the money fixed in a drowned position on its surface.

  The resulting silver-coated beads weighed 0.078 g and the conductive coating had a resistivity

specific of 5.6 x 10-1 ohms: cm.

* EXAMPLE 8

  The photocomposition C of Example 5 was printed on the screen in a circuit pattern (0.64 cm x, 16 cm) on a Mylar substrate through a nylon screen having 55 mesh per centimeter. The coated substrate has been exposed to the UV radiation of a pressure lamp of

  Addalux mercury (56 mW / cm2) for 2 minutes in the air.

  The thus-exposed composition adhered to the Mylar substrate but had a sticky and partially cured upper surface. Silver in the form of silver-coated glass beads (8% silver by weight) was sprayed onto the sticky surface of the composition. The excess silver was removed from the substrate by brushing and the silver coated sticky composition was heated at 1600C in an air oven for 5 minutes. A fully cured solid composition (0.122 + 0.005 mm thick) with the silver fixed in a sunken position on its surface was obtained. The resulting silver-coated pearls weighed 0.0508 g and the conductive coating had a

  Specific resistivity of 2.3 x 10-3 ohms-cm.

  This example was repeated. The silver-coated glass beads in the line circuit weighed 0.035 g and the conductive coating had a specific resistivity

1.48 x 10-3 ohms-cm.

EXAMPLE 9

  The photocomposition B of Example 4 was coated on an entire surface of a Mylar substrate to a thickness of 0.0254 mm. The coating was then exposed to the UV radiation of an Addalux mercury pressure lamp (56 mW / cm2) across a slide, which image is positive with respect to a 9.0 cm x 0 line circuit, 4 cm. The exposure lasted 2 minutes resulting in a hardened solid composition in all exposed areas. Silver in the form of silver-coated glass beads (8% silver by weight) was sprayed on

  the uncured and unexposed liquid part of the composition

  and the excess was removed by brushing the cured coating on the substrate. The substrate was placed in an oven

  air and heated at 1500C for 10 minutes. A composition

  solid solution completely hardened with the silver beads fixed in a flooded position of the circuit pattern resulted. The resulting glass-coated beads weighed 0.062 g and the conductive coating had a resistivity

specific of 2.03 x 10-2 ohm-cm.

  It will be understood that in order to obtain the best strength, solvent resistance, creep resistance, heat resistance without adhesiveness, the reaction components consisting of polyenes and polythiols according to the invention are formulated so as to give, during the curing, polythioether polymer systems in three-dimensional network, crosslinked and solid. In order to obtain such an infinite array formation, the individual polyenes and polythiols must have a functionality of at least 2 and the sum of the functionalities of the polyene and polythiol components must always be greater than 4. Mixtures of the polyenes and polythiols containing this feature are also

usable here.

Claims (13)

R E V E N D I C A T I 0 N S   A process for forming a conductive coating on a substrate, characterized in that it comprises: (1) applying an electrically conductive material to the surface of an uncured or partially cured organic resin composition having a surface adhesive, said composition being patterned as a circuit on a substrate and then, in any order, (2) curing said composition to fix said electrically conductive material in position on said surface by thermal or UV radiation , and (3) remove any electrically conductive material the free state.   2. Process according to claim 1, characterized in that the UV radiation curing mentioned above is   performed in an inert atmosphere.   3. A process according to claim 1, characterized in that the aforementioned composition contains a reactive diluent. A process for producing a circuit board, which comprises: (1) printing on a substrate a desired circuit pattern of an ultraviolet curable composition comprising (a) an ethylenically unsaturated compound of formula: -   (CH2 = C-C-O) n-R1 where R is H or CH3 and R1 is an organic moiety having the valence of n, where n is 2 to 4, and (b) a photoinitiator; (2) exposing said composition to UV radiation for a time sufficient to obtain a adherent and solid printed circuit pattern having a tacky surface; (3) coat at least the tacky surface of   said composition by an electrically conductive material   and then in any order; (4) re-irradiating at least said tacky surface coated with said composition with UV radiation in a substantially oxygen-free atmosphere to solidify   said tacky surface and form an electrical circuit therein   driver; and (5) remove any material electrically driver in the free state.   5. A process according to claim 4, characterized in that the aforementioned composition contains a reactive diluent. 6. A process according to claim 4, characterized in that the oxygen-free atmosphere mentioned above is an inert gas.   A method of forming a circuit board, characterized in that it comprises: (1) printing on a substrate a desired circuit pattern of an ultraviolet curable and heat-curable composition comprising: (a) a compound ethylenically unsaturated compound of the formula: (CH 2 = CCO) n -R 1 R is H or CH 3 and R 1 is an organic moiety having the valence of n, where n is 2 to 4; and (b) a photoinitiator; and (c) a thermal initiator: (2) exposing said composition to UV radiation for a time sufficient to obtain an adherent and solid printed circuit pattern having a tacky surface; (3) coating at least the tacky surface of said composition with an electrically conductive material and then in each order; (4) exposing the coated composition at a temperature between 50 and 2501C to solidify   said tacky surface and form an electrical circuit therein   driver; and (5) remove any material electrically driver in the free state.   8. A process according to claim 7, characterized in that the above composition contains a diluent reagent. 9. A process according to claim 7, characterized in that the aforementioned thermal initiator is a pinacol substituted or unsubstituted.   A process for forming a circuit board, which comprises: (1) coating a substrate with an ultraviolet curable composition comprising: (a) a liquid, reactive, curable and solvent-free organic resin containing at least two carbon-carbon olefinic double bonds per molecule and (b) a photoinitiator; (2) exposing said coating to UV radiation through an imaged slide, whose image is positive with respect to the desired circuit to form a cured adhesive coating on said substrate in the exposed non-circuit area; (3) coating the unexposed and uncured circuit area with the composition of an electrically conductive material and then in any order (4) re-irradiating at least the uncured area with UV radiation to harden said area and secure the material electrically conductive on its surface; and (5) remove any material electrically driver in the free state.   11. A method of forming a circuit board, characterized in that it comprises: (1) coating a substrate with an ultraviolet curable and heat-curable composition comprising (a) a liquid, reactive, curable, solvent-free organic resin containing at least two carbon-carbon olefinic double bonds per molecule, (b) a photoinitiator, and (c) a thermal initiator; (2) exposing said coating to UV radiation through an imaged slide, whose image is positive with respect to the desired circuit to form a cured coating adhered to said substrate in the exposed and non-circuited area; (3) coating the uncured and unexposed circuit zone with the composition of an electrically conductive material and then in any order (4) exposing at least the uncured circuit zone at a temperature in the range of 50 to 2500C for hardening said area and fixing the electrically conductive material to its surface; and (5) remove any material electrically driver in the free state.   12. A process according to any of the claims   cations 10 or 11, characterized in that the above-mentioned organic resin consists essentially of an ethylenically unsaturated compound of the formula (CH2 = cCO) n-R1, wherein R1 is H or CH3 and R1 is an organic moiety having the valence of n and n is between 2 and 4, and the exposure to UV radiation is carried out in a   substantially oxygen-free atmosphere.   13.- Method according to claim 1,   characterized in that the organic resin in the composition   The above-mentioned organic resin composition is a member of an ethylenically unsaturated group consisting of: (a) an ethylenically unsaturated monomer, oligomer or prepolymer having the formula 1I (CH 2 = CCo) R, R o R is H or CH3, R1 is an organic moiety and n is 2 to 4, (b) a polythiol in combination with (a) and (c) a polythiol in combination with an ethylenically unsaturated liquid monomer, oligomer or prepolymer having the formula : (CH2 = C-CH2) n R3 R2 R2 and H or CH3, R3 is an organic fragment and   n is at least 2> and mixtures thereof.