OLIGOORGANOSILASESQUIOXANES

Abstract: An oligoorganosilasesquioxane which is microgel free and has residual hydroxyl groups is prepared by dissolving an organo thrichlorosilane in an aromatic hydrocarbon solvent, injecting the solution into the reactor as an upwardly directed stream and simultaneously directing upward a mixture of water and a ketone and allowing both streams to undergo hydrolytic condensation. The oligoorganosilasesquioxane is used as binders for composites and film forming coatings.

Description: OLIGOORGANOSIIASESOUIOXANES TECHNICAL FIELD The present invention relates to oligoorganosilasesquioxanes (OOSSO) suitable for use in the production of film-forming coatings, as binders for filled composites, or the like. BACKGROUND OF THE INVENTION The synthesis and technology of the preparation of OOSSO by hydrolysis of organochlorosilanes is described in some detail by A.M. Tonshin, B.A. Kamarishii and V.N. Spektor in Russian Chemical Reviews, 52 (8) , 1983 pp 775- 803; OOSSO are defined in that article as having a "Functionality" of at least three. That is, the organochlorosilane starting material has an average number of chloro-substituents of at least three, the remaining silicon-bonded substituent in the organochlorosilane being organic groups, such as methyl, ethyl, vinyl, phenyl or higher alkyl radicals. However, it is desirable to produce OOSSO micro-gel free. The addition of metal fillers to POSSO to enhance the thermal stability of the latter is also known (V.N. Spektor et al, Russian Chemical Review, 1983, Vol. 52, No. 8, p.775 (1365); M.I. Bryk et al, Itogi Nauki i Tekhnidi. Ser. Khim i Tekhnol. Vysokomol Soed, 1982, Vol. 17, p. 238). In particular, it has been proposed to blend with metal fillers such as Pb, Fe, Ni, Bi, Cd, Cu and Co (the thermal effect of the metals increasing in the order as specified from Pb to Co) . Other types of materials have been used as coatings, films and binder materials in a variety of applications. Printed circuit boards have been provided with a protective coating in order to alleviate the problem of short circuiting between tracks provided on the board. The protective coating generally acts as an insulating medium preventing the passage of electrical current between the tracks. Presently available coatings tend to be sensitive to temperature and are often inflammable or give off poisonous gases such as HCN or isocyanates. Asbestos is known to have good thermal and fire resistant properties however its use has been severely curtailed during recent years because of its detrimental side effects in causing lung irritation and cancer. Solid state luminescent screens are known which comprise a phosphor and a resin coating matrix. The phosphor provides photo yield when excited with electric current (electric phosphor) , in which the exciting electric current can be either alternating or direct. It is often preferred however to use direct current but the use of the latter is often limited when the dielectric permeability of the resin matrix is lower than that of the phosphor. Micro-electronic chips have used silicon oxidation for forming a film. Other types of film forming materials have been used. The concentration of the surface states of the semi-conductor onocrystal becomes higher. As a result of the solid state interaction between silicon, germanium, gallium arsenide, etc. monocrystalline semiconductor substrates and polymethysilsesquioxanes of .functionality F=3.0 +0 - 90 -0.25 and having hydroxyl groups (OH) content between 2 and 4% atomic, the concentration of the surface states of a semiconductor monocrystal (irrespective of whether it is uniform or has a manufactured structure of electronic junctions) stays the same or becomes less than the concentration before such interaction as set forth in the publication by V.N. Spector, et al., Russian Chemical Reviews, 1983, vol. 52, No. 8, p. 775 [365]. As commonly known, the surface of any monocrystal is a collective defect and is mostly represented by the altered coordination of the surface atoms and their structural reconstruction, dangling bonds, point defects (atoms and vacancies) and their clusters, and physi and/or chemi-sorbed impurities (non-ideal monocrystals have growth steps and dislocation outlets added to defect structure of their surface. Electric and electronic properties of planar semiconductor structures, especially with a fabricated junction pattern, depend mainly on defect state of the respective monocrystals. Any kind of passivation (protection against temporal changes) of a semiconductor monocrystal leads to an increase in the surface states' concentration. Poly ethylsilsesquioxanes (non-modified) have dielectric characteristics virtually identical to ones of thermally grown silicone dioxide. Oligomethysilsesquioxanes have a definite concentration of hydroxyl groups of two types at varying chemical activity: more active external Oh-groups (approximately 90% of total amount) and less active internal Oh-groups. External Oh- groups are responsible for condensation of oligomers into larger moieties during the curing process. The internal Oh-groups facilitate higher temperature structural transition in the cured polymer, causing its transformation into three dimensional amorphous matrix. Depending upon the temperature, the dissociation of Oh- groups and ≡Si-0-Si-≡ bonds may be heterolytic (below 200°C) or homolytic (above 400°C. The surface point defects and impurities may either be charged or have a radical nature. SUMMARY OF THE INVENTION The invention includes a method of synthesis of OOSSO which is micro-gel free, and applications of the OOSSO as films, coatings, etc. The method includes the steps of: dissolving a chlorosilane of general formula RSiCl 3 with an aromatic hydrocarbon solvent; injecting the resulting solution into a reactor as an upwardly directed stream from an inlet proximate the base of said reactor; simultaneously injecting a compatible mixture of water and a ketone of formula C n H 2n+1 COC m H 2m+1 where n and m are each 1 or 2, into said reactor as a further upwardly directed stream from an inlet disposed proximate the base of said reactor; allowing the streams from the two reactors to undergo hydrolytic condensation in turbulent flow conditions so as to form a curable oligoorganosilasesquioxane having residual reactive hydroxyl groups, said streams being introduced into said reactor in such a way that a turbulent zone is disposed proximate said base of said reactor, whereby turbulent flow conditions are maintained substantially throughout a lower volume of the reactor such that said lower volume is substantially free of any dead zones, and adjacent to which turbulent zone is disposed an upper laminar flow zone. FIGURE OF THE DRAWINGS The Figure is a schematic diagram of the laboratory apparatus for use in the subject invention. DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the present invention, there is provided a method of synthesis (which is hereinafter referred to as the synthesis method) of OOSSO. The method includes the steps of: a) dissolving a chlorosilane of general formula RSiCl 3 (in which R is methyl, phenyl or ethyl) with an aromatic hydrocarbon solvent of formula in which at least two of R 1 to R 6 are hydrogen and the remainder of R 1 to R 6 are alkyl groups such that the total number of carbon atoms in R 1 to R 6 is 1 to 4; b) injecting the resulting solution into a reactor as an upwardly directed stream from an inlet proximate the base of said reactor; c) simultaneously injecting a compatible mixture of water and a ketone of formula C n H 2n+1 COC m H 2m+1 where n and m are each 1 or 2, into said reactor as a further upwardly directed stream from an inlet disposed proximate the base of said reactor; d) allowing the streams from the two reactors to undergo hydrolytic condensation in turbulent flow conditions so as to form a curable oligoorganosilasesquioxane having residual reactive hydroxyl groups, said streams being introduced into said reactor in such a way that a turbulent zone is disposed proximate said base of said reactor, whereby turbulent flow conditions are maintained substantially throughout a lower volume of the reactor such that said lower volume is substantially free of any dead zones, and adjacent to which turbulent zone is disposed an upper laminar flow zone. It is preferred that the lower volume of the reactor occupied by the turbulent zone has a height of not more than about one third of the total height of the reactor. The chlorosilane is typically methytrichlorosilane (R is CH 3 ) or phenyltrichlorosilane (R is C 6 H 5 ) although in some instances mixtures of chlorosilanes may be used. The aromatic hydrocarbon solvent is typically toluene; other suitable solvents include xylene, ethyl benzene and iso-propyl benzene. The ketone, which is water miscible in all proportions, is typically acetone; other suitable solvents include methyl ethyl ketone and diethyl ketone. The ketone is preferably used in an amount of 12% to 60% by weight, based on the combined weight of the ketone and the aromatic hydrocarbon solvent. Typically the reactor is substantially upright and substantially cylindrical, and the two streams are preferably injected into the reactor in such a way that the head (that is, the height by which the streams rise in the reactor) is from 7 to 15 times the internal diameter of the reactor. The stream comprising the solution of trichlorosilane and aromatic hydrocarbon solvent is typically injected through an upright nozzle having an outlet with axis substantially coaxial with the axis of the upright reactor; the ketone/water mixture is preferably also supplied to the reactor in a stream injected along the axis of the upright reactor. The ketone/water stream preferably coaxially surrounds the trichlorosilane/aromatic hydrocarbon stream such that condensation reaction takes place in the aqueous "sheath" phase. The reactants are preferably injected into the reactor at a temperature of O± 5°C; the reactants are preferably injected into the reactor via respective atomisation nozzles in such a way that the reaction time is controlled at 1.5 to 3 seconds. The specific chemical mechanism of preparation of the soluble, able-to-melt oligomers, free of microgel are as follows. The main reaction is a sequence of chlorine functional groups' hydrolysis and their condensation. RSiCl 3 + H 2 0 = RSiCl 2 0H + HC1 T ~ 10 "5 S RSiCl 2 OH + H 2 0 = RSi(OH) 2 Cl + HC1 T - 10" 4 S RSi(OH) 2 Cl + H 2 0 = RSi(0H) 3 + HCl T ~ 10 "3 S RSi(OH) 3 (OH) 3 can exist only in solution and it has a very short life-time τ lt < 10~ 3 S when cone is higher than 1% mass. All of these entities include RSiCl 3 ; RSiCl 2 OH; RSi(OH) 2 Cl, and RSi(0H) 3 are highly reactive. There are four possibilities for the interaction of the entities both in monomers and oligomers. 1. Intramolecular homofunctional, e.g. RSi(OH) 2 Cl- * RSiOCl + H 2 0 or RSi(OH) 3 →RSiO(OH) + H 2 0 The same holds for molecules containing several onomeric units. 2. Intramolecular heterofunctional, e.g. RSiCl 2 OH→RSiOCl + HC1 or RSi(OH) 2 Cl-.RSiO(OH) +Hcl The same holds for molecules containing several monomeric units. In cases 1 and 2, intramolecular condensation in molecules with a number of monomeric units, N>4, leads to cyclization and alteration of the chain growth at least in one dimension. 3. Intermolecular homofunctional, e.g. RSi(OH) 2 Cl + RSiCl 2 OH-,RSiOHCl-OSiRCl 2 +H 2 0 or RSi(OH) 2 Cl + RSi(OH) 3 →R(OH)ClSi-0- Si(OH) 2 R+H 2 0 The same holds for molecules containing several monomeric units. 4. Intermolecular Heterofunctional, e.g. RSi (OH) 2 Cl+RSiCl 2 0H→R(0H) 2 Si-0-SiCl 2 R+HCl or RSi(OH) 2 Cl+RSi(OH) 3 -»R(OH) 2 Si-0-Si(OH) 2 R+HC1 The same holds for molecules containing several monomeric units. In case 3 and 4, intermolecular condensation in molecules with an arbitrary number of monomeric units leads to polydimensional (I≤D<3) linear expansion resulting in macrogel formation, i.e. the substance unable to melt or dissolve. The real reaction, a need in the preparation of an oligomer of a certain molecular mass and of necessary molecular mass distribution, is a compromise between these two types (intra- and inter- molecular) of condensation. But the content of the resultant OH compromise between their homo-and hetero- functional varieties which becomes economically important where it concerns microgel-free preparations. The microgel (the kind of gel having approximately the same molecular mass as an oligomer, being able to dissolve and to filter as well as an oligomer) concept is it represents virtually the same molecular structure as a respective oligomer but it doesn't contain any hydroxyl group; and, during the subsequent curing process, it couldn't be incorporated into the respective polymeric matrix; but rather it crystallizes independently, producing macrodefects in the resulting fibers or coatings. The synthesis method as hereinbefore described may further comprise a monitoring step, wherein light scattering analysis is carried out to establish that the lower volume of the reactor, comprising the turbulent zone, is actually free of any dead zones. The resulting OOSSO is generally substantially microgel-free (as evidenced by the substantial absence of any peak in its light scattering spectroscopy or diffractometer trace) ; the present invention therefore further comprises an oligoorganosilasesquioxane of formula R χ SiO , 2 , where x+y is 4, x is substantially one (such as about 0.95 to 1.05) and y is substantially 3 (such as about 2.95 to 3.05), which oligoorganosilasesquioxane is substantially microgel-free and is curable to a polyorganosilasesquioxane. By "microgel-free", we mean a proportion of microgel which is no more than 1.0%; with suitable control of conditions, the microgel content may be not more than 0.05% by weight. According to a first aspect of the present invention, the resulting OOSSO is substantially cured and included in a film which consists essentially of the corresponding POSSO. According to a second aspect of the present invention, the OOSSO is combined with a filler material. Typically, the resulting mixture is further processed to form a composite body comprising the corresponding POSSO. According to the first aspect of the present invention, it is preferred that the synthesis method as hereinbefore described is controlled so as to produce OOSSO's of generally low molecular weight and having a narrow range of molecular weight distribution (MWD) . It is preferred that reaction conditions are such so as to substantially reduce the number of molecular collisions between reactant molecules; it is preferred that the reactant concentration (i.e. the concentration of at least one, preferably both reactants) and the reactor temperature are maintained at their lowest acceptable values. An OOSSO produced according to the latter method is preferably included in a surface coating formulation which is typically applied as a protective surface layer on a substrate surface of semi-conductor monocrystals (exemplary substrates being micro-electronic chips) . Printed circuit boards could have different materials for which affinity needs wide molecular mass distribution and usually has rather low average molecular mass but wide molecular mass distribution to provide for affinity with various sizes and chemical nature of components. The invention includes a method of preparation and application of a formulation suitable to be used as a coating for a printed circuit board, or for a solid sate luminescent screen which coating when applied to a printed board alleviates the above problems stated in the background. There is therefore provided a method of preparing and applying a coating to a substrate surface, which method (which is hereinafter described as the coating method) comprises: a) preparing at least one oligoorganosilasesquioxane according to the synthesis method as hereinbefore described; b) introducing said at least one oligoorganosilasesquioxane produced according to step (a) into an appropriate solvent, said one or more oligoorganosilasesquioxane (OOSSO) comprising oligophenysilasesquioxane and/or oligomethysilasesquioxane, being of functionality of about 2.75 to 3.14 and having a hydroxyl content of at least 4% by weight thereof, the resulting mixture being substantially fee of any filler; c) applying the resultant mixture as a coating to a substrate surface; and d) curing the assemblage resulting in hydrophobic coating as minimum or total hydrophobic impregnation of materials in the maximum. It is preferred that the OOSSO is present in the appropriate solvent (which is preferably toluene) in an amount of about 5-10% by weight of the solution. Preferably step (d) of the above method comprises a first stage of drying the coating in air, followed by substantially complete curing of the OOSSO. Typically the substrate is either a printed circuit board or a solid state luminescent screen and the resulting olyorganosilasesquioxand (POSSO) coating is present as a protective coating layer thereon covering substantially the entire surface thereof. A printed circuit board which is provided with a surface coating as described above is typically formed from a conventional substrate, such as a filled polyamide, a polyamine or an aromatic polyether. According to the second aspect of the present invention, it is preferred that the synthesis method as hereinbefore described is controlled so as to produce OOSSO's having a wide molecular weight distribution (i.e. of at least about 900 to 3,000) and generally being of relative high molecular weight. Preferably the reaction conditions are such (e.g. increased reactant concentration and increased temperature) , so as to promote the yield of such products by optimizing the number of molecular collisions between reactant molecules. The following exemplary embodiments are all concerned with the further processing and subsequent use of an OOSSO produced by a method according to the second aspect of the present invention. In a first embodiment, there is provided a method of producing a composite body comprising of asbestos intimately mixed with a binder. The invention includes an asbestos composite and a method of production thereof, the nature of the composite being such that the detri ental side effects of the asbestos have been considerably lessened. There is further provided by the present invention a method of preparing a composite body comprising asbestos intimately mixed with a binder, which method comprises: a) preparing at least one oligoorganosilasesquioxane according to the synthesis method as hereinbefore described; b) intimately mixing asbestos and said at least one oligoorganosilasesquioxane produced according to step (a) in an amphiphilic solvent medium, said at least one oligoorganosilasesquioxane bearing radical substituents of low molecular weight and being present in an amount of about 10-20% by weight of the mixture; and c) forming and drying the resultant mixture of step (a) . It is preferred that the amphiphilic solvent medium comprises about 50% acetone (MEK or diethylketone) to "wet" the asbestos "fibers", and about 50% toluene (xylene) to dissolve the oligoorganosilasesquioxane. Although less preferred, the solvent medium may alternatively comprise ethanol and xylene as the respective solvents. It may in some cases be advantageous to use a volatile solvent medium to substantially "speed-up" the drying process as described in step (c) of the above method. However, in an alternative embodiment it may be advantageous to use a substantially involatile solvent to increase the mechanical strength of a product obtained by the above method. If a product obtained by the above method is required to be used as a single multi- layered mat form, it is preferred that a composite body obtained by the above method is impregnated with about 5-15% oligoorganosilasesquioxane solution by weight of the composite body, calendaring the body to press out any excess solution, followed by drying and hot pressing the resultant mats into a desired shape. When it is required to produce a multi¬ layer mat it is generally advisable to produce a six-layer mat as the latter has superior mechanical properties comparable to those of light metal alloys. There is further provided by the present invention a composite body produced according to the latter method, which body comprising asbestos intimately mixed with a binder, said binder comprising at least one cyclic oligoorganosilasesquioxane being present in a proportion of at least 12%, but not exceeding 15% by weight of said binder, and in an amount of at least 1% by weight of said composite body. It is particularly preferred that when n=4, R in phenyl; when n is at least 6, R is preferably methyl; these preferences are based on the spatial properties of the resulting cyclic oligoorganosilasesquioxane (OOSSO) . (n cannot exceed 12 however because it is not sterically possible to produce under stated conditions a cyclic OOSSO having the formula [RSi0 1>5 ] 13 , or with higher values of n) . Although R can be ethyl, it is preferred that R is either methyl or phenyl; when R is ethyl the thermal and fire resistant properties of the resulting composite body are impaired. The composite body is generally a substantially rigid body; the rigidity is a function of the proportion of OOSSO present in the binder; for example when the OOSSO is present at a level greater than 15% by weight of the binder, the composite body becomes unacceptably brittle (for this reason the OOSSO is in an amount not exceeding 15%) . The asbestos may also be present as wool, as fibers or as powders. The composite asbestos body has a variety of applications including use as brake shoes, clutch plates, nautical bulkheads, bridges and control rooms, construction partitions, fire curtains, roof sheathing or other products which require thermal stability and any degree of non-flammability to total inflammability. In a second embodiment, a surface coating formulation suitable to be used as a thermally protective coating is produced from an OOSSO prepared according to the present invention. There is provided by the present invention a surface coating formulation which comprises a polyorganosilasesquioxane (POSSO) together with a metal filler, wherein the POSSO and metal filler are specifically chosen because of their superior properties when used in a thermally protective coating. The method comprises: a) preparing at least one oligoorganosilasesquioxane by the synthesis method as hereinbefore described, said at least one oligoorganosilasesquioxane comprising methylsilasesquioxane; b) introducing said at least one oligoorganosilasesquioxane produced according to step (a) together with a metal filler as hereinbefore described into a substantially oil- free solvent; c) providing a clean, substantially oil-free, metal surface for the resulting formulation; d) applying said formulation to said substrate, up to a thickness of the resulting coating of 0.5mm, anything in excess of 0.5 mm being redundant; and e) curing said coating (typically by means of microwave radiation) . Preferably when microwave radiation is used, it is directed at the coated substrate for at least 3 minutes per 1.20m length of the coated substrate so that the coating is heated to a temperature of at least 180°C, but not exceeding 700°C; a preferred temperature being about 230°C. However, curing is generally continued until the oligomer has been substantially completely cured. Microwave radiation is preferably used for the curing process because it can cause effective curing of the coating whilst being independent of the orientation of the coated substrate; the use of the microwave radiation therefore provides a non-directiόnal curing process for the coating. Preferred solvents for the coating formulation include a mixture of toluene/acetone, ethyl alcohol or isopropanol. Typically the solution of the coating formulation is sprayed onto the substrate, however other suitable methods of application (such as dipping the substrate into the coating formulation) could of course be used. It is preferred that the metal substrate, in addition to being substantially oil-free has also been subjected to de-rusting and sand blasting prior to application of the coating thereon. De-rusting is preferably effected by washing in a solvent such as tetrachloroethane, toluene, benzene or the like. There is further provided a thermal coating formulation suitable for application to a metal substrate, wherein said formulation comprises poly ethysilasesquioxane intimately mixed with a metal filler having a particle size of not more than 250 microns, said metal filler being below iron in the electrochemical series and being self-healing in the presence of oxygen. Preferably the oligomethylsilasesquioxane is present in an amount of 8 to 10% by weight of the coating formulation, the metal filler being present in an amount of 85-90%, by weight of the final coating. Preferably oligomethylsilasesquioxane is substantially the only OOSSO present in the coating formulation. However, if more than one OOSSO is present, the oligomethylsilasesquioxane preferably comprises at least 85% by weight of the OOSSO content; the remainder of the OOSSO content may comprise oligophenylsilasesquioxane or oligoethylsilasesquioxane (both can be tolerated at a level preferably not exceeding 15% by weight of the OOSSO content) . Oligomeric siloxanes may sometimes be present in the coating formulation, but it is generally preferred that the cured coating is substantially free of any such oligomers. Typically metal substrates include titanium, aluminum and ferrous metals or alloys (such as steel) . It is generally preferred that specific metal fillers are chosen to be used with particular substrates. When deciding substrate/filler combinations it is important to avoid a combination where the respective metals of the substrate and filler would undergo "metalloid-forming" reactions at the substrate/coating interface. For example, when the substrate is titanium, the filler is preferably zinc; when the substrate is aluminum, the filler is preferably aluminum, and when the substrate is ferrous, the filler is preferably aluminum and/or zinc. The preferred metal fillers are inert to oxidation at elevated temperatures (such as up to about 850°C) . Although a particle size of up to 250 microns can be tolerated for the filler, it is generally preferred that the filler comprises particles having a size in the range of 50 to 100 microns. The formulation is preferably provided in a substantially oil-free solvent. Typically the coating formulation is applied as a substantially continuous surface coating layer on a metal substrate which is exposed in use to elevated temperature (exemplary substrates include exhaust pipes, vehicle silencers or other metallic bodies which require a thermally protective coating) . The coating generally can resist temperatures of up to about 850°C. The thickness and particle size are correlated so as to ensure that the coating constitutes a layer having a substantially even surface, and preferably of substantially uniform thickness. Typically the coating layer has a thickness not exceeding 0.5mm, the thickness preferably being of the order of at least about four times the average size of the filler particles. There is further provided by the present invention a metal substrate having provided thereon a coating as hereinbefore described. There is also a kit comprising a metal substrate together with a coating formulation as hereinbefore described, such that said coating formulation, when applied as a coating onto said substrate, provides said substrate with a non- oxidizable surface coating at temperatures not exceeding 850°C. In a third embodiment, there is produced a printed circuit board comprising at least on POSSO. There is therefore further provided by the present invention a method of preparing a printed circuit board (which is hereinafter described as the preparation method) , which method comprises: a) preparing at least one oligoorganosilasesquioxane according to the synthesis method as hereinbefore described; b) intimately mixing said at least on OOSSO produced according to step (a) in a hydrophobic solvent; c) adding a substantially electrically inert filler to the mixture produced according to step (b) , the filler being substantially free of any contaminants; d) treating the mixture produced according to step (c) so as to substantially completely cure said OOSSO resulting in hydrophobization of bulk and surface of material. e) heat pressing at least one surface of the product produced according to step (d) against a foil sheet; f) etching at least one metallised face of the product of step (e) to produce desired tracks thereon; and g) coating the etched metallised circuit board produced by step (f) according to the coating method as hereinbefore described. It is preferred that the OOSSO is present in the said solvents (which is preferably toluene) in step (b) of the above preparation method in an amount of about 20-25% by weight of the solvent, such that the mixture produced according to step (c) of said method comprises the OOSSO in a proportion of about 7-13% by weight of the mixture. It is preferred that the foil sheet is of either Al or Cu foil. When it is required to produce a two-sided printed circuit board the heat pressing described in step (e) of the preparation method involves pressing the product of step (d) between two foil sheets; alternatively the product of step (d) can be pressed between a press-form foundation and a foil sheet when it is required to produce a one¬ sided printed circuit board. Preferably step (d) of the preparation method first comprises drying the mixture produced by step (c) in air followed by substantially complete curing of the OOSSO. There is further provided by the present invention a printed circuit board provided with a protective covering, said coating printed circuit board being produced by a method as hereinbefore described. Preferably the coated printed circuit board produced by a method according to the present invention is thermally resistant to temperatures up to about 550°C. In a fourth embodiment of the present invention, there is provided a composition comprising an OOSSO which can be used to make a solid state luminescent screen. We have developed a composition which can be used to make a solid state luminescent screen, which composition comprises a phosphor and a polymer matrix which can be successfully used in unipolar excitation (that is, operable by means of d.c. current). According to the present invention therefore there is provided a composition which can be used to prepare a solid state luminescent screen, which composition comprises: a) a multiplicity of phosphor microspheres having a maximum dimension in the range of about 0.8 to 1.2 microns; and b) at least one oligoorganosilasesquioxane (OOSSO) prepared according to a synthesis method as hereinbefore described, said at least one OOSSO having a molecular mass distribution of at least 900 to 3,000, a hydroxyl content in the range of about 1.8 to 2.2% by weight thereof and being substantially free of any cross-linking. Preferably the OOSSO comprises oligomethylsilasesquioxane, oligoethylsilasesquioxand and/or oligophenylsilasesquioxane. Preferably the phosphor microspheres are subjected to partial oxidation so as to form diffuse p-n junctions within the body of the microspheres. Typically the oxidation is carried out from the surfaces thereof, such that the p-n junctions diffuse into the bodies of the microspheres. It is also often preferred that the microspheres are provided on the surface thereof with electron collector material, generally of copper, which enhances electrical injection into the body of the microspheres. Preferably the phosphor microspheres comprise ZnS; however, any phosphor into which diffused p-n junctions could be introduced could be used. There is further provided by the present invention a method of preparing a composition as hereinbefore described, which method comprises: a) introducing a multiplicity of phosphor microspheres having a maximum dimension in the range of about 0.8 to 1.2 microns into a coating medium comprising at least one OOSSO having been prepared by the synthesis method as hereinbefore described, wherein said microspheres are substantially completely immersed within said coating medium such that there is substantially no contact between said microspheres, said OOSSO having a molecular mass distribution of at least 900 to 3,000, a hydroxyl content in the range of about 1.8 to 2.2% by weight and being substantially free of any cross-linking; b) substantially curing the OOSSO present in step (a) ; c) intimately mixing the cured product obtained according to step (b) with at least one OOSSO so as to form a paste. It is preferred that the microspheres are coated with a surface layer which serves to substantially prevent aggregation of the microspheres to form large "clusters" of spheres. Preferably the microspheres are coated with the non-adhesive layer prior to introduction into the OOSSO coating medium. Typically the surface layer comprises polyorganosilasesquioxane (such as polymethylsilasesquioxane) . Preferably, the OOSO coating medium described in step (a) of the method is a dilute solution comprising about 1.0 to 3.0% by weight of the OOSSO. It is preferred that curing of the OOSSO as described in part (b) of the above method comprises drying the phosphor/OOSSO mixture at a temperature in the range of about 10 to 100°C. It is important to ensure that during the drying process, the phosphor microspheres are maintained in their required positions i.e. spaced apart from one another. As indicated above, the composition is suitable to be used in the preparation of a solid state luminescent screen; the latter typically comprises an electrode assembly to which a paste (as produced by the above method) is applied. There is further provided a method preparing an electrode assembly as hereinbefore described, which method comprises: a) preparing a past comprising a multiplicity of phosphor microspheres and a coating medium comprising at least one polyorganosilasesquioxane (POSSO) as hereinbefore described; b) coating a first set of electrodes with said paste produced according to step (a) ; c) drying said electrodes produced according to step (b) ; and d) arranging a second set of electrodes substantially orthogonal to said first set. Preferably the first set of electrodes is arranged on a transparent support and subsequent drying of the coated electrodes (as described in step (c) ) is carried out at a temperature in the range of 10 to 100°C so as to substantially completely remove any solvent present. There is further provided by the present invention an electrode assembly comprising at least two sets of electrodes orientated substantially orthogonal to one another and having arranged therebetween a composition comprising a multiplicity of phosphor microspheres having a maximum dimension in the range of about 0.8 to 1.2 microns, said microspheres being substantially completely immersed within a coating medium such that said microspheres are spaced apart from one another, said coating medium comprising at least one polymethylsilasesquioxane, polyethylsilasesquioxane or polyphenylsilasesquioxane. Preferably the first set of electrodes comprises transparent electrodes; the second set of electrodes may in some embodiments be transparent, but this depends on the required use of the electrodes. There is further provided a method preparing said solid state luminescent screen, which method comprises: a) preparing an electrode assembly as hereinbefore described; b) heating the electrode assembly to a temperature in the range of about 150 to 200°C; c) cooling the heated assembly produced according to step (b) ; d) substantially sealing the product obtained according to step (c) ; and e) providing said sealed screen with electrode contacts. When the screen according to the invention is used for unipolar excitation (that is in a d.c. mode), the coating medium for the electrode assembly should be present in the luminescent screen at a level of about 1 to 20% by weight; below 1% the coating medium is insufficiently strong and has poor adhesion, while above 20% the dielectric properties of the POSSO render the coating medium non-conductive. Typically, in the d.c. mode, excitation of the screen is carried out by the unipolar electric pulses with period/pulse ratio varying from 20- 500, the preferred range being 50-200. There is further provided by the present invention a method of preparation of micro-electronic chips. The oligomer of the synthesis method may be applied to form passivating layers of thickness varying from 0.05 to 0.3 microns on a substrate. The passivating layers may be obtained by two methods: liquid process and dry process. The liquid process includes the steps of: a) centrifugation of the solution of oligomethysilsesquioxane produced by the synthesis method in organic solvents of concentration from 1.0 to 3.0% mass; b) subsequent drying up in air or vacuum and heat treatment at temperatures varying from 230 to 800° until the complete conversion of oligomer into polymer. The preferable solvents are ethyl or isopropyl alcohol, acetone, cyclohexanone. It is preferable to use a mixed solvent 49% vol. acetone, 2% vol. cyclohexanone, and 49% vol. toluene. The solvent used should be of electronic purity. The dry process includes the steps of a) spurting the dry oligomethysilsesquioxane in a vacuum not less than lxlO *"4 mmHg by heating a semi-opened container to a temperature of 100-150°C, or by the electronic beam or the laser irradiation combined with inert gas transportation process with the subsequent heat treatment above. The angle of beam incision affects the efficiency of deposition. Acceptable angles range from 30-60°, the optimal one being 40±2°; b) heat treatment as in the liquid process. The methods of centrifugation or spurting of a material are commonly known in the art of microelectronic chips and are applied as such with the oligomer discussed herein. In both the liquid and dry processes, heat treatment below the stated temperature does not effect the complete annihilation of the natural oxide or otherwise disturbed surface layer in the course of the solid state reaction and therefore does not lead to perfect (the maximally physically attainable) passivation of the surface states (dangling bonds, point defects, chemically and physically absorbed impurities) , and above the stated temperature is useless as it does not shorten the time of the treatment and leads to the waste of energy and above 1,300°C degrades the monocrystal structure. The liquid process and dry process described above may be used as protective layers for the surface of semiconductor chips of the thickness ranging from 0.1 to 0.8 microns depending upon the demands of their properties. When the micro-electronic devices are to be operating under standard conditions, the preparation of the layers is the same as the dry process described above and the liquid process with changes as follows. When using the liquid process, the solutions having concentration from 2 to 10% mass and temperatures ranging from 180 to 250°C must be used. The higher temperatures may certainly be applied, but does not attain a better end result. When micro-electronic devices are supposed to be protected against the action of sea fog or any media having a high concentration of alkali metal ions or are supposed to be operating under the load of ionizing radiation (specifically neutrons, electrons, alpha- particles, protons, etc.) , the preparation of the layers is as follows. In the liquid process, the preparation is as initially described but with concentration and temperature limits of the 2-10% mass and 180-250°C temperature, provided that the initial solutions are modified by an addition of 0.5-3% mass to the solid residue of aluminum iso- porpylate. Since aluminum iso-propylate is very unstable especially to hydrolysis, it should be freshly prepared or be used in the form of solution in absolute ethyl or isopropyl alcohol. The subject oligomer may also be applied as functional dielectric elements such as capacitance overlays in transistors and/or integral circuits. Preparation of the dielectric elements is carried out as the process in the previous paragraph provided that, depending upon the desired value of dielectric permeability (up to epsilon = 7.5), in place of the aluminum iso- porpylate modifying agent, tetrabuthoxytitanium is used in concentration from 3-15% mass of the solid residue of oligomethysilsesquioxane. Lower concentrations can be used, but the alteration of epsilon would be too small; and higher concentration, cannot be employed because the film structure becomes unstable to the formation of the separate phase of titanium dioxide and leads to degradation of dielectric characteristics. The subject invention may also be provided to prepare thermo-diffusion masks. Two methods are proposed. In the first method of preparing thermo-diffusion masks, the method includes the steps of: a) applying the OOSSO to a substrate by, the liquid or dry processes; b) placing an over-layer of photo¬ resist, or any other known kind of resist, c) preparing the pattern of windows as, commonly known in the art. d) etching through the polyorganosilsesquioxane layer with the same reagents as for silicon dioxide in the manner as commonly known in the art, and e) performing the thermo-diffusion as commonly known in the art. Two main advantages result. First, these masks could be used for making patterns over any semiconductor substrate; and, in the case of silicon, the material of substrate is not wasted in preparation of the masking layers, and temperatures are much lower. Second, the diffusant does not penetrate the materials of the masking layer to the same extent as silicon dioxide, thus making the junction patterns more precise. In the second method of preparing diffusion masks, the method includes the steps of: a) applying the OOSSO to a substrate by the liquid or dry processes, b) using a beam technique treatment (laser, ionic [protons included], electron gamma- , ultra violet irradiation of the substrate with oligomer film at temperatures 90-150°C to form a pattern, c) removing the unexposed portion of material with solvent or by evaporation and d) applying a thermo-diffusion process to the mask pattern as commonly known in the art. The subject invention may also provide for production of ionic implantation masks. In this method, the initial stage is the same as in the method of making the protective layer with protection against ions provided that, instead of aluminum isopropylate, the modifying agent is tetraethoxilead in a concentration from 2-8% mass. Lower concentrations could be used only to the level where they become ineffective, and higher concentrations, though highly desirable, do not provide against formation of the second phase. The subject invention also produces layers/carriers of optical information. At the initial stage the preparation is carried out in the same way as in the method of making the protective layer without ion protection. Thereafter, the semi-conductor substrate is implanted with hydrogen ions (protons) having energy of 150 keV and doze above 1.10 15 cm "2 preferably from the side of the polymer film, ions. Information is introduced to the structure by electronic beam having energy lOkeV and current density 1.10 "2 A. cm -2. Readout of the introduced information is carried out by scanning electronic beam having the same energy and current density. The use of the above described methods as applied to micro-electronic chips incudes a purified film layer free of microgels. It may be applied over any substrate material without oxidation of the substrate. It avoids the problems of impure layers, such as high back currents, low breakthrough voltages, etc. The subject invention provides dissociation of OH-group and/or siloxane bonds facilitated by/in the gradients of both electronic and magnetic field. Charge or free radical state of the surface states may be compensated for by their annihilation with the products of hetero- or homo- lytic dissociation of both hydroxyl groups and siloxane bonds which leads to an expressed decrease of surface state concentration and provides for better passivation of homocrystalline semiconductor wafers and/or semiconductor structures of p-n junctions. Chemical reaction with sorbed impurities and active sites on the monocrystal surface is connected with active external hydroxyl groups and takes place before or simultaneously with curing of oligomer. Chemical reaction of natural silicon oxide (SiO x , where 1 < X < 2) with polyorganosilsesquioxanes and annihilation of point defects is connected with the internal hydroxyl groups and ring opening process at elevated temperatures, above 200°C. The commencement of both processes results in an expressed decrease (up to less than 10" cm~ 2 ) of surface state concentration, provides for rise in stability, in reliability of electronic structures and devices, and an increase in yield of quality of items. The present invention will now be further illustrated, by way of example only, with reference to the accompanying drawing which illustrates a laboratory apparatus suitable for use in a synthesis method according to the present invention. Referring to the drawing, there is shown laboratory apparatus generally comprising a cooling jacket 1 having a fluid inlet la and a fluid outlet (not shown) , the jacket surrounding an upright, cylindrical reactor 2 into which the reagents are injected via the parallel arrangement of nozzles 3 and 4. Nozzle 3 (through which the solution of trichlorosilane and aromatic hydrocarbon is injected) has an outlet 3a arranged coaxial with the axis of the reactor. Outlet 4a of nozzle 4 (through which the water/ketone mixture is injected) coaxially surrounds outlet 3a. The reagents are introduced into the reactor in such a way that a turbulent zone 5 is disposed proximate the base of the reactor and a laminar flow zone 6 disposed above the turbulent zone; whereby the two reagent streams introduced via nozzle outlets 3a and 4a undergo hydrolytic condensation under turbulent flow conditions.

Claims: CLALMS: A method of synthesis of an OOSSO (as defined herein) which comprises the steps of: (a) providing a solution of at least one trichlorosilane of general formula RSiCl 3 in which R is methyl, phenyl or ethyl, in an aromatic hydrocarbon solvent; (b) simultaneously injecting into a reactor as separate upwardly directed streams; ( i) the solution of step (a); and (ii) a compatible mixture of water and a ketone of formula C n H 2n+ ,COC m H 2m+ ι. where n and m are each 1 or 2; (c) allowing the streams to undergo hydrolytic condensation under turbulent flow conditions so as to form a curable OOSSO having residual reactive hydroxyl groups, the two streams being introduced into the reactor in such a way that a turbulent zone is disposed proximate the base of the reactor, whereby turbulent flow conditions are maintained substantially throughout a lower volume of the reactor such that said lower volume is substantially free of dead zones, and adjacent to and above which turbulent zone is disposed a laminar flow zone. A method according to claim 1 , wherein the trichlorosilane comprises methyltrichlorosilaπe or phenyltrichlorosilane. A method according to claim 1 or 2, wherein the aromatic hydrocarbon solvent is of the following general formula in which at least two of R 1 to R ή are hydrogen and the remainder of R 1 to R 6 are alkyl groups such that the total number of carbon atoms in R 1 to R 6 is from 1 to 4. 4. A method according to any of claims 1 to 3, wherein the volume of the reactor occupied by the turbulent zone has a height of not more than about one third of the total height of the reactor. 5. A method according to any of claims 1 to 4, wherein the ketone is used in an amount of 12% to 60% by weight, based on the combined weight of the ketone and the aromatic hydrocarbon solvent. 6. A method according to any of claims 1 to 5, wherein the two streams are injected into the reactor from first and second inlets proximate the base of the reactor, in such a way that the height by which the streams rise in the reactor is from 7 to 15 times the internal diameter of the reactor. 7. A method according to any of claims 1 to 6, wherein said first inlet comprises a substantially upright nozzle with an axis substantially coaxial with the axis of the reactor. 8. A method according to any of claims 1 to 7, wherein the ketone and water mixture is . supplied to the reactor as a stream injected along the axis of the reactor. 9. A method according to any of claims 1 to 8, wherein the stream comprising the ketone and water mixture forms a sheath coaxially surrounding the stream comprising the solution of trichlorosilane and aromatic hydrocarbon such that the condensation reaction takes place substantially in said sheath. 10. A method according to any of claims 1 to 9, wherein the reactants are injected into the reactor at a temperature of O±. 5°C. 11. A method according to any of claims 1 to 10, wherein the first and second inlets are respective atomisation nozzles through which the reactants are injected in such a way that the reaction time is controlled so as to lie in the range 1.5 to 3 seconds. 12. A method according to any of claims 1 to 11, which further comprises a monitoring step, wherein light scattering analysis is carried out to establish that the turbulent zone is substantially free of dead zones. 13. An OOSSO obtained by a method according to any of claims 1 to 12, said OOSSO having a formula R x SiO y/2 , where x + y is 4, x is substantially one and y is substantially 3, which OOSSO is substantially microgel-free and is curable to a POSSO (as defined herein). 14. A method of producing a coating on a substrate surface, which method comprises: (a) preparing at least one OOSSO by a method of synthesis according to any of claims 1 to 12; (b) introducing at least one OOSSO prepared according to step (a) into a solvent, said at least one OOSSO comprising oligophenylsilasesquioxane and/or oligomethylsilasesquioxane, being of functionality of about 2.75 to 3.14 and having a hydroxyl content of at least 4% by weight thereof, the resulting mixture being substantially free of any filler; (c) applying the resultant mixture as a coating on a substrate; and (d) curing the coating. 15. A method according to claim 14, wherein the solvent used in step (b) is hydrophobic. 16. A method according to claim 15, wherein the hydrophobic solvent comprises toluene. 17. A method according to any of claims 14 to 16, wherein the OOSSO is present in the solvent used in step (b) in an amount of about 5-10% by weight of the solvent. 18. A method according to any of claims 14 to 17, wherein step (d) comprises a first stage of drying the coating in air, followed by substantially complete curing of the OOSSO. 19. A method according to any of claims 14 to 18, wherein the substrate comprises a printed circuit board. 20. A method according to any of claims 14 to 18, wherein the substrate comprises a solid state luminescent screen. 21. A method of preparing a composite body comprising asbestos intimately mixed with a binder, which method comprises: (a) preparing at least one OOSSO by a method of synthesis according to any of claims 1 to 12; (b) intimately mixing asbestos and said at least one OOSSO produced according to step (a) in an amphiphilic solvent medium, said at least one OOSSO being present in an amount of about 10-20% by weight of the mixture; and (c) forming and drying the resultant mixture of step (b). 22. A method according to claim 21, wherein the amphiphilic solvent medium comprises about 50% acetone, methyl ethyl ketone, or diethylketone, and about 50% toluene or xylene. 23. A method according to claim 21 or 22, which further comprises impregnating the composite body with about 5-15% OOSSO solution by weight of the composite body, calendering the body to press out any excess solution, followed by drying and hot pressing the resultant body into a desired shape. 24. A composite body which comprises asbestos intimately mixed with a binder, said binder comprising at least one cyclic OOSSO prepared by a method of synthesis according to any of claims 1 to 12, and having a general formula [RSiO ] n where n is 4,5,6 or an integer of 8 to 12, and where R is methyl, phenyl or ethyl, said OOSSO being present in a proportion of at least 12% , but not exceeding 15 % by weight of the binder, and in an amount of at least 1 % by weight of said composite body. 25. A composite body according to claim 24, wherein n is 4 and R is phenyl. 26. A composite body according to claim 24, wherein n is at least 6 and R is methyl. 27. A method of producing a thermal coating on a metal substrate, which method comprises: (a) preparing at least one OOSSO by a method of synthesis according to any of claims 1 to 12, said at least one OOSSO comprising oligomethylsilasesquioxane; (b) introducing the at least one OOSSO produced according to step (a) into a substantially oil-free solvent together with a metal filler having a particle size of not more than 250 microns, said metal filler being below iron in the electrochemical series and being self-healing in the presence of oxygen; (c) applying the resulting formulation to a clean, substantially oil-free, metal substrate, such that the thickness of the resulting coating does not exceed 0.5mm; and (d) curing the coating. 28. A method according to claim 27, wherein said curing is effected by means of microwave radiation. 29. A method according to claim 28, wherein the coated substrate is treated with microwave radiation for at least 3 minutes per 1.20m length of the coated substrate. 30. A method according to claim 28 or 29, wherein the coating is heated to a temperature of at least 180°C, but not exceeding 700°C. 31. A method according to claim 30, wherein the coating is heated to a temperature of about 230°C. 32. A method according to any of claims 27 to 31, wherein the substantially oil-free solvent comprises one or more of toluene, acetone or isopropanol. 33. A method according to any of claims 27 to 32, wherein said formulation is applied to the substrate by spraying. 34. A method according to any of claims 27 to 33, wherein the metal substrate has been subjected to de-rusting and sand blasting prior to application of the formulation thereon. 35. A method according to claim 34, wherein the derusting is effected by washing in a solvent comprising tetrachloromethane, toluene, or benzene. 36. A method according to any of claims 27 to 35, wherein the metal substrate comprises titanium, aluminium or a ferrous metal or an alloy thereof. 37. A method according to any of claims 27 to 36, wherein the metal filler is substantially inert to oxidation at temperatures up to about 850°C. 38. A method according to any of claims 27 to 37, wherein the metal filler comprises particles having a size in the range of 50 to 100 microns. 39. A method according to any of claims 27 to 38, wherein the substrate and filler comprise any of the following combinations: titanium substrate and zinc filler; aluminium substrate and aluminium filler; or ferrous substrate and aluminium and/or zinc filler. 40. A coating formulation suitable for application to a metal substrate, which formulation comprises an oligomethylsilasesquioxane prepared according to any of claims 1 to 12, said oligomethylsilasesquioxane being intimately mixed with a metal filler having a particle size of not more than 250 microns, said metal filler being below iron in the electrochemical series and being self-healing in the presence of oxygen. 41. A coating formulation according to claim 40, wherein the oligomethylsilasesquioxane is present in an amount of 8 to 10% by weight of the coating formulation. 42. A coating formulation according to claim 40 or 41, wherein the oligomethylsilasesquioxane is substantially the only OOSSO present in the coating formulation. 43. A coating formulation according to claim 40 or 41, wherein the oligomethylsilasesquioxane comprises at least 85% by weight of the OOSSO content. 44. A coating formulation according to claim 43, which further comprises one or more of oligophenylsilasesquioxane and oligoethylsilasesquioxane. 45. A coating formulation according to any of claims 40 to 44, wherein the metal filler is substantially inert to oxidation at temperatures up to about 850°C. 46. A coating formulation according to any of claims 40 to 45, wherein the metal filler comprises particles having a size in the range of 50 to 100 microns. 47. A method of preparing a printed circuit board, which method comprises: (a) preparing at least one OOSSO according to any of claims 1 to 12; (b) intimately mixing said at least one OOSSO produced according to step (a) with an organic solvent; (c) adding a substantially electrically inert filler to the mixture produced according to step (b), the filler being substantially free of any contaminants; (d) treating the mixture produced according to step (c) so as to substantially completely cure said OOSSO; (e) heat pressing at least one surface of the product produced according to step (d) against a foil sheet; (f) etching the at least one metallised face of the product of step (e) to produce desired tracks thereon; and (g) coating the etched metallised circuit board produced by step (f) by a method according to any of claims 14 to 20. 48. A method according to claim 47, wherein the solvent used in step (b) comprises toluene. 49. A method according to claim 47 or 48, wherein the OOSSO is present in the solvent used in step (b) in an amount of about 20-25% by weight of the solvent. 50. A method according to any of claims 47 to 49, wherein the foil sheet is of aluminium or copper foil. 51. A method according to any of claims 47 to 50, wherein step (d) comprises drying the mixture produced in step (c) in air followed by substantially complete curing of the OOSSO. 52. A printed circuit board obtained by a method according to any of claims 47 to 51 having a protective covering produced by a method according to any of claims 14 to 20. 53. A printed circuit board according to claim 52, which is thermally resistant to temperatures up to about 550°C. 54. A composition which can be used to prepare a solid state luminescent screen, which composition comprises: (a) a multiplicity of phosphor microspheres having a maximum dimension in the range of about 0.8 to 1.2 microns; and (b) at least one OOSSO prepared according to any of claims 1 to 12, the at least one OOSSO having a molecular mass distribution of at least 900 to 3,000, a hydroxyl content in the range of about 1.8 to 2.2% by weight thereof and being substantially free of cross-linking. 55. A composition according to claim 54, wherein the OOSSO comprises one or more of oligomethylsilasesquioxane, oligoethylsilasesquioxane and cligophenylsilasesquioxane. 56. A composition according to claim 55, wherein the phosphor microspheres are partially oxidised so as to form diffuse p-n junctions within the body of the microspheres. 57. A composition according to any of claims 55 to 56, wherein the surfaces of the microspheres are provided with electron collector material. 58. A composition according to claim 57, wherein the electron collector material comprises copper. 59. A composition according to any of claims 54 to 58, wherein the phosphor microspheres comprise zinc sulphide. 60. A method of preparing a composition which method comprises: (a) introducing a multiplicity of phosphor microspheres having a maximum dimension in the range of about 0.8 to 1.2 microns into a coating medium comprising at least one OOSSO which has been prepared by a synthesis method according to any of claims 1 to 12, wherein the microspheres are substantially completely immersed within the coating medium such that there is substantially no contact between the microspheres, the OOSSO having a molecular mass distribution of at least 900 to 3,000, a hydroxyl content in the range of about 1.8 to 2.2% by weight and being substantially free of cross- linking; (b) substantially curing the OOSSO present in step (a); (c) intimately mixing the cured product obtained according to step (b) with at least one OOSSO so as to form a paste. 61. A method according to claim 60, wherein the microspheres are coated with a non- adhesive layer prior to introduction into the OOSSO coating medium. 62. A method according to claim 61 , wherein the non-adhesive layer comprises a POSSO. 63. A method according to any of claims 60 to 62, wherein the OOSSO coating medium of step (a) comprises a solution containing about 1.0 to 3.0% by weight of the OOSSO. 64. A method according to any of claims 60 to 63, wherein curing of the OOSSO comprises drying the mixture of phosphor and OOSSO at a temperature in the range of about 10 to 100°C. 65. A method of preparing an electrode assembly, which method comprises: (a) preparing a paste comprising a multiplicity of phosphor microspheres and a coating medium comprising at least one POSSO according to any of claims 60 to 64; (b) coating a first set of electrodes with a paste produced according to step (a); (c) drying the coated electrodes produced according to step (b); and (d) arranging a second set of electrodes substantially orthogonal to the first set of electrodes. 66. A method according to claim 65, wherein the first set of electrodes is arranged on a transparent support. 67. A method according to claim 65 or 66, wherein drying of the coated electrodes is carried out at a temperature in the range of about 10 to 100°C. 68. An electrode assembly comprising at least two sets of electrodes orientated substantially orthogonal to one another and having arranged therebetween a composition comprising a multiplicity of phosphor microspheres having a maximum dimension in the range of about 0.8 to 1.2 microns, the microspheres being substantially completely immersed within a coating medium such that the microspheres are spaced apart from one another, the coating medium comprising at least one POSSO selected from polymethylsilasesquioxane, polyethylsilasesquioxane and poiyphenylsilasesquioxane, said at least one POSSO being obtained from the corresponding OOSSO produced by a method of synthesis according to any of claims 1 to 12. 69. An electrode assembly according to claim 68, wherein the first set of electrodes are transparent. 70. A method of preparing a solid state luminescent screen, which method comprises: (a) preparing an electrode assembly according to any of claims 65 to 67; (b) heating the electrode assembly to a temperature in the range of about 150 to 200°C; (c) cooling the heated assembly produced according to step (b); (d) substantially sealing the product obtained according to step (c); and (e) providing the sealed screen with electrode contacts. 71. A method according to claim 70, wherein the coating medium for the electrode assembly is included in the luminescent screen at a level of about 1 to 20% by weight. 72. An electronic component or integrated circuit provided with a passivating layer of thickness typically of from 0.05 to 0.3 microns, said passivating layer comprising at least one OOSSO produced by a synthesis method according to any of claims 1 to 12. 73. A method of preparing a passivating layer for an electronic component or integrated circuit, which method comprises: (a) preparing an oligomethylsilasesquioxane by a synthesis method according to any of claims 1 to 12; (b) centrifugation of a solution obtained by step (a) in an organic solvent medium at a concentration of 1.0 to 3.0% mass; and (c) substantially curing the solution obtained by step (b). 74. A method according to claim 73, wherein the curing comprises drying in air or vacuum and heating, to a temperature of 230 to 800°C. 54/1 75. A method of synthesis of oligoorganosilasesquioxanes (OOSSO) includes the steps of dissolving a chlorosilane of the formula: RSiCl 3 wherein R is selected from the group consisting of methyl, phenyl and ethyl, with an aromatic hydrocarbon solvent to form solution A; injecting the resulting solution A into a reactor as an upwardly directed stream; simultaneously with said first injecting step, injecting into the reactor a compatible mixture A of a ketone of the formula C n H 2n+1 COC m H 2m+1 wherein n and m are one or two, as an upwardly directed stream of said mixture A proximate to said stream of solution A; allowing said two streams to undergo hydrolytic condensation in turbulent flow conditions and forming a curable OOSSO having residual reactive hydroxyl groups.

Inventors: KAMARITSKII BORIS A, OVCHINNIKOV ALEXANDER, SPECTOR VALERY N, KAMARITSKII, BORIS A., OVCHINNIKOV, ALEXANDER, SPECTOR, VALERY, N.
Applicants: IMPACT INTERNATIONAL INC, IMPACT INTERNATIONAL, INC.
Application year: 1992
Main classification: B32B9
IPC codes: B05D7, C08G77, C09D183, H05K3