Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G77/00—Macromolecular compounds obtained by reactions forming a linkage containing silicon with or without sulfur, nitrogen, oxygen or carbon in the main chain of the macromolecule
  • C08G77/04—Polysiloxanes
  • C08G77/06—Preparatory processes
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D183/00—Coating compositions based on macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing silicon, with or without sulfur, nitrogen, oxygen, or carbon only; Coating compositions based on derivatives of such polymers
  • C09D183/04—Polysiloxanes

Definitions

• 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.
• OOSSO oligoorganosilasesquioxanes
• 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.
• 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.
• Solid state luminescent screens 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.
• 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 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.
• 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.
• 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
• the Figure is a schematic diagram of the laboratory apparatus for use in the subject invention.
• 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
• 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
• 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.
• 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 main reaction is a sequence of chlorine functional groups' hydrolysis and their condensation.
• 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 ⁇ 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.
• Intramolecular homofunctional e.g. RSi(OH) 2 Cl- * RSiOCl + H 2 0 or RSi(OH) 3 ⁇ RSiO(OH) + H 2 0
• 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
• 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 ⁇ 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.
• 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.
• the resulting OOSSO is substantially cured and included in a film which consists essentially of the corresponding POSSO.
• the OOSSO is combined with a filler material.
• the resulting mixture is further processed to form a composite body comprising the corresponding POSSO.
• 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) .
• MWD molecular weight distribution
• 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.
• a method of preparing and applying a coating to a substrate surface 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
• step (d) of the above method comprises a first stage of drying the coating in air, followed by substantially complete curing of the OOSSO.
• 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.
• POSSO olyorganosilasesquioxand
• 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.
• 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.
• 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.
• 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.
• a method of preparing a composite body comprising asbestos intimately mixed with a binder 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) .
• 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.
• 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.
• 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.
• 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.
• 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.
• 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.
• 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) .
• 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.
• a surface coating formulation suitable to be used as a thermally protective coating is produced from an OOSSO prepared according to 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.
• POSSO polyorganosilasesquioxane
• 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) .
• microwave radiation 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.
• 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-directi ⁇ nal curing process for the coating.
• Preferred solvents for the coating formulation include a mixture of toluene/acetone, ethyl alcohol or isopropanol.
• 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.
• 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.
• 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.
• 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.
• oligomethylsilasesquioxane is substantially the only OOSSO present in the coating formulation.
• 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.
• 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.
• 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.
• 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.
• 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.
• 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.
• a printed circuit board comprising at least on POSSO.
• a method of preparing a printed circuit board 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.
• step (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.
• 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.
• the foil sheet is of either Al or Cu foil.
• 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.
• 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.
• a printed circuit board provided with a protective covering, said coating printed circuit board being produced by a method as hereinbefore described.
• the coated printed circuit board produced by a method according to the present invention is thermally resistant to temperatures up to about 550°C.
• composition comprising an OOSSO which can be used to make a solid state luminescent screen.
• compositions 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).
• 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.
• OOSSO comprises oligomethylsilasesquioxane, oligoethylsilasesquio
• the phosphor microspheres are subjected to partial oxidation so as to form diffuse p-n junctions within the body of the microspheres.
• the oxidation is carried out from the surfaces thereof, such that the p-n junctions diffuse into the bodies of the microspheres.
• 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.
• the phosphor microspheres comprise ZnS; however, any phosphor into which diffused p-n junctions could be introduced could be used.
• a method of preparing a composition as hereinbefore described 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.
• the microspheres are coated with a surface layer which serves to substantially prevent aggregation of the microspheres to form large "clusters" of spheres.
• the microspheres are coated with the non-adhesive layer prior to introduction into the OOSSO coating medium.
• the surface layer comprises polyorganosilasesquioxane (such as polymethylsilasesquioxane) .
• 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.
• 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.
• 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.
• a method preparing an electrode assembly as hereinbefore described 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.
• POSSO polyorganosilasesquioxane
• 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.
• 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.
• 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.
• a method preparing said solid state luminescent screen 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.
• a method preparing said solid state luminescent screen 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.
• 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.
• 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.
• 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.
• 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.
• the preparation of the layers is the same as the dry process described above and the liquid process with changes as follows.
• 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.
• the preparation of the layers is as follows.
• 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 invention may also be provided to prepare thermo-diffusion masks. Two methods are proposed.
• 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.
• 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.
• 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.
• the preparation is carried out in the same way as in the method of making the protective layer without ion protection.
• 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 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.
• 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
• outlet 3a (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.

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• 1991
  • 1991-07-23 GB GB919115818A patent/GB9115818D0/en active Pending
  • 1991-12-04 GB GB919125754A patent/GB9125754D0/en active Pending
• 1992
  • 1992-07-23 EP EP19920917124 patent/EP0596025A4/en not_active Withdrawn
  • 1992-07-23 WO PCT/US1992/006185 patent/WO1993002126A1/en not_active Application Discontinuation
  • 1992-07-23 JP JP5503069A patent/JPH06510069A/ja active Pending

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