Patent GB-1116257-A (GB)
Title: Particulate reflective elements and method for forming the same
IPC: B44F9/08
Filed: 1965-06-28
Abstract: In the examples a luminescent nacreous pigment comprising a zinc sulphide- or tin sulphide-coated mica polystyrene or glass is incorporated into a cellulose lacquer containing nitrocellulose with and without ethanol and butyl acetate. In Example 16, polystyrene beads have their surfaces roughened by a solution of K2Cr2O7 and H2SO4 and are then coated with a layer of ZnS by boiling in a solution containing zinc acetate and thioacetamide.ALSO:In Example 13 a luminescent nacreous pigment is made by heating zinc sulphide-coated mica plates with NaCl and CuCl2, a manganese salt or a silver salt to 850 DEG  C. in about 1 hour, cooling and washing in water saturated with H2S. The resultant phosphor luminesces green, orange or blue respectively.ALSO:A reflective substance having a nacreous lustre is constituted of particles of maximum dimensions up to 10 mm., each of which includes at least one layer of high refractive index constituted of a water-insoluble metal sulphide. The layer has an optical thickness Nd of 40 to 1000 mm , wherein "N" is the index of refraction and "d" is the thickness thereof.  The particles are made of mica, glass, plastics or a lacquer or resin-coated substance.  The particles may be smooth platelets with a major dimension of 3 to 100m .  Preferably, the platelets are mica of 150 to 400 mesh having a B.E.T. surface are of 2 to 6 sq. m./gm. The reflective substance may be prepared by suspending platelets in a solution of a water-soluble salt of a metal having a water-insoluble sulphide and an organic sulphur-containing compound which releases sulphide ions in aqueous media, heating the mixture to 60 DEG  C. to the b.p. of the mixture for 1/4 to 5 hours with agitation, separating the coated particles and drying, e.g. at 110 DEG  C.  The particles may be then heated to 200 DEG  to 1000 DEG  C. for 1 to 4 hours, e.g. in air or non-oxidizing gas such as N2, He, Ar or CO2.  The organic compound may be thioacetamide, thiourea, thioglycollic acid, thioacetic acid, thioformamide or thiosalicylic acid.  The metal of metal sulphide may be Zn, Co, Pb, Hg, Mn, Cd, As, Sb, Ni, Fe, Cu, Bi or Sn.  The zinc salt used in the solution can be the acetate, chloride, sulphate, formate, nitrate or zinc oxide in a strongly alkaline media.  The zinc source is used in an amount expressed as ZnO of from 0.25 to 7.5% wt. of the solution. The molar proportion of zinc to the sulphur in the organic compound may be from 0.5 to 3 moles of S per mole of Zn.  A plurality of zinc sulphide layers can be built up.  The reflective substance may be made luminescent, e.g. by heating with NaCl and CuCl2, manganese salts or silver salts.  The nacreous reflective pigment may be incorporated into a nitrocellulose film. The reflective substance has a high pearl brilliance or colour, which can vary depending on the angle at which it is viewed due to interference effects.ALSO:A reflective substance having a nacreous lustre is constituted of particles of maximum dimensions up to 10mm each of which includes at least one layer of high refractive index constituted of a water-insoluble metal sulphide.  The layer has an optical thickness Nd of 40 to 1000mm  wherein "N" is the index of refraction and "d" is the thickness thereof.  The particles are made of mica, glass, plastics or a lacquer or resin-coated substance.  The particles may be smooth platelets with a major dimension of 3 to 100m .  Preferably the platelets are mica of 150 to 400 mesh having a B.E.T. surface area of 2 to 6 sq. m./gm. The reflective substance may be prepared by suspending platelets in a solution of water-soluble salt of a metal having a water-insoluble sulphide and an organic sulphur-containing compound which releases sulphide ions in aqueous media, heating the mixture to 60 DEG C to the b.p. of the mixture for 1/4 to 5 hrs. with agitation, separating the coated particles and drying e.g. at 110 DEG C.  The particles may be then heated to 200 to 1000 DEG C for 1 to 4 hrs. e.g. in air or non-oxidising gas such as N2, He, Ar or CO2.  The organic compound may be thioacetamide, thiourea, thioglycollic acid, thioactetic acid, thioformamide or thiosalicyclic acid.  The metal of metal sulphide may be Zn, Co, Pb, Hg, Mn, Cd, As, Sb, Ni, Fe, Cu, Bi, or Sn.  The zinc salt used in the solution can be the acetate, chloride, sulphate, formate, nitrate or zinc oxide in a strongly alkaline media.  The zinc source is used in an amount expressed as ZnO of from 0.25 to 7.5% wt of the solution. The molar proportion of zinc to the sulphur in the organic compound may be from 0.5 to 3 moles of S per mole of Zn.  A plurality of zinc sulphide layers can be built up.  The reflective substance may be made luminescent, e.g. by heating with NaCl and CuCl2, manganese salts or silver salts.  The nacreous reflective pigment may be incorporated into a nitrocellulose film.  The reflective substance has a high pearl brilliance or colour, which can vary depending on the angle at which it is viewed due to interference affects.