Particles with opalescent effect

Abstract

The invention relates to particles with opalescent effect-especially 3-D structural color pigments-based on solid colloidal crystals of monodispersed spheres and the manufacturing processes suitable for large-scale production of such solid colloidal crystal products. The particles with opalescent effect contain a sphere based crystal structure (or super-lattice) built up by monodisperse spheres and one or more secondary types of much smaller colloidal particles occupying partially or completely the empty spaces between the monodisperse spheres.

1 . Particles with opalescent effect contain a sphere based crystal structure (or super-lattice) built up by monodisperse spheres and one or more secondary types of much smaller colloidal particles occupying partially or completely the empty spaces between the monodisperse spheres.  
     
     
         2 . Particles according to  claim 1 , characterized in, that the size of the monodisperse spheres ranges from about 150 nm to about 450 nm.  
     
     
         3 . Particles according to at least one of claims  1  or  2 , characterized in, that the monodisperse spheres are transparent and comprise metal chalcogenide, metal pnictide or organic polymers, especially preferred a metal oxide, preferably silicon dioxide.  
     
     
         4 . Particles according to at least one of  claims 1  to  3 , characterized in, that the size of the secondary colloid species is in the range of about 5 nm up to about one-third in diameter of the size of the monodisperse spheres used, preferably, it is in the range from about 10 nm to about 50 nm.  
     
     
         5 . Particles according to at least one of  claims 1  to  4 , characterized in, that the colloidal species comprise metal oxide sols e.g. SiO 2 , Al 2 O 3 , TiO 2 , SnO 2 , Sb 2 O 5 , Fe 2 O 3 , ZrO 2 , CeO 2  and Y 2 O 3 ; and/or metal colloids e.g. gold, silver and copper; and/or colloidal polymers such as, for example, poly(methyl methacrylate), poly(vinyl acetate), polyacrylontrile and poly(styrene-co-butadiene).  
     
     
         6 . Particles according to at least one of  claims 1  to  5 , characterized in, that the colloidal species are present in an amount from about 5%-by-weight to about 25%-by-weight with respect to the monodisperse spheres used.  
     
     
         7 . Particles according  claims 1  to  6 , characterized in, that the particles show a opal structure.  
     
     
         8 . Particles according  claims 1  to  7 , characterized in, that the particles show a inverse opal structure  
     
     
         9 . Method of manufacturing thin layer (flaky) crystals of monodisperse spheres characterized in, that a substrate coating technology is used.  
     
     
         10 . Method according to  claim 9  characterized in, that in a first stage a suspension of monodisperse spheres is prepared at a suitable concentration, in an appropriate solvent, and with a suitable amount of one or more colloidal species with much; smaller particle size than the monodisperse spheres.  
     
     
         11 . Method according to at least one of claims  9  or  10 , characterized in that in a second stage the suspension is brought onto a flat substrate, static or constantly moving with desired thickness of the suspension layer and optionally the crystalline layer is then initially dried and removed from the substrate at small pieces of flakes.  
     
     
         12 . Method according to at least one of the  claims 9  to  11 , characterized in, that in a final stage the crystal flakes are further dried, optionally calcined, milled to reduce the particle size to an appropriate range, and optionally classified into different fractions of final products.  
     
     
         13 . Method according to  claims 9  to  12  characterized in that the concentration of the suspension of monodisperse spheres for crystallization is in the range from about 5%-by-weight to about 65%-by-weight, preferably the concentration is in the range from about 20%-by-weight to about 50%-by-weight.  
     
     
         14 . Method according to  claims 9  to  13 , characterized in, that the substrate materials that may be used for the production of the thin layer crystals of the monodisperse spheres are selected from the group that includes glass, metals, e.g. stainless steel and aluminum, and polymer materials e.g. polypropylene, polystyrene, poly(methyl pentene), polycarbonate, poly(ethylene terephthalate).  
     
     
         15 . Method according to  claim 14  characterized in, that the substrate surface is pretreated with dilute acids or bases in order to make it more wettable for the colloid suspension.  
     
     
         16 . Particles according to  claims 1  to  8 , characterized in, that the particles are thin layer crystals with layer thicknesses from about 20 μm to over 5 mm, preferably from about 100 μm up to about 1000 μm.  
     
     
         17 . Use of particles according to at least one of  claims 1  to  8  or  16  or of thin layer flaky crystals produced with a method according to at least one of the  claims 9  to  15  for photonic and optoelectronic device applications