Thermally developable materials with improved conductive layer
View Patent ↗Backside conductive layers with increased conductive efficiency can be provided for thermally developable materials by formulating hydrophilic metal oxide clusters in a hydrophobic environment using low shear mixing conditions. The dry thickness and coating weight of the conductive layer are thereby reduced.
1. A method of making a stable dispersion of a conductive hydrophilic metal oxide comprising:
A) adding a dispersion of nanoparticles of a conductive hydrophilic metal oxide in a first solvent to a mixing vessel,
B) adding a second, hydrophobic, solvent to said mixing vessel with sufficient agitation to maintain said metal oxide nanoparticles in dispersion or in clusters having an average size of less than 1 μm, and
C) adding a binder premix comprising a binder in said second solvent to said mixing vessel with a shear rate sufficient to allow growth of clusters of said metal oxide nanoparticles to an average size of 1 μm or less to form a stable dispersion of said metal oxide clusters,
wherein steps B and C can be carried out sequentially or simultaneously after step A.
2. The method of claim 1 wherein said first solvent is water or a water-miscible alcohol and said hydrophilic conductive metal oxide is a non-acicular metal antimonate having a composition represented by the following Structure I or II:
M +2 Sb +5 2 O 6 (I)
wherein M is zinc, nickel, magnesium, iron, copper, manganese, or cobalt,
M a +3 Sb +5 O 4 (II)
wherein M a is indium, aluminum, scandium, chromium, iron, or gallium.
3. The method of claim 2 wherein said hydrophilic conductive metal oxide is composed of zinc antimonate (ZnSb 2 O 6 ).
4. The method of claim 1 wherein said second solvent is a nonpolar organic solvent.
5. The method of claim 1 wherein step C is carried out with a shear rate sufficient to allow growth of clusters of said metal oxide nanoparticles to an average size of from about 50 nm to about 1 μm.
6. The method of claim 1 wherein steps B and C are carried out sequentially.
7. The method of claim 1 wherein said binder comprises a single-phase mixture of a polyester resin with either polyvinyl butyral or cellulose acetate butyrate.
8. The method of claim 1 further comprising filtering said stable dispersion of said metal oxide clusters.
9. A method of making a stable dispersion of a conductive hydrophilic metal oxide comprising:
A) adding a dispersion of nanoparticles of zinc antimonate (ZnSb 2 O 6 ) in an alcoholic solvent to a mixing vessel,
B) adding methyl ethyl ketone to said mixing vessel with sufficient agitation to maintain said zinc antimonate nanoparticles in dispersion or in clusters having an average particle size of from about 50 nm, to about 1 μm, and
C) adding a binder premix comprising a single phase mixture of a polyester resin with either polyvinyl butyral or cellulose acetate butyrate, in methyl ethyl ketone to said mixing vessel with a shear rate having a Reynolds number (N RE ) of less than from about 20,000 to about 23,000 to allow growth of clusters of said zinc antimonate nanoparticles to an average size of from about 50 nm to about 1 μm or less to form a stable dispersion of said zinc antimonate clusters,
wherein steps B and C are carried out sequentially after step A.