Coated sheet-like plastics material with reduced tendency toward algal colonization comprising a) as base, a thermoplastic substrate; and b) on the base, a photocatalytically active coating comprising - a water-spreading layer which involves either a sol-adhesion-promoter layer, layer b1+2), having a layer thickness of 1 μm to 50 μm, comprising an adhesion promoter and a colloid sol, or a colloid-sol layer b2) having a layer thickness of 0.05 μm to 2 μm arranged on an adhesion-promoter layer b1) applied on the substrate a), and - a photocatalytically active layer b3) arranged on the water-spreading layer b1+2) or b2), where b3) contains titanium dioxde and is obtainable through application and drying of a mixture comprising titanium dioxide and silicon dioxide and/or a water-insoluble metal oxide or an anionically modified silicon dioxide or metal oxide, characterized in that the water-spreading layer b2) is composed to an extent of more than 90% by weight of silicon dioxide and/or a metal oxide, the mixture has b31) from 2 to 15% of titanium dioxide and b32) from 85 to 98% of silicon dioxide and/or of a metal oxide which is not soluble in water or of an anionically modified silicon dioxide or metal oxide; based on the solids content of the mixture in percent by weight; and the particulate titanium dioxide has an average primary-particle size smaller than 10 nm, where to determine the average particle size, titanium dioxide particles are scanned by an electron microscope and the average primary-particle size of the titanium dioxide is determined as numeric average from measurements of the length of 100 different randomly selected primary particles. a) as base, a thermoplastic substrate; and b) on the base, a photocatalytically active coating comprising - a water-spreading layer which involves either a sol-adhesion-promoter layer, layer b1+2), having a layer thickness of 1 μm to 50 μm, comprising an adhesion promoter and a colloid sol, or a colloid-sol layer b2) having a layer thickness of 0.05 μm to 2 μm arranged on an adhesion-promoter layer b1) applied on the substrate a), and - a photocatalytically active layer b3) arranged on the water-spreading layer b1+2) or b2), where b3) contains titanium dioxde and is obtainable through application and drying of a mixture comprising titanium dioxide and silicon dioxide and/or a water-insoluble metal oxide or an anionically modified silicon dioxide or metal oxide, characterized in that the water-spreading layer b2) is composed to an extent of more than 90% by weight of silicon dioxide and/or a metal oxide, the mixture has b31) from 2 to 15% of titanium dioxide and b32) from 85 to 98% of silicon dioxide and/or of a metal oxide which is not soluble in water or of an anionically modified silicon dioxide or metal oxide; based on the solids content of the mixture in percent by weight; and the particulate titanium dioxide has an average primary-particle size smaller than 10 nm, where to determine the average particle size, titanium dioxide particles are scanned by an electron microscope and the average primary-particle size of the titanium dioxide is determined as numeric average from measurements of the length of 100 different randomly selected primary particles. - a water-spreading layer which involves either a sol-adhesion-promoter layer, layer b1+2), having a layer thickness of 1 μm to 50 μm, comprising an adhesion promoter and a colloid sol, or a colloid-sol layer b2) having a layer thickness of 0.05 μm to 2 μm arranged on an adhesion-promoter layer b1) applied on the substrate a), and either a sol-adhesion-promoter layer, layer b1+2), having a layer thickness of 1 μm to 50 μm, comprising an adhesion promoter and a colloid sol, or a colloid-sol layer b2) having a layer thickness of 0.05 μm to 2 μm arranged on an adhesion-promoter layer b1) applied on the substrate a), - a photocatalytically active layer b3) arranged on the water-spreading layer b1+2) or b2), where b3) contains titanium dioxde and is obtainable through application and drying of a mixture comprising titanium dioxide and silicon dioxide and/or a water-insoluble metal oxide or an anionically modified silicon dioxide or metal oxide, characterized in that the water-spreading layer b2) is composed to an extent of more than 90% by weight of silicon dioxide and/or a metal oxide, the mixture has b31) from 2 to 15% of titanium dioxide and b32) from 85 to 98% of silicon dioxide and/or of a metal oxide which is not soluble in water or of an anionically modified silicon dioxide or metal oxide; based on the solids content of the mixture in percent by weight; and the particulate titanium dioxide has an average primary-particle size smaller than 10 nm, where to determine the average particle size, titanium dioxide particles are scanned by an electron microscope and the average primary-particle size of the titanium dioxide is determined as numeric average from measurements of the length of 100 different randomly selected primary particles. b31) from 2 to 15% of titanium dioxide and b32) from 85 to 98% of silicon dioxide and/or of a metal oxide which is not soluble in water or of an anionically modified silicon dioxide or metal oxide;