Method for coating a building panel and a building panel

A method for coating a building panel, comprising:

• applying a first coating fluid comprising an organic binder on a surface of the building panel to obtain an uppermost coating layer, wherein the uppermost coating layer protects the visual impression of the building panel,
• applying a barrier coating fluid comprising barrier components onto said uppermost coating layer, thereby forming a barrier layer, wherein the barrier layer protects the uppermost coating layer from photocatalytic activity of a photocatalytic layer,
• wherein the size of the barrier components is less than 400 nm, and
• applying photocatalytic particles to form the photocatalytic layer on the barrier layer, wherein the photocatalytic layer reduces a level of indoor volatile organic compounds by its photocatalytic activity,
• wherein the first coating fluid is a radiation curing coating fluid,
• wherein the organic binder comprises an acrylate or methacrylate monomer, or an acrylate or methacrylate oligomer,
• wherein the barrier components are applied to the uppermost coating layer before gelation of the uppermost coating layer or before complete gelation of the uppermost coating layer, and
• wherein an area of mixed barrier and photocatalytic particles is between the barrier layer and the photocatalytic layer, wherein the area is defined by a surface of the barrier layer and a surface of the photocatalytic layer, wherein both surfaces face each other.