The profile of the interfacial plane of a diblock copolymer layer in its lamellar melt phase when it is brought into contact with a hard, smooth substrate is calculated. The chains are in the strong-stretching limit. Far from the substrate, the planes are perpendicular to the substrate, and they become distorted near it by a small wetting preference for one of the components of the copolymer. The profile of the distortion is calculated in an Alexander model by making an analogy to the steady flow of an incompressible fluid. The contact angle between the two components of the copolymer and the substrate is the same as it would be if the blocks were not joined to make diblock copolymers. The approach to this contact angle is characterized by a singularity which is calculated. For any molecular weight and elasticity asymmetry between the components of the copolymer, the curvature of the interface changes sign contrary to the case of the interface between two simple liquids. For most values of asymmetry, the interface is an exponentially damped oscillation.