A liquid crystal display device produces an image by applying an electric field to a liquid crystal layer between an array substrate and a package substrate (e.g. a color filter substrate). The electric field changes an alignment direction of the liquid crystal molecules in a liquid crystal layer. Light transmittance of the liquid crystal layer is adjusted when the alignment direction of the liquid crystal molecules changes. The liquid crystal molecules in a liquid crystal display device should be pre-aligned in a direction to normally operate the liquid crystal between two display substrates. Typically, a rubbing roller is used to align the liquid crystal molecules in a liquid crystal display device, i.e., by rubbing an alignment layer of a liquid crystal display substrate.
A conventional rubbing roller includes a rubbing cloth wrapped around a rotary roller. The rubbing cloth includes fibers on the surface of the rubbing cloth. When the rubbing roller is used to rub the alignment layer of the display substrate, fibers of the rubbing cloth are in contact with the alignment layer, which includes alignment polymers having a plurality of side chains. Fibers of the rubbing cloth form microgrooves in the alignment layer, aligning side chains of the alignment polymers in a direction along the microgroove. The liquid crystal molecules are arranged along the side chains of the alignment layer.