1. Field of the Invention
The present invention relates to a method of forming a transparent film having an aligned atomic structure. More particularly, the present invention relates to a method of forming an aligned transparent film that is deposited and aligned in a single step.
2. Description of the Prior Art
The alignment of liquid crystal molecules on a surface is one of the critical steps in the manufacturing of a liquid crystal display. The industry-wide method for producing such alignment is through the mechanical rubbing of a polyimide surface. This method requires a physical contact between a roller or brush and the polyimide surface. The rubbing process realigns the surface of the polyimide, which then acts as an alignment template for the orientation of the liquid crystal molecules in the preferred direction.
This approach has several disadvantages. For example, because the rubbing method is a contact technique, debris can be generated during the rubbing process resulting in a low process yield. Moreover, additional cleaning steps are generally required to remove the debris. Also, as the roller or brush rubs the surface of the display, electrostatic charges can build up which may discharge through the thin film transistors (TFT) resulting in a lowering of the process yield. Additionally, the rubbing process requires a relatively soft layer in order to modify the surface in a desired orientation. Thus, choice of materials that are suitable for use in the rubbing process is limited.
U.S. Pat. No. 5,770,826 to Chaudhari et al. describes the use of low energy ion beams to align surfaces for liquid crystal applications. In these cases, the alignment was performed on an alignment layer deposited by a distinct and separate process. While a wide variety of surfaces were found to be suitable for alignment by an ion beam technique, the reference does not teach the deposition of the alignment layer and the alignment of the layer in a single step.
One of the main driving forces in the liquid crystal industry is the constant reduction in the cost of production. In both the alignment of a polyimide layer via mechanical rubbing/brushing or the alignment of layers using ion beams as described in the previously incorporated U.S. Pat. No. 5,770,826, the alignment layer must be applied prior to the alignment procedure. Consequently, the deposition of an alignment layer and subsequent alignment of the alignment layer in separate process steps introduces additional costs into the manufacturing process. The applicants have found that deposition and alignment of such a layer can be accomplished in a single step, which significantly reduces the manufacturing cost.
The present invention includes a method of forming a film on a substrate, wherein said film exhibits an aligned atomic structure. The method comprises the step of bombarding said substrate with at least one ion beam from at least one ion beam source at a designated incident angle to simultaneously (a) deposit said film onto said substrate, and (b) arrange said atomic structure of said film in at least one predetermined aligned direction.
The method according to the present invention is a dry deposition and alignment technique, which reduces the need for pre- and post-wet processing. The present method is also a non-contact deposition and alignment technique, which reduces any potential contamination of the surface by extraneous debris, such as those commonly encountered in the contact rubbing techniques of the prior art.
Accordingly, the present invention provides a simple and cost effective method of forming easily processed aligned films on which liquid crystals can be aligned for use in wide viewing angle liquid-crystal displays.