This invention relates to a process for the production of a relatively thick composite of fibrous layers on a base product material which may serve a decorative or structural function, such as artificial wood or similar organic or inorganic dielectric materials, or which may have a plush surface and may be flexible like artificial fur or plush carpet.
Wood is a natural composite material comprising fibers in a lignin matrix. The structural and aesthetic qualities of wood are profoundly affected by the arrangement and orientation of the fibers within the matrix, which is called xe2x80x9cgrainxe2x80x9d or xe2x80x9cwoodgrainxe2x80x9d. For a very long time markets have highly valued certain woodgrain patterns. As a consequence, the forest products industry is producing large volumes of wood that has been culled out from the production process for products with high structural and aesthetic values. As the supply of mature trees diminishes, the selection of desired grain patterns becomes restricted and expensive.
Much of this scrap wood is separated into its component fibers and lignin by a variety of methods known in the present art. From these components, wood fiber reinforced composite materials have been made by several methods which have good structural properties due to an absence of knotholes and other defects. The arrangement of fibers in these prior-art composites may be either substantially random for products made by extrusion of a mixture of the fiber and matrix material and intended to have isotropic structural properties, or, substantially regular in spacing and orientation for fiberboard products.
To improve aesthetic values, decorative woodgrain patterns are applied to wood fiber reinforced composites, and to a wide variety of other substrates, by known methods including printing and painting. These methods produce an essentially two dimensional product that has the undesired property that the pattern can be obliterated by shallow abrasion. Also, if the product were to be machined after the pattern has been applied, the substrate would be revealed and the decorative pattern would be lost.
For products that have a plush surface, such as fur, there are other problems. Although fur can have excellent thermal insulation and aesthetic values, fur clothing has lost favor in the marketplace due to the killing of the animals that provide it. There is also great expense involved in the sewing together of many pelts of small animals, such as mink, to produce a garment. Thus, there is a market for artificial fur that might attain the valued qualities of the natural product yet be made in large pieces without killing the animals that provide the hair.
The present invention comprises a process that uses electrostatic forces among external electrodes, electrostatic charges placed on dielectric fibers or other, dielectric, rod-shaped components, and electrostatic latent images written either onto the intended product substrate itself or onto a transfer surface, or both, to assemble three dimensional composite structures of said fibers or rod-shaped components in a matrix of a second dielectric material. The fibers or other rod-shaped components may extend from the matrix to form a surface that is either plush or relatively smooth. The process need not employ a transfer surface but it is often convenient to use one when the product substrate is not flat but varies substantially in height and orientation. The transfer surface can be a photoconductor with an electrostatic latent image that is written with controlled light or it can be made of a dielectric material. The transfer surface can be either rigid and conforming to the intended product substrate or it can be a flexible film belt that is made to conform to the intended product substrate with suitable mechanical and/or fluidic apparatus such as rollers and air nozzles.