Stock material or miscellaneous articles – Structurally defined web or sheet – Including variation in thickness
Patent
1994-03-22
1996-03-19
Watkins, III, William P.
Stock material or miscellaneous articles
Structurally defined web or sheet
Including variation in thickness
428167, 428161, 428172, 428157, 428437, 428136, 428195, 428525, 428192, 428 34, 428 38, 428203, 428168, 26417318, 2641771, 264245, 264345, 427261, 427284, 427286, 4273722, 427287, 4251311, 4251335, 425466, B29C 4704
Patent
active
055002749
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to the preparation of composite coatings which provide a gradient coloration in the cross-web direction. More particularly, a process for preparing a composite coating having a variable thickness in the cross-web direction is provided in which premetered coatings are simultaneously applied to a carrier film, one layer of the coating being of a uniform thickness and another layer being colored and of variable thickness in the cross-web direction when measured either from the center or an edge of the web. Coloration of the layer of variable thickness provides a gradient in the optical density of the composite which makes it suitable for use as an interlayer for providing a vignette stripe in an automobile windshield.
A premetered coating apparatus consisting of dimensionally stable and chemically inert pieces forming a coating die may be modified in accordance with the invention for use in preparing the novel coatings. A flow channel for the coating fluid is formed by openings carved into the die pieces, by openings formed when the die pieces are assembled, or both. Typical practice is to configure the interior geometry of the die so that coating fluid is extruded in a sheet of uniform thickness.
BRIEF DESCRIPTION OF PRIOR ART
It is known to provide a color image having a continuous gradation in the cross-web direction by coating techniques such as gravure printing. Products having such a variation find utility in packaging applications as well as in safety glass for automobiles and in architectural applications.
In some applications, the gradated color stripe is formed by coextruding a molten colored layer along with a clear thermoplastic sheeting. U.S. Pat. No. 4,316,868 describes one such process. In these processes, the colored stripe is embedded in and forms an integral part of the thermoplastic sheeting.
Both of the just-mentioned processes have inherent limitations. For example, in applications such as gravure printing, the overall quality of the gradated image is dependent on the quality of the engraved gravure cylinder. Applications which utilize pigment based coating solutions place additional limitations on gravure printing due to accumulation of pigment particles under the doctor blade which is used in the gravure process. This causes streaks in the coated product which is unacceptable especially in applications requiring high optical quality such as in automobile windshields. Further, limited life of the cylinder due to scratching and wearing of the cylinder surface by the doctor blade requires re-engraving of the cylinders on a periodic basis, which adds additional expense. While colored gradations for thermoplastic sheeting for safety laminate applications by a coextrusion process overcomes the quality limitations inherent in gravure printing, flexibility with respect to colors and widths of the gradations is limited. Color and width changes require extensive cleaning of the die and modifications to the die assembly which are costly in terms of down time and labor requirements involved in the operations.
Blade, or knife coating, to provide a tapered cross-web profile is disclosed in Australian published application AU-A-56153/90. In a blade coating process, the wet coated thickness of a layer depends on the physical properties of the coating solution such as viscosity. Precise control of the coating thickness is especially difficult. Precise control is said to be achieved in the Australian application by using a complex pressure feed-back system. Optical density is said to be controlled by mixing two solutions in different proportions. This can lead to nonuniformity of a gradient pattern.
Premetered coating processes such as slot coating have been used to produce uniform coating thickness in the cross-web direction. U.S. Pat. No. 4,411,614 describes one such process wherein inserts in flow distribution channels are used to improve the flow uniformity of coating solutions in the cross-web direction. Such proces
REFERENCES:
patent: 3354025 (1967-11-01), Aykanian et al.
patent: 3405425 (1968-10-01), Buckley et al.
patent: 3471898 (1969-10-01), Krystof et al.
patent: 3540964 (1970-11-01), Nauta
patent: 3799718 (1974-03-01), Kiyono et al.
patent: 4177315 (1979-12-01), Ubersax
patent: 4302263 (1981-11-01), Postupack
patent: 4316868 (1982-02-01), Esposito et al.
patent: 4411614 (1983-10-01), Feathers
patent: 4469743 (1984-09-01), Hiss
patent: 4476075 (1984-10-01), Brinkmann et al.
patent: 4489154 (1984-12-01), Taylor, Jr.
patent: 4562023 (1985-12-01), Pabst et al.
patent: 4808357 (1989-02-01), Bourcier et al.
patent: 5024895 (1991-06-01), Kavanagh et al.
patent: 5087502 (1992-02-01), Esposito et al.
patent: 5130174 (1992-07-01), Esposito
Francis Debra C.
Vallabhaneni Siva V.
Wong Bert C.
Carroll Rodney B.
E. I. Du Pont de Nemours and Company
Watkins III William P.
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