Process and panel for providing fixed glazing for an automotive vehicle

A process and panel for fixed automotive glazing, the panel molded from polycarbonate, a UV radiation blocking hard coat deposited thereon, and a pigmented primer applied in a defined band extending about the perimeter. The hard coat protects the pigmented primer coating so that two separate coatings are not required.

BACKGROUND OF THE INVENTION
 This invention concerns automotive glazing and more particularly glazing
 panels of a molded synthetic resin, such as polycarbonate. Conventional
 glass panels have been used for automotive glazing applications for many
 years.
 In one type of automotive window construction currently in common use,
 fixed glazing panels have been installed using an adhesive bonding of the
 perimeter of the panels to a body structure defining a window opening.
 This construction requires masking of the perimeter to conceal the bonded
 joint for aesthetic purposes, and to prevent degrading of the adhesive by
 exposure to the ultraviolet radiation present in sunlight. An effective
 masking which is in widespread use is a black-out bond applied about the
 perimeter of the inside surface of the glazing panel. This black-out band
 must be accurately applied in order to be aligned with the bonded glazing
 joint to properly mask the same. In the case of glass glazing, a baked-on
 finish has typically been utilized to produce a black border, since the
 glass panel is usually formed after being heated in an oven, and the
 heating required for forming can be advantageously used to achieve curing
 of the black-out ink.
 The use of an adhesive joint also requires priming of the glazing surface
 to achieve proper bonding of the adhesive to the surface of the glazing
 panel.
 Thus, multiple coatings are required to be applied about the perimeter of
 the glazing panel in order to practice this type of automotive window
 construction.
 It has long been proposed to mold automotive glazing panels from a
 synthetic resin, such as polycarbonate, in order to reduce vehicle weight,
 improve occupant protection, and to allow greater body styling
 flexibility, due to the ease of producing markedly curved panels.
 Such molded panels are contemplated as being especially adapted for use in
 fixed glazing installations where a black-out border is necessary.
 It is the object of the present invention to provide a simplified process
 and panel for creating a masked bonded joint for fixed automotive glazing
 panels of molded synthetic resin of the type described above.
 SUMMARY OF THE INVENTION
 The above recited object and others which will be understood upon a reading
 of the following specification and claims are achieved by the step of
 applying an adhesive primer coating to an inside perimeter surface of a
 polycarbonate panel, the primer also containing a black-out pigmentation.
 The pigmented primer is applied in a band extending about the panel
 perimeter in a defined pattern so as to produce an aesthetically suitable
 masking border on the inside surface of the panel.
 The molded polycarbonate panel is hard coated prior to applying the
 pigmented primer to the panel inside surface to improve abrasion
 resistance. The hard coat also has a UV blocking function which serves to
 protect the pigmented primer coating from degradation by exposure to the
 UV radiation present in sunlight.

DETAILED DESCRIPTION
 In the following detailed description, certain specific terminology will be
 employed for the sake of clarity and a particular embodiment described in
 accordance with the requirements of 35 USC 112, but it is to be understood
 that the same is not intended to be limiting and should not be so
 construed inasmuch as the invention is capable of taking many forms and
 variations within the scope of the appended claims.
 Referring to FIG. 1, the present invention concerns a fixed glazing panel
 10, here shown as the rear side light of an automotive vehicle 12,
 disposed to the rear of a side door 20 and the "B" pillar 14 of the body
 structure.
 The panel 10 is fixedly mounted in a body structure opening 14 in
 conventional fashion.
 A black-out border 18 is provided, extending about the entire perimeter of
 the inner surface of the panel 10 in the well known manner.
 This black-out border comprises an opaque band concealing the Joint between
 the body structure and the glazing panel 10, to provide an attractive
 appearance at a relatively low cost.
 In a prior art glass panel installation, shown in simplified form in FIG.
 2A omitting moldings and details of the body structure, the border 18A is
 a baked on finish, cured when the panel 10A is heated for shaping of the
 panel 10A. The border 18A performs an additional function in this
 environment, i.e., it acts to block UV radiation, protecting a primer
 coating 22 and adhesive bead (or elastomeric seal) 24A from degradation
 which would otherwise occur upon exposure to the UV radiation in sunlight.
 FIG. 2B shows a glazing panel 10B according to the present invention,
 molded from a synthetic resin, here contemplated as being an injection
 molded polycarbonate.
 The entire glazing panel 10B is treated to deposit a hard coat 26 over the
 entire surface of the panel 10B. This hard coating is of a known type and
 may comprise several coating layers, including one or more dip coatings.
 Such dip coatings improve the abrasion resistance of the molded
 polycarbonate to some extent, but the scratch resistance of the dip coated
 panel 10B is still insufficient for automotive use. Polycarbonate panels
 are not themselves sufficiently resistant to weathering to be suitable for
 automotive glazing, since that material is subject to yellowing when
 exposed to sunlight even for relatively short periods. This characteristic
 requires that the dip coatings also provide UV blocking to improve
 weatherability of the polycarbonate panel. See U.S. Pat. No. 4,842,941 for
 a description of suitable dip coatings.
 To provide adequate abrasion resistance for automotive application, an
 additional process has heretofore been developed involving a plasma
 enhanced chemical vapor deposition (PECVD), often simply referred to as a
 plasma coating. In the PECVD process, reactants such as organosilicone are
 activated by a plasma to form a coating on panels disposed in a vacuum
 chamber into which the activated reactants are introduced.
 Such plasma coatings are applied over the previously applied dip coatings
 described above.
 Reference is made to U.S. Pat. Nos. 5,298.587; 5,320,875; 5,433,786;
 5,494,712; 5,718,967 and 5,900,284, which set forth further details of
 plasma coating) processes and apparatus which are hereby incorporated by
 reference.
 An improved process and apparatus for production of plasma coated panels is
 described in copending application U.S. Ser. No. 09621,203, filed on Jul.
 21, 2000.
 The hard coat 26 also functions to block UV to protect the panel 10B, which
 together with the dip coatings will also protect the adhesive bead or seal
 24B from the effects of sunlight.
 The present invention takes advantage of the UV blocking coatings in
 providing only a single coating 28 on the inner surface extending in a
 band about the perimeter of the panel 10B, which coating functions both as
 a primer for the adhesive and as a black-out border. The coating 28 is
 itself protected from UV radiation by the hard coat 26.
 A suitable black-out primer for this use is BETASEAL (trademark) which,
 while sold as a glass primer, will create a secure bond between the hard
 coat 26, and polyurethane adhesives, seals, etc.
 BETASEAL (trademark) is available from Essex Specialty Products, Inc.,
 under product code 15969, that company having a place of business at 1250
 Harmon Road, Auburn Hills, Mich. 48326.
 The BETASEAL material is a liquid including toluene (5-15%), methyl ethyl
 ketone (40-50%), n-butyl acetate (&lt;10%) having a suspended pigment
 comprised of carbon black (5-15% by weight), having sufficiently low
 viscosity such as to be able to be sprayed on to the panel 10B for coating
 the panel perimeter as described.
 The pigmented primer coating 28 must be applied in a band accurately
 located with respect to the panel edge so as to ensure that the coating 28
 thereby suitably masks the bonded joint. In addition, a neat edge should
 be maintained as the black-out border is prominently visible and thus
 comprises an aesthetic feature. A frosting treatment can be used on the
 opposite panel surface to lessen the need for a neat edge.
 Suitable application techniques for the combined primer and black-out
 material include first masking the regions of the panel adjacent the
 perimeter of the panel, as by use of a well known hinged masking screen,
 and then spray coating the unmasked border with the material to form a
 black band extending around the panel inside surface.
 Other suitable techniques could be utilized adapted to the particular flow
 characteristics of the primer-blackout material, such as ink jet printing,
 screen printing, flow coating, etc.
 The resulting band border has been found to successfully perform the
 functions as described.
 Handling of the panels 10B during these steps is facilitated by molding in
 one or more tabs, as described in detail in copending U.S. patent
 application Ser. No. 09/227,888, filed on Mar. 29, 1999, now U.S. Pat. No.
 6,183,678, issued on Feb. 6, 2001. The tab or tabs are trimmed off after
 the panel process is completed, as described in that application.
 The black-out border can take various forms in addition to a simple band,
 including a fade-out, or combined with additional treatments such frosting
 as described above, as long as it produces a defined aesthetic feature
 which effectively masks the adhesive joint.