Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Including a second component containing structurally defined...
Reexamination Certificate
2000-08-07
2002-04-23
Nakarani, D. S. (Department: 1773)
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Including a second component containing structurally defined...
C427S407100, C427S489000, C428S336000, C428S447000, C428S448000, C428S451000
Reexamination Certificate
active
06376064
ABSTRACT:
BACKGROUND
1. Field of the Invention
The present invention relates generally to layered articles, and more particularly to a layered article having improved resistance to microcracking.
2. Description of the Related Art
Plastics and other polymers are commercially available materials having physical and chemical properties which are useful in a wide variety of applications. For example, polycarbonates are a class of polymers which, because of their excellent breakage resistance, have replaced glass in many products, such as automobile head-lamps, safety shields, eyewear, and windows. However, many polycarbonates also have properties which may be disadvantageous in some applications, such as low abrasion resistance and susceptibility to degradation from exposure to ultraviolet (UV) light. Thus, polycarbonates are not commonly used in applications such as automotive and other windows which are exposed to ultraviolet light or an abrasive environment.
To lessen the problems of low abrasion resistance and UV degradation, known methods of treating polycarbonates involve the application of one or more layers of abrasion resistant material and UV absorbing material to the polycarbonate substrate. For example, U.S. Pat. No. 4,842,941 describes the application of a silicone layer to a polycarbonate substrate. The silicone layer comprises a dispersion of colloidal silica in a lower aliphatic alcohol-water solution of the partial condensate of a silanol. The silicone layer is applied in a wet process, for example by dipping, the polycarbonate in a silicone bath or by spraying silicone on the polycarbonate. The silicone layer provides abrasion resistance to the polycarbonate and may also include a constituent which absorbs UV radiation.
The silicone layer described in U.S. Pat. No. 4,842,941, however, may develop microcracks when exposed to prolonged weathering. The long term stability and weatherability of the silicone layer, as measured by adhesion and ductility tests, can also be improved.
Another method of providing abrasion resistance involves the application of a plasma polymerized organosilicon coating by plasma enhanced chemical vapor deposition (PECVD). U.S. Pat. No. 5,494,712, for example, describes a method of applying an abrasion resistant layer comprising a plasma polymerized organosilicon material by PECVD. The coatings are described as being able to withstand short term accelerated weathering, such as two hours in boiling water. However, these coatings typically do not adhere to polycarbonate after enhanced weathering such as a few hundred hours in a QUV or Xenon Arc weatherometer. Thus, there exists a need for coatings with improved weatherability.
It would be desirable, therefore, to have a coating with improved abrasion resistance, adhesion, and/or resistance to microcracking.
SUMMARY
The invention, according to one embodiment, relates to a multilayer article which includes a substrate, a first layer comprising a partial condensate of a diorganodiorganooxysilane having the formula R
2
Si(OR′)
2
or an organotriorganooxysilane having the formula RSi(OR′)
3
, or both, where R is independently selected from the group consisting of alkyl groups containing about 1-3 carbon atoms, aromatic groups containing about 6-13 carbon atoms, the vinyl radical, the 3,3,3-trifluoropropyl radical, the gamma-glycidoxypropyl radical and the gamma-methacryloxypropyl radical, and R′ is independently selected from the group consisting of alkyl groups containing about 1-8 carbon atoms, aromatic groups containing about 6-20 carbon atoms, and hydrogen; and a second layer deposited on the first layer, the second layer comprising an organosilicon material which has been polymerized and oxidized in a plasma, the second layer containing silicon, oxygen, carbon, and hydrogen.
The invention also relates to a method of forming a multilayer article comprising the steps of applying a first layer to a substrate, the first layer comprising a partial condensate of a diorganodiorganooxysilane having the formula R
2
Si(OR′)
2
or an organotriorganooxysilane having the formula RSi(OR′)
3
, or both, where R is independently selected from the group consisting of alkyl groups containing about 1-3 carbon atoms, aromatic groups containing about 6-13 carbon atoms, the vinyl radical, the 3,3,3-trifluoropropyl radical, the gamma-glycidoxypropyl radical and the gamma-methacryloxypropyl radical, and R′ is independently selected from the group consisting of alkyl groups containing about 1-8 carbon atoms, aromatic groups containing about 6-20 carbon atoms, and hydrogen; and applying a second layer on the first layer by plasma polymerizing an organosilicon material in excess oxygen.
The multilayer article, according to exemplary embodiments of the invention, provides improved abrasion resistance to a plastic substrate and increased resistance to microcracking. The embodiments described in the examples below demonstrate that the combination of the first layer and the second layer is surprisingly resistant to microcracking and has good adhesion after exposure to natural or simulated weathering.
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Standard Test Methods for Measuring Adhesion by Tape Test, ASTM D 3359-92a (Jul. 1992).
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Gasworth Steven Marc
Katsamberis Dimitris
Olson Daniel Robert
General Electric Company
Johnson Noreen C.
Nakarani D. S.
Santandrea Robert P.
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