Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02414380 2002-12-09
WINDOW FILM WTTH THERMOCHROMIC LAYER
FIELD OF THE INVENTION
This invention relates to window film for application to windows, in
particular automobile
windows.
BACKGROUND OF THE INVENTION
Decorative window film for automobiles is known and used to enhance the
appearance of the
vehicle, offer privacy, and shelter from strong sun rays. Such decorative
window film is commonly
made of a polyester material which may be dyed to provide the desired tint.
Alternatively, the
tinting may be provided in an adhesive layer for coupling the window film to
the glass surface and
the associated polyester material will be clear. Ultraviolet inhibitors may
also be included in the
adhesive material for absorbing ultraviolet light and thereby protecting the
occupants of the vehicle
from excessive heat from sun rays.
In order to add interest to such tinted window coverings, it is known to
incorporate a photochromic
material in the film which is sensitive to ultraviolet light and therefore
becomes darker when needed
and which tends to be clearer when the vehicle is not exposed to as much
ultraviolet light such as
on a cloudy day or in the nighttime. One disadvantage of such photochromic
materials is that their
sensitivity to ultraviolet light also limits their utility because the
material becomes damaged with
prolonged ultraviolet exposure.
An object of this invention is to provide an alternative window film structure
which has a changing
appearance but which does not suffer from the above described disadvantages.
SUMMARY OF THE INVENTION
In accordance with the invention, there is provided a window film consisting
of a multi-layer
synthetic plastic material. The window film has an inner adhesive layer which
is adapted to couple
the film to a window surface. Most preferably the adhesive layer will have an
ultraviolet inhibitor
incorporated therein. Optionally, the adhesive layer will have a release sheet
coupled to it so that
the adhesive will be protected during transportation of the window film and
storage before
application to a window. The next layer will be a transparent layer such as
polyester followed by
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CA 02414380 2002-12-09
' . a second adhesive layer which preferably also has an ultraviolet
inhibitor. A second transparent
layer, also preferably polyester, is coupled to the second adhesive layer and
a thermochromic layer
is formed adjacent the second transparent layer, the thermochromic layer being
adapted to change
colour with ambient temperatures. Finally, the window film has a protective
outer layer which is
scratch resistant to protect the film.
Optionally, a single layer of adhesive and transparent polyester are provided.
BRIEF DESCRIPTION OF THE DRAWINGS
In order that the invention can be more clearly understood, two embodiments
are described with
reference to Figs. 1 and 2 of the accompanying drawings in which:
Fig. 1 is a schematic cross-sectional view of a mufti-layer synthetic plastic
film made in accordance
with the invention and applied to a window; and
Fig. 2 is a second embodiment of a mufti-layer synthetic plastic film applied
to a window.
DESCRIPTION OF PREFERRED EMBODIMENTS WITH REFERENCE TO DRAWINGS
A first embodiment of a window film made in accordance with the invention is
generally indicated
by reference numeral 20 in Fig. 1. The window film 20 is applied to the
interior surface of a
window pane 22. The inner layer of the window film 20 is designated by
reference numeral 24 and
consists of an inner adhesive layer for coupling the film to the surface of
the window pane 22. 'The
adhesive will preferably have an ultraviolet inhibitor incorporated therein
and could optionally have
a dye for tinting the window film 20. The next layer 2fi is a transparent
polyester material and this
is followed by a section adhesive layer 28 and a second transparent polyester
layer 30. The second
adhesive layer 28 like the adhesive layer 24 will preferably have an
ultraviolet inhibitor and could
optionally have a dye incorporated therein. Associated with the second
transparent layer 30, there
is provided a thermochromic material 32. The thermochromic material is adapted
to change colour
in accordance with ambient temperature and therefore will change its
appearance in accordance with
the temperature inside the vehicle and this will in part be determined by the
exposure of the window
film to ultraviolet light and infrared radiation.
If desired, the thermochromic layer 32 may be masked in certain areas so that
the appearance of the
film may vary. It will be evident that an image could be formed which would
appear when the
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vehicle is warm and disappear when the vehicle is cold. Finally, an outer
protective layer 34 is
provided which is preferably scratch resistant in order to shield the
thermochromic material from
damage.
It will be understood that the basic structure described with reference to
Fig. 1 can vary as will be
appreciated by those skilled in the art. A second embodiment of the window
film made in
accordance with the invention is generally indicated in Fig. 2 by reference
numeral 40. The
remaining components of the window film which are identical to the components
of Fig. 1 are
identified by like numerals. It will be seen that in the window film 40, there
is a single inner
adhesive layer 24 and a single transparent layer 26 which is coupled to the
thermochromic material
32. It will be appreciated in both embodiments that exposure to ultraviolet
radiation indicated
generally by arrows 42 is minimized by incorporating an ultraviolet inhibitor
into the adhesive
layers 24, 28. In this way, the transparent polyester layers 26, 30 and the
thermochromic material
indicated by layer 32 are protected from degradation resulting from exposure
to ultraviolet radiation.
It will be appreciated that many more variations to the structure may be made
within the scope of
the appended claims. For example, as is common in the art, the inner adhesive
layer may be
protected during transportation and storage with a release sheet (not shown)
which is separated from
the film before application to a window pane 22.
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