U.S. patent application number 15/509555 was filed with the patent office on 2017-10-12 for trim for motor vehicle glazing systems.
The applicant listed for this patent is Covestro Deutschland AG. Invention is credited to ROLAND BRAMBRINK, Peter CAPELLEN, Florian DORIN, Alexander MEYER, Manfred NAWROTH.
Application Number | 20170291400 15/509555 |
Document ID | / |
Family ID | 51540991 |
Filed Date | 2017-10-12 |
United States Patent
Application |
20170291400 |
Kind Code |
A1 |
BRAMBRINK; ROLAND ; et
al. |
October 12, 2017 |
TRIM FOR MOTOR VEHICLE GLAZING SYSTEMS
Abstract
The invention relates to trims for motor vehicle glazing
systems, comprising a base layer and a coating and having
glass-like optical properties at least in some subsections,
composites consisting of such trims for motor vehicle glazing
systems, and car body parts, as well as preferred embodiments which
comprise suitable combinations of materials. Said trims comprising,
at least towards the front side thereof, an edge rounding having a
variable radius which allows a more uniform layer thickness for the
coating.
Inventors: |
BRAMBRINK; ROLAND;
(Leichlingen, DE) ; DORIN; Florian; (Koln, DE)
; MEYER; Alexander; (Dusseldorf, DE) ; CAPELLEN;
Peter; (Krefeld, DE) ; NAWROTH; Manfred;
(Wipperfurth, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Covestro Deutschland AG |
Leverkusen |
|
DE |
|
|
Family ID: |
51540991 |
Appl. No.: |
15/509555 |
Filed: |
August 28, 2015 |
PCT Filed: |
August 28, 2015 |
PCT NO: |
PCT/EP2015/069718 |
371 Date: |
March 8, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B32B 2605/00 20130101;
B32B 27/36 20130101; B32B 27/34 20130101; B32B 27/28 20130101; B32B
2270/00 20130101; B32B 27/18 20130101; B32B 2605/006 20130101; B32B
2255/10 20130101; B32B 1/00 20130101; B32B 27/365 20130101; B32B
2605/08 20130101; B32B 2307/712 20130101; B32B 27/08 20130101; B32B
27/302 20130101; B32B 27/32 20130101; B32B 27/325 20130101; B32B
2255/26 20130101; B32B 2307/40 20130101; B32B 2307/584 20130101;
B32B 27/283 20130101; B32B 27/308 20130101; B32B 2250/24 20130101;
B32B 3/30 20130101 |
International
Class: |
B32B 27/08 20060101
B32B027/08; B32B 3/30 20060101 B32B003/30; B32B 27/34 20060101
B32B027/34; B32B 27/36 20060101 B32B027/36; B32B 27/30 20060101
B32B027/30; B32B 27/32 20060101 B32B027/32 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 11, 2014 |
EP |
14184464.7 |
Claims
1.-15. (canceled)
16. A bezel for motor vehicle glazing systems, comprising a base
layer based on a thermoplastic, with a front side and a reverse
side, and also sides connecting the front side and the reverse
side, wherein the bezel has a coating on the front side, wherein
the edges between the sides connecting the front side and the
reverse side of the base layer and the front side of the base layer
have been rounded, wherein the rounding has a radius that is
variable across the rounding and wherein the bezel has a coating in
the rounded edge region of the front side.
17. The bezel as claimed in claim 16, wherein, in relation to the
reverse side and the front side of the bezel, the bezel is
U-shaped, O-shaped, double-O-shaped, T-shaped or I-shaped.
18. The bezel as claimed in claim 16, wherein the edges between the
sides connecting the front side and the reverse side of the base
layer and the reverse side of the base layer have been rounded.
19. The bezel as claimed in claim 18, wherein the bezel has a
coating on the reverse side.
20. The bezel as claimed in claim 16, wherein at least the rounding
of the edges between the sides connecting the front side and the
reverse side of the base layer and the front side of the base layer
has the shape of, or approximately the shape of, a Bezier
curve.
21. The bezel as claimed in claim 20, wherein the Bezier curve is
quadratic or cubic.
22. The bezel as claimed in claim 16, wherein the bezel is
U-shaped, O-shaped, double-O-shaped or T-shaped, where at least one
internal angle R1 situated between two legs of the bezel has been
rounded, where the internal angle R1 describes, precisely or
approximately, a quadrant.
23. The bezel as claimed in claim 22, wherein the radius of the
quadrant is at least 10 mm.
24. The bezel as claimed in claim 16, wherein the width b of the
region between the outermost point P at the rounded edge of the
bezel and the point E at the transition between the rounded region
and a surface without curvature is at least 2.5 mm.
25. The bezel as claimed in claim 16, wherein the wall thickness of
the bezel is from 1.5 mm to 5 mm.
26. The bezel as claimed in claim 16, wherein the bezel comprises a
plurality of layers of which one is a base layer comprising
polycarbonate, optionally carbon black, and a mold-release agent
based on a fatty acid ester, and where there is, on at least one
side of the base layer, a polysiloxane-based scratch-resistant
coating comprising at least one UV absorber.
27. The bezel as claimed in claim 26, wherein carbon black present
comprises nanoscale carbon black with average primary particle size
less than 100 nm, determined by scanning electron microscopy.
28. The bezel as claimed in claim 16, wherein the bezel has, on the
reverse side, a rib which, in relation to the cross section of the
bezel, is in the region of the edge rounding between the sides
connecting the front side and the reverse side of the base layer
and the front side of the base layer.
29. A compound-structure system comprising bodywork of a motor
vehicle and comprising a bezel as claimed in claim 16.
30. A process for the production of a bezel as claimed in claim 16,
comprising the following steps: closure of the injection mold,
injection of a first polymer composition, preferably by way of
injection-compression molding or cascade injection molding, then
cooling to a maximal component temperature lower than the glass
transition temperature of the first polymer composition, optionally
moving of the cavity into the next position or use of a mold with a
larger cavity for purposes of injection of a second polymer
composition, in such a way that on closure of the mold in this
position an intervening space is produced between the first
hardened polymer composition and the mold wall, optional injection
of the second polymer composition, then cooling to a maximal
component temperature lower than the glass transition temperature
of the second polymer composition, coating of the bezel.
Description
[0001] The invention relates to a bezel for motor vehicle glazing
systems, comprising a base layer, with a front side and a reverse
side, and also sides connecting the front side and the reverse
side. The invention further relates to a compound-structure system
comprising bodywork of a vehicle and comprising a bezel.
[0002] The present invention accordingly relates to bezels with, at
least in some regions, glass-like optical properties for motor
vehicle glazing systems, and also to compound structures made of
bezels for motor vehicle glazing systems and bodywork parts.
Combinations of materials suitable for production of these are
moreover described, as also is a process for the production of the
compound structures.
[0003] Bezels for motor vehicle systems are known. In order to
effect a transition between glazing systems and surrounding
bodywork parts, bezels are often used in automobile construction.
Not only do these bezels have to comply with the general
requirements for exterior components in the automobile: within this
context they also have to comply with ambitious detailed
requirements. The visual appearance therefore has to at least match
the good properties of glass, and indeed ideally is intended to
exceed these. It must furthermore be ensured that these properties,
examples being color depth, perceived blackness and perceived
gloss, color and surface quality remain constant, or undergo only
little change over long periods. High resistance of the entire
structure to weathering is therefore required. Mechanical
properties are moreover intended to be retained over a long period.
The thermoplastic parts should moreover have adequate scratch
resistance. A further intention is that the lacquer remains
unchanged in the composite with the polycarbonate. Because the
bezels often have a curved shape and edges and roundings, there are
differences in lacquer-run-off behavior, leading to different layer
thicknesses at different component positions. However, there should
be compliance with a defined layer-thickness range over the entire
component, including the edges. There should moreover be secure
attachment of the bezel to the bodywork, and the bezel should not
be damaged by thermal expansion or other mechanical influences. The
bezel is moreover optionally intended to incorporate functional
elements.
[0004] The selection of materials, and also the design of the
bezel, should moreover provide the greatest possible extent of
support to the function of the respective glazing system used. The
latter is in particular true for movable glazing structures in the
roof region of motor vehicles, examples being folding or sliding
roofs. It is therefore an object of the present invention to
provide bezels with, at least in some regions, glass-like visual
appearance for motor vehicle glazing systems, where the bezels are
preferably intended to have excellent optical properties, e.g. with
respect to perceived blackness, color depth and gloss, and also
high weathering resistance and adequate lacquer adhesion.
[0005] The bezels are usually multilayer systems comprising a base
layer and a coating which is usually produced from one or more
conventional lacquer layers. The coating is usually a UV-protection
coating and/or scratch-resistant coating. By way of example, the
coating comprises a base layer comprising UV absorber, and a
scratch-resistant coating applied on said layer. In order to
achieve ideal properties, the layer thicknesses of conventional
clearcoat lacquers have to be within a defined layer thickness
range. For ideal UV protection or for optimized processing time by
way of example the layer thickness must be above a minimum. It is
often also important that layer thicknesses are above a defined
minimum in order to permit successful adhesive bonding of the bezel
to the vehicle bodywork. However, excessive layer thicknesses of
the coating can lead very rapidly to embrittlement, with resultant
increased risk of cracking. The defects often have their source at
the lateral edges of the components. Layer thicknesses of the
coatings should therefore take into account the layer thicknesses
stated by the manufacturers. However, different lacquer thicknesses
conventionally occur across the surfaces of the bezels as a result
of the possible shapes of the components and/or of lacquering
processes such as dip-coating or flow-coating, therefore giving an
undesired lacquer thickness profile. In particular, lacquer
accumulations occur at the edges and corners of the bezels,
especially at areas directly adjacent to ribs, and this leads to
the abovementioned quality problems in practical situations.
[0006] It was therefore an object to provide bezels which avoid the
above disadvantages and which, even in the edge region, are
amenable to highly uniform coating.
[0007] The object addressed is achieved in the invention via a
bezel as claimed in claim 1. This bezel, which is intended for
motor vehicle glazing systems--but which can also be used
elsewhere--comprises a base layer based on a thermoplastic, with a
front side and a reverse side, and also sides connecting the front
side and the reverse side, characterized in that the edges between
the sides connecting the front side and the reverse side of the
base layer and the reverse side of the base layer have been
rounded; wherein the bezel has a coating on the front side and in
the rounded edge region of the front side; wherein the rounding has
a radius that is variable across the rounding.
[0008] The expression "front side" in the invention means the side
of the bezel that by way of example in the case of a bezel
installed in a motor vehicle faces outward. The term "edges" in the
plural takes account of the arrangement of the edges in
predominantly different spatial directions. Because there is
usually no distinct boundary between the edges at the various sides
of the bezel, the term "edges" also means a coherent edge running
around the bezel.
[0009] The expression "has a coating on the front side" preferably
means that the coating is also present in the edge region, i.e. in
the region of the rounded edge adjacent to the front side of the
bezel. It is particularly preferable that the coating covers the
entire front side and the entire edge region directly adjacent to
the front side.
[0010] Preference is given in the invention to the edge-rounding
shapes described hereinafter because for these it has been found
that the lacquer for a coating applied to a base layer of the bezel
is particularly uniformly distributed on the base layer of the
bezel, and thus forms a uniformly thick coating across the surface
of the front side/reverse side of the bezel.
[0011] The term "rounding" in the invention means that the
transition between two areas does not take the form of a sharp edge
but instead has been rounded. This means outward curvature when
viewed from the interior of the base layer.
[0012] The invention also comprises embodiments having curvature of
the entire bezel surface, including the front side and optionally
also the reverse side; this means that the front side and the
reverse side of the base layer do not necessarily have to be flat
surfaces.
[0013] In a first advantageous embodiment of the invention, not
only have the edges between the sides connecting the front side and
the reverse side of the base layer and the front side of the base
layer been rounded in the invention: the edges between the sides
connecting the front side and the reverse side of the base layer
and the reverse side of the base layer have also been rounded; the
bezel here preferably has a coating on the reverse side. In the
case of additional rounding between the sides connecting the front
side and the reverse side of the base layer and the reverse side of
the base layer, it is preferable that this rounding, too, has
variable radius.
[0014] In another advantageous embodiment of the invention, in
relation to the reverse side and the front side of the bezel, the
bezel is U-shaped, O-shaped, double-O-shaped, T-shaped or I-shaped.
Other shapes are, of course, also possible.
[0015] In a preferred embodiment, adjacent to the rounded edge on
that side of the bezel that has a coating there is a transition
region which has no rounding and which, in cross section through
the front side and the reverse side of the bezel, is characterized
by an ascending straight line and provides a transition between the
rounded edge region and the front side/reverse side of the
bezel--the coated side of the bezel. In so far as only the front
side of the bezel has been coated, this type of transition region
is present between the rounded edge that is in the direction of the
front side and the surface of the front side of the bezel. This
rounded edge that is in the direction of the front side is termed
here "upper rounded edge" and the rounded edge that is in the
direction of the reverse side is termed here "lower rounded edge".
An upper and a lower rounded edge can be present simultaneously,
but this is not essential. It is preferable that the upper rounded
edge and the lower rounded edge are connected either via a
straight-line transition region oriented perpendicularly to, or
substantially perpendicularly to, the front side and reverse side,
along the edge of the sides connecting the front side and the
reverse side of the bezel, or via the furthest outward situated
point of the rounding, or else that there is an immediate
transition between the upper rounded edge and the lower rounded
edge.
[0016] If the bezel has been attached in the transition region
between the bodywork and a transparent roof module, it is
preferable that the front side of the bezel is flush with the outer
contour of the motor vehicle.
[0017] In particular, if a coating is present only on the front
side of the base layer, the upper rounded edge has a larger radius
than the lower rounded edge. Bezels of the invention can also have
only an upper rounded edge; the lower edge can remain angular.
[0018] The rounding, in particular at the upper rounded edge,
alternatively preferably has the shape of, or approximately the
shape of, a Bezier curve, in particular a quadratic or cubic Bezier
curve. The rounding at the lower rounded edge can also have the
shape of, or approximately the shape of, a quadratic or cubic
Bezier curve. It is particularly preferable that there is a direct
transition between the rounding by way of this Bezier curve and the
surface of the front side/reverse side of the bezel.
[0019] A Bezier curve is a parametric curve which can be used in
description of freeform curves and surfaces. Very particular
preference is given in the invention to cubic Bezier curves.
[0020] Four points (P.sub.0, P.sub.1, P.sub.2 and P.sub.3)
determine a cubic Bezier curve. The curve begins at P.sub.0 and
proceeds in the direction of P.sub.1 and then proceeds from the
direction of P.sub.2 to P.sub.3. The curve does not generally
proceed through P.sub.1 and P.sub.2--these points serve merely to
state the direction; P.sub.1 here determines the direction in which
the curve reaches P.sub.0. P.sub.2 defines the direction from which
the curve reaches P.sub.3. The distance between P.sub.0 and P.sub.1
and the distance between P.sub.2 and P.sub.3 determine "how far"
the curve proceeds in the direction of the control points P.sub.1
and P.sub.2 before it proceeds in the direction P.sub.3.
C ( t ) = i = 0 3 t i ( 1 - t ) 3 - i P i = ( 1 - t ) 3 P 0 + 3 ( 1
- t ) 2 P 1 + 3 t 2 ( 1 - t ) P 2 + t 3 P 3 = ( - P 0 + 3 P 1 - 3 P
2 + P 3 ) t 3 + ( 3 P 0 - 6 P 1 + 3 P 2 ) t 2 + ( - 3 P 0 + 3 P 1 )
t + P 0 , t .di-elect cons. [ 0 , 1 ] ##EQU00001##
[0021] Expressed with the aid of the De-Casteljau algorithm this
is:
C ( t ) = C 0 3 ( t ) ##EQU00002## C 0 3 ( t ) = ( 1 - t ) { ( 1 -
t ) [ ( 1 - t ) P 0 + tP 1 ] C 0 1 ( t ) + t [ ( 1 - t ) P 1 + tP 2
] C 1 1 ( t ) } C 0 2 ( t ) ++ t { ( 1 - t ) [ ( 1 - t ) P 1 + tP 2
] C 1 1 ( t ) + t [ ( 1 - t ) P 2 + tP 3 ] C 2 1 ( t ) } C 1 2 ( t
) ##EQU00002.2##
[0022] Evaluation at the points with t=t gives the Bezier curve:
C.sub.0.sup.3(t)= .sub.0.sup.3(t,t).
[0023] The radius r for a point on the rounded edge, viewed within
the cross section through the front and the reverse side of the
bezel, is equal to the radius of an imaginary circle on which the
point would lie. The radius r is preferably variable across the
length of the region of the rounded edge, i.e. for various points
on the rounded edge there are various imaginary circles. This type
of rounding with integration of a transitional curve has proven to
be extremely advantageous in the invention.
[0024] It is also preferable that a clothoid is used for the
transition into the surface region of the front side of the bezel
and/or of the reverse side of the bezel.
[0025] The width b measured from the external edge of the bezel,
i.e. from the outermost point P of the bezel on side of the side
connecting the front side and the reverse side of the base layer,
to the end E of the curve of a rounded edge is preferably at least
1 mm, more preferably at least 1.5 mm, very particularly preferably
at least 2 mm, particularly preferably at least 2.5 mm, very
particularly preferably at least 3 mm.
[0026] The width b of the lower rounded region between the sides
connecting the front side and the reverse side of the base layer
and the reverse side of the base layer is preferably less than 2
mm, particularly preferably less than 1.75 mm, very particularly
preferably less than 1.5 mm.
[0027] If the bezel is imagined as arranged in a coordinate system,
the sides connecting the reverse side and the front side of the
bezel connect these along the z-direction. The front side and the
reverse side of the bezel lie, or lie approximately, within an
x/y-plane. It is preferable in the invention that, alongside the
rounding, essential in the invention, of the edges between the
sides connecting the front side and the reverse side of the bezel
and the front side of the bezel and/or between the sides connecting
the front side and the reverse side of the bezel and the reverse
side of the bezel, angles/corners resulting from the transition
regions of the legs extending longitudinally in the x/y-plane of
the bezel have also been rounded.
[0028] The term "leg" when applied to a bezel means a section which
is part of a bezel and which adjoins, at an angle, another section
in the same plane of a bezel.
[0029] The expression "internal angle R1" describes the rounded
region of the angle in the transition region between two legs. It
is preferable that the internal angle R1 in the imaginary x/y-plane
describes, precisely or at least approximately, a quadrant. In
order to minimize stresses in the component during thermal
expansion, the radius of this quadrant is preferably at least 8 mm,
ideally at least 10 mm. It is moreover preferable that, in addition
to this rounded shape of the internal angle, the edge-rounding
between the sides connecting the front side and the reverse side of
the base layer and the front side of the base layer follows a
Bezier curve.
[0030] Total expansion values <1%, in particular <0.8%, are
desirable. The radius of the internal angle R1 between the legs,
and also the edge-rounding, are important parameters particularly
when the component is then coated with a scratch-resistant coating.
Large stresses lead to premature failure of the lacquer. Thermal
expansion of bezels of particular shapes produces very complex
deformation which leads to high tensile stress on the upper side of
the bezel, the magnitude of which increases continuously in the
direction of the perimeter, in particular in the "interior corner
region". As the distance between the external edge and the neutral
fiber for this particular type of loading decreases, the expansion
values also decrease.
[0031] This problem is solved by minimizing the wall thickness of
the bezel. The wall thickness is preferably from 1.5 mm to 5 mm,
particularly preferably from 2 mm to 3.5 mm. The expression "wall
thickness" in the invention means the largest distance between
front side and reverse side of the bezel comprising the base layer
and the coating. In the event of expansion at low temperature, the
legs are bent outward (approximately linearly). As the radius of
the internal angle R1 decreases here, the local stresses (notch
effects) increase. A compromise therefore has to be found between
technical and design requirements.
[0032] It is therefore preferable that there is rounding of all of
the straight edges simultaneously in all directions, i.e. in the
x/y-plane and also in z-direction.
[0033] Surprisingly, it has been found that the molded part of the
invention has improved lacquerability. In particular, the molded
part can be lacquered substantially more uniformly, and this is
discernible in a more uniform layer thickness profile. It is thus
possible to achieve control of, and compliance with, the minimal
and maximal layer thickness for a given lacquer. This is in
particular true for an edge that is furthest upstream in the
direction of lacquer flow and drip edge. This results in improved
color depth when by way of example colored lacquers are used, or
improved weathering properties when functional lacquers are
used.
[0034] Another advantage is, without any intention to be bound to a
particular theory, that by virtue of the shaping of the edge that
is situated lowest in the coating process, the drip edge is placed
behind the visible region and thus behind the weathering edge of
the installed molded part, thus giving improved weathering
properties.
[0035] The bezels of the invention are preferably used [0036] in
the transition region between vehicle roof (bodywork) and
transparent roof modules, preferably transparent panorama roof
modules, folding roof modules or sliding roof modules, [0037] in
the transition region between engine hood and windshield, in the
transition region between A-column or A-column cladding and
windshield or [0038] in the transition region between tailgate
window and vehicle roof or [0039] as cladding for B-column,
C-column and D-column.
[0040] The bezels of the invention are connected to the vehicle
bodywork directly or by way of a support frame which can have been
manufactured from metal or plastic. The connection between bezel
and frame, and also between frame and vehicle bodywork, can be
realized via adhesive bonding and/or use of screw threads and/or by
way of snap connections. If the bezel is connected directly to the
vehicle bodywork, this is preferably achieved by way of adhesive
bonding.
[0041] The adhesive-bonding procedure can use wet adhesives,
contact adhesives, hotmelt adhesives or reactive adhesives.
Materials particularly suitable for this technology are single- or
two-component polyurethane-based structural adhesives with a
variety of stiffness properties. However, it is also possible by
way of example to use acrylic/acrylate-, methyl-methacrylate-,
silicone- or epoxy-resin-based adhesives. The adhesive can also be
a thermoplastically processable hot-melt adhesive.
[0042] The nature of the adhesive bead in the case of bezels of the
invention is preferably such that the bezel has maximal freedom of
deformation and expansion effects are therefore distributed over a
large, broad area. In order to achieve the best possible
positioning of the adhesive bead in the invention, therefore, the
region around the internal angle between two mutually contacting
legs should as far as possible be free from adhesive bonding; the
adhesive bead should specifically be interrupted here. It has
moreover proven to be advantageous to apply the adhesive bead with
additional interruptions along the legs. It is preferable that the
adhesive bead has been distributed in the form of thin strips
centrally on the two externally situated legs, and moreover in the
form of an elongated rectangle with rounded edges on the leg
connecting the two externally situated legs.
[0043] It is preferable that the width of the adhesive layer is
from 5 mm to 20 mm and that its thickness is from 0.5 mm to 10 mm.
It is particularly preferable that the width of the adhesive layer
is from 10 mm to 15 mm and that its thickness is from 3 mm to 6 mm.
The dimension of the adhesive layer in the third direction depends
on the dimensions of the component. It is preferable to use a
two-component adhesive of maximal softness with Shore A hardness
from 50-85. The hardness of the adhesive is particularly preferably
from 60-75 Shore A.
[0044] Preference is given to the bezel design of the invention in
those bezels which additionally have at least one rib in the
perimeter region, at or close to the external edge of the bezel.
Ribs are usually provided in order to increase stiffness and thus
to facilitate subsequent installation. They can also serve as
installation guides here in that their height prescribes the
distance between the external surface and the substructure. They
can also serve to receive or fix by way of example sealing
lips.
[0045] In the case of elements produced as one-piece injection
molded parts, ribs lead to local mass increases; on cooling this
can cause shrinkage of the material at these locations, resulting
in depressions at the surface of the element. Even if the extent of
the depression is minimized and the depression is not actually
visible, these depressions are in principle problematic during
coating, because accumulations of lacquer can occur in these, with
resultant delayed runoff; this leads to disadvantageous lacquer
flow, runs and/or curtaining. In order to minimize production of
depressions, it is preferable that the ratio of the width of the
rib to the wall thickness of the base layer of the bezel is at most
1:2. The edge-rounding of the invention, preferably implemented in
such a way that the rounding proceeds as far as the area behind the
ribs, and therefore as far as the area behind the depression, can
firstly render the depression in the base layer invisible and can
secondly permit better runoff of the lacquer in this region.
[0046] There can be conventional functional elements incorporated
into the bezels of the invention. These functional elements that
can have been integrally shaped, molded and/or bonded within/into
the bezels of the invention are in particular: [0047] a) antennas,
for example for the reception of analog or digital radio signals,
GPS and/or UMTS, where for the purposes of the present invention
the antennas can be realized by way of functionalized foils applied
to part of, or all of, that surface of the bezel that faces toward
the passenger compartment, i.e. foils applied to the reverse side
of the bezel. It is also alternatively possible that the antennas
are applied directly to the bezel surface via suitable printing
processes, preference being given for the purposes of the present
invention to printing by, for example, aerosol jet printing, or by
the screen-printing process; [0048] b) screw domes, engraved areas
for adhesive beads, ribs, snap-connection elements; [0049] c)
decorative effects or logos, preferably applied by way of
transparent printed foils on the side facing away from the
passenger compartment--i.e. on the front side of the bezel--to part
or all of the surface of the bezel; [0050] d) functional elements
for water management, and also spoilers, which in both cases for
the purposes of the invention are preferably not molded-on elements
but, by virtue of functional design, an integral constituent of the
actual bezel; [0051] e) driver-assistance systems/theft protection,
examples being distance radar, toll registration systems and
monitoring systems; [0052] f) transparent polycarbonate/PMMA foils
for UV-protection, preferably applied to all of the front side of
the bezel, i.e. on that side of the bezel that is directed toward
the environment of the vehicle; [0053] g) a black foil attached to
all of the surface of the reverse side of the bezel; [0054] h)
elements in the form of a foil or of an additional coating for heat
management via additional IR reflection/IR absorption.
[0055] It has been found advantageous to use the bezels of the
invention in the form of a multilayer system. This has the
particular advantage, by virtue of the various layers, of allowing
compliance with the strict requirements placed upon mechanical and
thermal properties, and at the same time ensuring high scratch
resistance and good protection from weathering.
[0056] For the purposes of the present invention it has proven
advantageous to provide additional layers as follows as external
coating to a base layer based on a thermoplastic, in particular on
polycarbonate, where other layers present are preferably the
following, in each case on the front side and optionally on the
reverse side of the bezel: [0057] a two-layer coating made of a
primer and of an outer lacquer layer, where the primer optionally
comprises a UV absorber and/or the outer layer is preferably
polysiloxane-based, in each case on the front side and/or the
reverse side of the bezel, where the reverse side of the bezel
means the side of the bezel facing toward the passenger compartment
and the front side of the bezel means the side of the bezel
directed toward the environment of the vehicle, [0058] or [0059] a
single-layer coating in the form of a clearcoat lacquer (e.g.
UV-curing or thermally curing lacquer), [0060] or [0061] a
single-layer coating in the form of a polysiloxane lacquer or of a
polyurethane-based lacquer system.
[0062] The expression "based on a thermoplastic" means that the
component predominantly present in the material of the base layer
is a thermoplastic. The composition of which the base layer is
composed can comprise content of other thermoplastics or
additives.
[0063] Between the base layer and the coating there can be an
additional layer arranged, for example a polycarbonate layer. This
layer is preferably a coextruded foil made of polycarbonate,
particularly preferably a polycarbonate foil with thin PMMA layer,
where the PMMA layer is external, on the front side of the bezel,
or a multilayer foil made of polycarbonate, of an IR-reflective
layer made of polycarbonate and optionally other layers.
[0064] It is also possible to integrate functions into the layer
structure by way of plasma layers. These functions can be:
scratch-resistant coatings, hydrophobic and hydrophilic properties,
antireflective layers, etc. It is preferable that the plasma layer
is a hard coating deposited via plasma processes, for example a
glassy layer, composed of siloxanes.
[0065] Thermoplastics which can be used for the production of the
bezels of the invention, the base layer therefore being based on
these, are in particular polycarbonate, copolycarbonate, polyester
carbonate, polystyrene, styrene copolymers, aromatic polyesters
such as polyethylene terephthalate (PET), PET-cyclohexanedimethanol
copolymer (PETG), polyethylene naphthalate (PEN), polybutylene
terephthalate (PBT), polyamide, cyclic polyolefin, poly- or
copolyacrylates and poly-or copolymethacrylate, for example poly-
or copolymethyl methacrylates (such as PMMA), and also copolymers
with styrene, for example transparent polystyrene-acrylonitrile
(PSAN), thermoplastic polyurethanes, polymers based on cyclic
olefins (e.g. TOPAS.RTM., a product commercially available from
Ticona), preferably polycarbonate, copolycarbonate, polyester
carbonate, aromatic polyesters or polymethyl methacrylate or a
mixture of the components mentioned, particular preference being
given to polycarbonate and copolycarbonate.
[0066] Suitable polycarbonates for the production of the plastics
composition of the invention are any of the known polycarbonates.
These are homopolycarbonates, copolycarbonates and thermoplastic
polyester carbonates.
[0067] Mixtures of a plurality of thermoplastic polymers are also
suitable as material for the base layer, in particular when they
can be mixed with one another to give a transparent material,
preference being given here to a mixture of polycarbonate with PMMA
or polyester.
[0068] The content of PMMA is particularly preferably 0.2% by
weight, very particularly preferably 0.1% by weight, based on the
quantity of polycarbonate, the molar mass (weight average) of the
PMMA here preferably being <40 000 g/mol.
[0069] A particularly suitable material for the base layer of the
bezels of the invention is a composition comprising the following
components: [0070] at least one thermoplastic, preferably
polycarbonate, with particular preference a polycarbonate based on
bisphenol A or a polycarbonate blend, more preferably with a melt
volume rate of [0071] i. from 7 cm.sup.3/(10 min) to 25
cm.sup.3/(10 min), [0072] ii. preferably from 9 to 21 cm.sup.3/(10
min), determined in accordance with ISO 1133 (at 300.degree. C.
with 1.2 kg load), [0073] nanoscale carbon black, preferably in a
quantity of [0074] i. from 0.05 to 0.50% by weight, [0075] ii.
preferably from 0.06 to 0.25% by weight, [0076] iii. with
particular preference from 0.08 to 0.20% by weight, [0077] and also
a mold-release agent based on a fatty acid ester, [0078] i.
preferably a stearic ester, [0079] ii. with particular preference
based on pentaerythritol, preferably at a concentration of from 0.1
to 0.5% by weight, [0080] iii. with particular preference from 0.20
to 0.45% by weight.
[0081] It is, of course, possible here to combine the features of
the preferred levels i. to iii. with one another in any desired
manner.
[0082] Nanoscale carbon black used preferably comprises pigment
blacks. The average primary particle size of these, determined by
scanning electron microscopy, is preferably less than 100 nm,
preferably from 10 to 99 nm, more preferably from 10 to 50 nm,
particularly preferably from 10 to 30 nm, in particular from 10 to
20 nm. Particular preference is given to pigment blacks of which
the particles are particularly fine.
[0083] Carbon blacks that are obtainable commercially and are
suitable for the purposes of the invention are obtainable with a
wide variety of trademarks and in a wide variety of forms, for
example pellets or powders: suitable carbon blacks are obtainable
with the trademark BLACK PEARLS.RTM., as wet-processed pellets with
trademarks ELFTEX.RTM., REGAL.RTM. and CSX.RTM., and in the form of
flakes as MONARCH.RTM., ELFTEX.RTM., REGAL.RTM. and MOGUL.RTM., all
from Cabot Corporation. Preference is in particular given to carbon
blacks marketed with trademark BLACK PEARLS.RTM. (CAS No.
1333-86-4).
[0084] Another preferred composition of the base layer comprises a
mixture of polycarbonate and PMMA with less than 2.0% by weight,
preferably less than 1.0% by weight, more preferably less than 0.5%
by weight, of PMMA, where at least 0.01% by weight of PMMA is
present, based on the quantity of polycarbonate, where the molar
mass (weight average) of the PMMA is preferably <40 000
g/mol.
[0085] It is particularly preferable that there is, on at least one
side of the base layer, a polysiloxane-based scratch-resistant
coating comprising at least one UV absorber, where the thickness of
the scratch-resistant layer is preferably from 2 .mu.m to 15 .mu.m,
with particular preference from 4.0 .mu.m to 12.0 .mu.m.
[0086] It is very particularly preferable that, arranged on the
base layer, there is at least one adhesion-promoting layer (primer
layer) between the base layer and the scratch-resistant layer
comprising at least one UV absorber, where the thickness of the
primer layer is preferably from 0.3 .mu.m to 6 .mu.m, with
particular preference from 1.2 .mu.m to 4.0 .mu.m.
[0087] The respective bezel can, as desired, be realized as
single-component or two-component injection molding. When a bezel
used takes the form of a 2-component injection molding it is
preferable for the purposes of the present invention that one
component is transparent, and also that one component is not
transparent. It is moreover preferable here to install the bezel in
such a way that the transparent component of the bezel is directed
toward the external side of the vehicle. The meaning of transparent
in this context is that at least the outline of an object situated
behind the bezel is visible to the human eye when the object is
covered by the bezel. The meaning of transparency in the invention
is therefore light transmittance Ty (10.degree., D65) greater than
5% and haze less than 5%, measured in accordance with ASTM D 1003.
Ty (10.degree., D65) here is calculated in accordance with ASTM
E308 and is equal to Y10, based on the standard D65 light
source.
[0088] A preferred embodiment of the invention is a U-bezel
produced as single-component injection molding made of a
polycarbonate as base layer, comprising nanoscale carbon black,
where the bezel is a multilayer compound-structure system, i.e. a
system made of at least two layers, where one layer is a
scratch-resistant coating. Scratch resistance in the invention
means a gloss level reduction of at most 20 units, determined in
accordance with the Amtec-Kistler test (ISO 20566).
[0089] In another preferred embodiment there is, applied on both
sides of the base layer, in each case an adhesion-promoting layer,
and also a scratch-resistant layer. The primer layer preferably
comprises an organic binder, preferably PMMA-based, which promotes
adhesion between the composition based on the thermoplastic
material, which is preferably polycarbonate, and the
scratch-resistant coating, preferably a polysiloxane-based
lacquer.
[0090] Rubber-modified vinyl(co)polymers can be used as blend
constituents. Examples of particularly preferred rubber-modified
vinyl(co)polymers are ABS polymers (emulsion ABS, bulk ABS and
suspension ABS; ABS=acrylonitrile-butadiene-styrene), these being
as described by way of example in DE 2 035 390 A (U.S. Pat. No.
3,644,574 A) or DE 2 248 242 A (GB 1 409 275 A) or in Ullmann,
Enzyklopadie der Technischen Chemie [Ullmann's Encyclopedia of
Industrial Chemistry], vol. 19 (1980), pp. 280 ff.
[0091] The polycarbonates are preferably produced by the
interfacial process or the melt transesterification process, these
being known to the person skilled in the art and widely described
in the literature.
[0092] For the interfacial process reference may be made by way of
example to H. Schnell, "Chemistry and Physics of Polycarbonates",
Polymer Reviews, vol. 9, Interscience Publishers, New York 1964 pp.
33 ff., to Polymer Reviews, vol. 10, "Condensation Polymers by
Interfacial and Solution Methods", Paul W. Morgan, Interscience
Publishers, New York 1965, chapter VIII, p. 325, to Dres. U. Grigo,
K. Kircher and P. R. Muller "Polycarbonate" in Becker/Braun,
Kunststoff-Handbuch [Plastics Handbook], vol. 3/1, Polycarbonate,
Polyacetale, Polyester, Celluloseester [Polycarbonates,
Polyacetals, Polyesters, Cellulose Esters], Carl Hanser Verlag,
Munich, Vienna, 1992, pp. 118-145, and also to EP 0 517 044 A1.
[0093] The melt transesterification process is described by way of
example in Encyclopedia of Polymer Science, vol. 10 (1969),
Chemistry and Physics of Polycarbonates, Polymer Reviews, H.
Schnell, vol. 9, John Wiley and Sons, Inc. (1964), and also in the
patent specifications DE 10 31 512 B and U.S. Pat. No. 6,228,973
B1.
[0094] The polycarbonates are preferably produced via reactions of
bisphenol compounds with carbonic acid compounds, in particular
phosgene, or in the melt transesterification process from diphenyl
carbonate or dimethyl carbonate.
[0095] Particular preference is given here to homopolycarbonates
based on bisphenol A and to copolycarbonates based on the monomers
bisphenol A and
1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane.
[0096] These and other bisphenol compounds or diol compounds that
can be used for polycarbonate synthesis here are disclosed inter
alia in WO 2008/037364 A1 (p. 7, line 21 to p. 10, line 5), EP 1
582 549 A1 ([0018] to [0034]), WO 2002/026862 A1 (p. 2, line 20 to
p. 5, line 14), WO 2005/113639 A1 (p. 2, line 1 to p. 7, line
20).
[0097] The polycarbonates can be linear or branched. It is also
possible to use mixtures of branched and unbranched polycarbonates.
Suitable branching agents for polycarbonates are known from the
literature and are described by way of example in the patent
specifications U.S. Pat. No. 4,185,009 A and DE 25 00 092 A1
(inventive 3,3-bis(4-hydroxyaryloxindols), see in each case entire
document), DE 42 40 313 A1 (see p. 3, lines 33 to 55), DE 19 943
642 A1 (see p. 5, lines 25 to 34), and also U.S. Pat. No. 5,367,044
A and literature cited therein. The polycarbonates used can
moreover also have intrinsic branching, no branching agent being
added here for the purposes of production of the polycarbonate. An
example of intrinsic branching is what are known as Fries
structures as disclosed for melt polycarbonates in EP 1 506 249
A1.
[0098] Production of the polycarbonate can moreover use chain
terminators. Chain terminators used preferably comprise phenols
such as phenol, alkylphenols such as cresol and 4-tert-butylphenol,
chlorophenol, bromophenol, cumylphenol or a mixture of these.
[0099] The polycarbonates can moreover comprise conventional
polymer additives, for example the flame retardants, optical
brighteners, flow improvers, organic or inorganic colorants, heat
stabilizers, inorganic pigments, mold-release agents or processing
aids described in EP 0 839 623 A1, WO 96/15102 A2, EP-A 0 500 496
A1 or in "Plastics Additives Handbook", Hans Zweifel, 5th edition
2000, Hanser Verlag, Munich. UV absorbers or IR absorbers can
moreover be present. Suitable UV absorbers are described by way of
example in EP 1 308 084 A1, in DE 10 2007 011 069 A1, and also in
DE 10311063 A1. Suitable IR absorbers are disclosed by way of
example in EP 1 559 743 A1, EP 1 865 027 A1, DE 10022037 A1, DE
10006208 A1, and also in the Italian patent applications
RM2010A000225, RM2010A000227, and also RM2010A000228. Among the IR
absorbers mentioned in the cited literature, preference is given to
those based on boride and on tungstate, and also to absorbers based
on ITO (indium tin oxide) and ATO (aluminum tin oxide), and also
combinations thereof.
[0100] It is preferable that the thermoplastic is a polycarbonate
with molar mass M.sub.w from 22 000 g/mol to 30 000 g/mol, more
preferably from 24 000 g/mol to 28 000 g/mol and particularly
preferably from 25 000 g/mol to 27 000 g/mol, determined via gel
permeation chromatography with polycarbonate calibration.
[0101] It has proven advantageous for the purposes of the present
invention that the bezels of the invention are produced with the
aid of injection-molding technology by the following operations:
[0102] optional insertion of a foil into the injection mold, [0103]
closure of the mold, [0104] injection of a first polymer
composition, preferably by way of injection-compression molding or
cascade injection molding, then cooling to a maximal component
temperature lower than the glass transition temperature, [0105]
optional rotation of the cavity into the next position for purposes
of injection of a second polymer composition, in such a way that on
closure of the mold in this position an intervening space is
produced between the first hardened polymer composition and the
mold wall, [0106] optional injection of the second polymer
composition, then cooling to a maximal component temperature lower
than the glass transition temperature.
[0107] An example of a method for the coating that follows the
production of the base layer of the bezels, for example as
described above, is as follows: [0108] demolding, [0109] cooling of
the component to room temperature, [0110] coating of the component
with the primer, for example with a PMMA-based primer system,
preferably comprising UV-protection, where the coating method here
can be flow coating, dip coating or spraying, [0111] evaporation of
the solvents until the material is dry to the touch, stoving of the
primer at at least 125.degree. C., where the stoving period is
preferably at least 15 min at object temperature >125.degree.
C., [0112] cooling to room temperature, [0113] coating with outer
lacquer, preferably with a polysiloxane-based outer lacquer,
preferably by way of flow coating or dip coating, [0114]
evaporation of the solvents, preferably until the material is dry
to the touch, [0115] stoving of the outer lacquer at an object
temperature of at least 125.degree. C., preferably for a period of
at least 30 minutes at object temperature >125.degree. C.,
[0116] cooling to room temperature.
[0117] The coating can alternatively be achieved by means of a
known direct coating step following injection molding, preferably
as follows: [0118] rotation of the cavity into the next position
for purposes of injection of the polyurethane (PU) component. On
closure of the mold in this position an intervening space arises
between the first hardened polymer composition and the mold wall
(this step can also optionally take place after in-mold coating
with the second polymer composition), [0119] injection of a
polyurethane system, [0120] demolding, [0121] cooling to room
temperature.
[0122] It is also possible to use a second mold with another
cavity, instead of rotation of the cavity during production of the
base layer or during the coating process.
[0123] A visually attractive bezel is obtained with excellent,
glass-like surface, good high-gloss appearance without depressions,
and particularly high scratch resistance.
[0124] The invention is explained in more detail below with
reference to some drawings depicting preferred embodiments.
[0125] FIG. 1: is a plan view of the front side of a U-shaped
bezel, particular attention being drawn to the region of the
internal angle between the legs of the bezel;
[0126] FIG. 2: is a plan view of the reverse side of the bezel of
FIG. 1; the section A'-A' is depicted in FIGS. 3a to 3f for various
embodiments;
[0127] FIG. 3a: is a cross-sectional view along the line A'-A' in
FIG. 2 of the bezel shown in FIG. 2 in a first embodiment;
[0128] FIG. 3b: is a cross-sectional view along the line A'-A' in
FIG. 2 of the bezel shown in FIG. 2 in a second embodiment;
[0129] FIG. 3c: is a cross-sectional view along the line A'-A' in
FIG. 2 of the bezel shown in FIG. 2 in a third embodiment;
[0130] FIG. 3d: is a cross-sectional view along the line A'-A' in
FIG. 2 of the bezel shown in FIG. 2 in a fourth embodiment;
[0131] FIG. 3e: is a cross-sectional view along the line A'-A' in
FIG. 2 of the bezel shown in FIG. 2 in a fifth embodiment;
[0132] FIG. 3f: is a cross-sectional view along the line A'-A' in
FIG. 2 of the bezel shown in FIG. 2 in a sixth embodiment;
[0133] FIG. 4: is a plan view of the reverse side of the bezel of
FIG. 1, particular attention being drawn to the region X which is
the location of the internal angle between two legs;
[0134] FIG. 5a: is a perspective view of ribs attached in the
internal angle region X shown in FIG. 4 in a first embodiment;
[0135] FIG. 5b: is a perspective view of ribs attached in the
internal angle region X shown in FIG. 4 in a second embodiment;
[0136] FIG. 5c: is a perspective view of ribs attached in the
internal angle region X shown in FIG. 4 in a third embodiment;
[0137] FIG. 6a: is a plan view of the front side of a U-bezel;
[0138] FIG. 6b: is a plan view of the front side of an O-bezel;
[0139] FIG. 6c: is a plan view of the front side of a
double-O-bezel;
[0140] FIG. 6d: is a plan view of the front side of a T-bezel;
[0141] FIG. 6e: is a plan view of the front side of an I-bezel;
[0142] FIG. 7: is a cross-sectional view of the perimeter region of
a bezel with rib in the perimeter region.
[0143] FIG. 1 shows a U-shaped bezel (abbreviated to: U-bezel)
having a first and second exterior leg S1, S2 and a leg S3
connecting the legs S1 and S2, particular attention being drawn to
region X of the internal angle R1 between the legs S2 and S3 of the
bezel. The internal angle between the legs S3 and S1 is preferably
the same as the internal angle between the legs S3 and S2, but it
can also differ. The internal angle R1 describes approximately a
quadrant. The radius of this quadrant is indicated by "Ri". For
easier understanding of the geometric relationships, the drawing
moreover includes a coordinate system for orientation. It can be
seen that the areas of the front side and of the reverse side of
the bezel extend within the x/y-plane, and this also applies
accordingly to the rounded transition region between the legs S3
and S1 with the internal angle R1. The feature, essential to the
invention, of the edge rounding in z-direction is explained
below.
[0144] FIG. 2 shows the rear view of the U-bezel of FIG. 1. The
adhesive beads H can clearly be seen here. The sectional line A'-A'
runs through the rounded internal angle between the legs S1 and S3.
The following FIGS. 3a to 3f show cross-sectional views of the
bezel along this sectional line in various alternative embodiments.
The upper rounded edge R.sub.o and the lower rounded edge R.sub.u
can be seen. "P" indicates the outermost endpoint of the bezel at
the rounded edge. An imaginary straight line A perpendicular to the
front side and the reverse side of the bezel runs through said
endpoint P. "E.sub.o" indicates the point of transition between the
rounded region of the rounded edge and the actual front side of the
bezel, i.e. generally a surface without curvature. "b" indicates
the distance between the straight line A running through the point
P and a perpendicular running through the point E.sub.o, where the
perpendiculars run orthogonally with respect to the reverse side of
the bezel.
[0145] In the embodiment shown in FIG. 3a, the upper edge rounding
takes the form of a Bezier curve. Between the upper and lower
rounded edge, R.sub.o and R.sub.u, there is no straight-line
transition region present that is perpendicular to the front side
and the reverse side. The endpoint P is therefore genuinely a
point, whereas in the case of the embodiment shown in FIG. 3d the
outermost endpoint P lies on a straight-line transition section on
the straight line A perpendicular to the front side and reverse
side of the bezel.
[0146] In FIG. 3b, the upper edge R.sub.o has been rounded in the
shape of a Bezier curve. The lower edge R.sub.u has been
non-specifically rounded. The point E.sub.o is the point at which
the Bezier curve ends. There is a straight-line transition section
present, perpendicular to the front side and the reverse side of
the bezel, between the two rounded edges at the sides connecting
the front side and the reverse side of the bezel.
[0147] In the embodiment in FIG. 3c, the upper edge R.sub.o has
been rounded in the shape of a Bezier curve. The lower edge R.sub.u
has likewise been rounded in the shape of a Bezier curve, and
specifically in the shape of a quadratic Bezier curve. There is no
straight-line transition section present, perpendicular to the
front side and the reverse side of the bezel, between the two
rounded edges at the sides connecting the front side and the
reverse side of the bezel.
[0148] In the embodiment shown in FIG. 3e, only the upper edge
R.sub.o has been rounded, whereas the lower edge R.sub.u is a
conventional "angular edge", where an "angular edge" can certainly
have minimal rounding caused by a manufacturing process. The upper
edge R.sub.o has been rounded with radius varying across the
rounding, and specifically in the shape of a Bezier curve. There is
a direct transition between the rounding of the upper edge R.sub.o
and the lower angular edge R.sub.u, and the vertical dimension of
the outermost end point P is therefore equal to 0.
[0149] In contrast to this, the dimension of the section P in the
embodiment shown in FIG. 3f is greater than 0, i.e. a portion of
the cross section of the side connecting the front side and the
reverse side of the bezel comprises a straight line.
[0150] FIG. 4 again shows, as in FIG. 2a, the reverse side of the
U-bezel, inclusive of the region indicated by "X" at the point of
intersection between two legs. This region "X" is depicted in
enlarged form for certain embodiments in FIGS. 5a to 5c, there
being ribs here placed perpendicularly onto the area of the reverse
side of the bezel. These ribs can, as shown in FIG. 5a, form a rib
structure interrupted by cutouts L or, as shown in FIG. 5b, can
form a coherent rib line G. Another possibility is a coherent rib
line G which has indentations F, as shown in FIG. 5c. It can
moreover be seen in FIG. 4 that the adhesive beads are not
continuous, but instead have gaps.
[0151] Cutouts L between two ribs are usually provided for, by way
of example, water management. However, it is preferable in the
invention to avoid cutouts between the individual ribs, or else if
necessary that these take the form of indentations F. The cutouts
imply local differences in stiffness which lead to concentrations
of stress and therefore to higher expansion values.
[0152] FIGS. 6a to 6e show various preferred bezel shapes, and
specifically a U-bezel (FIG. 6a), an O-bezel (FIG. 6b), a
double-O-bezel (FIG. 6c), a T-bezel (6d) and an I-bezel (FIG.
6e).
[0153] FIG. 7 shows a cross section of the perimeter region of a
bezel of the invention where a rib B is present in the perimeter
region. The drawing does not include the depression in the front
side of the base layer of the bezel, because although this is
present its extent is minimal. The upper edge R.sub.o has been
rounded in the shape of a Bezier curve. The location of the rib is
in front of the point E.sub.o, i.e. in front of the point of
transition between the rounded region of the rounded edge and the
actual front side of the bezel, i.e. a surface without
curvature.
KEY
[0154] R1 internal angle (rounded region between two legs) [0155] X
region shown enlarged around the internal angle R1 [0156] P
outermost endpoint of the bezel in the case of the rounded edge,
optionally in the form of straight-line transition section between
the upper and lower rounded edge [0157] A straight line through P,
perpendicular to the plane of the front side and the reverse side
[0158] r radius of an imaginary circle on which the respective
point of the rounded edge lies [0159] E.sub.o point of transition
between the rounded region of the rounded edge and the actual front
side of the bezel, i.e. generally a surface without curvature
[0160] b width of the region between A and E [0161] L cutout in a
rib structure [0162] G rib [0163] F indentation in a rib [0164] H
adhesive bead [0165] S leg [0166] R.sub.o upper rounded edge [0167]
R.sub.u lower rounded edge [0168] Ri radius of the rounded region
of the internal angle between two legs (x/y-plane) [0169] B rib
* * * * *