Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
`- 2149372
Al~ORNEY DOCKET NO.: 43760
PROCESS FOR PREPARING FRONT FnMS PRO~IDED
Wl l H A MULTICOLOR PRINT FOR KEYPADS
AND THE LIKE
s
FIELD OF THE INVENTION
The present invention pertains to a process for preparing front films
for keypads or the like, which consist of cover films, especially polyester
films. which have, on the top side, a scratch-proof. hard. possibly dulled
protective layer, which consists of. e.g., a two-component lacquer or a
lacquer cured by UV light, and which are provided with a multicolor printed
image on the underside (white also being available as a color, besides any
colors and shades), and the front film optionally has unprinted transparent
wlndows.
BACKGROUND OF THE INVENTION
Cover films made of polyester or polycarbonate. which are used as
front films for kevpads or the like. are frequently printed on the reverse
21~9372
.~
side, so that they exhibit, e.g., keypad boxes, text boxes or the like from the
front side, while window-like openings, which are used as transparent
windows, e.g., on displays or the like, are not printed on. The printing is
performed in the conventional manner by silk screen printing. This involves
S a separate printing process and also a special print screen as these are
necessary for each color used. This leads to very high printing costs.
While a white printing ink is not needed for printing on white paper
or a white background, white printing ink must also be available for printing
on cover films.
It has also been known that so-called overhead films (for use with
overhead-type projector) can be printed in multiple colors on one side in
color copying. The polyester films to be printed on are provided on both
sides with the same color toner adhesion layer and possibly with an
antistatic layer, even though only one side is to be printed on. The reason
for coating with the same color toner adhesion layer or antistatic layer on
both sides is that in the case of co~hng on one side only, uncontrollable
electrostatic charges may greatly impair the quality of the printed image and
lead to unsuitable print results.
However, white as a printing ink is not used or needed in the
overhead film application because the images of such overhead films are
usually projected onto a white projection surface.
`~ 2149372
-
SUMMARY AND OBJECTIVES OF THE INVENTION
The primary object of the present invention is to provide a process
for preparing front films of-the type described in the introduction, by which
the cost for preparing the printed images on the reverse side of the front
films can be reduced while maintaining an at least a~r~ tely equal
irnage quality.
This object is attained according to the present invention either by
providing the film with a color toner adhesion layer only on the underside
surface to be printed on and printing with color toner on the side with the
adhesion layer in a computer-controlled printer according to the
electrostatic printing process (laser printing process), and/or by subsequently
coating the printed surfaces with white ink, possibly leaving out window
openings.
To obtain higher print quality at a higher level of certainty, it is
advantageous to proceed by providing the scratch-proof protective layer with
an antistatic layer which neutralizes or avoids electrostatic charges of the
film at least during printing in an electronic printer or copier and/or to
proceed by providing the color toner adhesion layer with an antistatic layer
or providing the color toner adhesion layer with antistatic effects.
According to a further aspect of the invention, after printing, the
antistatic layer may be removed. This offers the possibility of removing the
antistatic layer from the protective layer after it has served its purpose.
~1 49372
Printing on front films by means of computer-controlled laser printers
or color copiers, which use a powdered toner, has not been used to date for
the purpose accordil,g to the present invention mainly because these
computer-controlled color printers and color copiers or printing procecces
S cannot print white color, and because the powdered toners available were
able to be printed with sufficient printed image quality only on films which
are provided on both sides with the same toner adhesion layer or with an
additional antistatic layer. Films with a scratch-proof, hard protective layer
on the top side have hitherto been con~idered to be unsuitable for being
printed on in this manner.
The process accordhlg to the plesent invention makes it possible to
prepare the multicolor printed images, which are needed for the front films
of, e.g., keypads, in series at a su~sld~-lially lower cost and more rapidly,
because not only the multiple operations needed, but also the multiple print
screens needed in the prior-art silk screen printing proces~, are elimin~te~l
The subsequent application of the white ink to the printed underside
of the cover film may be performed in different ways. Thus, it would
advantageously be possible to arrange an application station for the white
ink, in which the white ink is rolled on, directly behind the obligatory fixing
station of the printer or copier.
Another, equally advantageous possibility is to provide the white
color by the use of a white backing film, which can be bonded on the
- 2149~72
printed side of the cover film and the white backing film may have window
openings, if desired.
The backing film may be white in itself or have a white ink layer.
Especially good print results can be obtained according to the present
invention with a printer or copier which has an intermediate image carrier,
particularly in the form of a transfer strip, to transfer the scanned image
from a photoconductive drum to the film.
The various features of novel~h,r which characterize the invention,
including the general design of a keypad vith a display window and the
process accol dillg to the present invention, are pointed out with particularityin the claims annexed to and forming a part of this disclosure. For a better
understanding of the invention, its operating advantages and specific objects
attained by its uses, reference is made to the accompanying drawings and
descriptive matter in which a preferred embodiment of the invention is
illustrated.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings:
Figure 1 is a front view of a keypad;
Figure 2 is a side view of the keypad according to Figure 1;
Figure 3 is a partial cross sectional view of the keypad according to
Figure 1 on a larger scale;
~149372
Figure 4 is a perspective view of a printed cover film with a white-
coated backing film bonded to the underside, wherein the
right lower corner of the cover film is shown pulled off, and
Figure S is a perspective view of a corner of the cover fflm partially
pulled off from the printed layer with its toner adhesion layer
on the underside.
DET~.Pn DESCRIPTION
OF THE PREFERRED EMBODIMENT
Referring to the drawings in particular, the keypad shown in the
drawing has a sandwich structure. It has at least one base film 1, a spacer
film 2, a switching film 3, as well as a front film 4. The front film 4 is
cGI~lplised of a front-side cover film S and a b~rl~ing film 6, which is laid
directly behind it and is provided with a white ink layer 6' or is intrinsicallywhite. The cover film S and the b~rlring film 6 are bonded to each other
over their entire surface by a thin adhesive film 7, which was originally
applied to the backing film. For protection against scr~tching or other
rl~m~ging effects, the cover film 5 must be provided on its surface with a
cured or harder protective layer S'. The latter may consist of, e.g., a two-
component lacquer or a lacquer "baked" with W light. This protective
layer S' may also be dull, if desired. The base film 1, the spacer film 2, the
switching film 3, and the front film 4 are also bonded to one another over
their entire surface.
9372
An LCD display 8, which is visible through a display window 9 and
through the cover film 5, is located behind the base film 1. The display
window 9 is formed by corresponding cutouts 10, 11, 12 or 13 of the base
film 1, of the spacer film 2, of the switching film 3, as well as of the backingfilm 6, which are fittingly placed one on top of another. While the front-
side cover film S must be transparent, the base film 1, the spacer film 2, and
the switching film 3 may also be nontransparent. Such films usually
preferably consist of polyester. The spacer film 2 is additionally provided
with window-like cutouts 14, in which Cu contact elements 15 and 15' of the
base film 1 and of the switching film 3 are located. These contacts can be
actuated in a contacting manner by pressing the front film 4 with a finger.
Key-like printed images 16 and 17, which are arranged on the rear side of
the cover film 5 and are visible through same, are provided over these
window-like openings of the spacer film 2. These are numbers and function
keys and other indicia, which can be actuated by pressing the corresponding
area with a finger for contacting the contact elements 15, 15'.
While the front surface 19 of the keypad shown, which is visible in
Figure 1, is usually single-colored, the printed images 16 and 17, which
provide the appearance of the keys, are provided with at least two colors,
and the surfaces of the individual small boxes have a color that is clearly
distinguishable from the color of the base surface 19. The function keys
may have a different color than the number keys. In addition, the numbers
9372
and the individual function s~mbols are distinguished by their color from the
surface colors of the individual small boxes. The numbers and/or the
function svmbols or calculation svmbols mav also aD~ear in white. This also
applies to the text areas 18, which are arranged dil~ lly under the printed
images 17.
The color of the base surface 19 as well as the diLrereJlt colors of the
printed images 16 and 17 and of the text areas 18 are applied by the process
a~ordhlg to the present invention by p~ ;"g the multicolor printing in
a computer-controlled laser ~lhlter or laser copier, while the surface areas,
which shall later appear in white, remain blank and so do the window
cutouts, through which the display shall be visible. To do so, the front-side
cover film S is provided or prepared, on iS underside to be printed on, with
a special color toner adhesion layer 4', to which the color print is applied.
This color toner adhesion layer 4' is provided either with antistatic
properties or with an antistatic layer, by which elecl.o~tic charges of the
cover film, which could impair the quality of the printed image, are at least
greatly reduced.
To prevent uncontrolled ele~illu~l~lic charges, which are detrimental
to the quality of the printed image, from o~ulling to the highest possible
degree of certainty, the protective layer 5' is also provided with an antistaticlayer 4/1. More or less in a compen~ting cooperation with the antistatic
properties of the color toner adhesion layer 4' or with its antistatic layer,
`- ~149372
this additional antistatic layer 4/1 of the protective layer 5' allows for the
avoidance of harmful electrostatic charges during printing so that sharp and
exact printed images will be formed.
The white color is then produced by backing the printed underside
of the cover film S with the white backing film 6, wherein it is advantageous
to provide the backing film 6 with an adhesive film in advance, and to bond
this backing film to the printed area of the cover film 5 by means of this
adhesive film.
Figure 4 shows the printed layer 20 applied to the underside of the
cover film 5 and the adhesive film 7 on the top side of the backing film 6.
The toner adhesion layer 4' applied to the underside of the cover
film 5, which underside is to be printed on, is illustrated in a non-realistic
manner in Figure 5 insofar as the printed layer 20 can no longer be
separated from this toner adhesion layer 4'.
It is also possible, among other things, to apply the white ink to the
multicolor printed image by rolling it on in an application station arranged
downstream of the fixing station of a printer or of a copier, if desired, by
using an image mask.
Especially good print results have been obtained in color printers or
color copiers, in which an intermediate image carrier, especially in the form
of a transfer strip, is used to transfer the scanned image from a
photoconductive drum to the film.
~1~9372
While a specific embodiment of the invention has been shown and
described in detail to illustrate the application of the principles of the
invention, it will be understood that the invention may be embodied
otherwise without departing from such principles.
