Note: Descriptions are shown in the official language in which they were submitted.
3301/H/94 21~6I9O
LASER PRINTING ~IETHOD AND APPARATUS
Field of the Invention
This invention relates to a printing method and apparatus, more
specifically to a laser printing method and apparatus, particularly
intended for printing on bound substrates, e.g., bound in booklet form,
such as passports and the like.
Back~round of the Invention
Laser printing machines are known in the art and are widely used for a
variety of purposes. Basically, the laser printing process comprises, as a
first step, defining the subject matter to be printed in the form of an array
of instructions that can be used to control the printing machine. A
common way of doing this consists in sc~nning the subject matter to be
printed and registering the results of the sc~nning in a processor's
memory, in the form of an array of digital instructions. Said instructions
control the emission of laser rays from a laser source. The laser beams
impinge on a cylinder in a pattern controlled by the said instructions and
electrostatically charge the surface of said metal cylinder at selectively
predetermined spots. The selectively electrostatically charged cylinder
passes in the vicinity of a reservoir of coloring matter in powder form.
The coloring matter particles are attracted to the aforesaid selectively
charged spots of said cylinder and form thereon a desired pattern. A print
substrate is then passed into contact with the metal cylinder and the
pattern formed by the color particles is deposited thereon. This operation
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is repeated for each color if a multicolor print is desired, usually four
times to provide the basic colors magenta, cyan and yellow plus black, to
produce a complete colored image. At this stage a colored image has been
formed on the print substrate. In order to stabilize the image, the print
substrate is passed between heated rollers, which fix or set the print so
that it is permanent and stable.
This process is quite effective for a number of applications, but it
encounters difficulties, hitherto unsolved, when it is necessary to print on
on a substrate that is not in the form of a free sheet, but is in bound e.g.
in the form a booklet, typically a passport or ~imil~r bound document. It
would be highly desirable to print on a passport or like document, after it
has already been bound in booklet form, the passport holder's photograph,
signature, and/or other printed information. However, this is not possible
with the present laser printing techniques. Others difficulties would arise,
should the print substrate have a surface which is not absorbent with
respect to the colors: the coloring matter is then partly if not totally
transferred from the print substrate to the heat-setting rollers.
It is a purpose of this invention to overcome the aforesaid difficulties and
to make it possible satisfactorily to print subject matter including
multicolor subject matter such as photographs, on different kinds of
papers or substrates.
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It is another purpose of this invention to provide a method for printing
subject matter, including color photographs and the like, on bound
substrates, particularly in booklet form, such as passports and the like.
It is a further purpose of this invention to provide an apparatus for
achieving the aforesaid results, which apparatus is simple and not
expensive to make nor difficult to use.
Other purposes and advantages of this invention will appear as the
description proceeds.
S~lmm~ry of the Invention
In this application, the terms "substrate" or "printing substrate" mean
any backing on the which printing can be effected, regardless of its form
and composition, be it e.g. uncoated or coated paper, plastic or any other
sheet material, or a page of a booklet or other bound object intended to
carry printing on pages or other parts thereof. The terms "picture" or
"subject matter" or "graphic subject matter" synonimously indicate any
kind of printable or printed subject matter, and therefore comprise,
among other things, pictures representing persons or objects, portraits,
photographs, letters, words, signs and any figures or images that may be
carried by a substrate of any kind.
The method according to the invention comprises the following steps:
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1 - providing a set of digital instructions, such as a computer file,
which reverses of the subject matter to be printed (which will be
synonimously called hereinafter "the original picture" or "the
original subject matter"), viz. defines its specular image (which
will be synonimously called hereinafter "the reversed picture" or
"the reversed subject matter");
2 - providing a temporary or intermediate substrate, the surface of
which is substantially non-absorbent and non-adhesive for the
coloring matters to be used for the printing;
3 - depositing on said temporary substrate coloring matters,
whereby to produce thereon said reversed picture, by the
appropriate steps of the conventional laser printing method;
4 - provisionally setting said reversed picture without the
application of pressure, preferably by radiant heat or dielectric or
microwave heating;
5 - juxtaposing said temporary substrate face-to-face with the final
printing substrate;
6 - transferring the reversed picture from said temporary to said
final substrate, whereby said reversed picture is reversed and
reproduces said original picture on said final substrate (the
reproduction of the original picture on the final substrate will be
synonimously called hereinafter "the reproduced original subject
matter" or "the direct picture"); and
7 - setting said direct picture on said final substrate by the
application of pressure and heat.
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Optionally, a l~min~tion operation may be carried out after said last
mentioned step, in order to protect the heat-set direct picture by means of
a transparent plastic layer.
The operations of transferring-reversing the reversed picture onto the
final substrate and setting the resulting direct picture can be carried out
directly on a bound substrate, viz. substrate in booklet form, or it can be
carried out on a final substrate in sheet form, which sheet substrate is
then cut to the appropriate sizes and bound, if desired, to booklet form.
The basic requirement for a suitable intermediate or temporary substrate
is that it should have such a surface that it is possible to transfer from it
to the final substrate, by the application of heat and pressure, coloring
matter that has been provisionally set without the application of
pressure, e.g. by radiant heat. Therefore it is easy to determine, by a
simple test, whether a given substrate is suitable as temporary substrate
for a given application of the process of the invention. In general, the
temporary substrate should have a smooth surface, non-absorbent for the
colors used in the laser printing. Silicone coated papers have such
surfaces. A preferred example is paper SBL 42 MGA SILOX 8L/0, the
typical physical data of which are shown in the following Table.
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Table I
Proper ,y Target Test Method
Basis Weig lt (3,000 sq. ft.) 42 ''app ''-410
Caliper (mi ) 3.3 Tapp '.'-411
Tensile Strength MD 31 Tapp ' '-494
(lbs/inch) CD 15
Tear Strength MD 48 Tappi T-414
'grams) CD 60
~'elease Tape Cons -tent Release
mear ~ one
-,ub-Off ~ one
ilicone ContinuityNo pattern or streaks
The apparatus according to the invention comprises two components,
which may and often will not be structurally connected. The first
component is a laser printer, which is characterized in that the substrate
used (which, when the method of the invention is applied, is a temporary
substrate) carrying the reversed subject matter is passed through a heat-
setting section in which the picture is provisionally heat-set without the
application of pressure, preferably by the application of radiant heat, but
otherwise may be any type of known laser printer. The second component
is a pressure and heat-setting apparatus for transferring the reversed
picture from the temporary onto the final substrate and setting the
resulting direct picture on said final substrate, which may comprise, e.g.,
means for passing heated rollers under pressure over the juxtaposed
temporary and final substrates. If the final substrate is already bound in
booklet form, the size of pressure and heat-setting apparatus, e.g. of said
rollers, will be adapted to the size of the pages of the booklet.
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It is possible to transfer the temporary substrate with the reversed
picture from the first apparatus component to the second by hand, but it
is also possible to do it automatically by means that are readily provided
by persons skilled in the art, but an example of which will be described
hereinafter.
Laser-printed bound documents, such as passports, are part of the
mventlon.
Description of the Drawin~!s
In the drawings:
- Fig. 1 is a flow diagram schematizing the method of the invention;
- Fig. 2 is a schematic cross-section of the first component of an apparatus
according to an embodiment of the invention;
- Fig. 3 schematically illustrates the heat-setting section of the apparatus
of Fig. 2;
- Fig. 4 schematically illustrates the last step of the process according to
an embodiment of the invention;
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- Fig. 5 schematically illustrates an example of a mechanism connectingthe first to the second component of the apparatus according to the
invention; and
- Fig. 6 is an example of a reversed picture, comprising a photograph,
words and graphic signs.
Detailed Description of Preferred Embodiments
Fig. 1 is a flow diagram representing the method of the invention. As seen
therein, the original picture is scanned, by means of a scanner, which is a
well known apparatus, and is reversed by transmitting the information
provided by the scanner to a general purpose digital computer or a special
purpose processor, which elaborates the information of the scanner in an
obvious manner, thus defining the specular image of the original picture,
which is the reversed subject matter or picture. This operation is easily
carried out by persons skilled in the art and no further information is
required as to its performance. The information thus generated
constitutes the "reversed picture file", which is registered in the memory
of a general purpose or special computer which controls the laser printer.
Ways of providing the information relative to the original picture, other
than by means of a scanner, are known in the art and may be used in
carrying out the invention. e.g., the original picture may not exist as a
graphic entity and be provided from the start in the form of a processor
file.
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An intermediate substrate is fed to the laser printer. This intermediate
substrate must have a surface which has less adhesive and/or absorbent
to the colors used in the printing than the final substrate on which the
final printing is to be effected, as hereinbefore set forth. An example of
intermediate substrates are papers coated with silicones or Teflon, such
as are used for applying to them, for storage and transport, self-adhesive
stickers, but not limited, to which papers the silicone coating imparts a
smooth, non-adhesive-ret~ining surface to facilitate the removal of the
stickers. As has been said, the choice of the intermediate substrate
depends on the final substrate to be used, since all that is required from
the intermediate is that its capability of capturing and/or ret~ining the
printing colors to be used be less than that of the final substrate.
The intermediate substrate is fed to the laser printer and the reversedpicture file is used to control the operation of the printer to deposit on the
said substrate the various colors in such patterns as to form a reversed
picture in the conventional way in which this operation is carried out in
laser printers. Any type of laser printer can be used for this purpose.
After the formation of the reversed picture, however, the setting is not
carried out as in a conventional laser printer, but is carried out by radiant
or IR heating, thus producing, without the application of pressure, a
provisionally heat-set reversed picture. Said provisional setting is only
partial and not as complete as the setting normally carried out in laser
printers, but is sufficient for the reversed picture to stable enough to
permit carrying out the following steps of the process of the invention.
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Before the provisional setting, on the other hand, the reversed picture is
quite labile and would not stand the manipulations required by the
invention.
The intermediate substrate, carrying the provisionally heat-set reversed
picture, is juxtaposed face-to-face to the final substrate. This, as has been
said, does not occur in the laser printer but it may be a completely
manual operation or it may occure in a different part of the apparatus
according to the invention, which can be completely separated from the
structural viewpoint from the laser printer, or can be in some way
combined with it. At this stage the reversed picture is located between the
intermediate and the final substrate - it is sandwiched, it may be said,
therebetween. To the juxtaposed intermediate and final substrates, heat
and pressure are applied to transfer the reversed picture to the final
substrate, in which operation the picture is once more reversed and the
direct or reproduced original picture is obtained, and fully to set said
direct or reproduced original picture. In the case, of particular interest for
this invention, that the final substrate is bound in booklet form, e.g., in a
passport, the booklet is opened at the appropriate empty page, the
temporary substrate with the reversed picture is juxtaposed thereto, with
the picture being sandwiched, as has been said, between the two
substrates, and pressure is applied generally on the rear face of the
temporary substrate. This can be done by passing heated rollers on the
backside of the temporary substrate; however, other means, such as
presses or other suitable equipment, can be employed, to apply heat and
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pressure to the juxtaposed temporary and final substrates. The
juxtaposition of these latter can be effected manually, or by means of
pneumatic or other transfer equipment.
Fig. 2 schematically illustrates a laser printer according to the invention.
The laser printer is generally indicated at 10 and may be any
conventional laser printer except for the heat-setting portion, which is
indicated at 11. The conventional part of the laser printer structure is
already understood to persons skilled in the art. It comprises a feed
section 12 from which sheets are fed by means of a group of rollers 13 to a
drum 14. Printing colors are contained in powder form in containers 15.
Four containers are indicated in the drawing, since it is assumed that the
printing is multicolor printing and is carried out in the three basic colors,
magenta, cyan and yellow, plus black. Conventional means are provided
for shifting containers 15 so that each of them may come into contact with
drum 14 at the appropriate moments and transfer its coloring matter onto
said drum. A laser source, not shown, directs a lasetr beam, controlled by
digital control means, onto an octagonal mirror 16, from which the beam
is deviated according to a program and successively refelected by mirrors
17 and 18 to impinge on a drum 19, according to the patterns determined
by the reversed picture file and the controlling processor, which is not
shown. The colors are captured by drum 19 according to said patterns.
Drums 14 and 19 rotate in mutual contact and the reversed picture is
transferred to the temporary substrate that has been fed to drum 14.
This operation is repeated as many times as is required, depending on the
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number of colors of the picture. Thereafter, the print substrate, with the
picture formed thereon, but not yet set and still in a labile state, passes
through belt conveyor 20 to the provisional setting area 11, better
illustrated in Fig. 3. All the operations described so far and the apparatus
means for carrying them out are conventional and well known to persons
skilled in the art. As an example of laser printer which comprises all the
elements so far described, one may cite CLC-350 by CANON.
The setting area comprises a conveyor belt 21 which transports the
temporary substrate with the reversed picture, which is driven by a motor
22 through a tr~n.qmi.qsion chain 23, and is guided by rollers 24 and 25,
its tension being adjusted by controlling the distance between said rollers
by means of a spring 26. A paper sensor 29 qign~l.q the arrival of a
temporary substrate. Sources of radiant or IR heat, e.g. halogen lamps, 27
effect the provisional heat-setting of the reversed picture. Fans 28 are
conveniently provided to aerate the setting area 11.
The heat-set temporary pictures may be discharged from conveyor belt 21in any convenient way, juxtaposed to the final substrate and the reversed
picture is reverse-transferred to the final substrate and finally heat and
pressure-set. Fig. 4 illustrates one way of carrying out this operation,
though different ways are readily available to persons skilled in the art.
Numeral 40 represents an open booklet which may be a passport or other
document. The picture is to be printed on page 41, which is exposed by
opening the booklet. Numeral 42 represents the temporary substrate.
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The reversed picture is sandwiched between substrates 41 and 42.
Suitably heated rollers, such as roller 43, are passed along the backside of
the temporary substrate 42 and transfer the reverse picture onto
substrate 41, which is conveniently supported by means not shown,
whereby the picture is reversed and becomes a direct picture and is
detached from temporary substrate 42, absorbed into final substrate 41
and set therein. Thereafter, as has been said, a l~min~tion operation may
be carried out to cover the direct picture and the entire final substrate
with a layer of transparent plastic. Like means, of course, may be used
when the final substrate is in sheet form.
If it is desired to mechanize the last operation, various means, easilydevised by a person skilled in the art, may be adopted. For example, as
schematically indicated in Fig. 5, suction elements such as 50 may be
provided immediately after conveyor belt 20 to receive the intermediate
substrate 42. These suction elements may be box like elements provided
with a perforated upper surface 51, through which a vacuum is applied by
means of a vacuum pipeline 52. Once intermediate substrate 42 has been
delivered by conveyor 20 to the upper surface 51 of the suction element
50, this may be displaced and reversed to apply the intermediate
substrate onto the final substrate 41 (which in Fig. 5 is indicated as a
single sheet and not as a booklet, but could be part of a booklet)
whereupon the vacuum is cut off and the intermediate substrate will rest
by gravity on the final substrate 41. More than one vacuum support 50
may be provided and the entire mechanism may be synchronized so that
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the intermediate supports 42 will be delivered to the final stage of
transferring and heat-setting with satisfactory speed. However, it is often
preferable to carry out said final stage in an entirely manual manner.
Fig. 6 schematically show a picture, which could be a multicolor picture,
togehter with wordss and graphic signs, in reversed form.
While an embodiment of the invention has been described by way of
illustration, it will be apparent that the invention may be carried out by
persons skilled in the art with many modifications, variations and
adaptations, without departing from its spirit or exceeding the scope of
the claims.
