CA2146190A1 - Laser printing method and apparatus - Google Patents

Abstract

A laser printing method comprises the following steps: 1 - providing a set of digital instructions, which reverses the original subject matter to be printed to define a reversed subject matter file; 2 - providing a temporary 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 form thereon said reversed subject matter, by the appropriate steps of the conventional laser printing method; 4 - provisionally setting said reversed subject matter by radiant heat; 5 - juxtaposing said temporary substrate face-to-face with the final printing substrate; 6 - transferring the reversed subject matter from said temporary to said final substrate, whereby said reversed subject matter is reversed and reproduces said original subject matter on said final substrate; and 7 - setting said reproduced original subject matter on said final substrate by the application of pressure and heat.

Description

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 21~6190 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.

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:

3301/H/94 2 1 ~ 61 9 0 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.

3301/H/94 2lg6l9o 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.

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.

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;

- 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.

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.

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 3301/H/94 ~ 2 1 ~ 6 1 9 3 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 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.

21~6190 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 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.

Claims (17)

1. Laser printing method, characterized in that it comprises the following steps:
1 - providing a set of digital instructions, which reverses the original subject matter to be printed to define a reversed subject matter file;

2 - providing a temporary 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 form thereon said reversed subject matter, by the appropriate steps of the conventional laser printing method;

4 - provisionally setting said reversed subject matter by radiant heat;

5 - juxtaposing said temporary substrate face-to-face with the final printing substrate;

6 - transferring the reversed subject matter from said temporary to said final substrate, whereby said reversed subject matter is reversed and reproduces said original subject matter on said final substrate; and

7 - setting said reproduced original subject matter on said final substrate by the application of pressure and heat.

2. Printing method according to claim 1, further comprising laminating the final substrate carrying the reproduced original subject matter, after heat-setting the same, in order to protect said heat-set subject matter by means of a transparent plastic layer.

3. Printing method according to claim 1, wherein the operation of transferring the reversed subject matter from said temporary to said final substrate and setting said reproduced original subject matter on said final substrate by the application of pressure and heat, is carried out directly on a bound substrate.

4. Printing method according to claim 3, wherein the bound substrate is an identifying document in booklet form.

5. Printing method according to claim 1, wherein the intermediate substrate has a surface which has a weaker adhesion to the colors used in the printing than the final substrate.

6. Printing method according to claim 5, wherein the surface of the intermediate substrate is non-absorbent and non-adhesive for the printing colors.

7. Printing method according to claim 6, wherein the intermediate substrate is made of paper coated with silicone.

8. Printing method according to claim 6, wherein the intermediate substrate is made of SBL 42 MGA SILOX 8L/0 paper.

9. Laser printing apparatus, characterized in that it comprises means for defining a reversed subject matter file, as hereinbefore defined, means for controlling the deposition of colors on an intermediate substrate according to said file to form on said substrate a reversed subject matter, and means for provisionally heat-setting said reversed subject matter without the application of pressure.

10. Apparatus according to claim 11, wherein the means for provisionally heat-setting said reversed subject matter are radiant heating means.

11. Apparatus according to claim 9, further comprising a pressure and heat-setting apparatus for transferring the provisionally heat-set reversed subject matter from the temporary onto the final substrate and setting the resulting direct subject matter on said final substrate.

12. Apparatus according to claim 9, wherein the pressure and heat-setting apparatus comprise means for passing heated rollers under pressure over the juxtaposed temporary and final substrates.

13. Apparatus according to claim 12, wherein the final substrate is bound in booklet form and the size of pressure and heat-setting apparatus is adapted to the size of the pages of the booklet.

14. Apparatus according to claim 9, further comprising means for transferring the temporary substrate with the provisionally heat-set reversed subject matter to the pressure and heat-setting apparatus for transferring the provisionally heat-set reversed subject matter from the temporary onto the final substrate and setting the resulting direct subject matter on said final substrate.

15. Laser-printed bound documents.

16. Laser printing method, substantially as described and illustrated.

17. Laser printing apparatus, substantially as described and illustrated