PRINTING METHOD
INTRODUCTION TO THE INVENTION
This invention relates to a method of printing sheet like articles such as sheets of paper, card, plastics and the like including the printing of such articles with material having a generally metallic finish. The invention further relates to an application of the printing method for confidential communications.
BACKGROUND TO THE INVENTION
The use of printed material having a metallic type of finish is well known in the commercial printing industry. This effect may be achieved in a number of ways, for example by foiling where a thin metallic foil is applied to a substrate such as a sheet of paper, using heat dies (printing blocks) to transfer, under pressure, a portion of the foil onto the substrate.
Another commercial method is "bronzing". This is a wet method comprising applying finely grained metallic powder over wet printed images off a printing press - the powder is applied while the ink is wet which thus functions as an adhesive. The image is "honed" when dry to create metallic images.
Yet another method is known as "thermography" where a heat-expandable powder is applied to wet printer's ink. Once the ink is dry the image is heated and the powder expands and coalesces rises significantly off the substrate to give a metallic-embossed appearance to the image.
More recent developments to the foiling process include the selective transfer of metallic foils from a transfer sheet to a substrate carrying a previously inked surface. Thus US Patent Number 4,053,344 (Hirahara) discloses transfer of a foil having an adhesive on one side by placing it over ink which has not cured beyond the "tacky" stage. The adhesive reacts with and adheres to the ink but not to the uninked parts of the substrate. A similar process is described in US Patent Number 3,519.512 (Dawns).
The disclosure of US Patent Number 4,868,049 (Omnicrom Systems Limited) takes the technology further by providing for the transfer of metal foil from a transfer sheet onto the xerographic images on a substrate such as paper.
The summary of the invention as set out in the patent specification of the Omnicrom Patent states as follows:
"A method is provided for forming images overlaid with metallic foil. According to the method of the present invention, a sheet comprising xerographic images is provided and placed in face-to-face contact with a metallic coated transfer sheet, to form a sandwich with the xerographic images on the inside. Heat and pressure are applied to the sandwich, causing the xerographic images to become tacky and causing the metallic foil to selectively adhere to the images. The remainder of the transfer sheet is then stripped away from the resulting decorated sheet comprising xerographic images overlaid with metallic foil."
In the preferred embodiment of the invention, the metallic coated transfer sheet is provided with an adhesive of high filler content resin which has been found to produce transfers to xerographic images produced by a wide variety of toners and photocopy machinery.
Problems associated with this method include:
It results in all of the xerographic image being coated. Thus for example the process cannot be used to transfer foil into a letterhead (or part thereof) as distinct from the body of the letter if printed together with the letterhead using for example a so called "laser" printer;
the process tends to result in small enclosed areas being "filled in" with metallic foil even though no ink is present;
the raised xerographic images may be "squashed" and distorted in the pressure/heating process; and
- there is a great deal of wastage as only parts of the transfer foil are used.
Definitions
In this specification:
the term "image" means any intentionally printed mark or part thereof whether visible or not made on a substrate; the term "powder" means a powder having a colour or appearance different from the toner used in the process of the invention to create the primary images but, in use, being attracted to said toner; the term "toner type of printing process" means a printing process in which a powdered toner is applied to a substrate.
SUMMARY OF THE INVENTION
According to the invention a method of applying images to a substrate comprises the steps of:
a. applying at least one primary image/s to the substrate using a toner of a toner type of printing process;
b. applying powder to at least the primary image/s;
c. heating the toner of the primary image/s to soften the toner and bond the powder thereto.
Further according to the invention the method includes the step of removing unbonded powder from the substrate and the primary image/s.
Still further according to the invention the powder may be applied to the areas of the substrate surrounding the primary image/s and further may be applied to the whole area of the substrate.
Still further according to the invention the powder is retained on the primary image/s by attractive forces such as electrostatic forces prior to heating.
Still further according to the invention the primary image/s are metallic type images and the powder is a metallic powder.
According to an aspect of the invention the method of applying images to a substrate comprises the step of applying at least one primary image/s to the substrate using a toner of a toner type of printing process the colour of the toner and the substrate being substantially the same.
Still further according to the invention the primary image/s are applied by a facsimile or the like receiving apparatus
According to another aspect of the invention a method of printing on a substrate comprises the steps of:
a. applying at least one primary and at least one secondary image to the substrate, the primary image/s being applied using a toner of a toner type of printing process and the secondary image/s being applied using a non-toner type of process;
b. applying powder to at least the primary image/s;
c. heating the primary image/s and powder to bond the powder into the toner.
Further according to the invention the method includes the step of removing excess powder from the primary image/s and preferably the secondary image/s and the substrate.
Still further according to the invention the powder may be applied to the areas of the substrate surrounding the primary images and further may be applied to the whole area of the substrate.
Still further according to the invention the powder is retained on the primary images by attractive forces such as electrostatic forces prior to heating.
Still further according to the invention the non-toner type of process may be an ink jet or dot matrix or other fast drying ink type of process.
Still further according to the invention the powder is a metallic powder.
According to another aspect of the invention a method of printing on a substrate comprises the steps of:
a. applying primary images to the substrate using a toner of a toner type of printing process;
b. applying powder to at least the primary images;
c. heating the primary images and powder to bond the powder into the toner;
d. removing excess powder from the substrate; and
e. applying secondary images to the substrate.
Further according to this aspect of the invention the secondary image/s are applied using one of a toner and a non-toner type of process.
Still further according to the invention the powder may be applied to the areas of the substrate surrounding the primary image/s and further may be applied to the whole area of the substrate.
Still further according to the invention the powder is retained on the primary image/s by attractive forces such as electrostatic forces prior to heating.
Still further according to the invention the non-toner type of process may be an ink jet or dot matrix type of process.
Still further according to the invention the powder is a metallic powder.
According to a further aspect of the invention apparatus for applying images to a substrate comprises:
a. first means for applying at least one primary image to the substrate using a toner of a toner type of printing process;
b. second means for applying powder to at least the primary image/s;
c. third means for heating the primary images and powder to bond the powder into the toner.
Further according to the invention the apparatus includes fourth means for removing excess powder from at least the primary image/s.
Still further according to the invention the second means is adapted to apply the powder to the areas of the substrate surrounding the primary image/s and further may be applied to the whole area of the substrate.
According to a further aspect of the invention apparatus for printing on a substrate comprises:
a. first means for applying at least one primary and at least one secondary image to the substrate, the primary image/s being applied using a toner of a toner type of process and the secondary image/s being applied using a non-toner type of process;
b. second means for applying powder to at least the primary image/s;
c. third means for heating the primary image/s and powder to bond the metallic powder into the toner.
Further according to the invention the apparatus includes fourth means for removing excess powder from at least the primary images.
Still further according to the invention the second means is adapted to apply the powder to at least the areas of the substrate surrounding the primary image/s.
Still further according to the invention the means for applying powder is means for applying a metallic powder.
The invention also provides a substrate in the form of a sheet of paper the paper being characterised in that the major portion of at least one side thereof is of a colour, with a relatively small area, being of a contrasting colour.
Still further according to the invention the colour of the major portion may be black or white.
Still further according to the invention the colour of the major portion is substantially identical to that of the colour of the primary image/s to be printed thereon.
Still further according to this aspect of the invention the paper has a textured finish which is preferably an embossed finish.
Still further according to the invention the paper may have a printed finish with the printing comprising a jumble of at least one of characters, letters, numerals or the like.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings:-
FIG. 1 depicts sequentially the stages of a first embodiment of a printing process according to the invention;
FIG. 2 depicts sequentially the stages of a second embodiment of a printing process according to the invention;
FIG. 3 depicts sequentially the stages of a third embodiment of a printing process according to the invention;
FIG. 4 is a flow diagram of an embodiment of an apparatus according to the invention; and
FIG. 5 depicts sequentially the stages of a communication system embodying the invention.
DETAILED DESCRIPTION WITH REFERENCE TO THE DRAWINGS
In these embodiments and examples of the invention apparatus for and methods of printing standard sized rectangular sheets (1) of paper are provided.
In the first example of the method of printing the six sequential steps that the sheet (1) undergoes are shown in figure 1.
In this first method figure 1 a shows a sheet (1) to which no images have been applied. The first step of the method as shown by (1 b) is to apply a logo (2) (by way of example) to the sheet using a standard toner type of printing such as the xerographic or laser type. This primary image (2) thus consists of a layer of black or other coloured toner which is applied to the paper using known technology.
Thereafter in the third step of the process as shown by (1c) secondary images (3) are applied to the same surface of the sheet. These secondary images (3) may be in the form of writing, diagrams and the like and may also be close in position to and indeed fall within the boundaries of the primary image (2). It is important to note that the second images are not applied using toner processes such as xerographic or laser printing technology but are applied using other types of technology such as ink jet dot matrix printing or other fast drying inks. The reasons for this will become clear in subsequent steps.
Once the primary and secondary images have been printed on the sheet (1 ) the sheet is subjected to finely divided metal powder which may be dusted onto the sheet for example. This step is shown in Figure 1d in which the powder (4) covers the sheet in a thin layer. It is to be noted that the powder has an affinity to images printed using toner types of printing processes and thus has an affinity to the primary images (2). For this reason instead of dusting the sheet (1) the sheet may simply be brought in close proximity to the powder (4) which will immediately adhere to the toner of the primary images.
After adhesion of the metallic powder (4) to the primary image the sheet is subjected to a heating process which "fixes" and hardens the powder to the primary images but not to the secondary images. This is because in the first place the powder has a preferential attraction to the primary images and in the second place the heating process causes the toner of the primary images to melt slightly thereby providing a permanent bond between powder and toner. This is shown in figure 1e.
Finally the excess powder (4) is removed from the sheet by a brushing or blowing process to give a final product in which the sheet contains printed images with the primary printed images having a metallic appearance and the secondary images having remained in the ink in which they were originally printed.
A second embodiment of the invention is shown in figure 2.
In this example (2a) shows a sheet (1) of plain rectangular paper as was the case in the example of figure 1. In the second step the sheet (1) is imprinted with a primary image (2) using the same technology as the first embodiment.
The third step as shown by figure 2c this primary image is subjected to finally divided metallic powder (4) and in the fourth step (figure 2d) the "fixing" process takes place using heat to melt the toner of the primary image (2).
Once the excess metallic powder (4) has been removed in the fifth step (figure 2e) secondary images (3) are printed on the sheet (1) as shown in figure
2f. These secondary images are applied in the same manner as for the first embodiment.
In the third example the sheet (1) is printed with secondary images (3) in the second step (figure 3e) using non-toner and non-laser technology and thereafter the primary image (2) is printed in the third step (figure 3c). Once this has been done the process is the same as the first example of the remaining three steps shown by figures 3d, 3e and 3f respectively.
The invention thus provides firstly for a method of printing primary images on substrates the primary images having a metallic finish. It will readily be appreciated that the metallic finish may be one of a number of finishes such as gold, bronze, silver etc. Secondly the process allows for the metallic images to have non-metallic parts. This is achieved simply by printing a combination of primary and secondary images. It will be appreciated that the metallic powders will only adhere to the primary images. Thirdly the combination of secondary and primary images allows for the creation of printed substrates with a vast number of uses. It will readily be appreciated that metallic and composite metallic and non-metallic letterheads may be produced at substantially the same time as printing text on the substrate.
The invention also provides an apparatus for the above described printing process. This apparatus is described with reference to figure 4 which shows a component and flow diagram of a standard type of apparatus.
The apparatus includes a bin and feed means (11) for holding and feeding sheets of paper through the apparatus. These sheets are fed to a laser printing means (12) where they are printed with primary images as described above. After printing of these primary images the paper is fed to an ink jet printing means (13) where secondary images are printed these secondary images may include portions of a logo combining primary and secondary images.
After printing of the first and secondary images the primary images are subjected to a finely divided metallic powder in a powder dusting means (14). The powder adheres to primary images only and the sheet is then fed through a heating
means (15) which heats the sheet and primary and secondary images thereby softening the toner of the primary images to provide a permanent bond for the metallic powder. This heating may be effected by radiant heating or hot air for example which may be a universal method of fixing the powder to the toner while simultaneously removing excess powder from the substrate.
The excess metallic powder is then removed by a powder removal means (16). It is envisaged that if the heating is done by hot air the excessive powder has been removed already. Once the powder has been removed the sheet is fed to an out bin (17).
It will readily be appreciated that the invention provides a printing means with a great number of potential uses. For example in an office environment a single printer would be used to provide stationery brochures and other documents having a combination of metallic and non-metallic printing. Thus a letter may be produced on the machine at the same time with the letterhead which may be metallic or partially metallic in produced at substantially the same time as the text which may be in heavy design coloured ink.
Figure 5 of the drawings shows the steps in a confidential communication system including the printing method of the invention.
In this system a receiving fax machine (toner type - not shown) is loaded with a substrate in the form of sheets of black paper (21). The whole page is black-faced to match and blend with black toner both in colour as well as texture.
However, an addressing strip is required at the top of each page. To accommodate this titling and addressing facility, a 15 to 20 mm (say) strip is included, having a contrasting colour for both black as well as white - the ideal colour in this instance is grey, since both white over grey and black over grey is perfectly visible. This ensures that the titling and addressing details will always be visible, no matter at what stage of process the page is. When an incoming fax is received it is printed with black toner on the black paper (21) and is thus invisible to the naked eye, except for the name, address and page number which is visible at all times over the grey heading strip. The black paper as described above is suitable for confidential communication such as plain paper fax, inter-office
communication via copies photocopied onto the black paper, or information emanating from computers and printed via laser printers onto the black paper.
The printed sheet of paper (2) is then removed from the fax machine and taken to the intended recipient. This recipient then processes the paper (22) further by passing it through a machine which exposes the printed paper (22) to a powder being of a colour which contrasts with black (e.g. white, silver) and which powder is attracted to the toner of the now visible (and contrasting) printing. The page with toner and powder is then heated to bond the powder into the toner as shown in 5d. Thereafter the excess powder is removed to provide visible and permanent images or writing (23) on the black paper (21).
The processed page (white image over black background) may also be conveniently and economically changed back to read "normal" i.e. black image over white background by means of reverse (negative) scanning the page with existing electronic scanning/imaging equipment. However, the processed page (white over black) is extremely sharp and legible and should generally require no further process and by simply photocopying this processed page onto the system's black substrate (with its pertinent specifications intact) will render it "invisible" once more - with the added advantage of being able to file or store (even messenger hand deliver) this document in its confidential mode.
Should it be desired to have this printing as say black printing on white paper (i.e. reading "normal") the printed paper (21) of step 5d may be photocopied onto white paper. Although this page resembles the sheet it was photocopied from, there is a significant difference - the former black page (background) has now become a toner image and is receptive to white or contrasting powder. The former (white) images in their turn are now "non-images" since their white-visibility is now simply the white paper showing through via the white paper used to make the photocopy. A permanent hard copy ("standard" toner copy) of this last process can be made by simply photocopying once more onto white paper. Needless to say, all visible pages can be confidentially processed many times over again, simply by printing out onto the black paper.
In a further example the above black paper is substituted and white paper is used. The grey addressing strip remains at the top. The receiving fax apparatus utilises matching white toner. The processor has black or suitable dark coloured metallic powder and the white/white page is processed as with the black paper. The received fax is received as follows: the white toner is visible over the grey strip but the balance of the page contents being white on white is thus invisible. After processing with say black powder the page appears as follows: the addressing/titling grey strips shows these details in black (over the grey). The balance on the contents of the page reads black over white background - the white toner is now covered and fixed as black. This page can then be reverted back to confidentiality by making a copy via the white toner in the fax machine, using the same paper as loaded.
The invention allows for any further existing or future electronic confidential adaptations and/or equipment to run in conjunction with it since it is the final carrier of the image (the printed page) and is as such, non-electronic. Memory and codes, ID codes, etc. may be incorporated into the fax machine to enhance confidentiality.
The substrate in this case is ideally a text type paper, roughly 80 gsm weight with a grey (50% white, 50% black) addressing strip at the top to bleed top and sides, approximately 13mm deep (enough space to accept adequate titling and addressing details, as well as page and telephonic details/status). Recognition codes are impregnated or printed onto the substrate (the paper) during its manufacture. This is telephonic technology as it exists (code recognition) and it enables the receiving page to print the codes in a recognisable form. This is a simple security measure to guard against possible substitution of the paper. Furthermore the major portion of the paper may be printed with a jumble of characters such as letters, numerals, figures etcetera. This printing is effected in the same colour as that of the toner in the necessary fax apparatus. Furthermore the paper may also be embossed.
In general use, the addressing strip is hardly any loss of typing or imaging space on the page, since it is less than the average space used as a margin between the page top edge and the first line of typing or image.
The fax machine is the plain paper, toner image type, modified to suite requirements and specifications of this invention.
As it is universally accepted, most text and drawing correspondence or imaging is done in black on white. Any other colour or combination of colours, generally from dark on the one hand to light on the other, may also be incorporated, provided there is enough contrast between original document and converted document and incorporates a midtone (i.e. approximately 50% of each colour, or other "tint" as the background strip which enhances or makes visible such "camouflaged" addressing images.
Other embodiments are envisaged within the scope of the invention including apparatus designed to incorporate any of the preferred printing examples or for printing other substrates.