AU610614B2 - An anti-copying medium for writing or printing, and associated method - Google Patents

Description

1.25 .4 1.6 Z),XMAniSddONW1 ArIH0 1 UA V 'Id 8 o68L9917CsL I ZAXMAnjsj bdou w Ij!q 619p~q Z~kXMAnisNOdONW~mrIH0d9o3:2V 'Id 01 1.25 14 1 A I i i I I I j P R~ -w COMMONWEALTH OF AUSTRAL& 0 6 PATENTS ACT 1952 COMPLETE SPECIFICATION FOR OFFICE USE Form Short Tttie: Int. Cl: Application Nuoiber: Lodged.

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Name of Applicant: Address of Applicant: Actual Inventor: Address for Service: S. A. V1C A.T Tou~r Gan 16, Place de l'Ils, 92082 COURBEVOIE LA DEFENSE 2, FRANCE Rene Gautron and Pascale Escaf'fre GRIFFITH HACK CO.

71 YORK STREET SYDNEY NSW 2000

AUSTRALIA

'Complete Specification for the invention enltitled-, AN ANTI-COPYING MEDIUM FOR WRITING OR PRINTING, AND ASSOCIATED METHOD The following statement is a full description of this invention, including the best method of performing it known to me/us:- 729 1A:rk AN ANTI-COPYING MEDIUM FOR WRITING OR PRINTING, AND ASSOCIATED

METHOD

The present invention relates to protecting authentic documents (confidential, secret, title deeds, documents which are negotiable or otherwise, all or parts of valuable publications (books, magazines, reports, or any other document against copying, including fraudulent copying, by means of a photocopier, for example of the electrostatic or of the xerographic type.

10 BACKGROUND OF THE INVENTION Because of the easy access to xerographic or electrostatic.

copying machines, and given their ease of use and low reproduction cost, very widespread non-authorized and indiscriminate copying of documents is taking place more and 15 more. This may be prejudicial to the authors of the documents, for example enabling secrets to be divulged or infringing the legal rights of the authors.

The term "original document" is used herein to designate a any document that may be photocopied. Such an original document is constituted by a macromolecular type of medium having graphical information (text, drawings, thereon.

The graphical information is applied on or in the medium by any of the available graphic arts techniques.

Numerous French and foreign patents disclose means for 25 mitigating such unwanted copying. Thus, proposals have been made to use highly-colored special paper for original documents (Canadian patent CA-A-1187914 and US patent US-A-3 887 742).

Such paper is commercially available. Howc7,9r, in such cases the contrast between the graphical information and the background color of the special paper is low, thereby making the original document difficult to read and giving rise, over a period of time, to eye fatigue which may be considerable or even unbearable.

Numerous other patented means may also be mentioned which are not being industrially manufactured at present. This list is not exhaustive: original documents which are reflective (metallized paper); original documents which are luminescent; r' r 2 special markings; documents which are photochromic; This invention is particularly concerned with photochromic documents manufactured using photochromic substances.

It is known that such photochromic substances (or "photochromes" for short) have the property of imparting reversible coloring to the medium under the influence of visible or ultraviolet electromagnetic radiation (at a wavelength which generally lies in the range 200 nanometers (nm) to 800 nm).

1 10 Reversible photocoloration may be described in outline as *000 color passing from a state A to a state B under the effect of active electromagnetic radiation, and returning from state B to state A in the absence of said radiation.

States A and B have quite distinct spectral 15 characteristics. Thus, state A may be colorless and absorbent in the ultraviolet, which implies that active wavelenghts for inducing photocoloration are specifically in the ultraviolet.

When excited by a source of ultraviolet light, the passage from Oil. A to B takes place. B may be colored and thus absorb in the visible. By using such a substance, it becomes possible to have an original document on which the graphical information is distinguished from the background by very adequate visual contrast under normal illumination, but in which the background S..acquires very marked coloration under suitable irradiation.

25 Reference may be made to the following patent specifications GB-A-l 227 201, US-A-3 597 082, and DE-A-2 419 278.

These patents relate to using photocopiers provided with special lamps suitable for exciting photochromes that absorb in the ultraviolet.

Japanese patents JP 6053981 and 6079992 include detailed examples which specify spiropyran, and in particular the compound trimethyl-1',3,3' indolino spiro-2' nitrobenzopyran. It is not possible to activate this molecule sufficiently on a conventional photocopier to obtain a significant effect, even when it is used in high concentrations. The limiting factor is the energy delivered Lby the photocopier in the range of wavelengths susceptible of being absorbed by said molecule, i.e. shorter than 350 nm.

-L -I The glass which supports the document being copied itself filters out all radiation at less than 320 nm. The available energy between 320 nm and 350 rn is very low, regardless of the type of machine used.

The object of the preferred embodiThrnt of the invention is to propose a novel means for causing any photocopy to be unreadable or to differ from the original by using a photochromic system which is sensitive to the radiation delivered by lamps in conventional photocopiers.

SUMARY OF THE INVENTION This object is achieved, according to preferred embodiment of the invention, by associating at least one photosensitizer with at least one photochrome in the photochromic system.

o The energy received by a document when being photocopied lies mainly in the visible and in the near ultraviolet. The 0* 15 function of the photosensitizer is to absorb radiation in the *visible or the near ultraviolet and to excite the photochrome by transferring energy and thus causing it to become colored.

The term "photochromic system" is used herein to designate one or more photochromes or the association of one or more photochromes and one or more photosensitizers, optionally combined with a colorant is a pigment.

It has been observed in the context of the present invention that some photochromes may interact with the document medium (film, paper, Thus, for example, spiropyrans react with cellulose or paper additives to give rise, either by :chemical bonding, or by solvation, or by physicochemical interaction (absorption, Van der Walls bonds, to photochromic systems which are difficult to control (coloration, or which are even non-photochromic. It will readily be understood that by using such photochromes, it is difficult to obtain processes which are industrially reliable.

According to the invention, the photochromic system is incorporated in the medium in an individualized manner.

The term "incorporating in an individualized manner" is used to mean that the photochrome is integrated in the medium in such a manner as to prevent the interactions mentioned above.

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4 The medium may be of the paper type or it may be constituted by a polymer film. The invention extends, in particular, to cover a medium constituted by a transparent or translucent film having one face which is sticky for the purpose of being applied to a paper (or other) backing on which the graphical information is marked.

As mentioned above, it is generally possible to prevent photocopying using a photocopier of the xerographic type, for example by using specially colored paper. This method has been oo,~ 10 developed over a long period of time, and its basic ideas are briefly sumimarized below.

Most ordinary paper copiers use: too firstly, a light irradiation system (lamp, flashtube, having a well-defined spectrum energy distribution; and 15 secondly, a photoreceptor system for receiving the image of the original, with the sensitivity of said system varying as a function of the wavelength under consideration in the emission spectrum of the lamps.

With xerographic type copiers, the receptor varies depending on the machine: selenium; zinc oxide; cadmium 0 *allsulfide; or organic substainces (polyvinyl carbazol).

The quality of a photocopy depends on the contrast between the background of a document and its graphical information.

The contrast which appears to the eye is not the same as the 25 contrast detected by the optical system of the photocopier.

For any given association of background (colored or otherwise) and foreground, the quality of the photocopy depends on the emission spectrum of the photocopier's illuminating lamp and the spectral sensitivity of the photoconductive elements of the machine (in monochrome).

Light radiation striking an opaque medium may be absorbed or returned. The term "returned radiation" covers both diffused and reflected radiation. Any ray returned to the photoconductive element of the machine locally disturbs the charge density thereon, thus giving rise to white in the photocopy. When the medium is colored and the marking on it is black, for example, then the quality of the copy will depend on the color of the medium and on the sensitivity of the photoconductive element to the wavelengths actually returned by the original.

Some types of photocopier copy well from a blue background, but have difficulty with red or yellow. Other machines photocopy well with yellow but have difficulty with blue.

When performing single-color photocopying with black, it can immediately be seen that, depending on the photocopier, yellows or blues do not mark on the photocopy; only reds can be 10 relied on to mark the copy. However, in color photocopying based on trichromatic (or tectrachromatic) principles, these phenomena have been taken into account and they have been compensated for technically.

The following reasoning is based on monochrome photo- 15 copying using black), and extra details will be specified, where necessary, for color photocopying.

The patents CA 1187914 and US 3887742 make use of colored paper having a dominating red color to make a document non- @9..,.'photocopyable. The photoconductive element is not sensitive to the wavelength returned by the colored medium. So far as the photocopier is concerned there is no contrast between the medium and the markinc.s thereon, and as a result the copy is black.

The contrast of an original may be altered while photocopying is taking place if a photochromic system is added to 25 ce paper and changes its color under the effect of the illumination provided by the illuminating lamp of the photocopier. In this case, the photochromic system alters the radiation returned by the medium during the photocopying process. As mentioned above, "returned" radiation covers both diffused radiation and reflected radiation.

The coloration of the medium while photocopying is taking place should give rise to substantially zero contrast for the photocopier.

By combining a colored background with a photochromic system, a stronger effect may be obtained. However, adding photochromic substances to paper may make it possible to use a basic medium which is paler, or even to use paper which is

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6 white, providing the coloration effect of the photochromic system is strong enough to eliminate contrast between the medium and the markings thereon during photocopying.

It is therefore proposed to use a medium for the original document which may optionally be colored using a mixture of blue, yellow, and red (or even a small amount of black), but in such a manner that the visual contrast between the colored background and the printed markings is good so that the document is properly readable.

10 The desired intense or pale coloration depends on the relative proportions of the various basic colorants, which proportions depend on the nature of the photochromes used. As already mentioned, it is also possible to omit using any colorant.

In theory, any photochromic substance may be used in the 0 15 invention, regardless of whether it is in the solid state or is usable in solution. The term "solution" covers both solid solution and liquid solution. Thus, any substance incorporated in a polymer system is considered as being a solution.

6* .o The following constitute a non-exhaustive list of possible photochromes: Silver salts; metal oxides; mineral complexes; mineral glasses; nitrons; polymethane cationic colorants; tetrachloroketo dihydronaphthalane; sydnones; indigo derivative colorants; spiradihydroindolizins; indenone oxides; fulgenic anhydrides; 25 dianthrones; azobenzenes; triphenylmethane derivatives; metallic dithizone derivatives; spiropyrans; spirooxazines; These photochromes should preferably have good photocoloration capabilities (photocolorability) when subjected to the radiation emitted by photocopiers. As a general rule, this irradiation is at wavelengths greater than about 360 nm, It so happens that many photochromes respond poorly to such wavelengths, and thus have poor photocolorability. It is possible to give them good photocolorability by using photosensitizers which are sensitive at wavelengths longer than 360 nm and which serve to transfer the energy they absorb to the photochromes, thereby activating (coloring) them. The rules of photochemistry indicate how to adapt a photosensitizer suitably to the substance (photochrome) to be activated.

i I 7 Any known photosensitizer may be used. However, for organic substances, specific mention may be made of the derivatives of the following substances: benzene; acetone; xanthone; acetophenone; benzophenone; 1,2,3,4 dibenzo naphthalene; anthraquinone; Mischler cetone; naphthalene; chrysene; biacetyl; benzil; pyrene; anthracene; perylene; metallic complexes; They must be intimately bound to the photochrome under properly specified conditions, which means that a special implementation technique as described in detail below should be 10 used. In particular, the photosensitizer may be associated with the photochrome by grafting.

The photochromes may be used as such if they are solid, and they may be dispersed in the macromolecular medium of the original document. Unfortunately, it is often necessary to use 15 an auxiliary medium, in particular for certain sensitized photochromes. One problem is that the photochrome or the sensitizer may react with the macromolecular medium of the original document.

As a general rule it is therefore necessary to avoid interactions by putting the photochrome and its additives in or on a medium which is individualized relative to the remainder of the macromolecular medium of the original document.

This individualization may take place as follows: by means of a layer of polymer or varnish; 25 by plastic microbeads; by microcapsules; or by insoluble micromedia.

The invention therefore proposes an anti-copy original document medium which may optionally be colored and which is provided with a photochromic system sensitive to the energy delivered by the lamps of photocopiers. The photochromic system is individualized relative to the document medium so as to: obtain an optimum effect between the photosensitizer and the photochrome; and to avoid any interaction or reaction with the document medium.

8 The invention also provides a personalized document medium (checks, theater tickets, which is detectable by a color change under the influence of light radiation.

Each of the methods of individualization is now considered in detail.

1) A layer or film of polymer, varnish, paint, or ink.

The photochrome and the photosensitizer(s) are dissolved together with stabilization additives in a plastified polymer.

The result may be deposited: S* 10 a) on the macromolecular medium, either in the form of a film or using a solution in a common evaporatable or polymerizable solvent. This deposit may be performed over the entire surface or else over a portion of the surface only, for example in the form of a pattern.

15 b) mixed in the body of the medium.

Any polymer may be used, in particular film-forming polymers: polystyrene; polyesters; polyurethanes; polycarbonates; polyvinylic polymers; acrylic polymers; 2) Photochromic microbeads.

Plastic microbeads are formed containing the photochrome, I the photosensitizer(s), additives, polymer(s) and plastizicers.

The result may be obtained using conventional methods for making polymer microbeads: S a) by incorporation prior to polymerization of the *9 25 monomer(s); b) by diffusion into prefabricated microbeads using an evaporatable intermediate solvent, which is a good solvent for the photochrome and the other additives but which is merely a swelling agent for the polymer. The solvent is naturally evaporated off at the end of preparation. These microbeads may then be incorporated in the macromolecular material that constitute the basic medium of the original document.

Photochromic polymer microbeads may be prepared as follows. Microbeads are added to a photochromic solution containing, inter alia, a plasticizer, with the beads being added either in the dry state or else in the form of an aqueous suspension, and the mixture is stirred more or less slowly.

L~III i..J _I-1 .i c ripil _i I The stirring and the stirring time depend on the polymer substance and on its starting state. The degree of swelling is monitored using a microscope. The diameters of the microbeads must not swell by more than 1.5 to 2 times the initial mean diameter. As soon as swelling is deemed to be satisfactory, the mixture is filtered and the swelling solvent is eliminated by stirring the mixture at ambient temperature. A variant consists in spraying the mixture into a vertical tube using warm air and in recovering the photochromic microbeads in a 10 cyclone separator. Any other drying method may be used. After the swelling solvent has been eliminated, the photochromic microbeads should contain plasticizer. The photochromic microbeads prepared in this way are then incorporated, for example in an aqueous coating solution.

15 3) Photochromic microcapsules.

The preparation of microcapsules is known and any of the well-mastered manufacturing methods may be envisaged. In general, the photochrome(s), the photosensitizer(s), the additives, the polymer(s), and the plastizicers are dissolved in a common solvent having a high boiling point. The solution obtained in this way is dispersed under violent stirring in a immiscible secondary solvent water) optionally in the presence of a wetting agent, thereby forming an emulsion or a microemulsion, after which chemical agents are added for 25 forming insoluble macromolecular skins around the microdroplets constituting the emulsion by virtue of an interface reaction.

The microcapsules obtained in this way are separated by physical means from the secondary solvent and are optionally dried. The microcapsules can then be incorporated in or on the base material of the original document medium. The advantages of microcapsules lie firstly in individualizing a complex photochromic system containing, in this case, a solvent which plays an active role in the photochromic mechanism, and secondly in better control of the parameters which affect the photochromic effect, such as the concentrations of the substances used.

The manufacture of microcapsules requires a solvent having a high boiling point, low vapor pressure, density fairly close to unity, low absorption in the ultraviolet and in the visible (X max 320 nm), which is a good solvent of the photochromes, the photosensitizers, the additives, and the polymers, and which is not iriscible in polar solvents such as water, alcohols, Non-limiting examples include: aromatic derivatives which may optionally be hydrogenated (e.g.

hydrogenated terphenyl, cymene, Tetraline (Tetrahydro 10 naphthalene), Decaline (Decahydro naphthalene), esters which are sometimes used as plastizicers for plastics (e.g.

dioctyl phthalate, butyl laurate, butyl stearate, and .ethers diglyme diglycol methyl ether), diethylene glycol dibutyl ether, 15 The photochrome(s), the photosensitizer(s), the additives, the polymers, and the optional wetting agents are then put into solution, by heating, if necessary. It should be observed, that the term "additives" covers any of the substances that may 9* be needed to ensure that the photochromes operate properly, as described in the technical literature and also for ensuring stability in the other substances used (antioxydants, The use of polymers is advantageous since it increases the viscosity of the photochromic solution and makes it possible to develop its photochemical properties. Suitable polymers (or 25 co-polymers) include the following: polysytrene; polyvinyl chloride; methyl polymethacrylate; methyl polyacrylate; polyurethanes; polyimides; polyoxyethylene glycol; acetal polyvinyls; gelatin; rubbers. The concentrations of the various substances vary depending on their natures and on the desired effect, and it is difficult to lay down limits.

Microcapsules may be prepared using the following two modes of operation, for example: 1/ Incorporate 40 ml of photochromic solution at 55xC in 180 grams of 11% gelatin in aqueous solution likewise at 55xC, by violent stirring. Add 180 g of 11% aqueous gum arabic with a pH of 9 to the emulsion together with 630 g of water, still at t 6 0 0O*o e k 0

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I 00 w 00 11 While still stirring, the mixture is cooled rapidly to in the presence of 10 ml of 25% aqueous solution of glutaraldehyde.

After one hour, 15 ml of a solution of maleic anhydride ether polymethylvinyl copolymer is added and the mixture is stirred for one hour prior to adding 5 ml of a 20% solution of sodium carbonate together with the quantity of 10% aqueous sodium hydroxide required to bring the pH to The resulting dispersion is then ready for use.

10 2/ A mixture A is constituted by: g of urea-formaldehyde precondensate having 45% active resin and 35% solid matter content; 60 g of melamine-formaldehyde precondensate having about 76% active resin and about 71% solid matter content; 15 240 g aqueous solution of 20% acrylamide copolymer and acrylic acid; and 850 g of distilled water.

200 g of water is added to 800 g of said mixture A, and then under rapid stirring 800 g of photochromic solution is incorporated therein. Thereafter the remainder of mixture A is added together with 1400 g of distilled water as a diluant.

Stirring is continued for 30 minutes and then the pH is adjusted to 4.7 using acetic acid. Stirring is continued for another 30 minutes. The entire mixture is then raised to in a water bath and stirring continues for 2 hours at this temperature. It is allowed to cool slowly for 5 to 6 hours.

The pH is then adjusted to 10.0. This provides a solution o2 microcapsules ready for use.

4) Insoluble photochromic micromedia.

Micromedia exist in the form of powders constituted by solid microparticles which may be of inorganic origin (microbeads of silica, zeolite, molecular sieve, or of organic origin, e.g. based on cross-linked polymers (styrenedivinylbenzene copolymer). These minicromedia either have cavities (pores) in which chemical substances can be received, or else they have adsorption properties enabling them to retain chemical substances by a physicochemical interaction. Mixtures ,It 11 9~ *m

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4* ~4 .*4 I. 9 ~S *9 454' '4 59 4 .9 S 12 constituted by photochromes, photosensitizers, additives, and polymers can thus be deposited either on or in such micromedia.

The photochromic mixture can the-i be incorporated either on or in the base material of the original document medium.

Micromedia are prepared from particles of photochromic solids. These particles are obtained by mixing solid microparticles (3 jm to 5 Jm) in a photochromic solution as described above. The resulting nixture is fluid in appearance with each microparticle being individualized. The micro- 10 particles can then be coated as follows. The photochromic microparticles are dispersed in a polyvinyl alcohol suspension (having film-forming hydrosoluble properties) in water in the presence of a wetting agent. The mixture is stirred in a vane mixer for about one hour. Microscope inspection is then 23 performed to verify the quality of the coating. The suspension may be used directly or it may be filtered and dried under stirring. This preparation may use the following proportions: photochromic microparticles 10 to 30 parts polyvinyl alcohol 1 to 5 parts wetting agent 0 to 0.1 parts water 60 to 90 parts Other methods of coating may be used.

The anti-copy method of the invention can now be described. It consists in naking a special macromolecular 25 medium for use in preparing the original document by printing graphical information using conventional means: typewriting, offset printing, letter press, laser printing, ink jet printing, photocopying, manual drawing, This medium is manufactured using the principles explained above in detail, and given that the original documents need not be colored if the photochromes used cover the entire spectrum range so as to make photocopying illegible.

It may be observed tnat it is possible to combine the various individualization systems and also to use a plurality of photochromes having different chemical structures, and that it is possible to incorporate colorants in the individualizatio n system, if necessary.

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es 5 9 9*e The method proposed is effective particularly against single color photocopying (black). When color photocopying is being performed (trichromatic or tetrachromatic) it causes the colors to be greatly changed thus making the photocopy unlike the original, The special medium may be of various forms, but in most cases it is plane, thus facilitating its utilization. In the majority of cases, it is constituted either by a transparent, a translucent, or an opaque plastic film, or else by a sheet of 10 paper.

The special medium of the present invention is thus constituted by optional colorant, by photochromes, by photosensitizers, and above all by a background medium. This background medium is thus: 15 either a plastic film made using conventional techniques, and suitable polymers include, for example, cellulose and derivatives thereof, polyvinyl chloride, polyolef ins, copolymers of polyolef in and vinyl polyacetate, polyesters, polyvinyl acetates, polycarbonates, rubber hydrochlorides, or else papers having a fiber structure: paper based on natural fibers (such as cellulose); paper based on synthetic fibers (such as regenerated cellulose or polypropylene).

After manufacture, such papers generally also contain additives and fillers.

The special medium is manufactured by conventional means appropriate to each type oi material. The individualized photochromic systems and colorants may either be incorporated in the bulk of the medium, or else deposited on its surface, e.g. by coating.

The colorants used must be compatible with the polymer material of the background medium. For an opaque mediumn, it is possible to use pigments. For ordinary cellulose fiber based paper, the following base colors may be used, for example: blue yellow red brown black, as manufactured, for example, by any of the following companies: BAYER, BASF, SANDOZ, and CIBA.

14 Naturally, colored paper can be obtained equally well by using pure pigments or a mixture of pigments.

The dyes and the pigments may be encapsulated and deposited by coating.

Colored pigments may be incorporated in the photochromic preparation, thus giving rise to a photochromic paint. In this case, coating may also take place by using a brush over small areas or over the entire area.

Original documents obtained from anti-copy media. take on a -temporary auxiliary coloration during photocopying. This coloration is due to the photochromes and lasts for a length o~f go.

*064 time which varies depending on the substances used. Thus, after being photocopied, original documents return to their original appearance.

15 There follow a few examples of special media for making non-photocopyable original documents in accordance with the invention.

em In general, photocopies are made on three types of xerographic machine using a single color (black), and these types of machine illuminate the document usin~g either: goo* a flashlamp; a tungsten halogen lamp; a fluorescent tube.

*.*Photocopies obtained using single color photocopiers (e.g.

S 25 black and white) can be analyzed by measuring the contrast between areas corresponding to the background (the medium) of the original document and areas corresponding to marking. This measurement can. be made in two ways: 1/ visually on an original document including text. In this case, it is observed that the photocopy is illegible; or 2/ technically on an original document including a single.

black band. In this case, a reflectometer or a microdensitometer is used to measure the difference in reflection or absorption between the two zones formed.

When color photocopying is concerned, the test is purely visual.

-llZ LLc WIL-Hull are not being industrially manufactured at present. This list is not exhaustive: original documents which are reflective (metallized paper); original documents which are luminescent; EXAMPLE 1 An anti-copy paper including brown coloration (Pantone 173 C) (where Pantone is a registered trademark) and photochromatic microcapsules is manufactured as follows: the paper used is based on cellulose with conventional fillers; the photochromic microcapsules are manufactured from hydrogenated terphenyle having dissolved therein trimethylindolino 2' spiro- 2 nitro 7 naphtho pyran 10 at a concentration of 4.10- 2 Moles, and dihydroxy 1,2 anthraquinone at a concentration of 2.10-1 Moles using abovedescribed operating method No. 1.

These microcapsules are deposited in a coating using a binder (starch, polyvinyl alcohol, to a thickness of about 15 10 micrometers, i.e. 10 g per m 2 of paper.

After printing a text in black on this anti-copy paper, "o and photocopying it on the three single-color (black) types of photocopier, the resulting photocopies were illegible and had the appearance of a uniform black background.

i '20 Contrast measurement on the photocopies using a reflectometer showed up no difference between the background and the markings.

The original brown document is perfectly legible.

After being illuminated by the photocopiers, the original document returns to its original coloration after about seconds.

When photocopied using an electrostatic type of color photocopier, the copy had a blue cast compared with the original document.

EXAMPLE 2 An anti-copy paper having dark orange coloration (Pantone 166C) and photochromic microcapsules was manufactured as follows: the paper used was based on cellulose having conventional fillers; L, 16 the microcapsules were made from hydrogenated terphenyl with, dissolved therein, trimethyl indolino 2' spiro 2 dibromo 6,8 benzo pyran at a concentration of 5.10 2 Moles, amino-4 acetophenone at a concentration of 2.10- 1 Moles, and 3% polystyrene of average molecular mass using above-described operating method No. 2.

The microcapsules were deposited by coating with a binder to a thickness of about 10 micrometers, i.e. 10 g per m 2 of paper.

10 After printing a text in black on this anti-copy paper and photocopying it (in black), the resulting photocopies were illegible and had a uniform black background appearance.

Contrast measurement on a photocopy using a reflectometer showed no difference between the background and the printed 15 marks.

The original dark orange document remains perfectly legible. After being irradiated, it returns to its normal color after 2 seconds.

20 EXAMPLE 3 An anti-copy paper having brown coloration (Pantone 173C) and photochromic microcapsules was manufactured as follows: the paper used was conventional in type; n the photochromic microcapsules were prepared using S• 25 operating mode No. 1 and using decaline in which the following were dissolved: methylthio -6 methyl 3' benzothiazolino 2' spiro 2 methyl 3 methoxy 8 nitro 6 benzo pyran at a concentration of 4.10-2 Moles, phenyl 4 acetophenone at a concentration of 10-1 Moles, and 5% polystyrene. These microcapsules were deposited by coating using a binder to a thickness of about 10 micrometers, i.e. 10 g per m 2 of paper.

After having graphical information printed thereon, the original brown document was perfectly legible. After photocopying using single color black electrostatic type copiers, the resulting photocopies were illegible and had a uniform (black) background.

17 After being irradiated in a photocopier, the original document returns to its original color in 5 seconds.

EXAMPLE 4 Anti-copy paper having brown coloration (Pantone 173C) and microcapsules was manufactured as follows: the paper used was conventional in type (cellulose); photochromic microcapsules were prepared using tetraline as the solvent in which the following were dissolved: trimethyl indolino 2' spiro 2 nitro 7 naphtho (2,1-b) •pyran at a concentration of 3.10 2 Moles, phenyl 4 acetophenone at a concentration of 10-1 Moles, and 8% polystrene (having low molecular mass) using technique No. 2.

0 The photochromic microcapsules were deposited by coating using a binder (polyvinyl alcohol) on sample 1 to a thickness of about 10 micrometers, i.e. about 10 g per m 2 of paper.

After graphical information was printed thereon, the original brown document was perfectly legible. Photocopies obtained using single color (black) photocopiers were 20 illegible. Contrast measurements on the photocopies using a reflectometer showed no reflection differences.

EXAMPLE Anti-copy paper comprising brown coloration (Pantone 173C) and photochromic microcapsules was prepared as follows: the paper used was based on cellulose; the photochromic microcapsules were manufactured using hydrogenated terphenyl with the following dissolved therein: trimethyl indolino 2' spiro 2 nitro 7 naphtho pyran at a concentration of 4.10 2 Moles, phenyl 4 acetophenone and dihydroxy 1,2 anthraquinone each at a concentration of 10-1 Moles, and 3% methyl polymethacrylate using operating mode No. 1.

The microcapsules were deposited by coating on the paper using starch to a thickness of about 10 micrometers, i.e. about g per m2.

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4 8 9 99* 9 9 9 18 After printing black text, the document is perfectly legible. Photocopies obtained on electrostatic copiers are uniformly black and illegible.

EXAMPLE 6 Anti-copy paper comprising pale orange coloration (Pantone 164C) and photochromic microcapsules was prepared as follows: the paper was based on cellulose; two types of photochromic microcapsule were used: firstly capsules prepared as described in Example 1, and secondly as prepared as described in Example 3; these two types of capsule were mixed together in equal parts and the mixture was deposited by coating using a binder (polyvinyl alcohol) on the medium to a thickness of 15 micrometers, i.e. 10 g per m2.

The resulting medium is pale orange in color and original documents obtained after printing graphical information thereon are perfectly legible. Single color black photocopies obtained from the original docu'nent are uniformly black and illegible.

EXAMPLE 7 Paper was manufactured including photochromic microcapsules only, as follows: the paper used was based on cellulose; photochromic microcapsules were prepared using hydrogenated terphenyl, with the following dissolved therein; -7 mercuric dithizonate at a concentration of 4.10 2 Moles and hydroxy 4 benzophenone at a concentration of 10 Mles; the microcapsules were deposited by coating on the paper using a binder (polyvinly alcohol) to a thickness of micrometers, i.e. 10 g per m 2 The resulting paper is orange in color. After printing black text on this paper, a photocopy on a single color electrostatic copier is illegible and has a uniformly black surface.

After irradiation, the original document returns to a normal color in about 15 seconds.

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19 EXAMPLE 8 An anti-copy paper including only one photochromic micromedium was prepared as follows: the paper used was based on cellulose which had previously been subjected to treatment using polyvinly alcohol; the photochromic micromedium was prepared: firstly from microporous CPG (Controlled Pore Glass) 10-3000.10- 10 m having an average grain size of 10 micrometers, and secondly from a solution of tri (N,N-dimethylamino 4 phenyl ethane nitrile at a concentration of 3.10 3 Moles, potassium cyanide at a concentration of 10-2 Moles, and carbon tetrabromide at o* a concentration of 10-2 Moles in solution in a 1% polyoxethylene glycol 700 in water.

The solution was incorporated in the micromedium at a concentration of 0.5 milliliters per 1 g of micromedium.

In order to avoid any exudate, the system was coated with a layer of plyvinly alcohol using the technique described above. The micromedium and polyvinyl alcohol mixture was used as such for depositing a coat on the paper of the original 20 document medium.

The anti-copy paper obtained in this way is nearly colorless. After printing graphical information on this medium, photocopies obtained using a single color (black) electrostatic photocopier have a uniform illegible black appearance. The original document returns to its initial color after 2 minutes.

EXAMPLE 9 Anti-copy paper was prepared in accordance with Example 4, except that the cellulose paper was replaced by a synthetic paper. The synthetic paper was based on polyethylene fibers bonded by polyvinyl alcohol.

The results are entirely comparable with those of Example 4.

EXAMPLE A transparent plastic anti-copy film was prepared in accordance with Example 4, except that instead of using cellulose base paper, a cellulose acetate transparent plastic sheet having a thickness of 0.1 mm was used.

The results are entirely comparable with those of Example 4.

EXAMPLE 11 An anti-copy paper having brown coloration (Pantone 173C) and a macromolecular photochromic coating was manufactured as follows: the paper was based on cellulose; the coated paper was subjected to auxiliary treatment using polyvinyl alcohol in order to prevent any reaction with the cellulose fibers; coating was performed using a solution of trimethyl indolino 2' spiro 2 nitro -7 naphtho pyran at a 15 concentration of 4.10 3 Moles, of phenyl-4 acetophenone at a concentration of 2.10- 2 Moles, of 20% polyvinylbutyral, and of 1% butyl laurate as plastizicer in a 50/50 mixture of ethyl acetate and toluene as the solvent.

The photochromic polymer coating or varnish was spread 20 over the paper using a Meyer bar or a brush over the entire surface or over a portion only thereof.

After the solvent has evaporated, a brown colored medium is obtained. After printing graphical information thereon, the original document was photocopied in black. The photocopies obtained are uniformly black and thus illegible.

EXAMPLE 12 An anti-copy paper having brown coloration (Pantone 173C) and a photochromic micrcmedium was prepared as follows: the paper was based on cellulose; the photochromic micromedium was obtained using microporous 10 3000.10- 10 m CPG (Controlled Pore Glass) having an average grain size of 10 micrometers. A photochromic solution in decaline of trimethyl indolino spiro -2 nitro 7 naphtho pyran at a concentration of 4.10-2 Moles, and of phenyl-4 acetophenone at a concentration of 2.10 1 Moles was incorporated in the micromedium at a concentration of milliliters per 1 g of micromedium.

7' FI Rnr~ j 21 In order to avoid any possibility of exudate from this system, it was coated with a layer of polyvinyl alcohol using the above-described technique. In this case, the medium was used directly without drying. This preparation was then deposited on the colored paper and coated to a thickness of micrometers, i.e. about 10 g per m 2 The anti-copy paper obtained in this way is brown.

After printing a text in black on this medium, photocopies obtained using single color (black) electrostatic copiers are 10 of uniform black and illegible appearance.

em 9 EXAMPLE 13 Example 12 was performed with colored pigments being incorporated in the photochromic solution. The mixture behaved like a photochromic paint and was suitable for being spread by coating or by means of a paintbrush.

mm EXAMPLE 14 An anti-copy paper including coloration and photochromic 20 microbeads was manufactured as follows: the paper was of the cellulose type; the microbeads were based on cross-linked polystrene with 2% divinyl benzene. They were obtained by polymerization in emulsion and had a diameter of about 5 micrometers. They were made to be photochromic by swelling in a photochromic solution.

The photochromic solution was made using cyclohexane as the solvent with the following dissolved therein: trimethyl indolino 2' spiro -2 nitro 7 naphtho (2,1-b) pyran at a concentration of 10-2 Moles, phenyl 4 acetophenone at a concentration of 5.10-2 Moles, and a plastizicer: i.e. butyl laurate at 8% by weight.

The microbeads were caused to swell at 20xC in the solution under slow stirring. Bead growth was monitored using a microscope until the diameter reached 8 micrometers. After cooling, the swollen microbeads were filtered and allowed to dry.

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4* I A A #4 22 The microbeads were deposited on the paper by coating using a binder (polyvinyl alcohol) to a thickness of about micrometers, i.e. 10 g per m2.

The resulting medium is brown in color. After printing a text in black on this anti-copy medium, the original document is perfectly legible. Photocopies obtained using single color (black) electrostatic copiers are uniformly black and illegible.

10 EXAMPLE An anti-copy paper which is orange in color (Pantone 165C) and including photochromic microcapsules was prepared as follows: the paper was of the cellulose type; the microcapsules were prepared using Santosol as the solvent, including trimethyl indolino 2' spiro 2 naphtho (3H) oxazine- 1,4 at a concentration of 5.10-2 Moles and benzil at a concentration of 0.25 Moles.

The capsules were deposited by coating using a binder to a 20 thickness of 10 micrometers, i.e. about 10 g/m 2 of paper.

After graphical information has been printed in black, a photocopy of such a document using a monochrome (black) photocopier is completely illegible. The paper returns to its original color in about 3 seconds.

EXAMPLE 16 Anti-copy paper was prepared as described in Example but using benzyl grafted by means of an aliphatic chain on spirooxazine, i.e. dimethyl ((phenl oxalyl p-phenylene)- 4 butanediyl-l)-l' indolino-2' spiro-2 naphtho (3H) (2,1-b) oxazine-1,4.

EXAMPLE 17 A polymer layer or varnish was prepared by dissolving the following in a 50/50 mixture of toluene and ethyl acetate: trimethyl indolino spiro -2 (3H) pyrido (3,2-f) benzo (2,1b) oxazine -1,4 at a concentration of 5.10- 2 Moles .1 t, 23 and camphorquinone at a concentration of 2.5 Moles and ethyl polymethacrylate.

This may be coated on orange color (Pantone 164C) cellulose type paper using a Meyer bar to a thickness of micrometers.

A photocopy of such a medium printed in black is completely illegible. The document returns to its initial color after about 5 seconds.

S 10 EXAMPLE 18 Orange colored (Pantone 157C) anti-copy paper was provided with photochromic microbeads; These microbeads were based on cross-linked polystyrene having 2% vivinyl benzene and a size in the range 200 mesh to 400 mesh.

They were made photochromic by swelling in a toluene .O solution of chloro-6' trimethyl indolino spiro -2 naphtho (3H) oxazine -1,4 at a concentration of 5.10- 2 Moles and of benzil at a concentration of 0.25 Moles and 1% 20 butyl laurate.

The microbeads were deposited on paper by coating using a binder (polyvinyl alcohol).

After its photochromic system has been excited, the medium returns to its initial color in about 5 seconds.

25 A photocopy of such a medium printed in black is illegible.

Using media based on paper as described means that authentic documents can be protected against fraudulent copies made using a photocopier. The types of original document for which this may be useful include books, magazines, reports, letters,....

However, the user of non-photocopyable papers of this type, be they white or colored, must nevertheless be aware that various precautions need to be taken. Firstly precautions need to be taken concerning the inks used. Inks which are bhlack, red, dark blue, or dark violet do not present problems for 24 making the marking on the paper. However, any pale, white, or yellow inks should be avoided since they would prevent the anti-copy effect. For example, using a xerographic type of photocopier, white ink on anti-copy paper provides a black background photocopy on which white marks are visible.

Similarly, it is necessary to avoid making corrections to the medium which could spoil the properties of a non-photocopyable paper medium. In particular, the use of an erasor, or of a (white) corrector fluid for typing mistakes, the use of inkstain remover, or any chemical product or varnish, must be avoided.

In order to mitigate the problem of corrections, it is S possible to make a non-photocopyable paper which is sticky.

The user can thus stick a strip of non-photocopyable paper over a mistake and correct the marking without spoiling the properties of the medium as a .hole. Alternatively, the paints and varnishes described in Examples 11 and 13 could be used.

Non-photocopyable sticky paper can be prepared using conventional techniques.

EXAMPLE 19 A 10% aqueous solution of pregelatinized starch is coated in conventional manner on 60 g/m 2 anti-copy paper in order to obtain a film of glue (3 g of dry glue per m 2 After drying, the resulting sticky anti-copy paper can be used after moistening for gluing, for example, on the surface of a sheet of paper. The anti-copy paper performs in the same manner as described above.

Sticky non-photocopyable paper can be prepared using conventional methods.

EXAMPLE A coating of silicone is sprayed onto ordinary 60 g/m 2 paper to avoid any adherence. A 50% dry extract acrylic emulsion (methyl polyacrylate and polyacrylic acid) is sprayed on the silicone coating in a uniform layer and the anti-copy photochromic paper is applied thereto.

The adhesive is thus transferred to the anti-copy paper and a sticky anti-copy paper is obtained. Anti-copy papers as described above can be used for this purpose. Such sticky anti-copy papers can be used in the same way as any sticky paper system.

Such non-photocopyable sticky paper may also be used for making original documents which are partially nonphotocopyable. For example, if it is desired that a portion of a graphical image, some words, names, numbers, signatures, drawing details, should not be photocopied, then it suffices to stick a piece of non -photocopyable paper in the appropriate place and continue making the appropriate marks.

When an electrostatic photocopier is used to photocopy the document, the non-photocopyable portion will appear in black while the remainder of the original document will be legible.

It should be specified that there are problems which occur .with photocopying non-photocopyable media in accordance with **the invention. These media are most particularly effective with electrostatic or xerographic types of photocopier. Indeed 20 these are the commonest types of photocopier.

The effect of using single color (usually black) electrostatic photocopiers have been described at length.

In a single color system, color is provided by "toner" :after the image has been formed on the receiver system. Thus, in a single color photocopy, regardless of whether the "toner" is, in fact, black, red, blue, yellow, in color, the photocopy obtained using anti-copy paper in accordance with the invention will be uniformly colored, and as a result it will be illegible.

As for "color" photocopiers, they operate using electrostatic methods and three or four colors of "toner", and they do not make use of other color reproduction systems, e.g.

silver-based photography, or otherwise. Color photocopies obtained using anti-copy paper in accordance with the invention are clearly degraded since the reproduced colors do not match the originals.

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26 There are numerous possible uses of colorless or colored photochromic films. Firstly, there are original document films having a graphical image thereon. Such films behave like nonphotocopyable paper as described above, and anything said about paper applies similarly to them.

Non-photocopyable photochromic films may be used for protecting documents obtained using conventional cellulose based paper media or synthetic paper mdia, or films, and including a graphical mark. In these cases, said documents should be covered with non-photocopyable photochromic films.

These methods are lamination or plastification methods. Any eog.

lamination or plastification method may be used: gluing, hot ewe pressing, adhesive film, The laminaton or plastification may cover all or a part of the document to be protected and may cover one or both faces thereof.

It is thus possible to make non-photocopyable original documents.

20 EXAMPLE 21 A transparent anti-copy film was prepared in accordance with Example 10 and taking care to identify the non-coated Ce. face. The document to be laminated was covered by the transparent film taking care to put the non-coated face against the document and the assembly was hot pressed as between and 80xC. The resulting original document gives results which are entirely comparable with those of Example 11. Photocopies obtained using monochronomatic (black) photocopiers are uniformly black and illegible.

EXAMPLE 22 A sticky anti-copy film was prepared as described in Example 10 thus providing a sticky film. However, the. acrylic emulsion adhesive could be replaced by a styrene-butadiene rubber solution in a mixture of ethyle-acetone-toluene acetate solvent. The resulting film may be used to laminate documents and in particular paper-based documents. Non-photocopyable 111 27 laminated original documents obtained in this way have exactly the same properties as anti-copy original documents described in the examples above.

It may be observed that all original documents prepared using photochromes show a slight increase in coloration when exposed to intense light radiation such as sunlight, or a high power lamp (in particular a halogen lamp), or lighting from multiple fluorescent tubes. Thus, a pale or a white original document, if exposed to daylight takes on a pale color, but that does not make the document any less legible. If the original documents are themselves colored, the change in color Sis hardly perceptible.

It is therefore advantageous for such original documents to be processed, read, and handled under moderate lighting conditions, e.g. about 50 lux.

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Claims (9)

1. A photosensitive medium suitable for use in printing and writing, of the type including at least one photochrome, wherein the medium further includes at least one photosensitizer associated with the photochrome in individualized manner in the medium, and wherein the photochrome and the photosensitizer are incorporated in at least one of the following forms a polymer or ink layer, microcapsules, microbeads, and an insoluble micromedium, whereby said photosensitive medium is sensitive to the radiation delivered by conventional photocopiers.

2. A medium according to claim 1 further including at least one colorant.

3. A medium according to claim i, wherein pnotocGpies of original documents comprising said medium are made to differ from the original or to be illegible by reducing the contrast between the background of the document and the marking thereon,

4. A medium according to claim 1, wherein it constitutes a paper type of medium.

5. A medium according to claim i, wherein it is Sconstituted by a polymer film.

6. A medium according to claim 5, wherein it includes a sticky face.

7. A medium according to claim 5, wherein the polymer film is applied to a paper background.

8. A method for creating non-photocopiable documents consisting in first preparing a photosensitive medium according to anyone of claims 1 through 7, and in subsequently printing or writing indicia thereon.

9. A photosensitive medium for printing and writing, substantially as described herein ir conjunction with anyone of the Examples. Dated this 26th day of February 1991. S. A. VICAT R By their Patent Attorney 7" GRIFFITH HACK CO. S<N 7' 0