FR2643661A1 - Substrate for printing-writing capable of being authenticated using heat - Google Patents

Abstract

The substrate for printing-writing comprises at least one metal salt which is coloured in the moist state and has a different colour in the dry state, incorporated into or onto the said printing-writing substrate, the quantity of salt in relation to the substrate, on a dry weight basis, being such that the colour of the substrate at ambient temperature is substantially the colour of a substrate which does not comprise a metal salt, and that the colour of the substrate is modified reversibly when the temperature of the substrate is raised. When employed by itself, the metal salt is not a cobalt salt. The substrate can be employed as security paper capable of being authenticated using heat and proof against tampering using a chemical agent.

Description

SUPPORT FOR HEAT AUTHENTICABLE PRINT-WRITING.

The present application relates to a support for printing-writing, in particular paper, reacting to a possible falsification by chemical agent and authenticated by heat by reversible change in coloring.

It mainly concerns the area of security papers which can be used for the production of handwritten payment documents and official documents such as, in particular, checks, paper money, savings bank vouchers, account books, accounting books, securities. , stamped papers, notarial deeds, transport tickets, entrance tickets to sporting, cultural or other events and, in general, all comparable security papers and means of security such as credit cards, etc.

In patent application No. 87 12243 of September 3, 1987, the use of cobalt salts distributed in the mass or on the surface of a print-write support has been described to authenticate this support to heat by reversible change in color. and to detect, by means of a colored reaction, a falsification of this support by a reducing solution of sodium bisulfite used in erasers of the CORECTOR R type
Papers containing chemical reagents to chemical agents have already been proposed in the past which can be used to falsify writings by chemically bleaching the inks (documents ARJOMARI FR-A-2 365 656, FR-A-2 399 505, FR- A-2 402 739, EP-A-174 885, documents from VOIRON ET DES GORGES stationery
FR-A-2 406 027).

We have described the use of thermochromy for the authentication of security papers in DE documents.
Al 228 972 and AT-A-362 658. However, these methods used unusual products, expensive and difficult to use in stationery. GB-A-1 565 243 describes a thermochromic authentication using thermochromic and thermomagnetic substances.

Furthermore, in the document AUSEDAT-REY FR-A2 597 897, a security paper which can be authenticated by thermochromy containing a violet lactone and an organic acid has been described, but such a paper tends to be colored over time.

Document US-A-2 005 105 has also described a paper reacting to bleaching or oxidizing agents, this paper being treated with an ink containing cobalt ferrocyanide. Document US-A-1 804 978 describes a paper which reacts to ink erasers, treated with a solution containing water, alcohol, iodine, cobalt nitrate and thiosulphate. sodium.

Document DE-A-42 260 describes a paper reacting to chlorine-based erasers, this paper being treated with an ink containing a sulfated manganese oxide or cobalt chloride.

Document FR-A-I 509 715 describes a paper intended to react to bisulfite containing manganese ferrocyanide and a metal salt insoluble in water and forming a colored ferrocyanide.

It is this ferrocyanide which confers the coloring to the paper by the action of bisulfite. The metal salt can be a transition metal salt.

Thus, according to these publications; the transition metal salts are always used in combination with other salts to obtain either a reaction with bleaching or oxidizing agents, or a reaction with bisulfite. A person skilled in the art was therefore led to associate the metal salts with other salts.

In addition, most security papers available on the market do not have a simple and reversible authentication process which can be combined with protection against falsification.

An object of the invention is therefore to obtain a support for printing-writing, security and preferably non-fluorescent, authenticated with heat in a reversible manner, thanks to a simple chemical composition which does not significantly modify the coloring of the paper. and also being compatible with the other known reagents for sensitizing to acids, bases, oxidants, erasers, organic solvents.

Another object of the invention is to obtain a security paper, reacting with bisulfite.

The Applicant, after intensive and prolonged tests, finally accepted that the object of the invention could be achieved by incorporating, in or on the print-write support, a chemical composition containing at least one metallic salt colored with wet state and of a different color when dry, the amount of salt relative to the support, in dry weight, being such that the coloring of the support is not substantially affected at room temperature, and the coloring of the support being reversibly changed with temperature. When the chemical composition contains only one metal salt, it is not a cobalt salt of oxidation state 2, and in particular cobalt chloride.

Preferably, metal salts which can pass from a crystalline state of one color to a crystalline state of another color are chosen, and more particularly copper salts and preferably of oxidation state 2.

The print-write support is preferably a paper based on cellulose fibers or a plastic support coated with a tick giving it the property of being able to be printed or to receive a writing. It always contains 5 to 7% water after going through drying. The amount of metal salts with respect to the support by dry weight is sufficiently low (0.1 to 4%), so as not to impart color to the paper under normal conditions of use, even after drying the print-write support . Given the small amount of metal salt incorporated in the support and the water content remaining in this support, the metal salt remains in the hydrated state.

In fact, the metal and in particular copper salts of oxidation state 2 are generally colored, but their introduction into the paper has little effect on the original tint of the paper with normal dryness and does not bring any fluorescence. Copper chloride dihydrate is blue-green. If this salt is incorporated into a paper and at a content of 1% by dry weight relative to the paper, the paper obtained is white at ambient atmosphere. When this paper is heated to about 1000C, it takes on a dull yellow color which spontaneously and quickly fades when the paper is returned to the ambient atmosphere.

This coloring phenomenon, brought about by the presence of copper salts of degree of oxidation 2 in the paper, is only visible at high temperatures; it is therefore not annoying in the daily conditions of use of security papers. On the contrary, this coloring when the paper is dehydrated can be used as an easy and non-destructive heat authentication system for this type of security paper.

The paper can be authenticated by a specific heating with heating jaws, a breath of hot air, a heating pen.

According to the invention, desiccant salts, in particular sodium chloride, can be added to the paper, by lowering the amount of water available, which makes it possible to lower the temperature threshold for color change.

On the other hand, it has surprisingly been found that the addition of copper salts in the paper makes it possible to obtain a reaction (and therefore protection) with several falsifying agents such as hypochlorite, alkalis and sodium bisulfite . This reaction is obtained by introducing the copper salt alone.

Thus, the invention makes it possible to obtain a print-writing medium, which can be authenticated by heat and cannot be forged by chemical agent, by introducing a single compound into the paper.

According to the invention, the paper can have any fibrous composition, purely cellulosic, or synthetic part, from synthetic fibers or coated synthetic films, more briefly hereinafter "paper", to which the conventional stationery additives can be added. , namely - mineral fillers, various resistance agents, binders, resins, tinting dyes, neutral, acid or basic bonding products, alumina sulfate for acid bonding or pH adjustment, etc.

Since the copper salts are generally very soluble, the introduction of these products according to the invention can preferably be carried out by impregnation by means of a size press or by coating.

The reaction to heat is perceptible to the naked eye from 500 ppm of metal salt of oxidation state 2 in the paper, but, for a clearly visible and rapid reactivity, industrial doses of between 0.1% and 4% of salts of a metal with an oxidation state of 2 are more suitable.

These papers may also contain in their mass, in the dispersed pigmentary state, dyes insoluble in water but organosoluble, so as to preserve the writings or mentions made on these papers vis-à-vis attempts at falsification with using organic solvents. In addition, these papers can be watermarked or contain various devices intended to ensure recognition.

Thus, the invention makes it possible to manufacture a white, non-fluorescent paper, authentically reversible by heat and which develops, in the presence of an attempt at chemical falsification, colors detectable with the naked eye on this paper.

The paper which is the subject of the present invention can be printed by any of the printing methods, and can be used as a handwriting medium when it is desired that the information given be permanent and that any attempts be discovered. of falsification of these writings. It is particularly interesting to apply it to the production of non-fluorescent handwritten payment documents such as checks, cash vouchers, savings account books, official documents, banknotes, etc.

Although most of the security papers used are white, one can also consider incorporating this tamper-evident means into a security paper that is not white, but colored.

The following examples illustrate the invention without, however, reducing its scope.

EXAMPLE 1
The aqueous coating solution comprising, per liter of liquid - 100 g of starch, - 15 g of copper chloride, dihydrate, is deposited on the surface of a printing-writing paper support by a conventional papermaking technique (size press).

The paper, if worn locally around 1000C, immediately takes on a yellow tint which disappears in a few minutes after the heating has stopped.

A white paper is obtained which reacts in orange to sodium bisulfite or to the subsequent application of a solution of permanganate and sodium bisulfite.

EXAMPLE 2
On a paper support identical to Example 1, is deposited on the surface by a conventional papermaking technique (size press) the aqueous coating solution comprising per liter of liquid - 100 g of starch - 15 g of copper sulphate, pentahydrate - 10 g of sodium chloride
The paper, if worn locally around 1000C takes on a yellow tint which disappears in a few minutes after the heating has stopped. An orange-sodium bisulfite reaction is obtained.

EXAMPLE 3 oak process and same results as for example 2 with 13 g of copper acetate monohydrate in place of copper sulphate.

EXAMPLE 4
On a banknote-type support is deposited on the surface by a conventional papermaking technique (size press) the coating solution comprising per liter of liquid - 100 g of polyvinyl alcohol - 15 g of cobalt chloride dihydrate - 12 g of chloride sodium
We get a white paper. This paper takes a yellow color from 800C. It is therefore easily authenticated by occasional heating of the paper. The paper returns to its original color spontaneously in a few minutes after the heating has stopped. In addition, the paper reacts strongly to sodium bisulfite.

EXAMPLES 5
On a plastic support in high density polyethylene is coated by a conventional papermaking technique (drag blade, air knife, ...) the aqueous coating sauce comprising no liter of liquid - 400 g of dispersed fillers (kaolin, talc, carbonate) - 200 g of latex - 25 g of copper chloride dihydrate.

The coated plastic is white. When heated locally, it takes on a yellow color which disappears spontaneously in a few minutes after the heating has stopped.

Claims (10)

REVlVDICA RIONS 1. Support for print-write, intended to be authenticated  by heat1 characterized in that it comprises at least one  metallic salt colored wet and of a color  different in the dry state incorporated in or on said support  print-write, the amount of salt compared to  dry weight support, being such that the coloring of the  medium at room temperature is noticeably staining  of a support not containing metal salt, and that the  support coloring is changed -reversibly  when the temperature of the support is raised; metallic salt  used alone not being a cobalt salt. 2. Support according to claim I, characterized in that the  metallic salt to pass from a crystalline state of a color  to a crystalline state of another color and preferably is  a salt of a metal of degree of oxidation 2. 3. Support according to one of claims 1 to 2, characterized in  what the metal salt is a copper salt. 4. Support according to claim 3, characterized in that the  copper salt is a hydrated salt preferably chosen from the  group including copper sulfate, chloride  copper, copper acetate. 5. Support according to one of claims 1 to 4, characterized in  what it contains a desiccant salt whose function is  to lower the temperature to which the support is brought to  change its coloring. 6. Support according to one of claims 1 to 5, characterized in  what the amount of metal salt in relation to the support,  by dry weight, is between 0.1 and 48 7. Support according to one of claims 1 to 6, characterized in  what the desiccant salt is sodium chloride. 8. Support according to one of. claims 1 to 7, characterized in  what it cannot be forged by sodium bisulfite,  reacting with bisulfite. 9. Support according to one of claims 1 to 8, characterized in  that the aforementioned metal salt is deposited on the surface of said  support by a conventional papermaking technique from a  aqueous coating solution containing said metal salt. 10. Security document, characterized in that it comprises a  support according to one of claims 1 to 9.