FR2758574A1 - OPAQUE SAFETY PAPER, AUTHENTICABLE BY RIP, SCRAPING PLAY TICKETS PRODUCED FROM SUCH PAPER AND METHOD OF MANUFACTURING THE SAME - Google Patents

Abstract

The present invention relates to fibrous writing and / or printing, security supports (e.g. paper). In particular, the invention relates to an opaque security paper, authenticated by tearing, non-delaminable, tamper-proof, economical and printable, characterized in that it consists in particular of one and the same fibrous mat, homogeneous in particular in its thickness and obtained from a single fibrous ply, and in that it comprises, in its thickness, at least one substantially median slice (2) of color (C2) and at least one outer slice (3, 4) white or colored (C1, C3) different and / or less dark than that (C2) of the middle section (2). Preferably, C1 and C3 = C2 discolored and C2 = dark color. The subject of the invention is also the method for obtaining said paper and the articles made from said paper (e.g. scratch-off game ticket).

Description

The field of the present invention is that of fibrous supports

  writing and / or printing, said security, in particular paper. These fibrous supports or security paper are useful for the realization of security documents such as admission or travel tickets, checks, legal or official documents, credit documents, insurance certificates, tickets, show, train, plane or similar, or even game tickets or

  scratch lottery, also known as instant lottery tickets.

  More specifically, the invention relates to fibrous supports such as tamper-proof security papers as authenticatable by a tear revealing a multicolored sandwich structure. This mode of authentication and fight against

  Counterfeits are used in ticketing, where important values may be at stake.

  The present invention also relates to fibrous supports, in particular security papers which are specific to writing and printing and which can be used for making scratch-game tickets whose printed and masked information need not be revealable by transvision and which allow

  also to avoid another type of delamination fraud.

  The direct authentication by tearing of a sheet of fibrous support, for example made of paper, makes it possible to reveal a multicolored sandwich structure: a colored interior and two white, clear or different colored external slices. This characteristic structure makes it possible to certify with certainty the good origin of certain titles, of sometimes very high value, such as transport tickets, show tickets or others. Since this technique of tear authentication is fast and safe, it is perfectly competitive with other known systems such as watermarking, which has existed for a long time, or even the introduction of fibers or threads. of security. Some of these known systems (whose points or fluorescent or phosphorescent fibers) have the disadvantage of requiring a revelation apparatus for authentication. A typical example of such an apparatus is the

UV lamp.

  It follows that the fibrous supports or opaque security papers and multicolored sandwich structure giving them a tear authenticity should not have difficulty in carving out a place of choice, especially in applications falsified transport ticket and ticketing, as long as it is possible to eliminate a major defect consisting in the delaminable nature of fibrous supports or papers that can be authenticated by tearing, which exists at present. This unacceptable defect is related to the structure and the manufacturing method of these fibrous supports or

known security papers.

  Thus, a first type of structure is known in which three layers of paper are assembled to each other by lamination, the center layer being colored and the outer layers being white. The second known type of structure is formed by a sheet of colored paper, which is treated by coating on at least one of its faces with the aid of a

  white or opacifying coating composition.

  The coating of colored media in the field of security papers has been disclosed for a very long time already, even if the purpose then sought and displayed was not to provide authentically tearable papers. Thus, US Pat. No. 1,417,820 describes a process for rendering tamperproof a paper by coating both sides of a black paper with an opaque and solvent-sensitive coating material contained in the coatings. ink erasers usable for forgery purposes. We are here in the presence of a sandwich structure of the type coating coating of light color / black paper or

  dark color / light colored coating.

  Also known in the field of security papers, that disclosed by British Patent No. 1,435,686, which is designed to resist surface abrasion fraud attempts to eliminate printing and writing ink. . This security paper comprises a paper base sheet, coated with an opaque, abrasion-sensitive coating consisting of a non-metallic pigment (clay or TiO2) dispersed in a binder (synthetic polymer = vinyl copolymer /

  acrylic-styrene / acrylic-styrene / butadiene or natural polymer starch-cellulose-

  casein). The paper base sheet has a color that contrasts with that of the coating so as to be able to reveal abrasion traces of the top layer by transvision. This patent does not teach sandwich structure: light or white color / different color or darker / light or white color. The coating of a colored paper with an opacifying or white composition is also implemented in the field of security papers dedicated to a particular destination, which is the production of instant lottery tickets or any other analogous type of scratch game tickets. Such articles contain printed, masked information that can be, on the one hand, a number, a symbol, a message possibly giving rise to a gain, and on the other hand, a security number to prevent counterfeiting. The masking of this information conventionally is obtained by means of an opaque scratchable layer comprising, for example, a metal pigment (aluminum) dispersed in a binder formed by a rubber latex or other hydrocarbon polymers (see layer 28 of the ticket Lottery, described in US Patent No. 4,726,608). In addition to this opaque layer, the ticket comprises, as a coating of a paper substrate 18, from top to bottom, a non-stick layer 26, made of polyamide, a protective layer of maleated vinyl acetate copolymer, the printed characters 24, a primer layer. amorphous silica + maleated vinylacetate polymer + n-propyl acetate solvent

  and finally an aluminum foil 20 contiguous to the paper substrate 18.

  In an attempt to eliminate the drawbacks associated with the presence of aluminum foil in this type of scratch board ticket, European Patent No. 0 428 489 proposes the use of coated paper for the manufacture of such articles. The security paper disclosed by this patent comprises a base substrate made of paper, with a grammage of the order of 225 g / m 2, stained with carbon black, so as to be totally opaque and coated with the aid of a composition comprising pigments such as clay or titanium dioxide, latex or starch. The sides of the coated paper thus obtained are white, smooth and uniform, so printable. These papers are presented as non delaminable. In order to manufacture an instant lottery ticket, it is intended to print on the faces of the coating and then to make a final coating using conventional colored and scratch-resistant latex. This patent therefore discloses a sandwich structure: coating coating

  white / black opaque paper substrate / white coating.

  European Patent Application N 668 092 discloses an invention relating to instant lottery (scratch) ticket papers which advocate opacity to paper not through the base paper substrate as proposed in the present invention. European Patent No. 428,489, but via an opaque coating coating applied to said paper base substrate and comprising a carbon black type pigment dispersed in a styrene / butadiene copolymer latex binder. This opaque layer is furthermore coated with a top printing layer, obtained from a composition comprising

  styrene / butadiene latex, CaCO3 and styrene-acrylic polymer microspheres.

  It emerges from this review of the prior art that the known security papers, authenticatable by tearing and / or opaque enough to be used as instant lottery ticket holders or scratch-free game tickets (no transvision), are the more often multilayer fibrous supports

  obtained by the coating technique.

  However, it is known that this technique is relatively expensive especially because it is necessary to achieve most of the time out of the conventional circuit of the paper machine. It is clear that this affects the productivity and profitability of the paper manufacturing process. Moreover, sleeping is an operation that can be very easily reproduced with artisanal means. This

  increases the risk of counterfeiting.

  In addition, it is clear that the coating does not provide a really satisfactory solution, with regard to the problem of delamination. The persistence, in coated structures, of this problem originally inherent to multi-lamellar structures, is emphasized in the European patent application.

No. 668,092 page 2 lines 29-30.

  In this state of affairs, one of the essential objectives of the present invention is to provide a fibrous support, in particular a security paper, which can be authenticated by tearing and which can constitute an opaque substrate suitable for making a game ticket. scratch, which overcomes the disadvantages of the papers of

  security coated according to the prior art.

  Another essential objective of the invention is that this security paper meets the following specifications: - authenticatable by tearing, not delaminable, - tamper-proof, - completely opaque so as not to be subject to fraud by transvision in the game tickets scratching, - economic, - offering good printability and writing,

  - not reproducible easily by artisanal means.

  Another essential objective of the present invention is to provide a method for obtaining a fibrous support, in particular a security paper, which can be authenticated by tearing, which is not delaminable and totally opaque, said process being easy to put into practice. implemented and economic, because of its perfect integration

  in the classic paper manufacturing lines.

  Another essential object of the present invention is to provide a paper

  of security authentiable by tearing, constituted by the fibrous support mentioned above.

  above in the objectives of the invention.

  Another essential objective of the present invention is to provide a ticket

  scratch game made from the aforesaid fibrous support.

  Having set these objectives, the Applicant has had the merit of highlighting, after much research and experimentation, that it is necessary to provide an opaque fibrous support, in particular made of paper, formed by a single and homogeneous fibrous network. initially colored and then subsequently converted at these two external faces over a certain thickness, by fading and / or transcolouring, so as to obtain a sandwich structure of the type: external white slice or of color C, / middle slice of color C2 = or - of C / and optionally white outer slice or of color Cl or C3, with in the case where CI = C2 = C3 a gradient of light color ---> dark

from the outside to the inside.

  It follows that the subject of the present invention is an opaque fibrous support 1, in particular paper, characterized in that it consists in particular of one and the same fibrous mat, homogeneous in particular in its thickness and obtained from a single fibrous jet, * and in that it comprises, in its thickness, at least a substantially middle wafer 2 of color (C2) and at least one outer wafer 3, 4 white or of different color (CI, C3) and /or less

  darker than that (C2) of the median slice.

  Such a fibrous support, in particular a security paper, has the advantage of being non-delaminable, of being totally opaque, inexpensive and easily obtainable in a paper machine, without substantial modifications of the latter. Moreover, its industrial nature somewhat limits the risks of

  counterfeit according to a traditional way.

  As far as fibrous supports are concerned, in particular security papers that can be authenticated by tearing, it follows that the preferred but nonlimiting embodiment of the invention corresponds to a fibrous support comprising a substantially median colored wafer, adjoining each of its faces to a white outer edge or of different color and / or less dark than the edge

  median, the two outer slices being of the same color or not.

  We will have recognized there a multicolored structure, for example two-colored, of sandwich type: color C / color C / color C3 with Ci identical or different to C3 and C2 identical or different to C1 and

C3,

  with the condition that if C2 = C1 or C3 then C1 or C3 is no longer

clear that C2.

  This opaque, non-delaminable structure is perfectly suited to

specifications mentioned above.

  The homogeneous and coherent fibrous network structure of the support according to

  the invention is related to its formation in a single fibrous jet on the paper machine.

  The single appended figure shows a cross-sectional view of such a support according to the preferred embodiment of the invention, by way of non-limiting example only. This figure shows a support 1 formed of a single and same fibrous network of thickness e comprising in its thickness a middle slice 2 of color C2, said slice 2 forming a fibrous structural continuum with the two slices

  external 3 and 4 of color Cl and C3 respectively.

  In this example C ", C2 and C3 correspond to the same basic color knowing that

  C, and C3 are clearly clearer than C2, so much so that they are close to white.

  Such a two-color, non-delaminable opaque structure is imbued with a tamper-evident recognition mark, corresponding to the color C2 of the median slice 2, this

  which makes it perfectly authenticated by tearing.

  According to a variant of the fibrous safety support according to the invention, this

  characterized in that it is obtained from a fibrous mat initially colored, then faded at least partially on at least one of its two faces, preferably both, to form the two outer slices 3 and 4 located of share and

  on the other side of the colored median slice 2.

  This variant corresponds to the sandwich structure: white or very light brown / brown / white light brown, shown in the single figure attached and described above. In this variant, the external / internal color contrast is obtained by means of a bleaching agent absorbed by the faces of the fibrous support considered, over a variable thickness as a function of the penetrability of said agent

inside the support.

  According to another variant, corresponding to the case where C2 is different from C, and / or C3, the fibrous support is obtained from a fibrous mat initially colored and then colored at least partially differently on at least one of these two faces, preferably both, to form the two outer slices 3, 4 located in

  on both sides of the middle 2 colored slice.

  In the first case, the coloring agent reacts with the bleaching agent while in the second case, it reacts with a coloring agent

  transforming C2 into C, and C3 into the surface layers of the fibrous support 1.

  The existence of these two structural variants (among others) for the support according to the invention results in constitutional features. Thus, the fibrous support is characterized in that it comprises at least one coloring agent and optionally at least one bleaching agent and / or at least one transcoloration agent, which has not reacted but is capable of reacting with the agent

  staining in the outer slices.

  Advantageously, the pairing of coloring agent / bleaching agent and / or transcoloration is chosen from the following group: Coloring agent Discoloration agent and / or transcoloration metal oxide reducer metal salt sequestering colored indicator pH pH medium selected color indicator oxidation-reduction medium with redox potential chosen dye-degrading agent dye and mixtures thereof Oxides or metal colored salts, such as iron or manganese salts, may be decolorized by reducing agents or by sequestering agents,

  such as, for example, EDTA or mono-potassium phosphate.

  Without this being limitative, mention may be made of other examples of a coloring agent / bleaching agent pair, eg: - metal oxide / reducing agent = copper or cobalt / bisulphite oxide in an acid medium, - metal salt / sequestering agent = iron or vanadium / ascorbic acid salt. The colored pH indicators that can be used as coloring agents are easily decolourable, by penetrating onto the faces of the fibrous mat a liquid medium of pH such that it returns the indicator in a colorless form or in a different color. Thus, for example, the phenolphthalein initially introduced into the pulp, is brought to a basic pH which causes a pink coloration of the latter. Subsequent surface coating of the fibrous mat with an acid,

  brings the phenolphthalein in a colorless form, corresponding to an acidic pH.

  Another example of a pH indicator that may be used as a coloring agent is phenol red, bromocresol purple or blue.

bromophenol.

  The colored oxidation-reduction indicators work on the same principle as the pH indicators mentioned above, with the difference of course that the key parameter is not the pH but the redox potential. As an example of a pair of coloring agent / bleaching agent or transcoloration, mention may be made of methylene blue or neutral red in combination with bleach. Dyestuffs are another class of suitable coloring agents according to the invention. It may be in particular dyes capable of being decomposed by oxidizing reagents, for example water

  bleach or else sulphites, bisulphites, acids, bases ...

  By way of illustration, mention may be made, as an example, of the dyes with the chemical structure of triphenyl methane, such as the BLEU DUASYN FOR INKS BJT from HOESCHT. This coloring agent may be associated with bleaching agents formed by bleach and / or a weak base, or even

by sodium sulphite.

  As another example of a dye used in the constitution of the fibrous support according to the invention and capable of reacting with degradation agents causing a color change, mention may be made of cresol red associated with bleach in

  the fading / transcolouring bath.

  To illustrate the variant embodiment according to which the fibrous support comprises at least one coloring agent and at least one coloring agent, the following examples will be mentioned: YELLOW LEVACELL 3 GX from the company BAYER in combination

with a basic solution.

  * SAFRANINE O with a solution of dejavel water.

  In addition to the chemical means of discoloration and discoloration, it is possible to use, in addition to or in substitution for the latter, physical means having the same effects. It can be for example: - actinic radiation such as UV and / or infra-red - heat, - electron bombardment, - exposure to a laser beam, - ultrasonic treatments or in the microwave - etc. The fibrous safety support according to the invention can also be defined through its particular physical characteristics. Thus, advantageously, its basis weight is greater than or equal to 80 g / m 2, preferably between 100 and

  400 g / m2 and even more preferably between 120 and 300 g / m2.

  The basis weight of the paper is an important parameter with regard to the penetrability of the fading / transcolouring agents. It is important for these to penetrate the fibrous support within a sufficient thickness so that the color change is apparent, but it is obvious that this penetration must not be too great so as to preserve a slice. median colored in dark or differently colored, which is of significant thickness to allow the authentication by tearing. This control of the penetration of the bleaching agents can also be obtained by adjusting the rate of refining of the fibers constituting the support and therefore its porosity as well as the bonding, that is to say its ability to rewet later

  by the fading / decolourising solution.

  Preferably, the degree of refining of the fibrous support will be between 15 and 55 SR (SHOPPER RIEGLER), and still more preferably between 30 and 45 SR. It goes without saying that the value of refining will also depend on the grammage of the paper. The skilled person is perfectly able to determine the appropriate values of these two

related parameters to each other.

  As regards the bonding, the agent used may be a conventional rosin glue, a dimeric alkyl ketene or any other product which makes it possible to achieve a value which is conventional for this parameter, of between 15 and 30 g / m 2 in COBB value, and more

especially from 16 to 20 g / m2.

  We will return below in the context of the description of the process, on a

  Another important factor regarding penetrability, namely the viscosity of the liquid

  containing the fading / transcolouring agents.

  In any case, these parameters can vary enormously depending on the weight of the fibrous support considered. Indeed, the problem of penetration of fading / transcolouring agents is different for a light weight, less than 120 g / m2 and for a heavier weight, above 200 g / m2. It is very rare in the latter case that, even without special precautions at the level of the support, the solution of discoloration / discoloration penetrates until

  heart of the leaf and fades or changes the color of the paper on its total thickness.

  According to a preferred embodiment of the invention, it is chosen to produce a paper or fibrous support with colored interior and enhanced opacity, by using an intense coloring agent capable of forming a dark color (e.g. brown or brown).

manganese oxide).

  According to the invention, the fibrous safety support considered may have any fibrous composition: either purely cellulosic or in part synthetic. Typically, the appropriate cellulosic fibers may be hardwood fibers, softwood fibers, or mixtures thereof. With regard to synthetic fibers, it may be for example polyester fibers,

polyamide or polyolefins.

  In practice, the proportion of synthetic fibers relative to the total dry weight of cellulosic + synthetic fibers is of the order of 10 to 30% by weight and preferably

15%.

  Advantageously, the fibrous support according to the invention may comprise conventional additives for papermaking, namely: mineral or organic fillers of the kaolin type, carbonate of

calcium, talc ...

  resins or various resistance agents, in particular to bring about wet strength properties, starch or carboxymethyl cellulose type binders to improve the mechanical characteristics of the papers, shading dyes, neutral, acidic or basic bonding (alumina sulphate for acidic bonding or pH adjustment - etc. It may also be envisaged, according to the invention, to incorporate additional authentication agents within the fibrous support. It may be, for example, security threads, planks and colored fibers, whether or not fluorescent, or not, as well as agents for tampering, namely for example water-insoluble but organoluble dyes, in the pigmented state, so as to preserve the writings or the printed mentions carried on these fibrous supports, vis-à-vis the attempts of falsification, with the aid of erasers

comprising organic solvents.

  Finally, many additives can be included in the fibrous support according to the invention, provided that they are not degradable by the fading / transcolouring means, which must penetrate inside said

fibrous support.

  According to another of these aspects, the present invention also relates to a process for obtaining a fibrous support, in particular paper, constituted in particular by a single fibrous mat, homogeneous in particular in its thickness, opaque and comprising, in its thickness, at least one (preferably one) substantially median colored slice and at least one (preferably two) outer slice white or different in color and / or less dark than the middle slice, characterized in that it consists essentially, - 1 - to prepare a fibrous pulp - preferably a pulp, by incorporating at least one coloring agent, - 2 - to put this paste in the form of a support constituted by a single fibrous sheet, made by monojet ,

  - 3 - at least partly to eliminate the water present in the support-

  sheet, - 4 - to discolor and / or to discolor at least one outer slice of

  support-sheet before, during or after the removal of water.

  Such a process is one of those which makes it possible to obtain the fibrous support

  constituting the first object of the present invention described above.

  According to a preferred embodiment of the method, the targeted fibrous support (eg paper) has a substantially median colored wafer and, on either side thereof, a white or different colored outer wafer and / or less dark than the median slice. These two external slices are of identical or different colors. According to the preferred mode, the fading is carried out

  and / or the discoloration using chemical and / or physical means.

  Such a fibrous support corresponds to the preferred embodiment of the product according to the invention as described above and shown in the single appended figure. The preparation step 1 of the fibrous pulp corresponds to a relatively conventional operation in the field of paper milling. In a paper machine, this operation occurs at the headbox or during the preparation of the pulper pulper. In this case, it is simply a matter of adding to the dough at least

  a coloring agent and make a homogeneous mixture.

  Step 2 is carried out via the die of the paper machine headbox which makes it possible to produce in monojet a fibrous mat containing the coloring agent, this mattress then being conveyed to the modules.

  dewatering, pressing and then drying the paper machine.

  These three modules are designed to satisfy Stage 3 of water removal

present in the sheet-support.

  In the case where one is dealing with a decolorization and / or a chemical transcoloration, according to a preferred embodiment of the method according to the invention, step 4 is carried out by applying a bath of fading agent and / or discoloration, using a device preferably provided in the paper machine. More preferably still, this coating device is a conventional size press or "Size Press", or even a "blade metering size press", or a "gate-roll". Such gluing press is usually located after the preschool. In the less advantageous hypothesis where the coating of the discoloration bath or discolouration is carried out, at the end of the paper machine, it is possible to envisage either the use of in-line coating means, such as metal blade or air knife, the traditional printing techniques. It should be noted that any suitable means for penetrating a solution of discoloration / transcoloration in the fibrous support, can be substituted for the means

classics mentioned above.

  It goes without saying that the concentrations of fading / trans-

  The coloration used in the coating baths is determined as a function of the amount of coloring agent contained in the fibrous support and as a function of the stoichiometry of the corresponding reaction. These operating methods are

  perfectly within the reach of the skilled person.

  As regards the nature of the coloring agents and the agents

  discoloration / discoloration, see description and definitions

  data in this regard supra, in this part of this media brief

fibrous taken as such.

  As already mentioned above, the penetration of the fading or discolouration agent into the fibrous support is a fundamental provision of the process according to the invention. The parameters used to control this point are, on the one hand, the grammage, the refining rate and the bonding

  fibrous support and, on the other hand, the viscosity of the coating bath.

  Thus, the viscosity of the fading / transcolouring solution is adjusted by adjusting the dry matter and / or by using film-forming binders (starch, cellulose, etc.). This viscosity adjustment is made according to the nature of the reagent of

  discoloration / discoloration, as well as its reactivity.

  It goes without saying that the parameters acting on the penetrability of the bleaching agent / transcoloration are interdependent. Thus, at most the grammage of

  fibrous support will be low, the higher the viscosity of the coating bath must be.

  In practice it can be indicated, by way of example: that for a basis weight of 120 g / m 2, the viscosity of the bath is advantageously greater than or equal to 100 mPa · s, and that for a basis weight of 150 g / m 2, the viscosity is advantageously greater than or equal to 80 mPa.s, and that for a basis weight of 200 g / m 2, the viscosity of the bath is

  advantageously greater than 30-50 mPa.s.

  By way of example of a water-soluble binder, mention may be made, for example, of carboxymethylcellulose, starch or polyvinyl alcohol which are natural binders, employed in a more privileged manner, without excluding synthetic binders such as

  than acrylic latexes or styrene-butadienes.

  Advantageously, for step 4, in the case of chemical decolorization / transcoloration, a pair of coloring agent / bleaching agent and / or transcoloration chosen from the following group is used: Agent agent decolorization and / or transcoloration metal oxide reducer metal salt sequestering colored indicator of pH pH medium selected colored indicator of oxidation-reduction medium with potential Redox chosen dye degradation agent dye and mixtures thereof According to a preferred mode of the process according to invention: - the discoloration / transcoloration agent is a chemical means, - the fibrous support is paper made using a paper machine, - and for the realization of step 4, it applies the fading / decolourising agent in and / or out of the paper machine on at least one of the outer faces of the sheet, preferably using at least one of the following means: gluing press,

  rewetting system or sleeping system.

  Another subject of the present invention is the use of the fibrous support as defined above and as obtained by the process, for the production of security paper that can be authenticated by tearing, as well as scratch or scratch game tickets.

instant lottery tickets.

  The present invention thus relates to a security paper that can be authenticated by tearing, characterized in that it consists in particular of the fibrous support such as

  than defined above and / or obtained by carrying out the process as defined above.

  Finally, the present invention aims a scratch game ticket characterized in that it consists in particular of the fibrous support as defined above, and / or

  obtained by carrying out the process as defined above.

  The fibrous support according to the invention appears to be capable of being a security paper which can be authenticated by tearing, opaque, non-delaminable, at low cost, and perfectly suitable for tamper-proof, authentically tear-proof document applications, as well as for application of game tickets to

  scratch not falsifiable by transvision.

  The different examples below will shed some light on

  the invention but are in no way limiting.

EXAMPLES:

EXAMPLE 1

  A colored indicator: phenolphthalein solubilized in a hydroalcoholic medium is introduced at a rate of 2% relative to the dry pulp at the mixer in a pulp composed of 50% hardwood and 50% softwood, refined at 30 SR and carried at a pH of 11, an intense pink color develops. A support paper

  colored 250 g / m2 is produced on the paper machine.

  The sizing press is coated with a sulfuric acid solution diluted in such a way as to reduce the surface pH of the paper and thereby destroy the pink-red color.

  the support; the final paper obtained is white on the outside and pink in the center.

  The paper is authenticated by tearing.

  The recovery of the gluing bath is 30% by weight relative to the colored carrier paper.

EXAMPLE 2

  An authenticatable ticket is made by introduction into the dye of blue dye DUASYN FOR INKS BJT of HOECHST Company at a rate of 0.2% in

  weight relative to the dry pulp, the pH of the dough is adjusted to 4 with acid.

  The blue paper thus produced with a grammage of 300 g / m2 arrives at the gluing press of the paper machine where the following bath is applied at a rate of 20% of weight by weight with respect to the paper: Starch: 15% by dry weight per compared with the coating bath, bleach at 12: 15% by weight in the state with respect to the coating bath. After drying, the paper is white on its external parts and blue on the inside:

  tearing allows direct visual authentication.

  In addition the paper with this specific dye can be authenticated at a second level: a line of ink eraser felt or the application of a basic solution on

  the colored inner part allows discoloration of this part.

EXAMPLE 3

  A tamper-proof bill is obtained by coating on the blue paper support of Example 2, with a bath containing 10% of sodium sulphite relative to the bath, in

  replacement of bleach. The same end product is manufactured.

EXAMPLE 4

  A colored paper of 200 g / m 2 as a support is made on a paper machine using the YELLOW LEVACELL 3 GX dye from BAYER, the yellow paper thus manufactured is coated with a sizing press with a dilute solution of caustic soda. to develop a red color on the surface of the paper; the coloring of the inside of the sheet remaining yellow, the paper is authentiable by tearing. However, the paper thus colored has the drawback of not being easily

  usable in various applications by printers.

EXAMPLE 5

  250 g / m2 carrier paper containing 3% manganese oxide

  compared to the dry pulp is strongly colored brown.

  This support is coated with a sizing press with a weakly acid solution of formamidinesulfinic acid (at a rate of 5% relative to the coating bath) and a carboxymethylcellulose of high viscosity (at a rate of 0.7% by dry weight). compared

  in the coating bath) serving as a bath binder.

  The recovery of bath gluing is 30% by weight relative to the support paper.

  The final paper is white on its surfaces and colored brown in the center.

  Such a paper has a greatly improved opacity, it is noticeably impossible, even under a strong light to read inscriptions marked on the back of the paper,

  whereas a paper of equivalent grammage does not have this ability.

  This white product is printable and can therefore be used as instant lottery ticket paper without the need to laminate

  with aluminum foil to avoid transvision.

Claims (11)

CLAIMS:   1 - Opaque fibrous support (1), in particular paper, characterized in that it is constituted in particular by one and the same fibrous mat, homogeneous especially in its thickness and obtained from a single fibrous jet, and in that it comprises, in its thickness, at least one slice (2) substantially median of color (C2) and at least one slice (3,4) outside white or different color (C1, C3)   and / or less dark than that (C2) of the median slice (2).   2 - fibrous support according to claim 1, characterized in that it comprises a substantially middle colored edge, adjacent by each of its faces to a white outer edge or different color and / or less dark than the   middle slice, the two outer slices being of the same color or not.   3 - fibrous support according to claim 1 or claim 2, characterized in that it is obtained from a fibrous mat initially colored, then discolored at least partially on at least one of its two faces, preferably both, to form, the two outer slices (3) and (4) located on either side of the slice (2) median colored.   4 - fibrous support according to claim 1 or claim 2, characterized in that it is obtained from a fibrous mat initially colored and then colored at least partially differently on at least one of these two faces, preferably both, to form the two outer slices (3, 4) located on both sides   other of the middle (2) colored slice.   - fibrous support according to claim 1, characterized in that it comprises at least one coloring agent and optionally at least one bleaching agent and / or at least one transcoloration agent, unreacted but capable of   react with the coloring agent in the outer slices.   6 - fibrous support according to claim 5, characterized in that the pairing agent stain / bleaching agent and / or transcoloration is selected from the following group: dyeing agent bleaching agent and / or transcoloration metal oxide reducer metal salt sequestering colored pH indicator medium pH selected colored oxidation-reduction indicator medium potential Redox selected dye degradation agent dye and mixtures thereof   7 - fibrous support according to any one of claims 1 to 6,   characterized in that its basis weight is greater than or equal to 80 g / m 2, preferably between 100 and 400 g / m 2, and still more preferably between 120 and 300 g / m2.   8 - Process for obtaining a fibrous support, in particular paper, constituted in particular by one and the same fibrous mat, homogeneous in particular in its thickness, opaque and comprising, in its thickness, at least one (preferably one) slice substantially median colored and at least one (preferably two) outer slice white or different in color and / or less dark than the middle slice, characterized in that it consists essentially in - 1 - to prepare a fibrous pulp - preferably a pulp, incorporating at least one coloring agent, to put this paste in the form of a support consisting of one and the same fibrous sheet, produced by monojet,   - 3 - at least partly to eliminate the water present in the support-   sheet, 4 - to discolor and / or to discolor at least one outer slice of the   support-sheet before, during or after the removal of water.   9 - Process according to claim 8, characterized in that the target fibrous support (eg paper) has a substantially median colored slice and, on either side of it, a white or different external slice and / / or less dark than the middle edge, these two   external slices are of the same or different colors.   - Method according to claim 8 or 9, characterized in that in the case of a decolorization / transcoloration by chemical means, it uses a pair of coloring agent / bleaching agent and / or transcoloration chosen from the following group: Agent staining agent Discoloration agent and / or transcoloration metal oxide reducer metal salt sequestering colored indicator of pH medium at selected pH colored indicator of oxidation-reduction medium with potential Redox chosen dye degradation agent of the dye and their mixtures   11 - Process according to any one of claims 8 to 10, characterized   in that the bleaching / decolourising agent is a chemical means, in that the fibrous support is paper made with the aid of a paper machine, and that the bleaching agent is applied. discolouration in and / or out of the paper machine on at least one of the outer faces of the sheet, preferably using at least one of the following: gluing press, rewetting system or sleeping system.   12 - security paper authenticizable by tearing characterized in that it consists in particular of the fibrous support according to any one of   1 to 7 and / or obtained by carrying out the method according to one of   any of claims 8 to 11.   13 - Scratching game ticket, characterized in that it is notably   constituted by the fibrous support according to any one of claims 1 to 7, and / or   obtained by carrying out the method according to any one of claims 8 to