EP0169750B2 - Process for the production of luminescent security fibres and other related materials - Google Patents

Abstract

The invention relates to security fibers and other allied materials made luminescent by a dyeing process employing rare-earth compounds and their applications in fiduciary documents and other materials requiring authentication.

Description

The present invention relates to a process for producing safety fibers, safety threads, textile materials, plastic films and regenerated cellulose, luminescent resins.

Security fibers are fibers which are incorporated in fiduciary documents or other matters for the purpose of ensuring identification, authentication, protection against counterfeiting, imitation or falsification. Security threads are continuous threads or strips of film, introduced in fiduciary documents for the same purposes as security fibers.

The expression "fiduciary documents" designates here and in the following papers such as papers for banknotes, checks, stocks, securities, stamps, official documents, identity cards, passports, booklets, tickets, tickets, vouchers , newsletters, books of account, as well as credit, payment, access, multi-function cards and similar documents necessarily presenting a high level of security.

The expression “other materials” designates here materials which, in order to fight against their counterfeiting, imitation or falsification require a means of identification, authentication and protection obtained by the incorporation of security fibers in or on these materials.

• fibres visibles en lumière solaire ou artificielle,
• fibres visibles en lumière solaire ou artificielle et présentant une fluorescence sous les rayons ultra-violets, infra-rouges ou X,
• fibres invisibles en lumière solaire ou artificielle mais présentant une fluorescence sous les rayons ultra-violets, infra-rouges ou X. L'expression « fibres invisibles en lumière solaire ou artificielle » signifie que ces fibres qui sont fluorescentes sous les rayons infra-rouges, ultra-violets ou X, ont, à la lumière solaire ou artificielle, une couleur identique à celle qui était la leur avant le traitement qu'elles ont subi et qui les a rendu fluorescentes. Dans le cas le plus général de la fabrication d'un papier de sécurité blanc avant son impression, des fibres de sécurité blanchâtres sont incorporées à la pâte à papier blanche et ces fibres sont donc invisibles ou indiscernables en ayant la même couleur que le papier; cependant, sous excitation par exemple de rayons ultra-violets, ces fibres émettent une fluorescence par exemple dans le bleu.

The security fibers incorporated in these fiduciary documents and other matters can generally be classified as follows:

• fibers visible in sunlight or artificial light,
• fibers visible in sunlight or artificial light and exhibiting fluorescence under ultraviolet, infrared or X rays,
• fibers invisible in sunlight or artificial light but exhibiting fluorescence under ultraviolet, infrared or X rays. The expression "fibers invisible in sunlight or artificial light" means that these fibers which are fluorescent under infrared rays, ultraviolet or X, have, in sunlight or artificial light, a color identical to that which was theirs before the treatment which they underwent and which made them fluorescent. In the most general case of manufacturing a white security paper before printing, whitish security fibers are incorporated into the white paper pulp and these fibers are therefore invisible or indistinguishable by having the same color as the paper; however, under excitation, for example of ultraviolet rays, these fibers emit fluorescence, for example in blue.

The present invention relates to the production of fibers preferably from the last group which are therefore invisible in sunlight or artificial light and which, under excitation of IR, UV, or X rays, exhibit luminescence in one or more parts of the IR, visible, UV spectrum. , or X.

The dyes used in the context of this invention are Rare Earth compounds, or Lanthanides, with atomic number 57 to 71 to which we usually attach Yttrium and Thorium with atomic number 39 and 90. The Rare Earth compounds which have these luminescence characteristics used in this invention are Chelates.

In the state of the prior art, we have seen the use of numerous luminescent lanthanide compounds for identification purposes in particular in fiduciary documents, with French patents 1,471,367, 4,520,520, 2,289,976, 2 423,522, French patent applications 2,483,334, 2,484,920, 2,484,921, 2,484,922.

These patents and patent applications, when they envisage the use of rare earth chelates, describe the incorporation of these chelates into inks or varnishes by dissolution, or by incorporation into the mass of paper.

This is also the case with patent FR-A-1,522,465 which describes coating compositions incorporating a rare earth chelate intended to be applied to various substrates.

Fluorescent substances other than Lanthanide chelates have also been used for identification purposes, for example in accordance with patent GB-A-713,351 which describes the use of fluorescent substances sensitive to chemical reagents generally used for the falsification of fiduciary documents and the treatment of fibers with these substances.

When these patents and patent applications envisage the use of rare earth chelates in safety fibers, these patents and patent applications state only the idea thereof but without giving the embodiment thereof. It is found, for example, in French patent applications 2,484,922 and 2,484,334 that "the luminescent substance is represented in the paper by security fibers prepared accordingly during the manufacture of the paper". However, it is known on the one hand that the preparation of security fibers is not made during the manufacture of paper, except by dyeing the mass of paper and not of security fibers, and on the other hand that the preparation real security fibers is a different operation and chronologically prior to papermaking; this operation is carried out by the dyeing industries.

Those skilled in the art, in this case, the fiber dyeing expert, cannot, on the sole statement of the idea, carry out a fiber dyeing with these rare earth phosphors. Indeed the dyeing process with these chelates is not described because the realization of the idea comes up against a major difficulty: these chelates, introduced into a fiber dye bath, are insoluble in water and therefore cannot penetrate the fibers by the usual fiber dyeing processes.

To resolve this difficulty, it has been proposed, in particular in German patent application 31 224 70, to add these chelates to the spinning mass used to extrude continuous threads subsequently cut into fibers.

This embodiment of safety fibers, satisfactory on the theoretical level, presents in practice heavy constraints: in fact the manufacturers-extruders of continuous threads, which could incorporate into their spinning mass rare earth chelates do not wish to modify the composition of their spinning mass for small productions, while the fibers of Safety, obtained from these cut continuous yarns, would represent, considering their uses and their price, only a tiny proportion of the monthly or even daily production of these manufacturers-extruders of continuous yarns.

The present invention therefore proposes to resolve these difficulties by describing a process for producing safety fibers in which the incorporation of luminescent chelates of lanthanides, Yttrium or Thorium is made not in the spinning mass of continuous threads, but by a dyeing process of fibers already extruded and cut into fibers (see Claim 1).

Being a dyeing process, this invention has the advantage of having a certain similarity with the dyeing processes used by fiber dyers and therefore of using almost standard apparatuses in this industry, and of offering the possibility of carrying out manufacturing cycles compatible with the small quantities of safety fibers used by the industries which use them.

This dyeing process, which dyes fibers with Rare Earth chelates, is carried out in two different ways.

In the first embodiment, the method basically consists in using as a dyeing medium a bath containing a combination of one or more solvents in which the rare earth chelates used are soluble, and one or more diluents in which the earth chelates Few are insoluble or sparingly soluble, and take all or part of the solvent in liquid or vapor phase from the dye bath. This dyeing process, already known in the prior art, has been used to dye with acid dyes and metalliferous acids, and those skilled in the art can find all the details in the literature, and in particular in French patents 2,054,430, 2,061,574, 2,088,081, 2,124,193.

Example 1: Numerous exemplary embodiments of dyeing safety fibers with luminescent rare earth chelates according to this first embodiment of the invention were produced by replacing in Examples 1 to 7 of French patent 2,054,430, and 1 to 9 of French patent 2,124,193 textile materials used by fibers, dyes used by luminescent chelates from Rare Earths; the proportions of chelates used to replace the dyes are of the same order of magnitude and are fixed as a function of the intensity of the fluorescent emission desired in the safety fibers.

The applicant has also found that a good dyeing of safety fibers is obtained by using a dyeing bath comprising only a solvent in which the chelates are soluble.

In the second embodiment of dyeing safety fibers with Rare Earth chelates, this process basically consists in forming and synthesizing Rare Earth chelate in the dye bath which contains the fibers to be dyed, and therefore in fibers to be dyed.

The single example which follows illustrates, without limitation, this second embodiment of the invention.

Example 2; 1 kg of Fibranne® fibers of 27 dtex and 5 mm in length is introduced into a bath at 85 ° C. formed from an aqueous solution of 20 liters of 4.4.4. Trifluoro.1.Phenyl.1.3.Butanedione of Sodium for 30 minutes; an aqueous solution of Terbium chloride which then causes the synthesis of the corresponding chelate and its precipitation in the fibers is then added with stoichiometric amount. The fibers taken out of the dye bath and dried, still have their original whitish appearance, but are fluorescent in green under UV rays due to the presence of the chelate precipitated in the fibers.

We can replace the aqueous bath of this example with a water-solvent or pure solvent bath and usefully refer to the literature on the manufacture of rare earth chelates.

The respective amounts of chelating agents and rare earth salts are set according to the nature of the chelate to be synthesized and the luminescence intensity sought in the fibers.

The working conditions of the dye bath are those usually used in the dyeing of textile fibers, in particular with regard to the temperature and the pressure which are selected according to the nature of the fibers to be dyed.

The fibers which can be used according to the first or second embodiment of this invention can be natural, artificial or synthetic, and without departing from the scope of this invention, textile materials can be dyed according to either of these two modes. of the same nature as fibers, as well as continuous threads, films, natural, artificial or synthetic resins.

This dyeing process can also be applied to fibers of the first and second group, that is to say already colored fibers (their color, for example yellow, being visible in sunlight or artificial dye) which will present after their dyeing according to this invention a very interesting characteristic of additional luminescent emission (in this example the yellow fibers will also have a green fluorescence under UV if they have been dyed with a Terbium chelate according to one of the two methods described).

The fibers produced according to Examples 1 and 2 of this invention were added in small quantities to the paper pulp; a paper machine transformed this paper pulp into paper and an excellent security paper was thus produced comprising authentication marks which are invisible except under certain lighting conditions (UV, IR, or X).

Claims (5)

1. Processes for the production of safety fibers, safety threads, textile materials, plastic or regenerated cellulose films, natural, artificial synthetic resins, luminescent because of the introduction of luminescent rare earth chelates, or chelates of yttrium or thorium, characterized by the fact that the introduction of luminescent chelates is effected at a stage subsequent of their production in which said chelates have not been used, by a dyeing process comprising a liquid dye bath containing at least one of said luminescent chelates and optionally a coloring agent for the dyeing, dissolved in said dyeing bath.
2. Process for the production of safety fibers and other related materials according to claim 1, characterized by the fact that said materials are made luminescent by a dyeing process consisting :

   - in immersing the material to be dyed in a liquid bath containing :

   -- at least a luminescent chelate,

   -- at least a solvent in which the chelate is soluble, and in sufficient quantity to dissolve the chelate,

   -- at least a diluent in which the chelate is insoluble or hardly soluble, miscible with the solvent, and added in such proportion that the chelate is kept in solution in the dye bath,

   - in removing from the dye bath all or part of the solvent in liquid or steam phase, at the end of the dyeing,

   - in removing from the dye bath the material thus dyed with the luminescent chelate.
3. Process for the production of safety fibers and other related materials according to claim 1, characterized by the fact that these materials are made luminescent by a dyeing process comprising in the dye bath only one or more than one solvents in which at least one luminescent chelate is dissolved.
4. Process for the production of safety fibers or other related materials according to claim 1, characterized by the fact that said materials are made luminescent by a dyeing process during which the synthesis of a luminescent chelate is carried out and induces its precipitation in the materials to be dyed.
5. Process for dyeing safety fibers and other related materials according to any one of claims 1 to 4, characterized by the fact that said dyeing process confers to said materials dyed in this way the property exhibiting at least a luminescence in one part of the IR, visible, UV or X-ray spectrum, and that it does not modify the color, visible sunlight or artificial light, of said materials.