EP1934400A2 - Papier de surete - Google Patents

Papier de surete

Info

Publication number
EP1934400A2
EP1934400A2 EP06792172A EP06792172A EP1934400A2 EP 1934400 A2 EP1934400 A2 EP 1934400A2 EP 06792172 A EP06792172 A EP 06792172A EP 06792172 A EP06792172 A EP 06792172A EP 1934400 A2 EP1934400 A2 EP 1934400A2
Authority
EP
European Patent Office
Prior art keywords
core
paper
security
shell
shell particles
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP06792172A
Other languages
German (de)
English (en)
Inventor
Burkhard Krietsch
Matthias Kuntz
Holger Winkler
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Merck Patent GmbH
Original Assignee
Merck Patent GmbH
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Merck Patent GmbH filed Critical Merck Patent GmbH
Publication of EP1934400A2 publication Critical patent/EP1934400A2/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H21/00—Non-fibrous material added to the pulp, characterised by its function, form or properties; Paper-impregnating or coating material, characterised by its function, form or properties
    • D21H21/14—Non-fibrous material added to the pulp, characterised by its function, form or properties; Paper-impregnating or coating material, characterised by its function, form or properties characterised by function or properties in or on the paper
    • D21H21/40—Agents facilitating proof of genuineness or preventing fraudulent alteration, e.g. for security paper
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H21/00—Non-fibrous material added to the pulp, characterised by its function, form or properties; Paper-impregnating or coating material, characterised by its function, form or properties
    • D21H21/50—Non-fibrous material added to the pulp, characterised by its function, form or properties; Paper-impregnating or coating material, characterised by its function, form or properties characterised by form
    • D21H21/52—Additives of definite length or shape
    • D21H21/54—Additives of definite length or shape being spherical, e.g. microcapsules, beads
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00—Stock material or miscellaneous articles
    • Y10T428/24—Structurally defined web or sheet [e.g., overall dimension, etc.]
    • Y10T428/24802—Discontinuous or differential coating, impregnation or bond [e.g., artwork, printing, retouched photograph, etc.]
    • Y10T428/24893—Discontinuous or differential coating, impregnation or bond [e.g., artwork, printing, retouched photograph, etc.] including particulate material

Definitions

  • the present invention relates to a security paper for the production of documents of value, wherein the paper comprises a sheet-like cellulosic substrate containing core-shell particles, which give the paper an optically variable appearance, an improved mechanical stability and an improved tear strength.
  • the invention further relates to methods for producing such a security paper as well as value documents containing such a security paper.
  • Securities and security documents such as banknotes, passports, identity documents, stocks, bonds, certificates, checks, vouchers, tickets, tickets and the like are often made of paper or of materials having at least one layer of cellulosic material.
  • Banknotes are usually very porous due to the primary use of cotton fibers and therefore have a high tendency to circulate
  • DE 198 29 004 A1 describes a security paper which, at least on one of its surfaces, has a coating which consists only of a binder. This layer is to form a closed surface film on the surface of the paper, which minimizes dirt access to the fiber.
  • binders acrylates or polyurethanes can be used.
  • DE 103 27 083 A1 discloses a security paper which has a coating of two layers, the lower of which closes the pores of the paper substrate, while the upper lacquer layer protects the substrate from physical and chemical influences. Both layers can contain common polymers.
  • DE-OS 2 307 894 also discloses a process in which plastic-containing papers are produced by adding polymeric materials to the paper stock.
  • the suspension used must contain particles with sizes of 4 to 30 microns, so that they during of the papermaking process can be attached to the paper fibers to give strength to the paper.
  • EP 0 441 559 A2 discloses core / shell particles which have a cavity between core and shell and can likewise be used for papermaking. These give opacity, brightness and gloss to the paper treated with it and can replace some of the usual additives such as kaolin or titanium dioxide.
  • corresponding dyes in particulate or dissolved form are either added to the paper pulp or applied by sizing.
  • paper can either be dyed uniformly or provided with functional dyes, for example with photoluminescent color pigments.
  • an optically variable appearance can not be achieved by the use of optically variable pigments in the paper pulp, since the paper fibers at least partially cover the pigments and hinder their alignment.
  • Process can be prepared by the addition of substantially a single substance.
  • an optically variable security paper for the production of value documents which comprises a sheet-like cellulosic substrate containing core / shell particles whose core is substantially solid and dimensionally stable and has a substantially monodisperse size distribution, wherein the Core is chemically bonded to the shell via an intermediate layer, the weight of the shell is equal to or greater than the weight of the core and a
  • the object of the invention is also achieved by a method in which core / shell particles whose core is substantially solid and dimensionally stable and having a substantially monodisperse size distribution and wherein the core is chemically bonded to the shell via an intermediate layer, the weight of the shell is equal to or greater than the weight of the core and a difference between the refractive indices of the core material and the cladding material, introduced into an aqueous paper pulp and then processed together with the usual paper raw materials into a paper sheet.
  • the object of the invention is also achieved by a method in which an aqueous dispersion of core / shell particles whose core is substantially solid and has a substantially monodisperse size distribution and wherein the core is chemically bonded to the shell via an intermediate layer in that the weight of the jacket is equal to or greater than the weight of the core and a difference between the refractive indices of the core material and the cladding material is applied to at least part of the surface of an unsized or glued paper and then dried.
  • the object of the invention is also achieved by the use of the above-mentioned security paper for the production of value documents such as banknotes, passports, identity documents, shares, bonds, certificates, checks, vouchers, tickets, tickets and the like as well as the provision of such value documents.
  • Security papers like other papers, are produced in a paper machine in which the following work steps are usually carried out successively: stock extraction, stock preparation, wire section, press section, dryer section, surface finishing, smoothing and cutting.
  • the material extraction serves primarily to obtain the cellullose-containing starting material for papermaking. This can be obtained from various plant fibers or from rags. To produce security paper cotton fibers are preferably used, which can be obtained either directly from cotton plants, but also from rags.
  • the various paper ingredients consisting of the cellulosic base stock and various additives are mixed with water to form a pulp, the pulp.
  • the additives are chosen so that they affect a variety of desired properties of the paper such as color, smoothness, whiteness, basis weight, strength, water-repellent properties, etc., but may also contain particles or fibers, which already give the finished security paper security features, such as Planchets (small paper or plastic flakes), fibers of different materials (eg plastics), which may also have photoluminescent properties, fluorescent starlets, detectable by specific light sources or specific chemical reactions chemical additives and the like.
  • Planchets small paper or plastic flakes
  • fibers of different materials eg plastics
  • the wire section of the highly diluted aqueous pulp is evenly distributed on a rotating sieve. Excess water runs off or is sucked off. In this wire section also the introduction of genuine watermarks in the paper takes place.
  • the paper is subjected to a so-called sizing or coating process, by which the absorbency of the paper is usually reduced.
  • This sizing is usually done with binders and / or pigments and serves to produce the desired surface properties, such as basis weight, relative humidity, toner adhesion and fixation, porosity, pH, gloss, whiteness, and the like.
  • the security paper according to the present invention comprises a cellulose-containing substrate which consists of the materials customary for the production of security papers, ie preferably cellulose from vegetable fibers and / or hardern and in particular cellulose fibers from cotton.
  • the cellulosic substrate may also contain plastic fibers as well as other common additives.
  • the choice of additives depends on the desired paper properties and can vary widely. For the purposes of the present invention, the nature of the additives is not critical and therefore not limiting, as long as they do not chemically react with the core / shell particles of the present invention. In this respect, it is the expertise of the paper manufacturer which additives he adds to the production process for producing the security paper according to the invention.
  • the cellulose-containing substrate is preferably a sized or unsized paper.
  • the cellulose-containing substrate for the security paper according to the present invention contains core / shell particles whose core is substantially solid and dimensionally stable and has a substantially monodisperse size distribution, the core being chemically bonded to the shell via an intermediate layer.
  • the weight of the shell is equal to or greater than the weight of the core and the material of which the core is made and the material of which the shell is made (the core material and the shell material) are chosen so that there is a difference in refractive index between the two , Preferably, the weight of the shell is greater than the weight of the core.
  • the cores of the core / shell particles have a substantially spherical, in particular spherical shape and have a substantially monodisperse size distribution, ie they are present in a very narrow particle size distribution.
  • the average particle diameter of the core particles is in the range of 30-400 nm, in particular in the range of 60-350 nm and particularly preferably in the range of 90-300 nm. In general, the particle diameter of the core particles is about 60 to about 80%, in particular about 65 to about 75% of the total diameter of the core / shell particles.
  • the core / shell particles have an average particle diameter in the range of about 50-800 nm.
  • particles in the range of 100-500 nm are used and particularly preferably particles having a particle diameter of 150-400 nm.
  • optical effects in the visible wavelength range of the light can be expected to be preferred.
  • core / shell particles whose size corresponds to a multiple of the particle sizes described here.
  • the cores of the core / shell particles are substantially solid and dimensionally stable. This means that under the processing conditions in the papermaking process or in the production of the core / shell particles, the cores either do not become flowable or become fluid at a temperature which is above the flow temperature of the shell material. Under the same conditions, the material that makes up the cores is also virtually non-swellable.
  • organic polymeric materials having a correspondingly high glass transition temperature (T g ) or else inorganic core materials are selected as the core materials.
  • the cores are made of an organic polymeric material, which is especially crosslinked, or contain this predominantly.
  • Suitable polymers are both polymers and copolymers of polymerizable unsaturated monomers and polycondensates and copolycondensates of monomers having at least two reactive groups, such as.
  • As high molecular weight aliphatic, aliphatic / aromatic or wholly aromatic polyester polyamides, polycarbonates, polyureas and polyurethanes, but also aminoplast and phenolic resins, such as.
  • Epoxy resins are also suitable as core material.
  • the polymers of the core material in a preferred variant of the invention are crosslinked (co) polymers, since these usually show their glass transition only at high temperatures.
  • These crosslinked polymers may either have been crosslinked in the course of the polymerization or polycondensation or copolymerization or copolycondensation, or they may have been postcrosslinked in a separate process step after completion of the actual (co) polymerization or (co) polycondensation.
  • the monodisperse cores are obtained from organic polymeric materials by emulsion polymerization.
  • auxiliaries and additives used for example polymerization initiators, dispersing aids, emulsifiers, crosslinkers and the like, reference is expressly made to the corresponding statements in EP 0 955 323 A1 and in WO 03/025035 A2.
  • the core consists wholly or predominantly of an inorganic material, preferably a metal or semimetal or a metal chalcogenide or metal pnictide.
  • an inorganic material preferably a metal or semimetal or a metal chalcogenide or metal pnictide.
  • Chalcogenide be referred to in the context of the present invention, such compounds in which an element of the 16th group of the Periodic Table is the electronegative binding partner;
  • pnictides are those in which an element of the 15th group of the periodic table is the electronegative binding partner.
  • Preferred cores consist of metal chalcogenides, preferably metal oxides, or metal pnictides, preferably nitrides or phosphides.
  • Metal in terms of these terms are all elements that can occur as electropositive partner in comparison to the counterions, such as the classical metals of the subgroups, or the main group metals of the first and second main group, as well as all elements of the third main group, as well Silicon, germanium, tin, lead, phosphorus, arsenic, antimony and bismuth.
  • the preferred metal chalcogenides and metal pnictides include in particular
  • monodisperse cores of silicon dioxide which can be obtained, for example, by the process described in US Pat. No. 4,911,903.
  • the cores are produced by hydrolytic polycondensation of tetraalkoxysilanes in an aqueous-ammoniacal medium, wherein first of all a sol of primary particles is produced and subsequently the resulting SiO 2 particles are brought to the desired particle size by a continuous, controlled metered addition of tetraalkoxysilane.
  • monodisperse SiO 2 cores with average particle diameters between 0.05 and 10 ⁇ m can be produced with a standard deviation of 5%.
  • SiO 2 cores which are coated with (semi-) metals or non-absorbing metal oxides in the visible range, for example TiO 2 , ZrO 2 , ZnO 2 , SnO 2 or Al 2 O 3 .
  • the production of SiO 2 cores coated with metal oxides is described in more detail, for example, in US Pat. No. 5,846,310, DE 198 42 134 and DE 199 29 109.
  • Monodisperse cores of nonabsorbing metal oxides such as TiO 2 , ZrO 2 , ZnO 2 , SnO 2 or Al 2 O 3 or metal oxide mixtures can also be used as starting material. Their preparation is described, for example, in EP 0 644 914. Furthermore, the process according to EP 0 216 278 for the production of monodisperse SiO 2 cores is readily transferable to other oxides with the same result.
  • suitable starting materials for the production of the core-shell particles are also monodisperse cores of polymers which contain embedded particles, which consist for example of metal oxides.
  • Such materials are offered, for example, by the company micro capseries- undmaschines GmbH in Rostock. According to customer requirements, microencapsulations based on polyesters, polyamides and natural and modified carbohydrates are manufactured.
  • monodisperse cores of metal oxides which are coated with organic materials, for example silanes.
  • the monodisperse cores are dispersed in alcohols and modified with common organoalkoxysilanes. The silanization of spherical oxide particles is also described in DE 43 16 814.
  • the size and particle size distribution of the cores can be adjusted particularly well if the cores predominantly or exclusively consist of organic polymers and / or copolymers.
  • the cores preferably consist predominantly of a single polymer or copolymer, and more preferably of polystyrene.
  • the cores of the core / shell particles may also contain a contrast material. It may be a soluble or insoluble colorant.
  • Soluble colorants are generally soluble, mostly organic, dyes, which may be of natural or synthetic origin and are typically selected from the classes of compounds of carbonyl colorants such as quinones, indigoid colorants and quinacridones, cyanine colorants such as di- and triarylmethanes, and quinone imines.
  • Insoluble colorants are organic or inorganic color pigments. These are preferably absorption pigments and in a variant of the invention particularly preferably black pigments, for example carbon black.
  • these contrast materials are usually inorganic or organic pigments, which may be of natural or synthetic origin.
  • pigments are understood to mean any solid substance which exhibits an optical effect in the visible wavelength range of the light or which has certain functional properties.
  • such substances are referred to as the pigments, the definition of Pigments according to DIN 55943 or DIN 55944 correspond.
  • a pigment is a practically insoluble in the application medium, inorganic or organic, colored or achromatic colorant or a practically insoluble in the application medium substance which has special properties, such as magnetic, electrical or electromagnetic properties.
  • the shape of these pigments is immaterial, in particular they may be spherical, platy or needle-shaped nature or have irregular particle shapes.
  • pigments which are incorporated into the cores of the core / shell particles have an average particle size which is not greater than the average particle size of the cores.
  • Luminescent compounds are understood as meaning substances which emit mechanically measurable and optionally visible radiation by excitation in the visible wavelength range, in the IR or in the UV wavelength range of the light, by electron beams or by X-rays. These also include substances which emit radiation by excitation in the electromagnetic field, the so-called electroluminescent substances which, if appropriate, additionally luminesce by excitation in the UV or IR wavelength range. Suitable for this purpose are all known particulate and soluble substances having the abovementioned properties. The particulate
  • Substances are present in a suitable particle size, ie with an average particle size which does not exceed the mean particle diameter of the cores.
  • the luminescent particles are therefore particularly preferably in the form of nanoparticles or in the form of the so-called quantum dots.
  • the particulate substances need not necessarily be in pure form but may also comprise microencapsulated particles as well as doped or coated carrier materials impregnated with luminescent substances. For this reason, luminescent substances can be incorporated into the cores or as nuclei of the core / shell particles. This applies to both soluble and particulate luminescent materials.
  • luminescent substances besides any kind of organic luminescent substances, there may be mentioned, for example, Ag-doped zinc sulfide ZnS: Ag, zinc silicate, SiC, ZnS, CdS which is activated with Cu or Mn, ZnS / CdS: Ag; ZnS: Cu, ZnS: Tb; ZnS: Al; ZnSTbF 3 ; ZnS: Eu; ZnS: EuF 3 ; Y 2 O 2 SrEu; Y 2 O 3 : Eu; Y 2 O 3 Tb; YVO 4 : Eu; YVO 4 : Sm; YVO 4 : Dy; LaPO 4 : Eu; LaPO 4 : Ce; LaPO 4 : Ce, Tb; Zn 2 SiO 4 : Mn; CaWO 4 ; (Zn, Mg) F 2 : Mn; MgSiO 3 : Mn; ZnO: Zn; Gd 2 O 2 STb; Y
  • Magnetic particles whose average particle diameter does not exceed the mean particle diameter of the cores of the core / shell particles can also be incorporated into the cores of the core / shell particles. This is particularly possible when an organic polymer is used as the core material.
  • all magnetic particles which consist of magnetizable materials or contain magnetizable materials as the core, coating or doping are suitable for this purpose.
  • all known materials such as magnetizable metals, magnetizable metal alloys or metal oxides and oxide hydrates, such as ⁇ -Fe 2 O 3 or FeOOH, can be used as the magnetizable materials.
  • Their application availability is only determined by the average particle size, which may not be greater than the mean particle size of the cores.
  • Their shape is not essential, especially needle-shaped magnetic particles can be incorporated.
  • the term "contrast agent” should also be understood to mean fibrous or particulate additives which are essentially transparent and colorless. These are preferably particles or fibers of plastics, glass or other solid, transparent, different from the core material materials that are introduced into the core material to increase the mechanical strength of the core / shell particles.
  • polymers of the classes already mentioned above are suitable, provided that they are selected or constructed in such a way that they correspond to the specification given for the cladding polymers.
  • the cladding material must have a refractive index that is different from the refractive index of the core material.
  • the core and cladding must not be made of the same material at the same time. It is not essential whether the core or the cladding has the higher refractive index.
  • the core consists of a material with a higher refractive index than that of the cladding material.
  • the difference between the indices of refraction of the core and cladding materials should be at least 0.01 and in particular at least 0.1.
  • the jacket material is filmable. That is, the jacket material can be heated to a temperature at which the jacket is flowable.
  • the shell is softened, visco-elastic plasticized or liquefied.
  • the jacket material has a flow temperature which is significantly lower than the flow temperature of the core material.
  • the flowability of the jacket material can be achieved by the action of increased pressure alone, but also by the action of elevated pressure and elevated temperature.
  • the shell material is already softened during the usual papermaking process by the action of pressure or pressure and temperature such that it becomes filmable.
  • the cladding material is softened only in a process step subsequent to the papermaking process by pressure or pressure and heat in a pressing and / or embossing process in such a way that it becomes filmable.
  • the jacket material is already softened during the customary papermaking process by application of pressure or pressure and temperature, wherein the degree of softening is further increased by subsequent pressing and / or embossing processes and thus the filmability of the material can be improved.
  • Polymers which meet the specifications for the shell material can also be found in the groups of polymers and copolymers of polymerizable unsaturated monomers, as well as the polycondensates and copolycondensates of monomers having at least two reactive groups, such as.
  • the high molecular weight aliphatic, aliphatic / aromatic or wholly aromatic polyester and polyamides As the high molecular weight aliphatic, aliphatic / aromatic or wholly aromatic polyester and polyamides.
  • selected building blocks from all groups of organic film formers are suitable for their preparation.
  • Some other examples may illustrate the wide range of polymers suitable for the manufacture of the sheath.
  • polymers such as polyethylene, polypropylene, polyethylene oxide, polyacrylates, polymethacrylates, polybutadiene, polymethyl methacrylate, polytetrafluoroethylene, polyoxymethylene, polyesters, polyamides, polyepoxides, polyurethane, rubber, polyacrylonitrile and polyisoprene, and the like are suitable copolymers.
  • the sheath have a comparatively high refractive index
  • polymers having preferably aromatic basic structure such as polystyrene, polystyrene copolymers such.
  • It can be used as a shell material and elastically deformable polymers such as various polyurethanes, low molecular weight polyesters, silicones, polyether- or polyester-modified silicones.
  • the sheaths of the core / shell particles may contain a contrast agent.
  • a contrast agent In this case, essentially all contrast agents come into question, which have already been described in advance for inclusion in the cores of the core / shell particles.
  • the particulate contrast agents are not subject to any significant size restriction when incorporated into the shells. Much more can be incorporated into the shells of the core / shell particles and solid, particulate contrast agents whose particle sizes are significantly larger than the average particle diameter of the core / shell particles themselves. This is due to the fact that the sheath materials used a significant "sticking" in Even when incorporated into the shells of the core / sheath particles, the form of the insoluble contrast agent used is not limited, but contrast agents can be used in any suitable form.
  • coats of the core / shell particles can also be incorporated with auxiliaries and additives which are not of a particulate nature, for example flow improvers, dispersants, emulsifiers and the like.
  • the cores of the core / shell particles used according to the invention are chemically bonded to the shell via an intermediate layer.
  • This means that the nuclei are modified in such a way that binding of the shell takes place via chemical bonds, but not by mere attachment.
  • these are covalent bonds.
  • an electrostatic binding of the jacket to the core is sufficient.
  • the intermediate layer in a preferred embodiment of the invention is a polymeric intermediate layer, for example a layer of crosslinked or at least partially crosslinked polymers.
  • the crosslinking of the intermediate layer via free radicals, for example induced by UV irradiation, or preferably via di- or oligofunctional monomers take place.
  • Preferred intermediate layers of this embodiment contain from 0.01 to 100% by weight, particularly preferably from 0.25 to 10% by weight, of di- or oligofunctional monomers.
  • Preferred di- or oligofunctional monomers are in particular isoprene and allyl methacrylate (ALMA).
  • Such an intermediate layer networked or at least partially crosslinked polymers preferably has a thickness in the range of less than 1 nm to 20 nm.
  • the refractive index of this layer is chosen so that it corresponds to either the refractive index of the core material or the refractive index of the cladding material.
  • copolymers are used as intermediate layer which, as described above, contain a crosslinkable monomer, it is no problem for the skilled person to suitably select corresponding copolymerizable monomers.
  • corresponding copolymerizable monomers can be selected from a so-called Qe scheme (see Textbooks in Macromolecular Chemistry).
  • monomers such as methyl methacrylate and methyl acrylate may be polymerized with ALMA.
  • the shell polymers are directly via a corresponding
  • the surface functionalization of the core forms the above-mentioned intermediate layer.
  • the type of surface functionalization depends mainly on the material of the core.
  • Silica surfaces can be suitably modified, for example, with silanes bearing corresponding reactive end groups, such as epoxy functions or free double bonds.
  • Other surface functionalizations for example, for metal oxides, can be carried out with titanates or aluminum organyls, each containing organic side chains with appropriate functions.
  • an aromatic-functionalized styrene such as bromostyrene, can be used for surface modification. This functionalization can then be used to achieve the growth of the sheath polymers.
  • the intermediate layer can also bring about adhesion of the shell to the core via ionic interactions or complex bonds.
  • the shell of the core / shell particles consists of substantially uncrosslinked organic polymers, which are preferably grafted onto the core via an at least partially crosslinked intermediate layer.
  • the jacket may consist of either thermoplastic or elastomeric polymers. Since the jacket substantially determines the material properties and processing conditions of the core-shell particles, those skilled in the art will select the jacket material according to common considerations in polymer technology.
  • the intermediate layer in the core / shell particles used according to the invention guarantees a stability of the core / shell particles against the influence of increased pressure and elevated temperature, which ensures that no phase separation of core and shell occurs under these conditions.
  • the structure of core / shell particles whose cladding is merely attached to the core can not be maintained under the effect of elevated pressure and temperature.
  • pressure exerted in this case will cause the cladding material is separated from the core material and thus the previously achieved by the different refractive indices of core and clad optical effect is canceled.
  • the weight of the shell in the core / shell particles used according to the invention is equal to or greater than the weight of the core.
  • the weight ratio of core to shell in the range of 1: 1 to 1: 5, more preferably in the range of less than 1: 1 to 1: 3 and in particular in the range of 1: 1, 1 to 2: 3.
  • This weight ratio of core to shell is an essential feature of the present invention. Only by means of a sufficiently large proportion by weight of the shell and the large number of polymer chains thus present is it possible that the core / shell particles in the papermaking process also in total small particle sizes can be held on the fibrous paper raw materials and are not removed by the sieve from the pulp.
  • the core / shell particles used according to the invention can be arranged in a largely regular structure during drying and smoothing of the paper substrate, since the polymeric shell material already softens to a certain extent under the usual production conditions of the paper and within the Fiber structure of the paper is at least partially filmed.
  • Core / shell particles suitable for the security paper according to the present invention can be prepared, for example, according to the examples set forth in WO 03/025035.
  • the core / shell particles described above are contained in the security paper according to the present invention in a first embodiment in the cellulose-containing substrate.
  • the core / shell particles are added to the customary starting materials.
  • these include the celulose-containing paper stock and the various additives. These are selected by the paper manufacturer according to the desired paper properties and are limited only insofar as they do not undergo any chemical reactions with the above-mentioned core / shell particles which alter the optical properties of the core / shell particles.
  • the pulp produced from the starting materials already additives can be added, which are suitable in the finished security paper to form independent security features, such as planchettes, fibers of different materials, photoluminescent fibers, photoluminescent particles such.
  • independent security features such as planchettes, fibers of different materials, photoluminescent fibers, photoluminescent particles such.
  • fluorescent starlets or even with the help of special light sources detectable or specific chemical reactions pointing chemical additives.
  • magnetic or electrically conductive substances may be included.
  • the core / shell particles used according to the invention impart an optically variable character to the security paper according to the present invention.
  • the cores apparently form at least partially regular structures that form a diffraction grating that causes interference phenomena.
  • the effect of pressure and temperature under the usual conditions in the paper machine is sufficient to soften the shell of the core / shell particles so far that the shell material at least partially forms a matrix in the paper in which the cores can arrange regularly.
  • This can form three-dimensional structures, which reaches a long-range order of the cores, which corresponds at least domain-wise approximately a cubic-area-tented dense spherical packing.
  • the regularly arranged cores form a diffraction grating, at which reflection, interference and scattering of the incoming or incident light take place simultaneously.
  • the achievable visual appearance In this case, it is also decisively determined by the refractive index difference of the core and sheath materials and by the particle diameter of the cores.
  • Optically variable effects are understood to mean those which lead to a different visually perceptible color and / or brightness impression at different illumination and / or viewing angles. For different color impressions, this property is called a color flop. These impart to the security paper according to the present invention non-duplicable color and gloss impressions which are readily perceptible to the naked eye.
  • the optically variable color impressions can be perceived as an interplay of two or more clearly distinguishable discrete colors or as a color gradient between different color end stages. Both effects can be well perceived by the human eye, but can not be copied in commercially available color copiers, especially since these effects, while the core / shell particles are present in the cellulosic substrate of the security paper, are clearly visible but not obtrusive.
  • the optically variable coloring of security paper can be easily controlled, for Different colorations for different denominations are desired without having to change the papermaking in other components or process steps.
  • the security paper according to the present invention Due to the usual paper thicknesses produced by conventional papermaking processes, the security paper according to the present invention has a certain degree of transparency. This makes it easy to observe a special feature of the security paper according to the invention. Namely, this has complementary optically variable colors in reflected light and in transmitted light. This means, for example, that a color flop perceived in the top view is connected from violet to blue-green with a complementary color flop from yellow-green to orange in the view.
  • the optically variable properties of the security paper according to the invention can also be subsequently enhanced, for example by a subsequent pressure or temperature and pressure treatment.
  • by partial pressing and / or embossing operations can thus produce specific effects at predetermined locations of the security paper.
  • the genuine watermarks in the paper are characterized in that the paper layer is particularly thin at these points. If core / shell particles are now present in the paper pulp, then by means of a specific embossing process at the location of the watermark, this can be highlighted in a particularly transparent and visually variable manner. At the same time, the complementary color flops in the view can be observed particularly well at the points highlighted in this way.
  • the watermark as a popular security feature in paper and paper-like products is thus strongly emphasized and upgraded both visually and in terms of security.
  • the addition of the core / shell particles to the security paper according to the invention achieves an increased mechanical strength of the paper, in particular an increased tensile strength and improved water-repellent properties of the security paper.
  • the porosity of the security paper is also reduced, whereby a reduced tendency to fouling can be determined.
  • the tactile properties of the security paper according to the present invention improve.
  • the addition of the core / shell particles gives it a so-called “soft touch", which means that the surface of the security paper feels very supple and smooth, but not purely papery, depending on the amount of added core / shell particles tactile surface properties which can not be assigned to pure paper or pure polymer film and which combine the surface properties of both materials
  • the addition amount of core / shell particles also determines the degree of "film-like" nature of the paper, ie at an increased level of addition the visible and tactile paper properties and the visible and tactile film properties.
  • the core / shell particles are contained on the cellulose-containing substrate. This can be done by introducing a preferably aqueous dispersion of core / shell particles in the usual sizing layer, by applying a dispersion of core / shell particles in place of the usual sizing or by applying a dispersion of core / shell particles to a pre-applied sizing layer done.
  • the application of these layers can take place both over the entire area and over part of the area on the cellulose-containing substrate, so that targeted control of the areas is possible, on which the optically variable effect achieved by the core / shell particles is visible.
  • a sizing layer may, regardless of whether the core / shell particles are in or not, all otherwise usual in papermaking ingredients such as pigments, binders and the like, as long as they do not contain the core / shell particles react so that they adversely affect their optical properties.
  • this layer at least partially seals the pores present on the surface of the cellulose-containing substrate and penetrates to a certain extent into the substrate one.
  • the smoothing process following the usual sizing is sufficient to allow a regular arrangement of the cores in a matrix formed from the cladding material.
  • the above-described three-dimensional structures can form at which reflection, interference and scattering of the incident light take place.
  • the more porous the cellulose-containing substrate the greater is an increase in the transparency of this substrate by adding the core / Sheath particles while maintaining the optically variable properties recorded.
  • the person skilled in the art can vary whether he preferably introduces the core / shell particles into the paper substrate, a layer directly thereon, or into a coating following the usual sizing.
  • optically variable effect can be intensified over a whole or partial area by a specific subsequent pressure or temperature and pressure treatment.
  • the core / shell particles may also be contained both in the cellulose-containing substrate and on this. This enhances the optically variable properties of the security paper as well as its film nature.
  • a major advantage of the security paper of the invention is that, in addition to the core / shell particles and the associated effects, it may contain all the usual security features commonly used in security papers.
  • security features such as fluorescent particles or fibers, planchettes, watermarks or the like, which may already be contained in the paper pulp, but also, for example, security features which, after completion of the papermaking, are or in the security paper or introduced, such as security threads, fluorescent dyes, infrared or UV-active dyes, magnetic Particles, electrically conductive particles, optically variable pigments, optically variable layers, optically variable prints, liquid-crystalline coatings, holograms, kinegrams, RFID elements, laser markings, chemical additives which become visible under illumination at certain wavelengths or during manipulation, Microtexts, guilloches and the like.
  • security threads such as security threads, fluorescent dyes, infrared or UV-active dyes, magnetic Particles, electrically conductive particles, optically variable pigments, optically variable layers, optically variable prints, liquid-crystalline coatings, holograms, kinegrams, RFID elements, laser markings, chemical additives which become visible under illumination at certain wavelengths or during manipulation, Microtexts
  • the security paper additionally has at least one further security feature, in particular one of the security features described above, in addition to the core / shell particles.
  • the present invention also provides a process for producing an optically variable security paper, wherein core / shell particles whose core is substantially solid and dimensionally stable and having a substantially monodisperse size distribution and wherein the core is chemically bonded to the shell via an intermediate layer , the
  • Weight of the shell is equal to or greater than the weight of the core and a difference between the refractive indices of the core material and the cladding material, introduced into an aqueous paper pulp and then processed together with the usual paper raw materials into a sheet of paper.
  • the core / shell particles are usually introduced in an amount of about 0.01 to 50 wt.%, Preferably 1 to 20 wt.%, Based on the dry weight of the paper in the paper pulp.
  • the degree of "filminess" of the paper can also be controlled be like its surface properties and the optically variable appearance.
  • the core / shell particles can be introduced into the aqueous paper pulp both in solid form and in dispersion.
  • the core / shell particles can be introduced into the aqueous paper pulp both in solid form and in dispersion.
  • the core / shell particles can be introduced into the aqueous paper pulp both in solid form and in dispersion.
  • the dispersion may optionally also contain various alcohols customary as solvents.
  • the papermaking process then proceeds while retaining the usual process steps.
  • the paper production method itself or at least one of the subsequent method steps is accompanied by a printing or temperature and pressure treatment of the paper, since this makes it possible to set or reinforce the optically variable inherent shading of the paper particularly well.
  • the present invention also relates to a process for producing an optically variable security paper, wherein a predominantly aqueous dispersion of core / shell particles whose core is substantially solid and has a substantially monodisperse size distribution and wherein the core with the shell via an intermediate layer is chemically bonded, the weight of the shell is equal to or greater than the weight of the core and a difference between the refractive indices of the core material and the cladding material is applied to at least a portion of the surface of an unsized or glued paper and then dried.
  • the proportion of the core / shell particles in the aqueous dispersion is 0.1 to 50% by weight, preferably 2 to 40% by weight and in particular 10 to 40% by weight, based on the weight of the aqueous dispersion.
  • the application of the dispersion to the surface of the glued or unsized paper can take place completely or partially, depending on where in the paper an optically variable appearance is desired.
  • Suitable for this are all customary application techniques such as, for example, the various printing methods, coating and coating methods, spraying methods, etc.
  • aqueous dispersions may also be mixed with any suitable solvents, binders or auxiliaries commonly used for application processes, as long as the latter do not adversely affect the optical properties of the core / shell particles.
  • a subsequent pressure treatment or pressure and temperature treatment can highlight the optically variable properties of the security paper according to the invention, enhance the film-like design of the paper surface or
  • Such a subsequent process may be, for example, a smoothing, pressing and / or embossing treatment, which is carried out wholly or partially on the substrate containing the core / shell particles.
  • the cellulose-containing substrate already has other security features such as Watermarks, planchettes, fibers etc included. Then on the cellulose-containing substrate further security features, such as security threads, fluorescent dyes, infrared or UV-active dyes, magnetic particles, electrically conductive particles, optically variable pigments, optically variable layers, optically variable
  • Prints liquid crystalline coatings, holograms, kinegrams, RFID elements, laser markings, chemical additives that are visible under illumination at certain wavelengths or manipulation, microtext, Guillochen and the like in a suitable form and / or bring. This preferably takes place at the locations of the substrate on which previously only the usual, but not a subsequent pressure treatment has taken place.
  • the subsequent pressure treatment can be done not only part of the surface but even the entire surface, which virtually results in a "seal" of the other security features, since depending on the proportion of core / shell particles in the cellulose-containing substrate can form a film-like surface, depending on the desired security product may be advantageous.
  • Another object of the present invention is the use of optically variable security paper according to the invention for the production of value documents of all kinds, for example for the production of banknotes, passports, identity documents, shares, bonds, certificates, checks, vouchers, tickets, tickets and the like.
  • security paper according to the invention it is possible to produce all value documents which are traditionally produced from paper or paper-bonded materials (eg laminates), but also those value documents which are traditionally made of plastics are manufactured, for example, ID cards, access authorization documents of all kinds and the like.
  • the security paper according to the present invention has optically variable both in plan and in transparency
  • Character as well as high mechanical strength, tear strength and water-repellent properties and is insensitive to rapid soiling. It has a surface that differs tactfully from a clean paper surface with a particularly smooth, soft touch.
  • the optically variable properties of the security paper according to the invention can be selectively controlled in color and intensity.
  • the amount of core / shell particles added not only influences the mechanical and tactile properties of the security paper, but also the degree of film-like properties that can be achieved.
  • the optically variable properties and the transparency of the security paper can be emphasized by a subsequent pressure or temperature and pressure treatment targeted.
  • the security paper according to the invention can be additionally provided with all the usual further security features that are generally used for security products.
  • the present security paper according to the invention is thus outstandingly suitable for the simple production of a wide variety of value documents and gives them both a non-copyable optical appearance and outstanding mechanical properties. It can therefore be used with great success both for high-security products and for the medium security segment.

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  • Paper (AREA)

Abstract

L'invention concerne un papier de sûreté optiquement variable utilisé pour produire des documents de sécurité, qui comprend un substrat à base de cellulose contenant des particules à noyau-gaine, des procédés permettant de produire un papier de sûreté de ce type et son utilisation pour produire des documents de sécurité.
EP06792172A 2005-10-14 2006-09-20 Papier de surete Withdrawn EP1934400A2 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE102005049167A DE102005049167A1 (de) 2005-10-14 2005-10-14 Sicherheitspapier
PCT/EP2006/009131 WO2007042130A2 (fr) 2005-10-14 2006-09-20 Papier de surete

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EP1934400A2 true EP1934400A2 (fr) 2008-06-25

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EP06792172A Withdrawn EP1934400A2 (fr) 2005-10-14 2006-09-20 Papier de surete

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US (1) US20080295983A1 (fr)
EP (1) EP1934400A2 (fr)
DE (1) DE102005049167A1 (fr)
WO (1) WO2007042130A2 (fr)

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FR2894164B1 (fr) * 2005-12-01 2008-02-29 Centre Nat Rech Scient Preparation de substrats fibreux superhydrophobes
US8269987B2 (en) * 2007-10-30 2012-09-18 Xerox Corporation Using application side truetype or other outline fonts to create specialty imaging fonts on digital front-end
CN104160430B (zh) * 2012-02-23 2017-12-01 锡克拜控股有限公司 用于视障人士的可听凭证识别
GB2531584B (en) * 2014-10-23 2019-07-10 Portals De La Rue Ltd Improvements in security papers and documents

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BR0212478A (pt) * 2001-09-14 2004-08-24 Merck Patent Gmbh Moldagens feitas de partìculas de núcleo/casca
DE10337331A1 (de) * 2003-08-12 2005-03-17 Giesecke & Devrient Gmbh Sicherheitselement mit Dünnschichtelement

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Title
See references of WO2007042130A2 *

Also Published As

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WO2007042130A2 (fr) 2007-04-19
DE102005049167A1 (de) 2007-04-19
WO2007042130A3 (fr) 2007-07-26
US20080295983A1 (en) 2008-12-04

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