FR2646378A1 - SHEET FOR BEING SUBJECT TO THE ACTION OF LIGHT, COMPRISING MEANS OF RECOGNITION AND SECURITY, AND APPLICATION OF SUCH SHEET - Google Patents

Abstract

The invention concerns a sheet intended for prolonged exposure to light. It carries one at least light-resistant imprint having a first colour in natural light with a wavelength between 400 and 700 nanometres and a second colour, different from the first, in an artificial light with a wavelength of less than 400 nanometres and greater than 700 nanometres. The imprint is produced by photogravure printing with liquid ink containing at least one luminescent pigment capable of withstanding temperatures above 100 DEG C for at least 10 minutes. Use especially as a decorative sheet for laminates.

Description

I 2646378

  SHEET FOR BEING SUBJECT TO THE ACTION OF LIGHT,

  PROVIDING MEANS OF RECOGNITION AND SECURITY, AND

APPLICATION OF SUCH SHEET

  The invention relates to a decorative sheet that can be used, for example, for the manufacture of laminated panels, this sheet

  further comprising recognition and security means.

  The invention further relates to a composition for printing a

such sheet.

  We know that there are mainly two kinds of laminated panels: so-called high pressure panels and so-called panels

low pressure.

  For many years, laminates have been used as materials in homes, commercial and industrial premises. Typical applications of such laminates are the surface coating of walls, table tops, furniture

and others.

  The so-called high pressure laminates are produced from a core made of resin impregnated sheets. The sheets are generally sheets of kraft paper which has been impregnated with a thermosetting resin and more particularly a phenolic resin. When the kraft paper has been impregnated with resin, the sheets are dried, cut, and then stacked on top of one another. The number of stack sheets depends on the applications

  and may vary between 3 and 9, but may be higher.

  Then placed on the pile of sheets consti-killing-the soul, a decorative sheet which is in geront a sheet of paper with a printed pattern or light color, and impregnated with a heat-curable resin not deviating to heat, for example, melamine-maleate resins, benzoguanamine-formaldehyde resins, unsaturated polyester resins. In general, there is placed on top of the decorative sheet, a protective cover sheet, devoid of pattern and transparent in the final laminate. In terms of occupation, this protective sheet is called "over-lay". The stack of impregnated sheets is then placed in a press fitted with a sheet that confers the surface state. The pile is then densified by heating and

  pressing to obtain a unitary structure.

  During densification, the thermosetting resins are transformed into thermoset form and a material is obtained.

  extremely hard and having a decorative effect.

  So-called low-pressure laminates are produced in a manner similar to that of high-pressure laminates, but the decorative sheet is laminated directly to a panel

  of wood particles or any other basic support.

  The decorative sheet is traditionally manufactured in the following manner. A paper sheet is made by driping on a flat canvas an aqueous suspension of cellulose fibers, long and / or short, bleached and / or unbleached, fillers, binders. The thus formed sheet is drained, pressed and dried to form a sheet of paper. This sheet is then printed. The usual printing is gravure printing, using engraved rolls. The technique of engraving consists of drawing, for example reproducing a wood or a purely artistic drawing of fantasy. Then we take the photograph of this drawing and from the films obtained, we engrave one or more printing rolls. Each cylinder then passes into an ink bath, and the depressions or cavities engraved in the cylinder are filled with ink which is then transferred to the paper. Usually one to three impressions

  d: st nctes and successive with one to three rolls.

  It is understood that the gravure printing process allows from a drawing to print a sheet of paper. This poses a problem for the printer of the decorative sheet. Indeed, if the drawing is an original drawing, created by the printer, any other printer, from a decorative sheet imprifmée, can take photographs of this sheet and have engraved cylinders to get the same impression. Counterfeits can therefore be numerous and it is generally not possible to detect them or to have the intangible proof that

these are counterfeits.

  The invention therefore aims to solve this problem.

  Another problem that arises is the identification of the laminate manufacturer. Indeed, the decorative foil manufacturer can sell the genuine foil to several laminate manufacturers. Each laminate manufacturer generally wears their mark on the laminate, using a more or less removable label. Here again, there is the problem of identifying the manufacturer of a particular laminate. The invention aims to solve

this second problem.

  Another problem that arises is the recognition of the origin of the sheets that can be used for packaging cartons, for polyvinyl chloride sheets, and for polypropylene sheets. Another problem which arises is that the sheets which are generally used for the manufacture of furniture are subject to periods of time set out in the following manner: An object of the invention is therefore to provide a decorative sheet comprising security means. to prevent unauthorized reproduction of original drawings printed on the sheet. Another object of the invention is to provide a decorative sheet for laminated panels comprising recognition means

the origin of the laminates.

  To this end, the invention relates to a sheet intended to be subjected to the prolonged action of light, characterized in that it comprises an impression at least resistant to light, this impress having a first hue to light natural and a second hue, different from the first, to artificial light. Preferably, the first drawing is invisible to natural light and the second drawing is visible in artificial light. By natural light is meant a light source whose wavelengths are between 400 and

  800 nanometers and by artificial light, a light source -

  whose wavelengths are less than 400 nanometers and

greater than SO0C nanometers.

  We know that some pigments and dyes are

  luminescent. These materials are commonly called "phosphors".

  These pigments can be fluorescent or phosphorescent. The color sensation produced by non-luminescent convernal pigments or dyes results from selective absorption of wavelengths in the visible part of the spec: re. Wave Iongruers that are not absorbed are

  reflective or transmitted, which gives the sensation of color.

  This sensation of color is absent when there is no visible source of light, because there is no reason to reflect.

or to transmit.

  Unlike conventional dyes or pigments, luminescent pigments do not reflect light, but they are themselves sources of light. They possess the property of absorbing certain wavelengths, generally wavelengths less than 400 nanometers and invisible to the eye, and of transforming these wavelengths into visible wavelengths. The

  wavelengths thus emitted produce a sensation of color.

  When the emission of light continues for a significant period of time, after the extinction of the energy source

  excitation, the material is said phosphorescent.

  Many publications have described the synthesis of such

luminescent materials.

  Reference is made to the following publications: EP-A-15382,

EP-A-21342, EP-A-123947.

  It is known, moreover, that it is known to introduce pigments

  the inside of the paper, in particular by the FR-A-

  2,478,695 and P-A-226367. These pigments are scattered in the paper and the latter is used as security paper for checks, banknotes, etc. EP-A-147252 discloses a mixture of a phosphor and an anti-stored substance. Such a mixture can be used for marking documents to prevent counterfeiting, for example banknotes, fiduciary papers. The compositions can be introduced on the

  paper and can be introduced in printing ink.

  These inks are these crushed inks, that is to say containing a hull and impressicn is made by offset or soft ta-ille. Now, however, the problem of marking heat-resistant sheets that can be used to decorate laminates

t.n'a iana: s been laid.

  A first technical problem to be solved is that the sheets are intended to be subjected to heat during a

  duration of several tens of minutes, or even several hours.

  Indeed, when it comes to sheets for laminates, during densification, the sheet is subjected to temperatures of more than 1006C for 20 minutes. Likewise, when metal-coated or metallized papers are made, these papers are subjected to high temperatures, especially when

hot gilding.

  Marking of sheets, for example for laminates, also poses different and additional problems of paper marking.

  for banknotes and other security documents.

  Indeed, the decorative sheets for laminates are

  necessarily impregnated with a thermosetting resin.

  When densification is performed, the impregnated sheet is placed on a particle board or stack of impregnated krafz paper sheets. Then we press together against a sheet. However, a technical problem is that the prints should not be transferred from the decorative sheet to the sheet metal that must

stay clean

  A second technical problem to be solved is that during the impregnation; the decorative sheet goes into an impregnation bath. Impressions must not migrate into the impregnation bath and must not pollute it. Indeed, if the impregnating resin is polluted by printing, during the subsequent lamination, the thermosetting resin-fuels under heat and pressure e: - and it contains printing substances luinescent, these fluent in mnme

  time and provoke one. maculace of the Linale print.

  Another technical problem to be solved is that when the printed sheet is rubbed, the luminescent substance must not be

  come off. The resistance to friction must therefore be high. In-

  in addition, the impregnability of the decorative sheet must be preserved. Finally, it is essential that the luminescent substances used have a very good resistance to light. Indeed, these sheets can be used for panels used as materials in homes and furniture tops and they are therefore intended to be subjected to the action of light during periods of

extended time.

  The applicant has tried many commercially available luminescent substances and has found that those which are suitable are inorganic pigments. Indeed, organr.ic molecules are very sensitive to external conditions

  and easily degrade in light and heat.

  On the contrary, the inorganic pigments have a very good light fastness and withstand high temperatures for long periods of time, namely temperatures above 1000C, preferably between 140 and 200C, for example 140-150C.

  for at least 10 minutes to 2 hours, for example 20 to 30 minutes.

  Preferably, the luminescent substances used according to the invention are zinc sulphides or their mixture with

other metallic sulphides.

  Most preferably, phosphors are zinc sulphide compounds in admixture with cadmium sulphide. These pigments may have a particle size

i ... above iOC micrometers.

  It is possible to use pigments of zinc sulphide or sulphide

  zinc and cadmium which are activated by copper. Their method

  preparation is known and is for example described in H.W.

  Leverenz, An introduction to luminescence of solids: S. John, Wiley & Sons, Inc. New York, Chapman & Hall Ltd. London, 1950. Zinc sulphide pigments emitting in various

  wavelengths have been described in EP-patent applications.

  A-34059, EP-A-78538, EP-A-91184 filed by the Japanese company

KASEI OPTONIX.

  Of course, according to the invention, it is possible to use mixtures of phosphors, provided that they are resistant to light, heat, pressure, as mentioned above.

  The following description, in comparison with the examples, will

  understand how the invention can be put into practice.

EXAMPLE 1

  18.9 parts of pigment sold by the company OPTONIX are successively mixed under the

  reference 2200. It is a zinc sulphide.

  9 parts water 3 parts alcohol, preferably ethanol 8.8 parts varnish or binder 992209 sold by SICPA 26.9 parts varnish 991129 sold by SICPA

  33.5 parts of an ethanol mixture (2/3) water (1/3).

  This mixture is applied to a white paper sheet of 90 g / m2

by gravure printing.

  The cylinder was etched by electronic etching, the cells having a depth of 37 micrometers, the height of the weft being 190 micrometers, and the width of the weft being

210 micrometers.

  The size of the pigment particles is about 4 to 10

  micrometers, which allows printing with such cells.

  A paper is obtained which is white in the light of day, but when it is illuminated by ultraviolet rays, a blue print appears while the white paper becomes brown

  because it does not reflect and does not transmit light.

  This sheet is subjected to a temperature of 160 C by placing it between two heating plates for 15 minutes. Then the paper is illuminated by U.V. rays. The blue impresion appears

again.

COMPARATIVE EXAMPLE

  The same mixture was prepared as in Example 1, but the mineral pigment was replaced by an organic pigment which is an acid

  an I-substituted antimonyl compound of the type described in DE-A-

  3225966. When submitting the paper at a temperature of 200 C

  for 0.5 seconds, the fluorescent print no longer appears.

EXAMPLES 2 to 9

  The same mixture is made as in Example 1, with pigments

  sold by a company OPTONI-X, under different numbers.

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  The resistance to daylight is from 3 to 6 measured according to the Wool scale test and the resistance to ultraviolet rays is from 5 to 6. The Wool Scale test corresponds to NF T 51056 standards. and NF T 51058. It consists in illuminating a sample having a print with a Xenon lamp for 90 hours or 300 hours and comparing the sample obtained with woolen strands having staggered tints of 1 to 8, the corresponding number 1 to the degratation of hue, the number 8

  corresponding to no degradation.

EXAMPLE 10

  It prints by heliography a paper by performing from one to three color prints in a traditional way. This paper is then decorated and has this decorative appearance and visible by lighting in natural light. Heelographic printing is then performed by carrying out one to three prints using the ink mixtures of Examples 1 to 9. The initial design is not modified in natural light. When illuminating the paper in ultraviolet light, the initial drawing disappears and this is the

  superimposed drawing that becomes visible.

  The invention relates not only to a means for marking and recognizing sheets subjected to temperature, and / or pressure and light, for long periods, but also relates to a novel means for decorating these sheets. Polyvinyl chloride sheets can also be printed laminated to particle boards by gluing and pressing. These plates used for furniture must be resistant to light. It is also possible to print sheets of polyethylene, polypropylene, possibly diapers and

  possibly impregnated with a resin.

Claims (8)

  1. Sheet intended to be subjected to the prolonged action of light, characterized in that it comprises an impression at least resistant to light, having a first hue to natural light of wavelength between 400 and 800 nanometers and a second shade different from the first, to artificial light of wavelength less than 400 nanometers and greater than 800 nanometers.   2. Sheet according to claim 1, characterized in that the printing is a heliographic printing liquid ink comprising at least one luminescent pigment resistant to temperatures above 100 C for at least 10 minutes. 3. Sheet according to claim 2, characterized in that the pigment is resistant to temperatures of 140 to  C for 20 to 30 minutes.   4. Sheet according to one of claims 2 and 3, characterized   in that the pigment is a mineral pigment.   5. Sheet according to one of claims 2 to 4, characterized   in that the pigment contains at least one zinc sulphide, optionally a second metal sulphide and   optionally at least one activating agent.   Fire according to one of Claims 2 to 5, characterized   by the fact that the p-gmentr is a mixture of zinc sulphide   and cacmium sulphide activated by cupping.   Sheet according to one of Claims 2 to 6, characterized   by the fact that the pigeon has an ultraviolet resistance   violets greater than 5, preferably 6.   Sheet according to one of Claims 2 to 7, characterized   in that the pigment has a particle size less than 10 micrometers.   9. Sheet according to one of Claims 2 to 8, characterized   in that it consists of paper, polyvinyl chloride, polyethylene, polypropylene, possibly coated and possibly impregnated with a thermosetting resin. 10. Ink composition for heliographic printing of a   Sheet according to one of Claims 1 to 9, characterized by the fact that it includes:   at least one luminescent pigment resistant to ultraviolet radiation   violet and possibly with heat, - water, - at least one alcohol solvent, at least one binder for ink.   11. Application of a sheet according to one of claims 1 to   9 in the manufacture of laminated panels, cardboard   packaging, metallized labels.