IE57213B1

IE57213B1 - Laser marking of pigmented systems

Info

Publication number: IE57213B1
Application number: IE316/86A
Authority: IE
Original assignee: Ciba Geigy Ag
Priority date: 1985-02-05
Filing date: 1986-02-04
Publication date: 1992-06-03
Also published as: CA1284125C; FI860493A; MX167831B; NZ215036A; DE3681804D1; KR860006500A; AU5281286A; IE860316L; ES551607A0; JPS61192737A; PT81957B; CN86100977A; ATE68138T1; ES8706000A1; AR244599A1; KR920007677B1; CN1011497B; DK54086A; FI81528B; FI860493A0

Abstract

Process for the inscription of organic material of high molecular weight containing at least one radiation-sensitive additive capable of producing a discolouration, characterised in that laser light with a wave length lying in the near UV- and/or visible and/or near IR-region is used as radiation energy and at least one inorganic and/or organic pigment and/or one polymer-soluble dye as additive.

Description

The present Invention relates to a method for the inscription of high molecular weight organic material and to the inscribed material. i> It is known, for example from a reprint of Pack Report No. 1, January 1981, page 4, to inscribe plastics such as PVC by laser irradiation such that the energy applied effects a mechanical change or a change in colour of the plastic at the area which is labelled. C02 lasers are used for this purpose, which operate in the IR range at .6 pm.

It is also known to inscribe plastics parts containing a filler that is 10 capable of being changed in colour hy means of irradiated energy. Thus, according to US patent specification 4 307 047, plastic keys based on ABS and containing as colour-changeable filler a so-called thermal dye are Inscribed by laser irradiation, the thermal dye producing a permanent change in colour upon Irradiation with heat in the form of the character which is to be applied. The lasers employed are Nd:YAG lasers having a wavelength of 1.06 pm (- 1064 nm) in the IR range.

EP-A-111 357 discloses a method for the inscription of polyolefins containing an amount of a substance absorbing laser radiation which is sufficient to guarantee the destruction of the polyolefin by the energy of the laser beam. The lasers used are C02 lasers having a wavelength of .6 pm.

EP-A-36 680 describee a method for the laser inscription of plastics of which the surface contains a dye and a silicon-containing Inorganic compound or a silicon-containing dye only. * i Finally, German Auslegeschrlft 2 542 680 discloses a method for recording information, in which an acetyl acetonate, dissolved in a polymer, le used as light-absorbing substance and a laser beam having a wavelength in the visible range is used as light source.

The present invention relates to a method for the inscription of high molecular weight organic material which contains at least one radiation* sensitive additive which effects a change in colour, wherein the radiated energy which is used is laser light having a wavelength in the close UV and/or visible and/or close IR range and the additive which is used is at least one inorganic and/or organic pigment and/or a polymersoluble dye.

The high molecular weight organic material can be of natural or synthetic origin. Such material may comprise for example natural resins, drying oils or rubber. However, it may also comprise modified natural materials, for example chlorinated rubber, oil-modified alkyd resins or cellulose derivatives such as cellulose esters or cellulose ethers and, in particular, fully synthetic organic polyplastics, that is to say plastics which are prepared by polymerisation, polycondensation or polyaddition. The following may be mentioned in particular from this class of plastics: polyethylene, polypropylene, polyisobutylene, polystyrene, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetals, polyacrylonitrile, polyacrylates, polymethacrylates or polybutadiene, and copolymers thereof, in particular ABS or EVA; polyesters, in particular high molecular weight esters of aromatic polycarboxylic acids with polyfunctional alcohols: polyamides, polyimides, polycarbonates, polyurethanes, polyethers such as polyphenylene oxide, polyacetals; the condensation products of formaldehyde with phenols, the so-called phenolic resins, and the condensation products of formaldehyde with urea, thiourea and melamine, the so-called amino resins, the polyaddition or polycondensation products of epichlorohydrin with diols or polyphenols, which are known as epoxy resins, and also the polyesters used as surface-coating resins, namely saturated polyesters, for example alkyd resins, as well as unsaturated polyesters, for example maleic resins. It must be emphasised that not only the homogeneous compounds can be used in accordance with the invention, but also mixtures of polyplastics, as well as co-condensates and copolymers, for example those based on butadiene.

Also suitable are high molecular weight organic materials in dissolved form as film-formers or hinders for surface-coating compositions or printing'inks, e.g. linseed oil varnish, nitrocellulose, alkyd resins, phenolic resins, melamine resins, acrylic resins and urea/formaldehyde resins, the films obtained from which may be inscribed in accordance with the invention. Particularly preferred plastics, suitable for the method of the invention are linear polyesters, polystyrene, polyethylene, polypropylene, ABS, polyacetals, polyphenylene oxide, polyamide, polycarbonate, polymethyl methacrylate and epoxy resins.

Eligible additives which effect a change in colour are inorganic and organic pigments and polymer-soluble dyes which absorb preferably in the close UV and/or visible or close IR range.

Visible range is understood as meaning the range between 0.38 gm and 0.78 μα, close IR range the range between 0.78 pm and 2 pm, and close UV range the range between 0.25 pm and 0.38 pm. Particularly suitable additives are those which absorb in the visible range.

Examples of inorganic pigments as additives which effect a change in colour are white pigments such as titanium dioxides (anatase, rutile), zinc oxide, antimony trioxide, zinc sulfide, lithopones, basic lead carbonate, basic lead sulfate or basic lead silicate, and also metal oxides such as iron oxides, chromium oxides, nickel antimony titanate, chromium antimony titanate, manganese blue, manganese violet, cobalt blue, cobalt chromium blue, cobalt nickel grey or ultramarine blue, Berlin blue, lead chromates, lead sulfochromates, molybdate orange, molybdate red, as well as metal sulfides such as cadmium sulfide, arsenic disulfide, antimony trisulfide or cadmium sulfoselenides, zirconium silicates such as zirconium vanadium blue and zirconium praseodymium yellow, and also carbon black or graphite at a low concentration.

Examples of organic pigments as additives are azo, azome thine, me thine, anthraquinone, indanthrone, pyran throne, flavanthrone, benzanthrone, phthalocyanine, perinone, perylene, dioxazine, thioindigo, isoindoline, isoindolinone, quinacridone, pyrrolopyrrole or quinophthalone pigments, and also metal complexes of, for example, azo, azomethlne or methine s dyes, or meCel sales of azo compounds.

Suitable polymer-soluble dyes are for example disperse dyes such as those of the anthraquinone series, for example hydroxyanthraquinones, aminoanthraquinones, alkylaminoanthraquinones, cyclohexylaminoanthraquinones, arylamlnoanthraquinones, hydroxyaminoanthraquinones or phenylmercaptoanthraquinones, as veil as metal complexes of azo dyes, in particular 1:2 chromium or cobalt complexes of monoazo dyes, and fluorescent dyes such as those of the coumarin, naphthalimide, pyrazoline, acridine, xanthene, thioxanthene, oxazine, thiazine or benzothiazole series.

The polymer-soluble dyes are preferably used in combination with fillers and/or pigments, in particular with inorganic pigments such as titanium dioxide.

According to the invention, pigments or polymer-soluble dyes can be used with or without pigment additives. Care must only be taken that they are compatible with the high molecular weight organic material employed according to the invention and that they do not impair its mechanical or other properties.

Suitable pigment additives are for example fatty acids having at least 12 carbon atoms, for example stearic acid or behenlc acid and the amides, salts or esters thereof such as magnesium stearate, zinc stearate, aluminium stearate or magnesium behenate, and also quaternary ammonium compounds such as tri(C1-C4)alkylbenzylammonium salts, waxes such as polyethylene wax, resin acids such as ahletlc acid, colophonium soap, hydrogenated or dimerised colophonium, C12-C1S paraffindisulfonic acids or alkylphenols.

According to the invention it is preferred to use the me tai-containing pigments such as the inorganic pigments and the metal complexes of azo, azomethine or methine dyes.

Also preferred are azo, azomethine, methine, anthraquinone, phthalocyanine, perylene, dioxazine, thioindigo, isoindoline, isoindolinone, quinacridone or pyrrolopyrrole pigments.

• The high molecular weight organic material eligible in accordance with the invention contains the additive effecting a change in colour in kamounts from 0.001 to 10 Z by weight, in particular from 0.01 to 3 Z by weight, based on the high molecular weight organic material.

The addition of the additive which effects a change in colour to the high molecular weight organic material to be processed to give mouldings takes place by methods known per se, for example by admixing such an additive, if appropriate in the form of masterbatches, to this substrate using extruders, roll mills, mixing or grinding machines. The resultant material is then brought into the desired final form by processes which are known per se, such as calendering, press-moulding, linear-extruding, coating, casting, extruding or by injection moulding. It is often desired to incorporate so-called plasticisers into the high molecular weight organic compounds before deformation in order to produce nonbrittle mouldings or to diminish their brittleness. Suitable examples are esters of phosphoric acid, phthalic acid or sebaelc acid. The plasticisers may be incorporated before or after incorporating the additive into the polymers.

Depending on the intended use, further substances may also be added to the high molecular weight organic material, for example fillers such as kaolin, mica, feldspar, vollastonlte, aluminium silicate, barium sulfate, calcium sulfate, chalk, calcite and dolomite, as well as light stabilisers, antioxidants, flame retardants, heat stabilisers, glass fibres or processing auxiliaries conventionally employed in the processing of plastics and known to the person skilled in the art.

To prepare the surface-coating compositions and printing inks suitable I for use according to the invention, the high molecular weight organic materials and the additive which effects a change in colour, with or without further additives of surface-coating compositions and printing inks, are finely dispersed or dissolved in a common organic solvent or mixture of solvents. The procedure may be such that the individual components, or also several components jointly, are dispersed or dissolved and only then are all the components combined. The homogenised surface-coating composition or printing ink is then applied to a substrate by methods known per se and baked or dried, and the surfacecoating or printing ink film obtained is subsequently inscribed according to the invention.

Energy-rich sources such as lasers are used to inscribe the high molecular weight organic materials suitable in accordance with the invention. The procedure comprises applying the radiated energy to the surface of the material to be labelled, according to the form of the graphic symbol to be applied, and optionally focusing said energy, such that a change in colour takes place at the irradiated areas without visually perceptible damage to the surface of the inscribed material.

Examples of such sources are solid-state pulsed lasers such as ruby lasers or frequency-multiplied Nd:YAG lasers, pulsed lasers with a booster such as a pulsed dye laser or Raman shifter, and also continuous-wave lasers with pulse modifications (Q-switch, mode locker), for example on the basis of CW Nd:YAG lasers with frequency multiplier or CW ion lasers (Ar, Kr) , as well as pulsed metal vapour lasers, for example copper vapour lasers or gold vapour lasers, or high-performance pulsed semiconductor lasers.

Depending on the laser system employed, pulse energies of up to several joules, intensities of up to terawatts per cm2, pulse widths of up to femtoseconds and repetition rates of up to gigahertz are possible. Pulse energies of a microjoule to joules, intensities of a kilowatt per cm2 to 100 megawatts per cm2, pulse widths of microseconds to picoseconds, and repetition rates of a hertz to 250 megahertz are advantageously used.

It is preferred to use lasers with pulsed light, for example those listed in the following table. Especially preferred lasers are pulsed or pulse-modified, frequency-doubled Nd:YAG lasers or metal vapour lasers such as Au or, in particular, Cu vapour lasers.

The following table lists a number of commercially available lasers which may be suitable in accordance with the invention.

Table Type/Representative Commercial example Principal wavelength (subsidiary wavelengths) [nm] Solid-state .pulled iaaexa •ruby laser Lasermetries (938R6R4L-4) 694 (347) •Nd:YAG laser Quanta Ray 1064, (532 (DCR 2A) 355,266) •Alexandrite laser Apollo (7562) 730-780 Pulsed lasers with booster such as •Raman shifter Quanta Ray UV-IR •dye laser (RS-1) Lambda Fhysik FL 2002 ! about 300-1000 CW lasers with pulse modification •Nd:YAG (Q-Switch,2ω) Lasermetries (9560QTG) 532 •argon (mode-locked) Spectra- Physics 514,5 Pvlgefl nrctftl vaRgvr lasers •Cu vapour laser PlasmaKinetics 751 510,578 •Au vapour laser PlasmaKinetics • 628 •Mn vapour laser I Oxford 534, 1290 •Fb vapour laser j Laser CU 25 723 Semiconductor diode M/A COM 905 lasers Type LD 65 * Array STAMTEL Type LF 100 905 According to the method of the invention, the laser employed will be for example a pulsed, frequency-doubled Nd:YAG laser with a pulse energy of about 250 millijoules per cm2, a maximum capacity of about 40 megawatts, pulse widths of 6-8 nanoseconds and a frequency of 20 Hz (Quanta Ray model DCR-2A, available from Spectra Physics, Mountain View, California).

If a copper vapour laser (Plasma Kinetics model 151) is used, exposure will be carried out with a pulse energy of, for example, 250 millijoules per cm2, a maximum capacity of about 10 kilowatts, a pulse width of 30 nanoseconds and a frequency of 6 kHz.

Lasers whose parameters, for example pulse content and pulse duration, can be readily adjusted permit the best possible adaptation to the requirements of the materials to be inscribed.

The best wavelength to be selected for irradiation is that at which the additive effecting a change in colour absorbs most strongly and the high molecular weight organic material in contrast least strongly.

Three different methods are suitable for laser inscription: the mask method, linear inscription and the dot matrix method. In these last two mentioned inscription methods (dynamic beam control) , the laser is preferably combined with a laser inscription system so that the high molecular weight organic material can be inscribed with any, for example computer-programmed, digits, letters and special symbols at the point where the laser beam strikes.

The choice of the laser system in respect of capacity and repetition rate depends basically on the inscription method employed. High capacity and low frequency as in solid-state pulsed lasers are preferred for mask exposures. The average to low capacities and rapid repetitioA rates of pulsed metal vapour lasers or of continuous-wave lasers with pulse modifications are preferred for inscriptions which require dynamic beam control. Beam deflection can he effected, for example, acoustoop t ically, holographically, with electroplated mirrors or polygon scanners. Dynamic beam control makes possible extremely flexible inscription or marking, as the symbols can be produced electronically.

• A very wide range of inscriptions can be produced by the method according to the invention. Examples of these are: variable text I' programming of numerical symbols by Inputting text with a video display unit, test programs of standard symbols or special symbols such as monograms, logos, or frequently recurring data, continuous piece numbering, input of measured variables, input of a stored program, linear inscription or also decorations.

In accordance with the method according to the invention it is possible to inscribe a very wide range of plastics parts or mouldings as well as surface-coating and printing ink films. Strips, plates, tubes and profiles, keys and plastlcs-coated electronic components are examples of these.

Typical exemplary applications are the inscription of circuits, printed circuit boards, printed circuits, active and passive electronic components, encapsulated hlgh’voltage transformers, plug sockets, casings, mechanical components in precision technology and in the horological industry, automotive components, keyboards, electronic components, cables, tubes, surface coatings, sheets and packaging sheets, as well as currency notes and securities documents.

The method according to the invention makes possible a marking which is indelible and which is therefore abrasion-proof and scratch-proof. The markings obtained by the invention are also corrosion-resistant, dimensionally stable, free from deformation, fast to light, heat and weathering, easily legible, and have sharply defined edge zones. In · addition, there is virtually no impairment of the mechanical and physical properties of the material thus inscribed. The penetration b depth of the marking depends on the inscribed material. It is up to about 1 mm. In the procedure, minimum damage is caused to the high molecular weight organic material. Hence it is possible to obtain inscriptions which give rise to no perceptible loss of surface gloss.

In accordance with the present method, a.change in colour of marked contrast occurs at the irradiated area of the material upon laser irradiation. Usually the change in colour is towards black. However, it is also possible to effect other colour changes, for example red or yellow to brown, red or yellow to white or black to white, depending on the additive employed which effects a change in colour.

With the method according to the invention, semi-transparent boards and sheets can be inscribed in a particularly attractive manner, characterised in that the inscription appears opaque when viewed in reflected light, but becomes almost transparent in a shade of the starting colour before marking when viewed in transmitted light. The contrast when viewed in reflected light as well as the shade of the transparent colour can he controlled in a simple manner by adjusting the laser pulse parameters.

In the following examples parts are by weight, unless otherwise indicated.

ExgffipU 1: a) Coating of small metal plates with sintering powders Small steel plates measuring 40 x 40 x 2 mm, which have been degreased but not deflashed, are heated in an oven to 120*C. The plates are then immersed rapidly for 3 seconds in a fluidised bed with epoxy resin sintering powders known per se [e.g. a mixture comprising 38 parts of a pre-extended epoxy resin based on bisphenol A and having an epoxide content of 1.3 equivalents per kg, 14 parts of a bromine-containing epoxy resin based on tetrabrominated bisphenol A having an epoxide content of 2.0 to 2.2 equivalents per kg, 4.5 parts of an acrylate-based levelling agent, 5.8 parts of benzophenonetetracarboxylic dianhydride as hardener, 29.5 parts of A12O3-3H2O and 18.5 parts of ground quartz as fillers, 0.3 parts of silicic acid Aerosil* 380 from Degussa, Germany and 1.3 parts of imidazole as accelerator] and 2 parts of the additive that effects a change in colour. This procedure of heating and immersing is repeated once, affording a glossy flame-retardant coating with a layer thickness of 250-400 pm. For complete curing, the coated plates * Trade Mark are stored for 15 minutes at 180*C. h) Inscription The small steel plates coated by the general procedure described above and containing, as addition that effects a change in colour, 1.8 Z hy i, weight of C.I. Figment Violet 19 (quinacridone), are then irradiated hy the beam of an Nd:YAG pulsed laser (Quanta Ray model DCR-2A from Spectra Physics, Mountain View, USA) with light pulses of 6-8 ns (ns » nanoseconds) at a wavelength of 0.532 μα (frequency-doubled beam) and a pulse energy of 120 mJ (mJ - millijoules). An intense black inscription is formed on the epoxy plates without any visible surface damage.

Example 2: 99.7 g of polybutylene terephthalate [Crastin* S 600 (from Ciba-Geigy, Switzerland) hereinafter abbreviated to PBTP] are mixed with 0.3 g of a red iron oxide pigment (Bayferrox* 140 from Bayer, Germany, C.I. Pigment Red 101) and this mixture is shaped to give small plates measuring 4 x 5 cm (3 mm thick) in an injection moulding machine at a cylinder temperature of 25O*C, a mould temperature of 80"C and a cycle time of 40 seconds^ These plates are irradiated with an Nd:YAG pulsed laser as described in Example lh. A black Inscription is obtained which shows no change in colour after 250 hours* exposure in a weatheroaeter (cycle 45*).

Example 3: Epoxy plates prepared in accordance with Example 1, but using g of C.I. Pigment Yellow 139 (isoindoline) as additive that effects a change in colour, are inscribed in dark brown with good contrast in accordance with Example lb.

Example 4: Epoxy plates prepared in accordance with Example 1, but using . g of Irgazln^ Red BPT [Perylene Red from Ciba-Geigy, Switzerland, C.I.

Pigment Red 224] as additive that effects a change in colour, are h inscribed in black with good contrast in accordance with the procedure described in Example lh.

Example 5: PBTP plates prepared in accordance with Example 2, hut using * Trade Mark 3 0.3 g of a chromium yellow pigment (Chromium Yellow Pigment* GMN 35 from Ciba-Geigy, Switzerland, C.I. Pigment Yellow 34) as additive that effects a change in colour, are inscribed in black with good contrast in accordance with Example lb.

Example 6: Following the procedure of Example 2, but using 0.2 g of a cadmium red pigment (Cadmium Red* cone. X-2948 from Ciba-Geigy, Switzerland, C.I. Pigment Red 108) Instead of 0.3 g of an iron oxide pigment, the PBTP plates thus obtained can be inscribed in black with good contrast by laser irradiation in accordance with Example lb.

Example 7: PBTP plates prepared in accordance with Example 2, but using 0.15 g of a molybdate red pigment (Molybdate Red* AA-3 from Ciba-Geigy, Switzerland, C.I. Pigment Red 104) as additive that effects a change in colour, when exposed to irradiation by laser in accordance with Example lb at low intensity (< 50 mJ/cm2) develop a yellow inscribed image, whereas at laser irradiation of greater intensity (> 50 mJ/cm2) a black inscribed image is produced.

Example 8: PBTP plates prepared in accordance with Example 2, but using 8 g of white antimony trioxide as additive that effects a change in colour, develop a black inscribed image when exposed to laser irradiation in accordance with Example lh.

Example 9: 30 g of a 55 Z by weight solution of an alkyd resin and a me lamine/formaldehyde resin [mixture of 67.5 g of a 60 Z by weight solution of an alkyd resin in xylene (from Bayer, Germany; trade name Alkydal F27), 26.4 g of a 55 Z by weight solution of a melamine/formaldehyde resin in a 1:1 mixture of butanol/xylene (from Casella, Germany; trade name Maprenal MF 590), 1.1 g of xylene, 4.0 g of ethylene glycol, 1.0 g of silicone oil A* (1 % in xylene) from Bayer, Germany, and 2 g of methylcellosolve], 8 g of methyl isobutyl ketone and 2 g of Molybdate Red AA-3 (from Ciba-Geigy, Switzerland, C.I. Pigment Orange 104) as additive that effects a change in colour, are mixed in a 100 ml glass flask with screw top containing 135 g of glass beads of 3.5 mm diameter, end this mixture is dispersed for * Trade Mark 4 hours in a laboratory vibratory mill. The surface coating thus obtained is then applied by conventional methods with an applicator to a 150 μα wet-film thickness on sheet metal and on a black/white contrast card conventionally employed in the surface-coatings industry, and the films are baked for 30 minutes at 130°C. The surface coatings thus obtained are then irradiated in accordance with Example lb. In both cases a grey inscription is obtained without any perceptible damage to the surface of the coatings.

Example 10: Surface coatings produced on sheet metal and on a black/white contrast card as described in Example 9, except that 2 g of Cadmium Yellow* X-2822 (cadmium pigment from Ciba-Geigy, Switzerland, C.l. Pigment Yellow 35) are used instead of 2 g of Molybdate Orange, are in both cases inscribed in black with good contrast in accordance with Example lb.

Example 11: Surface coatings produced on sheet metal and on a black/white contrast card as described in Example 9, except that 2 g of Bayferrox 140 M (iron oxide red pigment from Bayer, Germany, C.l.

Red 101) are used instead of Molybdate Red, are inscribed in both cases in grey with good contrast in accordance with Example lb.

Example 12: 30 g of the 55 Z by weight solution of an alkyd resin and a melamine resin indicated in Example 9, 8 g of methyl isobutyl ketone, 7.6 g of titanium dioxide (Bayer Titan* RKB 3 from Bayer, Germany) and 0.4 g of Molybdate Red AA-3 (from Ciba-Geigy, Switzerland) as additive that effects a change in colour, are mixed in a 100 ml glass flask with screw top containing 135 g of glass beads of 3.5 n diameter, and this mixture is dispersed for 16 hours in a laboratory vibratory mill. The surface coating thus obtained is applied with an applicator to a 150 pm wet-film thickness on sheet metal and on a black/white contrast card conventionally employed in the surface-coatings industry, and the films are baked for 30 minutes at 130*G. The surface coatings obtained are then irradiated in accordance with Example lb. A grey inscription is obtained.

* Trade Mark Example 13: Surface coatings produced on sheet metal and on a black/white contrast card as described in Example 12, except that 2 g of Cadmium Yellow X-2822 (Ci I. Pigment Yellow 35 frora Ciba-Geigy, Switzerland) are used instead of 0.4 g of Molybdate Red, are inscribed in grey with good contrast in both cases in accordance with Example lb.

Example 14: Surface coatings produced on sheet metal and on a black/white contrast card as described in Example 12, except that 2 g of Bayferrox 140 M (iron oxide red pigment from Bayer, Germany) are used instead of 0.4 g of Molybdate Red, are inscribed in light blue with good contrast in both cases in accordance with Example lb.

Example 15: Surface coatings produced on sheet metal and on a black/white contrast card as described in Example 12, except that 2 g of Filester* Yellow 2648 A (anthraquinone derivative from Ciba-Geigy, Switzerland, C.l. Pigment Yellow 147) are used instead of 0.4 g of Molybdate Red, are inscribed in grey with good contrast in both cases in accordance with Example lb.

Example 16: Following the procedure of Example 2, but using laser light having a wavelength of 355 nm (trebled frequency of an Nd:YAG laser, Quanta Ray model DCR-2A, from Spectra Physics, USA), instead of laser light having a wavelength of 0.532 pm, with pulses of duration 6-8 ns and pulse energy 50 mJ and focusing the radiation through a glass lens with a focal length of 250 mm to give a beam diameter of 1-2 mm, a black inscription is obtained.

Example 17: Repeating Example 5, but inscribing with laser light having a wavelength of 355 nm (trebled frequency of an Nd:YAG laser, Quanta Ray model DCR-2A, from Spectra Physics, USA), with pulses of duration 6-8 ns and pulse energy 50 mJ and focusing the beam through a glass lens with a focal length of 250 mm to give a beam diameter of 1-2 mm, black inscriptions with good contrast are obtained.

Example 18: In accordance with Example 7, but irradiating with laser light having a wavelength of 355 nm (trebled frequency of an Nd:YAG * Trade Mark laser, Quanta Ray model DCR-2A, from Spectra Physics, USA), with pulses of duration 6-8 ns and pulse energy 50 mJ and at the same time focusing the beam through & glass lens with a focal length of 250 mm to give a beam diameter of 1-2 mm, a grey inscribed image is obtained.

Example 19: Inscription is effected in accordance with Example 7, but irradiating with laser light having wavelengths of 511 and 578 nm from a copper vapour laser (Plasma Kinetics model 151 from Plasma Kinetics, USA), with pulses of duration 20-60 ns and pulse energy 0.5 mJ. To this effect the radiation used is through a glass lens with a focal length of 250 mm to give a beam diameter of 0.5-1 mm. A grey marking with a yellow edge is obtained at a beam diameter of 0.5 mm, whereas a yellow marking is obtained at a beam diameter of 1 mm.

Example 20: .Inscription Is effected in accordance with Example 5, but irradiating with laser light having wavelengths of 511 and 578 nm from a copper vapour laser (Plasma Kinetics model 151 from Plasma Kinetics, USA), with pulses of duration 20-60 ns and pulse energy 0.5 mJ. To this effect the radiation ia focused through a glass lens with a focal length of 250 mm to give a beam diameter of 0.5-1 mm. In this procedure PBTP plates are inscribed in black with good contrast.

Example 21: Marking is effected in accordance with Example 2, but irradiating with laser light having wavelengths of 511 and 578 nm from a copper vapour laser (Plasma Kinetics model 151 from Plasma Kinetics, USA), with pulses of duration 20-60 ns and pulse energy 0.5 mJ. To this . effect the radiation is focused through a glass lens with a focal length of 250 mm to give a beam diameter of 1-2 mm. In this procedure PBT [sic] plates are inscribed in black.

Example 22: 10 parts of a PVC copolymer with a vinyl acetate content of 10 X (Vinylite VYNS* from Union Carbide) are stirred into a mixture of solvents (77 parts of a 1:1 mixture of methyl ethyl ketone/methyl isobutyl ketone and 10 parts of toluene) and dissolved. 8 parts of s yellow azo condensation pigment (Mikrolith* Yellow 3G-K from Ciba-Geigy, base pigment G.I. Pigment Yellow 93) are then stirred in and * Trade Mark subsequently dispersed in a dissolver for 15 minutes at 6000 rpm. The resultant pigment dispersion is used as a printing ink for whitepigmented soft PVC sheets containing about 35 Z of plasticiser. The sheets printed hy rotogravure at etching depths of 4, 8, 15, 28, 40 and 40 μα are inscribed in grey with good contrast hy the method described in Example la.

Example 23: 99.7 g of acryllc/butadiene styrene (Terluran* 84BS from BASF, Germany) are mixed with 0.3 g of a red iron oxide pigment (Bayferrox 140 from Bayer, Germany, C.I. Pigment Red 101) and the mixture is processed to small plates measuring 4 x 5 cm (thickness 3 mm) in an injection moulding machine at a cylinder temperature of 200-230"C. These plates are irradiated with an Nd:YAG pulsed laser in accordance with Example lb. A black inscription with good contrast is obtained.

Example 24: PBTP plates, in accordance with Example 2, but provided with 0.15 g of a copper phthalocyanine pigment (Mikrolith Green G-FP from Ciba-Geigy, Switzerland, base pigment C.I. Pigment Green 7) as additive that effects a change in colour, are inscribed in black hy the basic frequency (1064 nm) of an Nd:YAG laser (Quanta Ray model 0CR-2A from Spectra Physics, USA), with pulses of duration 6-8 ns and pulse energy 250 mJ.

Example 25: PBTP plates, according to Exainple 24, but provided with 0.3 g of Fllestex Yellow 2648A (anthraquinone derivative from Ciba-Geigy, Switzerland, C.I. Pigment Yellow 147) as additive that effects a change in colour, are inscribed in black with good contrast, with in this case a pulse energy of 500 mJ instead of 250 mJ.

ElWple 2fc- Following the procedure of Example 24, but using laser light having wavelengths of 511 and 578 nm of a copper vapour laser (Plasma Kinetics model 151 from Plasma Kinetics, USA) , with pulses of duration 20-60 ns and pulse energy 0.5 mJ, PBTP plates are irradiated. · To this effect the radiation is focused through a glass lens with a focal length of 250 mm to give a beam diameter of 0.5 mm and produces a black inscription.

* Trade Mark 9 Example 27: 99.7 g of polycarbonate (Makrolon* 2800 from Bayer, Germany) are mixed with 0.3 g of a yellow cadmium pigment (Cadmium Yellow X-2822 from Ciba-Geigy, C.l. Pigment Yellow 35), and the mixture is processed to small plates measuring 4 x 5 cm (thickness 3 mm) in an injection moulding machine at a cylinder temperature of 260-280*C. These p plates are irradiated with an Nd:YAG pulsed laser in accordance with Example lb. A black inscription with good contrast is obtained.

Example 28: 99.7 g of polyoxymethylene (Hostaform* C 9020 from Hoechst, Germany) are mixed with 0.3 g of a yellow pigment (Filester Yellow 2648 A from Ciba-Geigy, Switzerland, C.l. Pigment Yellow 147), and the mixture is processed to small plates measuring 4 x 5 cm (thickness 3 mm) in an injection moulding machine at a cylinder temperature of 190-210°C. These plates are irradiated with an Nd:YAG pulsed laser in accordance with Example lb. A black inscription with good contrast is obtained.

Example 29: 99.7 g of HO polyethylene (Lupolen* 1030 K froa BASF, Germany) are mixed with 0.3 g of a red iron oxide pigment (Bayferrox 140 from Beyer, Germany, C.l. Pigment Red 101) and the mixture is . processed to small plates measuring 4 x 5 cm (thickness 3 am) in an injection moulding machine at a cylinder temperature of 19O-23O*C. These plates are irradiated with an Nd'.YAG pulsed laser in accordance with Example lb. A black inscription with good contrast is obtained.

Evamnle 30: 99.7 g of polyamide (Vestamid* L 1901 from Chem. tferke Hflls, Germany) are mixed with 0.3 g of a yellow anthraquinone pigment (Filester Yellow 2648 A from Ciba-Geigy, Switzerland, C.l. Pigment Yellow 147) , and the mixture is processed to small plates measuring x 5 cm (thickness 3 mm) in an injection moulding machine at a cylinder t temperature of 210-250®C. These plates ere irradiated with an Nd:YAG pulsed laser in accordance with Example lb. A black inscription with I good contrast is obtained.

Example 31: 99.7 g of polyamide 66 (Ultramid* A3K from BASF, Germany) are mixed with 0.3 g of a yellow anthraquinone pigment (Filester* * Trade Mark Yellow 2648 A from Ciba-Geigy, Switzerland, C.I. Pigment Yellow 147), and the mixture is processed to small plates measuring 4 x 5 cm (thickness 3 mm) in an injection moulding machine at a cylinder temperature of 250-280*0. These plates are irradiated with an Nd:YAG pulsed laser in accordance with Example lb. A black inscription with good contrast is obtained.

Example 32: 100 g of polyvinyl chloride (Vestolit* S 6558 from Chem. Werke Huis, Germany), 1.2 g of Irgastab* 17 N (butyltin sulfur stabiliser from Ciba-Geigy, Switzerland), 0.4 g of Irgawax* 361 (lubricant, glycerol monooleate from Ciba-Geigy, Switzerland) and 0.2 g of Wax* E (from Hoechst, montanic acid ester wax) are mixed with 0.3 g of a yellow anthraquinone pigment (Filester Yellow 2648 A from Ciba-Geigy, Switzerland, C.I. Pigment Yellow 147) and the mixture is rolled for 8 minutes on a two-roll mixer at a roll temperature of 160*C. The coloured rigid PVC sheet is stripped from the roller and pressed to plates for 5 minutes at 160"C on a multi-daylight press. The plates thus obtained are irradiated with an Nd:YAG pulsed laser in accordance with Example lb. A black inscription with good contrast is obtained.

Example 33: 99.7 g of polystyrene (Polystyrol* 143 E from BASF, Germany) are mixed with 0.3 g of a red iron oxide pigment (Bayferrox 140 from Bayer, Germany, C.I. Pigment Red 101) and the mixture is processed to small plates measuring 4 x 5 cm (thickness 3 mm) in an injection moulding machine at a cylinder temperature of 200-240*C. These plates are Irradiated with an Nd:YAG pulsed laser in accordance with Example lb. A black inscription with good contrast is obtained.

Example 34: For colouring epoxy compositions, a colour paste is prepared from 85 g of basic epoxy resin AY 105* (from Ciba-Geigy, Switzerland), 1.5 g of a yellow azo condensation pigment (Cromophtal Yellow* 3G, C.I. Pigment Yellow 93) and 13.5 g of a red azo condensation pigment (Cromophtal Red* G, Pigment Red 220, both from Ciba-Geigy, Switzerland). 1 g of this colour paste is mixed with 24 g of an aliphatic amine HY 956* (from Ciba-Geigy, Switzerland) and 100 g of a basic epoxy resin AY 105 (fran Ciba-Geigy, Switzerland) and cast to 1 ran plates. The * Trade Mark plates are cured for 3-4 hours at 40-50*0. When these plates are irradiated with laser light in accordance with Example lb, but Irradiating with a pulse energy of 1 mJ and with simultaneous focusing * through a glass lens having a focal length of 250 mm to give a beam diameter of 0.5 mm, the markings obtained appear black when viewed v normally with light in the direction of viewing but have a yellowish transparent appearance when viewed against a light source.

Example 35: 65 g of stabilised polyvinyl chloride, 35 g of dioctyl phthalate and 0.2 g of 1,4-diketo-3,6-di-parachlorophenylpyrrolo-[3,4-c]pyrrole (according to US patent 4 415 685) are stirred together and rolled for 7 minutes at 160*0 on a two-roll calender. A sheet coloured red is obtained. This sheet is irradiated with an Nd:YAG pulsed laser in accordance with Example lb. A black inscription with good contrast is obtained.

Example 36: 99.7 g of melamine resin (Melopas* N 37601 from Ciba-Geigy AG, Switzerland) are mixed with 0.3 g of a red pigment (Bayferrox 1420 from Bayer, Germany, C.I. Pigment Red 101) and the mixture is processed to small stepped plates measuring 4 x 5 cm (thickness 1-3 mm) in an injection moulding machine at a cylinder temperature of 95*C, a mould temperature of 170*C and a cycle time of 35 seconds. These plates are irradiated with an Nd:YAG pulsed laser in accordance with Example lh. A grey inscription with good contrast is obtained.

Example 37: 98 g of polycarbonate granules (Lexan* 101-111 from General Electric Plastics BV, Holland) are mixed dry for 10 minutes with 0.25 g of a soluble anthraquinone dye (Oracet* Yellow GHS from Ciba-Geigy Switzerland, C.I. Solvent Yellow 163) and 1.5 g of T1O2 (type CL 220 from Kronos Titan GmbH). The mixture is injection-moulded at a temperature of * 310*C in moulds at 80*C, reground, and cast under the same conditions to plates measuring 1.5 x 6.5 cm (thickness 1.5 mm). On irradiation with * laser light in accordance with Example lb black markings with good contrast is obtained.

* Trade Mark

Claims

1. Patent claims

1. A method for the visible inscription of high molecular weight organic material which is processed to give mouldings or surface-coating and printing ink films and which contains at least one radiatlon5 sensitive additive which effects a change in colour, where the high molecular weight organic material is a natural resin, drying oil, rubber, chlorinated rubber, oil-modified alkyd resin, cellulose derivative, polyethylene, polypropylene, polyisobutylene, polystyrene, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetal, 10 polyacrylonitrile, polyacrylate, polymethacrylate or polybutadiene or a copolymer thereof, a polyester, polyimide, polycarbonate, polyurethane, polyether, polyacetal, a condensation product of formaldehyde with a phenol, a so-called phenolic resin, a condensation product of formaldehyde with urea, thiourea or melamine, a so-called amino resin, 15 or one of the polyaddition or polycondensation products of epichlorohydrin with diols or polyphenols, which are known as epoxy resins, and where the radiated energy is directed on to the surface of the material to be labelled in accordance with the form of the inscription to be applied and a change in colour occurs at the 20 irradiated areas, wherein the radiated energy which is used is laser light having a wavelength in the UV range between 0.25 and 0.38 pa and/or in the visible range and/or in the IR range between 0.78 and 2 pa and the additive which effects a change in colour which is used is at least one inorganic and/or organic pigment and/or a polymer-soluble dye, 25 without the surface of the inscribed material being visibly damaged.

2. A method according to claim 1, wherein a laser with pulsed light is used.

3. A method according to claim 1, wherein a laser beam having a wavelength in the visible and/or close IR range is used. 30

4. A method according to claim 1, wherein a pulsed or pulse-modified, frequency-doubled Nd:YAG laser or a metal vapour laser is used.

5. A method according to claim 1, wherein the high molecular weight organic material used is polyethylene, polypropylene, polyisobutylene, polystyrene, polyvinyl chloride, polyvinylidene chloride, a polyvinyl acetal, polyacrylonitrile, a polyacrylate or polymethacrylate, ( polybutadiene, an ABS or EVA copolymer, a polyester, polyamide, polyimide, polycarbonate, polyurethane, polyether, polyacetal, phenolic ,i. resin, amino resin or epoxy resin.

6. A method according to claim 1, wherein the high molecular weight organic material used is a linear polyester, polystyrene, polyethylene, polypropylene, ABS, a polyacetal, polyphenylene oxide, polyamide, polycarbonate, polymethyl methacrylate or epoxy resin.

7. A method according to claim 1, wherein the additive used is a metalcontaining pigment selected from the series of the inorganic pigments and the metal complexes of azo, azomethlne or methine dyes.

8. A method according to claim 1, wherein the additive used is a polymer-soluble dye with an inorganic pigment.

9. A method according to claia 8, wherein titanium dioxide is used as the Inorganic pigment.

10. A method according to claim 1, wherein the additive used is an azo, azomethlne, methine, anthraquinone, phthalocyanine, perylene, dioxazine, thioindigo, Isoindoline, isoindolinone, quinacrldone or pyrrolopyrrole pigment.

11. Use of an additive which effects a change in colour for the laser inscription of high molecular weight organic aaterial according to claia 1. *

12. A method according to claim 1, substantially as herein- ί before described and exemplified.

13. Inscribed material whenever obtained by a method claimed in a preceding claim.