AU597240B2

AU597240B2 - Laser marking of pigmented systems

Info

Publication number: AU597240B2
Application number: AU52812/86A
Authority: AU
Inventors: Franz Breitenfellner; Niklaus Buhler; Heinrich Gugger; Manfred Hofmann
Original assignee: Ciba Geigy AG
Current assignee: Novartis AG
Priority date: 1985-02-05
Filing date: 1986-01-29
Publication date: 1990-05-31
Anticipated expiration: 2006-01-29
Also published as: FI860493A; MX167831B; NZ215036A; DK54086A; IL77772A; AR244599A1; BR8600463A; IE57213B1; ES8706000A1; EP0190997A3; JPS61192737A; EP0190997A2; ES551607A0; EP0190997B1; IE860316L; FI81528C; PT81957B; KR860006500A; FI860493A0; AU5281286A

Description

COMMONWEALTH OF AUSTRALIA 597240 FORM Regulation 13 (2) PATENTS ACT, 1952 COMPLETE SPECIFICATION

(ORIGINAL)

FOR OFFICE USE Short Title: Int. Cl.: Application Number: Lodged: This document contaLns tlhe .medlmenz lts mde uic 2tion 49 and is corcLt

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Complete Specification Lodged: Accepted: Lapsed: Published: LODGED AT SUB OFFICE 2 9 JAN 1986 Sydney Priority: Related Art: TO BE COMPLETED BY APPLICANT Name of Applicant: Address of Applicant: CIBA-GEIGY AG Klybeckstrasse 141, 4002 Basle, Switzerland d ;1 ii Actual Inventor: Dr Heinrich Gugger, Dr Niklaus Buhler, Dr Franz Breitenfellner, Dr Manfred Hofmann Address for Service: ARTHUR S. CAVE CO., Paten( and Trade Mark Attorheys, 1 Alfred Street, Sydney, New South Wales, Australia, 2000.

Complete Specification for the invention entitled: LASER MARKING OF PIGMENTED SYSTEMS The following statement is a full description of this invention, including the best method of performing it .known to me:- ASC 49 1 la- 3-15253/1+2/+/CGM 296 Laser marking of pigmented systems i| The present invention relates to a process for marking high molecular organic material and to the marked material.

It is known e.g. from a reprint of Pack Report No. 1, January 1981, i page 4, to mark plastics materials such as PVC by irradiation wiih a laser beam such that the energy applied thereto effects a mechanical I change or discolouration of the plastics material at the area which is so marked. The lasers used for this purpose are CO lasers which operate in the infra-red range at a wavelength of 10.6 lm.

It is also known to mark plastics parts containing a filler that is capable of being changed in colour by means of an applied energy radiation. Thus, according to US patent specification 4 307 047, plastic keys made of a base plastic material of ABS and containing as colour changeable filler a colouring powder that responds to heat irradiation (heat radiation indicator) aie marked by irradiation with a laser beam, said filler producing a permanent change in colour when subjected to irradiation with heat in the form of the mark which it is desired to apply. The laser employed is an Nd:YAG a. hlaser having a wavelength of 1.06 pm 1064 nm) in the infra-red range.

Finally, German Auslegeschrift 2 542 680 discloses a process for recording information, in which an acetyl acetonate, dissolved in a polymer, is used as light-absorbing substance and a laser beam having a wavelength in the visible range is used as light source.

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-2 The present invention relates to a irocess for marking a coating, film or molded article of high molecular weight organic material composition containing at least one radiation-sensitive additive that effects a change in colour, in which the organic material of the composition is selected from the group consisting of polyethylene, polypropylene, polyisobutylene, polystyrene, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetals, polyacrylonitrile, polyacrylates, polymethacrylates, polybutadiene, and copolymers thereof, polyesters, polyamides, polyimides, polycarbonates, polyurethanes, polyethers, polyacetals, formaldehyde/phenol condensates, the condensates of formaldehyde and urea, thiourea and melamine, epoxy resins, surface-coating saturated or unsaturated polyesters, mixtures of said polyplastics, as "i well as co-condensates and copolymers thereof; further film formers or binders for varnishes or printing inks selected from the group consisting of linseed oil varnish, nitrocellulose, alkyd resins, phenolic resins, a t melamine resins, acrylic resins or urea/formaldehyde resins, and thD organic material composition containing from 0.001 to 10 by weight of S. said polymer, of at least one radiation-sensitive additive selected from the group consisting of an inorganic pigment selected from the group consisting of titanium s.*c dioxide, zinc oxide, antimony trioxide, zinc sulfide, lithopones, basic i lead carbonate, basic lead sulfate or basic lead silicate, iron oxides, chromium oxides, nickel antimony titanate, chromium antimony titanate, manganese blue, manganese violet, cobalt blue, cobalt chromium blue, cobalt nickel grey, ultramarine blue, Berlin blue, lead chromates, lead sulfochromates, molybdate orange, molybdate red, cadmium sulfide, arsenic Hri disulfide, antimony trisulfide, cadmium sulfoselenides, zirconium silicate, and carbon black or graphite in low concentration, (ii) an organic pigment selected from the group consisting of azo, azomethine, methine, anthraquincna, indanthrone, pyranthrone, flavanthrone, benzanthrone, phthalocyanine, perinone, perylene, dioxazine, thioindigo, isoindoline, isoindolinone, quinacridone, pyrrolopyrrole or quinophthalone pigments, and metal complexes and salts of azo, azomethine or methine dyes, and 3 IL

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"d "'~rL i il- s~ 2a (iii) a polymer soluble dye selected from the group consisting of disperse dyes of the anthraquinone series, metal complexes of azo dyes and fluorescent dyes of the coumarin, naphthalimide, pyrazoline, acridine, xanthene, thioxanthene, oxazine, thiazine, and benzthiazole series, which process comprises utilising as radiation energy a laser beam having a wavelength in the close ultraviolet and/or visible range and/or close infrared range, wherein the energy source is applied to the surface of the material to be marked according to the form of the graphic symbols to be applied, such that a change in colour is induced at the irradiated areas without perceptible damage to the surface of the marked material.

SThe high molecular organic material can be of natural or synthetic origin. Such material may comprise for example natural resins, drying Soils or rubber. However, it may also comprise modified natural materials, for example chlorinated rubber, oil-modified alkyd resins or viscose or cellulose derivatives such as acetyl cellulose and nitrocellulose and, in S' particular, man-made organic polyplastics, that is to say, plastics which are obtained by polymerisation, polycondensation and polyaddition. The following products may be mentioned in particular as belonging to this class of plastics: polyethylene, polypropylene, polyisobutylene, poly- 4a4r oo° styrene, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetals, o polyacrylonitrile, polyacrylates, polymethacrylates or polybutadiene, and j copolymers thereof, in particular ABS or EVA; polyesters, in particular o high molecular esters of aromatic polycarboxylic acids and polyfunctional alcohols: polyamides, polyimides, polycarbonates, polyurethanes, i polyethers such as polyphenylene oxide, polyacetals, the condensates of t formaldehyde and phenols (phenolic plastics), and the condensates of j formaldehyde and urea, thiourea And melamine (aminoplasts); the poly- A' adducts and polycondensates of epichlorohydrin and diols or polyphenols 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 mileic resins. It must be emphasised that not only the homogeor example maleic resins. It must be emphasised that not only the homogeneous compounds can be used in the practice of this invention, but also mixtures of polyplfstics, as well as co-condnsates and copolymers, for example those based on butadiene.

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I III -3- Also suitable are high molecular organic materials in dissolved form as film formers or binders for varnishes 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 marked by the method of this invention. Particularly preferred plastics for use in the method of this invention are linear polyesters, polystyrene, polyethylene, polypropylene, ABS, polyacetals, polyphenylene oxide, polyamide, polycarbonate, polymethylmethacrylate and epoxy resins.

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

E By "visible range" is meant the range between 0.38 4m and 0.78 mn, by "close infra-red range" the range between 0.78 Pm and 2 pm, and by "close ultraviolet range" the range between 0.25 im and 0.38 Pm.

Particularly suitable additives are those that absorb light in the 'on vistble range.

Examples of inorganic pigments suitable for use as additives that q are able to effect a change in colour are white pigments such as titanium dioxides (anatas, rutile), zinc oxide, antimony trioxide, zinc sulfide, lithopones, basic lead carbonate, basic lead sulfate Sor basic lead silicate, and also metal oxides such as iron oxides, S 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 preseodyme yellow, and also carbon black or graphite in low concentration.

:i -4- Examples of organic pigments as additives are azo, azomethine, methine, anthraquinone, indanthrone, pyranthrone, flavanthrone, benzanthrone, phthalocyanine, perinone, perylene, dioxazine, thioindigo, isoindoline, isoindolinone, quinacridone, pyrrolopyrrole L or quinophthalone pigments, and also metal complexes of e.g. azo, azomethine or nethine dyes or metal salts of azo compounds.

Suitable polymer-soluble dyes are e.g. disperse dyes such as those of the anthraquinone series, for example hydroxyanthraquinones, aminoanthraquinones, alkylaminoanthraquinones, cyclohexylaminoanthraquinones, arylaminoanthraquinones, hydroxyaminoanthraquinones or phenylmercaptoanthraquinones, as well 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 benzthiazole series.

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

In the practice of this 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 material employed and that they do not impair its mechanical or other properties.

Suitable pigment additives are e.g. fatty acids of at least 12 carbon atoms, for example stearic acid or behenic acid and the amides, salts or esters thereof such as magnesium stearate, zinc stearate, S3 aluminium stearate or magnesium behenate, and also quaternary ammonium compounds such as tri(Ci-C4)alkylbenzylammonium salts, waxes such as polyethylene wax, resin acids such as abietic acid, colophonium soap, hydrogenated or dimerised colophonium, Ci1-Claparaffin disulfonic acids or alkylphenols.

'T 5 In the practice of this invention it is preferred to use the metal-containing pigments such as 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 organic material contains the additive effecting a change in colour in amounts from 0.001 to 10 by weight, preferably from 0.01 to 3 by weight, based on said high molecular organic material.

The addition of the additive that effects a change in colour of the high molecular organic material for processing to moulded articles o is made in a manner known per se, for example by incorporating such an additive, which may be in the form of a masterbatch, into the S substrates using extruders, roll mills, mixing or grinding nachines.

The res.ultant material is then brought into the desired final form by methods which are known per se, for example calendering, moulding, extruding, coating, casting or by injection moulding. It is often d*as ble to incorporate plasticisers into the high molecular *orgarnic compounds before processing in order to produce non-brittle mouldings or to diminish their brittleness. Suitable plasticisers are for example esters of phosphoric acid, phthalic acid or sebacic acid. In the method of this invention, the plasticisers may be incorporated before or after working the additive into the polymer.

Depending on the end use, further substances may be added to the high molecular organic material, for example fillers such as kaolin, mica, feldspar, wollastonite, 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 which are known to the skilled person.

6 To prepare the varnishes and printing inks suitable for use in this invention, the high molecular organic materials and the additive that effects a change in colour, with or without the addition of further auxiliaries of varnishes and printing inks, are finely dispersed or dissolved in a joint 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 then all the components are combined. The homogenised varnish or printing ink is then applied to a substrate by a method which is known per se and baked and dried, and the film so obtained is subsequently marked by the process of this invention.

Energy-rich sources such as lasers are used to mark the high molecular organic materials suitable for use in the practice of this invention. The procedure comprises applying the energy source to the surface of the material to be marked, according to the form of the graphic symbols to be applied, and optionally focussing said energy source such that a change in colour is induced at the irradiated areas without perceptible damage to the surface of the marked material.

Exemplary of such energy sources are solid state pulsed lasers such *as ruby lasers or frequency multiplied Nd:YAG lasers, pulsed lasers with booster such as pulsed dye lasers 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 capacity pulsed semi-conductor lasers.

Depending on the laser system employed, pulee contents of up to several Joules, intensities of up to 1012 W/cm 2 pulse durations of up to 10 seconds and frequencies of up to 10 Hz are possible.

Pulse contents of micro-Joule to Joule, intensities of kilowatt/cm 2 to 100 megawatt/cm 2 pulse durations of microseconds to picoseconds, and frequencies of hertz to 250 megahertz are advantageously used.

-7- 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 the practice of this invention.

0 0 S Pa 1 o p a r 2 ~0~0 -8 00 0 000 0 ft ft~0 0 ft 0 Table Type/Representative Examples of Principal wavelength commercially (subsidiary waveavailable lengths) types [nm] Solid state pulsed lasers 'ruby laser Lasermetrics 694 (347) (938R6R4L-4) '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 IJV-IR (RS -1) -dye laser Lambda Physik ca.300-1000 FL 2002 CW4 laser with pulse modification- 'Nd:YAG (Q-Switch,2wo) Lasermetrics 532 (9560QTG) *argon (mode-locked) Spectra- 514,5 Phlysics pulsed metal vapour laser -Cu vapour laser Plasma- 510,578 Kinetics 751 'Au vapour laser Plasma- 628 Kinetics 4 p vapour laser Oxford 534, 1290 'Pb vapour laser Laser CU 25 723 Semi-conductor diode N/A CON 905 lasers Type LD Array STANTEL 905 LF 100 -T I-

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9- In the practice of this invention, the laser employed will be for example a pulsed, frequency doubled Nd:YAC laser with a pulse content of about 250 milli-Joules/cm 2 a maximum capacity of about megawatts, pulse durations of 6-8 nanoseconds and a frequency of Hz (Quanta Ray DCR-2A, available from Spectra Physics, Mountain V' r (fornia).

It vapour laser (Plasma Kinetics 151) is used, exposure will o t irried out with a pulse content of e.g. 250 milli- Joules/cm 2 a maximum capacity of about 10 kW, a pulse duration of nanoseconds and a frequency of 66 kHz.

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

O 4 04 The best wavelength to be selected for radiation is that at which the additive effecting a change in colour absorbs light most strongly and the high molecular organic material least strongly.

Three different methods are suitable for laser marking in the practice of this invention: the mask method, the linear marking method and the point matrix method. In these last two mentioned methods (dynamic focussing), the laser is preferably combined with a laser marking system so that high molecular organic material can be marked with any, eg. computer-programmed, digits, letters and special symbols at the point where the laser beam strikes.

The choice of laser system in respect of capacity and freque.cy 41 depends basically on the marking method employed. The high capacity and low frequency of the solid state pulsed lasers are preferred for mask exposure. The average to low capacities and rapid frequencies of pulsed metal vapour lasers or of continuous wave lasers with pulse modifications are preferred for producing markings that require dynamic focussing. Beam deflection can be effected e.g.

i I 10 acousto-optically, holographically, with galvo-mirrors or polygon scanners. Dynamic focussing makes possible an extremely flexible marking, as the marks can be produced electronically.

A very wide range of markings can be produced by the present invention. Examples are: variable text programming of numerical symbola 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 measurable variables, input of a stored program, linear marking or also decorations.

It is also possible in the practice of this invention to mark a very wide range of plastics parts or mouldings as well as varnish or printing ink films. Ribbons, plates, tubes and profiles, keys and plastics-coated electronic components may be cited by way of example.

Typical utilities are the marking of circuits, printed circuit boards, printed circuits, active and passive electronic components, encapsulated high voltage transformers, plug sockets, casings, mechanical components of precision technology and of the watchmaking industry, automotive components, keyboards, electronic components, cables, tubes, varnishes, sheets and packaging sheets, as well as currency notes and security documents.

The present invention makes it possible to produce a marking that is indelible and which is therefore abrasion- and scratch proof. The markings obtained in this invention are also corrosion-proof, dimensionally stable, free from deformation, fast to light, heat and weathering, easily legible, and have good edge definition, In addition, there is virtually no impairment of the mechanical and physical properties of the marked material. The impression depth of the marking depends on the marked material and is about 1 mm with 11 minimum damage to the high molecular organic material. Hence it is possible to obtained markings that give rise to no perceptible loss J of surface gloss.

In the process of this invention, a change in colour of marked contrast occurs at the irradiated area of the material upon exposure to a laser beam. Usually the change in colour will be towards black; but is is possible to effect other colour changes, e.g. red or yellow to brown, red or yellow to white or black to white, depending on the additive employed that effects the change in oolour.

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

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

Example 1 :1 a) Coating of metal plates with sintering powders Small steel plates measuring 40 x 40 x 2 mm, which have been degreased but not deflaAhed, are heated in an oven to 120 0 C. Then the plater are immersed rapidly for 3 seconds in a fluidised bed with per se known epoxy resin sintering powders a mixture comprising 38 par.a of an advanced 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, parts of an acrylate-based levelling agent, 5.8 parts of bonzophenonetetracjrboxylic dianhydride as hardener, 29.5 parts of Ala2033HZO and 18.5 parts of quartz flour as fillers, 0.3 part of I .1, p 0 1 0p 0 #00 I O 00 0 0 I 12 silicic acid (Aerosil® 380, ex Degussa, West Germany) and 1.3 parts of imidazole as accelerator] and 2 parts of an 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 jim. For complete curing, the coated plates are stored for 15 minutes at 180C0.

b) Marking The steel plates coated by the general procedure described in a), and containing as additive that effects a change in colour 1.8% by weight of C.I. Pigment Violet 19 (quinacridone), are then irradiated by the beam of an Nd:YAG pulsed laser (Quanta Ray DCR-2A, available from Spectra Physics, Mountain View, USA) with light pulses of 6-8 ns (nanoseconds) at a wavelength of 0.532 pm (frequency doubled beam) and a pulse content ot 120 mJ (milli-Joules), to give a strong black marking on the epoky plates without any perceptible surface damage.

Example 2: 99.7 g of polybutylene terephthalate [Crastin® S 600, ex Ciba-Geigy AG, Switzerland, hereinafter abbreviated to PBTP] are mixed with 0.3 g of a red iron oxide pigment (BayferroxI 140, ex Bayer, West Germany, C.I. Pigment Red 101) and this mixture is processed to small plates measuring 4 x 5 cm (3 mm thick) in an injection moulding machine at a cylinder temperature of 2500C, a mould temperature of 8000 and a cycle time of 40 seconds. These plates are irradiated with an Nd:YAG pulsed laser as described in Example 1 The black marking so obtained shows no change in colour after 250 hours exposure in a Weather-Ometer (cycle 450).

Example 3: Epoxy plates prepared in accordance with Example 1, but using 2 g of C.I. Pigment Yellow 139 (isoindoline) as additive that effects a change of colour, are marked in dark brown with good contrast in accordance with the procedure described in Example Ib).

II L 13 Example 4: Epoxy plates prepared in accordance with Example 1, but using 2 g of Irgazin Red BPT [Perylene Red, ex Ciba-Geigy, Switzerland, C.I. Pigment Red 224] as additive that effects a change of colour, are marked in black with good contrast in accordance with the procedure described in Example 1 b).

Example 5: PBTP plates prepared in accordance with Example 2, but using 0.3 g of a chromium yellow pigment (Chromium Yellow® GMN ex Ciba-Geigy, Switzerland, C.I. Pigment Yellow 34) as additive that effects a change of colour, are marked in black with good contrast in accordance with the procedure described in Example Ib).

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

Example 7: PBTP plates prepared in accordance with Example 2, but using 0.15 g of a molybdate red pigment (Molybdate Red® AA-3, ex Ciba-Geigy, Switzerland, C.I. Pigment Red 104) as additive that effects a change in colour, are exposed to irradiation by a laser beam in accordance with Example 1 b) at lower intensity (5 50mJ/cm 2 to produce a yellow marking and at greater intensity 50 mJcm 2 to produce a black marking.

Example 8: PBTP plates prepared in accordance with Example 2, but using 8 g of antimony trioxide as additive that effects a change of colour, are marked in black when exposed to laser irradiation in accordance with Example Ib).

Example 9:30 g of a 55 by weight solution of an alkyd resin and a melamine/formaldehyde resin [mixture of 67.5 g of a 60 by weight solution of an alkyd resin in xylene (available from Bayer under the registered trademark Alkydal® F27), 26.4 g of a 55 by weight solution of a melamine/formaldehyde resin in a 1:1 mixture of -i "iy -14butanol/xylene (available from Casella under the registered trademark Maprenal® MF 590), 1.1 g of xylene, 4.0 g of ethylene glycol, g of silicone oil A® (1 in xylene) [available from Bayer] and 2 g of methylcellosolve], 8 g of methyl isobutyl ketone and 2 g of Molybdate Red® AA-3 (ex Ciba-Geigy, Switzerland, C.I. Pigment Orange 104) as additive that effects a change of colour, are mixed in a 100 ml glass flask with screw top containing 135 g of glass beads of 3.5 mm diameter. This mixture is dispersed for 16 hours in a laboratory vibratory mill. The varnish so obtained is then applied .by conventional methods with an applicator to give wet films with a thickness of 150 pm on metal and on a black-white contrast panel conventionally employed in the paint industry. The films are then baked for 30 minutes at 130°C. The finishes so obtained are then irradiated in accordance with Example Ib). In both cases a grey marking is obtained without any perceptible damage to the surfaces of the varnish films.

Example 10: Varnish films produced on metal and on a black-white contrast panel as described in Example 9, except that 2 g of Cadmium Yellow® X-2822 (cadmium pigment of Ciba-Geigy, Switzerland, C.I. Pigment Yellow 35) are used instead of 2 g of Molybdate Orange, are marked in black with good contrast in accordance with Example Ib).

Example 11: Varnish films produced on metal and on a black-white contrast p'nel as described in Example 9, except that 2 g of Bayferrox® 140 M (iron oxide red pigment of Bayer, C.I. Pigment Red 101) are used instead of 2 g of Molybdate Red, are marked in grey with good contrast in accordance with Example Ib).

Example 12: 30 g of the 55 by weight solution of an alkyd resin and a melamine resin described in Example 9, 8 g of methyl isobutyl ketone, 7.6 g of titanium dioxide (Bayer Titan® RKB 3, ex Bayer) and 0.4 g of Molybdate Red® AA-3 (ex 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 i I, CIC- C 15 diameter. This mixture is then dispersed for 16 hours in a laboratory vibratory mill. The varnish so obtained is applied with an applicator to give 150 pm wet films on metal and on a black-white contrast panel conventionally employed in the paint industry and the films are baked for 30 minutes at 1300C. The finishes are then irradiated in accordance with Example Ib). A grey marking is obtained.

Example 13: Varnish films produced on metal and on a black-white contrast panel as described in Example 12, except that 2 g of Cadmium Yellow® X-2822 (cadmium pigment of Ciba-Geigy, Switzerland, C.I. Pigment Yellow 35) are used instead of 0.4 g of Molybdate Red, are marked in grey with good contrast in both cases in accordance with Example Ib).

Example 14: Varnish films produced on metal and on a black-white contrast panel as described in Example 12, except that 2 g of Bayferrox® 140 M (iron oxide red pigment of Bayer) are used instead °of 0.4 g of Molybdate Red, are marked in light-blue with good contrast in both cases in accordance with Example ib).

Example 15: Varnish films produced on metal and on a black-white contrast panel as described in Example 12, except that 2 g of Filester® Yellow 2648 A (anthraquinone derivative of Ciba-Geigy, Switzerland, C.I. Pigment Yellow 147) are used instead of 0.4 g of Molybdate Red, are marked in grey with good contrast in accordance with Example Ib).

Example 16: Following the procedure of Example 2, marking is effected with a laser beam having a wavelength of 355 nm (triple frequency of an Nd:YAG laser, Quanta Ray DCR-2A, available from Spectra Physics, USA) instead of a laser beam having a wavelength of 0.532 pm. The pulse duration is 6-8 ns and the pulse content 50 mJ and the beam is focussed through a glass lens with a focal length of 250 mm to give a beam diameter of 1-2 mm. A black marking is obtained.

16 Example 17: Following the procedure of Example 5, marking is effected out with a laser beam having a wavelength of 355 nm (triple frequency of an Nd:YAG laser, Quanta Ray DCR-2A, available from Spectra Physics, USA). The pulse duration is 6-8 ns and the pulse content 50 mJ and the beam is focussed through a glass lens with a focal length of 250 mm to give a beam diameter of 1-2 mm. Black markings with good contrast are obtained.

Example 18: Marking is effected out in accordance with Example 7, but irradiating with a laser beam having a wavelength of 355 nm (triple frequency of an Nd:YAG laser, Quanta Ray DCR-2A, available from Spectra Physics, USA). The pulse duration is 6-8 ns and the pulse content 50 mJ and the beam is focussed through a glass lens f with a focal length of 250 mm to give a beam diametei of 1-2 im. A grey marking is obtained.

Example 19: Marking is effected in accordance with Example 7, but irradiating with a laser beam having wavelengths of 511 and 578 nm of a copper vapour laser (Plasma Kinetics 151, available from Plasma I Kinetics, USA). The pulse duration is 20-60 ns and the pulse content S, is 0.5 mJ. Irradiation is made through a glass lens with a focal Slength of 250 mm to give a beam diameter of 0.5-1 mm. A grey narking with yellow edge is obtained at a beam diameter of 0.5 mm and a yellow marking at a beam diameter of 1 mm.

Example 20: Marking is effected in accordance with Example 5, but irradiating with a laser beam having wavelengths of 511 and 578 nm of a copper vapour laser (Plasma Kinetics 151 available from Plasma Kinetics, USA). The pulse duration is 20-60 ns and the pulse content is 0.5 mJ. The beam is focussed through a glass lens with a focal length of 2L0 mm to give a beam diameter of 0.5-1 mm. PBTP plates are marked in grey with good contrast.

r -17 Example 21: Marking is effected in accordance with Example 2, but irradiating with a laser beam having wavelengths of 511 and 578 nm of a copper vapour laser (Plasma Kinetics 151 available from Plasma Kinetics, USA). The pulse duration is 20-60 ns and the pulse content is 0.5 mJ. The beam is focussed through a glass lens with a focal length of 250 mm to give a beam diameter of 1-2 mm. PBTP plates are marked in black.

Example 22: 10 parts of a PVC copolymer with a vinyl acetate content of 10 (Vinylite VYNS®, available from Union Carbide) is 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. Then 8 parts of a yellow azo condensation pigment (Microlith® Yellow 3G-K, ex Ciba-Geigy, base pigment C.I. Pigment Yellow 93) are stirred in and subsequently dispersed in a dissolver for 15 minutes at 6000 rpm. The resultant pigment dispersion is used as a printing ink for white pigmented soft PVC sheets containing about 35 of plasticiser. The sheets printed by rotogravure at etching depths of 4, 8, 15, 28, 40 and 45 pm are marked in grey with good contrast by the method described in Example la).

r I Ir r o, r r ri Example 23: 99.7 g of acrylic/butadiene styrene (Terluran® 84BS, available from BASF, West Germany) are mixed with 0.3 g of a red iron oxide pigment (Bayferrox® 140, available from Bayer, C.I.

Pigment Red 101) and the mixture is processed to small plates measuring 4 x 5 cm (thickness 3 mm) in an injection noulding machine at a cylinder temperature of 200 0 -230 0 C. These plates are irradiated with an Nd:YAG pulsed laser in accordance with Example lb). A black marking with good contrast is obtained.

Example 241t PBTP plates obtained in accordance with Example 2, but using 0.15 g of a copper phthalocyanine pigment (Microlith® Green G-FP, ex Ciba-Geigy, Switzerland, base pigment C.I. Pigment Green 7) as additive that effects a change in colour, are marked 18 black by the basic frequency (1064 nm) of an Nd:YAG laser (Quanta Ray DCR-2A, available from Spectra Physics, USA). The pulse duration is 6-8 ns and the pulse content 250 mJ.

Example 25: PBTP plates obtained according to Example 24, but containing 0.3 g of Filester® Yellow 2648A (anthraquinone derivative, ex Ciba-Geigy, Switzerland, C.I. Pigment Yellow 147) as additive that effects a change in colour, are marked black with good contrast. The pulse content is 500 mJ instead of 250 mJ.

Example 26: Following the procedure of Example 24, PBTP plates are irradiated with a laser beam having wavelengths of 511 and 578 nm of a copper vapour laser (Plasma Kinetics 151 available from Plasma oO a o Kinetics, USA). The pulse duration is 20-60 ns and the pulse content is 0.5 mJ. The beam is focussed through a glass lens with a focal 0o a length of 250 mm to give a beam diameter of 0.5 mm and produces a o black marking.

a0 0 a oa Example 27: 99.7 g of polycarbonate (Makrolan® 2800, ex Bayer, West Germany) are mixed with 0.3 g of a yellow cadmium pigment (Cadmium 2 oYellow® X-2822, ex Ciba-Geigy, Switzerland, C.I. Pigment Yellow a 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 0 -280 0 C. These plates are irradiated with an Nd:YAG pulsed laser in accordance with Example Ib). A black marking with good contrast is obtained.

Example 28: 99.7 g of polyoxymethylene (Hostaform® C 9020, available from Hoechst, West Germany) are mixed with 0.3 g of a yellow pigment (Filester® Yellow 2648 A, ex 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 190 0 -210°C. These plates are irradiated with an Nd:YAG pulsed laser in accordance with Example Ib). A black marking with good contrast is obtained.

r ""7 19 Example 29: 99.7 g of HD polyethylene (Lupolen® 1030 K, available from BASF, West Germany) are mixed with 0.3 g of a red iron oxide pigment (Bayferrox® 140, available from Bayer, 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 190 0 -230 0 C. These plates are irradiated with an Nd:YAG pulsed laser in accordance with Example Ib). A black marking with good contrast is obtained.

xample 30: 99.7 g of polyamide 12 (Vestamid® L 1901, available from Chem. Werke HUls, West Germany) are mixed with 0.3 g of a yellow anthraquinone pigment (Filester Yellow® 2648 A, ex 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 210°-250OC. These plates are irradiated with an Nd:YAG pulsed laser in accordance with Example Ib). A black marking with good contrast is obtained.

Example 31: 99.7 g of polyamide 66 (Ultramid® A3K, available from BASF, West Germany) are mixed with 0.3 g of i yellow anthraquinone pigment (Filester Yellow® 2648 A, ex 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 2500-280°C. These plates are irradiated with an Nd;YAG pulsed laser in accordance with Example Ib). A black marking with good contrast is obtained.

Example 32: 100 g of polyvinyl chloride (Vestolite®S 6558, available from Chem. Werke HUls, West Germany), 1,2 g of Irgastab® 17M -(butyltin sulfur stabiliser available from Ciba-Geigy, Switzerland), J 0.4 g of Irgawax® 361 (lubricant, glycerol monooleate available from Ciba-Geigy, Switzerland) and 0.2 g of Wax® E (available from Hoechst, West Germany) are mixed with 0.3 g of a yellow anthraquinone pigment (Filester Yellow® 2648 A, ex Ciba-Geigy, Switzerland, C.1. Pigment Yellow 147) and the mixture is rolled for 8 minutes on a two-roll mill at a temperature of 160°C. The coloured 20 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 so obtained are irradiated with an Nd:YAD pulsed laser in accordance with Example lb). A black marking with good contrast is obtained.

Example 33: 99.7 g of polystyrene (Polystyrene® 143 E, available from BASF, West Germany) are mixed with 0.3 g of a red iron oxide pigment (Bayferrox® 140, available from Bayer, 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 0 -240 0 C. These plates are irradiated with an Nd:YAG pulsed laser in accordance with Example Ib). A black marking with good contrast is obtained.

t Example 34: For colouring epoxy compositions, a colour paste is prepared from 85 g of basic epoxy resin AY 105® (ex 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, C.I. Pigment Red 220, both available from Ciba-Geigy, Switzerland), 1 g of this paste is mixed with 24 g of an aliphatic amine HY 956® (ex Ciba-Geigy, Switzerland) and 100 g of a basic epoxy resin AY 105® (ex Ciba-Geigy, Switzerland) and cast to 1 mm plates. These plates are then cured for 3-4 hours at 40*°-50°C. The plates are irradiated with a laser beam in accordance with Example Ib), except that the pulse content is 1 mJ and the beam is focussed through a glass lens having a focal length of 250 amm to give a beam diameter of 0.5 mm. The markings obtained appear black when viewed normally in the direction of viewing but have a transparent yellowish 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 specification 4 415 685) are 6tirred together and rolled for 7 minutes at 160°C on a two-roll

I

21mill. The resultant red sheet is irradiated with an Nd:YAG pulsed Slaser in accordance with Example Ib). A black marking with good contrast is obtained.

Example 36: 99.7 g of melamine resin (Melopas® N 37601, available from Ciba-Geigy, Switzerland) are mixed with 0.3 g of a red iron oxide pigment (Bayferrox® 140, available from Bayer, C.I. Pigment Red 101) and the mixture is processed to small plates measuring 4 x 5 cm (thickness 1-3 mm) in an injection moulding machine at a cylinder temperature of 95 0 C, a mould temperature of 170°C, and a cycle of 35 seconds. These plates are irradiated with an Nd:YAG pulsed laser in accordance with Example ib). A grey marking with good contrast is obtained.

Example 37: 98 g of polycarbonate granules (Lexan® 101-111, available frum General Electric Plastics BV, Holland) are mixed dry for minutes with 0.25 g of a soluble anthraquinone dye (Oracet® Yellow GHS, ex Ciba-Geig" Switzerland, C.I. Solvent Yellow 163) and i 1.5 g of TiQO (type CL 220 ex Kronos Titan GmbH). The mixture is moulded at 310°C cylinder temperature and 80"C mould temperature by injection mouldirig, ground, and under the same conditions cast to plates measuring 1.5 x 6.5 cm (thickness 1.5 mm). The plates are irradiated with a laser beam in accordance with Example Ib) to give black markings with good contrast.

'-44~a

Claims

22- j The Claims defining the invention are as follows: 1. A process for marking a coating, film or molded article of high molecular weight organic material composition containing at least one radiation-sensitive additive that effects a change in colour, in which the organic material of the composition is selected from the group consisting of polyethylene, polypropylene, polyisobutylene, polystyrene, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetals, poly- 4 nt a acrylonitrile, polyacrylates, polymethacrylates, polybutadiene, and copolymers thereof, polyesters, polyamides, polyimides, polycarbonates, 0 4 0 polyurethanes, polyethers, polyacetals, formaldehyde/phenol condensates, 04 0 So the condensates of formaldehyde and urea, thiourea and melamine, epoxy 4 0. S resins, surface-coating saturated or unsaturated polyesters, mixtures of said polyplastics, as well as co-condensates and copolymers thereof; further film formers or binders for varnishes or printing inks selected from the group consisting of linseed oil varnish, nitrocellulose, alkyd i resins, phenolic resins, melamine resins, acrylic resins or urea/form- a" o aldehyde resins, and the organic material composition containing from 0,001 to 10 by weight of said polymer, of at least one radiation- o0 4 '04 sensitive additive selected from the group consisting of an inorganic pigment selected from the group consisting of titanium dioxide, zinc oxide, antimony trioxide, zinc sulfide, lithopones, basic 'lead carbonate, basic lead sulfate or basic lead silicate, iron oxides, chromium oxides, nickel antimony titanate, chromium antimony titanate, manganese blue, manganese violet, cobalt blue, cobalt chromium blue, cobalt nickel grey, ultramarine blue, Berlin blue, lead chromates, lead sulfochromates, molybdate orange, molybdate red, cadmium sulfide, arsenic disulfide, antimony trisulfide, cadmium sulfoselenides, zirconium silicate, and carbon black or graphite in low concentration, r -23- (ii) an organic pigment selected from the group consisting of azo, azomethine, methine, anthraquinone, indanthrone, pyranthrone, flavan- throne, benzanthrone, phthalocyanine, perinone, perylene, dioxazine, thioindigo, isoindoline, isoindolinone, quinacridone, pyrrolopyrrole or quinophthalone pigments, and metal complexes and salts of azo, azomethine or methine dyes, and (iii) a polymer soluble dye selected from the group consisting of disperse dyes of the anthraquinone series, metal complexes of azo dyes and fluorescent dyes of the coumarin, naphthalimide, pyrazoline, acridine, xanthene, thioxanthene, oxazine, thiazine, and benzthiazole series, which process comprises utilising as radiation energy a laser beam having Sa wavelength in the close ultraviolet and/or visible range and/or close infrared range, wherein the energy source is applied to the surface of the material to be marked according to the form of the graphic symbols to be applied, such that a change in colour is inducqd at the irradiated areas without perceptible damage to the surface of the marked material, 2. A process according to claim 1, wherein a laser with pulsed light is used. I' 3, A process according to claim 1, wherein a laser beam having a wavelength in the visible and/or close infra-red range is used. 4. A process according to claim 1, wherein a pulsed or pulsp-modified, frequency doubled Ndt:YAG laser or a metal vapour laser is used. A process according to claim 1, wherein the high molecular organic material is selected from polyethylene, polypropylene polyisobutylene, polystyrene, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetals, polyacrylonitrile, polyacrylates and polymethatcrylates, poly- butadiens, ABS or EVA copolymers, polyesters, polyamides, polyimides, polyearbonates, polyurethanes, polyethert, polyacotals, phenoplasts, aminoplasts and epoxy resins. -24- A process according to cla-lXm I, wI-erein the high molecular organic material is a linear polyester, polystyrene, polyethylene, pol~ypropylene, ABS, a polyacetaJ, polyphenylene oxide, polyamide, polycarbonate, polymethylmethacrylate or an epoxy resin. 7. A process according to claim 1, wherein the additive is a metal- containing pigment sel~ected from the series of the inorganic pigments and the metal complexes of azo, azomethine or mqthine dyes. A proce, according to claim 1, wherein the additive is a comnbination ofapolynmer-soluble dye and an inorganic pigment. 9. A process according co, claim 8, wherein titanium dioxide is used as inorganic pigiient. A process acoirding to claim 1, wherein the additive is an azo, azomethioe, methine, anthraquinone, pht'halocyanine, perylene, dioxazine, thioindigo, isoindo],ine, isoincdolinone, quinacridone or pyrrolopyrrole pigment. 11, A process for marking a coating, filmt or molded article sub~stantially as herein dencriLbed with reference to any one of the Examples. 12, A coating* film or molded article whenever marked by the proces doiined in ainy one of claims 1 to 11. DATED tis 26th day of Vebrua-ry, 1990 CIfa,-,GEIGY AKTIENGESELSCAF By Its Patent Attorneys LTWrHLJ S. CAVE CO.