EP2678132A1 - Heat treatment of a laser coating - Google Patents

Heat treatment of a laser coating

Info

Publication number
EP2678132A1
EP2678132A1 EP12709945.5A EP12709945A EP2678132A1 EP 2678132 A1 EP2678132 A1 EP 2678132A1 EP 12709945 A EP12709945 A EP 12709945A EP 2678132 A1 EP2678132 A1 EP 2678132A1
Authority
EP
European Patent Office
Prior art keywords
coating
laser
substrate
substrates
laser radiation
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP12709945.5A
Other languages
German (de)
French (fr)
Inventor
Mattieu BILAINE
Vincent Rachet
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Saint Gobain Glass France SAS
Original Assignee
Saint Gobain Glass France SAS
Compagnie de Saint Gobain SA
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Saint Gobain Glass France SAS, Compagnie de Saint Gobain SA filed Critical Saint Gobain Glass France SAS
Publication of EP2678132A1 publication Critical patent/EP2678132A1/en
Withdrawn legal-status Critical Current

Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D3/00—Pretreatment of surfaces to which liquids or other fluent materials are to be applied; After-treatment of applied coatings, e.g. intermediate treating of an applied coating preparatory to subsequent applications of liquids or other fluent materials
    • B05D3/06—Pretreatment of surfaces to which liquids or other fluent materials are to be applied; After-treatment of applied coatings, e.g. intermediate treating of an applied coating preparatory to subsequent applications of liquids or other fluent materials by exposure to radiation
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F26—DRYING
    • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
    • F26B3/00—Drying solid materials or objects by processes involving the application of heat
    • F26B3/28—Drying solid materials or objects by processes involving the application of heat by radiation, e.g. from the sun
    • F26B3/30—Drying solid materials or objects by processes involving the application of heat by radiation, e.g. from the sun from infrared-emitting elements
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
    • B23K26/02—Positioning or observing the workpiece, e.g. with respect to the point of impact; Aligning, aiming or focusing the laser beam
    • B23K26/06—Shaping the laser beam, e.g. by masks or multi-focusing
    • B23K26/073—Shaping the laser spot
    • B23K26/0738—Shaping the laser spot into a linear shape
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
    • B23K26/08—Devices involving relative movement between laser beam and workpiece
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
    • B23K26/08—Devices involving relative movement between laser beam and workpiece
    • B23K26/083—Devices involving movement of the workpiece in at least one axial direction
    • B23K26/0838—Devices involving movement of the workpiece in at least one axial direction by using an endless conveyor belt
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
    • C03C17/00—Surface treatment of glass, not in the form of fibres or filaments, by coating
    • C03C17/28—Surface treatment of glass, not in the form of fibres or filaments, by coating with organic material
    • C03C17/32—Surface treatment of glass, not in the form of fibres or filaments, by coating with organic material with synthetic or natural resins
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D2203/00—Other substrates
    • B05D2203/30—Other inorganic substrates, e.g. ceramics, silicon
    • B05D2203/35—Glass
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D2502/00—Acrylic polymers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D2503/00—Polyurethanes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D3/00—Pretreatment of surfaces to which liquids or other fluent materials are to be applied; After-treatment of applied coatings, e.g. intermediate treating of an applied coating preparatory to subsequent applications of liquids or other fluent materials
    • B05D3/02—Pretreatment of surfaces to which liquids or other fluent materials are to be applied; After-treatment of applied coatings, e.g. intermediate treating of an applied coating preparatory to subsequent applications of liquids or other fluent materials by baking
    • B05D3/0254—After-treatment
    • B05D3/0263—After-treatment with IR heaters
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D5/00—Processes for applying liquids or other fluent materials to surfaces to obtain special surface effects, finishes or structures
    • B05D5/06—Processes for applying liquids or other fluent materials to surfaces to obtain special surface effects, finishes or structures to obtain multicolour or other optical effects
    • B05D5/061—Special surface effect
    • B05D5/063—Reflective effect
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
    • C03C2218/00—Methods for coating glass
    • C03C2218/30—Aspects of methods for coating glass not covered above
    • C03C2218/32—After-treatment

Definitions

  • the invention relates to the field of substrate painting and describes a method of drying and / or cooking by laser especially suitable for paints or inks comprising an organic solvent or aqueous based.
  • the paints are then dried and / or baked or in an oven.
  • Three main techniques are currently available to ensure this drying and / or cooking: drying in ambient air, drying / baking, UV crosslinking.
  • the running speed of substrates coated with paint in a drying oven or oven or firing can range from a few 1 m / min for glass substrates to 1 km / min in the case of press presses for example.
  • UV crosslinking cooking is carried out purely by photochemical means by irradiating the paint with UV radiation causing crosslinking.
  • This technique allows higher rates than drying / baking but causes environmental problems, particularly because of the significant generation of ozone, acrylates and free radicals in the production area.
  • the present invention proposes to combine the power of intense radiation of the laser type (which of course covers the possibility of having several such radiations) with traditional paints or inks for a baking process.
  • the invention is particularly suitable for the heat treatment of coated substrates having large areas, in particular ranging from 1 to 25 m 2 .
  • the invention relates to a method for heating an organic coating applied to substrates, wherein laser radiation is applied to the organic coating while the substrates are continuously moving.
  • the coating is organic to the extent that it comprises at least one organic compound before the laser treatment according to the invention.
  • a paint commonly used to protect the backs of mirrors is an organic coating because it contains an organic solvent or an organic resin.
  • the coating may comprise an organic pigment. After treatment with the process according to the invention, the coating generally still contains an organic compound.
  • the invention is particularly suitable for drying or baking paints applied to a glass substrate such as the back of mirrors, especially in the latter case to protect the silver layer from corrosion.
  • the laser treatment according to the invention also has the particularity, unlike the annealing or quenching treatments, of not significantly heating the substrate. It is thus not necessary to carry out a slow and controlled cooling of the coated substrate before it is cut or stored.
  • This method also makes it possible to integrate a heating device on existing continuous production lines, in particular a mirror production line, which may include a silver layer preheating zone to eliminate traces of moisture.
  • the substrate may in particular comprise or be a glass sheet, glass-ceramic, or an organic polymer.
  • it is transparent preference. It can be colorless (it is then a clear or extraclear glass) or colored, for example in blue, green, gray or bronze.
  • the glass is preferably of the silico-soda-lime type, but it may also be of borosilicate or alumino-borosilicate type glass.
  • the preferred organic polymers are polycarbonate or polymethylmethacrylate or polyethylene terephthalate (PET).
  • PET polyethylene terephthalate
  • the substrate may have at least one dimension greater than or equal to 1 m, or even 2 m and even 3 m.
  • the thickness of the substrate is generally from 0.5 mm to 20 mm, in particular for the mirror application from 0.7 to 9 mm, in particular from 2 to 8 mm, or even from 4 to 6 mm.
  • the substrate may be flat or curved. It can be rigid or flexible.
  • the glass substrate is generally of the float type, that is to say likely to have been obtained by a process of pouring the molten glass on a bath of molten tin ("float" bath).
  • the layer to be treated may be deposited on the "tin” side as well as on the "atmosphere” side of the substrate.
  • the term "atmosphere” and “tin” faces means the faces of the substrate having respectively been in contact with the atmosphere prevailing in the float bath and in contact with the molten tin.
  • the tin side contains a small surface amount of tin that has diffused into the glass structure.
  • the glass substrate can also be obtained by rolling between two rollers, a technique which makes it possible in particular to print patterns on the surface of the glass.
  • the substrate may in particular be of the glass type, coated with ink (comprising at least one pigment, in particular in the form of nanoparticles or comprising at least one organic dye) or organic solvent-based paint, hydro diluted or even water-soluble.
  • ink comprising at least one pigment, in particular in the form of nanoparticles or comprising at least one organic dye
  • organic solvent-based paint hydro diluted or even water-soluble.
  • the invention is particularly suitable for inks and paints of alkyd, acrylic and polyurethane type but not exclusively.
  • the temperature ranges accessible by the technique according to the invention are particularly suitable for technologies based on urea / formaldehyde, epoxide or isocyanate crosslinking mechanisms, but not exclusively.
  • the heat treatment is carried out using at least one laser radiation.
  • the pfd of the laser radiation at the coating is preferably greater than or equal to 20 and even greater than or equal to 30 kW / cm 2 .
  • This very high energy density makes it possible to reach the desired temperature very rapidly at the coating level (generally in a time of less than or equal to 1 second) and consequently to limit the duration of the treatment by as much, the heat generated as then having no time to diffuse within the substrate.
  • the portion of the substrate (particularly glass) located at 0.5 mm from the coating does not generally undergo temperatures above 100 ° C.
  • the substrate therefore does not generally undergo a temperature greater than 100 ° C at a depth of 0.5 mm from the substrate / coating interface.
  • the coating undergoes a uniform temperature that allows drying or baking of paints or inks without inducing defects.
  • the method according to the invention is continuous: a relative movement is created between the coated substrate and the laser beam heating means so as to treat the desired surface, in general the entire surface.
  • the laser radiation preferably has a wavelength of between 266 and 1000 nm, especially between 530 and 1200 nm. It is indeed in this range of wavelengths that the absorption of the coating (paint or ink) is maximum. Thus the radiation is absorbed specifically by the coating and little by the substrate, which allows to quickly heat the layer without heating the substrate.
  • glass especially clear or extra-clear glass, absorbs very little in this range of wavelengths so that the radiation mainly heats the layer.
  • the absorption is defined as being equal to the value of 100% to which the transmission and the reflection of the layer are subtracted.
  • Laser diodes emitting for example at a wavelength of the order of 808 nm, 880 nm, 940 nm, or 980 nm or 1032 nm, are preferably used.
  • very high powers can be obtained, making it possible to achieve surface powers at the level of the layer to be treated greater than 20 kW / cm 2 , or even greater than 30 kW / cm 2 .
  • the lasers used in the context of the invention can be fiber-reinforced, which means that the laser radiation (any gain medium: gas, liquid, solid) is injected into an optical fiber and then delivered near the surface to be treated by a focusing head.
  • the laser can also be fiber, in the sense that the amplification medium (that is to say gain medium) is itself an optical fiber, generally doped with rare earth ions ("fiber laser " in English)
  • the laser radiation may be from at least one laser beam forming a line (called "laser line” in the rest of the text) which simultaneously radiates the entire width of the substrate coated with the coating to be heated.
  • laser line a line
  • the in-line laser beam can in particular be obtained using high power laser diode systems associated with focusing optics.
  • the thickness of the line is preferably between 0.01 and 1 mm.
  • the length of the line is adapted to the width of the substrate to be treated, it is typically between 5 mm and 4 m.
  • the intensity profile of the line (in its width) can in particular be a Gauss curve or a slot.
  • the laser radiation is applied along a line substantially transverse to the direction of travel of the substrates.
  • the laser line simultaneously radiating all or part of the width of the substrates may be composed of a single line (then radiating the entire width of the substrate), or of several lines, possibly disjointed. When several lines are used, it is preferable that they are arranged so that the entire surface of the coating to be heated is treated.
  • the laser line can be arranged obliquely to the direction of travel of the substrate, but is preferably disposed perpendicular to the running direction of the substrate. In the case of several laser lines, these can process the substrate simultaneously or in a time-shifted manner.
  • different laser beams are either physically focused in the same place to have a simultaneous treatment of the substrate, or they are shifted in space to treat one by one a given width of the moving substrate. The important thing is that the entire surface to be treated is.
  • a relative displacement is applied between the substrate coated with the layer and the laser line.
  • the substrate coated with the layer to be treated by laser can thus be set in motion, in particular in translation translation with respect to the fixed laser line, generally below, but possibly above the laser line.
  • the difference between the respective speeds of the substrate and the laser is greater than or equal to 1 meter per minute, or even 4 and even 6, 8, 10 or 20 meters per minute, in order to ensure a high processing speed.
  • the substrates scroll at a speed of 1 to 20 meters per minute.
  • the setting in motion can be carried out using any mechanical means of conveying, for example using strips, rollers, trays in translation.
  • the conveyor system controls and controls the speed of travel.
  • the substrate is of flexible organic material, generally of the polymer type such as PVC or PTFE
  • the displacement can be achieved using a film feed system comprising a succession of rollers.
  • the laser may also be moved to adjust its distance to the substrate, which may be useful especially when the substrate is curved, but not only. Indeed, it is preferable that the laser beam is focused on the coating to be treated so that the latter is located at a distance less than or equal to 1 mm of the focal plane. Ideally, the coating merges with the focal plane. If the substrate or laser displacement system is not sufficiently precise as to the distance between the substrate and the focal plane, it is preferable to be able to adjust the distance between the laser and the substrate. This adjustment can be automatic, in particular regulated by measuring the distance upstream of the treatment.
  • the substrate is generally arranged horizontally, but it can also be arranged vertically, or in any possible inclination.
  • the laser is generally arranged to irradiate the upper face of the substrate.
  • the on-line laser can be integrated into a lacquered glass production line or mirrors, in particular solar mirrors.
  • the on-line laser is located in the production process after the silvering steps, for example as a preheating element of the glass before depositing a layer of paint or just after the deposition of this layer .
  • the coated substrate can thus be treated in line after the deposition of the layer to be treated (ink or paint), at the exit of the deposition installation and before the optical control devices, or after the optical control devices and before the devices for stacking substrates.
  • a laser line as for example described in FIG. 1 makes it possible to heat a coating (ink or paint) with a thickness of generally between 1 ⁇ and 200 ⁇ extremely rapidly before laser treatment (that is to say heating) according to FIG. the invention.
  • Inks and paints used for baking are naturally very absorbent in the infrared, a laser typically emitting in a wavelength range of 266 nm to 1 1000 nm and allows an optimal transfer of energy between the source of radiation and the layer of paint.
  • the laser heating method according to the invention can in particular be used in four main modes: drying, rapid rise in temperature, baking or powder coating:
  • drying mode in this case, the laser irradiation makes it possible to very rapidly transfer energy corresponding to the latent heat of vaporization (L) of the solvent to be volatilized; in this case, a strong air flow ensures the extraction of the solvent vapors; - rapid temperature rise: after drying, the coating (paint or lacquer or ink) retains its absorbent properties in the infrared; the laser treatment then allows an extremely fast rise of the dry coating for subsequent cooking in a baking oven; the drying itself can be carried out in an oven or by the treatment according to the invention, the drying being followed by a heat treatment by laser according to the invention;
  • - powder coating the application of a powder coating allows the use of a single treatment with a laser beam to melt the powder and then harden it.
  • the laser treatment according to the invention makes it possible to heat the coating mainly by heating the substrate to a minimum. This therefore makes it possible to reduce the total energy required to treat the coating and / or to increase the treatment rates.
  • the process according to the invention can be used for drying or baking paints for indoor or solar mirrors, and also for finishing the paint of a lacquered glass.
  • the method according to the invention can be used to shorten the lengths of drying or cooking ovens.
  • the laser treatment according to the invention provides for the removal of a combustible organic material (a solvent for example) from the coating, it is possible to ensure dilution and sufficient convection with the aid of a gas such as air above the coated substrate to thereby reduce the risk of ignition or explosion.
  • a combustible organic material a solvent for example
  • P [W / m 2 ] power density of the laser radiation
  • L [m] length of the beam or of all the laser beams
  • p density of the wet or dry coating layer respectively according to whether it is dried (solvent evaporation) or baked coating (no solvent evaporation)
  • V speed of travel of the substrate
  • Figure 1 shows the method according to the invention.
  • Substrates 1 coated with a coating to be dried or cooked, run one behind the other continuously in a direction represented by the arrow, being conveyed by a bed of rollers (not shown). They pass under a laser source 2 which delivers a laser line 3 focused on the surface of the moving substrates and along their entire width. The laser line produces heating to dry or bake the coating.
  • a drying according to the invention of a layer of paint deposited on the back of the mirror as a protective coating.
  • the coating before drying had a thickness of 50 ⁇ , a density of 2 T / m 3 , a heat capacity of 0.7 kJ / Kg / K, an absorbance of 1.
  • the density of the coating is 1, 3 T / m 3 and each KW / m 2 leads to an increase in the paint temperature of 4 Kelvin.
  • the laser radiation essentially heats the coating, the glass being heated solely by conduction from the coating and in a very short time ( ⁇ 1 s) limiting the increase in its average temperature to less than 1 K on its total thickness.

Abstract

The invention relates to a method for heating an organic coating applied onto substrates (1), particularly mirror substrates. Laser radiation is applied onto the organic coating while the substrates continuously move. Said method in particular makes it possible to dry or cure paints or inks with little heat being transferred to the substrate.

Description

TRAITEMENT THERMIQUE DE REVETEMENT  THERMAL COATING TREATMENT
PAR LASER  BY LASER
L'invention concerne le domaine de la peinture sur substrat et décrit un procédé de séchage et/ou de cuisson par laser notamment adapté à des peintures ou encres comprenant un solvant organique ou à base aqueuse. The invention relates to the field of substrate painting and describes a method of drying and / or cooking by laser especially suitable for paints or inks comprising an organic solvent or aqueous based.
Différents procédés d'application de peinture ou d'encre liquide ou en poudre sur des substrats plans ou faiblement déformés par rapport au plan (sin (angle/verticale) > 0,95) sont aujourd'hui disponibles, notamment l'application par rouleau, par un rideau de peinture, la pulvérisation électro assistée ou non.  Various methods of applying paint or liquid or powder ink to flat or slightly deformed substrates with respect to the plane (sin (angle / vertical)> 0.95) are nowadays available, in particular the application by roller , by a paint curtain, electro-assisted spraying or not.
Les peintures sont ensuite séchées et/ou cuites au four ou en étuve. Trois techniques principales sont aujourd'hui disponibles pour assurer ce séchage et/ou cette cuisson : le séchage à l'air ambiant, le séchage/cuisson au four, la réticulation UV. La vitesse de défilement des substrats revêtus de peinture dans un four ou une étuve de séchage ou cuisson peut aller de quelques 1 m/min pour des substrats verriers à 1 km/min dans le cas des rotatives de presse par exemple.  The paints are then dried and / or baked or in an oven. Three main techniques are currently available to ensure this drying and / or cooking: drying in ambient air, drying / baking, UV crosslinking. The running speed of substrates coated with paint in a drying oven or oven or firing can range from a few 1 m / min for glass substrates to 1 km / min in the case of press presses for example.
La technique du séchage à l'air est très lente (plusieurs heures d'attente sont nécessaires) et se limite à l'utilisation de peinture à séchage siccatif (sans cuisson).  The technique of air drying is very slow (several hours of waiting are necessary) and is limited to the use of drying drying paint (without cooking).
La technique du séchage/cuisson au four est industriellement la plus répandue aujourd'hui. Basée sur des fours à rayonnement infrarouge court/moyen, ces installations nécessitent des fours de plusieurs dizaines de mètres de long selon les vitesses de défilement du substrat et le temps de cuisson nécessaire.  The technique of drying / baking is industrially the most widespread today. Based on short / medium infrared radiation furnaces, these installations require furnaces that are several tens of meters long depending on the speed of travel of the substrate and the necessary cooking time.
Basée sur une technologie utilisant très peu de solvant, la cuisson dite de réticulation UV est réalisée par voie purement photochimique en irradiant la peinture par un rayonnement UV entraînant une réticulation. Cette technique permet des cadences plus élevées que le séchage/cuisson au four mais engendre des problèmes environnementaux, notamment du fait de la génération importante d'ozone, d'acrylates et de radicaux libres dans la zone de production. La présente invention propose d'allier la puissance d'un rayonnement intense de type laser (ce qui recouvre bien entendu la possibilité d'avoir plusieurs rayonnements de ce type) avec des peintures ou encres traditionnelles destinées à un procédé au four. L'invention est particulièrement adaptée au traitement thermique de substrats revêtus ayant de grandes surfaces, notamment allant de 1 à 25 m2. Based on a technology using very little solvent, so-called UV crosslinking cooking is carried out purely by photochemical means by irradiating the paint with UV radiation causing crosslinking. This technique allows higher rates than drying / baking but causes environmental problems, particularly because of the significant generation of ozone, acrylates and free radicals in the production area. The present invention proposes to combine the power of intense radiation of the laser type (which of course covers the possibility of having several such radiations) with traditional paints or inks for a baking process. The invention is particularly suitable for the heat treatment of coated substrates having large areas, in particular ranging from 1 to 25 m 2 .
L'invention concerne un procédé de chauffage d'un revêtement organique appliqué sur des substrats, un rayonnement laser étant appliqué sur le revêtement organique alors que les substrats défilent en continu.  The invention relates to a method for heating an organic coating applied to substrates, wherein laser radiation is applied to the organic coating while the substrates are continuously moving.
Le revêtement est organique dans la mesure où il comprend au moins un composé organique avant le traitement laser selon l'invention. Par exemple, une peinture couramment utilisée pour protéger le dos des miroirs est un revêtement organique car elle contient un solvant organique ou une résine organique. Le revêtement peut comprendre un pigment organique. Après traitement par le procédé selon l'invention, le revêtement contient généralement encore un composé organique.  The coating is organic to the extent that it comprises at least one organic compound before the laser treatment according to the invention. For example, a paint commonly used to protect the backs of mirrors is an organic coating because it contains an organic solvent or an organic resin. The coating may comprise an organic pigment. After treatment with the process according to the invention, the coating generally still contains an organic compound.
L'invention est particulièrement adaptée au séchage ou à la cuisson de peintures appliquées sur un substrat verrier comme au dos des miroirs, notamment dans ce dernier cas en vue de protéger la couche d'argent de la corrosion.  The invention is particularly suitable for drying or baking paints applied to a glass substrate such as the back of mirrors, especially in the latter case to protect the silver layer from corrosion.
Le traitement laser selon l'invention a en outre la particularité, contrairement aux traitements de recuit ou de trempe, de ne pas chauffer le substrat de manière significative. Il n'est ainsi pas nécessaire de procéder à un refroidissement lent et contrôlé du substrat revêtu avant sa découpe ou son stockage. Ce procédé rend également possible l'intégration d'un dispositif de chauffage sur des lignes de production continue existantes, notamment une ligne de production de miroirs, laquelle peut comprendre une zone de préchauffage de couche d'argent pour éliminer les traces d'humidité.  The laser treatment according to the invention also has the particularity, unlike the annealing or quenching treatments, of not significantly heating the substrate. It is thus not necessary to carry out a slow and controlled cooling of the coated substrate before it is cut or stored. This method also makes it possible to integrate a heating device on existing continuous production lines, in particular a mirror production line, which may include a silver layer preheating zone to eliminate traces of moisture.
Le substrat peut notamment comprendre ou être une feuille de verre, de vitrocéramique, ou en un polymère organique. Pour l'application miroir, il est de préférence transparent. Il peut être incolore (il s'agit alors d'un verre clair ou extraclair) ou coloré, par exemple en bleu, vert, gris ou bronze. Le verre est de préférence de type silico-sodo-calcique, mais il peut également être en verre de type borosilicate ou alumino-borosilicate. Les polymères organiques préférés sont le polycarbonate ou le polyméthacrylate de méthyle ou encore le polyéthylènetérephtalate (PET). Le substrat peut présenter au moins une dimension supérieure ou égale à 1 m, voire 2 m et même 3 m. L'épaisseur du substrat va généralement de 0,5 mm à 20 mm, notamment pour l'application miroir de 0,7 à 9 mm, notamment de 2 à 8 mm, voire de 4 à 6 mm. Le substrat peut être plan ou bombé. Il peut être rigide ou flexible. The substrate may in particular comprise or be a glass sheet, glass-ceramic, or an organic polymer. For the mirror application, it is transparent preference. It can be colorless (it is then a clear or extraclear glass) or colored, for example in blue, green, gray or bronze. The glass is preferably of the silico-soda-lime type, but it may also be of borosilicate or alumino-borosilicate type glass. The preferred organic polymers are polycarbonate or polymethylmethacrylate or polyethylene terephthalate (PET). The substrate may have at least one dimension greater than or equal to 1 m, or even 2 m and even 3 m. The thickness of the substrate is generally from 0.5 mm to 20 mm, in particular for the mirror application from 0.7 to 9 mm, in particular from 2 to 8 mm, or even from 4 to 6 mm. The substrate may be flat or curved. It can be rigid or flexible.
Le substrat de verre est généralement du type flotté, c'est-à-dire susceptible d'avoir été obtenu par un procédé consistant à déverser le verre fondu sur un bain d'étain en fusion (bain « float »). Dans ce cas, la couche à traiter peut aussi bien être déposée sur la face « étain » que sur la face « atmosphère » du substrat. On entend par faces « atmosphère » et « étain », les faces du substrat ayant été respectivement en contact avec l'atmosphère régnant dans le bain float et en contact avec l'étain fondu. La face étain contient une faible quantité superficielle d'étain ayant diffusé dans la structure du verre. Le substrat de verre peut également être obtenu par laminage entre deux rouleaux, technique permettant en particulier d'imprimer des motifs à la surface du verre.  The glass substrate is generally of the float type, that is to say likely to have been obtained by a process of pouring the molten glass on a bath of molten tin ("float" bath). In this case, the layer to be treated may be deposited on the "tin" side as well as on the "atmosphere" side of the substrate. The term "atmosphere" and "tin" faces means the faces of the substrate having respectively been in contact with the atmosphere prevailing in the float bath and in contact with the molten tin. The tin side contains a small surface amount of tin that has diffused into the glass structure. The glass substrate can also be obtained by rolling between two rollers, a technique which makes it possible in particular to print patterns on the surface of the glass.
Selon l'invention le substrat peut notamment être du type verrier, revêtu d'encre (comprenant au moins un pigment, notamment sous forme de nanoparticules ou comprenant au moins un colorant organique) ou de peinture à solvant organique, hydro diluées ou même hydrosolubles. L'invention est particulièrement adaptée aux encres et peintures de type Alkyde, Acrylique et Polyuréthane mais non exclusivement. Les gammes de températures accessibles par la technique selon l'invention sont particulièrement adaptées aux technologies basées sur des mécanismes de réticulation de type urée/formol, époxyde ou isocyanate, mais non exclusivement.  According to the invention the substrate may in particular be of the glass type, coated with ink (comprising at least one pigment, in particular in the form of nanoparticles or comprising at least one organic dye) or organic solvent-based paint, hydro diluted or even water-soluble. The invention is particularly suitable for inks and paints of alkyd, acrylic and polyurethane type but not exclusively. The temperature ranges accessible by the technique according to the invention are particularly suitable for technologies based on urea / formaldehyde, epoxide or isocyanate crosslinking mechanisms, but not exclusively.
Le traitement thermique est réalisé à l'aide d'au moins un rayonnement laser. La puissance surfacique du rayonnement laser au niveau du revêtement est de préférence supérieure ou égale à 20 et même supérieure ou égale à 30 kW/cm2. Cette très forte densité d'énergie permet d'atteindre au niveau du revêtement la température souhaitée très rapidement (en général en un temps inférieur ou égal à 1 seconde) et par conséquent de limiter d'autant la durée du traitement, la chaleur générée n'ayant alors pas le temps de diffuser au sein du substrat. The heat treatment is carried out using at least one laser radiation. The pfd of the laser radiation at the coating is preferably greater than or equal to 20 and even greater than or equal to 30 kW / cm 2 . This very high energy density makes it possible to reach the desired temperature very rapidly at the coating level (generally in a time of less than or equal to 1 second) and consequently to limit the duration of the treatment by as much, the heat generated as then having no time to diffuse within the substrate.
Grâce au très fort coefficient d'échange thermique associé au procédé selon l'invention, même la partie du substrat (notamment en verre) située à 0,5 mm du revêtement ne subit généralement pas de températures supérieures à 100°C. Le substrat ne subit donc généralement pas de température supérieure à 100°C à une profondeur de 0,5 mm de l'interface substrat/revêtement.  Thanks to the very high heat exchange coefficient associated with the process according to the invention, even the portion of the substrate (particularly glass) located at 0.5 mm from the coating does not generally undergo temperatures above 100 ° C. The substrate therefore does not generally undergo a temperature greater than 100 ° C at a depth of 0.5 mm from the substrate / coating interface.
Grâce à la très grande homogénéité de la puissance de la ligne laser associé au procédé selon l'invention, ladite puissance ne variant pas plus de 5% sur la ligne, voire ne variant pas plus de 1 % sur la ligne, le revêtement subit une température uniforme qui permet un séchage ou une cuisson des peintures ou encres sans induire de défauts.  Thanks to the very great homogeneity of the power of the laser line associated with the process according to the invention, said power not varying more than 5% on the line, or even not varying more than 1% on the line, the coating undergoes a uniform temperature that allows drying or baking of paints or inks without inducing defects.
Le procédé selon l'invention est continu : on crée un mouvement relatif entre le substrat revêtu et les moyens de chauffage par rayon laser de manière à traiter la surface voulue, en général la totalité de la surface.  The method according to the invention is continuous: a relative movement is created between the coated substrate and the laser beam heating means so as to treat the desired surface, in general the entire surface.
Le rayonnement laser possède de préférence une longueur d'onde comprise entre 266 et 1 1 000 nm, notamment entre 530 et 1200 nm. C'est en effet dans cette gamme de longueurs d'onde que l'absorption du revêtement (peinture ou encre) est maximale. Ainsi le rayonnement est-il absorbé spécifiquement par le revêtement et peu par le substrat, ce qui permet de chauffer rapidement la couche sans chauffer le substrat.  The laser radiation preferably has a wavelength of between 266 and 1000 nm, especially between 530 and 1200 nm. It is indeed in this range of wavelengths that the absorption of the coating (paint or ink) is maximum. Thus the radiation is absorbed specifically by the coating and little by the substrate, which allows to quickly heat the layer without heating the substrate.
De préférence, l'absorption par le revêtement avant traitement thermique laser selon l'invention (encre ou peinture) à la longueur d'onde du rayonnement laser est supérieure ou égale à 20%, notamment 30% (absorption=100%- transmission-réflexion, la transmission et la réflexion étant mesurées sur l'ensemble couche/substrat par exemple par un appareillage du type Iambda900) pour une épaisseur de revêtement caractéristique de 10 μιτι en transmission normale (perpendiculairement au substrat revêtu). Au contraire, le verre, surtout le verre clair ou extra-clair, absorbe très peu dans cette gamme de longueurs d'onde si bien que le rayonnement chauffe principalement la couche. L'absorption est définie comme étant égale à la valeur de 100% auxquelles sont soustraites la transmission et la réflexion de la couche. Preferably, the absorption by the coating before laser thermal treatment according to the invention (ink or paint) at the wavelength of the laser radiation is greater than or equal to 20%, in particular 30% (absorption = 100% - transmission- reflection, the transmission and reflection being measured on the layer / substrate assembly for example by a device of the Iambda900 type) for a typical coating thickness of 10 μιτι in normal transmission (perpendicular to the coated substrate). On the contrary, glass, especially clear or extra-clear glass, absorbs very little in this range of wavelengths so that the radiation mainly heats the layer. The absorption is defined as being equal to the value of 100% to which the transmission and the reflection of the layer are subtracted.
On utilise de préférence des diodes laser, émettant par exemple à une longueur d'onde de l'ordre de 808 nm, 880 nm, 940 nm, ou encore 980 nm ou 1032 nm. Sous forme de systèmes de diodes, de très fortes puissances peuvent être obtenues, permettant d'atteindre des puissances surfaciques au niveau de la couche à traiter supérieures à 20 kW/cm2, voire supérieures à 30 kW/cm2. Laser diodes, emitting for example at a wavelength of the order of 808 nm, 880 nm, 940 nm, or 980 nm or 1032 nm, are preferably used. In the form of diode systems, very high powers can be obtained, making it possible to achieve surface powers at the level of the layer to be treated greater than 20 kW / cm 2 , or even greater than 30 kW / cm 2 .
Pour une simplicité de mise en œuvre accrue, les lasers employés dans le cadre de l'invention peuvent être fibrés, ce qui signifie que le rayonnement laser (milieu à gain quelconque : gaz, liquide, solide) est injecté dans une fibre optique puis délivré près de la surface à traiter par une tête de focalisation. Notamment, le laser peut également être à fibre, au sens où le milieu d'amplification (c'est-à-dire milieu à gain) est lui-même une fibre optique, généralement dopée avec des ions de terre rare (« fiber laser » en anglais)  For greater simplicity of implementation, the lasers used in the context of the invention can be fiber-reinforced, which means that the laser radiation (any gain medium: gas, liquid, solid) is injected into an optical fiber and then delivered near the surface to be treated by a focusing head. In particular, the laser can also be fiber, in the sense that the amplification medium (that is to say gain medium) is itself an optical fiber, generally doped with rare earth ions ("fiber laser " in English)
Le rayonnement laser peut être issu d'au moins un faisceau laser formant une ligne (appelée « ligne laser » dans la suite du texte) qui irradie simultanément toute la largeur des substrat revêtus du revêtement à chauffer. Ce mode de réalisation évite l'utilisation de systèmes de déplacement coûteux, généralement encombrants, et d'entretien délicat. Le faisceau laser en ligne peut notamment être obtenu à l'aide de systèmes de diodes laser de forte puissance associées à une optique de focalisation. L'épaisseur de la ligne est de préférence comprise entre 0,01 et 1 mm. La longueur de la ligne est adaptée à la largeur du substrat à traiter, elle est typiquement comprise entre 5 mm et 4 m. Le profil d'intensité de la ligne (dans sa largeur) peut notamment être une courbe de Gauss ou un créneau.  The laser radiation may be from at least one laser beam forming a line (called "laser line" in the rest of the text) which simultaneously radiates the entire width of the substrate coated with the coating to be heated. This embodiment avoids the use of expensive moving systems, generally bulky, and delicate maintenance. The in-line laser beam can in particular be obtained using high power laser diode systems associated with focusing optics. The thickness of the line is preferably between 0.01 and 1 mm. The length of the line is adapted to the width of the substrate to be treated, it is typically between 5 mm and 4 m. The intensity profile of the line (in its width) can in particular be a Gauss curve or a slot.
Généralement, le rayonnement laser est appliqué selon une ligne sensiblement transversale par rapport au sens de défilement des substrats.  Generally, the laser radiation is applied along a line substantially transverse to the direction of travel of the substrates.
La ligne laser irradiant simultanément toute ou partie de la largeur des substrats peut être composée d'une seule ligne (irradiant alors toute la largeur du substrat), ou de plusieurs lignes, éventuellement disjointes. Lorsque plusieurs lignes sont utilisées, il est préférable qu'elles soient disposées de sorte que toute la surface du revêtement à chauffer soit traitée. La ligne laser peut être disposée de manière oblique par rapport à la direction de défilement du substrat, mais est de préférence disposée perpendiculairement à la direction de défilement du substrat. Dans le cas de plusieurs lignes laser, celles-ci peuvent traiter le substrat simultanément, ou de manière décalée dans le temps. En pratique différents faisceaux laser sont soit focalisées physiquement au même endroit pour avoir un traitement simultané du substrat, ou alors ils sont décalées dans l'espace pour traiter l'un après l'autre une largeur donnée du substrat en défilement. L'important est que toute la surface à traiter le soit. The laser line simultaneously radiating all or part of the width of the substrates may be composed of a single line (then radiating the entire width of the substrate), or of several lines, possibly disjointed. When several lines are used, it is preferable that they are arranged so that the entire surface of the coating to be heated is treated. The laser line can be arranged obliquely to the direction of travel of the substrate, but is preferably disposed perpendicular to the running direction of the substrate. In the case of several laser lines, these can process the substrate simultaneously or in a time-shifted manner. In practice, different laser beams are either physically focused in the same place to have a simultaneous treatment of the substrate, or they are shifted in space to treat one by one a given width of the moving substrate. The important thing is that the entire surface to be treated is.
Afin de traiter toute la surface de la couche en continu, on met en œuvre un déplacement relatif entre d'une part le substrat revêtu de la couche et la ligne laser. Le substrat revêtu de la couche à traiter par laser peut ainsi être mis en déplacement, notamment en défilement en translation en regard de la ligne laser fixe, généralement en dessous, mais éventuellement au-dessus de la ligne laser. De préférence, la différence entre les vitesses respectives du substrat et du laser est supérieure ou égale à 1 mètre par minute, voire 4 et même 6, 8, 10 ou 20 mètres par minute, ce afin d'assurer une grande vitesse de traitement. Généralement, les substrats défilent à une vitesse de 1 à 20 mètres par minute.  In order to treat the entire surface of the layer continuously, a relative displacement is applied between the substrate coated with the layer and the laser line. The substrate coated with the layer to be treated by laser can thus be set in motion, in particular in translation translation with respect to the fixed laser line, generally below, but possibly above the laser line. Preferably, the difference between the respective speeds of the substrate and the laser is greater than or equal to 1 meter per minute, or even 4 and even 6, 8, 10 or 20 meters per minute, in order to ensure a high processing speed. Generally, the substrates scroll at a speed of 1 to 20 meters per minute.
Pour le déplacement du substrat en translation, la mise en mouvement peut être réalisée à l'aide de tous moyens mécaniques de convoyage, par exemple à l'aide de bandes, de rouleaux, de plateaux en translation. Le système de convoyage permet de contrôler et réguler la vitesse du déplacement. Si le substrat est en matière organique souple, généralement du type polymère comme le PVC ou PTFE, le déplacement peut être réalisé à l'aide d'un système d'avance de films comprenant une succession de rouleaux.  For displacement of the substrate in translation, the setting in motion can be carried out using any mechanical means of conveying, for example using strips, rollers, trays in translation. The conveyor system controls and controls the speed of travel. If the substrate is of flexible organic material, generally of the polymer type such as PVC or PTFE, the displacement can be achieved using a film feed system comprising a succession of rollers.
Le laser peut également être mis en mouvement de manière à ajuster sa distance au substrat, ce qui peut être utile en particulier lorsque le substrat est bombé, mais pas seulement. En effet, il est préférable que le faisceau laser soit focalisé sur le revêtement à traiter de sorte que ce dernier soit situé à une distance inférieure ou égale à 1 mm du plan focal. Idéalement, le revêtement se confond avec le plan focal. Si le système de déplacement du substrat ou du laser n'est pas suffisamment précis quant à la distance entre le substrat et le plan focal, il convient de préférence de pouvoir ajuster la distance entre le laser et le substrat. Cet ajustement peut être automatique, notamment régulé grâce à une mesure de la distance en amont du traitement. The laser may also be moved to adjust its distance to the substrate, which may be useful especially when the substrate is curved, but not only. Indeed, it is preferable that the laser beam is focused on the coating to be treated so that the latter is located at a distance less than or equal to 1 mm of the focal plane. Ideally, the coating merges with the focal plane. If the substrate or laser displacement system is not sufficiently precise as to the distance between the substrate and the focal plane, it is preferable to be able to adjust the distance between the laser and the substrate. This adjustment can be automatic, in particular regulated by measuring the distance upstream of the treatment.
Toutes les positions relatives du substrat et du laser sont possibles du moment que la surface du substrat soit convenablement irradiée. Le substrat est le plus généralement disposé de manière horizontale, mais il peut aussi être disposé verticalement, ou selon toute inclinaison possible. Lorsque le substrat est disposé horizontalement, le laser est généralement disposé de manière à irradier la face supérieure du substrat.  All relative positions of the substrate and the laser are possible as long as the surface of the substrate is properly irradiated. The substrate is generally arranged horizontally, but it can also be arranged vertically, or in any possible inclination. When the substrate is disposed horizontally, the laser is generally arranged to irradiate the upper face of the substrate.
Le laser en ligne peut être intégré dans une ligne de fabrication de verres laqué ou de miroirs, en particuliers de miroirs solaires.  The on-line laser can be integrated into a lacquered glass production line or mirrors, in particular solar mirrors.
Dans le cas de l'application miroir, le laser en ligne est situé dans le procédé de production après les étapes d'argenture par exemple comme élément de préchauffage du verre avant dépôt d'une couche de peinture ou juste après le dépôt de cette couche. Le substrat revêtu peut ainsi être traité en ligne après le dépôt de la couche à traiter (encre ou peinture), à la sortie de l'installation de dépôt et avant les dispositifs de contrôle optique, ou après les dispositifs de contrôle optique et avant les dispositifs d'empilage des substrats.  In the case of the mirror application, the on-line laser is located in the production process after the silvering steps, for example as a preheating element of the glass before depositing a layer of paint or just after the deposition of this layer . The coated substrate can thus be treated in line after the deposition of the layer to be treated (ink or paint), at the exit of the deposition installation and before the optical control devices, or after the optical control devices and before the devices for stacking substrates.
Une ligne laser comme par exemple décrite à la figure 1 permet de chauffer extrêmement rapidement un revêtement (encre ou peinture) d'épaisseur comprise généralement entre 1 μιτι et 200 μιτι avant le traitement laser (c'est-à-dire le chauffage) selon l'invention. Les encres et peintures utilisées pour la cuisson au four sont naturellement très absorbantes dans l'infra rouge, un laser émettant typiquement dans une bande de longueur d'onde allant de 266 nm à 1 1 000 nm permet ainsi un transfert optimale d'énergie entre la source de rayonnement et la couche de peinture.  A laser line as for example described in FIG. 1 makes it possible to heat a coating (ink or paint) with a thickness of generally between 1 μιτι and 200 μιτι extremely rapidly before laser treatment (that is to say heating) according to FIG. the invention. Inks and paints used for baking are naturally very absorbent in the infrared, a laser typically emitting in a wavelength range of 266 nm to 1 1000 nm and allows an optimal transfer of energy between the source of radiation and the layer of paint.
Le procédé de chauffage par laser selon l'invention peut notamment être utilisé selon quatre modes principaux : séchage, montée rapide en température, cuisson ou peinture en poudre :  The laser heating method according to the invention can in particular be used in four main modes: drying, rapid rise in temperature, baking or powder coating:
- mode séchage : dans ce cas, l'irradiation laser permet de transférer très rapidement une énergie correspondant à la chaleur latente de vaporisation (L) du solvant à volatiliser ; dans ce cas, un fort flux d'air assure l'extraction des vapeurs de solvant ; - monté rapide en température : après séchage, le revêtement (peinture ou laque ou encre) conserve ses propriétés absorbantes dans l'infra rouge ; le traitement laser permet alors une montée extrêmement rapide du revêtement sec en vue de sa cuisson ultérieur dans un four de cuisson; le séchage lui-même peut être réalisé en étuve ou par le traitement selon l'invention, le séchage étant suivi d'un traitement thermique par laser selon l'invention ; drying mode: in this case, the laser irradiation makes it possible to very rapidly transfer energy corresponding to the latent heat of vaporization (L) of the solvent to be volatilized; in this case, a strong air flow ensures the extraction of the solvent vapors; - rapid temperature rise: after drying, the coating (paint or lacquer or ink) retains its absorbent properties in the infrared; the laser treatment then allows an extremely fast rise of the dry coating for subsequent cooking in a baking oven; the drying itself can be carried out in an oven or by the treatment according to the invention, the drying being followed by a heat treatment by laser according to the invention;
- cuisson : il s'agit ici de maintenir le revêtement au dessus de la température de cuisson un temps suffisant pouvant généralement aller de quelque secondes à quelques minutes ; notamment, deux possibilités de traitement sont alors possibles :  cooking: this is to maintain the coating above the cooking temperature sufficient time can generally go from seconds to minutes; in particular, two treatment possibilities are then possible:
-> utilisation successive de plusieurs lignes laser de façon à maintenir la température de la couche au dessus du seuil de cuisson le temps suffisant ;  -> successive use of several laser lines so as to maintain the temperature of the layer above the cooking threshold sufficient time;
-> balayage laser de la surface à traiter ;  -> laser scanning of the surface to be treated;
- peinture en poudre : l'application d'une peinture en poudre permet d'utiliser un traitement unique par une rampe laser pour fondre la poudre et ensuite la durcir.  - powder coating: the application of a powder coating allows the use of a single treatment with a laser beam to melt the powder and then harden it.
Le traitement par laser selon l'invention permet de chauffer principalement le revêtement en chauffant au minimum le substrat. Cela permet donc de diminuer l'énergie totale nécessaire au traitement du revêtement et/ou d'augmenter les cadences de traitement.  The laser treatment according to the invention makes it possible to heat the coating mainly by heating the substrate to a minimum. This therefore makes it possible to reduce the total energy required to treat the coating and / or to increase the treatment rates.
Notamment, le procédé selon l'invention peut servir au séchage ou la cuisson des peintures pour miroirs d'intérieur ou solaire, et aussi pour la finition de la peinture d'un verre laqué. Le procédé selon l'invention peut être mis à profit pour raccourcir les longueurs des fours de séchage ou cuisson.  In particular, the process according to the invention can be used for drying or baking paints for indoor or solar mirrors, and also for finishing the paint of a lacquered glass. The method according to the invention can be used to shorten the lengths of drying or cooking ovens.
Pour le cas ou le traitement laser selon l'invention procure l'élimination d'une matière organique combustible (un solvant par exemple) du revêtement, on peut assurer une dilution et une convection suffisante à l'aide d'un gaz comme l'air au-dessus du substrat revêtu pour ainsi limiter les risques d'inflammation voire d'explosion.  For the case where the laser treatment according to the invention provides for the removal of a combustible organic material (a solvent for example) from the coating, it is possible to ensure dilution and sufficient convection with the aid of a gas such as air above the coated substrate to thereby reduce the risk of ignition or explosion.
Pour la mise en œuvre du procédé selon l'invention, les paramètres suivants sont généralement à prendre en considération: P [W/m2] : densité de puissance du rayonnement laser ; For the implementation of the method according to the invention, the following parameters are generally to be taken into consideration: P [W / m 2 ]: power density of the laser radiation;
I [m]: largeur du faisceau laser (c'est-à-dire épaisseur de la ligne laser); I [m]: width of the laser beam (i.e., thickness of the laser line);
L[m] : longueur du faisceau ou de l'ensemble des faisceaux laser ; L [m]: length of the beam or of all the laser beams;
e : épaisseur du revêtement avant traitement laser ;  e: thickness of the coating before laser treatment;
p : densité de la couche de revêtement humide ou sèche selon respectivement que l'on sèche (évaporation de solvant) ou cuit le revêtement (pas d'évaporation de solvant)  p: density of the wet or dry coating layer respectively according to whether it is dried (solvent evaporation) or baked coating (no solvent evaporation)
τ : taux de solvant dans le revêtement avant traitement laser;  τ: solvent level in the coating before laser treatment;
a : coefficient d'absorption du revêtement avant traitement laser;  a: absorption coefficient of the coating before laser treatment;
Cp [J/Kg/K] : capacité calorifique du revêtement avant traitement laser; Cp [J / Kg / K]: heat capacity of the coating before laser treatment;
Lv : chaleur latente de vaporisation de la matière organique à éliminerLv: latent heat of vaporization of the organic matter to be eliminated
(solvant) lors du traitement laser; (solvent) during laser treatment;
V : vitesse de défilement du substrat ;  V: speed of travel of the substrate;
On a rassemblé dans le tableau 1 les valeurs entre lesquelles ces paramètres peuvent généralement se situer, bornes comprises.  The values between which these parameters can generally be located, including limits, are shown in Table 1.
Tableau 1  Table 1
Alors, la quantité de chaleur cédée par unité de surface s'estime par :  So, the amount of heat transferred per unit area is estimated by:
Q [J/m2] = P.l/V , Q [J / m 2 ] = Pl / V,
et la température atteinte s'estime par and the temperature reached is estimated by
ΔΤ =——— ΔΤ = ---
Cp.V.e.p ΔΤ représentant la différence entre la température atteinte et la température ambiante. Cp.Vep ΔΤ representing the difference between the temperature reached and the ambient temperature.
La figure 1 représente le procédé selon l'invention. Des substrats 1 , revêtus d'un revêtement à sécher ou à cuire, défilent les uns derrière les autres en continu selon une direction représentée par la flèche, en étant convoyés par un lit de rouleaux (non représentés). Ils passent sous une source laser 2 qui délivre une ligne laser 3 focalisée à la surface des substrats défilants et selon toute leur largeur. La ligne laser produit un chauffage permettant de sécher ou cuire le revêtement.  Figure 1 shows the method according to the invention. Substrates 1, coated with a coating to be dried or cooked, run one behind the other continuously in a direction represented by the arrow, being conveyed by a bed of rollers (not shown). They pass under a laser source 2 which delivers a laser line 3 focused on the surface of the moving substrates and along their entire width. The laser line produces heating to dry or bake the coating.
Exemple 1 Example 1
Sur une ligne de fabrication de miroirs défilants à la vitesse de 5 m/min, on réalise un séchage selon l'invention d'une couche de peinture déposée au dos du miroir à titre de revêtement de protection. Le revêtement avant séchage avait une épaisseur de 50 μιτι, une densité de 2 T/m3, une capacité calorifique de 0,7kJ/Kg/K, une absorbance a de 1 . Le taux de solvant (xylène : Lv=300kJ/Kg) τ était de 30% en poids (soit 0,3 dans la formule ci-dessus). Une puissance de 330 kW/m2 convient. Une fois la peinture sèche, la densité du revêtement est de 1 ,3 T/m3 et chaque KW/m2 conduit à une augmentation de la température de la peinture de 4 Kelvins. Le rayonnement laser chauffe essentiellement le revêtement, le verre étant chauffé uniquement par conduction à partir du revêtement et dans un lapse de temps très court (<1 s) limitant l'augmentation de sa température moyenne à moins de 1 K sur son épaisseur totale. Exemple 2 On a production line of mirrors scrolling at a speed of 5 m / min, is carried out a drying according to the invention of a layer of paint deposited on the back of the mirror as a protective coating. The coating before drying had a thickness of 50 μιτι, a density of 2 T / m 3 , a heat capacity of 0.7 kJ / Kg / K, an absorbance of 1. The solvent level (xylene: Lv = 300 kJ / Kg) was 30% by weight (ie 0.3 in the formula above). A power of 330 kW / m 2 is suitable. Once the paint dries, the density of the coating is 1, 3 T / m 3 and each KW / m 2 leads to an increase in the paint temperature of 4 Kelvin. The laser radiation essentially heats the coating, the glass being heated solely by conduction from the coating and in a very short time (<1 s) limiting the increase in its average temperature to less than 1 K on its total thickness. Example 2
On réalise la cuisson d'une peinture du type polyuréthane à isocyanate bloqué de type industrielle nécessitant une température de 180°C pour déblocage et réticulation de la couche. Par le procédé selon l'invention, une puissance de 40 kW/m2 convient. The firing of an industrial-type blocked isocyanate-type polyurethane paint which requires a temperature of 180.degree. C. for unblocking and crosslinking of the layer is carried out. By the method according to the invention, a power of 40 kW / m 2 is suitable.

Claims

REVENDICATIONS
1 . Procédé de chauffage d'un revêtement organique appliqué sur des substrats, caractérisé en ce qu'un rayonnement laser est appliqué sur le revêtement organique alors que les substrats défilent en continu. 1. A method of heating an organic coating applied to substrates, characterized in that laser radiation is applied to the organic coating while the substrates continuously scroll.
2. Procédé selon la revendication précédente, caractérisé en ce que le rayonnement laser est appliqué selon une ligne sensiblement transversale par rapport au sens de défilement des substrats. 2. Method according to the preceding claim, characterized in that the laser radiation is applied along a line substantially transverse to the direction of travel of the substrates.
3. Procédé selon la revendication précédente, caractérisé en ce que l'épaisseur de la ligne est comprise entre 0,01 et 1 mm. 3. Method according to the preceding claim, characterized in that the thickness of the line is between 0.01 and 1 mm.
4. Procédé selon l'une des revendications précédentes, caractérisé en ce que le substrat ne subit pas de température supérieure à 100°C à une profondeur de 0,5 mm de l'interface substrat/revêtement. 4. Method according to one of the preceding claims, characterized in that the substrate does not undergo a temperature greater than 100 ° C to a depth of 0.5 mm of the substrate / coating interface.
5. Procédé selon l'une des revendications précédentes, caractérisé en ce que le rayonnement laser présente une longueur d'onde de 266 nm à 1 1000 nm, notamment entre 530 et 1200 nm. 5. Method according to one of the preceding claims, characterized in that the laser radiation has a wavelength of 266 nm to 1 1000 nm, in particular between 530 and 1200 nm.
6. Procédé selon l'une des revendications précédentes, caractérisé en ce que l'absorption par le revêtement à la longueur d'onde du rayonnement laser est supérieure ou égale à 20%. 6. Method according to one of the preceding claims, characterized in that the absorption by the coating at the wavelength of the laser radiation is greater than or equal to 20%.
7. Procédé selon l'une des revendications précédentes, caractérisé en ce que les substrats défilent à une vitesse de 1 mètre à 20 mètres par minute. 7. Method according to one of the preceding claims, characterized in that the substrates scroll at a speed of 1 meter to 20 meters per minute.
8. Procédé selon l'une des revendications précédentes, caractérisé en ce que le rayonnement laser est focalisé, le plan focal dudit rayonnement étant à une distance inférieure ou égale à 1 mm du revêtement. 8. Method according to one of the preceding claims, characterized in that the laser radiation is focused, the focal plane of said radiation being at a distance less than or equal to 1 mm of the coating.
9. Procédé selon l'une des revendications précédentes, caractérisé en ce que l'épaisseur du revêtement avant chauffage est comprise entre 1 et 200 μηη. 9. Method according to one of the preceding claims, characterized in that the thickness of the coating before heating is between 1 and 200 μηη.
10. Procédé selon l'une des revendications précédentes, caractérisé en ce que la puissance du rayonnement laser est supérieure ou égale à 20 kW/cm2. 10. Method according to one of the preceding claims, characterized in that the power of the laser radiation is greater than or equal to 20 kW / cm 2 .
1 1 . Procédé selon des revendications précédentes, caractérisé en ce que les substrats comprennent une feuille de verre. 1 1. Method according to one of the preceding claims, characterized in that the substrates comprise a glass sheet.
12. Procédé selon l'une des revendications précédentes, caractérisé en ce que les substrats sont des miroirs. 12. Method according to one of the preceding claims, characterized in that the substrates are mirrors.
13. Procédé selon l'une des revendications précédentes, caractérisé en ce que le substrat a une épaisseur de 2 à 8 mm. 13. Method according to one of the preceding claims, characterized in that the substrate has a thickness of 2 to 8 mm.
14. Procédé selon l'une des revendications précédentes, caractérisé en ce que le revêtement est une peinture. 14. Method according to one of the preceding claims, characterized in that the coating is a paint.
15. Procédé selon la revendication précédente, caractérisé en ce que la peinture est Alkyde ou Acrylique ou Polyuréthane. 15. Method according to the preceding claim, characterized in that the paint is Alkyd or Acrylic or Polyurethane.
16. Procédé selon l'une des revendications précédentes, caractérisé en ce que les substrats ont au moins une dimension supérieure ou égale à16. Method according to one of the preceding claims, characterized in that the substrates have at least one dimension greater than or equal to
1 m. 1 m.
17. Procédé selon l'une des revendications précédentes, caractérisé en ce que le rayonnement laser est issu d'au moins un faisceau laser formant une ligne qui irradie simultanément toute la largeur des substrats. 17. Method according to one of the preceding claims, characterized in that the laser radiation is derived from at least one laser beam forming a line that simultaneously radiates the entire width of the substrates.
EP12709945.5A 2011-02-25 2012-02-21 Heat treatment of a laser coating Withdrawn EP2678132A1 (en)

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FR1151576A FR2971960B1 (en) 2011-02-25 2011-02-25 THERMAL COATING TREATMENT WITH LASER
PCT/FR2012/050365 WO2012114038A1 (en) 2011-02-25 2012-02-21 Heat treatment of a laser coating

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AU (1) AU2012220431B2 (en)
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MX2013009726A (en) 2013-09-16
EA201391227A1 (en) 2013-12-30
FR2971960A1 (en) 2012-08-31
KR20140005262A (en) 2014-01-14
JP5902721B2 (en) 2016-04-13
BR112013020034A2 (en) 2016-10-18
CN103379980B (en) 2016-08-10
MX362398B (en) 2019-01-16
EA027409B1 (en) 2017-07-31
US20140059878A1 (en) 2014-03-06
CN103379980A (en) 2013-10-30
CA2826149A1 (en) 2012-08-30
FR2971960B1 (en) 2013-02-22
AU2012220431B2 (en) 2015-11-26
JP2014511268A (en) 2014-05-15
WO2012114038A1 (en) 2012-08-30
AU2012220431A1 (en) 2013-10-03

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