Laser marking process and installation

Abstract

The present invention relates to a method for marking containers (2), in particular bottles or flasks made of thermoplastic material, said containers (2) comprising at least one body, a shoulder in the extension of said body at an upper end thereof, a neck in the extension of the shoulder, a wall (25), said wall (25) comprising a marking area (20), an outer skin (250) and an inner skin (251) and a bottom at the lower end of said body, said method comprising at least the following steps: - a step (E1) consisting of carrying out a treatment on said containers (2), preferably filling and capping said containers (2), - a marking step (E2), consisting of generating a mark (310) at at least one marking area (20) of each container (2),said marking step being carried out by projecting a laser beam (31) by means of a laser marking optical head (30) equipped with a laser head unit (300) and an optical system (320) for focusing said laser beam (31) to mark said area (20), a method characterized in that the projection of said laser beam (31) is carried out so as to generate bubbles (200) and particles (201) of degraded material in all or part of the thickness of the wall (25) of said container (2) at said marking area (20). The invention also relates to a container marking installation and a container obtained by the marking method according to the invention. Figure for the abstract: Fig.1,

Description

Title of the invention: Laser marking method and installation

[0001] Technical Field: The invention relates to a laser marking method and installation, as well as a container comprising a mark obtained by laser marking according to the method in accordance with the invention. State of the art

[0002] It is known to include information and decorations on containers, particularly plastic bottles. Information on a container may, for example, include the expiration date of the contents or the formula of the product contained in the container. Decorations may, for example, feature the product manufacturer's logo.

[0003] It is well known to include such information and decorations on paper or plastic labels. The labels are glued onto the final container after the container forming step, i.e. when the containers are formed into their final shape.

[0004] However, labeling containers has many disadvantages. Indeed, the manufacturing of labels, their printing and their gluing on the containers represents a high cost, particularly for the manufacture of containers in large series. In addition, the label is likely to be torn off during handling of the container. The end user can then no longer access certain important information, such as the expiry date. Finally, recycling plastic containers is complicated by the presence of the label and glue. Indeed, to promote recycling, it is preferable to ensure that containers, labels, or other items are collected separately based on their different materials. However, manually removing labels from containers for separate collection can be a tedious task. Therefore, removing labels from containers is one of the factors that hinder the provision of separate collection.

[0005] For the recording of important information, methods of marking the wall of the container have already been proposed. Thus, it is known to print certain important information directly onto the wall of the container using a special ink. However, this method of marking by printing is not satisfactory because, for hygiene reasons, the ink used for marking must dry almost instantly, and it must also remain on the surface of the wall without penetrating into the interior of the container by a migration phenomenon. As a result, the ink has a specific composition which is very expensive to manufacture. Furthermore, the use of ink also complicates the recycling processes for plastic containers.

[0006] To circumvent these problems, a marking method by etching the wall of the container has also been proposed. The etching is generally carried out using a carbon dioxide laser. Such a marking method is carried out by removing material from the wall of the container, in particular by evaporation. As a result, the wall has a locally reduced thickness. However, in the interests of economy and ecology, efforts are being made to reduce the thickness of container walls. This makes it possible to produce a container using less plastic than before. However, removing material from a very thin wall risks weakening the wall to the point of cracking the container at the slightest stress.

[0007] Other known laser marking devices have quality problems with respect to parts or substrates that are not planar and / or have a variable focal distance relative to the optics, as is the case for a large majority of containers. In such a case, the markings on the substrate are blurred, vary in height or spacing, and may otherwise be illegible, thus making the characters unsatisfactory for use.

[0008] Furthermore, depending on the nature or dimensions of the container, the quality of the marking becomes very random: the focal distance between the laser device and the wall of the container to be marked is not the same over the entire surface of the area to be marked. In particular, when the wall of the container is cylindrical, the marking generated is of lower quality at the periphery of the area to be marked.

[0009] Finally, depending on the contents of the container, the marking will be more or less legible. For example, when the container contains water, the marking may be difficult to read, whereas when it contains a dark or colored liquid, such as soda, the marking is legible. This difference in readability is restrictive and requires adjusting the marking parameters according to the container production and packaging line.

[0010] To solve these marking quality problems while remaining compatible with large-scale production of containers, the present invention proposes to provide a laser marking method making it possible to obtain quality marking, with good readability regardless of the contents. This also makes it possible to mark containers at a rate compatible with the productivities required in the industrial sector.

[0011] The invention advantageously provides a method for obtaining high-quality laser marking, without the need for tedious adjustments, and with a great versatility of application.

[0012] The invention firstly relates to a method for marking containers, in particular bottles or flasks made of thermoplastic material, said containers comprising at least one body, a shoulder in the extension of said body at an upper end thereof, a neck in the extension of the shoulder, a wall, said wall comprising a marking zone, an external skin and an internal skin and a bottom at the lower end of said body, said method comprising at least the following steps: - a step consisting of carrying out a treatment on said containers, preferably filling and capping said containers, - a marking step, consisting of generating a mark at at least one marking area of ​​each container, said marking step being carried out by projecting a laser beam by means of a laser marking optical head equipped with a laser head unit and an optical system for focusing said laser beam to mark said area.

[0013] The method is characterized in that the projection of said laser beam is carried out in such a way as to generate bubbles and particles of degraded material in all or part of the thickness of the wall of said container at the level of said marking zone.

[0014] According to a possible additional characteristic, the projection of the laser beam is carried out in such a way as to generate at least one marking zone: - a first layer extending from the outer skin towards the inner skin of said container, said first layer comprising both said bubbles and said particles of degraded material and - a second layer extending from said first layer and towards said inner skin, said second layer comprising said particles of degraded material.

[0015] In embodiments, the projection of the laser beam is carried out so as not to generate bubbles or particles of degraded material within a third layer at the marking zone, said third layer extending from said second layer towards said internal skin.

[0016] In embodiments, the projection of the laser beam is carried out by generating pulses of a fixed duration, between 10 and 200 nanoseconds, said laser beam being emitted at a fixed wavelength, said wavelength having an absorption less than or equal to 5% for a thickness of the thermoplastic material of 0.25 millimeters (mm).

[0017] According to a possible additional characteristic, the laser beam is emitted at a fixed wavelength having an absorption less than or equal to 3% for a thickness of the thermoplastic material of 0.25 millimeters (mm).

[0018] In embodiments, the laser beam is emitted at a fixed wavelength between 700 and 1600 nanometers.

[0019] In embodiments, during the marking step, the power of said laser beam is adjusted.

[0020] According to a possible additional feature, the scanning speed of the laser beam is variable.

[0021] In embodiments, the method comprises, before the marking step, the following steps: - a step consisting of rotating said containers, preferably filled and capped, around a vertical axis around which laser marking stations are rotated, in a manner synchronized with said containers, - a step of adjusting the focal point of the laser marking stations preferably according to the dimensions and / or shape of said containers, and - the marking step being carried out during the rotation of said containers.

[0022] The invention also relates to an installation comprising at least: - a device for laser marking containers, in particular bottles or flasks made of thermoplastic material, said marking device comprising a plurality of laser marking stations, each station comprising along an optical path at least one laser marking optical head for projecting a laser beam, said optical head being equipped with a laser head unit and an optical system for focusing said laser beam in order to generate a mark at at least one marking area of ​​each container to mark said area, said optical head being connected to a laser processing apparatus via an optical channel, - control means connected to the marking stations and comprising said laser processing apparatus and means for supplying the laser marking stations. The installation is characterized in that it comprises means for generating bubbles and particles of degraded material in all or part of the thickness of the wall of said container at the level of said marking zone.

[0023] In embodiments, the means for generating bubbles and particles of degraded material in all or part of the thickness of the wall of said container at said marking zone generate at said marking zone: - a first layer extending from the outer skin towards the inner skin of said container, said first layer comprising both said bubbles and said particles of degraded material and

[0024] - a second layer located extending from said first layer and in direction of said inner skin, said second layer comprising said particles of degraded material.

[0025] In embodiments, the means for generating bubbles and carbon particles in all or part of the thickness of the wall of said container at said marking area consist of an optical head configured to generate a laser beam of a fixed pulse duration of between 10 and 200 nanoseconds.

[0026] In embodiments, the means for generating bubbles and carbon particles in all or part of the thickness of the wall of said container at said marking area consist of an optical head configured to emit a laser beam at a fixed wavelength, said wavelength having an absorption less than or equal to 5% for a thickness of the thermoplastic material of 0.25 millimeters (mm).

[0027] In embodiments, the means for generating bubbles and particles of degraded material in all or part of the thickness of the wall of said container at said marking zone consist of an optical head configured to emit a laser beam at a fixed wavelength of between 700 and 1600 nanometers.

[0028] The invention also relates to a container comprising at least one body, a shoulder in the extension of said body at an upper end thereof, a neck in the extension of the shoulder, a wall, said wall comprising a marking zone, an external skin and an internal skin, and a bottom at the lower end of said body. The container is characterized in that, at the level of the marking zone, said wall comprises, at the level of said marking zone, in all or part of its thickness, bubbles and particles of degraded material.

[0029] According to a possible additional characteristic, the wall of said container comprises: - a first layer extending from the outer skin towards the inner skin of said container, said first layer comprising both said bubbles and said particles of degraded material and - a second layer extending from said first layer and towards said inner skin, said second layer comprising said particles of degraded material.

[0030] Brief description of the figures: The invention will be better understood thanks to the description below, which is based on possible embodiments, explained in an illustrative and in no way limiting manner, with reference to the appended figures, in which: - [Fig.l] schematically represents an example of implementation of the method according to the invention; - [Fig.2] schematically represents an example of implementation of the process according to the invention with a view of a marked container obtained; - [Fig.3] schematically represents an example of implementation of the method according to the invention with a view of a marked container obtained; - [Fig.4] schematically represents an example of implementation of the process according to the invention with rotation of the containers, - [Fig.5] schematically represents an example of a marking device according to the invention, with a carousel for rotating the containers, - [Fig.6] schematically represents an example of a device of the marking installation, - [Fig.7] schematically represents an example of a marking installation according to the invention.

[0031] Detailed description: In the remainder of the description, elements having an identical structure or similar functions will be designated by the same reference.

[0032] The invention firstly relates to a method for laser marking containers 2. In the context of the invention, the container 2 is a bottle or flask. It is made of plastic. Preferably, the container is made of polyethylene terephthalate, hereinafter PET. The container 2 can therefore be rigid or semi-rigid. It is intended to contain a fluid, a liquid, powders or granules, in particular of the agri-food or cosmetic type. The container 2 can have any type of shape, symmetrical or not. It can have a rounded section, generally circular or ovoidal in shape, or else a polygonal section, in particular rectangular or square. Preferably, said containers 2 have a rounded section, in particular generally circular.

[0033] The containers 2 have at least one body, a shoulder in the extension of said body and a bottom at the end of said body. The container 2 comprises a wall 25. The wall 25 of a container 2 can be cylindrical, rectangular, or of any shape. The wall 25 is the surface which constitutes the boundary between the inside and the outside of the container 2, that is to say between the contents of the container 2 and its external environment, the ambient air for example. The wall 25 comprises an external skin 250 and an internal skin 251, and at least one marking zone 20, notably visible in figures 1 and 2. In other words, the container 2 comprises at least one marking zone 20, at the level of the body, and / or at the level of the shoulder, and / or the neck and / or the bottom, the wall 25 constituting the surface delimiting the contents of the container 2 and its external environment. When the container 2 is filled, for example with a fluid, said fluid is in contact with the internal skin 251.

[0034] In a normal orientation, the container 2 rests on its bottom and the main direction is vertical. The bottom may be generally flat, petaloid in shape or otherwise. Preferably, the containers 2 are obtained by forming from thermoplastic preforms. Such preforms are generally obtained by injection.

[0035] In the context of the invention, the container 2 has at least one marking zone 20, located on its wall. The at least one marking zone 20 is intended to receive a mark 310, produced by laser marking. The marking area 20 can be oriented such that the mark 310 is parallel to the main direction of the container 2, or orthogonal, or even have any possible orientation relative to the wall 25 of the container 2 according to its main direction.

[0036] The invention relates to a method for marking containers 2 comprising at least the following steps: - a treatment step E1 consisting of carrying out a treatment on said containers 2, preferably filling and capping said containers 2, - a marking step E2, consisting of generating a mark 310 at at least one marking area 20 of each container 2, said marking step being carried out by projecting a laser beam 31 by means of a laser marking optical head 30 equipped with a laser head unit 300 and an optical system 320 for focusing said laser beam 31 to mark said area 20.

[0037] The laser marking method is characterized in that the projection of said laser beam 31 is carried out in such a way as to generate bubbles 200 and particles 201 of degraded material in all or part of the thickness of the wall 25 of said container 2 at the level of said marking zone 20.

[0038] Preferably, the treatment step E1 is a step of filling and capping the containers 2. Indeed, it has been found that the laser marking with the laser beam 31 is of better quality (in terms of readability in particular) when the container 2 is filled. It has been found that it is generally difficult to use laser systems to mark containers 2 made of plastic, and in particular PET, because laser marking tends to damage the container 2, due to the high power required to mark the containers 2 at high speed. This involves, for example, the formation of holes in the wall of the container 2. Advantageously, in embodiments, the method therefore consists of marking a filled container 2, preferably with liquid. This allows the liquid to quickly diffuse the heat of the transmitted laser beam 31 and to prevent degradation of the wall of said container 2. The internal integrity of the container 2 in contact with the liquid is therefore maintained while it is possible to generate a strong contrast with a lot of power to achieve a high marking rate and confine it to the external surface of the wall 25 of said container 2. Preferably, the containers 2 are therefore filled and capped before being marked.

[0039] The marking step, which consists of generating a mark 310 at the level of at least one marking zone 20 of each container 2, is carried out by the projection of a laser beam 31, by means of an optical laser marking head 30. The optical head 30 comprises a laser head unit 300 and an optical system 320, removably mounted on said laser head unit 300. Preferably, the laser head unit 300 emits a beam 31 of laser light directed in a predetermined direction.

[0040] In the context of the invention, the projection of said laser beam 31 is carried out so as to generate bubbles 200 and particles 201 of degraded material in all or part of the thickness of the wall 25 of said container 2 at the level of said marking zone 20. Thus, at the level of the marking zone 20, in all or part of the thickness of the wall 25 of the marked container 2, there are found both bubbles 200 and particles 201 of degraded material, as visible in [Fig.l].

[0041] By bubble 200, we mean any shape, perfectly spherical or not, for example an ovoid shape. In particular, the bubble 200 is generated via a phenomenon called "foaming". Foaming consists of raising the temperature of the material to a threshold, for example the melting point, which causes a release of gas and generates bubbles that expand, forming a bead on the surface, bubbles that will remain trapped upon cooling. The strength of the material is very little affected. In addition, the legibility of the mark 310 obtained is much better because the gas bubbles in the material reflect light in a diffuse manner. In other words, the bubbles 200 are non-solid cavities or spaces whose shape causes a variation in the refractive index or reflection.

[0042] In addition, the laser beam 31 causes the formation of particles 201 of degraded material. More precisely, the particles 201 of degraded material are particles of material, at least partially carbonized. The particles 201 are made of the thermoplastic material of the container 2 which has been degraded by local heating, at the marking area 20, to the point that its coloring changes. The particles 201 of degraded material have different properties from the bubbles 200: while the bubbles 200 reflect the light, the particles 201 will absorb or reduce the light following the application of the laser beam 31 during the marking.

[0043] Thus, by the simultaneous or substantially simultaneous generation of bubbles 200 and particles 201 of degraded material, the quality of the mark 310 is greatly improved. In particular, the contrast of the mark 310, depending on the contents of the container 2, can be adjusted, so that the mark 310 is for example more lighter than the unmarked parts or darker.

[0044] The improvement in the legibility of the mark 310 is obtained by the presence, in the marking zone 20, and in all or part of the thickness of the wall 25 of the container 2, of both bubbles 200 and particles 201 of degraded material.

[0045] In embodiments, the projection of the laser beam 31, during the marking of the container, is carried out so as to generate at least one marking zone 20: - a first layer extending from the outer skin 250 towards the inner skin 251 of said container 2, said first layer comprising both said bubbles 200 and said particles 201 of degraded material and - a second layer extending from said first layer and towards said inner skin 251, said second layer comprising said particles 201 of degraded material.

[0046] In other words, while particles 201 of degraded material are found inside the first and second layers, only the first layer also comprises bubbles 200. This embodiment is illustrated in [Fig.2]. Indeed, the bubbles 200 are generated by the foaming phenomenon, by a volume thermal elevation effect, while the particles 201 of degraded material are generated by a self-focusing of a portion of the laser light in the material, created by a shock wave generated by the pulsed laser energy. This wave leads to an extremely temporary change in the local refractive index of the medium, which multiplies by several orders of magnitude the energy of the pulse on different focal points placed behind the point of impact, and causes a local degradation of the material at these points. When approaching the internal skin 251 of the container 2, the volume temperature drops, all the more quickly as the internal skin 251 is in contact with the contents.The foaming phenomenon is therefore quickly stopped while the shock wave continues to propagate, which continues to create 201 particles of degraded matter, until in turn the shock wave also loses its energy. Depending on this energy we can therefore see the appearance of a third layer containing neither bubbles nor degraded particles. Having a third layer is particularly advantageous, as this allows for a layer of virgin material to be in contact with the contents of the container 2, which greatly reduces the risk of migration of unwanted substances into said contents.

[0047] Advantageously, the density of particles 201 of degraded material decreases from the first layer to the second layer. In other words, the density of particles 201 of degraded material is greater within the first layer than within the second layer.

[0048] This example of embodiment is visible in [Fig.3].

[0049] In embodiments, the projection of the laser beam 31 is carried out by generating pulses of a fixed duration, between 10 and 200 nanoseconds (ns), preferably 100ns, said laser beam 31 being emitted at a fixed wavelength, said wavelength having an absorption less than or equal to 5% for a thickness of the thermoplastic material of 0.25 millimeters (mm). Surprisingly, it has been found that, for a thickness of the thermoplastic material of the wall 25 of the container 2 of 0.25 millimeters (mm), when the laser beam 31 is emitted with pulses of a fixed duration, between 10 and 200 nanoseconds and at a fixed wavelength, said wavelength having an absorption less than or equal to 5%, the projection of the laser beam 31 generates bubbles 200 and particles 201 of degraded material over all or part of the thickness of the wall 25 of said container 2. It has been found that the self-focusing phenomenon occurs advantageously in a specific pulse width range. In addition, the foaming phenomenon, different from the etching marking phenomenon, also appears preferentially in a specific wavelength range. In order to improve the marking quality, in embodiments, it is therefore advantageous to generate pulses of fixed duration at a fixed wavelength.

[0050] Furthermore, by fixing the pulse width and wavelength values, the marking method makes it possible not to have to adapt the adjustment parameters of the laser beam 31, whatever the contents of the container 2, while making it possible to obtain a high quality of marking. This is very advantageous for the operator, by simplifying the adjustment of the optical head 30.

[0051] The absorption, or absorbance A, characterizes the capacity of the wall 25 of the container 2 to absorb the light which passes through it. The absorption of the wavelength of the laser beam 31 by the wall 25 of the container 2 is modeled by the Beer-Lambert law: A=logi0*T where T is the transmittance; and which can also be written in the following form: I = Io * exp(-a*d) where -1 is the intensity of the radiation, - Io is the incident intensity of the radiation at a given wavelength, - a is the absorption coefficient specific to the material of container 2 and to the given wavelength, - d is the distance traveled in the medium, which takes into account the thickness of the wall 25. This results in a predictable distribution in the material of the container 2, at the marking area 20, when using a semi-transparent thermoplastic material such as PET. Thus, the person skilled in the art will be able to define precisely what the absorption value of the wavelength should be as a function of the thickness of the thermoplastic material of the wall 25 of the container 2 to be marked. In embodiments, the method comprises a preliminary calibration step in order to define the wavelength of the laser beam 31 to be applied as a function of the thickness of the wall 25 of the container 2 to be marked.

[0052] In embodiments, the projection of the laser beam 31 is carried out by generating pulses of a fixed duration, between 10 and 200 nanoseconds (ns), preferably 100ns, said laser beam 31 being emitted at a fixed wavelength, said wavelength having an absorption less than or equal to 3% for a thickness of the thermoplastic material of 0.25 millimeters (mm). Similarly, the person skilled in the art knows how to define the fixed wavelength to be defined as a function of the thickness of the wall 25 of the container 2 to be marked as well as as a function of its material. It should be noted that since the wall thickness of the bottles varies within a relatively small range, it is possible to define a wavelength compatible with most of the bottle formats produced for a defined type of material.

[0053] Thus, for a polyethylene terephthalate container, the laser beam 31 is emitted at a fixed wavelength between 700 and 1600 nanometers, preferably 1064nm.

[0054] In embodiments, during the marking step E2, the power of said laser beam 31 is adjusted. This advantageously makes it possible to further improve the quality of the marking as a function of the mark 310 to be produced by making it possible to generate the appropriate quantity of bubbles 200 and / or particles 201 of degraded material.

[0055] In embodiments, the scanning speed of the laser beam 31 is variable.

[0056] In embodiments, the marking method comprises a step of rotating said containers 2, preferably filled and capped, around a vertical axis around which laser marking stations 3 are rotated, in a synchronized manner with said containers 2, - a step of adjusting the focal point of the laser marking stations 3 preferably as a function of the dimensions and / or the shape of said containers 2, and - the marking step being carried out during the rotation of said containers 2.

[0057] This embodiment is shown in [Fig.4]. Advantageously, carrying out the marking during the rotation of the containers 2 makes it possible to have a fixed distance between the optical head 30 and the at least one marking zone 20 of a container 2. This greatly reduces the need to modify the laser marking parameters with each change of format, type of container 2, or contents of container 2.

[0058] Furthermore, in order to adapt to the different diameters of containers 2, the method comprises in embodiments a step of adjusting the focal point, and the stations 3 are equipped with an optical head 30 allowing the focal distance to be adjusted to the container 2 according to the format of said container 2 and optionally to follow the curvature of the shape of the container 2.

[0059] [Fig.4] schematically shows the steps of a method according to an embodiment where the containers 2 are filled and capped during a step E1. Then, according to a possible variant, the filled and sealed container 2 is transferred to holding members 54. The gripped containers 2 are then rotated, in a synchronized manner with marking stations 3. Preferably, the rotation step is carried out continuously, without interruption: the container 2 is placed in the trajectory of the device 1 then gripped and rotated.

[0060] During the marking step E2, and during their rotation, the containers 2 are marked.

[0061] According to an additional technical characteristic, the method according to the invention comprises a step of adjusting the focal point. For each point of the mark 310, the device 1 adjusts the focal point simultaneously with the positioning of the laser beam 31 by the optical system 320. This focal point adjustment step can be done after loading the containers 2, during their rotation, prior to carrying out the marking, or even during carrying out the marking, as will be described below.

[0062] In embodiments, the characteristics of the container 2, for example its shape, its dimensions, and the mark 310 are previously recorded in a database of a central control unit 12. Advantageously, an electronic unit 400 then transmits instructions to the central control unit 12 and the adjustment of the focal point of the laser beam 31 is done for each point of the mark 310 during the production of the mark 310. These embodiments are preferred in cases where the at least one marking zone 20 is located on a complex surface of the container 2.

[0063] In embodiments, no data has been previously recorded. A sensor 340 will then transmit the information to the central control unit 12 which, via a calculation unit, will transmit instructions to the electronic unit 400. In other words, the marking method then comprises a preliminary step of measuring the distance between the optical output 321 and the at least one marking zone 20.

[0064] It is also possible to adjust the focal point of the laser beam 31 only once, prior to the marking step E2, in cases where the mark 310 and / or the marking zone 20 is of the simple type.

[0065] In other words, the step of adjusting the focal point of the laser beam 31 can be done prior to or simultaneously with marking step E2.

[0066] Finally, and following step E2, the containers 2 are unloaded during an unloading step E3.

[0067] In embodiments, the marking step E2 is performed during rotation over an angular sector less than 360 degrees around the vertical axis. In other words, each container 2 makes approximately a single convolution, more precisely less than a complete rotational turn.

[0068] In embodiments, the method comprises: - after step E1 of processing containers 2, a step of loading the containers at a loading point, - after the marking step E2, the method comprises an unloading step E3 at a point for unloading the containers 2, each station 3 and each container 2 being moved respectively around said vertical axis of rotation between said point for loading said containers 2 and said point for unloading said containers 2 marked at a zone 20 called the marking zone before resuming a new cycle comprising at least steps E1 to E3.

[0069] Advantageously, after the loading step and / or before step E2, the containers 2 are moved vertically. According to a possible variant, the laser marking stations 3 are moved vertically during or after said loading step. Thus, in embodiments, the containers 2 are moved vertically after their loading, in order to adjust the positioning of the at least one marking zone 20 opposite the marking stations 3, and in particular opposite the optical output 321 of an optical system 320. Containers 2 are therefore moved from a vertical position - or initial height - to a vertical marking position.

[0070] The containers 2 and / or the stations 3 can also be moved during their rotation, and / or during the marking step E3.

[0071] In embodiments, the marking step E2 is carried out by a pulsed laser in the near infrared.

[0072] In embodiments, the marking method comprises an additional step, after the marking step E2, of inspecting the marked containers 2.

[0073] The invention also relates to an installation 100 for marking containers, an exemplary embodiment of which is illustrated in [Fig.7].

[0074] The installation 100 comprises: - a device 1 for laser marking containers 2, in particular bottles or flasks made of thermoplastic material, said marking device 1 comprising a plurality of laser marking stations 3, each station 3 comprising along an optical path at least one optical laser marking head 30 for projecting a beam laser 31, said optical head 30 being equipped with a laser head unit 300 and an optical system 320 for focusing said laser beam 31 in order to generate a mark 310 at at least one marking area 20 of each container 2 for marking said area 20, said optical head 30 being connected to a laser processing apparatus 40 via an optical channel 600, - control means 4 connected to the marking stations 3 and comprising said laser processing apparatus 40 and supply means 41 of the laser marking stations 3.

[0075] The device 1 according to the invention comprises at least a plurality of laser marking stations 3. A laser marking station 3 comprises along an optical path at least one optical head 30 which is connected to control means 4 of the station 3. The control means 4 comprise the laser processing apparatus 40 and the power supply means 41 of the stations 3. The laser treatment apparatus 40, or laser 40, comprises a light emission source, or pump source and optionally an amplifying medium for emitting laser light in the form of a laser beam 31. According to a possible variant, the optical head 30 comprises the amplifying medium.

[0076] The optical head 30 is connected to the laser processing apparatus 40 by a network of optical fibers and electrical connections, or optical channels 600. The optical channels 600 comprise at least one optical fiber which is an optical waveguide for the laser light emitted for example by the laser processing apparatus 40. According to a possible variant, the amplifying medium is incorporated into the optical channel 600 in the form of a doped optical fiber into which the emitted light is injected towards a laser head unit 300. Station 3 controls the optical head 30 and the emission of the laser beam 31 from the control means 4.

[0077] Thus, the optical head 30 comprises a laser head unit 300 and an optical system 320, removably mounted on said laser head unit 300. Preferably, the laser head unit 300 emits a beam 31 of laser light directed in a predetermined direction.

[0078] The optical system 320 comprises at least one mirror for moving the laser beam 31 in a horizontal plane and / or in a vertical plane, and optionally a lens at the optical output 321 of the optical system 320, for focusing the light beam in the plane and at the at least one marking area 20, for generating a mark 310 at the said at least one area 20. By optical path is meant the path taken by the laser light from its emission from, for example, the laser treatment apparatus 40 to the optical output 321 of the optical system 320 in the form of a laser beam 31. In other words, the at least one marking zone 20 corresponds to a treatment surface within which the laser beam 31 is applied in a horizontal and / or vertical direction. Depending on the type of mark 310 to be affixed, the focal point of the laser beam 31 is not necessarily located directly on the wall of the container 2, that is to say that, in a longitudinal direction relative to the at least one marking zone 20 of said container 2, the focal point of the laser beam 31 may in particular be located above the wall, directly on the wall 25, at the level of the external skin 250 of the container 2, or inside said wall 25, for example at the level of the internal skin 251 of said container 2, or even beyond, in a focusing zone.

[0079] In embodiments, the device 1 comprises a fixed lens, said fixed lens being able to be of the spherical type, flat field, or preferably of the F-theta type in order to maintain the dimension of the focal point relatively constant in the plane.

[0080] According to a possible variant, the laser head unit 300 and the optical system 320 are in one piece.

[0081] In embodiments, the control means 4 of the laser station 3 comprise a plurality of cooling units, not shown.

[0082] In the context of the invention, the laser marking on at least one zone 20 of a container 2 can be done in particular by local modification of the refractive index, and / or by local modification of the transmission index, and / or by local modification of the reflection index of the material of said container 2.

[0083] Each marking station 3 comprises at least one optical head 30 which emits and focuses the laser beam 31. According to a possible variant, said at least one optical head 30 generates the optical beam 31.

[0084] In embodiments, the optical system 320 consists of a 3D three-dimensional laser marking system, including dynamic focusing means. In this case, the dynamic means are in the form of a focusing module for each point 200 to be marked of the at least one marking zone 20 of a container 2. The use of a 3D three-dimensional marking system is particularly advantageous, as it allows for full coordination of the scanning of the focal point of the laser beam 31, simultaneously horizontally, vertically and longitudinally with respect to the at least one marking area 20. The focal point of the laser beam 31 then moves longitudinally with respect to the marking area 20, so as to adjust the focus. This ensures uniformity of the focal point on all the points to be marked in the marking zone 20, regardless of the shape or orientation of this zone 20 relative to the main direction of the container 2.

[0085] In embodiments, the optical head 30 comprises a sensor for measuring the distance between the optical system 320 and the at least one marking zone 20 of the container 2. This embodiment is very advantageous because, as will be described later, it makes it possible to adjust in real time the focus of the focal point of the laser beam 31, and therefore to obtain a precise, very readable mark 310, and this on all the points of the marking zone 20.

[0086] The control means 4 comprise an electronic unit 400 for controlling the movement of the laser beam 31. The unit 400 can be configured at will to modify the mark 310 to be inscribed; for example, it is a digital control. The parameters to be modified concern, for example, the movement coordinates of the beam 31, the speed of movement of the beam 31, etc. The 310 mark may consist of characters, patterns, barcodes, etc. Typically the distance DI between the output of the beam 31 and the marking zone 20 of the container 2 can vary, depending on the shape and / or the dimensions of the container 2.

[0087] The laser beam 31 can trace the mark 310 indifferently in a vector mode, that is to say by continuous tracing, or in a matrix mode, that is to say by point-by-point tracing.

[0088] In embodiments, the optical head 30 comprises a pulsed laser unit 300. The unit 300 generates the laser beam 31 which is then diffused by the optical system 320. Preferably, the wavelength of the emitted laser is between 700 and 1600 nanometers (nm). In embodiments, and depending on the type of marking sought, it will also be possible to select a laser emitting a beam 31 of different wavelengths, for example of the Ytterbium, Erbium type fiber laser. According to different possible configurations, the laser light is emitted in particular from the device 40, and / or the optical channel 600 or even from the laser unit 300. Preferably, the wavelength of the emitted laser beam 31 is therefore between 1000 and 1100 nm, or between 1500 and 1600 nm, or between 1900 and 2000 nm, depending on the type of containers 2 to be marked and / or depending on the type of mark 310 to be affixed to the marking zone 20 of a container 2.

[0089] The installation 100 according to the invention further comprises means for generating bubbles 200 and particles 201 of degraded material in all or part of the thickness of the wall 25 of said container 2 at the level of said marking zone 20.

[0090] In embodiments, the means are formed by an optical head 30 comprising a MOPA “Master Oscillator Power Amplifier” type laser head unit 300 whose pulse width is adjustable.

[0091] As described previously, it has been found that the “PET” wall marking areas 20 of the container 2 targeted by the laser beam 31 in the near infrared range with a suitable power and / or exposure time are subject to a phenomenon known as “foaming”. Foaming consists of melting the material and generating bubbles which expand, forming a bead on the surface, bubbles which will remain trapped during cooling. The strength of the material is very little affected. In addition, the legibility of the mark 310 obtained is much better because the gas bubbles in the material reflect the light in a diffuse manner.

[0092] Preferably, the marking station 3 uses a laser with a pulsed operating mode to generate short pulses with a duration of less than 500ns (nanosecond) and peak power of the order of kW (kilowatt) to several tens of kW depending on the desired marking and by focusing the beam around the wall of the container 2, at the level of the marking zone 20.

[0093] According to other variants of the invention not shown, other types of laser can be used within the framework of the present invention. As explained previously, the laser is selected and adjusted to allow the wall made of thermoplastic material to be marked, on the surface or in depth, without however engraving the wall.

[0094] In embodiments, the means for generating bubbles 200 and particles 201 of degraded material in all or part of the thickness of the wall 25 of said container 2 at said marking zone 20 generate at said marking zone 20: - a first layer extending from the outer skin 250 towards the inner skin 251 of said container 2, said first layer comprising both said bubbles 200 and said particles 201 of degraded material and - a second layer located extending from said first layer and towards said internal skin 251, said second layer comprising said particles 201 of degraded material.

[0095] In embodiments, the means for generating bubbles 200 and carbon particles 201 in all or part of the thickness of the wall 25 of said container 2 at the level of said marking zone 20 consist of an optical head 30 configured to generate a laser beam 31 with a fixed pulse duration of between 10 and 200 nanoseconds.

[0096] According to an additional technical characteristic, the means for generating bubbles 200 and carbon particles 201 in all or part of the thickness of the wall 25 of said container 2 at the level of said marking zone 20 consist of an optical head 30 configured to emit a laser beam 31 at a fixed wavelength, said wavelength having an absorption less than or equal to 5% for a thickness of the thermoplastic material of 0.25 millimeters (mm).

[0097] According to an additional technical characteristic, the means for generating bubbles 200 and carbon particles 201 in all or part of the thickness of the wall 25 of said container 2 at the level of said marking zone 20 consist of an optical head 30 configured to emit a laser beam 31 at a fixed wavelength of between 700 and 1600 nanometers.

[0098] In embodiments, the device 1 comprises a carousel 5 with a vertical rotation axis X, said carousel 5 being driven in rotation by at least one motor relative to a frame 7. A schematic view of an exemplary embodiment of the device 1 and of the carousel 5 is visible in [Fig.5].

[0099] The rotation of the carousel 5 relative to the frame 7 is done by means of a rolling means.

[0100] In embodiments, the carousel 5 is carried by a rotating chassis 6, rotating around the vertical axis of rotation X, in the form of an orientation ring which comprises the rolling means. The rolling means may be, for example, produced in the form of two rings capable of being rotated relative to one another, each ring comprising a raceway, and the crown further comprising a rotation device consisting of rolling members or bodies (such as balls or ball bearings) interposed between the two raceways and a device for fixing the constituent elements of the crown to prevent them from becoming detached while allowing the two rings to rotate relative to each other. The rotation of the carousel 5 around the vertical axis of rotation X can then be done by connecting one ring to the frame 7, the chassis 6 of the carousel 5 being carried by the other ring. Thus, the carousel 5 can rotate relative to the frame 7. The ring connected to the frame 7 is called the fixed ring, and the other ring is called the rotating ring.

[0101] In embodiments, the frame 6 in the form of a slewing ring may comprise external teeth mounted on the rotating ring. According to a possible variant, the rotating chassis 6 is in the form of a cup which is mounted on the rotating ring, for example through blind or through fixing holes, smooth or tapped. On this cup are fixed various parts of the machine, not shown, the assembly forming a carousel. In embodiments, the rotating chassis 6 is in the form of a column.

[0102] According to an additional characteristic, visible in [Fig.5], the carousel 5 comprises at least one first tray 50, or platform. The axis of rotation of the at least one tray 50 is coaxial with the axis of rotation of the carousel 5. The tray 50 can be of any shape, but is preferably circular. Advantageously, the plate 50 supports a plurality of holding members for positioning a container 2 along an axis substantially parallel to the axis of vertical X rotation of the carousel 5. In other words, a container 2 is held by a holding member and is rotated by the first plate 50 of the carousel 5.

[0103] As seen in [Fig.6], in embodiments, the carousel 5 also comprises a barrel 53. The barrel 53 supports the plurality of marking stations 3 such that each optical system 320 is located opposite a container 2, itself held by a holding member. Preferably, the diameter of the barrel 53 is less than the diameter of the first plate 50 in order to facilitate the implementation of the device 1.

[0104] Advantageously, the containers 2 and the optical heads 30 are both driven in rotation along a rotation axis X vertical relative to the frame 7. The synchronized rotation of the marking stations 3 and the containers 2 and the vertical position of the container 2 opposite the optical system 320 of an optical head 30 is particularly advantageous. Indeed, the working distance D2 between the optical system 320 and the marking zone 20 of the container 2 is then constant or substantially constant: the containers 2 are immobilized during the marking, as are the optical systems 320, and the marking produced is of high quality.

[0105] The marking stations 3, the control means 4 and the containers 2 are therefore driven in rotation in a synchronized manner relative to the frame 7. The 5 carousel also includes a 60 rotating swivel joint that supplies electricity to the 4L power sources For this purpose, the rotating joint 60 comprises a rotating electrical collector, located at the head of said rotating joint 60, which is powered by a fixed electrical cable. Conventionally, the rotating electrical collector comprises tracks, fixed or rotating, on which fingers, respectively rotating or fixed, bear elastically, the assembly being housed under a casing, not shown, which is fixed to the chassis 6 and retained by an anti-torque structure secured to the frame 7. Preferably, the barrel 53 is hollow so as to accommodate the rotating joint 60 in this hollow central part.

[0106] Thus, the installation 100, in embodiments, makes it possible to mark the containers 2 during their rotation, which is extremely advantageous. It is then possible to mark containers 2 at a high rate, of the order of 8000 to 100000 markings per hour.

[0107] In embodiments, at least one optical head 30 of each marking station 3 is capable of moving the laser beam 31 in a horizontal plane and / or in a vertical plane. Preferably, the laser beam 31 is emitted in a direction orthogonal or substantially orthogonal to the vertical axis of rotation X of the carousel 5. The vertical plane corresponds to the plane that passes through the vertical X axis of rotation of carousel 5 and the horizontal plane corresponds to the plane perpendicular to the X axis of rotation of carousel 5.

[0108] In embodiments, the barrel 53 of the carousel 5 comprises means for vertical movement of each marking station 3 or of each laser head 30, so that each of said stations 3 or of said laser heads 30 can move vertically along the barrel 53, for example by means of slides placed on the barrel 53 and an actuation means (not shown). This has the advantage of being able to position the optical system 320 opposite the marking zone 20 of a container 2. Indeed, the type of container 2, its dimensions, its shape, can change and it is then necessary to adjust the relative vertical positioning of the optical systems 320 and the marking zones 20, so that the optical output 321 is located opposite the at least one marking zone 20. This adjustment can be done for example automatically via an electronic control unit 400 included in the control means 4, by a mechanical cam adjusted by an operator or by means of an actuator, or even manually by the operator.

[0109] In embodiments, the carousel 5 comprises a third tray 52, the axis of rotation of which is coaxial with the axis of rotation of the first tray 50. The third tray 52 supports the control means 4 and is preferably, but not limited to, located above the first tray 50. It is particularly advantageous to position the control means 4 on the upper part of a third plate 52 located in the upper part of the barrel 53. Indeed, this makes it possible to have a primitive displacement of the containers 2 smaller than that of the control means 4. Also, this makes it possible to avoid possible leakage problems, in cases where the containers 2 are filled before marking.

[0110] The installation 100 also comprises a treatment station 10 for containers 2 located upstream of the device 1. The treatment station 10 directly or indirectly supplies the device 1 at a loading point. Such a treatment station 10 may be, for example, a filler, a capper, a blower, a labeler, or any other treatment station for containers 2 on a packaging line.

[0111] Advantageously, the installation 100 allows a continuous supply of containers 2.

[0112] The installation 100 may also comprise, in embodiments, an inspection system 11. Such an inspection system 11 comprises at least one camera and a control unit (not shown) for verifying whether the mark 310 is compliant. In the event of non-compliance, the container 2 must be destroyed or at least rejected so as not to undergo further processing. The installation 100 may include means 110 for ejecting a container 2 whose mark 310 is not compliant. For these control purposes, in embodiments, the installation 100 comprises a central control unit 12 making it possible to enter information concerning the type of container 2, the format, the type of mark 310 to be affixed, the location of the marking zones 20, 20a, 20b, etc. According to a possible variant, the central control unit 12 communicates with the electronic unit 400 of the control means 4. In embodiments, the central control unit 12 comprises: - a database in which are recorded programs for controlling the marking device 1 and possibly other container processing stations 2, said database being recorded in a memory device or stored on an independent server, - a processor connected to the memory to apply the instructions of the programs and - a communication interface connected to the processor for communication at least with the electronic unit 400 of the control means 4. According to a possible variant, the central control unit 12 comprises a calculation unit making it possible to generate instructions in real time based on the measurements taken by different sensors, for example a sensor for measuring the height of a container 2, or the sensor 340 for measuring the distance between the optical output 321 and the at least one marking zone 20 of the container 2.

[0113] The electronic control unit 400 acts as a slave controller controlled by the central unit 12, called the master unit. The electronic control unit 400 is programmed to control the device 1 for the complete completion of a marking cycle, and in particular to transmit the instructions necessary for the proper performance of the marking.

[0114] The central control unit 12 can also be connected to an inspection system 11 to enable the level of conformity of the mark 310 of a container 2 to be configured. The conformity can be, for example, the readability, the positioning of the mark, etc. According to a possible variant, the inspection system 11 transmits information concerning the quality of the marking to the central control unit 12, which can then send instructions to the electronic unit 400 of the control means 4, for example aimed at correcting the height adjustment of the mark 310, the focusing carried out by the optical head 30, or any other parameter linked to the marking.

[0115] Advantageously, the central control unit 12 comprises different sensors, in particular speed sensors, or even the sensor for measuring the distance between the optical output 321 and the at least one zone 20 to be marked, the collected information of which is stored in the database or transmitted to a calculation unit of the central control unit 12. For example, the database of the central control unit 12 records the information concerning the formats of containers 2 to be marked, for example their dimensions and / or their shape.

[0116] In embodiments, the central control unit 12 makes it possible to configure the mark 310 to be affixed to the at least one marking zone 20 of a container 2.

[0117] An operator can enter the various parameters at a dedicated interface of the central control unit 12, or possibly remotely. For these purposes, the central control unit 12 may comprise a control screen for the installation 100 with a dedicated human-machine interface allowing the entry of information, for example the entry of the format of the container 2, the choice of the brand 310, etc.

[0118] The installation 100 described previously is capable of implementing the method described previously.

[0119] The invention also relates to a container 2 comprising at least one body, a shoulder in the extension of said body at an upper end thereof, a neck in the extension of the shoulder, a wall 25, and a bottom at the lower end of said body. The wall 25 is the surface which constitutes the boundary between the inside and the outside of the container 2. The wall 25 comprises an external skin 250 and an internal skin 251, and at least one marking zone 20. In other words, the container 2 comprises at least one marking zone 20, at the level of the body, and / or at the level of the shoulder, and / or the neck and / or the bottom, the wall 25 constituting the surface delimiting the contents of the container 2 and its external environment. Such a container 2 is characterized in that, at the level of the marking zone 2, said wall 25 comprising an external skin 250 and an internal skin 251, comprises, at the level of said marking zone 20, in all or part of its thickness, bubbles 200 and particles 201 of degraded material.

[0120] In embodiments, the wall 25 of said container 2 comprises:

[0121] - a first layer extending from the outer skin 250 towards the skin internal 251 of said container 2, said first layer comprising both said bubbles 200 and said particles 201 of degraded material and - a second layer located extending from said first layer and towards said internal skin 251, said second layer comprising said particles 201 of degraded material.

[0122] The container 2 comprising at least one mark 310 can be obtained by implementing the method described previously.

[0123] The container 2 comprising at least one mark 310 can be obtained by using of the installation 100 previously described.

[0124] The marking method according to the invention makes it possible to obtain marked containers 2, comprising at least one mark 310 of very high legibility, while benefiting from simplified adjustment parameters. It is possible to implement the method according to the invention regardless of the contents of the container 2 to be marked, whether the container 2 is previously or subsequently filled.

Claims

Claims

1. Method for marking containers (2), in particular bottles or flasks made of thermoplastic material, said containers (2) comprising at least one body, a shoulder in the extension of said body at an upper end thereof, a neck in the extension of the shoulder, a wall (25), said wall (25) comprising a marking zone (20), an outer skin (250) and an inner skin (251) and a bottom at the lower end of said body, said method comprising at least the following steps: - a step (El) consisting of carrying out a treatment on said containers (2), preferably filling and capping said containers (2), - a marking step (E2), consisting of generating a mark (310) at at least one marking zone (20) of each container (2),said marking step being carried out by projecting a laser beam (31) by means of a laser marking optical head (30) equipped with a laser head unit (300) and an optical system (320) for focusing said laser beam (31) to mark said area (20), a method characterized in that the projection of said laser beam (31) is carried out so as to generate bubbles (200) and particles (201) of degraded material in all or part of the thickness of the wall (25) of said container (2) at said marking area (20).,

2. Laser marking method according to claim 1, characterized in that the projection of the laser beam (31) is carried out so as to generate at least one marking zone (20): - a first layer extending from the outer skin (250) towards the inner skin (251) of said container (2), said first layer comprising both said bubbles (200) and said particles (201) of degraded material and - a second layer extending from said first layer and towards said inner skin (251), said second layer comprising said particles (201) of degraded material.

3. Laser marking method according to the preceding claim, characterized in that the projection of the laser beam (31) is carried out in such a way as to generate neither bubbles (200) nor particles (201) of degraded material within a third layer at the level of the marking zone (20), said third layer extending from said second layer in the direction of said internal skin (251).

4. Laser marking method according to any one of the preceding claims, characterized in that the projection of the laser beam (31) is carried out by generating pulses of a fixed duration, between 10 and 200 nanoseconds, said laser beam (31) being emitted at a fixed wavelength, said wavelength having an absorption less than or equal to 5% for a thickness of the thermoplastic material of 0.25 millimeters (mm).

5. Laser marking method according to any one of the preceding claims, characterized in that the laser beam (31) is emitted at a fixed wavelength having an absorption less than or equal to 3% for a thickness of the thermoplastic material of 0.25 millimeters (mm).

6. A laser marking method according to any one of the preceding claims, characterized in that the laser beam (31) is emitted at a fixed wavelength between 700 and 1600 nanometers.

7. Method for marking containers (2) according to any one of the preceding claims, characterized in that, during the marking step, the power of said laser beam (31) is adjusted.

8. Method for marking containers (2) according to any one of the preceding claims, characterized in that the scanning speed of the laser beam (31) is variable.

9. Method for marking containers (2) according to any one of the preceding claims, characterized in that said method comprises, before the marking step, the following steps: - a step consisting of rotating said containers (2), preferably filled and capped, around a vertical axis around which laser marking stations (3) are rotated, in a synchronized manner with said containers (2), - a step of adjusting the focal point of the laser marking stations (3) preferably as a function of the dimensions and / or the shape of said containers (2), and - the marking step being carried out during the rotation of said containers (2).

10. Marking installation (100) for implementing the method for marking containers (2) according to any one of claims 1 to 9, said installation (100) comprising at least: - a device (1) for laser marking containers (2), in particular bottles or flasks made of thermoplastic material, said marking device (1) comprising a plurality of laser marking stations (3), each station (3) comprising along an optical path at least one laser marking optical head (30) for projecting a laser beam (31), said optical head (30) being equipped with a laser head unit (300) and an optical system (320) for focusing said laser beam (31) in order to generate a mark (310) at at least one marking area (20) of each container (2) for marking said area (20), said optical head (30) being connected to a laser processing apparatus (40) via an optical channel (600), - control means (4) connected to the marking stations (3) and comprising said laser processing apparatus (40) and power supply means (41) of the laser marking stations (3),said installation (100) being characterized in that it comprises means for generating bubbles (200) and particles (201) of degraded material in all or part of the thickness of the wall (25) of said container (2) at the level of said marking zone (20).,

11. Installation (100) according to the preceding claim, characterized in that the means for generating bubbles (200) and particles (201) of degraded material in all or part of the thickness of the wall (25) of said container (2) at said marking zone (20) generate at said marking zone (20): - a first layer extending from the outer skin (250) towards the inner skin (251) of said container (2), said first layer comprising both said bubbles (200) and said particles (201) of degraded material and - a second layer located extending from said first layer and towards said inner skin (251), said second layer comprising said particles (201) of degraded material.

12. Installation (100) according to claim 10 or 11, characterized in that the means for generating bubbles (200) and carbon particles (201) in all or part of the thickness of the wall (25) of said container (2) at the level of said marking zone (20) consist of an optical head (30) configured to generate a laser beam (31) with a fixed pulse duration of between 10 and 200 nanoseconds.

13. Installation (100) according to any one of claims 10 to 12, characterized in that the means for generating bubbles (200) and carbon particles (201) in all or part of the thickness of the wall (25) of said container (2) at said marking area (20) consist of an optical head (30) configured to emit a laser beam (31) at a fixed wavelength, said wavelength having an absorption less than or equal to 5% for a thickness of the thermoplastic material of 0.25 millimeters (mm).

14. Installation (100) according to any one of claims 10 to 13, characterized in that the means for generating bubbles (200) and particles (201) of degraded material in all or part of the thickness of the wall (25) of said container (2) at the level of said marking zone (20) consist of an optical head (30) configured to emit a laser beam (31) at a fixed wavelength between 700 and 1600 nanometers.

15. Container (2) comprising at least one body, a shoulder in the extension of said body at an upper end thereof, a neck in the extension of the shoulder, a wall (25), said wall (25) comprising a marking zone (20), an external skin (250) and an internal skin (251), and a bottom at the lower end of said body, container (2) characterized in that, at the level of the marking zone (20), said wall (25) comprises, at the level of said marking zone (20), in all or part of its thickness, bubbles (200) and particles (201) of degraded material.

16. Container (2) according to the preceding claim, characterized in that the wall (25) of said container (2) comprises: - a first layer extending from the outer skin (250) towards the inner skin (251) of said container (2), said first layer comprising both said bubbles (200) and said particles (201) of degraded material and - a second layer located extending from said first layer and towards said inner skin (251), said second layer comprising said particles (201) of degraded material.

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