Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
  • H01J37/32—Gas-filled discharge tubes
  • H01J37/32431—Constructional details of the reactor
  • H01J37/32532—Electrodes
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
  • H01J37/32—Gas-filled discharge tubes
  • H01J37/32009—Arrangements for generation of plasma specially adapted for examination or treatment of objects, e.g. plasma sources

Definitions

• An electrode device for plasma treatment of the inner faces of a container and a method of treatment thereof An electrode device for plasma treatment of the inner faces of a container and a method of treatment thereof.
• the present invention relates to a method of treatment by plasma flow on the inner faces of the walls of a container and more generally of a hollow object.
• the present invention also relates to an electrode device to be placed between a high voltage electrical generator and the orifice of a container for plasma deposition of a product on the inner faces of its walls.
• the many applications of plasma are known in many fields such as the medical, industrial, food and many other fields.
• It is used in particular as an active means for producing surface deposits on objects thus realizing a real surface treatment in order to improve the physical and especially mechanical properties, to establish or reinforce the sealing, to render inert or preserve some media from external aggression.
• plastics do not have a durable seal to liquids but above all. to the current state-of-the-art lubricant fluids compatible with the operating requirements.
• the plastics used to make standard beverage bottles are selected from low cost ones. However, they exhibit properties of 1 gastightness is degrading over time. In addition, it also seeks to save weight and therefore to reduce the thickness.
• outside air can cross the walls of the container and denature its content, at best by distorting its taste.
• Fruit juices or canned food can be altered by oxidation from the passage of outside air through the walls.
• Electrode plasma electrodeposition apparatus plunging into the neck of a bottle. Some of these devices relate to vacuum deposition and others to the use of a microwave high voltage generator.
• the present invention aims to improve the treatment and reduce the energy required. It relates to faster, effective atmospheric plasma flow plating under lower energy, and requiring only a reduced amount of activator gas.
• an electrode device for applying the high voltage between a high-voltage generator and the orifice of a container, especially a plastics container, for plasma electroplating treatment on its inner faces. a product forming a sealing barrier, this product being brought to the gaseous state in the plasma stream.
• This electrode device for the application of a layer by atmospheric plasma treatment on the inner faces of the walls of a hollow object, in particular a container using an activator gas and a treatment gas, is characterized in that is formed of a body consisting of a fixed upper part and another part or block movable in rotation, the latter comprising means for injecting gases and having a receptacle receiving cavity of the container equipped with means for holding and retaining the container and in that a fixed central electrode electrically connected to a high voltage generator passes through the body of the device and is surrounded on its inner part at the neck of at least one coaxial conductive ring and kept at a distance from the central electrode by spacer means, said conductive ring having at least one through-channel of ionization of the activator gas communicating with at least one arrived e of activator gas, in that the neck and the coaxial electrode assembly inside the neck between them define an annular volume forming an injection chamber and mixing the gas or gaseous treatment mixture and that a means of evacuation of gases is further provided.
• the invention also relates to a process for atmospheric pressure plasma electrodeposition on the inner faces of a hollow object, in particular a container for forming a sealing layer and protecting the inner faces of the walls of a hollow object and more particularly of a container driven in rotation, in which the container is held by its neck and its neck is introduced into a central electrode electrode device connected to a high voltage electrical generator characterized in which is injected separately along two different paths in an injection and mixing chamber developing in the neck between the latter and around a conductive ring surrounding the central electrode, on the one hand in the lower part of the the injection and mixing chamber an ionized activator gas and secondly from the top of this chamber a gas or a gaseous treatment mixture, in that a secondary electric field is established by the conductive ring surrounding the central electrode at a distance therefrom representing an interval in order to give rise to a second plasma under a lower voltage electric arc and in that mixing the gas or gaseous treatment mixture having passed through the lower voltage electric arc with the ionized activator gas.
• the at least one ionization traversing channel opens into this annular volume creating at the outlet of this passage a current of ions of the activator gas and the conductive ring makes it possible to generate a second plasma at lower voltage.
• the injection chamber and mixture is passed through the gaseous treatment mixture before mixing with the ionized activator gas.
• the device according to the invention provides several important advantages.
• the treatment is fast and uniform and only requires rotation speeds of a few revolutions per second for a surface plasma.
• the electrode device according to the invention is intended to receive the neck of a container, for example that of a bottle, for the purpose of plasma treatment of the inner lateral faces of its walls in order to make them impermeable to liquids and contaminants. gas under normal operating conditions and benefit in addition to improved mechanical rigidity and strength.
• the electrode device has the following main function: to constitute a specific head of application of the atmospheric plasma treatment in connection with a less powerful electric generator of high voltage, head comprising at
• FIG. 1 is a schematic longitudinal view of a basic variant illustrating the essential means of the device according to the invention
• Figure 2 is a schematic longitudinal sectional view of a flared end variant
• Figure 3 is a more detailed sectional view of the basic variant according to the invention
• FIG. 4 is an enlargement of the circled portion of FIG. 3
• FIG. 5 is a graph of an example of a waveform of the high voltage of the generator showing by G1 and G2 the voltage gain, and by d1 and d2 the gain in duration, provided by the invention.
• the device according to the present invention is in the general form of a set 1 forming a plug and receiving recessed and holding in its lower part a neck 2 of a container 3 for example a bottle.
• the stopper caps the neck 2 in its upper part.
• the plug has a fixed upper base 4 secured to or mounted on an external support and a block 5 free in rotation, driven in rotation by external means, for example, by a belt 6 which engages in a peripheral groove 7 existing in the central part of block 5 or by any other means of transmission between a source of rotational movement and the body 5 for rotating the plug on itself with the container 3 it maintains.
• the transmission is carried out by means of gears, either separated from the block 5, or integrated therein, or shaped in its lateral surface.
• any other mixed or known solution for driving the container is suitable.
• the container may rest on a turntable and the block 5 then rotates on itself being held by suitable mechanical means.
• the rotational movement can also come from a lateral drive in the case of a container with a lateral surface of revolution.
• the body of the plug has a receiving cavity 8 open downwards.
• This receiving cavity 8 is intended to receive and hold the neck 2 of the container 3, represented in the form of "0 of a bottle in FIG. 1, by any means, for example that described above.
• the reception cavity 8 has at its lower end by which it is open and through which penetrates the neck 2, a retaining and holding means 9, for example by snap-fastening.
• an anti-wear intermediate part forming a bearing 10 or by a direct rotating contact for example treated surfaces to promote sliding.
• the invention comprises in its essential function means for applying the high voltage, means for conditioning the activation gas, admission means for the gas or mixture process gas and means for mixing and injecting gases into the container.
• the high voltage is applied via a fixed central electrode 11 longitudinally through the block 5 of the plug 1 around which it rotates.
• its side surface can be treated to allow rotation without friction.
• This central electrode 11 is hollow over part of its length at least equal to the crossing of the plug.
• a central evacuation channel 12 opens out from its lower end face 13 in contact with the fluid of the interior volume to the container 3 and outside the plug 1. This central evacuation channel 12 is used for the exit of the gases injected into the container 3 for the treatment atmospheric plasma in accordance with the process according to the invention.
• the central electrode 11 dips into the neck 2 over a certain length considered sufficient to generate a plasma inside the container 3 and more particularly along and near the inner faces of its side walls.
• the central electrode is surrounded at least in its interior part at the neck 2 of an electrically insulating sleeve 14 itself surrounded by a second cylindrical electrode made of an electrically conductive material, for example copper in the form of a conductive ring. coaxial 15.
• the conductive ring 15 is kept away from the center electrode 11 by means of one strut whose basic example is the insulating sleeve 14.
• These means 1 strut may take different forms. It may be first of intercalary insulating elements transverse, for example of the type pins pins, pins or other transverse forms allowing a descent of the activator gas to its output through the conductive ring 15.
• These spacer means may consist of also, as indicated, in an electrically highly insulating sleeve 14 having, for example, internal longitudinal ducts 16 for supplying the activator gas and at least one outlet duct 17 passing therethrough and extending through the conductive ring 15 via a channel 18 .
• This conductive ring 15 is not electrically connected to any support. She is electrically in the air and therefore behaves like any conductive element near a high voltage electrode. The high voltage gives rise to a stream of electrons that borrows various conductive paths existing between the two electrodes.
• the conductive ring 15 In operation, placed in the vicinity of the high-voltage electrode 11, the conductive ring 15 will be electrically energized and electrically-energized which is used in the process as will be seen hereinafter to give rise to a second plasma under low voltage.
• the conductive ring 15 may comprise a flared lower end 19, that is to say of frustoconical shape, more or less open angle depending on its position and according to the shape of the part 3. It is simply necessary to leave sufficient space between the wall of the container 3 and the rim of the flared lower end 19 for the unconstrained passage of gases.
• This form has the advantage of constituting a deflector for deflecting the flow of gas to direct it from the beginning to the adjacent wall of the container allowing it to better walk along the walls.
• the above coaxial assembly formed of the central electrode portion 11 inside the neck 2, the insulating sleeve 14 and the conductive ring 15 occupies most of the interior volume of the neck 2. Of a diameter smaller than that of the neck 2 for its introduced portion, it delimits with the neck 2 an annular injection and mixing volume called hereinafter after injection and mixing chamber 20.
• the arrival of the gas or gaseous treatment mixture is carried out at an upper point of this chamber.
• the insulating sleeve 14 and the conductive ring 15 are traversed by at least one of the transverse channels or channels of ionization, on the one hand communicating with an inlet of the activating gas in the other.
• this assembly for example argon injected in the upper part of the plug and passing through the latter by internal channels which run along the central electrode 11 or for example inside the insulating sleeve 14 to come out by the ring conductive 15 to the right of the neck 2 or the birth thereof.
• the transverse ionization channel 18 may be perpendicular to the insulating sleeve 14 and to the conductive ring 15 or directed downwardly as shown in FIGS. 2 and 4.
• transverse channels evenly distributed angularly, for example four in number.
• the injection and mixing chamber 20 is fed from the top 21 of treatment gas or of a gaseous treatment mixture, for example silicon oxide, reacting under plasma and activator gas to form by plasma electrodeposition on the inner faces a thin layer of silicon oxide known to constitute a sealing barrier and improve the physical and mechanical properties of the side walls on which it is deposited.
• treatment gas or of a gaseous treatment mixture for example silicon oxide
• the means described above make it possible to ionize the activator gas as soon as it leaves the coaxial assembly before it is mixed with the gas or the gaseous treatment mixture and allows the conductive ring 15 to generate a low voltage electric arc.
• This preliminary phase of ionization of the activator gas greatly improves the efficiency of the reaction and therefore the quality of the oxide deposition on the inner faces of the walls to gain energy and time over the duration of the treatment.
• the bottom wall is exhausted by continuing the path of the gases before their ascent through the central part of the interior volume of the container and their evacuation via the central electrode 11.
• the high voltage is then applied, which, as represented, conventionally consists of low frequency and high voltage pulse trains, pulses each formed of a succession of pulses or of a high frequency sinusoidal wave whose amplitude is above the priming threshold.
• the repetition frequency of the high voltage pulses and their duration determine the applied energy.
• the present invention makes it possible to operate at lower energy than previously.
• the high voltage ionizes the argon and causes the generation of a plasma. Thanks to the transverse channel of ionization 18, the ionization phenomenon is accelerated and more efficient. Thanks to the electric field established by the conductive ring 15, the ignition is performed at a lower voltage level than previously known and is more energetic in terms of the reaction.
• the injection and mixing annular chamber is then injected with a treatment gas or a gaseous process mixture carrying a gaseous oxide, for example silicon.
• the ionized activating gas is injected as soon as it leaves the ionization channel into the flow of the gaseous treatment mixture which goes down along the injection and mixing chamber 20 and passes through the electric field existing between the conductive ring 15 and the neck 2.
• the activating gas forming a first plasma is charged with free electrons which will favor with the secondary electric field coming from the conductive ring 15 the initiation of a second plasma.
• the previously formed silicon oxide ions are carried by the plasma flow and deposited by it on the inner faces of the walls.
• the process gas is a gas or a gaseous mixture charged with volatile components of particles to be ionized which is deposited under the effect of the plasma flow generated by the high electrical voltage and the activator gas.
• the invention makes it possible to target a cheap treatment of the containers and to improve the oxide deposition.
• the waveforms of the high voltage shown in Figure 3 illustrate the efficiency of the invention.
• FIGS. 5 and 5 show the points G1 and G2 two levels of ignition voltage for the same receptacle respectively on the one hand with a generator G1 connected to the coaxial electrode assembly according to the present invention and a conventional generator. G2 connected to an electrode assembly according to the state of the art. Note ⁇ ⁇ la__ su conclusionsràor Institut__de_JLJ inve.n_t_ip_n_ why priming takes place more quickly and to a lower voltage. Note also the gain in plasma establishment time by the difference in length of the two horizontal arrows: dl and d2.
• a starting voltage value of about 2 kV with the invention is given instead of 10 kV at 15 kV usually for this type of application with a conventional arrangement.
• the high voltage generator is significantly lightened and simplified and therefore lower cost.
• the present invention also relates to the process carried out with the means described above.
• the container is rotated.
• the container 3 is purged beforehand or at the beginning of the rotation of its air by the injection of the activator gas.
• the occluded air escapes through the evacuation channel 12 of the central electrode 11.
• the ionization of the activator gas takes place in the ionization channel before mixing with the gas or the gaseous treatment mixture.
• the activator gas is pre-ionized and then ionized by passing it through the insulating sleeve 14 and then by channeling the channel 18 of the conductive ring 15 which surrounds the central electrode 11. at a distance from it.
• the activator gas is ionized entirely at its outlet from the conductive ring 15 opening into the injection and mixing chamber 20.
• the electrode for establishing a secondary electric field thus constituted by the conductive ring 15 gives rise to a second plasma from this conductive ring 15 surrounding the central electrode 11 at a distance from it occupied alternately by a sleeve 14 highly electrically insulating.
• the gas or the gaseous treatment mixture is injected from above into 21 in the injection and mixing chamber 20.
• the gas or the gaseous treatment mixture is passed through, firstly the electric field coming from the conductive ring 15 and then the stream of ionized activating gas leaving the ionization channel in the lower part of the injection chamber and mixture and the two gases mix.
• a low rotational speed for example up to 5 revolutions / sec, is in the field of surface plasmas whereas for a higher rotation speed the plasma becomes volumic.
• the essence of the process according to the invention comes from the following characteristics according to which two different paths are injected separately into an injection and mixing chamber 20 developing in the neck 2 between the latter and around a conductive ring. surrounding the central electrode 11, first in the lower part of the chamber 20 of injection_et__de__mé_lang e_ i ionized activator gas and secondly by the top 21 of the chamber 20, a gas or a treatment gas mixture in that a secondary electric field is formed by the conductive ring 15 surrounding the central electrode 11 at a distance therefrom representing an interval for generating a second plasma from a weaker electric arc. voltage and in that mixing the gas or the gaseous treatment mixture having passed through the electric arc of lower voltage, with the ionized activator gas.

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• Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• Plasma & Fusion (AREA)
• Chemical & Material Sciences (AREA)
• Analytical Chemistry (AREA)
• Chemical Vapour Deposition (AREA)
• Details Of Rigid Or Semi-Rigid Containers (AREA)
• Physical Or Chemical Processes And Apparatus (AREA)

Applications Claiming Priority (2)

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• 2004
  • 2004-09-21 FR FR0409978A patent/FR2875641B1/fr not_active Expired - Fee Related
• 2005
  • 2005-09-19 WO PCT/FR2005/002321 patent/WO2006032773A2/fr active Application Filing
  • 2005-09-19 EP EP05805780A patent/EP1803143A2/de not_active Withdrawn

Non-Patent Citations (1)

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