WO2000019791A1 - Device for protecting an electric circuit against interface microdischarge phenomena - Google Patents

Abstract

The invention concerns a device for protecting an electric circuit against interface microdischarge phenomena, comprising at least a protective element (1) consisting of an electromagnetic absorbent web, with electrical resistivity ranging between 0.004 10-3 Φ x m and 5 10-3 Φ x m, enabling to attenuate interface microdischarge phenomena. The invention is useful for protecting elements of audio and video frequency equipment.

Description

 DEVICE FOR PROTECTING AN ELECTRICAL CIRCUIT AGAINST INTERFACE MICRODECHARGE PHENOMENA

The interface micro-discharges, hereafter designated by MDI, appear to be the phenomenon mainly responsible for the degradation of the transmission and the detection of electronic signals. This is particularly the case with regard to the degradation of musicality observed in audio and / or video frequency signal processing devices, such as High Fidelity channels, HiFi, even in the case where these devices satisfy to conventional noise reduction standards and criteria.

These micro-discharges occur whenever electric charges, linked to insulators, in particular when these charges are present at the interface of this insulator, are subjected to variable electric fields. The phenomenon of micro-discharges is further favored by the existence of mechanical vibrations of which the electronic or electrical circuits can be the seat. Finally, these electrical charges are most often located on the surface of the aforementioned electrical insulators, either at the conductor / insulator interface itself, as in the case of electric or electronic cables, or at the junction between two insulators, like this systematically appears to be the case at the level of the insulator / air interfaces.

The electric field, which excites these micro-discharges, can be either of internal origin or of external origin such as for example the electric field generated by the sector at industrial frequencies. When an electric charge, or a set of electric charges linked to electric insulators, is subjected to a variable electric field, the new state of equilibrium of the electrostatic system thus formed can only be obtained through the phenomenon of micro-discharges , which can be analyzed as a local dielectric breakdown phenomenon, on the scale of the roughness of the insulating and / or conductive materials which house them.

These micro-discharges, although of very low amplitude, of the order of a millivolt, however have very short rise or fall times, close to, or even less than a nanosecond. Corresponding measurements could indeed allow the identification of frequencies associated with the transient phenomena and waves generated by the MDI between 1 and 100 GHz or more.

At such frequency levels, and due to their mode of creation, the aforementioned electromagnetic phenomena propagate in the form of electromagnetic waves, hereinafter referred to as MDI waves, in particular in the form of surface electromagnetic waves. along the aforementioned conductor / insulator, insulator / insulator and insulator / air interfaces.

Due to the excitation provided by the electric fields, the MDI phenomena are synchronous with the latter and result in the generation of an electromagnetic wave correlated with, if not modulated by, these electric fields or these vibrations.

At the high frequencies considered above, all the metal / metal junctions present on the electronic circuits have substantially properties dressers. Consequently, these junctions in fact fulfill a parasitic function for detecting the MDI wave, by reinjecting, in the useful signal, a parasitic signal correlated with the excitatory electric fields but highly distorted. The resulting signal is ultimately felt to be highly distorted, particularly by the discerning audiophile.

While excitatory electric fields play an essential role, mechanical vibrations and, of course, external electrostatic fields, play a complementary role.

In particular, the presence of external electrostatic fields in fact facilitates the extraction of electric charges, during variations in the excitatory electric field, by superposition of the equilibrium states. On the contrary, such a phenomenon is highlighted by the known use and the effectiveness of antistatic products on cables or other organs of HiFi devices.

Mechanical vibrations, on the other hand, appear to be a multiplier of MDIs of considerable importance. These vibrations cause a variation, a reduction, at least temporarily, in the electrical breaking distance, which accentuates the number of MDIs generated. The existence of such mechanical vibrations is of course critical for an audio or HiFi installation whose primary technical effect is none other than to make the surrounding air vibrate by means of loudspeakers or the like.

In addition, due to the fact that these vibrations are strongly correlated with the audio signal, the MDIs generated under these conditions are, for this reason, likely to disturb listening appreciably.

Various research works, relating to MDIs and their eradication, have so far been carried out.

First, we can cite the work done by Pierre JOHANNET.

During this work, the detection of MDIs could be highlighted by means of suitable antennas, in this case doublets or dipoles of 4 to 10 cm.

The MDIs could in particular be highlighted:

- on an amplifier, where it has been found quite significantly that the signals generated by the MDIs are correlated with the input signal, in low frequency baseband, the amplitude and the frequency of recurrence of the signals generated by MDI varying according to the low frequency input signal;

- on a power cable;

- on a loudspeaker, a particularly significant phenomenon because the amplitude of the electrical input voltages, in this case, does not exceed a few volts, and these voltages are exclusively at low frequency.

Following this initial work, various solutions were proposed by Pierre JOHANNET. These solutions were the subject of a complete description in French patent applications No. 96 12369, 97 06045 and 97 07837 filed in the name of ELECTRICITE DE FRANCE, introduced in the present patent application by way of reference. The solutions proposed above give satisfaction. They essentially consist in avoiding the creation of MDIs by generating, near the interfaces, local equipotentiality aimed at attenuating excitatory or electrostatic electric fields, absorbing MDIs when these are produced, reducing or eliminating undesirable mechanical vibrations, eliminating signals electrical interference generated by MDIs at the input and output of electrical or electronic intermediate circuits by means of suitable passive filters, to design specific circuits intrinsically protected against MDIs.

Secondly, we can also cite the work carried out by Pierre FONTAINE.

During this work, the latter noted that by superimposing on a baseband audio signal, 10 Hz to 20 kHz approximately, a low amplitude signal, not exceeding 500 mV, but at very high frequency, higher at 200 kHz, at the input of an operating audio amplifier, the sound generated by the resulting output signal appeared hard, distorted and ultimately very unpleasant.

Thirdly, we can cite the work described in the article published by Olivier DRUANT, Jacques BAUDET, Bernard DEMOULIN, entitled "Characterization of operational amplifiers subjected to frequency signals much higher than their bandwidth", article published by the review of Electriciens et Electroniciens, n ° l, January 1998. The aforementioned work has shown that the operation of operational amplifiers is very disturbed in the presence of parasitic signals whose frequency is close to 700 MHz. Fourth, distortion measurements made on an audio frequency amplifier, measurements of a signal resulting from the difference between the output signal, attenuated by the gain value of the amplifier, and the input signal allowed the highlighting of spurious signals in the 1 to 2 GHz band.

Fifth, we must mention, during tests of compliance of amplifiers, or other devices with open hoods, with electromagnetic compatibility standards, the detection of high radiation rates at high frequency.

Finally, the use of microwave absorbents and other filters at very high frequencies for the eradication of MDI indirectly shows, thanks to the manifest efficiency in improving the sound quality thus obtained, the undeniable existence parasitic phenomena caused by MDI.

The object of the present invention is to remedy the drawbacks of the solutions proposed previously by the implementation of new or complementary solutions with regard to them.

Another object of the present invention is, consequently, the implementation of a device for protecting an electric circuit against the phenomena of interface micro-charges having the object of suppressing the creation and the propagation of the MDI wave associated with these phenomena.

Another object of the present invention is, also, the implementation of a device for protecting an electrical circuit against the phenomena of interface micro-discharges capable of application to the majority. t of the constituent elements of audio- and / or video-frequency devices, that these elements in fact constitute active or passive elements, capable of generating MDI phenomena and the MDI wave which is generated by the latter.

The device for protecting an electrical circuit against the phenomena of interface micro-discharges, object of the present invention, these phenomena being generators of radio interference in audio frequencies, is remarkable in that it comprises at least one protective element formed by a electromagnetic absorbent veil, the electrical resistivity of which is between 0.004 x 10 ^"3 Ω xm and 5 x 10 ^{" 3} Ω xm, this absorbent veil making it possible to attenuate the phenomena of interface micro-discharges.

It finds application, preferably but not limiting, to the protection of all the elements of audio- and / or video-frequency devices, active elements of the latter such as amplification circuits, electrical supply or high -speakers, or passive elements such as cables for connection or power supply and media for recording and playing audio and / or video signals.

The device, object of the present invention, will be better understood on reading the description and on observing the drawings below, introduced by way of pure nonlimiting examples, and in which:

- Figure 1 shows a sectional view of a device for protecting an electrical circuit against the phenomena of interface micro-discharges, according to the subject of the present invention; - Figures 2a to 2c relate to different embodiments of the device for protecting an electrical circuit against the phenomena of interface micro-discharges, in the case of a protective veil formed, either by a non-woven fabric, or by a veil woven protector or by a protective film placed on a support;

FIGS. 3a and 3b to 3f relate to a particular embodiment of a device according to the object of the present invention, more particularly intended for systems for reading media from recordings of audio signals or data such as microgroove reading table and device for reading an optical compact audio and / or video disc;

- Figures 4a and 4b relate to a specific embodiment of a device according to the object of the present invention more particularly intended for electroacoustic transducer systems such as loudspeakers implemented in a High Fidelity chain ; - Figures 5a and 5b relate to a particular embodiment of a device according to the object of the present invention more particularly intended for the protection of a drive motor for reading table microsillon, d '' a compact disc or the capstan of a magnetic tape, in a High Fidelity recording / playback device for audio and / or video signals;

- Figures 6a to 6c show a device for protecting an electrical circuit against interface micro-charges, in accordance with the object of the present invention, applied to plug-in boxes or housings audio and / or video recording / playback devices;

- Figures 7a to 7c show a sectional view of a protection of a circuit device that electrically against the interface microdischarges phenomena according to the object of the present invention, more particu larly ^¬ applied to circuits electrical of any type, when the latter are produced in the form of a printed circuit, respectively of specific printed circuits in which, thanks to the integration into the latter of a device in accordance with the object of the present invention, the phenomena interface micro-downloads are substantially eliminated;

FIGS. 8a to 8c represent a sectional view of a device for protecting an electrical circuit against the phenomena of interface micro-discharges, in accordance with the object of the present invention, applied to connection cables used in the High Fidelity audio and / or video installations; FIG. 9a represents a device for protecting an electrical circuit against the phenomena of interface micro-discharges produced in the form of a passive component making it possible to filter and attenuate the electromagnetic wave associated with these phenomena; - Figure 9b shows an impedance diagram, as a function of frequency, of a component as shown in Figure 9a, when the latter is wound to form a sleeve;

- Figures 9c to 9f show different modes of making and implementing a component in rolled form and making it possible to filter and attenuate the wave electromagnetic associated with the phenomena of interface micro-discharges;

FIG. 9g represents an embodiment in rolled-up form of a component having characteristics of a filter with capacitance resistances of the electromagnetic wave associated with the phenomena of interface micro-discharges;

- Figure 9h shows an electrical equivalent diagram of the component shown in Figure 9g; - Figures 10a to 10f show, in section, an optical recording / reading medium for digital audio- and / or video frequency data, provided with a device for protecting an electrical circuit against the phenomena of micro-discharges of conforming interface to the subject of the present invention, this type of optical recording / reading medium for digital audio- and / or video frequency data being particularly remarkable in that the phenomena of interface micro-discharges and the parasites associated with the latter are substantially deleted at source, when these are read by a conventional reading device;

- Figure 11 shows, in an illustrative manner, different successive stages of implementation of a method of manufacturing a support for optical recording / reading of digital audio- and / or video frequencies data, in accordance with object of the present invention;

- Figure 12a and Figure 12b show an alternative implementation of the method shown in Figure 11 for the implementation of a multi-layer electromagnetic absorbent web. PC1YFR99 / 02300

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A more detailed description of a device for protecting an electrical circuit against MDI phenomena, in accordance with the object of the present invention, will now be given in conjunction with FIG. 1. In general, the device protection of an electrical circuit, in accordance with the object of the present invention, relates to any circuit or any object involving the creation of electric potentials and / or currents, either specifically for the purpose of electrical supply or the transmission of electrical signals carrying information to other electrical circuits, either by the creation of electrical charges, electrical currents and parasitic electrical potentials during the use of the latter, these electrical circuits and objects, seat of electrical phenomena, then being capable of generating phenomena of interface micro-discharges generating radio interference in audi frequency.

As such, and consequently in the context of a nonlimiting example, the circuit shown in a section view in FIG. 1 relates to a printed circuit provided with elements such as resistor R, capacitance C, transistor T and self-inductance L installed on a PCB printed circuit board. In accordance with a particularly remarkable aspect of the protection device, object of the present invention, it comprises at least one protective element 1, formed by an electromagnetic absorbent veil whose electrical resistivity is between 0.004 10 ^"3 Ω xm and 5 10 ^"3 Ω x m. This absorbent veil 1 person puts to mitigate the phenomena of MDI, by absorption of the MDI wave.

In Figure 1, there is shown the absorbent veil completely surrounding and enveloping the electrical circuit considered, in order to ensure complete protection. However, as will be noted in the aforementioned figure, the electromagnetic absorbent veil, placed in the vicinity of the metallized face of the PCB printed circuit, face opposite to the face containing the components, is preferably constituted by an electromagnetic absorbent veil itself 1 ₀ which is superimposed a layer of electrically insulating material li, in order to avoid any short circuit between the metallizations of the metallized face of the PCB printed circuit. With regard to the electrical resistivity values mentioned above, it is indicated that these aforementioned values will be given by way of example for different products for specific thicknesses of surface haze between 10 ^{~ 3} mm and 0.5 mm for the absorbent haze. electromagnetic considered. Under these conditions, the above-mentioned resistivity values will be expressed in surface resistance in Ω per square for the thickness considered.

In a first embodiment, as shown in FIG. 2a, the electromagnetic absorbent veil can consist of a texture formed from organic fibers covered with an electrically conductive coating. In such a case, the texture corresponds to a non-woven element, called non-woven, formed on the basis of metallic or organic fibers, in particular carbon or conductive polymer, covered if necessary with conductive metal. tor. The aforementioned surface resistance parameter can then be chosen as a function of the percentage of conductive fibers used.

According to another embodiment as shown in FIG. 2b, the above-mentioned electromagnetic absorbent veil 1 can be constituted by a fabric formed from woven electrically conductive fibers. It is recalled that a fabric designates a flexible, resistant surface constituted by a regular assembly of interlaced textile threads, either woven or meshed. In this case, these fabrics are mainly used in the semiconductor industry, in order to limit the static charges in the manufacturing processes. These fabrics can also be used to protect enclosures confined to electromagnetic radiation during transmission and / or reception. A particularly suitable textile, commercially available, is the textile marketed under the name ISOWAVE by the company SCHLEGEL BVA, Roc esterlaan 4, 8470 GISTEL Belgium, in France and in Europe. The aforementioned fabric has an impedance of 0.05 ohm per square and very high electromagnetic wave absorption coefficients, of the order of 100 dB for a frequency band of radio signals between 1 GHz and 10 GHz . In all the test cases implemented, it was found that such a fabric typically had an absorption coefficient of 65 dB, depending on the experimental conditions, that is to say a higher absorption coefficient from 30 to 40 dB to that of the absorbent masses commonly used. Such a fabric appears particularly well suited to constitute an electromagnetic absorbent veil consisting of titutive of a protection device in accordance with the object of the present invention, insofar as, firstly, such a fabric is available in a metallic copper version and a metallic silver version whose resistance per square is more on the other hand, such a fabric appears particularly thin, light and very handy, this fabric having a mass not exceeding 40 g / m ² .

In addition, the aforementioned fabric can be shaped, and ultimately molded, by thermoforming, for the coating of organs or components, as shown in FIG. 1, in order to ensure sufficient cohesion between the protected circuit and the protection device of such a circuit, in accordance with the object of the present invention. Finally, as shown in FIG. 2c, the electromagnetic absorbent web 1 can be formed by an electromagnetic absorbent film, this electromagnetic absorbent film naturally having an electrical surface resistance whose value corresponds to the range of values previously mentioned in the description. In such a case, however, the electromagnetic absorbent film is deposited on a substrate S, this substrate corresponding for example to the insulating layer of an electrical or electronic conductor whose insulator / conductor interface is the seat of MDI phenomena. By way of nonlimiting example, it is indicated that such an electromagnetic absorbent veil may consist of a veil of semiconductor material, a plastic film charged with electrically conductive particles, the corresponding film 1 being deposited on the substrate S, thus that will be described in more detail later in the description. A more detailed description of a device for protecting an electrical circuit against MDI phenomena, in accordance with the subject of the present invention, more particularly intended for protecting electrical circuits for reading a signal recording medium or video frequency data in a device for reading an audio and / or video recording, from a rotary signal or audio and / or video data recording medium, will now be given in connection with FIGS. 3a and 3b .

FIG. 3a relates to the protection of a microgroove disc, denoted DMS, which, during common use, is placed on the rotary plate PR of a reading table TL in order to ensure the reading of this micro disc - DMS groove by a TLE reading head carried by a BL reading arm.

It will be recalled that the microgroove discs are in particular produced from a material such as vinyl, a material recognized as being particularly electrostatic, which therefore attracts dust and other particles present in the air.

Such a phenomenon results in crackles caused by MDI phenomena generating audible parasites, or by the friction of the diamond of the TLE read head on the dust accumulated on the microgroove disc.

Indeed, the permanent friction of the read tip in the groove of the microgroove disc in fact generates, continuously, microdischarges very correlated with the read signal. PC17FR99 / 02300

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These micro-discharges propagate by surface waves on the surface of the microgroove disc and are picked up by the read head and then reinjected via the read signal into the amplification circuits, which, by detection, causes parasites. cited above.

In accordance with a particularly remarkable aspect of the protection device, object of the present invention, as shown in FIG. 3a, it consists in placing, on the rotary plate PR, between the microgroove disc DMS and the rotary plate PR, a protective element consisting of an electromagnetic absorbent sheet 1, which can advantageously have the shape of the rotary plate PR and the dimensions of the latter. In a nonlimiting embodiment, it is indicated that the protective element 1 was constituted by a cover plate produced by one to four layers of non-woven copper metal, sold by the company SCHLEGEL, of thickness 0.1 mm and intended absorption of the above-mentioned high frequency electromagnetic waves. A dramatic improvement in the musicality of playing a DMS microgroove disc has thus been systematically observed.

In addition, an additional precaution may consist in surrounding the TLE read head with an envelope constituted by the protective element formed by the abovementioned absorbent veil, only the support rod of the read point being thus free, as shown in section in Figure 3a. In addition, in Figure 3b, there is shown the application of a protection device, according to the ob- jet of the present invention, to a compact disc, denoted CD, with optical reading. In this case, the TLE reading head is constituted by a laser allowing the reading on the reading face CDi of the compact disc CD, the reading face CDi being constituted by a layer of etched polycarbonate, covered with a metallization ME , and the face opposite to the reading face CD ₂ comprising for example a screen printing and a layer of varnish V deposited on the metallization ME. In accordance with a particularly remarkable aspect of the protection device, object of the present invention, it consists, for a CD compact disc installed on its drive support, of placing an electromagnetic absorbent web disc 1 on the CD compact disc, that is to say on the layer of varnish thereof, as shown in section in Figure 3b. The absorbent sail disc 1 can then advantageously have the same dimensions as those of the compact disc CD. It can be constituted by a woven veil, sold by the company SCHLEGEL, as mentioned previously in the description. It then has a central hole with the dimensions of the capstan for driving the compact disc CD and also of the absorbent sail disc 1 which is thus superimposed on the latter. The implementation of an absorbent veil disc as shown in FIG. 3b has shown a very noticeable improvement in the musicality of the assembly during reading by means of optical reading, as mentioned previously. While by nature the compact disc appears less generator of electrostatic phenomena than the microgroove disc, the higher rotation speed of the compact disc can however lead to electrostatic discharge phenomena in the air.

In addition, an additional phenomenon appears if the reading laser beam itself generates micro-discharges at the metallization ME / polycarbonate CD ₀ interface by photoelectric effect. Consequently, the corresponding electromagnetic wave propagates in the thickness of the compact disc CD and is then liable to be picked up by the reading circuits.

Indeed, the aforementioned phenomenon can be highlighted in the following way. When playing a CD compact disc, switching to pause mode for a few tens of seconds, followed by a new passage to playback mode, allows a much more defined and clearer signal to be highlighted , an impression of gain in the low frequencies and an appreciation of better level sound planes being clearly perceptible. In pause mode, the reading laser beam scanning the same reading range, the excitation of these same areas by the laser beam leads to exhaustion of the MDI phenomenon, which of course reduces the parasitic phenomena associated with the latter.

The main phenomena which come into play in the generation of MDI during the rotation of a recording-reading medium of type CD with optical reading are:

- electrostatic discharges due to the friction of the insulating surface of the CD support with air; - the photoelectric effect of the laser beam on the aluminum layer, the metallization, carrying the digital information.

Tests and observations have made it possible to conclude that the latter phenomenon is predominant. In fact, treatments of CD media with purely anti-static products give variable results depending on the player, while devices for protection against MDI by electromagnetic absorbent film conforming to the object of the present invention give very consistent subjective results. , regardless of the type of player, including reverse readers.

This preponderance of photoelectric effects is explained by the material structure of the CD medium. In general, the reading face CDi is formed by a thin aluminized layer constituting the metallization ME, with a thickness of 0.6 to 0.8 nm (nanometer), deposited on the etched polycarbonate with a thickness of 0.8 mm, metallization on which a layer of epoxy varnish with a thickness of 7 to 8 μm is formed.

The metallization ME, of extremely thin thickness - a lighted electric bulb is visible by transparency through the latter - does not constitute a reflective screen for electromagnetic waves. For this reason, the major part of the electromagnetic waves associated with the MDI phenomena induced by photoelectric effect is in fact transmitted by the unread surface CD ₂ of the support CD.

In addition, these electromagnetic waves only depend on the CD medium and the reading laser beam. The corresponding electromagnetic energy cannot be PC17FR99 / 02300

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absorbed in the material making up the CD support and is evacuated via the free surfaces of the CD support, ie:

- above and below for conventional readers; - on the surface read for readers with TEAC and reverse PIONEER type reading;

- on the side for all the readers.

Consequently, the electromagnetic wave associated with MDI phenomena thus disturbs nearby analog circuits, following a classic process of this type of phenomenon.

It therefore appears essential to cause the most complete possible absorption of the electromagnetic wave associated with MDI phenomena at the level of the CD supports.

Different types of electromagnetic absorbent veil have thus been able to be implemented, these protective elements proving to be particularly effective: a) Bristol board disc coated on both sides with a texture of non-woven silver type with conductive polymer, marketed by the company SCHLEGEL BVA under the reference N MP.61027. b) protective element, constituted by an electromagnetic absorbent veil in the form of a disc, constituted by a non-woven copper texture sold by the company SCHLEGEL BVA under the reference IWCO.60830. c) absorbent veil disc, constituted by a flexible conductive polymer film.

Different materials have been the subject of particularly conclusive tests for the use of absorbent fleece discs, ie in the form of a disc 1 e- fectively superimposed on the optical disc CD as shown in FIG. 3b, or in the form of a disc attached for example on the reading face side on the external face of the polycarbonate layer CD ₀ , layer l as also shown in FIG. 3b .

Production of disc 1 superimposed on the compact disc CD:

- nickel-copper non-woven texture, sold under the brand FLECTRON, referenced 3027-217, having a thickness of 0.487 mm, with an electrical surface resistance of 1 ohm per square, product distributed by the APM, 3481 Rider Trail South, Saint-Louis MO 63045, USA.

- flexible PVC disc, G406AS-ELSON / DC manufactured by SEKISUI CHEMICALS, under the reference SOFT PVC G406-AS, with an area resistance between 10 ⁸ and 10 ⁹ ohms / square for thicknesses of 0.1, 0.3 and 0.5 mm.

- absorbent fleece disc made from a copper non-woven or silver-nickel non-woven, referenced CO.60830 and N MP 61027 respectively, manufactured by the company SCHLEGEL BVA. This disc can be used, either for compact discs with optical reading, or for microgrooves.

Regarding the implementation of the flexible PVC absorbent disc marketed by the company SEKISUI CHEMICALS, these absorbent veil discs can be kept permanently on each optical disc, or, if necessary, used on a case-by-case basis.

With regard to absorbent webs produced in the form of electromagnetic absorbent films, it is indicated that these can be used on any digital disc with optical reading, DSD disc or DVD. In such a case, the aforementioned digital disks can then be coated with an intrinsic semiconductor product in the last stages of their treatment by simple spraying, deposition and then centrifugation for example. A particularly advantageous product appears to be the semiconductor product produced and marketed under the brand name BAYTRON by the company BAYER CHEMIE in Germany.

This product has the advantage of being transparent, very stable and insensitive to ultraviolet radiation, while the surface resistance can be adjusted over large ranges of values.

Specific tests implemented using the aforementioned BAYTRON product have shown that the best results are obtained by processing the so-called label side corresponding to the CD _{2 side} opposite the reading side, in order to produce a film bearing the reference 1 in FIG. 3b, as well as by the treatment of the free surface of the polycarbonate CD ₀ in order to produce the film l as shown in FIG. 3b. The film is transparent to the wavelength of the reading laser beam.

Under these conditions, the optimal resistivity of the films thus produced is close to 0.68 ohm / m, which corresponds to a resistance of 0.68 × 10 ⁶ ohm per square for a thickness of 1 μm.

In any event, it is possible to act on the intrinsic resistivity of the aforementioned BAYTRON material, on the quantity deposited, on the speed of rotation of the disc to ensure for example a correct diffusion of the film over the entire protected area, as well as the duration of this rotation.

Finally, as shown in FIG. 3c, the protection device, object of the present invention, can advantageously comprise, in addition to the aforementioned electromagnetic absorbent veil disc, bearing the reference 1, as in FIG. 3b, a device electrically conductive, referenced ₂₀ , in electrical contact via conductive elements 2χ with the absorbent web disc 1, the electrically conductive device assembly 2 _. and conductive elements

being connected to a damping resistor RT to earth for example, in order to ensure the evacuation of static electrical charges stored in the vicinity of the electromagnetic absorbent web 1. It is understood in particular that the assembly constituted by the electrically conductive device 2 ₀ and the conductive elements 2ι directly in contact with the disc in electromagnetic absorbent web 1 can be articulated around an axis 2 _{3 in} order to allow the adapted positioning of the assembly, which can then be aligned on one of the spokes of the CD compact disc.

Other embodiments of the absorbent veil disc, in accordance with the object of the present invention, as represented in FIG. 3d, can consist in providing a first electromagnetic absorbent veil disc, bearing the reference l ', constituted by a fabric or texture as mentioned previously in the description, on which is superimposed an absorbent veil disc, bearing the reference 1. Depending on the nature of the materials retained, the superposition of a first and a second absorbent fleece disc has also been shown to be satisfactory.

A particularly advantageous embodiment of a multilayer absorbent web disc, in accordance with the object of the present invention, is described in relation to FIG. 3e.

According to the aforementioned figure, the absorbent web 1 is in fact formed by a plurality of electromagnetic absorbent webs la, lb, le, ld, superimposed so as to form a multi-layer composite absorbent web. According to a particularly remarkable aspect, each successive electromagnetic absorbent veil, la to ld, has an electrical resistivity pa, pb, pc, pd increasing from the electromagnetic absorbent contact veil la, intended to come into physical contact with the support d 'recording. Thus, the external electromagnetic absorbent veil ld, opposite the electromagnetic absorbent veil la in the sandwich structure thus produced, is constituted by a material that is substantially electrically insulating, the resistivity pd of which is greater than 10 ⁸ Ω x m.

In a preferred embodiment, the electromagnetic absorbent veil 1a consisted of a non-woven ISOWAVE copper marketed by the company SCHLEGEL BVA under the reference IWCO.60830. This electromagnetic absorbent veil had an electrical resistivity pa = 0.04 10 ^-3 Ω xm, that is a surface resistance of 0.04 Ω per square for a thickness of about 0.1 mm. The electromagnetic absorbent veil lb was formed by a non-woven silver marketed by the company SCHLEGEL BVA under the reference NWMP 61027 and had an electrical resistivity pb = 0.25 10 ^{~ 3} Ω xm, i.e. a surface resistance of 0.5 Ω per square for a thickness of approximately 0.1 mm. The electromagnetic absorbent sheet le consisted of a dissipative PVC material with a pc resistivity of between 2 10 ^{~ 3} and 3 10 ^"3 Ω xm for a thickness of 0.3 to 0.5 mm. The material used was the product marketed by SEKISUI CHEMICALS under the reference G406 AS-ELSON / DC The electromagnetic absorbent veil ld consisted of a polypropylene plastic sheet with a thickness of 0.1 mm and a resistivity pd> 10 ⁸ Ω x m.

With regard to the use of multi-layer electromagnetic absorbent sheets, it is indicated that the sheets of the aforementioned materials have been superimposed and then assembled using an aerosol adhesive, by pressing, then cut to the dimensions of a recording medium, such as '' a CD disc, outside diameter 12 cm, inside diameter 16 mm. Following experiments, it appeared advantageous not to put the protective device and the CD disc in direct contact, but to interpose an insulating sheet of polycarbonate or polypropylene type, a material commonly used with overhead projectors, of thick between 50 and 150 μm. Furthermore, as shown in FIG. 3f, the combination of absorbent sheets of different resistivities as described above can be replaced by a stack of 3 to 5 sheets of SCHLEGEL BVA non-woven absorbent copper, ref. I CO.60830 or SCHLEGEL BVA absorbent non-woven silver, ref. NWMP.61027.

In this case, 4 sheets of non-woven fabric 1a, 1b, 1c, 1d being represented in FIG. 3f, the different layers are bonded using a permanent adhesive in aerosol. A clear improvement is obtained:

- either by replacing a layer of non-woven copper with a carbon fleece veil,

- either by depositing a very small quantity or veil of graphite at the copper-copper interfaces. This veil is represented by hatching between the layers la, le; la, lb; lb, ld in Figure 3f. The layers la, lb, le, ld absorbent copper SCHLEGEL BVA, IWCO.60830 had a surface resistance of 0.05 ohm per square and a thickness of 0.1 mm.

The variety of absorbent materials thus used makes it possible to widen the absorption band for the waves emitted. Similarly, the interposition of an insulating layer le between the CD disc and the first conductive layer ld of the device, object of the invention, leads to creating an interval where the emitted wave can be propagated by undergoing multiple reflections and absorptions. , which considerably attenuates it. The layers le and lf are thus insulating, 0.1 mm thick. According to a variant, one or other of the layers la or lb can be replaced by a non-woven silver SCHLEGEL BVA isowave ref. NWMP.61027 or by a graphite veil.

Another example of implementation of the device for protecting an electrical circuit against MDIs, in accordance with the object of the present invention, more particularly adapted to the protection of a transducer electromagnetic such as a loudspeaker used in a sound reproduction device of an audio recording and / or video frequencies, will now be described in connection with FIGS. 4a and 4b. As shown, in section, in the aforementioned figures, it is recalled that a loudspeaker is formed by a cylinder head, denoted SH, provided with an air gap E in which a mobile electric coil Co can move, this mobile electric coil being associated with a membrane M, the assembly thus formed constituting an audiofrequency transducer such as a loudspeaker.

In such a case, the protection device, object of the present invention, makes it possible to protect the moving winding Co against the phenomenon of MDI. For this purpose, the aforementioned device is constituted by a protective coating formed by an electromagnetic absorbent veil, bearing the reference l _a , as described above, and further thermoformed on the walls of the air gap E of the cylinder head SH, as well as 'an absorbent veil, bearing the reference l _b applied, and if necessary thermoformed, on the wall of the membrane M in particular in the vicinity of the moving winding Co.

In addition, the support for the mobile electrical Co winding can also be formed by means of the electromagnetic absorbent veil bearing in this case, in FIG. 4b, the reference 1.

It should be remembered that the moving coils Co of the loudspeakers are subjected to the vibrations they generate and are therefore a considerable privileged source of MDI phenomena. If necessary, it is also possible to cover the part called salad bowl Sa allowing the tensioning of the membrane M. It is the same with regard to the cylinder head SH when the magnet used, constituent of this cylinder head, n is not electrically conductive, in particular in the case where it is made of ferrite.

When, in addition, in the case of FIG. 4b, the support of the voice coil Co is produced from an electromagnetic absorbent veil, bearing the reference 1, the membrane M itself can also be produced from such a material, in order to allow the drainage of the static charges which appear on the surface of this membrane M and which, consequently, modify its sound by RAHBECK effect. In an alternative embodiment, it is indicated that the membrane M can also be covered with a veil of semiconductor product such as the BAYTRON product previously mentioned in the description.

Another application of the devices for protection against MDI phenomena, in accordance with the object of the present invention, for the protection of vibrating organs such as motors or transformers used in an apparatus for reading an audio recording and / or video frequencies, will now be given in connection with FIGS. 5a and 5b.

In FIG. 5a, there is shown, in section, a motor for driving a reading medium such as a compact disc for example, this motor conventionally comprising, in a carcass Ca, a stator winding Stat, a rotor winding Ro and connection and supply wires for the AStat stator and the Aro rotor. A tree transmission ensures the training of a capstan, itself adapted to the drive of the recording medium.

In such a case, it is indicated that the MDI phenomena are increased in considerable proportions by triboelectric effect, that is to say at the level of the interfaces subjected to vibrations of all origins, in particular electromagnetic and / or sound. This is the case of transformers and motors, which radiate parasitic electromagnetic energy through the external surface of their windings in particular.

As shown in FIG. 5a, the protection device according to the invention comprises a protective element 1, which can then be thermoformed around the motor, so as to encapsulate the latter by the aforementioned protective element. In addition, and in a nonlimiting manner, the protective veil thus formed can be connected to the ground by a damping impedance RT. This can be made up of a resistance of 1.5 MΩ and an earth choke of 2.5 mH for example. Similarly, the power cables of these motors can be screened under conditions which will be described later in the description.

With regard to transformers, the parasitic radiation phenomenon is the same, and the transformer carcass shown in FIG. 5b can, in the same way, be provided with a protective element 1 constituting an encapsulation of the assembly, as shown in Figure 5b. This encapsulation can then be carried out by thermoforming in a similar manner. In addition, a metallic fabric ME can be superimposed on the encapsulating veil. lation 1, this metallic textile then being connected to earth by the above-mentioned damping impedance. Although not shown in FIG. 5b, the same measure can be taken for the protection of the transformers. Another application of the devices for protection against MDI phenomena, in accordance with the object of the present invention, relates to the protection of boxes of electronic devices, in particular of devices used in the composition of a HiFi system. Such an application relates, on the one hand, to the metal boxes, as shown in FIG. 6a, on the other hand, to the electrically insulating boxes, as shown in FIG. 6b, or also to the cable entries in the boxes or boxes of any type, as shown in Figure 6c.

In the case of a metal box, as shown in FIG. 6a, these boxes or boxes can contain a device for reading an audio and / or video frequency recording from a signal or data recording medium. mobile audio and / or video frequencies driven by a motor, a sound amplification and restitution device for these audio and / or video frequencies signals, the device for protecting these electronic circuits against MDI phenomena comprises at least one protective coating, denoted 1, formed by an electromagnetic absorbent veil, as described previously in the description. As shown in partial cutaway perspective in FIG. 6a, the electromagnetic absorbent sheet 1 is placed on the internal face of the box. The box being electrically conductive, in the embodiment of FIG. 6a, this the latter is also electrically connected to earth via an RT damping impedance. The electromagnetic absorbent veil 1 thus makes it possible to prevent the interface micro-discharges generated by the parts of the electrical circuits contained inside the boxes from being thus collected by others, the propagation of the electromagnetic wave associated with these phenomena being thus substantially suppressed.

In the case of electrically insulating boxes or boxes, as shown in FIG. 6b, in addition to an internal coating 1, as shown in the above-mentioned figure, it appeared particularly advantageous to provide an external coating, total or partial, this external coating which eliminates static electric charges present on the surface of the cabinet in question. When the box is made of semiconductor material such as a plastic loaded with carbon for example, the external coating can then be eliminated, these boxes making it possible to remove static charges and therefore to reduce the MDI type phenomena which are associated with them.

As regards the materials capable of being used to produce the above-mentioned internal coatings 1 or external coatings 1, it is indicated that all of the materials previously mentioned in the description can be used. However, in an advantageous embodiment, it is indicated that the production of a semiconductor film using the BAYTRON product from the company BAYER CHEMIE has made it possible to obtain particularly significant results. The semiconductor film thus produced on the internal face of the electrical insulating box was produced by spraying of the BAYTRON product considered, using a film of thickness not exceeding 10 to 20 μm.

Finally, a particularly advantageous application of the protection device, object of the present invention, relates, as shown in FIG. 6c, to the grommets constituting the cable entries in the insulating and / or conducting boxes. Indeed, the electromagnetic wave associated with MDI phenomena propagates as a surface wave at the insulator / air interface of the conductors. The implementation of such a grommet can be carried out in the following manner: when the box is provided with a box body COF and a cover COU covering this box body, the gap between the closed cover and the box body constitutes a grommet for cables such as flat cables comprising for example at least the flat cable CP, as shown in section in FIG. 6c, a covering of this flat cable formed by an electromagnetic absorbent veil , bearing the reference 1, formed by an electromagnetic absorbent veil, and an elastic joint JE coating the assembly constituted by the flat cable CP, the coating 1. This elastic joint JE makes it possible to ensure the seal between the body of the COF box and the COU cover.

The electromagnetic wave associated with the phenomena of interface micro-discharges is thus absorbed on arrival in a housing by the coating 1, which makes it possible to reduce the corresponding level of radiation. The grommet described in connection with FIG. 6c appears particularly advantageous when the cable CP is a cable sold under the brand FLATLINE, consisting of copper ribbons coated with polytetrafluoroethylene coating.

Another particularly advantageous application of a device for protection against MDI phenomena of which an electrical circuit is likely to be the seat, will now be described in the case where this electrical circuit constitutes a printed circuit board, in relation to FIGS. 7a at 7c.

In FIG. 7a, substantially the same elements are shown as in the case of FIG. 1 previously described in the description. It is understood in particular that the printed circuit board PCB has a first face, on which the components are mounted, and a second face, opposite the first face, comprising the printed circuits, and therefore the metallizations, to which these components are connected.

In the case of the more specific embodiment represented in FIG. 7a, the device for protection against the phenomena of interface micro-discharges, object of the present invention, comprises a protective element formed by an electromagnetic absorbent veil as described previously in the description. , this protective element bearing the reference 1.

While on the upper part, comprising the components, the protective element can be formed by a simple electromagnetic absorbent veil, as described previously with FIG. 1, in the lower part, on the metallization side, the electromagnetic absorbent veil 1 can be advantageously made up, not only of the veil itself absorbing electromagnetic bearing the reference 1_, but also a layer of insulating material 1 ₂ affixed on the metallization side.

More specifically, it is indicated that the layer of insulating material 1 ₂ may in fact be constituted by a semiconductor material of sufficiently low resistivity not to cause the short circuit of the metallizations, but of sufficiently high conductivity to ensure proper flow of electrical charges and thus reduce the phenomenon of interface micro-discharges and propagation of the electromagnetic wave associated with them. Under these conditions, the protective element in the lower part of the PCB printed circuit shown in Figure 7a is formed by the protective veil itself 1 ₀ and the insulating or semiconductor layer 1 ₂ above. This layer can for example be produced by spraying a layer or film of BAYTRON product manufactured by the company BAYER CHEMIE.

In addition to the structure shown in FIG. 7a, a specific printed circuit board, allowing the implementation of audio frequency components in an apparatus for reproduction and amplification of audio and / or video signals, comprising, integrated in this board, a device for protection according to the object of the present invention will now be described in connection with FIG. 7b.

As shown in section in the aforementioned figure, the printed circuit board advantageously comprises an elementary printed circuit board, denoted PCB, comprising a first face free of printed circuits, the upper face in FIG. 7b, and a second face , opposite this first face and corn- carrying the printed circuits considered, the underside of this printed circuit board PCB shown in FIG. 7b.

In addition, constituting a device for protection against MDI phenomena, the printed circuit board comprises an electromagnetic absorbent veil, bearing the reference 1, as described previously in the description, this veil being placed on the first face, upper face, of the basic printed circuit board PCB.

Finally, an elementary plate, denoted IB, of electrically insulating material, also comprising a first and a second face, is superimposed on the electromagnetic absorbent veil 1, the second face of the elementary plate IB being placed on the electromagnetic absorbent veil 1 The assembly thus formed by the elementary printed circuit board PCB, the electromagnetic absorbent web 1 and the elementary plate IB, forms a sandwich structure. The first face of the elementary wafer made of insulating material referenced IB, of this sandwich structure, is intended to receive the audio frequency components, while the second face of the elementary printed circuit board PCB comprising the printed circuits, is intended to receive the connection of the audio frequency components to these printed circuits. The electromagnetic absorbent sheet 1 consisting of a metallic textile or, if necessary, a non-woven fabric, forming the above-mentioned sandwich structure, is then laminated between the two PCB and IB wafers. Preferably, the PCB and IB boards can be made of polyethylene. PC17FR99 / 02300

36

trafluoroethylene, a material that offers good resistance to interface micro-discharges.

The sandwich structure thus obtained, as shown in FIG. 7b, can then be stabilized by pressing or scaling, optionally followed by baking, in order to ensure sintering of the polytetrafluoroethylene. The assembly can then be accompanied by a coating of a semiconductor film from the BAYTRON product previously mentioned in the description. The semiconductor film can be affixed to either of the aforementioned faces of the sandwich structure, the upper face or the lower face.

This latter embodiment is shown in FIG. 7c in which the film attached to the upper face of the aforementioned sandwich structure bears the reference l ′ and therefore corresponds to a semiconductor film attached under the conditions mentioned above. In the same way, and in an advantageous embodiment, it is indicated that the upper face of the elementary printed circuit board PCB can be separated from the electromagnetic absorbent sheet itself separating the first elementary printed circuit board PCB from the board in insulating material IB via a layer or film of semiconductor material, also bearing the reference l 'because corresponding to a material of the same kind as the layer l' previously mentioned and represented on the upper face of the sandwich structure in Figure 7c. The second layer of semiconductor material 1 ′ is then affixed to the upper face of the elementary printed circuit board PCB and thus separates this upper face from the semi-absorbent web. driver 1 above. The assembly thus produced can be subjected to the aforementioned scaling and sintering operations.

Another particularly remarkable application of a device for protecting against micro-discharges from the interface of an electrical circuit, in accordance with the object of the present invention, will now be described in connection with FIGS. 8a to 8c relative to connection cables of apparatus for reading an audio and / or video frequency recording from a medium for recording signals or audio and / or video frequencies, apparatus for amplifying these signals or audio data and / or video frequencies, and audio reproduction of these signals and audio and / or video frequencies.

In general, it is indicated that the cables likely to benefit from the installation of a protection device, in accordance with the object of the present invention, can be cables substantially of any kind such as coaxial cables, as well as shown in Figures 8a and 8b, or flat cables such as FLATLINE cables as shown in Figure 8c.

In all cases, the cable comprises, on the peripheral face of the latter, a coating bearing the reference 1, formed by an electromagnetic absorbent veil as described previously in the description. In the case of FIG. 8a, a coaxial cable was wrapped from an electromagnetic absorbent veil constituted by a woven or non-woven material as described above in the description, this veil being shaped and cut out in the form of strips of given given length. The wrapping is carried out by covering the parts of tape to ensure total recovery of the whole. The junction points of the overlapping strip parts can then be subjected to a spot welding process or the like, in order to maintain the cohesion of the assembly. In the case of FIG. 8b, the recovery of the entire coaxial cable is carried out from a longitudinal winding of the material, folding along the edges of a generator of the external part of the coaxial cable considered, and welding of the two raised edges thus formed.

In the case of a flat cable, as shown in FIG. 8c, the edges of the covering are simply overlapped and fixed by welding, for example.

In addition to the previous embodiments described in FIGS. 8a to 8c relative to electric or electronic cables, it is indicated, in a particularly advantageous embodiment, that it is possible to produce the conductors themselves from a metallic textile , provided that the overall resistance obtained is sufficiently low.

Finally, the bare conductors used for wiring or inductance in HiFi installation circuits can be covered with metallic textile by wrapping or wrapping, or any other suitable method, as described in connection with the figures. 8a to 8c.

Another remarkable application of the devices for protection against the MDI phenomena of the electrical circuits inherent in the mode of propagation of the electromagnetic wave associated with these phenomena will now be described in conjunction with FIGS. 9a to 9h. Indeed, given the impulse nature of these MDI phenomena, the parasites and the electromagnetic wave associated with these phenomena occupy a frequency band whose lower limit is between 0.1 and 10 GHz.

The filtering of the parasitic currents thus generated is difficult because the conventional methods by inductance or ferrite are substantially inoperative from approximately 1 GHz. Indeed, the stray capacitances of the coils where the skin effect in the ferrites reduce any inductance effect from a critical frequency corresponding most often to the low threshold of MDI phenomena, that is to say of around 1 GHz.

In order to reduce the aforementioned drawback, the device for protection against the MDI phenomena of an electrical circuit, in accordance with the object of the present invention, can also consist, from the electromagnetic absorbent veil previously mentioned in the description, to constitute a protection circuit proper, associated with the electrical circuit to be protected.

For this purpose, as shown in FIG. 9a, the aforementioned electromagnetic absorbent sheet, bearing the reference 1, can then advantageously be provided with an electrical input connection, denoted Ci, and an electrical outlet connection, denoted Cost .

Under these conditions, the electromagnetic absorbent sheet 1, the input connection and the output connection form a transmission line with very low attenuation below the cut-off frequency thereof and a transmission line with very high attenuation at from and beyond this cutoff frequency. Of course, the absorption of the electromagnetic wave associated with the MDI phenomena being a function of the overall length of the transmission line thus formed, it is advantageous, in a preferred embodiment, to wind the electromagnetic absorbent veil 1 on itself in order to reduce the ohmic resistance and to increase the length of the path for electromagnetic wave ^¬ gnétique and absorption thereof while reducing the overall size of the component thus produced. The aforementioned component then has the following properties:

- absence of internal parasitic capacity as in the case of turns during the implementation of a conventional self-induction; - skin effect reduced, because of the large resistivity of the material used, which is understood by ^¬ be 4 x 10 ^"6 Ω xm and 50 x ^{10" 6} Ω xm;

- operation similar to that of a very weak attenuation line from the cut-off frequency thereof.

In FIG. 9b, the transfer function of such a component is shown when the electromagnetic absorbent veil was a silver woven fabric, sold by the company SCHLEGEL BVA. This transfer function, represented in logarithmic impedance / frequency coordinates, clearly highlights the characteristics of the aforementioned component for which, for a frequency band between 0 kHz and 15 MHz, the abscissa axis being graduated in frequencies, the impedance of this component varies substantially linearly in a range of values between 0.024 ohm and 00

41

20 ohms, while from a frequency of 15 MHz, the growth of the impedance of the aforementioned component is substantially exponential as a function of the frequency.

In a preferred embodiment shown in section in FIG. 9c, such a component is constituted by a ribbon wound on itself to form a substantially cylindrical element such as a sleeve MA, the electrical input connection Ci and the Cost output electrical connection being formed at the opposite end of the aforementioned cylindrical member or sleeve.

For the implementation of this type of component, it is indicated that the winding can be made from a woven fabric or nonwoven tape sold by the so ^¬ ciety SCHLEGEL mentioned above, corresponding to a texture formed from son of silver 5 μm in diameter coated with conductive polymer.

The length of the tape or ribbon used for winding can vary from one to ten meters depending on the final resistance to be obtained. The table below gives the value of the approximate resistances obtained as a function of the length of the ribbon used.

Length (meters) Resistance (ohms) 2 0.035

4 0.015

10 0.005

The resistance value indicated corresponds to a resistance value measured at the line cutoff frequency as shown in FIG. 9b. Finally, the ends of the sleeve thus formed can be tied using a copper wire or an electrically conductive wire, in order to ensure the connections of the aforementioned input and output connections. The aforementioned ligatures or input / output connections can then advantageously be protected by means of encapsulation sheaths, denoted Gi and Go.

Resistances of larger values can be obtained by using shorter lengths of electromagnetic absorbent web or, if necessary, by placing several elements in series.

Another embodiment of a component constituting a protection device in accordance with the object of the present invention, but more particularly adapted to the implementation of a component itself free of parasitic electromagnetic radiation or to the removal of the latter will now be described in connection with FIG. 9d. In FIG. 9d, there are substantially the same elements as in the case of FIG. 9c, these same elements having the same references.

In addition to the input / output connector elements Ci, Cost and sleeve MA, the input sheaths Gi and output Go can be replaced by a single sheath, denoted Gi in FIG. 9d. In addition, an electromagnetic absorbent veil 1 is provided, which surrounds the encapsulation sheath Gi, this electromagnetic absorbent veil 1 being provided with a connection so as to allow the connection of the latter to a reference electrical potential, such as that the earth potential for example, by means of an impedance depreciation, as mentioned previously in the description.

A second encapsulation sheath G ₂ can then be provided so as to ensure the cohesion of the assembly and the protection of the electromagnetic absorbent web 1, as shown in FIG. 9d.

In general, it is indicated that the input / output sheaths Gi, Go, the first and the second sheath d, G ₂ can be produced by a heat-shrinkable sheath.

With regard to the use of the components as shown in FIG. 9a and in particular 9c, 9d, it is indicated that these components can advantageously be installed at the critical locations of a HiFi installation, these critical locations being defined as the locations which appreciably allow the free propagation of the electromagnetic wave associated with MDI phenomena by propagation of surface waves type.

These critical points are for example: - the inputs and outputs of circuits,

- the input points of the power supplies on the electronic cards,

- the mains supply points, and in particular the supply to the power transformers, - the ends of the mains cables,

- feedback loops which are very sensitive to high frequency disturbances,

- the terminals of the loudspeakers in the loudspeakers, - the terminals of arrival and departure of the filters for distributing the aforementioned loudspeakers. Such components have been tested by introducing components of this type into a mains cable in series on the neutral and the phase. The implementation of these components immediately made it possible to perceive a better definition in the bass of the audio signal transmitted by the high fidelity device supplied from such circuits, this better definition being associated moreover with a great cleanliness of the sounds on all the audio spectrum. The tests were repeated with similar results with regard to the cables for connecting the sources such as tuners or optical disc players of the CD disc type, as well as for the amplifiers. Finally, a comparable test was carried out at the terminals of an acoustic enclosure, these components having been connected in series with the power supply wires of the loudspeakers, with comparable efficiency.

It is understood in particular that for the aforementioned components, with reference to FIG. 9b, the rapid growth of the impedance beyond the cutoff frequency at a rate of 60 dB per octave, explains the efficiency of the filtering of the wave electromagnetic associated with MDI phenomena. In addition to the metallic textiles previously mentioned in the description, it is indicated that, for the implementation of the aforementioned components, it is possible to envisage the use of gauzes loaded with powders or semiconductor mixtures formed by conductive particles. and insulating particles, where appropriate of semiconductor powders or mixtures, so that the overall conductivity of the assembly is satisfactory.

The aforementioned powders can be compressed graphite powders and metallic powders in air or insulating media such as semiconductor polymers.

It is indicated that the structures with compressed graphite resemble appreciably the resistances in agglomerated carbon whose musicality is unanimously recognized in the audiophile community.

In addition, the general structure obtained by the implementation of such powders is similar to that of the BRANLY coherer whose manifestations are linked to the phenomena of MDI. The above tests were carried out under the following conditions:

- sector filtering performed by insertion of two circuits, as shown in FIG. 9c or 9d, produced from a silver-nickel textile marketed by the company SCHLEGEL BVA under the reference NWMP 61027, a device being connected in series on the phase and a device being connected in series on the neutral and connected to a spectrum analyzer device. The above devices or components provide a 30 dB attenuation at 1.8 GHz.

- device consisting of two tubes containing graphite in compressed powder, the tube having a diameter of 27 mm and a length of 50 mm, 0.1476 ohm and 0.62 ohm. The loss obtained is 32 dB at 1.8 GHz and the absorption slope is faster, absorption peaks appearing for certain frequencies. The corn- behavior of such a component is similar to that of the BRANLY coherer.

- component made of fine steel wool, quality 0000, of length 75 mm and diameter 25 mm thus constituting a sleeve. There is a very regular attenuation throughout the spectrum between 0 and 1.8 GHz.

- filter consisting of two components in series on the phase, respectively the neutral, these two components consisting of a copper component and a silver-nickel component.

Under such conditions, the attenuation is increased at high frequency where it reaches 50 dB at 1.8 GHz while the attenuation is moderate but regular up to 900 MHz.

- Attenuation obtained with a filtering consisting of a copper component, a silver-nickel component and a steel wool component in series on the phase, respectively on the neutral of the power cable. The attenuation in this case reaches 58 dB at 1.8 GHz, which is very satisfactory, all the more so since the curve obtained is very regular. In this test configuration, the best listening tests have been highlighted. The complete diagram of the filtering device produced in the last mentioned test case is shown in Figure 9e. In this figure, PM denotes a male mains socket intended to be connected directly to the mains, CCu denotes a copper component as previously mentioned, CAg-Ni a silver-nickel component as previously mentioned, and CFe a steel wool component previously mentioned. The three components are connected in series and connected on the phase, respectively on the neutral, from the male plug PM and connected to a female plug PF intended to constitute an output plug connected to the spectrum analyzer. In addition, a box or box made up of a semiconductor material, or if necessary by an insulating material but coated with a semiconductor external coating, as mentioned previously in the description and referenced CO, carried out the maintenance of the the assembly, the external part or the semiconductor case CO being connected by a damping resistor to earth. The junction points of the components CCu, CAg-Ni and CFe were themselves connected to the semiconductor package CO or semiconductor coating of the latter, via a resistance circuit R of a few ohms and a capacitance C with a value of 25 pF. The RT earth resistance had a value of 1 MΩ and was accompanied by a SCHAFFNER type filter, referenced RE1-16 / 4.

With regard to the resistors R, it is indicated that the latter were produced by the filament of a vacuum bulb of low power, thus achieving a vacuum resistance free from phenomena of interface micro-discharges. Finally, semiconductor partitions, denoted Cl, made it possible to separate the filtering branch relating to the phase of the filtering branch relating to neutral.

In general, as mentioned previously in the description, it is indicated that the efficiency of the filtering, and therefore of the absorption of the electromagnetic wave associated with the phenomena of interface micro-discharges, is related to the length. signal path in the components or circuits as shown above in connection with FIGS. 9a to 9e.

A particular nonlimiting embodiment, making it possible to increase the aforementioned path length, without however unacceptably multiplying the number of components used in series, will now be described in connection with FIG. 9f.

As shown in the above-mentioned figure in longitudinal section, this component may advantageously comprise, in addition to an external sheath G of insulating material such as a heat-shrinkable material, a first component or circuit Ci and a second component or circuit C ₂ . The two circuits are connected in series but they are physically separated by means of a substantially cylindrical permanent magnet PM making it possible to generate a longitudinal magnetic excitation H, along the longitudinal axis of symmetry of the first and second component Ci, C ₂ . Under these conditions, the aforementioned magnetic field or excitation allows, on the currents, to exert a magnetron effect, the currents no longer propagating along substantially rectilinear lines, but, due to the magnetron effect thus produced, according to circular paths having as axis of symmetry the longitudinal axis of symmetry XX above. Under these conditions, it can be seen that the travel distance is considerably increased, which makes it possible to further increase the absorption of the electromagnetic wave associated with MDI phenomena. The circuits or components Ci, C ₂ as shown in FIG. 9f can be identical or distinct, in accordance with the embodiment previously mentioned with FIG. 9e. A end sealing Se is provided at each end of the sleeve G.

Finally, a device for protection against MDI phenomena constituting a filter of the capacitance resistance type with respect to the electromagnetic wave associated with these phenomena will now be described with reference to FIGS. 9g and 9h.

As shown in the abovementioned FIG. 9g, this device comprises a first cylindrical element, denoted Ei, formed by an electromagnetic absorbent veil ribbon wound on itself by means of one of the materials previously mentioned in the description and constituting a core central with an input connection and an output connection, denoted Cii respectively Coi. A succession of substantially tubular elements denoted E ₂ , E ₃ in FIG. 9g is also provided, these elements forming sleeves in successive overlap and alternately constituted by a tubular element of electrically insulating material I _x , I ₂ and a tubular element - Area formed by a winding of electromagnetic absorbent web ribbons E ₂ , E ₃ , as shown in the aforementioned Figure 9g. The tubular elements E ₂ , E ₃ are produced in a similar manner to the tubular element Ei. They are also provided with an input connection Ci ₂ , respectively Ci ₃ , and with an output connection Co ₂ , respectively Co ₃ .

The assembly thus formed by the first substantially cylindrical element Ei and the succession of tubular elements E ₂ , E ₃ and their insulating elements Ii, I ₂ has, in a cross section plane of this first cylindrical element Ei and of the succession tubular elements Iχ, E ₂ I _2f E ₃ , a succession of concentric circular zones made of electromagnetic absorbent veil tape and electrically insulating material respectively. All of these elements and the input connections Cii to Ci ₃ and output Coi to Co ₃ thus form a radioelectric filter with capacitance resistances making it possible to attenuate the electromagnetic wave associated with the phenomena of MDI.

An electrical diagram equivalent to the interface micro-discharge protection device according to the subject of the present invention, as shown in FIG. 9g, is represented in FIG. 9h. It is a symmetrical T filter made up of elementary T filters with capacity resistances. It is indicated that the capacities C shown in FIG. 9h correspond in fact in a particularly advantageous manner to capacities free from micro-discharges, which are immediately absorbed by the textile in the case where these interface micro-discharges occur.

Finally, a major application of a device for protecting an electrical circuit against MDI phenomena will now be described in the storage medium for video and / or audio data, this device being directly integrated into this support. We understand in particular the character of major importance of such an application insofar as the direct integration of the device for protecting an electrical circuit against MDI phenomena, in accordance with the object of the present invention, allows of course to appreciably suppress all creation and propagation of an electromagnetic wave associated with this phenomenon of micro-discharges and finally, to prevent the existence and appearance of corresponding parasites.

This embodiment applies in particular to an optical data recording / reading medium such as a CD disc for example. Such a recording medium, provided with its protection device in accordance with the object of the present invention, will now be described in connection with FIGS. 10a to 10e, which show a view in section along a radial plane of a support d CD-type recording with this device.

In the aforementioned figures, the same references represent the same elements as in the case of FIG. 3b for example. As shown in FIG. 10a, it is indicated that the optical data recording medium comprises a metal disk, or a metallization denoted ME, this metallization being associated with a face for recording / reading this data, constituted by a polycarbonate layer, denoted CD. In fact, it is understood that the polycarbonate layer CD ₀ has an etched face, which is metallized by the metallic layer ME, the metallic layer interface ME-etched face of the polycarbonate layer CD ₀ , constituting the reading face CDi of the aforementioned CD recording medium. The face of the metal disc or of the metallic layer ME in the form of a disc opposite to the recording face comprises a protective layer of varnish V and, where appropriate, an appropriate serigraphy. According to a particularly advantageous characteristic of the data recording / reading medium to optical reading in accordance with the subject of the present invention, it is indicated that the latter also comprises an electromagnetic absorbent veil, bearing the reference 1, whose surface electrical resistance is between 0.004 ohm per square and 0.5 ohm per square. This electromagnetic absorbent veil makes it possible to attenuate the MDI phenomena and the parasites associated with these phenomena. In FIG. 10a, the web 1 is shown superimposed on the layer of varnish V and permanently attached to the latter. It may therefore consist, as mentioned previously in the description, of a layer of semiconductor material such as the BAYTRON material sold by the company BAYER CHEMIE.

In another nonlimiting embodiment as shown in FIG. 10b, the optical data recording / reading medium provided with a device in accordance with the object of the present invention, comprises an electromagnetic absorbent sheet 1 constituted by a film of transparent semiconductor material formed on the polycarbonate layer CD ₀ on the free face of the latter, and therefore facing the recording / reading face denoted CDi.

In such an embodiment, it is indicated that the electromagnetic absorbent veil may consist of a film of BAYTRON material also marketed by the company BAYER CHEMIE. The conditions for forming such a film will be described later in the description.

According to an alternative embodiment of a data recording / reading medium with optical reading fitted with a device according to the object of the present invention as shown in FIG. 10c, it is indicated that the absorbent fleece 1 may consist of at least one metallized plastic film affixed to the face opposite to the recording / reading face, that is to say on the free face of the layer of varnish V. In such a mode of embodiment, it is indicated that the layer 1 of metallized conductive plastic material may be a plastic material marketed by SEKISUI CHEMICALS under the reference ELSON G406AS or SOFT PVC of thickness 0.5 or 0.3 mm.

In a preferred nonlimiting embodiment, the absorbent web 1 constituted by a metallized plastic film affixed to the opposite face of the recording / reading face, that is to say on the free face of the layer of varnish V, may further include, as shown in Figure lOd, a coating of electrically insulating material, bearing the reference 3. This insulating material, referenced 3, may be constituted by a very insulating synthetic sheet of thickness 0.1 to 0.3 mm and made of a material such as polypropylene. The fact of providing the layer of insulating material 3 superimposed on the layer of metallized conductive plastic material 1, as represented in FIG. 10d, in fact makes it possible to prevent the propagation of the electromagnetic wave associated with the phenomena of MDI, this electromagnetic wave being returned to the metallized conductive plastic layer 1 which ensures the absorption of the latter.

The improvement obtained by the implementation of the device and of the recording / reading medium as described in connection with FIG. 10d in accordance with the object of the present invention, is decisive insofar as comfort is thus obtained. unparalleled listening. Finally, in a particular nonlimiting embodiment, a specific sandwich structure, providing a plurality of semiconductor layers each playing the role of an electromagnetic absorbent veil, can be provided, as shown in FIG. 10e.

In this embodiment, on the one hand, the layer of varnish V, the free surface thereof, comprises a layer of semiconductor material 1, in a manner analogous to the embodiment of FIG. 10c, while in addition, the interface produced by metallization ME and the polycarbonate layer CD ₀ , that is to say the etched part thereof, is produced by means of a layer of semi-material conductor thin enough to ensure reading of the reading face CDi shown for this reason in the same way as in the case of FIG. 10c. It is thus understood that, due to the existence of the layers of semiconductor material 1, the, the layer allows it, on the one hand, to ensure the reading of the reading face CD _X that is that is to say during the illumination by a laser beam, the transmission of this laser beam by the etched face of the polycarbonate layer towards the metallization ME, then the reflection by the latter and the return towards the reading device in l absence of notorious attenuation, whereas this layer of semiconductor material allows it, on the other hand, to appreciably suppress the phenomenon of interface micro-discharges between the polycarbonate insulator and the metallization and, consequently, the phenomena of micro-discharges during excitation by the read laser beam. A preferred embodiment of an optical reading data recording-reading medium, such as a CD, in which the absorbent web has a multilayer structure, will now be described in conjunction with FIG. 10O.

According to the aforementioned f igure, the recording medium, in accordance with the object and of the present invention, further comprises a plurality of superimposed electromagnetic absorbent sails, denoted la, lb, le. The aforementioned electromagnetic absorbent webs are interposed between the metallization ME and the layer of varnish V, which can constitute the layer le.

According to a particularly remarkable characteristic of the aforementioned electromagnetic absorbent webs, these have an increasing electrical resistivity from the electromagnetic absorbent web of contact la, in physical contact with the surface CD ₂ opposite the reading face CDi. The electromagnetic absorbent veil can then be constituted by the layer of V epoxy varnish whose electrical resistivity is greater than 10 ⁸ Ω xm and serving as a final protective layer. In a specific embodiment, the electromagnetic absorbent sheet 1a, in physical contact with the metallization layer ME, was constituted by a layer of BAYTRON semiconductor polymer material referenced CCP105T, marketed by BAYER CHEMIE. This layer had a thickness of 7 μm after hardening and a surface resistance of 10 ³ to 10 ⁴ Ω per square. The electromagnetic absorbent veil 1b, in physical contact with the electromagnetic absorbent veil 1a, consisted of a layer of the above-mentioned BAYTRON semiconductor polymer material, of appreciably thick thickness but having after hardening an over-resistance. facie from 10 ⁸ to 10 ⁹ Ω per square. The variation in the surface resistance, decreasing variation, is obtained by diluting the aforementioned BAYTRON product and adapting the thickness accordingly. The method of implementing the successive layers of the multilayer structure will be described later in the description.

With regard to the manufacture of storage media in accordance with the object of the present invention, as described above in connection with FIGS. 10a to 10f, it is indicated, with reference to FIG. 11, that a preferred manufacturing process may consist, from a coded Ep test, of producing by molding, by injection of polycarbonate into an M mold, an engraved pancake GG made of polycarbonate, of depositing by metallic vapor deposition the metallization ME on the engraved face to constitute the CDi reading side, then deposit a layer of varnish on the metallization by centrifugation.

In accordance with the process which is the subject of the invention, a film of semiconductor material such as the BAYTRON material is then deposited on the layer of varnish V by centrifugation.

The centrifugation operation, more commonly called "spin coa ting" operation in Anglo-Saxon language in the corresponding technical field, consists in placing the engraved wafer GG provided with its metallization layer ME, provided with its layer of varnish V, on a TE rotary drive table. A nozzle A makes it possible to deposit, in the vicinity of the center of the engraved wafer GG, on the layer of varnish V, as shown in FIG. 11, a rod of semiconductor material BSC, while the drive table TE and the wafer engraved GG are moving rotation at low speed, less than or equal to four or five revolutions per minute for example. When the flange BSC is formed, the nozzle A is closed and the drive table TE and the engraved wafer GG are driven at high speed, greater than 1500 rpm in two seconds. The centrifugal force applied to the strand of BSC semiconductor material causes it to spread into a homogeneous layer over the entire surface of varnish V. Curing processes by crosslinking with UV radiation can be applied when the material MSC semiconductor used is a polymer such as BAYTRON. According to a first variant implementation of this method, the layer of varnish V is replaced directly by the layer of semiconductor material. According to a second variant of implementation of this method, a film of semiconductor material, such as BAYTRON material, is deposited on the free face, not etched, of the polycarbonate wafer GG. The deposition is carried out by centrifugation. According to a third variant implementation of this method, a film of semiconductor material is deposited during an intermediate step prior to the metallization step. The deposit is also made by centrifugation. According to a fourth variant implementation of this method, the deposition of the film of semiconductor material on the varnish layer V, or of the latter, is followed by a step of depositing a layer of material insulator, layer 3 shown in Figure lOd. It is indicated in particular that for the implementation of the aforementioned variants, the same process can be implemented on the ME metallization layer or on any suitable intermediate surface.

In particular, for the implementation of multi-layer electromagnetic absorbent webs, as shown in FIG. 10f, each layer of electromagnetic absorbent web can, as shown in FIG. 12a, be implemented by centrifugation, as described in relation to the Figure 11. After obtaining the layer, from an MSC semiconductor polymer material such as the above-mentioned BAYTRON, each layer 1a, 1b can then be subjected to a curing process by UV crosslinking for implementation. of the next superimposed layer, as shown in Figure 12b.

Claims

1. Device for protecting an electrical circuit against the phenomena of interface micro-discharges, generators of radio interference in audio frequencies, characterized in that it comprises at least one protective element formed by an electromagnetic absorbent film, the electrical resistivity is between 0.004 10 ^"3 Ω xm and 5 10 ^{" 3} Ω xm, said absorbent veil making it possible to attenuate the phenomena of interface micro-discharges.

2. Device according to claim 1, characterized in that said electromagnetic absorbent veil is constituted by a texture formed from organic fibers covered with an electrically conductive coating.

3. Device according to one of claims 1 or 2, characterized in that said electromagnetic absorbent web is formed by an electromagnetic absorbent film.

4. In a device for reading an audio and / or video frequency recording, from a rotary audio or video and / or video signal or data recording medium, a device for protection against the phenomenon of interface micro-discharges of electric circuits for reading this video or video signal or data recording medium comprising at least one disc in electromagnetic absorbent web, according to one of claims 1 to 3, said disc in electromagnetic absorbing web and said rotary recording medium - tif being superimposed.

5. In a device for reading an audio and / or video frequency recording, from a recording of rotary audio or video and / or video signals or data, a device for protecting the electrical circuits for reading this recording medium from audio and / or video signals or data, comprising:

a first disc in electromagnetic absorbent web, according to claim 4, and

- a second disc in absorbent veil, superimposed on the first.

6. In a device for reading an audio and / or video frequency recording, from a rotary recording medium for audio or video and / or video signals or data, a device for protection against the phenomenon of interface micro-discharges of electrical circuits for reading this video signal or data recording medium comprising at least one disc in electromagnetic absorbent web according to claim 4 or 5, characterized in that this device is formed by a plurality of superimposed electromagnetic absorbent webs, each web electromagnetic absorbent having increasing electrical resistivity from the electromagnetic contact absorbing veil intended to come into physical contact with said recording medium, the external electromagnetic absorbing veil, opposite to said electromagnetic contact absorbing veil, being made of a substantially electrically insulating material stick.

7. In an apparatus for reading an audio and / or video frequency recording from a recording medium of audio and / or video signals or data these rotary, a device for protecting the electrical circuits for reading this medium for recording signals or audio and / or video frequencies comprising: - at least one disc in electromagnetic absorbent web according to one of claims 4 to 6;

- An electrically conductive device, in electrical contact with said disc in electromagnetic absorbent web, said device making it possible to ensure the evacuation of static electric charges stored in the vicinity of said electromagnetic absorbent web.

8. In an apparatus for sound reproduction of an audio and / or videofrequency recording provided with at least one loudspeaker formed by a cylinder head provided with a gap and by a mobile electrical winding associated with a membrane, the assembly of the cylinder head provided with an air gap, the mobile electrical winding and the membrane forming an audio-frequency transducer of the loudspeaker type, a device for protecting the mobile winding against the phenomenon of interface micro-discharges comprising at least one protective coating formed by an electromagnetic absorbent sheet according to one of claims 1 to 4, thermoformed on the walls of the air gap of said cylinder head and on the wall of said membrane.

9. Device according to claim 8, characterized in that the support of said mobile electrical winding is formed by means of said electromagnetic absorbent web.

10. In an apparatus for playing an audio and / or video recording from a medium for recording audio and / or video signals or data mobile frequencies driven by a motor, respectively a sound amplification and restitution device of these audio and / or video signals or data provided with an electrical transducer or transformer, this motor, this transducer and this transformer being the seat mechanical vibrations capable of increasing, by triboelectric effect, the phenomena of interface micro-discharges, a device for protection against these phenomena of interface micro-discharges comprising a protective element formed by an electromagnetic absorbent veil, according to one of claims 1 at 3, this protective element being thermoformed around this motor, this transducer and this transformer respectively, so as to achieve an encapsulation of the latter by said protective element.

11. In an apparatus for reading an audio and / or videofrequency recording from a recording medium for audio signals and / or audio and / or videofrequency data driven by a motor, respectively a sound amplification and restitution apparatus of these audio and / or video signals or data, these amplification and sound reproduction playback devices being provided with electronic circuits contained in a box forming these devices, a device for protecting these electronic circuits against the phenomena of micro-discharges interface comprising at least one protective coating formed by an electromagnetic absorbent veil according to one of claims 1 to 3, this electromagnetic absorbent veil being placed on the internal face of said box.

12. Protective device according to claim 11, characterized in that the box being a box made of electrically conductive material, this box is also electrically connected to earth by means of a damping impedance.

13. Protective device according to claim 11, characterized in that, the box being a box made of electrically insulating material, this device also comprises at least one protective coating formed by an electromagnetic absorbent veil according to one of claims 1 to 3 , this electromagnetic absorbent veil being placed on the internal face of said box.

14. Device according to claim 11, characterized in that, said box being provided with a box body and a cover closing this box body, the gap between the closed cover and the box body constitutes a pass wires for flat cables comprising at least:

- the flat cable; - a coating of this flat cable formed by an electromagnetic absorbent veil according to one of claims 1 to 3;

- an elastic seal coating the assembly consisting of the flat cable and the covering, and ensuring the seal between said box body and the cover.

15. In an apparatus for amplifying and reproducing audio and / or video signals provided with audio frequency components mounted on at least one printed circuit board, this board comprising a first side on which these components are mounted and a second side , opposite the first side comprising the printed circuits to which these components are connected, a device for protection against the phenomena of interface micro-discharges comprising:

- a protective element formed by an electromagnetic absorbent veil, according to one of claims 1 to

3; and

a layer of insulating material covering said second face of the printed circuit board, said absorbent web forming a sheath surrounding the assembly formed by the printed circuit board and the layer of insulating material.

16. Printed circuit board for implementing audio frequency components in an apparatus for reproducing and amplifying audio and / or video signals, characterized in that it comprises:

a first elementary printed circuit board comprising a first face free of printed circuits and a second face, opposite this first face, and comprising the printed circuits; - an electromagnetic absorbent sheet according to one of claims 1 to 3, placed on the first face of said first elementary printed circuit board;

a second elementary plate of electrically insulating material, comprising a first and a second face, the second face of this second elementary plate being placed on the electromagnetic absorbent veil, the assembly formed by the first elementary plate, the electromagnetic absorbent veil and the second elementary plate forming a sandwich structure, the first face of the second plate elementary insulating material being intended to receive said audio frequency components, and the second face of said first elementary wafer being intended to receive the connection of these audio frequency components to these printed circuits.

17. A printed circuit board according to claim 16, characterized in that at least one of the two faces of the first or of the second elementary board comprises a film of semiconductor material.

18. Cable for connection of devices for reading an audio and / or video frequency recording from a medium for recording audio and / or video signals or data, for amplifying these signals or audio data and / or videofrequencies and sound reproduction of these audio and / or videofrequency signals or data, characterized in that this cable comprises, on the peripheral surface of the latter, a coating formed by an electromagnetic absorbent film according to one of claims 1 to 3.

19. Device according to one of claims 1 to

3, characterized in that said electromagnetic absorbent veil is provided with an electrical input connection and an electrical output connection, the electromagnetic absorbent veil, the input connection and the output connection forming a transmission line to very low attenuation below its cutoff frequency and a transmission line with very high attenuation from and beyond its cutoff frequency.

20. Device according to claim 19, characterized in that said electromagnetic absorbent web is constituted by a ribbon wound on itself to form a substantially cylindrical element, the electrical connection of input, respectively output, being formed at the opposite end of this cylindrical element.

21. Device according to claim 19, characterized in that it further comprises: a first encapsulation sheath surrounding the assembly formed by the substantially cylindrical element, the inlet connection and the outlet connection;

- An electromagnetic absorbent veil according to one of claims 1 to 3, surrounding said encapsulation sheath, this electromagnetic absorbent veil being intended to be electrically connected to a reference electrical potential; a second encapsulation sheath surrounding the assembly formed by this absorbent veil and this first encapsulation sheath.

22. Device according to one of claims 19 or 20, characterized in that it comprises:

- a first cylindrical element formed by a strip of electromagnetic absorbent web wound on itself and constituting a central core provided with an inlet connection and an outlet connection;

a succession of substantially tubular elements forming sleeves in successive overlap, these sleeves being alternately constituted by a tubular element made of electrically insulating material and a tubular element formed by a winding of electromagnetic absorbent web according to one of claims 1 to 3 , the assembly formed by the first substantially cylindrical element and the succession of substantially tubular elements having, in a cross section plane of this first substantially cylindrical element and from this succession of substantially tubular elements, a succession of concentric substantially circular zones of electromagnetic absorbent web and of electrically insulating material respectively, each sleeve constituted by a tubular element formed by a winding of absorbent web comprising a connection d input and output connection to form a resistance capacitance radio filter.

23. Optical reading data recording / reading support comprising a metal disc, comprising a recording / reading face of this data covered with a polycarbonate layer and the face of said metallic disc opposite this recording face. reading comprising a protective layer of varnish, characterized in that said recording medium further comprises an absorbent veil whose electrical resistivity is between 0.004 10 ^"3 Ω xm and 5 10 ^{" 3} Ω xm, said absorbent veil allowing to mitigate the phenomena of interface micro-discharges.

24. Optical reading data recording / reading medium according to claim 23, characterized in that said electromagnetic absorbent sheet consists of a film of transparent semiconductor material formed on the polycarbonate layer, facing of said recording-reading face.

25. optical reading data recording / reading medium according to one of claims 23 or 24, characterized in that said absorbent veil consists of at least one metallized plastic film affixed to said face opposite to said recording face -reading.

26. optical reading data recording / reading medium according to claim 25, characterized in that the free face of the metallized plastic film further comprises a coating of electrically insulating material.

27. optical reading data recording-reading medium according to claim 25, characterized in that said coating of insulating material is made of a material chosen from polyprolylene.

28. optical reading data recording / reading medium according to claim 23, characterized in that this recording medium further comprises a plurality of superimposed electromagnetic absorbent webs, each electromagnetic web having an increasing electrical resistivity from the web electromagnetic contact absorbent in physical contact with the face opposite to the reading face, the external electromagnetic absorbent web, opposite to said electromagnetic contact absorbing web, being made of a material that is substantially electrically insulating.

29. Method for manufacturing an optical reading data recording / reading medium, of the CD optical disc type, this recording / reading medium comprising a device for protecting an electrical circuit against the phenomena of micro-discharges of interface for generating radio interference in audio frequencies, according to one of claims 23 to 28, characterized in that this method consists at least: a) of molding, from an engraved test, a wafer engraved by polycarbonate injection; b) metallizing the etched side of this etched wafer to form a reading face of the data recording medium; c) depositing a layer of varnish on this metallization; d) depositing on the varnish layer a film of semiconductor material.

30. Method according to claim 29, characterized in that step c) is omitted, step d) consisting in depositing the film of semiconductor material being substituted for step c).

31. Method according to one of claims 29 or

30, characterized in that it also consists in depositing on the non-etched face, opposite the etched face, of said etched wafer a film of semiconductor material.

32. Method according to one of claims 29 to

31, characterized in that the latter further comprises a step a ') prior to metallization step b), said anterior step consisting in depositing a film of semiconductor material on the etched face of this etched wafer, l 'step b) of metallization being carried out on the film of semiconductor material deposited following the implementation of this previous step.

33. Method according to one of claims 29 to 32, characterized in that said step d) of depositing the film of semiconductor material on the layer of varnish, or in replacement of step c) is followed by a step of depositing a layer of insulating material.