WO2002005892A1

WO2002005892A1 - Textile fabrics with emf-attenuating materials

Info

Publication number: WO2002005892A1
Application number: PCT/EP2001/007996
Authority: WO
Inventors: Lutz-Henning Block
Original assignee: Mondobiotech AG
Current assignee: Relief Therapeutics International SA
Priority date: 2000-07-18
Filing date: 2001-07-11
Publication date: 2002-01-24
Anticipated expiration: 2003-01-18
Also published as: EP1174162A1; AU2001291671A1

Abstract

The invention relates to textile fabrics in general, but in particular to garments of any type, which contain materials which are capable of attenuating electromagnetic fields (EMF), and to their use for shielding high-frequency radiation (HF radiation). Fabrics of this type are consequently outstandingly suitable for attenuating or shielding radiation which emanates from equipment and devices emitting radio waves or microwaves, in particular mobile phones, hand-held phones or other radio-telephone systems, and their base stations.

Description

TEXTILE FABRICS WITH EMF-ATTENUATING MATERIALS

The invention relates to textile fabrics in general, but in particular to garments of any type which contain materials which are capable of attenuating electromagnetic fields (EMF), and to their use for shielding high-frequency radiation (HF radiation). Fabrics of this type are consequently outstandingly suitable for attenuating or shielding radiation which emanates from equipment and devices emitting radio waves or microwaves, in particular mobile phones, hand-held phones or other radio-telephone systems, and their base stations.

Radio waves and microwaves are classified as high-frequency electromagnetic radiation (HF radiation). While radio waves have a frequency of between 0.5 MHz and approximately 150 MHz (for example VHF: 88 - 108 MHz), the frequency range of microwaves extends from approximately 300 MHz to 300 GHz and consequently covers numerous currently used fields of application, in particular in communications. In the lower range of this frequency band (300 to approximately 890 MHz), television programmes (UHF range) are broadcast; radar devices operate in a frequency range of approximately 1 - 50 GHz, while domestic microwave appliances generate radiation generally between 2 - 4 GHz.

In addition to the so-called "C band" (400 - 600 MHz), modern mobile radio devices currently use in particular frequencies in three different bands: 890 - 960 MHz, approximately 1750 - 1850 MHz and approximately 1890 - 2000 MHz. A new generation of mobile cordless phones will transmit at a frequency of approximately 4000 MHz.

Radio telephone devices, such as CB radio ("walkie-talkies") or police radio generally operate in frequency ranges of radio waves, namely between approximately 20 and 80 MHz.

While in the past heavy and cumbersome devices were accessible only to a small group of persons, predominantly in military and non-public areas (police, customs etc.), in recent years increasingly smaller, lighter and less expensive mobile phones (hand-held phones) have found great appeal among an increasing number of members of the public for private and business use, especially since the development of full-coverage networks - a basic prerequisite for the commercialization of this technology - has been continually pushed ahead. At present, approximately 400 million such devices are in use worldwide, and their number will approximately double in three to four years.

Consequently, the microwave radiation, in particular in the range between 400 and 4500 MHz, will also increase considerably in everyday life. Mobile phones or radiotelephone devices of the type mentioned differ from most other everyday items of equipment which generate HF radiation in that they have to be carried or used on or in the direct vicinity of the body and the duration of the radiation exposure on the head and chest region in particular is sometimes considerable. The question whether health is endangered by the increasing HF radiation has been the subject of increased discussion recently.

HF fields are generally emitted by the antenna of the transmitting section. The electric and magnetic fields can, depending on the frequency, interact with the corresponding fields of electrically charged particles in the human body. Electrical charges also occur, however, in certain molecules/ions and for example on cell walls. Stimulations of nerves are based on changes of electric potentials at the synapses and the human brain itself generates measurable electric fields. All such charges or fields can under certain circumstances resonate with the external fields generated by HF radiation and bring about biological changes.

How deeply the HF radiation penetrates into biological tissue depends on the transmission frequency. At the currently customary mobile frequencies of approximately 890/960 or 1800/1900 MHz, the depth of penetration into the human body is several centimetres (more in the C band), with the higher-frequency systems of the new generation (1900 - 2070 and 2100 - 2300, UMTS) it is correspondingly less. In the case of high-frequency systems (over 10 GHz), such as radar devices, a depth of penetration of only 1 mm and below can be found. However, it is to be observed that evidence shows that during telephoning even the side of the head away from the antenna is exposed, and measurable radiation leaves the head again. Microwave radiation in the radio transmission range (television, mobile phones) produces in biological tissue in particular a more or less pronounced evolvement of heat. This evolvement of heat can even be physically perceived if the effect is intensive. Since the evolvement of heat leads at most to a local temperature increase of approximately 1°C, it is however unlikely to cause a serious pathological effect.

For some time, however, HF radiation effects which are based on non-thermal causes have also been discussed. In fact, there are widespread reports of in some cases unspecific health-related irritations, such as headaches, poor memory, fatigue, motor dysfunctions, dizziness, cardiac palpitations and feelings of being unwell associated with excessive use of mobile phones.

Partly contradictory investigations on animals exposed to permanent increased microwave radiation of an intensity usual for customary mobile phones reports of an increase in enzyme activities, high blood pressure, increase in brain current activity, changes in the permeability of the blood-brain barrier, changing of the REM phase, hormone production and the inducement of Alzheimer's symptoms and even the initiation of tumour growth. Although the energy of microwave radiation should not be enough to ionize atoms or break chemical bonds of molecules, findings have been published in which it has been found that the effect of HF radiation has caused an increase in the shortening of DNA chains in rats.

For all these investigations there is currently not yet any or any generally recognized rational, in particular because the level of radiation biologically absorbed due to HF radiation, predominantly in the microwave range, appears to be too low, according to current understanding, to explain the predicted, in some cases considerable effects mentioned. The level of radiation absorbed (specific absorption rate SAR, W/kg) may be considerable, however, in spite of a relatively low output power of the transmitter, in particular if the mobile telecommunication unit is used or carried for long periods in the switched-on state (continuous exposure). This is because the SAR takes into account not only the amounts of HF energy transmitted, but also the time in which this energy is transmitted to a certain mass of biological tissue. The SAR and its distribution in the body is dependent on many factors. Apart from the frequency, spatial and temporal changes of the field play a part. In addition, electrical properties and structures of the biological tissue which generate their own electromagnetic fields which can resonate with the external transmission field are of significance. For example, bone tissue absorbs the energy differently than muscle tissue with a good flow of blood through it. Individually different physiologies can also lead to different charging states and consequently interactions and changes in certain body regions and cells. The influence and interaction of local electric or electromagnetic mini-fields and micro-fields on biological or pathological changes have not been adequately investigated so far. An additional aggravating factor is that the SAR is not easy to record by measuring instruments. For this reason, derived field variables, such as the power flux density (W/m²) or the electric or magnetic field strength (V/m or A/m) are often used in practice, sometimes resulting in test arrangements and results which cannot be compared. For instance, an SAR of 1 - 4 W/kg, which is approximately the average value of the radiation absorption in the body of an adult when using a mobile phone (950 MHz), is equivalent to approximately 20 to 40 V/m.

Irrespective of the to some extent controversial and scientifically inconsistent position, it appears necessary to take precautionary measures for the use of mobile phones or other radio telephone units which transmit in the HF range generally in direct ^' proximity to the body, in order to avoid both verifiable yet often unspecific subjective symptoms and disorders possibly induced by HF radiation. The object of this invention was consequently to provide adequate protection for persons carrying or using ready-to-operate mobile phones in the direct proximity of their body. In this respect there is the problem that the obvious protection, that of shielding the devices themselves by the measures customary and known for this, cannot be realized, or not adequately, since the transmitting and receiving capacity is prevented or greatly impaired as a result. Consequently, the protection can only be provided on or at the user of the mobile phone.

The invention consequently concerns the use of fabrics based on textile fibres and at least one component which comprises a material which attenuates electromagnetic fields (EMF), for shielding radio- frequency (HF) radiation in the immediate vicinity of the human body which is emitted by cordless mobile phones and radio-telephone devices. According to the invention, this also includes that radiation which is emitted by the base stations or repeater units, even if they generally represent a risk only in the direct proximity of the transmission equipment/transmission masts.

HF radiation for the purposes of the invention covers electromagnetic radiation in the radio-wave range between 20 and 100 MHz, preferably between 20 and 50 MHz, in particular between 20 and 35 MHz, and also microwave radiation between 400 and 5000 MHz. The latter preferably covers the frequency bands from 400 to 650 MHz, 850 to 1000 MHz, 1500 to 2300 MHz and 3000 to 4500 MHz. Of particular interest among these are in turn the ranges of 880 to 960 MHz, 1750 to 1890 MHz and 1900 to 2300 MHz.

Consequently, the invention concerns in particular the said use for shielding microwave radiation in the range from 400 to 4500 MHz (mobile radio) and for shielding radio radiation in the range from 20 to 50 MHz (radio telephony/CB radio).

The fabrics according to the invention essentially comprise customary textile fibres and at least one further material component which is capable of fully or partially shielding electromagnetic fields generated by high-frequency radiation of the said frequencies. This fabric has, depending on the composition, an attenuation factor of 2 to 1000, preferably 5 to 500, in particular 5 to 100. Sometimes, attenuation factors of 2 to 15 are also already adequate, which makes only a small proportion (below 3%) of the EMF-shielding material necessary.

Referred to as the attenuation factor for the purposes of the invention is that factor by which the electric or magnetic field strength (and the variables indirectly related to it, see above) can be reduced by the material properties. An attenuation factor of, for example, 5 means that, for example, the field strength of a certain initial value (unattenuated) is reduced to a fifth on passing through the material according to the invention. The attenuation factor may also be converted to a power attenuation specified in decibels (dB). The power attenuation is in this case 10 times the decimal logarithm of the attenuation factor. A power attenuation of, for example, 30 dB corresponds to an attenuation factor of approximately 1000. Consequently, the invention concerns the use of corresponding fabrics which are characterized in that they have an EMF-attenuating material which brings about an attenuation factor of the fabric of between 2 and 1000, in particular between 5 and 100.

Metals, semiconductor materials or corresponding polymeric materials are suitable as EMF-attenuating materials.

In principle, all common known metals may be mentioned as metals according to the invention. Preferred are, however, in particular noble metals, that is to say those which have a positive value-of the normal potential εo (V) (in acid solution); these are, in particular, copper, silver, platinum or gold. Of the less preferred, but in principle suitable, base metals (negative εo), iron and nickel may be mentioned. According to the invention, alloys of the said noble metals, but also alloys of noble metals with base metals, are also ideally suited, thus for example Ag/Cu, Ag/Au, Au/Cu, Cu/Ni, Cu/Fe, Ag/Ni, Cu/Pt, Fe/Pt, Cu/Ag/Au and Cu/Fe/Ni alloys.

To be understood as semiconductor materials for the purposes of the invention are those materials which obtain their conductivity by defects existing in their crystal structure. These are, for example, materials which contain silicon, germanium, boron or selenium. Nonconductive materials which gain electrical conductivity by incorporation of dopants are also included according to the invention. Such materials and their preparation are sufficiently known and numerously described in the literature.

Considered as polymer materials for the purposes of the invention are polymeric materials which exhibit electrical conductivity or absorption of electromagnetic fields. These are generally polymers which have an increased number of hydrophilic groups. Examples of suitable materials are polyaniline, polypyrrole, polyacetylene, poly(para)phenylene or poly(ortho)toluidene, which if appropriate may likewise be doped. Further materials and their physical, in particular electromagnetic, properties are reported in detail in "Microwave Properties of Conductive Polymers" (Handbook of Organic Conductive Molecules and Polymers, Vol. 3, 1997, John Wiley & Sons). However, the invention preferably concerns use of corresponding fabrics which contain metal as the EMF-shielding material, the metal being copper, silver, gold, platinum or an alloy of these metals with one another or an alloy of these metals with other metals, preferably nickel and/or iron.

The invention relates also to preferred materials based on textile fibres and at least one component which comprises a material attenuating electromagnetic fields (EMF) for shielding high-frequency radiation, which is emitted by cordless mobile phones and radio-telephone devices, including their base stations, within a frequency range of 800 until 2300 MHz; said EMF- attenuating material having an electromagnetic attenuation factor between 20 and 1000, and is characterized in that it (i) essentially consists of noble metals or noble metal containing alloys or a polymer material, (ii) is connected to the textile fibres, and (iii) its amount is 5 - 15% related to the complete amount of fibres.

As one preferred embodiment, the EMF-attenuating material are fibres having a diameter of 10 - 50 μm which are woven with the textile fibres. As another preferred embodiment the EMF-attenuating material are particles which are distributed on or within the textile fibres or on or within carrier polymer fibres.

It is a further object of the invention to provide such materials for the use and manufacture of garments and textile fabrics which are especially effective in the immediate vicinity of the human body. Thus, the materials of the invention are suitable for the prevention of health damages caused by the specific high-frequency radiation, which is emitted by cordless mobile phones and radio-telephone devices, including their base stations.

The EMF-attenuating materials may be incorporated into or applied to the fabric in various ways. One possibility is to prepare the material in the form of fibres which are woven with the customary fabric fibres during production of the fabric. The fibres themselves may in this case be made completely of the material concerned, that is to say metal fibres, semiconductor-material fibres or polymer fibres. The material may, however, also be in the form of particles, for example flakes, beads or grid structures. These particles can then be incorporated directly onto or between the conventional fabric fibres. The particles may, however, also be accommodated initially in suitable carrier materials, for example conventional polymers, preferably those suitable for textiles, during the production of the said polymers. These carrier polymers charged with the said particles may either be drawn into fibres of their own, which are processed with the customary fabric fibres, or else they may serve as a coating material for the customary fabric fibres. Finally, the conventional fabric fibres may also be coated directly, i.e. without the use of an additional carrier material. The respective coating (for example by vapour deposition or spraying) takes place in this case by common techniques known in the textiles industry, it being possible for the individual fibres or else the finished fabric to be coated.

The EMF-attenuating material is preferably in the form of fibres which are interwoven with the customary fabric fibres during the production of the fabric.

If the EMF-attenuating material is in the form of fibres or particles which are embedded in carrier materials drawn into fibres, the diameter of these fibres should be, according to the invention, 10 to 100 μm, preferably 10 to 50 μm, in particular 15 to 35 μm. These diameters ensure not only adequate reflection of the irradiating electromagnetic field, but also good working and comfortable properties of the fabric.

The proportion of EMF-shielding material in the overall fabric depends on the desired attenuation factor to be achieved. This in turn is dependent on the energy (frequency) of the emitted radiation. It has surprisingly been found that an attenuation factor of 20 (10 dB) to 1000 (30 dB) can be achieved under a radiation of between 400 and 2300 MHz with a proportion of the EMF-shielding material of 5 to 15%, preferably 8 to 12% (15% means here: 15 out of 100 fibres consist of or contain the EMF-shielding material). An attenuation factor of between 2 and 15, preferably between 4 and 10, can be achieved already with a corresponding proportion of 1 to 5%. The proportions relate here to proportions of fibres of the EMF-shielding material with respect to the total fibres of the fabric. Also if particles are used, in whatever form, comparable attenuation factors can be achieved with the said contents (1 - 15% in relation to the fabric, here w/w). Radiation at higher frequencies (energy) is attenuated more strongly by the materials according to the invention than radiation for example in the radio-wave or low microwave range.

Conventional fabric for the purposes of the invention is understood as meaning fabric which includes all types of textiles in the widest sense. Preferably, all natural fibres, in particular wool, cotton, linen or silk, or mixtures of these fibres, are suitable. The natural fibres can be processed with the EMF-shielding fibres, or the latter can be introduced into the said natural fibres, without any problem. With a proportion of up to 15%, in particular between 1 and 5%, the fabrics maintain their original quality, both in terms of appearance and in terms of feel, and can consequently be generally used. The fabric may, however, also be made up entirely or partly on the basis of conventional textile polymer fibres, such as for example polyester, polyacrylic, polyethylene etc., if special requirements for water repellency or crease resistance are to be met.

The textile fabrics can be processed according to the invention into garments, for example in the form of shirts, blouses, jackets, coats, neck and head scarves and head coverings of any type. There is also the possibility, however, of using inserts of the fabric according to the invention, for example in pockets, for example breast and jacket pockets, in which the ready-to-operate mobile phone is very often kept or carried. Here, the insert is expediently provided between the mobile phone and the body. Protection during telephoning, that is to say in the head or ear region, can be established by use of suitable head coverings or head bands.

Example 1 :

The attenuation of the electromagnetic field strength by a fabric according to the invention is measured. To do so, an electromagnetic alternating field of a certain frequency, which corresponds to a frequency of a mobile phone or a radio-telephone device, is generated by means of an HF-signal generator and an HF amplifier. The respective EMF-shielding fabric is arranged between the generator and a probe, provided with a field-strength measuring instrument, to be precise in such a way that the fabric is provided directly on or above the probe. A field strength of 10 V/m is generated as the initial value. This corresponds approximately to the field strength which occurs in the direct proximity (3 - 5 cm) of the antenna of a customary mobile phone (400 - 2000 MHz). The attenuation is specified in dB. For conversion into attenuation factors, see above.

Example 2:

The arrangement described in Example 1 is used to measure the attenuation at 900 MHz excitation frequency for a cotton fabric which contains a metal fibre in a proportion of 4% (96 cotton fibres, 4 metal fibres). The metal fibre (30 μm) is a copper/silver alloy (75/25 w/w). Fabric in direct proximity (1 - 3 cm) of the measuring probe: attenuation with horizontal alignment of the antenna: 15 (dB) attenuation with vertical alignment of the antenna: 5 (dB). Fabric at 10-15 cm from the measuring probe: attenuation with horizontal alignment of the antenna: 8 (dB) attenuation with vertical alignment of the antenna: 1 (dB).

Example 3:

As example 2, but 1800 MHz excitation frequency. Fabric in direct proximity (1 - 3 cm) of the measuring probe: attenuation with horizontal alignment of the antenna: 20 (dB) attenuation with vertical alignment of the antenna: 26 (dB). Fabric at 10 - 15 cm from the measuring probe: attenuation with horizontal alignment of the antenna: 9.5 (dB).

Example 4:

The arrangement described in Example 1 is used to measure the attenuation at 900 MHz excitation frequency for a cotton/linen fabric (75/25) which has a polymer fibre (65 μm) which contains copper flakes (approximately 20 μm) (polymer/copper 65/35 w/w). The proportion of the polymer fibre is 20% (80 natural fibres and 20 polymer- copper fibres).

Attenuation factors of between 8 and 20 are obtained.

Claims

Patent claims

1. Use of fabrics based on textile fibres and at least one component which comprises a material which attenuates electromagnetic fields (EMF), for shielding high-frequency (HF) radiation in the immediate vicinity of the human body, whereby said radiation is emitted by cordless mobile phones and radio-telephone devices, including their base stations.

2. Use according to Claim 1 for shielding microwave radiation in the range from 400 to 4500 MHz (mobile radio).

3. Use according to Claim 1 for shielding radio radiation in the range from 20 to 50 MHz (radio telephony/CB radio).

4. Use according to one of Claims 1 to 3, characterized in that the EMF- attenuating material brings about an attenuation factor of between 2 and 1000.

5. Use according to Claim 4, characterized in that the EMF-attenuating material brings about an attenuation factor of between 5 and 100.

6. Use according to Claim 4, characterized in that the EMF-attenuating material is selected from at least one metal and/or one semiconductor material and/or one polymer material.

7. Use according to Claim 6, characterized in that the EMF-attenuating material is a metal.

8. Use according to Claim 7, characterized in that the metal is copper, silver, gold, platinum or an alloy of these metals with one another or an alloy of these metals with other metals.

9. Use according to Claim 4, characterized in that the EMF-attenuating material is in the form of fibres which are woven with the textile fibres, or in the form of separate particles or structures which are incorporated into the textile fabric, or in that the textile fibres are coated with the said EMF-attenuating material.

10. Use according to Claim 9, characterized in that the EMF-attenuating material is in the form of fibres.

11. Use according to Claim 10, characterized in that the fibres have a diameter of 10 - 100 μm.

12. Use according to one of the preceding claims, characterized in that cotton, wool, linen, silk or mixed fabrics of these fibres are used as textile fibres, it being possible for a proportion of man-made fibres to be contained.

13. Material based on textile fibres and at least one component which comprises a material which attenuates electromagnetic fields (EMF) for shielding high-frequency radiation, which is emitted by cordless mobile phones and radio-telephone devices, including their base stations, within a frequency range of 800 until 2300 MHz having an electromagnetic attenuation factor between 20 and 1000, characterized in that the EMF attenuating material (i) essentially consists of noble metals or noble metal containing alloys or a polymer material, (ii) is connected to the textile fibres, and (iii) the amount of the EMF-attenuating material is 5 - 15% related to the complete amount of fibres.

14. Material according to claim 13, wherein the EMF-attenuating material are fibres having a diameter of 10 - 50 μm which are woven with the textile fibres.

15. Material according to claim 13, wherein the EMF-attenuating material are particles which are distributed on or within the textile fibres or on or within carrier polymer fibres.

16. Use of a material according to any of the claims 13 - 15 as garments.

17. Use of a material or a garment according to any of the claims 13 - 16 for the prevention of health damages caused by high-frequency radiation, which is emitted by cordless mobile phones and radio-telephone devices, including their base stations.