A new method and apparatus to produce drops with diameters several tens of nanometers and/or positive or negative ions with a wide range of chemical composition and masses as large as several kiloDalton is based on creating Taylor cone-jets of high electrical conductivity, moderate viscosity, and low volatility liquids under reduced pressure. The liquid is supplied at a controlled flow rate into a region at low pressure exposed to an electric field sufficient to electrically atomize it. Suitably charged, shaped and placed electrodes create the necessary electric field to form the Taylor cone and extract the charged particles it produces, with a desired energy and direction. Subsequent ion manipulation supplies beams of ions and/or nanoparticles for applications such as electrical propulsion or surface treatment. No liquids suitable to practice this invention have been known in the past and are introduced here as a key aspect of the invention. They are such as electrolytes of formamide (or organic liquids such as amides, alcohols, glycols, esters, ketones, organic phosphates or carbonates, etc., and mixtures of one or more of these components), ionic liquids (neat or mixed with other ionic liquids, molecular solvents and/or salts), molten salts and inorganic acids.

This invention relates to the production of beams of ions for applications such as electrical propulsion or ion milling and writing, as well as to the production of beams of charged particles with nanometer sizes.
Beams of charged particles in moderate or high vacuum are useful in many applications. Cluster beams of metals have been used for depositing thin films with special properties, exploiting the fact that the kinetic energy per cluster molecule may be controlled in the range below 1 eV. Closely related considerations have led to the use of beams of glycerol clusters for surface cleaning, such as in U.S. Pat. Nos. 5,796,111 and 6,033,484. Beams of charged colloids are useful also in electrical propulsion. Similarly, beams of atomic or molecular ions have been used in applications such as surface treatment (ion implantation), surface writing, etching or milling, high resolution lithography for microelectronic and other purposes. Also for sputtering and secondary ion mass spectrometry, and electrical propulsion among others. As discussed in U.S. Pat. No. 6,137,110, focused ion beams play a very useful role in the semiconductor industry by greatly reducing the time and costs associated to integrated circuit development and repair.
Ion beams may be generated in a variety of ways: by producing ions and extracting them from gas or plasma sources; from positively charged liquid metal surfaces by field evaporation from the tip of a Taylor cone; from solid surfaces, for instance by laser ablation ionization; etc. Charged beams of metal clusters have been produced by electron bombardment of neutral clusters formed by evaporation-condensation. Unfortunately, these methods are able to yield only relatively restricted classes of ionic species.
Gas sources may form ion beams only of gaseous or volatile substances.
Liquid metal ion sources (LMIS) have been described by P. D. Prewett and G. L. R. Mair in the book Focused ion beams from LMIS (Wiley, N.Y.; 1991). They are based on charging the surface of a molten metal held in a vacuum to a high voltage with respect to a neighboring extractor electrode. Within a suitable range of voltage differences, the meniscus of molten metal forms a so-called Taylor cone, whose sharp apex region emits predominantly metal ions. Such liquid metal ion sources (LMIS) have high brilliance and can be focused into submicron spots. But they can deliver only ions of metals and the few substances soluble in them, with exclusion of all negative ions. Liquid metal ion sources are generally operated in the low-current regime, where they emit predominantly individual metal ions. Although LMIS can also be run under conditions where larger ion clusters, nanometer drops and considerably larger drops are emitted together with neutral atoms and clusters, such regimes involve quite complex distributions of mass over charge ratios m/q, and are generally far less suitable than the pure ionic regime for most applications.
Laser sources involve high energy deposition on a surface. Although they may produce large and moderately charged clusters as well as small atomic and molecular species, they are unsuitable to generate beams of intact labile substances. Furthermore, in the regime where they would produce large clusters, they would have a wide distribution of charge over mass q/m and would be mixed with neutrals, being therefore unfit for applications such as electrical propulsion.
Existing ion beam sources are therefore limited to m/q values smaller than 200 Dalton, such as Cs+ (133 Dalton) or Au+ (197 Dalton) in liquid metal ion sources, or Xe+ (131 Dalton) in plasma sources. They are also severely restricted in chemical composition, limiting the possibilities to combine chemical attack with purely physical erosion in applications such as etching. Hence, no chemically assisted focused ion beam analog exists to the etching processes commonly performed with the assistance of masks. Because chemical composition and mass/charge are key parameters determining the properties and breadth of applications of ion beams, there is a need to introduce new ion sources able to cover a much wider range of ionic chemical composition and m/q than previously available. To do so is one of the objectives of this invention.
Electrostatic atomization via Taylor cones of organic electrolytes (rather than liquid metals) has provided a related but different scheme to produce charged beams of small drops (rather than atomic ions) in a vacuum environment. In these systems, a liquid of low volatility and electrical conductivity K is supplied at a flow rate, Q (cm3/s) to the tip of a capillary tube. A voltage difference V=V1xe2x88x92V2 is established between this tip and a neighbouring electrode, generally called the extractor. Within a suitable range of values of Q and V (where Q depends on K), the liquid meniscus takes the form of a cone, whose tip ejects a steady microjet, which in turn breaks into drops. This structure is often referred to as a cone-jet, following the classification discussed by M. Cloupeau in the Journal of Aerosol Science, Volume 25, pages 1143-1157, 1994. The spray of drops streaming from the end of the jet is generally referred to as an electrospray, and this terminology will be used here also. When the cone-jet forms in a vacuum environment, the charged drops produced are accelerated towards the extractor by the voltage difference V, and pass through an orifice in the extractor forming a relatively narrow beam. These beams of charged drops have proven useful in applications such as electrical propulsion and surface cleaning. This approach has been successful mainly with glycerol electrolytes, having high dielectric constant and a relatively small volatility. Furthermore, Taylor cones of glycerol held in vacuum in a multicone highly stressed regime under high voltage are capable also of producing ions of dissolved substances, and this feature has found applications in mass spectrometry, as explained by K. D. Cook in Mass Spectrometry Reviews, volume 5, pages 467-519, 1986. However, the electrospraying technique to produce beams of small drops and ions in vacuo has been limited by the relatively large size and associated large m/q of the drops, and by the relatively small concomitant ion currents. Also by the wide range of energies and solvation states in which the ions are produced in this highly stressed regime. In other words, Taylor cones of glycerol are ineffective as ion sources, with poor ion intensities, and wide energy and m/q distributions. As sources of drops, electrosprays of glycerol tend to produce drop diameters of several hundred nanometers, rather than the more desirable range of tens of nanometers. As a result, there is an inaccessible gap of many orders of magnitude in m/q space between values typical of ions (xcx9c100 Dalton), and those accessible with electrosprayed glycerol drops (xcx9c106 Dalton). This forbidden region includes the range of greatest practical interest for a number of applications, including electrical propulsion. Hence, a further object of this invention is to narrow down this m/q gap both on its upper and lower ends, by developing means to produce beams of much heavier ions as well as much smaller drops than previously possible.
It is known that the m/z ratio of electrospray drops can be decreased by reducing drop size, which in turn requires increasing the electrical conductivity K of the electrosprayed liquid. Furthermore, an article by J. J. Perel, et al. in the AIAA Journal, 7, 507-511 (1969) has revealed that Taylor cones of sulfuric acid with K values in excess of 10 S/m tend to yield dominantly ions rather than drops, in a regime presenting some analogies with the behaviour of liquid metal ion sources. Hence, those skilled in the art must have known for years that electrospraying solutions with electrical conductivities K larger than those available in glycerol electrolytes would have considerable advantages from the point of view of producing both ions and small microscopic drops. However, other than the corrosive and therefore inconvenient case of sulfuric acid (which is furthermore too conductive for nanodrop production), no solvent of low volatility has been known with the properties required to produce either considerably smaller drops than glycerol, or able to produce dominantly ionic emissions. It follows that attaining the objectives of this invention requires first identifying such suitable solvents, and this is a major objective of the present invention.
A key step in this invention is the recognition that traditional glycerol electrolytes do not have the desirable properties for the generation of high quality beams of either ions or nanodrops. The high viscosity of glycerol greatly hinders the mobility of ions dissolved in it, so that its room temperature electrical conductivity is below 0.02 S/m, even under the most favorable conditions of salt seeding. According to the scaling laws published by J. Rosell-Llompart and J. Fernxc3xa1ndez de la Mora, in J. Aerosol Sci., 25, 1093-1119, 1994, or by J. Fernxc3xa1ndez de la Mora, and I. G. Loscertales in J. Fluid Mechanics, 260, 155-184, 1994, this conductivity leads at best to jet diameters above 100 nm, whereby ion evaporation directly from the apex region of the Taylor cone-jet is essentially impossible. However, the high viscosity of glycerol leads to production of anomalously large drops upon jet breakup. In other words, whereby Taylor cone-jets of weakly viscous liquids such as water tend to break up into drops with a diameter approximately twice the jet diameter (ddrop/djetxcx9c2), this diameter ratio increases with increasing liquid viscosity. This effect has been analyzed for the case of tetraethylene glycol in the above mentioned article by Rosell et al. (1994). Extrapolation of their data to the case of the considerably more viscous glycerol indicates that ddrop/djet ratios up to some three times the inviscid ratio would arise. The electric field on the surface, of these drops scales as q/d2. But the charge density q/d3 has been shown by L. de Juan et al. (J. Colloid and Interface Science, 186, 280-293, 1997) to be fixed only by the current over flow rate through the cone-jet, which is not anomalous in glycerol. It follows that the surface field Excx9c(q/d3) d is anomalously large for glycerol drops, possibly by a factor as large as three. Since this field scales as the ⅓ power of electrical conductivity, the conclusion is that glycerol drops have electric fields similar to those that would be expected in liquids some 27 times more conductive than glycerol itself (some 0.5 S/m). Such conditions are therefore sufficient to produce ion evaporation from electrosprayed glycerol drops, but by far insufficient to evaporate ions directly from the meniscus. This situation hence explains the weak ion currents observed from electrosprays of glycerol, as well as their wide spread in energy. Note further that the estimate just made on the anomalously large fields on the surface of glycerol drops would in reality be limited by the mechanism of Rayleigh explosions, whereby a drop with too large a charge explodes into smaller drops. But the final result would be qualitatively the same as just discussed, since the smaller daughter drops resulting from such explosions would in turn have surface electric fields even higher than their mother drops. This different scenario would again lead to anomalously large ion production from glycerol drops, but would still preclude ion formation directly from the Taylor cone.
In conclusion, in order to develop electrospray sources of ions and nanoparticles in vacuum one needs to identify liquids other than glycerol having suitable properties of high dielectric constant, high electrical conductivity (modest viscosity) and small vapor pressure. An article by M. Gamero-Castaxc3x1o and J. Fernxc3xa1ndez de la Mora in the Journal of Chemical Physics, 113, 815, 832, 2000 provides much of the basis of the provisional patent application on which the following considerations are supported. This article shows that the organic solvent formamide is sufficiently involatile at room temperature to form Taylor cone-jets in vacuum. It further teaches that, in spite of the finite volatility of formamide, use of carefully sharpened capillaries with inner diameters as small as 20 xcexcm enables forming electrosprays in vacuum even at the smallest flow rates at which the Taylor cones of formamide are stable at electrical conductivities above 1 S/m. It further shows first by analysis and then by experiment that electrical conductivities in excess of 1 S/m are necessary for ion evaporation to proceed at substantial rates directly from the meniscus of a Taylor cone (rather than indirectly from the drops). At smaller electrical conductivities, small rates of ion evaporation are produced, but they originate from the drops rather than from the meniscus. The distinction between ions originating from either the meniscus or the drops is important, because, given their secondary origin, ion currents from the drops cannot have the properties of brilliance (intensity) and narrow energy distribution necessary for a high quality ion beam. On the other hand, ions emitted directly from the meniscus originate from a virtually fixed voltage (narrower energy distribution), and are associated to currents that may be considerably larger (high brilliance) than either the total drop current or the secondary ion current from the drops. This distinction substantiates our prior conclusions on the limitations of glycerol, and confirms further the need for solvents exhibiting electrical conductivities in the range of 1 S/m to attain some of the objectives of the present invention.
The results just discussed based on formamide electrolytes are useful in applications requiring the production in a region at reduced pressures of nanometer drops, as well as of mixtures of drops and ions. The contributions of either the drop or the ionic component may dominate, depending on operating conditions. However, the regime of almost pure ionic emission typical of liquid metal ion sources has not yet been observed in formamide electrolytes. Hence, the production of drop-free ion beams from formamide electrolytes currently requires prior separation of the ions and the drops simultaneously present in the beam. This separation can be carried out with the help of magnetic fields. It can be performed also with purely electrostatic means because the drops are ejected in the direction of the axis, while the ions originating from the meniscus evaporate in the direction normal to the meniscus, which is between 90 and 60xc2x0 off the axis. If the charged beam is focused on the axis by an electrostatic lens of sufficient geometric aberration, the ionic and drop components will focus at widely different positions and will hence be cleanly separated.
In addition to requiring separation of ions from drops, ion sources based on formamide electrolytes have so far been limited to ion currents generally smaller than 1 xcexcA per Taylor cone, well below those attainable in liquid metal ion sources. Hence, still another goal of the present invention is to identify electrolytes such that their Taylor cones in vacuo would produce ion currents of many xcexcA, with negligible or very small contributions of drops. We have already mentioned the experiments by Perel et al. with sulfuric acid. They showed directly that the sought almost pure ionic regime does indeed exist in liquids having electrical conductivities somewhere above 10 S/m. In spite of their new method to create negative as well as positive ions, we are not aware of a single subsequent study making use of acids as ion sources analogous to liquid metal sources. Evidently, the corrosive nature of sulfuric acid must have contributed to discourage further exploitation of this interesting source. We note also that sulfuric acid sources would not yield the wide range of m/q and chemical composition sought here, nor would other common acids of low volatility. It is therefore clear that other liquids having electrical conductivities well in excess of 2 S/m must be sought for this application. Moderately heated formamide electrolytes will evidently approach the pure ionic regime better than the room temperature formamide electrolytes already tested. Today""s micromachining techniques can produce supporting electrodes for a heated Taylor cone of formamide with a base having a diameter smaller than 1 xcexcm. The corresponding liquid emitters would have an exposed area some three orders of magnitude smaller than in earlier experiments with 20 xcexcm bases. They would therefore have comparable or smaller evaporative losses at temperatures substantially above ambient, ant which K values in excess of 10 S/m may be expected. Microemitters of heated formamide are hence capable in principle of approaching and attaining the pure ionic regime. Other substances which are likely to reach this pure ion regime are molten salts. Although most salts melt at relatively high temperatures and many of them are reactive in the molten state, their volatility is often small at the melting point. They also offer a tremendous range of m/q ratios and chemical compositions. Of particular interest to attain the pure ion regime is a special class of salts which are liquid at or near room temperature and are commonly referred to as ionic liquids.
A More Detailed Description of some Liquids Suitable for the Practice of this Invention
Among the main liquid properties required for the practice of this invention are the following:
i) electrical conductivity in the range from 0.1 to several tens of S/m
ii) vapor pressure below (preferably much below) 0.01 torr at operating temperature.
iii) Viscosity coefficient in the range of 5 cP, preferably below. The larger the viscosity, the higher the tendency for the jet break-up process to form bigger and less monodisperse drops (Rosell et al., J. Aerosol Science 25, 1093-1119, 1994).
Several classes of liquids have been identified enjoying such properties to various degrees.
A. The first type includes organic solvents of high dielectric constant, low viscosity and low volatility. The preferred solvent is formamide, HCONH2, which, among all known organic solvents of moderate viscosity, is singular both for its low volatility and its high dielectric constant (∈ greater than 100 at room temperature). As a result, formamide has an exceptional ability to dissolve salts, as illustrated in an article by E. Colton and R. E. Brooker appeared in 1958 in the Journal of the American Chemical Society, Vol. 80, pages 1595-1596. These authors report that many salts are soluble in formamide at 25xc2x0 C. at levels in the range of 1 Kg/liter, and a few even above that level. For instance, at 25xc2x0 C., KF.2H2O is soluble in formamide at 8.75 moles/liter. Most interesting for our purposes is the fact that, although formamide is a few times more viscous than water, many of its electrolytes have nonetheless room temperature electrical conductivities exceeding 2 S/m. Perhaps the main limitation of this solvent for the purposes of this invention is that its vapor pressure is substantially higher than that of glycerol. In the first published report of an attempt to produce Taylor cones of formamide in a vacuum, M. Gamero-Castaxc3x1o et al. (J. Appl. Phys., 83 2428-2434, 1998) concluded that its volatility was excessive, and proceeded instead to use the considerably more viscous and less polar liquid tributyl phosphate. As a result, they could not reach the electrical conductivities required for this invention. Note further that their work with formamide was at the rather limited levels of vacuum afforded by a simple rotary pump (in the range of 0.1 torr). Also, they used unseeded formamide, with electrical conductivity levels much smaller than required for ion evaporation from the meniscus. Although they did not discuss how the finite volatility of formamide did interfere with the formation of a Taylor cone, the reasons are relatively clear. If the rate of solvent evaporation from the meniscus is comparable to the liquid flow rate Q pushed into the meniscus apex, the concentration of salt inside the remaining liquid increases comparably, leading possibly to salt precipitation. This problem is evidently much more serious in the case of concentrated solutions, since, for solid and involatile solutes, it can lead to clogging of the line supplying the liquid to the meniscus (this difficulty can, however, be avoided by use of volatile ammonium salts, or salts which are liquid at the operating temperature). Furthermore, the range of operating flow rates in Taylor cone-jets varies inversely with liquid conductivity, so that the relative component of liquid evaporating from the meniscus becomes considerably more serious as the conditions of high electrical conductivities required for the present invention are approached. In spite of the difficulties perceived in earlier work, formamide electrolytes can be electrosprayed in a vacuum, even at background pressures of 10xe2x88x925 torr, and even at the high electrical conductivities and minuscule flow rates required to reach the ion evaporation regime. This possibility was first demonstrated by Gamero et al. in the article in J. Chem. Phys. (2000) forming the basis of the present invention. They did so by limiting the area of liquid exposed to the vacuum to relatively small values. They used commercially available silica capillaries with inner diameters of 20 xcexcm, which they sharpened to a conical shape, such that the basis of the meniscus was itself nearly as small as 20 xcexcm. They further made the silica capillaries conducting by chemical vapor deposition of tin oxide. Since the diameters of the jets of Taylor cones in the ion evaporation regime are typically in the range of 10 nm, supporting electrodes considerably smaller than 20 xcexcm would be able to achieve comparable results, with even smaller interference from the finite volatility of formamide. As already mentioned, such microelectrodes could run in a vacuum with moderately heated formamide electrolytes at K values close to 10 S/m.
We have discussed the case of salt electrolytes dissolved in formamide. However, similar or even superior results can be achieved by use of a solution of an electrolyte in a solvent chosen from the class of compounds that comprises amides, alcohols, glycols, esters, ketones, organic carbonates and phosphates, etc., and mixtures of one or more of these components.
B. Ionic liquids. Ionic liquids are salts enjoying the remarkable property of being liquid at ambient or near-ambient conditions. Most ionic liquids have negligible volatility, not only at room temperature, but also at several hundred xc2x0 C. Ngo et al. (Thermoch. Acta, 357, 97-102, 2000) have investigated the temperatures at which a large number of ionic liquids begin to degrade thermally, which in many cases exceeds 400xc2x0 C. Some ionic liquids exhibit room temperature electrical conductivities larger than 2 S/m, though with viscosity coefficients generally in excess of 10 cP. Although not ideal, these values may be sufficient to make such materials potentially superior to formamide solutions in certain applications. For instance, the mixtures of Aluminum Chloride and 1-methyl-3-ethylimidazolium chloride (EMIm+Clxe2x88x92) have been studied extensively at varying molar factions xAl of AlCl3. At room temperature, and xAl=0.44, Q. Liao and C. Hussey (J. Chem. Eng. Data 41, 1126-1130, 1996) report K=2.186 S/m, xcexc=17.29 cP. The corresponding values at xAl=0.44 are K=1.1 S/m, xcexc=34.2; and K=1.423 S/m, xcexc=13.79 at xAl=0.667. These ionic liquids have also been studied in mixtures with a few organic solvents such as benzene by Liao and Hussey (1996), and in benzene, acetonitrile and dichloromethane by R. L. Perry et al. (J. Chem. Eng. Data 40, 615-619, 1995). At xAl=0.51, 40% mass fraction of benzene reduces the viscosity to 3.93 cP and increases K slightly above 3 S/m. At xAl=0.49, 40% mass fraction of acetonitrile reduces xcexc well below 2 cP and yields K values above 6 S/m. Drastic reductions of viscosity and increases in electrical conductivity can therefore be obtained by mixing with organic solvents. Most interesting for our purposes is the fact these two advantages can be obtained even in moderately polar and non-polar solvents.
Of course, the mixtures just discussed are inappropriate for our purposes due to the high volatility of these solvents. However, mixtures of formamide with ionic liquids will evidently reduce their viscosity and increase their electrical conductivity. Although the vapor pressure of formamide in such mixtures will be lower than that of pure formamide, they will nonetheless be somewhat volatile. However, formamide-ionic liquid mixtures would have the advantage that no solid precipitates can form, so that there is no danger of clogging the emitter tip during the periods when the Taylor cone is not running. It is worth pointing out that the compatibility of ionic liquids with moderately polar solvents makes it possible to design mixtures of molecular solvents with ionic liquids with very small vapor pressure yet electrical conductivities above the value for the neat ionic liquid.
We have discussed the case of EMIm+ based chloroaluminates. In spite of their interest, these molten salts have the problem of being air and water sensitive. Of similar or greater interest is the case of other ionic liquids also based on EMIm+, though with non chloride anions which make them air and water compatible (Wilkes, J. S. and M. J. Zawarotko, J. Chem. Soc. Chem. Commun., 13, 965-967, 1992). Among others, one should mention EMIm+ salts with either BF4xe2x88x92(tetrafluoroborate), CF3SO2xe2x88x92(triflatexe2x88x92), (CF3SO2)2Nxe2x88x92(Imxe2x88x92) or PF6xe2x88x92(hexafluorophosphate). Their room temperature electrical conductivities range from 0.85 S/m to 1.3 S/m, and their viscosity coefficients from 45 cP to 34 cP (J. Fuller, R. T. Carlin, R. A. Osteryoung, J. Electrochem. Soc. 144, 3881-3886, 1997; P. Bonhote et al., Inorg. Chem. 35, 1168-1178, 1996). Recently, R. Hagiwara et al. (J. Fluorine Chemistry, 99, 1-3, 1999) have investigated a compound based on HF and the ionic liquid 1-ethyl-3-methylimidazolium fluoride (EMIm+Fxe2x88x92), which is liquid at room temperature, has low volatility, reaches K values of 12 S/m (25 C.), and, unlike HF, is not reactive with glass.
The miscibility of some of these and other air-compatible ionic liquids with several organic solvents have also been investigated by Bonhote et al. (1996). The group at Covalent (A. B. McEwen, S. F. McDevitt, V. K. Koch, J. Electrochem. Soc. 144, L84-L86, 1997; A. B. McEwen, H. L. Ngo, K. LeCompte, J. L. Goldman, J. Electrochem. Soc. 146, 1687-1995, 1999) has provided further information on the physical properties of some of these ionic liquids mixed with a diversity of solvents. Their 1999 paper reports K=6 S/m and xcexc=1 cP for mixtures of EMIm-PF6 with acetonitrile. No data are included for EMIm-BF4, which has even more favorable properties as a pure liquid. Some of these air-compatible ionic liquids are miscible with formamide and with the less polar tributyl phosphate, as recently established by M. Gamero, M. and V. Hruby (AIAA paper 2000-3265, 36th AIAA/ASME/SAE/ASEE joint propulsion conference and exhibit, Jul. 16-19, 2000, Huntsville, Ala., 2000). McEwen et al. (1997) have studied mixtures of EMIm+ salts with organic carbonates, some of which have moderately small volatilities. For instance, ethylene carbonate (EC) has a boiling point higher than formamide, though with a comparable extrapolated vapor pressure at 20xc2x0 C. Interestingly, pure EC freezes at 36xc2x0 C., but its 2 Molar solution with EMIm+PF6xe2x88x92 and EMIm+Imxe2x88x92 are liquid at room temperature. This suggests the possibility of using mixtures of ionic liquids with other high boiling point solvents which, when pure, are solid at room temperature. The maximum room temperature conductivity reported by McEwen et al. (1997, 1999) for mixtures of EMIm+PF6xe2x88x92 or EMIm+Imxe2x88x92 with organic carbonates is 2.7 S/m (2.2 S/m for EC).
Another effective means to improve the properties of pure ionic liquids in relation to this invention is to elevate their temperature. Several of the references cited show that this increases their electrical conductivity and decreases their viscosity quite substantially, while generally keeping their volatility unmeasurably small. We are not aware of data on electrical conductivities at temperatures approaching decomposition conditions (300-400xc2x0 C.). But the measurements of McEwen et al. with EMIm+BF4xe2x88x92 show Kxcx9c8 S/m at 100xc2x0 C., and extrapolate to values in excess of 30 S/m at 200xc2x0 C. Similar extrapolations can be based on the data published by Bonhote et al.
In conclusion, moderately heated ionic liquids are among the most promising materials known able to match the characteristics of acids for ionic propulsion in the pure ion regime. Their considerable advantages over acids lie not only in their chemical stability, but also, and principally, in the enormous variety of possible ionic liquids, and therefore the high likelihood to find suitable candidates with molecular weights in the kiloDalton range. The added complexity associated to the required temperature control would be compensated in applications such as electrical propulsion by an ability to run a given ionic liquid as either mainly a drop emitter (at or below room temperature), or mainly an ion emitter (at elevated temperatures).
One important goal of this invention is to greatly increase the range of ionic chemical compositions and m/q ratios that can be produced with respect to those available from alternative ion sources. The vastly wider range of chemical compositions offered by the present invention is evident from the enormous variety of anions and cations in either formamide-soluble salts, or in existing or potentially synthesizable ionic liquids. We have mentioned the high solubility of KF.2H2O in formamide. The corresponding electrolytes will therefore easily attain electrical conductivities at which xcexcA currents of Fxe2x88x92 ions would be evaporated directly from the Taylor cone, thereby yielding a bright ion source where physical and chemical attack of surfaces could be used simultaneously for directional or conformal etching. Similarly, a variety of salts composed of very heavy anions and cations exist which would allow production of beams of rather heavy ions. For instance, dodecatungstates with molecular weights as large as 3000 amu exist, some of which are highly soluble in formamide. Although these anions are polyvalent and their m/q would be closer to 1000 than to 3000 Dalton, emission in the positive mode of sodium dodecatungstate electrolytes would yield dominantly a singly charged salt molecule attached to a sodium ion. The reason is that the energy barrier for ion evaporation is considerably larger for Na+ than for this bulkier complex.
Another goal of the present invention is not only to produce beams of ions in a wide range of masses and compositions, but also to do so as close as possible to the pure ion evaporation regime of Taylor cones. Although this goal might be reached from high temperature molten salts or from moderately heated microsources of formamide electrolytes, we wish to argue here that heated ionic liquids are ideal sources not only for moderately small ions such as EMIm+, but also for many other ions, some with kiloDalton masses. Table 1 lists the masses of the cations and anions comprising some of the ionic liquids for which published data are available. The most common anion and cation are BF4xe2x88x92 and EMIm+, with masses (87 and 111 amu) comparable to those of alternative ion propulsion materials (Cs and Xe). The heaviest anion in common use is (CF3SO2)3Cxe2x88x92(m=411.2 amu). In spite of its relatively large mass, it has fairly favorable viscosity and melting point (xe2x88x9234xc2x0 C. when paired with EMIm+). This is by no means an upper limit for attainable anionic mass, as indicated by more exotic examples collected in the Table, for which only one or a few articles have been published to date. Noteworthy examples are those based on tetrachloroaureate Cl4Auxe2x88x92. The Br4Auxe2x88x92 and I4Auxe2x88x92 ions have masses of 516.6 and 704.6, are common in inorganic salts (i.e. KI4Au), and have been included in the Table as hypothetical because corresponding dialkylimidazolium salts have not yet been synthesized, and their chemical stability and liquidus range are still unknown. The heaviest (non-hypothetical) anion included in the Table, CB11H6Br6xe2x88x92 (616.4 amu), is based on the carborane ion CB11H12xe2x88x92. A most interesting feature of the related study of Larsen et al. (e in Table 1) is the slight effect of hallogenation on melting temperature (Tm=122xc2x0 C. for EMImCB11H12, and 114xc2x0 C. and 139xc2x0 C. for the hexachlorinated and hexabrominated counterparts). Similarly, Hasan et al. (f in the Table) report almost the same melting point (Tm=58xc2x0 C.) for EMImCl4Au than for EMImPF6. If this trend is general, and substitution of the widely used fluorinated anions (CF3SO2)2Nxe2x88x92, (C2F5SO2)2Nxe2x88x92 and (CF3SO2)3Cxe2x88x92 by their brominated or iodinated counterparts leads to stable ionic liquids with comparable melting points, one would then reach molecular masses as high as 1459.2 in (C2I5SO2)2Nxe2x88x92 (included in the Table also as hypothetical). Notice that this relatively compact anion would be well over an order of magnitude heavier than Cs+ or Xe+. The possibility to add larger and therefore substantially heavier appendages in the anion or cation remains open. Its consequences on dialkyl-imidazolium-based salt properties have already been explored to a limited extent by Gordon et al. (c in the Table) with a single long alkyl chain (up to C18H37), and Merrigan et al. (d in the Table) by appendage of long fluorinated tails (up to C8F17) to the ethylene group in xe2x88x92EMIm+ or xe2x88x92EBIm+. Gordon et al. have emphasized the liquid crystalline structure of their salts, also enjoyed by the fluorous salts. Merrigan et al. discuss the strong surfactant properties introduced by their fluorotails. Most interesting is the fact that the long hydrocarbon chain does not increase substantially the melting point, and, in some cases, actually decreases it. For instance, the melting point of CnH2n+1MImPF6 goes from 63xc2x0 C. at n=2, down to 40xc2x0 C. at n=3, to recover the value of EMImPF6 (n=2) only beyond n=12 (Tm=60, 74, 74 and 80xc2x0 C. for n=12, 14, 16 and 18, respectively). Similarly, CmF2m+1C2H2MImPF6 have melting points at 61 and 87xc2x0 C. for m=6 and 8, respectively. Since these melting temperatures are relatively close to that of the small EMImPF6, it appears that they are to a large measure fixed by the anion PF6xe2x88x92. Hence, the same long tailed cations paired with BF4xe2x88x92 should melt at considerably lower temperatures (11xc2x0 C. for EMImBF4 versus 62xc2x0 C. for EMImPF6). It is important to note also that almost all these salts remain in the liquid state for very long times considerably below the melting point. Hence, the actual freezing temperatures of CnH2n+1MImPF6 are +5, xe2x88x9281 (Ngo et al.) and xe2x88x9261xc2x0 C. for n=2, 3 and 4 (a in the Table), respectively. This means that sources of ions or drops can be run at room temperature by simply heating up the liquids initially to a molten state, and then letting them cool back to room temperature.
Another important consideration could be that the viscosity coefficient xcexc of ionic liquids with long tails might be larger than in their tailless counterparts. Viscosity is known to decrease q/m in the pure drop regime by increasing drop size. But its role in the pure ion regime could be favorable, by decreasing the emission of drops. This point will have to be investigated experimentally, as there is no experience in electrospraying such substances. An increased viscosity coefficient would also have the indirect consequence of decreasing the electrical conductivity of the liquid making it harder to reach the pure ion evaporation regime. Neither Gordon et al. nor Merrigan et al. give quantitative information on either K or xcexc for their long tailed species. But the comparable work of Ito et al. (Electrochimica Acta, 45, 1295-1298, 2000) with CnH2n chains joining together two MIm+groups in EIm+xe2x80x94CnH2nxe2x80x94EIm++2(CF3SO2)2Nxe2x88x92 shows a negligible effect of the chain length on electrical conductivity K, from n=2 up to 8. This holds as long as the salt remains in the molten state (however, Tm does depend on n).
In conclusion, anion and cation mass can be greatly increased in many ionic liquids by appendage of longer tails, hallogenation, addition of heavy metals, etc., without serious property deterioration. Considering the excellent ionic liquid properties and large masses already attained without a concerted synthetic effort to actually maximize molecular weight, and considering further the enormous variety of potential ionic liquids and the rapid pace at which many of them are being synthesized and studied, it is evident that many more ionic liquids with rather large masses and electrical conductivities exceeding 10 S/m will become available in the future. In conjunction with such materials, the present invention constitutes the only available high quality source of heavy ions, and has the additional advantage that it can run close to the pure ion emission regime.
A source of ions and/or drops comprising a reservoir containing a liquid with electrical conductivity K between 0.1 S/m and 100 S/m; means to convey this liquid at a controlled flow rate Q into a supporting electrode in a vacuum environment, where it forms a meniscus; means to create an electric field between the meniscus and a surrounding extractor electrode, such that a Taylor cone-jet forms and produces a beam of ions and/or drops which passes through an opening suitably placed in the extractor electrode; means to control the temperature of the liquid meniscus; means to manipulate the beam of charged particles produced prior to its use in applications such as electrical propulsion, surface treatment, etc. This beam manipulation may include electromagnetic separation of its components, collimation, focusing, further acceleration or deceleration, combination with another beam of opposite polarity for partial or complete neutralization, etc. Suitable liquids are electrolytes of formamide or its mixtures with other non-volatile solvents such as amides, alcohols, glycols, esters, ketones, organic carbonates and phosphates and mixtures of one or more of these components. Also mixtures of these solvents with ionic liquids. Other suitable liquids are inorganic acids, molten salts, ionic liquids, and electrolytes of salts dissolved in these liquids and their mixtures. Preferred liquids for the production of ion beams are moderately heated ionic liquids whose melting points are near room temperature. Preferred liquids for the production of beams of heavy anions or cations are moderately heated ionic liquids composed of heavy anions or cations, paired with lighter cations or anions.

Method and apparatus to produce ions and nanodrops from Taylor cones at reduced pressure


A glass cleaning wipe comprising a nonwoven fabric containing wood pulp fibers, the nonwoven fabric is impregnated with a glass cleaning composition.

The present invention relates to a nonwoven fabric which has been impregnated with a liquid glass cleaning composition.
The patent literature describes numerous wipes for both body cleaning and cleaning of hard surfaces but none describe the instant glass cleaning wipes which have improved cleaning characteristics in the minimization of streaking and residue.
U.S. Pat. Nos. 5,756,612; 5,763,332; 5,908,707; 5,914,177; 5,980,922 and 6,168,852 teach cleaning compositions which are inverse emulsions.
U.S. Pat. Nos. 6,183,315 and 6,183,763 teach cleaning compositions containing a proton donating agent and having an acidic pH.
U.S. Pat. Nos. 5,863,663; 5,952,043; 6,063,746 and 6,121,165 teaches cleaning compositions which are out in water emulsions.
A glass cleaning wipe comprising a nonwoven fabric containing wood pulp fibers, wherein is the nonwoven fabric is impregnated with a liquid glass cleaning composition containing an anionic surfactant, a cosurfactant, an alkanol, a quaternary alkylol amine salt and water, wherein the liquid glass cleaning composition is not an emulsion and does not contain proteins, metallic salts, enzymes, amides, sodium hypochlorite, dimethicone, a proton donating agent, N-methyl-2-pyrrolidone, monoalkyl phosphate or silicon based sulfosuccinate.
The present invention relates to a glass cleaning wipe which comprises approximately:
(a) 30 wt. % to 40 wt. % of a nonwoven fabric consisting of 60 wt. % to 95 wt. % of wood pulp fibers, 2.5 wt. % to 10 wt. % of viscose fibers and 2.5 wt. % to 10 wt. % of polyester fibers; and
(b) 60 wt. % to 70 wt. % of a liquid glass cleaning composition being impregnated in said nonwoven fabric, wherein said liquid glass cleaning composition comprises:
(i) 0.1 wt. % to 5 wt. %, 0.25 wt. % to 4 wt. % of an anionic surfactant;
(ii) 0.5 wt. % to 10 wt. %, more preferably 1 wt. % to 6 wt. % of a C1-C4 alkanol;
(iii) 0.5 wt. % to 8 wt. %, more preferably 1 wt. % to 5 wt. % of a cosurfactant;
(iv) 0.1 wt. % to 1 wt. %, more preferably 0.2 wt. % to 0.8 wt. % of an antirain or antidust agent, a cationic quaternary alkylolamine salt, or choline chloride;
(v) 0 to 0.25 wt. %, more preferably 0.01 wt. % to 0.1 wt. % of a perfume;
(vi) 0 to 0.1 wt. %, more preferably 0.01 wt. % to 0.1 wt. % of a preservative such as iodo propynyl butyl carbanate; and
(vii) the balance being water, wherein the composition has a pH of about 7 to about 9.5, more preferably about 7.5 to about 8.5.
The anionic surfactant used in the instant invention are selected from the group consisting of sulfate anionic surfactants and sulfonate anionic surfactants, wherein the preferred anionic surfactant is a C8-C18 ethoxylated alkyl ether sulfate surfactant.
The anionic sulfonate surfactants which may be used in the detergent of this invention are water soluble and include the sodium, potassium, ammonium and ethanolammonium salts of linear C8-C16 alkyl benzene sulfonates; C10-C20 paraffin sulfonates, alpha olefin sulfonates containing about 10-24 carbon atoms and C8-C18 ethoxylated alkyl ether sulfates and mixtures thereof. The preferred anionic sulfonate surfactant is a C12-18 paraffin sulfonate.
The paraffin sulfonates may be monosulfonates or di-sulfonates and usually are mixtures thereof, obtained by sulfonating paraffins of 10 to 20 carbon atoms. Preferred paraffin sulfonates are those of C12-18 carbon atoms chains, and more preferably they are of C14-17 chains. Paraffin sulfonates that have the sulfonate group(s) distributed along the paraffin chain are described in U.S. Pat. Nos. 2,503,280; 2,507,088; 3,260,744; and 3,372,188; and also in German Patent 735,096. Such compounds may be made to specifications and desirably the content of paraffin sulfonates outside the C14-17 range will be minor and will be minimized, as will be any contents of di- or poly-sulfonates.
Examples of suitable other sulfonated anionic detergents are the well known higher alkyl mononuclear aromatic sulfonates, such as the higher alkylbenzene sulfonates containing 9 to 18 or preferably 9 to 16 carbon atoms in the higher alkyl group in a straight or branched chain, or C8-15 alkyl toluene sulfonates. A preferred alkylbenzene sulfonate is a linear alkylbenzene sulfonate having a higher content of 3-phenyl (or higher) isomers and a correspondingly lower content (well below 50%) of 2-phenyl (or lower) isomers, such as those sulfonates wherein the benzene ring is attached mostly at the 3 or higher (for example 4, 5, 6 or 7) position of the alkyl group and the content of the isomers in which the benzene ring is attached in the 2 or 1 position is correspondingly low. Preferred materials are set forth in U.S. Pat. No. 3,320,174, especially those in which the alkyls are of 10 to 13 carbon atoms.
The C8-18 ethoxylated alkyl ether sulfate surfactants have the structure
Rxe2x80x94(OCHCH2)nOSO3xe2x88x92M+
wherein n is about 1 to about 22 more preferably 1 to 3 and R is an alkyl group having about 8 to about 18 carbon atoms, more preferably 12 to 15 and natural cuts, for example, C12-14 or C12-16 and M is an ammonium cation or a metal cation, most preferably sodium.
The ethoxylated alkyl ether sulfate may be made by sulfating the condensation product of ethylene oxide and C8-10 alkanol, and neutralizing the resultant product. The ethoxylated alkyl ether sulfates differ from one another in the number of carbon atoms in the alcohols and in the number of moles of ethylene oxide reacted with one mole of such alcohol. Preferred ethoxylated alkyl ether polyethenoxy sulfates contain 12 to 15 carbon atoms in the alcohols and in the alkyl groups thereof, e.g., sodium myristyl (3 EO) sulfate.
Ethoxylated C8-18 alkylphenyl ether sulfates containing from 2 to 6 moles of ethylene oxide in the molecule are also suitable for use in the invention compositions. These detergents can be prepared by reacting an alkyl phenol with 2 to 6 moles of ethylene oxide and sulfating and neutralizing the resultant ethoxylated alkylphenol.
As used herein and in the appended claims the term xe2x80x9cperfumexe2x80x9d is used in its ordinary sense to refer to and include any non-water soluble fragrant substance or mixture of substances including natural (i.e., obtained by extraction of flower, herb, blossom or plant), artificial (i.e., mixture of natural oils or oil constituents) and synthetically produced substance) odoriferous substances. Typically, perfumes are complex mixtures of blends of various organic compounds such as alcohols, aldehydes, ethers, aromatic compounds and varying amounts of essential oils (e.g., terpenes) such as from 0% to 80%, usually from 10% to 70% by weight, the essential oils themselves being volatile odoriferous compounds and also serving to dissolve the other components of the perfume.
In the present invention the precise composition of the perfume is of no particular consequence to cleaning performance so long as it meets the criteria of water immiscibility and having a pleasing odor. Naturally, of course, especially for cleaning compositions intended for use in the home, the perfume, as well as all other ingredients, should be cosmetically acceptable, i.e., non-toxic, hypoallergenic, etc. The instant compositions show a marked improvement in ecotoxocity as compared to existing commercial products.
The cosurfactants in the instant compositions are selected from the group consisting of polypropylene glycol of the formula HO(CH3CHCH2O)nH wherein n is a number from 1 to 18, and mono and di C1-C6 alkyl ethers and esters of ethylene glycol and propylene glycol having the structural formulas R(X)nOH, R1(X)nOH, R(X)nOR and R1(X)nOR1 wherein R is C1-C6 alkyl group, R1 is C2-C4 acyl group, X is (OCH2CH2) or (OCH2(CH3)CH) and n is a number from 1 to 4, diethylene glycol, triethylene glycol, an alkyl lactate, wherein the alkyl group has 1 to 6 carbon atoms, 1methoxy-2-propanol, 1methoxy-3-propanol, and 1methoxy 2-, 3- or 4-butanol.
Representative members of the polypropylene glycol include dipropylene glycol and polypropylene glycol having a molecular weight of 150 to 1000, e.g., polypropylene glycol 400. Satisfactory glycol ethers are ethylene glycol monobutyl ether (butyl cellosolve), diethylene glycol monobutyl ether (butyl carbitol), triethylene glycol monobutyl ether, mono, di, tri propylene glycol monobutyl ether, tetraethylene glycol monobutyl ether, mono, di, tripropylene glycol monomethyl ether, propylene glycol monomethyl ether, ethylene glycol monohexyl ether, diethylene glycol monohexyl ether, propylene glycol tertiary butyl ether, ethylene glycol monoethyl ether, ethylene glycol monomethyl ether, ethylene glycol monopropyl ether, ethylene glycol monopentyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, diethylene glycol monopentyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monopropyl ether, triethylene glycol monopentyl ether, triethylene glycol monohexyl ether, mono, di, tripropylene glycol monoethyl ether, mono, di tripropylene glycol monopropyl ether, mono, di, tripropylene glycol monopentyl ether, mono, di, tripropylene glycol monohexyl ether, mono, di, tributylene glycol mono methyl ether, mono, di, tributylene glycol monoethyl ether, mono, di, tributylene glycol monopropyl ether, mono, di, tributylene glycol monobutyl ether, mono, di, tributylene glycol monopentyl ether and mono, di, tributylene glycol monohexyl ether, ethylene glycol monoacetate and dipropylene glycol propionate. While all of the aforementioned glycol ether compounds provide the described stability, the most preferred cosurfactant is propylene glycol N-butyl ether.
The preferred C1-C4 alkanols are ethanol or isopropanol and mixtures thereof
The final essential ingredient in the instant is water. The proportion of water in the compositions generally is in the range of 70 wt. % to 98.5 wt. %.
The liquid glass cleaning composition of this invention may, if desired, also contain other components either to provide additional effect or to make the product more attractive to the consumer. The following are mentioned by way of example: Colors or dyes in amounts up to 0.5% by weight; preservatives or antioxidizing agents, such as formalin, 5-bromo-5-nitro-dioxan-1,3; 5-chloro-2-methyl-4-isothaliazolin-3-one, 2,6-di-tert.butyl-p-cresol, etc., in amounts up to 2% by weight; and pH adjusting agents, such as sulfuric acid or sodium hydroxide, as needed.
The liquid glass cleaning compositions are prepared by simple batch mixing at 25xc2x0 C.-30xc2x0 C. The nonwoven fabric is impregnated with the liquid glass cleaning composition by means of a positive impregnation process. The liquid is positively fed into the nonwoven fabric through a controlled gear pump and injection bar at a ratio of about 2 grams of liquid glass cleaning composition to about 1 gram of the nonwoven fabric.
The nonwoven fabric which is manufactured by Dexter Corporation under the name Hydraspun comprises about 60% to 95% of wood pulp fabrics, 2.5 wt. % to 20 wt. % of viscose fibers and 2.5 wt. % to 20 wt. % of polyester fibers. Excluded as substrates for the wipes are any nonwoven fabric substitute that does not contain at least 50 wt. % of wood pulp fibers such as Spunlace nonwoven fabric substrate.
The following examples illustrate liquid cleaning compositions of the described invention. Unless otherwise specified, all percentages are by weight. The exemplified compositions are illustrative only and do not limit the scope of the invention. Unless otherwise specified, the proportions in the examples and elsewhere in the specification are by weight.


Systems and methods are provided for reducing intraocular pressure in an eye. A perpendicular incision is made through a conjunctiva of the eye to access a trabecular meshwork of the eye. Electromagnetic energy is focused through the perpendicular incision to ablate a portion of the trabecular network, where said ablation creates a channel for outflow flow of fluid through a sclera venous sinus to reduce pressure within the eye.

1. Field of the Invention
The present invention relates generally to medical treatments and, more particularly, to methods and apparatus for treating eye disorders such as glaucoma using energies including laser energies.
2. Description of Related Art
Glaucoma is an eye disorder in which the optic nerve suffers damage, permanently damaging vision in the affected eye(s) and progressing to complete blindness if untreated. It is often, but not always, associated with increased pressure of the fluid in the eye (aqueous humor). The term 'ocular hypertension' is used for cases having constantly raised intraocular pressure (IOP) without any associated optic nerve damage. Conversely, the term 'normal' or 'low tension glaucoma' is suggested for the typical visual field defects when associated with a normal or low IOP.
The nerve damage involves loss of retinal ganglion cells in a characteristic pattern. There are many different subtypes of glaucoma, but they can all be considered a type of optic neuropathy. Raised intraocular pressure is a significant risk factor for developing glaucoma (above 21 mmHg). One person may develop nerve damage at a relatively low pressure, while another person may have high eye pressure for years and yet never develop damage. Untreated glaucoma leads to permanent damage of the optic nerve and resultant visual field loss, which can progress to blindness.
Glaucoma can be divided roughly into two main categories, "open angle" and "closed angle" glaucoma. Closed angle glaucoma can appear suddenly and is often painful; visual loss can progress quickly, but the discomfort often leads patients to seek medical attention before permanent damage occurs. Open angle, chronic glaucoma tends to progress at a slower rate at which patients may not even notice they have lost vision until the disease has progressed significantly.
Glaucoma has been nicknamed the "silent thief of sight" because the loss of vision normally occurs gradually over a long period of time, and is often only recognized when the disease is quite advanced. Once lost, this damaged visual field cannot be recovered. Worldwide, it is the second leading cause of blindness. It is also the leading cause of blindness among African Americans. Glaucoma affects one in 200 people aged fifty and younger, and one in 10 over the age of eighty. If the condition is detected early enough, it is possible to arrest the development or slow the progression with medical and surgical means.


Protective clothing for protection against puncture injuries is constructed from more than one layer of a fabric coated with hard solids. The hard solids are applied in accordance with abrasives technology. This protective clothing offers equally good protection against both knife- and needle-like puncture implements. For clothing intended to protect against puncture and projectile injuries, a package of 2-20 layers of a fabric coated with hard solids is combined with a package of 6-50 layers of an uncoated aramid woven fabric.

1. Field of Invention
The invention relates to protective clothing, in particular clothing for protecting against puncture or projectile injuries, consisting of a plurality of fabric layers made from high-strength materials.
In the line of duty, police and other security forces are subject not only to the danger of projectile injuries but also increasingly to attacks with knives, daggers, and other puncture implements, which often have needle-like character. The resulting safety requirements for police forces cannot be adequately satisfied by conventional bulletproof vests, which often are part of the standard equipment of this group of individuals, since these vests do not provide sufficient protection against puncture injuries.
2. Description of Related Art
For this reason, special protective clothing has been developed that is primarily intended to offer protection against puncture injuries. There have also been attempts to produce clothing that protects against both projectile and puncture injuries, however. While many of the proposals meet the requirements of police forces, they are poorly suited for use when a high degree of physical mobility is required, due to their heavy weight and frequent lack of flexibility.
Moreover, police forces demand that protective clothing protect not only against injuries by knives, daggers, and similar puncture implements, but also against needle-like puncture implements, which are in part also employed in attacks on police.
Although various problem solutions, primarily involving the use of aramid woven fabrics either wholly or in part, have been suggested for manufacturing puncture-proof clothing, none has been completely satisfactory.
For example, GB-A 2 283 902 describes puncture-proof clothing constructed from aramid woven fabrics, with metal plates affixed to the surface. Such clothing has a low degree of wearing comfort, since it does not ensure the needed flexibility and also forces the wearer to accept the heavy weight. Protective clothing in a similar embodiment is described in WO-A 91-06 821.
In DE-C 4 407 180, the use of a metal insert embedded in a polyurethane matrix is proposed for puncture-proof clothing. This metal insert takes the form of a network-like structure of steel chains. The disadvantage of this type of puncture-proof clothing is that it offers good protection only from blade-type puncture implements such as knives, daggers, etc., but not from sharply pointed, needle-like implements.
U.S. Pat. No. 4,933,231 describes a dense foamed-plastic-encased woven fabric made from high-strength aliphatic polyamide fibers, the fabric appearing to be suitable especially for clothing protecting against incisions. This embodiment cannot provide the puncture protection demanded by security forces.
This is also true for the puncture-proof clothing proposed by EP-A 224 425, which is produced from knitted fabrics made from aramid fibers. In this case as well, there are insufficient puncture protection characteristics. The proposed knitted fabric is more suited to incision protection.
Particularly breathable puncture-proof clothing, intended to be produced by employing a so-called climatic membrane made from dense woven fabric, is described in U.S. Pat. No. 5,308,689. The embodiment proposed in this case does not offer sufficient puncture-proof characteristics.
Puncture-proof clothing made from overlapping glass-fiber-reinforced plastic plates arranged on a textile base is described in WO 92-08 094. Due to its lack of flexibility, such protective clothing does not offer the desired wearing comfort.
Furthermore, several proposals have been made for protective clothing for combined puncture and bullet protection, in various embodiments.
For example, U.S. Pat. No. 5,562,264 proposes the use of extremely dense woven fabrics made from relatively fine yarns. These are intended to provide protection in a similar manner against puncture and projectile injuries. This problem solution is not satisfactory, since the production of the fabrics is very expensive and the weaving at a high density can cause fiber damage, leading primarily to reduced retention characteristics for projectiles. Moreover, the puncture protection in this embodiment does not adequately meet the specifications of all countries.
In DE-A 4 413 969, puncture-proof clothing made from multiple layers of metal foils is proposed. By combination with laminates made from aramid-fiber woven fabrics, protection against bullets is also attained. In addition to the high cost of metal foils, this protective clothing also does not provide satisfactory wearing comfort due its low degree of flexibility. Moreover, the rustling caused by the metal foils is regarded as disagreeable when the clothing is worn. A similar embodiment of puncture-proof clothing is found in EP-A 640 807, which proposes fabrics made from narrow metal foil strips.
A package of woven fabrics, such as those made from aramid fibers, formed into a plate using a thermoplastic matrix resin, is described in EP-A 597 165. This relatively rigid structure does not offer the desired wearing comfort.
In WO 97-21 334, aramid fabrics coated with thermoplastic resins are proposed for combined puncture and bulletproof protective clothing. This embodiment does not allow puncture-proof clothing that meets the requirements of security forces in all countries in the acceptable weight ranges.
According to DE-A 4 214 543, clothing intended to provide combined protection against punctures and projectiles and also against impact is manufactured in the puncture-proofing layers from metal plates displaceable with respect to one another and forming the outer layer of the protective clothing. Underneath is a fabric package intended for bulletproofing. This protective clothing as well shows the usual disadvantages of metal plates: a low degree of flexibility and relatively heavy weight, thus adversely affecting wearing comfort.
In DE-U 94 08 834, a package of superimposed layers with alternating textile fabrics made from aramid fibers and metal netting is proposed for combined puncture and bullet protection. The disadvantage of this embodiment is the low degree of protection from needle-like implements.
WO 96-03 277 describes protective clothing containing at least one layer of a fabric to which a ceramic layer has been applied by plasma spray coating. While this type of protective clothing attains good protection against puncture and projectile injuries, the manufacture is complicated, due to the plasma spray coating process employed, and also uneconomical from a cost standpoint. Moreover, application of the ceramic layer can lead to a partial fusion of the ceramic particles by sintering, due to the high temperatures in the plasma, so that the protective action against puncture implements can suffer somewhat. Furthermore, there are also some problems with respect to abrasion resistance.
The use of abrasive materials has been proposed for protective clothing. According to GB-A 2 090 725, for example, the protective action against projectiles is intended to be increased if the outer layer of an antiballistic package contains abrasive material such as aluminum oxide, boron carbide, etc. Tests have shown that a layer of such a material does not have a positive effect on the protective action against projectiles. To what extent the puncture-proof characteristics can be improved using the proposed embodiment cannot be determined from the document. Moreover, it contains no information whatsoever concerning the amount of abrasive material or the process for manufacturing such a protective layer.
According to a proposal in U.S. Pat. No. 5,087,499, a very thin layer of abrasive material is applied to aramid yarns that are subsequently to be subjected to fibrillation. This is intended primarily to provide protection from puncture injuries by surgical instruments. The very thin layer disclosed in this document can provide no protection at all against injuries inflicted by knives.
Even using prior art abrasive materials, the described embodiments do not allow manufacture of protective clothing for security forces that offers adequate protection against puncture injuries as well as those from projectiles.
For this reason, the object arose to develop puncture-proof clothing that not only offers the same protection for puncture injuries inflicted by knives, daggers, etc. as provided by the known puncture-proof clothing, but that moreover ensures protection against needle-like implements. Furthermore, the object arose to improve wearing comfort compared to the prior art puncture-proof clothing, while ensuring good protective action.
A further object was to design the materials for puncture protection such that they are also usable for combined puncture- and bulletproof clothing.
Surprisingly, it was discovered that this object can be satisfied in a particularly advantageous manner if the protective clothing comprising multiple layers has more than one layer coated with a hard-solid layer, whereby the hard solids are embedded in phenolic resins, urea resins, latex in cross-linked or non-cross-linked form, epoxy resins, or polyacrylate resins.
Clothing to protect against injuries from punctures and projectiles is normally constructed from multiple layers. Existing clothing has varying numbers of layers. The selection of the number of layers depends on various factors such as the protective action required, the desired wearing comfort, clothing costs, etc. In general, the number of layers must be as low as possible but high enough to satisfy the protection requirements.
WO 98/45 662, not previously published, discloses a puncture-proof material consisting of a base coated with solid particles, which is arranged on a package of fabric structures. The coating consists of abrasive particles with a diameter of 0.1 to 3 mm, and the package of fabric structures is thicker than 1.5 mm. Also in accordance with WO 98/45 662, multiple coated bases can be employed. The solid particles, however are applied to the base with a bituminous adhesive or one containing polyurethane.
The protective layers of the puncture- and bulletproof clothing are normally constructed from fabrics made from high-strength materials. These fabrics are preferably textile fabrics, whereby woven fabrics are especially preferred. In addition to woven fabrics, however, other textile fabrics such as knits, nonwoven fabrics, thread composites, etc. can be employed.
Non-textile fabrics include in particular sheeting, foils, or thin foamed-plastic layers.
High-strength materials are those exhibiting a high degree of strength and good protection against the effects of projectiles and puncture implements. They are primarily polymers processed into fibers.
Preferred materials used for the manufacture of the protective layers of the protective clothing of the invention are aramid fibers, polyethylene fibers spun using the gelspinning process, polyimide fibers, polybenzoxazol fibers, fully aromatic polyester fibers, high-strength polyamide fibers, high-strength polyester fibers, and fibers with similar properties. Aramid fibers are particularly preferred.
Aramid fibers, often also referred to as aromatic polyamide fibers, are frequently used in protective clothing. They are fiber materials made from polyamides that are substantially generated by polycondensation of aromatic acids or their chlorides with aromatic amines. Especially well known are aramid fibers consisting of poly-p-phenylene terephthalamide. Such fibers are commercially available under the trade name Twaron, for example.
Aramid fibers, however, are not limited to fibers constructed solely from aromatic acid or amine components. Rather, they also include fiber materials whose polymer has a fraction of aromatic acids and aromatic amines exceeding 50% and that in addition contain aliphatic, alicyclic, or heterocyclic compounds in the acid and/or amine fraction.
For the woven fabrics to be employed preferably for producing the protective layers of the protective clothing of the invention, the preferred aramid fibers can be present in the form of filament yarns or spun-fiber yarns. Filament yarns are preferred. Spun-fiber yarns also include yarns produced by the tow-to-top breaking process.
The titers of the yarns to be used are between 200 and 3 400 dtex, preferably between 400 and 1 500 dtex. The filament titers are generally under 5 dtex, preferably under 1.5 dtex.
The woven fabrics are preferably produced in linen weave. Other weaves such as hopsack or twill can also be selected for fabric production, however.
The thread count depends on the yarn titer used and the desired weight per unit area of the fabrics to be used for the protective layers. The weight per unit area of these fabrics should be between 50 and 500 g/m2, preferably between 100 and 300 g/m2.
An example of a fabric advantageously used for the protective clothing of the invention is produced in linen weave from a yarn with a titer of 930 dtex. The thread counts in this case are 10.5/cm in warp and weft. With such a weave density, a fabric with a weight per unit area of approx. 200 g/m2 is obtained. The data given here should be understood as exemplary and not restrictive.
Synthetic fibers generally contain a lubricant remaining from the fiber production process, which, among other things, has a positive influence on the rolling qualities of the yarn during fabric manufacture. Prior to conducting subsequent processes, such as the coating in preparation for applying a hard-solid layer, the fabric coming from the power loom, i.e., in the loom state, is subjected to a washing treatment. This treatment is normally performed on a full-width washing machine, although other full-width washing apparatus known in the textile finishing industry can also be used. The washing conditions such as temperature, treatment time, and additives to the washing bath are known to one skilled in the art. The washing conditions are selected so that the residual lubricant content following this treatment is less than 0.1%. Finally, drying of the fabric takes place, normally on a tenter frame.
Fabrics intended to form the actual bulletproof layers in the protective clothing of the invention, and which are not provided with a hard-solid coating, can be used in this form. In many cases, the washing treatment is followed by a hydrophobizing treatment, for example using a polymeric or polymerizable fluorocarbon compound.
Washed fabrics are preferred for the hard-solid coating, but it is also possible to use fabrics in the loom state, i.e., unwashed. In a preparatory step for the hard-solid coating, a precoating is applied to the fabric. This is necessary to prevent penetration of the subsequently applied binder layer, needed to incorporate the hard solids, into the base fabric.
A large number of different products can be used for the precoating. Examples are phenolic resins, urea resins, latex in cross-linked or non-cross-linked form, epoxy resins, or polyacrylate resins. In addition to the dispersed resin or the precursors for the resin, the compound for the precoating also contains fillers in a ratio of 30%-70%. An example of a filler is calcium carbonate.
The precoating is applied with a coverage of 40-100 g/m2. After evaporation of the liquid present in the coating compound, about 30-75 g/m2 remains on the fabric.
Normally, application of the precoating is followed by an intermediate drying stage, for example at a temperature of 100xc2x0 C. It is also possible, however, to work wet-on-wet, i.e., to apply the subsequent main coating without intermediate drying.
For the main coating, the classes of compounds previously discussed for the precoating are suitable. Phenolic resins find preferred use for the main coating. However, the products for the pre- and main coatings are subject to differing requirements depending on the differences in the desired objectives. The product for the precoating must form a well-closed, preferably elastic film, to prevent subsequent penetration of the main coating into the base material. On the other hand, the essential characteristic of the product forming the main coating is the optimum incorporation of the hard solids.
In the main coating as well, there is a filler fraction, which can amount to 20-50% of the total amount of binder. The quantity of main coating to be applied is between 90 and 150 g/m2 in the wet state. After drying, the amount of main-coating binder is 60-120 g/m2.
Hard solids are understood to be inorganic substances with a high grade of hardness, such as are also used in the abrasive layer of abrasives, for example. Examples are silicon carbide, corundum (aluminum oxide), tungsten carbide, titanium carbide, molybdenum carbide, zirconium corundum (fused corundum with 40% zirconium oxide), boron carbide, or boron nitride. This list of hard solids is not intended to be exhaustive; it serves only to provide examples and should not be considered restrictive. Preferably, silicon carbide and/or corundum are used to form the hard-solid layer.
The cited substances are preferably used alone, but mixtures of different hard solids can also be employed.
The hard solids can be used in various forms. Preferred are so-called block and pointed forms. The former are preferably round particles. These have the advantage that they permit a high bulk density. The shape of the hard-solid particles, however, is significant only in the case of larger particle diameters. For smaller diameters, the differences in the particle shape are barely noticeable.
The application of the hard solids is performed on a substrate provided with a binder layer using a method commonly employed when applying abrasives.
In these methods, there is preferably a spreading of the hard solids or their application in an electrostatic field. In the first method, normally referred to as gravity spreading, the hard solids fall from the slit of a spreading funnel onto the course of fabric to which the precoating and main coating have been applied. The spreading density is controlled on the one hand by the width of the slit and on the other hand by the speed at which the fabric is moving.
In the electrostatic method, the application is performed using an electrostatic field. The hard-solid particles orient themselves in this field along the lines of flux of the electrostatic field and migrate along these lines to the opposite pole. The mobility of the hard-solid particles in the electrostatic field is utilized in abrasives technology in that the base layer to which the precoating and main coating has been applied is moved along the upper electrode through the electrostatic field. The coated side of the base is positioned toward the opposite electrode. The hard-solid particles, which are located at the lower electrode, migrate in the electrostatic field upward toward the opposite electrode and are anchored in the binder film of the base.
The introduction of the hard-solid particles into the electrostatic field is performed using a continuous conveyor belt that moves along the lower electrode and onto which the hard-solid particles are applied outside the electrostatic field using a spreading funnel.
The electrodes are preferably plate electrodes, but linear or pointed electrodes can also be used.
A further possibility to apply the hard-solid layer is by forming a paste, which is also known in abrasives manufacturing. Here, the hard solids are stirred into the binder compound, which is then poured or brushed onto the base.
The fabrics for the protective clothing of the invention, coated with hard solids, are preferably produced by gravity spreading, since this method enables a high density of the hard-solid particles to be achieved.
After applying the hard solids, a hardening of the binder film takes place at a temperature of approx. 130xc2x0 C. Through the evaporation of liquid, the thickness of the binder film decreases somewhat, so that the hard-solid particles appear to an increased extent on the surface of the coated side. This decrease in thickness of the binder film is also utilized with the paste process, since the evaporation of liquid and reduction of the film thickness enable the hard solids stirred into the binder compound to migrate to the surface after drying.
In addition to the hot-air drying normally conducted in abrasives manufacture, it is also possible to employ other processes for hardening the binder film, such as the use of electron beams, microwaves, UV rays, etc.
When producing the fabric of the invention, which is coated with hard solids, it is possible to also perform a surface sealing of the hard-solid layer. In this case, a thin layer of an elastomeric polymer is applied to the hard-solid layer, for example by spraying it with a dispersion of an elastomer. Another possibility is to use a roller application. Here, a roller moves through a reservoir trough containing the dispersion to be applied. After leaving the trough, the excess dispersion taken up is scraped off, for example with a doctor blade, so that a thin film is produced on the applying roller for transfer to the hard-solid layer.
Hardening of the sealing layer is done in a manner similar to that for the binder layer, preferably by a drying treatment.
In a final work step, a flexing process is conducted. Flexing is a defined break-up of the rigid covering layer using mechanical means, resulting in the creation of small islands of binder layer, including the hard solids anchored in this layer, on the base material. The flexibility, resulting from flexing, of the base coated with hard solids is probably attributable to the fine crack structures formed thereby in the adhesive film. The conditions for flexing and the machinery it requires are well known in the adhesives industry.
Preferably, production of the fabric coated with hard solids is performed using cross-flexing, i.e., a flex treatment is performed in the transverse as well as longitudinal direction of the fabric.
The flexing produces a good elasticity of the fabric coated with hard solids for use in the protective clothing of the invention, manifesting itself quite favorably in the wearing comfort of this clothing.
The fabrics coated with hard solids and produced in the described manner exhibit a thickness between 0.1 and 1.5 mm, preferably between 0.2 and 0.8 mm, depending on the diameters of the hard solids used.
Determination of the thickness of the hard-solid layer is performed using the known method in the textile industry for measuring woven fabrics. Here, the thickness of the uncoated fabric is first determined and then that of the fabric coated with hard solids. The measurement is performed according to DIN 53 353. The difference in thickness yields the thickness of the hard-solid layer.
The fabrics coated with hard solids and produced in the described manner can be used for clothing providing protection against puncture injuries or combined protection against puncture and projectile injuries. Preferably, fabrics are used that are coated on only one side with hard solids. It is possible to use fabrics coated on both sides, however.
Clothing intended to protect only against puncture injuries is produced from more than one layer of the fabric coated with hard solids, preferably 2-20 layers, with 6-15 layers being especially preferred. In this case, the layers are superimposed and cut to shape as required for the clothing. The mutual reinforcement of the individual layers is performed, for example, by two cross-forming seams of approx. 10 cm each in the center of the cut piece. Another possibility of reinforcing the layers is pointwise application of adhesive.
The essential element is that there is no rigid joining of the individual layers with respect to each other and that the individual layers remain mobile.
It has been shown, however, that it is also possible to introduce the layers into the protective clothing without mutual reinforcement, since with the fabrics coated with hard solids there is much less shifting of the layers than if the fabrics are uncoated. Presumably, the hard-solid layer, especially in adjacent layers coated with hard solids but also in those that are uncoated, effects an anchoring with a type of Velcro(R) effect, so that slippage can largely be avoided. This is especially true if textile fabrics such as wovens or knits are used as the base material for the coating with hard solids. In the case of woven fabrics and knits, interstices are present that are not covered by the yarns. The hard solids of the adjacent layer can penetrate these interstices and become anchored therein. In the case of sheeting with a substantially well-closed surface, this is not possible, or possible only to a limited extent.
The hard-solid coated fabrics, combined into a package with 2-20 layers and cut to shape for the clothing required, are placed into an envelope made from PVC or thermoplastic polyurethane sheeting and sealed therein. Instead of sheeting, a woven fabric coated with a fusible polyurethane layer and made from polyamide fibers, for example, can also be used. In this case, the coated side is the inside.
The package thus formed is then placed into a cover of cotton woven fabric or a woven fabric of polyester-cotton blended yarns. Blended yarns made from viscose fibers and m-aramid fibers can be used in this case. This fabric is dyed or printed on the side visible when worn. Special attention must be paid that the actual protective package, consisting of fabrics coated with hard solids, can easily be removed, in order to permit uncomplicated cleaning, especially of the cover.
In the case of protective clothing intended to provide protection only against puncture injuries, a padding layer can be applied under the actual protective layers on the side adjacent to the body. This padding layer should consist of a compressible material. Suitable in this case are foamed plastics, felts, needle felts, superimposed layers of nonwoven fabrics, pile wovens, pile knits, etc. When a puncture implement such as a knife is applied, these padding layers produce a cushioning effect that can contribute to reduced penetration of the implement. Furthermore, it cushions somewhat the pressure acting on the body when a puncture implement is used.
For the manufacture of this padding layer, textile fabrics are preferred, and needle felts or nonwoven fabrics made from high-strength fibers are especially preferred. Aramid fibers are especially suited in this case. In addition to the aforementioned cushioning effect, they also offer added protection against punctures.
The fabrics coated with hard solids are preferably arranged in the protective clothing such that the hard-solid layer is on the side away from the wearer. In this way, the best puncture-protective action is obtained when using fabrics coated on one side. It is also possible, however, to arrange the coated side toward the inside, i.e., toward the wearer, or to select an alternating arrangement of fabrics coated with hard solids in the puncture-proofing package. Clothing that is to offer combined puncture and bullet protection is produced from more than one layer coated with hard solids, preferably from 2-20 layers, with 6-15 layers being especially preferred, and 6-50 layers of uncoated fabrics. The number of layers of uncoated fabrics in protective clothing for combined puncture and bullet protection is preferably 8-40, and 16-35 are especially preferred. Woven fabrics of aramid fibers are preferably used as the uncoated fabrics. The uncoated aramid fabrics, which form the actual bulletproof package, are arranged on the side facing the body. These fabrics are produced in the same manner as previously described for the aramid fabrics used as base materials for the hard-solid coating.
The protective package for combined puncture and bullet protection can be designed such that the actual puncture-proofing layers, which are those coated with hard solids, are joined to the uncoated aramid fabrics. For example, cut-to-shape pieces made from 6-50 layers of uncoated aramid fabrics are superimposed. 2-20 layers of fabrics coated on one side with hard solids are laid thereon such that the coated side is the outside. The individual layers of the package so formed are, for example, reinforced in the aforementioned manner with a crosswise double seam or by pointwise application of adhesive.
In the production of the protective clothing, the package is then, as previously described, sealed into a sheeting envelope and then in a woven-fabric cover, made for example of a fabric of polyester-cotton blended yarns. This insertion is performed such that the fabrics coated with hard solids are on the side facing away from the wearer and that a puncture implement or projectile first strikes the layers coated with hard solids.
The previously described construction of combined puncture and bulletproof clothing is understood to be the preferred embodiment. It is also possible to arrange the fabrics with hard solids in the packaging comprising a total of 8-70 layers such that they are not just on the outside of the protective clothing but rather, for example, distributed across the protective package, on the outside, in the middle, and on the inside. The arrangement of layers coated with hard solids is not limited to an embodiment in which the hard-solid layers are positioned away from the wearer toward the outside. The opposite arrangement, or an alternating arrangement, is possible, although the arrangement of the hard-solid layer toward the outside is preferred.
A particularly preferred embodiment of combined puncture and bulletproof clothing is provided by a variation that can optionally be used for protection against one of these threat types, i.e., protection against puncture injuries or against projectile injuries. It can be also be used simultaneously for protecting against both types of threats.
In this case, the actual bulletproof package is first formed from 6-50 layers of an aramid fabric not coated with hard solids, by superimposing suitable cut-to-shape pieces and reinforcing in the previously described manner. This package is sealed into a sheeting envelope.
In addition, a package is formed from 2-20 layers of a fabric coated with hard solids and also sealed into a sheeting envelope.
To accommodate both packages, a cover is made from a dyed or printed polyester-cotton woven fabric, for example. This fabric cover is then provided with a Velcro(R)-type fastening or zipper to enable simple insertion and removal of either or both of the packages.
If protective clothing is now to be offered for combined puncture and bullet protection, the two packages are, for example, inserted together into an envelope which then forms the outside layer of a bulletproof vest. The arrangement of the actual puncture-proof package, i.e., the package consisting of fabrics with hard-solid coating, is preferably accomplished by locating it on the side directed away from the wearer, i.e., the side initially subjected to an attack.
If puncture protection is not required, and only the threat of projectiles is anticipated, the actual puncture-proofing package made from fabrics coated with hard solids can be removed and the protective clothing used solely with a package of aramid woven fabrics to which no hard-solid coating has been applied.
An analogous approach is used if only the threat of puncture injuries is expected. In this case, the bulletproofing package consisting of uncoated aramid woven fabrics is removed from the clothing, and the protective package then consists solely of fabrics coated with hard solids. It is practical in this case to additionally insert a padding layer into the protective clothing where the bulletproof package formerly was. This padding layer, designed in the previously described manner, is also in an envelope, for example made from sheeting, so that simple insertion or removal of the padding layer is ensured.
The action of the hard-solid layer when encountering puncture implements has not yet been sufficiently explained. The observations noted in tests indicate that the hard solids present such high resistance to a puncture implement, such as a knife, that the implement is diverted somewhat laterally on encountering the first protective layer. The next resistance is produced by the base of the hard-solid layer, provided that it consists of suitable materials such as aramid fibers. This combined action of hard-solid layer and base causes the energy acting on the protective clothing by the puncture implement to be dissipated. Since the puncture implement must penetrate multiple layers, and this energy reduction occurs in each layer, the puncture energy in the lowermost layers is insufficient to allow the implement to penetrate and enter the body.
An additional effect is probably attributable to the fact that the acuity of a blade is reduced by the passage along the hard-solid particles. This reduces the opportunity for penetrating the layers underneath. Sharp-edged hard-solid particles appear to act in an especially favorable manner.
The protective action shows a dependence on the average grain diameter of the hard-solid particles. A diameter range of 10-500 xcexcm has proven suitable. A range of 20-200 xcexcm is preferred, and a range of 25-150 xcexcm especially preferred.
In the abrasives industry, it is in part common to classify the hard solids with granulation indices. A granulation index of P 220 in accordance with FEPA corresponds in the case of fused alumina or silicon carbide, for example, to an average grain diameter of 66 xcexcm. Of course, the grain diameters are subject to variation. In the average grain diameter of 66 xcexcm cited as an example, the variation, normally subject to a normal distribution, can be expected to range from 40 to 90 xcexcm.
It has been shown that for small average grain diameters under about 10 xcexcm the desired protective action is no longer provided to the extent required, since small hard-solid particles have only slight action in the previously described manner. The cited limit of about 10 xcexcm, however, does not apply generally. Depending on the overall thickness of the hard-solid layer, displacement to one side or the other can occur. Surprisingly, however, it was determined that relatively large average grain diameters exceeding 500 xcexcm also do not provide better puncture protection compared to those in the mid-range. This can probably be explained by the fact that the coverage of the base material with hard solids is not as uniform for coarse particles as for finer particles, so that, overall, a larger surface portion of base material is produced that is inadequately coated with hard solids and allows a relatively high number of opportunities for the puncture implement to penetrate through the hard solids and the base material without significant obstruction.
The test of puncture-proof characteristics was conducted in accordance with the Research and Development Center for Police Technology in Munster, Germany. In this case, a puncture is made with a stiletto with double-edged pointed blade and weighing 2.6 kg. The test blade must act on the object under test with an energy of 35 J (corresponding to a fall height of 1.35 m). Prior to each puncture trial, a homogeneous film of lithium soap fat was applied to the test blade.
As the background material, a plastilina block is placed behind the test object. The penetration into this block or extent of bulging are the parameters for assessing the puncture-proof characteristics. According to the guidelines of the German police, a puncture-proof material exhibiting a penetration under 20 mm or a bulge under 40 mm is suitable for security force equipment.
In addition to the puncture test with a knife-like implement, tests were also carried out with a needle-like puncture implement. In this case, an ice pick, which is used in the U.S. standard for puncture testing, is employed. Determination is made whether the puncture implement is stopped or penetrates the sample.
To test the objects in the trial, the fall height and weight were varied, resulting in different puncture energy levels. In this case as well, the test is conducted by assessing the penetration. The fall heights and weights used in the trials correspond to the following puncture energy levels.
The bombardment test was also conducted on the basis of the guidelines issued by the Research and Development Center for Police Technology, Mxc3xc{umlaut over (n)}{umlaut over (s)}{umlaut over (t)}xc3xa{umlaut over (r)}.
The bombardment of the test object in this case takes place at a distance of 10 m, whereby the projectile speed is determined in each case. A plastilina block is positioned behind the object under test. From the depth of penetration into the plastilina, the so-called trauma effect is assessed.
As show in detail in the embodiment example, good protection against puncture implements can be attained with the protective clothing of the invention. This is true not only for puncture implements with cutting edges such as knives, daggers, but also for needle-like implements. In contrast to previously proposed protective clothing, the protective clothing of the invention offers, due to its relatively low weight, relatively low thickness, and its flexibility, the wearing comfort that security forces need in the line of duty when requiring a high degree of physical exertion.
This also applies when the puncture-proof layers are used in combination with bulletproof layers for combined protective clothing, i.e., for clothing that is to offer protection not only from puncture implements but also from projectiles.

Puncture-and bullet proof protective clothing