MXPA97005539A - Composite film moisture barrier for on-cell tester - Google Patents

Abstract

A light transparent moisture barrier (60) useful for preventing moisture from destroying the effectiveness of a moisture sensitive cell condition tester (10) on an electrochemical cell (50), comprises a plurality of very thin layers of amorphous silicon nitride and a hydrophobic fluorocarbon polymer on a flexible, polymeric substrate (20, 16, 18, 14, 12). The layers are formed on the substrate by a deposition process such as sputtering. The thickness of any individual layer is less than one micron.

Description

BARRIER OF MULTIPLE COATS FOR MOISTURE FOR ELECTROCHEMICAL CELL TESTER BACKGROUND OF THE INVENTION Field of the Invention This invention relates to a moisture barrier, multi-layered, transparent to light. More particularly, this invention relates to a thin film, light transparent multilayer composite comprising a plurality of alternating layers of an inorganic material and an organic material useful as a moisture barrier, for a sensitive tester. the humidity on the cell, a process for the elaboration of said barrier and also refers to an electrochemical cell that has a tester sensitive to humanity on the cell, and the barrier • Background of the Invention the use of cell condition testers, such as thermochromic voltage testers, to visually indicate the condition of REF: 25232 an electrochemical cell, commonly referred to as a battery or battery, has become very popular and provides a advantage of added value to the manufacturer of the battery and to the consumer. These testers are used with primary electrochemical cells, although these can also be used by consumers to test the condition of a secondary or rechargeable electrochemical cell, if desired. The most popular tester currently in use is a thermochromic material in contact with an electrical resistance element which forms an integral part of a container or battery pack in which the batteries are alkaline primary cells. The user places the terminals of the cell between the contacts of the tester and tightens the contact ends of the tester to make electrical contact with the terminals of the cell, which are the ends of the cell. The resistance element of the tester is heated in proportion to the voltage of the cell and the thermochromic material provides a quantitative indication of the condition of the cell over a range indicating "good" or "rebound". This type of tester is described, for example, in U.S. Patent No. 4,723,656. An integral thermochromic package tester, which can also be removed from the package or package, is described in U.S. Patent No. 5,188,231. More recently, testers have been developed on the cell in which the condition indicator of the cell is an integral part of the cell label. These testers on the cell include the thermochromic type and a new one, the type of electrochemical tester. An example of a thermochromic type of a tester on cell is described in European Patent Publication No. 0,523,901 Al, the disclosure of which is incorporated by reference herein. Contrary to the thermochromic type that uses a resistance element to produce heat, and which may therefore not be permanently coupled to the cell terminals without continuously discharging it, the new electrochemical type does not draw current from the cell and may so be permanently coupled to the terminals of the cell without downloading to the cells. This new type of tester is described in U.S. Patent Nos. 5,250,905 and 5,339,024 the descriptions of which are incorporated by reference herein. As described in U.S. Patent No. 5,355,089 some electrochemical types of condition testers, on cell, employ hygroscopic or otherwise moisture sensitive electrolytic compositions, and means are needed to prevent moisture from reaching the electrolyte which will deteriorate the effectiveness of the tester. This patent describes a number of solutions to this problem, the best of which is mica, however, although mica is relatively inexpensive, it is not available in long ribbons or in other forms that allow it to be wound on a mica roll. which is necessary for commercial, economically viable production methods.

BRIEF DESCRIPTION OF THE INVENTION The invention relates to a light-transparent composite, useful as a moisture barrier, which comprises at least one layer of silicon nitride and at least one layer of fluorocarbon polymer, preferably at least two layers of nitride silicon and at least two layers of fluorocarbon polymer, and which is formed by the deposition or formation of said silicon nitride and fluorocarbon polymer layers on a substrate. In one embodiment, the compound of the invention comprises at least four layers, with at least one layer of silicon nitride and at least one layer of fluorocarbon polymer on one side of the substrate, and at least one layer of silicon nitride and minus one layer of fluorocarbon polymer on the opposite side of the substrate. In yet another embodiment, more than one layer of silicon nitride and more than one layer of the fluorocarbon polymer are on one side or surface only of the substrate. In this embodiment, and in the embodiment in which there is more than one layer of each of the silicon nitride and the fluorocarbon polymer, on each of the opposite sides (eg, top and bottom) of the substrate, the composite comprises alternating layers of fluorocarbon polymer silicon nitride. The invention includes multi-layer composite materials in which there are more than two layers of each of silicon nitride of the fluorocarbon polymer, with the effective number of layers depending on the desired properties of the compound, and which is limited only by the ability of the practitioner to deposit a large number of layers. In an embodiment in which the compound of the invention is used as a moisture barrier for an on-cell tester for an electrochemical cell, the substrate is a flexible polymer and the composite is a thin film composite, transparent to the light, flexible, in which the thickness of each of the silicon nitride layers of the fluorocarbon polymer is less than one. In a further embodiment, the compound of the invention is used as a transparent packaging material for materials and articles sensitive to moisture. When used as a moisture barrier for a tester over cell, the light transparency of the composite material makes it possible for a user to observe the condition of the cell, as shown by color, by printed signs or other visual means used by the tester to indicate the condition of the cell. The over cell tester means a tester that visually indicates the condition of the cell and is permanently coupled to the cell either by means of a cell tag or by other means, although the invention is not limited to this mode. One type of a moisture-sensitive cell tester, for which the moisture barrier composite of the invention is useful, is a tester that includes at least one hygroscopic material which, if it absorbs water vapor , deteriorates or destroys the effectiveness of the tester. Another type is a tester that includes at least one component that requires the presence of a predetermined amount of water to function, and which therefore needs a moisture barrier to maintain that level of water in the tester.

The silicon nitride and the fluorocarbon polymer are insoluble in water, with the fluorocarbon polymer selected to have a water vapor permeation rate or rate as low as possible, for applications in moisture barriers. For moisture barrier applications it is preferred that the fluorocarbon polymer be hydrophobic. The process for making the multilayer composite comprises the deposition of a layer of silicon nitride on a substrate, followed by the deposition of a fluorocarbon polymer layer on the silicon nitride layer. If more than one layer of silicon nitride and fluorocarbon polymer are required, the process of deposition of alternating layers is continued until the desired number of layers has been applied. Thus, the composite material of the invention is distinguished by laminates in which various pre-existing layers are adhesively or otherwise bonded to one another, and because the alternating layers of the composite material of the invention are formed in-house. on the sulfate, and on other layers of the composite material, by deposition or coating processes which include electronic deposition or sputtering, physical vapor deposition, including the deposition of physical vapor enhanced by plasma, chemical vapor deposition and the like.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 schematically illustrates a four-layer moisture barrier on a polymeric substrate according to the invention. Figure 2 (a) schematically illustrates a cross-section of a tester on cell, on a cell with a moisture barrier of the invention, and Figure 2 (b) illustrates schematically, in partial broken lines, a side view of a cell having a tester on cell and a moisture barrier, of the invention.

DETAILED DESCRIPTION Figure 1 illustrates schematically a thin film moisture barrier 10 of the invention, comprising a flexible plastic substrate 12, with a layer of silicon nitride, layers 14 and 16, deposited on both sides of the substrate. A layer of the fluorocarbon polymer, hydrophobic, layers 18 and 20, is shown as deposited on each of the layers of silicon nitride. Thus, the multi-layer moisture barrier illustrated in this figure is a four-layer composite material (excluding the substrate). If desired, the composite material of four layers is deposited only on one side of the substrate. Additional layers of the silicon nitride and the fluorocarbon polymer are alternately deposited one on the other either on one side of the substrate or on both sides of the substrate, to form six, eight, ten, twelve or even one hundred layers of composite material if you want In this way, a first layer of silicon nitride is deposited on one or both sides of the substrate, and then a first layer of fluorocarbon polymer is deposited on the layer or layers of silicon nitride. A second layer of silicon nitride is then deposited on the first layer or layers of the fluorocarbon polymer and a second layer of the fluorocarbon polymer is then deposited on the second layer or layers of silicon nitride. This alternate layer deposition process is repeated until a multilayer, thin film composite having the desired number of layers is formed. The thickness of each of the silicon nitride layers is within the range of about 200 angstroms to about 5,000 angstroms, preferably from about 250 angstroms to 2,500 angstroms, and still more preferably from 500 to 1,000 angstroms. The thickness of each of the layers of the fluorocarbon polymer is within the range of about 250 angstroms to one miera, and preferably from 300 to 5,000 angstroms. Increasing the thickness of the silicon nitride will increase its tendency to crack, and increasing the thickness of the fluorocarbon polymer layer increases the tension in each deposited layer, which increases the tendency of the polymer layers to become detached from the silicon nitride. . On the other hand, decreasing the thickness of the layer increases the possibility of empty spaces and incomplete coverage. Either of these situations reduces the effectiveness of the compound as a moisture barrier. The number of layers and layer thicknesses will, of course, depend on the intended use of the multilayer composite and the particular fluoride polymer. In addition, silicon nitride is radially brittle and is prone to cracking when flexed or bent. By depositing a layer or coating of polymers on the silicon nitride layer, its tendency to crack is greatly reduced and it is also protected from damage when handled. In the embodiment illustrated in Figure 1, both sides of surfaces of the silicon nitride layers are protected by an adjacent polymer layer, one of which is the fluorocarbon polymer and the other is the substrate. A preferred embodiment in the practice of the invention is that the surfaces of the silicon nitride be protected, and that the outer layer or layers of the composite material be polymeric. However, it is desired that the outer layer or layers of the composite material be made of silicon nitride. The invention includes the embodiments in which (a) not all silicon nitride layers of composite material are of the same thickness, (b) not all layers of fluorocarbon polymer are of the same thickness, and (c) combinations of the same ones in which not all the layers of silicon nitride are of the same thickness, and not all the fluorocarbon layers are of the same thickness. Other embodiments include a composite material in which not all layers of the fluorocarbon polymer are of the same composition, and also in which some of the polymer layers are not fluorocarbon polymers. In yet another embodiment, the substrate 12 is a network having a releasable surface on which the first layer is deposited, so that the multilayer composite is removed and used without the substrate on which it was formed. In yet another embodiment, a composite material of the invention is formed on a first substrate, which is a network having a release surface and then transferred to a second substrate to which it is attached by any appropriate means. For most applications, a substrate is needed to make it possible for the multilayer composite material to be handled and used in manufacturing processes without breaking. As described above, the transparent composite material of the invention is useful as a thin film moisture barrier material, for electrochemical testers and as a packaging material for moisture sensitive foods, chemicals, biological materials and pharmaceuticals , electronic materials and articles. In addition to its moisture barrier properties and transparency to visible light, yet another advantage of the composite material of the invention is the inert chemical nature of the silicon nitride of the fluorocarbon polymer. Those skilled in the art will appreciate that the composite material of the invention can also be designed and used for other applications, including optical applications such as transmission and selective reflection of various portions of the electromagnetic spectrum. The composite material of the invention is different from the prior art compounds for the combination of the silicon nitride and the fluorocarbon polymer, and also in that the silicon nitride layers and the fluorocarbon polymer layers are formed by processes of deposition and are not laminated by tapes or preformed sheets adhesively or otherwise, of material to form a layered structure. However, it is also within the scope of the invention, and forms a mode thereof, that one or more composite materials of the invention can be laminated to one another or to other compounds or materials, or combinations thereof, to form a laminated structure comprising at least one and preferably two or more composite materials of the invention. The silicon nitride layers formed by the deposition processes useful in the practice of the invention are transparent to light and amorphous. Silicon nitride also has very good resistance to moisture permeation and good resistance to corrosion, in a variety of corrosive environments, as well as being transparent to light. As described above, the fluorocarbon polymer useful in the practice of the invention is transparent to light, and preferably hydrophobic. A particular type of fluorocarbon polymer useful in the practice of the invention comprises a family of amorphous polymers, transparent to light, having excellent chemical resistance, formed by the reaction of 2,2-bistrifluoromethyl-4, 5-difluoro-1,3-dioxol (PDD) with itself to form a homopolymer or by reaction of the PDD with other monomers containing fluorine, such as tetrafluoroethylene (TFE), vinylidene fluoride, chlorotrifluoroethylene, vinyl fluoride, and perfluoro (vinylalkyl ethers). Commercially available copolymers of PDD with TFE, where PDD is the main monomer, are available as Teflon AF from DuPont. Illustrative but non-limiting examples of other fluorocarbon polymers useful in the practice of the invention include polytetrafluoroethylene or PTFE, as is known, copolymers of TFE with hexafluoropropylene, commercially available as Teflon FEP from DuPont, and copolymers of TFE with perfluoro (alkyl vinyl ethers) commercially available from DuPont as Teflon PFA. While some or all of these fluorocarbon polymers may be apparent light-opaque, they are transparent to light at the thickness of the layer used in the invention. Layer deposition processes, useful in the practice of the present invention, include the various PVD processes such as sputtering or electron deposition and evaporation. Also useful is plasma polymerization, monomer vapor deposition, various chemical vapor deposition processes, chemical vapor deposition at high pressure and chemical vapor deposition enhanced by plasma, which are known to those skilled in the art. High-speed methods for the application of a coating or layer to a substrate on a roll or reel are also known, and are described, for example, in U.S. Patent Nos. 4,543,275 and 5,032,461. In general, only one layer at a time is deposited in a vacuum chamber. In this way, a layer of silicon nitride is deposited on one or both sides of the substrate. Subsequently the target material in the vacuum chamber is changed to the fluorocarbon polymer or the substrate coated with silicon nitride is transferred to another chamber in which the target material is the fluorocarbon polymer. The fluorocarbon polymer is then deposited as a layer on the layer or layers of silicon nitride. However, if desired, at least one layer of silicon nitride and at least one layer of the fluorocarbon polymer are deposited on one or both sides of the substrate within a vacuum chamber, by use in the chamber, at least Two sizzle goals for deposition. For example, in a vacuum chamber in which the deposition of the layers occurs by magnetron-enhanced crackling, the substrate is an electrode and the target material to be deposited on the substrate is the other electrode, with the plasma in-between the electrodes in the case of the deposition of a layer on one side of the substrate. Alternatively, the target material and the plasma are on both sides of the substrate to deposit a layer on both sides at the same time, in which case a layer of either silicon nitride or fluorocarbon polymer is deposited on both sides of the substrate or the substrate coated with silicon nitride. In addition, if the substrate is a moving film or ribbon, then more than one material is deposited in one step, of the substrate when sequentially more than one lens is used in the vacuum chamber. Thus, if the substrate is a moving tape or film, as the substrate moves beyond the first objective or group of objectives which, for purposes of illustration is silicon nitride, a layer of silicon nitride is deposited on the silicon nitride. one or both sides of the substrate. As the substrate coated with silicon nitride continues to move toward a second objective or group of targets in the chamber downstream of the first or first targets, a layer of fluorocarbon polymer is deposited on the silicon nitride layer, and so on. In this way, a multiple number of layers can be applied to the substrate in one step of the substrate in the vacuum chamber, to form a compound such as that illustrated in Figure 1., or a composite material having much fewer layers than that illustrated in Figure 1. This process allows the production of a relatively large volume of the composite material of the invention at a reasonable manufacturing cost. As described above, U.S. Patent Nos. 5,250,905 and 5,339,024 describe cell testers which may contain one or more moisture sensitive components, and which therefore require that a moisture barrier be employed in conjunction with the tester. , to prevent moisture from deteriorating the effectiveness of the tester as described in U.S. Patent No. 5,355,089. One method which has worked with some success is the use of a small sheet of mica placed on the tester above the cell, and sealed by means of a suitable moisture resistant material, such as polyisobutylene, as described in the patent. ? 089 * Figures 2 (a) and 2 (b) schematically illustrate a side view on a cell tester on a cell with a moisture barrier of the invention, and a top view on partial broken lines, respectively. Thus, Figure 2 illustrates schematically an electrochemical cell 50 having a cell tester 60 of the type described in the '089 patent, and which contains at least one hygroscopic component (not shown), with a moisture barrier 70 multilayer, thin film, of the invention, placed on the tester and sealed to the outer side of the container 52 of the metal cell by means of the sealant 62 and with the plastic label 70 wrapped around the cell, and placed on the tester , the seal and the barrier against moisture.

Tester 60 is approximately 254 microns (10 mils) thick and is coupled to positive terminals 54 and negative 56 of the cell by means not shown. As described in the '089 patent, the tester 60 contains, for example, a polymer electrolyte containing 0.5 M lithium trifluorosulfonate in an aprotic solvent (eg, ethylene carbonate and propylene carbonate) and polyvinylidene fluoride, which It is very hygroscopic. The sealant material is, for example, a polybutylene elastomer modified with maleic anhydride, available as Vestoplast V3645 from Huís, Inc. in Piscataway, NJ. The label is a PVC film wrapped around the cell and the age barrier / tester / sealer and then shrinks with heat. As a practical matter, for use as a moisture barrier for an over cell tester over an electrochemical cell, such as the cell tag testers described in the patents referred to above, the total thickness of the barrier against moisture is not greater than about 38.1 microns (1.5 mil) and preferably within about 25 microns (1 mil). The moisture barrier 10, of the invention, comprises a polyethylene naphthenate film 25 microns thick, as the substrate on both sides of which a layer of silicon nitride has been deposited, with a layer of Teflon AF deposited on each layer of the silicon nitride, as illustrated in Figure 1, to produce a moisture barrier essentially of 25 microns (1 mil), and having a moisture vapor transmission rate of less than 51.6 micrograms of water per cm- (8 micrograms of water per square inch) of surface area in a period of 24 hours, measured according to the procedure described below. Each layer of silicon nitride is 500 angstroms thick and each layer of Teflon AF is 1,500 angstroms thick. The silicon nitride layers and the Teflon AF layers are deposited by magnetron sputtering at radio frequency (RF) at 31 ° C in argon, at a pressure of 1.5 millitor. The water permeation or the rate or rate of transmission of the moisture vapor of the moisture barrier composite is measured by placing a 6.35 mm (0.25 inch) wide, 2.54 cm (1 inch) polymer electrolyte strip ) in length and 76.2 microns (3 mils) thick, and which contains 70 wt.% of lithium trifluorosulfonimide salt 0.5 M in 3-methylsulfolane and 30 wt.% of polyvinylidene fluoride, on a sheet of mica 38.1 microns (1.5 thousandths of an inch) thick. A rectangle 2.54 cm (1 inch) wide and 4.32 cm (1.7 inch) in length of the barrier against moisture of the invention, is placed on the strip and then sealed the mica by an elastomeric sealant of polybutylene modified with maleic anhydride , 63.5 microns (2.5 mils) thick to form a laminate, as generally illustrated in Figure 2. In this way, the hygroscopic strip or tape is sealed between the mica and the moisture barrier, by of the sealant. This is done by anhydrous conditions in a sealed box for handling with gloves. The laminate thus formed is then maintained at 60 ° C and 100% relative humidity for one week, after which the polyvinylidene fluoride strip containing the solvent and the salt is removed and analyzed for its water content by the method Titration of Karl Fischer. This is the test method and test conditions referenced and used in the following examples.

The invention will also be understood by reference to the following examples, in all of which the moisture barrier is transparent to light.

EXAMPLES Example 1 In this example, a movie of 25.4 micras (1 thousandth of an inch) thick polyethylene naphthenate (Kalodex) is the substrate and a layer of 500 angstroms thick silicon nitride is coated by sizzle to RF on each side of the substrate, at 1.5 millitorr of argon from a target of silicon nitride. The layers of silicon nitride deposited by this process are amorphous. After this, a 1,500 angstroms thick layer of Teflon AF is coated by magnetron sputtering to RF over each of the two layers of silicon nitride in 1.5 millitorr of argon from a Teflon AF lens. The multilayer, thin film, light-transparent moisture barrier formed in this way has a water vapor transmission rate of less than 51.6 micrograms of water per cm2 (8 micrograms of water per square inch) of surface in a period of 24 hours, as determined by the test method referred to in the DETAILED DESCRIPTION above.

Example 2 In this example, a film of 25 microns (1 thousandth of an inch) thick polyethylene naphthenate (Kalodex) is the substrate, and it is covered by crackling in 1.5 millitorr of argon with silicon nitride, to form a layer or coating of Amorphous silicon nitride approximately 500 angstroms thick, on only one side of the substrate. PTFE is then bombarded or sizzled on the silicon nitride layer to form a PTFE layer of 1,500 angstroms in thickness. This process is repeated once again to form a moisture barrier, multi-layered, thin film, transparent to light, comprising four alternating layers of amorphous silicon nitride and PTFE (2 silicon nitride and 2 PTFE). ) on one side of the substrate, and the moisture barrier has a water vapor transmission rate of 180.6 micrograms of water per cubic meter (28 micrograms of water per square inch) of surface area over a period of 24 hours, using the test method of Example 1.

Comparative Example A This experiment is similar to that of Example 1, with respect to RF sputtering in argon, the polyethylene naphthenate substrate and the moisture transmission test method. In this experiment, only one side of the substrate is sputter coated with a layer of silicon oxide 500 angstroms thick, from a SiO2 target, and this layer of silicon oxide was then coated by crackling by a layer of silicon oxide. 500 angstroms thick PTFE, from a polytetrafluoroethylene (PTFE) lens. This process was repeated twice, alternately depositing a layer of silicon oxide and a layer of Teflon AF to produce a composite material transparent to light, comprising six alternating layers of SiOx and PTFE (three SiOx and three PTFE), excluding the substrate, with the sixth outer layer that is PTFE. The light-moisture barrier, formed in this way, has a water vapor transmission rate of 1612.5 micrograms of water per cm2 (250 micrograms of water per square inch) of surface area, in 24 hours, using the Test method of Example 1.

Comparative Example B This experiment is also similar to that of Example 1, with respect to sputtering deposition to RF in argon, the polyethylene naphthenate substrate and the humidity transmission test method. In this experiment, both sides of the substrate film are coated with a 150 angstroms thick layer of TiOr on which a Teflon AF layer of 500 angstroms thickness is deposited, to produce a composite material such as that illustrated in FIG. Figure 1. The moisture barrier, transparent to light, formed in this way, has a water vapor transmission rate of approximately 3418.5 micrograms of water per cm2 (530 micrograms of water per square inch) of surface area in 24 hours, using the test method of Example 1.

Comparative Example C This example is also similar to that of Example 1 with respect to sputtering deposition to RF in argon, the polyethylene naphthenate substrate and the humidity transmission test method. In this experiment, both sides of the substrate film are coated with a layer of ZrO? 200 angstroms thick on which a layer of Teflon AF of 500 angstroms thickness is deposited to produce a four layer composite material on the substrate, such as that illustrated in Figure 1. The moisture barrier transparent to light , formed in this way has a water vapor transmission rate of about 1935 micrograms of water per cm2 (300 micrograms of water per square inch) in 24 hours, using the test method of Example 1.

Comparative Example D This experiment is also similar to that of Example 1, with respect to sputtering deposition to RF in argon, the polyethylene naphthenate substrate and the humidity transmission test method. In this experiment, both sides of the substrate film are coated with a layer of A1203 of 500 angstroms in thickness, on which a layer of (PTFE) of 500 angstroms thick to produce a composite material such as that illustrated in Figure 1. The moisture barrier, transparent to light, formed in this way, has a water vapor transmission rate of approximately 1935 micrograms of water per cm '(300 micrograms of water per square inch) of surface area, in 24 hours, using the test method of Example 1.

Comparative Example E This experiment is similar to that of Example 1 with respect to sputtering deposition to RF in argon, the polyethylene naphthenate substrate and the moisture transmission test method. In this experiment, both sides of the substrate film are coated with an SiOx layer of 500 angstroms thick on which a layer of 500 angstroms thick Teflon Af was deposited. This process is repeated twice to produce a composite material (excluding the substrate) that has six alternating layers of (three layers of SiOx and three layers of Teflon AF) with the sixth layer or outer layer that is Teflon Af. The moisture barrier, transparent to light, formed in this way, has a water vapor transmission rate of approximately 1935 micrograms of water per cm2 (300 micrograms of water per square inch) of surface area, in 24 hours, using the test method of Example 1.

Comparative Example F This experiment is similar to that of Comparative Example D, except that Teflon AF is used instead of PTFE. The light-moisture barrier thus formed has a water vapor transmission rate of approximately 1935 micrograms of water per cm2 (300 micrograms of water per square inch) of surface area in 24 hours, using the test method of Example 1. It is understood that various other embodiments and modifications in the practice of the invention will be apparent and readily realized by those skilled in the art, without departing from the spirit and scope of the invention described above. Accordingly, it is not intended that the scope of the claims appended hereto be limited to the description described above, but rather that the claims be construed as encompassing all the patentable novelty characteristics that lie within the invention, including all characteristics and modalities that could be treated as equivalents thereof by those experts in the field, to which the invention belongs.

It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention. Having described the invention as above, property is claimed as contained in the following:

Claims (9)

1. An electrochemical cell that has a tester of the condition of the cell, sensitive to humidity, and a moisture barrier, transparent to light, to protect said tester from humidity, characterized in that the moisture barrier comprises ur-material Composite on a polymeric substrate, the composite material comprises at least one layer of amorphous silicon nitride and at least one layer of hydrophobic fluorocarbon polymer, wherein the thickness of the layers of silicon nitride and the fluorocarbon polymer is in the range approximately 250 and 2,500 angstroms, and between approximately 250 angs-trans to about 1 miera, respectively, "where the Darrera against moisture is not greater than one and a half miera of" thickness

2. A cell according to claim 1, characterized in that the composite material comprises at least two layers of silicon nitride and at least two layers of polymer of --luorccarburc.

3. A cell according to claim 2, characterized in that the outer layers of the moisture barrier are polymeric.

4. A cell according to claim 2, characterized in that the fluorocarbon polymer comprises at least one polymer selected from the group consisting essentially of (i) PTFE, (ii) copolymers of TFE with hexafluoropropylene, (iii) copolymers of TFE with perfluoro ( alkyl vinyl ethers), and (iv) polymers formed by the reaction of 2,2-bistrifluoromethyl-4,5-difluoro-1,3-dioxole (PDD) with at least one monomer selected from the group consisting essentially of PDD , TFE, vinylidene fluoride, chlorotrifluoroethylene, vinyl fluoride, perfluoro (alkyl vinyl ethers) and mixture thereof.

5. A composite material transparent to light, characterized in that it comprises at least one layer of silicon nitride and at least one layer of fluorocarbon polymer.

6. A composite material according to claim 5, characterized in that the fluorocarbon polymer comprises at least one polymer selected from the group consisting essentially of (i) PTFE, (ii) copolymers of TFE with hexafluoropropylene, (iii) copolymers of TFE with perfluoro (alkyl vinyl ethers), (iv) polymers formed by the reaction of 2,2-bistrifluoromethyl-4,5-difluoro-1,3-dioxole (PDD) with at least one monomer selected from the group consisting essentially of PDD , TFE, vinyl fluoride, chlorotrifluoroethylene, vinyl fluoride, perfluoro (alkyl vinyl ethers) and mixture thereof.

. A non-laminated, light-transparent composite useful as a moisture barrier, characterized in that it comprises at least two layers of amorphous silicon nitride and at least two layers of a hydrophobic fluorocarbon polymer on a flexible polymeric substrate, wherein the thickness of the silicon nitride and fluorocarbon polymer layers is in the range of from about 200 to 5,000 angstroms and from about 250 angstroms to about 1 miera, respectively.

8. A composite material according to claim 7, characterized in that the fluorocarbon polymer comprises at least one polymer selected essentially from the group consisting of (i) PTFE, (ii) copolymers of TFE with hexafluoropropylene, (iii) copolymers of TFE with perfluoro (alkyl vinyl ethers), (iv) polymers formed by the reaction of 2,2-bistrifluoromethyl-4,5-difluoro-1,3-dioxole (PDD) with at least one monomer selected from the group consisting essentially of PDD , TFE, vinyl fluoride, chlorotrifluoroethylene, vinyl fluoride, perfluoro (alkyl vinyl ethers) and mixture thereof.

9. A process for the production of a light-transparent, non-laminated composite material of at least one layer of amorphous silicon nitride and at least one layer of fluorocarbon polymer, characterized in the process because it comprises the formation of layers of silicon nitride. or of fluorocarbon polymer as a first layer on a substrate, and then the formation of one layer of the other silicon nitride or fluorocarbon polymer on the first layer.