Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Physical dimension specified
Reexamination Certificate
1999-12-13
2001-03-06
Nakarani, D. S. (Department: 1773)
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Physical dimension specified
C427S108000, C427S165000, C427S389700, C336S174000, C336S174000, C336S174000, C336S174000, C336S174000, C441S040000
Reexamination Certificate
active
06197418
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a laminate provided with an organic electroconductive layer, the laminate comprising a thin glass layer and a support which is preferably a plastic support. This material can be used as an electrode in devices such as displays, photovoltaic cells and light-emitting diodes.
BACKGROUND OF THE INVENTION
The specific properties of glass make it a suitable substrate for carrying electroconductive layers in electric or semiconductor devices such as flat panel displays, electroluminescent panels, cathode ray tubes (CRTs), photovoltaic cells, etc. In addition to a high thermal and dimensional stability, glass has many other beneficial properties compared to plastic materials, e.g. the ease of recycling, excellent hardness and scratch resistance, high transparency, good resistance to chemicals such as organic solvents or reactive agents, low permeability of moisture and gases, and a very high glass transition temperature, enabling the use of high-temperature processes for applying an electroconductive layer. However, the main problems associated with the use of glass as a substrate in electric or semiconductor devices are its high specific weight, brittleness and low flexibility. The latter problems require that the coating of a functional layer on glass is typically carried out in a batch process (sheet by sheet), whereas the application of layers on a plastic support is generally performed as a continuous process, e.g. by using a web coater or continuous printing techniques such as screen or offset printing. It is well-known that the productivity and cost efficiency of a continuous (web) coating process is significantly higher than of a batch (sheet) coating process.
Some applications require electroconductive substrates which are characterised by a low weight and sufficient flexibility, e.g. liquid crystal displays in portable devices, electroconductive substrates having a curved geometry such as in car dashboards or batteries, and photovoltaic cells (often called solar cells) for use on roofs or as a power supply of satellites, etc. For these applications, plastic foils may be used as substrate for carrying electroconductive layers in spite of the many disadvantages compared to glass. The high permeability of oxygen and water through plastic substrates degrades the electroconductive layers rapidly. Some progress has been made on producing plastic foils with barrier layers to limit said permeability; however the lifetime of electric devices in which such conducting plastic foils are used is still limited and needs to be improved.
In addition, an inorganic conducting layer such as indium-tin oxide (ITO) is brittle and as a result, the electroconductivity of an ITO layer is susceptible to deterioration by simply bending the flexible plastic substrate. All these effects limit the lifetime of such plastic-based devices considerably. Other problems associated with inorganic electroconductive layers such as ITO are
the high cost associated with vacuum-deposition techniques such as sputtering which are required to apply the inorganic layer;
the high surface roughness of the inorganic layer which makes it difficult to apply thereon thin layers such as electroluminescent polymer layers used in organic light-emitting displays or diodes (OLEDs) or photoconductive polymer layers in solar cells;
ITO requires an annealing step at an elevated temperature which is not compatible with most plastic substrates;
ITO may generate oxygen which attacks adjacent layers such as poly(p-phenylenevinylene) used in OLEDs.
sputtered inorganic layers are often characterised by the presence of a large number of pinholes.
Organic conducting layers have been developed which are not characterised by the above disadvantages. The production and the use of electroconductive polymers are well known in the art. In DE-A-41 32 614 the production of film-forming, electroconductive polymers by anodic oxidation of pyrroles, thiophenes, furans or aromatic amines (or their derivatives) is effected with a sulphone compound present in the electrolyte solution. The preparation of electroconductive polythiophenes and polypyrroles is described in U.S. Pat. No. 5,254,648 and in U.S. Pat. No. 5,236,627 respectively. In EP-A-440 957 a method for preparing polythiophene in an aqueous environment and applying polythiophene from an aqueous solution has been described. Such a solution is up until now mostly used in photographic materials as disclosed in e.g. U.S. Pat. No. 5,312,681, U.S. Pat. No. 5,354,613 and U.S. Pat. No. 5,391,472. In EP-A-686 662 it has been disclosed that layers of polythiophene coated from an aqueous composition could be made with high conductivity.
Such organic electroconductive layers can be coated on glass for various applications. WO 98/01909 describes a light-emitting diode wherein an ITO layer has been overcoated with an organic polymer selected from polyfurans, polypyrroles, polyanilines, polythiophenes and polypyridines. A similar combination has been described in Philips Journal of Research, Vol.51, No.4, p518-524 (1998). DE-A-41 29 282 discloses heat protection windows obtained by coating a polythiophene on glass or plastic sheets and DE-A-42 26 757 describes a similar antistatic and heat protection layer on a laminated glass such as a car windshield. The glass layers in a car windshield have a typical thickness of 2.1 mm. The electric resistivity of such antistatic and heat protection coatings has a typical value of >10
5
&OHgr;/square, which is far too high to be suitable as an electroconductive layer. EP-A-669 205 describes a glass/plastic laminate wherein an electroconductive layer is applied between the glass and plastic sheets of the laminate for de-icing or thermally insulating safety glass in vehicles. Such material can neither be used as an electrode because the electroconductive layer is insulated between the glass and plastic layer.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a material wherein an electroconductive layer is provided on a substrate which is characterised by the known advantages of glass, i.e. a high dimensional and thermal stability, excellent hardness and scratch resistance, good resistance to chemicals and low permeability of water vapour and oxygen. This object is realised by the material defined in claim
1
.
It is a particular object of the present invention to provide a material which, in addition to the above advantageous properties, has a low specific weight and which can be manufactured by using a continuous web or roll coating or printing method for applying said electroconductive layer on said substrate, i.e. on a substrate which is characterised by sufficient flexibility and which does not easily break. These objects are realised by the material defined in claim
2
. Preferred embodiments of the material according to the present invention are specified in the dependent claims.
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, organic conducting layers are provided on a glass/support laminate so that an improved material is obtained which can be used as an electrode for making electric or semiconductor devices characterised by a much longer lifetime than known devices. A laminate, wherein the glass layer has a thickness of at most 500 &mgr;m, is further characterised by a low specific weight and improved mechanical flexibility. The latter advantage enables the use of continuous web coating or printing methods for making such devices at a reduced cost.
The feature “flexible” as used herein means that the material is capable of being wound around a core without breaking. A preferred laminate according to the present invention is capable of being wound around a cylindrical core having a radius of 1.5 m without breaking. The lower the thickness of the glass, the higher is its flexibility and thus the lower the minimum radius of the core around which the material can be wound without breaking. However, the brittleness of the glass is inversely proportional to the thickn
Andriessen Hieronymus
Cloots Tom
Goedeweeck Rudi
Leenders Luc
Louwet Frank
Agfa-Gevaert N.V.
Breiner & Breiner
Nakarani D. S.
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