Abstract:
A device for detecting and/or transmitting at least one environmental influence, and a method for producing the same. The device comprises at least one receiver element and an evaluation circuit that is substantially composed of organic functional material.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This is the 35 USC 371 national stage of international application PCT/DE01/04370 filed on Nov. 21, 2001, which designated the United States of America. 
     FIELD OF THE INVENTION 
     The invention relates to a device for detecting and/or transmitting at least one environmental influence, to uses thereof and a method for producing the said device. 
     BACKGROUND OF THE INVENTION 
     A photodiode, a photoelectric barrier, a solar cell, a humidity, pressure and/or temperature sensor are examples of a device for detecting and/or transmitting at least one environmental influence, said device comprising at least one receiver element that records an environmental influence and an evaluation circuit that receives, evaluates, possibly amplifies and transmits a signal from the receiver element. 
     Devices of this type are known which are based on conventional inorganic semiconductor materials such as silicon and gallium arsenide. These devices, such as sensors for example, are produced in manufacturing processes of conventional semiconductor technology. The raw materials used as well as the process steps result in the devices being expensive and accordingly being used only very selectively. 
     However, since a comprehensive sensor technology has advantages for virtually all areas of industry, energy, transportation and life in general because it allows better recording of currently obtaining conditions and/or more efficient use of energy, there is a demand for cheaper devices of the aforementioned kind to be produced. 
     SUMMARY OF THE INVENTION 
     The object of the present invention is therefore to provide a device for detecting and/or transmitting at least one environmental influence which is comparable in performance with the conventional devices from the semiconductor industry and/or is cheaper in comparison with these. 
     There are essentially two approaches to achieve this object. On the one hand, at least one cheaper raw material can be used for the production process; on the other, the complex production method used in semiconductor technology, comprising coating, patterning, etching and etching back etc., can be simplified. 
     Both these starting points are taken into account in the object of the invention, which introduces the new organic semiconductor technology (integrated plastic circuits (IPC) and/or organic field effect transistors (OFET)) in this field. 
     The object of the invention is a device for detecting and/or transmitting at least one environmental influence, said device substantially being composed of organic material and comprising at least one receiver element which records at least one environmental influence and/or converts this environmental influence into an electrical signal and at least one evaluation circuit which processes and transmits a received signal. A further object of the invention is a method for producing a device for detecting and/or transmitting at least one environmental influence, in which method at least one receiver element, one evaluation circuit and/or an associated connection arrangement is constructed by coating at least one substrate with organic material. Finally, an object of the invention is to use a device for detecting and/or transmitting at least one environmental influence in industry, in monitoring/sensor technology and/or in transportation. 
     Any quantifiable impulse of the environment which can be converted into a current and/or a voltage is referred to here as an environmental influence. An example of this from nature is a solar ray, a change in atmospheric pressure or, in the industrial domain, an increase in the concentration of a certain gas and a change in temperature and/or humidity. All these influences can lead via suitably sensitive chemical compounds (which are present in the receiver element) to a situation in which a conducting material becomes non-conducting or substantially less conducting and/or in which voltage or current is generated in a material and/or that the electrical resistance in a material is changed. These effects are measurable and can be converted into defined signals via an evaluation circuit or stored in order to generate energy. 
     Also conceivable is a tactile and/or pressure sensor in which an electrical signal is generated by pressure, as in the case of a keyboard for example. 
     A particularly advantageous embodiment of the device for detecting and/or transmitting at least one environmental influence has the receiver element and an element of the evaluation circuit integrated on a substrate. This results in very compact devices which exhibit a large saving in volume compared with the conventional devices of the silicon-dominated semiconductor technology. While it is possible that the Si sensors are smaller than the new devices, more important as an alternative is first and foremost the ease of attachment e.g. to flexible substrates and/or to substrates (package, packing) which are already present in any case. This also opens up totally new uses for the devices because, thanks to their cheapness, the devices according to this embodiment can be used as single-use products and, thanks to their small volume, are suitable for use as e.g. labels etc. Also possible by this means is, for example, a form of pharmaceutical packaging which, by comprising a corresponding device, can provide information on how long the preparation has been stored and at what temperatures. 
     According to the embodiment of the device, it is a temperature, humidity and/or pressure sensor, a photoelectric barrier, an optical sensor, a solar cell and/or something similar. 
     According to an advantageous embodiment, the device can receive, process and forward (transmit) a plurality of environmental influences in parallel. Also, it is possible, for example, for the temperature, pressure and composition of a gas and/or liquid mixture to be detected, stored together with the duration and/or passed on to a closed-loop and control system. A particular threshold value for temperature, humidity, pressure and/or light intensity can be measured and represented. This process can be either reversible and record the current value or irreversible, for example to indicate whether a deep-frozen product has been briefly thawed out or whether a package/medicine was ever exposed to a high temperature or a high level of humidity. All previously known application areas for devices for detecting and/or transmitting at least one environmental influence can be realized by means of the new semiconductor technology which is primarily based on organic materials. At the same time the choice of sensitive chemical compounds which can be used in the receiver element is unlimited and can be geared specifically to the particular problem and/or developed for the particular task in question. 
     The term “organic material/functional material” as used here comprises all types of organic, organometallic and/or inorganic synthetic materials referred to as e.g. “plastics”. This includes all types of materials with the exception of the semiconductors which form the traditional diodes (germanium, silicon) and the typical metallic conductors (e.g. copper, aluminum) which are mainly used in the context of electrodes and/or contact pins. A restriction in the dogmatic sense to organic material as material containing carbon is accordingly not provided. To the contrary, consideration is also given to the widespread use of e.g. silicons. Moreover, the term is not to be subject to any restriction with regard to the molecule size, especially to polymer and/or oligomer materials, but instead the use of “small molecules” is also entirely possible. 
     The expression “substantially composed of organic material” serves to indicate that it is altogether possible for functional elements to be fashioned also from metal, silicon or some other material. 
     A particularly advantageous embodiment is one in which at least one organic functional material such as e.g. the organic conductor, the organic insulator and/or the organic semiconductor are identical in at least one receiver element and in at least one element of the evaluation circuit of the device. This embodiment is noteworthy by virtue of particularly advantageous production costs if an organic material is deposited on multiple points of the substrate in a single operation e.g. by printing or coating using the doctor blade technique. 
     In the event that the change in temperature is received as an environmental influence, the conductor track of the receiver element, for example, can be composed of organic material such as polyaniline and/or be an organic conductor which changes its resistance at or above a certain temperature in such a manner that it becomes an insulator or virtually an insulator. This may be a reversible or an irreversible process within the material. In any case the receiver element for this device is furnished with an organic conductor in which a change in temperature either causes voltage or current to be generated by charge separation or leads to an abrupt change in resistance. The receiver element is thus not only placed in a position to record and measure the environmental influence “temperature change”, but also to pass on a signal to the evaluation circuit. Examples of such a material are PTC (positive temperature coefficient) thermally sensitive resistors which can be produced from doped polycrystalline ceramic material based on barium titanate. 
     In the event that the composition of a gas mixture such as e.g. atmospheric moisture is to be measured, an organic conducting material can be used in which, depending on the concentration of the material to be measured, e.g. water in air, a current is generated in the conductor track or there is a change in the resistance (for example through a change in solubility behavior, cf. PEDOT). Here, the change in resistance may be reversible or irreversible, depending on material. 
     In the event that the pressure is to be measured, organic piezoelectric plastics are known that generate a voltage when they are stretched or compressed. 
     For light sensors there are also examples where the organic functional materials of a diode are chosen such that they generate voltage under the action of light and/or their physical properties change reversibly or irreversibly. 
     According to an advantageous embodiment, the device amplifies recorded environmental influences or signals and transmits them in either linear (analog) or digital form. 
     According to an advantageous embodiment of the method, at least one layer of organic functional material is generated on the substrate by printing (e.g. pad printing, offset printing) or by application using the doctor blade technique, i.e. by structured deposition on a lower layer or the substrate or by introducing material into/filling in recesses. It is particularly advantageous here that structured layers can be generated simply by printing/application by doctor blade and do not have to be produced, as in traditional semiconductor technology, by means of photomasks and etching steps. 
     The preferred use of a device for detecting and/or transmitting at least one environmental influence is in industry, monitoring/sensor technology and/or transportation. In medical engineering such devices are of interest as single-use sensors. 
     For example, the device serves as a label or part of a label in order to make clear which environmental influences the labeled object was exposed to. It can also be usefully attached as an RFID tag, as a postage stamp, on transport packaging, in a pharmaceutical product, in a deep-frozen product, on moisture-sensitive parts, as part of a photocell, and in toys. Not least, the device can serve as a temperature sensor (conversely, it can also be a mini-heater which can be controlled by the electronics), as a pressure sensor (conversely, it can also be a mini-speaker), as a gas sensor, and/or as a safety element (warning of CO poisoning). 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention is explained in more detail in the following with reference to six figures which show various embodiments of the present invention wherein: 
         FIG. 1  is a block diagram of a device for detecting and/or transmitting at least one environmental influence; 
         FIG. 2  is a sectional elevation view of a device for detecting and/or transmitting at least one environmental influence; 
         FIG. 3  is a schematic diagram of a structure of a receiver element for receiving at least one environmental influence; 
         FIG. 4  is a schematic layout of a simple organic field-effect transistor, such as can be used as evaluation electronics; 
         FIG. 5  is an elevation diagrammatic view of a continuous coating process according to an embodiment of the present invention; and 
         FIG. 6  is a schematic diagram of a further embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows a block diagram of the device for detecting and/or transmitting at least one environmental influence  1 . At least one environmental influence  4  causes a change in a resistance in the receiver element or sensor  2  and/or generates a voltage which either changes and/or initiates a current flow to an element  3  of the evaluation circuit. The element  3  of the evaluation circuit is connected to a supply voltage  5  and a ground  6 . The evaluation circuit comprises evaluation electronics based on organic field-effect transistors, with the aid of which the received signal is transmitted by either digital or analog means to signal output  7 . 
       FIG. 2  shows a cross-section through a device for detecting and/or transmitting at least one environmental influence  1 . On the extreme left on the substrate or carrier  9 , which can therefore be e.g. flexible, in other words a film, can be seen the encapsulation  8 , which can be applied differently according to environmental influence, in other words e.g. transparently or by chasing out the receiver element  2  (e.g. if the pressure or the gas composition is to be measured). Residing under the encapsulation  8  in the case shown is the receiver element  2 , on which the environmental influence  4 , e.g. light, heat and/or humidity (depending on the type of encapsulation) etc., acts through the encapsulation  8 . Depending on which environmental influence is to be received, the encapsulation for this is permeable or exposed at the receiving point. 
     Also located under the encapsulation  8  is the element  3 , which comprises the organic evaluation electronics. Outside of the encapsulation  8  are the output signal and/or the connecting contacts  7 . Depending on sensor type, the actual sensor element may also be located outside of an encapsulation, e.g. humidity sensor. 
       FIG. 3  shows the simplest schematic structure of a receiver element  2  which can receive an environmental influence, e.g. light. Here can be seen the device  10  for measuring the photovoltage or the photocurrent, which is connected via a first feed line  11  to a first organic conductor material  12 . The light  4  strikes this first organic conductor material  12  and generates current or voltage, e.g. by charge separation in the material. This current travels through the organic semiconducting material  13  and flows to the second conductor material  14 , which is connected in turn via the second feed line  15  to the device  10  for measuring the photovoltage or the photocurrent. 
       FIG. 4  shows a schematic layout of a simple organic field effect transistor, such as can be used as evaluation electronics. Mounted at a distance from each other on a substrate  9  are two electrodes, the source S and the drain electrode D, which are connected through a layer to semiconducting organic material  18 . The drain electrode C is connected to the supply voltage  5  and the source electrode S is connected to the ground  6 . The upper gate electrode G is connected to the feed line of the receiver element  2 . As soon as current flows via the receiver element  2  to the gate electrode C, a conducting channel  16  is generated in the semiconducting layer  18  between the source and the drain electrode owing to the resulting field effect which acts through the insulator layer  17 . 
       FIG. 5  illustrates a continuous process which includes a conveyor belt  22  which is displaced in direction  28  by a drive mechanism (not shown). A film substrate  24  is on and conveyed by belt  22 . The substrate carries a recessed mold layer  30  in which circuit recesses  32 ,  34  and  36  were previously formed in the mold layer by known techniques. A doctor blade  38  applies a coating  40  of organic material into the recesses  32 ,  34  and  36  in a continuous process to form a receiver circuit  42 , an evaluation circuit  44  and connections  46 . A continuous process using a doctor blade, by way of example, is disclosed for structuring an OFET in commonly owned U.S. Pat. No. 6,960,489 which matured from an application cited in applicants&#39; disclosure statement filed Sep. 30, 2004 and published as a PCT application WO 02/19443 on Mar. 7, 2002. 
       FIG. 6  shows a cross-section through a device  48 , which is somewhat similar to the device  1  of  FIG. 2 , but is for detecting at least one environmental influence such as the concentration of material in the environment. Encapsulation  52  on the substrate  50 , which may be flexible. e.g.. a film, is applied to expose the receiver element  54  to the surrounding atmosphere for detecting the material in the environment, which in this case is a gas composition to be analyzed. Also, the organic evaluation electronics  56  is covered by the encapsulation  52 . Connecting contacts  58  are external the encapsulation  52 . A closed loon circuit and control  60  is coupled to the contacts  58  by conductors  62 .