Semiconductor device manufacturing: process – Making device or circuit emissive of nonelectrical signal
Reexamination Certificate
2002-03-07
2003-11-04
Trinh, Michael (Department: 2822)
Semiconductor device manufacturing: process
Making device or circuit emissive of nonelectrical signal
Reexamination Certificate
active
06642069
ABSTRACT:
FIELD OF THE INVENTION
The present invention is related to electrochemical devices, in particular to printable, electrochemical pixel devices based on conducting organic materials and electrochromic materials. The invention also relates to a process for the production of an electrochemical pixel device, and to matrices of electrochemical pixel devices.
BACKGROUND OF THE INVENTION
Semiconducting and conducting organic materials, both polymers and molecules, have successfully been included in a large range of electronic devices, e g electrochemical devices, for instance as dynamic colorants in smart windows and in polymer batteries. Reversible doping and de-doping involving mobile ions:switches the material between different redox states.
Use has been made of semiconducting polymers for the realisation of field effect transistor (FET) devices. The transistor channel of these devices comprises the semiconducting polymer in question, and their function is based on changes in charge carrier characteristics in the semiconducting polymer, caused by an externally applied electric field. In such transistors, the polymer is used as a traditional semiconductor, in that the electric field merely redistributes charges within the polymer material. One such transistor has been realised, which is adapted for miniaturisation and can be used for the production of integrated circuits consisting entirely of polymer material (PCT publication WO99/10939). A stack of sandwiched layers is described, with either a top-gate or a bottom-gate structure. A transistor device with a similar architecture, also using a polymer as semiconducting material in the channel of the transistor, is described in the European patent application EP1041653.
Another type of transistor device based on organic materials utilises electrochemical redox reactions in the organic material. These devices comprise an electrolyte and a conducting polymer that can be switched between an oxidised and a reduced state. One of these oxidation states then corresponds to low, preferably zero, conductivity in the material, whereas the other oxidation state corresponds to a high conductivity relative to the first state. Electrochemical transistor devices have been used as sensors, e g for detection of oxidant in a solution (see, for review, Baughman and Shacklette, Proceedings of the Sixth Europhysics Industrial Workshop (1990), p 47-61). Furthermore, a transistor of the electrochemical type is reported in Rani et al, J Solid State Electrochem (1998), vol 2, p 99-101. The gate electrode architecture in this prior art transistor is shown in
FIG. 1
of this reference.
Electrochromic materials exhibit colour changes or changes in optical density as a result of electrochemical reduction and/or oxidation reaction;. An electrochromic material can either be present as a solid, or exist as molecular, neutral or ionic species in an electrolyte solution. These materials have been used for the creation of electrochromic cells, where the passage of electric charge causes colour changes in the materials. Electrochromic cells are used in electrochromic devices of different kinds, and two principal categories of these devices can be distinguished. The two categories differ from each other mainly in the arrangement of the elements of the electrochromic cell.
The first category of electrochromic devices utilises a sandwich construction, and is used in applications such as automobile windows, building windows, sunglasses, large billboards, mirrors with variable reflectance, sunroofs etc. In this type of electrochromic device, continuous layers of electrochromic material and electrolyte (as well as other layers of e g ion reservoir material) are confined between two electrodes that completely cover the layers of electrochromic material and electrolyte. For the electrochromic device to be of use, at least one of said electrodes has to be transparent to let light through the device. This requirement is met in the prior art through the use of electrode materials such as indium-doped tin oxide (ITO), tin dioxide or fluorine-doped tin dioxide. The electrochromic materials used in these applications vary, but are often based on heavy metal oxides such as WO
3
or conducting polymers such as polyaniline or polypyrrole. The conducting, electrochromic polymer poly-(3,4-ethylendioxythiophene) (PEDOT) has attracted much study, and sandwich devices incorporating this polymer have been realised.
The second category of electrochromic devices aim at providing an electrically updateable display for realisation on a flexible support. U.S. Pat. No. 5,754,329 describes such a display, in which the electrodes of the electrochromic device are placed in one and the same plane, contacting a layer of electrochromic material for the generation of local colour effects at the interface between the electrochromic material and the electrodes. U.S. Pat. No. 5,877,888 represents a further development of this device, describing a two-sided display. However, the arrangement of the component layers of the electrochromic device is similar to that of the device of the U.S. Pat No. 5,754,329, considering that the electrodes on either side of the display support contact electrochromic material only, and the generation of electrochromic effects is confined to the area of the electrodes. The electrochromic materials that are used in these devices are described in detail in U.S. Pat. No. 5,812,300.
Active addressing of pixel displays is described e g by Firester A H, in “Active Matrix Technology”, chapter 5 of “Flat-Panel Display Technologies”, eds Tannas, Glenn, Doane et al, 1995 (ISBN 0-8155-1387-9) The prior art in this field may furthermore be represented by U.S. Pat. Nos. 6,157,356, 6,023,259 and 6,072,517. Active matrix driven OLED-displays (organic light emitting displays) have been realised by e g Philips and Cambridge Display Technology (CDT). In parallel to what was noted in connection with transistors above, the transistors used in all of these applications, when employing a polytler material, utilise the polymer material as a traditional semiconductor.
Problems with the pixel matrices in the displays of the prior art mentioned above include the fact that they are difficult and expensive to manufacture. In particular, no electrochemical pixel devices have been disclosed which are truly capable of being mass produced. Furthermore, the practical use of the pixel elements in the prior art devices has been hampered by their comparatively high power consumption. Also, materials used in prior art devices suffer from a lack of environmental friendliness, processability and economic production possibilities. There is therefore a need for new and improved pixel devices for incorporation in matrices that may be used in displays.
SUMMARY OF THE INVENTION
One of the objects of the present invention is then to meet this demand, by developing the art of electrochemical pixel devices, and by providing a device with handling, production, disposal and other characteristics superior to those of the prior arts.
Another object of the present invention is to provide an electrochemical pixel devict which can be deposited on a large range of different rigid or flexible substrates by conventional printing methods.
Yet another object of the present invention is to provide an environmentally safe electrochemical pixel device, so that the disposal of the device, along with any support onto which it has been deposited, doesn't give rise to handling problems, and so that no safety restrictions have to be imposed on the use of the device.
Another object of the present invention is to provide an actively addressed matrix display, offering versatility and ease of design, and enabling a good picture quality.
Still another object of the present invention is to make possible new applications of conpducting organic materials, using several different properties of such materials in combination.
A further object of the invention is to provide processes for the production of such devices, which processes utilise conventi
Andersson Karl P.
Armgarth Mårten
Berggren Rolf M.
Kugler Thomas
Nilsson David A.
Acreo AB
Burns Doane Swecker & Mathis L.L.P.
Trinh Michael
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