Apple patent is for imprint circuit patterning

Posted by Dennis Sellers Dec 13, 2007 at 7:27am

Apple has been granted a patent (number 20070283832) for imprint circuit patterning by the US Patent & Trademark Office. According to Apple, an imprint circuit patterning technique that shrinks the minimum feature dimension of circuit features formed on plastic substrates is provided.

The imprint circuit patterning technique may be applied to the fabrication of LCDs, particularly LCDs including integral touch sensing. Substrates having patterned substantially transparent electrodes for use with such touch-sensing LCDs and the touch-sensing LCDs are also provided.

In one aspect, the present invention can relate to a method for fabricating an imprinted substrate. The method may include providing a substrate, which may be translucent and, in some embodiments, substantially optically transparent. The substrate may then be imprinted by applying a tool having features formed thereon to the substrate in the presence of increased heat and/or pressure relative to normal room conditions. On this imprinted substrate, one or more materials may be deposited with varying degrees of uniformity to form a variety of structures. In one embodiment, the structures may be substantially transparent, substantially electrically conductive electrodes as would be used in a touch screen having integral touch sensing. Such structures may also include electrically conductive traces for routing electrical signals to and from the electrodes.

In another aspect, the invention can relate to a touch screen comprising a substantially optically transparent imprinted substrate, which can be processed by the above-described fabrication method. In some embodiments, the imprinted substrate may have a plurality of imprinted features on which a plurality of electrically isolated, substantially transparent electrodes can be formed. Additional structures, such as electrically conductive leads for routing electrical signals to and from the substrate can be formed by depositing conductive materials on the substrate.

Here’s Apple’s background on the invention: “Semiconductor and integrated circuit fabrication are highly developed arts. Recently, a variety of techniques, such as photolithography, laser etching, etc., have further developed for creating multi-layered structures of conductors, insulators, and semi-conductors for many types of electronic devices, from simple integrated circuits to microprocessors, and even liquid crystal displays (LCDs).

“However, a particular area for advancement in this field has been perceived with respect to the techniques for fabrication of LCDs, and more particularly LCDs featuring integrated touch sensing, such as co-pending U.S. Patent Application No. 60/804,361, referenced above.

“One area of interest relates to the replacement of glass substrates with plastic substrates. In the field of LCDs, and particularly touch-sensing LCDs, this replacement has a number of advantages, including potentially reduced cost, flexibility in the selection of dielectric materials for various layers, and a reduced thickness. However, patterning circuitry on plastic substrates with the same resolution as glass substrates can be difficult. For example, using current technology, the minimum feature dimensions on plastic substrates are on the order of 200 .mu.m (e.g., using printed resist and wet etching). Laser ablation is an alternative technique that may attain 20 .mu.m features; however, laser ablation equipment is relatively expensive and the ablation process creates significant debris, which is undesirable in a clean room setting. Conversely, features 5 .mu.m and even smaller are easily attainable on glass. This is desirable for touch-sensing electrodes incorporated in a touch screen, as 20-30 .mu.m features are visible to the human eye and therefore produce undesired decreases in the performance of the display.”

The inventor is Steven P. Hotelling. The graphic below is a sectional view of a polymer substrate on which a circuit will be patterned according to an embodiment of the invention.

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