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(12) United States Patent ao) Patent No.: us 6,927,761 B2
Badaye et al. (45) Date of Patent: Aug. 9,2005
(54) MOISTURE DEFLECTOR FOR CAPACITIVE NFI TOUCH SCREENS FOR USE WITH BEZELS OF CONDUCTIVE MATERIAL
(75) Inventors: Massoud Badaye, Vancouver (CA);
Gary O. Kaga, West Vancouver (CA)
(73) Assignee: 3M Innovative Properties Company,
St. Paul, MN (US)
( * ) Notice: Subject to any disclaimer, the term of this patent is extended or adjusted under 35 U.S.C. 154(b) by 454 days.
(21) Appl. No.: 10/113,006
(22) Filed: Mar. 29, 2002
(65) Prior Publication Data
US 2003/0184523 Al Oct. 2, 2003
(51) Int. CI.7 G08C 21/00
(52) U.S. CI 345/173; 345/174; 345/905;
349/149; 349/153; 349/155; 349/190; 361/679;
(58) Field of Search 345/173, 174,
345/905; 349/149, 153, 155, 190; 361/679,
(56) References Cited
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* cited by examiner
Primary Examiner—Bipin Shalwala
Assistant Examiner—-Vincent E. Kovalick
(74) Attorney, Agent, or Firm—Robert J. Pechman
A non-conductive barrier between a touch screen and a conductive bezel is described. The non-conductive barrier attaches to a capacitive touch screen and forms a lip over a grounded bezel. The non-conductive barrier is constructed of a material and dimension sufficient to prevent liquid streaming down the touch screen from electrically coupling an active area of the touch screen to the grounded bezel.
21 Claims, 2 Drawing Sheets
MOISTURE DEFLECTOR FOR CAPACITIVE NFI TOUCH SCREENS FOR USE WITH BEZELS OF CONDUCTIVE MATERIAL
Touch screens are becoming very popular as an input mechanism for computer systems. Various types of touch screens have emerged, but one format is a Near Field
Imaging (NFI) capacitive touch screen. With an NFI capacitive touch screen, an electric field is created on conductive bars within the active portion of the touch screen. When an object, such as a user's finger, comes in close proximity to the active area of the touch screen, it causes a modulation of the electric field, which is sensed by a controller connected to the conductive bars. By analyzing the modulation of the electric field, a location of the contact on the touch screen can be resolved. Typically, the touch screen is surrounded at the edges by a grounded conductive surface (a bezel). To avoid an influence on the electric field due to the conductive bezel, a small region of the touch screen immediately proximate to the bezel is left inactive.
The term "inactive" is intended to mean any mechanism or process by which a region or portion of the touch screen 25 is made to be less susceptible to variations in the electric field than other regions or portions of the touch screen. For example, portions of the underlying sensing circuit may be shielded to avoid recognizing contact or touches in that area. Alternatively, the sensing circuitry may be omitted from a 30 portion of the screen to turn it inactive. Moreover, some combination of eliminating active components together with shielding other active components may be employed.
Some aspects of NFI capacitive touch screens have made them popular for use in difficult environments, such as 35 outdoors applications and applications in the manufacturing industry. For example, NFI capacitive touch screens are effective at discriminating between near field signals and far field signals. Thicker protective layers may be used over the conductive bars while still achieving satisfactory perfor- 40 mance. Thicker protective layers enable NFI touch screens to be manufactured that can withstand many of the environmental challenges of these difficult environments. However, certain environmental conditions continue to pose a problem. For instance, NFI capacitive touch screens may 45 be used in environments where the screen is susceptible to conductive liquids like water. These are common in manufacturing and other such applications. A problem occurs if the conductive liquid streams down the touch screen to effectively bridge the inactive region between the active area 50 of the touch screen and the conductive bezel. A similar problem occurs if the conductive liquid streams down at the top of the screen from the conductive bezel over the inactive region onto the active area. If this occurs, errors or false touches are generally registered. 55
Attempts have been made to address this problem. For instance, the inactive region has sometimes been made of sufficient width that accumulated liquids along the bottom lip of the bezel did not reach the active area of the touch screen. However, this solution did not address the more 60 likely situation that the liquid forms a stream running down the touch screen. Another attempted solution was to try and filter out false touch signals created by streaming liquids. The controller was configured to filter out touch profiles that were highly likely to have been caused by streaming liquids. 65 Although this solution was effective at substantially reducing errors and false touches, it introduced a longer process
ing delay to register actual touches, which is an undesirable byproduct. Unfortunately, an acceptable solution to this and other similar problems has eluded those skilled in the art.
SUMMARY OF THE INVENTION
The present invention addresses the above-described problems, among others, by providing a non-conductive barrier between a touch screen and a conductive bezel. Briefly stated, a non-conductive barrier is provided that attaches to a capacitive touch screen and forms a lip over a grounded bezel. The non-conductive barrier is constructed of a material and dimension sufficient to prevent liquid streaming down the touch screen from electrically coupling an active area of the touch screen to the grounded bezel.
In one aspect, the invention is directed at a nonconductive barrier configured to be attached to a display unit. The display unit includes a capacitive touch screen and a bezel at least partially surrounding the capacitive touch screen. The non-conductive barrier forms a discontinuity in a stream of liquid flowing between the capacitive touch screen and the bezel.
In another aspect, the invention is directed at a touch sensitive display unit including a capacitive touch screen, a grounded bezel, and a non-conductive barrier. The capacitive touch screen includes an active portion and an inactive portion. The grounded bezel at least partially surrounds the touch screen. The non-conductive barrier is positioned to separate the capacitive touch screen from the grounded bezel such that a liquid streaming down the touch sensitive display unit does not form a conductive path coupling the active portion of the capacitive touch screen to the grounded bezel.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a cross-sectional cutaway view of a nonconductive barrier affixed to a capacitive touch screen, in accordance with one embodiment of the invention.
FIG. 2 is a frontal view of a non-conductive barrier affixed to a capacitive touch screen and having a portion at the upper end that slopes in two directions to cause a liquid to drain off to the side before overflowing onto the touch screen, in accordance with one embodiment of the invention.
FIG. 3 is a cross-sectional cutaway view of the upper portion of the non-conductive barrier illustrated in FIG. 2 and connected to the upper portion of the touch screen 301, in accordance with the invention.
FIG. 4 is a perspective view of a capacitive touch screen fitted with a non-conductive barrier between the active area of the touch screen and the conductive bezel to address the problem of streaming liquids, in accordance with the invention.
DETAILED DESCRIPTION OF THE
Briefly described, the present invention is directed at a non-conductive barrier for use in conjunction with a touch screen to prevent streaming liquids from directly or capacitively coupling an active portion of the touch screen with a conductive bezel around the touch screen. The nonconductive barrier is also configured to direct liquids streaming downward from an upper portion of the touch screen outward and away from the active portion of the touch screen.
FIG. 1 is a cross-sectional cutaway view of a touch screen display 100 including one embodiment of the present invention. Preferably, the touch screen display 100 includes a