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Method for Minimizing Touch-Sensitive Screen Distortion on a Liquid Crystal Display

IP.com Disclosure Number: IPCOM000039161D
Original Publication Date: 1987-Apr-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 2 page(s) / 38K

Publishing Venue

IBM

Related People

Demke, KR: AUTHOR [+2]

Abstract

A method is described to minimize touch sensitive screen distortion on a liquid crystal display without introducing other usability problems. The liquid crystal in a liquid crystal display (LCD), shown in Fig. 1, occupies an envelope that is 5-10 microns thick, as shown in Fig. 2. The thickness of this envelope must remain uniform over the entire screen area for proper operation. If the envelope thickness varies, it effects the optical properties of the liquid crystal and this appears as a distortion pattern to the operator. A common practice in the industry is to place small, spherical spacers through out the envelope to maintain tight control of the thickness (Fig. 3). These spacers work well under normal operation.

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Method for Minimizing Touch-Sensitive Screen Distortion on a Liquid Crystal Display

A method is described to minimize touch sensitive screen distortion on a liquid crystal display without introducing other usability problems. The liquid crystal in a liquid crystal display (LCD), shown in Fig. 1, occupies an envelope that is 5-10 microns thick, as shown in Fig. 2. The thickness of this envelope must remain uniform over the entire screen area for proper operation. If the envelope thickness varies, it effects the optical properties of the liquid crystal and this appears as a distortion pattern to the operator. A common practice in the industry is to place small, spherical spacers through out the envelope to maintain tight control of the thickness (Fig. 3). These spacers work well under normal operation. However, if a person happens to press the LCD screen with his finger, the envelope thickness still depresses under the pressure and a disturbing distortion becomes visible to the operator. A method commonly used in the industry to eliminate touch sensitive distortion is to cover the LCD screen with a piece of clear PLEXIGLAS*. An air gap is left between the PLEXIGLAS and LCD so that finger pressure cannot be applied to the LCD screen. This approach works well for touch-sensitive distortion; however, it creates a whole new set of problems. These problems can be summarized as follows: 1) the PLEXIGLAS is soft and susceptible to scratching, 2) the air gap creates glare,...