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COLOR FILTERS WITH SCATTERING CENTERS FOR USE IN REFLECTIVE COLOR DISPLAYS

IP.com Disclosure Number: IPCOM000009760D
Original Publication Date: 2000-May-01
Included in the Prior Art Database: 2002-Sep-17
Document File: 2 page(s) / 83K

Publishing Venue

Motorola

Related People

Rob Akins: AUTHOR [+2]

Abstract

Reflective color displays are coming to the market from several vendors. Most use patterned color filters to impart color to white light, and arrange the patterned color filters over independently switched sub-pixels. Three sub-pixels generally form a full color pixel, though occasionally four or more subpixels are employed per pixel. Various color generation schemes are used. The most common is three sub-pixels in a red, blue and green set. However subtractive filter sets are also used, such as a cyan, magenta, yellow etc. The actual color filter materials generally use either a dye material, or a dispersion of pigmented particles.

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MOTOROLA

Technical Developments

COLOR FILTERS WITH SCATTERING CENTERS FOR USE IN REFLECTIVE COLOR DISPLAYS

by Rob Akins and George Ventouris

Reflective color displays are coming to the market from several vendors. Most use patterned color filters to impart color to white light, and arrange the patterned color filters over independently switched sub-pixels. Three sub-pixels generally form a full color pixel, though occasionally four or more subpixels are employed per pixel.

Various color generation schemes are used. The most common is three sub-pixels in a red, blue and green set. However subtractive filter sets are also used, such as a cyan, magenta, yellow etc. The actual color filter materials generally use either a dye material, or a dispersion of pigmented particles.

In all reflective color displays, optical gain is required to offset the ]osses associated with the color filters. A key component of optical gain is the control of diffusion in the display. A Lambertian diffuser provides too much diffusion, resulting jn a very dark display. No diffusion would provide a very bright display, but with an unrealjstically narrow viewing cone.

A second problem with diffusion in reflective color displays is the location in the light path of the diffusing element. If the diffuser is located above the modulation plane of the display (by a distance

Q Motorola. Inc. 2(XK)

about equal to a lateral dimension of a pixel, a criteria generally met when diffusers are placed above an upper glass substrate in a liquid crystal type displa...