Optical: systems and elements – Projection screen
Reexamination Certificate
2001-01-17
2004-11-16
Gray, David (Department: 2851)
Optical: systems and elements
Projection screen
C359S453000, C359S457000, C359S459000, C359S460000
Reexamination Certificate
active
06819486
ABSTRACT:
FIELD
This invention relates to projection screens having an elongated dispersed phase polymeric material disposed in another polymeric material.
BACKGROUND
Optical films and other devices have been developed for a variety of applications, including for use as decorative articles and to enhance or alter characteristics of displays. In particular, there are instances when it is desirable to anisotropically reflect or otherwise scatter light. For example, in many display and projection screen applications, a broad horizontal viewing angle is desirable because a user or viewer may be positioned to the side of the display or projection screen. On the other hand, the vertical viewing angle typically does not need to be as broad because the user or viewer is typically positioned with the display or projection screen at or near eye level. Accordingly, it can be desirable to have an anisotropic display with a relatively broad horizontal viewing angle, but a relatively narrow vertical viewing angle.
One method to modify the viewing angle includes the use of surface structure, such as a lenticular lens screen, where one dimensional lens structures are molded onto plastic substrates. Light is focused by the cylindrical-like lens structures onto a diffusive film to achieve asymmetric diffusion. However, lenticular screens contain a series of tangible grooves which can be expressed as a frequency. This frequency can interfere with the pixel frequency in liquid crystal based projection displays and generate Moire fringes. Thus, the use of current lenticular screens is limited for high definition image display in which pixel frequencies are higher.
SUMMARY OF THE INVENTION
Generally, the present invention relates to screens for managing light such as a rear projection screen or a front projection screen. The present invention may be useful as the screen itself or as a component of such as screen. Optical systems incorporating such screens or components are also included in the ambit of the present invention. The present invention utilizes polymeric compositions that can be used to anisotropically scatter light or otherwise manage light. One embodiment is a polymeric composition that includes a first polymeric material, and a second polymeric material disposed as a plurality of elongated structures within the first polymeric material. Each elongated structure has a major axis and the major axes are substantially aligned. The first polymeric material has an index of refraction that differs by at least 0.01 from an index of refraction of the second polymeric material. In some instances, a pressure sensitive adhesive material is selected as the first polymeric material. The orientation of the elongated structures and the difference in indices of refraction results in the polymeric composition scattering light asymmetrically.
Yet another embodiment of the invention is a method of making an optical element such as a screen or display. A polymeric composition is formed using a first polymeric material and a second polymeric material dispersed in the first polymeric material. An index of refraction of the first polymeric material differs by at least 0.01 from an index of refraction of the second polymeric material. The polymeric composition is then dispensed on a substrate. This dispensing results in the second polymeric material forming multiple elongated structures within the first polymeric. Each of the elongated structures has a major axis and the major axes of the elongated structures are substantially aligned.
The above summary of the present invention is not intended to describe each disclosed embodiment or every implementation of the present invention. The Figures and the detailed description which follow more particularly exemplify these embodiments.
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Everaerts Albert I.
Ma Jiaying
Moshrefzadeh Robert S.
Zhou Zhiming
3M Innovative Properties Company
Cruz Magda
Gray David
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