This disclosure relates to flexible displays, and more particularly to devices and methods for forming color filters on such displays.
Flat panel displays include color filters to remove particular color components from light illuminating from sub-pixels of the display. In conventional devices, the color filter is formed on or applied to internal portions of a display. The top substrate tends to be relatively thick. The larger thickness creates parallax and aperture problems that are common to flat panel displays. In addition, thicker displays are less flexible.
Further, non-intrinsic color displays include a display effect layer, which reflects or emits light with a broad spectrum (white), and a color filter layer, which changes the white light into colored light. The display effect layer and the color filter layer need to be properly aligned to prevent parallax or aperture problems. When making a conformable, flexible or even roll-up display in this way, alignment problems between the display effect layer and the color filter layer can occur due to the different radii of these layers during bending or rolling. Alignment problems can also occur due to the dimensional accuracy and instability of the separately fabricated pixel matrix and color filter matrix. In addition, the distance between the reflecting or emitting layer and the color filter can give rise to significant parallax problems. These alignment and parallax problems may decrease brightness or even color errors and moiré effects.
Referring to
Referring to
Embodiments or the present disclosure describe color filters formed or applied to an outside (exterior surface) of a rollable or flexible display. By employing specially dimensioned substrates for color filters, rollable displays may employ color filters that are not only properly aligned but permit the display to be flexibly folded or rolled. In addition, parallax and aperture problems are reduced or eliminated by employing the present principles.
One advantage that is gained by the color filters applied in accordance with these principles includes enablement of the possibility of using alternative depositing methods for forming the color filter. Another advantage includes that the color filter can be formed at a last step or nearly a last step in the fabrication process. This enables optimal alignment with sub-pixels in a display during color filter deposition and permits applying corrections for dimensional changes during color filter processing.
A flexible display includes a display effect layer formed on a back plane substrate configured and dimensioned to be flexible. A front plane substrate is configured and dimensioned to be flexible and is mounted on the display effect layer. The front plane substrate includes a color filter formed thereon such that aperture and a parallax effects are controlled due to proximity between the display effect layer and the color filter. Methods for fabricating flexible displays are also disclosed.
These and other objects, features and advantages of the present disclosure will become apparent from the following detailed description of illustrative embodiments thereof, which is to be read in connection with the accompanying drawings. This disclosure will present in detail the following description of preferred embodiments with reference to the following figures wherein:
The present disclosure provides embodiments for a flexible or roll up display that includes improved alignment between sub-pixels and a color filter to improve display viewing quality. In addition, a color filter is placed outside the display to permit the formation of the color filter to be completed later in the fabrication process to customize the color filter placement relative to the pixels.
It should be understood that the elements shown in the FIGS. may be implemented in various configurations. For illustrative purposes, embodiments will be described herein in terms of a liquid crystal display type that includes polymeric substrates, which permit flexible or roll up displays to be formed. Other types of displays may also benefit from the teachings herein. For example, electrophoretic display medium (such as those from the manufacturer E Ink Corporation which are based on encapsulated electrophoretic ink particles) displays, electroluminescent displays, etc. may employ the teachings herein.
Referring now to the drawings in which like numerals represent the same or similar elements and initially to
A black matrix 72 may be formed on substrate 71 or between substrate 71 and common electrode 70. Black matrix 72 blocks out stray light to remove fuzziness from viewed displayed images. Black matrix 72 also forms apertures for pixel light to pass through. The apertures (spaces between portions of black matrix 72) are aligned to the pixels 66 and may be formed using a photolithography process/patterning.
Advantageously, a color filter layer 74 is formed on substrate 71 (and possible on black matrix 72). By depositing the color filter layer very near to the reflecting or emitting layer formed by the display effect layer 78, alignment and parallax problems can be prevented. In conformable, flexible or roll-up displays, the substrates 64 and 71 used in both backplane and front plane are thin to enable the display to fold or roll-up. The color filter 74 is preferably formed on the front plane surface and due to the thin substrates, without parallax problems. The thinness of the substrates can be determined by comparing pixel size with the cell gap 68 (the difference between the pixel and the common electrode). The pixel size is preferably larger than the cell gap 68 to achieve a good quality display. In an illustrative embodiment, the substrates 64 and 71 are about 200 microns or less and preferably about 25 microns or less (the cell gap is, e.g., about 200 microns or less). Pixel size may be, for example, about 300 microns by about 300 microns.
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Apertures to screen out stray light may be employed (e.g., black matrix 72 of
The color filter layer 124 may be formed in a plurality of steps as described with respect to
Deposition of color filters 134, 136 and 138 may be performed by spin coating, spray coating, evaporating, doctor blading or similar deposition methods. The deposition is followed by photolithography to pattern color filters into stripes or patches, followed by a next color filter deposition and patterning until all color filter are formed. Screen-printing or inkjet printing may be employed to directly deposit patterned color filters.
Referring to
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In block 408, the color filter is formed. Many processes may be employed for forming the color filter. These options for deposition techniques are afforded by the fact that the color filter layer is advantageously formed at a late stage in the processing. For example, spin coating, spray coating, evaporating, doctor blading, ink jetting, silk screening or similar deposition methods may be employed to form the color filters, among other techniques. The formation of the color filter may include photolithography to pattern color filters into stripes or patches, followed by a next color filter deposition and patterning until all color filters are formed. Screen-printing or inkjet printing may also be employed to directly deposit patterned color filters.
In block 410, alignment of the color filters is performed relative to the pixels in the pixel structure of the display device. Depending on the method of forming the color filter, the alignment step may be performed simultaneously with the formation of the color filters. For example, in ink jet printing, the alignment is performed while the color filters are being printed. When ink jet printing the color filter, a high resolution print head can be used to ensure proper alignment. By inspecting the exact location of the display pixel structure, the color filter can be printed at the correct position on the display.
When using photolithography to pattern the color filters, projection optics may be used to project a photo mask unto a surface to be patterned (e.g., a front plane of the display) which can be used to scale and align the projected image to the pixel structure of the display.
When using screen printing or shadow mask evaporation, a silkscreen or shadow mask can be used with a slightly smaller pitch than the pixel structure of the display. The silk screen or shadow mask can then be stretched to align the color filter structure to the pixel structure of the display.
In block 412, the front plane with the color filter formed thereon is placed over the display effect layer if the front plane substrate with color filter was separately manufactured. This is optional. Scaling or other alignment methods are employed to ensure proper alignment between the pixels and the color filters, in block 414. The color filter may be installed with the color filter on top or on the bottom of the front plane substrate.
In block 416, a protective layer, such as a scratch protection layer or humidity barrier may be deposited on the color filter to protect the color filter during operation.
Having described preferred embodiments for a roll up display with color filters and methods for fabrication of the same (which are intended to be illustrative and not limiting), it is noted that modifications and variations can be made by persons skilled in the art in light of the above teachings. It is therefore to be understood that changes may be made in the particular embodiments of the disclosure disclosed which are within the scope and spirit of the embodiments disclosed herein as outlined by the appended claims. Having thus described the details and particularity required by the patent laws, what is claimed and desired protected by Letters Patent is set forth in the appended claims.
In interpreting the appended claims, it should be understood that:
Number | Date | Country | Kind |
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60740470 | Nov 2005 | US | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/IB2006/054253 | 11/14/2006 | WO | 00 | 9/26/2008 |