WO2016054618A1

WO2016054618A1 - Filterless color display

Info

Publication number: WO2016054618A1
Application number: PCT/US2015/053899
Authority: WO
Inventors: Regina Mueller-Mach; Gerd O. Mueller
Original assignee: Individual
Current assignee: Individual
Priority date: 2014-10-03
Filing date: 2015-10-03
Publication date: 2016-04-07
Anticipated expiration: 2017-04-03

Abstract

A wide color gamut display without color filters is obtained by supplying pump light, modulated according to the electronically prescribed brightness values, to an arrangement of red, green and blue emitting quantum dots that have non-zero Stokes' shift. The pump-light modulating matrix can be an (AM-) LCD without color filters. Any electronically brightness controlled blue or near-UV emitting matrix can be used instead of the pump-light modulating LC matrix as an excitation source for geometrically aligned quantum dots. Filter losses and design constraints for the liquid crystal cells and viewing angle limitations are eliminated.

Description

FILTERLESS COLOR DISPLAY

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority to U.S. provisional patent application no. 62/059,303 filed October 3, 2014 by inventors Gerd O. Mueller and Regina Mueller-Mach and entitled "Wide Gamut Color Display Without Filters", the contents of which are incorporated by reference in their entirety as if put forth in full herein.

FIELD OF THE INVENTION [0002] This invention relates to color liquid crystal displays and, in particular, to a technique to avoid color filters and their inherent reduction of efficiency and to widen the color gamut.

BACKGROUND

[0003] Liquid crystal displays (LCDs) are the most commonly-used displays, from small displays such as smart-phones to moderate (e.g. tablet and notebook computers) and large display sizes (e.g. televisions). Drawbacks of such LCDs continue to include limited brightness, low efficiency, limited viewing angle, and reducing efficiency markedly to increase color gamut.

[0004] An active matrix (AM) is often used in an LCD (AM-LCD) to modulate light. Pixel brightness information is placed in a storage capacitor, the voltage of which controls the transmittance of adjacent liquid crystals (LC) for a significant portion of the frame time. The main disadvantage of main stream LC displays is the fact that each of the three (or more) colors used is selected by color filters aligned to the respective LC sub-pixels. The light is supplied by a backlight, which today in most cases is powered by one or more LEDs on its periphery.

[0005] In most cases the light input of all colors to the backlight is "always on".

Consequently, even if the picture to be displayed consists, e.g. only of one basic color - green for instance - all other colors, blue and red, are fed into the backlight, accounting for about two thirds light lost. The absorptive color filters usually have narrower spectral pass bands than the spectral widths of the respective light sources, which often provide a rather continuous 'white' spectrum. Consequently, the color filters transmit only a small portion of the light used to illuminate them, especially if a wide color gamut is desired.

[0006] The last mentioned disadvantage has been addressed recently by some manufacturers by using a blue-only backlight, fed by blue InGaN LED(s) on the edge(s), and an additional color converter plate - e.g. Nanosys' "Quantum Dot Enhancement Film" -, which exposes green- and red-emitting Quantum Dots (QDs) to the blue excitation. The red and green QDs are in separate polymer layers of a bi-layer film, and the film is positioned adjacent to the LED so that light transmits through the bilayer film and then as white light to the LC layer. This arrangement can widen the gamut and can also expose the QDs to much lower excitation powers to help preserve longevity of the QDs. However, even in the most favorable cases the total light output of the display per electrical Watt into the blue LED hardly exceeds 9 lm/W.

[0007] Further, it is still difficult to provide a bright LCD display, even where a quantum dot bi-layer is used in conjunction with a blue-emitting LCD light source. Quantum dots absorb photons emitted by other quantum dots. Most conventional quantum dots have a Stokes' shift that is not measurable or, if detectable, is characterized as having zero Stokes' shift (e.g. less than about 1 nm). They will therefore absorb light of the same wavelength that the dots emit. Quantum dots that emit green light absorb that green light from adjacent quantum dots. Red-emitting quantum dots act similarly. This property that quantum dots have reduces the light output per electrical Watt into the blue LED and also limits the luminous emittance of each sub-pixel and therefore the display.

S U MMA RY

[0008] The invention provides various devices and methods that may address one or more of the issues discussed above. In one instance, a device has a light source and a transparent body positioned to receive light from the light source. The transparent body may have one or more of the following:

a. a first sub-pixel with first quantum dots that convert light from the light source to light having a first color;

b. a second sub-pixel with second quantum dots that convert light from the light source to light having a second color; the first sub-pixel having an area and a density of said first quantum dots within said area to provide a first light component of a pixel of light, said first light component having an intensity such that the first light component is visible in sunlight when only the first quantum dots are illuminated by the light source;

the second sub-pixel having an area and a density of said second quantum dots within said area to provide a second light component of said pixel of light, said second light component having an intensity such that the second light component is visible in sunlight when only the second quantum dots are illuminated by the light source;

wherein the first quantum dots have a Stokes' shift greater than zero; and wherein the second quantum dots have a Stokes' shift greater than zero. another instance, a liquid crystal display has one or more of the following: a backlight for outputting light;

a liquid crystal layer positioned to receive the light from the backlight, said liquid crystal layer being configured to modulate the light from the backlight and transmit the light through the liquid crystal layer;

a first quantum dot material being irradiated by the light transmitted through said liquid crystal layer, the first quantum dot material, when irradiated by said light transmitted through said liquid crystal layer, generating red light, said first quantum dot material being located in first areas overlying the liquid crystal layer and constituting red sub-pixels of said display, and the first quantum dot material having a non-zero Stokes' shift; and

a second quantum dot material being irradiated by the light transmitted through said liquid crystal layer, the second quantum dot material, when irradiated by said light transmitted through said liquid crystal layer, generating green light, said second quantum dot material being located in second areas overlying the liquid crystal layer and constituting green sub- pixels of said display, and the second quantum dot material having a nonzero Stokes' shift. [0010] In a further instance, a method involves generating a pixel of light involving: a. attenuating a portion of light from a light source to the desired intensity for the respective pixel;

b. illuminating a first set of quantum dots with the attenuated light; c. emitting light of a first color from the first set of quantum dots and reabsorbing less than 20% of the light of the first color in the first set of quantum dots;

d. illuminating a second set of quantum dots with attenuated or unattenuated light from the light source;

e. emitting light of a second color from the second set of quantum dots and reabsorbing less than 20% of the light of the second color in the second set of quantum dots;

f. said first set and said second set of quantum dots being positioned adjacent to one another sufficiently closely to form a single pixel of light.

[0011] In another instance, a method of making a display comprises:

a. applying a first liquid layer containing a plurality of first color-emitting

quantum dots to a surface;

b. using a LC material having a TFT array to allow actinic radiation to expose the liquid layer to light to polymerize a portion of the first liquid layer;

c. applying a second liquid layer containing a plurality of second color-emitting quantum dots to the surface after removing un-polymerized material of the first liquid layer; and

d. using the LC material having the TFT array to allow the same or different actinic radiation to expose the liquid layer to light to polymerize a portion of the second liquid layer, and removing un-polymerized material of the second liquid layer.

[0012] These and other devices, methods, and compositions of matter are apparent from the discussion herein. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Fig. 1 is a cross-sectional view of a particular display according to the invention (a Filter-less Color Display - FLCD™).

[0014] Fig. 2 is a perspective view of the filter-less color display of Fig. 1.

[0015] Fig. 3 is an illustration of color gamut that is made possible by the invention.

[0016] Elements in the various figures designated by the same numerals may be similar or identical to one another.

DETAILED DESCRIPTION

[0017] The invention provides a color light-producing device in which quantum dots having non-zero Stokes' shift are incorporated, permitting one to make a display that is sufficiently bright to be observed in ambient sunlight outdoors or, if operated at conventional brightness levels, drains less than l/6^th of the (battery) power.

Various benefits can result from a device as disclosed herein, such as:

• no color filter losses;

• instead of using QDs in a color enhancement sheet near the backlight, QDs can be used in a place where the pump intensities are most tolerable and temperature is lowest to enhance QD life;

• Lambertian distribution of emitted light to provide a 180 degree viewing angle in all planes, due to the nature of the QDs' emission, their position at the device's viewing surface, and the elimination of pump light in some instances as viewed light;

• a single LED or identical LEDs can be used to feed into the light guide or diffuser, avoiding problems with proper color mixing, different emission cones, different temperature dependence, and different aging characteristics of different color LEDs; and/or

• the LC cells can be optimized for light of the pump wavelength.

[0018] The following discussion provides one particular example of an LCD display to aid in understanding the invention. Fig. 1 is a cross-sectional view and Fig. 2 is a perspective view of a portion of an LCD 30 in accordance with one embodiment of the invention. Other embodiments may include additional, well known features such as wavelength-dependent phase retarders and diffusers to increase viewing angle, if desired. [0019] The LCD includes a light guide 32, which may be conventional. A light source such as a LED or LED one- or two-dimensional array 34 is optically coupled to an edge of the light guide 32, and deformities are formed in or on a surface of the light guide 32 to leak out the pump light through the upper surface of the light guide 32. The light guide may also be a diffuser with the light source located behind the diffuser. Lenses may be formed on the top surface of the light guide 32 to collimate the light output from the light guide 32.

Numerous types of well-known light guides or diffusers may be used to output the light. Preferably, the light output is non-Lambertian, forward collimated.

[0020] LED 34 may output pump light with a wavelength in a range that includes the blue, aquamarine, indigo, violet, near-UV, and UV wavelength ranges, depending on the quantum dots selected for incorporation into the device and depending in part on whether blue-emitting quantum dots were incorporated into the device. Various parts of the device may be optimized for the pump light, such as the LC cells and any other attendant components such as the quantum dot layer, light guide, collimator, lenses, and other components.

[0021] A conventional scanner 36, well known to those skilled in the art, receives red, green, and blue data from a conventional circuit and selectively energizes the transistors in the TFT array 16 using known row and column addressing circuitry. The light from light guide 32 is polarized by filter 14. The TFT array 16 then selectively energizes areas of the liquid crystal layer 20 to selectively shutter (i.e., polarize or pass) the light incident on the bottom surface of the liquid crystal layer 20. The polarizing filter 24 then passes any of the light polarized by the liquid crystal layer 20 and absorbs any light that has not been polarized by the liquid crystal layer 20.

[0022] The modulated light output from the polarizing filter 24 is then applied to quantum dots deposited in areas coinciding with the red (40), green (42), and blue (44) subpixels. These quantum dots are excitable by the pump light from e.g. a commercially available LED. The LED may emit light having a peak wavelength in the e.g. blue, ultramarine, indigo, violet, near-ultraviolet, or ultraviolet range.

[0023] These quantum dots have non-zero Stokes' shift, meaning the quantum dots will reabsorb little of the light that they themselves emit. Consequently, the red-emitting quantum dots will reabsorb very little, if any, of the red light emitted by other red-emitting quantum dots. Likewise, the green-emitting quantum dots reabsorb very little, if any, of the green light emitted by other green-emitting quantum dots, and blue-emitting quantum dots (if present) reabsorb very little, if any, of the blue light emitted by the blue-emitting quantum dots. This provides a quantum efficiency of or near 100%. The luminous emittance from each of the red, green, and blue subpixels is therefore greater than the luminous emittance of a comparative subpixel formed using conventional quantum dots having zero Stokes' shift. The density of quantum dots, both in terms of subpixel viewing area and volume, is lower than what one might expect as a result of the non-zero Stokes' shift.

[0024] Quantum dots may have emission FWHM values of < 32 nm, for instance. Red- emitting quantum dots may have a peak wavelength greater than 615 nm. Green-emitting quantum dots may have a peak wavelength between 525 and 535 nm. Blue-emitting quantum dots may have a peak wavelength between 440 and 475 nm.

[0025] The Stokes' shift of quantum dots may be at least half of the full-width at half- maximum (FWHM) value of the emission band for a particular type of quantum dot. For example, the Stokes' shift may be at least 10, 15, 20, 25, or 30 nm or more for each of the red-emitting and green-emitting quantum dots. The blue-emitting quantum dots may likewise have a Stokes' shift that meets these criteria.

[0026] Quantum dots may be non-spherical. Non-spherical quantum dots can absorb more pump light than spherical quantum dots absorb so that very little unintended "leakage" of pump light occurs through a subpixel. Quantum dots, and particularly non-spherical quantum dots, may be present at an areal density and area thickness which allows a transmission of pump light of only 5% for the green and/or 1.5 % for the red to achieve maximum gamut, for example without reducing the efficiency since they have non-zero Stokes' shift.

[0027] A backlight light guide is incorporated to redirect light emitted e.g. along edges of the backlight. Light guide 32 can be tuned or optimized for a narrow color band, and forward collimation and/or polarization can be achieved by the light guide by suitable design, eliminating the need for the lower polarizing filter 14.

[0028] The deformities in the light guide 32 may take various shapes and may be formed in the light guide surface or internal to the light guide. Examples of deformities are described in U.S. patent Nos. 6,072,551; 5,876, 107; 5,857,761; and 4,573,766, all incorporated herein by reference. Other issued patents describing light guides and LCDs provide techniques for improving light extraction efficiency, and any of these techniques may be employed, as appropriate, in the present invention. These patents include U.S. patents numbers 7,248,310; 6,844,903; 6,094,283 ; 6,079,838; 6,078,704; 6,073,034; 6,060,727; 6,057,966; 5,975,71 1 ; 5,883,684; 5,841,494; 5,580,932; 5,479,328; 5,404,277; 5,202,950; 5,050,946; and 4,929,062, all incorporated herein by reference.

[0029] Additional information about liquid crystal displays may be found in the books entitled "Liquid Crystal Flat Panel Displays," by William O'Mara, 1993, published by Van Nostrand Reinhold, and "Color TFT Liquid Crystal Displays," by T. Yamazaki, published by SEMI, incorporated herein by reference.

[0030] Using the device illustrated in Fig. 1 and 2, the 86% loss incurred by the RGB filter of conventional displays is eliminated. Advantages of this technique over backlighting an LCD with a light source having R, G, and B components include those discussed above.

[0031] Improved viewing angle due to the Lambertian emission from quantum dots as well as from having the color component emission sources as a top layer in the radiation pattern. This can minimize or avoid use of additional optical elements (special foils) to improve angular spreading. In e.g. devices having three or more types of quantum dots that produce three or more subpixel colors as discussed herein, the angular distribution of the LC-modulated pump light is of no concern, since this light is used essentially only to excite a proximity color converter layer. The LC cell can be optimized for throughput (efficiency) with no further constraints on its optimization.

[0032] Using an LED as the light source allows for an instant on display having a long lifetime and using low voltage dimming to adjust for ambient light changes can easily be accomplished by lowering the drive current of the pump LED(s) or by reducing the duty cycle, as the quantum dots work in proportion to the light exciting them, and their decay time is below one microsecond, well below any reasonable pulse width in duty cycles schemes. This avoids having to compensate or tolerate different output vs. drive behaviors of the color components in conventional devices.

[0033] The pump wavelength can be selected according to any of several criteria such as e.g. highest efficiency of light generation, LC modulation preferences, using the pump wavelength for blue light directly, or converting pump wavelength to another blue to provide the desired efficiency and/or gamut, appearance, etc. One special selection to mention as an example would be pump with 435 nm, for efficiency of the pump LED(s), and convert it in the BLUE subpixels into 465 nm light for gamut reasons - quantum dots allow for this if quantum dots that emit blue light and have zero Stokes' shift are selected in this instance. Of course the real case needs to consider numerics as well as criteria such as gamut versus efficiency. [0034] The quantum dots may be deposited from liquid suspension using a stencil, or the regions of the device that contain quantum dots may be produced using contact photolithography. An active matrix such as the one used in forming an AM-LCD can be used to pattern the red-emitting, green-emitting, and optional blue-emitting layers of quantum dots by orienting the liquid crystals to allow light from an appropriate light source to illuminate and therefore polymerize consecutively-applied liquid films of red-emitting, green-emitting, and blue-emitting monomer-containing quantum dots. The quantum dots may be suspended in or chemically bonded to monomers that are polymerized to form the regions containing quantum dots having non-zero Stokes' shift. A black matrix (e.g. a solution of monomers with black pigment or dye) may be applied to voids between these regions and polymerized to prevent light leakage from a region of quantum dots emitting one color of light into another region of quantum dots emitting a different color.

Alternatively or additionally, a light-guiding material may be applied to voids in a similar manner to prevent light from one subpixel entering another subpixel. A material that has a higher refractive index such as T1O2 nanoparticles, Fe203 nanoparticles, etc. can be used to fill voids.

[0035] A display may therefore be formed by applying a first liquid layer containing first color-emitting quantum dots to a surface, and using a liquid crystal material having a thin- film transistor array to allow light that activates the liquid to polymerize material of the layer to form solid regions containing the first color-emitting quantum dots. The remaining liquid can be removed, and the process can be repeated for a second liquid that contains second color-emitting quantum dots. This method can be used to form a display have a quantum dot array where the quantum dots are as described above, are conventional quantum dots having zero Stokes' shift, or both. One can form e.g. strips of polymer- entrained quantum dots on the surface of a liquid crystal modulator or the surface of a separate polymer or of glass as desired.

[0036] The quantum dots may instead be incorporated in a single film using e.g. an ink- jet printer, light-activated polymer solution, and mask as well as traditional

photolithographic techniques to polymerize e.g. thin stripes of quantum dots that emit red, then thin stripes that emit blue, and then thin stripes that emit green to form a polymer sheet containing adjacent subpixel areas of red, blue, and green. Quantum dot-containing regions may also be jet printed using polymer containing the appropriate quantum dots and an appropriate printer. The quantum dot-polymer mixture may be deposited over the polarizing filter, or the quantum dot-polymer mixture may be deposited over a transparent film. A transparent protective layer 46 may overlie the quantum dot layer if desired.

[0037] A conventional active matrix-LCD as used for instance in a home TV may be used to form a device as disclosed herein. The AM-LCD does not have its color filter sheet applied and its white LED(s) are replaced by LED(s) that emit light in the blue, aquamarine, indigo, violet, near-ultraviolet, or ultraviolet wavelength range. By doing this an assembly of sheets as shown in Fig. 1 and Fig. 2 results. Stripes of QDs having non-zero Stokes' shift are arranged in the same manner as the stripped-off color filters, emitting BLUE - 460nm - GREEN - 527 nm -, RED - 630nm. The invention therefore provides a way of making an AM-LCD that is easily compatible with conventional manufacturing techniques.

[0038] This technique may be used for any pixel pattern. In one known pixel pattern, the display subpixels for a particular color are arranged in columns. In such a display, the quantum dot material for the red, green, and blue subpixels may be formed as strips, as shown in Fig. 2. To improve separation between subpixels, the quantum dot material for each subpixel may be isolated from all other quantum dot material. Additionally or alternatively, a grid mask (also called a black matrix) may be formed overlying or underlying the quantum dot layers to provide an opaque gap between each of the subpixels to reduce "cross-talk" and therefore provide improved color purity.

[0039] Quantum dots that have non-zero Stokes' shift may be obtained from or through, e.g., Quantum Materials Corp. of San Marcos, TX or Nanosys, Inc. of Milpitas, CA, for example.

[0040] The invention also provides a method of generating a pixel of light. In this method, light from a light source illuminates quantum dots of one or more subpixels. The quantum dots in a subpixel absorb less than 20% of the light that they emit and, preferably, absorb less than 15%, 10%, or 5% of the light that they emit. The quantum dots may also absorb at least 95% of the incident light from the light source, and preferably quantum dots absorb at least 98.5% of the incident light from the light source.

[0041] While particular embodiments of the present invention have been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made without departing from this invention in its broader aspects and, therefore, the appended claims are to encompass within their scope all such changes and modifications as fall within the spirit and scope of this invention.

[0042] Without deviating from the basic concept of the invention of a Filter-less Color Display, color filters 48 of Fig. 1 can be used on top of the quantum dots, between the person viewing the screen and the quantum dots, to further improve the visibility and contrast of the image content e.g. in direct sunlight. The non-zero Stokes' shift of the chosen quantum dots allows one to use filters which transmit the full emission spectrum but absorb light from the viewer's ambient to prevent the ambient light from exciting the quantum dots in similar manner that the blue to near UV emission from the light source excites the quantum dots. In contrast to color filters that are placed between the light source and the color converters, which the invention allows one to avoid if desired, these On-top' contrast enhancing color filters that block ambient light from exciting the quantum dots cause no efficiency loss.

[0043] Some such variations include substituting or supplementing any of the quantum dots above with one or more organic color converters, organic luminophors, the light- emitting constituents of OLEDs, or conventional inorganic phosphors. An FLCD™ device as described above is provided as one example of devices that can be formed in accordance with the invention. By careful selection of the QDs, gamut values of 130% NTSC or 150% Adobe can be achieved by using the already mentioned combination of peak emission wavelengths and FWHM values of or smaller than 30nm.

[0044] One or more other light redirectors can be used in addition to or instead of a light guide, such as mirrors (fixed or adjustable), waveguides, one or more optical fiber bundles, prisms, lenses, etc. to direct pump light toward LC cells or other light modulator.

[0045] A device as disclosed herein may have e.g. a direct electrically-addressed matrix of LEDs or OLED(s) that emit a single color instead of a light guide and light modulator, providing essentially direct illumination for a device incorporating quantum dots of non-zero Stokes' shift as disclosed herein.

[0046] A pixel of any of the devices and displays disclosed herein may have a fourth subpixel to provide the same color as or a different color from any of the other subpixels. The fourth subpixel may be e.g. yellow, and that sub-pixel may have quantum dots of non-zero Stokes' shift as described above that convert the pump light to yellow light. The fourth subpixel may have any of the substitutions or supplements as described in paragraph [0043] above. A fifth or sixth subpixel can be similarly provided.

[0047] One example based on the given values is shown in Fig. 3. This figure graphically illustrates how the invention can provide improved color accuracy, NTSC or Adobe gamut values, and other properties in a display.

Claims

WHAT IS CLAIMED IS;

1. A color light-producing device comprising:

a. a light source;

b. a transparent body positioned to receive light from the light source and having

i. a first sub-pixel with first quantum dots that convert light from the light source to light having a first color;

ii. a second sub-pixel with second quantum dots that convert light from the light source to light having a second color;

iii. the first sub-pixel having an area and a density of said first quantum dots within said area to provide a first light component of a pixel of light, said first light component having an intensity such that the first light component is visible in sunlight when only the first quantum dots are illuminated by the light source;

iv. the second sub-pixel having an area and a density of said second quantum dots within said area to provide a second light component of said pixel of light, said second light component having an intensity such that the second light component is visible in sunlight when only the second quantum dots are illuminated by the light source;

v. wherein the first quantum dots have a Stokes' shift greater than zero; and

vi. wherein the second quantum dots have a Stokes' shift greater than zero.

2. The device of claim 1 wherein the light source has a peak wavelength in the indigo to ultramarine color wavelength range.

3. The device of claim 1 wherein the light source has a peak wavelength in the violet to near ultraviolet color wavelength range.

4. The device of any of claims 1-3 wherein the light source has a single peak wavelength.

5. The device of any of claims 1-4 wherein the transparent body additionally has a third sub-pixel with third quantum dots that convert light from the light source to light having a third color, the third sub-pixel having an area and a density of said third quantum dots within said area to provide a third light component having an intensity such that the third light component is visible in sunlight when only the third quantum dots are illuminated by the light source, and wherein the third quantum dots have a Stokes' shift greater than zero.

6. The device of any of claims 1 -5 wherein the transparent body additionally has a fourth sub-pixel with fourth quantum dots that convert light from the light source to light having the same color as any of the first, second, or third quantum dots or to light having a different color from the first, second, and third quantum dots, and wherein the fourth quantum dots have a Stokes' shift greater than zero.

7. The device of any of claims 1-6 wherein any of the first, second, and third quantum dots have a Stokes' shift of at least half of the FWHM of their respective emission bands.

8. The device of claim 7 wherein each of the first, second, and third quantum dots have a Stokes' shift of at least half of the FWHM of their respective emission bands.

9. The device of claim 7 or claim 8 wherein the Stokes' shift is at least 10 nm.

10. The device of claim 9 wherein the Stokes' shift is at least 15 nm.

11. The device of claim 9 wherein the Stokes' shift is at least 20 nm.

12. The device of any of claims 1-1 1 wherein the quantum dots are non-spherical.

13. The device of any of claims 1-12 wherein the quantum dots have emission FWHM values of no more than 32 nm.

14. The device of any of claims 1-13 wherein the density of the first quantum dots is sufficiently high that less than 1.5% of the light from the light source transmits through the first sub-pixel.

15. The device of any of claims 1-14 wherein the density of the second quantum dots is sufficiently high that less than 5% of the light from the light source transmits through the second sub-pixel.

16. The device of any of claims 1-15 wherein the first quantum dots have a peak wavelength greater than 615 nm, the second quantum dots have a peak wavelength between 525 and 535 nm, and the third quantum dots where present have a peak wavelength between 440 and 475 nm.

17. The device of any of claims 1-16 and further comprising a light modulator in an optical path between the light source and the first quantum dots, the second quantum dots, and, where present, the third quantum dots and the fourth quantum dots, where the light modulator is optionally liquid crystals.

18. The device of any of claims 1-16 and further comprising a light modulator in an optical path between the light source and the transparent body.

19. The device of claim 18 wherein the light modulator comprises a liquid crystal.

20. A display comprising the device of any of claims 17-19 and wherein the light source comprises a light disperser and a light emitting diode.

21. The display of claim 20 wherein the light emitting diode is mounted along one or more edges of the display.

22. The display of claim 20 or claim 21 wherein the light disperser is a sheet.

23. The display of any of claims 17-22 wherein the light modulator is a sheet.

24. An OLED display in which the light source and the transparent body of the device of any of claims 1-16 are portions of an organic light emitting device.

25. The OLED display of claim 24 wherein the quantum dots receive light having a peak wavelength solely within a blue to an ultraviolet wavelength range from the organic light emitting device.

26. A color liquid crystal display comprising:

a. a backlight for outputting light;

b. a liquid crystal modulator positioned to receive the light from the backlight, said liquid crystal modulator being configured to modulate the light from the backlight and transmit the light through the liquid crystal modulator;

c. a first quantum dot material being irradiated by the light transmitted through said liquid crystal modulator, the first quantum dot material, when irradiated by said light transmitted through said liquid crystal modulator, generating red light, said first quantum dot material being located in first areas overlying the liquid crystal modulator and constituting red sub-pixels of said display, and the first quantum dot material having a non-zero Stokes' shift; and

d. a second quantum dot material being irradiated by the light transmitted through said liquid crystal modulator, the second quantum dot material, when irradiated by said light transmitted through said liquid crystal modulator, generating green light, said second quantum dot material being located in second areas overlying the liquid crystal modulator and constituting green sub-pixels of said display, and the second quantum dot material having a non-zero Stokes' shift.

27. The display of claim 26 wherein the light from the backlight has a peak wavelength in the indigo to ultramarine color wavelength range.

28. The display of claim 26 wherein the light from the backlight has a peak wavelength in the violet to near ultraviolet color wavelength range.

29. The display of any of claims 26-28 wherein the light source has a single peak wavelength

30. The display of any of claims 26-29 wherein the display comprises a third quantum dot material being irradiated by the light transmitted through said liquid crystal modulator, the third quantum dot material, when irradiated by said light transmitted through said liquid crystal modulator, generating blue light, said third quantum dot material being located in third areas overlying the liquid crystal modulator and constituting blue sub-pixels of said display, and the third quantum dot material having a non-zero Stokes' shift.

31. The device of any of claims 1-19 or the display of any of claims 20-30 wherein the device or display has no color filters between the light source and the quantum dots.

32. The device of any of claims 1-19 or 31 or the display of any of claims 20-31 wherein the device or display has one or more light filters in an optical path from the light source to the viewer and positioned in the optical path after the light source and after the quantum dots.

33. The device of any of claims 1-19, 31, or 32 or the display of any of claims 20-32 wherein the light source has a single or multiple light-emitting diodes that provides the excitation light for the quantum dots.

34. A method of generating a pixel of light, said method comprising

a. attenuating a portion of light from a light source;

b. illuminating a first set of quantum dots with the attenuated light;

c. emitting light of a first color from the first set of quantum dots and reabsorbing less than 20% of the light of the first color in the first set of quantum dots;

35. The method of claim 34 and further comprising

a. illuminating a third set of quantum dots with attenuated or unattenuated light from the light source;

b. emitting light of a third color from the third set of quantum dots and reabsorbing less than 20% of the light of the third color in the third set of quantum dots, the third set of quantum dots being positioned adjacent to the first set and the second set of quantum dots to form said pixel of light.

36. The method of claim 34 or claim 35 wherein less than 15% of the light of the first color, the second color, and the third color where present is reabsorbed by the first set, the second set and the third set respectively of quantum dots.

37. The method of claim 34 or claim 35 wherein less than 10% of the light of the first color, the second color, and the third color where present is reabsorbed by the first set, the second set and the third set respectively of quantum dots.

38. The method of claim 34 or claim 35 wherein less than 5% of the light of the first color, the second color, and the third color where present is reabsorbed by the first set, the second set and the third set respectively of quantum dots.

39. The method of any of claims 34-38 wherein each of the first set, second set, and third set of quantum dots are non-spherical.

40. The method of any of claims 34-39 wherein the first set of quantum dots absorbs at least 95% of the light-source's light illuminating the first set of quantum dots.

41. The method of any of claims 34-40 wherein the second set of quantum dots absorbs at least 98.5% of the light-source's light illuminating the second set of quantum dots.

42. The method of any of claims 34-41 further comprising filtering ambient light to prevent the ambient light from exciting the first set of quantum dots and the second set of quantum dots.

43. The method of claim 42 further comprising filtering the ambient light to prevent the ambient light from exciting the third set of quantum dots.

44. A method of making a display comprising

a. applying a first liquid layer containing first color-emitting quantum dots to a surface;

b. using a liquid crystal material having a thin-film transistor array to allow actinic radiation to expose the liquid layer to light to polymerize at least a portion of the first liquid layer, thereby providing a first quantum dot region;

c. applying a second liquid layer containing second color-emitting quantum dots to the surface; and d. using the liquid crystal material having the thin-film transistor array to allow the same or different actinic radiation to expose the liquid layer to light to polymerize at least a portion of the second liquid layer, thereby providing a second quantum dot region.

45. The method of claim 44 wherein the quantum dots have non-zero Stokes' shift.

46. The method of claim 44 or claim 45 and further comprising filling interstices with at least one of a light-blocking material and a light-directing material.

47. The method of any of claims 44-46 wherein the liquid crystal material having the thin- film transistor array is a liquid crystal layer of a LCD.

48. The method of any of claims 44-47 wherein the act of polymerizing the portion of the first liquid layer is followed by removing the first liquid layer that has not polymerized.

49. The method of any of claims 44-48 wherein the act of polymerizing the portion of the second liquid layer is followed by removing the second liquid layer that has not polymerized.

50. The method of any of claims 44-49 wherein the display contains no color filters.

51. The method of any of claims 44-49 and further comprising placing a first ambient- light filter upon at least the first quantum dot region.

52. The method of claim 51 and further comprising placing a second ambient-light filter upon the second quantum dot region.