Backlights including a variable diffuser pattern and methods for fabricating the backlights

Abstract

A backlight includes a plurality of white light sources, a carrier proximate the plurality of light sources, and a variable diffuser pattern applied to a surface of the carrier. The variable diffuser pattern is aligned with the plurality of light sources and configured to scatter a portion of light output by each light source. The variable diffuser pattern includes a white material and a first absorptive material applied on the carrier such that respective normalized CIE x and CIE y values of the backlight from a first location aligned with each respective light source to a second location halfway between respective adjacent light sources vary by less than plus or minus about 1 percent.

Description

Attorney Docket No.: SP24-015 BACKLIGHTS INCLUDING A VARIABLE DIFFUSER PATTERN AND METHODS FOR FABRICATING THE BACKLIGHTS CROSS-REFERENCE TORELATEDAPPLICATIONS

[0001] This application claims the benefit of priority under 35 U.S.C. §119 of U.S.Provisional Application Serial No. 63 / 620439 filed on January 12, 2024, the content of which is relied upon and incorporated herein by reference in its entirety. BACKGROUND Field

[0002] The present disclosure relates generally to backlights for displays. More particularly,it relates to backlights including white light sources and variable diffuser patterns. Technical Background

[0003] Liquid crystal displays (LCDs) are commonly used in various electronics, such ascell phones, laptops, electronic tablets, televisions, and computer monitors. LCDs are light valve-based displays in which the display panel includes an array of individually addressable light valves. LCDs may include a backlight for producing light that may then be wavelength converted, filtered, and / or polarized to produce an image from the LCD. Backlights may be edge-lit or direct-lit. Edge-lit backlights may include a light emitting diode (LED) array edge- coupled to a light guide plate that emits light from its surface. Direct-lit backlights may include a two-dimensional (2D) array of LEDs directly behind the LCD panel.

[0004] Direct-lit backlights may have the advantage of improved dynamic contrast ascompared to edge-lit backlights. For example, a display with a direct-lit backlight may independently adjust the brightness of each LED to set the dynamic range of the brightness across the image. This is commonly known as local dimming. To achieve desired light uniformity and / or to avoid hot spots in direct-lit backlights, however, a polymer diffuser plate may be positioned at a distance from the LEDs, thus making the overall display thicknessAttorney Docket No.: SP24-015 greater than that of an edge-lit backlight. The optical distance (OD) between the LEDs and the polymer diffuser plate in such configurations, however, still results in an undesirably high overall display thickness and / or these configurations may produce undesirable optical losses as the backlight thickness is decreased. In addition, thermal expansion of the polymer diffuser plate may detrimentally affect the backlight performance. SUMMARY

[0005] Some embodiments of the present disclosure relate to a backlight. The backlightincludes a plurality of white light sources, a carrier proximate the plurality of light sources, and a variable diffuser pattern applied to a surface of the carrier. The variable diffuser pattern is aligned with the plurality of light sources and configured to scatter a portion of light output by each light source. The variable diffuser pattern includes a white material and a first absorptive material applied on the carrier such that respective normalized CIE x and CIE y values of the backlight from a first location aligned with each respective light source to a second location halfway between respective adjacent light sources vary by less than plus or minus about 1 percent.

[0006] Yet other embodiments of the present disclosure relate to a backlight. The backlightincludes a plurality of white light sources, a carrier proximate the plurality of light sources, and a variable diffuser pattern applied to a surface of the carrier. The variable diffuser pattern is aligned with the plurality of light sources and configured to scatter a portion of light output by each light source. The variable diffuser pattern includes a first material and a second material different from the first material. The first material includes a first spectral reflectance, a first spectral transmittance, and a first spectral absorptance. The second material includes a second spectral reflectance, a second spectral transmittance, and a second spectral absorptance. The first spectral transmittance at a first wavelength equal to about 450 nanometers is less than the first spectral transmittance at a second wavelength equal to about 550 nanometers. The first spectral transmittance at the second wavelength is less than the first spectral transmittance at a third wavelength equal to about 630 nanometers. The first spectral reflectance at the first wavelength is greater than the first spectral reflectance at the second wavelength. The first spectral reflectance at the second wavelength is greater than the first spectral reflectance at the third wavelength. The first spectral absorptance is less than about 2 percent at each of the first wavelength, the second wavelength, and the third wavelength. The respective first spectralAttorney Docket No.: SP24-015 transmittance at each of the first wavelength, the second wavelength, and the third wavelength at a first location aligned with each respective light source is less than the respective first spectral transmittance at each of the first wavelength, the second wavelength, and the third wavelength at a second location halfway between respective adjacent light sources. The respective first spectral reflectance at each of the first wavelength, the second wavelength, and the third wavelength at the first location is greater than the respective first spectral reflectance at each of the first wavelength, the second wavelength, and the third wavelength at the second location. The second spectral absorptance at one wavelength of the first wavelength, the second wavelength, and the third wavelength is greater than 2 times the second spectral absorptance at the other two wavelengths of the first wavelength, the second wavelength, and the third wavelength.

[0007] Yet other embodiments of the present disclosure relate to a method for fabricating abacklight. The method includes arranging a carrier proximate a plurality of white light sources. The method includes printing a variable diffuser pattern on the carrier comprising printing a white ink and a first absorptive ink on the carrier such that respective normalized CIE x and CIE y values of the backlight from a first location aligned with each respective light source to a second location halfway between respective adjacent light sources vary by less than plus or minus about 1 percent.

[0008] The backlights disclosed herein include variable diffuser patterns that substantiallyreduce or eliminate color mura when using white light sources in the backlights. Since backlights including white light sources typically do not allow for a color conversion film, the variable diffuser patterns disclosed herein simultaneously turn discrete blue, green, and red light distributions into spatially uniform distributions. In addition, a polymer diffuser plate and the associated detrimental thermal expansion may be excluded from the backlights, reducing the thickness of the backlights and improving performance.

[0009] Additional features and advantages will be set forth in the detailed description whichfollows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the embodiments as described herein, including the detailed description which follows, the claims, as well as the appended drawings.

[0010] It is to be understood that both the foregoing general description and the followingdetailed description are merely exemplary and are intended to provide an overview or framework to understanding the nature and character of the claims. The accompanying drawings are included to provide a further understanding and are incorporated in and constituteAttorney Docket No.: SP24-015 a part of this specification. The drawings illustrate one or more embodiment(s), and together with the description explain principles and operation of the various embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] FIG. 1A is a cross-sectional view of an exemplary backlight including a patterneddiffuser;

[0012] FIG. 1B is a top view of a plurality of light sources of the exemplary backlight ofFIG. 1A;

[0013] FIG. 2 is a cross-sectional view of an exemplary liquid crystal display (LCD)including the exemplary backlight of FIGS.1A and 1B;

[0014] FIG. 3A is a cross-sectional view of an exemplary patterned diffuser including awhite material and an absorptive material.

[0015] FIG. 3B is a cross-sectional view of an exemplary patterned diffuser including awhite material with an absorptive material over the white material;

[0016] FIG. 3C is a cross-sectional view of an exemplary patterned diffuser including awhite material with an absorptive material under the white material;

[0017] FIG. 3D is a cross-sectional view of an exemplary patterned diffuser including awhite material with an absorptive material mixed with the white material;

[0018] FIG.3E is a cross-sectional view of an exemplary patterned diffuser including a whitematerial with a first absorptive material over the white material and a second absorptive material adjacent to the white material;

[0019] FIG. 4A is a chart illustrating normalized tristimulus X, Y, and Z values for anexemplary patterned diffuser including white ink and cyan ink;

[0020] FIG. 4B is a chart illustrating normalized CIE x and CIE y values for an exemplarypatterned diffuser including white ink and cyan ink;

[0021] FIG. 5A is a chart illustrating normalized tristimulus X, Y, and Z values for anexemplary patterned diffuser including white ink, cyan ink, and yellow ink;

[0022] FIG. 5B is a chart illustrating normalized CIE x and CIE y values for an exemplarypatterned diffuser including white ink, cyan ink, and yellow ink; and

[0023] FIGS. 6A-6C are flow diagrams of an exemplary method for fabricating a backlightincluding a patterned diffuser.Attorney Docket No.: SP24-015 DETAILEDDESCRIPTION

[0024] Reference will now be made in detail to embodiments of the present disclosure,examples of which are illustrated in the accompanying drawings. Whenever possible, the same reference numerals will be used throughout the drawings to refer to the same or like parts. However, this disclosure may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

[0025] Ranges can be expressed herein as from “about” one particular value, and / or to“about” another particular value. When such a range is expressed, another embodiment includes from the one particular value and / or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent “about,” it will be understood that the particular value forms another embodiment. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint.

[0026] Directional terms as used herein - for example up, down, right, left, front, back, top,bottom, vertical, horizontal - are made only with reference to the figures as drawn and are not intended to imply absolute orientation.

[0027] Unless otherwise expressly stated, it is in no way intended that any method set forthherein be construed as requiring that its steps be performed in a specific order, nor that with any apparatus, specific orientations be required. Accordingly, where a method claim does not actually recite an order to be followed by its steps, or that any apparatus claim does not actually recite an order or orientation to individual components, or it is not otherwise specifically stated in the claims or description that the steps are to be limited to a specific order, or that a specific order or orientation to components of an apparatus is not recited, it is in no way intended that an order or orientation be inferred, in any respect. This holds for any possible non-express basis for interpretation, including: matters of logic with respect to arrangement of steps, operational flow, order of components, or orientation of components; plain meaning derived from grammatical organization or punctuation, and; the number or type of embodiments described in the specification.

[0028] As used herein, the singular forms "a," "an," and "the" include plural referencesunless the context clearly dictates otherwise. Thus, for example, reference to “a” component includes aspects having two or more such components, unless the context clearly indicates otherwise.Attorney Docket No.: SP24-015

[0029] Many backlights including a patterned diffuser include light sources that emitprimarily a single blue color. In these backlights, full white color is achieved through the use of a color conversion film that converts a portion of the blue light into green light and red light. This type of backlight produces a larger color gamut than a typical broad band white light emitting diode (LED) backlight, in which the light source is a blue LED combined with a wide band yellow phosphor. Patterned glass diffusers for these types of LEDs may be fabricated by printing white ink on a glass carrier. These types of patterned glass diffusers may be used mainly in liquid crystal display (LCD) television / monitor applications.

[0030] In applications such as automotive backlights, which require higher reliability over abroad temperature and humidity range, color conversion films may not be suitable. Instead, the light source may be a blue LED covered with narrow band green and red phosphors, which convert a portion of the blue light into green light and red light, thus producing effective white light. In other applications, only narrow band green phosphor or narrow band red phosphor may be used to convert a portion of the blue light into green light or red light, thus producing a two-colored backlight.

[0031] When the patterned diffuser printed with white ink is used in such a backlight thatincludes a light source that emits two or more colored light, undesirable color mura occurs because white ink transmits and reflects differently with different colors. Accordingly, described herein are patterned diffusers that reduce or eliminate the color mura in a white LED backlight or a two-colored backlight.

[0032] Color mura refers to an appreciable separation in the normalized spatial distributionsof tristimulus values X, Y, and Z than can be measured with a colorimeter. As a result, the appearance of the backlight varies spatially and becomes unacceptable. When a patterned diffuser is used in a blue LED backlight that includes a color conversion film, the patterned diffuser only needs to turn the discrete blue light distribution into a spatially uniform distribution, because the subsequent color conversion film can convert the uniform blue spatial distribution into uniform green and red spatial distributions. The blue, green, and red light distributions correspond to the tristimulus values X, Y, and Z, respectively.

[0033] When a patterned diffuser is used in a white LED backlight, which typically does notinclude a color conversion film, the patterned diffuser must simultaneously turn the discrete blue, green, and red light distributions into spatially uniform distributions. This is not possible when the patterned diffuser includes only a conventional white material that transmits and reflects differently at different wavelengths. Accordingly, embodiments disclosed herein use multiple colored materials (e.g., two or three) to simultaneously adjust the distributions ofAttorney Docket No.: SP24-015 tristimulus values X, Y, and Z into spatially uniform distributions in a white LED backlight to reduce or eliminate the color mura.

[0034] Referring now to FIG. 1A, a cross-sectional view of an exemplary backlight 100 isdepicted. Backlight 100 may include a substrate 102, a reflective layer 104, a plurality of white light sources 106, and a patterned diffuser 110. Patterned diffuser 110 includes a carrier 108 (e.g., a light guide plate) proximate the plurality of light sources 106 and a variable diffuser pattern 111 applied to a surface of the carrier 108. The variable diffuser pattern 111 is configured to scatter a portion of light output by each light source 106. The variable diffuser pattern 111 may include a white material patterned to obtain spatially uniform distributions or close to uniform distributions of tristimulus values of either both X and Y or Z. Then, as described in detail below with reference to FIGS.3A-3E, one or two absorptive materials (e.g., yellow material, magenta material, and / or cyan material) may be added to variable diffuser pattern 111 to adjust the spatial uniformity of the remaining tristimulus Z or X and Y values, such that respective normalized tristimulus X, Y, and Z values of the backlight 100 from a first location 130 aligned with each respective light source 106 to a second location 132 halfway between respective adjacent light sources vary by less than plus or minus about 5 percent, such as by less than plus or minus about 3 percent. The variable diffuser patterns described below with reference to FIGS.3A-3E include a white material and a first absorptive material applied on the carrier 108 such that respective normalized CIE x and CIE y values of the backlight 100 from the first location 130 aligned with each respective light source 106 to the second location 132 halfway between respective adjacent light sources may vary by less than plus or minus about 3 percent, such as by less than plus or minus about 1 percent. As illustrated in FIG. 1B, the second location 132 is the maximum distance halfway between adjacent light sources 106, which in the embodiment of FIG.1B is located at the corner of each LED zone 128. Note that light sources may not always be arranged in a rectangle array as shown in FIG. 1B. For example, the light sources may be arranged in other patterns such as in a hexagonal pattern or a pattern that is deviated from a rectangular pattern.

[0035] The plurality of light sources 106 are arranged on substrate 102 and are in electricalcommunication with the substrate 102. Each light source 106 may emit a peak intensity ray as indicated at 107 along a normal axis. Each light source 106 may also emit a peak intensity ray along an off-axis (not shown). The reflective layer 104 is on the substrate 102 and surrounds each light source 106. In certain exemplary embodiments, the substrate 102 may be reflective such that the reflective layer 104 may be excluded. The patterned diffuser 111 is over the plurality of light sources 106 and optically coupled to each light source 106. In certainAttorney Docket No.: SP24-015 exemplary embodiments, an optical adhesive (not shown) may be used to couple the plurality of light sources 106 to the patterned diffuser 110. The optical adhesive (e.g., phenyl silicone) may have a refractive index greater than or equal to a refractive index of the carrier 108. The variable diffuser pattern 111 is arranged on the upper surface of the carrier 108 and includes a plurality of diffuser patterns 112. Each diffuser pattern 112 is aligned with a corresponding light source 106 of the plurality of light sources 106. In some embodiments, the variable diffuser pattern 111 may be arranged on the lower surface of the carrier 108. In other embodiments, a first portion of the variable diffuser pattern 111 may be arranged on the upper surface of the carrier 108, and a second portion of the variable diffuser pattern 111 may be arranged on the lower surface of the carrier 108.

[0036] Each diffuser pattern 112 includes a thickness profile along a width or diameter ofthe diffuser pattern and may include a substantially flat section as indicated at 113 and a curved section as indicated at 114 extending from and surrounding the substantially flat section 113. The size L0 (i.e., width or diameter) of each substantially flat section 113 as indicated at 120 (in a plane parallel to the substrate 102) may be greater than the size (i.e., width or diameter) of each corresponding light source 106 as indicated at 124 (in a plane parallel to the substrate 102). The size 120 of each substantially flat section 113 may be less than the size 124 of each corresponding light source 106 times a predetermined value. In certain exemplary embodiments, when the size 124 of each light source 106 is greater than or equal to about 0.5 millimeters, the predetermined value may be about two or about three, such that the size of each substantially flat section 113 is less than three times the size of each light source 106. When the size 124 of each light source 106 is less than 0.5 millimeters, the predetermined value may be determined by the alignment capability between the light sources 106 and the diffuser patterns 112, such that the size of each substantially flat section 113 of each of diffuser pattern 112 is within a range between about 100 micrometers and about 300 micrometers greater than the size of each light source 106. Each substantially flat section 113 is large enough such that each diffuser pattern 112 can be aligned to the corresponding light source 106 and small enough to achieve suitable luminance uniformity and color uniformity.

[0037] The size L1 (i.e., width or diameter) of each diffuser pattern 112 is indicated at 122(in a plane parallel to the substrate 102) and the pitch P between adjacent light sources 106 is indicated at 126. While the pitch is illustrated along one direction in FIG. 1A, the pitch may be different in a direction orthogonal to the direction illustrated. The pitch may, for example, be about 90, 45, 30, 10, 5, 2, 1, or 0.5 millimeters, larger than about 90 millimeters, or smaller than about 0.5 millimeters. In certain exemplary embodiments, the ratio L1 / P of the size 122Attorney Docket No.: SP24-015 of each diffuser pattern 112 over the pitch 126 is within a range between about 0.45 and 1.0. The ratio may vary with the pitch 126 of the light sources 106 and the distance between the emission surface of each light source and the corresponding diffuser pattern 112. For example, for a pitch 126 equal to about 5 millimeters and a distance between the emission surface of each light source and the corresponding diffuser pattern 112 equal to about 0.2 millimeters, the ratio may equal about 0.50, 0.60, 0.70, 0.80, 0.90, or 1.0.

[0038] Each diffuser pattern 112 reflects at least a portion of the light emitted from thecorresponding light source 106 into the carrier 108. Each diffuser pattern 112 has a specular reflectance and a diffuse reflectance. The specularly-reflected light exits from the bottom surface of the carrier 108. While specularly-reflected light travels laterally primarily due to the reflection between the reflective layer 104 and the carrier 108, or due to the reflection between the reflective layer 104 and the diffuser sheet or diffuser plate (shown below in FIG. 2), some loss of light may occur due to imperfect reflection from the reflective layer 104.

[0039] The diffusively reflected light has an angular distribution between 0° and 90°measured from the normal of the carrier 108. About 50 percent of the diffusively reflected light has an angle exceeding the critical angle (^TIR) of the total internal reflection. Thus, the diffusively reflected light can travel laterally due to the total internal reflection without any loss, until the light is subsequently extracted out of the carrier 108 by diffuser patterns 112.

[0040] In certain exemplary embodiments, each diffuser pattern 112 is a diffuse reflector,such that each diffuser pattern 112 further enhances the performance of the backlight 100 by scattering some light rays at high enough angles such that they can propagate in the carrier 108 by total internal reflection. Such rays will then not experience multiple bounces between the diffuser patterns 112 and the reflective layer 104 or between an optical film stack and the reflective layer 104 and therefore avoid loss of optical power, thereby increasing the backlight efficiency. In certain exemplary embodiments, each diffuser pattern 112 is a specular reflector. In other embodiments, some areas of each diffuser pattern 112 have a more diffuse character of reflectivity and some areas have a more specular character of reflectivity.

[0041] Each diffuser pattern 112 may be formed, for example, by printing (e.g., inkjetprinting, screen printing, microprinting, etc.) a pattern with white ink. Each diffuser pattern 112 may also be formed by first depositing a continuous layer of a white material, for example by physical vapor deposition (PVD) or any number of coating techniques such as for example slot die or spray coating, and then patterning the layer by photolithography or other known methods of area-selective material removal.Attorney Docket No.: SP24-015

[0042] FIG. 1B is a top view of the plurality of light sources 106 and reflective layer 104 onsubstrate 102. Light sources 106 are arranged in a 2D array including a plurality of rows and a plurality of columns. While nine light sources 106 are illustrated in FIG. 1B in three rows and three columns, in other embodiments backlight 100 may include any suitable number of light sources 106 arranged in any suitable number of rows and any suitable number of columns. Light sources 106 may also be arranged in other periodic patterns, for example, a hexagonal or triangular lattice, or as quasi-periodic or non-strictly periodic patterns. For example, the spacing between light sources 106 may be smaller at the edges and / or corners of the backlight.

[0043] Substrate 102 (FIG. 1A) may be a printed circuit board (PCB), a glass or plasticsubstrate, or another suitable substrate for passing electrical signals to each light source 106 for individually controlling each light source. Substrate 102 may be a rigid substrate or a flexible substrate. For example, substrate 102 may include flat glass or curved glass. The curved glass, for example, may have a radius of curvature less than about 2000 millimeters, such as about 1500, 1000, 500, 200, or 100 millimeters. The reflective layer 104 may include, for example, metallic foils, such as silver, platinum, gold, copper, and the like; dielectric materials (e.g., polymers such as polytetrafluoroethylene (PTFE)); porous polymer materials, such as polyethylene terephthalate (PET), Poly(methyl methacrylate) (PMMA), polyethylene naphthalate (PEN), polyethersulfone (PES), etc.; multi-layer dielectric interference coatings, or reflective inks, including white inorganic particles such as titania, barium sulfate, etc., or other materials suitable for reflecting light and tuning the color of the reflected and transmitted light, such as colored pigments.

[0044] Each of the plurality of light sources 106 may, for example, be an LED (e.g., sizelarger than about 0.5 millimeters), a mini-LED (e.g., size between about 0.1 millimeters and about 0.5 millimeters), a micro-LED (e.g., size smaller than about 0.1 millimeter), an organicLED (OLED), or another suitable white light source having wavelengths (^) ranging fromabout 400 nanometers to about 750 nanometers. In other embodiments, each of the plurality of light sources 106 may have wavelengths shorter than 400 nanometers and / or longer than 750 nanometers. In certain exemplary embodiments, each light source 106 may include a blue LED with green and red phosphors to emit blue, green, and red light. In certain exemplary embodiments, the light from each light source 106 is optically coupled to the carrier 108. As used herein, the term “optically coupled” is intended to denote that a light source is positioned at a surface of the carrier 108 and is in optical communication with the carrier 108 directly or through an optically-clear adhesive, so as to introduce light into the carrier that at least partiallyAttorney Docket No.: SP24-015 propagates due to total internal reflection. The light from each light source 106 is optically coupled to the carrier 108 such that a first portion of the light travels laterally in the carrier 108 due to the total internal reflection and is extracted out of the carrier by the diffuser patterns 112, and a second portion of the light travels laterally between the reflective layer 104 and the diffuser patterns 112 due to multiple reflections at the reflective surfaces of the reflective layer 104 and the diffuser patterns 112 or between an optical film stack (shown in FIG. 2) and thereflective layer 104. In other exemplary embodiments, the light from each light source 106travels through an air and then enters the carrier 108. A first portion of the light travels laterally in the carrier 108 due to the total internal reflection or reflection by the diffuser patterns 112 and the reflective layer 104, and a second portion of the light is transmitted through the diffuser patterns 112.

[0045] According to various embodiments, the carrier 108 may include any suitabletransparent material used for lighting and display applications. As used herein, the term “transparent” is intended to denote that the carrier has an optical transmission of greater than about 70 percent over a length of 500 millimeters in the visible region of the spectrum (about 420-750 nanometers). In certain embodiments, an exemplary transparent material may have an optical transmittance of greater than about 50 percent in the ultraviolet (UV) region (about 100-400 nanometers) over a length of 500 millimeters. According to various embodiments, the carrier may include an optical transmittance of at least 95 percent over a path length of 50 millimeters for wavelengths ranging from about 450 nanometers to about 650 nanometers.

[0046] The optical properties of the carrier 108 may be affected by the refractive index ofthe transparent material. According to various embodiments, the carrier 108 may have a refractive index ranging from about 1.3 to about 1.8. In other embodiments, the carrier 108 may have a relatively low level of light attenuation (e.g., due to absorption and / or scattering). The light attenuation (α) of the carrier 108 may, for example, be less than about 5 decibels per meter for wavelengths ranging from about 420-750 nanometers. The carrier 108 may include polymeric materials, such as plastics (e.g., polymethyl methacrylate (PMMA), methylmethacrylate styrene (MS), polydimethylsiloxane (PDMS)), polycarbonate (PC), or other similar materials. The carrier 108 may also include a glass material, such as aluminosilicate, alkali-aluminosilicate, borosilicate, alkali-borosilicate, aluminoborosilicate, alkali-aluminoborosilicate, soda lime, or other suitable glasses. Non-limiting examples of commercially available glasses suitable for use as a glass carrier 108 include EAGLE XG®, LotusTM, Willow®, IrisTM, and Gorilla® glasses from Corning Incorporated. In examples where substrate 102 includes curved glass, carrier 108 may also include curved glass to form aAttorney Docket No.: SP24-015 curved backlight. In other embodiments, the carrier 108 may have a relatively high level of light attenuation. The light attenuation (α) of the carrier 108 may, for example, be greater than about 5 decibels per meter for wavelengths ranging from about 420-750 nanometers.

[0047] FIG. 2 is a cross-sectional view of an exemplary liquid crystal display (LCD) 140including the exemplary backlight 100 of FIGS.1A and 1B including variable diffuser pattern 111. In addition, LCD 140 includes optionally a diffuser plate 146 over backlight 100, optionally a prismatic film 150 over the diffuser plate 146, optionally a reflective polarizer 152 over the prismatic film 150, and a display panel 154 over the reflective polarizer 152.

[0048] To maintain the alignment between the light sources 106 and the diffuser patterns112 on the carrier 108 for the proper functioning of the backlight 100, it is advantageous if the carrier 108 and the substrate 102 are made of the same or similar type of material so that both the diffuser patterns 112 on the carrier 108 and the light sources 106 on the substrate 102 are registered well to each other over a large range of operating temperatures. In certain exemplary embodiments, the carrier 108 and the substrate 102 are made of the same plastic material. In other embodiments, the carrier 108 and the substrate 102 are made of the same type of glass.

[0049] An alternative solution to keep the carrier 108 and light sources 106 on the substrate102 in alignment is to use a highly flexible substrate. The highly flexible substrate may be made of a polyimide or other high temperature resistant polymer film to allow component soldering. The highly flexible substrate may also be made of materials such as FR4 or fiberglass, but of a significantly lower thickness than usual. In certain exemplary embodiments, an FR4 material of 0.4 millimeters thickness may be used for substrate 102, which may be sufficiently flexible to absorb the dimensional changes resulting from changing operating temperatures.

[0050] FIG. 3A is a cross-sectional view of an exemplary patterned diffuser 210a. Patterneddiffuser 210a includes a carrier 108 and a variable diffuser pattern 211a applied to a surface (e.g., upper surface and / or lower surface) of the carrier 108. In some embodiments, patterned diffuser 210a may be used in backlight 100 of FIGS. 1A and 1B in place of patterned diffuser 110. Variable diffuser pattern 211a includes a plurality of diffuser patterns 212a aligned with the plurality of light sources 106 (FIG. 1A) and configured to scatter a portion of light output by each light source 106. In this embodiment, the variable diffuser pattern 211a includes a first material 240 (e.g., a white material) and a second material 246 (e.g., a first absorptive material) applied on the carrier 108 such that respective normalized CIE x and CIE y (i.e., CIE 19312^ observer) values of the backlight from a first location 230 aligned with each respective lightAttorney Docket No.: SP24-015 source to a second location 232 halfway between respective adjacent light sources may vary by less than plus or minus about 3 percent, such as by less than plus or minus about 1 percent. First location 230 may correspond to first location 130 aligned with each light source 106 in FIGS.1A and 1B, and second location 232 may correspond to second location 132 at the corner of each light source zone 128 in FIGS. 1A and 1B. Respective normalized tristimulus X, Y, and Z values of the backlight from the first location 230 to the second location 232 may vary by less than plus or minus about 5 percent, such as by less than plus or minus about 3 percent.

[0051] The first material 240 and the second material 246 are different materials. The firstmaterial 240 includes a first spectral reflectance R1, a first spectral transmittance T1, and a firstspectral absorptance A1. The second material 246 includes a second spectral reflectance R2,which may be different from the first spectral reflectance R1; a second spectral transmittanceT2, which may be different from the first spectral transmittance T1; and a second spectralabsorptance A2, which may be different from the first spectral absorptance A1. A location orradial distance r is defined within a range between a minimum value r=0 at the first location230 aligned with each respective light source 106 and a maximum value r=rmax at the secondlocation 232 halfway between respective adjacent light sources 106.

[0052] The first spectral transmittance T1 at a first wavelength equal to about 450 nanometersis less than the first spectral transmittance T1 at a second wavelength equal to about 550nanometers, and the first spectral transmittance T1 at the second wavelength is less than the firstspectral transmittance T1 at a third wavelength equal to about 630 nanometers, such that T1(r;^=450) < T1(r; ^=550) < T1(r; ^=630). The first spectral reflectance R1 at the first wavelengthis greater than the first spectral reflectance R1 at the second wavelength, and the first spectralreflectance R1 at the second wavelength is greater than the first spectral reflectance R1 at thethird wavelength, such that R1(r; ^=450) > R1(r; ^=550) > R1(r; ^=630). Accordingly, the firstspectral transmittance T1 is progressively lower and the first spectral reflectance R1 isprogressively higher as the wavelength increases from about 450 nanometers to about 550nanometers, and from about 550 nanometers to about 630 nanometers at the same location r.

[0053] The first spectral absorptance A1 is less than about 2 percent at each of the firstwavelength, the second wavelength, and the third wavelength, such that A1(r; ^=450, 550, or630) < 2%. The respective first spectral transmittance T1 at each of the first wavelength, thesecond wavelength, and the third wavelength at the first location 230 aligned with eachrespective light source 106 is less than the respective first spectral transmittance T1 at each ofthe first wavelength, the second wavelength, and the third wavelength at the second locationAttorney Docket No.: SP24-015232 halfway between respective adjacent light sources 106, such that T1(r=0; ^=450, 550, or630) < T1(r=rmax; ^=450, 550, or 630). The respective first spectral reflectance R1 at each ofthe first wavelength, the second wavelength, and the third wavelength at the first location 230is greater than the respective first spectral reflectance R1 at each of the first wavelength, thesecond wavelength, and the third wavelength at the second location 232, such that R1(r=0;^=450, 550, or 630) > R1(r=rmax; ^=450, 550, or 630). The first spectral reflectance R1, thefirst spectral transmittance T1, and the first spectral absorptance A1 for the first material 240 areapplicable to each embodiment described herein where the first material 240 includes a white material (e.g., a white ink).

[0054] The second spectral absorptance A2 at one wavelength of the first wavelength, thesecond wavelength, and the third wavelength is greater than 2 times the second spectral absorptance A2 at the other two wavelengths of the first wavelength, the second wavelength, and the third wavelength. The second spectral absorptance A2 may vary based on the second material as described below.

[0055] In some embodiments, the first material 240 includes a white material (e.g., whiteink) and the second material 246 (e.g., first absorptive material) includes a yellow material(e.g., yellow ink). The second spectral absorptance A2 of the yellow material at the firstwavelength is greater than 2 times the second spectral absorptance A2 at the second wavelength,such that A2(r; ^=450) > 2A2(r; ^=550). The second spectral absorptance A2 at the firstwavelength is greater than 2 times the second spectral absorptance A2 at the third wavelength,such that A2(r; ^=450) > 2A2(r; ^=630). The second spectral transmittance T2 at the firstwavelength at the first location 230 is less than the second spectral transmittance T2 at the firstwavelength at the second location 232, such that T2(r=0; ^=450) < T2(r=rmax; ^=450).

[0056] The above values for the first spectral reflectance R1, the first spectral transmittanceT1, the first spectral absorptance A1, the second spectral reflectance R2, the second spectraltransmittance T2, and the second spectral absorptance A2 may be obtained by adjusting thethickness profile and / or optical density profile of the white material 240 and the yellow material 246 within each diffuser pattern 212a. The white material 240 may include a first thickness and / or optical density at the first location 230 and a second thickness and / or optical density less than the first thickness and / or optical density at a third location 234 between the first location 230 and the second location 232. The thickness and / or optical density may be reduced gradually from the first thickness and / or optical density to the second thickness and / or optical density. The yellow material 246 may include a third thickness and / or optical density at theAttorney Docket No.: SP24-015 second location 232 and a fourth thickness and / or optical density less than the third thickness and / or optical density at the third location 234. The thickness and / or optical density may be reduced gradually from the third thickness and / or optical density to the fourth thickness and / or optical density.

[0057] The white material 240 thickness and / or optical density profile may be optimized toobtain uniformity of both normalized tristimulus values X and Y close to 1. The white material 240 has a greater thickness and / or optical density near the center of each LED zone that is gradually reduced towards the corner of each LED zone. With white material alone, however, uniformity in tristimulus value Z may not be acceptable, which may result in observable color mura over each LED zone. X and Y have a different variation trend from Z due to the reflection and absorption of blue light, which corresponds to Z, by the white material are higher than the reflection and absorption of red light and green light, which corresponds to X and Y, respectively. Therefore, to further reduce the color mura, the yellow material is added and the thickness profile and / or optical density profile of the yellow material is optimized to suppress the higher Z for blue color at the corner area of each LED zone. The yellow material has a greater thickness and / or optical density near the corner of each LED zone that is gradually reduced towards the center of each LED zone.

[0058] In some embodiments, the first material 240 includes a white material (e.g., whiteink) and the second material 246 (e.g., first absorptive material) includes a magenta material(e.g., magenta ink). The second spectral absorptance A2 of the magenta ink at the secondwavelength is greater than 2 times the second spectral absorptance A2 at the first wavelengthsuch that A2(r; ^=550) > 2A2(r; ^=450). The second spectral absorptance A2 at the secondwavelength is greater than 2 times the second spectral absorptance A2 at the third wavelength,such that A2(r; ^=550) > 2A2(r; ^=630). The second spectral transmittance T2 at the secondwavelength at the first location 230 is less than the second spectral transmittance T2 at thesecond wavelength at the second location 232, such that T2(r=0; ^=550) < T2(r=rmax; ^=550).

[0059] The above values for the first spectral reflectance R1, the first spectral transmittanceT1, the first spectral absorptance A1, the second spectral reflectance R2, the second spectraltransmittance T2, and the second spectral absorptance A2 may be obtained by adjusting thethickness profile and / or optical density profile of the white material 240 and the magenta material 246 within each diffuser pattern 212a. The white material 240 may include a first thickness and / or optical density at the first location 230 and a second thickness and / or optical density less than the first thickness and / or optical density at the third location 234 between theAttorney Docket No.: SP24-015 first location 230 and the second location 232. The thickness and / or optical density may be reduced gradually from the first thickness and / or optical density to the second thickness and / or optical density. The magenta material 246 may include a third thickness and / or optical density at the second location 232 and a fourth thickness and / or optical density less than the third thickness and / or optical density at the third location 234. The thickness and / or optical density may be reduced gradually from the third thickness and / or optical density to the fourth thickness and / or optical density.

[0060] The white material 240 thickness and / or optical density profile may be optimized toobtain uniformity of both normalized tristimulus values X and Y close to 1. The white material 240 has a greater thickness and / or optical density near the center of each LED zone that is gradually reduced towards the corner of each LED zone. To further reduce the color mura, the magenta material is added and the thickness profile and / or optical density profile is optimized to suppress the higher nit in blue color at the corner area of each LED zone. The magenta material has a greater thickness and / or optical density near the corner of each LED zone that is gradually reduced towards the center of each LED zone.

[0061] FIG. 3B is a cross-sectional view of an exemplary patterned diffuser 210b. Patterneddiffuser 210b includes a carrier 108 and a variable diffuser pattern 211b applied to a surface (e.g., upper surface and / or lower surface) of the carrier 108. In some embodiments, patterned diffuser 210b may be used in backlight 100 of FIGS. 1A and 1B in place of patterned diffuser 110. Variable diffuser pattern 211b includes a plurality of diffuser patterns 212b aligned with the plurality of light sources 106 (FIG. 1A) and configured to scatter a portion of light output by each light source 106. In this embodiment, the variable diffuser pattern 211b includes a first material 240 (e.g., a white material) and a second material 242 (e.g., a first absorptive material) applied on the carrier 108 such that respective normalized CIE 19312^ observer x and y (CIE x and CIE y in the following refer to CIE 19312^ observer x and y) values of the backlight from the first location 230 aligned with each respective light source to the second location 232 halfway between respective adjacent light sources may vary by less than plus or minus about 3 percent, such as by less than plus or minus about 1 percent. Respective normalized tristimulus X, Y, and Z values of the backlight from the first location 230 to the second location 232 may vary by less than plus or minus about 5 percent, such as by less than plus or minus about 3 percent.

[0062] In some embodiments, the first material 240 may be a white material (e.g., white ink)and the second material 242 may be a cyan material (e.g., cyan ink) over the white materialAttorney Docket No.: SP24-015240. The second spectral absorptance A2 of the cyan material at the third wavelength is greaterthan 2 times the second spectral absorptance A2 at the first wavelength, such that A2(r; ^=630)> 2A2(r; ^=450). The second spectral absorptance A2 at the third wavelength is greater than 2times the second spectral absorptance A2 at the second wavelength, such that A2(r; ^=630) >2A2(r; ^=550). The second spectral transmittance T2 at the third wavelength at the first location230 is less than the second spectral transmittance T2 at the third wavelength at the secondlocation 232, such that T2(r=0; ^=630) < T2(r=rmax; ^=630).

[0063] The above values for the first spectral reflectance R1, the first spectral transmittanceT1, the first spectral absorptance A1, the second spectral reflectance R2, the second spectraltransmittance T2, and the second spectral absorptance A2 may be obtained by adjusting thethickness profile and / or optical density profile of the white material 240 and the cyan material 242 within each diffuser pattern 212b. The white material 240 may include a first thickness and / or optical density at the first location 230 and a second thickness and / or optical density less than the first thickness and / or optical density at the third location 234 between the first location 230 and the second location 232. The thickness and / or optical density may be reduced gradually from the first thickness and / or optical density to the second thickness and / or optical density. The cyan material 242 may include a fifth thickness and / or optical density at the first location 230 and a sixth thickness and / or optical density less than the fifth thickness and / or optical density at the third location 234. The thickness and / or optical density may be reduced gradually from the fifth thickness and / or optical density to the sixth thickness and / or optical density.

[0064] The white material 240 thickness and / or optical density profile may be optimized toobtain uniformity of normalized tristimulus value Z close to 1. The white material 240 has a greater thickness and / or optical density near the center of each LED zone that is gradually reduced towards the corner of each LED zone. With white material alone, however, uniformity in tristimulus values X and Y may not be acceptable, which are higher in the center of each LED zone and lower in the corner of each LED zone. Therefore, the cyan material is added and the thickness profile and / or optical density profile of the cyan material is optimized to obtain uniformity of both normalized tristimulus values X and Y close to 1. The cyan material has a greater thickness and / or optical density near the center of each LED zone that is gradually reduced towards the corner of each LED zone.

[0065] FIG. 3C is a cross-sectional view of an exemplary patterned diffuser 210c. Patterneddiffuser 210c includes a carrier 108 and a variable diffuser pattern 211c applied to a surfaceAttorney Docket No.: SP24-015 (e.g., upper surface and / or lower surface) of the carrier 108. In some embodiments, patterned diffuser 210c may be used in backlight 100 of FIGS. 1A and 1B in place of patterned diffuser 110. Variable diffuser pattern 211c includes a plurality of diffuser patterns 212c aligned with the plurality of light sources 106 (FIG. 1A) and configured to scatter a portion of light output by each light source 106. In this embodiment, the variable diffuser pattern 211c includes a first material 240 (e.g., a white material) and a second material 242 (e.g., a first absorptive material) applied on the carrier 108 such that respective normalized CIE x and CIE y values of the backlight from the first location 230 aligned with each respective light source to the second location 232 halfway between respective adjacent light sources may vary by less than plus or minus about 3 percent, such as by less than plus or minus about 1 percent. Respective normalized tristimulus X, Y, and Z values of the backlight from the first location 230 to the second location 232 may vary by less than plus or minus about 5 percent, such as by less than plus or minus about 3 percent.

[0066] Variable diffuser pattern 211c is similar to variable diffuser pattern 211b of FIG. 3B,except that in variable diffuser pattern 211c, the white material 240 is over the cyan material 242. Both the white material 240 and the cyan material 242 of each diffuser pattern 212c include a similar thickness profile and / or optical density profile as described above withreference to FIG.3B. Therefore, the values for the first spectral reflectance R1, the first spectraltransmittance T1, the first spectral absorptance A1, the second spectral reflectance R2, the secondspectral transmittance T2, and the second spectral absorptance A2 described above withreference to variable diffuser pattern 211b of FIG. 3B also apply to variable diffuser pattern 211c of FIG.3C.

[0067] FIG.3D is a cross-sectional view of an exemplary patterned diffuser 210d. Patterneddiffuser 210d includes a carrier 108 and a variable diffuser pattern 211d applied to a surface (e.g., upper surface and / or lower surface) of the carrier 108. In some embodiments, patterned diffuser 210d may be used in backlight 100 of FIGS. 1A and 1B in place of patterned diffuser 110. Variable diffuser pattern 211d includes a plurality of diffuser patterns 212d aligned with the plurality of light sources 106 (FIG. 1A) and configured to scatter a portion of light output by each light source 106. In this example, the variable diffuser pattern 211d includes a first material 240 (e.g., a white material) and a second material 244 (e.g., a mixed material) applied on the carrier 108 such that respective normalized CIE x and CIE y values of the backlight from the first location 230 aligned with each respective light source to the second location 232 halfway between respective adjacent light sources may vary by less than plus or minus about 3 percent, such as by less than plus or minus about 1 percent. Respective normalized tristimulusAttorney Docket No.: SP24-015 X, Y, and Z values of the backlight from the first location 230 to the second location 232 may vary by less than plus or minus about 5 percent, such as by less than plus or minus about 3 percent.

[0068] Variable diffuser pattern 211d is similar to variable diffuser pattern 211b of FIG.3B,except that in variable diffuser pattern 211d, the second material 244 is a mixture of the white material 240 and the cyan material 242. In this embodiment, the white material 240 may include a first optical density at the first location 230 and a second optical density less than the first optical density at the third location 234 between the first location 230 and the second location 232. The optical density may be reduced gradually from the first optical density to the second optical density. The cyan material 242 may include a third optical density at the first location 230 and a fourth optical density less than the third optical density at the third location 234. The optical density may be reduced gradually from the third optical density to the fourth optical density. Both the white material 240 and the cyan material 242 of each diffuser pattern 212d may include a similar optical density profile as described above with reference to FIG.3B. Therefore, the values for the first spectral reflectance R1, the first spectral transmittanceT1, the first spectral absorptance A1, the second spectral reflectance R2, the second spectraltransmittance T2, and the second spectral absorptance A2 described above with reference tovariable diffuser pattern 211b of FIG. 3B also apply to variable diffuser pattern 211d of FIG. 3D.

[0069] FIG. 3E is a cross-sectional view of an exemplary patterned diffuser 210e. Patterneddiffuser 210e includes a carrier 108 and a variable diffuser pattern 211e applied to a surface (e.g., upper surface and / or lower surface) of the carrier 108. In some embodiments, patterned diffuser 210e may be used in backlight 100 of FIGS. 1A and 1B in place of patterned diffuser 110. Variable diffuser pattern 211e includes a plurality of diffuser patterns 212e aligned with the plurality of light sources 106 (FIG. 1A) and configured to scatter a portion of light output by each light source 106. In this embodiment, the variable diffuser pattern 211e includes a first material 240 (e.g., a white material), a second material 242 (e.g., a first absorptive material), and a third material 246 (e.g., a second absorptive material) applied on the carrier 108 such that respective normalized CIE x and CIE y values of the backlight from the first location 230 aligned with each respective light source to the second location 232 halfway between respective adjacent light sources may vary by less than plus or minus about 3 percent, such as by less than plus or minus about 1 percent. Respective normalized tristimulus X, Y, and Z values of the backlight from the first location 230 to the second location 232 may vary by less than plus or minus about 5 percent, such as by less than plus or minus about 3 percent.Attorney Docket No.: SP24-015

[0070] Variable diffuser pattern 211e is similar to variable diffuser pattern 211a of FIG. 3A,except that variable diffuser pattern 211e includes a third material 242 of FIGS. 3B-3D in addition to the first material 240 and the second material 246. In this embodiment, the third material 242 is different from the first material 240 and the second material 246. The thirdmaterial 242 includes a third spectral reflectance R3, which may be different from the firstspectral reflectance R1 and the second spectral reflectance R2; a third spectral transmittance T3,which may be different from the first spectral transmittance T1 and the second spectraltransmittance T2; and a third spectral absorptance A3, which may be different from the firstspectral absorptance A1 and the second spectral absorptance A2.

[0071] In some embodiments, the first material 240 includes a white material (e.g., whiteink), the second material 246 (e.g., first absorptive material) includes a yellow material (e.g., yellow ink), and the third material 242 (e.g., second absorptive material) includes a cyan material (e.g., cyan ink). In certain exemplary embodiments, the white material 240 may be mixed with the yellow material and / or the cyan material similarly as described above withreference to FIG. 3D. The second spectral absorptance A2 of the yellow material 246 at thefirst wavelength is greater than 2 times the second spectral absorptance A2 at the secondwavelength, such that A2(r; ^=450) > 2A2(r; ^=550). The second spectral absorptance A2 at thefirst wavelength is greater than 2 times the second spectral absorptance A2 at the thirdwavelength, such that A2(r; ^=450) > 2A2(r; ^=630). The second spectral transmittance T2 atthe first wavelength at the first location 230 is less than the second spectral transmittance T2 atthe first wavelength at the second location 232, such that T2(r=0; ^=450) < T2(r=rmax; ^=450).

[0072] The third spectral absorptance A3 of the cyan material 242 at the third wavelength isgreater than 2 times the third spectral absorptance A3 at the first wavelength, such that A3(r;^=630) > 2A3(r; ^=450). The third spectral absorptance A3 of the cyan ink at the thirdwavelength is greater than 2 times the third spectral absorptance A3 at the second wavelength,such that A3(r; ^=630) > 2A3(r; ^=550). The third spectral transmittance T3 at the thirdwavelength at the first location 230 is less than the third spectral transmittance T3 at the thirdwavelength at the second location 232, such that T3(r=0; ^=630) < T3(r=rmax; ^=630).

[0073] The above values for the first spectral reflectance R1, the first spectral transmittanceT1, the first spectral absorptance A1, the second spectral reflectance R2, the second spectraltransmittance T2, the second spectral absorptance A2, the third spectral reflectance R3, the thirdspectral transmittance T3, and the third spectral absorptance A3 may be obtained by adjustingthe thickness profile and / or optical density profile of the white material 240, the yellow materialAttorney Docket No.: SP24-015 246, and the cyan material 242 within each diffuser pattern 212e. The white material 240 may include a first thickness and / or optical density at the first location 230 and a second thickness and / or optical density less than the first thickness and / or optical density at the third location 234 between the first location 230 and the second location 232. The thickness and / or optical density may be reduced gradually from the first thickness and / or optical density to the second thickness and / or optical density. The yellow material may include a third thickness and / or optical density at the second location 232 and a fourth thickness and / or optical density less than the third thickness and / or optical density at the third location 234. The thickness and / or optical density may be reduced gradually from the third thickness and / or optical density to the fourth thickness and / or optical density. The cyan material may include a fifth thickness and / or optical density at the first location 230 and a sixth thickness and / or optical density less than the fifth thickness and / or optical density at the third location 234. The thickness and / or optical density may be reduced gradually from the fifth thickness and / or optical density to the sixth thickness and / or optical density.

[0074] In some embodiments, the first material 240 includes a white material (e.g., whiteink), the second material (e.g., first absorptive material) includes a cyan material 242 (e.g., cyan ink), and the third material (e.g., second absorptive material) includes a magenta material 246 (e.g., magenta ink). In certain exemplary embodiments, the white material 240 may be mixed with the cyan material and / or the magenta material similarly as described above withreference to FIG. 3D. The second spectral absorptance A2 of the cyan material at the thirdwavelength is greater than 2 times the second spectral absorptance A2 at the first wavelength,such that A2(r; ^=630) > 2A2(r; ^=450). The second spectral absorptance A2 at the thirdwavelength is greater than 2 times the second spectral absorptance A2 at the second wavelength,such that A2(r; ^=630) > 2A2(r; ^=550). The second spectral transmittance T2 at the thirdwavelength at the first location 230 is less than the second spectral transmittance T2 at the thirdwavelength at the second location 232, such that T2(r=0; ^=630) < T2(r=rmax; ^=630).

[0075] The third spectral absorptance A3 of the magenta material at the second wavelengthis greater than 2 times the third spectral absorptance A3 at the first wavelength, such that A3(r;^=550) > 2A3(r; ^=450). The third spectral absorptance A3 at the second wavelength is greaterthan 2 times the third spectral absorptance A3 at the third wavelength, such that A3(r; ^=550) >2A3(r; ^=630). The third spectral transmittance T3 at the second wavelength at the first location230 is less than the third spectral transmittance T3 at the second wavelength at the secondlocation 232, such that T3(r=0; ^=550) < T3(r=rmax; ^=550).Attorney Docket No.: SP24-015

[0076] The above values for the first spectral reflectance R1, the first spectral transmittanceT1, the first spectral absorptance A1, the second spectral reflectance R2, the second spectraltransmittance T2, the second spectral absorptance A2, the third spectral reflectance R3, the thirdspectral transmittance T3, and the third spectral absorptance A3 may be obtained by adjustingthe thickness profile and / or optical density profile of the white material 240, the cyan material 242, and the magenta material 246 within each diffuser pattern 212e. The white material may include a first thickness and / or optical density at the first location 230 and a second thickness and / or optical density less than the first thickness and / or optical density at the third location 234 between the first location 230 and the second location 232. The thickness and / or optical density may be reduced gradually from the first thickness and / or optical density to the second thickness and / or optical density. The cyan material may include a third thickness and / or optical density at the first location 230 and a fourth thickness and / or optical density less than the third thickness and / or optical density at the third location 234. The thickness and / or optical density may be reduced gradually from the third thickness and / or optical density to the fourth thickness and / or optical density. The magenta material may include a fifth thickness and / or optical density at the second location 232 and a sixth thickness and / or optical density less than the fifth thickness and / or optical density at the third location 234. The thickness and / or optical density may be reduced gradually from the fifth thickness and / or optical density to the sixth thickness and / or optical density.

[0077] Since three kinds of materials are used in the embodiment of FIG. 3E, the order ofadding the materials for optimizing the tristimulus X, Y, and Z values is important to a successful patterned diffuser design. The order of materials to print can result in different performance but the order of materials to print is not critical as long as the order of printing is consistent during the optimizing or the materials may be printed simultaneously and mixed in specific locations. First, the white material 240 thickness profile and / or optical density profile may be optimized to achieve uniformity of normalized tristimulus Z values close to 1. The white material 240 has a greater thickness and / or optical density near the center of each LED zone that is gradually reduced towards the corner of each LED zone. Second, the cyan material 242 is added and the cyan material thickness profile and / or optical density profile is optimized to achieve uniformity of normalized tristimulus X and Y values close to 1. The cyan material 242 has a greater thickness and / or optical density near the center of each LED zone that is gradually reduced towards the corner of each LED zone. Third, the yellow or magenta material 246 is added and the yellow or magenta material thickness profile and / or optical density profile is optimized to improve the normalized tristimulus X, Y, and Z values. The yellow or magentaAttorney Docket No.: SP24-015 material 246 has a greater thickness and / or optical density near the corner of each LED zone that is gradually reduced towards the center of each LED zone. In this way, the color mura of the backlight is improved and spatial variations of the white LED backlight are minimized.

[0078] In another embodiment, the first material 240 includes a white material (e.g., whiteink), the second material (e.g., first absorptive material) includes a yellow material (e.g., yellow ink), and the third material (e.g., second absorptive material) includes a magenta material (e.g., magenta ink). The second material may be a first portion of 246, and the third material may be a second portion of 246. In this embodiment, the cyan material 242 of FIG.3E is excluded. In certain exemplary embodiments, the white material 240 may be mixed with the yellow material and / or the magenta material similarly as described above with reference to FIG. 3D.The second spectral absorptance A2 of the yellow material at the first wavelength is greater than2 times the second spectral absorptance A2 at the second wavelength, such that A2(r; ^=450) >2A2(r; ^=550). The second spectral absorptance A2 at the first wavelength is greater than 2times the second spectral absorptance A2 at the third wavelength, such that A2(r; ^=450) >2A2(r; ^=630). The second spectral transmittance T2 at the first wavelength at the first location230 is less than the second spectral transmittance T2 at the first wavelength at the secondlocation 232, such that T2(r=0; ^=450) < T2(r=rmax; ^=450).

[0079] The third spectral absorptance A3 of the magenta material at the second wavelengthis greater than 2 times the third spectral absorptance A3 at the first wavelength, such that A3(r;^=550) > 2A3(r; ^=450). The third spectral absorptance A3 at the second wavelength is greaterthan 2 times the third spectral absorptance A3 at the third wavelength, such that A3(r; ^=550) >2A3(r; ^=630). The third spectral transmittance T3 at the second wavelength at the first location230 is less than the third spectral transmittance T3 at the second wavelength at the secondlocation 232, such that T3(r=0; ^=550) < T3(r=rmax; ^=550).

[0080] The above values for the first spectral reflectance R1, the first spectral transmittanceT1, the first spectral absorptance A1, the second spectral reflectance R2, the second spectraltransmittance T2, the second spectral absorptance A2, the third spectral reflectance R3, the thirdspectral transmittance T3, and the third spectral absorptance A3 may be obtained by adjustingthe thickness profile and / or optical density profile of the white material 240, the yellow material (e.g., a first portion of 246), and the magenta material (e.g., a second portion of 246) within each diffuser pattern. The white material may include a first thickness and / or optical density at the first location 230 and a second thickness and / or optical density less than the first thickness and / or optical density at the third location 234 between the first location 230 and the secondAttorney Docket No.: SP24-015 location 232. The thickness and / or optical density may be reduced gradually from the first thickness and / or optical density to the second thickness and / or optical density. The yellow material may include a third thickness and / or optical density at the second location 232 and a fourth thickness and / or optical density less than the third thickness and / or optical density at the third location 234. The thickness and / or optical density may be reduced gradually from the third thickness and / or optical density to the fourth thickness and / or optical density. The magenta material may include a fifth thickness and / or optical density at the second location 232 and a sixth thickness and / or optical density less than the fifth thickness and / or optical density at the third location 234. The thickness and / or optical density may be reduced gradually from the fifth thickness and / or optical density to the sixth thickness and / or optical density.

[0081] FIG. 4A is a chart 300 illustrating normalized tristimulus X, Y, and Z values for anexemplary patterned diffuser including white ink and cyan ink, such as patterned diffuser 210b of FIG. 3B, patterned diffuser 210c of FIG. 3C, or patterned diffuser 210d of FIG. 3D. Chart300 includes radial distance (e.g., location r) in millimeters on the x-axis, where 0 is alignedwith a respective light source 106. Chart 300 includes a ratio on the y-axis such that normalized tristimulus X [i.e., X / X(0)], Y [i.e., L / L(0)], and Z [i.e., Z / Z(0)] values of an exemplary backlight 100 are shown. As shown in chart 300, respective normalized tristimulus X, Y, andZ values of the backlight from the first location r=0 to the second location r=rmax (e.g., about6.4 millimeters in this example) vary by less than plus or minus about 3 percent. The tristimulus values may be collected using a Radiant Colorimeter positioned above the backlight. The X, Y, and Z data in a single LED zone may be arranged into 31x31 pixels, normalized to the pixel in the center and plotted versus the distance to the center pixel as shown in chart 300.

[0082] FIG. 4B is a chart 310 illustrating normalized CIE x and CIE y values for anexemplary patterned diffuser including white ink and cyan ink, such as patterned diffuser 210b of FIG. 3B, patterned diffuser 210c of FIG. 3C, or patterned diffuser 210d of FIG. 3D. Chart310 includes radial distance (e.g., location r) in millimeters on the x-axis, where 0 is alignedwith a respective light source 106. Chart 310 includes CIE color on the y-axis such that normalized CIE x [i.e., Cx / Cx(0)] and CIE y [i.e., Cy / Cy(0)] values of an exemplary backlight 100 are shown. As shown in chart 310, respective normalized CIE x and CIE y values of thebacklight from the first location r=0 to the second location r=rmax (e.g., about 6.4 millimetersin this example) vary by less than plus or minus about 1 percent. The CIE x and CIE y values refer to the 1931 CIE 19312^ observer x and y, where:Attorney Docket No.: SP24-015 x= XX+Y+Zand ywhere X, Y, and Z are the tristimulus values, which can be measured by a colorimeter.

[0083] FIG. 5A is a chart 320 illustrating normalized tristimulus X, Y, and Z values for anexemplary patterned diffuser including white ink, cyan ink, and yellow ink, such as patterneddiffuser 210e of FIG. 3E. Chart 320 includes radial distance (e.g., location r) in millimeters onthe x-axis, where 0 is aligned with a respective light source 106. Chart 320 includes a ratio on the y-axis such that normalized tristimulus X [i.e., X / X(0)], Y [i.e., L / L(0)], and Z [i.e., Z / Z(0)] values of an exemplary backlight 100 are shown. As shown in chart 320, respective normalizedtristimulus X, Y, and Z values of the backlight from the first location r=0 to the second locationr=rmax(e.g., about 6.4 millimeters in this example) vary by less than plus or minus about 3 percent. The tristimulus values may be collected using a Radiant Colorimeter positioned above the backlight as previously described above with reference to FIG.4A.

[0084] FIG. 5B is a chart 330 illustrating normalized CIE x and CIE y values for anexemplary patterned diffuser including white ink, cyan ink, and yellow ink, such as patterneddiffuser 210e of FIG. 3E. Chart 330 includes radial distance (e.g., location r) in millimeters onthe x-axis, where 0 is aligned with a respective light source 106. Chart 330 includes CIE color on the y-axis such that normalized CIE x [i.e., Cx / Cx(0)] and CIE y [i.e., Cy / Cy(0)] values of an exemplary backlight 100 are shown. As shown in chart 310, respective normalized CIE xand CIE y values of the backlight from the first location r=0 to the second location r=rmax (e.g.,about 6.4 millimeters in this example) vary by less than plus or minus about 1 percent.

[0085] FIGS. 6A-6C are flow diagrams of an exemplary method 400 for fabricating abacklight including a patterned diffuser, such as a backlight 100 of FIGS.1A and 1B including a patterned diffuser 210a-210e of FIGS.3A-3E, respectively. As illustrated in FIG.6A at 402, method 400 includes arranging a carrier (e.g., 108 of FIG 1A) proximate a plurality of white light sources (e.g., 106 of FIGS.1A and 1B). At 404, method 400 includes printing (e.g., inkjet printing) a variable diffuser pattern (e.g., 211a-211e of FIGS.3A-3E) on the carrier comprising printing a white ink (e.g., 240) and a first absorptive ink (e.g., 242 or 246) on the carrier such that respective normalized CIE x and CIE y values of the backlight from a first location (e.g., 130 or 230) aligned with each respective light source to a second location (e.g., 132 or 232) halfway between respective adjacent light sources vary by less than plus or minus about 1 percent.Attorney Docket No.: SP24-015

[0086] In certain exemplary embodiments, as illustrated in FIG. 6B, printing the variablediffuser pattern at 404 may further include method 404a. At 406, method 404a includes printing a second absorptive ink (e.g., 246 or 242) on the carrier. In certain exemplary embodiments, as illustrated in FIG. 6C, printing the variable diffuser pattern at 404a may further include method 404b. At 408, method 404b includes printing the white ink comprising a first optical density at the first location and a second optical density less than the first optical density at a third location (e.g., 234) between the first location and the second location. At 410, method 404b may further include printing the first absorptive ink comprising printing a yellow ink comprising a third optical density at the second location and a fourth optical density less than the third optical density at the third location. At 412, method 404b may further include printing the second absorptive ink comprising printing a cyan ink comprising a fifth optical density at the first location and a sixth optical density less than the fifth optical density at the third location. Similar methods as described above with reference to FIGS. 6A-6C may be used to fabricate backlights including a variable diffuser pattern 211a-211e described with reference to FIGS.3A-3E.

[0087] It will be apparent to those skilled in the art that various modifications and variationscan be made to embodiments of the present disclosure without departing from the spirit and scope of the disclosure. Thus, it is intended that the present disclosure cover such modifications and variations provided they come within the scope of the appended claims and their equivalents.

Claims

Attorney Docket No.: SP24-015 What is claimed is:

1. A backlight comprising:a plurality of white light sources; a carrier proximate the plurality of light sources; and a variable diffuser pattern applied to a surface of the carrier, aligned with the plurality of light sources, and configured to scatter a portion of light output by each light source, the variable diffuser pattern comprising a white material and a first absorptive material applied on the carrier such that respective normalized CIE x and CIE y values of the backlight from a first location aligned with each respective light source to a second location halfway between respective adjacent light sources vary by less than plus or minus about 1 percent.

2. The backlight of claim 1, wherein respective normalized tristimulus X, Y, and Z valuesof the backlight from the first location to the second location vary by less than plus or minus about 3 percent.

3. The backlight of claim 1, wherein the white material comprises a white ink comprisinga first thickness at the first location and a second thickness less than the first thickness at a third location between the first location and the second location, and wherein the first absorptive material comprises a yellow ink comprising a third thickness at the second location and a fourth thickness less than the third thickness at the third location.

4. The backlight of claim 1, wherein the white material comprises a white ink comprisinga first thickness at the first location and a second thickness less than the first thickness at a third location between the first location and the second location, and wherein the first absorptive material comprises a cyan ink comprising a fifth thickness at the first location and a sixth thickness less than the fifth thickness at the third location.

5. The backlight of claim 1, wherein the white material comprises a white ink and the firstabsorptive material comprises a cyan ink mixed with the white ink, wherein the white ink comprises a first optical density at the first location and a second optical density less than the first optical density at a third location between the first location and the second location, andAttorney Docket No.: SP24-015 wherein the cyan ink comprises a third optical density at the first location and a fourth optical density less than the third optical density at the third location.

6. The backlight of claim 1, wherein the white material comprises a white ink comprisinga first thickness at the first location and a second thickness less than the first thickness at a third location between the first location and the second location; and wherein the first absorptive material comprises a magenta ink comprising a third thickness at the second location and a fourth thickness less than the third thickness at the third location.

7. The backlight of claim 1, wherein the variable diffuser pattern further comprises asecond absorptive material applied on the carrier.

8. The backlight of claim 7, wherein the white material comprises a white ink comprisinga first thickness at the first location and a second thickness less than the first thickness at a third location between the first location and the second location, wherein the first absorptive material comprises a yellow ink comprising a third thickness at the second location and a fourth thickness less than the third thickness at the second location, and wherein the second absorptive material comprises a cyan ink comprising a fifth thickness at the first location and a sixth thickness less than the fifth thickness at the third location.

9. The backlight of claim 7, wherein the white material comprises a white ink, the firstabsorptive material comprises a yellow ink mixed with the white ink, and the second absorptive material comprises a cyan ink mixed with the white ink and the yellow ink, wherein the white ink comprises a first optical density at the first location and a second optical density less than the first optical density at a third location between the first location and the second location, wherein the yellow ink comprises a third optical density at the second location and a fourth optical density less than the third optical density at the third location, and wherein the cyan ink comprises a fifth optical density at the first location and a sixth optical density less than the fifth optical density at the third location.Attorney Docket No.: SP24-015 10. The backlight of claim 7, wherein the white material comprises a white ink, the first absorptive material comprises a yellow ink, and the second absorptive material comprises a magenta ink, wherein the white ink comprises a first optical density at the first location and a second optical density less than the first optical density at a third location between the first location and the second location, wherein the yellow ink comprises a third optical density at the second location and a fourth optical density less than the third optical density at the third location, and wherein the magenta ink comprises a fifth optical density at the second location and a sixth optical density less than the fifth optical density at the third location.

11. The backlight of claim 7, wherein the white material comprises a white ink, the first absorptive material comprises a cyan ink, and the second absorptive material comprises a magenta ink, wherein the white ink comprises a first optical density at the first location and a second optical density less than the first optical density at a third location between the first location and the second location, wherein the cyan ink comprises a third optical density at the first location and a fourth optical density less than the third optical density at the third location, and wherein the magenta ink comprises a fifth optical density at the second location and a sixth optical density less than the fifth optical density at the third location.

12. A backlight comprising: a plurality of white light sources; a carrier proximate the plurality of light sources; and a variable diffuser pattern applied to a surface of the carrier, aligned with the plurality of light sources, and configured to scatter a portion of light output by each light source, the variable diffuser pattern comprising a first material and a second material different from the first material; the first material comprising a first spectral reflectance, a first spectral transmittance, and a first spectral absorptance; and the second material comprising a second spectral reflectance, a second spectral transmittance, and a second spectral absorptance, wherein the first spectral transmittance at a first wavelength equal to about 450 nanometers is less than the first spectral transmittance at a second wavelength equal to aboutAttorney Docket No.: SP24-015 550 nanometers, and the first spectral transmittance at the second wavelength is less than the first spectral transmittance at a third wavelength equal to about 630 nanometers, wherein the first spectral reflectance at the first wavelength is greater than the first spectral reflectance at the second wavelength, and the first spectral reflectance at the second wavelength is greater than the first spectral reflectance at the third wavelength, wherein the first spectral absorptance is less than about 2 percent at each of the first wavelength, the second wavelength, and the third wavelength, wherein the respective first spectral transmittance at each of the first wavelength, the second wavelength, and the third wavelength at a first location aligned with each respective light source is less than the respective first spectral transmittance at each of the first wavelength, the second wavelength, and the third wavelength at a second location halfway between respective adjacent light sources, wherein the respective first spectral reflectance at each of the first wavelength, the second wavelength, and the third wavelength at the first location is greater than the respective first spectral reflectance at each of the first wavelength, the second wavelength, and the third wavelength at the second location, and wherein the second spectral absorptance at one wavelength of the first wavelength, the second wavelength, and the third wavelength is greater than 2 times the second spectral absorptance at the other two wavelengths of the first wavelength, the second wavelength, and the third wavelength.

13. The backlight of claim 12, wherein the second spectral absorptance at the first wavelength is greater than 2 times the second spectral absorptance at the second wavelength, and the second spectral absorptance at the first wavelength is greater than 2 times the second spectral absorptance at the third wavelength, and wherein the second spectral transmittance at the first wavelength at the first location is less than the second spectral transmittance at the first wavelength at the second location.

14. The backlight of claim 12, wherein the second spectral absorptance at the third wavelength is greater than 2 times the second spectral absorptance at the first wavelength, and the second spectral absorptance at the third wavelength is greater than 2 times the second spectral absorptance at the second wavelength, and wherein the second spectral transmittance at the third wavelength at the first location is less than the second spectral transmittance at the third wavelength at the second location.Attorney Docket No.: SP24-015 15. The backlight of claim 12, wherein the second spectral absorptance at the second wavelength is greater than 2 times the second spectral absorptance at the first wavelength, and the second spectral absorptance at the second wavelength is greater than 2 times the second spectral absorptance at the third wavelength; and wherein the second spectral transmittance at the second wavelength at the first location is less than the second spectral transmittance at the second wavelength at the second location.

16. The backlight of claim 13, wherein the variable diffuser pattern further comprises a third material different from the first material and the second material, the third material comprising a third spectral reflectance, a third spectral transmittance, and a third spectral absorptance, wherein the third spectral absorptance at the third wavelength is greater than 2 times the third spectral absorptance at the first wavelength, and the third spectral absorptance at the third wavelength is greater than 2 times the third spectral absorptance at the second wavelength, and wherein the third spectral transmittance at the third wavelength at the first location is less than the third spectral transmittance at the third wavelength at the second location.

17. The backlight of claim 13, wherein the variable diffuser pattern further comprises a third material different from the first material and the second material, the third material comprising a third spectral reflectance, a third spectral transmittance, and a third spectral absorptance, wherein the third spectral absorptance at the second wavelength is greater than 2 times the third spectral absorptance at the first wavelength, and the third spectral absorptance at the second wavelength is greater than 2 times the third spectral absorptance at the third wavelength; and wherein the third spectral transmittance at the second wavelength at the first location is less than the third spectral transmittance at the second wavelength at the second location.

18. The backlight of claim 14, wherein the variable diffuser pattern further comprises a third material different from the first material and the second material, the third material comprising a third spectral reflectance, a third spectral transmittance, and a third spectral absorptance,Attorney Docket No.: SP24-015 wherein the third spectral absorptance at the second wavelength is greater than 2 times the third spectral absorptance at the first wavelength, and the third spectral absorptance at the second wavelength is greater than 2 times the third spectral absorptance at the third wavelength, and wherein the third spectral transmittance at the second wavelength at the first location is less than the third spectral transmittance at the second wavelength at the second location.

19. A method for fabricating a backlight, the method comprising: arranging a carrier proximate a plurality of white light sources; and printing a variable diffuser pattern on the carrier comprising printing a white ink and a first absorptive ink on the carrier such that respective normalized CIE x and CIE y values of the backlight from a first location aligned with each respective light source to a second location halfway between respective adjacent light sources vary by less than plus or minus about 1 percent.

20. The method of claim 19, wherein printing the variable diffuser pattern further comprises printing a second absorptive ink on the carrier.

21. The method of claim 20, wherein printing the variable diffuser pattern comprises: printing the white ink comprising a first optical density at the first location and a second optical density less than the first optical density at a third location between the first location and the second location, printing the first absorptive ink comprising printing a yellow ink comprising a third optical density at the second location and a fourth optical density less than the third optical density at the third location, and printing the second absorptive ink comprising printing a cyan ink comprising a fifth optical density at the first location and a sixth optical density less than the fifth optical density at the third location.

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