Backlight comprising variable diffuser pattern and method for manufacturing backlight

Abstract

A backlight includes a plurality of white light sources; a carrier proximate to 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 is configured to scatter a portion of the light output by each light source. The variable diffuser pattern includes a white material and a first absorbent material, the white material and the first absorbent material being applied on the carrier, such that respective normalized CIE x and CIE y values of the backlight from a first position aligned with each respective light source to a second position intermediate between respective adjacent light sources change less than about + / -1%.

Description

[0001] Cross - reference to related applications

[0002] This application claims the benefit of priority of U.S. Provisional Application Serial No. 63 / 620,439, filed on January 12, 2024, the content of which is the basis of this application and is incorporated herein by reference in its entirety. Technical field

[0003] The present disclosure generally relates to backlights for displays. More specifically, the present disclosure relates to backlights including a white light source and a variable diffuser pattern. Background art

[0004] Liquid crystal displays (LCDs) are commonly used in various electronic devices, such as mobile phones, laptop computers, electronic tablets, televisions, and computer monitors. An LCD is a light - valve - based display in which a display panel includes an array of individually addressable light valves. An LCD may include a backlight for generating light, which can then be wavelength - converted, filtered, and / or polarized to produce an image from the LCD. The backlight can be edge - lit or direct - lit. An edge - lit backlight may include a light - emitting diode (LED) array that is edge - coupled to a light guide plate that emits light from its surface. A direct - lit backlight may include a two - dimensional (2D) LED array located directly behind the LCD panel.

[0005] Compared to edge - lit backlights, direct - lit backlights may have the advantage of improved dynamic contrast. For example, a display with a direct - lit backlight can independently adjust the brightness of each LED to set the dynamic range of brightness across an image. This is often referred to as local dimming. However, to achieve a desired light uniformity and / or to avoid hot spots in a direct - lit backlight, a polymer diffuser plate may be positioned at a certain distance from the LEDs, resulting in an overall display thickness greater than that of an edge - lit backlight. However, the optical distance (OD) between the LEDs and the polymer diffuser plate still results in an undesirably high overall display thickness in such configurations, and / or these configurations may produce undesired optical losses when the backlight thickness is reduced. In addition, the thermal expansion of the polymer diffuser plate can adversely affect backlight performance. Summary of the invention

[0006] Some embodiments of the present disclosure relate to a backlight. The backlight includes a plurality of white light sources; a carrier proximate to 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 the light output by each light source. The variable diffuser pattern includes a white material and a first absorptive material, the white material and the first absorptive material being applied on the carrier such that the corresponding normalized CIE x and CIE y values of the backlight vary by less than plus or minus about 1% from a first position aligned with each respective light source to a second position intermediate between the respective adjacent light sources.

[0007] Yet other embodiments of the present disclosure relate to a backlight. The backlight includes a plurality of white light sources; a carrier proximate to 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 the 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 or equal to the first spectral transmittance at a second wavelength of 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% at each of the first wavelength, the second wavelength, and the third wavelength. The respective first spectral transmittances at the first wavelength, the second wavelength, and the third wavelength at a first position aligned with each respective light source are less than the respective first spectral transmittances at the first wavelength, the second wavelength, and the third wavelength at a second position intermediate between the respective adjacent light sources. The respective first spectral reflectances at the first wavelength, the second wavelength, and the third wavelength at the first position are greater than the respective first spectral reflectances at the first wavelength, the second wavelength, and the third wavelength at the second position. The second spectral absorptance at one of the first wavelength, the second wavelength, and the third wavelength is greater than twice the second spectral absorptances at the other two of the first wavelength, the second wavelength, and the third wavelength.

[0008] Yet other embodiments of the present disclosure relate to a method for manufacturing a backlight. The method includes: disposing a carrier in proximity to a plurality of white light sources. The method includes: printing a variable diffuser pattern on the carrier, the printing of the variable diffuser pattern including printing white ink and a first absorbent ink on the carrier such that the corresponding normalized CIEx and CIEy values of the backlight vary by less than about plus or minus 1% from a first position aligned with each respective light source to a second position intermediate between the respective adjacent light sources.

[0009] The backlights disclosed herein include a variable diffuser pattern that significantly reduces or eliminates color non-uniformity when white light sources are used in the backlight. Since backlights including white light sources generally do not allow color conversion films, the variable diffuser patterns disclosed herein transform the discrete blue, green, and red light distributions into a spatially uniform distribution. Additionally, a polymer diffuser plate and associated detrimental thermal expansion may not be included in the backlight, thereby reducing the thickness of the backlight and improving performance.

[0010] Additional features and advantages will be set forth in the detailed description which follows, and in part will be readily understood by those skilled in the art from the description or recognized by practicing the embodiments as described herein, including the detailed description which follows, the claims, as well as the drawings.

[0011] It should be understood that the foregoing general description and the following detailed description are exemplary and intended to provide an overview or framework for understanding the nature and characteristics of the claims. Drawings are included to provide further understanding and are incorporated into and constitute a part of this specification. The drawings illustrate one or more embodiments and together with the description explain the principles and operations of the various embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1A is a cross-sectional view of an exemplary backlight including a patterned diffuser;

[0013] Figure 1B is Figure 1A a top view of a plurality of light sources of the exemplary backlight;

[0014] Figure 2 is including Figure 1A and Figure 1B a cross-sectional view of an exemplary liquid crystal display (LCD) of the exemplary backlight;

[0015] Figure 3A is a cross-sectional view of an exemplary patterned diffuser including a white material and an absorbent material.

[0016] Figure 3BCross-sectional view of an exemplary patterned diffuser including a white material and an absorptive material located on top of the white material;

[0017] Figure 3C Cross-sectional view of an exemplary patterned diffuser including a white material and an absorptive material located below the white material;

[0018] Figure 3D Cross-sectional view of an exemplary patterned diffuser including a white material and an absorptive material mixed with the white material;

[0019] Figure 3E Cross-sectional view of an exemplary patterned diffuser including a white material, a first absorptive material located on top of the white material, and a second absorptive material adjacent to the white material;

[0020] Figure 4A Graph illustrating the normalized tristimulus X, Y, and Z values of an exemplary patterned diffuser including white ink and cyan ink;

[0021] Figure 4B Graph illustrating the normalized CIE x and CIE y values of an exemplary patterned diffuser including white ink and cyan ink;

[0022] Figure 5A Graph illustrating the normalized tristimulus X, Y, and Z values of an exemplary patterned diffuser including white ink, cyan ink, and yellow ink;

[0023] Figure 5B Graph illustrating the normalized CIE x and CIE y values of an exemplary patterned diffuser including white ink, cyan ink, and yellow ink; and

[0024] Figures 6A to 6C Flowchart of an exemplary method for manufacturing a backlight including a patterned diffuser. Detailed Description

[0025] Reference will now be made in detail to embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numerals will be used throughout the drawings to refer to the same or like parts. However, the present disclosure may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

[0026] Ranges may 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 should also be understood that the end values of each of the ranges are significant with respect to the other end value, and independently of the other end value.

[0027] Directional terms used herein—for example, up, down, right, left, front, rear, top, bottom, vertical, horizontal—are made only with reference to the figures as drawn, and are not intended to imply absolute orientation.

[0028] Unless otherwise expressly stated, no method set forth herein is intended to be construed as requiring that its steps be performed in a particular order, nor is any apparatus herein intended to be construed as requiring a particular orientation. Accordingly, where a method claim does not actually recite an order to be followed by its steps, or any apparatus claim does not actually recite an order or orientation of individual components, or where the order or orientation is not otherwise specifically recited in the claims or description, no inference of order or orientation is intended in any respect. This applies to any possible non-representation basis for interpretation, including: logical issues regarding the order or arrangement of steps, operational flow, order of components, or orientation of components; the plain meaning obtained from grammatical organization or punctuation; and the number or type of embodiments described in the specification.

[0029] As used herein, unless the context clearly indicates otherwise, the singular forms “a,” “an,” and “the” include plural referents. Thus, for example, reference to “a” component includes aspects having two or more such components, unless the context clearly indicates otherwise.

[0030] Many backlights that include a patterned diffuser include a light source that primarily emits a single blue color. In these backlights, full white is achieved by using a color conversion film that converts a portion of the blue light into green and red light. This type of backlight produces a larger color gamut compared to a typical broadband white light-emitting diode (LED) backlight, where the light source is a blue LED combined with a broadband yellow phosphor. A patterned glass diffuser for these types of LEDs can be manufactured by printing white ink on a glass carrier. These types of patterned glass diffusers can be used primarily in liquid crystal display (LCD) television / monitor applications.

[0031] In applications that require higher reliability over a wide temperature and humidity range, such as automotive backlights, color conversion films may not be suitable. Instead, the light source can be a blue LED covered with narrow-band green and red phosphors that convert a portion of the blue light into green and red light, thereby producing effective white light. In other applications, only narrow-band green phosphors or narrow-band red phosphors can be used to convert a portion of the blue light into green or red light, thereby producing a two-color backlight.

[0032] When a patterned diffuser printed with white ink is used in a backlight including a light source that emits light of two or more colors, undesired color non-uniformity occurs because the white ink transmits and reflects differently for different colors. Thus, described herein is a patterned diffuser that reduces or eliminates color non-uniformity in a white LED backlight or a two-color backlight.

[0033] Color non-uniformity refers to an apparent separation in the normalized spatial distribution of the tristimulus values X, Y, and Z that can be measured using a colorimeter. Thus, the appearance of the backlight varies spatially and becomes unacceptable. When the patterned diffuser is used in a blue LED backlight including a color conversion film, the patterned diffuser only needs to convert 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.

[0034] When the patterned diffuser is used in a white LED backlight that typically does not include a color conversion film, the patterned diffuser must simultaneously convert the discrete blue, green, and red light distributions into a spatially uniform distribution. This is not possible when the patterned diffuser includes only conventional white materials that transmit and reflect differently at different wavelengths. Thus, the embodiments disclosed herein use multiple (e.g., two or three) colored materials to simultaneously adjust the distribution of the tristimulus values X, Y, and Z into a spatially uniform distribution in a white LED backlight to reduce or eliminate color non-uniformity.

[0035] Now referring to Figure 1A , a cross-sectional view of an exemplary backlight 100 is depicted. The backlight 100 can include a substrate 102, a reflective layer 104, a plurality of white light sources 106, and a patterned diffuser 110. The patterned diffuser 110 includes a carrier 108 (e.g., a light guide plate) proximate to the plurality of light sources 106 and a variable diffuser pattern 111 applied to the surface of the carrier 108. The variable diffuser pattern 111 is configured to scatter a portion of the light output by each light source 106. The variable diffuser pattern 111 can include a white material that is patterned to obtain a spatially uniform distribution or a distribution close to uniform of the tristimulus values of both X and Y or Z. Then, as described below with reference toFigures 3A to 3E As described in detail, one or two absorptive materials (e.g., yellow material, magenta material, and / or cyan material) can be added to the variable diffuser pattern 111 to adjust the spatial uniformity of the remaining tristimulus Z or X and Y values such that the corresponding normalized tristimulus X, Y, and Z values of the backlight 100 vary by less than plus or minus about 5 percent, such as less than plus or minus about 3 percent, from a first position 130 aligned with each corresponding light source 106 to a second position 132 intermediate between the corresponding adjacent light sources. Reference is made below to Figures 3A to 3E the variable diffuser pattern described, which includes a white material and a first absorptive material applied to the carrier 108 such that the corresponding normalized CIEx and CIEy values of the backlight 100 can vary by less than plus or minus about 3 percent, such as less than plus or minus about 1 percent, from a first position 130 aligned with each corresponding light source 106 to a second position 132 intermediate between the corresponding adjacent light sources. As Figure 1B illustrated, the second position 132 is half the maximum distance between adjacent light sources 106, and in the Figure 1B embodiment is located at the corner points of each LED region 128. Note that the light sources are not always arranged in a rectangular array as Figure 1B shown. For example, the light sources can be arranged in other patterns, such as in a hexagonal pattern or a pattern different from a rectangular pattern.

[0036] A plurality of light sources 106 are arranged on the substrate 102 and are in electrical communication with the substrate 102. Each light source 106 can emit peak intensity rays along the normal axis as indicated at 107. Each light source 106 can also emit peak intensity rays along an off-axis direction (not shown). The reflective layer 104 is located on the substrate 102 and surrounds each light source 106. In some exemplary embodiments, the substrate 102 can be reflective such that the reflective layer 104 can be omitted. The patterned diffuser 111 is located over the plurality of light sources 106 and is optically coupled to each light source 106. In some exemplary embodiments, an optical adhesive (not shown) can be used to couple the plurality of light sources 106 to the patterned diffuser 110. The optical adhesive (e.g., polyphenylsiloxane) can have a refractive index greater than or equal to the 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 among the plurality of light sources 106. In some embodiments, the variable diffuser pattern 111 can be arranged on the lower surface of the carrier 108. In other embodiments, a first portion of the variable diffuser pattern 111 can be arranged on the upper surface of the carrier 108, and a second portion of the variable diffuser pattern 111 can be arranged on the lower surface of the carrier 108.

[0037] Each diffuser pattern 112 includes a thickness distribution along the width or diameter of the diffuser pattern and may include a substantially flat section as shown at 113 and a curved section extending from the substantially flat section 113 and surrounding the substantially flat portion as shown at 114. 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 a predetermined value times the size 124 of each corresponding light source 106. 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 mm, the predetermined value may be determined by the alignment capability between the light sources 106 and the diffuser patterns 112, so that the size of each substantially flat section 113 of each of the diffuser patterns 112 is within a range between about 100 micrometers and about 300 micrometers larger than the size of each light source 106. Each substantially flat section 113 is large enough so that each diffuser pattern 112 can be aligned with the corresponding light source 106, and small enough to achieve suitable brightness uniformity and color uniformity.

[0038] The size L1 (ie, 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. Although the pitch is Figure 1A 126, but the spacing may be different in a direction orthogonal to the illustrated direction. The spacing may be, for example, about 90 mm, 45 mm, 30 mm, 10 mm, 5 mm, 2 mm, 1 mm, or 0.5 mm, greater than about 90 mm, or less than about 0.5 mm. In certain exemplary embodiments, the ratio L1 / P of the size 122 of each diffuser pattern 112 to the spacing 126 is in a range between about 0.45 and 1.0. The ratio may vary with the spacing 126 of the light sources 106 and the distance between the emitting surface of each light source and the corresponding diffuser pattern 112. For example, for a spacing 126 equal to about 5 mm and a distance between the emitting surface of each light source and the corresponding diffuser pattern 112 equal to about 0.2 mm, the ratio may be equal to about 0.50, 0.60, 0.70, 0.80, 0.90, or 1.0.

[0039] Each diffuser pattern 112 reflects at least a portion of the light emitted from the corresponding 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. Although the specularly reflected light travels laterally mainly due to reflection between the reflective layer 104 and the carrier 108 or due to reflection between the reflective layer 104 and the diffuser sheet or diffuser plate (as shown below Figure 2 as shown), some light loss may occur due to incomplete reflection from the reflective layer 104.

[0040] The diffusely reflected light has an angular distribution between 0° and 90° measured from the normal of the carrier 108. Approximately 50% of the diffusely reflected light has an angle exceeding the critical angle of total internal reflection (θ TIR ). Thus, the diffusely reflected light can travel laterally due to total internal reflection without any loss until the light is subsequently extracted from the carrier 108 by the diffuser pattern 112.

[0041] In certain exemplary embodiments, each diffuser pattern 112 is a diffuser such that each diffuser pattern 112 further enhances the performance of the backlight 100 by scattering some light rays at a high enough angle such that the some light rays can propagate in the carrier 108 by total internal reflection. Such rays will then not undergo multiple bounces between the diffuser pattern 112 and the reflective layer 104 or between the optical film stack and the reflective layer 104, and thus avoid loss of optical power, thereby improving the backlight efficiency. In certain exemplary embodiments, each diffuser pattern 112 is a specular reflector. In other embodiments, some regions of each diffuser pattern 112 have more diffuse reflectance characteristics and some regions have more specular reflectance characteristics.

[0042] Each diffuser pattern 112 can be formed, for example, by printing a pattern with white ink (e.g., inkjet printing, screen printing, microprinting, etc.). Each diffuser pattern 112 can also be formed by first depositing a continuous layer of white material (e.g., by physical vapor deposition (PVD) or any number of coating techniques such as, for example, slot die coating or spray coating), and then patterning the layer by lithography or other known area-selective material removal methods.

[0043] Figure 1B is a top view of the plurality of light sources 106 and the reflective layer 104 on the substrate 102. The light sources 106 are arranged in a 2D array including a plurality of rows and a plurality of columns. Although nine light sources 106 are shown in Figure 1BShown as three rows and three columns in the middle, but in other embodiments, the backlight 100 may include any suitable number of light sources 106 arranged in any suitable number of rows and any suitable number of columns. The light sources 106 may also be arranged in other periodic patterns (e.g., hexagonal lattice or triangular lattice), or arranged as a quasi-periodic pattern or a non-strictly periodic pattern. For example, the spacing between the light sources 106 may be smaller at the edges and / or corners of the backlight.

[0044] The substrate 102( Figure 1A ) may be a printed circuit board (PCB), a glass or plastic substrate, or another suitable substrate for transmitting electrical signals to each light source 106 for individually controlling each light source. The substrate 102 may be a rigid substrate or a flexible substrate. For example, the substrate 102 may include flat glass or curved glass. The radius of curvature of the curved glass may be, for example, less than about 2000 millimeters, such as about 1500 millimeters, 1000 millimeters, 500 millimeters, 200 millimeters, or 100 millimeters. The reflective layer 104 may include, for example, a metal foil, such as silver, platinum, gold, copper, etc.; a dielectric material (e.g., a polymer such as polytetrafluoroethylene (PTFE)); a porous polymer material, such as polyethylene terephthalate (PET), poly(methyl methacrylate) (PMMA), polyethylene naphthalate (PEN), polyethersulfone (PES), etc.; a multilayer dielectric interference coating, or a reflective ink including white inorganic particles such as titanium dioxide, barium sulfate, etc., or other materials suitable for reflecting light and tuning the color of the reflected and transmitted light (such as colored pigments).

[0045] Each of the plurality of light sources 106 may be, for example, an LED (e.g., having a size greater than about 0.5 mm), a mini-LED (e.g., having a size between about 0.1 mm and about 0.5 mm), a micro-LED (e.g., having a size less than about 0.1 mm), an organic LED (OLED), or another suitable white light source having a wavelength (λ) in the range from about 400 nm to about 750 nm. In other embodiments, each of the plurality of light sources 106 may have a wavelength shorter than 400 nm and / or longer than 750 nm. In certain exemplary embodiments, each light source 106 may include a blue LED having 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 represent that the light source is positioned at the surface of the carrier 108 and is in optical communication with the carrier 108 directly or through an optically transparent adhesive so as to introduce light that propagates at least in part due to total internal reflection into the carrier. 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 total internal reflection and is extracted from the carrier through the diffuser pattern 112, and a second portion of the light travels laterally between the reflective layer 104 and the diffuser pattern 112 due to multiple reflections at the reflective surfaces of the reflective layer 104 and the diffuser pattern 112 or at the ( Figure 2 shown) optical thin film stack and the reflective layer 104. In other exemplary embodiments, the light from each light source 106 travels through air and then enters the carrier 108. A first portion of the light travels laterally in the carrier 108 due to total internal reflection or reflection by the diffuser pattern 112 and the reflective layer 104, and a second portion of the light is transmitted through the diffuser pattern 112.

[0046] According to various embodiments, the carrier 108 may include any suitable transparent material for lighting and display applications. As used herein, the term "transparent" is intended to represent that the carrier has an optical transmittance greater than about 70% over a length of 500 mm in the visible spectral band (about 420 - 750 nm). In certain embodiments, the exemplary transparent material has an optical transmittance greater than about 50% over a length of 500 mm in the ultraviolet (UV) spectral band (about 100 - 400 nm). According to various embodiments, for wavelengths in the range from about 450 nm to about 650 nm, the carrier may include at least 95% optical transmittance over a path length of 50 mm.

[0047] The optical properties of the carrier 108 can be affected by the refractive index of the transparent material. According to various embodiments, the carrier 108 can have a refractive index in the range of about 1.3 to about 1.8. In other embodiments, the carrier 108 can have a relatively low level of light attenuation (e.g., due to absorption and / or scattering). For wavelengths in the range of about 420 - 750 nanometers, the light attenuation (α) of the carrier 108 can be, for example, less than about 5 decibels per meter. The carrier 108 can include a polymeric material such as plastics (e.g., polymethyl methacrylate (PMMA), methyl methacrylate styrene (MS), polydimethylsiloxane (PDMS)), polycarbonate (PC), or other similar materials. The carrier 108 can 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 the glass carrier 108 include EAGLE Lotus TM , Iris TM and glass. In examples where the substrate 102 includes curved glass, the carrier 108 can also include curved glass to form a curved backlight. In other embodiments, the carrier 108 can have a relatively high level of light attenuation. For wavelengths in the range of about 420 - 750 nanometers, the light attenuation (α) of the carrier 108 can be, for example, greater than about 5 decibels per meter.

[0048] Figure 2 is a cross-sectional view of an exemplary liquid crystal display (LCD) 140 of an exemplary backlight 100 including Figure 1A and Figure 1B the variable diffuser pattern 111. Additionally, the LCD 140 includes a diffuser plate 146 optionally located above the backlight 100, a prism film 150 optionally located above the diffuser plate 146, a reflective polarizer 152 optionally located above the prism film 150, and a display panel 154 located above the reflective polarizer 152.

[0049] To maintain the alignment between the light source 106 and the diffuser pattern 112 on the carrier 108 for the proper operation of the backlight 100, it is advantageous when the carrier 108 and the substrate 102 are made of the same or similar types of materials such that both the diffuser pattern 112 on the carrier 108 and the light source 106 on the substrate 102 are well registered with each other over a large operating temperature range. 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.

[0050] An alternative solution to keeping the light source 106 on the carrier 108 and the substrate 102 aligned is to use a highly flexible substrate. The highly flexible substrate can be made of polyimide or other high-temperature resistant polymer films to allow component soldering. The highly flexible substrate can also be made of materials such as FR4 or fiberglass, but with a significantly lower thickness compared to normal. In some exemplary embodiments, an FR4 material with a thickness of 0.4 mm can be used for the substrate 102, and the FR4 material can have significant flexibility to absorb dimensional changes caused by changes in operating temperature.

[0051] Figure 3A is a cross-sectional view of an exemplary patterned diffuser 210a. The patterned diffuser 210a includes a carrier 108 and a variable diffuser pattern 211a applied to the surface (e.g., upper surface and / or lower surface) of the carrier 108. In some embodiments, the patterned diffuser 210a can be used in place of the patterned diffuser 110 in Figure 1A and Figure 1B the backlight 100. The variable diffuser pattern 211a includes a plurality of diffuser patterns 212a that are aligned with a plurality of light sources 106 ( Figure 1A ) and are configured to scatter a portion of the light output by each light source 106. In the present 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) that are applied on the carrier 108 such that the corresponding normalized CIE x and CIE y (i.e., CIE 1931 2° observer) values of the backlight from a first position 230 aligned with each corresponding light source to a second position 232 intermediate between the corresponding adjacent light sources can vary by less than plus or minus about 3 percent, such as less than plus or minus about 1 percent. The first position 230 can correspond to Figure 1A and Figure 1B the first position 130 aligned with each light source 106 in Figure 1A and Figure 1B and the second position 232 can correspond to

[0052] The first material 240 and the second material 246 are different materials. The first material 240 includes a first spectral reflectance R1, a first spectral transmittance T1, and a first spectral 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 transmittance T2, which may be different from the first spectral transmittance T1; and a second spectral absorptance A2, which may be different from the first spectral absorptance A1. The position or radial distance r is defined as being between a minimum value r = 0 at a first position 230 aligned with each respective light source 106 and a maximum value r = r at a second position 232 intermediate between the respective adjacent light sources 106. max within the range of.

[0053] The first spectral transmittance T1 at a first wavelength equal to approximately 450 nanometers is less than the first spectral transmittance T1 at a second wavelength equal to approximately 550 nanometers, and the first spectral transmittance T1 at the second wavelength is less than the first spectral transmittance T1 at a third wavelength equal to approximately 630 nanometers, such that T1(r; λ = 450) < T1(r; λ = 550) < T1(r; λ = 630). The first spectral reflectance R1 at the first wavelength is greater than the first spectral reflectance R1 at the second wavelength, and the first spectral reflectance R1 at the second wavelength is greater than the first spectral reflectance R1 at the third wavelength, such that R1(r; λ = 450) > R1(r; λ = 550) > R1(r; λ = 630). Thus, as the wavelength increases from approximately 450 nanometers to approximately 550 nanometers and from approximately 550 nanometers to approximately 630 nanometers at the same position r, the first spectral transmittance T1 gradually decreases and the first spectral reflectance R1 gradually increases.

[0054] The first spectral absorptance A1 is less than approximately 2% at each of the first wavelength, the second wavelength, and the third wavelength, such that A1(r; λ = 450, 550, or 630) < 2%. The respective first spectral transmittance T1 at each of the first wavelength, the second wavelength, and the third wavelength at the first position 230 aligned with each respective light source 106 is less than the respective first spectral transmittance T1 at each of the first wavelength, the second wavelength, and the third wavelength at the second position 232 intermediate between the respective adjacent light sources 106, such that T1(r = 0; λ = 450, 550, or 630) < T1(r = r max ; λ = 450, 550, or 630). The respective first spectral reflectance R1 at each of the first wavelength, the second wavelength, and the third wavelength at the first position 230 is greater than the respective first spectral reflectance R1 at each of the first wavelength, the second wavelength, and the third wavelength at the second position 232, such that R1(r = 0; λ = 450, 550, or 630) > R1(r = r max; λ = 450, 550, or 630). The first spectral reflectance R1, the first spectral transmittance T1, and the first spectral absorptance A1 of the first material 240 are applicable to each embodiment described herein in which the first material 240 includes a white material (e.g., white ink).

[0055] The second spectral absorptance A2 at one of the first wavelength, the second wavelength, and the third wavelength is greater than twice the second spectral absorptance A2 at the other two of the first wavelength, the second wavelength, and the third wavelength. The second spectral absorptance A2 can vary based on the second material as described below.

[0056] In some embodiments, the first material 240 includes a white material (e.g., white ink), and the second material 246 (e.g., the first absorptive material) includes a yellow material (e.g., yellow ink). The second spectral absorptance A2 of the yellow material at the first wavelength is greater than twice the second spectral absorptance A2 at the second wavelength, such that A2(r; λ = 450) > 2A2(r; λ = 550). The second spectral absorptance A2 at the first wavelength is greater than twice the second spectral absorptance A2 at the third wavelength, such that A2(r; λ = 450) > 2A2(r; λ = 630). The second spectral transmittance T2 at the first wavelength at the first position 230 is less than the second spectral transmittance T2 at the first wavelength at the second position 232, such that T2(r = 0; λ = 450) < T2(r = r max ; λ = 450).

[0057] The above values of the first spectral reflectance R1, the first spectral transmittance T1, the first spectral absorptance A1, the second spectral reflectance R2, the second spectral transmittance T2, and the second spectral absorptance A2 can be obtained by adjusting the thickness distribution and / or the optical density distribution of the white material 240 and the yellow material 246 within each diffuser pattern 212a. The white material 240 can include a first thickness and / or optical density at the first position 230 and a second thickness and / or optical density less than the first thickness and / or optical density at a third position 234 located between the first position 230 and the second position 232. The thickness and / or optical density can gradually decrease from the first thickness and / or optical density to the second thickness and / or optical density. The yellow material 246 can include a third thickness and / or optical density at the second position 232 and a fourth thickness and / or optical density less than the third thickness and / or optical density at the third position 234. The thickness and / or optical density can gradually decrease from the third thickness and / or optical density to the fourth thickness and / or optical density.

[0058] The thickness and / or optical density distribution of the white material 240 can be optimized to obtain uniformities of two 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 region, and the greater thickness and / or optical density gradually decreases towards the corner points of each LED region. However, in the case of only having the white material, the uniformity of the tristimulus value Z may be unacceptable, which may result in observable color non-uniformity on each LED region. Since the white material has a higher reflection and absorption of blue light (which corresponds to Z) than that of red light and green light (which correspond to X and Y respectively), X and Y have different variation trends from Z. Therefore, in order to further reduce color non-uniformity, a yellow material is added and the thickness distribution and / or optical density distribution of the yellow material are optimized to suppress the higher Z of blue at the corner regions of each LED region. The yellow material has a greater thickness and / or optical density near the corner points of each LED region, and the greater thickness and / or optical density gradually decreases towards the center of each LED region.

[0059] In some embodiments, the first material 240 includes a white material (e.g., white ink), and the second material 246 (e.g., the first absorptive material) includes a magenta material (e.g., magenta ink). The second spectral absorptivity A2 of the magenta ink at the second wavelength is greater than 2 times the second spectral absorptivity A2 at the first wavelength, such that A2(r; λ = 550) > 2A2(r; λ = 450). The second spectral absorptivity A2 at the second wavelength is greater than 2 times the second spectral absorptivity A2 at the third wavelength, such that A2(r; λ = 550) > 2A2(r; λ = 630). The second spectral transmittance T2 at the second wavelength at the first position 230 is less than the second spectral transmittance T2 at the second wavelength at the second position 232, such that T2(r = 0; λ = 550) < T2(r = r max ; λ = 550).

[0060] The above values of the first spectral reflectance R1, the first spectral transmittance T1, the first spectral absorptance A1, the second spectral reflectance R2, the second spectral transmittance T2, and the second spectral absorptance A2 can be obtained by adjusting the thickness distribution and / or optical density distribution of the white material 240 and the magenta material 246 within each diffuser pattern 212a. The white material 240 can include a first thickness and / or optical density at a first position 230 and a second thickness and / or optical density less than the first thickness and / or optical density at a third position 234 located between the first position 230 and the second position 232. The thickness and / or optical density can gradually decrease from the first thickness and / or optical density to the second thickness and / or optical density. The magenta material 246 can include a third thickness and / or optical density at the second position 232 and a fourth thickness and / or optical density less than the third thickness and / or optical density at the third position 234. The thickness and / or optical density can gradually decrease from the third thickness and / or optical density to the fourth thickness and / or optical density.

[0061] The thickness and / or optical density distribution of the white material 240 can be optimized to obtain uniformity of two 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 region, and the greater thickness and / or optical density gradually decreases toward the corners of each LED region. To further reduce color non-uniformity, a magenta material is added and the thickness distribution and / or optical density distribution is optimized to suppress the higher nits of blue at the corner regions of each LED region. The magenta material has a greater thickness and / or optical density near the corners of each LED region, and the greater thickness and / or optical density gradually decreases toward the center of each LED region.

[0062] Figure 3B is a cross-sectional view of an exemplary patterned diffuser 210b. The patterned diffuser 210b includes a carrier 108 and a variable diffuser pattern 211b applied to the surface (e.g., upper surface and / or lower surface) of the carrier 108. In some embodiments, the patterned diffuser 210b can replace the patterned diffuser 110 in Figure 1A and Figure 1B the backlight 100. The variable diffuser pattern 211b includes a plurality of diffuser patterns 212b that correspond to a plurality of light sources 106 ( Figure 1A) Aligned and configured to scatter a portion of the light output by each light source 106. In the present 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), the first and second materials being applied on the carrier 108 such that the corresponding normalized 1931 2° observer x and y (wherein CIE x and CIE y below refer to CIE 1931 2° observer x and y) values of the backlight from a first position 230 aligned with each corresponding light source to a second position 232 intermediate between the corresponding adjacent light sources vary by less than plus or minus about 3 percent, such as less than plus or minus about 1 percent. The corresponding normalized tristimulus X, Y, and Z values of the backlight from the first position 230 to the second position 232 vary by less than plus or minus about 5 percent, such as less than plus or minus about 3 percent.

[0063] 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) located over the white material 240. The second spectral absorptance A2 of the cyan material at a third wavelength is greater than 2 times the second spectral absorptance A2 at a first wavelength, such that A2(r; λ = 630) > 2A2(r; λ = 450). The second spectral absorptance A2 at the third wavelength is greater than 2 times the second spectral absorptance A2 at a second wavelength, such that A2(r; λ = 630) > 2A2(r; λ = 550). The second spectral transmittance T2 at the third wavelength at the first position 230 is less than the second spectral transmittance T2 at the third wavelength at the second position 232, such that T2(r = 0; λ = 630) < T2(r = r max ; λ = 630).

[0064] The above values of the first spectral reflectance R1, the first spectral transmittance T1, the first spectral absorptance A1, the second spectral reflectance R2, the second spectral transmittance T2, and the second spectral absorptance A2 can be obtained by adjusting the thickness distribution and / or the optical density distribution 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 position 230 and a second thickness and / or optical density less than the first thickness and / or optical density at a third position 234 located between the first position 230 and the second position 232. The thickness and / or optical density may gradually decrease 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 position 230 and a sixth thickness and / or optical density less than the fifth thickness and / or optical density at the third position 234. The thickness and / or optical density may gradually decrease from the fifth thickness and / or optical density to the sixth thickness and / or optical density.

[0065] The thickness and / or optical density distribution of the white material 240 can be optimized to obtain a uniformity of the 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 region, and the greater thickness and / or optical density gradually decreases towards the corners of each LED region. However, in the case of only having the white material, the uniformity of the tristimulus values X and Y may be unacceptable, where the tristimulus values X and Y are higher in the center of each LED region and lower in the corners of each LED region. Therefore, a cyan material is added and the thickness distribution and / or optical density distribution of the cyan material is optimized to obtain a uniformity of the two 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 region, and the greater thickness and / or optical density gradually decreases towards the corners of each LED region.

[0066] Figure 3C is a cross-sectional view of an exemplary patterned diffuser 210c. The patterned diffuser 210c includes a carrier 108 and a variable diffuser pattern 211c applied to the surface (e.g., upper surface and / or lower surface) of the carrier 108. In some embodiments, the patterned diffuser 210c can replace the patterned diffuser 110 in Figure 1A and Figure 1B of the backlight 100. The variable diffuser pattern 211c includes a plurality of diffuser patterns 212c, which are aligned with a plurality of light sources 106 ( Figure 1A ) and are configured to scatter a portion of the light output by each light source 106. In the present embodiment, the variable diffuser pattern 211c includes a first material 240 (e.g., white material) and a second material 242 (e.g., a first absorptive material), and the first material and the second material are applied on the carrier 108 such that the corresponding normalized CIE x and CIE y values of the backlight from a first position 230 aligned with each corresponding light source to a second position 232 intermediate between the corresponding adjacent light sources can vary by less than plus or minus about 3 percent, such as less than plus or minus about 1 percent. The corresponding normalized tristimulus X, Y, and Z values of the backlight from the first position 230 to the second position 232 can vary by less than plus or minus about 5 percent, such as less than plus or minus about 3 percent.

[0067] The variable diffuser pattern 211c is similar to Figure 3B the variable diffuser pattern 211b, except that in the variable diffuser pattern 211c, the white material 240 is located above the cyan material 242. Both the white material 240 and the cyan material 242 of each diffuser pattern 212c include a thickness distribution and / or optical density distribution similar to that described above with reference to Figure 3B Therefore, as described above with reference toFigure 3B The values of the first spectral reflectance R1, the first spectral transmittance T1, the first spectral absorptance A1, the second spectral reflectance R2, the second spectral transmittance T2, and the second spectral absorptance A2 described for the variable diffuser pattern 211b are also applicable to Figure 3C the variable diffuser pattern 211c.

[0068] Figure 3D is a cross-sectional view of an exemplary patterned diffuser 210d. The patterned diffuser 210d includes a carrier 108 and a variable diffuser pattern 211d applied to a surface (e.g., an upper surface and / or a lower surface) of the carrier 108. In some embodiments, the patterned diffuser 210d can replace the patterned diffuser 110 in Figure 1A and Figure 1B the backlight 100. The variable diffuser pattern 211d includes a plurality of diffuser patterns 212d that are aligned with a plurality of light sources 106 ( Figure 1A ) and are configured to scatter a portion of the 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) that are applied to the carrier 108 such that the corresponding normalized CIE x and CIE y values of the backlight from a first position 230 aligned with each respective light source to a second position 232 intermediate between the corresponding adjacent light sources can vary by less than plus or minus about 3 percent, such as less than plus or minus about 1 percent. The corresponding normalized tristimulus X, Y, and Z values of the backlight from the first position 230 to the second position 232 can vary by less than plus or minus about 5 percent, such as less than plus or minus about 3 percent.

[0069] The variable diffuser pattern 211d is similar to Figure 3B the variable diffuser pattern 211b, except that in the 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 can include a first optical density at the first position 230 and a second optical density less than the first optical density at a third position 234 located between the first position 230 and the second position 232. The optical density can gradually decrease from the first optical density to the second optical density. The cyan material 242 can include a third optical density at the first position 230 and a fourth optical density less than the third optical density at the third position 234. The optical density can gradually decrease 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 can include an optical density distribution similar to that described above with reference to Figure 3B Thus, as described above with reference to Figure 3BThe values of the first spectral reflectance R1, the first spectral transmittance T1, the first spectral absorptance A1, the second spectral reflectance R2, the second spectral transmittance T2, and the second spectral absorptance A2 described for the variable diffuser pattern 211b are also applicable to Figure 3D the variable diffuser pattern 211d.

[0070] Figure 3E is a cross-sectional view of an exemplary patterned diffuser 210e. The patterned diffuser 210e includes a carrier 108 and a variable diffuser pattern 211e applied to the surface (e.g., upper surface and / or lower surface) of the carrier 108. In some embodiments, the patterned diffuser 210e can replace the patterned diffuser 110 in Figure 1A and Figure 1B the backlight 100. The variable diffuser pattern 211e includes a plurality of diffuser patterns 212e that are aligned with a plurality of light sources 106 ( Figure 1A ) and are configured to scatter a portion of the light output by each light source 106. In the present 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), which are applied to the carrier 108 such that the corresponding normalized CIE x and CIE y values of the backlight from a first position 230 aligned with each respective light source to a second position 232 intermediate between the corresponding adjacent light sources can vary by less than plus or minus about 3 percent, such as less than plus or minus about 1 percent. The corresponding normalized tristimulus X, Y, and Z values of the backlight from the first position 230 to the second position 232 can vary by less than plus or minus about 5 percent, such as less than plus or minus about 3 percent.

[0071] The variable diffuser pattern 211e is similar to Figure 3A the variable diffuser pattern 211a, except that the variable diffuser pattern 211e includes a third material 242 in addition to the first material 240 and the second material 246 Figures 3B to 3D . In the present embodiment, the third material 242 is different from the first material 240 and the second material 246. The third material 242 includes a third spectral reflectance R3, which can be different from the first spectral reflectance R1 and the second spectral reflectance R2; a third spectral transmittance T3, which can be different from the first spectral transmittance T1 and the second spectral transmittance T2; and a third spectral absorptance A3, which can be different from the first spectral absorptance A1 and the second spectral absorptance A2.

[0072] In some embodiments, the first material 240 comprises a white material (e.g., white ink), the second material 246 (e.g., the first absorbent material) comprises a yellow material (e.g., yellow ink), and the third material 242 (e.g., the second absorbent material) comprises 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 to that described above with reference to Figure 3D such that the second spectral absorptivity A2 of the yellow material 246 at the first wavelength is greater than 2 times the second spectral absorptivity A2 at the second wavelength, such that A2(r; λ = 450) > 2A2(r; λ = 550). The second spectral absorptivity A2 at the first wavelength is greater than 2 times the second spectral absorptivity A2 at the third wavelength, such that A2(r; λ = 450) > 2A2(r; λ = 630). The second spectral transmittance T2 at the first wavelength at the first position 230 is less than the second spectral transmittance T2 at the first wavelength at the second position 232, such that T2(r = 0; λ = 450) < T2(r = r max ; λ = 450).

[0073] The third spectral absorptivity A3 of the cyan material 242 at the third wavelength is greater than 2 times the third spectral absorptivity A3 at the first wavelength, such that A3(r; λ = 630) > 2A3(r; λ = 450). The third spectral absorptivity A3 of the cyan ink at the third wavelength is greater than 2 times the third spectral absorptivity A3 at the second wavelength, such that A3(r; λ = 630) > 2A3(r; λ = 550). The third spectral transmittance T3 at the third wavelength at the first position 230 is less than the third spectral transmittance T3 at the third wavelength at the second position 232, such that T3(r = 0; λ = 630) < T3(r = r max ; λ = 630).

[0074] The above values of the first spectral reflectance R1, the first spectral transmittance T1, the first spectral absorptance A1, the second spectral reflectance R2, the second spectral transmittance T2, the second spectral absorptance A2, the third spectral reflectance R3, the third spectral transmittance T3, and the third spectral absorptance A3 can be obtained by adjusting the thickness distribution and / or the optical density distribution of the white material 240, the yellow material 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 a 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 located between the first location 230 and the second location 232. The thickness and / or optical density may gradually decrease 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 gradually decrease 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 gradually decrease from the fifth thickness and / or optical density to the sixth thickness and / or optical density.

[0075] In some embodiments, the first material 240 includes a white material (e.g., white ink), the second material (e.g., the first absorptive material) includes the cyan material 242 (e.g., cyan ink), and the third material (e.g., the second absorptive material) includes the 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 to that described above with reference to Figure 3D The second spectral absorptance A2 of the cyan material at the third wavelength is greater than twice the second spectral absorptance A2 at the first wavelength, such that A2(r; λ = 630) > 2A2(r; λ = 450). The second spectral absorptance A2 at the third wavelength is greater than twice the second spectral absorptance A2 at the second wavelength, such that A2(r; λ = 630) > 2A2(r; λ = 550). The second spectral transmittance T2 of the cyan material at the third wavelength at the first location 230 is less than the second spectral transmittance T2 of the cyan material at the third wavelength at the second location 232, such that T2(r = 0; λ = 630) < T2(r = r max ; λ = 630).

[0076] The third spectral absorptance A3 of the magenta material at the second wavelength is greater than twice the third spectral absorptance A3 at the first wavelength, such that A3(r; λ = 550) > 2A3(r; λ = 450). The third spectral absorptance A3 at the second wavelength is greater than twice the third spectral absorptance A3 at the third wavelength, such that A3(r; λ = 550) > 2A3(r; λ = 630). The third spectral transmittance T3 at the second wavelength at the first position 230 is less than the third spectral transmittance T3 at the second wavelength at the second position 232, such that T3(r = 0; λ = 550) < T3(r = r max ; λ = 550).

[0077] The above values of the first spectral reflectance R1, the first spectral transmittance T1, the first spectral absorptance A1, the second spectral reflectance R2, the second spectral transmittance T2, the second spectral absorptance A2, the third spectral reflectance R3, the third spectral transmittance T3, and the third spectral absorptance A3 can be obtained by adjusting the thickness distribution and / or the optical density distribution 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 position 230 and a second thickness and / or optical density less than the first thickness and / or optical density at a third position 234 located between the first position 230 and the second position 232. The thickness and / or optical density may gradually decrease 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 position 230 and a fourth thickness and / or optical density less than the third thickness and / or optical density at the third position 234. The thickness and / or optical density may gradually decrease 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 position 232 and a sixth thickness and / or optical density less than the fifth thickness and / or optical density at the third position 234. The thickness and / or optical density may gradually decrease from the fifth thickness and / or optical density to the sixth thickness and / or optical density.

[0078] Since at Figure 3EIn an embodiment, three materials are used, so the order of adding materials for optimizing the tristimulus X, Y, and Z values is important for a successful patterned diffuser design. The order of the materials to be printed can result in different performances, but the order of the materials to be printed is not critical as long as the printing order is consistent during optimization or the materials can be printed simultaneously and mixed at specific locations. First, the thickness distribution and / or optical density distribution of the white material 240 can be optimized to achieve uniformity of the normalized tristimulus Z value close to 1. The white material 240 has a greater thickness and / or optical density near the center of each LED region, and the greater thickness and / or optical density gradually decreases towards the corners of each LED region. Second, the cyan material 242 is added and the thickness distribution and / or optical density distribution of the cyan material is optimized to achieve uniformity of the 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 region, and the greater thickness and / or optical density gradually decreases towards the corners of each LED region. Third, the yellow or magenta material 246 is added and the thickness distribution and / or optical density distribution of the yellow or magenta material is optimized to improve the normalized tristimulus X, Y, and Z values. The yellow or magenta material 246 has a greater thickness and / or optical density near the corners of each LED region, and the greater thickness and / or optical density gradually decreases towards the center of each LED region. In this way, the color non-uniformity of the backlight is improved, and the spatial variation of the white LED backlight is minimized.

[0079] In another embodiment, the first material 240 includes a white material (e.g., white ink), the second material (e.g., the first absorptive material) includes a yellow material (e.g., yellow ink), and the third material (e.g., the second absorptive material) includes a magenta material (e.g., magenta ink). The second material can be the first part of 246, and the third material can be the second part of 246. In this embodiment, the cyan material 242 is not included. Figure 3E In certain exemplary embodiments, the white material 240 can be mixed with the yellow material and / or magenta material similarly to that described above with reference to Figure 3D The second spectral absorptivity A2 of the yellow material at the first wavelength is greater than twice the second spectral absorptivity A2 at the second wavelength, such that A2(r; λ = 450) > 2A2(r; λ = 550). The second spectral absorptivity A2 at the first wavelength is greater than twice the second spectral absorptivity A2 at the third wavelength, such that A2(r; λ = 450) > 2A2(r; λ = 630). The second spectral transmittance T2 of the first wavelength at the first position 230 is less than the second spectral transmittance T2 of the first wavelength at the second position 232, such that T2(r = 0; λ = 450) < T2(r = r max; λ = 450).

[0080] The third spectral absorptance A3 of the magenta material at the second wavelength is greater than twice the third spectral absorptance A3 at the first wavelength, such that A3(r; λ = 550) > 2A3(r; λ = 450). The third spectral absorptance A3 at the second wavelength is greater than twice the third spectral absorptance A3 at the third wavelength, such that A3(r; λ = 550) > 2A3(r; λ = 630). The third spectral transmittance T3 at the second wavelength at the first position 230 is less than the third spectral transmittance T3 at the second wavelength at the second position 232, such that T3(r = 0; λ = 550) < T3(r = r max ; λ = 550).

[0081] The above values of the first spectral reflectance R1, the first spectral transmittance T1, the first spectral absorptance A1, the second spectral reflectance R2, the second spectral transmittance T2, the second spectral absorptance A2, the third spectral reflectance R3, the third spectral transmittance T3, and the third spectral absorptance A3 can be obtained by adjusting the thickness distribution and / or the optical density distribution of the white material 240, the yellow material (e.g., the first part of 246), and the magenta material (the second part of 246) within each diffuser pattern. The white material may include a first thickness and / or optical density at the first position 230 and a second thickness and / or optical density less than the first thickness and / or optical density at a third position 234 located between the first position 230 and the second position 232. The thickness and / or optical density may gradually decrease 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 position 232 and a fourth thickness and / or optical density less than the third thickness and / or optical density at the third position 234. The thickness and / or optical density may gradually decrease 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 position 232 and a sixth thickness and / or optical density less than the fifth thickness and / or optical density at the third position 234. The thickness and / or optical density may gradually decrease from the fifth thickness and / or optical density to the sixth thickness and / or optical density.

[0082] Figure 4A is an exemplary patterned diffuser including white ink and cyan ink (such as Figure 3B the patterned diffuser 210b, Figure 3C the patterned diffuser 210c, or Figure 3DGraph 300 of the normalized tristimulus X, Y, and Z values of the patterned diffuser 210d). Graph 300 includes a radial distance (e.g., position r) in millimeters on the x-axis, where 0 is aligned with the corresponding light source 106. Graph 300 includes a ratio on the y-axis such that the normalized tristimulus X [i.e., X / X(0)], Y [i.e., L / L(0)], and Z [i.e., Z / Z(0)] values of the exemplary backlight 100 are shown. As shown in Graph 300, the corresponding normalized tristimulus values X, Y, and Z of the backlight from the first position r = 0 to the second position r = r max (e.g., approximately 6.4 millimeters in this example) vary by less than approximately plus or minus 3 percent. A Radiant colorimeter positioned above the backlight can be used to collect the tristimulus values. The X, Y, and Z data in a single LED region can be arranged as 31x31 pixels, normalized to the pixel in the center, and plotted relative to the distance to the center pixel, as shown in Graph 300.

[0083] Figure 4B is an example of an exemplary patterned diffuser including white ink and cyan ink (such as Figure 3B the patterned diffuser 210b, Figure 3C the patterned diffuser 210c, or Figure 3D the patterned diffuser 210d) of the normalized CIE x and CIE y values of Graph 310. Graph 310 includes a radial distance (e.g., position r) in millimeters on the x-axis, where 0 is aligned with the corresponding light source 106. Graph 310 includes the CIE color on the y-axis such that the normalized CIE x [i.e., Cx / Cx(0)] and CIE y [i.e., Cy / Cy(0)] values of the exemplary backlight 100 are shown. As shown in Graph 310, the corresponding normalized CIE x and CIE y values of the backlight from the first position r = 0 to the second position r = r max (e.g., approximately 6.4 millimeters in this example) vary by less than approximately plus or minus 1 percent. The CIE x and CIE y values refer to the 1931 CIE 1931 2° observer x and y, where:

[0084] and

[0085] where X, Y, and Z are tristimulus values that can be measured by a colorimeter.

[0086] Figure 5A is an example of an exemplary patterned diffuser including white ink, cyan ink, and yellow ink (such as Figure 3EGraph 320 of the normalized tristimulus X, Y, and Z values of the patterned diffuser 210e). Graph 320 includes a radial distance (e.g., position r) in millimeters on the x-axis, where 0 is aligned with the corresponding light source 106. Graph 320 includes a ratio on the y-axis such that the normalized tristimulus X [i.e., X / X(0)], Y [i.e., L / L(0)], and Z [i.e., Z / Z(0)] values of the exemplary backlight 100 are shown. As shown in Graph 320, the corresponding normalized tristimulus values X, Y, and Z of the backlight from the first position r = 0 to the second position r = r max (e.g., approximately 6.4 millimeters in this example) vary by less than approximately plus or minus 3 percent. A radiometric colorimeter positioned above the backlight can be used to collect the tristimulus values, as described above with reference to Figure 4A as described.

[0087] Figure 5B is an exemplary patterned diffuser including white ink, cyan ink, and yellow ink, such as Figure 3E Graph 330 of the normalized CIE x and CIE y values of the patterned diffuser 210e). Graph 330 includes a radial distance (e.g., position r) in millimeters on the x-axis, where 0 is aligned with the corresponding light source 106. Graph 330 includes the CIE color on the y-axis such that the normalized CIE x [i.e., Cx / Cx(0)] and CIE y [i.e., Cy / Cy(0)] values of the exemplary backlight 100 are shown. As shown in Graph 310, the corresponding normalized CIE x and CIE y values of the backlight from the first position r = 0 to the second position r = r max (e.g., approximately 6.4 millimeters in this example) vary by less than approximately plus or minus 1 percent.

[0088] Figures 6A to 6C is a flowchart of an exemplary method 400 for manufacturing a backlight including a patterned diffuser, such as the backlight 100 including the patterned diffusers 210a - 210e respectively including Figures 3A to 3E and Figure 1A and Figure 1B As illustrated at 402 in Figure 6A the method 400 includes: disposing a carrier (e.g., 108 in Figure 1A and Figure 1B ) in proximity to a plurality of white light sources (e.g., 106 in Figure 1A ). At 404, the method 400 includes: printing (e.g., inkjet printing) a variable diffuser pattern (e.g., Figures 3A to 3Eof 211a - 211e), the printed variable diffuser pattern includes printing white ink (e.g., 240) and a first absorptive ink (e.g., 242 or 246) on a carrier such that the corresponding normalized CIE x and CIE y values of the backlight source change by less than approximately plus or minus 1% from a first position (e.g., 130 or 230) aligned with each corresponding light source to a second position (e.g., 132 or 232) intermediate between the corresponding adjacent light sources.

[0089] In certain exemplary embodiments, as Figure 6B illustrated, the printed variable diffuser pattern at 404 may further include method 404a. At 406, method 404a includes: printing a second absorptive ink (e.g., 246 or 242) on a carrier. In certain exemplary embodiments, as Figure 6C illustrated, the printed variable diffuser pattern at 404a may further include method 404b. At 408, method 404b includes: printing white ink that includes a first optical density at a first position and a second optical density less than the first optical density at a third position (e.g., 234) located between the first position and the second position. At 410, method 404b may further include: printing the first absorptive ink, where printing the first absorptive ink includes printing yellow ink that includes a third optical density at the second position and a fourth optical density less than the third optical density at the third position. At 412, method 404b may further include: printing the second absorptive ink, where printing the second absorptive ink includes printing cyan ink that includes a fifth optical density at the first position and a sixth optical density less than the fifth optical density at the third position. Similar methods as described above with reference to Figures 6A to 6C description can be used to manufacture a backlight source including the variable diffuser pattern 211a - 211e described with reference to Figures 3A to 3E description.

[0090] It will be apparent to those skilled in the art that various modifications and variations can be made to the embodiments of the present disclosure without departing from the spirit and scope of the present disclosure. Accordingly, the present disclosure is intended to cover such modifications and variations provided that they are within the scope of the appended claims and their equivalents.

Claims

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

2. The backlight according to claim 1, wherein the corresponding normalized tristimulus X, Y, and Z values of the backlight vary by less than plus or minus about 3% from the first position to the second position.

3. The backlight according to claim 1, wherein the white material includes white ink, the white ink having a first thickness at the first position and a second thickness less than the first thickness at a third position located between the first position and the second position, and Wherein the first absorptive material includes yellow ink, the yellow ink having a third thickness at the second position and a fourth thickness less than the third thickness at the third position.

4. The backlight according to claim 1, wherein the white material includes white ink, the white ink having a first thickness at the first position and a second thickness less than the first thickness at a third position located between the first position and the second position, and Wherein the first absorptive material includes cyan ink, the cyan ink having a fifth thickness at the first position and a sixth thickness less than the fifth thickness at the third position.

5. The backlight according to claim 1, wherein the white material includes white ink, and the first absorptive material includes cyan ink mixed with the white ink, Wherein the white ink has a first optical density at the first position and a second optical density less than the first optical density at a third position located between the first position and the second position, and Wherein the cyan ink has a third optical density at the first position and a fourth optical density less than the third optical density at the third position.

6. The backlight according to claim 1, wherein the white material includes white ink, the white ink having a first thickness at the first position and a second thickness less than the first thickness at a third position located between the first position and the second position; and Wherein the first absorptive material includes magenta ink, the magenta ink having a third thickness at the second position and a fourth thickness less than the third thickness at the third position.

7. The backlight according to claim 1, wherein the variable diffuser pattern further includes a second absorptive material applied on the carrier.

8. The backlight according to claim 7, wherein the white material comprises white ink, the white ink having a first thickness at the first position and a second thickness less than the first thickness at a third position between the first position and the second position, wherein the first absorptive material comprises yellow ink, the yellow ink having a third thickness at the second position and a fourth thickness less than the third thickness at the second position, and wherein the second absorptive material comprises cyan ink, the cyan ink having a fifth thickness at the first position and a sixth thickness less than the fifth thickness at the third position.

9. The backlight according to claim 7, wherein the white material comprises white ink, the first absorptive material comprises yellow ink mixed with the white ink, and the second absorptive material comprises cyan ink mixed with the white ink and the yellow ink, wherein the white ink has a first optical density at the first position and a second optical density less than the first optical density at a third position between the first position and the second position, wherein the yellow ink has a third optical density at the second position and a fourth optical density less than the third optical density at the third position, and wherein the cyan ink has a fifth optical density at the first position and a sixth optical density less than the fifth optical density at the third position.

10. The backlight according to claim 7, wherein the white material comprises white ink, the first absorptive material comprises yellow ink, and the second absorptive material comprises magenta ink, wherein the white ink has a first optical density at the first position and a second optical density less than the first optical density at a third position between the first position and the second position, wherein the yellow ink has a third optical density at the second position and a fourth optical density less than the third optical density at the third position, and wherein the magenta ink has a fifth optical density at the second position and a sixth optical density less than the fifth optical density at the third position.

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

12. A backlight, the backlight comprising: a plurality of white light sources; a carrier, the carrier being close to 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 the light output by each light source, the variable diffuser pattern including a first material and a second material different from the first material; the first material including a first spectral reflectivity, a first spectral transmittance, and a first spectral absorptance; and the second material including a second spectral reflectivity, 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 about 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 reflectivity at the first wavelength is greater than the first spectral reflectivity at the second wavelength, and the first spectral reflectivity at the second wavelength is greater than the first spectral reflectivity 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 transmittances at the first wavelength, the second wavelength, and the third wavelength at a first position aligned with each respective light source are less than the respective first spectral transmittances at the first wavelength, the second wavelength, and the third wavelength at a second position intermediate between the respective adjacent light sources, wherein the respective first spectral reflectivities at the first wavelength, the second wavelength, and the third wavelength at the first position are greater than the respective first spectral reflectivities at the first wavelength, the second wavelength, and the third wavelength at the second position, and wherein the second spectral absorptance at one of the first wavelength, the second wavelength, and the third wavelength is greater than 2 times the second spectral absorptances at the other two of the first wavelength, the second wavelength, and the third wavelength.

13. The backlight according to 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 position is less than the second spectral transmittance at the first wavelength at the second position.

14. The backlight according to claim 12, wherein the second spectral absorptance at the third wavelength is greater than twice the second spectral absorptance at the first wavelength, and the second spectral absorptance at the third wavelength is greater than twice the second spectral absorptance at the second wavelength, and wherein the second spectral transmittance at the third wavelength at the first position is less than the second spectral transmittance at the third wavelength at the second position.

15. The backlight according to claim 12, wherein the second spectral absorptance at the second wavelength is greater than twice the second spectral absorptance at the first wavelength, and the second spectral absorptance at the second wavelength is greater than twice the second spectral absorptance at the third wavelength; and wherein the second spectral transmittance at the second wavelength at the first position is less than the second spectral transmittance at the second wavelength at the second position.

16. The backlight according to claim 13, wherein the variable diffuser pattern further comprises a third material different from the first material and the second material, and the third material comprises 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 twice the third spectral absorptance at the first wavelength, and the third spectral absorptance at the third wavelength is greater than twice the third spectral absorptance at the second wavelength, and wherein the third spectral transmittance at the third wavelength at the first position is less than the third spectral transmittance at the third wavelength at the second position.

17. The backlight according to claim 13, wherein the variable diffuser pattern further comprises a third material different from the first material and the second material, and the third material comprises 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 twice the third spectral absorptance at the first wavelength, and the third spectral absorptance at the second wavelength is greater than twice the third spectral absorptance at the third wavelength; and wherein the third spectral transmittance at the second wavelength at the first position is less than the third spectral transmittance at the second wavelength at the second position.

18. The backlight according to claim 14, wherein the variable diffuser pattern further comprises a third material different from the first material and the second material, and the third material comprises 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 twice the third spectral absorptance at the first wavelength, and the third spectral absorptance at the second wavelength is greater than twice the third spectral absorptance at the third wavelength, and The third spectral transmittance at the second wavelength at the first position is less than the third spectral transmittance at the second wavelength at the second position.

19. A method for manufacturing a backlight, the method comprising: Arranging a carrier in proximity to a plurality of white light sources; And Printing a variable diffuser pattern on the carrier, the printing of the variable diffuser pattern comprising printing white ink and a first absorptive ink on the carrier such that the corresponding normalized CIE x and CIE y values of the backlight vary by less than plus or minus about 1% from a first position aligned with each respective light source to a second position intermediate between the respective adjacent light sources.

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, the white ink having a first optical density at the first position and a second optical density less than the first optical density at a third position between the first position and the second position, Printing the first absorptive ink, the printing of the first absorptive ink comprising printing yellow ink, the yellow ink having a third optical density at the second position and a fourth optical density less than the third optical density at the third position, and Printing the second absorptive ink, the printing of the second absorptive ink comprising printing cyan ink, the cyan ink having a fifth optical density at the first position and a sixth optical density less than the fifth optical density at the third position.

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