WO2022108899A1

WO2022108899A1 - Self-aligning backlight reflector

Info

Publication number: WO2022108899A1
Application number: PCT/US2021/059453
Authority: WO
Inventors: Guanglei DU; Horst Herbert Anton SCHREIBER; Bin Wang
Original assignee: Corning Incorporated
Priority date: 2020-11-23
Filing date: 2021-11-16
Publication date: 2022-05-27
Also published as: KR20230107359A; CN116547571A; TW202227752A; JP2023550917A

Abstract

A reflector and a backlight including a reflector wherein the reflector is configured to be optically coupled with a light source that emits a peak intensity wavelength (λpeak) and an incident peak intensity ray. The reflector is configured to reflect at least about 60% of the incident peak intensity ray and transmit at least about 60% of incident low intensity rays emitted from the light source.

Description

SELF- ALIGNING BACKLIGHT REFLECTOR

Cross Reference to Related Applications

[0001] This application claims priority under 35 U.S.C. § 119 from U.S. Provisional Patent Application Number 63/117,158 filed on November 23, 2020, which is incorporated by reference herein in its entirety.

Field

[0002] The present disclosure relates generally to a backlight reflector and more particularly to a self-aligning backlight reflector.

Background

[0003] Liquid crystal displays (LCDs) are commonly used in various electronics, such as cell phones, laptops, electronic tablets, televisions, and computer monitors. 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 as compared 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. To achieve desired light uniformity and/or to avoid hot spots in direct-lit backlights, a diffuser plate or film may be positioned at a distance from the LEDs, thus making the overall display thickness greater than that of an edge-lit backlight.

[0005] To reduce the thickness of the backlight, patterns with spatial variations may be incorporated on diffusive plates, clear plates, or standalone patterned reflective layers, wherein the spatial variation of the patterns are typically registered to the LED positions. However, though the patterns with spatial variations can reduce the thickness of the backlight, they typically require relatively precise alignment with the LEDs, which in addition to the production of the patterns, requires additional assembly and/or manufacturing steps. SUMMARY

[0006] Embodiments disclosed herein include a reflector. The reflector includes a first major surface, a second major surface, and a thickness extending in a perpendicular direction to the first major surface and the second major surface. The reflector is configured to be optically coupled with a light source that emits a peak intensity wavelength (k_pcak) and an incident peak intensity ray. The incident peak intensity ray extends along an axis oriented at an angle (9) relative to the perpendicular direction. In addition, the reflector is configured to reflect at least about 60% of the incident peak intensity ray and transmit at least about 60% of incident low intensity rays emitted from the light source. Each incident low intensity ray extends along an axis oriented at an angle relative to the perpendicular direction and emits a total incident light intensity that is less than about 25% of a total incident light intensity of the peak intensity ray.

[0007] Embodiments disclosed herein also include a backlight. The backlight includes a reflector. The reflector includes a first major surface, a second major surface, and a thickness extending in a perpendicular direction to the first major surface and the second major surface. The backlight also includes a substrate and a plurality of light sources proximate the substrate. Each light source is configured to emit a peak intensity wavelength (k_pcak) and an incident peak intensity ray. The incident peak intensity ray extends along an axis oriented at an angle (9) relative to the perpendicular direction. In addition, the reflector is configured to reflect at least about 69% of the incident peak intensity ray and transmit at least about 69% of incident low intensity rays emitted from the light source. Each incident low intensity ray extends along an axis oriented at an angle relative to the perpendicular direction and emits a total incident light intensity that is less than about 25% of a total incident light intensity of the peak intensity ray.

[0008] Additional features and advantages of the embodiments disclosed herein will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the disclosed embodiments as described herein, including the detailed description which follows, the claims, as well as the appended drawings.

[0009] It is to be understood that both the foregoing general description and the following detailed description present embodiments intended to provide an overview or framework for understanding the nature and character of the claimed embodiments. The accompanying drawings are included to provide further understanding and are incorporated into and constitute a part of this specification. The drawings illustrate various embodiments of the disclosure, and together with the description serve to explain the principles and operations thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] FIG. l is a cross-sectional view of an exemplary backlight including a reflector;

[0011] FIG. 2 is a cross-sectional view of an exemplary backlight including a reflector;

[0012] FIG. 3 is cross-sectional view of an exemplary backlight including a reflector;

[0013] FIG. 4 is cross-sectional view of an exemplary backlight including a reflector, diffusive layer, and transparent layer;

[0014] FIG. 5 is cross-sectional view of an exemplary backlight including a reflector, diffusive layer, and transparent layer;

[0015] FIG. 6 is a cross-sectional view of an exemplary reflector;

[0016] FIG. 7 is a chart of average transmittance of an exemplary reflector and light band intensity of an optically coupled light source as a function of wavelength;

[0017] FIG. 8 is a chart of average transmittance of an exemplary reflector at different incident angles and light band intensity of an optically coupled light source as a function of wavelength;

[0018] FIG. 9 is a chart of total incident light transmittance to an observation plane as a function of angle of incidence with differing reflector and/or diffusive layer configurations extending between the observation plane and an optically coupled light source;

[0019] FIG. 10 is a chart of total reflectance and transmittance of an exemplary reflector as a function of angle of incidence of an optically coupled light source;

[0020] FIG. 11 is a chart of total reflectance and transmittance of an exemplary reflector as a function of angle of incidence of an optically coupled light source;

[0021] FIG. 12 is a chart of total reflectance and transmittance of an exemplary reflector as a function of angle of incidence of an optically coupled light source; and

[0022] FIG. 13 is a chart of total reflectance and transmittance of an exemplary reflector as a function of angle of incidence of an optically coupled light source.

DETAILED DESCRIPTION

[0023] Reference will now be made in detail to the present preferred 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.

[0024] 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, for example 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.

[0025] Directional terms as used herein - for example up, down, right, left, front, back, top, bottom - are made only with reference to the figures as drawn and are not intended to imply absolute orientation.

[0026] Unless otherwise expressly stated, it is in no way intended that any method set forth herein 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.

[0027] As used herein, the singular forms "a," "an" and "the" include plural referents unless 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.

[0028] As used herein, the term “peak intensity wavelength (Apeak)” refers to the wavelength at which the highest intensity ray of light is emitted from a light source, such as an LED. [0029] As used herein, the term “incident peak intensity ray” refers to the highest angular intensity ray emitted from a light source as viewed from the perspective of (or incident to) an observation plane directly facing the light source.

[0030] As used herein, the term “incident low intensity rays” refers to angular rays emitted from a light source having less than about 25% of the total incident light intensity of the peak intensity ray as viewed from the perspective of (or incident to) an observation plane directly facing the light source.

[0031] As used herein, the term “half peak intensity wavelength width (FWHM)” refers to a wavelength range of a band of light emitted from a light source wherein the low end of the wavelength range corresponds to a wavelength below the peak intensity wavelength (Apeak) having half of the intensity of the peak intensity wavelength (A_pcak) and the high end of the wavelength range corresponds to a wavelength above intensity the peak wavelength (Apeak) having half of the intensity of the peak intensity wavelength (Apeak).

[0032] As used herein, the term “transparent” refers to a material or layer having an optical transmittance of at least about 30 percent over a length of 500 millimeters in the visible region of the spectrum (about 420-750 nanometers).

[0033] FIG 1 shows a cross-sectional view of an exemplary backlight 10 including a reflector 200. Reflector 200 includes a first major surface 202, a second major surface 204, and a thickness (T) extending in a perpendicular direction (P) to the first major surface 202 and the second major surface 204. Backlight 10 also includes a substrate 100 and a light source 102 positioned on or proximate the substrate 100. A gap, such as an air gap, may extend between substrate 100 and reflector 200.

[0034] Light source 102 is configured to emit one or more rays of light at one or more angles relative to the perpendicular direction (P). In FIG. 1, an exemplary ray (R) extends along an axis oriented at an angle (0) relative to the perpendicular direction (P).

[0035] In addition, light source 102 is configured to emit a peak intensity wavelength (Apeak) and an incident peak intensity ray, the incident peak intensity ray extending along an axis oriented at an angle (9) relative to the perpendicular direction (P). The incident peak intensity ray is the highest intensity ray emitted from the light source 102 as viewed from the perspective of (or incident to) an observation plane (OP) directly facing the light source. As shown in FIG. 1, observation plane (OP) is generally parallel to first major surface 202 and second major surface 204 of reflector 200.

[0036] Light source 102 is also configured to emit one or more low intensity rays, each incident low intensity ray extending along an axis oriented at an angle relative to the perpendicular direction (P) and emitting a total incident light intensity, as viewed from the perspective of (or incident to) observation plane (OP), that is less than about 25% of the total incident light intensity of the peak intensity ray.

[0037] FIG. 2 shows a cross-sectional view of an exemplary backlight 10 including a reflector 200. Reflector 200 includes a first major surface 202, a second major surface 204, and a thickness (T) extending in a perpendicular direction (P) to the first major surface 202 and the second major surface 204. Backlight 10 also includes a substrate 100 and a light source 102 positioned on or proximate the substrate 100. An air gap can extend between substrate 100 and reflector 200.

[0038] As shown in FIG. 2, light source 102 emits a plurality of light rays at a plurality of angles relative to the perpendicular direction (P) wherein the length of each illustrated ray represents the absolute intensity of that ray. As can be seen in FIG. 2, the absolute intensity of each ray of light at each angle is approximately constant, showing a generally Lambertian emission pattern (also referred to in the art as a “Type A” emission pattern).

[0039] The incident intensity of each ray of light emitted from light source 102 as viewed from the perspective of (or incident to) observation plane (OP), is a function of both the absolute intensity of that ray and the angle of incidence between that ray and observation plane (OP). Accordingly, in the embodiment illustrated in FIG. 2, the incident peak intensity ray emitted from light source 102 extends along an axis that is approximately normal to the observation plane (OP) or, in other words, extends along an axis oriented at an angle (0) of about 0° relative to the perpendicular direction (P). In addition, in the embodiment illustrated in FIG. 2, incident low intensity rays emitted from light source 102 each extend along an axis oriented at an absolute angle of greater than about 75° relative to the perpendicular direction (P).

[0040] Accordingly, embodiments disclosed herein include those in which the incident peak intensity ray extends along an axis oriented at an angle (9) ranging from about -20° to about 20°, such as from about -10° to about 10°, and further such as from about -5° to about 5°, including about 0° relative to the perpendicular direction (P).

[0041] FIG. 3 shows a cross-sectional view of an exemplary backlight 10 including a reflector 200. Reflector 200 includes a first major surface 202, a second major surface 204, and a thickness (T) extending in a perpendicular direction (P) to the first major surface 202 and the second major surface 204. Backlight 10 also includes a substrate 100 and a light source 102 positioned on or proximate the substrate 100. An air gap can extend between substrate 100 and reflector 200. [0042] As shown in FIG. 3, light source 102 emits a plurality of light rays at a plurality of angles relative to the perpendicular direction (P) wherein the length of each illustrated ray represents the absolute intensity of that ray. As can be seen in FIG. 3, the absolute intensity of each ray of light varies by emission angle, showing a generally wide-angle emission pattern (also referred to in the art as a “Type B” emission pattern).

[0043] The incident intensity of each ray of light emitted from light source 102 as viewed from the perspective of (or incident to) observation plane (OP), is a function of both the absolute intensity of that ray and the angle of incidence between that ray and observation plane (OP). Accordingly, in the embodiment illustrated in FIG. 3, the incident peak intensity ray emitted from light source 102 extends along an axis that is oriented at an angle (0) of about 45° relative to the perpendicular direction (P).

[0044] Accordingly, embodiments disclosed herein include those in which the incident peak intensity ray extends along an axis oriented at an angle (9) ranging from about -60° to about -20° or from about 20° to about 60°, such as from about -55° to about -25° or from about 25° to about 55°, and further such as from about -50° to about -30° or from about 30° to about 50°, including about -45°or 45° relative to the perpendicular direction (P).

[0045] FIG. 4 shows a cross-sectional view of an exemplary backlight 10 including a reflector 200, diffusive layer 300, and transparent layer 400. Reflector 200 includes a first major surface 202, a second major surface 204, and a thickness (T) extending in a perpendicular direction (P) to the first major surface 202 and the second major surface 204. Backlight 10 also includes a substrate 100 and a plurality of light sources 102 positioned on or proximate the substrate 100.

[0046] As shown in FIG. 4, diffusive layer 300 extends proximate to the second major surface 204 of reflector 200 and transparent layer 400 extends between substrate 100 and diffusive layer 300. An air gap can extend between substrate 100 and transparent layer 400. [0047] FIG. 5 shows a cross-sectional view of an exemplary backlight 10 including a reflector 200, diffusive layer 300, and transparent layer 400. Reflector 200 includes a first major surface 202, a second major surface 204, and a thickness (T) extending in a perpendicular direction (P) to the first major surface 202 and the second major surface 204. Backlight 10 also includes a substrate 100 and a plurality of light sources 102 positioned on or proximate the substrate 100.

[0048] As shown in FIG. 5, diffusive layer 300 extends proximate to the first major surface 202 of reflector 200 and reflector 200 extends between diffusive layer 300 and transparent layer 400. An air gap can extend between substrate 100 and transparent layer 400. [0049] In certain exemplary embodiments, thickness (T) extends a distance in the perpendicular direction (P) ranging from about 1 micron to about 4 microns, such as from about 2 microns to about 3 microns.

[0050] Substrate 100 may include a printed circuit board (PCB), a glass or plastic substrate, or another suitable substrate for passing electrical signals to each light source 102 for individually controlling each light source. Substrate 102 may comprise a rigid substrate or a flexible substrate.

[0051] The pitch between adjacent light sources 102, such as the light sources 102 shown in FIGS. 4 and 5 while not limited to any particular value, may, for example, be less than about 40 millimeters, such as less than about 20 millimeters, and further such as less than about 10 millimeters, and yet further such as less than about 5 millimeters, such as from about 1 millimeter to about 40 millimeters, and further such as from about 5 millimeters to about 20 millimeters.

[0052] In certain exemplary embodiments, such as the embodiments illustrated in FIGS. 1- 5, light source(s) 102 each comprise a light emitting diode (LED). In certain exemplary embodiments, such as the embodiments illustrated in FIGS. 1-5, light source(s) 102 each comprise a blue LED.

[0053] Diffusive layer 300 diffuses rays from light source(s) 102. Diffusive layer 300 also diffuses rays that otherwise would undergo total internal reflection. Diffusive layer 300 may comprise a generally uniform transmittance or a transmittance that varies in one or more directions (spatially varying transmittance).

[0054] In certain exemplary embodiments, diffusive layer 300 includes a uniform or continuous layer of scattering particles. The scattering particles may, for example, be within a clear or white ink that includes micro-sized or nano-sized scattering particles, such as AI2O3 particles, TiCh particles, polymethyl methacrylate (PMMA) particles, or other suitable particles. The particle size may vary, for example, within a range from about 0.1 micrometers and about 10.0 micrometers. In other embodiments, diffusive layer 300 may include an anti-glare pattern. The anti-glare pattern may be formed of a layer of polymer beads or may be etched.

[0055] Diffusive layer 300 can be engineered to adjust the ratio of light scattered by the diffusive layer 300 to the total light incident to the diffusive layer 300. For example, diffusive layer 300 may comprise a coating or layer of a specific material or materials, having a specific thickness, scattering particle size, and/or scattering particle load designed to achieve a desired ratio of scattered light to incident light. For example, a diffusive layer or coating having a thickness of less than or equal to about 500 nanometers comprising TiCh scattering particles having a median diameter of about 200 nanometers within a binder (e.g., acrylate, etc.) can be engineered to adjust the ratio of scattered light to incident light by tuning the scattering particle load within the binder.

[0056] In certain exemplary embodiments, transparent layer 400 has an optical transmittance of greater than about 30 percent, such as greater than about 50 percent, and further such as greater than about 70 percent, including from about 30 percent to about 99 percent, and further including from about 50 percent to about 95 percent over a length of 500 millimeters in the visible region of the spectrum (about 420-750 nanometers). In certain exemplary embodiments, transparent layer 400 may have an optical transmittance of greater than about 50 percent, such as from about 50 percent to about 90 percent, in the ultraviolet (UV) region of the spectrum (about 100-400 nanometers) over a length of 500 millimeters.

[0057] The optical properties of the transparent layer 400 may be affected by the refractive index of the material or materials from which it is comprised. In certain exemplary embodiments, transparent layer 400 may have a refractive index ranging from about 1.3 to about 1.8. In other embodiments, transparent layer 400 may have a relatively low level of light attenuation (e.g., due to absorption and/or scattering). The light attenuation of transparent layer 400 may, for example, be less than about 5 decibels per meter for wavelengths ranging from about 420 to about 750 nanometers.

[0058] While not limited to any particular material or materials, in certain exemplary embodiments, transparent layer 400 may comprise one or more polymeric materials, such as plastics (e.g., polymethyl methacrylate (PMMA), methylmethacrylate styrene (MS), polydimethylsiloxane (PDMS)), polycarbonate (PC), or other similar materials. Transparent layer 400 may also comprise one or more glass materials, such as aluminosilicate, alkalialuminosilicate, borosilicate, alkali-borosilicate, aluminoborosilicate, alkali- aluminoborosilicate, soda lime, or other suitable glasses. Non-limiting examples of commercially available glasses suitable for use as a transparent layer 400 include EAGLE XG®, Lotus™, Willow®, Iris™, and Gorilla® glasses from Corning Incorporated.

[0059] Embodiments disclosed herein include those in which reflector 200 is configured to reflect at least about 60%, such as at least about 70%, and further such as at least about 80%, including from about 60% to about 99%, such as from about 70% to about 95% of the incident peak intensity ray and transmit at least about 60%, such as at least about 75%, and further such as a least about 85%, including from about 60% to 99%, such as from about 75% to about 98% of incident low intensity rays emitted from the light source(s) 102, each SP20-324 incident low intensity ray extending along an axis oriented at an angle relative to the perpendicular direction (P) and emitting a total incident light intensity that is less than about 25% of the total incident light intensity of the peak intensity ray. [0060] In certain exemplary embodiments, the peak intensity wavelength (λ_peak) emitted from light source(s) 102 is in the visible region of the spectrum (between about 420 and about 750 nanometers). In certain exemplary embodiments, such as the embodiments illustrated in FIGS.1-5, the peak intensity wavelength (λ_peak) emitted from light source(s) 102 is in a range of from about 440 to about 500 nanometers, such as from about 450 to about 480 nanometers. [0061] In certain exemplary embodiments, the one or more light sources 102 emit a band of light comprising a half peak intensity wavelength width (FWHM) and: λ₁= λ_peak - FWHM; λ₂= λ_peak + FWHM; and λ₃= λ_peak + 3×FWHM. [0062] In such embodiments, the reflector 200 may comprise a reflectivity comprising an average total reflectance of wavelengths between λ₁ and λ₂ that is greater than an average total reflectance of wavelengths between λ₂ and λ₃, such as an average total reflectance of wavelengths between λ₁ and λ₂ that is at least about two times the average total reflectance of wavelengths between λ₂ and λ₃, and yet further such as an average total reflectance of wavelengths between λ₁ and λ₂ that is at least about three times the average total reflectance of wavelengths between λ₂ and λ₃, and still yet further such as an average total reflectance of wavelengths between λ₁ and λ₂ that is at least about four times the average total reflectance of wavelengths between λ₂ and λ₃. [0063] Alternatively stated, in certain exemplary embodiments, the reflector 200 may comprise a transmissivity comprising an average total transmissivity of wavelengths between λ₂ and λ₃ that is greater than an average total transmissivity of wavelengths between λ₁ and λ₂, such as an average total transmissivity of wavelengths between λ₂ and λ₃ that is at least about two times the average total transmissivity of wavelengths between λ₁ and λ₂, and yet further such as an average total transmissivity of wavelengths between λ₂ and λ₃ that is at least about three times the average total transmissivity of wavelengths between λ₁ and λ₂, and still yet further such as an average total transmissivity of wavelengths between λ₂ and λ₃ that is at least about four times the average total transmissivity of wavelengths between λ₁ and λ₂. [0064] In certain exemplary embodiments, λ₁ may, for example, range from about 400 nanometers to about 480 nanometers, λ₂ may, for example, range from about 450 nanometers to about 530 nanometers, and λ₃ may, for example, range from about 480 nanometers to about 10 660 nanometers. In certain exemplary embodiments, half peak intensity wavelength width (FWHM) may, for example, range from about 10 nanometers to about 100 nanometers, such as from about 20 nanometers to about 80 nanometers, and further such as from about 30 nanometers to about 60 nanometers.

[0065] FIG. 7 is a chart showing average transmittance (line ‘B’) of an exemplary reflector 200 and light band intensity (line ‘A’) of an optically coupled light source 102, specifically an optically coupled LED, as a function of wavelength. As shown in FIG. 7, the average transmittance of wavelengths between 2 and fa is at least about four times the average transmittance of wavelengths between i and fa. Alternatively stated, the average reflectance of wavelengths between i and fa is at least about four times the average reflectance of wavelengths between fa and fa.

[0066] FIG. 8 is a chart showing average transmittance of an exemplary reflector 200 at different incident angles and light band intensity of a light source 102, specifically an LED, as a function of wavelength. The LED emits a generally Lambertian emission pattern, such as the emission pattern illustrated in FIG. 2, wherein the incident peak intensity ray extends along an axis that is approximately normal to the observation plane (OP) or, in other words, extends along an axis oriented at an angle (0) of about 0° relative to the perpendicular direction (P).

[0067] In addition, as shown by line ‘A’ in FIG. 8, the LED emits a peak intensity wavelength (Apeak) of about 460 nanometers and a half peak intensity wavelength width (FWHM) of about 25 nanometers. The other curved lines in FIG. 8 represent light transmittance through the reflector 200 as a function of wavelength of rays emitted from the LED at different incident angles, specifically angles of about 0° (line ‘G’), 30° (line ‘F’), 45° (line ‘E’), and 60° (line ‘D’), wherein the reflector 200 has an effective refractive index of about 1.7.

[0068] As can be seen from FIG. 8, as the angle of incidence to the reflector 200 decreases, the reflector 200 reflects a greater percentage of the highest intensity wavelengths of the incident light and transmits a lower percentage of the highest intensity wavelengths of the incident light. Alternatively stated, as the angle of incidence to the reflector 200 increases, the reflector 200 transmits a greater percentage of the highest intensity wavelengths of the incident light and reflects a lower percentage of the highest intensity wavelengths of the incident light.

[0069] FIG. 9 shows a chart of total incident light transmittance to an observation plane (OP) as a function of angle of incidence with differing reflector 200 and/or diffusive layer 300 configurations extending between the observation plane (OP) and a light source 102, specifically an LED. The LED emits a generally Lambertian emission pattern, such as the emission pattern illustrated in FIG. 2, wherein the incident peak intensity ray extends along an axis that is approximately normal to the observation plane (OP) or, in other words, extends along an axis oriented at an angle (0) of about 0° relative to the perpendicular direction (P). [0070] The curves shown in FIG. 9 are the results of a modeled simulation corresponding to five different conditions, namely: (1) incident light transmittance to the observation plane (OP) in a configuration with no reflector 200 or diffusive layer 300 between the observation plane (OP) and the LED (line ‘G’); (2) incident light transmittance to the observation plane (OP) in a configuration with an exemplary reflector 200 and exemplary diffusive layer 300 with 0% incident light scattering (line ‘H’); (3) incident light transmittance to the observation plane (OP) in a configuration with the exemplary reflector 200 and exemplary diffusive layer 300 with 25% incident light scattering (line ‘I’); (4) incident light transmittance to the observation plane (OP) in a configuration with the exemplary reflector 200 and exemplary diffusive layer 300 with 50% incident light scattering (line ‘J’); and (5) incident light transmittance to the observation plane (OP) in a configuration with the exemplary reflector 200 and exemplary diffusive layer 300 with 75% incident light scattering (line ‘K’). In each of these conditions, only the first pass of light to the observation plane is accounted for (i.e., light recycling is not considered).

[0071] Specifically, the curves in FIG. 9 were calculated as follows:

[0072] And

[0073] Wherein:

[0074] & is the incident angle of the LED light to the observation plane (OP);

[0075] I( ,@) is the LED intensity at a given wavelength and emission angle;

[0076] Eo(@) is the illuminance of a system without the reflector at a given incident angle; [0077] y is the ratio of scattered light to total incident light to the diffusive layer;

[0078] t(λ,0) is the transmission of the reflector at a given wavelength and incident angle;

[0079] T(λ) is the total transmission rate of the reflector with a Lambertian light input at a given wavelength, wherein the Lambertian light input is from a layer optically coupled to the bottom surface of the reflector, while the reflector’s top surface is adjacent with air; and [0080] E(@,y) is the illuminance of a system with the reflector at a given incident angle with a set y.

[0081] As can be seen from FIG. 9, the presence of exemplary reflector 200 shifts the relative transmission of incident light toward a higher angle of incidence than the normal (i.e., 0°) angle. In addition, the degree of diffusive layer 300 light scattering affects the relative transmission of incident light as a function of wavelength, wherein higher degrees of light scattering result in lower overall transmission as a result of lower transmission between incident angles of about 15° to about 80°.

[0082] In certain exemplary embodiments, reflector 200 can comprise at least two layers of material having different refractive indices. For example, reflector 200 may comprise at least a first layer comprising a material having a first refractive index and at least a second layer comprising a material having a second refractive index that is at least about 0.1 greater, such as at least 0.2 greater, and further such as at least 0.3 greater, and yet further such as at least 0.5 greater, including from about 0.1 to about 1.3 greater, such as from about 0.5 to about 1.0 greater than the first refractive index in the visible wavelength range.

[0083] In certain exemplary embodiments, the first refractive index is no more than about 1.7, such no more than about 1.6, and further such as no more than about 1.5, and yet further such as no more than about 1.4, including from about 1.38 to about 1.7 in the visible wavelength range and the second refractive index is at least about 1.8, such as at least about 2.0, and further such as at least about 2.2, and yet further such as at least about 2.4, including from about 1.8 to about 2.7 in the visible wavelength range.

[0084] In certain exemplary embodiments, first layer comprises at least one material selected from SiCh, MgF2, or AIF3 and the second layer comprises at least one material selected from Nb2Os, TiCh, Ta20s, HfCh, SC2O3, SislS , Si2N2O, or AI3O3N. In certain exemplary embodiments, first layer comprises SiCh and second layer comprises Nb2Os. [0085] In certain exemplary embodiments, reflector 200 comprises a plurality of layers comprising the material having the first refractive index and a plurality of layers comprising the material having the second refractive index wherein at least one of the first plurality of layers is sandwiched between at least one of the second plurality of layers. For example, each of the first and second plurality of layers may comprise at least two layers (for a total of at least four layers), such as at least four layers (for a total of at least eight layers), and further such as at least six layers (for a total of at least twelve layers), and yet further such as at least eight layers (for a total of at least sixteen layers), and still yet further such as at least ten layers (for a total of at least twenty layers). Accordingly, embodiments disclosed herein include those in which first plurality of layers comprises, for example, between two and twenty layers and second plurality of layers comprises, for example, between two and twenty layers.

[0086] The at least two layers of material having different refractive indices may be formed or deposited according to methods known to persons having ordinary skill in the art. For example, the at least two layers of material having different refractive indices may be vapor or otherwise deposited onto each other and/or onto a substrate according to methods disclosed in US patent nos. 9,696,467, 5,882,774, or 6,208,466, the entire disclosures of which are incorporated herein by reference.

[0087] FIG. 6 shows a cross-sectional view of an exemplary reflector 200 comprising a plurality of first layers 200a comprising a material having a first refractive index and a plurality of second layers 200b comprising a material having a second refractive index wherein the second refractive index is at least about 0.1 greater than the first refractive index in the visible wavelength range. Specifically, reflector 200 comprises four first layers 200a comprising a material having a first refractive index and four second layers 200b comprising a material having a second refractive index for a total of eight layers, wherein members of first layers 200a and members of second layers 200b are sandwiched between each other in an alternating configuration.

[0088] Examples

[0089] Embodiments of the disclosure are further illustrated by the following non-limiting examples.

[0090] Example 1

[0091] A simulated reflector designed to be optically coupled to an LED having a Lambertian emission pattern with a maximum incident intensity angle of 0° and a maximum intensity wavelength of about 450 nanometers was designed using simulation software available from OptiLayer. The reflector was simulated to include eight layers of alternating materials having first and second refractive indices, wherein the material having a first refractive index was modeled to comprise SiCh, and the material having the second refractive index was modeled to comprise Nb₂O5. Specifically, the simulated reflector was modeled as set forth in Table 1 :

Table 1

[0092] The total reflectance (line ‘M’) and transmittance (line ‘L’) of the simulated reflector as a function of angle of incidence of the optically coupled LED is shown in FIG. 10. As can be seen from FIG. 10, the simulated reflector reflects more than 75% of the incident light at the normal (i.e., 0°) angle and transmits more than 85% of the incident light at angles of greater than about 25°.

[0093] Example 2

[0094] A simulated reflector designed to be optically coupled to an LED having a Lambertian emission pattern with a maximum incident intensity angle of 0° and a maximum intensity wavelength of about 450 nanometers was designed using simulation software available from OptiLayer. The reflector was simulated to include twenty layers of alternating materials having first and second refractive indices, wherein the material having a first refractive index was modeled to comprise SiO₂, and the material having the second refractive index was modeled to comprise Nb₂Os. Specifically, the simulated reflector was modeled as set forth in Table 2:

Table 2

[0095] The total reflectance (line ‘O’) and transmittance (line ‘N’) of the simulated reflector as a function of angle of incidence of the optically coupled LED is shown in FIG.

11. As can be seen from FIG. 11, the simulated reflector reflects more than 90% of the incident light at the normal (i.e., 0°) angle and transmits more than 95% of the incident light at angles of greater than about 20°.

[0096] Example 3

[0097] A simulated reflector designed to be optically coupled to an LED having a wide angle emission pattern with a maximum incident intensity angle of about 45° and a maximum intensity wavelength of about 450 nanometers was designed using simulation software available from OptiLayer. The reflector was simulated to include eight layers of alternating materials having first and second refractive indices, wherein the material having a first refractive index was modeled to comprise SiO₂, and the material having the second refractive index was modeled to comprise Nb₂Os. Specifically, the simulated reflector was modeled as set forth in Table 3:

Table 3

[0098] The total reflectance (line ‘Q’) and transmittance (line ‘P’) of the simulated reflector as a function of angle of incidence of the optically coupled LED is shown in FIG. 12. As can be seen from FIG. 12, the simulated reflector reflects more than 80% of the incident light at the maximum incident angle (i.e. 45°) and transmits more than 85% of the incident light at angles of less than about 30°.

[0099] Example 4 [00100] A simulated reflector designed to be optically coupled to an LED having a wide angle emission pattern with a maximum incident intensity angle of about 45° and a maximum intensity wavelength of about 450 nanometers was designed using simulation software available from OptiLayer. The reflector was simulated to include twenty-five layers of alternating materials having first and second refractive indices, wherein the material having a first refractive index was modeled to comprise SiO₂, and the material having the second refractive index was modeled to comprise Nb₂Os. Specifically, the simulated reflector was modeled as set forth in Table 4:

Table 4

[00101] The total reflectance (line ‘S’) and transmittance (line ‘R’) of the simulated reflector as a function of angle of incidence of the optically coupled LED is shown in FIG. 13. As can be seen from FIG. 13, the simulated reflector reflects more than 90% of the incident light at the maximum incident angle (i.e. 45°) and transmits more than 95% of the incident light at angles of less than about 30°. [00102] Embodiments disclosed herein include those in which backlight includes additional optical films above the reflector. For example, the backlight may include at least one diffuser plate, diffuser sheet, prism film, down converting film, quantum dot film, and/or reflective polarizer. Such can, for example, enable light rays emitted from the reflector to be oriented in desired directions.

[00103] Embodiments disclosed herein can, for example, enable thin direct-lit backlights with improved dynamic range and light uniformity without the necessity of precise alignment between patterned layers and light sources.

[00104] It will be apparent to those skilled in the art that various modifications and variations can be made to embodiment 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

What is claimed is:

1. A reflector comprising: a first major surface, a second major surface, and a thickness extending in a perpendicular direction to the first major surface and the second major surface; the reflector configured to be optically coupled with a light source that emits a peak intensity wavelength ( peak) and an incident peak intensity ray, the incident peak intensity ray extending along an axis oriented at an angle (9) relative to the perpendicular direction; and the reflector configured to reflect at least about 60% of the incident peak intensity ray and transmit at least about 60% of incident low intensity rays emitted from the light source, each incident low intensity ray extending along an axis oriented at an angle relative to the perpendicular direction and emitting a total incident light intensity that is less than about 25% of a total incident light intensity of the peak intensity ray.

2. The reflector of claim 1, wherein the light source emits a band of light comprising a half peak intensity wavelength width (FWHM) and: ki= Apeak - FWHM;

^2= Apeak + FWHM; and

Xpeak + 3*FWHM; and the reflector comprises a reflectivity comprising an average total reflectance of wavelengths between i and 2 that is greater than an average total reflectance of wavelengths between 2 and 3.

3. The reflector of claim 2, wherein the reflector comprises a reflectivity comprising an average total reflectance of wavelengths between i and fa that is at least about two times the average total reflectance of wavelengths between fa and fa. reflector of claim 1, wherein the incident peak intensity ray extends along an axis oriented at an angle (9) ranging from about -20° to about 20° relative to the perpendicular direction. reflector of claim 1, wherein the incident peak intensity ray extends along an axis oriented at an angle (9) ranging from about -69° to about -29° or from about 29° to about 69° relative to the perpendicular direction. reflector of claim 1, wherein the reflector comprises at least a first layer comprising a material having a first refractive index and at least a second layer comprising a material having a second refractive index that is at least about 9.1 greater than the first refractive index in the visible wavelength range. reflector of claim 6, wherein the reflector comprises a plurality of layers comprising the material having the first refractive index and a plurality of layers comprising the material having the second refractive index wherein at least one of the first plurality of layers is sandwiched between at least one of the second plurality of layers. reflector of claim 6, wherein the first refractive index no more than about

1.7 in the visible wavelength range and the second refractive index is at least about 1.8 in the visible wavelength range. reflector of claim 6, wherein the first layer comprises at least one material selected from Sit , MgF2, or AIF3 and the second layer comprises at least one material selected from Nb2Os, TiCh, Ta2Os, HfCh, SC2O3, SislSh, S12N₂O, or AI3O3N. reflector of claim 1, wherein the thickness extends a distance in the perpendicular direction ranging from about 1 micron to about 4 microns. acklight comprising: a reflector comprising a first major surface, a second major surface, and a thickness extending in a perpendicular direction to the first major surface and the second major surface; a substrate; and a plurality of light sources proximate the substrate, each light source configured to emit a peak intensity wavelength (Apeak) and an incident peak intensity ray, the incident peak intensity ray extending along an axis oriented at an angle (9) relative to the perpendicular direction; and the reflector configured to reflect at least about 60% of the incident peak intensity ray and transmit at least about 60% of incident low intensity rays emitted from the light source, each incident low intensity ray extending along an axis oriented at an angle relative to the perpendicular direction and emitting a total incident light intensity that is less than about 25% of a total incident light intensity of the peak intensity ray. The backlight of claim 11 wherein the light source is configured to emit a band of light comprising a half peak intensity wavelength width (FWHM) and: ki= Apeak - FWHM;

^2= Apeak + FWHM; and

Xpeak + 3*FWHM; and the reflector comprises a reflectivity comprising an average total reflectance of wavelengths between i and 2 that is greater than an average total reflectance of wavelengths between 2 and 3. The backlight of claim 12, wherein the reflector comprises a reflectivity comprising an average total reflectance of wavelengths between i and fa that is at least about two times the average total reflectance of wavelengths between fa and fa. The backlight of claim 11, wherein the incident peak intensity ray extends along an axis oriented at an angle (9) ranging from about -29° to about 29° relative to the perpendicular direction. backlight of claim 11, wherein the incident peak intensity ray extends along an axis oriented at an angle (9) ranging from about -60° to about - 20° or from about 20° to about 60° relative to the perpendicular direction. backlight of claim 11, wherein the backlight further comprises at least one diffusive layer extending proximate to at least one of the first major surface and the second major surface of the reflector. backlight of claim 16, wherein the diffusive layer comprises a spatially varying transmittance. backlight of claim 16, wherein the backlight further comprises a transparent layer extending between the substrate and the at least one diffusive layer. ethod of making the reflector of claim 6 comprising depositing at least one of the first layer onto at least one of the second layer. method of claim 19, wherein the depositing comprises vapor deposition of at least one of the first layer onto at least one of the second layer. ethod of making the backlight of claim 11 comprising assembling the reflector, the substrate, and the plurality of light sources. electronic device comprising the backlight of claim 11.

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