Optical system, light control film, and method of manufacturing light control film

Abstract

A light control film includes alternating transmissive regions and absorbing regions extending along a same in-plane first direction and arranged along an orthogonal in-plane second direction. The light control film further includes a light absorbing material disposed in each of the absorbing regions. The light absorbing material includes a plurality of particles dispersed in a matrix. Each of the plurality of particles has an outer layer including nanostructures.

Description

PA102788W002OPTICAL SYSTEM, LIGHT CONTROL FILM, AND METHOD OF MANUFACTURING LIGHT CONTROL FILMTechnical Field

[0001] The present disclosure relates to an optical system and a light control film. The present disclosure further relates to a method of manufacturing the light control film.Background

[0002] Light control films (LCF) are configured to regulate the transmission of light. LCFs typically include a light transmissive film having a plurality of light absorbing portions that includes a light-absorbing material. LCFs can be placed proximate a surface, such as a display surface, an image surface, or any other surface including an image to be viewed. As a viewing angle increases, an amount of light transmitted through the LCF decreases until a viewing cutoff angle is reached where substantially all the light is blocked by the light- absorbing material and the image displayed on the surface is no longer viewable. This can provide privacy (e.g., for laptops, ATM) to a viewer by blocking observation by others that are outside a typical range of viewing angles or safety (e.g., for windshield light reflection mitigation in cars).Summary

[0003] In a first aspect, the present disclosure provides a light control film. The light control film includes alternating transmissive regions and absorbing regions extending along a same in-plane first direction and arranged along an orthogonal in-plane second direction. The light control film further includes a light absorbing material disposed in each of the absorbing regions. The light absorbing material includes a plurality of particles dispersed in a matrix. Each of the plurality of particles has an outer layer including nanostructures.

[0004] In a second aspect, the present disclosure provides an optical system. The optical system includes a transparent display configured to emit an image for viewing by a viewer facing a first side of the transparent display. The optical system further includes a light control film (LCF) disposed on a second side of the transparent display opposite to the first side. The LCF includes alternating transmissive regions and absorbing regions extending along a same in-plane first direction and arranged along an orthogonal in-plane second direction. Each transmissive region has a first refractive index. The LCF further includes a light absorbing material disposed in each of the absorbing regions. The light absorbing material includes a plurality of particles dispersed in a matrix. The matrix has a second refractive index. A ratio between the first refractive index and the second refractive index is from about 0.99 to about 1.01. The viewer is configured to view an object located on the second side of the transparent display in a real-world scene through the transparent display andthe LCF. For a substantially collimated light from the second side incident at an oblique incident angle greater than about 2 degrees, and for a polar angle range PAR from about 0 to about 80 degrees, an optical luminance distribution of an exiting light from the LCF has a maximum optical luminance at a first polar angle PA, a metric 1 - (sum(PA ± 4 degrees) / sum(PAR)) is greater than about 0.25. Where, sum(PA ± 4 degrees) is a sum of positive optical luminances of PA ± 4 degrees and sum(PAR) is a sum of positive optical luminances of the polar angle range PAR.

[0005] In a third aspect, the present disclosure provides a method of manufacturing a light control film. The method includes providing a plurality of initial particles. Each of the initial particles includes an outer surface. The method further includes forming a plurality of particles by depositing an aluminum alloy using a vacuum reactive sputtering process. An outer layer including nanostructures is substantially disposed on the outer surface of each of the initial particles. The method further includes forming a light absorbing material by dispersing the plurality of particles in a matrix.

[0006] In a fourth aspect, the present disclosure provides an optical system. The optical system includes an optical waveguide. The optical waveguide includes an optical core configured to propagate an image light therealong. The optical waveguide further includes optical gratings disposed on the optical core. The optical gratings are configured to receive an image light emitted by an image projector and inject at least a portion of the received image light into the optical core, and extract at least a portion of the injected image light from the optical core for viewing by a viewer facing a first side of the optical waveguide. The optical system further includes a light control film (LCF) disposed on a second side of the optical waveguide opposite to the first side. The LCF includes alternating transmissive regions and absorbing regions extending along a same in-plane first direction and arranged along an orthogonal in-plane second direction. Each transmissive region has a first refractive index. The LCF further includes a light absorbing material disposed in each of the absorbing regions. The light absorbing material includes a plurality of particles dispersed in a matrix. The matrix has a second refractive index. A ratio between the first refractive index and the second refractive index is from about 0.99 to about 1.01. The viewer is configured to view an object located on the second side of the optical waveguide in a real-world scene through the optical waveguide and the LCF. For a substantially collimated light from the second side incident at an oblique incident angle greater than about 2 degrees, and for the polar angle range PAR from about 0 to about 80 degrees, an optical luminance distribution of an exiting light from the LCF has a maximum optical luminance at a first polar angle PA, a metric 1 - (sum(PA ± 4 degrees) / sum(PAR)) is greater than about 0.25. Where, sum(PA ± 4 degrees) is a sum of positive optical luminances of PA ± 4 degrees and sum(PAR) is a sum of positive optical luminances of the polar angle range PAR.

[0007] The details of one or more examples of the disclosure are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the disclosure will be apparent from the description and drawings, and from the claims.Brief Description of Drawings

[0008] Exemplary embodiments disclosed herein are more completely understood in consideration of the following detailed description in connection with the following figures. The figures are not necessarily drawn to scale. Like numbers used in the figures refer to like components. However, it will be understood that the use of a number to refer to a component in a given figure is not intended to limit the component in another figure labelled with the same number.

[0009] FIG. 1 illustrates a schematic sectional view of a light control film, according to an embodiment of the present disclosure;

[0010] FIG. 2A illustrates a schematic sectional view of a portion of the light control film including one of transmissive regions and adjacent absorbing regions, according to an embodiment of the present disclosure;

[0011] FIG. 2B illustrates a schematic magnified view of a light absorbing material, according to an embodiment of the present disclosure;

[0012] FIG. 3 illustrates a schematic sectional view of one of particles of the light absorbing material, according to an embodiment of the present disclosure;

[0013] FIG. 4 illustrates a schematic view of an optical system including a transparent display, according to an embodiment of the present disclosure;

[0014] FIG. 5 illustrates a schematic view of an optical system including an optical waveguide, according to an embodiment of the present disclosure;

[0015] FIGS. 6A and 6B illustrate exemplary graphs depicting an optical luminance as a function of polar angle for a substantially collimated light and for different oblique incident angles;

[0016] FIG. 7 illustrates a flowchart depicting a method of manufacturing a light control film, according to an embodiment of the present disclosure;

[0017] FIGS. 8A, 8B, 8C, 8D, and 8E show schematic views of steps of the method of manufacturing the light control film, according to different embodiments of the present disclosure;

[0018] FIG. 9A illustrates the light control film and an on-axis collimated light incident on the light control film, according to an embodiment of the present disclosure;

[0019] FIG. 9B illustrates the light control film and an off-axis collimated light incident on the light control film, according to an embodiment of the present disclosure;

[0020] FIGS. 10 A, 10B, and 10C show exemplary conoplots for a comparative light control film and different light control films when an incident angle is of about 5 degrees;

[0021] FIGS. 11A, 11B, and 11C show exemplary conoplots for the comparative light control film and the different light control films when the incident angle is of about 10 degrees;

[0022] FIGS. 12 A, 12B, and 12C show exemplary conoplots for the comparative light control film and the different light control films when the incident angle is of about 15 degrees; and

[0023] FIGS. 13 A and 13B show exemplary conoplots for the comparative light control film and the light control film when the incident angle is of about 20 degrees.Detailed Description

[0024] In the following description, reference is made to the accompanying figures that form a part thereof and in which various embodiments are shown by way of illustration. It is to be understood that other embodiments are contemplated and may be made without departing from the scope or spirit of the present disclosure. The following detailed description, therefore, is not to be taken in a limiting sense.

[0025] In the following disclosure, the following definitions are adopted.

[0026] As used herein, “a,” “an,” “the,” “at least one,” and “one or more” are used interchangeably.

[0027] As used herein as a modifier to a property or attribute, the term “generally,” unless otherwise specifically defined, means that the property or attribute would be readily recognizable by a person of ordinary skill but without requiring absolute precision or a perfect match (e.g., within + / - 20 % for quantifiable properties).

[0028] The term “substantially,” unless otherwise specifically defined, means to a high degree of approximation (e.g., within + / - 10% for quantifiable properties) but again without requiring absolute precision or a perfect match.

[0029] As used herein, all numbers should be considered modified by the term “about.” The term “about,” unless otherwise specifically defined, means to a high degree of approximation (e.g., within + / - 5% for quantifiable properties) but again without requiring absolute precision or a perfect match.

[0030] As used herein, the terms “first” and “second” are used as identifiers. Therefore, such terms should not be construed as limiting of this disclosure. The terms “first” and “second” when used in conjunction with a feature or an element can be interchanged throughout the embodiments of this disclosure.

[0031] As used herein, when a first material is termed as “similar” to a second material, at least 90 weight % of the first and second materials are identical and any variation between the first and second materials comprises less than about 10 weight % of each of the first and second materials.

[0032] As used herein, “at least one of A and B” should be understood to mean “only A, only B, or both A and B.”

[0033] As used herein, the term “between about,” unless otherwise specifically defined, generally refers to an inclusive or a closed range. For example, if a parameter X is between about A and B, then A < X < B.

[0034] Light control films (LCF) are configured to regulate the transmission of light. LCFs typically include a light transmissive film having a plurality of light absorbing portions that includes a light-absorbing material. LCFs can be placed proximate a surface, such as a display surface, an image surface, or any other surface including an image to be viewed. As a viewing angle increases, an amount of light transmitted through the LCF decreases until a viewing cutoff angle is reached where substantially all the light is blocked by the light- absorbing material and the image displayed on the surface is no longer viewable. This can provide privacy (e.g., for laptops, ATM) to a viewer by blocking observation by others that are outside a typical range of viewing angles or safety (e.g., for windshield light reflection mitigation in cars).

[0035] However, periodic nature of the light absorbing portions can diffract light and create ghost images. Further, reflections from sidewalls of the light absorbing portions may also create the ghost images.

[0036] In some applications where a spacing between the LCF and objects that users look at is large, the ghost images become objectionable. This may be because a spatial spacing between the ghost images and the image also becomes large when projected on the retina. These applications may include the LCF in front of see-thru augmented reality glasses to absorb high angle ambient light, the LCF in front of see-thru transparent displays, or the LCF on top of augmented reality waveguides in automotive HUDs to absorb high angle sunlight. Thus, there exists a need for an LCF with low diffraction and low sidewall reflections.

[0037] The present disclosure relates to a light control film. The light control film includes alternating transmissive regions and absorbing regions extending along a same in-plane first direction and arranged along an orthogonal in-plane second direction. The light control film further includes a light absorbing material disposed in each of the absorbing regions. The light absorbing material includes a plurality of particles dispersed in a matrix. Each of the plurality of particles has an outer layer including nanostructures.

[0038] The light control film of the present disclosure includes a light absorbing material including a plurality of particles. The particles may act like an embedded anti-glare surface to diffusively reflect any incident light besides absorption. Moreover, the nanostructures on the particles may further reduce reflections from sidewalls of the absorbing regions.

[0039] Referring now to the figures, FIG. 1 illustrates a schematic sectional view of a light control film (LCF) 100, according to an embodiment of the present disclosure.

[0040] The LCF 100 defines mutually orthogonal x, y, and z-axes. The x-axis is defined along a length of the LCF 100, while the y-axis is defined along a width of the LCF 100. The z-axis is defined along a thickness of the LCF 100.

[0041] The LCF 100 includes alternating transmissive regions 102 and absorbing regions 104 extending along a same in-plane first direction and arranged along an orthogonal in-plane second direction. In the illustrated embodiment of FIG. 1, the first direction is substantially along the y-axisand the second direction is substantially along the x-axis. Thus, the alternating transmissive regions 102 and the absorbing regions 104 extend along the y-axis and are arranged along the x-axis.

[0042] FIG. 2 A illustrates a schematic sectional view of a portion of the LCF 100 including one of the transmissive regions 102 and adjacent absorbing regions from the absorbing regions 104, according to an embodiment of the present disclosure. As shown, the LCF 100 further includes a light absorbing material 106 disposed in each of the absorbing regions 104.

[0043] FIG. 2B illustrates a schematic magnified view of the light absorbing material 106, according to an embodiment of the present disclosure.

[0044] The light absorbing material 106 includes a plurality of particles 108 dispersed in a matrix 110. In some embodiments, at least one of the particles 108 includes a polymeric bead. In some embodiments, the polymeric bead includes a cross-linked polymer. In some embodiments, the crosslinked polymer includes polystyrene. In some embodiments, the cross-linked polymer includes polymethyl methacrylate (PMMA).

[0045] In some embodiments, the at least one of the particles 108 includes a glass bead. In some embodiments, the at least one of the particles 108 includes at least one of a carbon black and a visible light absorbing dye. The particles 108 may diffusively reflect incident light, thereby may reduce reflections due to sidewalls of the absorbing regions 104.

[0046] Further, in some embodiments, each transmissive region 102 has a first refractive index and the matrix 110 has a second refractive index. In some embodiments, a ratio between the first refractive index and the second refractive index is from about 0.99 to about 1.01. In some embodiments, each of the transmissive regions 102 and the matrix 110 have a same composition. In such embodiments, the ratio between the first refractive index and the second refractive index may be equal to about 1. A very small or no difference between the first refractive index and the second refractive index may provide smooth optical interfaces and may reduce specular reflections. This may further reduce the reflections due to the sidewalls of the absorbing regions 104.

[0047] In some embodiments, the first refractive index is equal to or greater than about 1.48. In some embodiments, the first refractive index is greater than about 1.49, greater than about 1.49, or greater than about 1.5.

[0048] FIG. 3 illustrates a schematic sectional view of one of the particles 108, according to an embodiment of the present disclosure.

[0049] In some embodiments, each of the plurality of particles 108 has an outer layer 112. In some embodiments, the outer layer 112 includes a metal or a metal compound. In some embodiments, the metal compound includes at least one of an aluminum oxide, a copper oxide, and a stainless steel.

[0050] In some embodiments, each of the plurality of particles 108 includes an initial particle 118 including an outer surface 116, and the outer layer 112 disposed on the outer surface 116.

[0051] In some embodiments, an average diameter d of each of the particles 108 is greater than about 1 micrometer. In some embodiments, the average diameter d of each of the particles 108 is greater than about 200 nanometers (nm). In some embodiments, the average diameter d of each of the particles 108 is greater than about 250 nm, greater than about 300 nm, greater than about 350 nm, greater than about 400 nm, greater than about 450 nm, greater than about 500 nm, greater than about 550 nm, greater than about 600 nm, greater than about 650 nm, greater than about 700 nm, greater than about 750 nm, greater than about 800 nm, greater than about 850 nm, greater than about 900 nm, or greater than about 950 nm.

[0052] As shown in FIG. 3, in some embodiments, each of the plurality of particles 108 has the outer layer 112 including nanostructures 114. The outer layer 112 including the nanostructures 114 may further reduce the reflections due to the sidewalls of the absorbing regions 104.

[0053] FIG. 4 illustrates a schematic view of an optical system 200 including a transparent display 202, according to an embodiment of the present disclosure.

[0054] The transparent display 202 is configured to emit an image 204 for viewing by a viewer 206 facing a first side 202a of the transparent display 202. The optical system 200 further includes the LCF 100 disposed on a second side 202b of the transparent display 202 opposite to the first side 202a.

[0055] The viewer 206 is configured to view an object 208 located on the second side 202b of the transparent display 202 in a real- world scene 210 through the optical system 200. Specifically, the viewer 206 is configured to view the object 208 located on the second side 202b of the transparent display 202 in the real-world scene 210 through the transparent display 202 and the LCF 100.

[0056] In some embodiments, a distance 1 between the object 208 and the LCF 100 is greater than about 0.5 meters. In some embodiments, the distance 1 between the object 208 and the LCF 100 is greater than about 1 meter, greater than about 1.5 meters, greater than about 2 meters, greater than about 2.5 meters, greater than about 3 meters, greater than about 3.5 meters, greater than about 4 meters, greater than about 4.5 meters, or greater than about 5 meters.

[0057] FIG. 5 illustrates a schematic view of an optical system 600 including an optical waveguide 602, according to an embodiment of the present disclosure.

[0058] The optical waveguide 602 includes an optical core 604 configured to propagate an image light 606 therealong. The optical waveguide 602 further includes optical gratings 608 disposed on the optical core 604. The optical gratings 608 are configured to receive the image light 606 emitted by an image projector 610. The optical gratings 608 are further configured to inject at least a portion of the received image light 612 into the optical core 604. The optical gratings 608 are further configured to extract at least a portion of the injected image light 614 from the optical core 604 for viewing by the viewer 206 facing a first side 602a of the optical waveguide 602. As illustrated in FIG. 5, the portion of the injected image light 614 extracted from the optical gratings 608 is depicted as an extractedimage light 616. The optical system 600 further includes the LCF 100 disposed on a second side 602b of the optical waveguide 602 opposite to the first side 602a.

[0059] The viewer 206 is configured to view the object 208 located on the second side 602b of the optical waveguide 602 in the real-world scene 210 through the optical system 600. Specifically, the viewer 206 is configured to view the object 208 located on the second side 602b of the optical waveguide 602 in the real-world scene 210 through the optical waveguide 602 and the LCF 100.

[0060] FIGS. 4 and 5 further illustrate a substantially collimated light 212 from the second side 202b, 602b incident at an oblique incident angle al greater than about 2 degrees on the LCF 100 and an exiting light 214 from the LCF 100.

[0061] FIGS. 6A and 6B illustrate respective exemplary graphs 500, 700 depicting an optical luminance as a function of polar angle for the substantially collimated light 212 (shown in FIGS. 4 and 5) and for different oblique incident angles (e.g., the oblique incident angle al).

[0062] The polar angle is expressed in degrees (deg) in the abscissa. The optical luminance is expressed in the ordinate.

[0063] The exemplary graph 500 of FIG. 6Aincludes curves 31, 32, 33.

[0064] Referring to FIGS. 1 to 6 A, the curve 31 depicts the optical luminance as the function of the polar angle of the exiting light 214 from a comparative light control film CE when the substantially collimated light 212 from the second side 202b, 602b is incident at the oblique incident angle al of about 5 degrees.

[0065] The curve 32 depicts the optical luminance as the function of the polar angle of the exiting light 214 from the LCF 100 including the light absorbing material 106 which includes the plurality of particles 108 having the outer layer 112 (hereinafter interchangeably referred to as “the LCF EXI”) when the substantially collimated light 212 from the second side 202b, 602b is incident at the oblique incident angle al of about 5 degrees.

[0066] The curve 33 depicts the optical luminance as the function of the polar angle of the exiting light 214 from the LCF 100 including the light absorbing material 106 which includes the plurality of particles 108 having the outer layer 112 with the nanostructures 114 (hereinafter interchangeably referred to as “the LCF EX2”) when the substantially collimated light 212 from the second side 202b, 602b is incident at the oblique incident angle al of about 5 degrees.

[0067] The exemplary graph 700 of FIG. 6B includes curves 34, 35, 36.

[0068] Referring to FIGS. 1 to 6B, the curve 34 depicts the optical luminance as the function of the polar angle of the exiting light 214 from the comparative light control film CE when the substantially collimated light 212 from the second side 202b, 602b is incident at the oblique incident angle al of about 10 degrees.

[0069] The curve 35 depicts the optical luminance as the function of the polar angle of the exiting light 214 from the LCF EXI when the substantially collimated light 212 from the second side 202b, 602b is incident at the oblique incident angle al of about 10 degrees.

[0070] The curve 36 depicts the optical luminance as the function of the polar angle of the exiting light 214 from the LCF EX2 when the substantially collimated light 212 from the second side 202b, 602b is incident at the oblique incident angle al of about 10 degrees.

[0071] As is apparent from the graphs 500, 700, for the LCF 100 (i.e., the LCF EXI and LCF EX2), for the substantially collimated light 212 from the second side 202b incident at the oblique incident angle al greater than about 2 degrees, and for the polar angle range PAR from about 0 to about 80 degrees, an optical luminance distribution of the exiting light 214 from the LCF 100 has a maximum optical luminance at a first polar angle PA.

[0072] Further, for the curves 31, 34 for the comparative light control film CE, the substantially collimated light 212 from the second side 202b incident at the oblique incident angle al greater than about 2 degrees, and for the polar angle range PAR from about 0 to about 80 degrees, an optical luminance distribution of the exiting light 214 from the LCF 100 has a maximum optical luminance at a first polar angle PA’ .

[0073] As shown in the graph 500, for the curves 32, 33, and for the LCF 100, the first polar angles PA are about 0 degree and about 6 degrees, respectively.

[0074] As shown in the graph 700, for the curves 35, 36, and for the LCF 100, the first polar angles PA are about 9 degrees and about 7 degrees, respectively.

[0075] As shown in the graphs 500, 700, for the curves 31, 34, and for comparative light control film CE, the first polar angles PA’ are about 9 degrees.

[0076] Further, a metric 1 - (sum(PA ± 4 degrees) / sum(PAR)) is greater than about 0.25. The sum(PA ± 4 degrees) is a sum of positive optical luminances of PA ± 4 degrees and the sum(PAR) is a sum of positive optical luminances of the polar angle range PAR. A greater value of the metric may indicate a lower reflection of the substantially collimated light 212 from the sidewalls.

[0077] Table 1 provided below lists the metric for the comparative light control film CE, the LCF EXI, and the LCF EX2 for the oblique incident angle al of about 5 degrees and 10 degrees.Table 1

[0078] Referring to FIGS. 4, 5, and the curve 32 of FIG. 6A, in some embodiments, when the incident angle al is about 5 degrees, the metric is greater than about 0.4. For example, when the incident angle al is about 5 degrees, the metric is about 0.490 for the LCF EXI.

[0079] Referring to FIGS. 3, 4, 5, and the curve 33 of FIG. 6A, in some embodiments, when the incident angle al is about 5 degrees, the metric is greater than about 0.5. For example, when the incident angle al is about 5 degrees, the metric is about 0.674 for the LCF EX2.

[0080] Referring to FIGS. 4, 5, and the curve 35 of FIG. 6B, in some embodiments, when the incident angle al is about 10 degrees, the metric is greater than about 0.5. For example, when the incident angle al is about 10 degrees, the metric is about 0.659 for the LCF EXI.

[0081] Referring to FIGS. 3, 4, 5, and the curve 36 of FIG. 6B, in some embodiments, when the incident angle al is about 10 degrees, the metric is greater than about 0.6. In some embodiments, when the incident angle al is about 10 degrees, the metric is about 0.784 for the LCF EX2.

[0082] As is apparent from the graphs 500, 700 and Table 1, for the comparative light control film CE, the metric is less than about 0.2 when the incident angle al is about 5 degrees or 10 degrees.

[0083] FIG. 7 illustrates a flowchart depicting a method 400 of manufacturing an LCF 450, according to an embodiment of the present disclosure.

[0084] At step 402, the method 400 includes providing a plurality of initial particles (e.g., the plurality of initial particles 118 shown in FIG. 3). Each of the initial particles includes an outer surface (e.g., the outer surface 116 shown in FIG. 3).

[0085] At step 404, the method 400 includes forming a plurality of particles (e.g., the plurality of particles 108 shown in FIG. 3) by depositing an aluminum alloy using a vacuum reactive sputtering process. An outer layer (e.g., the outer layer 112 shown in FIG. 3) including nanostructures (e.g., the nanostructures 114 shown in FIG. 3) is substantially disposed on the outer surface of each of the initial particles.

[0086] In some embodiments, the aluminum alloy includes aluminum oxide. In some embodiments, the method 400 further includes mixing the initial particles with fumed silica before depositing the aluminum alloy using the vacuum reactive sputtering process.

[0087] At step 406, the method 400 includes forming a light absorbing material (e.g., the light absorbing material 106 shown in FIGS. 2A and 2B) by dispersing the plurality of particles in a matrix (e.g., the matrix 110 shown in FIG. 2B).

[0088] FIGS. 8A-8E show schematic views of steps of the method 400 of manufacturing the LCF 450, according to different embodiments of the present disclosure.

[0089] Referring to FIG. 8A, in some embodiments, the method 400 further includes providing a microstructured film 420. The microstructured film 420 includes a plurality of light transmissive regions 422 defining a plurality of channels 424 therebetween. In some embodiments, each light transmissive region 422 and the matrix have a same composition. In some embodiments, each light transmissive region 422 has a first refractive index and the matrix has a second refractive index and a ratio between the first refractive index and the second refractive index is from about 0.99 to about 1.01. In some embodiments, the first refractive index is equal to or greater than about 1.48.

[0090] Referring to FIG. 8B, in some embodiments, the method 400 further includes filling each of the plurality of channels 424 with the light absorbing material (e.g., the light absorbing material

[0091] Referring again to FIG. 8A, in some embodiments, the method 400 includes providing the microstructured film 420 including the plurality of light transmissive regions 422 defining the plurality of channels 424 therebetween. The microstructured film 420 has a microstructured surface 426 defined by a top surface 428 and sidewalls 430 of the light transmissive regions 422 and a channel bottom surface 432 of the channels 424.

[0092] Referring to FIG. 8C, in some embodiments, the method 400 further includes applying the light absorbing material 106 to the microstructured surface 426. As shown in FIG. 8C, in some embodiments, applying the light absorbing material (e.g., the light absorbing material 106) includes layer-by-layer self-assembly.

[0093] Referring to FIG. 8D, in some embodiments, the method 400 further includes removing at least a portion of the light absorbing material from the top surface 428 of the light transmissive regions 422 and the channel bottom surface 432 of the channels 424 to form the plurality of light absorbing regions 434. In some embodiments, removing the at least a portion of the light absorbing material includes reactive ion etching.

[0094] Referring to FIG. 8E, in some embodiments, the method 400 further includes filling the channel 424 with a polymeric material. In some embodiments, the polymeric material and the matrix have a same composition. In some embodiments, the polymeric material and each light transmissive region 422 have a same composition.

[0095] The disclosure is further described with reference to the following examples. The examples will be explained with reference to FIGS. 9A-9B to 13A-13B.

[0096] The following examples are intended for illustrative purposes only, since numerous modifications and variations within the scope of the present disclosure will be apparent to those skilled in the art. Unless otherwise noted, all parts, percentages, and ratios reported in the following examples are on a weight basis.

[0097] A list of raw materials is provided in Table 2 provided below.Table 2

[0098] PREPARATION OF CLEAR CHANNEL FILMS FOR THE EXAMPLES

[0099] Microstructured films were prepared as described in Gaides et al. “Light control films” US8213082B2. Microstructured films were made by molding and ultraviolet (UV) light curing a resin mixture on a 5 mil (0.127 millimeter (mm))-thick, primed PET film to give a cured resin having a refractive index of 1.58 in the green at a wavelength of 532 nanometer (nm). For these structured films, a cylindrically shaped metal roll with finely detailed channels cut into its outer surface served as the mold. The resinous mixture was first coated onto the PET substrate film, and then pressed firmly against the metal roll with a slightly heated (40 degrees (°C)) laminator in order to completely fill the mold. Upon UV-curing using UV radiation from a medium pressure mercury vapor “D” bulb (Total UVA dose = 2.2 Joules per square centimeter (J / cm2)) the structured film was removed by peeling from the mold onto the PET substrate. The resulting structure in the cured resin had a constant feature height of 200 micrometer (pm). The feature shape is non-varying: (1) width of narrow end: 17.5 pm; (2) sidewall angle is 1.5 degrees (relative to surface normal). Feature spacing was randomized from 50 pm to 150 pm.

[0100] PREPARATION OF CLEAR CHANNEL FILMS FOR THE COMPARATIVE EXAMPLE

[0101] Microstructured films were prepared as described in Gaides et al. “Light control films” US8213082B2. Microstructured films were made by molding and ultraviolet (UV) light curing a resin mixture on a 5 mil (0.127 mm)-thick, primed PET film to give a cured resin having a refractive index of 1.52 in the green at a wavelength of 532 nm. Relevant resin compositions are described inUS8012567 (Gaides et al.). For these structured films, a cylindrically shaped metal roll with finely detailed channels cut into its outer surface served as the mold. The resinous mixture was heated to about 50°C, coated onto the PET substrate film, and then pressed firmly against the metal roll with a slightly heated (50°C) laminator in order to completely fill the mold. Upon UV-curing using UV radiation from a medium pressure mercury vapor “D” bulb (Total UVA dose = 2.2 J / cm2), the structured film was removed by peeling from the mold onto the PET substrate. The resulting structure in the cured resin had a varying feature height, with an average of 200 pm. The features had a sidewall angle of 1.5 degrees (relative to surface normal) and a varying width. Feature spacing was randomized from 50 pm to 150 pm.

[0102] PREPARATION OF CORE-SHELL BEADS WITH SURFACE NANOSTRUCTURE

[0103] The metallization of particles by a physical vapor deposition method was described in US 20240201509 Al (Gaides et al.). The apparatus and coating method for metal coating of 300 milliliters (mL) volume size of cross-linked polystyrene beads were similar to those described in U.S. Pat. No. 7,727,931 (Brey et al). For 2000 mL volume batches, the particles were coated using a hollow cylinder particle agitator (24.3 centimeter (cm) long x 19.05 cm diameter horizontal) with a rectangular opening (16.51 cm x 13.46 cm) in the top.

[0104] CHEMISNOW SX-130H, a cross-linked polystyrene bead, (commercially available from Soken Chemical and Engineering Co., Ltd, Japan) is reported to have a mean particle size of 1.3 pm (per supplier web site). Wacker HDKH18 fumed silica was mixed into the SX-130H (1% concentration, by weight). The mixed SX-130H beads were introduced into a vacuum chamber equipped with a 1-gallon (3.8 Liters (L)) particle agitator and a 5-inch (12.7 cm) by 12-inch (30.5 centimeter (cm)) by 0.5-inch (1.3 cm) 1100 Aluminum Alloy sputtering target and cathode. During deposition, the particle agitator was operated at about 4 revolutions per minute (rpm). The chamber was pumped down to a base pressure of about 1x10-6 Torr (0.13 millipascal (mPa)). Aluminum was reactively sputtered at a pressure of about 10 millitorr (mTorr) (1.3 pascal (Pa)) using Argon and Oxygen gas (both 99.999% purity). Argon flow rate was 90 standard cubic centimeter per minute (seem) and oxygen flow rate was 15 seem. The aluminum was sputtered up to 4.5 kilowatts for 20 hours to create a thin film coating of an aluminum oxide on the surface of the beads. Longer process times will result in thicker coatings. The coated beads were filtered through a series of sieves and a 400-mesh filter serving as the final filtration.

[0105] PREPARATION OF RESIN LOADED WITH BEADS

[0106] The light absorptive material-containing resin mixture contains 80% by weight of a UV- curable acrylate blend with a photoinitiator (similar to that described in Hunt et al., US9360592B2, Example “R8”), and 20 wt.% of light-absorbing beads. The materials were charged in a polypropylene cup and placed in a speed mixer (DAC 1100.1, FLACKTEK, Landrum, SC) and mixed for 1 minute at 2300 rpm.

[0107] FILLING CHANNELS WITH BEAD-LOADED RESIN

[0108] Light collimating films were made by filling the gaps between the transparent channels of the microstructured film with the light absorptive material-containing resin described above. The resin was warmed to 50°C, and a stainless- steel doctor blade (Alison Systems, Riverside, NJ) was used to scrape material down-web into the exposed microchannels. Excess black-containing resin was wiped from the surfaces of the transparent channels using a clean room cloth. The filled channels were then cured using UV radiation from a medium pressure mercury vapor “D” bulb (total UVA dose = 2.2 J / cm2). The channels were overcoated with another layer of UV-curable resin by laminating the resin against primed PET, followed by another round of UV curing, resulting in a light collimating film.

[0109] PREPARATION OF COATING SOLUTIONS FOR LAYER-BY-LAYER (LBL) COATING

[0110] Two coating solutions were made as follows:

[0111] A CATION solution was made by first adding NaCl to DI water to a concentration of 200 millimolar (mM), then adding SANCURE 20072 to a concentration of 1% solids, and PLURONIC L- 92 to a concentration of 0.1% solids.

[0112] An ANION solution was made by first adding NaCl to DI water to a concentration of 50 mM, then adding JONCRYL2980 to a concentration of 2% solids, then adding EXPBCB to a concentration of 0.05% solids, and finally PLURONIC L-92 to a concentration of 0.1% solids.

[0113] METHOD FOR LAYER-BY-LAYER (LBL) COATING

[0114] LbL coatings were deposited using an apparatus purchased from Svaya Nanotechnologies, Inc. (Sunnyvale, CA) and modeled after the system described in US 8,234,998 (Krogman et al.) as well as Krogman et al. Automated Process for Improved Uniformity and Versatility of Layer-by-Layer Deposition, Langmuir 2007, 23, 3137-3141. The apparatus comprises pressure vessels loaded with the coating solutions. Spray nozzles with a flat spray pattern (from Spraying Systems, Inc., Wheaton, IL) were mounted to spray the coating solutions and rinse water at specified times, controlled by solenoid valves. The pressure vessels (Alloy Products Corp., Waukesha, WI) containing the coating solutions were pressurized with nitrogen to 30 pounds per square inch (psi) (207 kilopascal (kPa)), while the pressure vessel containing deionized (DI) water was pressurized with air to 30 psi (207 kPa). Flow rates from the coating solution nozzles were each 10 gallons (38 L) per hour, while flow rate from the DI water rinse nozzles were 40 gallons (150 L) per hour. The substrate to be coated (10”xl0” (25 cm x 25 cm)) was adhered at the edges with epoxy (Scotch- Weld epoxy adhesive, DP100 Clear, 3M Company, St. Paul, MN) to a glass plate (12” (30 cm) x 12” (30 cm) x 1 / 8” (0.3 cm) thick) (Brin Northwestern Glass Co., Minneapolis, MN). The surface of the film was then corona treated using a BD-20AC Laboratory Corona Treater (ElectroTechnic Products, Chicago, Illinois), and the plate was then mounted on a vertical translation stage and held in place with a vacuum chuck. In a typical coating sequence, the CATION solution was sprayed onto the substrate while the stage moved vertically downward at 76 milimeter per second(mm / sec). Next, after a dwell time of 12 second (sec), DI water was sprayed onto the substrate while the stage moved vertically upward at 102 mm / sec. The substrate was then dried with an airknife at a speed of 10 mm / sec. Next, the ANION solution was sprayed onto the substrate while the stage moved vertically downward at 76 mm / sec. Another dwell period of 12 sec was allowed to elapse. DI water was sprayed onto the substrate while the stage moved vertically upward at 102 mm / sec. Next, the substrate was dried with an airknife at a speed of 10 mm / sec. The above sequence of CATION and ANION deposition was repeated to deposit a desired number of “bi-layers” denoted as (CATIONZANION)n where n is the number of bi-layers. The coated substrate was stripped off the glass prior to subsequent processing.

[0115] METHOD FOR REACTIVE ION ETCHING

[0116] Reactive ion etching was performed in a home-built parallel plate capacitively coupled plasma reactor. The chamber has a central cylindrical powered electrode with a surface area of 18.3 square foot (ft2) (1.7 square meter (m2)). After placing the coated film on the powered electrode, the reactor chamber was pumped down to a base pressure of less than 0.3 Pa (2 mTorr). Oxygen was introduced into the chamber at a flow rate of 1000 SCCM. Treatment was carried out by coupling RF power into the reactor at a frequency of 13.56 megahertz (MHz) and an applied power of 8000 watts. The sample was taped to the surface of the cylindrical electrode. The electrode was rotated at a rate of 15 feet per minute (fpm) (4.6 meters per min). The total treatment time was 900 s. Following the treatment, the RF power and the gas supply were stopped and the chamber was returned to atmospheric pressure. Additional information regarding materials and processes for applying cylindrical PECVD and further details around the reactor used can be found in US8460568 B2.

[0117] COLLIMATED CONOSCOPE MEASUREMENT OF LCF REFLECTIONS

[0118] FIG. 9A illustrates the LCF 100 and an on-axis collimated light 902 incident on the LCF 100, according to an embodiment of the present disclosure.

[0119] FIG. 9B illustrates the LCF 100 and an off-axis collimated light 904 incident on the LCF 100, according to an embodiment of the present disclosure.

[0120] As shown in FIGS. 9A and 9B, the collimated light 902, 904 from a white LED is incident from the bottom side of the LCF 100. The LED is mounted on a rotating stage for incident angle control. Transmitted light, including directly a transmitted light (e.g., a light 906) and a light (e.g., a light 908) reflected by the sidewalls, is collected by a conoscope (model: Eldim L80 - Herouville-Saint-Clair FRANCE). This measurement collects all light in the entire hemisphere up to an 80 deg polar angle (360 deg azimuthal).

[0121] As shown in FIGS. 9 A and 9B, the directly transmitted light propagates along a direction of incident light, and the light reflected by the sidewalls (shown in FIG. 9B) propagates along an opposite direction.

[0122] This is how the directly transmitted light and the reflected light can be differentiated on the conoplots (shown in FIGS. 10A-10C to 13A-13B). Directly transmitted light (without diffusion)forms a bright spot on the conoplots. Specularly reflected light by the sidewall forms a bright spot (or spots) on the conoplots. Diffusively reflected light by the beads appears weak and hazy on the conoplots. This is the objective of breaking up the specular reflection like an anti-glare surface.

[0123] FIGS. 10 A, 10B, and 10C show exemplary conoplots for the comparative light control film CE, the LCF EXI, and the LCF EX2, respectively, when an incident angle (e.g., the oblique incident angle al) is of about 5 degrees.

[0124] FIGS. 11A, 11B, and 11C show exemplary conoplots for the comparative light control film CE, the LCF EXI, and the LCF EX2, respectively, when the incident angle is of about 10 degrees.

[0125] FIGS. 12 A, 12B, and 12C show exemplary conoplots for the comparative light control film CE, the LCF EXI, and the LCF EX2, respectively, when the incident angle is of about 15 degrees.

[0126] FIGS. 13 A and 13B show exemplary conoplots for the comparative light control film CE and the LCF EXI, respectively, when the incident angle is of about 20 degrees.

[0127] EXAMPLE 1 (LCF EXI)

[0128] Microstructured clear channel film was prepared using the “PREPARATION OF CLEAR CHANNEL FILMS FOR THE EXAMPLES”. Resin loaded with black beads was prepared as described in “PREPARATION OF RESIN LOADED WITH BEADS” using GR-004BK black beads (Negami Chemical Industrial Co., Ltd, Tokyo, JP) described above. The black beads are a crosslinked PMMA containing carbon black synthesized by a seed polymerization method. Next, a light collimating film was prepared using the method of “FILLING CHANNELS WITH BEAD-LOADED RESIN”. Collimated conoscope data are shown in FIGS. 10B, 11B, 12B, and 13B. The reflection peak is visible at the incident angles of 5 degrees (deg), 10 deg, and 15 deg, but is invisible at 20 deg and beyond. The reflection peaks are in the white dashed ovals.

[0129] EXAMPLE 2 (LCF EX2)

[0130] Microstructured clear channel film was prepared using the “PREPARATION OF CLEAR CHANNEL FILMS FOR THE EXAMPLES”. Beads were prepared as described in “PREPARATION OF CORE-SHELL BEADS WITH SURFACE NANOSTRUCTURE”. Resin loaded with these beads was prepared as described in “PREPARATION OF RESIN LOADED WITH BEADS”. Next, a light collimating film was prepared using the method of “FILLING CHANNELS WITH BEAD-LOADED RESIN”. Collimated conoscope data are shown in FIGS. FIGS. 10C, 11C, and 12C. The reflection peak is visible at the incident angles of 5 deg and 10 deg but is invisible at 15 deg and beyond. The reflection peaks are in the white dashed ovals.

[0131] COMPARATIVE EXAMPLE 1 (COMPARATIVE LIGHT CONTROL FILM CE)

[0132] Microstructured clear channel film was prepared using the PREPARATION OF CLEAR CHANNEL FILMS FOR THE COMPARATIVE EXAMPLE. A sheet of that film was coated with the “METHOD FOR LAYER-BY-LAYER COATING” above with 50 bi-layers, i.e.,(CATION / ANION)50 using the coating solutions made via the “PREPARATION OF COATING SOLUTIONS FOR LAYER-BY-LAYER (LBL) COATING” method described above. Next, the sheet was submitted to reactive ion etching (RIE) for 900 s as described in the “METHOD FOR REACTIVE ION ETCHING” above. Finally, the sheet was planarized / backfilled with the same resin using for making the microstructured film for index matching purposes. The resin was casted onto the channel structures against an unprimed PET surface, and then cured with same process conditions used in the clear channel film making process. Collimated conoscope data are shown in FIGS. 10A, 11 A, 12A, and 13A. The reflection peaks are visible at all the measured incident angles, from 5 to 40 deg. The reflection peaks are in the white dashed ovals.

[0133] Unless otherwise indicated, all numbers expressing feature sizes, amounts, and physical properties used in the specification and claims are to be understood as being modified by the term “about”. Accordingly, unless indicated to the contrary, the numerical parameters set forth in the foregoing specification and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by those skilled in the art utilizing the teachings disclosed herein.

[0134] Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that a variety of alternate and / or equivalent implementations can be substituted for the specific embodiments shown and described without departing from the scope of the present disclosure. This application is intended to cover any adaptations or variations of the specific embodiments discussed herein. Therefore, it is intended that this disclosure be limited only by the claims and the equivalents thereof.

Claims

CLAIMS:

1. A light control film comprising: alternating transmissive regions and absorbing regions extending along a same in-plane first direction and arranged along an orthogonal in-plane second direction; and a light absorbing material disposed in each of the absorbing regions, the light absorbing material comprising a plurality of particles dispersed in a matrix, wherein each of the plurality of particles has an outer layer comprising nanostructures.

2. The light control film of claim 1, wherein each transmissive region has a first refractive index and the matrix has a second refractive index, and wherein a ratio between the first refractive index and the second refractive index is from about 0.99 to about 1.01.

3. The light control film of claim 1, wherein at least one of the particles comprises a glass bead.

4. The light control film of claim 1, wherein at least one of the particles comprises at least one of a carbon black and a visible light absorbing dye.

5. An optical system comprising: a transparent display configured to emit an image for viewing by a viewer facing a first side of the transparent display, and a light control film (LCF) disposed on a second side of the transparent display opposite to the first side, the light control film comprising: alternating transmissive regions and absorbing regions extending along a same in-plane first direction and arranged along an orthogonal in-plane second direction, wherein each transmissive region has a first refractive index; and a light absorbing material disposed in each of the absorbing regions, the light absorbing material comprising a plurality of particles dispersed in a matrix, the matrix having a second refractive index, wherein a ratio between the first refractive index and the second refractive index is from about 0.99 to about 1.01, such that the viewer is configured to view an object located on the second side of the transparent display in a real- world scene through the transparent display and the LCF, wherein for a substantially collimated light from the second side incident at an oblique incident angle greater than about 2 degrees, and for a polar angle range PAR from about 0 to about 80 degrees, an optical luminance distribution of an exiting light from the LCF has a maximum optical luminance at a first polar angle PA, a metric 1 - (sum(PA ± 4 degrees) / sum(PAR)) is greaterthan about 0.25, wherein sum(PA ± 4 degrees) is a sum of positive optical luminances of PA ± 4 degrees and sum(PAR) is a sum of positive optical luminances of the polar angle range PAR.

6. The optical system of claim 5, wherein when the incident angle is about 5 degrees, the metric is greater than about 0.4.

7. The optical system of claim 5, wherein each of the plurality of particles has an outer layer comprising nanostructures.

8. A method of manufacturing a light control film, the method comprising: providing a plurality of initial particles, wherein each of the initial particles comprises an outer surface; forming a plurality of particles by depositing an aluminum alloy using a vacuum reactive sputtering process, such that an outer layer comprising nanostructures is substantially disposed on the outer surface of each of the initial particles; and forming a light absorbing material by dispersing the plurality of particles in a matrix.

9. The method of claim 8 further comprising mixing the initial particles with fumed silica before depositing the aluminum alloy using the vacuum reactive sputtering process.

10. The method of claim 8 further comprising: providing a microstructured film comprising a plurality of light transmissive regions defining a plurality of channels therebetween; and filling each of the plurality of channels with the light absorbing material to form a plurality of light absorbing regions.

11. The method of claim 10, wherein each transmissive region has a first refractive index and the matrix has a second refractive index, and wherein a ratio between the first refractive index and the second refractive index is from about 0.99 to about 1.01.

12. The method of claim 8, further comprising: providing a microstructured film comprising a plurality of light transmissive regions defining a plurality of channels therebetween, wherein the microstructured film has a microstructured surface defined by a top surface and sidewalls of the light transmissive regions and a channel bottom surface of the channels; applying the light absorbing material to the microstructured surface;removing at least a portion of the light absorbing material from the top surface of the light transmissive regions and the channel bottom surface of the channels to form a plurality of light absorbing regions; and filling the channel with a polymeric material.

13. The method of claim 12, wherein applying the light absorbing material comprises layer-by- layer self-assembly.

14. The method of claim 12, wherein each transmissive region and the matrix have a same composition.

15. The method of claim 12, wherein each transmissive region has a first refractive index and the matrix has a second refractive index, and wherein a ratio between the first refractive index and the second refractive index is from about 0.99 to about 1.01.

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