Light control film with adhesive-filled microstructures

Abstract

A light control film includes an optically transparent unitary film, a light absorbing interface layer, and an optically transparent adhesive material. The optically transparent unitary film includes spaced-apart structures arranged along the unitary film and defining a plurality of openings therebetween, and a first continuous land portion. The light absorbing interface layer is disposed between each pair of adjacent structure and opening. The interface layer covers at least 50% of one or more sides of the structure. The optically transparent adhesive material fills the openings between the structures such that the light absorbing interface layers are between the adhesive material and the sides of the structures. The adhesive material forms a second continuous adhesive land portion opposite the first continuous land portion. Each of the first and second continuous land portions extend across the length and the width of the unitary film and join the structures and the openings.

Description

[0001] LIGHT CONTROL FILM WITH ADHESIVE-FILLED MICROSTRUCTURES

[0002] Summary

[0003] In some aspects of the present description, a light control film is provided, the light control film including an optically transparent unitary film having a plurality of structures and a first continuous land portion, a light absorbing interface layer, and an optically transparent adhesive material. The optically transparent unitary film has a unitary construction. The plurality of spacedapart structures are arranged along substantially an entire length and an entire width of the unitary film and define a plurality of openings therebetween. Each of the structures has a top opposite a base and one or more sides joining the top to the base. The light absorbing interface layer is disposed between each pair of adjacent structure and opening in the plurality of spaced-apart structures and the plurality of openings. The interface layer is substantially co-extensive with the structure along a thickness direction of the unitary film and covers at least 50% of the one or more sides of the structure, but substantially absent from the top of the structure and a bottom surface of the opening between structures. The optically transparent adhesive material fills the openings between the structures such that the light absorbing interface layers are disposed between the adhesive material and the one or more sides of the structures. The adhesive material forms a second continuous adhesive land portion opposite the first continuous land portion. Each of the first and second continuous land portions extend continuously across substantially the entire length and the entire width of the unitary film and join the structures and the openings. The second continuous adhesive land portion has an average thickness of greater than about 5 microns.

[0004] In some aspects of the present description, a light control film is provided, the light control film defining a height direction orthogonal to mutually orthogonal in-plane first and second directions and including a plurality of spaced-apart substantially light absorbing linear walls extending along the first direction and arranged along the second direction. Each of the linear walls has an average thickness of less than about 2 microns along a thickness direction of the linear wall and a width along a width direction of the linear wall orthogonal to the thickness and the first directions. Optically transparent first non-adhesive layer and second adhesive layer, in combination, fully encapsulate the linear walls and form substantially parallel continuous first adhesive land portion and continuous non- adhesive second land portion extending continuously across substantially an entire length and an entire width of the light control film and uninterrupted by any of the linear walls. The continuous first adhesive land portion has an average thickness of greater than about 5 microns.

[0005] Brief Description of the Drawings

[0006] FIGS. 1A and IB provide a side view and top view, respectively, of a light control film having adhesive-filled microstructures, in accordance with an embodiment of the present description; FIG. 2A is a perspective view of a light control film having adhesive-filled microstructures, and FIG. 2B illustrates possible cross-sectional shapes of the structures of a light control film having adhesive-filled microstructures, in accordance with an embodiment of the present description;

[0007] FIGS. 3A and 3B provide perspective views of a light control film having adhesive-filled post microstructures, in accordance with an alternate embodiment of the present description;

[0008] FIG. 4 illustrates a variety of types of posts which may be used on a light control film, in accordance with an embodiment of the present description; and

[0009] FIG. 5A provides a side view of a light control film having adhesive-filled micro structures having a first substrate and an opposing second substrate, and FIG. 5B illustrates the behavior of the light control film relative to the angle of incidence of incoming light rays, in accordance with an alternate embodiment of the present description.

[0010] Detailed Description

[0011] In the following description, reference is made to the accompanying drawings that form a part hereof and in which various embodiments are shown by way of illustration. The drawings are not necessarily to scale. It is to be understood that other embodiments are contemplated and may be made without departing from the scope or spirit of the present description. The following detailed description, therefore, is not to be taken in a limiting sense.

[0012] A light control film with microstructures (e.g., a louver film) can be made by creating a fdm having a series of microstructures (e.g., ridges, posts, etc.) separated by one or more grooves or channels, applying a light absorbing material to the sides of the structures, and filling the grooves or channels with an optically transparent material (e.g., an acrylate resin that is curable with ultraviolet light). The optically transparent material used to fill the spaces between structures may be index matched to the material used to create the structures. In some applications, it may be desirable to place an adhesive layer on the light control film. However, this adhesive layer adds additional thickness and increases the space between the light control film and the image forming plane (e.g., the image plane of a display). This extra space can lead to unwanted optical artifacts, including ghost images. It is desirable in these applications to reduce the thickness of the adhesive layer, or to remove the adhesive layer all together. In some aspects of the present description, a light control film is backfilled with an optical adhesive, eliminating the need for an additional adhesive layer.

[0013] According to some aspects of the present description, a light control film includes an optically transparent unitary film, a light absorbing interface layer, and an optically transparent adhesive material. In some embodiments, the optically transparent unitary film may have a unitary construction and may include a plurality of spaced-apart structures (e.g., posts, ridges) arranged along substantially an entire length (e.g., an x-axis of the unitary film) and an entire width (e.g., an orthogonal y-axis of the unitary film), and a first continuous land portion (e.g., a land portion beneath and supporting the plurality of structures). In some embodiments, each of the structures may have a maximum height, h, of greater than about 1 micron, or greater than about 2 microns, or greater than about 3 microns, or greater than about 4 microns, or greater than about 5 microns, or greater than about 10 microns, or greater than about 15 microns. In some embodiments, the structures may have substantially a same cross-sectional shape. In some such embodiments, the same cross-sectional shape may include one or more of round, elliptical, oval, square, rectangular, triangular, trapezoidal, and polygonal.

[0014] In some embodiments, the optically transparent unitary film may define a plurality of openings between the structures of the plurality of spaced-apart structures. In some embodiments, the openings extend between the structures of the plurality of structures but do not extend into the first continuous land portion, or only extend partially into the first continuous land portion. In some embodiments, each of the structures may have a top (e.g., a top surface) opposite a base (e.g., a bottom surface) and one or more sides (e.g., side surfaces) joining the top to the base.

[0015] In some embodiments, the light absorbing interface layer may be disposed between each pair of adjacent structure and opening in the plurality of spaced-apart structures and the plurality of openings (e.g., may be disposed on at least a portion of the one or more sides of the structures). In some embodiments, the interface layer may be substantially co-extensive with the structure along a thickness direction (e.g., along a z-axis) of the unitary film and may cover at least 50%, or at least 60%, or at least 70%, or at least 80%, or at least 90%, or at least 95% of the one or more sides of the structure. In some embodiments, the interface layer may be substantially absent from the tops of the structures and / or the bottom surfaces of the openings between structures (i.e., may cover less than 10%, or less than 5%, or less than 1% of these surfaces).

[0016] In some embodiments, the optically transparent adhesive material may fill the openings between the structures such that the light absorbing interface layers are disposed between the adhesive material and the one or more sides of the stmctures. In some embodiments, the adhesive material may form a second continuous adhesive land portion opposite the first continuous land portion (e.g., such that the stmctures are sandwiched between the first continuous land portion and the second continuous adhesive land portion). In some embodiments, each of the first and second continuous land portions may extend continuously across substantially the entire length and the entire width of the unitary film and may join the structures and the openings. In some embodiments, the second continuous adhesive land portion may have an average thickness of greater than about 1 microns, or greater than about 3 microns, or greater than about 5 microns, or greater than about 7 microns, or greater than about 10 microns, or greater than about 12 microns, or greater than about 15 microns.

[0017] In some embodiments, the optically transparent adhesive material may be an optically clear pressure sensitive adhesive (PSA), which is used to fill the openings between the microstructures. In some embodiments, the PSA may be subjected to ultraviolet (UV) polymerization to form the adhesive / microstructure article. Suitable optically clear adhesive compositions may be formed by polymerizing a mixture of monomers that includes at least one (Cl-C18)alkyl (methjacrylate monomer and at least one polar (meth)acrylate monomer, a cross-linker (multifunctional acrylate monomers or oligomers) and at least one photo -initiator. Other materials, such as polyurethane acrylates (such as EBECRYL® 230 commercialized by allnex and CN9018 commercialized by Akama), vinyl functionalized monomers, such as n-vinyl-pyrrolidone, may be used in the adhesive formulations. Cured optically clear adhesive compositions typically have low modulus (typically less than 300 kPa at room temperature) and low cross-linking density, which provides good bonding function through pressure.

[0018] Optically clear resins (OCR) can also been used to fill in the structures. OCR typically refers to high modulus (typically > 5 MPa at 25C) and higher cross-linking materials that are non-tacky resins after UV-curing. Suitable OCR compositions can typically include polyurethane oligomer (such as Photomer 6210 commercialized by IGM resin), mono- or multifunctional acrylates (such as trimethylolpropane triacrylate), and photoinitiators.

[0019] In some embodiments of the light control film, the structures in the plurality of spaced-apart structures may be substantially linear ridges and the openings in the plurality of openings are substantially linear grooves. In some embodiments, the substantially linear ridges and substantially linear grooves may form substantially linear alternating ridges and grooves extending along substantially a same first direction (e.g., along the length or the x-axis of the unitary film) and arranged along an orthogonal second direction (e.g., along the width ory-axis of the unitary film). Stated another way, the pattern of alternating linear ridges and linear grooves may extend along the length of the unitary fdm, and the individual ridges and grooves may extend across the width of the unitary film. In some embodiments, the ridges may have an average height of less than about 300 microns, or less than about 275 microns, or less than about 250 microns, or less than about 225 microns, or less than about 200 microns, or less than about 175 microns, or less than about 150 microns, or less than about 125 microns, or less than about 100 microns, or less than about 90 microns, or less than about 80 microns, or less than about 70 microns, or less than about 60 microns, or less than about 50 microns, or less than about 40 microns, or less than about 30 microns, or less than about 20 microns along the height direction (e.g., the thickness direction) of the unitary film.

[0020] In some embodiments, in a planar cross-section of the unitary film that is substantially orthogonal to the light control film and the first direction, each of the ridges may have opposing substantially straight first and second sides. In some such embodiments, each of the straight first and second sides may make an angle of greater than about 80 degrees, or greater than about 82 degrees, or greater than about 84 degrees, or greater than about 85 degrees, or greater than about 86 degrees, or greater than about 87 degrees, or greater than about 88 degrees, or greater than about 89 degrees, or greater than about 89.5 degrees with a substantially planar major surface of the light control fdm.

[0021] In some embodiments of the light control film, the structures may be posts. In some embodiments, the posts may have average maximum heights H and average maximum lateral dimensions D, such that the ratio of H / D is greater than or equal to about 1 , or greater than or equal to about 2, or greater than or equal to about 3, or greater than or equal to about 4, or greater than or equal to about 5, or greater than or equal to about 10. In some such embodiments, the posts may include one or more of square posts, rectangular posts, cylindrical posts, truncated cone posts, truncated pyramidal posts, polygonal posts, and truncated polygonal posts.

[0022] In some embodiments of the light control film, the light control film may further include a first substrate layer disposed on the first continuous land portion opposite the second continuous adhesive land portion. In some such embodiments, the first substrate layer may be a removable first substrate, such that the removable first substrate layer may be removed from the first continuous land portion with no or very little damage to the first continuous land portion (i.e., less than 3%, or less than 2%, or less than 1%, or less than 0.5%, or less than 0.1% of the material of the first continuous land portion removed with the removable first substrate layer.

[0023] In some embodiments, the light control film may further include a second substrate layer disposed on the second continuous adhesive land portion opposite the first continuous land portion. In some such embodiments, the second substrate layer may be a removable second substrate, such that the removable second substrate may be removed from the second continuous adhesive land portion with no or very little damage to the second continuous adhesive land portion.

[0024] In some embodiments of the light control film, in a planar cross-section of the light control film that is substantially orthogonal to the light control film, the light absorbing interface layers may be substantially straight and may make a first angle with a thickness direction of the light control film. In some such embodiments, when in the cross-section of the light control film a collimated extend light that extends across at least one, or at least 2, or at least 5, or at least 10, or at least 50, or at least 100 light absorbing interface layers and is incident on the light control film at an incident angle of substantially the first angle, the light control film may transmit at least 50%, or at least 60%, or at least 70%, or at least 80%, or at least 90%, or at least 95% of the incident light. In some such embodiments, when in the cross-section of the light control film a collimated light that extends across at least one, or at least 2, or at least 5, or at least 10, or at least 50, or at least 100 light absorbing interface layers and is incident on the light control film at an incident angle that is greater than the first angle by at least 10 degrees, or at least 15 degrees, or at least 20 degrees, or at least 25 degrees, or at least 30 degrees, or at least 35 degrees, or at least 40 degrees, or at least 45 degrees, or at least 50 degrees, or at least 60 degrees, or at least 70 degrees, the light control film may transmit at most 30%, or at most 25%, or at most 20%, or at most 15%, or at most 10%, or at most 5%, or at most 1% of the incident light. In some embodiments, the first angle may be at least about 1 degree, or at least about 2 degrees, or at least about 3 degrees, or at least about 4 degrees, or at least about 5 degrees, or at least about 10 degrees, or at least about 15 degrees, or at least about 20 degrees. In some embodiments, the first angle is at most about 10 degrees, or at most about 9 degrees, or at most about 8 degrees, or at most about 7 degrees, or at most about 6 degrees, or at most about 5 degrees, or at most about 4 degrees, or at most about 3 degrees, or at most about 2 degrees, or at most about 1 degree. In some embodiments of the light control film, for at least one same visible wavelength in a visible (human-visible) wavelength range extending from about 420 nm to about 680 nm, the unitary film and the adhesive material may have indices of refraction that are within about 0.5, or within about 0.4, or within about 0.3, or within about 0.2, or within about 0.1, or within about 0.05 of each other.

[0025] In some embodiments, for at least one visible wavelength in a visible wavelength range extending from about 420 nm to about 680 nm, the unitary film may have an index of refraction in a range from about 1.45 to about 1.6, or from about 1.5 to about 1.58. In some embodiments of the light control film, the unitary film may include one or more of an acrylate, a polycarbonate, a polystyrene, a photo-curable material, and a UV curable material.

[0026] In some embodiments of the light control film, for at least one visible wavelength in a visible wavelength range extending from about 420 nm to about 680 nm, the optically transparent adhesive material may have an index of refraction in a range from about 1.40 to about 1.6, or from about 1.5 to about 1.58. In some embodiments, the optically transparent adhesive material may include one or more of a natural or synthetic rubber-based pressure sensitive adhesive, an acrylic pressure sensitive adhesive, a vinyl alkyl ether pressure sensitive adhesive, a silicone pressure sensitive adhesive, a polyester pressure sensitive adhesive, a polyamide pressure sensitive adhesive, a poly-alpha-olefin pressure sensitive adhesive, a polyurethane pressure sensitive adhesive, and a styrenic block copolymer based pressure sensitive adhesive.

[0027] In some embodiments of the light control film, the light absorbing interface layer may include one or more of a light absorbing pigment, a light absorbing dye, and carbon black. In some embodiments, the light absorbing interface layer may have a black or a dark gray color.

[0028] In some embodiments, the second continuous adhesive land portion may have an average thickness of less than about 50 microns, or less than about 45 microns, or less than about 40 microns, or less than about 35 microns, or less than about 30 microns, or less than about 25 microns, or less than about 20 microns, or less than about 15 microns. In some embodiments, the first continuous land portion may have an average thickness of less than about 30 microns, or less than about 25 microns, or less than about 20 microns, or less than about 15 microns, or less than about 10 microns, or less than about 5 microns.

[0029] In some embodiments, the ridges may have an average height of greater than about 5 microns, or greater than about 7 microns, or greater than about 10 microns, or greater than about 15 microns, or greater than about 20 microns, or greater than about 50 microns along the height direction of the unitary film.

[0030] In some embodiments, the unitary film may include a structured first major surface opposite a second major surface, wherein the structured major surface includes the plurality of spaced-apart stmctures and the plurality of openings. In some embodiments, in a planar cross-section of the unitary film that is substantially orthogonal to the light control film and the first direction, each of the structures may have a maximum width that is within 20%, or within 15%, or within 10%, or within 5% of a minimum width of the ridge. In some embodiments, the unitary film and the adhesive material may have different compositions.

[0031] According to some aspects of the present description, a light control film may define a height direction orthogonal to mutually orthogonal in-plane first and second directions and including a plurality of spaced-apart substantially light absorbing linear walls extending along the first direction and arranged along the second direction. In some embodiments, each of the linear walls may have an average thickness of less than about 2 microns, or less than about 1.75 microns, or less than about 1.5 microns, or less than about 1.25 microns, or less than about 1 microns, or less than about 0.9 microns, or less than about 0.8 microns, or less than about 0.7 microns, or less than about 0.6 microns, or less than about 0.5 microns along a thickness direction of the linear wall and a width along a width direction of the linear wall orthogonal to the thickness and the first directions.

[0032] In some embodiments, an optically transparent first non-adhesive layer and a second adhesive layer, in combination, may fully encapsulate the linear walls and form substantially parallel continuous first adhesive land portion and continuous non-adhesive second land portion extending continuously across substantially an entire length and an entire width of the light control film and uninterrupted by any of the linear walls. In some embodiments, the continuous first adhesive land portion may have an average thickness of greater than about 5 microns, or greater than about 6 microns, or greater than about 7 microns, or greater than about 8 microns, or greater than about 9 microns, or greater than about 10 microns, or greater than about 12 microns, or greater than about 15 microns.

[0033] In some embodiments, in a planar cross-section of the light control film that is substantially orthogonal to the light control film and the first direction, the light absorbing linear walls may be substantially straight. In some such embodiments, in the planar cross-section of the light control film, each pair of light absorbing linear walls in the plurality of spaced-apart substantially light absorbing linear walls may make an inclusion angle with each other that is less than about 20 degrees, or less than about 15, or less than about 10, or less than about 5 degrees. In some embodiments, the light control film may further include a first substrate layer disposed on the continuous first adhesive land portion opposite the continuous non-adhesive second land portion.

[0034] Turning now to the figures, FIGS. 1A and IB provide a side view and top view, respectively, of an embodiment of a light control film having adhesive-filled microstructures, according to the present description. Looking first at FIG. 1 A, light control film 300 includes an optically transparent unitary film 200 having a unitary construction, a light absorbing interface layer 50, and an optically transparent adhesive material 40. In some embodiments, the optically transparent unitary film 200 (also simply “unitary film 200”) may include a plurality of spaced-apart structures 10 arranged along substantially an entire length (e.g., the x-axis shown in FIG. 1A) and an entire width (e.g., the y-axis) of unitary film 200 and defining a plurality of openings 20 therebetween. In some embodiments, each of the structures has a top 11 opposite a base 12 and one or more sides 14 joining top 11 to base 12. In some embodiments, unitary film 200 may further include a first continuous land portion 30.

[0035] In some embodiments, a light absorbing interface layer 50 may be disposed between each pair of adjacent structure 10 and opening 20 in the plurality of spaced-apart stmctures 10 and the plurality of openings 20. For example, turning briefly to FIG. IB, which is a top view of the light control film 300 (shown without adhesive 40 for clarity), a light absorbing interface layer 50a is disposed between stmcture 10a and opening 20a. Similarly, light absorbing interface layer 50b is disposed between opening 20a and structure 10b.

[0036] Now, looking at FIGS. 1A and IB together, in some embodiments, interface layer 50 may be substantially co-extensive with each structure 10 along a thickness direction (e.g., the z-axis) of unitary film 200, and interface layer 50 may cover at least 50% of the one or more sides 14 of structure 10. For example, in the embodiment of FIGS. 1 A and IB, the interface layer 50 covers substantially all of sides 14a and 14b (see FIG. 1 A) of each structure 10, thereby, at least in this embodiment, creating “walls” or “louvers” along these sides and embedded within the light control film 300.

[0037] In some embodiments, optically transparent adhesive material 40 may fill or substantially fill openings 20 between the structures 10 such that light absorbing interface layers 50 are disposed between adhesive material 40 and the one or more sides 14 (e.g., sides 14a and 14b) of structures 10. In some embodiments, adhesive material 40 may form a second continuous adhesive land portion 45 opposite first continuous land portion 30. It should be noted that, in FIG. 1 A, thin, horizontal lines have been added to help distinguish the first continuous land portion 30 from structures 10 and second continuous land portion 45 from structures 10. In this embodiment, the thin lines are provided only as a means of visually marking and distinguishing land portions 30 and 45 from structures 10, and do not necessarily mean these land portions are physically separate from the structures.

[0038] In some embodiments, each of the first continuous land portion 30 and second continuous land portion 45 may extend continuously across substantially the entire length and the entire width of unitary film 200 and join stmctures 10 with openings 20.

[0039] In some embodiments, first continuous land portion 30 may have an average thickness ti of less than about 30 microns. In some embodiments, second continuous adhesive land portion 45 may have an average thickness t2 of greater than about 5 microns.

[0040] In some embodiments, each of the structures 10 may have a maximum height, h, of greater than about 1 micron, or greater than about 2 microns, or greater than about 3 microns, or greater than about 4 microns, or greater than about 5 microns, or greater than about 10 microns, or greater than about 15 microns.

[0041] In some embodiments of the light control film, the structures 10 in the plurality of spaced- apart structures 10 may be substantially linear ridges and the openings 20 in the plurality of openings 20 may be substantially linear grooves, such as shown in FIG. IB as well as FIG. 2A. In some embodiments, the substantially linear ridges 10 and grooves 20 form a substantially linear alternating ridges and grooves extending along substantially a same first direction (e.g., the “pattern” of alternating ridges and grooves extends across the x-direction, or the length direction, as shown in FIGS. IB and 2A) and arranged along an orthogonal second direction (e.g., the “lines” of the ridges and grooves are arranged across the light control film in the y-direction).

[0042] In some embodiments, the ridges may have an average height of less than about 300 microns along the height direction (e.g., the z-direction of FIG. 1A) of the unitary film. In some embodiments, the ridges may have an average height of greater than about 5 microns along the height direction of the unitary film.

[0043] In some embodiments, in a planar cross-section of the unitary film 200 that is substantially orthogonal to the light control film 300 and the first direction (such as the cross-section view of FIG. 1A), each of the ridges 10 may have opposing substantially straight first 14a and second 14b sides. In some such embodiments, each of the straight first 14a and second 14b sides may make an angle 01, 02 of greater than about 80 degrees with a substantially planar major surface of the light control film 300 (e.g., substantially orthogonal to the planar major surface).

[0044] In some embodiments, in a planar cross-section of unitary film 200 that is substantially orthogonal to the light control film 300 and the first direction (e.g., the x-direction of FIG. 1A), each of stmctures 10 may have a maximum width, w, that is within 20% of a minimum width of the ridge.

[0045] FIG. 2A is a perspective view of an embodiment of a light control film having adhesive-filled microstructures where the structures 10 are linear ridges. FIG. 2A is provided as an alternate view of light control film 300 of FIGS. 1A and IB, and components which share reference numbers with the components of FIGS. 1A and IB shall be assumed to have the same function unless otherwise specified herein. Each structure / ridge 10 extends in the width or y-direction across the unitary film 200 and is separated from other structures / ridges 10 by openings / grooves 20. Light absorbing interface layers 50 extend across and substantially cover (e.g., at least 50% of) first side 14a and second side 14b of each structure 10.

[0046] FIG. 2B illustrates possible cross-sectional shapes of the structures 10 of a light control film having adhesive-filled microstructures. 3. When viewed from a side of light control film 300 (e.g., looking into the film along the y-direction shown in the figures), the structures 10 may have substantially a same cross-sectional shape. In some embodiments, the same cross-sectional shape comprises one or more of round 10a, elliptical 10b, oval 10c, square lOd, rectangular lOe, triangular lOf, and trapezoidal and / or polygonal 10g. The shapes illustrated in FIG. 2B are not meant to be limiting, and any appropriate cross-sectional shape may apply.

[0047] FIGS. 3A and 3B provide perspective views of an embodiment of a light control film having adhesive-filled microstructures in which the microstructures are in the form of posts, as opposed to linear ridges and grooves such as the embodiment of FIGS. IB and 2 A. Many of the elements of FIGS. 3 A and 3B are labeled with reference numbers used in other figures discussed elsewhere herein, and it shall be assumed that like-numbered elements serve the same function unless otherwise noted herein.

[0048] Looking first at FIG. 3 A, in some embodiments, a light control film 300a may include an optically transparent unitary film 200a having a unitary construction, a light absorbing interface layer 50, and an optically transparent adhesive material 40. In some embodiments, the optically transparent unitary film 200a (also simply “unitary film 200a”) may include a plurality of spaced-apart stmctures 10 in the form of posts which are arranged along substantially an entire length (e.g., the x-axis shown in FIG. 1A) and an entire width (e.g., the y-axis) of unitary film 200a. Unitary film 200 may also, in some embodiments, define a plurality of openings 20 between and separating the structures / posts 10. In some embodiments, each of the structures has a top 11 opposite a base 12 and one or more sides 14 joining top 11 to base 12. Turning briefly to FIG. 3B, the one or more sides 14 of each stmcture / post 10 may include a first side 14a, a second side 14b, a third side 14c, and a fourth side 14d, such as those of the embodiment shown in FIG. 3B. However, in other embodiments, when the stmctures / posts 10 may have an alternate shape (e.g., a cylindrical post), the stmcture / post may have a single side 14 (i.e., the continuous surface of the cylindrical shape showing top 11 and base 12). Other embodiments are possible within the scope of the present description.

[0049] Returning to FIG. 3 A, in some embodiments, a light absorbing interface layer 50 may be disposed between each pair of adjacent structure 10 and opening 20 in the plurality of spaced-apart stmctures 10 and the plurality of openings 20. In an embodiment such as that shown in FIG. 3 A, where the stmctures 10 are in the form of discrete posts, the light absorbing interface layer 50 may be substantially co-extensive with each structure 10 along a thickness direction (e.g., the z-axis) of unitary film 200a, such that each stmcture / post 10 is effectively wrapped by light absorbing interface layer 50. That is, light absorbing interface layer 50 may cover at least 50% of the one or more sides 14a-14d (see FIG. 3B) of stmcture 10.

[0050] In some embodiments, optically transparent adhesive material 40 may fill or substantially fill openings 20 between stmctures / posts 10 such that light absorbing interface layers 50 are disposed between adhesive material 40 and the one or more sides 14 (e.g., sides 14a-14d) of stmctures 10. In some embodiments, adhesive material 40 may form a second continuous adhesive land portion 45 (i.e., a continuous land area disposed above, in the positive z-direction shown, and connecting the stmctures 10, similar to that shown in FIG. 1 A) opposite first continuous land portion 30. In some embodiments, each of the first continuous land portion 30 and second continuous land portion 45 may extend continuously across substantially the entire length and the entire width of unitary film 200a and join stmctures / posts 10 with openings 20.

[0051] Turning again to FIG. 3B, in some embodiments, stmctures / posts 10 may have average maximum heights H and average maximum lateral dimensions D, such that the ratio H / D is greater than or equal to 1, or greater than or equal to 2, or greater than or equal to 3, or greater than or equal to 4, or greater than or equal to 5, or greater than or equal to 10. The structures / posts 10 in the embodiment of FIGS. 3 A and 3B are shown as square or rectangular posts but can be any appropriate shape or configuration. FIG. 4 illustrates a variety of types of posts which may be used on light control film 300a of FIG. 3 A. In some embodiments, for example, the posts 10 may include one or more of square posts lOh, rectangular posts lOi, cylindrical posts lOj, truncated cone posts 10k, truncated pyramidal posts lOf, polygonal posts 10m, and truncated polygonal posts lOn. The post types shown in FIG. 4 are not intended to be limiting and are provided as examples only.

[0052] FIG. 5A provides a side view of an alternate embodiment of a light control film, such as light control film 300 of FIG. 1A, including a first substrate and an opposing second substrate. In some embodiments, light control film 300 may further include a first substrate layer 60 disposed on the first continuous land portion 30 opposite the second continuous adhesive land portion 45. In some embodiments, first substrate layer 60 may be a removable first substrate, such that the removable first substrate layer 60 may be removed from the first continuous land portion 30 with no or very little damage to the first continuous land portion 30. In some embodiments, light control film 300 may further include a second substrate layer 62 disposed on the second continuous adhesive land portion 45 opposite the first continuous land portion 30. In some embodiments, second substrate layer 62 may be a removable second substrate, such that the removable second substrate 62 may be removed from the second continuous adhesive land portion 45 with no or very little damage to the second continuous adhesive land portion 45.

[0053] Finally, FIG. 5B illustrates the behavior of an embodiment of the light control film, such as light control film 300 of FIG. 1A, relative to the angle of incidence of incoming light rays. In some embodiments, in a planar cross-section of the light control film that is substantially orthogonal to the light control film (such as the cross-section shown in FIG. 5B), the light absorbing interface layers 50 may be substantially straight and make a first angle 0a with a thickness direction of the light control film (e.g., the z-direction shown in FIG. 5B). That is, the light absorbing interface layers 50 may be substantially orthogonal to a surface of the light control film 300, such as the horizontal surface (e.g., bottom surface extending across the x-direction shown) of first continuous land portion 30, such that 0a is about 90 degrees.

[0054] In some embodiments, when in the cross-section of the light control film 300 a collimated light 80a that extends across at least one, or at least 2, or at least 5, or at least 10, or at least 50, or at least 100 light absorbing interface layers 50 and is incident on light control film 300 at an incident angle of substantially the first angle 0a, the light control film may transmit at least 50%, or at least 60%, or at least 70%, or at least 80%, or at least 90%, or at least 95% of the incident light. In some embodiments, when in the cross-section of light control film 300 a collimated light 80c that extends across at least one, or at least 2, or at least 5, or at least 10, or at least 50, or at least 100 light absorbing interface layers 50 and is incident on the light control film at an incident angle 0c that is greater than the first angle 0a by at least 10, or at least 15, or at least 20, or at least 25, or at least 30, or at least 35, or at least 40, or at least 45, or at least 50, or at least 60, or at least 70 degrees, light control film 300 may transmit at most 30%, or at most 25%, or at most 20%, or at most 15%, or at most 10%, or at most 5%, or at most 1% of the incident light. In some embodiments, first angle 0a may be at least about 1 degree, or least about 2 degrees, or least about 3 degrees, or least about 4 degrees, or least about 5 degrees, or least about 10 degrees, or least about 15 degrees, or least about 20 degrees. In some embodiments, the first angle 0a may be at most about 10 degrees, or at most about 9 degrees, or at most about 8 degrees, or at most about 7 degrees, or at most about 6 degrees, or at most about 5 degrees, or at most about 4 degrees, or at most about 3 degrees, or at most about 2 degrees, or at most about 1 degree. In some embodiments, light 80b that is incident at an angle 0b that is sufficiently close to first angle 0b (e.g., within about 5 degrees, or within about 10 degrees, or within about 15 degrees, or within about 20 degrees) may be substantially transmitted (e.g., at least 50%, or at least 60%, or at least 70%, or at least 80%, or at least 90%, or at least 95% of the incident light may be transmitted). The range of angles of incidence which may be substantially transmitted by light control film 300 can be controlled by factors including, but not limited to, the spacing (the period), angle, height, and width of the light absorbing interface layers 50, as well as other physical and material characteristics of the light control film 300.

[0055] Examples

[0056] Objects and advantages of this invention are further illustrated by the following examples, but the particular materials and amounts thereof recited in these examples, as well as other conditions and details, should not be construed to unduly limit this invention.

[0057] Unless otherwise noted, all parts, percentages, ratios, etc., in the examples and in the remainder of the specification are by weight. Unless otherwise noted, all chemicals were obtained from, or are available from, chemical suppliers such as Sigma- Aldrich Co., St. Louis, Mo.

[0058] The following is a list of materials used throughout the Examples, as well as their brief descriptions and origins.

[0059] The components of Resin A used in the cast-and-cure microreplication process (Preparative Example 1) are listed in Table 1 below. The raw materials for the layer-by-layer coating are listed in Table 2 below. The raw materials for reactive ion etching are listed in Table 3 below.

[0060] Table 1: Raw Materials for Resin A

[0061] Table 2: Raw Materials for Layer-By-Layer (LBL) Coatings Table 3: Raw Materials for Reactive Ion Etching

[0062] Table 4: Raw Materials for Adhesive Resins _

[0063] | Material | Abbreviation | Source

[0064] Preparative Example 1 (PEI): Preparation of "Square Wave" Microstructured Film

[0065] A diamond (26.0 gm tip width, 0° included angle, 69 pm deep) was used to cut a tool having a plurality of parallel linear grooves. The grooves were spaced apart by a pitch of 62.6 microns. Resin A was prepared by mixing the materials in Table 4 below.

[0066] Table 4: Composition of Resin A Used to Make Microstructured Film

[0067] A "cast-and-cure" microreplication process was carried out with Resin A and a tool, as described above. The line conditions used were: resin temperature 150° F, die temperature 150° F, coater IR 120° F edges / 130° F center, tool temperature 100° F, and line speed 70 fpm. Fusion D lamps (available from Fusion UV Systems, Gaithersburg, Md.), with peak wavelength at 385 nm, were used for curing and operated at 100% power. The resulting microstructured film comprised a plurality of protrusions (e.g. light transmissive regions) separated by channels. The base layer was PET film (3M, St. Paul, Minn.), having a thickness of 2.93 mils (74.4 microns). The side of the PET film that contacts the resin was primed with a thermoset acrylic polymer (Rhoplex 3208 available from Dow Chemical, Midland, Mich.). The land layer (L) of the cured resin had a thickness of 30 microns. The microstructured film is a topographical inverse of the tool such that the protrusions of the microstructured film are a negative replication of the grooves of the tool. The protrusions have a wall angle of 0 degrees resulting in the protrusions being slightly tapered (wider at the light input surface and narrower at the light output surface). The channels of the microstructured film are a negative replication of the uncut portions of the tool between the grooves. Method for Makins Layer-by-Layer Self-Assembled Coatings on Microstructured Film

[0068] Layer-by-layer self-assembled coatings were made using an apparatus purchased from Svaya Nanotechnologies, Inc. (Sunnyvale, Calif.) and modeled after the system described in U.S. Pat. No. 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.

[0069] The apparatus comprises pressure vessels loaded with the coating solutions. Spray nozzles with a flat spray pattern (from Spraying Systems, Inc., Wheaton, Ill.) were mounted to spray the coating solutions and rinse water at specified times, controlled by solenoid valves. The pressure vessels (Alloy Products Corp., Waukesha, Wis.) containing the coating solutions were pressurized with nitrogen to 30 psi, while the pressure vessel containing deionized (DI) water was pressurized with air to 30 psi. Flow rates from the coating solution nozzles were each 10 gallons per hour, while flow rate from the DI water rinse nozzles were 40 gallons per hour. The substrate to be coated was adhered at the edges with epoxy (Scotch-Weld epoxy adhesive, DP 100 Clear, 3M Company, St. Paul, Minn.) to a glass plate (12"xl2"xl / 8" thick) (Brin Northwestern Glass Co., Minneapolis, Minn.), which was mounted on a vertical translation stage and held in place with a vacuum chuck. In a typical coating sequence, the polycation (e.g., PDAC) solution was sprayed onto the substrate while the stage moved vertically downward at 76 mm / sec. Next, after a dwell time of 12 sec, the 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 3 mm / sec. Next, the polyanion (e.g., pigment nanoparticles) 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. The DI water was sprayed onto the substrate while the stage moved vertically upward at 102 mm / sec. Finally, the substrate was then dried with an airknife at a speed of 3 mm / sec. The above sequence was repeated to deposit a number of "bi-layers" denoted as (Polycation / Polyanion), where n is the number of bi-layers. The coated substrate (e.g., polymer film) was peeled off the glass substrate prior to subsequent processing.

[0070] Method for Reactive Ion Etching Microstructured Film

[0071] Reactive ion etching (RIE) was performed in a parallel plate capacitively coupled plasma reactor. The chamber has a central cylindrical powered electrode with a surface area of 18.3 ft2 After placing the microstructured film on the powered electrode, the reactor chamber was pumped down to a base pressure of less than 1.3 Pa (2 mTorr). A mixture of Ar (argon) and 02 (oxygen) gas was flowed into the chamber, each at a rate of 100 SCCM. Treatment was carried out using a plasma enhanced CVD method by coupling RF power into the reactor at a frequency of 13.56 MHz and an applied power of 6000 watts. Treatment time was controlled by moving the microstructured film through the reaction zone. Following the treatment, the RF power and the gas supply were stopped, and the chamber was returned to atmospheric pressure. Additional information regarding materials, processes for applying cylindrical RIE, and further details around the reactor used can be found in U.S. Pat. No. 8,460,568 B2.

[0072] Method for Adhesive Coating

[0073] Monomer premix of the examples was prepared according to the weight ratios described herein and partially polymerized by exposing them to UV rays in a nitrogen atmosphere to form coatable syrups having a viscosity of about 1000 cp. To each syrup, an additional 0.25%wt of Irgacure 651 was added and the syrups were mixed on a roller overnight. The resulting syrups were degassed and knife-coated at a thickness of 150 microns between two silicone treated release liners (RF02N and RF12N). Next, the resulting coating was exposed to a low-intensity UV-ray in an oven (total energy of 1920 mJ / cm2) having a maximum spectrum output from 300-400 nm. The cured OCA sheets were collected.

[0074] Preparation of Adhesive Solution:

[0075] Monomer premix was prepared according to the table above and partially polymerized by exposing it to UV-rays in a nitrogen atmosphere to form a coat-able syrup having a viscosity of about 800 centipoise. To this syrup, an additional 1.0 g of Omnirad 651, 0.6 g of HDDA, and 0.4 g Kbm- 403 were added and the syrups were mixed on a roller overnight to form a homogenous coating solution.

[0076] Preparation of OCA Planarized Micro-Structured Film:

[0077] After Layer-by-layer coating and reactive ion etching the microstructured film, the adhesive was degassed and knife coated onto the micro-structured film, and RF02 release liner (Nippa corporation, Osaka, Japan) was applied on top of the adhesive. The adhesive coating thickness were controlled by the gap of knife coater, and we obtained an adhesive land thickness of approximately 25 pm. Next the resulting coating was exposed to a low intensity UV-ray in an oven (total energy of 2280 mJ / cm2) having a maximum spectrum output from 300-400 nm.

[0078] Peel Testing

[0079] The sheets of adhesive coated microstructured film were cut into strips approximately 1” wide and 12” long, with the long direction of the strip either approximately parallel to the louvers (downweb) or approximately perpendicular to the louvers (crossweb). The liner was peeled and the adhesive strip was then laminated to glass and allowed to sit for approximately one hour before peeling on an Imass peel tester (Imass Inc., Strongsville, OH) at a rate of 300 mm / min and a peel angle of 180. From this test we observed a peel force in the downweb direction of 1.42 kg / ”, and in the crossweb direction of 1.61 kg / ”.

[0080] Optical Testins

[0081] Table 5 is a summary of comparative optical testing performed on two samples, a first microstructured film backfilled with a typical polymeric backfill resin and a second microstructured film backfilled with an optically clear adhesive.

[0082] Table 5: Comparative Optical Testing Results

[0083] Terms such as “about” will be understood in the context in which they are used and described in the present description by one of ordinary skill in the art. If the use of “about” as applied to quantities expressing feature sizes, amounts, and physical properties is not otherwise clear to one of ordinary skill in the art in the context in which it is used and described in the present description, “about” will be understood to mean within 10 percent of the specified value. A quantity given as about a specified value can be precisely the specified value. For example, if it is not otherwise clear to one of ordinary skill in the art in the context in which it is used and described in the present description, a quantity having a value of about 1, means that the quantity has a value between 0.9 and 1.1, and that the value could be 1.

[0084] Terms such as “substantially” will be understood in the context in which they are used and described in the present description by one of ordinary skill in the art. If the use of “substantially equal” is not otherwise clear to one of ordinary skill in the art in the context in which it is used and described in the present description, “substantially equal” will mean about equal where about is as described above. If the use of “substantially parallel” is not otherwise clear to one of ordinary skill in the art in the context in which it is used and described in the present description, “substantially parallel” will mean within 30 degrees of parallel. Directions or surfaces described as substantially parallel to one another may, in some embodiments, be within 20 degrees, or within 10 degrees of parallel, or may be parallel or nominally parallel. If the use of “substantially aligned” is not otherwise clear to one of ordinary skill in the art in the context in which it is used and described in the present description, “substantially aligned” will mean aligned to within 20% of a width of the objects being aligned. Objects described as substantially aligned may, in some embodiments, be aligned to within 10% or to within 5% of a width of the objects being aligned.

[0085] All references, patents, and patent applications referenced in the foregoing are hereby incorporated herein by reference in their entirety in a consistent manner. In the event of inconsistencies or contradictions between portions of the incorporated references and this application, the information in the preceding description shall control. Descriptions for elements in figures should be understood to apply equally to corresponding elements in other figures, unless indicated otherwise. 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

What is claimed:

1. A light control film comprising: an optically transparent unitary film having a unitary construction and comprising: a plurality of spaced-apart structures arranged along substantially an entire length and an entire width of the unitary film and defining a plurality of openings therebetween, each of the structures having a top opposite a base and one or more sides joining the top to the base; and a first continuous land portion; a light absorbing interface layer disposed between each pair of adjacent structure and opening in the plurality of spaced-apart structures and the plurality of openings, the interface layer substantially co-extensive with the structure along a thickness direction of the unitary film and covering at least 50% of the one or more sides of the structure; and an optically transparent adhesive material filling the openings between the structures such that the light absorbing interface layers are disposed between the adhesive material and the one or more sides of the stmctures, the adhesive material forming a second continuous adhesive land portion opposite the first continuous land portion, each of the first and second continuous land portions extending continuously across substantially the entire length and the entire width of the unitary film and joining the structures and the openings, the second continuous adhesive land portion having an average thickness of greater than about 1 micron.

2. The light control film of claim 1, wherein each of the structures has a maximum height of greater than about 1 micron.

3. The light control film of claim 1, wherein the structures have substantially a same cross- sectional shape.

4. The light control film of claim 3, wherein the same cross-sectional shape comprises one or more of round, elliptical, oval, square, rectangular, triangular, trapezoidal, and polygonal.

5. The light control film of claim 1, wherein the structures in the plurality of spaced-apart structures are substantially linear ridges and the openings in the plurality of openings are substantially linear grooves, and wherein the substantially linear ridges and grooves form a substantially linear alternating ridges and grooves extending along substantially a same first direction and arranged along an orthogonal second direction.

6. The light control film of claim 5, wherein the first direction is along the length of the unitary film.

7. The light control film of claim 5, wherein the ridges have an average height of less than about 300 microns along the height direction of the unitary film.

8. The light control film of claim 5, wherein in a planar cross-section of the unitary film that is substantially orthogonal to the light control film and the first direction, each of the ridges has opposing substantially straight first and second sides.

9. The light control film of claim 8, wherein each of the straight first and second sides makes an angle of greater than about 80 degrees with a substantially planar major surface of the light control film.

10. The light control film of claim 1, wherein the structures are posts, having average maximum heights H and average maximum lateral dimensions D, H / D > 1.

11. The light control film of claim 10, wherein the posts comprise one or more of square posts, rectangular posts, cylindrical posts, truncated cone posts, truncated pyramidal posts, polygonal posts, and truncated polygonal posts.

12. The light control film of claim 1 further comprising a first substrate layer disposed on the first continuous land portion opposite the second continuous adhesive land portion.

13. The light control film of claim 12, wherein the first substrate layer is a removable first substrate, such that the removable first substrate layer may be removed from the first continuous land portion with no or very little damage to the first continuous land portion.

14. The light control film of claim 1 further comprising a second substrate layer disposed on the second continuous adhesive land portion opposite the first continuous land portion.

15. The light control film of claim 14, wherein the second substrate layer is a removable second substrate, such that the removable second substrate may be removed from the second continuous adhesive land portion with no or very little damage to the second continuous adhesive land portion.

16. The light control film of claim 1, wherein in a planar cross-section of the light control film that is substantially orthogonal to the light control film, the light absorbing interface layers are substantially straight and make a first angle with a thickness direction of the light control film,17. The light control film of claim 16, wherein when in the cross-section of the light control film a collimated light that extends across at least one light absorbing interface layers and is incident on the light control fdm at an incident angle of substantially the first angle, the light control film transmits at least 50% of the incident light.

18. The light control film of claim 16, wherein when in the cross-section of the light control film a collimated light that extends across at least one light absorbing interface layers and is incident on the light control fdm at an incident angle that is greater than the first angle by at least 10 degrees, the light control film transmits at most 30% of the incident light.

19. The light control film of claim 16, wherein the first angle is at least about 1 degree.

20. The light control film of claim 16, wherein the first angle is at most about 10 degrees.

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