LIGHT DIRECTING SHEETING AND SYSTEMS EMPLOYING THE SAME
An optically transmissive light directing sheeting and a method of making the same are disclosed. The light directing sheeting includes a core sheet of an elastic material that can be laminated onto other surfaces or sandwiched between sheets of various rigid materials. The core sheet includes a plurality of deep and narrow parallel channels configured to direct light by means of a total internal reflection. The method includes a step of slitting of a soft, optically transmissive plastic sheet with a blade and forming at least one array of substantially parallel linear slits in a surface of the sheet, a step of stretching the sheet in a direction perpendicular to the linear slits, and a step of bonding the sheet to a different sheet of an optically transmissive, rigid material. Various light directing devices employing the light directing sheeting are also disclosed.
This application claims priority from U.S. provisional application Ser. No. 62/029,374 filed on Jul. 25, 2014, incorporated herein by reference in its entirety.STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not ApplicableINCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC
Not ApplicableNOTICE OF MATERIAL SUBJECT TO COPYRIGHT PROTECTION
A portion of the material in this patent document is subject to copyright protection under the copyright laws of the United States and of other countries. The owner of the copyright rights has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the United States Patent and Trademark Office publicly available file or records, but otherwise reserves all copyright rights whatsoever. The copyright owner does not hereby waive any of its rights to have this patent document maintained in secrecy, including without limitation its rights pursuant to 37 C.F.R. §1.14.BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to light directing sheeting, films, panels and light control devices incorporating same. More particularly, this invention relates to light directing sheets, panels and films capable of redirecting off-normal light rays at relatively high bend angles, including bend angles exceeding 90 degrees. This invention further relates to light directing sheet-form materials for the use in daylight-harvesting glazing for enhanced natural illumination of building interiors or other types of enclosed structures. It also further relates to window coverings, skylights, artificial light control devices and daylight control devices.
2. Description of Background Art
Various optical films and panels used to redirect light often incorporate prismatic surface microstructures such as linear prism arrays and the like. Such prismatic microstructures typically include surfaces that are not parallel to the prevailing plane of the film or panel and can thus redirect light by a prescribed angle by means of refraction or total internal reflection (TIR).
However, the bend angles that can be achieved using prismatic microstructures are limited and typically are below 60 degrees in practice. Additionally, the exposed micro-prismatic surfaces are prone to soiling and damage. Lamination of such surfaces onto other surfaces without impairing the optical performance of the device is problematic due to the unavoidable air gaps between surface microstructures. Furthermore, micro-prismatic surfaces redirect not only the off-normal rays but also rays that have normal incidence thus impeding the view of objects behind such surfaces.
Accordingly, practical light directing sheet materials are needed that could be implemented with smooth external surfaces and that can be configured to bend light by larger angles. Furthermore, practical light harvesting and light control devices and systems that employ such light directing sheet materials are also needed. These needs and others are met within the present invention, which provides an improved sheet-form structure for redirecting off-normal light rays at high bend angles without the need of outer surface texturing and also provides a method of making the same. The improved sheet-form structure employs internal TIR surfaces to efficiently redirect light and can also be made thin and flexible, finding utility in various light control devices and systems.BRIEF SUMMARY OF THE INVENTION
The present invention solves a number of light redirecting problems within a sheet-form optically transmissive material having a layered structure with a soft and elastic polymeric core material sandwiched between outer sheets of a rigid plastic or glass material. Apparatuses and methods are described for directing and redistributing light using such sheet-form material. The light redirecting functionality is provided by an array of thin reflectors embedded into the body of the core material and configured to reflect at least a portion of light incident onto the sheet surface from an off-normal direction. In at least one embodiment, the reflectors comprise deep and narrow channels formed in a surface of the core material and configured to reflect light by means of a total internal reflection (TIR). Off-normal light rays intercepted by the reflectors can be redirected at high deflection angles with respect to the incident direction.
In at least one embodiment, the invention features a light directing sheet having optically transmissive layers including a layer of an elastic material attached a layer of a rigid material and having one or more arrays of parallel channels formed in its surface and configured to reflect light by means of TIR. In at least one implementation, the light directing sheet includes another layer of a rigid material attached to opposite surface of the elastic layer. In at least one implementation, the layer(s) of a rigid material are permanently bonded or welded to the layer of an elastic material. In at least one implementation, the light directing sheet features smooth outer surfaces and configured to have a transparent or substantially transparent appearance along at least normal viewing angles. In different implementations, the light directing sheet can have various features that alter its optical properties, including but not limited to surface texture, light diffusing features, color tint or filtering features. In different implementations, the elastic material of the light directing sheet can include optically clear or translucent plasticized polyvinyl chloride (PVC-P), thermoplastic polyurethane (TPU), various thermoplastic elastomers or silicones.
According to an aspect of the invention, the TIR channels can be arranges in two parallel arrays crossed at an angle with respect to each other. In at least one implementation, such channel arrays are perpendicular to each other. In different implementations, the channel arrays are formed in the same layer or in different layers of the same or different optically transmissive clear materials.
In at least one implementation, the rigid material is selected from the group of optically transmissive materials consisting of glass, poly(methyl methacrylate), polycarbonate, polystyrene, rigid polyvinyl chloride, polyester, and cyclic olefin copolymer.
In different implementations, the light directing sheet has a rectangular shape and each of the plurality of channels is aligned parallel to either a longer or a shorter dimension of the rectangular shape.
According to an aspect of the invention, the TIR channels have substantially smooth surfaces characterized by a root mean square surface profile roughness parameter of at most about 60 nanometers at a sampling length of between 20 and 100 micrometers. According to another aspect, a root mean square surface profile roughness parameter of at least a substantial portion of the surface of each channel is at least about 10 nanometers at a sampling length of between 20 and 100 micrometers
In at least one implementation, the thickness of the layer of an elastic material is between 200 micrometers and 2 millimeters.
In at least one implementation, at least one edge of the light directing sheet material is made impermeable to moisture and/or air.
In various implementations, the light directing sheet can be attached to surfaces of various glazing materials. In one implementation, the light directing sheet is attached to a window of a building façade. In one implementation, the light directing sheet is attached to a light transmitting surface of a skylight structure. In one implementation, the light directing sheet is attached to the surface of glazing of a greenhouse structure.
In at least one embodiment, the invention features a method for making an optically transmissive light directing sheeting. According to one aspect, the sheeting includes an inner sheet of a soft and flexible material sandwiched between a first and a second outer sheets of rigid material, where the inner sheet including a plurality of narrow channels configured to reflect light by means of a total internal reflection. In at least implementation, the method includes a step of forming at least one array of substantially parallel slits in the inner sheet, a step of stretching the inner sheet in a direction perpendicular to the slits, and a step of bonding a major surface of the inner sheet to a major surface of the first outer sheet. In at least implementation, the step of forming at least one array of substantially parallel slits includes a process of slitting the surface of the inner sheet with one or more razors or rotary blades. In at least implementation, the method further includes a step of bonding an outer surface of the inner sheet to the second outer sheet.
In various embodiments the invention also features different devices for redistributing the light beam emitted by various sources.
In at least one embodiment, the invention features a lighting fixture including a light source, a sheet of optically clear plastic material having a plurality of linear reflectors embedded into the material, where each of the linear reflectors has at least one surface configured to intercept at least a portion of light emanated by the light source and reflect such portion of light by means of a total internal reflection.
In at least one embodiment, the invention features a window covering including a multi-layer sheet of an optically transmissive material having a first and a second outer layers of a rigid material and a core layer of a soft material. The core layer includes a plurality of linear reflectors aligned parallel to a reference line and configured to deflect light propagating through the sheet by means of a total internal reflection.
In at least one embodiment, the invention features a slat of a window or door blinds system. Such slat includes a strip of an optically clear plastic material having a plurality of linear reflectors embedded into the material where each of the linear reflectors has at least one surface configured to reflect light by means of a total internal reflection. In different implementations, each of the linear reflectors is aligned either parallel or perpendicular to a longitudinal dimension of the strip.
In at least one embodiment, the invention features a light redirecting awning including a sheet of an optically clear and flexible material stretched over a frame and having a plurality of parallel linear reflectors embedded into the flexible material, where each of the reflectors has at least one surface configured to reflect light by means of a total internal reflection.
In at least one embodiment, the invention features a light redirecting skylight structure including a plurality of optically transmissive vanes incorporated into a planar horizontal array, where each of the vanes is positioned at an angle with respect to a horizontal plane and comprises the light directing sheet material having a plurality of internal reflectors extending perpendicular to a vane surface. In various implementations, the optically transmissive vanes are arranged into one or more asymmetric or symmetric arrays. In at least one implementation, the optically transmissive vanes make an angle of less than 45 degrees with respect to a horizontal plane. In at least one implementation, the angle is less than 30 degrees.
In at least one embodiment, the invention features a light redirecting skylight insert, including the light directing sheet having a thickness of less than 1.5 millimeters. In different implementation, the shape is a truncated pyramid, a truncated cone, a combination thereon or a nested array of such shapes.
Further embodiments and elements of the invention will be brought out in the following portions of the specification, wherein the detailed description is for the purpose of fully disclosing preferred embodiments of the invention without placing limitations thereon.
The invention will be more fully understood by reference to the following drawings which are for illustrative purposes only:
Referring more specifically to the drawings, for illustrative purposes the present invention is embodied in the apparatus and method generally shown in the preceding figures. It will be appreciated that the apparatus and method may vary as to configuration and as to details of the parts without departing from the basic concepts as disclosed herein. Furthermore, elements represented in one embodiment as taught herein are applicable without limitation to other embodiments taught herein, and in combination with those embodiments and what is known in the art.
The present invention particularly seeks to provide a sheet-form light control material capable of angularly selective redirection of off-normal rays and to further provide illumination components employing such material. The material can be configured to transmit a portion of the incident light and redirect transmits a portion of the incident light with the proportions between the transmitted and redirected light depending on the angle of incidence and controlled by the material structure. The material can also be configured to deflect light at variable bend angles depending on the angle of incidence and particularly provide higher bend angles for relatively high angles of incidence.
The following embodiments of the present invention are generally directed to a sheet-form optical article or system which may be configurable for light redirecting operation in response to light incident onto such optical article or system from directions other than normal and may be further configurable for a generally unimpeded passage of light incident from a normal direction.
Sheets 4, 40, and 60 should be made from optically transmissive materials. Such materials should preferably be optically clear or at least translucent with relatively high light transmissivity so that sheet 2 can effectively transmit at least a substantial portion of light that enters onto either one of the outer surfaces 42 and 64.
The outer sheets 40 and 60 are made from rigid materials. Preferred materials for layers 40 and 60 include but are not limited to glass, poly(methyl methacrylate) (PMMA, acrylic), polycarbonate, polystyrene, rigid polyvinyl chloride, polyester, and cyclic olefin copolymer.
Sheet 4 is made from a relatively soft, flexible and highly elastic material. Such material can be exemplifies by plasticized polyvinyl chloride (also frequently referred to as PVC-P, plasticized PVC, flexible PVC or simply vinyl), thermoplastic polyurethane (TPU), and silicone rubber. More broadly, suitable materials for layer 4 may include various Thermoplastic Elastomers (TPEs) that can be repeatedly stretched to a considerable relative elongation with an ability to return to their approximate original length when stress is released. The material selected for layer 4 should preferably be optically clear but may also have some tint or haze that do not substantially impair its light transmissive properties.
The thickness of sheet 4 may be selected from a range of thicknesses that is typical to films or thin sheets of plastic materials. According to a preferred embodiment, the thickness of sheet 4 is between 200 micrometers and 2 millimeters.
Sheets 40 and 60 may be bonded to the respective surfaces of sheet 4 using optically transmissive adhesives. For example, referring to
The major surfaces of sheet 4 may have a smooth finish and may also be calendered for high gloss and optical transmissivity. Alternatively, either one or both major surfaces of sheet 4 may have some roughness to promote adhesion. However, such roughness should normally be kept to a minimum in order to maintain high overall transmissivity of sheet 2. The outer surfaces 42 and 64 may also be made smooth with a gloss finish or can be provides with a functional or decorative texture.
The rigidity of the outer sheets 40 and 60 should be sufficient to provide at least some minimum flexural rigidity and dimensional stability to sheet 2. Other structural functions of sheets 40 and 60 may include but are not limited to maintaining a planar or other pre-defined three-dimensional shape of sheet 2 as well as preventing wrinkling, elongation or excessive flexing of the panel which may otherwise result from employing soft and flexible materials, such as for example, TPU or plasticized PVC, for the inner sheet 4. It will be appreciated that the layered sandwich structure of sheet 2 may result in such panel having a considerably greater flexural rigidity compared to the individual sheets 40 and 60 and may even exceed the combined flexural rigidity of such sheets when used individually. In most applications, the flexural stiffness of common rigid plastic materials such as polycarbonate, rigid PVC, polyester or acrylic of comparable thickness should be deemed sufficient for finished sheet 2.
Since the thickness of a rigid sheet significantly impacts its flexural rigidity, the thickness of sheets 40 and 60 should be appropriately selected based on the desired application and the overall dimensional parameters of panel 4. In one embodiment, at least one of sheets 40 and 60 may have the thickness of at least one fifth of the thickness of sheet 4. For example, when the thickness of layer 4 is around 1 millimeter, the thickness of layer 40 may be 200 micrometers or greater. However, it should be understood that various applications may require such minimum thickness of sheet 40 and/or 60 to be different, e.g., 0.5 mm, 1 mm, 1.5 mm, 2 mm, etc.
In some cases, flexing of panel 4 may need to be even further minimized or almost eliminated. For example, when sheet 40 is made from glass, even limited bending may result in breakage of the sheet. In another example, sheet 2 may be required to maintain strictly planar shape even at some loads. In such cases, the thickness of sheet 40 can be made 3-4 millimeters or more. Substantially greater thicknesses (e.g., 6 mm or more) may be needed when sheet 2 form a panel that is several meters across.
Referring yet further to
The distance between walls 7 and 8 should be substantially less than the depth of the channel. According to an embodiment of the present invention, the depth of each channel 6 may be at least approximately ten times the average width of the channel. By way of example and not limitation, the average width of each channel 6 may be approximately 20 micrometers or less and the depth of the channel may be at least 200 micrometers. In at least some embodiments, the ratio between the depth and width of channels 6 may be advantageously selected to exceed 15 or 20 times. It may be appreciated that, since sheet 4 is sandwiched between rigid sheets 40 and 60, channels 6 disposed between surfaces 10 and 12 can be protected from the environment and resist soiling and moisture ingress. Furthermore, the rigid sheets 40 and 60 can ensure that the opposing walls 7 and 8 of channels 6 do not close upon each other when sheet 2 is subjected to stresses or deformations during use.
Each of the walls 7 and 8 should have a substantially smooth surface capable of reflecting light by means of a total internal reflection in a specular or near-specular regime while minimizing scattered light. It should be understood that the surfaces of walls 7 and 8 do not have to be absolutely smooth to provide such operation. It can be shown that walls 7 and 8 may provide good reflectivity even with some non-negligible surface roughness as long as such roughness is significantly less than the wavelength. According to one embodiment, a root-mean-square (RMS) roughness parameter of the surface of walls 7 and 8 may be within the range between 0.01 micrometers (10 nanometers) and 0.06 micrometers (60 nanometers), and more preferably between 0.01 micrometers (10 nanometers) and 0.03 micrometers (30 nanometers). The preferred sampling length for measuring such RMS roughness parameter should be between 20 and 100 micrometers and should not generally exceed the depth of channels 6.
By way of example, the inner sheet 4 may have a general structure, operation and/or manufacturing method described in U.S. Pat. No. 9,007,688 to Vasylyev (issued Apr. 14, 2015), herein incorporated by reference in its entirety. It is noted that, where a definition or use of a term in a reference, which is incorporated by reference herein is inconsistent or contrary to the definition of that term provided herein, the definition of that term provided herein applies and the definition of that term in the reference does not apply.
While sheets 4, 40 and 60 are shown having identical dimensions in
According to one embodiment, sheet 60 may represent a planar glass window pane in a building façade and may be a part of optically transmissive glazing such as a wall window, a clerestory window, a door window, a roof window, a skylight, and the like. In such a case, sheets 4 and 40 may have identical dimensions with an area smaller than the area of the glass pane (sheet 60) and thus cover only a certain portion of the pane. Sheets 4 may be first bonded to sheet 40 using optically clear adhesive layer 20 and the resulting sandwich of sheets 4 and 40 may subsequently be laminated onto the surface of the window pane using optically clear adhesive 30. In an exemplary case of the material of sheet 4 having a sufficiently high surface energy, surfaces 12 and 62 may be attached to each other by means of intermolecular attraction (often referred to as “static cling” mechanism) and without the use of adhesive layers.
Surface 12 may be specially configured to make sheet 4 attachable to a smooth glass surface by means of lamination. For this purpose, surface 12 may be optionally calendered using is a series of hard pressure rollers to enhance its smoothness. In order to further enhance the lamination efficiency and/or adhesion to glass, surface 12 may be specially treated for high surface energy or static cling properties, e.g., by using plasma, corona process or chemical treatment.
A predefined reference line 400 in
The dimensions of light directing sheet 2 may vary in a broad range. Particularly, referring to
A portion of ray bundle 202 is intercepted by one of channels 6 and redirected by means of TIR from wall 7 of the channel. It will appreciated that, when walls 7 and 8 are properly separated from each other by an air gap, the condition of TIR will generally be met for a wide range of incidence angle 50, which can take values of up to 90°. Accordingly, such portion of ray bundle 202 may losslessly reflect from the respective wall 7 and exit from the opposing surface 64, as indicated by a ray bundle 204. It will be appreciated that, due to the parallelism of surfaces 42 and 64 and the perpendicularity of channel 6 to such surfaces, ray bundle 204 will have an emergence angle (with respect to normal 644) equal to the incidence angle 50 and will mirror the propagation path of ray bundle 202 in relation to the prevailing plane of sheet 2. Accordingly, the bend angle provided by sheet 2 is simply a function of the incidence angle 50. More particularly, the bend angle is generally twice the angle of incidence 50.
A ray bundle 206 represents a portion of ray bundle 202 that is not intercepted by the respective channel 6 and can thus be transmitted through sheet 2 without redirection, resulting in ray bundle 206 maintaining the original propagation direction of ray bundle 202 upon the exit from surface 64. Accordingly, the depicted configuration of sheet 4 may be used to split an off-normal light beam into two beams propagating away from each other at an angle equal to twice the incidence angle 50. It is noted that the relative distribution of energy between redirected and transmitted light will mainly depend on the geometry of channels 6 and the incidence angle 50. At a given incidence angle, the proportions between the redirected and transmitted light will depend on the ratio between the depth of channels 6 and their spacing. Accordingly, light redirecting properties of sheet 2 may be controlled by selecting the appropriate density at a given depth of channels 6 or, conversely, by selecting the appropriate depth of channels 6 at a given spacing between individual channels.
A ray bundle 208 exemplifies light propagating along a normal direction with respect to a surface of sheet 2. Since ray bundle 208 propagates generally parallel to the plane of channels 6, each ray is transmitted by sheet 2 without any redirection. This illustrates the operation of sheet 2 in which it provides for a generally unimpeded normal-incidence light passage and can therefore have a substantially transparent appearance along the normal viewing direction. When a particularly good view through sheet 2 is required, the width of each channel 6 may be advantageously minimized to make such channels barely visible or even invisible by a naked eye. Obviously, minimizing the width of channels 6 may also increase the useful light throughput of sheet 2 due to minimizing light interception by the edges of channels 6. Accordingly, it may be generally preferred that the average width of channels 6 is below 50 micrometers and may further be preferred that the channel width is below 20 micrometers or even 10 micrometers.
Accordingly, sheet 2 represents an internally microstructured sheet-form structure in which an array of deep and narrow channels 6 embedded into the material of sheet 4 provides an angularly selective operation. The angularly selective operation of sheet 2 in response to the incidence of a light beam onto its major surface resulting in a portion of the incident light being either transmitted or redirected. The proportions between the redirected and transmitted light is defined by the angle of incidence and various parameters of channels 6.
Microstructures 18 may be particularly configured to “soften”, diffuse or otherwise redistribute light redirected and transmitted by sheet 2. Alternatively, or in addition to this, microstructures 18 may be configured to blur the view for privacy and/or provide decorative functions. Various finishes and patterns commonly used for decorative or light diffusing panels may be formed using microstructures 18, including but not limited to matte, microlens, prismatic, diamond, and “frosted glass”. Such microstructures may also be arranged in strips, blocks or various other geometrical or ornamental patterns.
Channels 6 may be formed in sheet 4 by any suitable technique that can produce walls 7 and 8 with sufficiently smooth surface for TIR operation. According to one embodiment, a preferred method of making sheet 2 may include the steps of slitting one of the surfaces of sheet 4 so that a plurality of parallel linear slits is formed that surface, stretching the sheet along a direction perpendicular to the linear slits so that the opposing walls of each slit can be separated from each other, and bonding such surface to a rigid sheet so that the opposing walls separated apart in the previous steps can be permanently fixed in that state and can form stable, yet narrow channels 6. Such method is illustrated in
Blade 9 penetrates relatively deep into the material of sheet 4 and makes the cut by wedging the material out to the sides on its way. The elasticity and easy deformability of the material is essential since it permits for a relatively easy cut formation. The material deforms elastically and relatively easily yields under the cutting pressure, leaving a clean cut without chipping, crazing or irregular tearing. The elastic-type of the deformation on the cutting pressure of blade 9 also ensures that the material returns to its original shape after slitting in the respective area and that channels 6 are formed with straight and parallel walls.
Accordingly, it is preferred that the material selected for sheet 6 has a sufficiently high elastic range. The elastic range can be defined as the maximum deformation (or strain) at which a material reaches its yield strength (or the so-called proportional limit). In other words, the elastic range represents the maximum deformation (e.g., elongation along a length direction) of the material at which the material is still capable to return to its approximate original dimensions using its elastic properties after the stress is removed.
The elastic range can be expressed in terms of a relative elongation of the material with respect to its original length. According to one embodiment, the material of sheet 4 is configured to have an elastic range of at least 10% of its original length, more preferably at least 30%, even more preferably at least 50%, and even more preferably, at least 100%.
On the other hand, it is preferred that the material of sheet 2 is relatively soft to allow for deep blade penetration without breakage or premature dulling. The hardness typical to most grades of TPU or plasticized PVC at room temperatures can be deemed appropriate for the formation of TIR-quality slits. More generally, the material of sheet 4 should preferably have hardness that is below a durometer hardness value of 95 Shore A (as measured in accordance with ASTM D2240 type A scale) at the time of slitting or at least does not significantly exceed such value. If the plastic material is not sufficiently soft at room temperature, it should be heated and softened before the slitting process begins.
Referring further to
Blade 9 should be sufficiently sharp with a sub-micrometer curvature radius of the tip, burr-free and made from a hard material. The surface of blade 9 at least near the cutting edge should be highly polished to a very low level of surface roughness. In one embodiment, the average RMS surface roughness parameter of the surface of blade 9 near the cutting edge should preferably be below 100 nanometers and, even more preferably, below 50 nanometers. The average radius of curvature and the peak to valley RMS surface roughness of the tip of the cutting edge should also be preferably less than 50 nanometers, more preferably, less than 20 nanometers, and even more preferably, less than 10 nanometers.
The penetration depth of blade 9 into sheet 4 is primarily defined by the desired depth of the slits 6 to be formed in the sheet. According to one embodiment, the slitting depth should be greater than 25% of the thickness of the sheet material, and more preferably, greater than 50%. On the other hand, the slitting depth should not generally exceed 95% of the overall thickness of the material so that sheet 4 could retain its structural integrity.
It will be appreciated that, since the effective thickness of the material in the areas below each slit is considerably smaller than the total thickness of sheet 4, the elongation will generally be greater in such areas compared to the adjacent “full thickness” areas. Accordingly, such disproportional elongation of sheet 4 along directions 582 and 584 will favor forming channels 6 and will require applying considerably lower stress compared to the case of stretching sheet 4 when it is intact.
The outer layers 40 and 60 may also be bonded to the inner sheet 4 using a suitable technique which does not involve any adhesives. Examples of such bonding include but are not limited to heat welding, ultrasonic welding, radio-frequency (RF) welding, solvent welding and the like.
It should be understood that the above-described sequence of steps in a method of making panel 4 is not prescriptive and may be modified on case by case basis. For example, in one embodiment, sheet 4 may be bonded or laminated to sheet 30 before bonding to sheet 40. Alternatively, sheet 4 may be encapsulated by a simultaneous bonding or lamination of layers 40 and 60 to respective surfaces 10 and 12. In one embodiment, the step of stretching sheet 4 along directions 582 and 584 (
In a further modification of the method of making sheet 2, heat source 550 can be adjusted to deliver temperatures to sheet 4 that are sufficient for annealing its material and permanently fixing the width of channels 6 that was formed during the material stretching. Sheet 4 can be exposed to such elevated temperature for a period of time sufficient to convert of at least a portion of the elastic deformation into the plastic one. Such annealing can be advantageous for removing the residual stresses in the finally formed sheet 2 and preventing its warping of the slippage of sheet 4 between sheets 40 and 60.
Referring back to
It will be appreciated that, as the temperature gradually increases and reaches a certain temperature, at least some polymeric materials would lose their stiffness and becomes elastic like a rubber. Accordingly, the method illustrated in
The arrangement of parallel channels 6 in sheet 4 is not limited to forming an array of such channels extending parallel to a particular reference line. Sheet 4 may also include other arrays of channels 6 crossed an angle to that array. Referring to
Such perpendicular arrays of channels 6 may be formed in the same layer of sheet 4, as illustrated in
It is noted that all of the layers of sheet 2 materials can be made of optically clear materials with smooth surfaces in which case sheet 2 can be made substantially transparent at least along normal or near-normal viewing directions. Since the proportions between transmitted and redirected light can be precisely controlled by the structure of sheet 4 (e.g., by varying the channel spacing at a constant channel width) sheet 2 can be configured to maintain at least some transparency even at off-normal viewing angles. This is illustrated in
It is further noted that the appearance of sheet 2 may also be configured in a number of ways. For instance, a pigment may be added to its materials thus altering its color or transparency. Particularly, the optical clarity either sheet of sheet 2 may be purposefully reduced so that objects behind the sheet can be masked and/or blurred. In one embodiment, one or more layers of sheet 2 may be tinted or configured for suitable light filtering properties, such as blocking of the infra-red or ultra-violet rays, etc. Also, any suitable image or pattern may be printed on either surface of sheet 2 for decorative purposes. The print may be opaque or transparent/semitransparent and suitable printing techniques may include but are not limited to digital printing, screen printing, stencil-printing, selective dyeing and painting.
Window film 90 incorporating sheet 2 can be attached to surface 80 using a removable or permanent adhesive or using the so-called static cling. Suitable techniques for attaching film 90 to surface 80 may include but are not limited to the dry or wet lamination often used for applying conventional window film products. A preferred mode of operation of such window film 90 can be intercepting at least a portion of daylight incident from off-normal and redirecting such daylight to the ceiling so as to provide improved natural illumination o the building interior while reducing the intensity of the transmitted solar beam and the associated effects that can be unpleasant to the building occupants (e.g., intense heat and glare).
Sheet 2 can be sized to cover a top portion of window pane 300 so that the bottom portion of the window can be used for an unimpeded view of the outside. In this case, sheet 2 may include a textured surface to diffuse the injected beam of sunlight and maximize the uniformity of light distribution within the illuminated space. Alternatively, sheet 2 may be sized to cover essentially the entire surface 80 of pane 300 in order to maximize solar beam filtering and redirection to the ceiling. In this case, sheet 2 may be configured for a maximum transparency so as to preserve the view. The thickness of sheet 2 can be selected from a useful range of film- and thin-sheet-thicknesses that would provide sufficient handling convenience of window film 90 and simplify its lamination onto surface 80. In one embodiment, the thickness of sheet 2 should not exceed 2 millimeters and more preferably should be below one millimeter. The edges of the laminated window film 90 may be optionally sealed to prevent its delamination from surface 80 or moisture ingress between the film and window pane 300.
Sheet 2 can be conveniently attached to bar 530 using brackets 74 and a pair of cords 72. Bar 530 can be attached to the wall surrounding the window pane 300 or directly to such window pane and can be provided with the associated hardware.
In one embodiment, sheet 2 of
It is noted that the illustrated method of hanging sheet 2 in a close proximity of window pane 300 is not prescriptive and can be replaced with any other suitable method known in the art. For example, window covering 70 can have a general design and structure of a track panel
By way of example and not limitation, sheet 2 can replace the woven-type fabric or cloth in stationary or sliding window panels. A representative example of sliding panel window coverings can be the Skyline™ FR Gliding Window Panels commercially available from Hunter Douglas Corporation. A representative example of stationary panel window coverings can be the Freeform Fixed Shade commercially available from MechoSystems Corporation. Similarly to the shadecloth, sheet 2 can be configured as a loose, flexible sheet trimmed to the size and shape of the window opening or glazing and attached to a mounting bar using velcro strips along the edges or using any other suitable means.
In some implementations, window covering 70 may be arranged in multiple bands that are considerably narrower than the respective window pane. Such multiple bands can be hung alongside each other so as to cover the entire window area. Such multiple bands can also be incorporated into stationary or sliding window shade structure that can be operated manually using a chain, cord or wand or automatically using a gear motor and electronic control system.
Window covering 70 may also include various additional functional or decorative layers. Such layer can include but are not limited to light control films, shadecloth, mini- or micro-blinds, and the like. Such layers can be co-laminated together with sheet 2, attached to sheet 2 in multiple locations, or simply hung parallel to sheet 2 with or without touching the sheet.
In one embodiment, window covering 70 can be positioned in a sloped orientation so as to make a prescribed angle with respect to a vertical axis. The slope angle can be advantageously selected provide an improved light control operation, such as enhanced daylight harvesting or direct beam shading. In case of a sloped window, the slope angle of covering 70 can approximate the slope of the window pane. In one embodiment, the slope angle of window covering 70 is made adjustable with manual or automatic control.
The incident daylight is represented by a ray 272 passing through window opening 500 into the room. Ray 272 may particularly exemplify the direct sunlight or diffuse skylight which naturally propagates in a downward direction and therefore tends to directly illuminate only the floor area in a vicinity of the window or various objects nearby.
Window covering 70 incorporating a large-area sheet 2 is disposed in the path of ray 272. Sheet 2 deflects ray 272 from its natural downward propagation direction and redirects it onto a ceiling 320 of room 366.
There are numerous ways of how sheet 2 may be positioned within or in a close proximity to such opening 500. For instance, in addition to the arrangements discussed above in reference to
The ceiling 320 further scatters and redistributes the redirected ray 272 thus enhancing the illumination level and improving lighting distribution within room 366. Redirecting daylight onto the ceiling has a number of advantages. For instance, considering that the incidence direction of daylight changes in a very broad angular during the daytime and seasonally, the large area of the ceiling and its typically uniform light scattering characteristics across the surface ensures that ray 272 is intercepted and properly scattered. Furthermore, since the ceiling is often painted white or in relatively light colors, it may generally have a higher albedo (reflection coefficient) than the floor or various objects in the room interior. As a result, the light energy of ray 272 may be scattered by the ceiling with a relatively low loss compared to scattering from other surfaces in the room and thus ensure more complete sunlight harvesting and utilization for daylighting purposes.
Additionally, it may be appreciated that the surface of a ceiling typically has very good light diffusing properties. Therefore, the reflection of light rays from the ceiling will be primarily of a diffuse type which may result in a relatively homogeneous light distribution in the room and in a reduced glare.
A yet further advantage of redirecting daylight to the ceiling or upper portions of the room interior is that such redirection effectively creates a diffuse source of daylight within the room well above the eye height rather than allowing the direct daylight to reflect or scatter from the lower surfaces and produce blinding glare. A yet further advantage will be apparent when room 366 includes partitions or various tall objects which may partially or totally obstruct natural daylight penetration deep into the room interior. The elevated position of the ceiling, well above the obstruction objects can thus ensure natural illumination of the areas that are otherwise shaded and inadequately illuminated.
Accordingly, positioning sheet 2 in a close proximity or within opening 500 may provide at least partial shading of the room interior and its occupants from the direct sunlight while using the ceiling to convert a substantial portion of the direct beam into diffuse daylight emanated from an overhead location and thus enhancing the overall daylighting level and improving light distribution in the room interior.
In one embodiment, window covering 70 may include one or more areas that are free from channels 16 and are either opaque or configured to provide enhanced light filtering. For example, window covering 70 can be dimensioned to cover the entire window area with a top portion being optically transmissive and configured for light redirection to the ceiling and a bottom portion being opaque and configured for shading the direct solar beam and rejecting the associated excessive glare and/or heat.
In window covering 70, one or more sheets of different materials can be attached to one or more edges of sheet 2. Such additional sheets can serve different purposes. Referring to
The top sheet 690 can also be made from a suitable fabric material but it can also have functions other than shading. In one example, it can have a decorative function or provide edge-strengthening hemming for the top edge of sheet 2. In another example, sheet 690 can be utilized for attaching sheet 2 to a headrail or other structure used to hang window covering 70 in front of a window.
Window covering 70 of
Sheet 2 is oriented in such a way in the awning panel that the longitudinal axis of the parallel array of channels 6 extends parallel to a horizontal plane. Each channel 6 is also formed perpendicular or nearly perpendicular to the surface of sheet 2.
By way of example and not limitation, the angle that the awning panel is making with respect to wall 847 can be around 45° which will position the individual planes of channels 6 at a 45° angle with respect to the vertical direction. Accordingly, when direct sunlight illuminates the stretched sheet 3 directly from the above (e.g., when the sun is near its zenith), awning 800 will bend such sunlight at a right angle and direct it towards window 300. Thus, awning 800 may be used for effectively collecting sunlight from high sun's elevations and directing it into the building interior.
Such operation is further illustrated in
According to some embodiments, light directing sheet 2 may be incorporated into a skylight in a roof or ceiling of a building. This is illustrated in reference to
In operation, by transmitting a first portion of the incident light beam and by redirecting a second portion of the light beam towards a sharply different direction, sheet 2 of
In operation, a ray 902 exemplifying low-angle sunlight impinges onto face 554 and passes through sheet 2 while experiencing redirection downward by a relatively high bend angle due to the interaction with TIR channels 6 (not shown). Such operation can be advantageous, for example, for enhanced harvesting of low-elevation sunlight, such as that occurring in early morning or evening hours or during winter in the Northern hemisphere. By bending the light ray 902 from an oblique propagation to a near vertical propagation direction, skylight 552 can ensure that such ray will be more efficiently transmitted into the interior of a room 372. The vertical or near-vertical propagation can be particularly advantageous in the case when skylight 552 includes a well or a shaft that can scatter or absorb some light at each reflection. In such a case, the vertical or near-vertical light propagation minimizes the number of reflections and can thus minimize the transmission losses.
A light ray 904 exemplifying sunlight incident from intermediate solar elevations is partially transmitted and partially redirected by sheet 2 into a downward direction, as illustrated by ray segments 906 and 908, respectively. Accordingly, in late-morning or afternoon hours or during spring or fall seasons, skylight 552 could redistribute the harvested direct sunlight into a broad angular range while still providing relatively high light transmittance.
A light ray 910 exemplifying a direct solar beam at around noon in summer time is deflected by sheet 2 by a relatively high angle and can thus be either scattered or even rejected. Accordingly, such operation could be advantageous for sunny climates with hot summers where such rejecting or filtering of the excess sunlight (and thus the associated heat) at high solar elevations could improve the occupants' comfort and reduce the space cooling load.
It is generally preferred that the slope angle of face 554 with respect to a horizontal plane is between 10° and 50° and more preferably between about 20° and 45°. According to one embodiment, the slope angle of face 554 is approximately 45°. According to one embodiment, such slope angle is approximately 35° or at least in a 30°-40° angular range. According to one embodiment, face 554 is approximately facing a south direction. According to one embodiment, face 554 is facing an east direction. According to one embodiment, face 554 is facing west direction.
Greenhouses are passive solar structures intended to trap heat from the sun while also admitting natural daylight to the crops using light-transmitting glazing. Many plants require significantly more light for efficient growth than it is normally available in existing greenhouse structures and require supplemental lighting or enhanced daylighting. On the other hand, in year-around greenhouses located in climates with hot summers, a problem exists of reducing the excess light and heat penetration into the greenhouses in summer time. Accordingly, capturing more sunlight with the existing greenhouse structures when such sunlight is scarce and/or rejecting the excess heat at other times could have a direct positive effect on energy saving and crop yield. By employing the light redirecting structure of sheet 2, harvesting of low-elevation sunlight and filtering of high-elevation sunlight can be accomplished thorough a relatively simple retrofit in which sheet 2 is attached to a surface of the existing glazing or otherwise incorporated into such glazing.
A light ray 1960 exemplifies low-elevation sunlight incident into greenhouse 374 through side walls or a lower portion of face 376. The structure of sheet 2 should preferably be designed to result in redirecting the low-elevation sunlight towards a canopy line 1500 of plants 1502 so that light rays that would otherwise miss the canopy line (e.g., rays 1902 and 1904) could be directed to plants 1502 and could also superimpose with other incident rays (e.g., ray 1960) thus effectively increasing the amount of light available to the plants. In addition to this, the structure of sheet 2 can be designed to redirect high-elevation sunlight away from the canopy line 1500.
Sheet 2 can be positioned parallel or at an angle to face 376 by means of hanging or stretching using suitable frame members (not shown) Alternatively, sheet 2 can be laminated onto the inside surface of face 376. Sheet 2 may also be sized to cover only a top portion of face 376 or the entire surface of face 376. According to one embodiment, sheet 2 covers at least a third of the surface of face 376 and the covered surface includes at least a top portion of the surface of face 376.
In the illustrated east-west orientation of the longitudinal axis and respectively north-south orientation of opposing faces 378 and 376 of greenhouse structure 374, such greenhouse can be configured to capture additional sunlight for plants 1502 in winter time (when such sunlight is particularly at premium). It can be further configured to reduce heat intake in the summer by providing enhanced light filtering and a partial shade due to redirecting a portion of incident light away from plants 1502 and out of the greenhouse structure. In an alternative configuration, a northern portion of the greenhouse structure 374 may be provided with a mirrored film to minimize light spillage at low solar elevations or capture additional direct sunlight in winter time. For example, a portion of face 378 can be covered such mirrored film.
In a north-south orientation, such greenhouse structure 374 can be configured to provide enhanced illumination of plants 1502 in early morning or late evening hours while rejecting or filtering the excess light and heat around the noon time. This is illustrated in
It is noted that, although light directing sheet 2 may be conventionally rectangular or square and may be made in forms of a large-format sheet or a roll, it may be cut to any size or shape using any suitable cutting technique to fit a particular application. Sheet 2 may also be bent to any suitable shape or wrapped around an object or a volume. In at least one embodiment, sheet 2 may be formed into a closed cylindrical, conical, or pyramidal shape. Alternatively, multiple sheets 2 may be connected together to form such shapes.
In operation, downlight module 98 emits a cone of light in a downward direction. At least a portion of such light is intercepted by one or more sheets 2 of diffuser lens 750 using embedded TIR reflectors of channels 6 and is redirected to a ceiling 760. Ceiling 760 further scatters the redirected light into different downward directions. Since diffuser lens blocks at least a substantial part of light rays from the direct propagation from downlight module 98 while redirecting the respective rays to the ceiling for indirect illumination, the apparent brightness of the source and the associated glare may be considerably reduced without appreciable reduction of the overall light output. When the reflectivity of ceiling 760 is not sufficient for high efficiency reflection, the ceiling area surrounding downlight module 98 may be covered with a bright light diffusing material to reduce energy losses. In one embodiment, sheet 2 of diffuser lens 750 may be made from an optically transparent material and provides with smooth outer surfaces. In one embodiment, such sheet 2 may be provided with light diffusing features such as surface texture or a light diffusing material to further mask the light source or improve light distribution pattern.
Slat 600 is defined by opposing broad area surfaces 42 and 64, opposing terminal edges 611 and 613, and opposing side edges 615 and 617. Slat 600 has a plurality of embedded TIR reflectors formed by a parallel array of channels 6. In an exemplary non-limiting case, the TIR reflectors are formed in a strip of 0.08 inch (around 2 mm) optically clear plasticized PVC sheet material which is sandwiched between two other identically shaped strips of optically clear, rigid plastic material. Clear plasticized PVC strips are commercially available, for example, from Tap Plastics in the form of clear vinyl strips having a width of 8 inch and sold by the foot. Similarly to conventional vertical blind slats, slat 600 may have a through notch 609 which can be used for attaching the slat to a headrail or other-type horizontal structures.
Referring further to
One of the broad-area surfaces 40 and 64 may be configured for light input and the one can be configured for light output, respectively. In
It will be appreciated that, when slats 600 are in a suspended position, each internal TIR surface formed by channels 6 in such slats will be generally parallel to the horizontal plane in any allowed slat orientation. Thus, in operation, when the blinds structure 700 is fully deployed and slats 600 are closed, daylight can enter into the room while being advantageously redirected by horizontal channels 6 towards the ceiling and can thus be redistributed through the interior more efficiently. When slats 600 are fully retracted or open, little or no direct sunlight will be intercepted and redirected by the slats. Accordingly, the daylighting operation of the vertical blinds structure 700 and the distribution of daylight in the building interior may be controlled by simple operations such as deploying, retracting, opening or closing of the blinds.
According to one embodiment, a strip of light directing material having the structure of sheet 2 may be incorporated into horizontal venetian blinds structure. In this case, one or more slats of the horizontal blinds may be formed by a strip-shaped sheet 2 where, unlike the vertical blinds slat of
An embodiment of a horizontal window blinds structure 900 is illustrated in
As illustrated in
When slats 920 are in a fully closed position (
Slats 920 may be adjusted to any intermediate angular orientation between the fully open and fully closed position in which case the amount of rejected and/or admitted light can be controlled for almost any solar elevation. It is noted that, similarly to the conventional venetian blinds, blinds structure 900 may be configured so that slats 920 can be rotated almost 360 angular degrees and either concave or convex surfaces of the slats may be exposed to the incident sunlight. It is further noted that, by adjusting the angular position of slats 920, the angular direction of the admitted daylight with respect to a horizontal plane may be varied in a broad range. Such operation is illustrated in
Light directing sheet 2 of skylight 544 may have a rectangular configuration which can be planar or bent to a slightly curved shape. Sheet 2 is positioned at an angle with respect to a horizontal plane which is preferably below 45°, and more preferably is within a 5°-35° angular range. Such sheet 2 may be mounted in a fixed position at a preselected slope angle which is optimized for specific geographical latitude and oriented with its light-receiving surface 42 facing south. It may also be rotatably mounted to provide with single- or dual-axis solar tracking. In one embodiment, light directing sheet 2 can be rotated around a horizontal axis. Alternatively, or in addition to that, sheet 2 can be rotated around a vertical axis.
In operation, a low-elevation light ray 472 striking sheet 2 is redirected downwards along a vertical direction. A high-elevation ray 474 passes through sheet 2 without being redirected. An opposite low-elevation ray 476 enters skylight 544 with its light path unimpeded by sheet 2. Accordingly, the light redirecting insert formed by sheet 2 intercepts and redirects at least a portion of sunlight that is incident onto the light receiving aperture of skylight 544 from low-elevation angles. It will be appreciated that, for a tubular skylight, redirecting low-angle light towards the vertical will typically increase the light output on the exit side due to fewer reflections from the mirrored walls of the skylight's light-guiding tube.
Strips of light redirecting sheet 2 may be used to form different configurations of slats, louvers or vanes which can be incorporated into a broad variety of daylighting systems and configured to improve sunlight harvesting efficiency.
Each of the vanes 560 is positioned at a predefined angle (slope angle) with respect to a horizontal plane. Such slope angle may be the same for each vane 560 or it may be different for each vane. According to one embodiment, the slope angle should preferably be between 0° and 45°, and more preferably between 5° and 30°.
In one embodiment, vanes 560 may be oriented horizontally and faced the south in northern hemisphere or the north in the southern hemisphere to maximize daylight capture in winter or in summer, respectively. Alternatively, vanes 560 may be faced towards the east or west to maximize daylight harvesting in the morning or evening hours, respectively.
It is noted that, unlike specularly reflective vanes sometimes utilized in skylights, vanes 560 can be made substantially transmissive for the normal incidence rays (see. e.g., the path of a ray 574 in
Vanes 560 may be made stationary and permanently oriented towards a predetermined direction. Alternatively, vanes 560 can be made rotatably movable around one or more axes. In one embodiment, each vane 560 is made rotatable around a horizontal axis. In one embodiment, a group of vanes 560 can be rotated around a vertical axis configuration. In such configuration, the entire light-redirecting insert can be mounted on a vertical shaft or placed on a turntable-type structure. Accordingly, vanes 560 may be configured for one- or two-axis solar tracking to maximize sunlight capture daily and/or seasonally.
Vanes 560 may be arranged into two symmetrically disposed arrays, for example, as shown in
The spacing areas between vanes 560 and the dimensions and parameters of the vanes may be designed so that that the skylight could provide a nearly constant light output during the day. This can be achieved, for example, by capturing more sunlight in early morning and late evening hours and by rejecting a portion of sunlight when the sun is near its zenith, according to the principles similar to those discussed in reference to
When the ability of a skylight to intercept low-angle light rays from all-directions is desired, light directing sheet 2 or multiple pieces of such sheet may be formed into a three-dimensional shape providing a multi-directional or omni-directional operation.
A multi-directional structure employing light-directing sheeting of the present invention is illustrated in
The pyramidal shape of skylight insert 1100 may be formed directly from a single sheet 2 pre-cut into an appropriate two-dimensional template. Alternatively, such structure may be formed from an optically transmissive sheet or rigid film material in which case individual sheets 2 may be laminated onto the respective faces of the structure. Furthermore, an appropriate skylight dome may be formed into such pyramidal shape and such sheets 2 may be laminated directly onto the inside surfaces of the shape.
Such inserts 1100 may also be made in different sizes and arranged in a nested configuration.
It is noted that sheet 2 may be formed in any other suitable three-dimensional shapes which are not limited to basic geometrical shapes. For this purpose, sheet 2 can be cut into appropriate two-dimensional templates that can be bent or otherwise formed into self-supporting 3D structures.
Further details of the structure and operation of light directing sheeting of the invention and the method for making the same, as shown in the drawing figures, as well as their possible variations will be apparent from the foregoing description of preferred embodiments. Although the description above contains many details, these should not be construed as limiting the scope of the invention but as merely providing illustrations of some of the presently preferred embodiments of this invention. Therefore, it will be appreciated that the scope of the present invention fully encompasses other embodiments which may become obvious to those skilled in the art, and that the scope of the present invention is accordingly to be limited by nothing other than the appended claims, in which reference to an element in the singular is not intended to mean “one and only one” unless explicitly so stated, but rather “one or more.” All structural, chemical, and functional equivalents to the elements of the above-described preferred embodiment that are known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the present claims. Moreover, it is not necessary for a device or method to address each and every problem sought to be solved by the present invention, for it to be encompassed by the present claims. Furthermore, no element, component, or method step in the present disclosure is intended to be dedicated to the public regardless of whether the element, component, or method step is explicitly recited in the claims. No claim element herein is to be construed under the provisions of 35 U.S.C. 112, sixth paragraph, unless the element is expressly recited using the phrase “means for.”
1. Light directing sheeting, comprising:
- a sheet of an optically transmissive and elastic material defined by a first major surface and an opposing second major surface extending parallel to said first major surface, said sheet of an optically transmissive and elastic material comprising a plurality of narrow channels extending between said first and second major surfaces, wherein each of the plurality of narrow channels comprises a first wall and an opposing second wall that are configured to reflect light by means of a total internal reflection.
2. Light directing sheeting as recited in claim 1, wherein the material of said sheet comprises optically clear or translucent plasticized polyvinyl chloride.
3. Light directing sheeting as recited in claim 1, wherein the material of said sheet comprises optically clear or translucent thermoplastic polyurethane.
4. Light directing sheeting as recited in claim 1, wherein the material of said sheet is selected from the group of polymeric materials consisting of optically clear or translucent thermoplastic elastomers, optically clear or translucent polyurethanes, and optically clear or translucent silicones.
5. Light directing sheeting as recited in claim 1, wherein said optically transmissive and elastic material has a durometer hardness below 95 Shore A.
6. Light directing sheeting as recited in claim 1, wherein said optically transmissive and elastic material has an elastic range of at least 10% relatively to its original length.
7. Light directing sheeting as recited in claim 1, wherein said optically transmissive and elastic material has an elastic range of at least 30% relatively to its original length.
8. Light directing sheeting as recited in claim 1, wherein said sheet of an optically transmissive and elastic material is sandwiched between a first sheet of a rigid material and a second sheet of a rigid material.
9. Light directing sheeting as recited in claim 6, wherein the material of at least one of said first and second sheets of a rigid material is selected from the group of optically transmissive materials consisting of glass, poly(methyl methacrylate), polycarbonate, polystyrene, rigid polyvinyl chloride, polyester, and cyclic olefin copolymer.
10. Light directing sheeting as recited in claim 6, further comprising at least one layer of optically clear adhesive for bonding together said sheet of an optically transmissive and elastic material and at least one of said first and second sheets of a rigid material.
11. Light directing sheeting as recited in claim 1, wherein each of the plurality of channels is aligned parallel to a predefined reference line.
12. Light directing sheeting as recited in claim 1, wherein said plurality of narrow channels is formed by a first array of said channels aligned parallel to a first reference line and a second array of said channels aligned parallel to a second reference line, said first and second reference lines being perpendicular to each other.
13. Light directing sheeting as recited in claim 1, wherein said sheet includes a first layer and a second layer, and wherein a first array of the plurality of said channels is formed in said first layer and a second array of the plurality of said channels is formed in said second layer.
14. Light directing sheeting as recited in claim 13, wherein channels of the first array are generally perpendicular to the channels of the second array.
15. Light directing sheeting as recited in claim 1, wherein a root mean square surface profile roughness parameter of each of said walls is at most about 60 nanometers at a sampling length of between 20 and 100 micrometers.
16. Light directing sheeting as recited in claim 1, wherein a root mean square surface profile roughness parameter of at least a substantial portion of the surface of each of said walls is at least about 10 nanometers at a sampling length of between 20 and 100 micrometers.
17. Light directing sheeting as recited in claim 1, wherein the thickness of said intermediate sheet is between 200 micrometers and 2 millimeters.
18. Light directing sheeting as recited in claim 1, wherein at least one edge of said sheet material is made impermeable to moisture and/or air.
19. Light directing sheeting as recited in claim 1, further comprising light diffusing features.
20. Light directing sheeting as recited in claim 1, further comprising surface microstructures.
Filed: Jul 11, 2015
Publication Date: Jan 28, 2016
Inventor: SERGIY VASYLYEV (ELK GROVE, CA)
Application Number: 14/797,102