WO2017004003A1 - Barrier elements for light directing articles - Google Patents

Barrier elements for light directing articles Download PDF

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Publication number
WO2017004003A1
WO2017004003A1 PCT/US2016/039750 US2016039750W WO2017004003A1 WO 2017004003 A1 WO2017004003 A1 WO 2017004003A1 US 2016039750 W US2016039750 W US 2016039750W WO 2017004003 A1 WO2017004003 A1 WO 2017004003A1
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WO
WIPO (PCT)
Prior art keywords
article
adhesive
barrier
major surface
layer
Prior art date
Application number
PCT/US2016/039750
Other languages
English (en)
French (fr)
Inventor
John P. Baetzold
Suman K. Patel
Denis TERZIC
Mikhail L. Pekurovsky
Erik A. AHO
Scott M. Tapio
Manoj Nirmal
John J. Stradinger
Original Assignee
3M Innovative Properties Company
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by 3M Innovative Properties Company filed Critical 3M Innovative Properties Company
Publication of WO2017004003A1 publication Critical patent/WO2017004003A1/en

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Classifications

    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/12—Reflex reflectors
    • G02B5/122—Reflex reflectors cube corner, trihedral or triple reflector type
    • G02B5/124—Reflex reflectors cube corner, trihedral or triple reflector type plural reflecting elements forming part of a unitary plate or sheet
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/04—Prisms

Definitions

  • the present disclosure relates to barrier elements and their use on a light directing articles, such as daylight redirecting articles, which comprise microstructured elements, for example, in the form of a microstructured optical film.
  • Light directing articles have an ability to manipulate incoming light.
  • Light directing films and sheeting typically include an optically active portion that may be microstructured elements or beads.
  • Light directing articles may allow portions of light to pass through the substrate in a controlled manner, such as light redirecting films.
  • the microstructured elements are typically microstructured prisms.
  • the light directing articles may not be transmissive to light and instead reflect all incident light. Throughout this disclosure the terms light directing articles and light redirecting articles are used interchangeably.
  • Daylight redirecting films provide natural lighting by redirecting incoming sunlight upward, onto the ceiling. This can lead to significant energy savings by reducing the need for artificial lights.
  • Light Redirection Films can consist of linear optical microstructures that reflect incoming sunlight onto the ceiling. DRFs are typically installed on the upper clerestory section of windows T and above. A typical configuration is shown on Figure 1.
  • Sunlight that would normally land on the floor can be used to provide natural lighting by using suitable constructions involving daylight redirecting films.
  • Figure 2 shows an example of the amount of light that can be redirected from the floor to the ceiling by the use of a DRF.
  • microstructured light redirecting films may be fragile under certain conditions
  • microstructured features may be subject to mechanical damage and/or chemical damage (e.g. window cleaners).
  • One challenge when attempting to protect the microstructured elements in a DRF is that the lamination process to add a cover or protective layer can cause damage to those microstructured elements.
  • the same challenge is present when attempting to laminate any other type of functional layer or film, such as a diffuser, to a DRF on the side of the microstructured elements.
  • the presence of an additional layer next to the DRF may also modify its optical properties and significantly decrease or nullify its light redirecting properties.
  • retroreflective articles may redirect incident light towards its originating source, and are referred to as retroreflective articles.
  • the ability to retroreflect light has led to the wide-spread use of retroreflective sheetings on a variety of articles.
  • the microstructured element typically is a microstructured prism that is a cube-corner.
  • U.S. Patent 5,450,235 shows an example of a cube-corner retroreflective sheeting.
  • a cube corner element typically includes three mutually perpendicular optical faces that intersect at a single apex.
  • light that is incident on a corner cube element from a light source is totally internally reflected from each of the three perpendicular cube corner optical faces and is redirected back toward the light source.
  • Presence of, for example, dirt, water, and adhesive on the optical faces can prevent total internal reflection (TIR) and lead to a reduction in the retroreflected light intensity.
  • TIR total internal reflection
  • the air interface is typically protected by a sealing film.
  • sealing films may reduce the total active area, which is the area over which
  • sealing films increase the manufacturing cost. Additionally, the sealing process can create a visible pattern in the retroreflective sheeting that is undesirable for many applications, such as, for example, use in a license plate and/or in commercial graphics applications where a more uniform appearance is generally preferred.
  • Metalized cube corners do not rely on TIR for retroreflective light, but they are typically not white enough for daytime viewing of, for example, signing applications. Furthermore, the durability of the metal coatings may be inadequate.
  • One of the goals of the present disclosure is to provide film constructions that allow the bonding of a microstructured film, to another functional film, without significantly sacrificing the optical performance of the microstructured film, while maintaining robust mechanical properties of the entire construction.
  • the disclosed light redirecting article comprises a structured layer, an adhesive layer, and barrier elements.
  • the structured layer comprises multiple microstructured elements that are opposite a major surface.
  • the adhesive layer has a first region and a second region. The second region is in contact with the structured layer.
  • the barrier elements are in contact with the first region.
  • the physical and rheological properties of the first and second regions are the same because they are part of the same adhesive material.
  • the barrier element comprises a crosslinked polymeric matrix having a modulus of elasticity from 1.5 Gpa to 4.4 Gpa.
  • the barrier element comprises a crosslinked polymeric matrix having a modulus of elasticity from 2 Gpa to 4.4 Gpa, or alternatively from 2.3 Gpa to 4.3 Gpa, or alternatively from 2.5 Gpa to 3.4 Gpa.
  • adheresive refers to polymeric compositions useful to adhere together two components (adherents).
  • window film adhesive layer refers to a layer comprising an adhesive suitable to bond a film to a window or glazing, such as, for example, a pressure sensitive adhesive.
  • adjacent refers to the relative position of two elements, such as layers in a film construction that are close to each other and may or may not be necessarily in contact with each other and may have one or more layers separating the two elements, as understood by the context in which "adjacent" appears.
  • immediately adjacent refers to the relative position of two elements, such as layers in a film construction, that are immediately next to each other without having any other layers separating the two elements, as understood by the context in which "immediately adjacent" appears.
  • construction or “assembly” are used interchangeably in this application when referring to a multilayer film, in which the different layers can be coextruded, laminated, coated one over another, or any combination thereof.
  • light redirecting layer refers to a layer that comprises microstructured prismatic elements.
  • light redirecting film refers to a film that comprises one or more light redirecting layers and optionally other additional layers, such as substrates or other functional layers.
  • Light redirection in general, may be called daylight redirection, sunlight redirection, or solar light redirection when the source of light is the sun.
  • film refers, depending on the context, to either a single layer article or to a multilayer construction, where the different layers may have been laminated, extruded, coated, or any combination thereof.
  • barrier elements refers to physical features laid on top of regions of an adhesive layer that help maintain the optical performance of the light redirecting layer when the adhesive layer and light redirecting layer are bonded to each other in opposing fashion.
  • the barrier elements prevent the adhesive layer from filling the space surrounding microstructured prismatic elements and are able to provide an interface between the DRF and a low refractive index material, such as air or aerogel.
  • the barrier elements are also called "passivation islands,” or "islands.”
  • microstructured prismatic element refers to an engineered optical element, wherein at least 2 dimensions of the features are microscopic, that redirects input light with certain angular characteristics into output light with certain angular characteristics.
  • the height of the microstructured prismatic element is less than 1000 microns.
  • a microstructured prismatic element may comprise a single peak structure, a multipeak structure, such as a double peak structure, structures comprising one or more curves, or combinations thereof.
  • microstructured prismatic elements including all of their physical and optical characteristics (e.g., glare, TIR angles, etc.), are disclosed in provisional applications titled “Room-Facing Light Redirecting Film with Reduced Glare” and “Sun-Facing Light Redirecting Film with Reduced Glare,” both filed on October 20, 2014, and having application nos. 62/066,307 and 62/066,302respectively, are hereby incorporated by reference.
  • the term "diffusing agent” as used herein refers to features or additives incorporated in the article that increase the angular spread of light passing through the same article.
  • reproducing 1-dimensional pattern refers to features that are periodic along one direction in reference to the article.
  • reproducing 2-dimensional pattern refers to features that are periodic along 2 different directions in reference to the article.
  • random-looking 1- or 2-dimensional pattern refers to features that appear not to be periodic or semi-periodic along one or two different directions in reference to the article. Those features may still be periodic but with a period sufficiently larger than the mean pitch of individual features so that the period is not noticeable to most viewers.
  • the index of refraction of a material 1 is said to "match" the index of refraction of a material 2 ("RI2”) if the value RI1 is within +/- 5% of RI2.
  • a light redirecting layer has a first major surface and second major surface opposite the first major surface and that the first major surface of the light redirecting film comprises microstructured prismatic elements.
  • the microstructured prismatic elements in a "room-facing" configuration are oriented facing the interior of the room.
  • the term “room-facing,” as defined herein can also refer to configurations where the light redirecting film is on a glazing, or other kind of substrate, that does not face the exterior of the building, but is in between two interior areas.
  • the term "sun-facing,” in the context of a light redirecting film or a construction comprising a light redirecting film, refers to a film or construction where the incident light rays pass through the major surface of the light redirecting film containing the
  • microstructured prismatic elements before they pass through the other major surface (the major surface not containing the microstructured prismatic elements).
  • the microstructured prismatic elements in a "sun-facing" configuration are oriented facing the sun.
  • the term "sun-facing,” as defined herein can also refer to configurations where the light redirecting film is on a glazing that does not face the exterior of the building, but is in between two interior areas.
  • the term “sealing” or “sealed” when referring to an edge of an article of this disclosure means blocking the ingress of certain undesired elements such as moisture or other contaminants.
  • setting refers to transforming a material from an initial state to its final desired state with different properties such as flow, stiffness, etc., using physical (e.g. temperature, either heating or cooling), chemical, or radiation (e.g. UV or e-beam radiation) means.
  • visible light refers to refers to radiation in the visible spectrum, which in this disclosure is taken to be from 400 nm to 700 nm.
  • FIGS. 1A and IB are schematic side views of one exemplary embodiment of a light redirecting article of the present disclosure.
  • FIG. 2 is schematic drawing of one exemplary intermediary step in forming the light redirecting article of FIG. 1.
  • FIG. 3 is a schematic drawing of one exemplary embodiment of a light redirecting article of the present disclosure.
  • FIG. 4 shows a construction having both clear view-through regions and light redirecting regions.
  • FIG. 5 shows a room-facing configuration having a light redirecting film and diffuser.
  • FIG. 6 shows two different sun-facing configurations having a light redirecting film and diffuser.
  • the panel on the left-hand side is Figure 6A and the panel on the right-hand side is Figure 6B.
  • FIG. 7 is a schematic diagram of a typical process to bond a microstructured film to a second film.
  • Figure 7A shows the film before bonding and
  • Figure 7B shows the film after bonding.
  • FIG. 8 shows three different patterns for barrier elements.
  • FIG. 8A shows an example of a daylight redirecting glazing construction with see-through regions.
  • FIG. 9 shows barrier elements that have partially merged.
  • FIG. 10 shows barrier elements that are well defined.
  • FIG. 11 shows a DRF laminate in which the barrier elements show evidence of widespread failure.
  • FIG. 12 is a cross-sectional view of failed barrier elements.
  • FIG. 13 is a photomicrograph of one embodiment of the invention, showing a DRF laminate in which the barrier elements show no sign of failure.
  • FIGS. 1A and IB are schematic side views of one exemplary embodiment of a light redirecting article 100 of the present disclosure, where the adhesive sealing layer 130 is a pressure sensitive adhesive.
  • FIG. 2 is a schematic drawing of one exemplary intermediary step in forming the light redirecting article 100 of FIG. 1.
  • FIG. 3 is a schematic drawing of one exemplary embodiment of a light redirecting article 100 of the present disclosure where the adhesive sealing layer 130 is a structured adhesive. Detailed descriptions of these constructions will be provided below. Similar elements in each of the figures are marked with similar reference numbers.
  • the disclosed light redirecting article 100 comprises a structured layer 110 and an adhesive sealing layer 130.
  • the structured layer 110 comprises multiple microstructured elements 112 that are opposite a major surface 116 of the structured layer 110.
  • the surface containing the microstructured elements 112 can be referred to as a structured surface 114 of the structured layer 110.
  • the adhesive sealing layer 130 has a first region and a second region wherein the second region is in contact with the structured layer 110.
  • a barrier element 134 is provided at the first region of the adhesive sealing layer 130. The first region with the barrier element and second region have sufficiently different properties to form a low refractive index region between the adhesive sealing layer 130 and the structured layer 110.
  • the barrier element comprises a crosslinked polymeric matrix having a modulus of elasticity from 1.5 Gpa to 4.4 Gpa. In other embodiments, the barrier element comprises a crosslinked polymeric matrix having a modulus of elasticity from 2 Gpa to 4.4 Gpa, or alternatively from 2.3 Gpa to 4.3 Gpa, or alternatively from 2.5 Gpa to 3.4 Gpa.
  • the type of bonding disclosed and taught in this application between two films refers to bonding only via selected areas in the light redirecting film in order to preserve the light redirecting function (or a suitable function in other microstructured optical films) of the film. Because the presence of the adhesive contacting the microstructured prismatic elements substantially destroys the ability to redirect light, there is a natural balance between the size of the areas that effect the bonding (partially optically active areas) between the two films and the size of the areas that are optically active (able to redirect light). Thus, to maximize the light management through the microstructured element, it is desired that the portions of the microstructured elements in contact with the barrier elements not be in contact with the adhesive or penetrate into the barrier element.
  • the barrier element forms a physical "barrier" between the adhesive of the adhesive sealing layer and the microstructured element.
  • Barrier element has sufficient structural integrity to prevent the adhesive sealing layer from flowing into a low refractive index region that is between structured surface and barrier layer.
  • Barrier layer can directly contact or be spaced apart from or can push slightly into the tips of microstructured elements.
  • the microstructured element is not in contact with the adhesive of the adhesive sealing layer in areas where the barrier elements are present or that the microstructured element penetrate into the barrier element because then that microstructured element's ability to manage the incoming light is lost or minimized at that portion of the microstructured element that has penetrated into the adhesive or the barrier element.
  • the light redirecting article is a retroreflective article
  • the cube-corner's ability to retroreflect the incident light is lost in the portion of the cube-corner prism that has penetrated into the barrier element.
  • the light redirecting article is a DRF, the ability to redirect light is lost or reduced because the refractive properties of the microstructure change in the portion that penetrates the barrier element.
  • compositions chosen may be based on mono-acrylate, diacrylate, and higher multifunctional acrylate materials.
  • the average functionality is the weight average of the functionalities of all the components in the mixture.
  • the chemistries may be chosen from many classes of acrylates, including urethane acrylates, polyester acrylates, acrylic acrylates, and pentaerythritol-based acrylates, for example.
  • the brittleness can be evaluated by creating thick films of the cured barrier element material and conducting tensile tests (stress versus strain) experiments. In general, brittle materials fail with little or no elongation. In addition, when cast into a film and cured, these films crack with little handling.
  • the barrier element comprises a crosslinked polymeric matrix having a modulus of elasticity from 1.5 Gpa to 4.4 Gpa. In other embodiments, the barrier element comprises a crosslinked polymeric matrix having a modulus of elasticity from 2 Gpa to 4.4 Gpa, or alternatively from 2.3 Gpa to 4.3 Gpa, or alternatively from 2.5 Gpa to 3.4 Gpa.
  • the barrier elements 134 should be sufficiently thick to prevent the microstructured element 1 12 from breaking through into the adhesive sealing layer 130.
  • the crosslinked polymeric matrix of the barrier element 134 is at least 1.6 microns thick. In one embodiment, the barrier element 134 is at least 1.75 microns thick. In one embodiment, the barrier element 134 is at least 2.0 microns thick. In other embodiments, the barrier element 134 is at least 3 microns thick. In other embodiments, the barrier element 134 is at least 5 microns thick. In other embodiments, the barrier element 134 is at least 7 microns thick. In other embodiments, the barrier element 134 is at least 8 microns thick. In other embodiments, the barrier element 134 is at least 10 microns thick.
  • the barrier element 134 has a thickness from 1.6 microns to 10 microns. In other embodiments, the barrier element 134 has a thickness from 1.6 microns to 8 microns. In other embodiments, the barrier element 134 has a thickness from 1.6 microns to 7 microns. In other embodiments, the barrier element 134 has a thickness from 1.6 microns to 5 microns. In other embodiments, the barrier element 134 has a thickness from 1.6 microns to 3 microns. In other embodiments, the barrier element 134 has a thickness from 1.6 microns to 2 microns.
  • the barrier element 134 has a thickness from 1.75 microns to 10 microns. In other embodiments, the barrier element 134 has a thickness from 1.75 microns to 8 microns. In other embodiments, the barrier element 134 has a thickness from 1.75 microns to 7 microns. In other embodiments, the barrier element 134 has a thickness from 1.75 microns to 5 microns . In other embodiments, the barrier element 134 has a thickness from 1.75 microns to 3 microns. In other embodiments, the barrier element 134 has a thickness from 1.75 microns to 2 microns.
  • the barrier element 134 has a thickness from 2 microns to 10 microns. In other embodiments, the barrier element 134 has a thickness from 2 microns to 8 microns. In other embodiments, the barrier element 134 has a thickness from 2 microns to 7 microns. In other embodiments, the barrier element 134 has a thickness from 2 microns to 5 microns. In other embodiments, the barrier element 134 has a thickness from 2 microns to 3 microns.
  • the barrier element 134 has a thickness from 3 microns to 10 microns. In other embodiments, the barrier element 134 has a thickness from 3 microns to 8 microns. In other embodiments, the barrier element 134 has a thickness from 3 microns to 7 microns. In other embodiments, the barrier element 134 has a thickness from 3 microns to 5 microns.
  • the disclosed barrier element prevents wetting of microstructured element 112 by the pressure sensitive and prevents the microstructured elements 1 12 from penetrating into the barrier element 134, for example, either initially during fabrication of the light redirecting article, during fabrication when the material is stacked, handled, or laminated, or over time due pressure and flexing of to the viscoelastic nature of the adhesive. Trapped air between pressure sensitive adhesive 130 and microstructured elements 1 12 creates low refractive index region 138. Other materials, such as aerogel, may be used in place of air, as long as the material has a refractive index that allows the microstructured elements to redirect light.
  • barrier element 134 permits the portions of structured surface 1 14 adjacent to low refractive index region 138 and/or barrier element 134 to redirect or retroreflect incident light 150.
  • Barrier layers 134 may also prevent pressure sensitive adhesive 130 from wetting out the microstructured layer (e.g., DRF or cube sheeting).
  • pressure sensitive adhesive 130 that is not in contact with a barrier layer 134 adheres to the microstructed elements, thereby effectively sealing the areas to form optically active areas or cells.
  • the pressure sensitive adhesive 130 also holds the entire construction together, thereby eliminating the need for a separate sealing film and sealing process.
  • the pressure sensitive adhesive is in contact with or is directly adjacent to the structured surface of the DRF or the cube corner elements, as the case may be.
  • any material that prevents the pressure sensitive adhesive from contacting microstructured elements 1 12 or flowing or creeping into low refractive index region 138 can be used in barrier element 134.
  • Exemplary materials for use in barrier element 134 include resins, polymeric materials, dyes, inks, vinyl, inorganic materials, radiation-curable polymers (for example, UV curable or e-beam curable), pigment.
  • exemplary materials used to form the barrier elements include crosslinkable acrylates.
  • exemplary materials used to form the barrier elements include crosslinkable urethane acrylates, acrylic acrylates, polyester acrylates.
  • exemplary materials used to form the barrier elements include crosslinkable molecule with at least 2 acrylate groups.
  • the composition further comprises a diluent to control viscosity of the composition.
  • the diluent has a viscosity of less than 200 cPS. In one embodiment, the diluent has a viscosity of less than 10 cPS. In one embodiment, the diluent has a viscosity of less than 50 cPS and greater than 3 cPS.
  • the composition for forming the barrier elements 134 has a viscosity of 2500 cPS or less. In one embodiment, the composition for forming the barrier islands 134 has a viscosity of 2000 cPS or less. In one embodiment, the composition for forming the barrier elements 134 has a viscosity of 1500 cPS or less. In one embodiment, the composition for forming the barrier elements 134 has a viscosity of 1000 cPS or less. In one embodiment, the composition for forming the barrier elements 134 has a viscosity of 100 cPS or greater. In one embodiment, the composition for forming the barrier elements 134 has a viscosity of 300 cPS or greater.
  • the composition for forming the barrier elements 134 has a viscosity of 400 cPS or greater. In other embodiments, the composition for forming the barrier elements 134 has a viscosity of 500 cPS or greater. In other embodiments, the composition for forming the barrier elements 134 has a viscosity of 800 cPS or greater. In other embodiments, the composition for forming the barrier elements 134 has a viscosity of 1000 cPS or greater.
  • the composition for forming the barrier elements 134 has a viscosity from 100 cPS to 2500 cPS. In other embodiments, the composition for forming the barrier elements 134 has a viscosity from 100 cPS to 2000 cPS. In other embodiments, the composition for forming the barrier elements 134 has a viscosity from 100 cPS to 1500 cPS. In other embodiments, the composition for forming the barrier elements 134 has a viscosity from 100 cPS to 1000 cPS. In other embodiments, the composition for forming the barrier elements 134 has a viscosity from 300 cPS to 2500 cPS.
  • the composition for forming the barrier elements 134 has a viscosity from 300 cPS to 2000 cPS. In other embodiments, the composition for forming the barrier elements 134 has a viscosity from 300 cPS to 1500 cPS. In other embodiments, the composition for forming the barrier elements 134 has a viscosity from 300 cPS to 1000 cPS. In other embodiments, the composition for forming the barrier elements 134 has a viscosity from 400 cPS to 2500 cPS. In other embodiments, the composition for forming the barrier elements 134 has a viscosity from 400 cPS to 2000 cPS.
  • the composition for forming the barrier elements 134 has a viscosity from 400 cPS to 1500 cPS. In other embodiments, the composition for forming the barrier elements 134 has a viscosity from 400 cPS to 1000 cPS. In other embodiments, the composition for forming the barrier elements 134 has a viscosity from 500 cPS to 2500 cPS. In other embodiments, the composition for forming the barrier elements 134 has a viscosity from 500 cPS to 2000 cPS. In other embodiments, the composition for forming the barrier elements 134 has a viscosity from 500 cPS to 1500 cPS.
  • the composition for forming the barrier elements 134 has a viscosity from 500 cPS to 1000 cPS. In other embodiments, the composition for forming the barrier elements 134 has a viscosity from 800 cPS to 1500 cPS. In other embodiments, the composition for forming the barrier elements 134 has a viscosity from 900 cPS to 1300 cPS. In other embodiments, the composition for forming the barrier elements 134 has a viscosity from 1000 cPS to 1300 cPS.
  • the composition for forming the barrier islands 134 further comprises a photoinitiator.
  • the photoinitiator is present in at least 0.5% and less than 2.0 wt. % of the total composition for forming the barrier islands 134.
  • composition for forming the barrier islands 134 further comprises a solvent that is ideally non-reactive and less than 10% wt. of the total composition for forming the barrier islands 134.
  • FIGS. 1A and IB show one exemplary embodiment of a light redirecting article 100.
  • Light redirecting article 100 includes a structured layer 110 including microstructured elements 112 that collectively form a structured surface 114 opposite a major surface 116.
  • Structured layer 1 10 also includes an optional overlay layer 1 18.
  • An adhesive sealing layer 130 is adjacent to structured layer 1 10, and specifically is adjacent to the microstructured elements 1 12 at the structured surface 114.
  • Adhesive sealing layer 130 includes one or more barrier elements 134. If the embodiment shown in FIGS. 1A and IB, is directed to retroreflective material, then the viewer 102 observes retroreflected light 150 from a microstructured element 1 12 that is a cube corner.
  • this basic construction for a light redirecting article 100 could be used when the microstructured element 1 12 is a prism that instead of retroreflects light the prism redirects the path of the light that enters the prism and leaves through the barrier element 134 and adhesive sealing layer 130. That is, if the embodiment shown in FIGS. 1A and IB is a DRF, then viewer 102 will observe refracted light exiting the construction on the opposite side (major surface) from where the incident light entered the construction.
  • a light ray 150 incident on a cube corner element 1 12 that is adjacent to low refractive index region 138 is retroreflected back to viewer 102.
  • a first region of light redirecting article 100 that includes low refractive index region 138 is referred to as an optically active area.
  • a second region does not include the low refractive index region 138 where the adhesive sealing layer 130 is in contact with the structured surface 1 14 of the structured layer 1 10.
  • incident light is not retroreflected and is referred to as an optically inactive area.
  • the prisms do not direct light out in the predetermined fashion as is accomplished in the first region and is referred to as an optically inactive area.
  • Examples of DRF are shown in Figures 4 to 6
  • Low refractive index region 138 includes a material that has a refractive index that is less than about 1.30, less than about 1.25, less than about 1.2, less than about 1.15, less than about 1.10, or less than about 1.05.
  • Exemplary low refractive index materials include air and low index materials are described in U.S. Patent Application Publication 2012/0038984, which is hereby incorporated herein by reference.
  • the adhesive layer includes a first region and a second region.
  • the first region is in contact with the barrier elements.
  • the second region is in contact with the structured surface.
  • the physical and rheological properties of the first and second regions are the same because they are part of the same adhesive material.
  • the second region includes a pressure sensitive adhesive and the first region differs in composition from the second region.
  • the first region and the second region have different polymer morphology.
  • the first region and the second region have different flow properties.
  • the first region and the second region have different viscoelastic properties.
  • the first region and the second region have different adhesive properties.
  • the retroreflective article or the DRF include a plurality of second regions that form a pattern.
  • the pattern is one of an irregular pattern, a regular pattern, a grid, words, graphics, and lines.
  • Exemplary pressure sensitive adhesives for use in the adhesive sealing include crosslinked tackified acrylic pressure -sensitive adhesives.
  • Other pressure sensitive adhesives such as blends of natural or synthetic rubber and resin, silicone or other polymer systems, with or without additives can be used.
  • the PSTC (pressure sensitive tape council) definition of a pressure sensitive adhesive is an adhesive that is permanently tacky at room temperature which adheres to a variety of surfaces with light pressure (finger pressure) with no phase change (liquid to solid).
  • Acrylic Acid and Meth(acrylic) Acid Esters are present at ranges of from about 65 to about 99 parts by weight, preferably about 78 to about 98 parts by weight, and more preferably about 90 to about 98 parts by weight.
  • Useful acrylic esters include at least one monomer selected from the group consisting of a first monofunctional acrylate or methacrylate ester of a non-tertiary alkyl alcohol, the alkyl group of which comprises from 4 to about 12 carbon atoms, and mixtures thereof.
  • Such acrylates or methacrylate esters generally have, as
  • Acrylate or methacrylate ester monomers include, but are not limited to, those selected from the group consisting of n-butyl acrylate (BA), n-butyl methacrylate, isobutyl acrylate, 2- methyl butyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, isooctyl acrylate (IOA), isooctyl methacrylate, isononyl acrylate, isodecyl acrylate, and mixtures thereof.
  • BA n-butyl acrylate
  • IOA isooctyl methacrylate
  • isononyl acrylate isodecyl acrylate
  • Acrylates include those selected from the group consisting of isooctyl acrylate, n-butyl acrylate, 2-methyl butyl acrylate, 2-ethylhexyl acrylate, and mixtures thereof.
  • Polar Monomers Low levels of (typically about 1 to about 10 parts by weight) of a polar monomer such as a carboxylic acid can be used to increase the cohesive strength of the pressure- sensitive adhesive. At higher levels, these polar monomers tend to diminish tack, increase glass transition temperature and decrease low temperature performance.
  • a polar monomer such as a carboxylic acid
  • Useful copolymerizable acidic monomers include, but are not limited to, those selected from the group consisting of ethylenically unsaturated carboxylic acids, ethylenically unsaturated sulfonic acids, and ethylenically unsaturated phosphonic acids.
  • Examples of such monomers include those selected from the group consisting of acrylic acid (AA), methacrylic acid, itaconic acid, fumaric acid, crotonic acid, citraconic acid, maleic acid, .beta.-carboxyethyl acrylate, sulfoethyl methacrylate, and the like, and mixtures thereof.
  • copolymerizable monomers include, but are not limited to, (meth)acrylamides, ⁇ , ⁇ -dialkyl substituted (meth)acrylamides, N-vinyl lactams, and N,N- dialkylaminoalkyl (meth)acrylates.
  • Illustrative examples include, but are not limited to, those selected from the group consisting of ⁇ , ⁇ -dimethyl acrylamide, ⁇ , ⁇ -dimethyl methacrylamide, ⁇ , ⁇ -diethyl acrylamide, ⁇ , ⁇ -diethyl methacrylamide, N,N-dimethylaminoethyl methacrylate, N,N-dimethylaminopropyl methacrylate, ⁇ , ⁇ -dimethylaminoethyl acrylate, N,N- dimethylaminopropyl acrylate, N-vinyl pyrrolidone, N-vinyl caprolactam, and the like, and mixtures thereof.
  • Non-polar Ethylenically Unsaturated Monomers The non-polar ethylenically unsaturated monomer is a monomer whose homopolymer has a solubility parameter as measured by the Fedors method (see Polymer Handbook, Bandrup and Immergut) of not greater than 10.50 and a Tg greater than 15°C. The non-polar nature of this monomer tends to improve the low energy surface adhesion of the adhesive.
  • These non-polar ethylenically unsaturated monomers are selected from the group consisting of alkyl (meth)acrylates, N-alkyl (meth)acrylamides, and combinations thereof.
  • Illustrative examples include, but are not limited to, 3,3,5-trimethylcyclohexyl acrylate, 3,3,5-trimethylcyclohexyl methacrylate, cyclohexyl acrylate, cyclohexyl methacrylate, isobornyl acrylate, isobornyl methacrylate, N-octyl acrylamide, N-octyl methacrylamide or combinations thereof.
  • from 0 to 25 parts by weight of a non-polar ethylenically unsaturated monomer may be added.
  • Tackifiers include terpene phenolics, rosins, rosin esters, esters of
  • Hydrogenated rosins synthetic hydrocarbon resins and combinations thereof. These provide good bonding characteristics on low energy surfaces. Hydrogenated rosin esters and hydrogenated C9 aromatic resins are the most preferred tackifiers because of performance advantages that include high levels of "tack", outdoor durability, oxidation resistance, and limited interference in post crosslinking of acrylic PSAs.
  • Tackifiers may be added at a level of about 1 to about 65 parts per 100 parts of the monofunctional acrylate or methacrylate ester of a non-tertiary alkyl alcohol, the polar monomer, and the nonpolar ethylenically unsaturated monomer to achieve desired "tack".
  • the tackifier has a softening point of about 65 to about 100. degree. C.
  • the addition of tackifiers can reduce shear or cohesive strength and raise the Tg of the acrylic PSA, which is undesirable for cold temperature performance.
  • Crosslinkers In order to increase the shear or cohesive strength of acrylic pressure-sensitive adhesives, a crosslinking additive is usually incorporated into the PSA. Two main types of crosslinking additives are commonly used.
  • the first crosslinking additive is a thermal crosslinking additive such as a multifunctional aziridine.
  • One example is 1, !'-(!, 3 -phenylene dicarbonyl)-bis-(2-methylaziridine) (CAS No. 7652-64-4), referred to herein as "bisamide”.
  • Such chemical crosslinkers can be added into solvent-based PSAs after polymerization and activated by heat during oven drying of the coated adhesive.
  • chemical crosslinkers that rely upon free radicals to carry out the crosslinking reaction may be employed.
  • Reagents such as, for example, peroxides serve as a source of free radicals. When heated sufficiently, these precursors will generate free radicals, which bring about a crosslinking reaction of the polymer.
  • a common free radical generating reagent is benzoyl peroxide. Free radical generators are required only in small quantities, but generally require higher temperatures to complete the crosslinking reaction than those required for the bisamide reagent.
  • the second type of chemical crosslinker is a photosensitive crosslinker that is activated by high intensity ultraviolet (UV) light.
  • UV high intensity ultraviolet
  • Two common photosensitive crosslinkers used for hot melt acrylic PSAs are benzophenone and 4-acryloxybenzophenone, which can be copolymerized into the PSA polymer.
  • Another photocrosslinker, which can be post-added to the solution polymer and activated by UV light is a triazine; for example 2,4-bis(trichloromethyl)-6-(4-methoxy-phenyl)-s- triazine.
  • These crosslinkers are activated by UV light generated from artificial sources such as medium pressure mercury lamps or a UV blacklight.
  • Hydrolyzable, free-radically copolymerizable crosslinkers such as monoethylenically unsaturated mono-, di- and trialkoxy silane compounds including, but not limited to,
  • methacryloxypropyltrimethoxysilane (SILANETM A- 174 available from Union Carbide Chemicals and Plastics Co.), vinyldimethylethoxysilane, vinylmethyldiethoxysilane, vinyltriethoxysilane, vinyltrimethoxysilane, vinyltriphenoxy silane, and the like are also useful crosslinking agents.
  • Crosslinker is typically present from 0 to about 1 part by weight based on 100 parts by weight of acrylic acid or meth(acrylic) acid esters, polar monomers, and non-polar ethylenically unsaturated monomers.
  • crosslinking may also be achieved using high-energy electromagnetic radiation such as gamma or e-beam radiation. In this case, no crosslinker may be required.
  • additives such as antioxidant and UV light absorbers are generally not needed. Small amounts of heat stabilizer can be utilized in hot melt acrylic PSAs to increase thermal stability during processing.
  • Plasticizers Optionally, low levels of plasticizer (e.g., less than about 10 parts by weight) may be combined with tackifier to adjust the Tg in order to optimize the peel and the low temperature performance of the adhesive.
  • Plasticizers that may be added to the adhesive of the invention may be selected from a wide variety of commercially available materials. In each case, the added plasticizer must be compatible with the tackified acrylic PSA used in the formulation.
  • Representative plasticizers include polyoxyethylene aryl ether, dialkyl adipate, 2-ethylhexyl diphenyl phosphate, t-butylphenyl diphenyl phosphate, di(2-ethylhexyl) adipate,
  • toluenesulfonamide dipropylene glycol dibenzoate, polyethylene glycol dibenzoate,
  • polyoxypropylene aryl ether dibutoxyethoxy ethyl formal, and dibutoxyethoxy ethyl adipate.
  • the structured layer may be a single layer or multi-layer film.
  • Illustrative examples of polymers that may be employed as the body layer film for flexible retroreflective articles include (1) fluorinated polymers such as poly(chlorotrifluoroethylene), poly(tetrafluoroethylene-co-hexafluoropropylene),
  • EAA poly(ethylene-co- acrylic acid)
  • EMA poly (ethylene - co-methacrylic acid)
  • the body layer is preferably an olefinic polymeric material, typically comprising at least 50 wt-% of an alkylene having 2 to 8 carbon atoms with ethylene and propylene being most commonly employed.
  • Other body layers include for example poly(ethylene naphthalate), polycarbonate, poly(meth)acrylate (e.g., polymethyl methacrylate or "PMMA”), polyolefms (e.g., polypropylene or "PP”), polyesters (e.g., polyethylene terephthalate or "PET”), polyamides, polyimides, phenolic resins, cellulose diacetate, cellulose triacetate, polystyrene, styrene-acrylonitrile copolymers, cyclic olefin copolymers, epoxies, and the like.
  • Exemplary liners for protecting the exposed adhesive surfaces for use in the light redirecting articles of the present disclosure include silicone coated materials such as papers and polymeric films, including plastics.
  • the liner base material may be single or multiple layer.
  • cube corner elements 112 are in the form of a tetrahedron or a pyramid.
  • the dihedral angle between any two facets may vary depending on the properties desired in an application. In some embodiments (including the one shown in FIGS. 1A and IB when the article is a retroreflective article), the dihedral angle between any two facets is 90 degrees.
  • the facets are substantially perpendicular to one another (as in the corner of a room) and the optical element may be referred to as a cube corner.
  • the dihedral angle between adjacent facets can deviate from 90° as described, for example, in U.S. Patent No. 4,775,219, the disclosure of which is incorporated in its entirety herein by reference.
  • the optical elements in the retroreflective article can be truncated cube corners.
  • the optical elements can be full cubes, truncated cubes, or preferred geometry (PG) cubes as described in, for example, U.S. Patent No. 7,422,334, the disclosure of which is incorporated in its entirety herein by reference.
  • structured layer 100 of FIGS. 1A and IB is shown as including overlay layer 1 18 and no land layer or land portion.
  • a land layer may be defined as continuous layer of material coextensive with the microstructured elements 1 12 and composed of the same material. This construction may be desirable for flexible embodiments.
  • structured layer 1 10 can include a land layer or land portion.
  • one method of making at least some of the light redirecting articles 100 of the present disclosure involves placing barrier elements 134 onto a pressure sensitive adhesive material 132 and then laminating the resulting pressure sensitive adhesive layer 130 to a structured layer 1 10.
  • the pressure sensitive adhesive layer 130 can be formed in a variety of ways including but not limited to the following exemplary methods.
  • the material(s) forming the barrier elements are printed onto the pressure sensitive adhesive.
  • the method of printing can be, a non-contact method such as, for example, printing using an inkjet printer.
  • the method of printing can be a contact printing method such as, for example, flexographic printing.
  • the material(s) forming the barrier elements are printed onto a flat release surface using, for example, an inkjet or screen printing method, and are then subsequently transferred from the flat release surface onto the pressure sensitive adhesive.
  • the material(s) forming the barrier elements are flood coated onto a microstructured adhesive surface (e.g. , a Comply liner manufactured by 3M Company of St. Paul, MN). The barrier elements are subsequently transferred from the microstructured liner to the pressure sensitive adhesive by, for example, lamination.
  • the light redirecting article may then, optionally, be adhesively bonded to a substrate (e.g. , a window pane or an aluminum substrate) to form, for example, covered window or a license plate or sign.
  • a substrate e.g. , a window pane or an aluminum substrate
  • Structured adhesive sealing layer 130 includes raised areas (a region that is raised relative to a surrounding region) of adhesive in a closed pattern, such as, for example, a hexagonal array.
  • Barrier element 180 is included in the bottom of the well formed by the structured adhesive sealing layer 130.
  • Structured adhesive sealing layer 130 includes structured adhesive liner 140 and exposed adhesive layer 150. Structured adhesive sealing layer 130, when bonded to structured layer 110, defines low refractive index regions 138 that permit the portions of structured surface 114 adjacent to low refractive index regions 138 to direct incident light 150. As such, portions with that include microstructured elements 112 adjacent to low refractive index regions 138 are optically active. In contrast, portions with the structured adhesive layer 130 adjacent to microstructured elements 112 are optically inactive areas. Structured adhesive sealing layer 130 holds the entire construction together, thereby eliminating the need for a separate sealing layer and sealing process.
  • the adhesive sealing layer 130 includes at least one of, for example, a thermoplastic polymer, a cross-linkable material, and a radiation curable material.
  • the adhesive sealing layer 130 comprises an adhesive, such as, for example, a heat activated adhesive, and/or a pressure sensitive adhesive or other material that can be formed using replication, heat embossing, extrusion replication, or the like.
  • the structured adhesive sealing layer 130 can be formed in several different ways.
  • the structured adhesive layer can include, for example, multiple layers formed at the same time or can be built through repeated coating steps.
  • One exemplary method starts with a flat film of adhesive, optionally on a carrier web. The adhesive is nipped between a flat roll and a roll with the required relief pattern. With the addition of temperature and pressure, the relief pattern is transferred to the adhesive.
  • a second exemplary method requires a castable or extrudable adhesive material. A film of the adhesive is created by extruding the material onto a roll with the required relief pattern. When the adhesive material is removed from the roll, it retains the relief pattern associated with the roll. The structured adhesive layer is then laminated to the retroreflective layer.
  • the structured adhesive sealing layer 130 is then bonded to the structured layer 110 by nipping the two films together in a nip consisting of two flat rolls. With the addition of temperature and pressure, the films adhesively bond, creating pockets of air that form the low refractive index region.
  • the structured adhesive layers can include, for example, a thermoplastic polymer, a heat- activated adhesive, such as, for example, an acid/acrylate or anhydride/acrylate modified EVA's such as, for example, Bynel 3101, such as described in, for example, U.S. Patent No. 7,611,251, the entirety of which is herein incorporated by reference.
  • the structured adhesive layers can include, for example, an acrylic PSA, or any other embossable material with adhesive
  • the interface between the seal film layer and the (e.g., cube-corner) microstructured layer typically include an adhesion promoting surface treatment.
  • adhesion promoting surface treatments include for example, mechanical roughening, chemical treatment, (air or inert gas such as nitrogen) corona treatment (such as described in US2006/0003178A1), plasma treatment, flame treatment, and actinic radiation.
  • the light redirecting article 100 is a retroreflective article.
  • the coefficient of retroreflection R A can be modified depending on the properties desired in an application.
  • RA meets the ASTM D4956 - 07el standards at 0 degree and 90 degree orientation angles.
  • R A is in a range from about 5 cd/(lux m 2 ) to about 1500 cd/(lux m 2 ) when measured at 0.2 degree observation angle and +5 degree entrance angle according to ASTM E-810 test method or CIE 54.2; 2001 test method.
  • R A is at least about 330 cd/(lux m 2 ), or at least about 500 cd/(lux m 2 ), or at least about 700 cd/(lux m 2 ) as measured according to ASTM E-810 test method or CIE 54.2; 2001 test method at 0.2 degree observation angle and +5 degree entrance angle.
  • RA is at least about 60 cd/(lux m 2 ), or at least about 80 cd/(lux m 2 ), or at least about 100 cd/(lux m 2 ) as measured according to ASTM E-810 test method or CIE 54.2; 2001 test method at 0.2 degree observation angle and +5 degree entrance angle.
  • Fractional retroreflectance is the fraction of unidirectional flux illuminating a retroreflector that is received at observation angles less than a designated maximum value, otmax.
  • RT represents the portion of light being returned within a prescribed maximum observation angle, otmax-
  • R T can be calculated as follows:
  • a is the observation angle (expressed in radians)
  • ⁇ is the presentation angle (also expressed in radians)
  • ⁇ is the entrance angle
  • Ra is the conventional coefficient of retroreflection expressed in units of candelas per lux per square meter.
  • RT refers to the fractional retroreflectance expressed as a decimal
  • fractional retroreflectance may be plotted as a function of maximum observation angle, otmax. Such a plot is referred to herein as an Rr-otmax curve, or a %Rr-a ma x curve.
  • RT Slope Another useful parameter for characterizing retroreflection is RT Slope, which can be defined as the change in RT for a small change or increment in the maximum observation angle, Aotmax.
  • a related parameter, %RT Slope can be defined as the change in %RT for a small change in maximum observation angle, Aotmax.
  • RT Slope (or %RT Slope) represents the slope or rate of change of the RT-otmax curve (or %RT-otmax curve). For discrete data points these quantities may be estimated by calculating the difference in RT (or %RT) for two different maximum observation angles a ma x, and dividing that difference by the increment in maximum observation angle, Aotmax, expressed in radians.
  • RT Slope (or %RT Slope) is the rate of change per radian.
  • RT Slope (or %RT Slope) is the rate of change per degree in observation angle.
  • this integration can be performed using RA measured at discrete observation angle amax values (0.1 degrees) separated by increments Aa max .
  • the structured surface exhibits a total light return that is not less than about 5%, not less than 8%, not less than 10%, not less than 12%, not less 15% for incident visible light at an entrance angle of -4 degrees.
  • the structured surface of the retroreflective article exhibits a coefficient of retroreflection RA that is not less than about 40 cd/(lux m2), not less than 50 cd/(lux m2), not less than 60 cd/(lux m2), not less than 70 cd/(lux m2), and not less than 80 cd/(lux m2) for an observation angle of 0.2 degrees and an entrance angle of -4 degrees.
  • the retroreflective articles of the present disclosure have a more uniform appearance than can be attained with conventional retroreflective articles including a sealing layer. Additionally, the retroreflective articles of the present disclosure do not require the inclusion or use of a sealing layer, reducing their cost.
  • Microsealed prismatic sheeting is especially suitable in applications such as license plates and graphics.
  • the prismatic sheeting provides benefits such as significantly lower manufacturing cost, reduced cycle time, and elimination of wastes including especially solvents and CO2 when replacing glass bead sheeting.
  • prismatic constructions return significantly increased light when compared to glass bead retroreflectors. Proper design also allows this light to be preferentially placed at the observation angles of particular importance to license plates, e.g., the range 1.0 to 4.0 degrees.
  • micro sealed sheeting provides the brilliant whiteness and uniform appearance at close viewing distances needed in these product applications.
  • retroreflective articles include, for example, retroreflective sheeting, retroreflective signage (including, for example, traffic control signs, street signs, highway signs, roadway signs, and the like), license plates, delineators, barricades, personal safety products, graphic sheeting, safety vest, vehicle graphics, and display signage.
  • the light redirecting article is a DRF comprising suitable barrier elements to bond a daylight redirecting layer comprising microstructured prismatic elements to another film.
  • the barrier elements of the present disclosure have sufficient structural integrity to substantially prevent flow of the adhesive into the microstructured prismatic elements, which would displace the air.
  • cross-linkable monomers include mixtures of multifunctional acrylates, urethane acrylates, or epoxies.
  • the barrier elements comprise a plurality of inorganic nanoparticles.
  • the inorganic nanoparticles can include, for example, silica, alumina, or Zirconia nanoparticles.
  • the nanoparticles have a mean diameter in a range from 1 to 200 nanometers, or 5 to 150 nanometers, or 5 to 125 nanometers.
  • the nanoparticles can be "surface modified" such that the nanoparticles provide a stable dispersion in which the nanoparticles do not agglomerate after standing for a period of time, such as 24 hours, under ambient conditions.
  • the barrier element traps a low refractive index material (such as air or aerogel) in the area adjacent the microstructured prismatic elements.
  • a low refractive index material such as air or aerogel
  • the type of bonding disclosed and taught in this application between two films refers to bonding only via selected areas in the daylight redirecting film in order to preserve the daylight redirecting function (or a suitable function in other microstructured optical films) of the film. Because the presence of the adhesive contacting the microstructured prismatic elements substantially destroys the ability to redirect light, there is a natural balance between the size of the areas that effect the bonding (partially optically active areas) between the two films and the size of the areas that are optically active (able to redirect light). That is, as the size of the bonding area between the two films increases, the strength of the bond increases, which is beneficial, but there is also less area left to perform the daylight redirecting function of the original daylight redirecting film. Conversely, as the size of the daylight redirecting area increases, the higher amount of light is redirected, but the size of the area available for bonding decreases as does the strength of the bond between the two films.
  • the inventors of the present application have surprisingly created articles where the optically area is greater than 90% of the total available area but that still have suitable bond strength to maintain both films bonded for certain applications, including preparation of window films for commercial, residential, and even automotive applications.
  • the present disclosure is directed to an article comprising: a) a daylight redirecting layer comprising a first major surface and a second major surface; b) one or more barrier elements; and c) an adhesive layer; subject to the following conditions (see also Figures 4 to 6):
  • the daylight redirecting layer comprises one or more microstructured prismatic elements on its first major surface defining a daylight redirecting area
  • the total surface area of the one or more barrier elements is greater than 60% of the daylight redirecting area
  • the adhesive layer comprises a first major surface and a second major surface
  • the first major surface of the adhesive layer has a first region and a second region
  • the first region of the first surface of the adhesive layer is in contact with one or more barrier elements; • the second region of the first surface of the adhesive layer is in contact with one or more microstructured prismatic elements;
  • the barrier element comprises a crosslinked polymeric matrix having a modulus of elasticity from 1.5 Gpa to 4.4 Gpa, or alternatively from 2 Gpa to 4.4 Gpa, or alternatively from 2.3 Gpa to 4.3 Gpa, or alternatively from 2.5 Gpa to 3.4 Gpa, and
  • the article further includes a first substrate adjacent the second major surface of the adhesive layer.
  • the first substrate includes a diffuser having an optical haze of 20 to 85 percent and an optical clarity of no more than 50 percent.
  • the daylight redirecting layer comprises a daylight redirecting substrate, and the one or more microstructured prismatic elements are on the daylight redirecting substrate.
  • the constructions of this disclosure further comprise a first substrate adjacent the second major surface of the adhesive layer.
  • While one of the main incentives for using daylight redirecting films is energy savings, visual comfort needs to be taken in account.
  • a fraction goes downwards. This downward light can cause glare for the occupants.
  • the microstructured prismatic elements are typically linear and oriented horizontally the incoming rays are refracted/reflected mainly in the vertical direction. Sunlight is highly collimated with about 0.5 degree spread and appears as a solar disk. The effect of the daylight redirecting film is to spread this light vertically to form a solar column, such as that shown in Figure 3.
  • One solution to reduce glare is to introduce a diffuser layer in the optical path.
  • the diffuser helps to spread out the solar column.
  • the diffuser layer provides more uniform ceiling illumination by diffusing the upward directed light.
  • the diffuser layer spreads both the upward and downward directed light. The use of the diffuser layer reduces glare and the visibility of the solar column significantly.
  • Enhancement Film with Substantially Non-imaging Embedded Diffuser filed 04/12/2013, (Boyd, et al.)
  • the diffusers disclosed in the patents and patent applications in this paragraph are herein incorporated by reference.
  • any diffuser or diffusive layer including those mentioned in this paragraph, and others known in the art, can be used in the constructions of this disclosure.
  • the article further includes a first substrate adjacent the second major surface of the adhesive layer.
  • the first substrate includes a diffuser having an optical haze of 20 to 85 percent and an optical clarity of no more than 50 percent.
  • One option to combine the effect of a diffuser layer with a daylight redirecting film is to adhere the daylight redirecting film to the window and mount the diffuser to an added pane.
  • the present disclosure presents a solution where the difiuser layer and the daylight redirecting film are in a single construction.
  • the diffusing properties can lie with the barrier elements, the adhesive, the window film adhesive, or any of the substrates that may be part of the daylight redirecting construction.
  • the diffusing properties of any of the elements mentioned in the preceding sentence may be modified by introducing surface roughness, bulk diffusion, or using embedded diffusers.
  • the surface of a layer part of a daylight redirecting construction can be treated in such a manner that the layer diffuses visible light.
  • Surface roughness to create diffusing properties in a layer can be accomplished by imparting a pattern on the surface of a layer that increases the angular spread of input light in a desired manner. Some methods used to impart such a pattern include embossing, replication, and coating.
  • bulk diffusion can be accomplished by adding one or more diffusing agents to the window film adhesive.
  • Diffusing agents can comprise opaque particles or beads. Examples of diffusing agents include: polymeric or inorganic particles and/or voids included in a layer.
  • a substrate or a layer part of a daylight redirecting construction can contain embedded diffusers.
  • An embedded diffuser layer is formed in between the daylight redirecting layer and the substrate. This layer may consist of a matrix with diffusing agents.
  • the layer may be a surface diffuser layer consisting of a material with a refractive index sufficiently different from the daylight redirecting layer to obtain a desired level of diffusion.
  • various types of diffusers may also be used in combination.
  • one solution to form an assembly between a daylight redirecting film and a second film, such as a diffuser involves "barrier elements,” also called “passivation islands.”
  • a base film or liner is typically coated with a continuous layer of adhesive, for example a pressure sensitive adhesive (PSA), a hot melt, a thermoset adhesive, or a UV-curable adhesive.
  • PSA pressure sensitive adhesive
  • the adhesive layer is then printed with "barrier elements” or “islands” comprising a curable, non-tacky ink. Exposed regions of the adhesive remain tacky while the regions with the printed barrier elements are typically hard, and non-tacky. That is, the adhesive is passivated in those regions.
  • the film with the printed barrier elements can be laminated to the daylight redirecting film.
  • Lamination typically occurs under heat and pressure to allow the adhesive to flow into the microstructured prismatic elements.
  • the two films are bonded in the regions with exposed, unprinted adhesive.
  • FIG.7 is a schematic diagram of a typical process to bond a microstructured film to a second film.
  • microstructured prismatic elements of a daylight redirecting film typically formed from resins, require an air interface to function.
  • the barrier elements prevent the adhesive from flowing into the microstructured prismatic elements in those regions and maintain an air interface. This situation can also be seen in Figure 7.
  • the microstructured prismatic elements retain their optical performance in those areas. In the bonded regions the adhesive "wets" out the
  • microstructured prismatic elements and their optical performance may be degraded. Light incident on these areas may not be redirected but instead would pass right through the construction. This phenomenon is referred to as punch through.
  • punch through could be eliminated if an opaque adhesive is used in the areas where the adhesive is in contact with the microstructured prismatic elements.
  • the optical performance of the assembly may be modified by varying the ratio of the area of barrier elements to the area of exposed adhesive.
  • the adhesion between the two substrates measured in peel strength, is proportional to the exposed adhesive area.
  • the required peel strength is dependent on the specific application.
  • the peel strength and the optical performance of the assembly must be balanced when determining the area exposed to adhesive.
  • the aesthetics of the pattern should also be taken into account because, not only the size of the area exposed to adhesive, but also the location of those regions within the entire film can affect how a user perceives the construction.
  • the peel strength for the bond between a the layer bonded to the daylight redirecting layer, such as a first substrate, and the daylight redirecting layer is from 25 g/in to 2,000 g/in. In other embodiments, the peel strength for the bond between the first substrate and the daylight redirecting layer is greater than 300 g/in, or greater than 400 g/in, or greater than 500 g/in.
  • a film with structured layer (e.g., comprising microstructure prismatic elements) is laminated onto the barrier element-modified adhesive.
  • the barrier element aids to maintain the optical performance of the structured film, including its ability to refract light.
  • the optical performance may be compromised if the structured layer penetrates into the barrier element or breaks through. This can result in light leakage, which may be manifested as glare in daylight redirecting films or a loss of brightness in retroreflected films.
  • the barrier element is formed by applying a curable fluid material (referred to as an ink) onto the adhesive and curing (e.g. radiation curing, drying, chemically cross-linking) to reach a final state.
  • a curable fluid material referred to as an ink
  • curing e.g. radiation curing, drying, chemically cross-linking
  • the barrier element properties can be characterized and related to the optical performance of the total construction.
  • the barrier element diffuses visible light. As mentioned before, diffusion can be accomplished by creating surface diffusers, bulk diffusers, and embedded diffusers.
  • the barrier elements can comprise one or more light stabilizers in order to enhance durability, for example in environments exposed to sunlight.
  • These stabilizers can be grouped into the following categories: heat stabilizers, UV light stabilizers, and free-radical scavengers.
  • Heat stabilizers are commercially available from Witco Corp., Greenwich, Conn, under the trade designation "Mark V 1923” and Ferro Corp., Polymer Additives Div., Walton Hills, Ohio under the trade designations "Synpron 1163", “Ferro 1237” and “Ferro 1720". In some embodiments, such heat stabilizers can be present in amounts ranging from 0.02 to 0.15 weight percent.
  • UV light stabilizers can be present in amounts ranging from 0.1 to 5 weight percent.
  • Benzophenone-type UV-absorbers are commercially available from BASF Corp., Parsippany, N.J. under the trade designation "Uvinol 400"; Cytec Industries, West Patterson, N.J. under the trade designation “Cyasorb UV1164" and Ciba Specialty Chemicals, Tarrytown, N.Y., under the trade designations "Tinuvin 900", “Tinuvin 123" and “Tinuvin 1130".
  • free-radical scavengers can be present in an amount from 0.05 to 0.25 weight percent.
  • Nonlimiting examples of free-radical scavengers include hindered amine light stabilizer (HALS) compounds, hydroxylamines, sterically hindered phenols, and the like.
  • HALS compounds are commercially available from Ciba Specialty Chemicals under the trade designation “Tinuvin 292” and Cytec Industries under the trade designation “Cyasorb UV3581.”
  • window film applications such as those that contemplate a daylight redirecting film with a diffuser in a single construction
  • FIG. 8 shows three different sample patterns.
  • the black areas represent the barrier elements while the white areas represent the exposed adhesive.
  • the left panel in FIG. 8 represents a 1-dimmensional pattern consisting of lines. The lines may be oriented in any direction. When laminated to the structured film, this construction would only be fully sealed along two edges. A full seal may still be achieved by providing an exposed adhesive border or by edge-sealing the laminate.
  • the barrier elements can be laid out in a pattern chosen from a repeating 1- dimensional pattern, a repeating 2-dimensional pattern, and a random-looking 1- or 2-dimensional pattern.
  • a fully sealed construction may also be achieved by using a 2-dimensional pattern as shown in the center panel of FIG. 8.
  • That pattern is an example of an ordered grid pattern consisting of a rectangular array of squares.
  • the right panel in FIG. 8 shows random-looking polygons and may be less visible to the human eye compared to the center panel in FIG. 8 due to the breakup of the long straight edges present in pattern 9b.
  • the edges in the 2- dimensional patterns may be straight or have curves.
  • Other patterns could include random or ordered arrays of dots or decorative features.
  • the patterns in FIG. 8 may be characterized by two independent parameters:
  • the pitch may represent the average distance between the centers of adjacent polygons.
  • the average pitch in the construction is from 0.035 millimeters to 100 millimeters.
  • the average pitch in the article is from 0.1 millimeters to 10 millimeters, or from 0. 5 millimeters to 5 millimeters, or from 0.75 millimeters to 3 millimeters. In the inventors view, patterns with smaller pitches may be less visible; and
  • Coverage which is understood as the ratio of the total surface area of barrier element area to the total area.
  • the total area refers to the area defined by the microstructured prismatic elements that form the daylight redirecting film. For that reason, in this disclosure, the total surface area is also called the daylight redirecting area. Patterns with higher coverage may have less "punch through” while patterns with lower coverage may have higher peel strength.
  • the total surface area of the barrier elements is greater than 50% of the daylight redirecting area. In other embodiments, the total surface area of the barrier elements is greater than 60%, or greater than 65%, or greater than 70%, or greater than 75%, or greater than 80%, or greater than 85%, or greater than 90%, or greater than 95%, or greater than 98%,of the daylight redirecting area
  • the gap which represents the exposed adhesive width between barrier elements may be deduced once the pitch and coverage are known.
  • the average gap in the construction is from 0.01 millimeters to 40 millimeters. In other embodiments, the average gap in the construction is from 0.05 mm to 20 mm; or from 0.1 mm to 20 mm; or from 0.2 mm to 20 mm.
  • both patterns in the left and center panels in FIG. 8 have about 80% coverage.
  • the "punch through” refers to glare due to incident light not being diffracted by the construction because the adhesive has fully or partially replaced air at the region immediately adjacent the microstructure elements. Punch through degrades redirection performance. Higher coverage patterns result in decreased punch through and bond strength between the films in the assembly.
  • Pattern visibility is also determined by feature sizes: size of the barrier elements (related to pattern pitch) and gap widths.
  • the gap visibility is determined by the gap width and the viewing distance. Gap visibility may be estimated based on the resolution of the human visual system for a given viewing distance.
  • the patterns of barrier elements may be printed by direct or offset printing using a variety of known printing methods such as flexographic printing, gravure printing, screen printing, letterpress printing, lithographic printing, ink-jet printing, digitally controlled spraying, thermal printing, and combinations thereof.
  • flexographic printing gravure printing
  • screen printing letterpress printing
  • thermal printing digitally controlled spraying
  • thermal printing thermal printing
  • barrier elements printed by flexographic printing can have thickness up to 10 micrometers
  • by gravure printing thickness can be up to 30 micrometers
  • screen printing the thickness can be up to 500 um.
  • the inks are typically printed in liquid form and then cured in place. Curing methods can include UV, E-beam, chemical, thermal curing, or cooling. Durability of the ink may be increased by additives such as light stabilizers.
  • cross-linker with optional: diluent molecules, fillers, diffusing
  • solvent embodiments solvent no more than 10w% molecules with at least 2 acrylate groups per molecule (functionality
  • cross-linker is the number of acrylates per molecule)
  • ⁇ functionality is the average number of acryaltes on a molecule
  • chemistry may be urethane acrylates, acrylic acrylates,
  • thermosetting resins more typically less than 100 cPS; even more typically 3 to 50 cPS ioptically transparent thermoplastic resins, thermosetting resins, : polyester resins, polyuurethane resins, polystyrenee resins, ipolyamide resins, polyimide resins, melamine resins, phenol resins, isilicone resins, flurocarbon resins, and others.
  • Addition of the filler a material which does not appreciably react with the other imust not make the viscosity of the composition out of range of a composition materials. Examples include resins, polymers, iprocessable composition. The filler also must not interfere with the inorganic materials. : required rheology for processing (e.g. splitting of a flexographic ink)
  • the particles used for barrier particles which have index mismatching/matching properties with ielements are typically in the range of 200 nm to 8 microns, more
  • photoinitiator for UV curable systems typically 0.5 to 2.0 w%
  • ⁇ functionality of a mixture is the average number of acryaltes over 11 the molecules in the system. These are the groups where cross-
  • viscosity allows for the processing of the radiation curable DRF) 500 to 2500 cPS at room temperature ⁇ composition with flexographic methods.
  • the optical properties of the ink may also be adjusted by modifying the ink's refractive index and/or its diffusing characteristics.
  • the diffusing properties of the ink may be modified, for example by introducing surface roughness or bulk 5 diffusers.
  • a barrier element with diffusion is used to prepare a daylight redirecting construction with both clear view-through regions and daylight redirecting regions, such as the construction exemplified in FIG. 4.
  • the diffuser is integrated in the barrier elements. Regions in which the adhesive wets out the microstructures would provide clear view through areas.
  • clear view through regions could be desirable to provide visibility past the construction.
  • the crosslinked polymeric matrix of the barrier element is at least 1.6 microns thick. In one embodiment, the barrier element 134 is at least 1.75 microns thick. In one embodiment, the barrier element 134 is at least 2.0 microns thick. In one embodiment, the barrier element 134 is at least 3.0 microns thick. In other embodiments, the barrier element 134 is at least 3 microns thick. In other embodiments, the barrier element 134 is at least 5 microns thick. In other embodiments, the barrier element 134 is at least 7 microns thick. In other embodiments, the barrier element 134 is at least 8 microns thick. In other embodiments, the barrier element 134 is at least 10 microns thick.
  • FIG. 5 A room-facing light redirecting assembly is shown in FIG. 5.
  • the redirecting film with the structures oriented towards the room is bonded to the cover/diffusing film using the barrier elements approach.
  • the cover film may include diffusing properties depending on the optical performance of the daylight redirecting microstructure.
  • the diffuser may be surface, bulk, or embedded diffuser. Diffusion may also be included in the adhesive or the barrier elements.
  • the assembly may be mounted to a window or glazing using window film adhesive.
  • the present disclosure is directed to a film comprising an article, wherein the article comprises:
  • a daylight redirecting layer comprising a first major surface and a second major surface; wherein the daylight redirecting layer comprises one or more microstructured prismatic elements on its first major surface defining a daylight redirecting area;
  • the total surface area of the one or more barrier elements is greater than 90% of the daylight redirecting area
  • the adhesive layer comprises a first major surface and a second major surface; wherein the first major surface of the adhesive layer has a first region and a second region; wherein the first region of the first major surface of the adhesive layer is in contact with one or more barrier elements; wherein the second region of the first major surface of the adhesive layer is in contact with one or more microstructured prismatic elements;
  • the first substrate is a diffuser
  • a window film adhesive layer adjacent the second surface of the daylight redirecting layer; wherein the article allows transmission of visible light;
  • the barrier element comprises a crosslinked polymeric matrix having a modulus of elasticity from 1.5 Gpa to 4.4 Gpa, or alternatively from 2 Gpa to 4.4 Gpa, or alternatively from 2.3 Gpa to 4.3 Gpa, or alternatively from 2.5 Gpa to 3.4 Gpa, and
  • the film optionally further comprises a liner immediately adjacent the window film adhesive layer.
  • the microstructures are oriented towards the incoming sunlight.
  • the microstructure substrate may also have diffusing properties integrated into it.
  • diffusive properties can be achieved by coating a surface diffuser on the substrate side opposing the microstructured prismatic elements. This substrate could also include bulk diffusion properties.
  • the daylight redirecting substrate is bonded to a second substrate using the barrier elements approach. This substrate may have a window film adhesive coated on the opposing face to attach to a glazing.
  • the present disclosure is directed to a film comprising an article, wherein the article comprises:
  • a daylight redirecting layer comprising a first major surface and a second major surface; wherein the daylight redirecting layer comprises one or more microstructured prismatic elements on its first major surface defining a daylight redirecting area;
  • the total surface area of the one or more barrier elements is greater than 90% of the daylight redirecting area
  • the adhesive layer comprises a first major surface and a second major surface; wherein the first major surface of the adhesive layer has a first region and a second region; wherein the first region of the first surface of the adhesive layer is in contact with one or more barrier elements;
  • the second region of the first surface of the adhesive layer is in contact with one or more microstructured prismatic elements; a diffuser adjacent the second major surface of the daylight redirecting layer;
  • the barrier element comprises a crosslinked polymeric matrix having a modulus of elasticity from 1.5 Gpa to 4.4 Gpa, or alternatively from 2 Gpa to 4.4 Gpa, or alternatively from 2.3 Gpa to 4.3 Gpa, or alternatively from 2.5 Gpa to 3.4 Gpa, and
  • the film optionally further comprises a liner immediately adjacent the window film adhesive layer.
  • the second substrate is eliminated and the bonding adhesive is used both to laminate the barrier elements to the microstructured prismatic elements and to attach the assembly to the glazing.
  • This configuration is potentially a simpler, lower cost, and thinner construction.
  • the present disclosure is directed to a film comprising an article, wherein the article comprises:
  • a daylight redirecting layer comprising a first major surface and a second major surface; wherein the daylight redirecting layer comprises one or more microstructured prismatic elements on its first major surface defining a daylight redirecting area;
  • the total surface area of the one or more barrier elements is greater than 90% of the daylight redirecting area
  • the adhesive layer comprises a first major surface and a second major surface; wherein the first major surface of the adhesive layer has a first region and a second region; wherein the first region of the first surface of the adhesive layer is in contact with one or more barrier elements;
  • the barrier element comprises a crosslinked polymeric matrix having a modulus of elasticity from 1.5 Gpa to 4.4 Gpa, or alternatively from 2 Gpa to 4.4 Gpa, or alternatively from 2.3 Gpa to 4.3 Gpa, or alternatively from 2.5 Gpa to 3.4 Gpa, and
  • the film optionally further comprises a liner immediately adjacent the adhesive layer.
  • the present disclosure is directed to a window comprising any of the films described above.
  • diffusion may be incorporated in the substrates and/or adhesives.
  • Diffusers may be surface, bulk, or embedded diffusers.
  • the window film adhesive diffuses visible light. As mentioned before, diffusion can be accomplished by creating surface diffusers, bulk diffusers, and embedded diffusers.
  • edges of the daylight redirecting construction may be useful to seal the edges of the daylight redirecting construction to prevent ingress of contaminants such as moisture and dirt.
  • one option to seal at least a portion of the edge is for the adhesive layer to fill the space between at least two immediately adjacent microstructured prismatic elements.
  • the entire edge can be sealed in this manner if the adhesive fills the space between the microstructured prismatic elements near the edge.
  • the construction has a rectangular or square shape and the edge of one or more sides, up to all four sides, is sealed.
  • the sealing can occur: by the use of a sealing agent, by the adhesive layer as described above, by using an edge sealing tape, or by using pressure, temperature, or some combination of both, including the use of a hot knife.
  • the shape of the construction is circular or ellipsoidal and the edge of the construction is sealed all around.
  • the sealing can occur: by the use of a sealing agent, by the adhesive layer as described above, by using an edge sealing tape, or by using pressure, temperature, or some combination of both, including the use of a hot knife.
  • the daylight redirecting construction can have: (a) a see-through region where the adhesive layer fills the space between adjacent microstructured prismatic elements such that no daylight redirecting occurs and light passes through the construction with no significant refraction, and (b) a daylight redirecting region as described in the embodiments disclosed above (that is, having barrier elements surrounded by the adhesive layer that bonds the daylight redirecting layer to a second layer or substrate).
  • Figure 8 A shows an example of such an embodiment.
  • the barrier elements within the active daylight redirecting region may optionally be diffusive, for example by comprising a diffusing agent or a surface diffuser.
  • constructions as described in the preceding paragraph may have a diffuser (bulk, surface, or embedded) on what originally was a see-through region.
  • Samples of light directing articles were provided, wherein the light directing articles comprising a structured layer having a first side (i.e., front side) and an opposite second side (i.e., back side), an optional top layer adjacent the first side of the structured layer, and an adhesive sealing layer adjacent the second side of the structured layer.
  • the adhesive sealing layer further included an adhesive layer and barrier elements disposed thereon.
  • the barrier elements comprising a crosslinked polymeric matrix.
  • the barrier elements were then embedded in an epoxy adhesive (available under the trade designation Struers SpeciFix Resin mixed with a curing agent Struers SpeciFix-20 at a ratio of 7: 1 by weight), cured for 24 hours and subsequently cryomicrotomed at a temperature of -20°C using a LEICA EM UC6 from Leica Mycrosystems of Illinois, USA.
  • the resulting multilayer construction comprised adhesive tape/adhesive layer/barrier elements/epoxy layer.
  • the multilayer construction was sectioned, exposing its cross-section.
  • Modulus of elasticity measurement modulus of elasticity of barrier elements was measured using nanoindentation.
  • a nanoindenter model G200 (from Keysight technologies) coupled to a DCM II transducer (from Keysight Technologies, Santa Rosa, CA), and a Berkovich diamond tip (commercially available from Microstar Technologies, Huntsville, TX) were used.
  • Indenter calibrations were performed on a fused silica standard prior to each test to verify integrity of tip area function. All tests were conducted such that surface contact criteria was greater than 50 N/m at approach velocity of 40 nm/s. Load, displacement, and harmonic contact stiffness were obtained after contact using constant strain rate of 0.05 s "1 and command depth of 300 nm.
  • Er corresponded to reduced modulus [N/m 2 ] or [GPa] measured directly by the instrument during experiment; S corresponded to contact stiffness [N/m]; vi corresponded to Poisson's ratio of sample material; Ei corresponded to the elastic modulus of diamond; and E corresponded to the elastic modulus of the sample material
  • Contact stiffness S was measured by a technique in which a harmonic wave is superimposed over the DC signal that drives motion of the indenter, so that contact stiffness is measured continuously during loading using a harmonic frequency of 75 Hz, with 1 nanometer amplitude. Values for Elastic Modulus and Poisson ratio of diamond were taken as 1141 GPa and 0.07 respectively.
  • Hardness was determined the ratio of maximum load (Pmax) by contact area (A). Contact area was determined via the calibration tests in which contact area (tip area function) was found as a function of penetration depth.
  • Light directing articles comprising a structured layer including multiple microstructured elements were prepared as generally described in U.S. Patent No. 8,371,703 (Smith et al), the disclosure of which is incorporated herein by reference in its entirety.
  • a master tool was prepared by cutting three grooves onto a machinable metal using a high precision diamond tool (such as "K&Y Diamond,” manufactured and sold by Mooers of New York, U.S.A) to form microprisms.
  • the tool comprised a 4.0 mil primary groove pitch and isosceles base triangles having base angles of 58 degrees.
  • a first generation negative tooling was made from the master by nickel electroforming the master in a nickel sulfamate bath as generally described in U.S. Patent Nos. 4,478,769 (Pricone) and 5,156,863 (Pricone), both of which are incorporated herein by reference in their entirety.
  • Multiple second generation negative tools containing microcube prism recesses were subsequently turned into an endless belt 20 feet (6.1 m) in length in the downweb direction and 3 feet (0.92 m) in the crossweb direction, as generally described in U.S. Patent No. 7,410,604 (Erickson), the disclosure of which is incorporated herein by reference in its entirety.
  • a polycarbonate resin (such as commercially available under the trade designation "MAKROLON 2407" by Mobay Corporation, Pennsylvania, U.S.A.) was cast at a temperature of 550°F (287.8°C) onto the endless belt, which was heated to 420° F (215.6°C).
  • additional polycarbonate was deposited in a continuous land layer above the endless belt with a thickness of approximately 102 micrometer (0.004 inch).
  • the polycarbonate was then cooled with room temperature air, allowing the material to solidify and resulting in a microstructured layer.
  • the microstructured layer was subsequently removed from the belt.
  • a radiation-polymerizable pressure sensitive adhesive was prepared as described in U.S. Patent No. 5,804,610 (Hamer), incorporated herein by reference.
  • the PSA composition was made by mixing 95 parts by weight isooctyl acrylate (IOA), 5 parts by weight acrylic acid (AA), 0.1 parts by weight of IRGACURE 651, 0.02 parts by weight of isooctylthioglycolate (IOTG), and 0.4 parts by weight of IRGANOX 1076.
  • the PSA composition was placed into packages made of an ethylene vinyl acetate copolymer film of 0.0635 mm thickness (commercially available under the trade designation "VA-24" from Pliant Corporation, Dallas, TX) measuring approximately 10 centimeters by 5 centimeters and heat sealed. The PSA composition was then polymerized. After polymerization, the PSA composition was compounded in a twin screw extruder with 50wt% FORAL 85 tackifier and 18 wt% of a mixture of T1O 2 /EVA pigment and cast as a film onto a silicone coated release liner at a thickness of about 15 grains per 4 in by 6 in sample as generally described in U.S. Patent No. 5,804,610. The PSA film was then subjected to a radiation crosslinking step.
  • VA-24 ethylene vinyl acetate copolymer film of 0.0635 mm thickness
  • Barrier compositions were prepared by mixing the ingredients listed in Table 1, below, in the order provided. Mixing was conducted at room temperature and using a magnetic plate and stir bar for up to 12 hours to ensure adequate homogenization. In some embodiments, the mixture was heated to a temperature of about 60°C to ensure adequate homogenization. The amount of each ingredient is shown as weight percent (wt%) based on the total weight of the composition. Average functionality of each barrier composition was calculated as weighted average of the functionality of each ingredient in the composition. Modulus of elasticity was calculated according to the procedure described above. Functionality and modulus of elasticity are also reported in Table 1, wherein N/M as used herein means not measured. Table 1
  • Barrier elements of Comparative Example A and Examples 1-6 were prepared by selectively applying, respectively, Barrier Composition A and Barrier Compositions 1-6 onto the PSA film.
  • the barrier elements were printed at a printing speed of 20 fpm using a flexographic printer comprising a printing plate made with 0.067 Cyrel DPR, commercially available from SGS Corporation.
  • the plate was designed to print squares arranged in a grid pattern, wherein each square was 400 by 400 microns. Pitch (distance between the centers of each adjacent square) was 730 microns. The distance between each square (width) was 330 microns.
  • the barrier elements were subsequently cured using UV H bulbs.
  • Light directing articles of Comparative Example A and Examples 1-6 were prepared by laminating the printed PSA films to the structured side of microstructured layers, prepared as described above.
  • Retroreflectivity was measured using a retroreflectometer (model RetroSign GR3, available from Delta Danish Electronics, Light & Acoustics, Denmark) at observation angles of 0.2, 0.5 and 1.0 degrees, entrance angle of -4 degrees, and orientation of 0 deg. Results are reported in cd/lux.m 2 as an average of four individual readings in Table 2, below.
  • the light directing articles were subjected to additional pressure using a platen press at room temperature (25°C) or heated to temperature of about 49°C (120°F), using a pressure of about 5000 lbs (2268 kg) or about 15000 lbs (6804 kg), a compression area of about 1-3/8 in by 1-7/8 in or about 2.6 in 2 (about 17 cm 2 ) and a dwell time of 15 sec.
  • Initial reflectivity at an observation angle of 0.2 (Rl), final reflectivity (after the platen press treatment) at an observation angle of 0.2 (R2), and retention (Rt) ((R2/R1)* 100) were measured and/or calculated.
  • Results obtained with the platen press heated to 25°C are reported in Table 3, below.
  • Results obtained with the platen press heated to about 49°C are reported in Table 4, below.
  • Barrier elements of Examples 3, 4, and 5 were found to have improved adhesion of the adhesive sealing layers to the structured layer when compared to other barrier elements.
  • Light directing articles of Examples 7-10 were prepared as described in Comparative Example A and Examples 1-6, with the following exceptions: (i) a different PSA adhesive was used; (ii) a different printing pattern was used; and (iii) different barrier compositions were used. These differences are further described below.
  • the PSA composition used in Examples 7- 10 was a solution polymerized pressure sensitive adhesive polymer prepared by adding about 90 parts of isooctyl acrylate monomer and 10 parts of acrylic acid monomer to about 80 parts of a solvent mixture comprising 65% heptane and 35% acetone.
  • a free-radical initiator (VAZO 64) was added at a level of about 0.08% as a percentage of the monomer mixture, and reacted at about 140°C for about 24 hours.
  • the resulting polymer solution was cooled to about room temperature and diluted with a solvent mixture comprising 65% heptane and 35% acetone to about 40 percent solids.
  • a color concentrate comprising about 58 parts of titanium dioxide and 42 parts of "G7758-MS- 16-60" was added to about 100 parts of the solvent based polymer solution.
  • About 8 parts of a bisamide crosslinker was added to about 100 parts of the polymer solution and the mixture was stirred well for about 15 minutes.
  • the mixture was coated onto a silicone coated paper liner using a roll coater set up with a smoothing bar, adjusted to attain a dry coating weight of about 15 grains per 4 in by 6 in (10.2 cm by 15.2 cm).
  • the wet adhesive was dried using a multi-zone oven with a line speed of about 60 fpm (18.3 m/min) and temperatures starting at 230°F (110°C) and ending at 270°F (132°C) to form an adhesive film on a silicone coated paper liner.
  • Barrier Compositions 7-10 were used to prepare, respectively, Examples 7-10.
  • the barrier compositions were prepared using the ingredients shown in Table 5, below, wherein amount of each ingredient is expressed as weight percent (wt%) based on the total weight of the composition. Functionality, hardness and modulus of each composition is also reported, wherein N/M means not measured.
  • the light directing articles were subjected to additional pressure as described above, except that the platen press was heated to a temperature of about 110°F (43°C).
  • Initial reflectivity at an observation angle of 0.2 (Rl), final reflectivity (after the platen press treatment) at an observation angle of 0.2 (R2), and retention (Rt) ((R2/R1)* 100) were measured and calculated. Results are reported in Table 6, below.
  • the modulus of elasticity of barrier elements was measured using nanoindentation.
  • a nanoindenter model G200 coupled to a DCM II transducer (Keysight Technologies, Santa Rosa, CA) and a Berkovich diamond tip (Microstar Technologies, Huntsville, TX) were used.
  • Indenter calibrations were performed on a fused silica standard prior to each test to verify integrity of tip area function. All tests were conducted such that surface contact criteria was greater than 50 N/m at approach velocity of 40 nm/s. Load, displacement, and harmonic contact stiffness were
  • E r corresponded to reduced modulus [N/m 2 ] or [GPa] measured directly by the instrument during experiment
  • S corresponded to contact stiffness [N/m]
  • v corresponded to Poisson's ratios of indenter
  • v corresponded to Poisson ratio of sample material
  • E corresponded to the elastic modulus of diamond
  • E corresponded to the elastic modulus of the sample material.
  • Contact stiffness S was measured by a technique in which a harmonic wave is superimposed over the DC signal that drives motion of the indenter, so that contact stiffhess is measured continuously during loading using a harmonic frequency of 75 Hz, with 1 nanometer amplitude.
  • Elastic Modulus and Poisson ratio of diamond were taken as 1141 GPa and 0.07 respectively.
  • Hardness was determined by dividing the maximum load (Pmax) by the contact area (A). Contact area was determined via the calibration tests in which contact area (tip area function) was found as a function of penetration depth.
  • the curable compositions (often referred to as inks) used to create the barrier elements were formulated by combining materials in the weight proportions provided in Table 2 until uniformly blended. Blending was normally done at room temperature, but formulations were heated at temperatures up to 60°C if necessary to obtain a uniform mixture.
  • Barrier elements were formed by applying fluid inks onto the surface of adhesive sheets and curing the inks with UV radiation.
  • the adhesive sheets were created by solution coating RD 2738 adhesive containing 0.1% of a bisamide cross-linker onto T50 silicone release liner to provide a dry film thickness of 3 mils.
  • Test samples of barrier elements were printed onto the adhesive sheets using a Flexiproof 100 test printer (RK PrintCoat Instruments Ltd., Royston, Hertfordshire, UK) outfitted with a 6.5 billion cubic microns per square inch (6.5 bcm), 8 bcm, or 10 bcm anilox roll. Printing was done using a print speed of 15 meters per minute and a random polygon stamp with a pitch of 1237 microns and a gap between barrier elements of 70 microns, yielding an area coverage of 89%. The inks were printed at 100% solids according to the formulations in Table 2. A Fusion UV Light Hammer UV curing system with an H bulb was used to cure the printed inks (Heraeus Noblelight America LLC, Gaithersburg, MD). Samples were cured at a line speed of 30 feet per minute under a nitrogen atmosphere using 100% UV power.
  • barrier elements were printed onto adhesive strips using the process described above in the combinations provided in Table 4.
  • Table 4 also provides the average acrylate functionality (f) of each ink, and further provides the elastic modulus (as provided by the nanoindentation test method), thickness, and rigidity of the cured barrier elements.
  • the rigidity of a barrier element composition (D) can be determined by using the plate equation:
  • :L E is the tensile or Young ' s Modulus.
  • the Young's storage modulus of a series of materials was determined with dynamic mechanical analysis of cast and cured films of the barrier element materials.
  • composition used volum acrylates/comp Nanoindentation elastic Barrier Rigidity Example e ⁇ modulus at 23 °C element (D)
  • Daylight Redirecting Films were made by laminating the adhesive layer coated with cured barrier elements to a film comprising microstructures according to the conditions in Table 5. The films were oriented in the laminate so that the barrier elements were adjacent to the
  • barrier elements were printed onto the adhesive and cured as described above using the ink and anilox roll specified in the barrier element compositions of Table 4.
  • microstructured film was fabricated using the methods provided in United States Patent
  • microstructure applied to the microstructured film was that provided in Example 2 of this patent application.
  • the laminated DRFs were inspected using microscopy to evaluate the degree of barrier element failure.
  • the structured layer will direct light away from the field of view in the barrier element region. This makes that area appear dark or gray when the structured layer is separated from the adhesive by the action of the barrier elements. Conversely, in the gaps between barrier elements, light will not be redirected, and so the gaps appear relatively bright.
  • Figure 11 shows a DRF with catastrophic barrier element failure, which appears as the fine vertical lines within individual barrier elements.
  • Fig. 12 a cross section of a DRF laminate that was made using the ink of the Comparative Example (C.E.) is shown, in which the adhesive has flowed through a breach in a barrier element and filled the gap between adjacent microstructures. Because the light redirecting ability of the DRF laminate depends on maintaining the air gap above the microstructures, this adhesive ingress results in failure.
  • Fig. 13 shows a photomicrograph of DRF Laminate Example 36, demonstrating a robust DRF construction. The individual barrier elements are distinct, have uniform optical properties, and do not show evidence of failure.
  • a light directing article comprising:
  • a structured layer comprising multiple microstructured elements that is opposite a major surface
  • an adhesive sealing layer having a first region and a second region wherein the second region is in contact with the structured layer
  • first region with the barrier element and second region have sufficiently different properties to form a low refractive index layer between the adhesive sealing layer and the structured layer;
  • the barrier element comprises a crosslinked polymeric matrix having a modulus of elasticity greater than 1.5 GPa and less than 4.4 GPa. 2. The light directing article of any one of the preceding embodiments, wherein the barrier element comprises a crosslinked polymeric matrix having a thickness greater than 1.6 microns. 3. The light directing article of any one of the preceding embodiments, wherein the barrier element comprises a crosslinked polymeric matrix having a thickness greater than 1.75 microns. 4. The light directing article of any one of the preceding embodiments, wherein the barrier element comprises a crosslinked polymeric matrix having a thickness greater than 3.0 microns.
  • the crosslinked acrylate polymeric matrix is one of a urethane acrylate, acrylic acrylate, epoxy acrylate, or polyester acrylate.
  • the barrier element comprises the reaction product of:
  • an acrylate polymer with at least two acrylate groups an acrylate polymer with at least two acrylate groups
  • reaction product mixture has a viscosity of greater than 100 and less than 2000 cPS.
  • an acrylate polymer with at least two acrylate groups an acrylate polymer with at least two acrylate groups
  • reaction product mixture has a viscosity of greater than 300 and less than 1500 cPS.
  • an acrylate polymer with at least two acrylate groups an acrylate polymer with at least two acrylate groups
  • reaction product mixture has a viscosity of greater than 400 and less than 1000 cPS. 10.
  • microstructured elements comprise prisms.
  • the light directing article of any one of the preceding embodiments is a retroreflective article and the microstructured elements comprise cube corners.
  • the adhesive sealing layer comprises a pressure sensitive adhesive.
  • the adhesive sealing layer comprises a structural adhesive.
  • the pressure sensitive adhesive layer is in intimate contact with the microstructured elements of the structured layer.
  • the adhesive sealing layer comprises a structured adhesive with legs and a base forming a well.
  • the low refractive index layer includes at least one of air or a low refractive index material.
  • the barrier element includes at least one of a resin, an ink, a dye, a pigment, an inorganic material, and a polymer. 22. The light directing article of any one of the preceding embodiments, further comprising a plurality of second regions that form a pattern.
  • the light directing article of any one of the preceding embodiments further comprising a plurality of first regions that form a pattern.
  • the light directing article of any one of the preceding embodiments wherein the pattern is one of an irregular pattern, a regular pattern, a grid, words, graphics, images, lines, and intersecting zones that form cells.
  • the first region is surrounded by the second region.
  • the light directing article of claim 1 wherein the structured surface at the second region is optically inactive .
  • the low refractive index layer is encapsulated by the barrier element.
  • a method of forming a light directing article comprising:
  • the adhesive sealing layer comprises a pressure sensitive adhesive layer.
  • the adhesive sealing layer comprises a structured adhesive layer.
  • An article comprising:
  • a light redirecting layer comprising a first major surface and a second major surface; one or more barrier elements;
  • the light redirecting layer comprises one or more microstructured prismatic elements on its first major surface defining a light redirecting area
  • the adhesive layer comprises a first major surface and a second major surface; wherein the first major surface of the adhesive layer has a first region and a second region wherein the first region of the first surface of the adhesive layer is in contact with one or more barrier elements;
  • the one or more barrier elements comprise a crosslinked polymeric matrix having a modulus of elasticity from 1.5 Gpa to 4.4 Gpa, and
  • An article comprising:
  • a light redirecting layer comprising a first major surface and a second major surface; one or more barrier elements;
  • the light redirecting layer comprises one or more microstructured prismatic elements on its first major surface defining a light redirecting area
  • the total surface area of the one or more barrier elements is greater than 60% of the light redirecting area
  • the adhesive layer comprises a first major surface and a second major surface; wherein the first major surface of the adhesive layer has a first region and a second region wherein the first region of the first surface of the adhesive layer is in contact with one or more barrier elements;
  • the one or more barrier elements comprise a crosslinked polymeric matrix having a modulus of elasticity from 1.5 Gpa to 4.4 Gpa, and
  • An article comprising:
  • a light redirecting layer comprising a first major surface and a second major surface; one or more barrier elements;
  • the light redirecting layer comprises one or more microstructured elements on its first major surface defining a light redirecting area
  • the adhesive layer comprises a first major surface and a second major surface; wherein the first major surface of the adhesive layer has a first region and a second region; wherein the first region of the first surface of the adhesive layer is in contact with one or more barrier elements;
  • the one or more barrier elements comprise a crosslinked polymeric matrix having a modulus of elasticity from 1.5 Gpa to 4.4 Gpa,
  • microstructured elements are retroreflective
  • the one or more barrier elements comprise a crosslinked polymeric matrix having a modulus of elasticity from 2 Gpa to 4.4 Gpa.
  • the one or more barrier elements comprise a crosslinked polymeric matrix having a modulus of elasticity from 2.3 Gpa to 4.3 Gpa.
  • the one or more barrier elements comprise a crosslinked polymeric matrix having a modulus of elasticity from 2.5 Gpa to 3.4 Gpa.
  • the barrier element comprises a crosslinked polymeric matrix having a thickness of 1.6 microns or greater.
  • the barrier element comprises a crosslinked polymeric matrix having a thickness of 1.75 microns or greater.
  • the barrier element comprises a crosslinked polymeric matrix having a thickness of 2 microns or greater.
  • the barrier element comprises a crosslinked polymeric matrix having a thickness of 3 microns or greater.
  • the barrier element comprises a crosslinked polymeric matrix having a thickness of 5 microns or greater.
  • the barrier element comprises a crosslinked polymeric matrix having a thickness of 7 microns or greater.
  • the barrier element comprises a crosslinked polymeric matrix having a thickness of 8 microns or greater.
  • the barrier element comprises a crosslinked polymeric matrix having a thickness of 10 microns or greater.
  • the barrier element comprises a crosslinked polymeric matrix having a thickness from 1.6 microns to 10 microns.
  • barrier element comprises a crosslinked polymeric matrix having a thickness from 1.6 microns to 8 microns.
  • barrier element comprises a crosslinked polymeric matrix having a thickness from 1.6 microns to 7 microns.
  • barrier element comprises a crosslinked polymeric matrix having a thickness from 1.6 microns to 5 microns.
  • barrier element comprises a crosslinked polymeric matrix having a thickness from 1.6 microns to 3 microns.
  • barrier element comprises a crosslinked polymeric matrix having a thickness from 1.6 microns to 2 microns.
  • barrier element comprises a crosslinked polymeric matrix having a thickness from 1.75 microns to 10 microns.
  • barrier element comprises a crosslinked polymeric matrix having a thickness from 1. 75 microns to 8 microns.
  • barrier element comprises a crosslinked polymeric matrix having a thickness from 1. 75 microns to 7 microns.
  • barrier element comprises a crosslinked polymeric matrix having a thickness from 1. 75 microns to 5 microns.
  • barrier element comprises a crosslinked polymeric matrix having a thickness from 1. 75 microns to 3 microns.
  • barrier element comprises a crosslinked polymeric matrix having a thickness from 1. 75 microns to 2 microns.
  • barrier element comprises a crosslinked polymeric matrix having a thickness from 2 microns to 10 microns.
  • the barrier element comprises a crosslinked polymeric matrix having a thickness from 2 microns to 8 microns.
  • the barrier element comprises a crosslinked polymeric matrix having a thickness from 2 microns to 7 microns.
  • the barrier element comprises a crosslinked polymeric matrix having a thickness from 2 microns to 5 microns.
  • the barrier element comprises a crosslinked polymeric matrix having a thickness from 2 microns to 3 microns.
  • the barrier element comprises a crosslinked polymeric matrix having a thickness from 3 microns to 10 microns.
  • the barrier element comprises a crosslinked polymeric matrix having a thickness from 3 microns to 8 microns.
  • the barrier element comprises a crosslinked polymeric matrix having a thickness from 3 microns to 7 microns.
  • the barrier element comprises a crosslinked polymeric matrix having a thickness from 3 microns to 5 microns.
  • the article of any one of the preceding embodiments, wherein the barrier element comprises a crosslinked acrylate polymeric matrix.
  • crosslinked acrylate polymeric matrix is one of a urethane acrylate, acrylic acrylate, epoxy acrylate, or polyester acrylate.
  • barrier element comprises the reaction product of:
  • an acrylate polymer with at least two acrylate groups an acrylate polymer with at least two acrylate groups
  • reaction product mixture has a viscosity of from 100 cPS to 2500 cPS.
  • the barrier element comprises the reaction product of: an acrylate polymer with at least two acrylate groups;
  • reaction product mixture has a viscosity of from 100 cPS to 2000 cPS.
  • barrier element comprises the reaction product of:
  • an acrylate polymer with at least two acrylate groups an acrylate polymer with at least two acrylate groups
  • reaction product mixture has a viscosity from 100 cPS to 1500 cPS.
  • barrier element comprises the reaction product of:
  • an acrylate polymer with at least two acrylate groups an acrylate polymer with at least two acrylate groups
  • reaction product mixture has a viscosity from 100 cPS to 1000 cPS.
  • barrier element comprises the reaction product of:
  • an acrylate polymer with at least two acrylate groups an acrylate polymer with at least two acrylate groups
  • reaction product mixture has a viscosity from 300 cPS to 2500 cPS.
  • barrier element comprises the reaction product of:
  • an acrylate polymer with at least two acrylate groups an acrylate polymer with at least two acrylate groups
  • reaction product mixture has a viscosity from 300 cPS to 2000 cPS.
  • barrier element comprises the reaction product of:
  • an acrylate polymer with at least two acrylate groups an acrylate polymer with at least two acrylate groups
  • reaction product mixture has a viscosity from 300 cPS to 1500 cPS.
  • barrier element comprises the reaction product of:
  • an acrylate polymer with at least two acrylate groups an acrylate polymer with at least two acrylate groups
  • reaction product mixture has a viscosity from 300 cPS to 1000 cPS.
  • barrier element comprises the reaction product of: an acrylate polymer with at least two acrylate groups;
  • reaction product mixture has a viscosity from 400 cPS to 2500 cPS.
  • barrier element comprises the reaction product of:
  • an acrylate polymer with at least two acrylate groups an acrylate polymer with at least two acrylate groups
  • reaction product mixture has a viscosity from 400 cPS to 2000 cPS.
  • barrier element comprises the reaction product of:
  • an acrylate polymer with at least two acrylate groups an acrylate polymer with at least two acrylate groups
  • reaction product mixture has a viscosity from 400 cPS to 1500 cPS.
  • barrier element comprises the reaction product of:
  • an acrylate polymer with at least two acrylate groups an acrylate polymer with at least two acrylate groups
  • reaction product mixture has a viscosity from 400 cPS to 1000 cPS.
  • barrier element comprises the reaction product of:
  • an acrylate polymer with at least two acrylate groups an acrylate polymer with at least two acrylate groups
  • reaction product mixture has a viscosity from 500 cPS to 2500 cPS.
  • barrier element comprises the reaction product of:
  • an acrylate polymer with at least two acrylate groups an acrylate polymer with at least two acrylate groups
  • reaction product mixture has a viscosity from 500 cPS to 2000 cPS.
  • barrier element comprises the reaction product of:
  • an acrylate polymer with at least two acrylate groups an acrylate polymer with at least two acrylate groups
  • reaction product mixture has a viscosity from 500 cPS to 1500 cPS.
  • barrier element comprises the reaction product of: an acrylate polymer with at least two acrylate groups;
  • reaction product mixture has a viscosity from 500 cPS to 1000 cPS.
  • barrier element comprises the reaction product of:
  • an acrylate polymer with at least two acrylate groups an acrylate polymer with at least two acrylate groups
  • reaction product mixture has a viscosity from 800 cPS to 1500 cPS.
  • barrier element comprises the reaction product of:
  • an acrylate polymer with at least two acrylate groups an acrylate polymer with at least two acrylate groups
  • reaction product mixture has a viscosity from 900 cPS to 1300 cPS.
  • microstructured elements comprise prisms.
  • the article of any one of the preceding embodiments is a retroreflective article and the microstructured elements comprise cube corners.
  • the adhesive layer comprises a pressure sensitive adhesive
  • the adhesive layer comprises a structural adhesive
  • the adhesive sealing layer comprises a structured adhesive with legs and a base forming a well.
  • the article of any one of the preceding embodiments further comprising a plurality of second regions that form a pattern.
  • the pattern is one of an irregular pattern, a regular pattern, a grid, words, graphics, images, lines, and intersecting zones that form cells.
  • barrier element has sufficient structural integrity to substantially prevent flow of the pressure sensitive adhesive into the low refractive index region.
  • the article of any one of the preceding embodiments including multiple optically active areas and multiple optically inactive areas and at least some of the optically inactive areas and optically active areas form a pattern.
  • a method of forming an article comprising:
  • the adhesive layer to the structured layer to define a low refractive index region between the first region of the adhesive sealing layer and the structured layer. 78.
  • the method according to any of the preceding embodiments directed to methods of forming an article, wherein the one or more barrier elements comprise a crosslinked polymeric matrix having a modulus of elasticity from 2 Gpa to 4.4 Gpa.
  • the one or more barrier elements comprise a crosslinked polymeric matrix having a modulus of elasticity from 2.3 Gpa to 4.3 Gpa.
  • the one or more barrier elements comprise a crosslinked polymeric matrix having a modulus of elasticity from 2.5 Gpa to 3.4 Gpa.
  • the light redirecting layer comprises a light redirecting substrate, and wherein the one or more microstructured prismatic elements are on the light redirecting substrate.
  • a barrier element diffuses visible light.
  • a barrier element comprises a diffusing agent.
  • window film adhesive layer comprises a diffusing agent
  • window film adhesive layer comprises particles as a diffusing agent.
  • a barrier element comprises one or more light stabilizers.
  • An article according to any of the preceding embodiments further comprising a first substrate adjacent the second major surface of the adhesive layer.
  • a film comprising an article according to any of the preceding embodiments,
  • the article further comprises a second substrate adjacent the second major surface of the adhesive layer;
  • the article further comprises a window film adhesive layer adjacent the second major surface of the light redirecting layer;
  • the article optionally further comprises a liner adjacent the window film adhesive layer.
  • a window comprising a film as claimed as in any of the preceding embodiments directed to a film, wherein the window further comprises a glazing immediately adjacent the window film adhesive layer.
  • a film comprising an article according to any of the preceding embodiments directed to an article,
  • the article further comprises a second substrate adjacent the second major surface of the light redirecting layer;
  • the article optionally further comprises a liner adjacent the adhesive layer.
  • a window comprising a film as claimed as in any of embodiments Error! Reference source not found, to Error! Reference source not found., wherein the window further comprises a glazing immediately adjacent the adhesive layer.
  • a film comprising an article according to any of the preceding embodiments directed to an article, wherein the article further comprises:
  • a window comprising a film as claimed as in any of embodiments Error! Reference source not found, to Error! Reference source not found., wherein the window further comprises a glazing immediately adjacent the window film adhesive layer.
  • a film according to any of the preceding embodiments directed to films that comprise a diffuser, wherein the diffuser is chosen from bulk diffusers, surface diffusers, and embedded diffusers or combinations thereof.
  • a window according to any of the preceding embodiments directed to windows that comprise a diffuser, wherein the diffuser is chosen from bulk diffusers, surface diffusers, and embedded diffusers or combinations thereof.
  • a film comprising an article
  • a light redirecting layer comprising a first major surface and a second major surface; wherein the light redirecting layer comprises one or more microstructured prismatic elements on its first major surface defining a light redirecting area;
  • the total surface area of the one or more barrier elements is greater than 90% of the light redirecting area
  • the adhesive layer comprises a first major surface and a second major surface; wherein the first major surface of the adhesive layer has a first region and a second region wherein the first region of the first surface of the adhesive layer is in contact with one or more barrier elements;
  • the first substrate comprises a diffuser
  • a window film adhesive layer adjacent the second surface of the light redirecting layer; wherein the article allows transmission of visible light;
  • the film optionally further comprises a liner immediately adjacent the window film adhesive layer.
  • a film comprising an article
  • a light redirecting layer comprising a first major surface and a second major surface; wherein the light redirecting layer comprises one or more microstructured prismatic elements on its first major surface defining a light redirecting area;
  • the total surface area of the one or more barrier elements is greater than 90% of the light redirecting area
  • the adhesive layer comprises a first major surface and a second major surface; wherein the first major surface of the adhesive layer has a first region and a second region wherein the first region of the first surface of the adhesive layer is in contact with one or more barrier elements;
  • a first substrate immediately adjacent the adhesive layer; a window film adhesive layer immediately adjacent the first substrate;
  • the film optionally further comprises a liner immediately adjacent the window film adhesive layer.
  • a film comprising an article
  • a light redirecting layer comprising a first major surface and a second major surface; wherein the light redirecting layer comprises one or more microstructured prismatic elements on its first major surface defining a light redirecting area;
  • the total surface area of the one or more barrier elements is greater than 90% of the light redirecting area
  • the adhesive layer comprises a first major surface and a second major surface; wherein the first major surface of the adhesive layer has a first region and a second region wherein the first region of the first surface of the adhesive layer is in contact with one or more barrier elements;
  • the film optionally further comprises a liner immediately adjacent the adhesive layer.
  • a light redirecting layer comprising a first major surface and a second major surface; one or more barrier elements;
  • the light redirecting layer comprises one or more microstructured prismatic elements on its first major surface defining a light redirecting area
  • the total surface area of the one or more barrier elements in at least a portion of the article defined as a light redirecting region is greater than 60% of the light redirecting area
  • the adhesive layer comprises a first major surface and a second major surface; wherein the first major surface of the adhesive layer has a first region and a second region wherein the first region of the first surface of the adhesive layer is in contact with one or more barrier elements;
  • a method of making an article comprising:
  • first substrate having a first major surface and a second major surface opposite the first major surface
  • the adhesive layer has a first major surface and a second major surface opposite the first major surface; and wherein the second major surface of the adhesive layer is immediately adjacent the first major surface of the first substrate;
  • the light redirecting layer comprises one or more microstructured prismatic elements on its first major surface defining a light redirecting area
  • the total surface area of the one or more barrier elements is greater than 60% of the light redirecting area
  • first major surface of the adhesive layer has a first region and a second region; wherein the first region of the first surface of the adhesive layer is in contact with the one or more barrier elements;
  • the first substrate comprises a diffuser chosen from bulk diffusers, surface diffusers, and embedded diffusers or combinations thereof.
  • a method according to any of the preceding embodiments directed to methods, wherein the light redirecting layer comprises a light redirecting substrate, and wherein the one or more microstructured prismatic elements are on the light redirecting substrate.
  • a method according to any of the preceding embodiments directed to methods, wherein the total surface area of the one or more barrier elements is greater than 65% of the light redirecting area.
  • a method according to any of the preceding embodiments directed to methods, wherein the total surface area of the one or more barrier elements is greater than 70% of the light redirecting area.
  • a method according to any of the preceding embodiments directed to methods, wherein the total surface area of the one or more barrier elements is greater than 80% of the light redirecting area.
  • a method according to any of the preceding embodiments directed to methods, wherein the total surface area of the one or more barrier elements is greater than 90% of the light redirecting area.
  • a method according to any of the preceding embodiments directed to methods, wherein the total surface area of the one or more barrier elements is greater than 95% of the light redirecting area.
  • a method according to any of the preceding embodiments directed to methods, wherein the total surface area of the one or more barrier elements is greater than 98% of the light redirecting area.
  • a method according to any of the preceding embodiments directed to methods, wherein a barrier element diffuses visible light.
  • a barrier element comprises a diffusing agent.
  • a barrier element comprises particles as a diffusing agent
  • window film adhesive layer comprises particles as a diffusing agent.
  • a method according to any of the preceding embodiments directed to methods, wherein the surface roughness of a barrier element provides visible-light diffusing properties to the barrier element.
  • a barrier element comprises one or more light stabilizers.
  • a method according to any of the preceding embodiments directed to methods, wherein the material of the barrier elements has been cured using UV radiation or heat.
  • a method according to any of the preceding embodiments directed to methods, wherein the barrier elements are laid out in a pattern chosen from a repeating 1 -dimensional pattern, a repeating 2-dimensional pattern, and a random-looking 1- or 2-dimensional pattern.
  • a method according to any of the preceding embodiments directed to methods, wherein the center-to-center distance between barrier elements defines the pitch; and wherein the average pitch in the article is between 0.035 millimeters and 100 millimeters.
  • a method according to any of the preceding embodiments directed to methods, wherein the width of a channel of the second region of the first surface of the adhesive layer defines a gap; and wherein the average gap in the article is between 0.01 millimeters and 40 millimeters.
  • a method according to any of the preceding embodiments directed to methods further comprising a first substrate adjacent the second major surface of the adhesive layer.
  • a method according to any of the preceding embodiments directed to methods, wherein the article has a rectangular or square shape and the edge of all four sides is sealed.
  • a method according to any of the preceding embodiments directed to methods, wherein the article has a rectangular or square shape and the edge of at least one side is sealed with a sealing agent.
  • a method according to any of the preceding embodiments directed to methods, wherein the article has a circular or ellipsoidal shape and the edge of the article is sealed all around.
  • a method according to any of the preceding embodiments directed to methods, wherein the article has a circular or ellipsoidal shape and at least a portion of the edge of the article is sealed by the adhesive layer.
  • a method according to any of the preceding embodiments directed to methods, wherein the article has a circular or ellipsoidal shape and at least a portion of the edge of the article is sealed with a sealing agent.
  • a method according to any of the preceding embodiments directed to methods, wherein the article has a circular or ellipsoidal shape and at least a portion of the edge of the article is sealed with an edge sealing tape.
  • a method according to any of the preceding embodiments directed to methods, wherein the article has a circular or ellipsoidal shape and at least a portion of the edge of the article is thermally sealed.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Laminated Bodies (AREA)
PCT/US2016/039750 2015-06-30 2016-06-28 Barrier elements for light directing articles WO2017004003A1 (en)

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WO2018026675A1 (en) * 2016-07-31 2018-02-08 3M Innovative Properties Company Light redirecting constructions and methods for sealing edges thereof

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JP6837460B2 (ja) * 2017-10-05 2021-03-03 住友化学株式会社 光学部材の製造方法及び製造装置
KR102671594B1 (ko) * 2018-03-22 2024-06-03 닛토덴코 가부시키가이샤 광학부재 및 그 제조 방법

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US20130034682A1 (en) * 2010-04-15 2013-02-07 Michael Benton Free Retroreflective articles including optically active areas and optically inactive areas
US20130114142A1 (en) * 2010-04-15 2013-05-09 3M Innovative Properties Company Retroreflective articles including optically active areas and optically inactive areas

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US20130034682A1 (en) * 2010-04-15 2013-02-07 Michael Benton Free Retroreflective articles including optically active areas and optically inactive areas
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