Dichroic polarizing film

Abstract

The dichroic polarizing film includes at least one film, which may be a multi-layer reflective polarizing film and an absorptive polarizing film. The absorption-type polarizing film is a modified film. The modified film is an oriented polyvinyl alcohol film containing a dichroic material, wherein the oriented polyvinyl alcohol film has been cross-linked, terminated, or both with a polyphenol compound, a nanosheet material, a hydrogen bond polymer, a non-phenolic polyacid, or a combination thereof.

Description

Summary of the Invention

[0001] This document discloses modified films, multilayer film articles including modified films, and methods for forming multilayer film articles. The modified film is an absorbing polarizer. In some embodiments, the modified film includes an oriented polyvinyl alcohol film containing a dichroic material, wherein the oriented polyvinyl alcohol film has been crosslinked, end-capped, or both of the following: a polyphenol compound, nanosheet material, hydrogen-bonded polymer, non-phenolic polyacid, or a combination thereof.

[0002] In some embodiments, the multilayer film article includes at least one film; and an absorptive polarizing film disposed on the at least one film. The absorptive polarizing film includes the modified film as described above.

[0003] Methods for forming multilayer film articles are also disclosed, comprising providing at least one film; providing a film-forming solution, wherein the film-forming solution comprises at least one solvent and polyvinyl alcohol; placing the film-forming solution on the at least one film; and drying the film-forming solution to form a composite structure. The composite structure comprises a polyvinyl alcohol film disposed on the film. The composite structure is oriented, and a dyeing composition is applied to the composite structure, wherein the dyeing composition comprises at least one dichroic material and at least one solvent. The composite structure on which the dyeing composition is disposed is dried, and a crosslinking agent / capping agent composition is applied to the polyvinyl alcohol film of the composite structure. The crosslinking agent / capping agent composition comprises a crosslinking agent, a capping agent, or both, wherein the crosslinking agent or capping agent comprises a polyphenolic compound, a nanosheet material, a hydrogen-bonded polymer, a non-phenolic polyacid, or a combination thereof, and at least one solvent. The composite structure on which the crosslinking agent / capping agent composition is disposed is dried. Attached Figure Description

[0004] This application can be more fully understood by referring to the following detailed description of various embodiments of this disclosure in conjunction with the accompanying drawings.

[0005] Figure 1 This is a cross-sectional view of the article disclosed herein.

[0006] Figure 2 This is a cross-sectional view of another article disclosed herein.

[0007] In the following description of the illustrated embodiments, reference is made to the accompanying drawings, in which various embodiments in which this disclosure may be practiced are shown by way of example. It should be understood that embodiments may be utilized and structural changes may be made without departing from the scope of this disclosure. The drawings are not necessarily drawn to scale. Similar numbers used in the drawings refer to similar components. However, it should be understood that the use of numbers to refer to parts in a given drawing is not intended to limit parts labeled with the same numbers in another drawing. Detailed Implementation

[0008] Optical polarizing films are widely used in optical applications. For example, they are used to reduce glare in sunglasses and to increase optical contrast in liquid crystal displays (LCDs). Two types of polarizers are typically used. One type is the dichroic polarizer, also known as an absorptive or absorbing polarizer. A dichroic polarizer absorbs light of one polarization and transmits light of orthogonal polarization. Dichroic polarizers can be prepared by incorporating dichroic materials, such as dyes, into a polymer sheet stretched in at least one direction. Alternatively, dichroic polarizers can be prepared by uniaxially stretching a semi-crystalline polymer, such as polyvinyl alcohol, and then dyeing the polymer with a dichroic material. Alternatively, dichroic polarizers can be prepared by coating a polymer with an oriented dichroic material. Dichroic materials include anthraquinone and azo dyes, as well as iodine / iodides.

[0009] Another type of polarizer is the reflective polarizer. A reflective polarizer reflects light of one polarization and transmits light of orthogonal polarization. One type of reflective polarizer is made by stacking alternating polymer layers.

[0010] These two types of polarizers can be combined to create a single optical polarizer, thus combining the useful features of both types. Dichroic polarizing films, methods for preparing these films, and methods for forming a single optical polarizer comprising a reflective polarizer and a dichroic polarizer remain needed. Desired goals include simplifying the methods for forming dichroic polarizing films and single optical polarizers. Furthermore, these films are typically prepared from polyvinyl alcohol crosslinked with boric acid. Boric acid is a hazardous material and requires special handling; therefore, it is desirable to develop other crosslinking and / or end-capping agents for use with polyvinyl alcohol.

[0011] This disclosure describes multilayer film articles and methods for preparing multilayer film articles. Multilayer film articles include those combining a reflective polarizer structure with a dichroic absorption polarizer. Modified films are also disclosed, wherein the modified film contains a dichroic material and may be an absorption polarizer.

[0012] The terms “room temperature” and “ambient temperature” are used interchangeably, referring to temperatures in the range of 20°C to 25°C.

[0013] The terms "Tg" and "glass transition temperature" are used interchangeably. If measured, unless otherwise specified, the Tg value is determined by differential scanning calorimetry (DSC) at a scan rate of 10 °C / min. Typically, the Tg value of the copolymer is not measured, but rather calculated using the well-known Fox formula, using the monomer Tg values ​​provided by the monomer supplier, as understood by those skilled in the art.

[0014] As used in this article, the term "adjacent" in the context of two floors means that the two floors are adjacent to each other and there is no intervening opening space between them. They may be in direct contact with each other (e.g., stacked together) or there may be an intervening floor.

[0015] As used herein, the terms “polymer” and “macromolecule” are consistent with their common usage in chemistry. Polymers and macromolecules are composed of many repeating subunits. As used herein, the term “macromolecule” is used to describe a group having multiple repeating units attached to a monomer. The term “polymer” is used to describe the material obtained by a polymerization reaction.

[0016] The terms “crosslinking” and “end-capping” for polyvinyl alcohol (PVA) polymers are used according to their common understanding in the polymer field. Crosslinking and end-capping are carried out by crosslinking and end-capping agents. These agents can covalently bond to the hydroxyl groups of the PVA polymer and / or interact with the hydroxyl groups through secondary / non-covalent interactions (e.g., hydrogen bonds). PVA polymers contain multiple PVA chains in a polymer mixture. If an agent reacts with a single hydroxyl group on a PVA polymer or a hydroxyl group on a single PVA polymer chain, it is described as end-capping. If an agent reacts with more than one hydroxyl group and the hydroxyl groups are on different PVA polymer lines, it is described as crosslinking. Agents can be used as end-capping agents, as crosslinking agents, or simultaneously as both. Typically, end-capping agents (whether monofunctional or polyfunctional) reside on the surface of the polymer layer, while crosslinking agents typically migrate into the polymer layer to form crosslinks.

[0017] The term "hydrogen bond" is used in this article according to its well-known meaning. A hydrogen bond is not a covalent bond or an ionic bond, but rather involves the interaction of a weak physical bond between two molecules, which is generated by the electrostatic attraction between a proton in one molecule and an electronegative atom (such as oxygen) in the other molecule.

[0018] As used herein, the term "dichroic material" refers to dichroic materials and includes dichroic dyes as well as dichroic materials such as iodine / iodide.

[0019] As understood by those skilled in the field of optics, when referring to dichroic staining solutions, the terms "iodine" and "iodine / iodide" are used interchangeably.

[0020] Unless otherwise specified, the terms "optically transparent" and "visible light transmittance" are used interchangeably and refer to articles, films, or adhesives having high transmittance over at least a portion of the visible light spectrum (about 400 nm to about 700 nm). Typically, optically transparent articles have at least 90% visible light transmittance and less than 10% haze.

[0021] Unless otherwise specified, "optically transparent" means an adhesive or article that has high transmittance and exhibits low haze (typically less than about 5%, or even less than about 2%) over at least a portion of the visible light spectrum (about 400 nm to about 700 nm). In some embodiments, the optically transparent article exhibits haze of less than 1% or even 0.5% at a thickness of 50 micrometers. Typically, the optically transparent article has a visible light transmittance of at least 95%, typically higher, such as 97%, 98%, or even 99% or higher.

[0022] This document discloses multilayer film articles. In some embodiments, the multilayer film article includes at least one film and an absorptive polarizing film disposed on the at least one film. In some embodiments, the absorptive polymer film includes an oriented polyvinyl alcohol film containing a dichroic material, wherein the oriented polyvinyl alcohol film has been crosslinked, end-capped, or both by a polyphenolic compound, nanosheet material, hydrogen-bonded polymer, non-phenolic polyacid, or a combination thereof. Each of these materials is described in more detail below.

[0023] In many embodiments, the multilayer film article is a polarizer. As will be described in detail below, the polyvinyl alcohol film can be an absorptive polarizer. In some embodiments, the at least one film layer is a reflective polarizer. In some cases, it is desirable to include both an absorptive polarizer and a reflective polarizer in display applications. For example, a reflective polarizer can be used for recirculated polarization in liquid crystal display applications, and an absorptive polarizer can be added to a reflective polarizer to improve extinction efficiency. The integration of an absorptive polarizer with a reflective polarizer is described in U.S. Patent Nos. 6,096,375 (Ouderkirk et al.), 6,697,195 (Weber et al.), 7,826,009 (Weber et al.), and 6,111,697 (Kausch et al.).

[0024] The multilayer film articles disclosed herein include at least one film. In many embodiments, the at least one film comprises a multilayer film structure. A particularly suitable example of a multilayer film structure is a multilayer reflective polarizing film. A multilayer reflective polarizing film is a polymer multilayer optical film comprising alternating polymer layers configured to reflect light polarized along an opacifying axis and transmit light polarized along a transmission axis orthogonal to the opacifying axis. For example, such films can be prepared by extruding a stack of alternating first and second type polymer layers and stretching the extruded stack uniaxially or approximately uniaxially to orient at least one of the first and second type polymer layers, as generally described in U.S. Patent No. 5,882,774 (Jonza et al.). Parabolic spreaders or tenters (e.g., those described in U.S. Patent No. 6,916,440 (Jackson) have been used to improve the degree of uniaxial orientation of the birefringent layers in reflective polarizers.

[0025] The multilayer film article disclosed herein also includes an absorptive polarizing film disposed on the at least one film. The absorptive polarizer is typically prepared by stretching a polyvinyl alcohol (PVA or PVOH) layer to align the PVA molecules in the layer and staining the aligned layer with a dichroic material such as iodine / iodide. The iodine / iodide molecules are aligned with the oriented PVA molecules. Incident light polarized along the alignment direction (i.e., polarized along the light-blocking axis of the polarizer) is absorbed or partially absorbed by the iodine / iodide, and incident light polarized along the orthogonal direction (i.e., polarized along the transmission axis of the polarizer) is transmitted or partially transmitted through the polarizer.

[0026] It has been found that polarizers comprising modified PVA layers prepared by including a suitable crosslinking agent in PVA impart improved optical properties if the modified PVA layer is oriented to a degree greater than that achievable using a conventional linear tenter frame. Specifically, it has been found that combining a suitable crosslinking agent in a PVA layer with stretching the layer by moving relative edge portions along a diverging nonlinear path (e.g., substantially uniaxially oriented the layer using a parabolic tenter frame) to form an absorbing polarizer simultaneously achieves a low minimum transmittance (e.g., less than 0.1%) for perpendicularly incident light polarized along the blocking axis in the wavelength range of interest and a high maximum transmittance (e.g., greater than 75%) for perpendicularly incident light polarized along the transmission axis in the wavelength range of interest. For example, the wavelength range of interest may be the visible range (400 nm to 700 nm) or may be 540 nm to 640 nm. In some embodiments, the absorbing polarizer has a polarization efficiency (PE) of at least 99.8% or at least 99.9%. The polarization efficiency is given by Equation 1:

[0027] in Max透光 This represents the maximum transmittance state when the light is incident perpendicularly within the wavelength range of interest, and Min 阻光 This represents the minimum light-blocking state for perpendicular incidence within the wavelength range of interest.

[0028] In this disclosure, a polyvinyl alcohol (PVA) film is formed by coating a polyvinyl alcohol solution onto a cast film, drying it to form a coating layer, and then orienting it in a tenter frame. The oriented PVA film is then dyed with at least one dichroic material. The dichroic material is described below. For high polarization efficiency, fully hydrolyzed (e.g., >98% hydrolyzed) grade PVA is particularly suitable. An example of a suitable PVA is POVAL 28-99 from Kuraray Corporation (Kuraray, Houston, TX).

[0029] Absorbing polarizing films also contain at least one dichroic material. A wide range of dichroic materials are suitable. Dichroic materials may include dyes, pigments, etc. Suitable materials for use in dichroic polarizing films include, for example, iodine / iodides and anthraquinone and azo dyes, such as Congo red (sodium diphenyl-bis-α-naphthylamine sulfonate), methylene blue, stilbene dyes (colorimetric index (CI) = 620), and 1,1'-diethyl-2,2'-anthocyanin chloride (374 (orange) or 518 (blue)). The properties of these materials and their preparation methods are described in EH Land's *Colloid Chemistry* (1946). Other dichroic materials and their preparation methods are discussed in the Kirk Othmer Encyclopedia of Chemical Technology, Vol. 8, pp. 652-661 (4th edition, 1993) and in the references cited herein. Iodine / iodides are particularly suitable dichroic materials.

[0030] As described above, it is desirable for polyvinyl alcohol (PVA) films to be crosslinked. In this disclosure, it has been found that desired oriented PVA films are crosslinked, end-capped, or a combination thereof. For PVA polymers, the terms “crosslinked” and “end-capped” are used according to their common understanding in the polymer field. Crosslinking and end-capping are carried out by crosslinking and end-capping agents. These agents may covalently bond to the hydroxyl groups of the PVA polymer and / or interact with the hydroxyl groups through secondary / non-covalent interactions (e.g., hydrogen bonds). PVA polymers contain multiple PVA chains in a polymer mixture. If an agent reacts with a single hydroxyl group on a PVA polymer or a hydroxyl group on a single PVA polymer chain, it is described as end-capped. If an agent reacts with more than one hydroxyl group and the hydroxyl groups are on different PVA polymer lines, it is described as crosslinked. Agents may be used as end-capping agents, as crosslinking agents, or simultaneously as both end-capping agents and crosslinking agents. Typically, end-capping agents (whether monofunctional or polyfunctional) reside on the surface of the polymer layer, while crosslinking agents typically migrate into the polymer layer to form crosslinks.

[0031] Examples of crosslinking and / or capping agents include polyphenolic compounds and nanosheet materials, hydrogen-bonded polymers, non-phenolic polyacids, or combinations thereof. These materials can be used as crosslinking agents, capping agents, or both.

[0032] Many polyphenolic compounds are suitable. Polyphenols are compounds containing more than one phenolic hydroxyl group. In some embodiments, the polyphenolic compound may be flavonoids, tannins, lignans, phenolic acids, or combinations thereof. In some embodiments, the polyphenolic compound may be pyrogallol (PG), epigallocatechin-3-gallate (EGCG), epigallocatechin (EGC), epicatechin gallate (ECG), flavin-3-gallate, tannic acid (TA), hydroquinone (HHQ), catechin, morin, quercetin, naringenin, rutin, phlorogallol, catechol, resorcinol, hydroquinone, gallic acid, ellagic acid, and / or their stereoisomers. Tannic acid is a particularly suitable polyphenol due to its availability and relatively low cost.

[0033] Nanosheet materials are also suitable crosslinking agents and / or end-capping agents. In some embodiments, the nanosheet materials include clay sheet materials. Clay sheet materials are layered silicates, including, for example, montmorillonite, vermiculite, kaolinite, sepiolite, glauconite, attapulgite, palygorskite, illite, chlorite, and serpentine. Particularly suitable clay sheet materials are synthetic montmorillonite, such as LAPONITE, a sodium magnesium lithium silicate. Another suitable clay sheet material is naturally occurring montmorillonite, such as montmorillonite or bentonite. Another suitable clay sheet material is vermiculite. In some embodiments, the nanosheet material may be a layered double hydroxide (LDH). In some embodiments, the nanosheet material may be a 2-D material, such as transition metal dichalcogenides, hexagonal boron nitride, graphene oxide, or Mxene. The nanosheets may be non-sheet-detached, partially sheet-detached, or completely sheet-detached. In some implementations, the thickness of a single sheet is in the range of about 1 nm to 100 nm, and the width (or lateral dimension) of the sheet is in the range of about 20 nm to 10,000 nm.

[0034] Suitable hydrogen-bonded polymers include polymeric acids, especially those containing carboxylic acid groups. Examples include polymers containing repeating units of acrylic acid or (meth)acrylic acid. Particularly suitable are polyacrylic acid, polymethacrylic acid, or combinations thereof.

[0035] Suitable non-phenolic polyacids can be α-hydroxy acids. Examples of suitable non-phenolic polyacids include citric acid, succinic acid, tartaric acid, or combinations thereof.

[0036] This document also discloses modified films. In some embodiments, the modified film comprises an oriented polyvinyl alcohol film containing a dichroic material, wherein the oriented polyvinyl alcohol film has been crosslinked, end-capped, or both of the following: a polyphenolic compound, nanosheet material, hydrogen-bonded polymer, non-phenolic polyacid, or a combination thereof. In some embodiments, the modified film comprises an absorptive polarizing film as described above.

[0037] The modified film is an oriented polyvinyl alcohol film as described above. The film also contains a dichroic material, a crosslinking agent, and / or a capping agent as described above.

[0038] This document also discloses a method for preparing multilayer film articles. In some embodiments, the method for forming a multilayer film article includes providing at least one film, providing a film-forming solution, placing the film-forming solution on the at least one film, drying the film-forming solution to form a composite structure comprising a polyvinyl alcohol film disposed on the at least one film, oriented the composite structure, placing a dyeing composition on the polyvinyl alcohol film of the composite structure, drying the composite structure on which the dyeing composition is disposed, placing a crosslinking agent / capping agent composition on the polyvinyl alcohol film of the composite structure, and drying the composite structure on which the crosslinking agent / capping agent composition is disposed.

[0039] The film-forming solution contains at least one solvent; and polyvinyl alcohol. Suitable solvents include water and water-miscible solvents, such as alcohols. Suitable polyvinyl alcohols are described above.

[0040] The dyeing composition comprises at least one dichroic material and at least one solvent. The dichroic material has been described above. Particularly suitable dichroic materials are iodine / iodides. Examples of suitable solvents include water and water-miscible solvents such as alcohols.

[0041] The crosslinking agent / capping agent composition comprises a crosslinking agent, a capping agent, or both, and at least one solvent. Suitable crosslinking agents or capping agents are polyphenolic compounds, nanosheet materials, or combinations thereof. The crosslinking agent / capping agent composition may also optionally comprise crosslinking agents / capping agents such as hydrogen-bonded polymers and non-phenolic polyacids as described above. Examples of suitable solvents include water and water-miscible solvents such as alcohols.

[0042] In some embodiments, the method further includes one or more rinsing steps. The method may include one, some, or all of these rinsing steps.

[0043] In some embodiments, the method further includes rinsing the composite structure after the dyeing composition has been placed on a polyvinyl alcohol film. The rinsing solution used for this rinsing step contains a solvent. Examples of suitable solvents include water and water-miscible solvents, such as alcohols.

[0044] In some embodiments, the method further includes rinsing the composite structure after the crosslinking agent / capping agent composition has been placed on a polyvinyl alcohol film of the composite structure. The rinsing solution used for this rinsing step contains a solvent. Examples of suitable solvents include water and water-miscible solvents, such as alcohols.

[0045] In some embodiments, the method further includes rinsing the composite structure after applying the dyeing composition to the polyvinyl alcohol film of the composite structure, and rinsing the composite structure after applying the crosslinking agent / capping agent composition to the polyvinyl alcohol film of the composite structure. The rinsing solution used for this rinsing step contains a solvent. Examples of suitable solvents include water and water-miscible solvents, such as alcohols.

[0046] The accompanying drawings illustrate some embodiments of this disclosure. Figure 1 The image shows an article 100 comprising a film 110 and a modified film layer 120. In this embodiment, the modified film layer 120 is an absorber polarizer comprising an oriented polyvinyl alcohol film containing a dichroic material, wherein the oriented polyvinyl alcohol film has been cross-linked, end-capped, or both as described above.

[0047] Figure 2Another article 200 is shown, which includes a multilayer film 210 and a modified film layer 220, wherein the multilayer film 210 is a reflective polarizer, and wherein the modified film layer 220 is an absorbent polarizer comprising an oriented polyvinyl alcohol film containing a dichroic material, wherein the oriented polyvinyl alcohol film has been cross-linked, end-capped, or both as described above.

[0048] Example

[0049] Unless otherwise stated, all parts, percentages, ratios, etc., in the examples and the remainder of this specification are by weight. Unless otherwise specified, all other reagents are derived from or purchased from fine chemical suppliers such as Sigma-Aldrich Company, St. Louis, Missouri, USA, or can be synthesized by known methods. The following abbreviations are used: cm = centimeter; mm = millimeter; min = minute; sec = second; h = hour; psi = pound per square inch; MPa = megapascal. The terms “weight%”, “by weight%”, and “wt%” are used interchangeably. Table 1 (below) lists the materials used in the examples and their sources.

[0050]

[0051] Test methods

[0052] Test Method 1: Thermal / Humidity Stability Test

[0053] The film was laminated onto the Corning EAGLE XG display glass using a barrier adhesive (described in US 8,232,350 (Fujita)) and placed in a 60°C / 90% RH chamber for 24, 250, 500 and 1000 hours.

[0054] Test Method 2: Measure the visible light transmittance and haze of the coated film.

[0055] Visible light transmittance (%T) was measured using a Haze-Gard Plus instrument (BYK, Geretsried, Germany). The sample was measured with the reflective side of the film facing the light source.

[0056] Test Method 3: Edge Intrusion

[0057] Edge intrusion was measured using a PROMETRIC I8 radiometric imaging colorimeter (Radiant Vision Systems, Redmon, WA) to image samples under cross-polarization. The area loss of iodine / iodide staining for each sample image was then calculated using ImageJ software (National Institutes of Health).

[0058] Example

[0059] Preparation Example 1 (PE-1): Preparation of Oriented Polyvinyl Alcohol on a Multilayer Reflective Polarizer

[0060] A 10% solids solution of POVAL 28-99 grade polyvinyl alcohol (PVOH) is prepared in water by first adding water to a temperature-controlled reactor at room temperature. PVOH resin is then added with stirring. The mixture is heated to 90°C to 105°C and stirred continuously at this temperature for 3 hours. The solution is then cooled and drained from the reactor. A surfactant is added to the cooled solution at 0.1% of the solution volume. If mixing is involved, a formaldehyde adduct-type crosslinking agent is added at a concentration of 5% to 40% based on the solids of the PVOH resin. Optionally, isopropanol is incorporated during the PVOH dissolution process, at a concentration up to 15%.

[0061] A birefringent reflective polarizer was fabricated as follows. A single multilayer optical group was co-extruded as described in U.S. Patent Application 2011 / 0102891 entitled "Low Layer Count Reflective Polarizer with Optimized Gain". Two polymers were used for the optical layers. The first polymer (first optical layer) was a polyethylene naphthalate (PEN) homopolymer (100 mol% PEN and 100 mol% ethylene glycol) with a Tg of 121°C to 123°C. The second polymer (second optical layer) was a blend of a first PEN copolymer (coPEN) with 90 mol% PEN and 10 mol% copolyester polyethylene terephthalate (PETG) in a ratio of approximately 45 mol% 90 / 10 PEN and 55 mol% PETG, wherein the Tg of the second optical layer material was approximately 97°C to 100°C. The polymer used for the top layer is the same as the polymer used for the second polymer layer. These polyesters can be formed, for example, as described in U.S. Patent No. 6,352,761. Materials are fed from a separate extruder into a multilayer co-extrusion feed block, where they are assembled into groups of 305 alternating optical layers, plus a thicker second optical layer protective boundary layer on each side, for a total of 307 layers. A top layer of the second optical layer material is added to a manifold specifically designed for this purpose, thus forming the final configuration with 307 layers. The multilayer melt is then poured through a die onto a cooling roll in a conventional manner for polyester films, where it is quenched.

[0062] A polyvinyl alcohol (PVOH) coating is adhered to the cast sheet. Prior to coating, the cast film is corona-treated. The solvent is removed at an elevated temperature (85°C, 45 seconds). After coating, the coated cast sheet is stretched in a standard tenter frame as described in U.S. Patent No. 5,882,774 (Jonza et al.). The resulting integrated polarizing film precursor has a physical thickness of approximately 40 micrometers, as measured by a PR2000 capacitance meter from SolveTech (Wilmington, DE), comprising approximately 1 micrometer of PVOH layer thickness.

[0063] Preparation Example 2 (PE-2): Preparation of Staining Solution

[0064] Iodine / iodide staining solution was prepared with 20% solids using a KI:I2 ratio of 60:1. DI water was used and the solution was heated to 30°C to dissolve the potassium iodide and iodine / iodide. The solution was then allowed to return to room temperature before use.

[0065] Preparation Example 3 (PE-3): Preparation of Borate / Borate Crosslinking Agent Solution

[0066] Two different borylation solutions were prepared: a 3% solid solution (abbreviated as B(3%)) and a 20% solid solution (abbreviated as B(20%)). Both used boric acid and borax in a ratio of 2.33:1. Both were heated to 60°C to dissolve the solids in the solution. The 3% solid solution remained in solution at room temperature, but the 20% solid solution required heating to retain the solids in solution.

[0067] Preparation Example 4 (PE-4): Preparation of Crosslinking Agent / Capping Agent Solution

[0068] Separate TA, GA, and CA solutions were prepared by dissolving 10g TA, 10g GA, and 10g CA separately in 950g deionized (DI) water in a plastic bottle. The plastic bottle was shaken vigorously by hand and left to stand on a roller overnight.

[0069] A PAA solution was prepared by adding 40g of ACUMER 1510 to 960g of DI water in a plastic bottle. The plastic bottle was shaken vigorously by hand and left to stand on a roller overnight.

[0070] A LapRD clay suspension was prepared by adding 10g of LAPONITE RD powder to a plastic bottle containing 950g of DI water. The bottle was shaken vigorously by hand and left to stand on a roller overnight.

[0071] A VMT clay suspension was prepared by adding 118g of MICROLITE 963++ to 882g of DI water in a plastic bottle. The plastic bottle was shaken vigorously by hand.

[0072] Method for applying dyeing solution and crosslinking agent / capping agent solution

[0073] The dyeing solution and crosslinking agent / capping agent solution were applied to an oriented polyvinyl alcohol-coated membrane (from PE-1) using equipment purchased from Svaya Nanotechnologies, Inc. (Sunnyvale, CA), and modeled according to the system described in U.S. Patent No. 8,234,998 (Krogman et al.) and Krogman et al., “Automated Process for Improved Uniformity and Versatility of Layer-by-Layer Deposition,” Langmuir, 2007, Vol. 23, pp. 3137-3141. The equipment included a pressure vessel containing the solution. A spray nozzle with a flat spray pattern (purchased from Spraying Systems, Inc., Wheaton, IL) was installed to spray the coating solution and rinsing water at specified times controlled by a solenoid valve. A pressure vessel containing the coating solution (AlloyProducts Corp., Waukesha, WI) was pressurized to 30 psi (0.21 MPa) using nitrogen, while a pressure vessel containing DI water was pressurized to 30 psi (0.21 MPa) using air. The flow rate of the solution nozzles was 10 gallons / hour (38 liters / hour) for each, while the flow rate of the DI water flushing nozzles was 40 gallons / hour (150 liters / hour). A substrate (12 inches × 12 inches) (30 cm × 30 cm) to be coated was adhered at the edges to a glass plate (12 inches × 12 inches × 1 / 8 inch thick) (30 cm × 30 cm × 0.3 cm) (Brin Northwestern Glass Co., Minneapolis, MN) using epoxy resin (Scotch-Weld epoxy adhesive, DP100 Clear, 3M Corporation, St. Paul, Minnesota). The glass plate was mounted on a vertical translation stage and held in place using a vacuum chuck. In a typical dyeing and crosslinking / sealing sequence, the dyeing solution was sprayed onto the substrate while the stage moved vertically downwards at 76 mm / s. Following a 12-second dwell time, the substrate was then dried with an air knife at 10 mm / s. This dyeing solution spraying and air knife drying sequence was repeated five times. Next, DI water is sprayed onto the substrate while the worktable moves vertically upward at 102 mm / s. Then, the substrate is dried using an air knife at a speed of 10 mm / s.Next, the crosslinking agent / capping agent solution is sprayed onto the substrate while the stage moves vertically downwards at 76 mm / s. Following a 12-second dwell time, DI water is sprayed onto the substrate while the stage moves vertically upwards at 102 mm / s. The substrate is then dried using an air knife at 10 mm / s. The film is then peeled off the glass before subsequent processing.

[0074] Examples 1-9 : The membrane sheets prepared in PE-1 were cut into 12-inch × 12-inch (30cm × 30cm) sizes, and then dyed and crosslinked / capped sequentially using the "Method for Applying Dyeing Solution and Crosslinking Agent / Capping Agent Solution". The corresponding crosslinking agents / capping agents are listed in Table 3.

[0075] Comparative Examples 1-4: Borate / Boric Acid Crosslinking

[0076] The membrane sheets prepared in PE-1 were cut into 12-inch × 12-inch (30 cm × 30 cm) dimensions and then stained using the "Method for Applying Dyeing Solution and Crosslinking Agent / Capping Agent Solution". The crosslinking agent solution was prepared as described in PE-3. For CE-1 to CE-4, the stained membranes were exposed to the crosslinking agent solution under the conditions shown in Table 2. For the immersion method, the crosslinking agent solution was poured into a glass crystallizing dish. A section of the membrane was manually immersed in the solution for 42 seconds with tweezers, rinsed with plenty of DI water, and dried with an air gun. For samples crosslinked at elevated temperatures, after drying with an air gun, they were dried in an oven at 70°C for 4 minutes. Crosslinking was performed by spraying as described in the "Method for Applying Dyeing Solution and Crosslinking Agent / Capping Agent Solution".

[0077]

[0078] Comparative Example 5: NO crosslinking

[0079] The membrane sheets prepared in PE-1 were cut into 12-inch × 12-inch (30cm × 30cm) dimensions and then stained using the "Method for Applying Dyeing Solution and Crosslinking Agent / Capping Agent Solution". Crosslinking was not performed.

[0080]

[0081] Compared with the examples, the comparative examples all have one or more of the following: lower polarization efficiency, larger Δ%T-500h, and larger edge intrusion.

Claims

1. A multilayer film product, the multilayer film product comprising: At least one membrane; and An absorptive polarizing film disposed on the at least one film, the absorptive polarizing film comprising: An oriented polyvinyl alcohol film containing a dichroic material, wherein the oriented polyvinyl alcohol film has been crosslinked, capped, or both of the following: a polyphenolic compound, a nanosheet material, a hydrogen-bonded polymer, a non-phenolic polyacid, or a combination thereof.

2. The multilayer film article according to claim 1, wherein the dichroic material comprises iodine / iodide.

3. The multilayer film article according to claim 1, wherein the at least one film comprises a multilayer reflective polarizing film.

4. The multilayer film article according to claim 1, wherein the oriented polyvinyl alcohol film has been crosslinked or capped with a polyphenol compound, wherein the polyphenol compound includes flavonoids, tannins, lignans, phenolic acids, or combinations thereof.

5. The multilayer film product according to claim 1, wherein the oriented polyvinyl alcohol film has been cross-linked or capped with nanosheet material, wherein the nanosheet material includes clay sheet material.

6. The multilayer film product according to claim 5, wherein the clay sheet material comprises montmorillonite, vermiculite, kaolinite, sepiolite, glauconite, attapulgite, palygorskite, illite, chlorite, serpentine, layered double hydroxides, or combinations thereof.

7. The multilayer film article of claim 1, wherein the oriented polyvinyl alcohol film has been crosslinked or capped with a hydrogen-bonding polymer, the hydrogen-bonding polymer comprising polyacrylic acid, polymethacrylic acid, or combinations thereof.

8. The multilayer film article according to claim 1, wherein the oriented polyvinyl alcohol film has been crosslinked or capped with a non-phenolic polyacid, wherein the non-phenolic polyacid includes citric acid, succinic acid, tartaric acid, or combinations thereof.

9. A modified membrane, said modified membrane comprising: An oriented polyvinyl alcohol film containing a dichroic material, wherein the oriented polyvinyl alcohol film has been crosslinked, capped, or both of the following: a polyphenolic compound, a nanosheet material, a hydrogen-bonded polymer, a non-phenolic polyacid, or a combination thereof.

10. The modified film according to claim 9, wherein the modified film comprises an absorptive polarizing film.

11. The modified film according to claim 9, wherein the dichroic material comprises iodine / iodide.

12. The modified membrane according to claim 9, wherein the oriented polyvinyl alcohol membrane has been crosslinked or capped with a polyphenol compound, wherein the polyphenol compound includes flavonoids, tannins, lignans, phenolic acids, or combinations thereof.

13. The modified membrane according to claim 9, wherein the oriented polyvinyl alcohol membrane has been cross-linked or capped with nanosheet material, the nanosheet material comprising clay sheet material.

14. The modified membrane according to claim 13, wherein the clay sheet material comprises montmorillonite, vermiculite, kaolinite, sepiolite, glauconite, attapulgite, palygorskite, illite, chlorite, serpentine, layered double hydroxides, or combinations thereof.

15. The modified film according to claim 9, wherein the oriented polyvinyl alcohol film has been crosslinked or capped with a hydrogen-bonding polymer, the hydrogen-bonding polymer comprising polyacrylic acid, polymethacrylic acid, or combinations thereof.

16. The modified membrane according to claim 9, wherein the oriented polyvinyl alcohol has been crosslinked or capped with a non-phenolic polyacid, the non-phenolic polyacid comprising citric acid, succinic acid, tartaric acid, or combinations thereof.

17. A method for forming a multilayer film article, the method comprising: Provide at least one membrane; A film-forming solution is provided, wherein the film-forming solution comprises: At least one solvent; and Polyvinyl alcohol; The film-forming solution is placed on at least one membrane; The film-forming solution is dried to form a composite structure, the composite structure comprising a polyvinyl alcohol film disposed on the at least one film; Orient the composite structure; The dyeing composition is placed on the polyvinyl alcohol film of the composite structure, the dyeing composition comprising: At least one dichroic material; and At least one solvent; The composite structure on which the dyeing composition is disposed is dried; The crosslinking agent / capping agent composition is placed on the polyvinyl alcohol film of the composite structure, wherein the crosslinking agent / capping agent composition comprises: Crosslinking agent, end-capping agent, or both, wherein the crosslinking agent or end-capping agent Including polyphenolic compounds, nanosheet materials, hydrogen-bonded polymers, non-phenolic polyacids, or combinations thereof; and At least one solvent; The composite structure on which the crosslinking agent / capping agent composition is disposed is dried.

18. The method of claim 17, wherein the dichroic material comprises iodine / iodide.

19. The method of claim 17, further comprising: The composite structure is rinsed after the dyeing composition is placed on the polyvinyl alcohol film of the composite structure.

20. The method of claim 17, further comprising: The composite structure is rinsed after the crosslinking agent / capping agent composition is placed on the polyvinyl alcohol film of the composite structure.

21. The method according to claim 17, further comprising: The composite structure is rinsed after the dyeing composition is placed on the polyvinyl alcohol film of the composite structure. as well as The composite structure is rinsed after the crosslinking agent / capping agent composition is placed on the polyvinyl alcohol film of the composite structure.

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