Thin film laminate for circular polarizers

Abstract

The film laminate comprises a quarter-wave retarder and a transparent aliphatic cross-linked polyurethane layer disposed on a major surface of the quarter-wave retarder, the transparent aliphatic cross-linked polyurethane layer having a glass transition temperature in the range of 11 to 27°C and a tan delta peak value in the range of 0.5 to 2.5.

Description

[Technical Field]

[0001] The present invention relates to a film laminate useful in a circular polarizer and a method for making the film laminate. [Background technology]

[0002] Light-emitting displays, such as organic light-emitting diode (OLED) displays, often utilize circular polarizers as anti-reflection films. Typically, circular polarizers comprise film components laminated together and are relatively thick. The development of new form factors, such as bendable and wrappable light-emitting displays, requires thinner display components. Conventional thick film laminate circular polarizers cannot withstand the tight bending radii required for bendable and wrappable displays. Past attempts to create thin (e.g., less than 50 μm thick) circular polarizers have had mechanical integrity issues and resulted in films that crack or break during bending and folding. Summary of the Invention

[0003] In view of the foregoing, the present inventors have recognized a need for thin yet mechanically robust circular polarizers.

[0004] In one aspect, the present invention provides a film laminate comprising a quarter-wave retarder and a transparent aliphatic crosslinked polyurethane layer disposed on a major surface of the quarter-wave retarder, the transparent aliphatic crosslinked polyurethane layer having a glass transition temperature in the range of 11 to 27°C and a tan delta peak value in the range of 0.5 to 2.5.

[0005] In another aspect, the present invention provides a film laminate comprising: a film comprising a layer of strain-hardened polyester; an oriented layer comprising polyvinyl alcohol disposed on the layer of strain-hardened polyester; and a layer of transparent aliphatic crosslinked polyurethane having a thickness of 100 μm or less disposed on the oriented layer comprising polyvinyl alcohol on the opposite side of the layer of strain-hardened polyester. The transparent aliphatic crosslinked polyurethane has a glass transition temperature in the range of 11 to 27°C and a tan delta peak value in the range of 0.5 to 2.5.

[0006] The film stacks of the present invention enable circular polarizers with total thicknesses of less than 35 μm, 25 μm, 20 μm, 15 μm, 10 μm, 5 μm, or 3 μm that are mechanically robust and therefore useful for highly curved, foldable, or wrappable displays.

[0007] In yet another aspect, the present invention provides a method for producing a film laminate, comprising: (a) coating a layer comprising polyvinyl alcohol onto a film comprising a layer of strain-hardened polyester; (b) orienting the coated film in a first direction; and (c) coating the layer comprising polyvinyl alcohol with a layer of transparent aliphatic crosslinked polyurethane having a thickness of 100 μm or less. The transparent aliphatic crosslinked polyurethane layer has a glass transition temperature in the range of 11 to 27°C and a tan delta peak value in the range of 0.5 to 2.5. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 2 is a cross-sectional view of a film laminate. [Figure 2A] 1 is a cross-sectional view of a film stack being made according to the process. [Figure 2B] 1 is a cross-sectional view of a film stack being made according to the process. [Figure 2C] 1 is a cross-sectional view of a film stack being made according to the process. [Figure 2D] 1 is a cross-sectional view of a film stack being made according to the process. [Figure 2E] 1 is a cross-sectional view of a film stack being made according to the process. [Figure 2F] 1 is a cross-sectional view of a film stack being made according to the process. DETAILED DESCRIPTION OF THE INVENTION

[0009] The present invention enables very thin circular polarizers comprising a dyed polyvinyl alcohol (PVOH) layer, a polyurethane primer, and a quarter-wave retarder. In some embodiments, the PVOH layer is less than 10 μm thick, the primer is less than 20 μm thick, the quarter-wave retarder is less than 5 μm, and the total thickness of the thin circular polarizer is less than 35 μm, 25 μm, 20 μm, 15 μm, 10 μm, 5 μm, or 3 μm.

[0010] The film laminate of the present invention includes a urethane primer layer bonding the polyvinyl alcohol layer and the quarter-wave retarder. Surprisingly, the urethane primer layer allows for very thin construction, which resists cracking of the polyvinyl alcohol layer. The urethane primer material also resists staining during the polyvinyl alcohol staining process. Additionally, the urethane primer layer allows for the use of many aggressive solvents for liquid crystal polymers without increasing haze.

[0011] In some embodiments, the urethane primer layer has a thickness of less than 100 μm, 50 μm, 30 μm, 20 μm, 10 μm, or 5 μm, hi some embodiments, the urethane primer has a thickness of 4 μm to 10 μm.

[0012] The urethane primer layer comprises a transparent, aliphatic, crosslinked polyurethane, such as that described in U.S. Patent Application Publication No. 2017 / 0165950. "Polyurethane" refers to a polymer prepared by the sequential polymerization of a hydroxyl-functional material (a material containing a hydroxyl group -OH) with an isocyanate-functional material (a material containing an isocyanate group -NCO), and therefore contains urethane linkages (-O(CO)-NH), where (CO) refers to a carbonyl group (CO). The term can include "polyurethaneureas," in which both urethane and urea linkages are present.

[0013] The transparent aliphatic crosslinked polyurethane layer can have a glass transition temperature in the range of 11 to 27° C. or 17 to 22° C. The phrase “glass transition temperature” as used herein refers to the onset glass transition temperature by DSC, measured according to ASTM E1256-08 2014.

[0014] The transparent aliphatic crosslinked polyurethane layer can have a tan delta peak value in the range of 0.5 to 2.5, or 1 to 2, or 1.4 to 1.8. The tan delta peak value and peak temperature are measured according to the DMA analysis described in the Examples. The transparent aliphatic crosslinked polyurethane layer can have a crosslink density in the range of 0.34 to 0.65 mol / kg.

[0015] A transparent aliphatic crosslinked polyurethane layer may be coated and then cured or crosslinked to form a thermoset polyurethane layer. Polyurethanes are polymers composed of organic units joined by carbamate (urethane) bonds. The polyurethanes described herein are thermoset polymers that do not melt when heated. Polyurethane polymers can be formed by reacting a diisocyanate or polyisocyanate with a polyol. Both the isocyanate and polyol used to make the polyurethane contain an average of two or more functional groups per molecule. The polyurethanes described herein can have a functionality of 2.4 or greater than 2.5.

[0016] A wide variety of polyols can be used to form the aliphatic crosslinked polyurethane layer. The term polyol generally includes hydroxyl-functional materials containing at least two terminal hydroxyl groups. Polyols include diols (materials with two terminal hydroxyl groups) and higher-functional polyols such as triols (materials with three terminal hydroxyl groups) and tetraols (materials with four terminal hydroxyl groups). Typically, the reaction mixture contains at least some diol and may also contain higher-functional polyols. Higher-functional polyols are particularly useful for forming crosslinked polyurethane polymers. Diols can generally be described by the structure HO-B-OH, where the B group can be an aliphatic group, an aromatic group, or a group containing a combination of aromatic and aliphatic groups, and may contain various linkages or functional groups, including additional terminal hydroxyl groups.

[0017] Polyester polyols are particularly useful. Among useful polyester polyols, linear and non-linear polyester polyols are useful, including, for example, polyethylene adipate, polybutylene succinate, polyhexamethylene sebacate, polyhexamethylene dodecanedioate, polyneopentyl adipate, polypropylene adipate, polycyclohexane dimethyl adipate, and polyε-caprolactone. Particularly useful are aliphatic polyester polyols such as K-FLEX 188 or K-FLEX A308, available under the trade name "K-FLEX" from King Industries (Norwalk, Conn.).

[0018] A wide variety of polyisocyanates can be used to form the aliphatic crosslinked polyurethane layer. The term polyisocyanate generally includes isocyanate-functional materials containing at least two terminal isocyanate groups. Polyisocyanates include diisocyanates (materials with two terminal isocyanate groups) and higher-functional polyisocyanates such as triisocyanates (materials with three terminal isocyanate groups) and tetraisocyanates (materials with four terminal isocyanate groups). Typically, when a difunctional polyol is used, the reaction mixture contains at least one higher-functional isocyanate. Higher-functional isocyanates are particularly useful for forming crosslinked polyurethane polymers. Diisocyanates can generally be described by the structure OCN-Z-NCO, where the Z group can be an aliphatic group, an aromatic group, or a group containing a combination of aromatic and aliphatic groups.

[0019] Higher functional polyisocyanates, such as triisocyanates, are particularly useful for forming crosslinked polyurethane polymer layers. Triisocyanates include, but are not limited to, polyfunctional isocyanates such as those formed from biurets, isocyanurates, and adducts. Some commercially available polyisocyanates include the DESMODUR and MONDUR series from Bayer Corporation (Pittsburgh, Pa.) and parts of the PAPI series from Dow Plastics, a business group of Dow Chemical Company (Midland, Mich.). Particularly useful triisocyanates include those available from Bayer Corporation under the trade names DESMODUR N3300A and MONDUR 489. One particularly suitable aliphatic polyisocyanate is DESMODUR N3300A.

[0020] The reaction mixture used to form the transparent aliphatic crosslinked polyurethane layer also contains a catalyst. The catalyst promotes the sequential reaction between the polyol and the polyisocyanate. Conventional catalysts generally recognized for use in urethane polymerization may be suitable for use in the present disclosure. For example, aluminum-, bismuth-, tin-, vanadium-, zinc-, or zirconium-based catalysts may be used. Tin-based catalysts are particularly useful. They have been found to significantly reduce the amount of outgassing present in polyurethanes. Dibutyltin compounds such as dibutyltin diacetate, dibutyltin dilaurate, dibutyltin diacetylacetonate, dibutyltin dimercaptide, dibutyltin dioctoate, dibutyltin dimaleate, dibutyltin acetonylacetonate, and dibutyltin oxide are most desirable. Specifically, the dibutyltin dilaurate catalyst DABCO T-12, commercially available from Air Products and Chemicals, Inc. (Allentown, Pa.), is particularly suitable. Catalysts are generally included at levels of at least 200 ppm or even 300 ppm or more.

[0021] The polyurethane composition described above can be used to make a film laminate such as that shown in Figure 1. Film laminate 100 includes a quarter-wave retarder 116, a polyurethane layer 120, and a layer 110 comprising PVOH. In some embodiments, quarter-wave retarder 116 has a thickness of 1 μm to 5 μm, polyurethane layer 120 has a thickness of 4 μm to 10 μm, and PVOH layer 110 has a thickness of less than 5 μm or less than 3 μm.

[0022] In some embodiments, the film laminate 100 can be fabricated and used, for example, according to the following process. As shown in FIG. 2A, in step 1, a PVOH layer 110 can be coated and oriented on an alignment layer 102. The alignment layer 102 can be, for example, a layer of strain-hardened polyester. The polyester has carboxylic acid subunits and glycol subunits and is produced by the reaction of carboxylic acid monomer molecules with glycol monomer molecules. Each carboxylic acid monomer molecule has two or more carboxylic acid or ester functional groups, and each glycol monomer molecule has two or more hydroxy functional groups. The carboxylic acid monomer molecules can all be the same, or there can be two or more different types of molecules. The same applies to glycol monomer molecules. The properties of the polymer layer or film vary depending on the specific selection of monomer molecules. One example of a polyester is polyethylene naphthalate (PEN), which can be produced, for example, by the reaction of naphthalenedicarboxylic acid with ethylene glycol.

[0023] Suitable carboxylic acid monomer molecules for use in forming the carboxylic acid subunits of the polyester layer include, for example, 2,6-naphthalenedicarboxylic acid and its isomers, terephthalic acid, isophthalic acid, phthalic acid, azelaic acid, adipic acid, sebacic acid, norbornene dicarboxylic acid, bicyclooctanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid and its isomers, t-butylisophthalic acid, trimellitic acid, sulfonated sodium isophthalate, 2,2'-biphenyldicarboxylic acid and its isomers, and lower alkyl esters of these acids, such as methyl or ethyl esters. The term "lower alkyl" in this context refers to a C1-C10 linear or branched alkyl group. The term "polyester" also includes polycarbonates derived from the reaction of glycol monomer molecules with carbonate esters.

[0024] Suitable glycol monomer molecules used to form the glycol subunits of the polyester layers include ethylene glycol, propylene glycol, 1,4-butanediol and its isomers, 1,6-hexanediol, neopentyl glycol, polyethylene glycol, diethylene glycol, tricyclodecanediol, 1,4-cyclohexanedimethanol and its isomers, norbornene diol, bicyclooctanediol, trimethylolpropane, pentaerythritol, 1,4-benzenedimethanol and its isomers, bisphenol A, 1,8-dihydroxybiphenyl and its isomers, and 1,3-bis(2-hydroxyethoxy)benzene.

[0025] Examples of useful strain hardening polyesters include polyethylene terephthalate, mixed diol-substituted copolyethylene terephthalate, polyethylene naphthalene-2,6-dicarboxylic acid, mixed diol-substituted copolyethylene naphthalene-2,6-dicarboxylic acid, polyethylene terephthalate-co-naphthalene-2,6-dicarboxylic acid, mixed diol-substituted polyethylene terephthalate-co-naphthalene-2,6-dicarboxylic acid, polyethylene terephthalate-co-biphenyl-4,4'-dicarboxylic acid, mixed diol-substituted copolyethylene terephthalate-co-biphenyl-4,4'-dicarboxylic acid, poly Examples of suitable diol-substituted polyethylene naphthalene-2,6-dicarboxylic acid-cobiphenyl-4,4'-dicarboxylic acid, mixed diol-substituted polyethylene naphthalene-2,6-dicarboxylic acid-cobiphenyl-4,4'-dicarboxylic acid, polyethylene terephthalate-co-naphthalene-2,6-dicarboxylic acid-co-biphenyl-4,4'-dicarboxylic acid, and mixed diol-substituted polyethylene terephthalate-co-naphthalene-2,6-dicarboxylic acid-co-biphenyl-4,4'-dicarboxylic acid, where the mixed diols can be linear, branched, or cyclic, with chain lengths ranging from two carbons C2 up to C10. Isophthalates, such as sodium dimethyl sulfonate isophthalate ionomer, can also be substituted for terephthalate, 2,6-naphthalenedicarboxylate, and 4,4'-biphenyldicarboxylate.

[0026] In some embodiments, the alignment layer 102 is PEN or low-melt PEN. PEN can be described as a 0.48 IV polyethylene 2,6-naphthalate polymer. Low-melt PEN can be described as a 0.48 IV copolyester, containing 90 mole % naphthalate and 10 mole % terephthalate moieties on an ester basis. Ethylene glycol is included as the diol in this polymer. The alignment layer functions as a carrier vehicle, allowing for the creation of a flat film during both the alignment and annealing processes. After annealing, the alignment layer functions to provide high elasticity and dimensional stability. In some embodiments, the alignment layer 102 includes multiple layers.

[0027] Preferably, the alignment layer 102 has a Tg that is at least 10° C. lower than the Tg of the PVOH layer. The Tg of the PVOH layer can be depressed based on the level of water present in the layer. The phrase "glass transition temperature" or "Tg" herein refers to the onset glass transition temperature by DSC, measured according to ASTM E1256-08 2014.

[0028] The orientation layer 102 can be coated with a PVOH solution, dried, and then stretched, for example, using a standard tenter, optionally with heat. Preferably, the orientation layer 102 is stretched lengthwise before coating with PVOH, so that the orientation layer 102 is biaxially oriented and the PVOH is stretched only uniaxially. A biaxially oriented orientation layer 102 provides beneficial mechanical properties, resulting in a film laminate that is more robust and less likely to tear.

[0029] The PVOH layer 110 may be of any suitable thickness, preferably less than 5 μm after orientation. In some embodiments, the PVOH layer may be 0.5 μm, 0.8 μm, or 1.2 μm to 1.5 μm, 2 μm, or 3 μm thick after orientation. The PVOH layer may be coated or extruded onto the multilayer film described above so that the multilayer film and PVOH layer can be oriented together. A typical process for manufacturing PVOH films is described, for example, in U.S. Pat. No. 6,096,375. PVOH coating solutions typically contain 2 to 20% polymer in water by weight, with a preferred concentration typically being 5 to 15%. In some embodiments, the PVOH coating comprises water, PVOH, and a surfactant. Kuraray 2899 from Kuraray America (Houston, TX) is an example of a suitable PVOH. The PVOH should have a degree of hydrolysis of 95 to 100%, preferably 97 to 99.5%. Coating dry weights typically range from 2 to 80 grams per square meter. The PVOH-coated multilayer film can then be stretched at an elevated temperature to create an oriented PVOH layer 110 and multilayer film 100. This temperature is preferably higher than the glass transition temperature of at least one of the components of multilayer film 100. Generally, the temperature is between 60 and 160°C. In some embodiments, the temperature is between 105 and 120°C. After stretching, the film laminate can be heat-set, preferably at a temperature between 160 and 220°C.

[0030] The film is typically stretched 2 to 10 times its original dimensions. Preferably, the film is stretched 3 to 6 times its original dimensions. The film may be allowed to relax dimensionally in the cross-stretch direction from natural cross-stretch contraction (equal to the square root of the stretch ratio) to restrained (i.e., no substantial change in cross-stretch dimension). The film may be stretched in the machine direction, as with a length orienter, or in the width direction using a tenter, or optionally in both directions if the cast web is stretched in one direction prior to PVOH coating.

[0031] As shown in Figure 2B, in step 2, the oriented PVOH layer 110 is coated with a polyurethane layer 120 using standard coating methods, such as using a slot coater. Typically, the polyurethane layer is coated from a solvent, but in some embodiments, it may be coated at 100% solids. In some embodiments, the PVOH layer is primed or corona treated to promote adhesion of the polyurethane layer.

[0032] 2C, in step 3, a quarter-wave retarder 116 is coated onto the polyurethane layer 120. The quarter-wave retarder may be provided, for example, from an oriented polymer material such as polycarbonate, polyethyl terephthalate, or polyvinyl alcohol, or from a coated liquid crystal material. Suitable materials include, for example, linear photopolymerizable polymer (LPP) and liquid crystal polymer (LCP) materials described in U.S. Patent Application Publication Nos. 2002 / 0180916 (Schadt et al.), 2003 / 028048 (Cherkaoui et al.), and 2005 / 0072959 (Moia et al.). A suitable LPP material includes ROP-131 EXP 306 LPP, and a suitable LCP material includes ROF-5185 EXP 410 LCP, both available from Rolic Technologies (Allschwil, Switzerland). In some embodiments, the quarter-wave retarder may be a quarter-wave retarder at at least one wavelength within a predetermined wavelength range. While shown in FIG. 2C as a single layer, the quarter-wave retarder 116 may include multiple layers, such as an LPP layer, an LCP half-wave plate, and an LCP quarter-wave plate.

[0033] As shown in FIG. 2D , in optional step 4, a pre-mask 118 is added to the quarter-wave retarder 116 to provide support during the dyeing step. The pre-mask 118 typically comprises polyethylene terephthalate. In some embodiments, the pre-mask 118 is optically clear to facilitate transmittance measurements, for example, to accurately measure defect measurements or dye levels without removing the pre-mask. The pre-mask 118 typically comprises a pressure-sensitive adhesive (PSA) layer, preferably an optically clear PSA, to adhere the pre-mask. The PSA is selected to withstand the dyeing step and be removable. In some embodiments, a thicker polyurethane layer (e.g., thicker than 25 μm) can be utilized to provide support during the dyeing step.

[0034] Next, in step 5, as shown in FIG. 2E, the alignment layer 102 is removed to expose the PVOH layer 110 for dyeing.

[0035] In step 6, shown in FIG. 2F, the PVOH layer 110 is dyed with an iodine solution to form an absorptive polarizer. This process includes iodine dyeing and boronization steps. The dye bath is typically an aqueous solution of iodine. In some embodiments, the amount of iodine is 0.1 to 0.5 parts by weight per 100 parts by weight of water. In some embodiments, the aqueous solution of iodine is blended with iodide, for example, to increase the solubility of iodine in water. Examples of useful iodides include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and titanium iodide. The composition can include, for example, water (e.g., 80% by weight), potassium iodide (e.g., 19.7%), and iodine (e.g., 0.3%).

[0036] The boration bath composition is an aqueous solution of boric acid. The composition can be obtained by dissolving boric acid and / or a borate in water as a solvent. The concentration of boric acid is typically 1 part by weight to 10 parts by weight per 100 parts by weight of water. In some embodiments, the boration bath can include, for example, water (e.g., 80% by weight), boric acid (e.g., 14%), and sodium borate (e.g., 6%).

[0037] The dye bath step is typically carried out for, for example, about 5 seconds to 5 minutes at a bath temperature of about 20-50° C. In some embodiments, the dye batch step is carried out at about 30° C. for about 30-40 seconds.

[0038] The boriding step is typically carried out for about 15 seconds to 5 minutes, for example, at a bath temperature of about 40-85° C. In some embodiments, the boriding step is carried out at about 65° C. for about 40-50 seconds.

[0039] After boronization, the film stacks can be rinsed with water and dried, for example, in an oven at 70°C for 5 minutes. The resulting film stacks are remarkably crack-free and mechanically robust. They are ready for integration into devices such as bendable or foldable display devices for use as circular polarizing films to reduce reflectance. [Example]

[0040] The objects and advantages of this invention are further illustrated by the following examples, but the particular materials and amounts thereof recited in these examples, as well as other conditions and details, should not be construed to unduly limit this invention.

[0041] [Table 1]

[0042] Examples 1 and 2 120 and 100 parts by weight of PD and HMDI, respectively, were added to toluene at 10% solids in a plastic beaker at room temperature. This was stirred by hand with a stir bar until a homogeneous mixture was obtained. DTD catalyst was then added to this mixture at 150 ppm, and the final mixture was stirred by hand with a stir bar until thoroughly mixed. The amount of catalyst was based on KFLEX 188 and Desmodur 3300.

[0043] The urethane mixture was coated onto a moving web of polyvinyl alcohol and removable polyethylene terephthalate substrate through a slot die at a speed of 10 ft / min with a target thickness of 7, 10 μm and heat cured in an oven for approximately 3 minutes at 210° F. The coating was applied directly onto the polyvinyl alcohol surface.

[0044] Examples 3 to 5 110 and 100 parts by weight of PD and HMDI, respectively, were added to toluene at 10% solids in a plastic beaker at room temperature. This was stirred by hand until a homogeneous mixture was formed. DTD catalyst was then added to this mixture at 150 ppm, and the final mixture was stirred by hand with a stir bar until thoroughly mixed. The amount of catalyst was based on KFLEX 188 and Desmodur 3300.

[0045] The urethane mixture was coated onto a moving web of polyvinyl alcohol and a removable polyethylene terephthalate substrate through a slot die at a speed of 10 ft / min at target thicknesses of 4, 7, and 10 μm and heat cured in an oven at 210° F. for approximately 3 minutes. The coating was applied directly onto the polyvinyl alcohol surface.

[0046] Examples 6 to 8 105 and 100 parts by weight of PD and HMDI, respectively, were added to toluene at 10% solids in a plastic beaker at room temperature. This was stirred by hand with a stir bar until a homogeneous mixture was obtained. DTD catalyst was then added to this mixture at 150 ppm, and the final mixture was stirred by hand with a stir bar until thoroughly mixed. The amount of catalyst was based on KFLEX 188 and Desmodur 3300.

[0047] The urethane mixture was coated onto a moving web of polyvinyl alcohol and a removable polyethylene terephthalate substrate through a slot die at a speed of 10 feet per minute with target thicknesses of 4, 7, and 10 μm and heat cured in an oven at 210° F. for approximately 3 minutes. The coating was applied directly onto the polyvinyl alcohol surface. The coating was applied directly onto the polyvinyl alcohol surface.

[0048] Examples 9-10 80 and 100 parts by weight of PD and HMDI, respectively, were added to toluene at 10% solids in a plastic beaker at room temperature. This was stirred by hand with a stir bar until a homogeneous mixture was obtained. DTD catalyst was then added to this mixture at 150 ppm, and the final mixture was stirred by hand with a stir bar until thoroughly mixed. The amount of catalyst was based on KFLEX 188 and Desmodur 3300.

[0049] The urethane mixture was coated onto a moving web of polyvinyl alcohol and removable polyethylene terephthalate substrate through a slot die at a speed of 10 ft / min with a target thickness of 7, 10 μm and heat cured in an oven for approximately 3 minutes at 210° F. The coating was applied directly onto the polyvinyl alcohol surface.

[0050] [Table 2]

[0051] Comparative Examples 1 to 4 9 grams of PEGDA and 0.9 grams of PI were added to 290.1 ​​grams of MEK in a 500 mL amber glass bottle at room temperature. The bottle was capped and shaken until all ingredients were uniformly mixed in solution.

[0052] The PEGDA mixture was coated through a slot die onto a moving web of polyvinyl alcohol and a non-removable substrate, such as that referenced in WO 2019 / 003107, at a speed of 50 feet per minute with target thicknesses of 100, 150, 200, and 250 nm. Solvent was removed from the coating by heating in an oven at 190°F for approximately 2 minutes before UV curing. The coating was applied directly onto the polyvinyl alcohol surface. Prior to coating, the substrate surface was exposed to 250 mJ / cm2 of UV light. 2 It was treated with corona virus.

[0053] Comparative Examples 5 to 7 72.7 grams of PEGDA and 7.3 grams of PI were added to 120 grams of MEK in a 500 mL amber glass bottle at room temperature. The bottle was capped and shaken until all ingredients were uniformly mixed in solution.

[0054] The PEGDA mixture was coated onto a moving web of polyvinyl alcohol and a removable substrate through a slot die at a speed of 10 feet per minute with target thicknesses of 4, 7, and 10 μm. The solvent was removed from the coating by heating in an oven at 190° F. for approximately 2 minutes before UV curing. The coating was applied directly onto the polyvinyl alcohol surface.

[0055] Comparative Examples 8 to 11 79.2 grams of TICTA and 0.8 grams of PI were added to 120 grams of MEK in a 500 mL amber glass bottle at room temperature. The bottle was capped and shaken until all ingredients were uniformly mixed in solution.

[0056] The TICTA mixture was coated through a slot die onto a moving web of polyvinyl alcohol and a non-removable substrate, such as that referenced in WO 2019 / 003107, at a speed of 45 ft / min with a target thickness of 210 nm. Solvent was removed from the coating by heating in an oven at 165-180°F for approximately 40 seconds before UV curing. The coating was applied directly onto the polyvinyl alcohol surface. Prior to coating, the substrate surface was exposed to 0, 250, 500, or 750 mJ / cm. 2 It was treated with corona virus.

[0057] Comparative Examples 12 to 14 79.2 grams of TICTA and 0.8 grams of PI were added to 120 grams of MEK in a 500 mL amber glass bottle at room temperature. The bottle was capped and shaken until all ingredients were uniformly mixed in solution.

[0058] The TICTA mixture was coated onto a moving web of polyvinyl alcohol and a removable substrate through a slot die at a speed of 10 feet per minute at target thicknesses of 4, 7, and 10 μm. The solvent was removed from the coating by heating in an oven at 190° F. for approximately 2 minutes before UV curing. The coating was applied directly onto the polyvinyl alcohol surface.

[0059] Comparative Examples 15 to 18 79.2 grams of AO and 0.8 grams of PI were added to 120 grams of MEK in a 500 mL amber glass bottle at room temperature. The bottle was capped and shaken until all ingredients were uniformly mixed in solution.

[0060] The AO mixture was coated through a slot die at a speed of 45 ft / min with a target thickness of 210 nm onto a moving web of polyvinyl alcohol and a non-removable substrate, such as that referenced in WO 2019 / 003107. Solvent was removed from the coating by heating in an oven at 165-180°F for approximately 40 seconds before UV curing. The coating was applied directly onto the polyvinyl alcohol surface. The substrate surface was then exposed to 0, 250, 500, or 750 mJ / cm prior to coating. 2 It was treated with corona virus.

[0061] Comparative Examples 19 to 21 79.2 grams of AO and 0.8 grams of PI were added to 120 grams of MEK in a 500 mL amber glass bottle at room temperature. The bottle was capped and shaken until all ingredients were uniformly mixed in solution.

[0062] The AO mixture was coated onto a moving web of polyvinyl alcohol and a removable substrate through a slot die at a speed of 10 feet per minute with target thicknesses of 4, 7, and 10 μm. The solvent was removed from the coating by heating in an oven at 190° F. for approximately 2 minutes before UV curing. The coating was applied directly onto the polyvinyl alcohol surface.

[0063] Comparative Examples 22 to 25 79.2 grams of PAO and 0.8 grams of PI were added to 120 grams of MEK in a 500 mL amber glass bottle at room temperature. The bottle was capped and shaken until all ingredients were uniformly mixed in solution.

[0064] The PAO mixture was coated through a slot die at a speed of 45 ft / min with a target thickness of 210 nm onto a moving web of polyvinyl alcohol and a non-removable substrate, such as that referenced in WO 2019 / 003107. Solvent was removed from the coating by heating in an oven at 165-180°F for approximately 40 seconds before UV curing. The coating was applied directly onto the polyvinyl alcohol surface. The substrate surface was then exposed to 0, 250, 500, or 750 mJ / cm prior to coating. 2 It was treated with corona virus.

[0065] Comparative Examples 26 to 28 79.2 grams of PAO and 0.8 grams of PI were added to 120 grams of MEK in a 500 mL amber glass bottle at room temperature. The bottle was capped and shaken until all ingredients were uniformly mixed in solution.

[0066] The PAO mixture was coated onto a moving web of polyvinyl alcohol and a removable substrate through a slot die at a speed of 10 ft / min with target thicknesses of 4, 7, and 10 μm. The solvent was removed from the coating by heating in an oven at 190° F. for approximately 2 minutes before UV curing. The coating was applied directly onto the polyvinyl alcohol surface.

[0067] Comparative Example 29 75 parts by weight of APETPU, supplied at 40% solids in water, was added to 925 parts by weight of water and mixed until homogeneous. The mixture was then coated onto a moving cast polyester web by hand via syringe and metered with a #18 Meyer rod. The cast web was then stretched in the cross direction and dried in a tenter oven until the web was six times its starting width. The final coating thickness was less than 500 nm.

[0068] Comparative Example 30 125 parts by weight of APETPU, supplied at 40% solids in water, was added to 875 parts by weight of water and mixed until homogeneous. The mixture was then manually coated onto a moving cast polyester web via syringe and metered with a #18 Meyer rod. The cast web was then stretched in the cross direction and dried in a tenter oven until the web was six times its starting width. The final coating thickness was less than 500 nm.

[0069] Comparative Example 31 175 parts by weight of APETPU, supplied at 40% solids in water, was added to 825 parts by weight of water and mixed until homogeneous. The mixture was then manually coated onto a moving cast polyester web via syringe and metered with a #18 Meyer rod. The cast web was then stretched transversely and dried in a tenter oven until the web was six times its starting width. The final coating thickness was less than 500 nm.

[0070] Comparative Example 32 86 parts by weight of APCPU, supplied at 35% solids in water, was added to 914 parts by weight of water and mixed until homogeneous. The mixture was then coated onto a moving cast polyester web by hand via syringe and metered with a #18 Meyer rod. The cast web was then stretched in the cross direction and dried in a tenter oven until the web was six times its starting width. The final coating thickness was less than 500 nm.

[0071] Comparative Example 33 143 parts by weight of APCPU, supplied at 35% solids in water, was added to 857 parts by weight of water and mixed until homogeneous. The mixture was then coated onto a moving cast polyester web by hand via syringe and metered with a #18 Meyer rod. The cast web was then stretched in the cross direction and dried in a tenter oven until the web was six times its starting width. The final coating thickness was less than 500 nm.

[0072] Comparative Example 34 200 parts by weight of APCPU, supplied at 35% solids in water, was added to 800 parts by weight of water and mixed until homogeneous. The mixture was then coated onto a moving cast polyester web by hand via syringe and metered with a #18 Meyer rod. The cast web was then stretched in the cross direction and dried in a tenter oven until the web was six times its starting width. The final coating thickness was less than 500 nm.

[0073] Subsequent steps for Examples 1 to 10 and Comparative Examples 1 to 4, 8 to 11, 15 to 18, 22 to 25, and 29 to 37 Next, a quarter-wave plate was fabricated. The material was solvent coated and UV cured onto a urethane coating with the optical slow axis oriented at 45 degrees to the pass direction of the integrated polarizer. The coated layer had a retardation of 138 nm at a wavelength of 550 nm. (Retardation is given by Re = (n i - n j ) * (The coefficient of curvature is defined by ∑ n i - n j ⁢ ...

[0074] Adhesion test method 1 measurement A sample consisting of the substrate, PVOH, primer, and QWP was taped to a glass panel above the linear polarizer and backlight with double-sided tape (3M 415, 3M Company, St. Paul, MN). The QWP was oriented face up toward the air. The sample was then carefully scored using an 11-tooth blade with teeth spaced 1 mm apart (such as a Gardco PA-2053, Paul N. Gardner Company, Pompano Beach, FL). The sample was then carefully scored again perpendicular to the first set of score marks to create a 10 x 10 square grid. A 1-inch piece of tape (3M 8403) was pressed against the scored grid at a 45-degree angle to the score marks, completely covering the scored grid. The 1-inch piece of tape was applied for 30 seconds before removal. The grid was visually observed through the linear polarizer, and the percent retention was recorded.

[0075] [Table 3]

[0076] Adhesion test method 2 measurement Adhesion was measured using a modified version of Test Method 1. This method was developed for cases where the primer coating was applied to a removable substrate. When the substrate was removable, the adhesion between the substrate and the primer coating was not sufficient for tape removal, so the substrate had to be removed first. Furthermore, the blade used in Adhesion Test Method 1 tore through the coating stack without a substrate to support it. Therefore, a very sharp razor blade was required to score the crosshatch grid. The test method is as follows:

[0077] First, a 2-inch double-sided tape with a paper liner (3M 415, 3M Company, St. Paul, MN) was applied in the machine direction to the quarter-wave plate side of the coated film. Next, the removable substrate was removed from the coated film laminate, leaving the polyvinyl alcohol, urethane coating, and quarter-wave plate adhered to the double-sided tape with the paper liner. The paper liner was then removed from the double-sided tape, and the tape / film laminate was laminated to a glass plate with a rubber roller. The glass plate was positioned above the backlight, with a linear polarizer (Sanritz HLC2-5618, Sanritz Corporation, Tokyo, JP)) positioned between the glass plate and the backlight panel. An aqueous iodine solution was applied to the exposed surface of the film laminate via a cotton-tipped applicator. If the film laminate was stained with iodine, it indicated that all layers had transferred successfully. If the film laminate was not stained, it indicated that some or all of the layers had not transferred. Five straight, parallel lines, spaced 2 mm apart and 2.5 inches long, were scored into the film laminate with a razor blade guided by a stencil device. Five more parallel lines, equal in dimension and oriented perpendicular to the first five lines, were scored to create a 5 x 5 square grid. One-inch tape (3M 8403, 3M Company, St. Paul, MN) was pressed onto the scored grid at a 45-degree angle relative to the score marks, completely covering the grid. The one-inch tape adhered to the grid for 30 seconds before removal. After removal, the grid was visually observed through a linear polarizer oriented approximately 15 degrees from the block position and attached to a magnifying glass, illuminating a quarter-wave plate to indicate any areas of missing polyvinyl alcohol. The percent retention within the grid area was then recorded. Failure of the complete film laminate to transfer indicated adhesion failure and was similarly recorded. Alternatively, the grid can be stained with an iodine solution and observed visually without linear polarizers, and the percent retention within the grid area recorded.

[0078] [Table 4]

[0079] Crack Test Method After the coating laminate including PVOH with carrier substrate, primer, and QWP was subjected to the iodine dye bath, boriding bath, rinsing, and drying according to the above process, cracks were evaluated on a pass / fail basis. If any cracks were present, it was considered a failure, while if the sample was free of cracks, it was considered a pass.

[0080] Iodine absorption test method The primer was coated on a substrate without PVOH, and then passed through the above process of iodine dye bath, boronizing bath, rinsing, and drying.The primer layer was then visually evaluated for yellowness, and if any color was observed, it was given a failing grade.If no color was found, it was considered to be passing.

[0081] [Table 5]

[0082] The complete disclosures of the publications cited herein are incorporated by reference in their entireties, as if each were individually incorporated. Various modifications and alterations to the present invention will become apparent to those skilled in the art without departing from the scope and spirit of the present invention. It is understood that this invention is not intended to be unduly limited by the illustrative embodiments and examples described herein, which examples and embodiments are presented by way of example only, and that the scope of the present invention is intended to be limited only by the claims set forth herein below. In the following, exemplary embodiments are presented. [Item 1] (a) A quarter-wave retarder; (b) a transparent, aliphatic, crosslinked polyurethane layer disposed on a major surface of the quarter-wave retarder, the transparent, aliphatic, crosslinked polyurethane layer having a glass transition temperature in the range of 11 to 27°C and a tan delta peak value in the range of 0.5 to 2.5; A film laminate comprising: [Item 2] Item 10. The film stack of item 1, further comprising an oriented layer comprising polyvinyl alcohol disposed on the polyurethane layer on the opposite side of the quarter wave retarder. [Item 3] Item 3. The film stack of item 2, further comprising a pre-mask disposed on the quarter wave retarder opposite the layer comprising polyvinyl alcohol. [Item 4] Item 4. The film laminate of item 3, wherein the pre-mask comprises polyethylene terephthalate. [Item 5] 5. The film laminate of any one of items 2 to 4, wherein the layer comprising polyvinyl alcohol is disposed on a film comprising a layer of strain-hardened polyester. [Item 6] 6. The film laminate according to any one of items 1 to 5, wherein the quarter wave retarder has a thickness of 1 μm to 5 μm. [Item 7] 7. The film laminate according to any one of items 1 to 6, wherein the polyurethane layer has a thickness of 4 μm to 10 μm. [Item 8] 8. The film laminate of any one of items 2 to 7, wherein the layer comprising polyvinyl alcohol has a thickness of less than 5 μm. [Item 9] 9. The film laminate of claim 8, wherein the layer comprising polyvinyl alcohol has a thickness of less than 3 μm. [Item 10] 10. The film laminate according to any one of items 1 to 9, wherein the film laminate has a total thickness of less than 35 μm. [Item 11] Item 11. The film laminate of item 10, wherein the film laminate has a total thickness of less than 20 μm. [Item 12] Item 12. The film laminate of item 11, wherein the film laminate has a total thickness of less than 15 μm. [Item 13] 13. The film stack of any one of items 1 to 12, wherein the quarter wave retarder comprises an oriented polymer material or a coated liquid crystal material. [Item 14] 14. The film laminate according to any one of items 2 to 13, wherein the layer comprising polyvinyl alcohol is dyed with a composition comprising iodine. [Item 15] Item 15. The film laminate of item 14, further comprising a second transparent aliphatic crosslinked polyurethane layer having a thickness of 2 to 5 μm disposed on the iodine-dyed layer comprising polyvinyl alcohol, the second transparent aliphatic crosslinked polyurethane layer having a glass transition temperature in the range of 11 to 27° C. and a tan delta peak value in the range of 0.5 to 2.5. [Item 16] 16. The film laminate according to any one of items 1 to 15, wherein the polyurethane layer is not dyed with iodine. [Item 17] (a) a film comprising a layer of strain-hardened polyester; (b) an oriented layer comprising polyvinyl alcohol disposed on said layer of strain-hardened polyester; a transparent, aliphatic, crosslinked polyurethane layer having a thickness of 100 μm or less, disposed on the oriented layer comprising polyvinyl alcohol and on the opposite side of the layer of strain-hardened polyester, the transparent, aliphatic, crosslinked polyurethane layer having a glass transition temperature in the range of 11 to 27° C. and a tan delta peak value in the range of 0.5 to 2.5; A film laminate comprising: [Item 18] Item 18. The film laminate according to item 17, wherein the polyurethane layer has a thickness of 4 μm to 10 μm. [Item 19] 19. The film laminate of item 17 or 18, wherein the oriented layer comprising polyvinyl alcohol has a thickness of less than 5 μm. [Item 20] 20. The film laminate of item 19, wherein the oriented layer comprising polyvinyl alcohol has a thickness of less than 3 μm. [Item 21] 21. The film laminate according to any one of items 17 to 20, wherein the film laminate has a total thickness of less than 35 μm. [Item 22] 22. The film laminate of claim 21, wherein the film laminate has a total thickness of less than 20 μm. [Item 23] 23. The film laminate of claim 22, wherein the film laminate has a total thickness of less than 15 μm. [Item 24] 24. The film laminate according to any one of items 17 to 23, wherein the polyurethane layer is not dyed with iodine. [Item 25] (a) coating a layer comprising polyvinyl alcohol onto a film comprising a layer of strain-hardened polyester; (b) orienting the coated film in a first direction; (c) coating the layer comprising polyvinyl alcohol with a transparent aliphatic crosslinked polyurethane layer having a thickness of 100 μm or less, the transparent aliphatic crosslinked polyurethane layer having a glass transition temperature in the range of 11 to 27° C. and a tan delta peak value in the range of 0.5 to 2.5; A method for producing a film laminate, comprising: [Item 26] 26. The method of claim 25, further comprising orienting the film comprising a layer of strain-hardened polyester in a direction opposite to the first direction prior to coating the layer comprising polyvinyl alcohol. [Item 27] 27. The method of claim 25 or 26, further comprising coating a quarter wave retarder layer on the polyurethane layer. [Item 28] 28. The method of any one of items 25 to 27, further comprising removing the film comprising a layer of strain-hardened polyester from the film laminate. [Item 29] 29. The method of claim 28, further comprising staining the layer comprising polyvinyl alcohol with iodine. [Item 30] 30. The method of any one of items 27 to 29, further comprising placing a pre-mask on the quarter wave retarder layer. [Item 31] 31. The film laminate according to any one of items 25 to 30, wherein the polyurethane layer is not dyed with iodine.

Claims

1. (a) a quarter wave retarder; (b) a transparent, aliphatic, crosslinked polyurethane layer disposed on a major surface of the quarter-wave retarder, the transparent, aliphatic, crosslinked polyurethane layer having a glass transition temperature in the range of 11 to 27°C and a tan delta peak value in the range of 0.5 to 2.5; A film laminate comprising:

2. 10. The film stack of claim 1, further comprising an oriented layer comprising polyvinyl alcohol disposed on the polyurethane layer on the opposite side from the quarter wave retarder.

3. 3. The film stack of claim 2, further comprising a pre-mask disposed on the quarter wave retarder opposite the layer comprising polyvinyl alcohol.

4. The film laminate of claim 3 , wherein the pre-mask comprises polyethylene terephthalate.

5. 5. The film laminate of claim 2, wherein the layer comprising polyvinyl alcohol is disposed on a film comprising a layer of strain-hardened polyester.

6. The film stack of any one of claims 1 to 5, wherein the quarter wave retarder has a thickness of from 1 μm to 5 μm.

7. The film laminate according to any one of claims 1 to 6, wherein the polyurethane layer has a thickness of 4 µm to 10 µm.

8. The film laminate of any one of claims 2 to 7, wherein the layer comprising polyvinyl alcohol has a thickness of less than 5 μm.

9. 9. The film laminate of claim 8, wherein the layer comprising polyvinyl alcohol has a thickness of less than 3 μm.

10. The film laminate of any one of claims 1 to 9, wherein the film laminate has a total thickness of less than 35 μm.

11. 11. The film laminate of claim 10, wherein the film laminate has a total thickness of less than 20 μm.

12. 12. The film laminate of claim 11, wherein the film laminate has a total thickness of less than 15 μm.

13. The film stack of any one of claims 1 to 12, wherein the quarter wave retarder comprises an oriented polymer material or a coated liquid crystal material.

14. (a) a film comprising a layer of strain-hardened polyester; (b) an oriented layer comprising polyvinyl alcohol disposed on said layer of strain-hardened polyester; a transparent, aliphatic, crosslinked polyurethane layer having a thickness of 100 μm or less, disposed on the oriented layer comprising polyvinyl alcohol and on the opposite side of the layer of strain-hardened polyester, the transparent, aliphatic, crosslinked polyurethane layer having a glass transition temperature in the range of 11 to 27° C. and a tan delta peak value in the range of 0.5 to 2.5; A film laminate comprising:

15. (a) coating a layer comprising polyvinyl alcohol onto a film comprising a layer of strain-hardened polyester; (b) orienting the coated film in a first direction; (c) coating the layer comprising polyvinyl alcohol with a transparent aliphatic crosslinked polyurethane layer having a thickness of 100 μm or less, the transparent aliphatic crosslinked polyurethane layer having a glass transition temperature in the range of 11 to 27° C. and a tan delta peak value in the range of 0.5 to 2.5; A method for producing a film laminate, comprising:

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