Flexible hard coating layer

Abstract

A hardcoat composition includes one or more multifunctional (meth)acrylate monomers and a mixture of nanoparticles dispersed within the one or more multifunctional (meth)acrylate monomers. The mixture of nanoparticles includes a first population of semi-reactive nanoparticles having an average particle size ranging from 5 nm to 60 nm and a second population of non-reactive nanoparticles having an average particle size ranging from 5 nm to 60 nm.

Description

[0001] This application is a divisional application of application number 2020800341847, filed on May 4, 2020, entitled "Flexible Hard Coating". Background Technology

[0002] Displays and electronic devices have evolved to bend, fold, roll, or fold, offering new user experiences. For example, these device architectures can include flexible organic light-emitting diodes (OLEDs), liquid crystal displays (LCDs), and more.

[0003] To enable such flexible displays and protect the components within them, flexible cover sheets or flexible window films replace conventional glass cover sheets. These flexible cover sheets have several design parameters such as high visible light transmittance, low haze, and excellent scratch and puncture resistance to protect the components included in the display device. In some cases, the flexible cover sheet may also need to withstand thousands of folding events around a tight bending radius (approximately 5 mm or less) without showing visible damage. In other cases, the flexible cover sheet must be able to unfold without leaving creases after bending under elevated temperatures and humidity.

[0004] A variety of hard-coated plastic substrates have been developed. More exotic materials, such as hard-coated colorless and transparent polyimide films, have also shown high hardness and good scratch resistance. However, many hard-coated films cannot withstand folding events around a tight bending radius without showing visible damage. Summary of the Invention

[0005] This disclosure relates to a flexible rigid coating or flexible rigid coating article that protects a display window and withstands flexural or folding tests. The flexible rigid coating or flexible rigid coating article maintains the optical properties of the display film while providing scratch resistance to the display.

[0006] In one aspect, a hard coating composition comprises one or more polyfunctional (meth)acrylate monomers and a mixture of nanoparticles dispersed within the one or more polyfunctional (meth)acrylate monomers. The nanoparticle mixture comprises 1% to 75% by weight of a first group of semi-reactive nanoparticles and 99% to 85% by weight of a second group of non-reactive nanoparticles. The semi-reactive nanoparticles have reactive and non-reactive functional groups. The first group of semi-reactive nanoparticles has an average particle size in the range of 5 nm to 60 nm. The second group of non-reactive nanoparticles has an average particle size in the range of 5 nm to 60 nm.

[0007] On the other hand, the hard coating composition comprises one or more polyfunctional (meth)acrylate monomers, and a mixture of nanoparticles dispersed within the one or more polyfunctional (meth)acrylate monomers. The nanoparticle mixture comprises 1% to 75% by weight of a first group of semi-reactive nanoparticles and 99% to 25% by weight of a second group of non-reactive nanoparticles. The first group of semi-reactive nanoparticles has non-reactive functional groups, which are formed by the use of nanoparticles with the general formula R-SiR'. m (OR'') 3-m The compound is formed by non-reactive surface treatment, wherein R is methyl or ethyl, R' is (C1-C4)alkyl, R'' is (C1-C4)alkyl, and m is an integer from 0 to 2. The first group of semi-reactive nanoparticles possesses reactive functional groups, which are formed by using compounds with the general formula X'-L'-SiR' m (OR'') 3-m The compound is formed by reactive surface treatment, wherein X' is a radical-polymerizable group and L' is a (C1-C2) group. 12 R' is a (C1-C4) alkyl group, R'' is a (C1-C4) alkyl group, and m is an integer from 0 to 2. The first group of semi-reactive nanoparticles has an average particle size in the range of 5 nm to 60 nm. The second group of non-reactive nanoparticles has an average particle size in the range of 5 nm to 60 nm. The second group of non-reactive nanoparticles uses nanoparticles with the general formula R-SiR'. m (OR'') 3-m The compound is subjected to non-reactive surface treatment, wherein R is methyl or ethyl, R' is (C1-C4)alkyl, R'' is (C1-C4)alkyl, and m is an integer from 0 to 2.

[0008] On the other hand, the hard coating comprises the reaction products of the hard coating composition described herein. The hard coating may have a uniform thickness ranging from 1 micrometer to 10 micrometers, 1 micrometer to 7 micrometers, 2 micrometers to 6 micrometers, or 2.5 micrometers to 5 micrometers.

[0009] In another aspect, the hard coating includes a substrate and the hard coating disposed on the substrate as described herein. This hard coating can exhibit excellent flexibility and abrasion resistance.

[0010] On the other hand, the article includes an optical display, a display film as described herein, and an optical adhesive layer for fixing the display film to the optical display. A rigid coating can be applied directly to the glass layer of the optical display.

[0011] These, and various other features and advantages, will become apparent from the following detailed description. Attached Figure Description

[0012] A more complete understanding of this disclosure can be achieved by referring to the accompanying drawings and the following detailed description of various embodiments thereof, wherein: Figure 1 A schematic side front view of an illustrative flexible hard coating or a flexible hard coating product; Figure 2 A schematic side front view of an exemplary flexible hard coating or a flexible hard coating article on an optical display for forming an article; and Figure 3 This is a schematic perspective view of an exemplary folded article, including an example of a flexible-rigid coating or a flexible-rigid coating article. Detailed Implementation

[0013] In the following detailed description, reference is made to the accompanying drawings, which form a part of this detailed description, and several specific embodiments are illustrated by way of example in the drawings. It should be understood that other embodiments can be conceived and made without departing from the scope or spirit of this disclosure. Therefore, the following detailed description should not be regarded as limiting.

[0014] Unless otherwise specified, all scientific and technical terms used herein have their common meaning in the art. The definitions provided herein will aid in understanding certain terms frequently used herein and are not intended to limit the scope of this disclosure.

[0015] Unless otherwise specified, all numbers used in this specification and claims to express characteristic dimensions, quantities, and physical properties should in all cases be understood to be modified by the term "about". Therefore, unless stated to the contrary, the numerical parameters listed in the foregoing specification and appended claims are approximations, which may vary according to the properties sought by those skilled in the art using the teachings disclosed herein.

[0016] The range of numbers expressed using endpoints includes all numbers contained within that range (e.g., 1 to 5 including 1, 1.5, 2, 2.75, 3, 3.80, 4, and 5) and any range within that range.

[0017] Unless otherwise expressly indicated, the singular forms “a,” “an,” and “described” as used in this specification and the appended claims cover embodiments having multiple referents.

[0018] Unless otherwise expressly stated in the content, the term "or" as used in this specification and the appended claims is generally used in its meaning including "and / or".

[0019] As used in this article, "having," "including," "containing," etc., are used in their open-ended sense and generally refer to "including but not limited to." It should be understood that "basically composed of," "composed of," etc., are included within "including," etc.

[0020] The terms “display film,” “protective film,” “covering film,” and “protective display film” are used interchangeably in this document.

[0021] "Transparent substrate" or "transparent layer" refers to a substrate or layer that has high light transmittance (typically greater than 85% or greater than 90%) on at least a portion of the surface of the substrate in a spectrum including the visible light spectrum (wavelengths from about 380 to about 750 nanometers).

[0022] "Reactive nanoparticles" refers to inorganic oxide nanoparticles, such as silica, that have been surface-modified with organic surface groups (e.g., in the case of silica, the reaction product of an organic trialkoxysilane with the surface of the silica particles), wherein the organic groups of the silane contain a chemical portion capable of reacting chemically with the matrix resin of the hard coating.

[0023] "Non-reactive nanoparticles" refers to inorganic oxide nanoparticles, such as silica, which have been surface-modified with organic surface groups (e.g., in the case of silica, the reaction product of an organic trialkoxysilane with the surface of the silica particles), wherein the organic groups of the silane contain a chemical portion that cannot chemically react with the matrix resin of the hard coating.

[0024] "Semi-reactive nanoparticles" or "partially reactive nanoparticles" refer to inorganic oxide nanoparticles, such as silica, which have been surface-modified with more than one organic surface group (e.g., in the case of silica, the reaction products of multiple organotrialkoxysilanes with the surface of silica particles), wherein at least one of the organic portions of the organosilane has a chemical portion (reactive functional group) capable of chemically reacting with the matrix resin of the hard coating, and wherein at least one of the organic portions of the organosilane has a chemical portion (non-reactive functional group) incapable of chemically reacting with the matrix resin of the hard coating.

[0025] This disclosure relates to a flexible hard coating or flexible hard coating article that can protect a display and withstand abrasion and folding tests. The flexible hard coating retains the optical properties of the display film while providing the display with excellent flexibility and scratch resistance. The hard coating composition comprises one or more polyfunctional (meth)acrylate monomers, and a mixture of nanoparticles dispersed within the one or more polyfunctional (meth)acrylate monomers.

[0026] The nanoparticle mixture comprises 1% to 75% by weight of a first group of semi-reactive nanoparticles and 99% to 25% by weight of a second group of non-reactive nanoparticles. The semi-reactive nanoparticles possess both reactive and non-reactive functional groups. The first group of semi-reactive nanoparticles has an average particle size in the range of 5 nm to 60 nm. The second group of non-reactive nanoparticles also has an average particle size in the range of 5 nm to 60 nm.

[0027] An exemplary nanoparticle mixture comprises 1% to 75% by weight of a first group of semi-reactive nanoparticles and 99% to 25% by weight of a second group of non-reactive nanoparticles. The first group of semi-reactive nanoparticles has non-reactive functional groups, which are formed by using nanoparticles with the general formula R-SiR'. m (OR'') 3-m The compound is formed by non-reactive surface treatment, wherein R is methyl or ethyl, R' is (C1-C4)alkyl, R'' is (C1-C4)alkyl, and m is an integer from 0 to 2. The first group of semi-reactive nanoparticles possesses reactive functional groups, which are formed by using compounds with the general formula X'-L'-SiR' m (OR'') 3-m The compound is formed by reactive surface treatment, wherein X' is a radical-polymerizable group and L' is a (C1-C2) group. 12 R' is a (C1-C4) alkyl group, R'' is a (C1-C4) alkyl group, and m is an integer from 0 to 2. The first group of semi-reactive nanoparticles has an average particle size in the range of 5 nm to 60 nm. The second group of non-reactive nanoparticles has an average particle size in the range of 5 nm to 60 nm. The second group of non-reactive nanoparticles uses nanoparticles with the general formula R-SiR'. m (OR'') 3-m The compound is subjected to non-reactive surface treatment, wherein R is methyl or ethyl, R' is (C1-C4)alkyl, R'' is (C1-C4)alkyl, and m is an integer from 0 to 2.

[0028] The nanoparticle mixture comprises 1% to 50% by weight of a first group of semi-reactive nanoparticles and 99% to 50% by weight of a second group of non-reactive nanoparticles. The semi-reactive nanoparticles possess both reactive and non-reactive functional groups. The first group of semi-reactive nanoparticles has an average particle size in the range of 5 nm to 60 nm. The second group of non-reactive nanoparticles also has an average particle size in the range of 5 nm to 60 nm.

[0029] The nanoparticle mixture comprises 1% to 25% by weight of a first group of semi-reactive nanoparticles and 99% to 75% by weight of a second group of non-reactive nanoparticles. The semi-reactive nanoparticles possess both reactive and non-reactive functional groups. The first group of semi-reactive nanoparticles has an average particle size in the range of 5 nm to 60 nm. The second group of non-reactive nanoparticles also has an average particle size in the range of 5 nm to 60 nm.

[0030] The nanoparticle mixture comprises 1 wt% to 10 wt% of a first group of semi-reactive nanoparticles and 99 wt% to 90 wt% of a second group of non-reactive nanoparticles. The semi-reactive nanoparticles possess both reactive and non-reactive functional groups. The first group of semi-reactive nanoparticles has an average particle size in the range of 5 nm to 60 nm. The second group of non-reactive nanoparticles also has an average particle size in the range of 5 nm to 60 nm.

[0031] The first group of semi-reactive nanoparticles may contain 1 mol% to 50 mol% of reactive functional groups and 99 mol% to 50 mol% of non-reactive functional groups.

[0032] The first group of semi-reactive nanoparticles may contain 1 mol% to 25 mol% reactive functional groups and 99 mol% to 75 mol% non-reactive functional groups.

[0033] The first group of semi-reactive nanoparticles may contain 5 mol% to 50 mol% reactive functional groups and 95 mol% to 50 mol% non-reactive functional groups.

[0034] The first group of semi-reactive nanoparticles may contain 5 mol% to 30 mol% reactive functional groups and 95 mol% to 70 mol% non-reactive functional groups.

[0035] The first group of semi-reactive nanoparticles may contain 1 mol% to 15 mol% of reactive functional groups and 99 mol% to 85 mol% of non-reactive functional groups.

[0036] The first group of semi-reactive nanoparticles may contain 1 mol% to 10 mol% of reactive functional groups and 99 mol% to 90 mol% of non-reactive functional groups.

[0037] The first group of semi-reactive nanoparticles may contain 1 mol% to 5 mol% of reactive functional groups and 99 mol% to 95 mol% of non-reactive functional groups.

[0038] Non-reactive and semi-reactive nanoparticles may each have an average particle size in the range of 10 nm to 40 nm, or 10 nm to 30 nm. The hard coating can withstand bending radii of 5 mm or less, or 4 mm or less, or 3 mm or less, or 2 mm or less, or even 1 mm or less (under tension or compression, or both) without failure or visible defects such as delamination, fracture, cracking, or turbidity. An understanding of various aspects of this disclosure will be gained from the following description of embodiments, but this disclosure is not limited thereto.

[0039] The hard coating composition comprises one or more polyfunctional (meth)acrylate monomers and a mixture of nanoparticles dispersed within the one or more polyfunctional (meth)acrylate monomers. The nanoparticle mixture comprises a first group of semi-reactive nanoparticles (i.e., having reactive functional groups that can react with the polyfunctional (meth)acrylate monomers and non-reactive functional groups that do not react with the polyfunctional (meth)acrylate monomers) and a second group of non-reactive nanoparticles (i.e., not reacting with the polyfunctional (meth)acrylate monomers). The semi-reactive and non-reactive nanoparticles may be inorganic oxide nanoparticles.

[0040] Hard coating compositions can be cured or reacted to form hard coatings or hard films. Curing can initiate a reaction with the reactive functional groups of semi-reactive nanoparticles by forming bonds with polyfunctional (meth)acrylate monomers, while curing can prevent the reaction of non-reactive nanoparticles or the non-reactive functional groups of semi-reactive nanoparticles with polyfunctional (meth)acrylate monomers.

[0041] Reducing the relative number of semi-reactive nanoparticles to non-reactive nanoparticles surprisingly improves flexibility while maintaining the abrasion resistance of hard coatings or films. Furthermore, applying surface-treatment compounds to non-reactive nanoparticles with short alkyl chain (e.g., methyl or ethyl) end groups appears to surprisingly improve flexibility while maintaining abrasion resistance and reducing curling of hard coatings or films.

[0042] The first group of semi-reactive nanoparticles and the second group of non-reactive nanoparticles can independently have an average particle size in the range of 5 nm to 60 nm, or 10 nm to 40 nm, or 10 nm to 30 nm. The first group of semi-reactive nanoparticles and the second group of non-reactive nanoparticles can have the same average particle size.

[0043] Compared to semi-reactive nanoparticles, nanoparticle mixtures contain a greater number of non-reactive nanoparticles. The nanoparticle mixture may contain 1% to 75% by weight of a first group of semi-reactive nanoparticles and 25% to 99% by weight of a second group of non-reactive nanoparticles. The nanoparticle mixture may contain 1% to 50% by weight of a first group of semi-reactive nanoparticles and 50% to 99% by weight of a second group of non-reactive nanoparticles. The nanoparticle mixture may contain 1% to 25% by weight of a first group of semi-reactive nanoparticles and 75% to 99% by weight of a second group of non-reactive nanoparticles. The nanoparticle mixture may contain 1% to 10% by weight of a first group of semi-reactive nanoparticles and 90% to 99% by weight of a second group of non-reactive nanoparticles. The nanoparticle mixture may contain 2% to 5% by weight of a first group of semi-reactive nanoparticles and 95% to 98% by weight of a second group of non-reactive nanoparticles.

[0044] The first group of semi-reactive nanoparticles and the second group of non-reactive nanoparticles are surface-modified inorganic oxide particles that enhance the mechanical strength and durability of hard coatings. These nanoparticles can be substantially spherical in shape and relatively uniform in size. They can have a substantially monodisperse size distribution. These inorganic oxide particles are typically non-aggregate (substantially discrete).

[0045] The total concentration of the nanoparticle mixture (inorganic oxide nanoparticles) may be at least 30 wt%, 40 wt%, or 50 wt% solids, and generally not greater than 75 wt%, 70 wt%, or 60 wt%. The total concentration of the nanoparticle mixture (inorganic oxide nanoparticles) may be present in the hard coating composition at a loading ranging from 30 wt% to 68 wt% total solids, or 40 wt% to 60 wt% total solids, or 50 wt% to 60 wt% total solids.

[0046] The average particle size of inorganic oxide particles can be measured by counting the number of inorganic oxide particles of a given diameter using a transmission electron microscope. Inorganic oxide particles can consist essentially of or be composed of a single oxide such as silica, or a composition that may contain oxides, or a core of one type of oxide (on which another type of oxide is deposited) (or a core of a material other than a metal oxide). Silica is a common inorganic oxide particle used in hard coating compositions. Inorganic oxide particles are typically provided in the form of sols, which contain a colloidal dispersion of inorganic oxide particles in a liquid medium. Sols can be prepared using various techniques and in various forms, including aqueous sols (where water is used as the liquid medium), organosols (where an organic liquid is used as the medium), and mixed sols (where the liquid medium contains both water and an organic liquid).

[0047] Aqueous colloidal silica dispersions are commercially available under the trade name “Nalco Collodial Silicas” from Nalco Chemical Co., Naperville, IL, such as products 2326, 1130, 1030, 1140, 1034A, 1050, 1060, 2327, and DVSZN004; and under the trade name Snowtex. ™ Products such as ST-XS, ST-S, ST-30, ST-50, ST-20L, ST-XL, ST-NXS, ST-NS, ST-N, ST-N-40, ST-OXS, ST-OS, ST-O, ST-O-40, and ST-OL were purchased from Nissan Chemical America Corporation, Houston, TX; and products such as NexSil were purchased from Nyacol Nano Technologies, Inc., Ashland, MA. ™ 5, 6, 12, 20, 85-40, 20A, 20K-30, and 20NH4. Organic dispersions of colloidal silica are commercially available from Nalco Chemical Company, such as product 1057; from Nissan Chemical USA, such as products NPC-ST-30, MA-ST, MA-ST-M, IPA-ST, IPA-ST-L, EG-ST, MEK-ST-40, MEK-ST-L, and TOL-ST; and from Nyacol NanoTechnologies, such as DP5820 and DP5840.

[0048] It is desirable to use mixtures of various types of inorganic oxide particles to optimize optical properties, material properties, or reduce the overall cost of the composition.

[0049] As an alternative to or in combination with silica, hard coatings may comprise a variety of high-refractive-index inorganic oxide nanoparticles. These nanoparticles have a refractive index of at least 1.60, 1.65, 1.70, 1.75, 1.80, 1.85, 1.90, 1.95, 2.00, or higher. High-refractive-index inorganic oxide nanoparticles include, for example, one or a combination of zirconium oxide (“ZrO2”), titanium dioxide (“TiO2”), antimony oxide, aluminum oxide, and tin oxide. Mixed metal oxides may also be used.

[0050] Zirconia used in high refractive index layers can be purchased from Nalco Chemical Company under the trade name "Nalco OOSSOO8" or from Buhler AG Uzwil, Switzerland under the trade name "Buhler zirconia Z-WO sol" and under the trade name NanoUse ZR. ™ The zirconia nanoparticles were purchased from Nissan Chemical America Corporation. Zirconia nanoparticles can also be prepared as described in, for example, U.S. Patent Publication 2006 / 0148950 and U.S. Patent 6,376,590. A nanoparticle dispersion comprising a mixture of tin oxide coated with antimony oxide and zirconia (refractive index of about 1.9) is commercially available from Nissan Chemical America Corporation under the trade name “HX-05M5”. A tin oxide nanoparticle dispersion (refractive index of about 2.0) is commercially available from Nissan Chemicals Corporation under the trade name “CX-S401M”. Zirconia nanoparticles can also be prepared as described in U.S. Patent 7,241,437 and U.S. Patent 6,376,590.

[0051] Typically, surface-treated compounds have a first end and a second end. The first end attaches to the particle surface (covalently, ionicly, or through strong physisorption), and the second end imparts compatibility with the resin and either reacts with the resin during curing (semi-reactive particles) or does not react with the resin during curing (non-reactive particles). Examples of surface-treated compounds include alcohols, amines, carboxylic acids, sulfonic acids, phosphonic acids, silanes, and titanates. The preferred type of treatment agent depends in part on the chemical properties of the inorganic oxide nanoparticle surface and whether the particles are semi-reactive or non-reactive.

[0052] Silanes are preferred for silica and other silicon-containing fillers. Silanes and carboxylic acids are preferred for metal oxides such as zirconium oxide. Surface modification can be performed after mixing with the monomer or after mixing. For silanes, it is preferable to react the silane with the surface of the nanoparticles before incorporating the silane into the resin. The amount of surface modifier required depends on several factors, such as particle size, particle type, molecular weight of the modifier, and type of modifier. Generally, it is preferred to attach approximately a monolayer of modifier to the surface of the particles. The required attachment procedure or reaction conditions also depend on the surface modifier used. For silanes, surface treatment at high temperature under acidic or alkaline conditions for approximately 1–24 hours is preferred. Surface treatment agents such as carboxylic acids may not require high temperature or longer treatment times.

[0053] When added to an inorganic oxide (e.g., silica) dispersion, the silane surface treatment agent comprises one or more alkoxysilyl groups. One or more alkoxysilyl groups hydrolyze with water (present in the nanoparticle dispersion) to form Si-OH (hydroxyl groups). These SiOH groups then react with SiOH groups on the surface of the nano-silica to form silane-surfaced nano-silica.

[0054] Inorganic oxide (e.g., silicon dioxide) nanoparticles are surface modified individually or independently with reactive surface treatment compounds (see A174 in the examples) or non-reactive surface treatment compounds (see methyl in the examples).

[0055] The first group of semi-reactive nanoparticles can be formed by combining nanoparticles (e.g., silica) with reactive and non-reactive surface treatment compounds. The reactive surface treatment compounds contain radically polymerizable groups, such as methyl (acryloyl) or vinyl groups. These radically polymerizable groups are copolymerized with radically polymerizable monomers (e.g., (meth)acrylate) of the hard coating composition.

[0056] Available reactive surface treatment compounds include (meth)acryloylsilanes, such as (meth)acryloylalkoxysilanes like 3-(methacryloyloxy)propyltrimethoxysilane, 3-acryloyloxypropyltrimethoxysilane, 3-(methacryloyloxy)propylmethyldimethoxysilane, 3-(acryloyloxypropyl)methyldimethoxysilane, 3-(methacryloyloxy)propyldimethylmethoxysilane, and 3-(acryloyloxypropyl)dimethylmethoxysilane. In some embodiments, (meth)acryloylsilanes may be more advantageous than acryloylsilanes. Suitable vinyl silanes include vinyl dimethyl ethoxysilane, vinyl methyl diacetoxysilane, vinyl methyl diethoxysilane, vinyl triacetoxysilane, vinyl triethoxysilane, vinyl triisopropoxysilane, vinyl trimethoxysilane, vinyl triphenoxysilane, vinyl tritert-butoxysilane, vinyl triisobutoxysilane, vinyl triisopropoxysilane, and vinyl tri(2-methoxyethoxy)silane. Suitable amino organosilanes are described, for example, in US2006 / 0147177; this document is incorporated herein by reference.

[0057] Reactive (silane) surface treatment compounds may have the general formula: X'-L'-SiR' m (OR'') 3-m , Where X' is a group that can be polymerized by free radicals. L' is (C1-C 12 )alkylene R' is a (C1-C4) alkyl group. R'' is a (C1-C4) alkyl group, and m is an integer from 0 to 2.

[0058] Reactive surface treatment compounds may have the formula X'-L'-SiR' m (OR'') 3-m Where X' is (meth)acryloyl or vinyl group, L' is (C3) alkylene, m is 0, and R'' is (C1) alkyl (as shown in A174 in the examples).

[0059] Available non-reactive surface treatment compounds include silane compounds that do not contain radically polymerizable groups (such as (meth)acryloyl or vinyl groups). Non-reactive and semi-reactive nanoparticles can be non-reactively surface treated using compounds having the following general formula: R-SiR' m (OR'') 3-m , Where R is methyl or ethyl. R' is a (C1-C4) alkyl group. R'' is a (C1-C4) alkyl group, and m is an integer from 0 to 2.

[0060] Non-reactive surface treatment compounds may have the formula R-SiR' m (OR'') 3-m In this formula, R is methyl, R' is (C1-C2)alkyl, R'' is (C1-C2)alkyl, and m is an integer from 0 to 2. Non-reactive surface treatment compounds may have the formula R-SiR'. m (OR'') 3-m , where R is methyl, m is 0, and R'' is methyl (as shown in the examples).

[0061] An exemplary hard coating composition comprises one or more polyfunctional (meth)acrylate monomers and a mixture of nanoparticles dispersed within the one or more polyfunctional (meth)acrylate monomers. The nanoparticle mixture comprises 1% to 50% of a first group of semi-reactive nanoparticles and 50% to 1% of a second group of non-reactive nanoparticles. The first group of semi-reactive nanoparticles has 5 mol% to 50 mol% of reactive functional groups and 95 mol% to 50 mol% of non-reactive functional groups. The first group of semi-reactive nanoparticles has an average particle size in the range of 5 nm to 60 nm, and the second group of non-reactive nanoparticles has an average particle size in the range of 5 nm to 60 nm.

[0062] The resin matrix that forms the hard coating can be formed from one or more (meth)acrylate monomers. The term "monomer" refers to an oligomer or monomer.

[0063] The polymerizable resin composition comprises at least one first (meth)acrylate monomer, the first (meth)acrylate monomer comprising at least three (meth)acrylate groups and an alkoxy (i.e., alkylene oxide) repeating unit. The alkoxy (i.e., alkylene oxide) repeating unit typically has the formula —[OL]-, where L is a straight-chain or branched alkylene oxide. In some embodiments, the alkylene oxide is a straight-chain or branched C2-C6 alkylene oxide.

[0064] In some embodiments, the first (meth)acrylate monomer comprises a linear alkoxy repeating unit, such as an ethylene oxide repeating unit. Such monomers can be represented by the following general formula: R((OC n H 2n ) m OC(O)C(R 6 )═CH2) p Where R represents an organic residue with a valence p, n is the number of carbon atoms in the alkoxy repeating unit, and m is the number of alkoxy repeating units. 6 R is hydrogen or methyl, and p is at least 3. For each m, n may independently range from 1 to 4. In some embodiments, the number of alkoxy repeating units m is greater than 6 and typically less than 20. In some embodiments, p is at least 4, 5, or 6. In some embodiments, R is a hydrocarbon residue, optionally also containing one or more oxygen, sulfur, or nitrogen atoms. In some embodiments, R contains at least 3, 4, 5, or 6 carbon atoms and typically no more than 12 carbon atoms.

[0065] In other embodiments, the first (meth)acrylate monomer comprises a branched alkoxy repeating unit, such as an isopropylidene and / or isobutylidene repeating unit. Some embodiments of the monomer can be represented by the following general formula: R((OC n (CH3) q H 2n-q ) m OC(O)—C(R 6 )═CH2) p R and p are the same as previously described. For the branched isopropylidene repeating unit, n is 2 and q is 1. For the branched isobutylidene repeating unit, n is 2 and q is 2.

[0066] A first (meth)acrylate monomer comprising at least three (meth)acrylate groups and a C2-C4 alkoxy repeating unit may comprise any combination of straight-chain and / or branched C2-C4 alkoxy repeating units. Therefore, a first (meth)acrylate monomer may comprise only an ethylene oxide repeating unit, only a propylene oxide repeating unit, only a butyl oxide repeating unit, and combinations thereof. In one embodiment, the first (meth)acrylate monomer comprises a combination of both ethylene oxide and propylene oxide repeating units.

[0067] In some embodiments, the molecular weight of the first (meth)acrylate monomer divided by the number of (meth)acrylate groups is in the range of about 220 g / mol to 375 g / mol. In other words, the molecular weight of each (meth)acrylate group is in the range of about 220 g / mol to 375 g / mol per (meth)acrylate. As demonstrated in the examples below, the addition of such a first (meth)acrylate monomer is suitable for providing a hard coating that is both flexible and abrasion-resistant. In some embodiments, the cured hard coating (with a thickness of at least 2.5 micrometers) did not exhibit cracking when tested with a #4H pencil and a 1 kg load. Alternatively or otherwise, the cured hard coating is durable enough that the hard coating exhibits no scratch (NS) or slight scratch (SS) after an abrasion test (according to the test method described in the examples). The no-scratch (NS) or slight-scratch (SS) film produced by the abrasion test has a measured haze (or measured haze increase) of less than 5%, preferably less than 4%, more preferably less than 3%, or less than 2%, or less than 1%.

[0068] Commercially available ethoxylated trimethylolpropane triacrylate monomers that meet this standard include, for example, SR9035 and SR502, available from the Sartomer Arkema Group, Exton, PA. Other monomers that meet this standard can be synthesized, for example, by reacting polyalkylene oxide polyols with acrylic acid.

[0069] The concentration of the first (meth)acrylate monomer in the cured hard coating composition is typically at least 5% by weight and, in some embodiments, at least 10% by weight solids, and generally not greater than 40% by weight, or 35% by weight, or 25% by weight solids. In some embodiments, the concentration of the first monomer is at least 11, 12, 13, 14, or 15% by weight solids. In some embodiments, the concentration of the first monomer is in the range of 5 to 10% by weight solids. As used herein, % by weight solids refers to the total amount of the hard coating composition after drying and / or curing following the evaporation of any solvents that may be present.

[0070] The polymerizable resin of the hard coating composition contains at least one second polyfunctional (meth)acrylate monomer. The second (meth)acrylate monomer is a monomer different from the first monomer.

[0071] Available multifunctional (meth)acrylate monomers and oligomers include: (a) Monomers containing a di(meth)acryloyl group, such as 1,3-butanediol diacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, 1,6-hexanediol monoacrylate monomethacrylate, ethylene glycol diacrylate, alkyl oxidized aliphatic diacrylate, alkyl oxidized cyclohexanedimethyl diacrylate, alkyl oxidized hexanediol diacrylate, alkyl oxidized neopentyl glycol diacrylate, caprolactone-modified neopentyl glycol hydroxypentyl acrylate diacrylate, caprolactone-modified neopentyl glycol hydroxypentyl acrylate diacrylate, cyclohexanedimethyl diacrylate, diethylene glycol diacrylate, dipropylene glycol diacrylate, ethoxylated bisphenol A diacrylate, hydroxy-neopentaldehyde-modified trimethylolpropane diacrylate, neopentyl glycol diacrylate, polyethylene glycol diacrylate (e.g., purchased from Sartomer Arkema Group, Exton, Pennsylvania). PA) SR344), propoxylated neopentyl glycol diacrylate, tetraethylene glycol diacrylate, tricyclodecyl glycol diacrylate, triethylene glycol diacrylate, tripropylene glycol diacrylate; (b) Monomers containing a tri(meth)acryloyl group, such as glyceryl triacrylate, trimethylolpropane triacrylate, ethoxylated triacrylate (such as ethoxylated trimethylolpropane triacrylate (e.g., SR9035 purchased from Sartomer Arkema Group, Exton, PA)), propoxylated triacrylate (e.g., propoxylated glyceryl triacrylate, propoxylated trimethylolpropane triacrylate), trimethylolpropane triacrylate, tri(2-hydroxyethyl)-isocyanurate triacrylate; (c) Monomers containing a higher functional (meth)acryloyl group, such as bis(trimethylolpropane)tetraacrylate, dipentaerythritol pentaacrylate, pentaerythritol triacrylate, ethoxylated pentaerythritol tetraacrylate and caprolactone-modified dipentaerythritol hexaacrylate.

[0072] Oligomeric (meth)acryloyl monomers, such as polyester acrylates and epoxy acrylates, can also be used.

[0073] These (meth)acrylate monomers are widely available from suppliers such as Sartomer Arkema Group (Exton, PA); Allnex (Alpharetta, GA) (Alpharetta, GA); and Aldrich Chemical Company (Milwaukee, WI) (Milwaukee, WI).

[0074] In some embodiments, the hard coating composition comprises a second (meth)acrylate monomer containing at least three (meth)acrylate functional groups. In some embodiments, the second monomer contains at least four, five, or six (meth)acrylate functional groups. Acrylate functional groups are generally more advantageous than (meth)acrylate functional groups.

[0075] Preferred commercially available second (meth)acrylate monomers include, for example, trimethylolpropane triacrylate (e.g., SR351 from Sartomer Arkema Group, Exton, PA, Pennsylvania), and ethoxylated trimethylolpropane triacrylate (e.g., from Sartomer Arkema Group, Exton, PA, Pennsylvania). SR454 of PA), a mixture of pentaerythritol tetraacrylate and pentaerythritol triacrylate (e.g., SR444c from the Sartoma Arkema Group), dipentaerythritol pentaacrylate (e.g., SR399 from the Sartoma Arkema Group), a mixture of ethoxylated pentaerythritol tetraacrylate and ethoxylated pentaerythritol triacrylate (e.g., SR494 from the Sartoma Arkema Group), dipentaerythritol hexaacrylate and tri(2-hydroxyethyl) isocyanate triacrylate (e.g., SR368 from the Sartoma Arkema Group).

[0076] In some implementations, the second monomer does not contain a C2-C4 alkoxy repeating unit.

[0077] The total concentration of one or more second monomers in the cured hard coating composition is typically at least 5% or 10% by weight solids, and generally not greater than 40, 35, or 30% by weight solids. In some embodiments, the total amount of one or more second monomers is in the range of 10 to 25% by weight solids. In other embodiments, the total amount of one or more second monomers is in the range of 5 to 15% by weight solids.

[0078] In other embodiments, the hard coating composition may comprise a blend of two or more monomers comprising at least three (meth)acrylate functional groups and at least one di(meth)acrylate monomer or oligomer. The concentration of the di(meth)acrylate monomer or oligomer is typically no more than 15% by weight, 10% by weight, or 5% by weight solids of the total hard coating composition.

[0079] Carbamates are typically added to hard coating compositions to increase the flexibility of the cured hard coating. However, the addition of carbamates (such as polyfunctional acrylate carbamate oligomers) reduces the abrasion resistance of the cured hard coating. The hard coating compositions and cured hard coatings described herein are substantially carbamate-free. The hard coating compositions may contain less than 5% by weight, or less than 3% by weight, or less than 2% by weight, or less than 1% by weight of carbamate. One or more polyfunctional (meth)acrylate monomers constitute at least 95% by weight, or at least 97% by weight, or at least 98% by weight of monomers in the hard coating composition. At least 95% by weight, or at least 97% by weight, or at least 98% by weight of monomers in the hard coating composition are composed of (meth)acrylate monomers. The term "monomer" is assumed to include the term "oligomer" herein.

[0080] Hard coatings or hard films can be formed by curing (polymerizing) the hard coating compositions described herein. The hard coatings described herein are reaction products of the hard coating compositions described herein. To facilitate curing of the hard coating, the polymerizable compositions described herein may further comprise at least one free radical thermal initiator and / or photoinitiator. When such initiators and / or photoinitiators are present, they constitute less than about 5% by weight, and more typically less than about 2% by weight of total solids in the polymerizable composition, based on the total weight of the polymerizable composition. Free radical curing techniques are well known in the art and include, for example, thermal curing methods and radiation curing methods such as electron beam or ultraviolet radiation. Available free radical photoinitiators include, for example, those known for their use in the UV curing of acrylate polymers, such as those described in WO2006 / 102383.

[0081] The hard coating composition may optionally contain a variety of additives. For example, silicone or fluorinated additives may be added to reduce the surface energy of the hard coating. In one embodiment, the hard coating composition further comprises one or more perfluoropolyether urethane additives, such as those described in US 7,178,264. The total amount of perfluoropolyether urethane additives, alone or in combination with other fluorinated additives, is typically in the range of 0.05% by weight to 1% by weight solids.

[0082] Certain silicone additives have also been found to provide ink repellency and low lint attraction, as described in WO 2009 / 029438, which is incorporated herein by reference. These silicone (meth)acrylate additives typically comprise a polydimethylsiloxane (PDMS) backbone and at least one alkoxy side chain terminated with a (meth)acrylate group. The alkoxy side chain may optionally contain at least one hydroxyl substituent. These silicone (meth)acrylate additives are commercially available from various suppliers, such as Tego Chemie, Essen, Germany, under the trade names “TEGO Rad 2250,” “TEGO Rad 2300,” “TEGO Rad 2500,” and “TEGO Rad 2700.” Among these additives, “TEGO Rad 2100” provides the lowest lint attraction.

[0083] Hard coating compositions can be applied to substrates in single or multiple layers using conventional film coating techniques. A variety of techniques can be used to apply the film, including dip coating, forward and reverse roll coating, wire-wound rod coating, and die coating. Die coating machines include doctor blade coaters, tank coaters, sliding coaters, hydraulic bearing coaters, sliding curtain coaters, falling die curtain coaters, and extrusion coaters, among others. Many types of die coating machines are described in the literature. Although the substrate is often conveniently in the form of a continuous fiber web roll, the coating can be applied to individual sheets.

[0084] The hard coating composition can be dried in an oven to remove the solvent, and then preferably cured under an inert atmosphere (oxygen content less than 50 ppm), for example by exposure to ultraviolet radiation at the desired wavelength (using an H bulb or other lamp). This reaction mechanism causes crosslinking of the material, which is capable of free radical polymerization.

[0085] The (cured) hard coating may have a uniform thickness ranging from 1 micrometer to 10 micrometers, 1 micrometer to 7 micrometers, 2 micrometers to 6 micrometers, or 2.5 micrometers to 5 micrometers.

[0086] A hard coating includes a substrate and a hard coating disposed on the substrate as described herein. The substrate may be transparent to visible light.

[0087] The substrate or transparent substrate layer may have a yield stress value greater than 70 MPa, or greater than 90 MPa, or greater than 120 MPa, or greater than 160 MPa. The phrase “yield stress” or “offset yield stress” in this document refers to the “0.2% offset yield strength” as defined in ASTM D638-14. Section A2.6 of ASTM D638-14 defines the test method for “offset yield strength” and it is defined as the stress that extends beyond the initial proportional portion of the stress-strain curve by a specified amount (offset). It is expressed as force per unit area, typically in megapascals (lbf / sq inch).

[0088] The transparent substrate layer can be formed from any available polymer material that provides the display film with the required mechanical properties (such as dimensional stability) and optical properties (such as light transmittance and clarity). Examples of suitable materials for the substrate layer include polyacrylate, polymethyl methacrylate, polycarbonate, polyamide, polyimide, polyesters such as poly(ethyl terephthalate) (PET) or poly(ethyl naphthate) (PEN), polycyclic olefin polymers (COP), thermoplastic polyurethane, or triacetyl cellulose (TAC). The transparent substrate layer can also be a multilayer optical film having alternating layers of multiple polymer materials (such as PET or PEN) that cooperate with each other to reflect or transmit light.

[0089] One available polymeric material for forming the transparent polymeric substrate layer is polyimide. In many embodiments, the polyimide substrate layer is colorless. Colorless polyimides can be formed chemically or via nanoparticle bonding. Some exemplary colorless polyimides formed chemically are described in WO 2014 / 092422.

[0090] In one embodiment, the multilayer film may include a peelable layer, a removable layer, or a sacrificial layer, wherein the externally cured rigid coating rests on an alternative substrate once removed. The multilayer substrate may be co-extruded, wherein the removed rigid coating has a particularly thin substrate (e.g., less than or equal to about 13 micrometers); a substrate with adhesive properties; and / or a particularly smooth and debris-free substrate, thus facilitating the coating of conductive or barrier layers.

[0091] The transparent substrate may be a transparent thermoplastic substrate having a uniform thickness ranging from about 20 micrometers to about 350 micrometers, or from about 20 micrometers to about 150 micrometers, or from about 20 micrometers to about 100 micrometers. The rigid coating may have an overall uniform thickness ranging from about 25 micrometers to about 360 micrometers, or from about 25 micrometers to about 160 micrometers, or from about 25 micrometers to about 110 micrometers. In some embodiments, the rigid coating has an overall uniform thickness ranging from about 20 micrometers to about 160 micrometers, or from about 20 micrometers to about 110 micrometers, or from about 20 micrometers to about 80 micrometers.

[0092] The transparent substrate layer may be primed or treated to impart certain desired properties to one or more of its surfaces. Specifically, the transparent substrate layer may be primed to improve the adhesion of hard coatings having a transparent substrate layer. Examples of such treatments include corona treatment, flame treatment, plasma treatment, and chemical treatments (such as acrylate or silane treatments).

[0093] Abrasion is a method of wearing down or rubbing away material through friction. Abrasion resistance helps a material withstand mechanical action and tends to protect it from material removal from its surface. This allows the material to retain its integrity and shape. Abrasion resistance can be measured by rubbing or wiping a hard coating with a rough material such as steel wool or a scrubbing pad for a specified number of cycles, and then inspecting the layer for visible changes such as fine scratches or haze.

[0094] In one embodiment, the hard coating comprises a hard coating layer (with a thickness ranging from 1 micrometer to 10 micrometers) disposed on a transparent polymer or thermoplastic substrate layer (with a thickness ranging from 20 micrometers to 100 micrometers).

[0095] The hard coating may have a haze value of 4% or less, or 2% or less, or 1% or less, or 0.5% or less. In some embodiments, the hard coating may have a haze value of 5% or less. The hard coating may have a clarity of 98% or more, or 99% or more. The hard coating may have a visible light transmittance of 85% or more, or 87% or more, or 90% or more, or 93% or more.

[0096] Hard coatings may have a yellowness index of 5 or less, or 4 or less, or 3 or less, or 2 or less, or 1 or less, or b. Value. In many embodiments, the display film may have a yellow index of 1 or less or value.

[0097] The hard coating retains a haze value of 2% or less, or 1.5% or less, or 1% or less after at least 500, 1,000, 5,000, 10,000, 100,000, or 200,000 bending or folding cycles around a 3 mm radius. The hard coating retains a stable haze value, or remains intact without cracking, splitting, or delamination, after at least 500, 1,000, 5,000, 10,000, 100,000, or 200,000 bending or folding cycles around a 5 mm radius, or around a 4 mm radius, or around a 3 mm radius, or around a 2 mm radius, or around a 1 mm radius. The hard coating can remain intact after at least 500, 1,000, 5,000, 10,000, 100,000 or 200,000 bending or folding cycles around a radius of 4 mm or smaller (under stretching or compression).

[0098] Figure 1 Here is a schematic side front view of an illustrative hard coating 10.

[0099] Figure 2 A schematic side front view of an exemplary flexible hard coating or flexible hard film 10 formed on the optical display 26 of the article 70.

[0100] Figure 3 This is a schematic perspective view of an exemplary folded article 80 including an exemplary flexible hard coating or hard coating film 10.

[0101] The hard coating 10 includes a transparent substrate 14 and a hard coating 12 disposed on the transparent substrate 14 as described herein. The hard coating 10 exhibits excellent flexibility and abrasion resistance.

[0102] The optical display 70 includes the hard coating 10 described herein and an optical adhesive layer 24 that attaches the hard coating 10 to the optical display 26. The hard coating 12 may form the outer surface of the optical display 34.

[0103] The hard coating 10 can be applied to an optical element, such as an optical display 34, to form a display device 80. The display device 80 can be folded onto itself such that portions of the hard coating 10 contact each other, as... Figure 3 As shown in the figure. The display device 80 may not be a folding article and may be flexible only within a certain range, or it may be a statically bent display device.

[0104] Optical display 34 may form at least a portion of a display device. Display device 80 may include display window 32. Display device 80 may be any available article of manufacture, such as a telephone or smartphone, electronic tablet computer, electronic notebook computer, computer, etc. Optical display may include an organic light-emitting diode (OLED) display panel. Optical display may include a liquid crystal display (LCD) panel or a reflective display. Examples of reflective displays include electrophoretic displays, electrofluid displays (such as electrowetting displays), interference displays, or electronic paper display panels, and are described in US 2015 / 0330597.

[0105] The hard coating 10 and the optical display 34 can be flexible, bendable, or foldable, such that a portion of the hard coating 10 and the optical display 34 can be hinged relative to another portion of the hard coating 10 and the optical display 34 to form a bending radius of 3 mm or less at the bend or fold line in the hard coating 10. The hard coating 10 and the optical display 34 can be flexible, bendable, or foldable, such that a portion of the hard coating 10 and the optical display 34 can be hinged relative to another portion of the hard coating 10 and the optical display 34 to form a bending radius, such that the hard coating 10 overlaps itself and is spaced apart from each other by a distance of 10 mm or less, or 6 mm or less, or 3 mm or less, or is in contact with each other.

[0106] While the purposes and advantages of this disclosure are further illustrated by the following embodiments, the specific materials and quantities listed in these embodiments, as well as other conditions and details, should not be construed as undue limitations on this disclosure.

[0107] Example

[0108] The embodiments of the present invention illustrate a novel and effective strategy for preparing hard coatings that are both flexible and wear-resistant. The hard coating compositions of the embodiments are based on blends of semi-reactive and non-reactive nanoparticles. Examples of semi-reactive nanoparticles are those having both reactive (e.g., A174 (acrylate)) and non-reactive (e.g., methyl) functional groups. Non-reactive nanoparticles are illustrated using non-reactive (e.g., methyl) functional groups. Examples show increased flexibility in the hard coating and decreased nanoparticle reactivity. Furthermore, despite the reduced nanoparticle reactivity, the examples maintain good abrasion resistance. Current techniques for hard coatings on rigid (non-flexible) surfaces focus on reactive nanoparticles to achieve good abrasion resistance. Comparative examples are included to illustrate strategies incorporating flexibility into hard coatings. The comparative examples illustrate combinations of strategies, including the common use of urethane acrylates in hard coating compositions. The comparative examples also illustrate the use of larger nanoparticles with inherently lower reactivity. The comparative examples do exhibit flexibility, but at the cost of sacrificing abrasion resistance. Hard coatings for the emerging flexible OLED display market must combine flexibility and abrasion resistance.

[0109]

[0110] Surface-modified SiO2 nanodispersions

[0111] SiO2 Nanodispersion: A174 20nm: Place 400g of NALCO 2327 in a 32oz wide-mouth glass flask. Begin stirring and slowly add 450g of PM. Slowly add 22.01g of A174. Stir the nanodispersion for another 20 minutes. Place the nanodispersion in an oven at 80°C for 24 hours to modify the nanoparticle surface with reactive acrylate functional groups derived from silane. Cool the nanodispersion to room temperature. Add 330g of PM to the nanodispersion. Remove water by solvent exchange using rotary evaporation (from Buchi, New Castle, DE, Newcastle, WA) at 64°C under vacuum. Adjust the final nanoparticle content of the nanodispersion to 45% by weight.

[0112] SiO2 Nanodispersion: A174 / METHYL 20nm: Place 400g of NALCO 2327 in a 32oz wide-mouth glass flask. Begin stirring and slowly add 450g of PM. Slowly add 2.20g of A174. Slowly add 10.56g of METHYL-TMOS. Stir the nanodispersion for another 20 minutes. Place the nanodispersion in an oven at 80°C for 24 hours to modify the nanoparticle surface with reactive acrylates and non-reactive methyl functional groups derived from silane. Cool the nanodispersion to room temperature. Add 330g of PM to the nanodispersion. Remove water by solvent exchange at 64°C under vacuum using rotary evaporation (Buchi, Newcastle, DE). Adjust the final nanoparticle content of the nanodispersion to 45% by weight.

[0113] SiO2 Nanodispersion: Methyl 20nm: Place 400g of NALCO 2327 in a 32oz wide-mouth glass flask. Start stirring and slowly add 450g of PM. Slowly add 12.07g of METHYL-TMOS. Stir the nanodispersion for another 20 minutes. Place the nanodispersion in an oven at 80°C for 24 hours to modify the nanoparticle surface with non-reactive methyl functional groups from silane. Cool the nanodispersion to room temperature. Add 330g of PM to the nanodispersion. Remove water by solvent exchange using rotary evaporation (from Buchi, New Castle, DE, Newcastle, WA) at 64°C under vacuum. Adjust the final nanoparticle content of the nanodispersion to 45% by weight.

[0114] SiO2 Nanodispersion: A174 / CYANO 20nm: Place 400g of NALCO 2327 in a 32oz wide-mouth glass flask. Start stirring and slowly add 450g of PM. Slowly add 11.00g of A174. Slowly add 8.39g of CYANO-TMOS. Stir the nanodispersion for another 20 minutes. Place the nanodispersion in an oven at 80°C for 24 hours to modify the nanoparticle surface with reactive acrylates and non-reactive cyano functional groups derived from silane. Add 330g of PM to the nanodispersion. Cool the nanodispersion to room temperature. Remove water by solvent exchange at 64°C under vacuum using rotary evaporation (from Buchi, New Castle, DE, Newcastle, WA). Adjust the final nanoparticle content of the nanodispersion to 45% by weight.

[0115] SiO2 Nanodispersion: A174 75nm: Place 400g of NALCO 2329K in a 32oz wide-mouth glass flask. Begin stirring and slowly add 450g of PM. Slowly add 6.92g of A174. Stir the nanodispersion for another 20 minutes. Place the nanodispersion in an oven at 80°C for 24 hours to modify the nanoparticle surface with reactive acrylate functional groups derived from silane. Cool the nanodispersion to room temperature. Add 330g of PM to the nanodispersion. Remove water by solvent exchange using rotary evaporation (from Buchi, New Castle, DE, Newcastle, WA) at 64°C under vacuum. Adjust the final nanoparticle content of the nanodispersion to 45% by weight.

[0116] SiO2 Nanodispersion: A174 / PHENYL 75nm: Place 400 g of NALCO 2329K in a 32 oz wide-mouth glass flask. Start stirring and slowly add 450 g of PM. Slowly add 4.64 g of A174. Slowly add 1.82 g of PHENYL-TMOS. Stir the nanodispersion for another 20 minutes. Place the nanodispersion in an oven at 80°C for 24 hours to modify the nanoparticle surface with reactive acrylates and non-reactive phenyl functional groups derived from silane. Cool the nanodispersion to room temperature. Add 330 g of PM to the functionalized nanodispersion. Remove water by solvent exchange at 64°C under vacuum using rotary evaporation (Buchi, New Castle, DE). Adjust the final nanoparticle content of the nanodispersion to 45% by weight.

[0117] SiO2 Nanodispersion: A174 / iC8 75nm: Place 400 g of NALCO 2329K in a 32 oz wide-mouth glass flask. Start stirring and slowly add 450 g of PM. Slowly add 4.64 g of A174. Slowly add 2.16 g of iC8-TMOS. Stir the nanodispersion for another 20 minutes. Place the nanodispersion in an oven at 80°C for 24 hours to modify the nanoparticle surface with reactive acrylates from silane and non-reactive iC8 functional groups. Cool the nanodispersion to room temperature. Add 330 g of PM to the functionalized nanodispersion. Use rotary evaporation (from Buchi, New Castle, DE) at 64°C under vacuum to remove water. Adjust the final nanoparticle content of the nanodispersion to 45% by weight.

[0118] SiO2 Nanodispersion: PHENYL 75nm: Place 400 g of NALCO 2329K in a 32 oz wide-mouth glass flask. Start stirring and slowly add 450 g of PM. Slowly add 1.82 g of PHENYL-TMOS. Stir the nanodispersion for another 20 minutes. Place the nanodispersion in an oven at 80°C for 24 hours to modify the nanoparticle surface with reactive acrylate functional groups derived from silane. Cool the nanodispersion to room temperature. Add 330 g of PM to the functionalized nanodispersion. Use rotary evaporation (from Buchi, New Castle, DE, Newcastle, WA) at 64°C under vacuum to remove water. Adjust the final nanoparticle content of the nanodispersion to 45% by weight.

[0119] Hard coating

[0120] Hard coating formulation: HF 1-10

[0121] The hard coating formulations (HF) used in the examples are shown in Table 2. Multifunctional acrylates (SR344, SR399, SR444c, and SR9035) were placed in a brown glass wide-mouth flask. MEK was added and stirring was initiated. A174 20nm, A174 / METHYL 20nm, and / or METHYL 20nm (one or more) nanoparticle dispersions were added and stirring continued until a uniform nanodispersion was formed in the hard coating formulation. ESACURE 1 was dissolved in the hard coating formulation. PM-1501 was added to the hard coating formulation and stirring was continued for another 20 minutes.

[0122]

[0123] Control hard coating formulation CHF 1-4 : The control hard coating formulations (CHF) used for comparative examples CE 1-4 are shown in Table 3. One or more acrylates were placed in a brown glass wide-mouth bottle. MEK was added and stirring was started. One or more surface-modified SiO2 nanodispersions were added and stirring was continued until a uniform nanodispersion was formed in the control hard coating formulation. ESACURE 1 was dissolved in the hard coating formulation. PM-1501 was added to the hard coating formulation and stirring was continued for another 20 minutes.

[0124]

[0125] Control Hard Coating Formulations CHF 5-8: The control hard coating formulations (CHF) used for control examples CE 5-8 are shown in Table 4. Multifunctional acrylates (SR344, SR399, SR444c, and SR9035) were placed in a brown glass wide-mouth bottle. MEK was added and stirring was started. Surface-modified SiO2 nanodispersions were added and stirring continued until a uniform nanodispersion was formed in the control hard coating formulations. ESACURE 1 was dissolved in the hard coating formulations. PM-1501 was added to the hard coating formulations and stirring was continued for another 20 minutes.

[0126]

[0127] Hard Coating: EX 11-16: Hard coating formulations HF 1-10 and control hard coating formulation CHF 1-8 were applied to a 3-mil primer-coated PET film using a continuous roll-to-roll process. The hard coating formulations were metered using a slot die with coating thickness controlled by a metering pump and mass flow meter. Volatile components of the coating were removed in a 3-zone air-float oven (zone 1 at 65.6°C, zone 2 at 93.3°C, and zone 3 at 121.1°C), each zone approximately 9.1 m long. The dried coating was cured using an H-bulb light source under an inert atmosphere using an embedded 600W / in fusion UV curing station with a dichroic reflector, where the temperature-controlled support rollers were set to 48.9°C. The cured hard coating thicknesses are shown in Tables 5, 6, and 7.

[0128] Hard coating film: optical properties

[0129] Tables 5 and 6 show the optical properties of the hard coatings for EX 1-10 and CE 1-8, along with details of the hard coating compositions: the concentration of each type of nanoparticle, total nanoparticle loading (NP loading), resin, and hard coating thickness. All hard coatings for EX1-10 exhibit high transmittance (T) and clarity (C), low haze (H), and low yellowness index (b). Optical grade quality is essential for front surface display applications. Similarly, hard coatings of CE 1-4 containing urethane acrylate (UA) exhibit optical grade quality. Hard coatings of CE 5-8 containing the same multifunctional acrylate (MFA) as EX 1-10 exhibit optical grade quality at 58 wt% NP loading, as shown in CE5 and CE 6, but exhibit high haze at higher NP loadings of 76 wt%, as shown in CE 7 and CE 8.

[0130]

[0131] Hard coatings: mechanical properties

[0132] Tables 7 and 8 show the mechanical properties of the hard coatings of EX 1-10 and CE 1-8, along with details of the hard coating compositions: the concentration of each type of nanoparticle, the total nanoparticle loading (NP loading), and the resin. EX 1-10 demonstrates that a mixture of semi-reactive and non-reactive nanoparticles is an effective strategy for achieving both flexibility and abrasion resistance in hard coatings. EX 1 shows that a nanocomposite hard coating with all reactive nanoparticles exhibits good abrasion resistance but poor flexibility under tension (mandrel bending, dynamic folding). EX 1 also shows a commonly used strategy in the art when abrasion resistance is a primary requirement for hard coatings on rigid (non-flexible) surfaces. EX 10 shows that a nanocomposite hard coating with all non-reactive nanoparticles exhibits good flexibility but poor abrasion resistance after 1,000 cycles. EX 2-9, incorporating both semi-reactive and non-reactive nanoparticles, demonstrates a novel nanocomposite hard coating exhibiting excellent flexibility and abrasion resistance, essential for next-generation displays. In addition to its good flexibility and abrasion resistance, EX 2-9 also exhibits good curling properties.

[0133] CE 1-4 uses a combination of strategies, including the common use of urethane acrylates to introduce flexibility into hard coatings of nanocomposite materials. CE 1-4 exhibits good flexibility (mandrel bending, dynamic folding) but poor abrasion resistance. CE 1-4's ​​curling properties are good due to soft urethane acrylates. CE 5-8 does not contain urethane acrylates but uses multifunctional acrylates. CE 5-8 also contains larger nanoparticles (75 nm) and contains a higher nanoparticle loading than CE 7-8. CE 5-8 exhibits good flexibility due to the larger, less reactive nanoparticles and surface modification with added non-reactive nanoparticles, but its abrasion resistance is worse than EX 1-10. CE 5-8 also has poor curling properties.

[0134]

[0135] Test methods

[0136] Hard coating thickness: The thickness of the hard coating was measured using white light interferometry and analyzed using FTM-ProVis Lite software.

[0137] Transmittance, sharpness, and haze: Optical properties were measured according to ASTM D1003-00 using a Gardner Haze-Guard Plus Model 4725 (obtained from BYK Gardner, Columbia, MD).

[0138] Yellowness index or b : By measuring b using a D65 light source To assess yellowness, measurements were taken using the transmission of a Konica Minolta spectrophotometer, model CM3700d.

[0139] Pencil Hardness: Pencil hardness was measured using pencils of 6B to 8H from Mitsubishi, weighing 1 kg, according to the JIS K 5600-5-4:1999 test procedure. The hard coating was visually inspected to identify any first visual defects or appearances of deformation of the substrate beneath the hard coating. Microscopy was then used to determine the pencil at which cracks in the hard coating were observed to have begun. The reported value is the highest value passed by the sample.

[0140] Wear: Wear was tested using a mechanical device capable of oscillating the abrasive adhered to the contact across the hard coating. Oscillation was performed perpendicular to the coating direction. The contact oscillated at a rate of 210 mm / s (2 swipes per second) over a 60 mm wide scan width, where a swipe was defined as a single 60 mm travel. The contact was a cylinder with a flat base and a diameter of 3.2 cm. The abrasive used for this test was steel wool, purchased under the trade name "#0000 Ultrafine" from Rhodes-American (a subsidiary of Homax Products, Bellingham, WA) and used as is. A 3.2 cm diameter disc was cut from the pad material and adhered to the base of the contact using 3M Scotch permanent adhesive transfer tape. Tests were conducted at a weight of 3.0 kg and with 50, 500, and 1,000 swipes. After wear, the hard coating was graded based on this visual standard for scratches. NS indicates no scratches, and SS indicates minor scratches. Both NS and SS show essentially no change in haze before and after the wear test. S indicates severe scratches, and HS indicates severe scratches; both show a significant change in haze (>1%).

[0141] Mandrel Bending: The bending of the mandrel was tested using ASTM Method D522 / 522M-13, “Mandrel Bending Test with Organic Coating,” Test Method B, a modified version of the cylindrical mandrel test. Instead of bending to 90 degrees as specified in the ASTM method, all specimens were wound around the mandrel 180 degrees, and the damage was then assessed. All specimens were tested with the hard coating on the outer radius (i.e., the hard coating under tension) and the hard coating facing the mandrel on the inner radius (i.e., the hard coating under compression). The smallest cylindrical dimension at which no cracking was observed was reported as the minimum bending radius (on a pass / fail basis).

[0142] Dynamic Folding: Dynamic folding was evaluated using a dual-pivot dynamic folding tester. The dynamic folding tester has two coplanar plates with parallel pivot axes, each capable of rotating 90 degrees to face each other with a specified gap between them. When closed, the gap between the plates is set to approximately 8 mm. The motor drives are adjusted so that both plates rotate simultaneously from zero to 90 degrees. A mechanical cutter is used to process each sample of 7.0 inch × 1.0 inch sheet and remove the liner. Three duplicate samples of each sample configuration were attached to a folded plate using a 1.0” wide strip of double-sided adhesive tape, with the coated side facing down (for a hard coating under tension). The tape was applied to the plate to create a central free zone approximately 24 mm wide (3 times the gap) where the film was unconstrained. The folding rate was set to approximately 30 folds / minute, and the test was conducted for 300,000 cycles or until all samples failed. The samples were visually inspected approximately every 1,000 cycles in the first 10,000 cycles, approximately every 5,000 to 10,000 cycles in the 100,000 cycles, and then visually inspected between 10,000 and 25,000 cycles in up to 200,000 cycles to look for signs of failure such as coating breakage, cracking, delamination, or cloudiness.

[0143] Curl: Curl was measured by cutting a 3"×3" sample of the hard coating, wherein the square was cut such that two corners of the film were aligned with the transverse direction and two corners of the film were aligned with the longitudinal direction. The 3"×3" sample was placed on a table, and the edge lift at the film corners was measured and the average value was recorded.

[0144] Therefore, an implementation scheme for a flexible hard coating is disclosed.

[0145] All references and publications cited herein are expressly incorporated in their entirety by reference, except for those that may directly conflict with this disclosure. While specific embodiments have been illustrated and described herein, those skilled in the art will recognize that various alternative and / or equivalent embodiments may be used instead of the illustrated and described embodiments without departing from the scope of this disclosure. This application is intended to cover any modifications or variations of the specific embodiments discussed herein. Therefore, this disclosure is intended to be limited only by the claims and their equivalents. The disclosed embodiments are for illustrative purposes only and not for limitation.

Claims

1. A hard coating composition, said hard coating composition comprising: One or more polyfunctional (meth)acrylate monomers, wherein the one or more polyfunctional (meth)acrylate monomers comprise: At least one first (meth)acrylate monomer, the first (meth)acrylate monomer comprising at least three (meth)acrylate groups and an alkoxy repeating unit; and At least one second polyfunctional (meth)acrylate monomer different from the first monomer; and A mixture of silica nanoparticles dispersed within one or more multifunctional (meth)acrylate monomers, the silica nanoparticle mixture comprising: A first group of semi-reactive silica nanoparticles, comprising 1 wt% to 75 wt% of a first group, wherein the semi-reactive silica nanoparticles have reactive and non-reactive functional groups, and wherein the first group of semi-reactive silica nanoparticles have an average particle size in the range of 10 nm to 40 nm; and The second group of non-reactive silica nanoparticles, comprising 99% to 25% by weight, having an average particle size in the range of 10 nm to 40 nm, exhibit no visible scratches after at least 500 wiping cycles when tested for abrasion resistance at a weight of 3.0 kg using a mechanical device capable of causing the abrasive adhered to the contact to oscillate across the hard coating, wherein the oscillation is performed perpendicular to the coating direction, and the contact has a flat base and 3. A 2cm diameter cylinder is oscillating at a rate of 210mm / s (2 wipes per second) over a 60mm wide scanning width, and the abrasive is steel wool #0000 attached to the contact; and when the curvature of the hard coating composition is tested by the following method, the hard coating formed after curing exhibits an average curvature of less than or equal to 2.0 mm: a 7.6cm × 7.6cm (3 inch × 3 inch) sample is cut out, and the sample is placed on a table surface, and the lift force from the edge of the table surface at the four corners of the sample is measured and averaged.

2. A hard coating composition, said hard coating composition comprising: One or more polyfunctional (meth)acrylate monomers, wherein the one or more polyfunctional (meth)acrylate monomers comprise: At least one first (meth)acrylate monomer, the first (meth)acrylate monomer comprising at least three (meth)acrylate groups and an alkoxy repeating unit; and At least one second polyfunctional (meth)acrylate monomer different from the first monomer; and A mixture of silica nanoparticles dispersed within one or more multifunctional (meth)acrylate monomers, the silica nanoparticle mixture comprising: The first group of semi-reactive silica nanoparticles, comprising 1% to 75% by weight, having reactive and non-reactive functional groups, and having an average particle size in the range of 10 nm to 40 nm. The non-reactive functional group is obtained by using a general formula R-SiR' m (OR'') 3-m The compound is formed by non-reactive surface treatment, wherein R is methyl or ethyl, R' is (C1-C4)alkyl, R'' is (C1-C4)alkyl, and m is an integer from 0 to 2; and The reactive functional group is obtained by using the general formula X'-L'-SiR' m (OR'') 3-m The compound is formed by reactive surface treatment, wherein X' is a radical-polymerizable group and L' is a (C1-C2) group. 12 ) alkylene, R' is (C1-C4) alkyl, R'' is (C1-C4) alkyl, m is an integer from 0 to 2; 99% to 25% by weight of a second group of non-reactive silica nanoparticles, the second group of non-reactive silica nanoparticles having an average particle size in the range of 10 nm to 40 nm, the non-reactive silica nanoparticles being made with the general formula R-SiR' m (OR'') 3-m The compound undergoes a non-reactive surface treatment, wherein R is methyl or ethyl, R' is (C1-C4)alkyl, R'' is (C1-C4)alkyl, m is an integer from 0 to 2, and the hard coating composition, after curing, exhibits no visible scratches when tested for abrasion resistance at a weight of 3.0 kg using a mechanical device capable of causing the abrasive adhering to the contact to oscillate across the hard coating, after at least 500 wiping cycles, wherein the oscillation is performed perpendicular to the coating direction, and the contact has a flat base and 3.2c A cylinder with a diameter of m oscillates at a rate of 210 mm / s (2 wipes per second) across a 60 mm wide scanning width, and the abrasive is steel wool #0000 attached to the contact; and when the curvature of the hard coating composition is tested by the following method, the hard coating formed after curing exhibits an average curvature of less than or equal to 2.0 mm: a 7.6 cm × 7.6 cm (3 inch × 3 inch) sample is cut out, and the sample is placed on a table surface, and the lift force from the edge of the table surface at the four corners of the sample is measured and averaged.

3. The hard coating composition according to claim 2, wherein the compound used for the non-reactive surface treatment of the first group and the second group is a compound having the formula R-SiR'. m (OR'') 3-m The compound, wherein R is methyl, R' is (C1-C2)alkyl, R'' is (C1-C2)alkyl, and m is an integer from 0 to 2.

4. The hard coating composition according to claim 2, wherein the compound used for the non-reactive surface treatment of the first group and the second group is a compound having the formula R-SiR'. m (OR'') 3-m The compound wherein R is methyl, m is 0, and R'' is ethyl or methyl.

5. The hard coating composition according to claim 2, wherein the reactive surface treatment compound has the general formula X'-L'-SiR' m (OR'') 3-m Where X' is (meth)acryloyl or vinyl group, L' is (C3) alkylene, m is 0, and R'' is ethyl or methyl.

6. The hard coating composition of claim 1, wherein the silica nanoparticle mixture comprises: 1% to 50% by weight of the first group of semi-reactive silica nanoparticles; and 99% to 50% by weight of the second group of non-reactive silica nanoparticles.

7. The hard coating composition of claim 1, wherein the semi-reactive silica nanoparticles comprise: 5 mol% to 50 mol% of reactive functional groups; and 95 mol% to 50 mol% of non-reactive functional groups.

8. The hard coating composition of claim 1, wherein the semi-reactive silica nanoparticles comprise: 5 mol% to 30 mol% of reactive functional groups; and 95 mol% to 70 mol% of non-reactive functional groups.

9. The hard coating composition of claim 1, wherein the one or more polyfunctional (meth)acrylate monomers form at least 95% by weight of the monomers in the hard coating composition, and the hard coating composition contains less than 5% by weight of urethane.

10. The hard coating composition of claim 1, wherein the average particle size of the first group of semi-reactive silica nanoparticles is substantially equal to the average particle size of the second group of non-reactive silica nanoparticles.

11. The hard coating composition of claim 1, wherein the silica nanoparticle mixture is present in the hard coating composition at a loading ranging from 30% to 68% of total solids by weight.

12. The hard coating composition of claim 1, wherein the silica nanoparticle mixture is present in the hard coating composition at a loading ranging from 40% to 60% of total solids by weight.

13. The hard coating composition of claim 1, wherein the first group of semi-reactive silica nanoparticles has an average particle size in the range of 10 nm to 30 nm, and the second group of non-reactive silica nanoparticles has an average particle size in the range of 10 nm to 30 nm.

14. A hard coating comprising the reaction product of the hard coating composition according to claim 1.

15. The hard coating of claim 14, wherein the hard coating has a uniform thickness in the range of 1 micrometer to 10 micrometers.

16. A hard coating film, comprising: Substrate; as well as The hard coating according to claim 14 is disposed on the substrate.

17. The hard coating of claim 16, wherein the substrate is a visible light transparent thermoplastic substrate having a uniform thickness in the range of about 20 micrometers to about 350 micrometers.

18. The hard coating composition of claim 1, wherein the hard coating composition, after curing, forms a hard coating without breakage, cracking, or delamination after at least 200,000 dynamic folding cycles, the dynamic folding cycles being tested using a dual-pivot dynamic folding tester having two coplanar plates with parallel pivot axes, wherein both plates can be rotated 90 degrees to face each other, wherein the gap is 8 mm, and a motor drive causes the two plates to simultaneously rotate from zero to 90 degrees at a rate of 30 folds / minute, wherein the tested samples are three sets of 7.0-inch × 1.0-inch (17.8 cm × 2.5 cm) sheets, each sample being attached to the folding plate using a 1.0-inch (2.5 cm) wide double-sided tape strip, with the coated side facing down (hard coating under tension).

19. The hard coating composition of claim 2, wherein the hard coating composition, after curing, forms a hard coating without breakage, cracking, or delamination after at least 200,000 dynamic folding cycles, the dynamic folding cycles being tested using a dual-pivot dynamic folding tester having two coplanar plates with parallel pivot axes, wherein both plates can be rotated 90 degrees to face each other, wherein the gap is 8 mm, and a motor drive causes the two plates to simultaneously rotate from zero to 90 degrees at a rate of 30 folds / minute, wherein the tested samples are three sets of 7.0-inch × 1.0-inch (17.8 cm × 2.5 cm) sheets, each sample being attached to the folding plate using a 1.0-inch (2.5 cm) wide double-sided tape strip, with the coated side facing down (hard coating under tension).

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