CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a national phase application under 35 U.S.C. § 371 of International Application No. PCT/EP2015/078674 filed 4 Dec. 2015, the entire contents of which is specifically incorporated by reference herein without disclaimer.

FIELD OF THE INVENTION

The invention relates to the field of film laminates, including transparent laminates for display devices and optical articles such as spectacles and sunglasses.

BACKGROUND

During the manufacture of structured film laminates, which are primarily composed of insulating materials, localized static charges may accumulate at the laminate layer surface. These localized static charges are capable of attracting small, lightweight foreign particles such as dust particles. As a result of the electrostatic attraction between foreign particles and the laminate layer surface, the foreign particles cling to and accumulate on the laminate layer surface. As successive layers are added to a structure film laminate during assembly, clinging foreign particles are incorporated between the laminate layers. The integrated foreign particles disperse light passing through the laminate, thereby increasing haze and reducing optical clarity. It is therefore desirable that no foreign particles be attracted to laminate layer surfaces during the assembly of a structured film laminate.

There is a need in the industry for techniques that render existing film laminate layers antistatic. The methods described herein provide several different approaches for embedding antistatic molecules within laminate layer compositions. The laminate layer compositions are commonly used in the manufacture of film laminates. The incorporation of antistatic molecules into existing laminate layer compositions will reduce costs associated with providing new or additional layers into existing film laminate production methods.

Cellulose and derivatives thereof are commonly employed in the production of transparent film laminates. Cellulose is a natural glucose polysaccharide obtained from plant products. Cellulose acetate is a semi-synthetic cellulose derivative that is obtained by acetylation (or esterification) of free glucose hydroxyl groups. Cellulose acetates with different properties are obtained depending on the esterification degree or degree of substitution. Cellulose triacetate includes three acetate esters per glucose monomer, and is currently manufactured by reacting the alcohol groups with acetic anhydride, glacial acetic acid and sulfuric acid catalyst.

The majority of cellulose triacetate is manufactured by a solvent casting process to provide a TAC film. Cellulose polymer films are often supplied with protective liners in order to keep their surface pristine. Upon removal of the liners, static charges can build up, which will attract particles and reduce optical quality. There is a need to minimize static buildup within commonly-used transparent laminate components like cellulose and cellulose derivatives. Antistatic additives may be incorporated during film production to bestow antistatic properties on the film product. Antistatic films may then be incorporated into structured film laminates.

SUMMARY

It is an object of the disclosure to provide a structured film laminate layer with one or more conductive antistatic substances. Incorporation of an antistatic substance into an existing laminate layer prevents or reduces attraction of foreign particles during manufacturing. Furthermore, incorporation of an antistatic substance into an existing laminate layer reduces the overall thickness and weight of the resulting laminate.

According to a first aspect of the disclosure, an antistatic film structure comprising a transparent antistatic support structure is provided. In some embodiments, the transparent antistatic support structure comprises a polymer selected from the group consisting of native or derivatized cellulose or cellulosic material, polyesters, polyvinyl acetates, polyacrylonitriles, polybutadienes, polystyrenes, polycarbonates, polyacrylates, copolymers and mixtures thereof. The derivatized cellulose may be selected from the group consisting of cellulose alkyl ethers, cellulose hydroxyalkyl ethers, cellulose esters, cellulose functionalized with anionic or cationic functional groups, crosslinked cellulose, and combinations thereof. In a particular embodiment, the transparent antistatic support structure comprises TAC.

In some embodiments, the antistatic film structure further comprises a polarizing element. In a particular embodiment, the polarizing element comprises polyvinyl alcohol (PVA) film.

The transparent antistatic support structure comprises at least one antistatic component. The antistatic component may be selected from the group consisting of graphene, single or multi-wall native or derivatized carbon nanotubes, semiconducting materials, core-shell conductive nanoparticles, organic conductive materials or polymers or co-polymers thereof, organic or inorganic ionic salts or materials, conductive colloids, ionic resins, and mixtures thereof. The inorganic ionic salt or material may comprise vanadium oxide, antimony oxide, tantalum oxide, cerium oxide, tin oxide, titanium oxide, indium oxide, zinc oxide, tin-doped indium oxide, antimony-doped tin oxide, fluorine-doped tin oxide, phosphorus-doped tin oxide, zinc antimonate, indium antimonite, indium-doped zinc oxide, lithium salts, silver, gold, nickel, aluminum, silicon nitride, magnesium fluoride, and combinations thereof. In some aspects, the transparent antistatic support structure comprises a thickness ranging from 50 nm to 2 μm, more preferably from 100 nm to 1.5 μm, even more preferably from 100 nm to 1 μm. In further embodiments, the inorganic ionic material may comprise a metal oxide selected from the group consisting of vanadium oxide, antimony oxide, tin oxide, titanium oxide, indium oxide, silver oxide, gold oxide, aluminum oxide, zinc oxide, lithium oxide, and combinations thereof. The metal oxide may be any known oxide of the corresponding metal. For example, the vanadium oxide inorganic ionic material may be selected from vanadium (II) oxide (VO), vanadium (III) oxide, (V2O3), vanadium (IV) oxide, (VO2), and vanadium (V) oxide (V2O5).

In some embodiments, the transparent antistatic support structure is produced by combining a transparent support structure with at least one antistatic component by a process selected from the group consisting of imbibing, melt extruding, blown film extruding, calendaring, solvent casting, mold casting, wet transfer, sublimation, and solidification of a liquid to a solid using heat, UV or other means.

In some embodiments, the antistatic film structure comprises a relative light transmission factor in the visible spectrum, Tv, preferably greater than 85%, more preferably greater than 90%. In some aspects, the antistatic film structure comprises a haze value of less than 1.0%, preferably less than 0.5%.

According to a second aspect of the disclosure, a method for producing an antistatic film structure comprises combining at least one antistatic component with a transparent support structure by a process selected from the group consisting of imbibing, melt extruding, blown film extruding, calendaring, solvent casting, mold casting, wet transfer, sublimation, and solidification of a liquid to a solid using heat, UV or other means. The combining process confers antistatic activity to the transparent support structure. In some embodiments, the transparent support structure comprises a polymer selected from the group consisting of native or derivatized cellulose, polyesters, polyvinyl acetates, polyacrylonitriles, polybutadienes, polystyrenes, polycarbonates, polyacrylates, copolymers and mixtures thereof. In a particular embodiment, the transparent support structure comprises cellulose triacetate.

In some embodiments, the antistatic component comprises at least one component selected from the group consisting of graphene, single or multi-wall native or derivatized carbon nanotubes, semiconducting materials, core-shell conductive nanoparticles, organic conductive materials or polymers or co-polymers thereof, organic or inorganic ionic salts or materials, conductive colloids, ionic resins, and mixtures thereof.

In some embodiments, a method for producing an antistatic film structure further comprises combining a polarizing element with the antistatic film structure. In a particular embodiment, the polarizing element comprises polyvinyl alcohol (PVA) film.

In some aspects, the antistatic film structure may comprise a substrate or coating that enhances the antistatic performance. In some embodiments, an enhancing layer may comprise an additive to enhance antistatic performance. In some aspects, the enhancing layer additive may comprise diethylene glycol, diethylene monoether, diethylene diether, polyethylene, or any combination thereof. In some aspects, the enhancing layer additive is added in an amount ranging from 1-10 wt % of the enhancing layer. In some aspects, the antistatic film structure laminate may comprise a neutral layer that inhibits or prevents negative influence from a laminate layer or substrate.

In some embodiments, the antistatic film structure further comprises one or more abrasion- and/or scratch-resistant layers. The abrasion- and/or scratch-resistant layer is defined as a coating which improves the abrasion- and/or scratch-resistance of the finished film structure as compared to a same film structure without the abrasion- and/or scratch-resistant layer. Any known optical abrasion- and/or scratch-resistant coating composition may be used herein.

Examples of abrasion- and/or scratch-resistant layers are (meth)acrylate based coatings and silicon-containing coatings. (Meth)acrylate based coatings are typically UV-curable. The term (meth)acrylate means either methacrylate or acrylate. The main component of a (meth)acrylate based curable coating composition may be chosen from monofunctional (meth)acrylates and multifunctional (meth)acrylates such as difunctional (meth)acrylates; trifunctional (meth)acrylates; tetrafunctional (meth)acrylates, pentafunctional (meth)acrylates, hexafunctional (meth)acrylates. Examples of monomers which may be used as main components of (meth)acrylate based coating compositions are:1) monofunctional (meth)acrylates: allyl methacrylate, 2-ethoxyethyl acrylate, 2-ethoxyethyl methacrylate, caprolactone acrylate, isobomyl methacrylate, lauryl methacrylate, and polypropylene glycol monomethacrylate.2) difunctional (meth)acrylates: I,4-butanediol diacrylate, I,4-butanediol dimethacrylate, 1,6-hexanediol diacrylate, 1,6-hexanediol dimethacrylate, ethoxylated bisphenol A diacrylate, polyethylene glycol di(meth)acrylates such as polyethylene glycol diacrylate, tetraethylene glycol diacrylate, polyethylene glycol dimethacrylate, polyethylene glycol diacrylate, tetraethylene glycol diacrylate, tripropylene glycol diacrylate, neopentyl glycol diacrylate, tetraethylene glycol dimethacrylate, and diethylene glycol diacrylate.3) trifunctional (meth)acrylates: trimethylolpropane trimethacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, ethoxylated trimethylolpropane triacrylate, and trimethylolpropane trimethacrylate.tetrafunctional to hexafunctional (meth)acrylates: dipentaerythritol pentaacrylate, pentaerythritol tetraacrylate, ethoxylated pentaerythritol tetraacrylate, and pentaacrylate esters.4) Silicon-containing abrasion- and/or scratch-resistant coatings are preferably sol-gel coatings, which may be obtained by curing a precursor composition containing silanes or hydrolyzates thereof. The sol-gel silicon based coating compositions which may be used are homogeneous mixtures of a solvent, a silane and/or an organosilane, option ally a surfactant, and optionally a catalyst which are processed to form a coating suitable for optical application.5) The term “homogeneous” as used herein refers to a form which has a uniform or similar structure throughout and is given the ordinary meaning known to persons skilled in the art. Examples of abrasion- and/or scratch-resistant coatings are epoxytrialkoxysilane-based hard coatings, more preferably γ-glycidoxypropyl-trimethoxysilane-based hard coatings.

The antistatic film structure substrate may be made of mineral glass or organic glass, preferably organic glass. The organic glasses can be either thermoplastic materials such as polycarbonates and thermoplastic polyurethanes or thermosetting (cross-linked) materials such as diethylene glycol bis(allylcarbonate) polymers and copolymers (in particular CR-39® from PPG Industries), thermosetting polyurethanes, polythiourethanes, polyepoxides, polyepisulfides, poly(meth)acrylates and copolymers based substrates, such as substrates comprising (meth)acrylic polymers and copolymers derived from bisphenol-A, polythio(meth)acrylates, as well as copolymers thereof and blends thereof. Examples of materials for the lens substrate are polycarbonates and diethylene glycol bis(allyl carbonate) copolymers, in particular substrates made of polycarbonate.

Carbon nanotubes (CNT) contained in the antistatic composition refer to tubular structures grown with a single wall or multi-wall, comprising primarily sp2-hybridized carbon atoms. The carbon nanotubes preferably have a diameter on the order of half nanometer to less than 10 nanometers. Carbon nanotubes can function as either an electrical conductor, similar to a metal, or a semiconductor, according to the orientation of the hexagonal carbon atom lattice relative to the tube axis and the diameter of the tubes.

By “nanoparticles”, it is meant particles with a diameter (or longest dimension) less than 1 pm, preferably less than 150 nm and more preferably less than 100 nm.

Any embodiment of any of the disclosed compositions and/or methods can consist of or consist essentially of—rather than comprise/include/contain/have—any of the described elements and/or features and/or steps. Thus, in any of the claims, the term “consisting of” or “consisting essentially of” can be substituted for any of the open-ended linking verbs recited above, in order to change the scope of a given claim from what it would otherwise be using the open-ended linking verb.

