CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to European Patent Application No. 18 196 703.5 filed Sep. 25, 2018, the disclosure of which is hereby incorporated by reference in its entirety.

FIELD OF THE INVENTION

The present invention is directed to an inkjet printable flexible film for packaging applications. In particular the present invention relates to a flexible film comprising a polymer film and an ink-receiving layer. The ink-receiving layer can be printed by means of industrial digital inkjet printing.

BACKGROUND OF THE INVENTION

Inkjet printing is widely used for various applications on substrates provided both in standard sheets and on roll. Nowadays, papers and films with microporous ink-receiving layers are common and described in the prior art.

EP 0 634 286 B1 concerns an alumina sol coating fluid containing an alumina hydrate, such as boehmite, a polyvinyl alcohol and boric acid or a borate for forming an ink-receiving layer of a recording sheet to be primarily used as a transparency for overhead projection. In the inventive example the coating fluid is applied to a transparent polyethylene terephthalate film having a thickness of 125 μm.

EP 1 644 348 A1 relates to a process for preparing a dispersion of surface-modified silica by modifying the surface of the silica with the reaction products of an Al(III) compound and an aminosilane. Also described is a recording material comprising an ink-receiving layer containing said dispersion and a binder.

U.S. Pat. No. 7,585,553 B2 is directed to a recording sheet for inkjet photo printing comprising a support layer, such as a transparent film, a basecoat layer comprising an alumina-based composition containing a binder and a topcoat layer comprising a colloidal cationic silica composition. Preferably, the basecoat comprises pseudo-boehmite. It is taught that in the printed sheet a high amount of color is maintained in the topcoat since the cationic silica serves to hold the anionic dye of the printing ink, whereas the lower alumina-containing basecoat serves to attract the solvent of the printing ink. In the examples the basecoat is applied with coating weights of more than 40 g/m2.

U.S. Pat. No. 7,906,187 B2 describes an inkjet printing medium for near-photographic prints comprising a polyethylene-based substrate, a first ink-receiving layer containing a cationic silica and a binder, and a second gloss-enhancing layer containing a second cationic silica.

EP 1 861 258 B1 is directed to a process for preparing an inkjet printable microporous medium for indoor and outdoor graphic displays, selected from paper or film, comprising a substrate, an intermediate layer comprising a specific mixture of acrylic (co)polymers, and an ink-receptive topcoat. The porous ink-receptive topcoat comprises inorganic particles and a polymeric binder. In the examples PET films having a thickness of 96 μm are coated with an intermediate layer and an ink-receptive top layer comprising boehmite and a poly(vinyl alcohol) binder.

DE 10 2009 014 635 A1 relates to an opaque multilayer recording material for photo prints and advertising prints comprising two polyolefin layers, two paper layers arranged between the two polyolefin layers, an opaque layer between the two paper layers, and at least one inkjet printable outer ink-receiving layer. In the examples the outer ink-receiving layers comprising boehmite and a polyvinyl alcohol binder in a weight ratio of about 4.3:1 are coated on various multilayer substrates.

WO 2018/021572 A1 concerns an inkjet recording medium comprising a transparent support and a transparent porous layer containing inorganic particles, preferably selected from silica, alumina, and pseudo-boehmite.

JP 11309800 A is about a packaging material that can be printed by electrophotographic, thermal transfer, inkjet, offset or flexographic printing and comprises a plastic film and an ink receiving layer containing at least one of inorganic particles, organic particles, dyes, and pigments. Exemplary inorganic particles are silica, clay, talc, diatomaceous earth, calcium carbonate, barium sulfate, aluminum silicate, synthetic zeolite, alumina, zinc oxide, and mica.

EP 1 884 371 A1 is directed to a package for an inkjet recording material wherein an inkjet recording material in which an ink-receiving layer including fine inorganic particles, e.g. fumed silica, colloidal silica, alumina, and alumina hydrate; and a thioetheric compound is disposed on a support is packaged by a material comprising a polylactic acid resin.

SUMMARY OF THE INVENTION

Although various inkjet recording media are described in the art, there is still a need for a highly flexible packaging material that can be printed with aqueous inks in high speed ink jet printing and results in high quality water-resistant prints. The recording medium should be able to be readily processed further to the final packaging. Conformity of the recording medium as contact material for food, pharmaceuticals, and personal care products is essential if used accordingly.

This need is met by an inkjet printable flexible film for packaging applications comprising:

(a) a biaxially oriented polymer film having a thickness in the range of from 8 to 70 μm; and

(b) at least one ink-receiving layer comprising boehmite particles and poly(vinyl alcohol) having a degree of hydrolysis of from 78 to 96 mol % in a weight ratio ranging from 6.5:1 to 20:1 coated over one surface of the biaxially oriented polymer film at a dry coating weight being in the range of from 5 to less than 25 g/m2, wherein the ink-receiving layer (b) is formed by

(i) applying an aqueous coating composition comprising boehmite particles, an acidic dispersing agent, poly(vinyl alcohol), and boric acid and/or a borate, or

(ii) applying boric acid and/or a borate in a first step and then an aqueous coating composition comprising boehmite particles, an acidic dispersing agent, poly(vinyl alcohol), and optionally further boric acid and/or borate.

The present invention is also directed to a multilayer laminate comprising the inkjet printable flexible film and to a packaging comprising the printed inkjet printable flexible film or printed multilayer laminate.

The present invention further concerns the use of the printed inkjet printable flexible film, the printed multilayer laminate or the packaging for packaging food, pet food, beverages, pharmaceuticals and/or personal care products.

Moreover, the present invention relates to a method of making a filled packaging wherein the inkjet printable flexible film or the multilayer laminate is inkjet printed in line as part of a form fill seal process.

The thin inventive inkjet printable flexible film comprising the specific ink-receiving layer is highly flexible and has excellent mechanical stability. It exhibits a high crack resistance as required for packaging applications. The ink-receiving layer is optimized for fast inkjet-printing and waterfast and flake-off resistant inkjet prints can be produced. It was surprisingly found that despite the low film thickness and low coating weight, the inventive inkjet printable flexible film withstands strong mechanical impact, i.e. folding, stretching, and bending, and is well suited for automatic processing. Moreover and quite importantly, the chemistry of the ink-receiving layer does not necessitate the presence of any low molecular organic substances which are prone to migration. Thus, such substances, e.g. surfactants, wetting agents, defoamers, and antistatic agents, can be omitted or reduced to a minimum to obtain a food-safe packaging material

