EP2323834A1 - Film - Google Patents

Abstract

A polymeric film has at least one region thereon having altered appearance and/or tactility compared to the surrounding film, the region being formed in the film by means of ultrasonic treatment of the film in that region The region may be of reduced opacity compared to the surrounding film The region is embossed or debossed and contrast may be highlighted by the use of fluorescent, photochromic or other additives due to thickness variation and light-piping

Description

FiLM

The present invention relates to a film in particular to a film of non uniform appearance and/or tactility and also to an opaque polymeric film having regions of reduced opacity and to cavitated fiims and packages produced therefrom having regions of reduced opacity and to a manufacturing method for such a film

Polymer films are extensively used in many industries for countless different uses With such a variety of uses it is desirable to introduce features in a film to meet the requirements of a particular use such as for example functional or aesthetic display features of the film

Regions of films having altered appearance are useful not only in assisting identification but also in enhancing aesthetic appeal The aoDearance of films in many applications is of key importance in increasing the desirability and apparent value to the user or consumer This is particular!¹/ the case in the field of packaging where user behaviour is heavily influenced by the nature and features on packaging film

More features are required on films in order to enhance their appeal to the potential user or purchaser These features include not only ways in which the appearance are manipulated but also ways in which the feel or tactility of the product can be altered One desired feature is the ability to produce regions which are aesthetically enhanced, for example on solid films which are clear or opaque

Another desired feature is variation of thickness to produce regions of thinned film with thicker boundaries

Yet another desirable feature is the ability to produce an opaque film with regions or "zones" which are substantially transparent, or have a reduced opacity These regions in the film can be used as windows which enable light to pass through the film at predetermined regions Such windows are used in industry for a variety of purposes, including enabling visual inspection of items within a container covered by an opaque film and enabling a light source, such as a light emitting diode (LED), to radiate through the film Such regions may also be used for decorative effect on a film surface displaying rnrnrjratθ lo^o information Of" artwork for PYamnl^p

There die Sβvβidi known methods for Creating windows in an Opaque film including printing an opaque coating onto a clear film and leaving regions without a printed coating, adding an opaque layer to the film with regions ' cut out" of the layer and even physically cutting a window in an opaque fiim and locating a transparent insert into the window

A method for forming transparent regions m a material using ultrasonic vibraiions is disclosed in US 8890892 of Eastman Kodak Co wnere there is described a method for embossing indicia onto an article of coated transparent malleable material by providing an anvil which has the appropriate indicia defined by a plurality of individual protuberant dots The article is positioned against the anvil in contact with the protuberant dots and an ultrasonically vibrating horn is applied to the article forcing IT against the dots to form indentations When the material is embossed as described the coatings at the points of indentation become stretched and fragmented with the result that even though the major portion of the material may be opaque to light, it becomes transparent or translucent at the indentations

One apparent disadvantage of US 3890892 is that a coating or additional layer must be used to cover the inherently transparent materia! to create the opaque regions, which increases the complexity and cost of manufacturing the resultant film

Ultrasonic vibrations can he used tc ceate patterned τ»arks or "identatioπs in a film for a variety of purposes for example to increase the tactility of the treated region to display information and to create foidable regions within ihe film WO2006034502 of Meadwestvaco Corp discloses a method of forming a polymeric container blank having flexible fold lines which includes the steps of providing a polymeric material for use as a substrate for a container blank, providing a creasing tool which includes an applicator on one surface of the material and a creasing rule on the other surface The applicator is resonated at an ultrasonic frequency so as to apply ultrasonic energy to the materia! and form at least one flexible line therein It is an object of the invention to provide a polymer film having enhanced functionality with regard to display or decorative regions on the film for example a film which is selectively thsnned aesthetically enhanced, or clarified in a region thereof for decorative or functional purposes, in particular a film which is an opaque film selectively claπfied in a region thereof for decorative or functional purposes

According to the present invention there is provided a polymeric film the film having at least one treated region therein having an altered appearance and/or tactility compared to the surrounding film the treated region being formed by means of ultrasonic treatment of the film in that region

The treated region may be formed by embossment and/or debossment by means of ultrasonic treatment of the film in that region

Thus in one alternative the region has altered appearance in another alternative the ieyiun ha& aϊteied taotiiity and in yet another alternative the region has both altered appearance and altered tactility compared to the surrounding film

The regions may comprise features or patterns created by the localised heating or melting via the application of ultrasonic energy

In one preference ine treated regions nave ^raised Dounαaπes This enaoles deep features tc be created which are clearly visible and/or highly tactile The appearance can be enhanced by additives which contrast the embossed features, for example due to the variation in thickness or light-piping effects Such additives can for example be fluorescent photochrome or pigmented This in effect ' highlights' the embossed features

In other words additives can be used which have particular appearances, for example in terms of colour brightness or fluorescence or which have appearances which alter depending on the environment, for example under UV light The effect of the invention is enhanced because of the difference between the appearance of the additive-carrying film in the treated areas and the appearance of the additive-carrying film in the untreated areas, which itself is affected by the thickness variations the boundary between treated and untreated areas the altered aspect refraction reflection and light-piping

Pigmented additives include for example photochrome materials Photochromic materials such ss photochromic dyβs and printing inks mauc therefrom, are well known in the art and may comprise for example spiro- indolmo-naphthoxazines fulgides and fulgimides and/or spiro(18a)~ dihydromdolizines Such printing inks may be printed onto the substrate by any one of a number of known printing methods including gravure reverse gravure heliogravure flexographic plate intaglio letterpress dry offset indirect letterpress lithographic wet offset or screen printing Alternatively trie phoiochromic materials may be incorporateα into tne film rather than ppnteα onto it Fluorescent materials are also well known and may comprise for example inorganic materials in particular doped rare earth compounds such as yttrium oxysulphide doped with europium barium magnesium alumttiate doped with 5 europium and barium magnesium aluminate doped with europium and manganese available under the trade name UVEDA from Nemoto & Co Ltd 1-15-1 Kamiogi Suginamι-ku Tokyo 167 Japan specifically as YS A4/Red ALN-BP4/BIue and ALN-GP4/Green respectively Other fiuorescers include organic materials such as stilbenes coumarins thioxanthones rhodamines

10 benzoxazoles azo dyes polycyclic aromatic hydrocarbons and heterocycles including Lumogen TM dyes and pigments (BASF Mt Olive N J ) thioxazoles decacyclene fluorescein fluorene 9-fluorenone fluoranthene and the like Preferred among the foregoing are thioxazoles and polycyclic aromatics Such materials can be \n the form of solubilised or dispersed i s nowders dissolved liquids dispersed microspheπcal particles and the like Other suitable materials include those organic rare earth complexes available under the trade name LUITIIIUΛ frorr Honeyweϋ Specialty Chemicals Seelze Gmbh Postfach 10 02 62 D-30918 Seelze Germany Particular examples include Lumilux Red E9498 Lumilux Green CD 302 Lumiiux Green CD 333 0 lumilux Green CD 321 and tumifux Yellow-Green CD 342 The fluorescent materials may be incorporated into the τιιm or printed onto it

The luminescent material rnav also or instead comprise another class of optically sensitive compounds for example trie luminescent aromatic heferocycles available under the trade designations 1-88 and L- 187 from Beaver Luminescers

Phosphorescent materials may also be used as the additive which enhances contrast by virtue of difference in thickness or by virtue of light-piping Examples of suitable phosphorescent materials include zinc sulphides and radioisotopic compounds, and doped metal oxides such as the strontium oxide based compounds such as the strontium oxide aluininates available under the trade name LumiNova™ from Nemoto & Co Ltd of Tokyo, Japan

The additive may be a UV-sensitive material, for example so that indicia on the material provide an image (which may or may not be invisible to the naked eye) which alters its appearance, or becomes visible or becomes invisible, when exposed to UV radiation in particular radiation of wavelength from ahni it 1 QD in about 4DOiIm It mav in ςnmp annliratinnς hp rlpςirahlp fnr thp indicia to undergo no change of appearance on exposure to light in the visible region of the spectium (eg fiorn about 400 to about 700nm) when unaccompanied by UV radiation

The additives to contrast the appearance may be used singly or in combination for example more than one may be used selected from the same or different classes

Whilst the variation in appearance between the regions ana trie surrounding film may be observed in coloured pigmented or non-clear film the present invention is also applicable to clear film Variations in appearance may still be visible even in clear films. Tactility is unaffected by the colour, pigmentation or appearance of the material, nevertheless the tactility and appearance of the regions may combine to produce enhanced effect on the user

The regions of altered appearance may be regions of reduced opacity relative to the other parts of a substantially opaque film, and such a possibility will now be discussed in more detail.

Thus, according to the present invention there is provided a substantially opaque polymeric film, the film having at least one region thereon having reduced opacity compared to the surrounding film, the region being formed in the film by means of ultrasonic treatment of the film in that region.

Preferably, the film (in the untreated region) has an opacity of at least about 25%, more preferably at least about 40%, and most preferably at least about 60%

The opacity of the film (in the untreated region) is preferably at least partially provided by the presence in the film of voided (or cavitated) regions Such voided regions may for example be created by providing in the film at least one voiding agent The production of voided films is of course well known, and any suitable voiding agent may be used here Voiding agents are generally particulate materials and may be selected from organic, inorganic or polymeric materials US 4,377 616 of Mobil Oil Corporation describes a number of these Voiding agents may be substantially spherical particulate in nature, or may have a higher aspect ratio For example, the voiding agents described in WO-A-03/033574 may be used

The opacity of the film may be supplemented with further materials which are not voiding agents but are opacifying agents Inorganic fillers such as TiOa may be mentioned in this connection

The opacity of the film in the treated region is preferably at least about 10% more preferably at least about 20%, and most preferably at least about 30% lower than the untreated film

in a film opacified only with voiding agents and not with supplemental opacifying agents, the untreated region of the film may be substantially opaque whilst the treated region may be substantially dear or transparent

The region of the film may be at !ea&t one line pattern and/oi area on the film or a combination of two or more of these, and there may be any suitable number of such regions on the film The purpose of such a region may be, for example, to provide a visibility window on an otherwise opaque film forming a package or part of a package for a commercial product or to provide visible indicia to indicate the presence of, for example a tear line or peel strip of a packaged film or may be used to display decorative artwork or other information on sucri a pacKage Preferably the reduced opacity region of the film has a greater density than the density of the untreated film It is possible that the mechanism by which reduced opacity pertains in a treated region of the film has to do with the densification of the treated region of the film for example in the case of a voided film by the collapse under ultrasonic stimulus of at least some of the voids within the film in the treated region

Ultrasonic vibration may be applied to the film region in any suitable manner and at any suitable power Such vibration may for example be delivered to the film through an applicator head known as an anvil vibrating at ultrasonic frequency and pressed against the surface of the film Experimentation on various polymer films has found that surprisingly opaque cavitated films become less opaque m regions where an anvii resonating at ultrasonic frequencies is applieα at pressure to a surface of the film

In general the region of the film may be at least one line, pattern and/or area on the film or a combination of two or more of thθsβ and there may be any suitable number of such regions on the film If the film is substantially opaque the purpose of such a region may be for example to provide a visibility window on an otherwise opaque film forming a package or part of a package for a commercial product or to provide visible indicia to indicate the presence of for example a tear line or peel strip of a packaged film or may be jsed to display decorative artwork or other information on such a package With respect to cavitated films the treated region of the film may have a greater density than the density of the untreated film In the case of reduction in opacity it is possible that the mechanism by which reduced opacity pertains in a treated region of the film has to do with the densification of the treated region of the film for example in the case of a voided film by the collapse under ultrasonic stimulus of at least some of the voids within the film in the treated region

For solid films (clear or opaque) as opposed to cavitated films the present invention effects melting and displacement of the resultant molten polymer to produce a region of thinned film with thicker boundaries The contrast between the thinned treated area & its thickened boundary give enhanced tactility & aesthetic effects

U'trason'c yibrat'on ^may be applied to the film region m any suitable manner and at any suitable power Typically the polymeric film may be sandwiched under pre&bure between a boπotioue ur hυm (vibiatiπy at ultiasoiliC frequencies for example 20 to 40 kHz) and an anvil The anvil is this sense acts as an embossing tool concentrating the ultrasonic vibrations into the polymer at desired positions thereby causing localised melting and movement of the polymer

One suitable ultrasonic treatment apparatus available from Herrmann Ultrasonics me of 620 Estes Ave SchaumDurg SL 60193 USA However many other suitable apparatus mav also be used The present invention is advantageous in transmitting energy in a controlled manner at particular locations and only where the polymer film is sandwiched or contacts the raised features of the anvil in other areas the film remains cold and untreated This focus can be particularly useful where films are thermally sensitive, for example if they have low temperature seaiable coatings on one or both outer surfaces, if they have a controlled response

(such as shrinking) in response to treatment, or if they are damaged in response to treatment In contrast, polymeric films generally suffer from large- scale macro-deformation when exposed to external heat sources

The depth and characteristics of the embossed/ debossed feature can easily be controlled by adjustment of the ultrasonic processing parameters (for example contact pressure dwell or amplitude)

In a preferred embodiment of the invention the anvil is in the form of an afifiuidi embossing too! with the laised βrnboss'πg feature situated around the circumference of the tool This rotary anvil design enables continuous processing on reel to reel operations

The films used in accordance with the present invention can be of a variety of thicknesses according to the application requirements For example they can be from about 10 to about 240μm thick and preferably from about 15 to about 90μm thick The treated region of the film is preferably of a slightly narrower gauge than the rest of the film - for example the treated region of the film may have a gauge of at least about 1%, preferably at ϊeast about 2% more preferably at least about 5% and most preferably at least about 10% lower than the rest of the film,

The films of the present invention may be a variety of different types and used for a variety of different purposes One possibility, amongst many is overwrap film, for use for example in wrapping cigarette packets, CDs and DVDs, confectionery and cosmetics cartons and many other types of package. Other types of packaging film may also be envisaged, as may labelling films,

In general the embossing pattern can be either a solid image, or be a larger image made up from a multiplicity of smaller components (eg dots) The use of a dot matrix enables large composite images to be generated, requires reduced energy & pressure inputs, and is compatible with even delicate films Furthermore the dot matrix images are particulary effective with fluorescing or photochromic films because the fluorescent or photochrornic βnβct is enhanced at the boundary of each embossed dot so the entire image in enhanced rather than just the peripheral boundary (as with the solid embossing too!

The films used in the present invention, prior to deposition of any coating and/or skin or lamination layer may comprise any suitable polymeric filmic substrate such as films made from biopoiymers such as any of those described herein (preferably polylactic or polygalactic films) thermoplastic films, polymeric films (for example films comprising polyolefins [e g polypropylene and/or polyethylene] polyurethanes polyvmylhalides [e g PVC], polyesters [e g polyethylene terephthalate-PET], polyamicles [e g nylons] and/or non-hydrocarbon polymers) and/or multilayer and/or composite sheets formed by any suitable combinations and/or mixtures of thereof Suitable filmic substrates therefore include polyolefinic films but also polyester films polyurethane films and PLA films

The substrate must be thermoplastic for the substrate material to be allowed to melt and be displaced (or "densified" for cavitated films)

The film may therefore comprise any thermoplastic polymer and may conveniently comprise polymers of low surface energy More preferably the sheet comprises a homopolymer a crystalline polymer and^or a polymer of ^randomly nnenfed amorphous non-crystalline polymer chains Most preferably the sheet comprises polyolefins [e g polypropylene and/or polyethylene] poiyurethanβs, poiyvioyihahdes [β g polyvinyl chloride (PVC)], polyesters [e g polyethylene terephthalate-PET] polyamides [e g nylons] and/or non-hydrocarbon polymers)

Conveniently the polyolefin films to De used with the present invention may comprise one or more polyolefins [e g polypropylene homopolymer, polyethylene homopolymer (e g linear tow-density polyethyiene-ltDPE) and/or polypropylene/polyethylene copolymers), optionally in one or more layers] The constituent polymers and/or layers in a film of the present invention may be oriented, blown, shrunk, stretched, cast, extruded, co- extruded and/or comprise any suitable mixtures and/or combinations thereof. Preferred films comprise a major proportion of polypropylene and/or an olefin block copolymer containing up to about 15% w/w of the copolymer of at least one copolymerisable olefin (such as ethylene). More preferred films comprise polypropylene homopolymer, most preferably isotactic polypropylene homopolymer.

Films may optionally be cross-linked by any suitable means such as electron beam (EB) or UV cross-linking, if necessary by use of suitable additives in the film.

The definition of polyolefin, as intended herein, is a polymer assembled from a significant percentage, preferably >50% by weight of one or more olefinic monomers

The definition of copolymer herein, is a polymer assembled from two υi more monomers Such polymers may include, but are not limited to polyethylene homopolymers, ethylene-α-olefin copolymers, polypropylene-α-olefin copolymers, polypropylene homopclymers, ethylene-vinyl acetate copolymers. βthySene-metnacrylϊc acid copolymers and their salts ethylene-styrene polymers and/or blends of such polymers The polymers may be produced by any suitable means, for example one or more of free radical polymerisation (e.g peroxy compounds), metailocene catalysis and/or coordination catalysis (e.g. Ziegler and/or Natta catalysts and/or any variations thereof). Polymeric resins used to produce the films of the present invention are generally commerciaSIy available in pellet form and may be melt blended or mechanically mixed by well-know methods known in the art using commercially available equipment including tumblers, mixers and/or blenders The resins may have other additional resins blended therewith along with well- know additives such as processing aids and/or colorants Methods for producing polyolefin films are well-known and include the techniques of casting films as thin sheets through narrow slit dies and blown-film techniques wherein an extruded tube of molten polymer is inflated to the desired bubble diameter and/or film thickness

For example to produce a polymeric film the resins and additives may be introduced into an extruder where the resins are melt plastified by heating and then transferred to an extrusion die for formation into 3 film tube Extrusion and die temperatures will generally depend upon the particular resin being processed and suitable temperature ranges are generally known n the art or provided in technical bulletins made available by resin manufacturers Processing temperatures may vary depending upon process parameters chosen

Thus, the polymeric film can be made by any process known in the art, including but not limited to cast sheet cast film or blown film This invention may be paπicuiariy applicable to films comprising cavitated or non-caviated polypropylene films with a block copolymer polypropylene/polyethylene core

. 1 (. . and skin layers with a thickness substantially below that of the core layer and formed for example from random co-polymers of ethylene and propylene or random terpolymers of propylene, ethylene and butylene The film may comprise a biaxially orientated polypropylene (BOPP) film which may be prepared as balanced films using substantially equal machine direction and transverse direction stretch ratios, or can be unbalanced where the film is significantly more orientated in one direction (MD or TD) Sequential stretching can be used, in which heated rollers effect stretching of the film in the machine direction and a stenter oven is thereafter used to effect stretching in the transverse direction Alternatively, simultaneous stretching, for example, using the so-called bubble process, or simultaneous draw stenter stretching may be used

Polymeric resins used to produce the films of ϊhe present invention are generally commercially available m pellet form and may be melt blended or mechanically mixed by well-know methods known in the art, using commercially available equipment including tumblers mixers and/or blenders

The resins may have other additional resins blended therewith along with well- know additives such as processing aids and/or colorants Methods for producing polyolefin films are well-know and include the techniques of casting films as thin sheets through narrow slit dies and blown-film techniques wherein an extruded tube of molten polymer is inflated to the desired bubble diameter and/or film thickness For example to produce a polymeric film the resins and additives may be introduced into an extruder where the resins are melt plastified by heating and then transferred to an extrusion die for formation into a film tube. Extrusion and die temperatures will generally depend upon the particular resin being processed and suitable temperature ranges are generally known in the art or provided in technical bulletins made available by resin manufacturers. Processing temperatures may vary depending upon process parameters chosen.

A film of the present invention may be oriented by stretching at a temperature above the glass transition temperature (Tg) of its constituent polymer(s) The resultant oriented film may exhibit greatly improved tensile and stiffness properties.

Conveniently a film πomnrisinπ a nrπnvlpnp hnmnnolvmpr is oripntpri at a temperature within a range of from about 145⁰C to 165°C. Orientation may be along one axis if the film is stretched in only one direction, or may be biaxial if the film is stretched in each of two mutually perpendicular directions in the plane of the film A biaxial oriented film may be balanced or unbalanced, where an unbalanced film has a higher degree of orientation in a preferred direction, usually the transverse direction Conventionally the longitudinal direction (LD) is the direction in which the film passes through the machine (also known as the machine direction or MD) and the transverse direction (TD) is perpendicular to MD Preferred films are oriented in both IVID and TD Orientation of the film may be achieved by any suitable technique For example in the bubble process the polypropylene film is extruded in the form of a composite tube which is subsequently quenched, reheated, and then expanded by internal gas pressure to orient m the TD and withdrawn at a rate greater than that at which it is extruded, to stretch and orient it in the MD Alternatively a flat film may be oriented by simultaneous or sequential stretching in each of two mutually perpendicular directions by means of a stenter, or by a combination of draw rolls and a stenter A preferred oriented film comprises biaxially oriented polypropylene (known herein as BOPP)₁ more preferably the BOPP film described in EP 0202812

The degree to which the film substrate is stretched depends to some extent on the ultimate use for which the film is intended, but for a polypropylene film satisfactory tensile and other properties are generally developed when the film is stretched to between three and ten preferably, seven or eight times its

;ach of TD and MD

After stretching the polymeric film substrate is normaiϊy neat-set, while restrained against shrinkage or even maintained at constant dimensions, at a temperature above the Tg of the polymer and below its melting point The optimum heat-setting temperature can readily be established by simple experimentation Conveniently a polypropylene film is heat-set at temperatures in the range from about 100^cC to about 180^rC Heat-setting may be effected by conventional techniques for example by means one or more of the following a stenter system, one or more heated rollers ie g as

- i 9 described in GB 1124886) and/or a constrained heat treatment (e g as described in EP 023776)

The film may comprise a major proportion of polypropylene such as isotactic polypropylene homopolymer, but also may comprise coextruded multilayer films where the polymer of at least one layer is isotactic polypropylene homopolymer and the polymer of one or both outer layers is a surface layer polymer having different properties to the isotactic polypropylene homopolymer

The sheet of the present invention may consist of only one layer, or the sheet may be multi-layered i e comprise a plurality of layers The layers can be combined by lamination or co-extrusion Preferably the sheet comprises at least three layers where at least one layer(s) are sandwiched between other layers such that none of such sandwiched !ayer(s) form eιthe^r surface of the sheet The treated region of the film may be located in just one in more than one, or in ail such layers

Thus for example a film of the invention may comprise a three layer film where the polymer of a central or core layer comprises one polymeric material The core layer may have a thickness of about 90 to about 98% of the tota! thickness of the film The remainder of such a three layer film may comprise two outer layers of another polymeric material with each outer layer having substantially identical thickness Preferably at least the core layer is treated In a coextruded film it may be convenient to treat all layers of the coextrudate In the case of a laminated film it may be desirable to treat the film prior to lamination, in which case only part of the laminated structure will have the treated region thereon - or it may in some cases be desirable to treat the film after lamination, in which case all of the laminated structure will have the treated region thereon Likewise with coatings - the treatment of the film to provide a treated region of substantially different opacity to the remainder of the film can take place before or after any such coating

Another film of the present invention may comprise a coextruded five layer film comprising a central core layer, two layers contiguous to the central core layer and two outermost layers where the central core layer and such contiguous layers comprise one polymeric materia! and the two outer layers comprise another polymeric material

Preferably the central core layer has a thickness at least about 70% more preferably at least about 80% and most preferably at least about 90% - even uμ iu auuut au /o ui i nui c ui u ic iuiet u ii^M iβaa ui u ic l in n π cici αuiy cαυn wι such contiguous layers has substantially the same thickness which is more preferably from about 1 % to about 6% most preferably from about 1 % to about 2%, of the total thickness of the film Preferably each outer layer has substantially the same thickness which is more preferably from about 1 % to about 6%, most preferably from about 1 % to about 2% of the total thickness of the film A film of the invention may also be made by lamination of two coextruded films.

One or more layers of the films of the film may be opaque. Other layers of the film may be opaque or transparent depending on the end use of the film.

Opaque layers may comprise voids introduced by stretch orienting such a layer containing spherical particles of a material higher melting than and immiscible with the layer material (e.g. if the layer comprises isotactic polypropylene homopoiymβr, then such particles may be, polybutyleneterephthalate, as shown, for example, in US 4632869 and US

4720716).

Multiple-layer films of the invention may be prepared in a range of thicknesses governed primarily by the ultimate application for which a particular film is to be employed. For genera! use films, having a mean thickness from about 2.5 μm to about 150 μm, preferably from about 4 μm to about 100 μm are suitable. For certain applications, such as packaging, preferred films have a mean thickness of from about 10 μm to 50 μm, most preferably from about 8 urn to about 40 μm.

If desired, before coating a sheet of the present invention (e.g. with a gas barrier coating of the present invention and/or any other coating and/or layer) may be subjected to a chemical or physical surface-modrfyϊng treatment to ensure that the coating and/or layer will better adhere to the sheet thereby reducing the possibility of the coating peeling or being stripped from the sheet. Known prior art techniques for surface pre-treatment prior to coating comprise, for example film chloπnation, i e exposure of the film to gaseous chlorine , treatment with oxidising agents such as chromic acid, hot air or steam treatment, flame treatment and the like A preferred treatment because of its simplicity and effectiveness is the so-called electronic treatment in which the sheet is passed between a pair of spaced electrodes to expose the sheet surface to a high voltage electrical stress accompanied by corona discharge

Optionally if even adhesion of the coating is desired an intermediate continuous coating of a primer medium and/or anchor coating can be applied to a sheet surface treated by any of the methods described herein Primer materials may comprise titanates and poly (ethylene imine) and may be applied as conventional solution coatings [such as poly (ethylene iminβ) applied as either an aqueous or organic solvent solution e g m ethanol comprising aboutO 5 wt % of the tmine] Another primer medium comprises the interpolyrπeribed condensation auyiic rθSiπs μiepβied in the presθ'icθ of a Ci ealkanol as described in either GB 1134876 (condensing amonoaldehyde with an interpolymer of acrylamide or methacrylamide with at least one other unsaturated monomer), or in GB 1174328 (condensing amonoaldehyde with acrylamide or methacrylamide and subsequently interpolymerising the condensation product with at least one other unsaturated monomer)

Trie film may comprise one or more additive materials Additives may comprise dyes pigments, colorants metallised and/or pseudo metallised

_ ^") 1 coatings (e g aluminium), lubricants, anti-oxidants, surface-active agents, stiffening aids, gloss-improvers prodegradants UV attenuating materials (e g UV light stabilisers) seaϊabiiity additives tackifiers anti-blocking agents, additives to improve ink adhesion and/or printability cross-linking agents (such as melamine formaldehyde resin) adhesive layer (e g a pressure sensitive adhesive), and/or an adhesive release layer (e g for use as the backing material in the peel plate method for making labels) Further additives comprise those to reduce coefficient of friction (COF) such as a terpolymer described in US 3753769 which comprises from about 2% to about 15% w/w of acrylic or methacrylic acid, from about 10% to about 80% w/w of methyl or ethyl acrylate and from about 10% to about 80% w/w of methyl methacrylate together with colloidal silica and carnauba wax

Still further additives comprise siip aids such as hot slip aids or cold slip aids caticfar^»trιril\/ clgrlA arrnce QI irfarvsc at about room temperature for example micro-crystalline wax Preferably the wax is present in the coating in an amount from about 0 5% io aboui 5 0% w/w more preferably from about 1 5% to about 2 5% w/w The wax particles may have an average size conveniently from about 0 1 μm to 0 6μm, more conveniently from about 0 12 μm to abut 0 30 μm

Yet further additives comprise conventional inert particulate additives, preferably having an average particle size of from about 0 2 μm to about

4 5μm more preferably from aoout 0 7 μm to about 3 0 μπτ» Decreasing the particle size improves the gloss of the film The amount of additive preferably spherical incorporated into the or each layer is desirably in excess of about 0 05% preferably from about 0 1 % to about 0 5% for example about 0 15% by weight Suitable inert particulate additives may comprise an inorganic or an organic additive or a mixture of two or more such additives

Suitable particulate inorganic additives include inorganic fillers such as talc and particularly metal or metalloid oxides such as alumina and silica Solid or hollow, glass or ceramic micro-beads or micro-spheres may also be employed A suitable organic additive comprises particles preferably spherical, of an acrylic and/or methacrylic resin comprising a polymer or copolymer of acrylic acid and/or methacrylic acid Such resins may be cross- linked, for example by the inclusion therein of a cross-linking agent, such as a methylated melamineformaldehyde resin Promotion of cross-linking may be assisted by the provision of appropriate functional groupings such as hvrfrnw rarhny_*/ anri amtrlo πmnninπς in thp arrvlir and'nr mptharrvlir polymer

Yet still further additives comprise fumed silica for the purpose of further reducing the tack of a coating at room temperature The fumed silica is composed of particles which are agglomerations of smaller particles and which have an average particle size of for example from about 2 μm to about 9μm preferably from about 3 μm to about 5 μm and is present in a coating in an amount for example from about 0 1 % to about 2 0 % by weight preferably about 0 2% io about 0 4% by weignt Some or all of the desired additives listed above may be added together as a composition to coat the sheet of the present invention and/or form a new layer which may itself be coated (i.e. form one of the inner layers of a final multi- layered sheet) and/or may form the outer or surface layer of the sheet, Alternatively some or all of the preceding additives may be added separately and/or incorporated directly into the bulk of the sheet optionally during and/or prior to the sheet formation (e.g. incorporated as part of the original polymer composition by any suitable means for example compounding, blending and/or injection) and thus may or may not form layers or coatings as such. These conventional other coatings and/or layers may thus be provided on top of or underneath the gas barrier coatings of the present invention and may be in direct contact thereto or be separated by one or more other intermediate layers and/or coats.

Such additives mav be added to the oolvmer resin before the film is made or may be applied to the made film as a coating or other layer. If the additive is added to the resin, the mixing of the additives into the resin is done by mixing it into molten polymer by commonly used techniques such as roll-milling, mixing in a Banbury type mixer, or mixing in an extruder barrel and the like. The mixing time can be shortened by mixing the additives with unhealed polymer particles so as to achieve substantially even distribution of the agent in the mass of polymer, thereby reducing the amount of time needed for intensive mixing at molten temperature The most preferred method is to compound the additives with resin in a twin-screw extruder to form concentrates which are then blended with the resins of the film structure immediately prior to extrusion

Formation of a fslm of the invention (optionally oriented and optionally heat-set as described herein) which comprises one or more additional layers and/or coatings is conveniently effected by any of the laminating or coating techniques well known to those skilled in the art

For example a layer or coating can be applied to another base layer by a coextrusion technique in which the polymeric components of each of the layers are coextruded into intimate contact while each is still molten Preferably, the coextrusion is effected from a multi-channel annular die such that the molten polymeric components constituting the respective individual layers of the multi-layer film merge at their boundaries within the die to form a sinnie composite Structure which is then eluded from a common die orifice in the form of a tubular extrudate

A film of the invention may also be coated with one or more of the additives described herein using conventional coating techniques from a solution or dispersion of the additive in a suitable solvent or dispersant An aqueous latex (for example prepared by polymerising polymer precursors of a polymeric additive) in an aqueous emulsion in the presence of an appropriate emulsifying agent is a preferred medium from which a polymeric additive or coating may be applied Coatings and/or layers may be applied to either or both surfaces of the sheet The or each coating and/or layer may be applied sequentially simultaneously and/or subsequently to any or all other coatings and/or layers If a gas-barrier coating of the present invention is applied to only one side of the sheet (which is preferred) other coatings and/or layers may be applied either to the same side of the sheet and/or on the reverse (other) side of the sheet

A coating composition may be applied to tne treated surface of sheet (such as the polymer film) in any suitable manner such as by gravure printing roll coating rod coating dipping spraying and/or using a coating bar Solvents diluents and adjuvants may also be used in these processes as desired The excess liquid (e g aqueous solution) can be removed by any suitable means such as squeeze rolls doctor knives and/or air knives The coating composition will ordinarily be applied in such an amount that there will be dpnnςjtpri fnllnwinn rlrvinπ a Qmnnth HiQtπhi itprl IPIWPΓ hm/tnn a thickness of from about 0 02 to about 10 μm preferably from about 1 to about 5 μm In geneia! the thiokπtjbb of the applied coating ib buoh ihat it is sufficient to impart the desired characteristics to the substrate sheet Once applied to the sheet a coating may be subsequently dried by hot af radiant heat or by any other suitable means to provide a sheet of the present invention with the properties desired (such as an optionally clear optionally substantially water insoluble highly oxygen impermeable coated film useful for example in the fields of authentication packaging labelling and/or graphic art)

IE It would also be possible to use combinations of more than one of the above methods of applying additives and/or components thereof to a film. For example one or more additives may be incorporated into the resin prior to making the film and the one or more other additives may be coated onto the film surface.

In a multi-layer film in accordance with the invention having at least a substrate later and a skin layer, the skin layer is preferably ink printable. The skin layer has a thickness of from about 0.05μm to about 2μm, preferably from about 0.1 μm to about 1.5μm, more preferably from about 0.2μm to about 1.25μm, most preferably from about 0.3μm to about 0.9μm.

Embodiments of a film and according to the present invention will now be described, by way of example only, with reference to the accompanying drawings and examples, in which: Figure 1 is an illustration (not to scale) of a film according to one aspect of the present invention; Figure 2 is a magnified illustration (not to scale) of the film of Figure 1 from the direction of arrow A; Figure 3 shows details of a solid male embossing die for logo embossing, dimensions a 10.5mm, b 2mm, c 0.25mm having flat faced characters engraved at a 30° side angle, 0.3mm deep with softened (slightly radiused) sharp edges; and Figure 4 shows details of a dot-matrix male embossing die for logo embossing, dimensions a 21mm, b 4mm, c 0.5 mm having a 25° rake angle, the characters being made up from 0.1mm diameter dots, 0.2mm deep at minimum possible pitch, the back and front die face being skimmed to produce accurate flat surfaces on blanks 20 x 35 x 3mm. A cavitated polymeric films is a polymeric film which contain cavities or "voids" within the material. It is possible to eliminate these cavities in the film, and thereby "flatten" or density the film using a combination of pressure and temperature focused on the film.

If cavitated polymeric film is exposed to heat from external sources then large- scale macro-deformation of the film can occur, which is undesirable for applications where a localised densification is required, it has been found that by using ultrasonic energy, heat is generated internal to the film, making it much easier to localise the affected area on the film.

Suitable equipment for producing the densified regions in the film comprise a horn and an anvil for applying pressure to two surfaces of the film, where the horn is capable of oscillating at ultrasonic frequencies. An exemplary machine with the desired characteristics is that supplied by Herrrmann Uitraschalitechπik, which has a horn capable of oscillating at 3OkHz. The anvil/horn can be designed to apply pressure only to designated regions on the film where the densification is to occur. In the regions where the combination of pressure and ultrasonic radiation is applied to the cavitated film, the cavities in the film collapse and are eliminated. This increases the density of the film in the designated regions without reducing the strength of the film. An unexpected characteristic of the densϊfϊed regions that was observed was that where the cavities in the film had collapsed, it had resulted in the film becoming less opaque in those regions, and in some cases the regions had become substantially transparent,

Figure 1 is an illustrative example of the opaque film 10 according to one embodiment of the present invention, having two regions of increased density and reduced opacity.

The first region 12 is in the form of an oval, but in practice it could be arranged in any pattern, for example a company logo or alphanumeric characters. The region 12 proves a two-way window though the opaque film which could be used, for example, as an inspection window to view an object on the other side of the film if the film was being used as part of a packaging, or as in window through which light (not limited to viable light) could radiate as part of a display console. If it is desirable, the recessed surface of the film could be utilised IOΓ its tctctiie or aestnΘtϊc characteristics.

The second region 14 is in the shape of a narrow band which extends from one edge of the film 10 to the opposite edge of the film 10. This second region

14 provides a narrow "slit" window in the film, and can also be used as a fold

Creating folds in this manner is advantageous because the fold region is well defined and there is no degradation in the strength of the film. Figure 2 is an illustration showing how the densification process changes the profile of the film. The densified region 14 is thinner (smaller gauge) than the untreated film 10 but because the change is the result of the voids in the film collapsing there is no ripple effect on the surrounding film Advantageously there is also no weakening of the film in the densified region as no material is displaced in the process 5

EXAMPLES

Example 1 O Commercially available cavitated polypropylene-based film available from Innovia Films Ltd under the designation TB22160 was folded and sealed using the Herrmann Ultraschalltechnik device at energy levels of 3OJ 40J

5OJ and 8OJ and at pressures of 1000 or 1200N Excellent seal strength was obtained with vastly improved clarity of the film in the seal region The same <; pffprt in fprmς nf rlarrfv WP»Q nntpd yuhpn the (jltrasnnir treatment was conducted on a single unfolded sheet of film without forming any seal

Example 2 0 Commercially available coextryαed polypropylene film available from Innovia Films Ltd under the designation GLT20 was embossed with a steel anvil incorporating the Innovia films logo as detailed in Figure 3 using the Herrmann UltraschaSltechnik device at energy levels of 30 35 & 40J and at pressures of 1000 1200 ⁱ500 and 1800N The embossed logo produced in the turn was5 found to have excellent clarity & definition of image By increasing the applied energy &/or pressure the degree of definition & in particular the level of tactility could be affected by controlling the depth of the emboss produced.

To prevent the anvil cutting or spϊitting the film is was found necessary to engrave the embossing tool with a slight angle of at least 10 degrees & preferably 25 to 35 degrees. Additionally it was found to be advantageous to machine a slight radius to the edges of the embossing pattern to further prevent the film being split during the embossing process.

Example 3

Embossing dies with the Innovia logo design were produced in a wide range of dimensions ranging from an overall size of 10.5 x 2mm to 43 x 8mm. It was found during experimentation that embossing could readily be achieved in thick DolvoroDvlene films (> SOiim) but that for the thin films tvoicallv used in the tobacco overwrap applications (< 25μm) only the smallest dimension logo could easily be embossed with sufficient definition & tactiifty. To overcome this limitation on thin films an embossing tool was manufactured whereby the desired larger image was constructed from a plurality of smaller component images - in this case 0.1 mm diameter raised dots, as shown in Figure 4.

CommercialSy available coextruded polypropylene film available from Innovia

Films Ltd under the designation GLT20 was embossed with the dot matrix die using the Herrmann Ultraschalltechnik device at energy levels of 10, 15 & 2£U and at pressures of 800, 1000, and 1200N. The embossed logo produced in the film was found to have excellent clarity & definition of image but reduced tactility It can be seen that the energy & pressure required to achieve the emboss is significantly reduced for the dot matrix image compared to a solid image

Example 4

Production variants of GLT20 were produced where 0 075% of a UV fluorescent material was incorporated into the core layer during extrusion The resultant film was embossed the using the Herrmann Ultraschalltechnik device using the same conditions and parameters as for standard GLT20 When the embossed film was exposed to UV light of the correct wavelength the embossed image strongly fluoresced providing a significant and desirable visual enhancement to the embossed feature

Example 5

Production variants of GLT20 were produced where 0 075% of a photochrome material was incorporated into the core layer during extrusion The resultant film was embossed the using the Herrmann Ultraschalltechnik device using the same conditions and parameter as for standard GLT20 When the embossed film was exposed to UV light of the correct wavelength the photochromic material in the film generated a colour change (for example from coiouriess to purple) that was significantly more prominent in The embossed areas relative to the non-embossed areas providing a significant and desirable visual enhancement to the embossed feature.

Claims

1. A polymeric film, the film having at least one treated region therein having an altered appearance and/or tactility compared to the surrounding film, the treated region being formed by means of ultrasonic treatment of the film in that region,

2. A polymeric film according to claim 1 wherein the treated region is formed by embossment and/or debossment by means of ultrasonic treatment of the film in that region.

3. A film as claimed in claim 1 or claim 2 wherein the altered appearance is highlighted by the presence of an additive in the film which enhances the contrast between a the treated region and the surrounding film,

4. A film as claimed in claim 3 wherein the altered appearance is enhanced by virtue of a difference in opacity, thickness and/or a light- piping effect,

5. A film as claimed in claim 3 or claim 4 comprising a fluorescent additive,

6. A film as claimed in any of claims 3 to 5 comprising a photochromic additive. A film as claimed in any of claims 2 to 6 comprising a pigmented additive

A film as claimed in any preceding claim wherein the treated region of the film is substantially transparent and either clear or pigmented

A film as claimed in any preceding claim wherein the altered appearance is at least partially due to the film having at least one region thereon having reduced opacity compared to the surrounding film the region being formed in the film by means of ultrasonic treatment of the film in that region

A film as claimed in claim 9 which is substantially opaque

A film according to claim 9 or claim 10 having (in the untreated region) an opacity of at least about 25%

A film according to any of claims 9 to 11 the opacity of which (in the untreated region) is at least partially provided by the presence in the film of voided (or cavitated) reg'ons

A film according to darn 12 wherein such voided regions are created by providing in the film at teas! one voiding agent

A film according to claim 13 Λ/herem the voiding agent is selected from optionally particulate organic inorganic or poiymeπc materials and mixtures of two or more thereof A film according to any one of claims 11 to 14 wherein the opacity of the film is supplemented with one or more opacifying agents

A film according to any one of clams 9 to 15 wherein the opacity of the film in the treated region is at least about 10% lower than the untreated film

A film as claimed in any preceding claim having a raised boundary around an embossed/ debossed feature

A film as claimed in any preceding claim wherein the non- embossed/debossed regions comprise film which has a function which changes on application of heat, or which is damaged on application of heat

A film as claimed in claim 18 wherein the non-embossed/debossed regions comprise thermally sensitive material for example thermally shπnkable film

A fflm according to any preceding claim wherein the density of the treated region of the fnm is greater than the density of the untreated film

A film according to any preceding claim wherein the treated region of the film is of a narrower gauge than the rest of the film

^"*& A film according to any preceding claim having an embossed feature made up from a multiplicity of smaller components

A film according to claim 22 wherein the embossed feature is a dot matrix pattern

A film according to any preceding claim which is an overwrap film a packaging film or a labelling film

An article of commerce being overwrapped packaged or labelled with the film of claim 24

A method of creating a region of altered appearance and/or tactility in a polymeric film comprising the steps of a selecting one or more regions on a polymeric film to have an altered appearance and/or tactility h nrrwirlinπ a firςt mpanς ^ rrannpH tn annlv in th<=» selected regions of a first surface of the polymeric film o piuvfdiπy a beυυrid mearib anangeu to apply prebbure to the selected regions of a second surface of the polymeric film opposite the first surface d resonating the first means at an ultrasonic frequency so as to cause localised heating in the polymeric film at the selected regions of the polymeric film

19 A method as claimed in claim 28 wherein the film contains a fluorescent photochrome and/or pigmented additive, voiding agent and/or other additive to enhance the contrast of treated areas

A method as claimed in claim 26 or claim 27 wherein the film is a cavitated polymeric film the altered appearance is due to reduced opacity and increased density and the first means is resonated at an ultrasonic frequency so as to increase the density and collapse the cavities m the polymeric film at the selected regions of the polymeric film

A method according to any of claims 26 to 28 wherein the first means to apply pressure to the selected regions of the polymeric film comprises a horn or sonotrode resonating at ultrasonic frequency

A method according to any of claims 26 to 29 wherein the second means to appiy pressure to the selected regions of the polymeric film comprises an anvil

A method according to any one of claims 26 to 30 wherein the first and/or second means to apply pressure to the selected regions comprises a patterned surface

A method according to any one of claims 26 to 31 wherein the f'lrr is a thermally sensitive film A method according to any one of claims 26 to 32 wherein the ultrasonic frequency is within the range 20 - 40 kHz

A method according to any one of claims 26 to 33 wherein the first or second means arranged to apply pressure to the selected regions of the polymeric film is in the form of an annular embossing tool comprising raised embossing feature(sj situated on the outside circumference of the tool

A method according to any one of claims 26 to 34 wherein the first or second means arranged to apply pressure to the selected regions of the polymeric film have an embossing feature made up from a multiplicity of smaller components

A method according to claim 35 wherein the embossing feature is a dot matrix

A method accoidiήg to any one of claims 26 to 36 which is suitable for continuous processing of the film

An apparatus for creating a region of altered appearance and/or tactihty in a polymeric film comprising a first means capable of resonating at ultrasonic frequency arranged to apply pressure to selected regions of a first surface of the polymeric film and a second means arranged to apply pressure to selected regions of a second surface of the polymeric film opposite the first surface wherein the features of the apparatus are suitable for carrying out the method of any of claims 26 to 37.