GB2529517A

GB2529517A - Method For Preparing A Three-Dimensional Article

Info

Publication number: GB2529517A
Application number: GB1510792.3A
Authority: GB
Inventors: Gemma Osborne; Sean Slater
Original assignee: Fujifilm Speciality Ink Systems Ltd
Current assignee: Fujifilm Speciality Ink Systems Ltd
Priority date: 2014-07-11
Filing date: 2015-06-19
Publication date: 2016-02-24
Anticipated expiration: 2035-06-19
Also published as: GB2529517B; GB201412384D0; GB201510792D0

Abstract

A method for preparing a printed article having a desired three-dimensional shape the method comprises the steps of applying a curable composition 3b to selected areas of a printed sheet 1b; curing the curable composition 3b present on the printed sheet 1b, thereby providing a laminate comprising the printed sheet 1b and a discontinuous layer of cured composition 3b; and forming the laminate into a desired three-dimensional shape. The laminate may be formed into a three dimensional shape using a mold (4, Fig.2). There is also provided a substantially colourless curable composition comprising (a) 5 to 50 wt% of cycloaliphatic compound(s) comprising one ethylenically unsaturated group; (b) 10 to 60 wt% of compound(s) comprising two ethylenically unsaturated groups; and (c) 0 to 10 wt% of compound(s) comprising three or more ethylenically unsaturated groups. Component (a) may comprise at least two cycloaliphatic compound(s) comprising one ethylenically unsaturated group and may comprise isobornyl acrylate.

Description

Intellectual Property Office Application No. GB1510792.3 RTTVI Date:tS December 20t5 The following terms are registered trade marks and should be read as such wherever they occur in this document: Conan Windows Irga cure Darocur Intellectual Property Office is an operating name of the Patent Office www.gov.uk/ipo

METHOD FOR PREPARING A THREE-DIMENSIONAL ARTICLE

This invention relates to a method for preparing a printed article having a desired three-dimensional (3D") shape.

The use of ink jet printers to print paper documents in the small office and home field has been known for sometime. In some cases, it is desirable to apply a protective coating to the printed paper. A protective coating can improve the durability of the printed image and also change its appearance by creating a gloss or matt finish.

Typically protective coatings are applied as a continuous layer to the entire surface of the printed paper in a process called flood coating'. In an alternative but less commonly used process, the protective coating is applied to printed paper in only selected areas, instead of the entire image-printed surface, to highlight a part of the printed paper. For example, a protective coating maybe applied to a printed company name or logo in order to add gloss and make the appearance of that area stand out from the rest of the document. The application of a protective coating to highlight a selected area of a printed document is sometimes called spot coating'.

US 4,841,903 describes an offset printing machine which can be used to apply protective coatings to copy paper using flood coating' or spot coating'.

Protective coatings are used in graphics applications to prevent unformed (i.e. flat) prints from sticking together when stacked.

In the field of preparing 3D, printed articles it is known to first print a substrate and then form the printed substrate onto a desired 3D shape by, for example, pressing the printed substrate onto a mold. However when the printed substrate carries a protective layer over its entire surface, the step of forming the desired 3D shape can cause the protective layer to crack and flake-off, giving rise to an unsightly appearance. There is therefore a need for a method for preparing printed articles which are protected against subsequent abrasion, have an attractive appearance and which remain so even when formed into a desired 3D shape, e.g. by molding.

WO 03/020529 describes the application of a protective topcoat to the whole of a substrate, rather than to selected areas of the substrate.

Wa 2004/007207, US 4,841,903, US 2011/249051, EP 481,01 91 and GB 2488097 describe process for preparing flat, two-dimensional substrates.

Therefore these documents do not address the technical problem of protective layer cracking when forming a laminate into a desired three-dimensional shape.

According to the present invention there is provided a method for preparing a printed article having a desired three-dimensional shape, the method comprising the steps: (a) applying a curable composition to selected areas of a printed sheet; (b) curing the curable composition present on the printed sheet, thereby providing a laminate comprising the printed sheet and a discontinuous layer of cured composition; and (c) forming the laminate into a desired three-dimensional shape.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. is is a schematic view of a laminate comprising a printed sheet and a continuous protective layer applied by flood-coating, shown before and after bending (Comparative).

Fig. lb is a schematic view of a laminate comprising a printed sheet and a discontinuous protective layer applied by the method of the present invention, shown before and after bending.

Fig. 2 is a schematic view of a 3D article obtained by the present method, together with a mold.

Fig. 3 shows a 3D article made by a flood-coating process (Comparative) and two 3D articles made by the presently claimed method.

Fig. 4 is a schematic illustration of four patterns in which the curable composition may be applied to selected areas of a printed sheet.

Fig. 5 is a photograph of a laminate made by the method of the present invention (except that the sheet was unprinted), taken at x 10 magnification.

Fig. 6 is a photograph of three flat laminates made by steps (a) and (b) of the method of the present invention (except that the sheet was unprinted) using different curable compositions, taken at x 10 magnification.

The left side of Fig. la is a schematic view of a flat laminate comprising a sheet la, print 2a and continuous protective layer 3a prepared by flood coating (Comparative). The right side of Fig. is schematically shows what happens when the laminate of Fig la is bent. The continuous coating 3a is damaged through cracking, affecting its visual appearance and creating random, unprotected areas where the protective layer has flaked-off.

The left side of Fig. lb is a schematic view of a flat laminate comprising a sheet 1 b, print 2b and a discontinuous protective layer 3b prepared by the method of the present invention. The right side of Fig. lb schematically shows what happens when the laminate of Fig lb is bent. The discontinuous coating 3b is not damaged because of the gaps between islands of cured protective coating. As a result, the visual appearance of the laminate is not significantly affected by bending the laminate.

Fig. 2 is a schematic view of a printed article having a desired 3D shape, obtained by the present method. The printed article comprises a sheet 1 b, print 2b and a discontinuous protective layer 3b. The article is shown above a mold 4 used to form the laminate into the desired 3D shape.

In Fig. 3, photograph A, shows a 3D article made by pressing a sheet carrying a continuous (flood-coated) protective layer onto a mold to form a stylized human face mask. The protective layer has cracked, resulting in significant and unsightly banding on the face mask. In contrast, photographs B and C show analogous human face masks prepared by the present method with a curable composition (and cured composition) % coverage (%C) of 25% and 11% respectively. The resultant face masks in photographs B and C have a cleaner and more homogenous finish than the face mask in photograph A, with the face mask in photograph C being best of all due to its smooth finish.

The photograph of Fig. 5 shows part of a 3D article made by the method of the present invention except that the sheet was unprinted so that the pattern of the discontinuous layer of cured composition can be seen more clearly. The photograph is taken at x 10 magnification using a confocal microscope. One can clearly see that the curable composition has been applied to selected areas of the sheet in a patternwise manner, to form a symmetrical and repeating pattern of curable composition islands on the sheet. In this photograph the islands of curable composition have been cured. The coverage (%C) in Fig. 5 is 8%, the islands have an average diameter of 324pm and are on average 1 72pm apart.

The printed sheet typically comprises a formable sheet material carrying a printed image on one or both sides. The printed sheet may be prepared by printing an ink onto a formable sheet material. The preferred printing process is ink jet printing. The preferred ink is a radiation-curable ink, especially a UV-curable ink.

Suitable radiation-curable inks may be obtained from FUJIFILM Speciality Ink Systems in the United Kingdom.

The preferred formable sheet materials are thermoformable sheet materials or thermosetting materials, especially thermoplastic materials. Typically the formable sheet material is not pliable at room temperature (e.g. 20°C), it becomes pliable or moldable when heated (e.g. to a temperature above 40°C or above 60°C) and returns to a non-pliable state when returned to room temperature (e.g. 20°C). Thermoplastic sheet materials can be subjected to the cycle of heating, forming into a desired 3D shape and cooling many times to make different 3D articles in succession. In contrast, thermosetting materials can be heated and formed into the desired 3D article only once, due to the formation of irreversible chemical bonds during the first heating step.

The formable sheet material typically has a glass transition temperature (Yg) below its melting point (Yr). Preferably the formable sheet material has a Yg in the range 30 to 250°C, more preferably 65 to 120°C.

The formable sheet material preferably has an average thickness in the range 0.1 to 20 mm, more preferably 0.5 to 10 mm.

Examples of formable sheet materials include polybenzimidazole (e.g. Celazole® PBI), polyethylene (e.g. high density polyethylene and low density polyethylene), polypropylene, polystyrene, polyvinyl chloride acrylonitrile butadiene styrene, polyethylene terephthalate, polyethylene terephthalate glycol, polycarbonate and acrylic polymers, e.g. polymethyl methacrylate and composite material comprising an acrylic polymer and an inorganic material (e.g. alumina trihydrate) such as, for example, the CorianTM composite materials available from DuPont.

The curable composition may be applied to selected areas of the printed sheet by any suitable technique, including screen printing or gravure printing and especially ink jet printing.

In a preferred embodiment the curable composition is applied to selected areas of the printed sheet by means of an ink jet printhead comprising a nozzle plate having a surface energy of 10 to 30 mN/m or 10 to 40 mN/rn. The surface energy of the material used to construct the nozzle plate may be obtained from the manufacturer.

The surface energy of many materials can be found at http://www.surface-tension.de/solid-surface-energy. htm and in Properties of Polymers' by D.W. van Krevelen, ISDN 9780080548197, 2009, CHAPTER 8, TABLE 8.2 page 235. Although there exist several methods to calculate the surface free energy from contact angle measurements, the preferred method for the purposes of this invention is the Fowkes method. Details of the Fowkes method can be found in F.M. Fowkes, J. Adhesion Sci. Tech.,1, 7-27 (1987). In the Fowkes method, a drop of liquid with a known surface tension is placed on the surface whose energy is to be determined. The shape of the drop, specifically the contact angle, and the known surface tension of the liquid are the parameters which can be used to calculate the surface energy of the support. The liquid used for such experiments is referred to as the probe liquid, and several different probe liquids are used. Preferably 3 or 4 different probe liquids to calculate the average surface energy.

The contact angle of the material used to construct the nozzle plate may be determined using a VCA-2500XE Contact Angle Surface Analysis System from AST Products Inc. The contact angle may be measured from a photo taken within 2 seconds, mostly within 1 second, after applying the droplet of liquid to the material under investigation. The surface energy may then be calculated using the Fowkes method as presented in the software program Drop Shape Analysis (DSA) for Windows, Version 1.90.0.13 from KrUss. In this method, preferably four single-component liquids of different polarities are used to determine the surface energy.

The curable composition may be applied to selected areas of one side of the printed sheet or to selected areas of both sides of the printed sheet.

Typically the printed sheet comprises a printed face and an unprinted face or the printed sheet comprises two printed faces.

Applying the curable composition to selected areas of a printed face provides protection against mechanical damage and reduces or completely avoids cracking of the cured composition when step (c) is performed.

If desired the curable composition may be applied to the printed sheet in order to act as a release agent. Thus the curable composition is optionally applied to selected areas of the unprinted face of a printed sheet comprising a printed face and an unprinted face, either instead of or in addition to the application of a curable composition to selected areas of the printed face. In the case of a printed sheet comprising two printed faces, the curable composition may be applied to selected areas of either or both of the printed faces, e.g. to provide the desired release properties and/or protection against mechanical damage and cracking.

When the process comprises applying a curable composition to selected areas of both faces of the printed sheet, the composition applied to one face may be different to the composition applied to the other face or, more preferably, the curable compositions applied to both faces are identical (i.e. they contain the same components and the components are present in the same amounts).

The curable composition is preferably applied to selected areas of the printed sheet in a patternwise manner, for example to form a symmetrical and repeating pattern of curable composition islands on the printed sheet. Examples illustrating suitable patterns are shown schematically in Fig. 4. The islands can be of any shape, for example round, oval, polygonal (e.g. square, rectangular, hexagonal etc), star-shape, potato-shape, doughnut-shape, floral-shape, raspberry shaped and so on. The islands may all be the same shape or they may be of two or more different shapes. Examples of island shapes are shown in Fig. 4. Typically the curable composition is applied to the printed sheet in step (a) such that islands of curable composition are provided on the printed sheet. When deciding what pattern to applying the curable composition to selected areas of a printed sheet in order to form the discontinuous layer, one will usually aim for a pattern which (when the curable composition is cured) provides good protection for the printed sheet and does adversely affect the formability of the laminate in step (c). One will therefore generally apply the curable composition in step (a) to provide islands of curable composition which, when cured, are sufficiently large and close together to provide good protection for the printed sheet while not being so large and close together to interfere with forming step (c) or to crack or flake-off in step (c).

Bearing the above in mind, the islands preferably have an average diameter of at most 400pm. In this way, step (b) may be used to provide a laminate comprising the printed sheet and a discontinuous layer of cured composition in the form of islands having an average diameter of at most 400pm. The aforementioned islands preferably have an average diameter of at least 10pm. The aforementioned islands preferably have an average height of 10 to 100pm. Preferably the average distance between the aforementioned islands is 5 to 500pm.

Preferably the discontinuous layer of cured composition covers from 3 to 49%, more preferably 4 to 42%, especially 5 to 37%, more especially 5 to 26%, particularly 7 to 15% of the side of the printed sheet to which it has been applied.

One may determine the % coverage of the cured composition on the side of the sheet to which it has been applied (%C) using Formula (1): = (Acovered/Atotal) x 100% Formula (1) wherein: %C is as defined above; Acovered is the area of the printed sheet covered by the cured composition; Atotai is the total area of printed sheet.

The areas Acoveled and A102 refer to the relevant side of the printed sheet to which the curable composition has been applied.

The curable composition is preferably a thermally-curable composition or a radiation-curable composition, especially a UV-curable composition.

Preferred curable compositions comprise an initiator (e.g. a photoinitiator) and one or more radiation-curable compounds.

The radiation-curable compounds preferably comprise one or more ethylenical ly unsaturated groups.

The compounds having one or more than one ethylenically unsaturated group are optionally monomeric, oligomeric or polymeric, with monomeric compounds being preferred.

Preferred ethylenically unsaturated groups are vinyl groups, (meth)acrylic groups, especially (meth)acrylate and (meth)acrylamide groups. Examples of ethylenically unsaturated groups include acrylamide (H2G=GHGON<) groups, methacrylamide (H2C=C(CH3)CONc) groups, acrylate H2C=CHCO2 groups and methacrylate (H2C=C(CH3)C02-) groups.

Preferably the curable composition is a substantially colourless, curable composition comprising: (a) 5 to 50 wt% of compound(s) (especially cycloaliphatic compounds) comprising one ethylenically unsaturated group; (b) 10 to 60 wt% of compound(s) comprising two ethylenically unsaturated group; and (c) 0 to 10 wt% of compound(s) comprising three or more ethylenically unsaturated groups.

Preferably component (a) comprises at least two cycloaliphatic compound(s) comprising one ethylenically unsaturated group.

Preferably component (a) comprises isobornyl acrylate.

In a preferred substantially colourless composition component (a) comprises (al) isobornyl acrylate; and (a2) one or more further cycloaliphatic compound(s) comprising one ethylenically unsaturated group; wherein the weight ratio of component(al):(a2) is in the range 0.7:1 to 1.3:1, preferably in the range 0.8:1 to 1.2:1, more preferably in the range 0.9:1 to 1.1:1 and especially preferably the weight ratio of component (al):(a2) is approximately 1:1.

The aforementioned substantially colourless, curable compositions form a further feature of the present invention.

For the avoidance of doubt, "comprising one ethylenically unsaturated group" means having one, and only one, ethylenically unsaturated group.

"Comprising two ethylenically unsaturated groups" means having two, and only two, ethylenically unsaturated groups.

As examples of compounds having one ethylenically unsaturated group there may be mentioned (meth)acrylamide, (meth)acryloylmorpholine, isobutoxymethyl(meth)acrylam ide, isobornyloxyethyl (meth)acrylate, isobornyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, ethyldiethylene glycol (meth)acrylate, t-octyl (meth)acrylamide, diacetone (meth)acrylamide, lauryl (meth)acrylate, dicyclopentadiene (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, dicyclopentenyl (meth)acrylate, N5N-dimethyl(meth)acrylamide, tetrachlorophenyl (meth)acrylate, 2-tetrachlorophenoxyethyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, tetrabromophenyl (meth)acrylate, 2-tetrabromophenoxyethyl (meth)acrylate, 2-trichlorophenoxyethyl (meth)acrylate, tribromophenyl (meth)acrylate, 2-tribromophenoxyethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, N-vinylcaprolactam, N-vinylpyrrol idone, phenoxyethyl (meth)acrylate, butoxyethyl (meth)acrylate, pentachiorophenyl (meth)acrylate, bornyl (meth)acrylate and methyltriethylene diglycol (meth)acrylate and mixtures comprising two or more thereof.

Commercially available compounds having one ethylenically unsaturated group include: SR256 (2(2-ethoxyethoxy ethyl acrylate), SR339 (2-phenoxy ethyl acrylate), SRS3I (cyclic trimethylolpropane formal acrylate), SR4Q5B (caprolactone acrylate), SR535 (dicyclopentadienyl methacrylate), SR 506D (isobornyl acrylate), SR423 (isobornyl methacrylate), SR 313A, 313B and 313D (C12-C14 alkyl (meth)acrylates), all available from Sartomer Co. Inc. and Ciba Ageflex FM6 (n-hexyl (meth)acrylate available from Ciba Specialty Chemicals).

As examples of compounds having more than one ethylenically unsaturated group there may be mentioned ethylene glycol di(meth)acrylate, dicyclopentenyl di(meth)acrylate, triethylene glycol diacrylate, tetraethylene glycol di(meth)acrylate, tricyclodecanediyldimethylene di(meth)acrylate, tris(2-hydroxyethyisocyanurate d i(meth)acrylate, tris(2- hydroxyethyisocyanurate tri(meth)acrylate, caprolactone-modified tris(2-hydroxyethyisocyanurate tri(meth)acrylate, trimethylolpropane tri(meth)acrylate, E0-modified trimethylolpropane tri(meth)acrylate, P0-modified trimethylolpropane tri(meth)acrylate, tripropylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, polyester di(meth)acrylate, polyethylene glycol di(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol tetra(meth)acrylate, caprolactone-modified dipentaerythritol hexa(meth)acrylate, caprolactone-modified dipentaerythritol penta(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, EQ-modified bisphenol A di(meth)acrylate, P0-modified bisphenol A di(meth)acrylate, EQ-modified hydrogenated bisphenol A di(meth)acrylate, P0-modified hydrogenated bisphenol A di(meth)acrylate, EQ-modified bisphenol F di(meth)acrylate and mixtures comprising two or more thereof.

Commercially available compounds having more than one ethylenically unsaturated group include: SR 295 (pentaerythritol tetracrylate); SR 350 (trimethylolpropane trimethacrylate); SR 351 (trimethylolpropane triacrylate); SR 367 (tetramethylolmethane tetramethacrylate); SR 368 (tris(2-acryloxy ethyl) isocyanurate triacrylate); SR 399 (dipentaerythritol pentaacrylate); SR 444 (pentaerythritol triacrylate); SR 454 (ethoxylated (3) trimethylolpropane triacrylate); SR 8333 (tricyclodecane dimethanol diacrylate), SR 9041 (dipentaerythritol pentaacrylate ester) and CN964A85, available from Sartomer Co Inc. Preferably the curable composition comprises at least one compound having one (and only one) ethylenically unsaturated group and at least one compound having more than one (e.g. two or three) ethylenically unsaturated groups.

In a preferred embodiment the curable composition comprises one or more cycloaliphatic compounds comprising one ethylenically unsaturated group, e.g. one or more aliphatic (meth)acrylate compounds comprising a cyclohexyl and/or cyclopentyl group, e.g. from 5 to 30 wt% thereof.

Examples of (meth)acrylate compounds comprising a cyclohexyl and/or cyclopentyl group include isobornyl acrylate ( IBOA"), dihydrodicyclopentadienyl acrylate (DCPA") and (meth)acrylates of the Formula (1): CR) CIX Formula (1) wherein: each R independently is C14-alkyl; n hasavalue of 1,2 or3; and 0 isHorCH3; Preferred (meth)acrylates of Formula (1) include t-butylcyclohexyl acrylate (particularly 4-(t-butycycolexyl acrylate (TBCHA)), trimethyl cyclohexyl acrylate (particularly 2,4,6-trimethyl cyclohexyl acrylate (TMCHA)) and mixtures thereof.

TBCHA has the following structure: C42=CH.-j-O--{' Ni a TMCHA has the following structure:

N -

N

IBOA has the following structure: 1⁄4.

DCPA has the structure: When UV light is used to cure the curable material the composition preferably contains one or more photoinitiators. Whilst any commercially photoinitiators can be used which matches the radiation, those with a low tendency for yellowing are preferred. Examples of suitable photoinitators include alpha-hydroxyalkylphenones, such as 2-hydroxy-2-methyl-1 -phenyl propan-1 -one, 2-hydroxy-2-methyl-1 -(4-tert-butyl-) phenylpropan-1 -one, 2-hydroxy-[4 -(2-hydroxypropoxy)phenyl]-2-methylpropan-1 -one, 2-hydroxy-1 -[4-(2-hydroxyethoxy)phenyl]-2-methyl propan-1 -one, 1 -hydroxycyclohexylphenylketone and oligo[2-hydroxy-2-methyl-1 -{4-(1 -methylvinyphenyl}propanone], alpha-aminoalkylphenones, alpha-sulfonylalkylphenones and acylphosphine oxides such as 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, ethyl-2,4,6-trimethylbenzoylphenylphosphinate and bis(2,4,6-trimethylbenzoy-phenylphosphine oxide, benzophenone, 1-hydroxycyclohexyl phenyl ketone, benzil dimethylketal, bis(2,6-dimethylbenzoy-2,4, 4-trimethylpentylphosphine oxide and mixtures comprising two or more thereof. Such photoinitiators are known and commercially available such as, for example, under the trade names lrgacureTM, DarocurlM and LucerinTM (from BASF). An especially preferred photoinitiator is lrgacureTM 2959.

Where desired, a surfactant or combination of surfactants may be included in the composition, for example as a wetting agent or to adjust surface tension.

Commercially available surfactants may be utilized, including radiation-curable surfactants. Surfactants suitable for use in the composition include non-ionic surfactants, ionic surfactants, amphoteric surfactants, fluorinated surfactants and combinations thereof. Preferred surfactants are silicones, especially acrylated silicones, for example TegoradTM 2010 and TegoradTM 2100 from Evonik.

The curable composition preferably has a surface tension of 16 to 40 dynes, when measured at 25°C.

Preferably the curable composition is applied to selected areas of the printed sheet by means of an ink jet printer comprising a nozzle plate and the curable composition has a de-wetting time on the material from which the nozzle plate is constructed of <60 seconds, more preferably <50 seconds] especially <30 seconds, more especially <20 seconds. The dewetting time may be determined using the conditions described in more detail in the Examples. Preferably the curable composition is substantially colourless and/or transparent.

By substantially colourless" it is meant that the composition is colourless or only weakly coloured such that when it is applied to the printed sheet the print on the sheet remains visible through the composition, preferably without changing the colour of the underlying print.

When the curable composition is cured it preferably has a Tg >40°C, more preferably >60°C, and especially >80°C.

The curing may be performed by any suitable means. For example, when the composition is thermally curable, heat may be applied to either side or to both sides of the printed sheet carrying the curable composition, for example by the use of heated plates (resistive heaters, inductive heaters) or radiant heaters (heater bars, IR lamps, solid state IR).

When the composition is radiation-curable the curing may be performed by a method comprising irradiating the curable composition, for example using ultra-violet light or an electron beam. The source of radiation may be any source which provides the wavelength and intensity of radiation necessary to cure the composition.

The printed article may carry any image, for example, the image may be text, numbers, a picture or a combination of two or more thereof. The image may cover all or just a part of the sheet and may be any colour or combination of colours.

Preferably the curing uses ultraviolet light. Suitable wavelengths are for instance UV-A (390 to 320nm), UV-B (320 to 280nm), UV-C (280 to 200nm) and UV-V (445 to 395nm), provided the wavelength matches with the absorbing wavelength of any photoinitiator included in the curable composition.

Suitable sources of ultraviolet light include mercury arc lamps, carbon arc lamps, low pressure mercury lamps, medium pressure mercury lamps, high pressure mercury lamps, swirlflow plasma arc lamps, metal halide lamps, xenon lamps, tungsten lamps, halogen lamps, lasers and ultraviolet light emitting diodes.

Particularly preferred are ultraviolet light emitting lamps of the medium or high pressure mercury vapour type. In most cases lamps with emission maxima between 200 and 450nm are particularly suitable.

Preferably the laminate has an elastic modulus (Er") of: 4 x 106 to 6.7 x 1 o Pascal when measured at 80°C; 4 x 106 to 3 x 108 Pascal when measured at 100°C; and 4 x io6 to 2 x i08 Pascal when measured at 120°C. More preferably the laminate has an Er of: 5.9 x i07 to 1.9 x i08 Pascal when measured at 80°C; 2.9 x io7 to 6.6 x io7 Pascal when measured at 100°C; and 2.6 x io7 to 4.7 x io7 Pascal when measured at 120°C.

In an especially preferred embodiment, the laminate has an Er of: 8.3 x -1o7 to 1.5 x io Pascal when measured at 80°C; 3.6 x i07 to 5.4 x io7 Pascal when measured at 100°C; and 3.05 x i07 to 4.0 x io7 Pascal when measured at 120°C.

The Er may be measured using a kinematic viscoelasticity meter, as illustrated in the Examples below.

The Er of the laminate is measured before performing step (c).

Preferably the laminate is formed into the desired 3D shape by a method comprising heating the laminate to make the laminate pliable and contacting the pliable laminate with a mold. The laminate may be contacted with the mold by any suitable means, for example the laminate may be contacted with a mating mold to impart the desired 3D shape on the laminate. Preferably in step (c) the laminate is formed into a desired 3D shape step by a process comprising compression molding, blow molding or vacuum molding. Subsequently, the laminate may be cooled or allowed to cool. The cooling (e.g. to room temperature) freezes' the laminate in the desired 3D shape.

Optionally the method comprises the further step (d) of trimming the laminate.

The present method may be performed in a continuous or batchwise manner. For example, the method may be performed using an apparatus comprising: a curable composition application station; ii. a curing station; and iii. a station for forming a laminate into a desired 3D shape; and optionally iv. a trimming station.

Typically the apparatus comprises a means for transporting a printed sheet from station i. to station ii. and from station ii. to station iii. and, when apparatus comprises a trimming station, from station iii. to iv.

Optionally the apparatus further comprises an ink jet printer for providing the printed sheet. The printed sheet may be provided as a web to station i. where step (a) of the present method is performed, followed by station H. where step (b) of the present method is performed, followed by station iii. where step (c) of the present method is performed.

The curing station preferably comprises a curing device, for example a heater and/or irradiation lamp (e.g. a UV lamp).

The station for forming a laminate into a desired 3D shape preferably comprises a heater and a mold.

According to a second aspect of the present invention there is provided a laminate comprising a printed sheet and a discontinuous layer of cured composition comprising islands of cured polymer having an average diameter of from 100 to 400pm and optionally an average height of 10 to 100pm.

In one embodiment the printed sheet comprises at least one printed face and the discontinuous layer of a cured composition is present on said at least one printed face. In another embodiment the printed sheet comprises one printed face and one unprinted face and the discontinuous layer of a cured composition is present on said unprinted face.

According to a third aspect of the present inventions there is provided a printed article comprising a laminate according to the second aspect of the present invention formed into a desired 3D shape.

The preferences for the laminate according to the second aspect of the present invention and the printed article according to the third aspect of the present invention are as described above in relation to the method of the first aspect of the present invention and for brevity are not repeated here.

The invention will now be illustrated by the following, non-limiting

Examples.

The following abbreviations are used in the Examples: TMPTA is trimethylol propane triacrylate.

DPGDA is dipropylene glycol diacrylate.

DCPA is as defined above.

IBOA is as defined above.

SRB33S is tricyclodecane dimethanol diacrylate, from Sartomer.

MEHQ is the mono methyl ether of hydroquinone.

UV12 is a 3Owt% suspension of an aluminium tris (N-hydroxy-N-nitroso phenylaminato-O-O' salt in phenoxy ethyl acrylate. Therefore 0.32 parts of UV12 consisted of 0.096 parts of an aluminium tris (N-hydroxy-N-nitroso phenylaminato-O-O' salt and 0.224 parts of phenoxy ethyl acrylate having one acrylate group.

IPO is a photoinitiator (ethyl-2, 4, 6 trimethylbenzoylphenyl phosphinate).

hg 184 is an cx-hydroxy ketone photoinitiator (lrgacureTM 184).

Tegorad 2100 is a radiation-curable silicone acrylate, used as a wetting and flow additive.

CTFA is cyclic trimethyloipropane formal acrylate.

NPGPODA is neopentyl glycol propoxylate diacrylate.

NVC (OH-TEMPO) is N-vinyl caprolactam stabilized with hydroxy tempo at 1 ppm from ISP.

SR341 is 3-methyl 1,5-pentanediol diacrylate, from Sartomer.

CN964A85 an aliphatic urethane diacrylate diluted with 15% of TPGDA, available from Sartomer.

HIP is high impact polystyrene.

GMPTP is glycol-modified polyethylene terephthalate.

The Er values of the laminates described in Table 2 were measured using a kinematic viscoelasticity meter (Vibron DVA-225 (by IT Keisoku Seigyo KK) as follows, using the following settings: -the distance between clamps was 20 mm -the heating speed was 2°C/rn in, -the test temperature range was from 30° C to 200°C, and -the frequency is 1 Hz.

The Vibron DVA-225 apparatus generates what it refers to as real' and imaginary' elastic modulus data curves. For the avoidance of doubt, the Er values described herein are the real' Er values derived from the real' elastic modulus data curves.

Using the software supplied with the kinematic viscoelasticity meter a graph was generated showing the elastic modulus of the laminate on the vertical, logarithmic axis and the temperature (°C) on the horizontal, linear axis. The temperature of the laminate was increased at a rate of 2°C/mm and the elastic modulus of the laminate was measured as the heating progressed. The elastic modulus at 80°C, 100°C and 120°C were recorded.

Abrasion Resistance ("AR") -in order to test the abrasion resistance the flat described in the Examples and Comparative Example carrying the cured composition were abraded using a Calibrase CS-b abrasion resistance testing device fitted with a Taber 5750 reciprocating wearaser', set under a 2.5N load and working at a speed of 30 cycles per minute for 500 cycles. The printed sides were then visually assessed abrasion resistance of the laminates were then scored 1 to 5, where 1 indicates very poor abrasion resistance (>50% of ink removed) and 5 indicates excellent abrasion resistance (image unaltered). The scores are shown

in Table 2.

Cracking resistance (CR") when the laminates were formed into the desired 3D shape was measured by visual assessment and scored 0 to 5, where 0 is least crack resistant and 5 is most crack resistant.

Ease of Release from Mold (ERM") was determined by how easily the print came away from the mould and scored 0 to 5, where an ERM score of 0 indicates significant adhesion between the printed face of the laminate and mold and an ERM score of 5 indicates very easy release of the printed face of the laminate from the mold (the print was released from the mould via application of air pressure only).

The Dewetting times in seconds for each of the curable compositions on the nozzle plate of the ink jet printer were determined as follows: The nozzle plate material was stored in a vessel filled with the curable composition under test for at 50°C for 48 hours. The material was then dried, inclined at an angle of 45° and a droplet of the curable composition under test (3 p1) was placed on a piece of the nozzle plate material. The time taken for the droplet to travel 2cm down the material at ambient temperature (20°C) was measured. The test was performed 5 times for each curable composition and the average of the five time measurements in seconds was deemed to be the dewetting time.

Examples and Comparative Examples Preparation of Curable Compositions CC1 to CCS Curable Compositions CC1 to CCS were prepared by mixing together ingredients indicated in Table 1 in order to dissolve any solid components and then filtering the resultant mixtures through a filter having an average pore size of 1.5 pm.

Table 1-Preparation of Curable Compositions ____________ _____________ Raw Material CC1 CC2 CC3 CC4 Name Amount (%) Amount (%) Amount (%) Amount (%) TMPTA 4.8 4.8 4.9 4.9 DPGDA 43.4 43.4 45.3 45.3 DCPA 10.2 15.3 12 17.1 IBOA 5.1 0 5.1 0 SRB33S 19.7 19.7 19.7 19.7 MEHQ 1 1 1 1 UV-12 1 1 1 1 TPO 13.8 13.8 0 0 1rg184 0 0 10 10 Tegorad 2100 1 1 1 1 TOTAL 100 100 100 100 Dewetting Time (sec) 21 22 38 30

Table 1 (continued)

CCS

Amount Raw Material (%) CTFA 35.0 NPGPODA 10.0 NVC (OH-TEMPO) 10.0 SR341 29.5 CN964 ABS 9.0 lrg 184 6.0 TPO 0 UV-12 0.5 Tegorad 2100 0 Total 100.0 Dewetting Time (sec) 9 Preparation of Laminates Laminates Li to L7 of the invention and Comparative Laminates CU and CL2 were prepared by printing UV curable inks onto the formable sheet materials indicated in Table 2 and the over-printing selected areas of the printed face of the resultant prints with a dot pattern, using the curable composition indicated in Table 2. The ink printing and application of the curable compositions were performed using an Acuity Advance Select 4008 printer comprising two magenta, two cyan, one yellow, one black and one white ink tank and one curable composition tank.

The lamp settings of the printer were 5, 5 (leading and trailing lamps). This printer comprises of print-heads having nozzle plates with a surface energy of 10-20 mN/m.

The curable compositions were applied to selected areas of the printed formable sheet material and cured to provide the pattern of cured composition islands described in more detail in Table 2 below.

The resultant laminates Li to [5 were examined using a microscope and the cured composition was found to be present on the printed sheet in the form of islands having an average diameter of 324 pm and an average height of iS pm.

The average distance between the islands was 172 pm.

Step (C) -forming the laminate into a desired three-dimensional shape Laminates Li to [7 of the invention and Comparative Laminates CL and CL2 described in Table 2 below were formed into the desired 3D shape using a pre-heated 75OFLB Thermo Former obtained from C.R.Clarke with heating elements set to full. Following the manufacturer's instructions for forming, one of three molds (of varying morphology) was loaded into the frame. The contact angle of the mould and board in both cases were greater than 80° with a draw (or height) >6cm and >12 cm.

The laminates were heated flat in the Thermo Former for 20 seconds to render them pliable and then formed into the desired 3D shape by pressing onto the mold for 30 seconds and then allowing the laminate to partially cool. The printed articles having the desired three-dimensional shapes were then released from the Thermo Former and allowed to cool to room temperature.

Table 2-Preparation and Testing of the Laminates Laminate Formable Thickness of Curable %C on printed Er at 80°C, 100°C and 120°C AR CR Sheet Formable Sheet Composition side (not in Material Material contact with the __________ ____________ _________________ _____________ mould) ________________________________ _____ ______ CL1 HIP 1mm None 0 N/A 1 N/A Li HIP 1mm CC1 11 8.4 x io, 3.85 x lO7and 3.07 x i0 3.5 5 L2 HIP 1mm CC2 11 1.11 x io7, 4.58 x lO7and 3.55 x i07 3 5 [3 HIP 1mm CC3 11 n.d 4 5 L4 HIP 1mm CC4 11 n.d 5 5 L5 HIP 1mm CC5 11 2.64x io, 1.48xi07and3.36x107 3.5 5 [6 GMPTP 1mm CC5 11 2.64x i07, 1.48xi07and3.36x107 n.d 5 L7 GMPTP 1mm CC5 25 n.d 4 LB GMPTP 1mm CC5 50 2.64x io, 1.48xiO7and3.36x107 n.d 1 CL2 GMPTP 1mm CC5 100 2.64x i07, 1.48xi07and3.36x107 n.d 0 n.d means not determined. N/A means not applicable.

Examples 8 to 17 and Comparative Examples CL3 and CL4 The method described above for Laminates Li to L7 of the invention and Comparative Laminates CU and CL2 were repeated except that the side of the laminates carrying the cured composition was applied to the mold in order to assess the release properties of the cured composition. The print was visible through the laminate because the formable sheet materials used to prepare the laminate were transparent. The results are shown in Table 3 below: Table 3-Preparation and Testing of the Laminates where the Curable Composition acts as a Release Layer _________ _____ ________ ______________ ____________ Laminate Formable Curable %C ERM ERM Score for ERM Score Sheet Composit Score Small dome for Large Material and ion for Face mould dome mould thickness mould CL3 GMPTP None N/A 2 4 4 ______ (1mm) ______ ___ _____ _________ ________ CL4 GMPTP None N/A 2 4 N/A ______ (2mm) _______ ___ ______ __________ ________ L8 GMPTP CC1 11 5 5 4 ______ (1mm) ______ ___ _____ _________ ________ L9 GMPTP CC1 11 5 N/A 5 ______ (2mm) _______ ___ ______ __________ ________ LiO GMPTP CC2 11 5 5 N/A ______ (1mm) ______ ___ _____ _________ ________ Lii GMPTP CC2 11 4 5 S ______ (2mm) _______ ___ ______ __________ ________ Li2 GMPTP CC3 11 5 N/A 5 ______ (1mm) ______ ___ _____ _________ ________ Li3 GMPTP CC3 11 5 4 N/A ______ (2mm) _______ ___ ______ __________ ________ Li4 GMPTP CC4 11 5 4 4 ______ (1mm) ______ ___ _____ _________ ________ US GMPTP CC4 11 4 4 4 ______ (2mm) _______ ___ ______ __________ ________ Li6 GMPTP CCS 11 5 N/A 4 ______ (1mm) ______ ___ _____ _________ ________ Li7 GMPTP CC5 11 2 5 N/A ______ (2mm) _______ ___ ______ __________ ________

Claims

CLAIMS1. A method for preparing a printed article having a desired three-dimensional shape, the method comprising the steps: (a) applying a curable composition to selected areas of a printed sheet; (b) curing the curable composition present on the printed sheet, thereby providing a laminate comprising the printed sheet and a discontinuous layer of cured composition; and (c) forming the laminate into a desired three-dimensional shape.
2. A method according to claim 1 wherein the curable composition is applied to selected areas of one side of the printed sheet or to selected areas of both sides of the printed sheet.
3. A method according to claim 1 or 2 wherein the discontinuous layer of cured composition covers from 3 to 49% of the side of the printed sheet to which it has been applied.
4. A method according to claim 1 or 2 wherein the discontinuous layer of cured composition covers from 7 to 15% of the side of the printed sheet to which it has been applied.
5. A method according to any one of the preceding claims wherein the curable composition is applied to selected areas of the printed sheet in step (a) such that islands of curable composition are provided on the printed sheet.
6. A method according to any one of the preceding claims wherein the curable composition is applied to selected areas of the printed sheet in step (a) in a patternwise manner to form a symmetrical and repeating pattern of curable composition islands on the printed sheet.
7. A method according to any one of the preceding claims wherein the curable composition is IJV-curable.
8. A method according to any one of the preceding claims wherein the printed sheet comprises a formable sheet material carrying a printed image on one or both sides.
9. A method according to claim 8 wherein the formable sheet material is thermoformable.
10. A method according to any one of the preceding claims wherein the printed sheet comprises a formable sheet material carrying a printed image on one or both sides and in step (c) the laminate is formed into the desired three-dimensional shape by a method comprising contacting the laminate with a mold.
11. A method according to claim 10 wherein the formable sheet material is thermoformable and step (c) comprises heating the laminate to make the laminate pliable and contacting the pliable laminate with a mold to impart the desired three-dimensional shape on the laminate.
12. A method according to any one of the preceding claims wherein step (b) provides a laminate comprising the printed sheet and a discontinuous layer of cured composition in the form of islands having an average diameter of at most 400pm.
13. A method according to any one of the preceding claims wherein step (b) provides a laminate comprising the printed sheet and a discontinuous protective layer of cured composition in the form of islands having an average diameter of at least 10pm.
14. A method according to claim 12 or 13 wherein the islands have an average height of 10 to 100pm.
15. A method according to any one of claims 11 to 14 wherein the average distance between the islands of cured composition is 5 to 500pm.
16. A method according to any one of the preceding claims wherein the curable composition is applied to selected areas of the printed sheet in step (a) by ink jet printing, screen printing or gravure printing.
17. A method according to any one of the preceding claims wherein the curable composition has a surface tension of 16 to 40 dynes, when measured at 20°C.
18. A method according to any one of the preceding claims wherein the curable composition comprises a surfactant.
19. A method according to any one of the preceding claims wherein the curable composition is substantially colourless and/or transparent.
20. A method according to any one of the preceding claims which is performed using an apparatus comprising: a curable composition application station; H. a curing station; and Hi. a station for forming a laminate into a desired three-dimensional shape; and optionally iv. a trimming station.
21. A method according to any one of the preceding claims wherein the laminate has an elastic modulus of: 4 x 106 to 6.7 x 108 Pascal when measured at 80°C; 4 x i0 to 3 x lO8Pascal when measured at 100°C; and 4 x io to 2 x io6 Pascal when measured at 120°C.
22. A method according to any one of the preceding claims wherein the curable composition is applied to selected areas of the printed sheet by means of an ink jet print-head comprising a nozzle plate having a surface energy of 10 to 30 mN/m or to 40 mN/m.
23. A method according to any one of the preceding claims wherein the curable composition is applied to selected areas of the printed sheet by means of an ink jet print-head comprising a nozzle plate and the curable composition has a de-wetting time on the material from which the nozzle plate is constructed of <60 seconds.
24. A laminate comprising a printed sheet comprising at least one printed face and a discontinuous protective layer of a cured composition present on said at least one printed face, wherein the discontinuous protective layer of cured composition comprises islands of cured composition having an average diameter of from 100 to 400pm and optionally an average height of 10 to 100pm.
25. A laminate according to claim 24 wherein the average distance between the islands of cured composition is 5 to 500pm.
26. A laminate according to claim 24 or 25 which has a real elastic modulus of: 4 x 106 to 6.7 x io Pascal when measured at 80°C; 4 x 106 to 3 x io° Pascal when measured at 100°C; and 4 x i08 to 2 x 108 Pascal when measured at 120°C.
27. A printed article comprising a laminate according to any one of claims 24 to 26 formed into a desired three-dimensional shape.
28. A substantially colourless, curable composition comprising: (a) 5 to 50 wt% of cycloaliphatic compound(s) comprising one ethylenically unsaturated group; (b) 10 to 60 wt% of compound(s) comprising two ethylenically unsaturated group; and (c) 0 to 10 wt% of compound(s) comprising three or more ethylenically unsaturated groups.
29. A composition according to claim 28 wherein component (a) comprises at least two cycloaliphatic compound(s) comprising one ethylenically unsaturated group.
30. A composition according to claim 28 wherein component (a) comprises isobornyl acrylate.
31. A composition according to claim 28 wherein component (a) comprises (al) isobornyl acrylate; and (a2) one or more further cycloaliphatic compound(s) comprising one ethylenically unsaturated group; and wherein the weight ratio of component(al):(a2) is in the range 0.7:1 to 1.3:1.
32. A composition according to claim 31 wherein the weight ratio of component (al):(a2) is in the range 0.8:1 to 1.2:1.
33. A composition according to claim 31 wherein the weight ratio of component (al):(a2) is in the range 0.9:1 to 1.1:1.
34. A composition according to claim 31 wherein the weight ratio of component (al):(a2) is approximately 1:1.
35. A method according to any one of claims 1 to 23 wherein the curable composition is as defined in any one of claims 28 to 34.
36. A laminate according to any one of claims 24 to 26 wherein the cured composition is a composition according to any one of claims 28 to 34 which has been cured.
37. A printed article comprising a laminate according to claim 36 formed into a desired three-dimensional shape.