Low leakage current dielectric

Abstract

A composition for use in the manufacture of an in-mould electronic (IME) component, the composition comprising titanium dioxide particles dispersed in a binder, wherein the binder comprises: a cross-linking agent comprising melamine formaldehyde, a thermoplastic resin comprising a hydroxyl group, and a solvent; and the titanium dioxide particles comprise a titanium dioxide core and an outer shell comprising one or more of alumina, silica and zirconia.

Description

[0001] LOW LEAKAGE CURRENT DIELECTRIC

[0002] The invention relates to a composition for use in the manufacture of an in-mould electronic (IME) component, a method of manufacturing the composition, a method of manufacturing an in-mould electronic (IME) component, and an inmould electronic (IME) component.

[0003] There is a desire to produce 3D injection molded, light-weight plastic structures capable of performing electronics functionalities. These structures can be produced by screen printing of interconnect circuitries on flexible polymer substrates such as, for example, polycarbonate (PC) and polyethylene terephthalate (PET); attaching / assembling electronic components to these screen-printed circuitries; thermoforming to produce a 3D structure of such electronics devices and pouring of liquid resins to the backside of the thermoformed structures by injection molding to produce a robust and solid plastic structures. Such structures can be designed to perform capacitive and resistive touch switch applications, for wireless or blue tooth connectivity, controlling volumes or light intensity and many such applications. These injection molded electronics structures are termed as In-Mould Electronics (IME) or Injection molded Structural Electronics (IMSE) or Plastronics or Surface Electronics.

[0004] IME technology consists of the integration of several electronic and plastics manufacturing process steps: screen printing of electronic inks (conducting and dielectric inks), drying or curing of electronic inks, component attachment or electronic assembly using electronic adhesives, thermoforming and trimming to produce curved or 3D structures, and back filling of these curved or 3D structures with molten resins by injection molding. Figure 1 depicts a schematic representation of generic manufacturing process steps of IME. In Figure 1 four broad manufacturing processing steps are schematically represented. At A (screen printing and drying) there is shown a schematic representation of 2D, screen-printed interconnects: 10 represents thermoformable PC or PET substrates, 20 represents screen printed, electrically conducting interconnects, 30 represents screen printed, electrically insulating, dielectric layers. At B (electronic component assembly (SMT components, LEDs etc.) there is shown a schematic representation of 2D, electronic circuitries, where electronic components, LEDs, etc. are attached; 40, 50 and 60 represent different SMT components or LEDs. At C (thermoforming [vacuum or high air pressure and temperature (140-210°C)]) there is shown a schematic representation of thermoformed, 3D, electronic circuitries (70). At D (injection molding [temperature (170-330°C)]) there is shown a schematic representation of injection molded (filled with injection molded resin), thermoformed, 3D, electronic circuitries (80).

[0005] WO2022073647A2, the disclosure of which is hereby incorporated by reference, in the name of Alpha Assembly Solutions Inc., describes compositions for use in the manufacture of an IME component. The composition may be in the form of a dielectric ink and may comprise non-conducting filler particles and a binder. The filler particles may help to impart thickness, thereby reducing the need for multilayer printing of the same dielectric layer, unlike filler-free binder which gives lower thicknesses and increases printing process time. The filler particles may comprise titanium dioxide particles. Titanium dioxide particles may provide the compositions with a favourably high dielectric constant. They may also impart high mechanical strength and high reflectiveness. A high reflectiveness may be beneficial, for example, when the IME comprises a LED, where transfer or reflection of light needs to be carried out without loss of light intensity.

[0006] However, cured compositions containing titanium dioxide typically exhibit high leakage voltage, i.e. the gradual transfer of electrical energy across a boundary normally viewed as insulating. When the cured composition forms a dielectric part of an IME component, this may result in reduced battery life, increase power consumption, increased RF noise, increased risk of electrocution for an operator and / or increased risk of fire. In addition, it can be difficult to disperse titanium dioxide particles in the binder. The present invention seeks to tackle at least some of the problems associated with the prior art or at least to provide a commercially acceptable alternative solution thereto.

[0007] In a first aspect, the present invention provides a composition for use in the manufacture of an in-mould electronic (IME) component, the composition comprising titanium dioxide particles dispersed in a binder, wherein the binder comprises: a cross-linking agent comprising melamine formaldehyde, a thermoplastic resin comprising a hydroxyl group, and a solvent; and the titanium dioxide particles comprise a titanium dioxide core and an outer shell comprising one or more of alumina, silica and zirconia.

[0008] Each aspect or embodiment as defined herein may be combined with any other aspect(s) or embodiment(s) unless clearly indicated to the contrary. In particular, any features indicated as being preferred or advantageous may be combined with any other feature indicated as being preferred or advantageous.

[0009] The inventors have surprisingly found that, in comparison to conventional titanium dioxide-containing compositions for use in the manufacture of an IME component, the compositions of the present invention, once cured, may cause the IME to exhibit reduced current leakage. Advantageously, such reduced current leakage may be retained following thermoforming. Accordingly, the electrical performance of an IME component manufactured using the composition may be improved.

[0010] Without being bound by theory, it is considered that the reduced current leakage may result from the presence of the outer shell. This is because, in comparison to titanium dioxide, alumina, silica and zirconia may exhibit lower electrical conductivities, in particular lower surface electrical conductivities. Titanium dioxide typically exhibits a slightly higher bulk electrical conductivity than that of silica, alumina and zirconia. However, crucially, titanium dioxide typically exhibits a significantly higher surface electrical conductivity than that of silica, alumina and zirconia. Without being bound by theory, it is considered that the surface conductivity of titanium dioxide results from the occurrence of oxide vacancies at the surface of titanium dioxide particles, which form a thin, conductive layer. This thin, conductive layer may allow current to flow through the cured composition, even though the relatively low bulk electrical conductivity of titanium dioxide should be preventing it. The occurrence of oxide vacancies at the surface of silica, alumina and zirconia is typically less pronounced than that of titanium dioxide, and therefore such materials typically exhibit lower surface electrical conductivities than that of titanium dioxide. By including an outer shell of silica, alumina and / or zirconia, which have lower surface electrical conductivities than titanium dioxide, current leakage resulting from the titanium dioxide particles may be reduced in comparison to compositions with titanium dioxide particles devoid of such an outer shell.

[0011] Titanium dioxide can vary between hydrophilic and hydrophobic states, depending on the environment and exposure to UV light. In contrast, the hydrophobicity of alumina, silica and zirconia is generally higher and more consistent. Accordingly, the presence of the outer shell may render the titanium dioxide particles more hydrophobic, thereby reducing the absorption of moisture. The presence of moisture in the cured composition may increase the leakage current.

[0012] Table 1 lists some commercial sources of such titanium dioxide shell-protected particles and their characteristics.

[0013] Table 1 : The characteristics of various commercial grades of inorganic shell protected titanium dioxide core (rutile structure) fillers.

[0014]

[0015] Due to the capability of the binder to undergo a high degree of cross-linking (see further discussion below), in comparison to conventional IME compositions, the cured composition of the present invention may be more compact. This may result in lower levels of moisture being absorbed, typically substantially no moisture being absorbed. As a result, the leakage current may be further reduced.

[0016] In comparison to conventional titanium dioxide particles devoid of the outer shell, the titanium dioxide particles having the outer shell may be more easily dispersed in the binder.

[0017] Advantageously, the titanium dioxide particles may impart mechanical strength to the composition once cured. In addition, the titanium dioxide particles may provide the cured composition with a high reflectiveness and / or a favourable colour.

[0018] Due to its relatively high dielectric constant in comparison to other inorganic oxides, the presence of the titanium dioxide core, in particular a rutile titanium dioxide core, may increase the dielectric constant of the composition. Accordingly, the composition may provide a favourable combination of high dielectric constant and high reflectiveness due to the titanium dioxide core and low current leakage due to the outer shell.

[0019] Once dried I cured, the binder itself may possess excellent dielectric properties and may be highly flexible and moderately stretchable, have superior adhesion and compatibility with other ink materials and substrates and have excellent weather resistance (moisture, gas and chemicals).

[0020] The composition, once cured I dried, may exhibit one or more of low leakage, high degree of insulation (high breakdown voltage), non-damage or carbonization (carbon tracking) when breakdown occurs, high breakdown voltage, and a low concentration of free halogens which may cause leakage and capacitive currents. To help in achieving this, the compositions may be produced using materials with low impurities, reduction in voids of the final materials and low loss (low Tan Delta) materials.

[0021] The cured composition may exhibit excellent thermoformability and may be stable under injection-molding ink wash-out, thus be suitable for IME manufacturing. The viscosity and rheology of the composition may be suitable for printing using, for example, screen, stencil, gravure or flexographic techniques; spraying; dispensing; and jetting techniques to produce insulating layers for protecting conducting interconnect circuitries on various polymeric substrates, such as PC and PET. Once thermally dried or cured, the thickness of the composition can be controlled to > 3 pm and may possess excellent dielectric break-down voltages (>300 V) and may have adhesion (as per ASTM standard > 3B) suitable for manufacturing of flexible electronics circuits. The cured composition may provide protection of conducting circuitries from environments, such as moisture and gases.

[0022] The composition comprises titanium dioxide particles and a binder. The composition may consist of or consist essentially of the titanium dioxide particles and the binder. The term “consist essentially” as used herein may encompass that further components can be present, but only to the extent that these components do not materially affect the essential characteristics of the composition.

[0023] The titanium dioxide particles comprise a titanium dioxide core and an outer shell comprising one or more of alumina, silica and zirconia. The outer shell may partially coat the core or may entirely coat the core. Typically, the outer shell entirely coats the core. In other words, the titanium core is typically not exposed. This may advantageously reduce the leakage current and / or increase the dispersibility. The outer shell comprises one or more of alumina, silica and zirconia. Typically, the outer shell consists of, or consists essentially of, the one or more of alumina, silica and zirconia. The term “consists essentially” as used herein may encompass that the outer shell may contain components other than alumina, silica and zirconia, but only to the extent that these components do not materially affect the essential characteristics of the outer shell.

[0024] The composition is particularly suitable for use in the manufacture of an IME component, for example as a dielectric ink, and may result in the manufacture of IME components with superior robustness, environmental durability / ruggedness, mechanical flexibility, and improved operational life for electronics applications in comparison to conventional IME components.

[0025] The composition comprises titanium dioxide particles dispersed in a binder. As discussed in more detail below, the composition may comprise solid particles other than titanium dioxide such as, for example, silica particles and / or talc particles. In such a case, the titanium dioxide particles typically comprise from 80 to 99 wt.% of the total solid particles.

[0026] Alternatively, the composition may be substantially devoid of solid particles other than titanium dioxide particles. By “substantially devoid” in this context, it is mean that the composition may comprise less than 1 wt.% solid particles other than titanium dioxide particles, based on the total weight of the composition, typically less than 0.5 wt.%, more typically less than 0.1 wt.%, still even more typically no solid particles other than titanium dioxide particles. Of the total weight of solid particles contained in the composition, typically at least 99 % may be titanium dioxide particles, more typically at least 99.9 %.

[0027] The titanium dioxide particles may be in the form of flakes and / or spheres and / or irregularly shaped particles. Preferably, the titanium dioxide particles are in the form of flakes and / or irregularly shaped particles. This is because, in comparison to spheres, flakes and irregularly shaped particles may have improved adhesion to a substrate and may have a reduced propensity to delaminate during a thermoforming process.

[0028] The titanium dioxide particles are preferably electronic grade titanium dioxide particles, i.e. substantially devoid of ionic or halogen impurities. The binder serves to “bind” the components of the composition together. The binder may form the remainder of the composition together with any unavoidable impurities. When the composition does not contain solid particles, then the binder together with any unavoidable impurities may constitute the entire composition.

[0029] The term “melamine formaldehyde” as used herein may encompass a resin with melamine rings terminated with multiple hydroxyl groups derived from condensation products of two monomers, melamine, and formaldehyde. Melamine formaldehyde is sometimes referred to a “melamine formaldehyde resin”, “melamine resin” or simply “melamine”.

[0030] The term “thermoplastic resin” as used herein may encompass a plastic polymer material that becomes pliable or mouldable at a certain elevated temperature and solidifies upon cooling.

[0031] The term “component” as used herein may encompass, for example, a part of an electronic component or an entire electronic component.

[0032] During a typical IME manufacturing method, a composition, such as a conductive ink or a dielectric ink, is printed on a thermoformable substrate. Prior to thermoforming, the composition is then dried, typically at an elevated temperature of up to 150 °C, for example from 50 to 120 °C, for a period of time to remove solvent from the composition. Without being bound by theory, it is considered that upon thermal heating of the composition of the present invention, e.g. using such typical drying temperatures and times, the melamine resin may react with the hydroxyl groups of the thermoplastic resins to form a “nitrogen-carbon-oxygen” linked, polymeric network.

[0033] Advantageously, once dried under such conditions, the binder of the present invention may exhibit two contradictory properties. At a normal operation temperature of an IME device (e.g. from about -20 °C to +50 °C) the binder may act like a thermoset showing exceptional strength, cohesion and interlayer adhesion, and a reasonable stretch-ability. However, at higher temperatures that are used during thermoforming, the binder may transform into a thermoplastic material that can be readily thermoformed into 3D structures without necking, breaking or delaminating.

[0034] Without being bound by theory, it is considered that these contradictory properties may result from the use of the cross-linking agent comprising melamine formaldehyde with the hydroxyl group-containing resins. In particular, it is considered that this advantageous balance of thermoplastic and thermoset properties is achieved by the occurrence of partial, i.e. not full, cross-linking. This is presumably because, in comparison to cross-linking agents used in conventional IME methods, melamine formaldehyde is a relatively “slow” crosslinking agent, and results in only partial cross-linking as a result of the drying temperatures and times used in a typical IME manufacturing method.

[0035] During a typical IME manufacturing process multiple thermoformable compositions are used so as to form the final component, e.g. conductive inks, dielectric inks, conductive adhesives, non-conductive adhesives, encapsulants, barrier layers etc. Advantageously, the compatibility of these materials can be improved when binders of the present invention are used as a common platform. While each of these materials may of course include different species (e.g. conductive particles, non-conductive particles, etc.), the use of the common binder may ensure the inter-material (e.g. inter-ink) compatibility. As a result, problems with, for example, de-lamination of layers of different materials, may be reduced.

[0036] The compositions are compatible with conventional graphic ink-coated substrates, which is a desirable criterion for constructing highly functional IME structures and devices.

[0037] Flexible electronic circuits constructed using the composition may show excellent electrical performance. The compositions may be highly compatible with injection-molding resins typically employed in an IME manufacturing method.

[0038] Use of the composition may also reduce the occurrence of ink wash-out in comparison to compositions used in conventional IME methods.

[0039] Thermoformed and injection molded structures prepared using the compositions show excellent environmental reliability features and thus are particularly suitable for IME applications for automotive, consumer electronics and white goods applications.

[0040] Advantageously, the composition may be stable at normal storage and ambient temperatures. Again, without being bound by theory, it is considered that this is due to the substantial absence of any cross-linking by the melamine formaldehyde at such temperatures.

[0041] The cross-linking agent preferably further comprises isocyanate and / or polyisocyanate and / or blocked polyisocyanate. Such species may increase the degree of cross-linking under the drying conditions employed in conventional IME manufacturing methods. This may be advantageous when the composition is required to have increased “thermoset” properties. A “blocked”, or “masked”, isocyanate may encompass an isocyanate that contains a protected isocyanate. The isocyanate functional group is typically masked through the use of a blocking agent producing a compound that is seemingly inert at room temperature yet yields the reactive isocyanate functionality at elevated temperatures.

[0042] Suitable isocyanates, polyisocyanates and blocked polyisocyanates include, for example, toluene diisocyanate (TDI), hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), Desmodur BL 3175A, Desmodur BL 3272 MPA, Desmodur BL 1100 / 1 and Vestanat B 1358A from Evonik. These can be used alone or in a combination of melamine formaldehyde resins. VESTANAT B 1358A comprises methyl-ether-ketone-oxime (MEKO) blocked cycloaliphatic polyisocyanate based on isophorone diisocyanate (IPDI). The composition preferably comprises from 1 to 18 wt.% of the isocyanate and / or polyisocyanate and / or blocked polyisocyanate, based on the total weight of the composition, more preferably from 2 to 17 wt.%, even more preferably from 3 to 16 wt.%.

[0043] The titanium dioxide comprises rutile titanium dioxide. In comparison to other polymorphs of titanium dioxide, such as anatase, rutile titanium dioxide may advantageously exhibit a higher dielectric constant. In addition, rutile titanium dioxide may scatter light more efficiently, thereby imparting a higher level of whiteness, brightness and opacity.

[0044] The titanium dioxide particles preferably comprise from 0.5 to 15 wt.% outer shell based on the total weight of the titanium dioxide particles, more preferably from 1 to 9 wt.% outer shell based on the total weight of the titanium dioxide particles. Such amounts may be particularly suitable for providing a favourable combination of high dielectric constant and low leakage current.

[0045] The outer shell preferably comprises alumina, silica and zirconia. The titanium dioxide particles preferably comprise, based on the total weight of the titanium dioxide particles: from 1 .7 to 7 wt.% alumina, and / or from 1 .4 to 9 wt.% silica, and / or from 0.1 to 3 wt.% zirconia. This may further reduce the leakage current and / or increase the dispersibility.

[0046] The composition preferably comprises from 10 to 85 wt.% of the binder based on the total weight of the composition, more preferably from 15 to 80 wt.%. This may provide the composition with favourable rheological properties, such as those required for handling and / or thermoforming. Alternatively, the composition preferably comprises from 10 to 60 wt.% of the binder based on the total weight of the composition, more preferably from 15 to 55 wt.%.

[0047] The composition preferably comprises from 4 to 90 wt.% of the titanium dioxide particles based on the total weight of the composition, more preferably from 5 to 85 wt.%. This may further improve the dielectric properties of the composition. Alternatively, the composition preferably comprises from 40 to 90 wt.% of the titanium dioxide particles based on the total weight of the composition, more preferably from 45 to 85 wt.%.

[0048] The titanium dioxide particles preferably comprise an organic coating on the surface thereof. This may increase the dispersibility of the titanium dioxide particles in the binder. The organic coating is preferably hydrophobic or hydrophilic, more preferably hydrophobic. The organic coating may comprise, for example, a functional group selected from an acid, an alcohol and ester and a silane. The organic coating may be aliphatic or aromatic.

[0049] The solvent preferably comprises an aromatic alcohol. The aromatic alcohol preferably comprises benzyl alcohol. The solvent preferably comprises one or more of a glycol ether acetate, a glycol ether, an ester, a ketone, an alcohol and a hydrocarbon. Such solvents may be used alone or in combination. The binder preferably comprises two or more solvents selected from aromatic alcohol, glycol ether acetate and glycol ether. Such solvents may be particularly suitable for dissolving the thermoplastic resins and / or cross-linking agent, and may be particularly compatible with substrates and the titanium dioxide in the composition. Such solvents may have a favourable combination of polarity, solvency properties (Hansen solubility parameters), compatibility with substrates, toxicity and other physical properties, such as boiling and flash points. Such solvents may improve the composition’s storage stability, drying profile, drying stability during processing (e.g. on-screen during screen printing), and reactivity with substrates and other printed ink layers (such as graphic inks or electronic inks layers). Such solvents may result in a homogeneous composition that will be stable upon storing and also satisfy performance requirements. Non-limiting examples of solvents include methanol, ethanol, 2-propanol, benzyl alcohol, ethylene glycol, propylene glycol, dipropylene glycol, 1 ,3-butane diol, 2,5- dimethyl-2,5-hexane diol, ethylene glycol methyl ether, ethylene glycol monobutyl ether, propylene glycol phenyl ether, diethylene glycol mono-n-butyl ether, propylene glycol n-propyl ether, dipropylene glycol methyl ether, terpineol, butyl carbitol, butyl carbitol acetate, glycol ether acetates, 2-(2-ethoxyethoxy)ethyl acetate, dipropylene glycol methyl ether acetate, propylene glycol monomethyl ether acetate, 2-Butoxyethyl acetate, carbitol acetate, propylene carbonate butyl carbitol, butyl cellosolve, heptane, hexane, cyclohexane, benzene, xylene, Cyrene, dibasic ester, isophorone, C11 -ketone, and toluene.

[0050] The solvent preferably comprises: up to 95 wt.% glycol ether acetate, preferably up to 85 wt.% glycol ether acetate, and / or up to 95 wt.% glycol ether, preferably up to 85 wt.% glycol ether (e.g. 1-85 wt.%), and / or up to 15% ester, preferably up to 5 wt.% ester (e.g. 1-5 wt / %), and / or up to 40 wt.% ketone, preferably up to 32 wt.% ketone (e.g. 1-32 wt.%, and / or up to 80 wt.% alcohol, preferably up to 70 wt.% alcohol (e.g. 1-70 wt.%), and / or up to 30 wt.% hydrocarbon, preferably up to 22 wt.% hydrocarbon (e.g. 1-22 wt.%), based on the total weight of the solvent. Such amounts may be particularly suitable for providing the advantages described above.

[0051] The titanium dioxide particles preferably have a D50 (median particle size) of from 0.05 to 30 pm, more preferably from 0.1 to 10 pm, even more preferably from 0.2 to 0.7 pm, still even more preferably from 0.25 to 0.6 pm. This may further improve the dispersibility of the titanium dioxide particles in the binder. The D50 may be measured using techniques known in the art, for example using laser diffraction or dynamic light scattering on a number basis.

[0052] The titanium dioxide particles preferably have a L* value of greater than or equal to 97 %, more preferably greater than or equal to 98 %. This may provide the composition with a favourably high lightness.

[0053] The titanium dioxide particles preferably have a specific resistance of greater than or equal to 3000 Q.cm. This may further reduce the leakage current.

[0054] The titanium dioxide particles preferably have a specific gravity of from 3.5 to 4.5 g / cm3, preferably from 3.7 to 4.2 g / cm3 When suspended in water, the titanium dioxide particles preferably have a pH of greater than 6, preferably greater than 6.5, more preferably from 7 to 9.5. This may further reduce the leakage current and / or increase the dispersibility.

[0055] In a preferred embodiment, the composition is in the form of a dielectric ink. In other words, the present invention provides a dielectric ink comprising the composition described herein.

[0056] In a preferred embodiment, the composition is in the form of a non-conductive adhesive. In other words, the present invention provides a non-conductive ink comprising the composition described herein.

[0057] In a preferred embodiment, the composition is in the form of an encapsulant. In other words, the present invention provides an encapsulant comprising the composition described herein.

[0058] In a preferred embodiment, the composition is in the form of a gap filler, e.g. a gap filler for thermal management of a battery. In other words, the present invention provides a gap comprising the composition described herein.

[0059] In a preferred embodiment, the composition is in the form of a thermal interface material (TIM). In other words, the present invention provides a thermal interface material comprising the composition described herein.

[0060] The melamine formaldehyde preferably comprises hexamethoxym ethyl melamine. Hexamethoxymethyl melamine is a particularly suitable cross-linking agent. In addition, hexamethoxym ethyl melamine is soluble in most common organic solvents except aliphatic hydrocabons.

[0061] Suitable commercial melamine formaldehyde resins include, for example, Maprenal BF 891 / 77SNB, Maprenal MF 600 / 55BIB, Maprenal MF 650 / 55IB, Maprenal MF 800 / 55IB, CYMEL 370, CYMEL 373, and CYMEL 380. Maprenal MF 600 / 55BIB is an imino type, highly reactive, isobutylated melamineformaldehyde resin.

[0062] The thermoplastic resin preferably comprises one or more of polyurethane resin, polyester resin, polyacrylate resin, polyvinyl ester resin, phenoxy resin and ketonic resin, i.e. a hydroxyl group containing polyurethane resin, polyester resin, polyacrylate resin, polyvinyl ester resin, phenoxy resin and / or ketonic resin. Such resins are particularly suitable for use in the present invention and under the drying conditions of a typical IME manufacturing method react with melamine formaldehyde to provide the desired degree of cross-linking.

[0063] These thermoplastic resins may be used alone or in combinations with other thermoplastic resins.

[0064] The polyurethane resin may comprise, for example, a reaction product of hydroxy terminated polyol, hydroxy terminated polyethylene oxide), hydroxy terminated poly(dimethylsiloxane) or trimethylolpropane ethoxylate with a diisocyanate, e.g. isophorone diisocyanate, hexamethylene diisocyanate, m-xylylene diisocyanate, 1 ,4-cyclohexylene diisocyanate, polypropylene glycol), and / or tolylene 2,4-di- isocyanate. Monoisocyanates may also be involved in the reaction, for example ethylbenzyl isocyanate, (trimethylsilyl) isocyanate, 1 -naphthyl isocyanate, 3- (triethoxysilyl) propyl isocyanate, phenyl isocyanate, allyl isocynate, butyl isocyanate, hexyl isocyanate, cyclohexyl isocyanate and furfuryl isocyanate. As will be appreciated, such species will at as chain stoppers and will remain at the end of the polymeric chains. The polyurethane resin may comprise one or mixture of a thermoplastic polyurethane, such as Pearlstick series of polyurethane like Pearlstick 5701 , Pearlstick 5703, Pearlstick 5707, Estane series of polyurethane like ESTANE FS M92B4P, Desmocoll series of polyurethane like Desmocoll 540 / 4, Desmocoll 400, Desmomelt series of polyurethane like Desmomelt 540 / 3, Desmomelt 540 / 4.

[0065] The phenoxy resin is preferably a thermoplastic bisphenol-A or bisphenol-F (preferably bisphenol-A) based polyether containing polyester or polyacrylate or polyurethane compounds. In other words, the phenoxy resin may be a polyester, polyacrylate or a polyurethane formed from a bisphenol-A or bisphenol-F based diol. For example, with regard to a polyester, which is typically formed from a diol and a dicarboxylic acid, a bisphenol-A or bisphenol-F based diol is used. Likewise, with regard to a polyurethane, which is typically formed from the reaction product of a diol and a diisocyanate, bisphenol-A or bisphenol-F is used as the diol. Likewise, with regard to a polyacrylate, the polyacrylate may be formed from a bisphenol-A or bisphenol-F based acrylate monomer, e.g.

[0066] Examples of suitable phenoxy resins containing polyester or poly acrylate or polyurethanes include phenoxy resins available under the tradenames LEN-HB, PKHW-35, PKHH, PKHA, PKHM-301 and PKHS-40.

[0067] The polyester resin, polyacrylate resin and / or polyurethane resin may contain one or more of polyols, hydroxyls, amines, carboxyl acids, amides and aliphatic chains, i.e. the resins may contain one or more of these functional groups. Such functional groups typically terminate the resin. For example, when the polyester contains polyol, the polyester may be a polyester polyol rein, e.g.

[0068] The phenoxy resin contain polyester or polyacrylate or polyurethane or polyether or polyamide backbone. The thermoplastic resin preferably comprises polyurethane resin, polyester resin and phenoxy resin. More preferably, the thermoplastic resin comprises: from 20 to 60 wt.% polyurethane resin, preferably 35 to 47 wt.% polyurethane resin, from 5 to 30 wt.% polyester resin, preferably 13 to 19 wt.% polyester resin, and from 20 to 60 wt.% phenoxy resin, preferably 34 to 51 wt.% phenoxy resin, based on the total weight of the thermoplastic resin.

[0069] Such thermoplastic resins, particularly in the amounts recited above, are particularly suitable for obtaining the desired degree of cross-linking with the melamine formaldehyde. The presence of polyurethane resin(s), particularly in the recited amount, may provide the dried composition with a desirable level of flexibility. The presence of polyester resin(s), particularly in the recited amount, may provide the dried composition with a desired degree of flexibility and also promote adhesion to the substrate. The presence of phenoxy resin(s), particularly in the recited amount, may promote adhesion to the substrate. The combination of these three resins, particularly in the recited amounts, may provide a favourable combination of high flexibility and high adhesion to the substrate.

[0070] Preferably, the thermoplastic resin: comprises a homo-polymer, and co-polymer and / or a ter-polymer; and / or has a glass transition temperature of less than 100 °C; and / or has a weight average molecular weight of from 1000 to 100000 g / mol; and / or has a softening point of less than 100 °C; and / or has a hydroxyl content (OH number) of greater than 20 mgKOH / g.

[0071] The composition preferably comprises from 1 to 20 wt.% of the cross-linking agent based on the total weight of the composition, more preferably from 2 to 19 wt.%, even more preferably from 3 to 18 wt.%, still even more preferably from 4 to 17 wt.%. Higher levels of cross-linking agent may result in an unfavourably high degree of cross-linking, resulting in an unfavourable plastic-like structure. In addition, the adhesion to a polycarbonate substrate after thermoforming may be reduced. Lower levels of cross-linking agent may result in insufficient crosslinking.

[0072] In a preferred embodiment, the composition comprises: from 1 to 40 wt.% of the cross-linking agent, preferably 7 to 24 wt.% of the cross-linking agent, and from 60 to 99 wt.% of the thermoplastic resin, preferably 76 to 93 wt.% of the thermoplastic resin, based on the total amount of cross-linking agent and thermoplastic resin. Such amounts may help to provide the desired level of cross-linking under the drying conditions of conventional IME manufacturing methods.

[0073] The binder may preferably further comprise: a thermosetting resin, preferably comprising one or both of acrylic resin and epoxy resin; and a curing catalyst for curing the thermosetting resin, preferably for thermally curing the thermosetting resin and / or for UV curing the thermosetting resin.

[0074] The presence of the thermosetting resin and curing catalyst may serve to form a three-dimensional thermoset network. This may be beneficial when the dried composition is required to have more “thermoset” properties. The thermosetting resin preferably comprises one or both of acrylic resin and epoxy resin, and may be cured using a thermal curing agent and / or a UV curing agent.

[0075] The thermosetting resin may contain, for example, a polyester or a polyacrylate or a polyether or a polyurethane or a polyamide backbone. The thermosetting resin may contain different combinations of monomer, dimer, trimer, tetramer, penta- or hexamer and oligomers having epoxy, polyurethane, polyester, polyether, and acrylic backbones.

[0076] Examples of the epoxy resin include bisphenol-A epoxy, 4-vinyl-1 -cyclohexene 1 ,2-epoxide, 3,4-epxoy cyclohexyl mehyl-3',4'-epoxy cyclohexene carboxylate, 1 ,4-butanediol dig lycidy I ether, trimethylolpropane triglycidy I ether, triglycidy I isocyanurate, epoxy siloxane, epoxy silane and phenol novolac epoxy. The epoxy resins may comprise one or a mixture of epoxy resins, such as EPON 862, DYCK-CH, JER 828, 1 ,4-butanediol diglycidyl ether, 1 ,6-hexanediol diglycidylether (DER 731 ), orho-Cresyl glycidyl ether (DER 723) and C12-C14 alkyl glycidyl ether (DER 721 ). One or more hardeners may be present, and such hardeners may be either amine such as butyl amine, N, N-diethyl amino ethanol, or amino ethanol, acid such as oleic acid, adipic acid, or glutaric acid, or anhydrides such as succinic anhydrides, phthalic anhydrides and maleic anhydride. Epoxy acrylates may also be used. (Meth)acrylates are produced by a ring opening reaction of 1 ,4-butanediol diglycidyl ether, bisphenol-A epoxy, 4- vinyl-1 -cyclohexene 1 ,2-epoxide, 3, 4-epxoy cyclohexyl mehyl-3',4'-epoxy cyclohexene carboxylate, trimethylolpropane triglycidyl ether, triglycidyl Isocyanurate, epoxy siloxane, epoxy silane, phenol novolac epoxy with methacrylic acid. The epoxy acrylate may comprise one or more of epoxy backbone based (meth)acrylates such as Ebecryl 3503, Ebecryl 3201 , Photomer 3005, Photomer 3316, Ebecryl 3411 , and Ebecryl 3500, by way of example and not limitation. Polyurethane acrylates such as urethane acrylate, methacrylate terminated polyurethane and modified isocynate with hydroxy ethyl methacrylate may also be used. The urethane acrylate may comprise one or more of a urethane backbone based (meth)acrylate such as SUO2371 , SUO-300, SUO- 7620, Photomer 6891 , SUO S3000, Ebecryl 8413, Ebecryl 230, Ebecryl 4833, Ebecryl 8411 , Ebecryl 270, Ebecryl 8804, and Photomer-6628, by way of example and not limitation. Polyester acrylates such as fatty acid modified pentaerythritol acrylate, trimethylolpropane triacrylate and methacrylated monosaccharides may also be used. Polyether acrylates such as polyethylene glycol) methyl ether acrylate, poly(ethylene glycol) methacrylate, poly(ethylene glycol) dimethacrylate may also be used. The polyester acrylate may comprise one or more of polyester backbone based (meth)acrylate such as Photomer- 4006, Ebecryl 450, Photomer 5429, and Ebecryl 812, by way of example and not limitation. Non-limiting examples of monomer acrylates include, but are not limited to, methacrylic acid, 3-(trimethoxysilyl)propyl methacrylate, isoborynyl acrylate, tetrahydrofufuryl acrylate, polyethylene glycol) methyl ether acrylate, hydroxypropyl methacrylate, dimethylaminoethyl methacrylate, 2-ethyl hexyl acrylate, butyl acrylate, isooctyl acrylate, methyl methacrylate, lauryl acrylate, dodecyl acrylate and tetrahydrofurfuryl acrylate. Non-limiting examples of dimer acrylates include dimer methacrylates such as polyethylene glycol) dimethacrylate, 1 ,6-bis(acryloyloxy)hexane, bisphenol A-ethoxylate dimethacrylate and neopentyl glycol diacrylate 1 ,3-butanediol diacrylate. Non-limiting examples of trimer acrylates include trimer methacrylates such as trimethylolpropane triacrylate, pentaerythritol triacrylate and 1 ,3,5- triacryloylhexahydro-1 ,3,5-triazine. Non-limiting examples of tetramer acrylates include pentaerythritol tetracrylate and di(trimethylolpropane) tetraacrylate. Non-limiting examples of penta or hexamer acrylates include dipentaerythritol penta-acrylate and dipentaerythritol hexa-acrylate. The siloxane acrylate may comprise one or more of siloxane backbone based (meth)acrylate such as BYK- UV3570, BYK-UV3575, BYK-UV3535, BYK-UV3530, BYK-UV3505, BYK- UV3500, Ebecryl 350, Ebecryl 1360, and SUO-S3000, by way of example and not limitation. The aliphatic acrylate may comprise one or more of hydrocarbon backbone based (meth)acrylate such as Ebecryl 1300, SAP-M3905, Ebecryl 525, and SAP-7700HT40, by way of example and not limitation.

[0077] The binder preferably further comprises one of more performance booster materials, preferably selected from one or more of surfactants, rheology modifiers, dispersants, de-foamers, de-tackifiers, slip additives, anti-sag agents, levelling agents, surface active agents, surface tension reducing agents, adhesion promoters, anti-skinning agents, matting agents, coloring agents, dyes, pigments and wetting agents. De-foamers may remove the foam from the binder, and de-tackifiers may remove tack from the binder. The surfactants may comprise anionic, cationic or non-ionic surfactants. Non-limiting examples include surfactants available under the tradenames SPAN-80, SPAN-20, Tween-80, Triton-X-100, Sorbitan, IGEPAL-CA-630, Nonidet P-40, Cetyl alcohol, FS-3100, FS-2800, FS-2900. FS-230, FS-30, BYK-UV3500 / UV3505 / 077 / UV3530, FS-34, Modaflow 2100, Omnistab LS 292, Omnivad-1116 and Additol LED 01 . Rheology Modifiers are organic or inorganic additives that control the rheological characteristics of the formulation. These can be used alone or in a mixture. Examples of suitable rheology modifiers include, but are not limited to, those available under the tradenames THIXIN-R, Crayvallac-Super, Brij 35, 58, L4, 020, S100, 93, C10, 010, L23, 010, S10 and S20. Performance booster materials can also be coloring agents, dyes and pigments. Non-limiting examples of coloring agents, dyes and pigments include anthraquinone dyes, azo dyes, acridine dyes, cyanine dyes, diazonium dyes, nitro dyes, nitroso dyes, quinone dyes, xanthene dyes, fluorene dyes and rhodamine dyes. Non-limiting examples of antioxidants and inhibitors include 2,6-di-tert-butyl-4-methylphenol, 2 ,6-di-tert- butyl-p-cresol, butylhydroxytoluene, 3,5-di-tert-4-butylhydroxytoluene, Omnistab IC, Omnistab In 515 / 516, hydroquinone and phenothiazine.

[0078] The composition preferably comprises from 1 to 10 wt.% performance booster materials based on the total weight of the composition, preferably from 2 to 8.6 wt.% performance booster materials.

[0079] In addition to the elements recited herein, it will be understood that the composition and binder may comprise unavoidable impurities. Such unavoidable impurities, if present, are typically present in an amount of up to 1 wt.% of the composition or binder, more typically up to 0.5 wt.%, even more typically up to 0.1 wt.%, even more typically up to 0.05 wt.%.

[0080] In a preferred embodiment, the binder comprises: from 0.5 to 12 wt.% of the cross-linking agent, preferably from 1 .5 to 7.7 wt.% of the cross-linking agent; from 10 to 40 wt.% of the thermoplastic resin, preferably from 11 to 30.4 wt.% of the thermoplastic resin; and from 40 to 85 wt.% solvent, preferably from 46.7 to 78.8 wt.% solvent; optionally: from 0.1 to 30 wt.% thermosetting resin and from 0.1 to 3 wt.% curing catalyst for curing the thermosetting resin, preferably from 1 to 10 wt.% thermosetting resin and from 0.1 to 1 wt.% curing catalyst for curing the thermosetting resin; and / or from 0.1 to 20 wt.% performance booster materials, preferably 1.7 to 17 wt.% performance booster materials.

[0081] Such a binder is particularly suitable for providing the composition with the advantages described above. Higher levels of cross-linking agent may result in an unfavourably high degree of cross-linking, resulting in an unfavourable plasticlike structure. In addition, the adhesion to a polycarbonate substrate after thermoforming may be reduced.

[0082] Preferably, the binder comprises a low level of: ionics, more preferably substantially no ionics; and / or free halogens, more preferably substantially no free halogens; and / or deliberately added halogens, more preferably no deliberately added halogens.

[0083] The composition may comprise solid particles other than titanium dioxide particles, for example other non-conductive particles. The other non-conductive particles preferably comprise organic non-conductive particles, preferably selected from one or more of cellulose, wax (for example, Ceraflour 991 , Ceraflour 929 and Ceraflour 920 from BYK), polymer microparticles, non- conductive carbon particles and graphene oxide. Alternatively, or in addition, the non-conductive particles preferably comprise inorganic non-conductive particles, preferably selected from one or more of mica, fused silica (SiC ) such as from Denka and Tokuyama, fumed silica, talc like Micro Ace P3 from Nippon Talc, alumina, titania (without the outer shell of silica, alumina and / or zirconia), barium titanate (BaTiOs), zinc oxide (ZnO) and boron nitride (BN) from Momentive, optionally wherein the inorganic non-conductive particles are submicron to micron sized (e.g. from 5 to 50000 nm, preferably from 10 to 30000 nm). Organic non- conductive particles may increase the homogeneity of the composition but may have lower dielectric strength in comparison to inorganic non-conductive particles. Inorganic non-conductive particles may increase the dielectric strength but may result in decreased homogeneity in comparison to organic non- conductive particles. Thus, it may be preferable to functionalize the non- conductive particles with a functional group such as, for example, carboxylic acid, amine or alcohol to enable them to be better dispersed very well through interaction with the polymer system. The organic coating may vary in chain length and may comprise a saturated or unsaturated fatty acid or ester, or a glycerol based derivative or amine or amide or phosphate or thiol. This may also help to improve the long-term storage stability of the composition.

[0084] The non-conductive particles preferably exhibit a mean particle size (D50) from 1 to 30 pm or less than or equal to 10 pm. Higher ratio of very small particle size distributions increases the viscosity and makes the processing difficult, whereas presence of higher distribution of very larger particle size distributions lowers the viscosity and creates problem of slumping.

[0085] The non-conductive particles may be in the form of flakes and / or spheres and / or irregularly shaped particles. Preferably, the non-conductive particles are in the form of flakes and / or irregularly shaped particles. This is because, in comparison to spheres, flakes and irregularly shaped particles may have improved adhesion to a substrate and may have a reduced propensity to delaminate during a thermoforming process.

[0086] The non-conductive particles preferably have a low ionic content, preferably substantially zero.

[0087] When the composition comprises solid particles other than the titanium dioxide particles, the titanium dioxide particles preferably comprise from 70 to 99 wt.% of the total solid particles, more preferably from 80 to 99 wt.% of the total solid particles. When the composition comprises higher amounts of solid particles other than the titanium dioxide particles, the composition may exhibit poor adhesion to a PC injection moulding resin after injection moulding.

[0088] In a preferred embodiment, the composition comprises: from 10 to 85 wt.% of the binder based on the total weight of the composition, preferably from 15 to 80 wt.%, and from 4 to 90 wt.% of the total amount of the titanium dioxide particles and, if present, the solid particles other than the titanium dioxide particles, based on the total weight of the composition, preferably from 5 to 85 wt.%, and the binder comprises: from 0.5 to 10 wt.% cross-linking agent, preferably from 1.9 to 6.1 wt.% cross-linking agent, from 2 to 12 wt.% polyurethane resin, preferably from 4.8 to 8.4 wt.% polyurethane resin, from 0.5 to 10 wt.% polyester resin, preferably from 1 .9 to 5.3 wt.% polyester resin, from 2 to 18 wt.% phenoxy resin, preferably from 4.5 to 12.4 wt.% phenoxy resin, from 0 to 30 wt.% thermosetting resin, preferably from 0 to 19.6 wt.% thermosetting resin (e.g. 1-19.6 wt.%), from 0 to 3 wt.% curing catalyst, preferably from 0 to 2 wt.% curing catalyst (e.g. 0.1-2 wt.%), from 0.3 to 17 wt.% performance booster materials, preferably 1.4 to 12.5 wt.% performance booster materials, from 0 to 60 wt.% glycol ether acetate, preferably from 4.9 to 41 .7 wt.% glycol ether acetate, from 0 to 60 wt.% glycol ether, preferably from 0 to 43.8 wt.% glycol ether (e.g. 1-43.8 wt.%), from 0 to 30 wt.% ketone, preferably from 0 to 19.9 wt.% ketone (e.g. 1- 19.9 wt.%), from 0 to 50 wt.% alcohol, preferably from 0 to 35.5 wt.% alcohol (e.g. 1- 35.5 wt.%), and from 0 to 20 wt.% hydrocarbon, preferably from 0 to 13.3 wt.% hydrocarbon (e.g. 1-13.3 wt.%).

[0089] The composition may preferably further comprise a colorant and / or dye and / or pigment, and may be the form of a graphic ink. In other words, the present invention provides a graphic ink comprising the composition described herein. The dye and / or pigment may form part of the performance booster materials discussed above.

[0090] The composition, once cured, preferably has a contact angle of greater than 80°, more preferably greater than 82°, even more preferably greater than 85°, still even more preferably greater than 90°. The composition preferably has a contact angle of from 90 to 105°, more preferably from 93 to 102°. This may cause the composition to strongly adhere to injection moulding resin. The contact angle may provide an indication of the surface energy, which may affect adhesion.

[0091] In a preferred embodiment, the composition is in cured form. Preferably, the current leakage at 500V is 200 nA or less, more preferably 150 nA or less, even more preferably 140 nA or less, still even more preferably 130 nA or less, still even more preferably 120 nA or less; and / or preferably the current leakage at 1000 V is 800 nA or less, more preferably 700 nA or less, even more preferably 500 nA or less, still even more preferably 200 nA or less, still even more preferably 100 nA or less, still even more preferably 80 nA or less.

[0092] In a further aspect, the present invention provides a composition comprising titanium dioxide particles dispersed in a binder, wherein the binder comprises: a cross-linking agent comprising melamine formaldehyde, a thermoplastic resin comprising a hydroxyl group, and a solvent; and the titanium dioxide particles comprise a titanium dioxide core and an outer shell comprising one or more of alumina, silica and zirconia.

[0093] The advantages and preferable features of the first aspect apply equally to this aspect.

[0094] In a further aspect, the present invention provides use of the composition described herein in the manufacture of an in-mould electronic (IME) component. The advantages and preferable features of the first aspect apply equally to this aspect.

[0095] In a further aspect, the present invention provides a method of manufacturing the composition described herein, the method comprising: providing a solvent, providing a thermoplastic resin having a hydroxyl group, dissolving the thermoplastic resin in the solvent at a temperature of from 50 to 100 °C, preferably from 70 to 100 °C, cooling the solution to room temperature, adding to the cooled solution a cross-linking agent comprising melamine formaldehyde and titanium dioxide particles comprising a titanium dioxide core and an outer shell comprising one or more of alumina, silica and zirconia.

[0096] The advantages and preferable features of the first aspect apply equally to this aspect.

[0097] The step of adding to the cooled solution a cross-linking agent comprising melamine formaldehyde and titanium dioxide particles comprising a titanium dioxide core and an outer shell comprising one or more of alumina, silica and zirconia, may comprise mixing. For example, the step may employ either three roll process, orbital mixer, or Cowie blade mixture. This may increase the dispersion of the titanium dioxide particles. Preferably, the step is carried out until the fineness of grandness (FOG) of the composition does not have any scratch on the Hegman Fineness Grinding Gauge.

[0098] In a further aspect, the present invention provides a method of manufacturing an in-mould electronic (IME) component, the method comprising: preparing a blank; thermoforming the blank to form a thermoformed structure; and injection molding the thermoformed structure, wherein preparing the blank comprises forming one or more structures on a thermoformable substrate, each structure formed by a method comprising: disposing the composition described herein on a thermoformable substrate, and drying the composition at a temperature of from 20 to 150 °C for from 0.5 to 60 minutes.

[0099] The advantages and preferable features of the first aspect apply equally to this aspect.

[0100] The term “thermoforming” as used herein may encompass a manufacturing process where a plastic sheet is heated to a pliable forming temperature, formed to a specific shape in a mould, and trimmed to create a usable product. The sheet is typically heated in an oven to a high-enough temperature that permits it to be stretched into or onto a mould and cooled to a finished shape. Its simplified version is vacuum forming. A pressure may be applied during the thermoforming. The thermoforming may comprise high-pressure thermoforming.

[0101] Drying the composition is carried out at a temperature of from 20 to 150 °C, preferably from 30 to 130 °C, for from 0.5 to 60 minutes, preferably for from 1 to 30 minutes.

[0102] Preferably two or more structures are formed. Use of the composition as disclosed herein ensures that the one or more structures, for example one or more layers in a multilayer stack, are compatible with each other.

[0103] The one or more structures are preferably selected from a dielectric layer, an encapsulant layer, a graphic layer and a barrier layer.

[0104] Preparing the blank preferably comprises forming one or more further structures on a thermoformable substrate, wherein the further structures comprise conductive layers

[0105] The one or more structures and / or one or more further structures preferably comprises a multilayer stack. The one or more structures and / or one or more further structures preferably comprises a printed circuit board.

[0106] Disposing the composition preferably comprises printing the composition, more preferably screen-printing the composition.

[0107] The substrate preferably comprises polycarbonate (PC) and / or polyethylene terephthalate (PET). The composition as described herein is compatible with, and forms strong adhesion with, such materials. Such materials also exhibit favourable thermoforming properties.

[0108] The thermoforming is preferably carried out at a temperature of from 140 °C to 210°C. Such a temperature is particularly suitable for thermoforming, and the composition described herein may be stable at such a temperature. The thermoforming may comprise vacuum thermoforming. In a preferred embodiment, the vacuum thermoforming is carried out at a pressure of from 0.25 MPa to 0.4 MPa. In another preferred embodiment, the high-pressure thermoforming is carried out at a pressure of from at a pressure ranging from 6 MPa to 12 MPa.

[0109] Preferably, the method further comprises attaching one or more electronic devices to the blank using a conductive adhesive or a non-conductive adhesive, such as the non-conductive adhesive described herein, wherein the attaching takes place before and / or after thermoforming.

[0110] Preferably, the method further comprises, after thermoforming, applying a layer of resin to the substrate using injection molding, preferably wherein the resin comprises one or more of polycarbonate (PC), polyethylene terephthalate (PET), acrylonitrile butadiene styrene (ABS), polypropylene (PP), polyester, poly(methyl methacrylate) (PMMA), low density polyethylene (LDPE), high-density polyethylene (HDPE), polystyrene (PS), and thermoplastic polyurethane (TPU). Other similar resins may also be used. Such a layer of resin may provide the final IME component with favourable mechanical and / or aesthetic properties. The injection molding is preferably carried out at a temperature of from 170 to 330 °C. Such a temperature is particularly suitable for injection molding, and the composition described herein may be stable at such a temperature.

[0111] The in-mould electronic (IME) component preferably comprises a capacitive touch switch or a resistive touch switch. In comparison to conventional capacitive touch switches and resistive touch switches, such a capacitive touch switch and resistive touch switch may exhibit improved performance and / or reliability.

[0112] The in-mould electronic (IME) component preferably comprises one or more of a display, a light / lamp, a sensor, an indicator and a haptic / touch feedback device.

[0113] The in-mould electronic (IME) component preferably comprises one or more of a transparent conducting film, printed resistive heater, transparent resistive heater, transparent capacitive touch-based device, and transparent flexible and circuit element.

[0114] In a further aspect, the present invention provides in-mould electronic (IME) component manufactured according to the method described herein. In comparison to conventional IME components, the IME component may exhibit improved performance and / or reliability.

[0115] In a further aspect, the present invention provides an in-mould electronic (IME) component comprising the composition described herein. As will be appreciated, the composition will have undergone at least partial cross-linking. In comparison to conventional IME components, the IME component may exhibit improved performance and / or reliability. The composition may be in cured and / or dried form. In other words, the composition may be substantially devoid of the solvent, or completely devoid of the solvent.

[0116] The in-mould electronic (IME) component preferably comprises a capacitive touch switch or a resistive touch switch. In comparison to conventional capacitive touch switches and resistive touch switches, such a capacitive touch switch and resistive touch switch may exhibit improved performance and / or reliability.

[0117] The in-mould electronic (IME) component preferably comprises one or more of a display, a light / lamp, a sensor, an indicator and a hepatic / touch feedback device. In comparison to conventional, display, a light / lamp, a sensor, an indicator and a hepatic / touch feedback device such a display, a light / lamp, a sensor, an indicator and a hepatic / touch feedback device may exhibit improved performance and / or reliability.

[0118] The in-mould electronic (IME) component preferably comprises one or more of a transparent conducting film, printed resistive heater, transparent resistive heater, transparent capacitive touch-based device, and transparent flexible and circuit element. In such case, preferably the composition comprises conductive fillers may comprise conducting, metallic nanowires and / or conducting carbon nanotubes and carbon nanofibers; and / or conducting polymers; and / or conducting graphene flakes, as described above.

[0119] The invention will now be described in relation to the following non-limiting drawings in which:

[0120] Figure 1 shows a schematic representation of generic manufacturing process steps of In-mould Electronics Structures (IME).

[0121] Figure 2 shows plots of leakage current versus exposure time for a cured composition.

[0122] Figures 3a-f shows images of printed compositions.

[0123] Figures 4a and 4b show printed compositions.

[0124] Figure 5a is a schematic of dielectric measurement set-up. Figure 5b shows an image of prepared sample for the dielectric measurement. Figure 5c shows an image of a thermoformed dielectric composition from transmitted light. Figure 5d shows a plot of leakage current versus applied current for two levels of strain.

[0125] Figure 6a shows a dielectric composition as cross-over layer before injection moulding. Figure 6b shows the dielectric measurement of injection moulded parts. Figure 6c shows a plot of leakage current observed before and after injection moulding against applied voltage for a dielectric composition.

[0126] Figures 7a-d show results of injection moulding.

[0127] Figure 8 shows a power-up LED on a PC substrate.

[0128] The invention will now be described in relation to the following non-limiting examples. The characteristics of various commercial grades of inorganic shell protected titanium dioxide (rutile structure) fillers are listed in table 1 .

[0129] Examples:

[0130] Several polymeric binder compositions were prepared by dissolving mixtures of thermoplastic polyester resins, polyurethane resins and phenoxy resins having hydroxyl functional groups in mixtures of different categories of solvents at 70- 100 °C. The performance enhancing materials were added to the reaction mixtures on cooling. Reactive cross-linkers and curing catalysts I agents or hardener were then mixed well with the above polymer resin mixtures. The polymeric binder compositions were further mixed with several different non- conductive particles for the preparation of dielectric inks, coatings and adhesive compositions. The non-conductive particles were mixed using an orbital mixer (1000 rpm for 1 min for 3 cycles). Certain compositions were also milled in a three-roll mill for a few minutes to obtain a homogeneous paste. Examples 1-10 are the dielectric compositions and further without fillers such binder solution can also be used as filler free dielectric composition, encapsulation layer or as adhesion promotor for the injection molding process. Example 1 :

[0131] 34.11 weight % of non-conductive fillers and 65.89 weight % of polymer binder solution of were mixed using an orbital mixer at 1000 rpm for 1 min for 3 cycles. After mixing, the mixture was milled in a three-roll mill for a few minutes to obtain a homogeneous composition. The viscosity of the paste was found to be suitable for the screen printing. Table 2 shows the dielectric composition of Example 1 .

[0132] Table 2: Dielectric composition of Example 1 .

[0133] Reliability data in relation to Example 1 is shown in Figure 2. Referring to Figure 2, the observed leakage current is plotted for voltages of (from left to right) 100 V, 200 V, 300 V, 400 V, 500 V, 600 V, 700 V, 800 V, 900 V and 1000 V for various cured compositions after being exposed to 85 °C / 85% RH for 0 hours (first block from the left), 24 hours (second block), 115 hours (third block), 148 hours (fourth block), 196 hours (fifth block), 262 hours (sixth block), 546 hours (seventh block), 810 hours (eight block), 1125 hours (ninth block), 1724 hours (tenth block) and 32736 hours (eleventh block). The sample has very good dielectric performance even after exposure to > 500 h of reliability conditions.

[0134] Examples 2 to 9:

[0135] Compositions having the components specified in Table 3 were prepared as per the process described in Example 1 .

[0136] Table 3: Dielectric composition of Example 2 to 9.

[0137]

[0138] The disclosed dielectric compositions are characterized thoroughly and tested for screen printing and drying, before and after thermoforming adhesion testing, electrical performances, thermoforming and injection molding performance. The performance testing was carried out as per the procedures described below. In the process and fabrication steps, examples of standard machines, equipment and process steps were employed. The intent is to describe and show general sequence and procedures used. Other Equipment and approaches can also be used to achieve similar results.

[0139] Viscosity measurements:

[0140] The viscosity of dielectric compositions was measured using Brookfield viscometer, model DV3TRV and spindle 14. All viscosity measurements were carried out at 10 rpm at 25 ± 0.1 °C. The temperature is controlled using a Brookfield TC-550 digital temperature controller chiller.

[0141] Printing:

[0142] The disclosed dielectric compositions were screen printed for various test patterns using polyester, stainless steel and nylon mesh having varied sizes. Additionally, other test patterns were stencil-printed using stainless steel stencils. Commercial screen and stencil printers (e.g., DEK printer, ATMA Printer) were used to perform the printing tasks. Using this set-up, various test patterns, test vehicles and technology demonstrators were fabricated. Print features, print repeatability and stability during printing are excellent and meet specific requirements for IME and similar structure fabrications. In general, this set-up produced highly repeatable and consistent results. The fine line as well as angle dependent printability and film forming capability of dielectric compositions is shown in Figures 3a-f. Figure 3a shows the printabi lity of the dielectric composition of Example 7. Figures 3b and 3c show that the said dielectric composition has capability to print fine gap and fine line. Figure 3d shows the adhesion test results, establishing excellent compatibility with nascent PC substrate. Figure 3e shows the transmitted light image of thermoformed of two stack materials of dielectric composition and conductive circuit showing very good thermoformability of dielectric composition and good compatibility with conductive circuits. Figure 3f shows a free standing dried film of the dielectric composition.

[0143] Drying and Curing Procedure:

[0144] The as-printed test patterns and structures were cured or dried using commercial jet dryers (Natgraph Air Force Dryer Model 90) and convection oven (Binder 05012-31 ). These inks can be dried at very low temperatures ranging from 60- 150 °C in a box oven or in a jet-dryer, for 1-90 minutes. The thicknesses of the cured or dried printed features / structures were measured with an optical microscope (Keyence VHX 7000) or a mechanical thickness gauge (CDI gauge model number Q3110).

[0145] Adhesion Testing Procedure:

[0146] The test circuit structures were tested for the adhesion of the printed or laminated layers to the polymer substrates. A standard adhesion testing protocol, namely, ASTM D3359 was used. The degree of adhesion is rated from 0B to 5B as per ASTM D3359 method. Here 0B denotes no adhesion, while 5B denotes excellent adhesion.

[0147] Contact Angle Measurement Procedure:

[0148] Static contact angle on PC substrate was measured using the sessile drop method in Drop Shape Analyzer DSA30 (Kruss GmbH. Germany). The measurement accuracy for the contact angle was ± 1 °. The average of 10 measurements was taken to obtain the contact angle of each liquid on the surface while measuring contact angle on both the sides of the drop. All the tests were carried out at 25 °C with the liquid drop volume of 0.5 pL. Electrical Continuity Test:

[0149] For the dielectric properties I electrical continuity test, the disclosed dielectric compositions and compatible silver inks were screen-printed in 3-stack circuit test structures silver-dielectric-silver as shown in test pattern of in Figure 4a. The procedure involves first printing and drying of silver ink followed by printing and drying of dielectric composition. Top layer again printed with silver ink and dried. The 3-stacks test pattern tested for electrical continuity by holding a multimeter’s electrode (Fluke 179 True RMS multimeter) on the bottom layer and the top layer silver inks as shown in Figure 4b. The electrical shortening of the test observation is referred as “Fail” in electrical continuity test.

[0150] Electrical Leakage Current Measurement Procedure:

[0151] The electrical leakage current measurement of dielectric compositions was carried out on a 3-stack circuit test pattern of silver-dielectric-silver as shown in Figure 4a. The changes in leakage current were measured by applying voltage using Keithely 237 high voltage source measurement unit through 3-stack circuit test pattern.

[0152] Thermoforming Procedure:

[0153] Vacuum thermoforming was performed using Formech 686 semi-automatic equipment. 3-stack circuit test structures of silver-dielectric-silver were formed (printed and cured as described above) on thermoformable polymer sheets. Varying thickness sheets can be employed for thermoforming. In a typical thermoforming process, a PC substrate (for Example 100 microns thick) was heated to ~170°C for 35 seconds and vacuum applied for 10 seconds to form the heated sheet into the shape of the mold thus creating a 3D structure. After cooling, this 3D structure is removed from the mold and trimmed as needed. Depending on the thermoforming machine various sizes of 3D parts can be created. Electronic components can be attached to a circuit structure either before thermoforming or after thermoforming. The leakage current observed before and after thermoforming procedure is compiled in Figure 5 (dielectric measurement in 2D & 3D form: (a) dielectric measurement set-up, (b) image of prepared sample for the dielectric measurement, (c) image of thermoformed dielectric composition from transmitted light). Figure 5(d) shows a plot of leakage current versus applied current for two levels of strain.

[0154] Injection Molding Procedure:

[0155] Injection Molding was performed on the Toshiba injection molding machine using a center gate design. The cavity dimension was 100 mm x 80 mm. Injection molding was carried out in flat square shape. PC resin was used for making the injection molded part. Other resins such as ABS, PP, etc. can be employed for injection molding. Depending on the Injection Molding machine being used, 3D parts of various sizes and complexities can be produced. The leakage current observed before and after injection molding procedure is compiled in Figure 6 (dielectric measurement of injection molded parts: (a) dielectric composition as cross-over layer before injection molding (b) dielectric measurement of injection molded parts and (c) leakage current observed before and after injection molding against applied voltage of Example 7 dielectric compositions). Further, the failure mode of adhesion strength of dielectric composition during injection molding testing performance is shown in Figure 7 (injection molding results: (a) example of delamination - No adhesion during Injection molding (b) example of moderate adhesion - larger ink wash-off around gate, (c) good adhesion ink wash off only at gate, and (d) excellent adhesion - No ink wash off at the gate).

[0156] Accelerated Environmental Testing:

[0157] The disclosed dielectric ink compositions are highly robust and stable when tested at accelerated environmental test conditions as per JEDEC 22-A101 (Environmental Testing, 85 °C 185 % RH). 3-stack circuit test structures of silver- dielectric-silver were formed (printed and cured as described above) on thermoformable polymer sheets. Electrical leakage current of dielectric compositions was measured before initiation of accelerated environmental testing. Further, these 3-stack circuits are exposed to 85 °C 185 % RH accelerated environmental testing conditions for various exposure time as shown in Figure 2. Samples were taken out at various time intervals from testing chambers and allowed to cool at 25 °C. The electrical leakage current was measured on post cooling for the exposed samples. The measured samples were further placed in testing chambers and cycle of leakage current measurement continued till specified exposure time. The observed testing performance is shown in in Figure 2.

[0158] Figure 8 shows a functional demonstration of power-up LED on PC substrate prepared using the dielectric composition of Example 7. Table 4 summarizes basic characteristics and testing performance attributes of non-conducting dielectric compositions as described in Example 1 to Example 9.

[0159] able 4: Characteristics and performance testing results of various non-conducting dielectric compositions (Example 1 to Example )

[0160]

[0161] Examples 1-9 all exhibited a high degree of insulation (breakdown voltage). In addition, as shown in Table 4, Examples 1-9 all exhibited low leakage current. Example 3 exhibited less favourable adhesion to a polycarbonate substrate after thermoforming. This is likely due to a high degree of cross-linking, resulting from the large amount of isocyanate cross-linking agent and / or the large amount of total cross-linking agent. Examples 4 and 5 exhibited less favourable adhesion to PC injection moulding resin after injection moulding. This may be due to the larger amounts of performance booster materials and / or the larger amounts of talc in comparison to the amounts of titanium dioxide particles, i.e. titanium dioxide particles comprising less than 70 wt.% of the total solid particles.

[0162] The foregoing detailed description has been provided by way of explanation and illustration, and is not intended to limit the scope of the appended claims. Many variations in the presently preferred embodiments illustrated herein will be apparent to one of ordinary skill in the art and remain within the scope of the appended claims and their equivalents.

Claims

Claims1 . A composition for use in the manufacture of an in-mould electronic (IME) component, the composition comprising titanium dioxide particles dispersed in a binder, wherein the binder comprises: a cross-linking agent comprising melamine formaldehyde, a thermoplastic resin comprising a hydroxyl group, and a solvent; and the titanium dioxide particles comprise a titanium dioxide core and an outer shell comprising one or more of alumina, silica and zirconia.

2. The composition of claim 1 , wherein the cross-linking agent further comprises isocyanate and / or polyisocyanate and / or blocked polyisocyanate.

3. The composition of claim 1 or claim 2, wherein the titanium dioxide comprises rutile titanium dioxide.

4. The composition of any preceding claim, wherein the titanium dioxide particles comprise from 0.5 to 15 wt.% outer shell based on the total weight of the titanium dioxide particles, preferably from 1 to 9 wt.% outer shell based on the total weight of the titanium dioxide particles.

5. The composition of any preceding claim, wherein the outer shell comprises alumina, silica and zirconia.

6. The composition of claim 5, wherein the titanium dioxide particles comprise, based on the total weight of the titanium dioxide particles: from 1.7 to 7 wt.% alumina, and / or from 1 .4 to 9 wt.% silica, and / or from 0.1 to 3 wt.% zirconia.

7. The composition of any preceding claim, comprising from 10 to 85 wt.% of the binder based on the total weight of the composition, preferably from 15 to 80 wt.%.

8. The composition of any preceding claim, comprising from 4 to 90 wt.% of the titanium dioxide particles based on the total weight of the composition, preferably from 5 to 85 wt.%.

9. The composition of any preceding claim, wherein the titanium dioxide particles comprise an organic coating on the surface thereof.

10. The composition of claim 9, wherein the organic coating is hydrophobic or hydrophilic, preferably hydrophobic.11 . The composition of any preceding claim, wherein the solvent comprises an aromatic alcohol.

12. The composition of claim 11 , wherein the aromatic alcohol comprises benzyl alcohol.

13. The composition of cany preceding claim, wherein the binder comprises two or more solvents selected from aromatic alcohol, glycol ether acetate and glycol ether.

14. The composition of any preceding claim, wherein the titanium dioxide particles have a D50 (median particle size) of from 0.05 to 30 pm, preferably from 0.1 to 10 pm, more preferably from 0.2 to 0.7 pm, even more preferably from 0.25 to 0.6 pm.

15. The composition of any preceding claim, wherein the titanium dioxide particles have a L* value of greater than or equal to 97 %, preferably greater than or equal to 98 %.

16. The composition of any preceding claim, wherein the titanium dioxide particles have a specific resistance of greater than or equal to 3000 Q.cm.

17. The composition of any preceding claim, wherein the titanium dioxide particles have a specific gravity of from 3.5 to 4.5 g / cm3, preferably from 3.7 to 4.2 g / cm318. The composition of any preceding claim, wherein, when suspended in water, the titanium dioxide particles have a pH of greater than 6, preferably greater than 6.5, more preferably from 7 to 9.5.

19. The composition of any preceding claim in the form of a dielectric ink.

20. The composition of any preceding claim in the form of a non-conductive adhesive.21 . The composition of any preceding claim in cured form.

22. The composition of claim 21 , wherein: the current leakage at 500V is 200 nA or less, preferably 150 nA or less, more preferably 140 nA or less, even more preferably 130 nA or less, still even more preferably 120 nA or less; and / or the current leakage at 1000 V is 800 nA or less, preferably 700 nA or less, more preferably 500 nA or less, even more preferably 200 nA or less, still even more preferably 100 nA or less, still even more preferably 80 nA or less.

23. Use of the composition of any preceding claim in the manufacture of an inmould electronic (IME) component.

24. A method of manufacturing the composition of any of claims 1 to 22, the method comprising: providing a solvent, providing a thermoplastic resin having a hydroxyl group,dissolving the thermoplastic resin in the solvent at a temperature of from 50 to 100 °C, preferably from 70 to 100 °C, cooling the solution to room temperature, adding to the cooled solution a cross-linking agent comprising melamine formaldehyde and titanium dioxide particles comprising a titanium dioxide core and an outer shell comprising one or more of alumina, silica and zirconia.

25. A method of manufacturing an in-mould electronic (IME) component, the method comprising: preparing a blank; thermoforming the blank to form a thermoformed structure; and injection molding the thermoformed structure, wherein preparing the blank comprises forming one or more structures on a thermoformable substrate, each structure formed by a method comprising: disposing the composition of any of claims 1 to 20 on a thermoformable substrate, and drying the composition at a temperature of from 20 to 150 °C for from 0.5 to 60 minutes.

26. An in-mould electronic (IME) component manufactured according to the method of any of claim 25.

27. An in-mould electronic (IME) component comprising the composition of any of claims 1 to 22.

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