GB2595683A

GB2595683A - A capacitive object, conductive plastic composition and method of manufacture

Info

Publication number: GB2595683A
Application number: GB2008325.9A
Authority: GB
Inventors: Clemson Wesley
Original assignee: Individual
Current assignee: Individual
Priority date: 2020-06-03
Filing date: 2020-06-03
Publication date: 2021-12-08
Also published as: GB202008325D0

Abstract

A conductive composition for use in a capacitive object (e.g. stylus-like object) comprises a base plastics material and a conductive additive present as agglomerates in the composition and in the object. Preferably, the conductive additive is a nanoscale carbon, such as carbon nanotubes, which may be present in the base plastics material in amounts of less than 10 wt.%, preferably less than 3 wt.%. The base plastics material may be polyvinyl chloride, polyvinyl chloride acetate, silicone, a polyethylene terephthalate polyester, polyurethane, acrylonitrile, butadiene-styrene, or polycarbonate. A capacitive object comprising a conductive area 13 formed from the conductive composition is also disclosed. The object may be a smartcard 10, mobile telephone case (11, Fig. 3), magnetic strip card, identification card, membership card, driver’s licence, residence permit, bespoke pointer device, keyring, or fob. The conductive area may be a conductive contact surface, which may be provided as discrete portions at one or more corners of a rectangular object.

Description

A CAPACITIVE OBJECT, CONDUCTIVE PLASTIC COMPOSITION AND METHOD OF MANUFACTURE

Technical Field of the Invention

The present invention relates generally to capacitive everyday objects and more particularly to capacitive objects formed from one or more conductive materials such as cases for personal devices such as smartphone cases, bank cards and the like.

Background to the Invention

Most plastics are inherently electrically insulating materials, they do not conduct electricity. However, in certain applications, electrically conductive plastic materials are useful for example in the case of a stylus used as an input or control device for use with a capacitive touch screen.

A stylus of this kind includes an electrically conductive tip made of electrically conductive plastic that is able to absorb some of the device's electrostatic field. A capacitive stylus will work with a capacitive touch screen but a capacitive stylus also works with nearly all touchscreens, including resistive and surface acoustic wave (SAW) touch screens.

Butyl and/or silicone rubbers are available loaded with carbon-black to make them conductive. A tip of such rubber with a conductive path can function as a stylus tip.

Carbon black loadings of over 20%w/w are frequently needed to achieve effective conductive performance in most thermoplastic resins. At this loading level, the physical properties of the polymer are frequently compromised.

The conductive property of the touching material is important in a stylus tip, but the size of contact area is also important in convention styluses utilising carbon black.

Generally speaking, the larger the contact surface, the more effective the tip is such that the stylus tip covers the portion where touch input is applied to the screen. This results in the stylus tip being enlarged to provide a more effective tip but in the increase in size, decreases the precision of the tip.

Embodiments of the invention seek to at least partially overcome or ameliorate any one or more of the abovementioned disadvantages or provide the consumer with a useful or commercial choice.

Summary of the Invention

According to a first aspect of the invention there is provided a capacitive object comprising at least one conductive portion or area formed from at least one base plastic material and a conductive additive present in agglomerates in the at least one base plastic material after forming the capacitive object.

According to a second aspect of the invention there is provided a conductive plastic composition used to form at least one conductive portion or area of a capacitive object, the composition comprising at least one base plastic material and a conductive additive present in agglomerates in the composition, after forming the object.

According to a third aspect of the invention there is provided a method of forming a capacitive object using a conductive plastic composition, the method comprising the steps of providing at least one base plastic material, mixing a conductive additive into the at least one base plastic material to form a mixture, forming at least one conductive portion or area from the mixture so that the conductive additive is present in agglomerates in the at least one conductive portion or area, after forming the capacitive object.

The method may further comprise the step of controlling the viscosity of the mixture until forming at least one conductive portion or area of the capacitive object.

Typically, the conductive additive is a carbon additive Typically, the conductive additive is a nanoscale conductive carbon additive.

In an embodiment, the nanoscale conductive carbon additive is added to the at least one base plastic material at a loading of less than 20%w/w, preferably less than 10%w/w, preferably less than 5%w/w and most preferably less than 3%w/w.

The conductive additive may be present in agglomerates in the mixture or not, but the presence of the conductive additive in agglomerates in the capacitive object may provide the technical advantages.

According to a fourth aspect of the invention there is provided a capacitive object formed from at least one base plastic material and a conductive additive mixed in the at least one base plastic material after forming the capacitive object, the capacitive object comprising at least one portion shaped to provide a conductive contact surface.

Providing a conductive plastic composition and at least a portion or area of a capacitive object formed from the conductive plastic composition gives the plastic composition and a capacitive object formed using the conductive plastic composition good conductive properties suitable to allow the object to be used as an input and/or control device on a capacitive touchscreen, whilst minimising the loading of the conductive additive and maintaining the material properties of the at least one base plastic, both during and after formation.

For clarity, a capacitive object is normally designated as such because of the ability of the capacitive object to interact with a capacitive screen but the capacitive object is able to do so because it is conductive.

Without wishing to be limited by theory, a variety of factors influence conductivity of plastic compounds including, the inherent conductivity of the plastic, the level of dispersion achieved for the conductive additive, the intrinsic conductivity of the conductive additive, and the applied electric potential.

Further, the level of conductivity achieved depends on the loading rate of conductive fillers, which is in turn related to the aspect ratio of the conductive additive particles.

In an embodiment, the conductive object is preferably an object that a user is likely to carry with them as a matter of course, every day. Incorporation of at least one conductive portion into an everyday object at the formation of the object is therefore preferred.

The conductive object will typically be a smartcard, a magnetic strip card (not smart), an identification card such as a driver's licence or residence permit, a membership card or similar which are often carried by a user in a wallet or purse or similar or an everyday object such as a keyrin2, fob, a mobile telephone case or a bespoke pointer device for attachment to any one of the aforementioned objects.

The conductive object may be a unitary object or a complex object formed of at least two component parts. The object will preferably be folioed from one or more plastic or polymer materials. This may allow the use of the mixture to form the object and/or incorporation of the mixture in at least one portion or area of the object when formed, minimising separation of the at least on portion or area from the remainder of the object is it is a complex object.

The conductive object will preferably comprise at least one portion shaped to provide a conductive contact surface. The at least one conductive portion may be provided as a result of a functional shape of the object itself such as a corner of a rectangular object for example as is likely to be the case with a card. smartcard or phone case. If the object is a bespoke object, then any sufficiently sized and shaped portion can be provided.

As mentioned above, the larger the contact surface, the more effective the conductive contact surface is such that conductive contact surface covers the portion where touch input is applied to a capacitive screen. This results in the conductive contact surface being enlarged to provide a more effective conductive contact surface but in the increase in size, the precision of the conductive contact surface decreases (a conductive contact surface which is too large may cover more than one portion where touch input is applied to the capacitive screen). Therefore, there is a compromise between increasing the size of the conductive contact surface for effectiveness and potential loss of precision.

A corner or similar, preferably one that encloses an angle of between 100' and 10° may be preferred.

The at least one conductive portion may be arcuate. The at least one conductive portion may be part-spherical or elliptical (arcuate in two directions).

The at least one conductive portion or area is preferably formed by or comprising the conductive plastic composition. The at least one conductive portion may be formed or provided at one or more corners of a generally rectangular object. Typically, at least one conductive portion may be formed or provided at all corners of a generally rectangular object.

In an embodiment, at least one L-shaped conductive portion may be provided at at least one corner of a generally rectangular object. This may reduce the amount of conductive plastic mixture used, which although the conductive plastic mixture will normally bc optimised to maximise material properties, will minimise any loss of integrity of the material used to form the object due to the inclusion of the conductive plastic mixture. This will preferably allow the formation of an object of one or more materials chosen for their mechanical properties and/or appearance and/or functional properties and comprise at least one conductive portion formed in or on the object using the conductive plastic mixture.

A conductive portion may extend substantially continuously about a perimeter of the object. In practice however, a user is going to use an exposed part of the object as a capacitive pointer rather than a planar side edge.

The at least one conductive portion may be provided in a particular location on the object.

The at least one conductive portion may be provided with a particular appearance in order to be easily identifiable by a user. The appearance of the at least 20 one conductive portion may be different to the appearance of the remainder of the object.

The at least one conductive portion may be provided through a part of the thickness of the object. The at least one conductive portion may be provided across a part of the height of one or more sidewalls of the object.

The at least one conductive portion is preferably formed with a surface area which is optimised relative to the size of the object to provide a sufficiently large area to effectively operate as a conductive input portion or pointer.

The at least one conductive portion may be formed concurrently with the formation of the object itself.

The at least one conductive portion may be formed separately and incorporated into the object when the object is formed.

In an embodiment, the conductive plastic mixture may be used to form the object.

In an embodiment, the conductive plastic mixture may be formed and then used in the forming process to form the object to provide at least one conductive portion in or on the object, which is typically formed from one or more materials. In this embodiment, the at least one conductive portion formed by or including the conductive plastic mixture is preferably located on or in the object to provide at least one conductive contact surface on or in the object.

The conductive plastic mixture may be used when molten (if moulding) or when set.

The at least one base plastic used to form the conductive plastic mixture may be any suitable plastic. The at least one base plastic will generally be selected for properties in the finished portion or object. The at least one base plastic may be the same plastic as used in the object or different thereto.

For a unitary object, for example a card, smartcard or bespoke plastic pointer, the at least one base plastic is preferably the at least one plastic selected for the object. For example, most identification cards, bank cards, and smartcards are formed from one or more of polyvinyl chloride (PVC) or polyvinyl chloride acetate (PVCA), but sometimes polyethylene-terephthalate-based polyester, polyurethane, acrylonitrile butadiene styrene or polycarbonate. These cards are normally formed using an extrusion process. A card may be formed in one or more layers. The conductive plastic mixture may be used in any one or more layers.

In this configuration, the at least one base plastic used in the conductive plastic mixture is preferably polyvinyl chloride (PVC) or polyvinyl chloride acetate (PVCA).

For a complex object formed from one or more component parts or portions or more than one material, the at least one base plastic may be any one or more plastic. The one or more plastic may be the same as one of the materials used to form the object 30 or may be different. For example, a case for a mobile telephone may be made of one or more than one material. Preferred materials used in manufacture of plastic phone cases include silicone aml polycarbonate amongst others. Silicone provides high friction properties as well as cushioning properties. Polycarbonate provides high impact. resistance. Phone cases are normally molded.

Use of a molding process in the formation of the phone case allows at least one portion of conductive plastic mixture to be located as desired and the phone case to be formed around the at least one conductive portion. The phone case may be formed entirely of conductive plastic mixture. The at least one conductive portion may be formed over at least a part of the height of the sidewall of the phone case and/or at a corner position at a corner edge between the rear wall of the phone case and one or more sidewalls.

Whilst any appropriate conductive additive can be used, a nanoscale carbon conductive additive is preferred.

Conductive element carbon nanotubes (CNTs) are a preferred conductive additive in the context of the present invention because of their good electrical and thermal properties at low loading levels (much lower than conventional conductive additives such as carbon black), leading to substantial mechanical property improvement in the mixture of the formed object, at a relatively low density.

The high aspect ratio together with the thermal and electrical conductivity of carbon nanotubes make them an attractive candidate for use in plastic applications requiring conductivity. Due to the high aspect ratio (long size grain with nano-sized diameter), CNT particles remain in contact with each other even at low filler levels and thus allow for good conductivity with improved mechanical, thermal, and physical properties.

In contrast, spherical conductive fillers such as carbon black filler particles only match CNT-loaded compounds' conductivity at higher loading levels which has a correlated diminution of mechanical properties of the mixture of base plastic with carbon black filler.

Further, the preferred CNT particles have high surface area and higher 30 interaggregate attractive force between CNT particles which result in agglomerates and a pseudo "secondary structure" within the mixture. Consequently, the pseudo-structure results in higher conductivity than would have been predicted based on the intrinsic structure of the nascent CNT particles. However, this secondary structure can cause a reduction in mechanical properties and an increase in the mixture matrix viscosity.

However, due to the inclusion of the CNT particles even at low CNT particles %w/w levels, leads to the formation of agglomerates and pseudo "secondary structure" within the mixture which in turn leads to good conductivity with improved mechanical, thermal, and physical properties even at low CNT particles %w/w levels. Maintaining the agglomerates and pseudo "secondary structure" in at least a part of the capacitive object when formed is important to maintaining the conductivity in the at least one part.

Preferably the at least one conductive CNT additive will be added to the at least one base plastic at or above a critical CNT content. Above the critical CNT content, the CNT particles agglomerate at the micro-scale which favours the formation of a percolating network.

The critical CNT content required to form a percolation network depends mainly on the CNT type (single-wall carbon nanotube. SWCNT. or multi-wall carbon nanotube. MWCNT), intrinsic CNT quality (amorphous carbon content and ratio metallic/semi-conductive tubes), aspect ratio (L/d), morphology, polymer matrix and dispersion state.

For the same polymer and CNT intrinsic quality, dispersion state and CNT aspect ratio are likely to be critical factors governing conductivity of the mixture.

The final dispersion state of CNTs within the plastic mixture typically results from a competition between van der Waals interactions among the CNTs and the viscous forces acting within the plastic mixture.

Low viscosity facilitates dispersion during processing but also promotes CNT re-agglomeration as soon as external energy supplied for dispersion stops. On the other hand, high viscosity may make processing more difficult but prevents CNT re-agglomeration after forming. Therefore, the dispersion state of the CNTs within the plastic mixture is preferably controlled by modifying the viscosity of the mixture of the at least one base plastic and at least one conductive additive.

The formation of a percolation network within the mixture is preferably achieved. The formation of a percolation network is preferably maintained when the mixture is used in the formation of the at least one conductive portion or area of a capacitive object.

Higher conductivity in the mixture is typically increased by agglomeration, even at lower loadings due to the formation of CNT-to-CNT contact/junctions in the agglomerated state. The formation of CNT-to-CNT contact/junctions in the agglomerated slate typically minimises the 'tunnelling distance' which allows electron hopping for conductivity. The tunnelling distance (the distance between the CNT agglomerates in the mixture) may be between 5-30 nm.

The percolation threshold of the at least one conductive additive in the at least one base plastic is typically the controlling factor and once the percolation threshold has been achieved with the corresponding agglomeration of the at the at least one conductive additive at the micro-scale resulting in a sufficient number of CNT-to-CNT contact/junctions, further increases in the amount of at least one conductive additive the conductive network once will typically only see marginal further increases in electrical conductivity.

In an embodiment, the capacitive object formed using the conductive plastic composition will preferably comprise at least one portion shaped to provide a conductive contact surface.

Preferably, the nanoscale conductive carbon additive agglomerates in the at least one base plastic material may be confined to one or more portions or areas of the capacitive object once formed. This can be achieved using an appropriate capacitive object forming process such as co-extrusion or co-molding. The conductive plastic composition of an embodiment may be provided relative to one or more plastic materials used to form the object, with the conductive plastic composition provided in one or more portions or areas of the object.

In other words, the conductive object may be formed from the mixture, which will lead to a capacitive object in which all parts are (equally) conductive.

Alternatively, the mixture may be used in a capacitive object forming process to provide a capacitive object in which only one or more parts or areas of the capacitive object are conductive

Detailed Description of the Invention

In order that the invention may be more clearly understood one or more embodiments thereof will now be described, by way of example only, with reference to the accompanying drawings, of which: Figure 1 is a schematic plan view of a smartcard according to an embodiment.

Figure 2 is a schematic end view of the smartcard illustrated in Figure 1.

Figure 3 is an axonometric view of a smartphone case (opening uppermost) from the lower end according to an embodiment.

Figure 4 is an axonometric view of the smartphone case shown in Figure 3 from the right side.

Figure 5 is an axonometric view of the smartphone case shown in Figure 3 from the left side.

Figure 6 is an axonometric view of the smartphone case shown in Figure 3 from the rear.

With reference to the accompanying figures, a capacitive smartcard 10 is illustrated in Figures 1 and 2 and a capacitive smartphone case 11 is illustrated in 20 Figures 3 to 6. Both embodiments comprise a conductive portion or area formed from a conductive plastic composition, after Forming the capacitive smartcard 10/case 11.

The conductive plastic composition used to form the conductive portion or area of the capacitive smartcard 10/case 11 comprises at least one base plastic material and a conductive additive present in agglomerates in the at least one base plastic material after forming the capacitive smartcard 10/case 11.

The method used to form the capacitive smartcard 10/case 11 and/or the conductive plastic composition is preferably such that the viscosity of the mixture of the conductive additive present and at least one base plastic material is controlled until the at least one conductive portion or area of the capacitive smartcard 10/case 11 is completed as this will preferably balance the ease of processing of the plastic mixture whilst maintaining the agglomerates in the at least one conductive portion or area of the capacitive smartcard 10/case 11 once formed.

There are two ways to ensure that the agglomerates are present in the at least one conductive portion or area of the capacitive smartcard 10/case 11 once formed and there are: a) Form the at least one conductive portion or area first, and then form the capacitive smartcard 10/case 11 relative to the at least one conductive portion or area; or b) Form the at least one conductive portion or area and the capacitive smartcard 10/case 11 at the same time which adds to processing complexity.

The conductive additive used in the preferred embodiments is a nanoscale carbon nanotube additive added to the at least one base plastic material at a loading of less than 10%w/w, preferably less than 5%w/w and most preferably less than 3%w/w.

A variety of factors influence conductivity of plastic compounds including, the inherent conductivity of the plastic, the level of dispersion achieved for the conductive additive, the intrinsic conductivity of the conductive additive, and the applied electric potential. Further, the level of conductivity achieved depends on the loading rate of conductive fillers, which is in turn related to the aspect ratio of the conductive additive particles.

The conductive card 10 illustrated in Figures 1 and 2 is be a smartcard which may include a magnetic strip. Card of this type are typically used as identification cards such as a driver's licence or residence permit, or bank cards which are often carried by a user in a wallet or purse or similar. The inclusion of at least one conductive portion or area in such an object allows the user to use the card itself as a pointer for a capacitive screen such as may be found on a payment terminal or checkout as the user will typically already have the car in their hand to pay. This gives the user a physical device with conductive properties, that can be used to separate themselves from the payment terminal or checkout which other users may have touched and therefore, may act as a carrier for microorganisms or disease.

The conductive object will preferably comprise at least one portion shaped to provide a conductive contact surface. The at least one conductive portion may be provided as a result of a functional shape of the object itself such as a corner of a rectangular object such as the smartcard 10 illustrated in Figures 1 and 2 or the phone case illustrated in Figures 3 to 6.

For a unitary object, for example the smartcard 10 illustrated in Figures 1 and 2, the at least one base plastic is the at least one plastic selected for the smartcard 10. Most smartcards 10 are formed from polyvinyl chloride (PVC) or polyvinyl chloride acetate (PVCA). These cards are normally formed using an extrusion process and incorporate an embedded integrated circuit (IC) chip 12 and a pattern of metal contacts to electrically connect to the internal chip. A card may be formed in one or more layers.

The dimensions of the smartcard 10 will normally be similar to those of a credit card. ID-1 of the ISO/IEC 7810 standard defines cards as nominally 85.60 by 53.98 millimetres (3.37 in x 2.13 in) and 0.76 millimetres (0.030 in) thick. This allows the smartcard 10 to be stored in a wallet or purse for example and so it will normally be carried by a user.

In the smartcard embodiment, the conductive plastic mixture may be used in any one or more layers of the smartcard.

In this embodiment, a conductive portion or area is formed by or comprising the conductive plastic mixture/composition. As illustrated in Figure 1 and Figure 2, a conductive portion 13 is formed or provided at all four corners of the generally rectangular smartcard 10. This allows a user to use any of the four corners as a conductive pointer or input surface.

The conductive portions or areas illustrated in Figure 1 and Figure 2 are crescent shaped but L-shaped conductive portions could be used. The provision of conductive portions or areas 13 incorporate in the bulk plastic used to form the smartcard 10 allows reduction in the amount of conductive plastic mixture used, which although the conductive plastic mixture will normally be optimised to maximise material properties, will minimise any loss of integrity of the material used to form the smartcard 10 due to the inclusion of the conductive plastic mixture. This will preferably allow the formation of the smartcard 10 of one or more materials chosen for their mechanical properties and/or appearance and/or functional properties and comprise at least one conductive portion 13 formed in or on the object using the conductive plastic mixture.

For a complex object formed from one or more component parts or portions or more than one material such as the phone case 11 illustrated in Figures 3 to 6, the at least one base plastic may be any one or more plastic. For example, a case for a mobile telephone may be made of one or more than one material. The phone case 11 illustrated in Figures 3 to 6 has a main body manufactured from clear polycm-bonate to provide high impact resistance. This phone case is formed using a molding process which allows the portions of conductive plastic mixture 13 to be located as desired and the phone case to be formed around the conductive portions 13.

The illustrated conductive portions 13 are formed over at least a part of the height of the sidewall of the phone case 11.

As illustrated, the conductive portions 13 extend substantially continuously about a perimeter of the phone case 11. The conductive portions 13 are discontinuous in the embodiment illustrated. The phone case 11 has a pair of volume buttons 14 and an opening 18 for user access to the lock button on one lateral side. Similarly, three openings 15, 16 are provided in a lower sidewall for the speakers and the charging port and a side button 17 is provided opposite the volume buttons 14. No conductive portions 13 are provided in these areas.

Importantly, the conductive portions 13 are provided in the corners of the phone case 11 as these are the portions most likely to be used by an operator as a conductive pointer or input surface. In practice, a user is going to use an exposed part of the phone case 11 as a capacitive pointer rather than a planar side edge.

The at least one conductive portion may be provided with a particular appearance in order to be easily identifiable by a user. The appearance of the at least one conductive portion may be different to the appearance of the remainder of the object, such as is illustrated in the phone case 11 shown in Figures 3 to 6, where the case is clear and the conductive portions are darker in colour.

The at. least. one conductive portion may be provided through a part of the thickness of the object. The at least one conductive portion may be provided across a part of the height of one or more sidewalls of the object. Both of these are shown in the phone case 11 shown in Figures 3 to 6.

The conductive portions are preferably formed with a surface area which is optimised relative to the size of the object to provide a sufficiently large area to effectively operate as a conductive input portion or pointer. The height of the conductive portions illustrated in Figures 3 to 6 extending over a part of the height of the sidcwalls provides a sufficiently large surface areas to function as a conductive pointer or input surface The at least one conductive portion is preferably formed separately and incorporated into the object when the object is formed as this will typically allow the properties and/or makeup of the at least one conductive portion to be fixed and remain unaffected by the formation of the object.

Whilst any appropriate conductive additive can be used a nanoscale carbon conductive additive such as conductive element carbon nanotubes (CNTs) because of their good electrical and thermal properties at low loading levels (much lower than conventional conductive additives such as carbon black), leading to substantial mechanical property improvement in the mixture of the formed object, at a relatively low density.

Typically, the conductive additive is a nanoscale conductive carbon additive. In an embodiment, the nanoscale conductive carbon additive is added to the at least one base plastic material at a loading of less than 10%w/w, preferably less than 5%w/w and 10 most preferably less than 3%w/w.

The formation of the conductive plastic mixture may be achieved using a method of forming a capacitive object using a conductive plastic composition. The preferred method comprises the steps of providing at least one base plastic material, mixing a conductive additive such as a nanoscale conductive carbon additive into the at least one base plastic material to form a mixture, then forming at least one conductive portion or area of the capacitive object from the mixture so that the conductive additive is present in agglomerates in the at least one conductive portion or area, after forming the capacitive object.

The control of the viscosity of the mixture may be important in the formation of the aggregates.

The conductive object may be formed from the mixture, which will lead to a capacitive object in which all parts are (equally) conductive. Alternatively, the mixture may be used to form one or more conductive parts or areas 13 which can either be formed during a capacitive object forming process to provide a capacitive object in which only one or more conductive parts or areas of the capacitive object are conductive or can be formed prior (to fix the characteristics of the one or more conductive parts) and then the one or more conductive parts are used during a capacitive object forming process to provide a capacitive object.

The one or more embodiments are described above by way of example only. Many variations are possible without departing from the scope of protection afforded by the appended claims.

Claims

CLAIMSI. A conductive plastic composition used to form at least one conductive portion or arca of a capacitive object, the composition comprising at least one base plastic material and a conductive additive present in agglomerates in the composition, after forming the object.
2. A conductive plastic composition as claimed in claim 1 wherein the conductive additive comprises conductive carbon additive.
3. A conductive plastic composition as claimed in claim 1 or claim 2 wherein the conductive additive is a nanoscale carbon conductive additive.
4. A conductive plastic composition as claimed in claim 3 wherein the nanoscale conductive carbon additive is added to the at least one base plastic material at a loading of less than 10%w/w.
5. A conductive plastic composition as claimed in claim 3 wherein the nanoscale conductive carbon additive is added to the at least one base plastic material at a loading of less than 5%w/w.
6. A conductive plastic composition as claimed in claim 3 wherein the nanoscale conductive carbon additive is added to the at least one base plastic material at a loading of less than 3%w/w.
7. A conductive plastic composition as claimed in any one of the preceding claims wherein the nanoscale conductive carbon additive comprises conductive element carbon nanotubes.
S. A conductive plastic composition as claimed in claim 7 wherein the at least one conductive element carbon nanotubes are present in the composition at or above a critical conductive element carbon nanotubes content based on any one or more of the group including conductive element carbon nanotube type, intrinsic conductive element carbon nanotube quality, aspect ratio, morphology, the at least one base plastic and dispersion state.
9. A conductive plastic composition as claimed in any one of the preceding claims wherein the at least one base plastic is any one or more plastic chosen from the group including polyvinyl chloride, polyvinyl chloride acetate, silicone, polyethylene-terephthalate-based polyester, polyurethane, acrylonitrile butadiene styrene or polycarbonate.
10. A capacitive object comprising at least one conductive portion or area formed from the conductive plastic composition of any one of the preceding claims.
11. A capacitive object as claimed in claim 10 comprising a smartcard, a magnetic strip card, an identification card, driver's licence or residence permit, a membership card, a keyring, fob, a mobile telephone case or a bespoke pointer device.
12. A capacitive object as claimed in either claim 10 or claim 11 comprising at least one conductive portion or area shaped to provide a conductive contact surface.
13. A capacitive object as claimed in claim 12 wherein the at least one conductive portion or area is provided at one or more corners of a rectangular object.
14. A capacitive object as claimed in either claim 12 or claim 13 wherein the at least IS one conductive portion or area part-spherical or part-elliptical.
15. A capacitive object as claimed in any one of claims 12 to 14 wherein the at least one conductive portion or area is provided as a discrete portion at at least one corner of a generally rectangular object.
16. A capacitive object as claimed in any one of claims 10 to 15 wherein the at least one conductive portion or area is provided through a part of the thickness of the object.
17. A capacitive object as claimed in any one of claims 10 to 16 wherein the at least one conductive portion or area is provided across a part of a height of one or more sidewalls of the object.
18. A method of forming a capacitive object using a conductive plastic composition, the method comprising the steps of providing at least one base plastic material, mixing a conductive additive into the at least one base plastic material to form a mixture, forming at least one conductive portion or area from the mixture so that the conductive additive is present in agglomerates in the at least one conductive portion or area, after forming the capacitive object.
19. A method of forming a capacitive object as claimed in claim 18 further comprising the step of controlling the viscosity of the mixture until forming at least one conductive portion or area of the capacitive object.
20. A method of forming a capacitive object as claimed in claim 18 or claim 19 wherein the conductive object is formed from the mixture.
21. A method of forming a capacitive object as claimed in claim 18 or claim 19 wherein the mixture is used to form one or more conductive parts or areas which are formed during a capacitive object forming process to provide a capacitive object in which only one or more conductive parts or areas of the capacitive object are conductive.
22. A method of forming a capacitive object as claimed in claim 18 or claim 19 wherein the mixture is used to form one or more conductive parts or areas and then the one or more conductive parts are used during a capacitive object forming process to provide a capacitive object.
23. A capacitive object formed from at least one base plastic material and a conductive additive mixed in the at least one base plastic material after forming the capacitive object, the capacitive object comprising at least one portion shaped to provide a conductive contact surface.
24. A capacitive object as claimed in claim 23 wherein the at least one conductive additive is present in the at least one base plastic material at or above a critical additive content based on any one or more of the group including additive type, intrinsic additive quality, aspect ratio, morphology, the at least one base plastic and dispersion state.