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Title:
CONTACT CLEANING SURFACE ASSEMBLY AND METHOD OF MANUFACTURING THEREOF
Document Type and Number:
WIPO Patent Application WO/2019/177950
Kind Code:
A1
Abstract:
Contact cleaning surface assembly and a method of manufacturing same, the contact cleaning surface assembly comprising an elastomeric layer with bulk conductivity (e.g. electrical conductivity), the elastomeric layer (112) having a conductive surface (114) for contact with a part to be cleaned and a further conductive surface (113) in electrical contact with a conductive pathway (110) for charge extraction from the conductive layer (112).

Inventors:
HAMILTON, Sheila (155 Harlem AvenueGlenview, Illinois, 60025, US)
MITCHELL, Stephen Frank (155 Harlem AvenueGlenview, Illinois, 60025, US)
Application Number:
US2019/021580
Publication Date:
September 19, 2019
Filing Date:
March 11, 2019
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
ILLINOIS TOOL WORKS INC. (155 Harlem Avenue, Glenview, Illinois, 60025, US)
International Classes:
B08B7/00; G03G21/00
Foreign References:
US20080146427A12008-06-19
US20110275502A12011-11-10
JP2015217355A2015-12-07
GB1411198A1975-10-22
US5978630A1999-11-02
Attorney, Agent or Firm:
PAHNKE, Chad A. (McAndrews, Held & Malloy Ltd.,500 W. Madison, 34th Floo, Chicago Illinois, 60661, US)
Download PDF:
Claims:
CLAIMS

1 . A contact cleaning surface assembly comprising an elastomeric layer with bulk conductivity (e.g. electrical conductivity), the elastomeric layer having a conductive surface for contact with a part to be cleaned and a further conductive surface in electrical contact with a conductive pathway for charge extraction from the conductive layer.

2. A contact cleaning surface assembly according to claim 1 , wherein the elastomeric layer is in electrical contact with the conductive pathway.

3. A contact cleaning surface assembly according to claim 2, wherein the elastomeric layer is in intimate contact with the conductive pathway.

4. A contact cleaning assembly according to claim 1 or claim 2, wherein the conductive pathway is a conductive support for the elastomeric layer.

5. A contact cleaning surface assembly according to claim 3, wherein the elastomeric layer is in intimate contact with the support.

6. A contact cleaning surface assembly according to any one of claims 1 to 5, wherein charge extraction path is from conductive layer to the conductive pathway.

7. A contact cleaning surface assembly according to any one of the preceding claims, wherein the assembly is a roller.

8. A contact cleaning surface assembly according to any one of claims 1 to 6, wherein the assembly comprises a planar (or substantially planar) sheet.

9. A contact cleaning surface assembly according to any one of the preceding claims, wherein the elastomeric layer comprises conductive elements.

10. A contact cleaning surface assembly according to claim 9, wherein the conductive elements form a network.

1 1 . A contact cleaning surface assembly according to claim 9 or claim 10, wherein the network is electrically conductive (e.g. in proximity or contact with one another).

12. A contact cleaning surface assembly according to any one of the preceding claims, wherein the elastomeric layer comprises an interconnected network of conductive elements.

13. A contact cleaning surface assembly according to claim 12, wherein the conductive elements are elongate.

14. A contact cleaning surface assembly according to claim 12 or claim 13, wherein the elongate conductive elements are hollow.

15. A contact cleaning surface assembly according to any one of claims 12 to 14, wherein the conductive elements are carbon.

16. A contact cleaning surface assembly according to any one of claims 12 to 15, wherein conductive elements are nanotubes.

17. A contact cleaning surface assembly according to any one of claims 12 to 16,

wherein conductive elements are carbon nanotubes.

18. A contact cleaning surface assembly according to claim 16, or claim 17, wherein nanotubes are single walled carbon nanotubes.

19. A contact cleaning surface assembly according to claim 18, wherein the carbon nanotubes are a single carbon atom wall thickness.

20. A contact cleaning surface assembly according to any one of the preceding claims, wherein surface resistance the, or each conductive surface is less than 1 x 109 W.

21 . A contact cleaning surface assembly according to any one of the preceding claims, wherein surface resistance the, or each conductive surface is in the range of about 1 x 106 W to about 1 x 109 W.

22. A contact cleaning surface assembly according to any one of claims 4 to 21 , wherein the support is a shaft.

23. A contact cleaning surface assembly according to any one of the preceding claims, wherein the elongate conductive elements are dispersed uniformly throughout the elastomer material.

24. A contact cleaning surface assembly according to any one of claims 9 to 23, wherein the conductive elements are dispersed such that they are embedded and retained in the elastomeric material.

25. A contact cleaning roller according to any one of claims 9 to 24, wherein the

conductive elements are orientated randomly in the elastomeric material.

26. A contact cleaning surface assembly according to any one of claims 9 to 25, wherein the conductive elements have length within the range about 5 pm to about 30pm.

27. A contact cleaning surface assembly according to any one of claims 9 to 26, wherein the conductive elements have diameter within the range about 1 nm to about 200nm.

28. A contact cleaning surface assembly according to any one of claims 9 to 28, wherein the concentration of conductive elements in the elastomer is at least about 0.015% by weight of elastomer.

29. A contact cleaning surface assembly according to any preceding claim, wherein the elastomer comprises one of silicone rubber or polyurethane.

30. A contact cleaning surface assembly according to any preceding claim, wherein the elastomer comprises one of: a heat cured silicone, or polyurethane.

31 . A contact cleaning surface assembly according to claim 30, wherein the elastomer is a two-part, room-temperature curing silicone rubber.

32. A contact cleaning surface roller comprising: a core region,

and a surface region sheathing the core region, wherein the surface region comprises an elastomer and a plurality of elongate elements dispersed within the elastomer material, wherein the elongate elements are formed of an electrically noninsulating material.

33. Use of a contact cleaning surface assembly according to any one of claims 1 to 31 in a contact cleaning process.

34. A contact cleaning apparatus comprising a contact cleaning surface assembly

according to any one of claims 1 to 31 .

35. A method of manufacturing a contact cleaning roller, said method comprising:

providing an elastomer in fluid form,

dispersing elongate elements formed of electrically non-insulating material into the elastomer,

providing the core region of a contact cleaning roller,

and sheathing the core region with the elastomer.

36. A method according to claim 35, said method subsequently comprising curing the elastomer.

37. A method of manufacturing a contact cleaning surface assembly, said method

comprising:

providing a pre-polymer of an elastomer,

adding a polymer modifying agent formed of electrically non-insulating material into the pre-polymer,

causing polymerisation of the pre-polymer,

curing the polymer to form an elastomeric cleaning surface having bulk conductivity.

38. A method according to any one of claims 35 to 37, wherein, after curing, the

conductive elements are dispersed throughout the elastomer.

39. A method according to any one of claims 35 to 38, wherein, after curing, the

conductive elements form a network.

40. A method according to any one of claims 35 to 39, wherein the conductive elements are orientated in random orientation.

Description:
CONTACT CLEANING SURFACE ASSEMBLY AND METHOD OF MANUFACTURING THEREOF

FIELD OF THE INVENTION

The present invention relates to a contact cleaning surface assembly for use in a contact cleaning process, in particular, but not exclusively, to a contact cleaning surface assembly comprising an elastomeric layer having a bulk conductivity. The present invention also relates to a method of manufacturing a contact cleaning surface assembly.

BACKGROUND

Contact cleaning is used to clean substrate surfaces. Once cleaned, the substrate surfaces may be used in a variety of sophisticated processes such as in the manufacturing of electronics, photovoltaics and flat panel displays. Usually, a rubber or elastomeric cleaning roller is used to remove contaminating particles from a substrate surface and an adhesive roller can then be used to remove the contaminating particles from the cleaning roller.

In operation, a contact cleaning roller contacts at least the upper surface of the substrate, removing the debris by means of adhesion removal mechanisms (e.g. Van der Waals forces and adhesion forces), where the inherent properties of the material used to form the contact cleaning roller attracts the debris and causes it to stick to the surface of the contact cleaning roller. It is thought that the contact cleaning roller pulls the contaminating particles away from the substrate surface in this manner due the attractive van der Waals forces between the particles and the roller. Consequently, existing contact cleaning rollers may ensure effectiveness in removing contaminating particles by maximising contact with the substrate surface.

Aside from the weak van der Waals electrostatic forces inherent in the material of the contact cleaning roller, other electrostatic charges may arise. The contact cleaning process, which relies on contact between different surfaces, has the potential to be source of electric charge from triboelectric effects and accumulation of electrostatic charges. As such, any equipment used in an electronics assembly factory within close proximity (for example within 100mm) of a substrate must be non-insulating and have sufficiently low surface resistance that it will prevent damage of a substrate from electrostatic charges.

When the contact cleaning roller has sufficient surface adhesion to clean a substrate (i.e. a part to be cleaned), electrostatic charges are likely to be generated during the contact cleaning process.

Surface resistance, R s , is defined by the ratio of a voltage to the current along the surface of a material. It is a property of the material measured in Ohms (W) is defined as: U

R s

Is

where U is DC voltage, and surface current is l s .

A well-known method of measuring surface resistance is provided in American National Standard Institute (ANSI) ESD STM1 1 .1 1 -2015. According to this method, any equipment for an electronics assembly factory used within 100mm of a substrate must have surface resistance of less than 1 x10 9 W.

Bulk conductivity is normally found by measuring Volume Resistance. A well-known method of measuring volume resistance is provided in American National Standard Institute (ANSI) ESD STM1 1 .12-2015.

Typical rubber or elastomeric cleaning rollers do not ordinarily have surface resistance below 1 x10 9 W, in other words, they are insulating and not conducting. It would be desirable to provide a cleaning roller that will provide for dissipation of electrostatic charges away from the substrate to be cleaned.

It is not uncommon to alter the properties of materials such as those used in contact cleaning rollers with the use of one or more additives during the manufacturing process. However, additives will necessarily have different properties to the original material and changes to the original material risk inhibiting its primary function, namely contact cleaning. This risk is especially high when attempting to modify the surface properties of a contact cleaning roller when the same surface is critical to the roller’s cleaning effectiveness. Anything that reduces the amount of the elastomer on the roller surface will potentially mean the elastomer is less able to make contact with the substrate to be cleaned, resulting in a reduced ability to contact and to attract dirt and debris. Further, a modifying additive may interfere with the usual process, as described above, by which debris is attracted to the surface of the cleaning roller. In both situations, the cleaning effectiveness of the roller will be inhibited or reduced.

Typical conductive additives, such as fibres and particulates may not disperse evenly throughout the elastomer’s matrix. Thus, the roller will have uneven surface resistance, combining portions that conduct charge away from the cleaning surface with portions that allow charge to accumulate and cause damage to the substrate.

A further consideration is that the incorporation of an additive into the elastomer should not affect the integrity of the elastomer or the roller. A loss of integrity or a decrease in its wear resistance may result in the roller abrading too quickly or the surface becoming damaged or pitted which further reduces its effectiveness. All these factors may increase running costs for the contact cleaning process.

Furthermore, additive materials which are not sufficiently similar to the elastomer, for example with a low bonding surface area, will mean that the surrounding elastomer cannot bind or adhere effectively to the additives. If this material is not securely embedded within the elastomer, then as the roller operates material will become dislodged and free from the roller surface, thereby contaminating the substrate being cleaned and / or being picked up by the adhesive roller, thereby shortening its life and increasing running costs. Yet further, if material is dislodged from the roller then it may result in the damage to the roller surface, again reducing cleaning effectiveness and increasing costs.

It is important to not use excessive quantities of additives in order to achieve a suitable reduction in surface resistance as the material will not be cost effective and may make the cost of the contact cleaning roller prohibitively high. It is therefore important to maximise the electrical connectivity provided by an additive while minimising the quantity used.

A further, related consequence of using a large quantity of additive is that it would lead to an increased amount of that material, and less of the elastomer, on the roller surface. The problems of reduced elastomer at the roller surface have already been described above.

As the cleaning roller wears down, it is important that its surface resistance is not affected, otherwise the risk of electrostatic build up will increase during the life of the cleaning roller. If this happens, then the roller may need to be replaced early and operating costs will increase. It is therefore important that anything that improves the surface resistance of the roller must continue to do so, without loss of effectiveness, through the life of the roller.

As mentioned above, it is a condition of certain cleaning applications that the surface resistance of the cleaning surface is less than 1 x10 9 W. Not only does this place a requirement on a contact cleaning roller to have a surface resistance less than 1 c10 9 W but, necessarily, the roller must be capable of allowing electrostatic charges to be conducted away from the cleaning surface to ground. It must also do this while it is in continuous operation, that is, the roller must allow charges to be conducted all the time it is rotating. Therefore, it may not be sufficient to provide a roller with low resistance in a localised region but it must be capable of conducting charges from the substrate surface to a suitable earthing device (i.e. to ground) at all times during its operation.

It is an object of the invention to alleviate or mitigate at least one or more of the aforementioned problems. An object of the invention is to alleviate or mitigate the problem of electrostatic charge build up derived from the contact cleaning surface assembly.

A further object is to alleviate or mitigate the problem of electrostatic charge without reducing or inhibiting the cleaning effectiveness of the contact cleaning roller, or without reducing the operating life of either the contact cleaning surface assembly or of the adhesive roller.

It is a yet further object of the invention to reduce the surface resistance of the contact cleaning surface assembly to less than 1 x10 9 W and, further, to achieve this while providing a path to allow electrostatic charge to be conducted to ground.

A further object of the invention is to reduce the surface resistance while minimising the quantity and maximising electrical connectivity of a non-insulating additive.

A yet further object of the invention is to improve connectivity while alleviating any decrease in, or yet improving, the integrity of the contact cleaning surface assembly.

A further object of the invention is to alleviate or mitigate electrostatic charge when using a contact cleaning surface assembly used in a suitable contact cleaning apparatus.

Also, a yet object aim is to provide a method manufacturing a contact cleaning surface assembly capable of alleviating or mitigating electrostatic charge.

BRIEF SUMMARY OF THE DISCLOSURE

According to an aspect of the present invention, there is provided a contact cleaning surface assembly comprising an elastomeric layer with bulk conductivity (e.g. electrical conductivity), the elastomeric layer having a conductive surface for contact with a part to be cleaned and a further conductive surface in electrical contact with a conductive pathway for charge extraction from the conductive layer.

In certain embodiments the elastomeric layer is in electrical contact with the conductive pathway.

In certain embodiments the elastomeric layer is in intimate contact with the conductive pathway.

In certain embodiments the conductive pathway provides charge extraction from the elastomeric layer to ground (i.e. an electrical earth).

In certain embodiments the conductive pathway comprises a metallic charge extraction element in contact with the conductive surface of the elastomeric layer. In certain embodiments the conductive pathway is a conductive support for the elastomeric layer.

In certain embodiments the elastomeric layer is in intimate contact with the support.

In certain embodiments the charge extraction path is from conductive layer to the conductive pathway.

In certain embodiments the elastomeric layer is attached to the conductive support.

In certain embodiments the elastomeric layer is in intimate contact with the conductive support. More specifically, the elastomeric layer is in intimate contact with the support across the entire further conductive surface of the elastomeric layer. In this way, charge extraction from the elastomeric layer to the support occurs across the entire further conductive surface of the elastomeric layer.

In certain embodiments the conductive support is formed of a metallic conductor material. More specifically, the metallic conductor support is stainless steel.

In certain embodiments the conductive support is formed of a non-metallic conductor material. More specifically, the non-metallic conductor support is carbon fibre.

In certain embodiments the support is a shaft.

In certain embodiments the charge extraction path is from conductive layer to the conductive support. More specifically, the charge extraction path is from the conductive surface of the elastomeric material through the elastomeric material to the further conductive surface of the elastomeric material to the conductive support.

In certain embodiments the assembly is a roller.

In certain embodiments the assembly comprises a planar (or substantially planar) sheet.

In certain embodiments the elastomeric layer comprises conductive elements. More specifically, the elastomeric layer comprises a modifying agent comprising conductive elements. In this way, the modifying agent reduces the bulk resistance and surface resistance of the elastomeric layer and provides the elastomeric layer with bulk conductivity.

In certain embodiments the conductive elements form a network. More specifically, the network of conductive elements is electrically conductive. The conductive elements in the elastomeric layer are in proximity or contact with one another such that the network of conductive elements provides a charge path from the outer conductive surface of the elastomeric layer, through the elastomeric layer to the further conductive surface of the elastomeric layer to the conductive support. In this way, charge can be extracted away from a substrate (i.e. part to be cleaned), through the elastomeric layer to the conductive support and to ground.

In certain embodiments the elastomeric layer comprises an interconnected network of conductive elements.

In certain embodiments the conductive elements are elongate. In this way, the surface area of the conductive elements in contact with the elastomer of the elastomeric layer is increased and the retention of the elements in the elastomeric layer is enhanced.

In certain embodiments the elongate conductive elements are hollow.

In certain embodiments the conductive elements are carbon.

In certain embodiments the conductive elements are nanotubes.

In certain embodiments conductive elements are carbon nanotubes.

In certain embodiments nanotubes are single walled carbon nanotubes. In this way, a balance is maintained between the cleaning properties of the elastomeric layer and the bulk conductivity thereof. The high surface area of the nanotubes provides improvements in bonding the carbon into the elastomer when compared to particulate carbon or carbon fibres.

More specifically, the carbon nanotubes are a single carbon atom wall thickness.

In certain embodiments the surface resistance of the, or each conductive surface is less than 1 x 10 9 W. More specifically, the surface resistance of both the conductive surface and the further conductive surface of the elastomeric layer is less than 1 x 10 9 W. Yet more specifically, the surface resistance of both the conductive surface and the further conductive surface of the elastomeric layer are substantially equal.

In certain embodiments the surface resistance the, or each conductive surface is in the range of about 1 x 10 6 W to about 1 x 10 9 W. More specifically, the surface resistance of both the conductive surface and the further conductive surface of the elastomeric layer is in the range of about 1 x 10 6 W to about 1 x 10 9 W. Yet more specifically, the surface resistance of both the conductive surface and the further conductive surface of the elastomeric layer are substantially equal.

In certain embodiments the elongate conductive elements are dispersed uniformly throughout the elastomer material.

In certain embodiments conductive elements are dispersed such that they are embedded and retained in the elastomeric material.

In certain embodiments the conductive elements are orientated randomly in the elastomeric material. In certain embodiments the conductive elements have length within the range about 5 pm to about 30pm.

In certain embodiments the conductive elements have diameter within the range about 1 nm to about 200nm.

In certain embodiments the concentration of conductive elements in the elastomer is at least about 0.015% by weight of elastomer.

In certain embodiments the elastomer comprises one of silicone rubber or polyurethane.

In certain embodiments the elastomer comprises silicone. In this way, a conductive silicone layer can be formed when carbon nanotubes are dispersed within the silicone material. The nanotubes are retained within the silicone polymer matrix through covalent bonding. Other additives, such as particulate materials are prone to migrate out of the silicone matrix due to the mobility of the silicone matrix. Thus, carbon nanotubes provide a retained modifying agent retained within the silicone matrix.

In certain embodiments the elastomer is a two-part, room-temperature curing silicone rubber.

According to a further aspect of the invention there is provided a contact cleaning roller comprising:

a core region,

and a surface region sheathing the core region, wherein the surface region comprises an elastomer and a plurality of elongate elements dispersed within the elastomer material, wherein the elongate elements are formed of an electrically noninsulating material.

According to a yet further aspect of the invention there is provided use of a contact cleaning surface assembly according to the present invention in a contact cleaning process.

According to another aspect of the invention there is provided a contact cleaning apparatus comprising a contact cleaning surface assembly according to the invention.

According to a further aspect of the invention there is provided a method of manufacturing a contact cleaning roller, said method comprising:

providing an elastomer in fluid form,

dispersing elongate elements formed of electrically non-insulating material into the elastomer,

providing the core region of a contact cleaning roller,

and sheathing the core region with the elastomer. In certain embodiments the method subsequently comprises curing the elastomer.

According to a yet further aspect of the invention there is provided a method of

manufacturing a contact cleaning surface assembly, said method comprising:

providing a pre-polymer of an elastomer,

adding a polymer modifying agent formed of electrically non-insulating material into the pre-polymer,

causing polymerisation of the pre-polymer,

curing the polymer to form an elastomeric cleaning surface having bulk conductivity.

In certain embodiments, after curing, the conductive elements are dispersed throughout the elastomer.

In certain embodiments, after curing, the conductive elements form a network.

In certain embodiments, the conductive elements are orientated in random orientation.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described by way of example only, and with reference to the accompanying drawings, in which:

Figure 1 is a schematic side view of a contact cleaning apparatus employing a roller having a contact cleaning surface assembly in accordance with an embodiment of the present invention;

Figure 2 is a schematic cross- section of a contact cleaning surface assembly in accordance with an embodiment of the present invention;

Figure 3a is a further schematic cross-section of a contact cleaning surface assembly in accordance with a first embodiment of the present invention;

Figure 3b is a schematic magnified cross-section of a section of contact cleaning surface assembly in Figure 3a; and

Figure 4 is a schematic of an elongate single-walled carbon nanotube of one embodiment of the present invention. DETAILED DESCRIPTION

Figure 1 is a schematic side view of a contact cleaning apparatus employing a contact cleaning surface assembly being a roller in accordance with embodiments of the present invention. The contact cleaning apparatus 1 comprises a contact cleaning roller 2 and an adhesive roller 3 mounted above a conveyor 4 on which a plurality of substrates 5 for cleaning are carried. The contact cleaning roller 2 is elongate and generally cylindrical in shape, and is mounted on a holder (not shown) having an axis perpendicular to the plane of view about which the contact cleaning roller 2 is free to rotate. The specific structure of the contact cleaning roller 2 is described in more detail below. The adhesive roller 3 is generally cylindrical in shape, and comprises a body having a surface on which adhesive is present, and is also mounted on a holder (not shown) having an axis perpendicular to the plane of view and parallel to that of the contact cleaning roller 2 about which the adhesive roller 3 is free to rotate. The contact cleaning roller 2 and adhesive roller 3 are mounted in such a manner so as to be in contact with one another such that clockwise rotational movement of the contact cleaning roller 2 results in counter-clockwise rotational movement of the adhesive roller 3 and vice versa. The need for the contact cleaning roller 2 and adhesive roller 3 to be in contact will be clear from the description of use below. The contact cleaning roller 2 is also mounted so as to be able to be in contact with the surface of a substrate 5 to be cleaned as it passes on a conveyor located below the axis of the conveyor 4.

Substrates 5 to be cleaned are processed as follows. A substrate 5 is positioned on the upper surface 6 of a conveyor 4, which in Figure 1 moves from right to left as indicated by arrow A. The substrate 5 to be cleaned passes underneath the contact cleaning roller 2, which rotates in a clockwise direction as indicated by arrow B. Before coming into contact with the contact cleaning roller 2, the upper surface of the substrate 5 is covered with debris 7 requiring removal, such as dust. The contact cleaning roller 2 contacts the upper surface of the substrate 5, removing the debris 7 by means of an electrostatic removal mechanism, where the inherent polarity of the material used to form the contact cleaning roller 2 attracts the debris 7 and causes it to stick to the surface of the contact cleaning roller 2. The relative attractive force between the surface of the contact cleaning roller 2 and the debris 7 is greater than that between the debris 7 and the surface of the substrate 5, hence the debris 7 is removed. The now clean substrate 5 continues along the conveyor 4 to a removal station (not shown) and the lower surface 8 of the conveyor passes back, forming a loop, in a left-right direction in Figure 1 , as indicated by arrow D. In order to clean the contact cleaning roller 2, the adhesive roller, rotating in a counter-clockwise direction as indicated by arrow C contacts the surface of the contact cleaning roller 2. At this point the adhesive force between the debris 7 and the adhesive present on the surface of the adhesive roller 3 is greater than the adhesion force holding the debris 7 onto the surface of the contact cleaning roller 2, and the debris is removed. The contact cleaning roller 3 then rotates to present a clean surface to the next substrate 5 to be cleaned.

Figure 2 is a schematic cross-section of a contact cleaning surface assembly in accordance with a first embodiment of the present invention. The contact cleaning surface assembly, in the form of a roller, is used as a contact cleaning roller in a contact cleaning system 1 as described above. The roller 102 comprises a conductive pathway, being conductive support 1 10 sheathed in a conductive elastomeric layer 112. The roller 102 is elongate and generally cylindrical in shape, and is mounted via a mounting mechanism onto a holder (not shown) for use in a contact cleaning apparatus 1 . The conductive shaft 1 10 is coaxial with the conductive elastomeric layer 1 12. The shaft 1 10 may be used to mount the roller 102, and in the rotational movement of the roller 102 in use. Aptly, such a shaft 1 10 is formed from a conductive material such as, for example metal or non-metallic or composite conductive material (e.g. stainless steel, or carbon fibre composite). The conductive shaft 1 10 is sheathed in an elastomeric material 1 12, such as, for example, rubber or other natural or synthetic elastomer material. The elastomer material is substantially homogeneous.

The conductive elastomeric layer 1 12 has a conductive outer surface 1 14 having a surface resistance of less than 1 x 10 9 W. The conductive elastomeric layer 1 12 has a conductive inner surface 1 13 having a surface resistance of less than 1 x 10 9 W and in contact with conductive shaft 1 10. In this way a conductive pathway is formed from the outer surface 1 14 to the inner surface 1 13 and to the shaft 1 10. The electrostatic charge created at the surface 1 14 during use of the contact cleaning roller 102 to clean a part (not shown), is conducted through the layer 1 12 to the conductive pathway provided by the conductive shaft 1 10.

Figure 3a is a schematic cross-section of a contact cleaning surface assembly, in the form of roller 102, in accordance with an embodiment of the present invention. Figure. 3b is a schematic magnified cross-section of a section of the same roller 102. The roller 102 comprises an elastomeric layer 1 12 having an outer conductive surface 1 14 and an inner conductive surface 1 13. The conductive elastomeric layer 1 12 sheathes and is attached to a conductive stainless steel shaft 1 10. The outer surface 1 14 is available to clean debris from a substrate surface in the manner described above.

In the depicted arrangement the elastomeric layer is a two-part, room temperature curing silicone rubber.

The elastomeric layer 1 12 comprises a plurality of elongate single-walled carbon nanotubes 1 16 dispersed and embedded within the elastomer material. The elongate single-walled carbon nanotubes 1 16 are dispersed within the elastomer of the layer 1 12 and form an interconnected network of carbon nanotubes 1 18. The dispersal of the nanotubes 1 16 within the elastomer is such that the members are spread in random orientation through substantially the whole thickness of the surface region 1 12, from the inner conductive surface 1 13 in contact with conductive shaft 1 10 to the outer conductive surface 1 14. The nanotubes also spread substantially across the axial width of the roller 102. Furthermore, as the nanotubes 1 16 comprise electrically non-insulating material then the whole surface region 1 12 has reduced electrical resistance, or increased electrical conductivity, compared to the elastomer alone. In this way, the elastomeric layer 1 12 has a bulk conductivity provided by the interconnected network of carbon nanotubes 1 18.

The bulk conductivity of the elastomer material in layer 1 12 provides a charge path to ground for electrical charges generated during the cleaning operation. Consequently, not only does the roller exhibit reduced electrical resistance when it is new, but the effect will last throughout its useful life, even as the outer surface 1 14 wears down.

The dispersal of the elongate carbon elements 1 16 and formation of the network 1 18 is such that the decreased surface resistance at conductive surface 1 13 and 1 14, as measured according to ANSI ESD STM1 1 .1 1 -2015, is less than 1 x10 9 W. Furthermore, as the whole elastomeric layer 1 14 has reduced electrical resistance, the roller 102 can provide a path to allow electrostatic charge to be conducted to ground away from the substrate surface.

Fig. 4 depicts an elongate single-walled carbon nanotube 1 16 of one embodiment of the present invention. The nanotube 1 16 is one of a plurality of similar elongate single-walled carbon nanotubes that are dispersed within the elastomeric layer 1 12.

Each single-walled carbon nanotube 1 16 can vary in length within the range 5-30pm and have a diameter within the range 1 -200nm. In the embodiment of Figures 3a and 3b, single-walled carbon nanotubes comprise 0.02% by weight of the elastomer comprising the elastomeric layer 1 12.

The elongate single-walled carbon nanotubes 1 16 are dispersed so that they form a conductive network (1 18, Figure 3b) extending substantially throughout the elastomeric layer 1 12. Hence, should any electrostatic charge begin to accumulate on the outer surface 1 14, it will immediately be dissipated away from the surface substrate to the shaft 1 10 before causing damage to the substrate.

The elongate single-walled carbon nanotubes 1 16 ensure efficient interconnectivity in network 1 18. In other words, the nanotubes 1 16 sufficiently reduce the electrically insulating properties of the elastomer when added in very low amounts due to their low weight per unit length and high surface area per unit length. Hence, compared to other conductive additives, only a small quantity is required to ensure effective reduction of the surface resistance of the roller 102 and to provide the elastomeric layer with the required bulk conductivity.

The hollow shape of elongate single-walled carbon nanotubes 1 16 provides high surface area for a given weight of elements which ensures sufficient bonding with the surrounding elastomer that each elongate member 1 16 is embedded securely within the elastomeric layer 1 12. Hence, as the elastomeric layer conductive surface 1 14 wears down in use, elongate elements 1 16 cannot detach or come loose from the roller 102.

Furthermore, the embedding of the elongate single-walled carbon nanotubes 1 16 ensures that the integrity of the elastomer does not deteriorate and may even improve or reinforce the surface region 1 12.

The nanotubes 1 16 form a charge path from the outer conductive surface 1 14, through the interconnected network 1 18 to the inner conductive surface 1 13 and on to conductive shaft 1 10. From the shaft 1 10 the charge can be earthed with any suitable grounding device (not shown).

Various modifications and embodiments to the described embodiments are envisaged. For example, the earthing device may be electrically connected to the contact cleaning roller by any suitable means.

In a further embodiments of the invention, the elastomer of the surface region 1 12 comprises a polyurethane or silicone rubber. In yet further embodiments, the elastomer may also be a heat-cured silicone, or other material appropriate for contact cleaning rollers, as known to the person skilled in the art.

In embodiments of the invention, the cleaning surface assembly may clean both sides of a substrate (i.e. part to be cleaned). Both sides may be cleaned simultaneously or separately.

Throughout the description and claims of this specification, the words“comprise” and“contain” and variations of them mean“including but not limited to”, and they are not intended to (and do not) exclude other moieties, additives, components, integers or steps. Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.

Features, integers, characteristics, compounds, chemical moieties or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. The invention is not restricted to the details of any foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.