[0001] RELATED APPLICATIONS

[0002] This international application claims priority to United Kingdom Patent Application Serial No. GB1805800.8, filed April 6, 2018, entitled“Improved

Adhesive Roll.” The entirety of United Kingdom Patent Application Serial No.

GB1805800.8 is incorporated herein by reference.

[0003] TECHNICAL FIELD

[0004] This invention relates to an improved adhesive roll. More particularly, though not exclusively, the present invention relates to an improved adhesive roll comprising a microscopically discontinuous adhesive surface.

[0005] BACKGROUND

[0006] Contact cleaning processes are used to clean work piece surfaces. Once cleaned, the work piece 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 work piece surface and an adhesive roll can then be used to remove the contaminating particles from the cleaning roller. This allows the cleaning roller to maximise its efficiency in removing contaminating particles from the work piece surface.

[0007] In contact cleaning, an adhesive roll typically comprises a wound length, or sheeted lengths, of substrate material wrapped around a core. The substrate material may comprise an adhesive side and a non-adhesive side, the adhesive side of which can be used to remove impurities from the surface of the cleaning roller.

[0008] As the adhesive roll removes impurities from the cleaning roller, the outermost length of the adhesive material will require to be removed and replaced. This may be done by a user cutting away the outer circumference of the used portion of a continuous length of adhesive material, leaving behind a new portion of continuous adhesive material for use. [0009] Alternatively, the adhesive material is sheeted and, when the outermost sheet of the adhesive material requires to be removed and replaced, this is done simply be tearing away the contaminated sheet to reveal a fresh, uncontaminated sheet of adhesive material.

[0010] 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, contact between the adhesive roll and the cleaning roller should generate as little static charge as possible during use in order to prevent damage of a work piece from electrostatic charges.

[0011] When the contact cleaning roller has sufficient surface adhesion to clean a work piece (i.e. a part to be cleaned), electrostatic charges are likely to be generated during the contact cleaning process. Similarly, contact between the contact cleaning roller and the adhesive roll may generate further electrostatic charges.

[0012] Furthermore, in contact cleaning, adhesive rolls have a substrate comprising an adhesive side and a non-adhesive side. The non-adhesive side may comprise a release coating, for example, a silicone release liner, or may be embossed, to prevent the adhesive from permanently sticking to the non-adhesive side when the substrate is wound up in a roll. The adhesive must however have some adhesion to the release coating to maintain the integrity of the roll.

[0013] Contact cleaning processes are known where a wound sheeted roll is used to remove impurities form a surface. In this regards we refer to W003/091 138 which is incorporated herein by reference. Previous contact cleaning processes have used a thin coating of silicone to form the release coating on a paper substrate. However, whilst the paper substrate has beneficial static charge dissipative properties (as an insulator material), silicones have been found to present several disadvantages. For example, silicone release coatings generate a high capacitance static charge accumulation in contact cleaning processes which static charge is highly undesirable in contact cleaning processes which typically involve electronic components which are sensitive to electrostatic charge.

[0014] In order to combat the problems associated with silicones (lack of biodegradability, environmental impact and the like), filmic substrates with no silicone release coating have been used. However, filmic substrates can themselves generate high capacitance static charge accumulation in contact cleaning processes which static charge is highly undesirable in contact cleaning processes which typically involve electronic components which are sensitive to electrostatic charge.

[0015] In addition, previous contact cleaning processes have used a cleaning roller comprising a microscopically roughened surface, for which see

WO2013/01 1471 which is incorporated herein by reference, to enhance the cleaning process of removing debris from a surface to be cleaned (e.g. plastic electronics, films, photovoltaics, flat panel displays and the like). The adhesive roll removes the debris from the cleaning roller to ensure the cleaning roller remains effective and free from debris. A microscopically roughened cleaning roller surface has adhesion properties sufficiently strong to potentially damage an adhesive roll comprising a paper substrate.

[0016] The present invention provides at least an alternative to the adhesive rolls of the prior art.

[0017] It is an object of at least one aspect of the present invention to obviate or mitigate at least one or more of the aforementioned problems.

[0018] The present invention aims to provide an improved adhesive roll which maintains roll integrity in a contact cleaning process whilst minimising the static charge accumulation whilst the adhesive roll is in use.

BRIEF SUMMARY OF THE DISCLOSURE

[0019] In accordance with an aspect of the present invention there is provided an adhesive roll for use in contact cleaning comprising a roll core; at least one sheet of adhesive material removably attached to the roll core; wherein the adhesive sheet has two sides, a first side comprising adhesive and a second non-adhesive side; wherein the adhesive side comprises a discontinuous adhesive surface.

[0020] In certain embodiments the adhesive side comprises an adhesive having a discontinuous adhesive surface.

[0021] In certain embodiments the adhesive surface is microscopically

discontinuous. That is to say, the surface of the adhesive is disrupted by microscopic particles protruding above the surface of the adhesive layer. In this way, the microscopic particles form discontinuities in the adhesive surface sufficient to reduce the strength of the adhesion forces between the adhesive layer and another surface by reducing the surface area of adhesive layer available for contact with the another surface.

[0022] In certain embodiments the adhesive comprises microspheres. In this way, the surface area of the adhesive layer providing physical contact with the cleaning roller is reduced to avoid damaging the substrate whilst providing sufficient adhesion force to remove the debris from the surface of the cleaning roller. In addition, the surface area of the adhesive layer providing physical contact with the non-adhesive side of the adhesive roll in a wound roll is sufficient to ensure roll integrity whilst allowing for removal of a soiled length of the adhesive material.

[0023] In certain embodiments the microspheres have diameters in range from about 20 microns to about 80 microns.

[0024] In certain embodiments the microspheres have a substantially uniform diameter. More specifically, the majority, typically substantially all of the

microspheres have a diameter of 26 microns.

[0025] In certain embodiments, the at least one sheet comprises a substrate.

More specifically, the substrate is paper. The microspheres in the discontinuous adhesive layer provide reduced adhesion to a cleaning roller surface in use, therefore mitigating the possibility of tearing the substrate away from the adhesive roll, damaging same and contaminating the cleaning roller in use.

[0026] In certain embodiments, the non-adhesive surface comprises a release coating.

[0027] In certain embodiments the release coating is free from silicones.

[0028] In certain embodiments the release coating is a film. More specifically, the film is a polyethylene release film. The polyethylene release film enables the roll integrity to be maintained whilst allowing the adhesive layer to release from the polyethylene release film as the at least one sheet is unwound from the core. In this way, the at least one adhesive sheet can be refreshed without damaging the clean adhesive layer. Further the paper substrate and the polyethylene release film generate low or no static charge during use of the roll in a contact cleaning process. [0029] In certain embodiments the at least one sheet of adhesive material may be wound around the circumference of the roll core. The sheets of adhesive material may be greater in length than the circumferential length of the roll core. Each end of the sheets of the adhesive material may be abutted to an end of another sheet. The other end of each sheet may be abutted to another end of said sheet.

[0030] Typically, there may be at least two or more or a plurality of sheets of adhesive material wound, for example, around each other. On top of a first sheet of adhesive material there may be subsequent sheets of adhesive material removably attached thereon. The subsequent sheets may therefore be wound onto and removably attached on previous sheets of material on, for example, the roll core. The said at least one sheet and subsequent sheets of adhesive material may therefore provide an adhesive surface holding the sheets to one another on the roll core. The adhesive surface is discontinuous.

[0031] In certain embodiments each sheet of the plurality of sheets has the same length dimension as the other sheets in the plurality of sheets. More specifically, each sheet has the same length, width and thickness as the other sheets. The length dimension of each sheet is measured around the circumference of the roll (i.e. equidistant the edges of the sheet) and the width dimension is measured across the roll (i.e. in a direction parallel to the longitudinal axis of the core). In embodiments where each sheet has the same length dimension, the overlap distance between a sheet and the underlying sheet is decreased from the innermost sheet on the roll core to the outermost sheet on the roll core.

[0032] In certain embodiments each sheet of the plurality of sheets has the different length dimension as the other sheets in the plurality of sheets. More specifically, each sheet, from the innermost sheet on the roll core to the outermost sheet on the roll core has an increasing length dimension. The width and thickness dimensions of each sheet are the same as the other sheets. The length dimension of each sheet is measured around the circumference of the roll (i.e. equidistant the edges of the sheet) and the width dimension is measured across the roll (i.e. in a direction parallel to the longitudinal axis of the core). In such embodiments, the overlap distance between each sheet and the next sheet on the roll is maintained constant from the innermost sheet on the roll core to the outermost sheet on the roll core. [0033] In certain embodiments the sheets may be separable along lines of perforation, for example.

[0034] In certain embodiments the sheets are embossed making up a sheeted roll.

[0035] In certain embodiments the sheet(s) contains no silicones.

[0036] Typically the adhesive used on one side of the at least one sheet may be any suitable adhesive which permit removal of impurities from a contaminated surface.

[0037] In certain embodiments the adhesive may be pressure sensitive adhesive.

[0038] In accordance with a further aspect of the present invention there is provided an apparatus for contact cleaning comprising a contact cleaning roller and an adhesive roll, the adhesive roll comprising a roll core; at least one sheet of adhesive material removably attached thereon; wherein the adhesive sheet has two sides; and wherein at least one side comprises an adhesive having a discontinuous adhesive surface.

[0039] In certain embodiments the apparatus may be used to form electronic components such as plastic electronics, photovoltaics and flat panel displays.

[0040] In accordance with a yet further aspect of the present invention there is provided a use of an adhesive roll according to the first aspect in cleaning a contaminated surface.

[0041] In certain embodiments the adhesive roll according to the first aspect may be used in a contact cleaning apparatus in conjunction with a contact cleaning roller comprising a contact cleaning surface assembly having 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.

BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Embodiments of the invention are further described hereinafter with reference to the accompanying drawings, in which: Figure 1 is a schematic side view of a contact cleaning apparatus employing an adhesive roll in accordance with an embodiment of the invention;

Figure 2 is a view from one end of an adhesive roll according to an embodiment of the present invention illustrating how sheets of material are superimposed onto a roll core; and

Figure 3 is a cross-section view through a sheet of adhesive material of the roll of Figure 2.

DETAILED DESCRIPTION

[0043] Figure 1 is a schematic side view of a contact cleaning apparatus employing an adhesive roll 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 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 specific structure of the adhesive roll 3 is described in more detail below. 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.

[0044] 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 3, 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.

[0045] Figure 2 is a detailed end view of the adhesive roll 3. The sheeted adhesive roll 3 comprises a roll core 210 with three individual adhesive sheets 212, 214, 216 (although any number of sheets may be used) removably attached around the circumference of the roll core 210 superimposed onto one another.

[0046] The roll core 210 has an attachment means 21 1 in the form of an adhesive coating (layer) to allow the first individual adhesive sheet 212 to be removably attachable around the circumference of the roll core.

[0047] The individual adhesive sheets 212, 214, 216 have an adhesive surface 218a, 218b, 218c facing outwardly and have a non-adhesive surface 219a, 219b, 219c facing inwardly. Alternatively the individual sheets can be rolled such that the adhesive surfaces are facing inwardly and the non-adhesive surfaces are facing outwardly. [0048] The sheeted adhesive roll 3 is formed by attaching a first end 220 of the first sheet 212 onto the roll core 210 and wrapping the first sheet 212 around the circumference of the roll core 210.

[0049] The other end 222 of the first sheet 212 will overrun end 220 by virtue of the first sheet 212 being greater in length than the circumference of the roll core 210.

[0050] The end 222 is removably attached on end 220 by adhesive surface 218a of the first sheet 212.

[0051] A second sheet 214 is then wrapped around the outer circumference of the first sheet 212 with end 224 of the second sheet 214 being abutted to end 222 of the first sheet 212. The term abutted is to be understood to include being adjacent to; there may be a gap between successive sheets.

[0052] The adhesive surface 218a of the first sheet will securely hold in place the second sheet 214.

[0053] A third sheet 216 is then wrapped around the outer circumference of the second sheet 214 with end 228 of the third sheet 216 being abutted to end 226 of the second sheet 214.

[0054] The adhesive surface 218b of the second sheet 214 will securely hold in place the third sheet 216.

[0055] Similarly, further individual adhesive sheets (not shown) are abutted to end

230 of the third sheet 216 and so on until the roll core 210 is“full”.

[0056] It will be realised that because the sheets 212, 214, 216 are all of the same length, the overrun (overlap) or circumferential offset of the respective ends 222, 226, 230 and so on, will decrease as the roll core 210 becomes“full”. The length of each sheet can however be adjusted as desired or required.

[0057] The offset of the abutment of the ends of the sheets disperses the load on the roll core 210 making the roll core 210 more stable when rotating.

[0058] In use, the roll core 210 is positioned such that the outermost sheet is positioned in contact at a point on a surface to be cleaned. [0059] As both the roll core 210 and the cleaning roller 2 rotate, impurities located in the surface to be cleaned will be transferred to the adhesive surface 218c of the outer sheet 216.

[0060] When the adhesive surface 218c of the outer sheet 216 becomes contaminated, replacement is simply achieved by peeling the contaminated sheet 216 away by virtue of lip 232, thus leaving behind a clean sheet 214 to be applied to a cleaning surface of the cleaning roll 2, until that too needs replaced, and so on.

[0061] The non-adhesive surfaces 219a, 219b, 219c facing inwardly on the individual adhesive sheets 212, 214, 216 have a polyethylene film release liner (not shown). The adhesive sheets 212, 214, 216 therefore have a polyethylene film release liner on the inwardly facing surface 219a, 219b, 219c. The polyethylene film facilitates removal of the sheets 212, 214, 216 when they need to be refreshed/replaced and avoid the static charge build up associated with silicone- containing release liners.

[0062] In one embodiment, the adhesive sheets 212, 214, 216 are manufactured from a paper substrate to which an adhesive is applied to one surface and the polyethylene film release coating is applied to the opposite side. In this way, the adhesive and non-adhesive surfaces of the sheets 212, 214, 216 are formed. The paper has a basis weight of about 65gsm a thickness of approximately 61 microns.

[0063] As best seen in Figure 3, the sheets of adhesive material 212, 214, 216 have an adhesive layer 21 1 forming the adhesive side of the sheet 212, 214, 216. The adhesive layer 21 1 is coated on a paper substrate 236. The adhesive material of the adhesive layer contains microspheres 238 having a particle size in the range 20 to 80 microns. The microspheres are larger in diameter than the thickness of the adhesive layer 21 1 on each of the sheets 212, 214, 216. In this way, the microspheres protrude from the adhesive layer surface 213 so as to provide a microscopically discontinuous adhesive surface 213. The microspheres 238 in the adhesive layer 21 1 reduce the surface area of adhesive 21 1 on outwardly facing surfaces 218a, 218b, 218c sufficiently to allow each sheet to be peeled away from the inwardly facing surfaces 219a, 219b, 219c whilst maintaining sufficient adhesion force to remove debris from the surface of cleaning roller 2.

[0064] The non-adhesive side of the paper substrate 236 comprises a

polyethylene film release coating 234. The release coating being free of silicones reduces the static charge build up that is a drawback of utilising silicone release liners. Thus, combining the static dissipative effects of a paper substrate and the polyethylene film release coating reduces the likelihood of static charge

accumulation resulting from the rollers (2, 3) during use in a contact cleaning process.

[0065] 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.

[0066] 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.