WO2013011471A1

WO2013011471A1 - Contact cleaning roller assembly

Info

Publication number: WO2013011471A1
Application number: PCT/IB2012/053668
Authority: WO
Inventors: Sheila Hamilton
Original assignee: Itw Cs (Uk) Limited
Priority date: 2011-07-19
Filing date: 2012-07-18
Publication date: 2013-01-24
Also published as: GB201112412D0; GB2492991A

Abstract

The application relates to a contact cleaning surface assembly (100) having a pair of opposing rotatably mounted surface cleaning rollers (102, 104). Each cleaning roller (102, 104) has a cleaning surface (106, 108) capable of collecting and/or removing contaminating small particles (12a, 12b) from one of the surfaces (18a, 18b) of a double-sided contaminated thin film (16). The adhesion profiles of the cleaning surfaces (106, 108) of the assembly (100) are reverse matched to those of the surfaces (18a, 18b) of the contaminated sheet material (16) in order to prevent adhesion of the sheet material (16) to the cleaning surfaces (106, 108) and/or creasing of the sheet material (16) as it is processed and cleaned. The apparatus (100) further comprises a pair of rotatably mounted adhesive rollers (110, 112) each being separately capable of removing the contaminating small particles (12a, 12b) collected on the cleaning surfaces (106, 108) of one of the rotatably mounted surface cleaning rollers (102, 104).

Description

Contact Cleaning Roller Assembly Field of Invention

The present invention relates to an improved contact cleaning surface assembly and an improved method for cleaning surfaces. More particularly, the present invention relates to a contact cleaning surface assembly adapted to collect and/or remove contaminating material from a double-sided contaminated substrate having different adhesion forces associated with each of its surfaces.

Background of the Invention

There is an increasing trend towards the application of functional coatings to sheet materials such as films and foils to enhance their functionality and, in particular, their optical properties. Thin sheets such as films and foils (hereinafter collectively referred to as "films") of 100μιη thickness or less have little inherent mechanical strength and, as a result, are difficult to process and clean due to their tendency to deform during processing.

The application of functional coatings such as those containing

nanoparticles, dry adhesives, hard coatings and other coatings to enhance the functionality of these thin films changes the adhesive forces associated with their surfaces. As a result, cleaning and processing of these coated thin films becomes even more difficult.

It is now increasingly common for a thin film to be coated on one or both sides with different functional coatings in order that a double-sided thin film be produced.

The functional coatings are extremely thin and as such are very susceptible to defects caused by contamination on the surface of the film. The only effective method of removing such small particles from the surface of sensitive films is through the use of contact cleaning

technology. Contact cleaning involves touching the surface of the film with a cleaning roller causing an interfacial reaction between the roller and the substrate. Removal of particles down to the submicron level is provided by and is dependent upon the adhesion forces applied to the particles by the contact roller cleaning surface being greater than the adhesion forces existing between the particles and the substrate.

The growing markets for plastic electronics, photovoltaics and flat panel displays are driving the film coating industry towards the limits of current coating technology by demanding thinner, more consistent, defect free coatings. This level of quality can impact process yields and therefore increase costs for the coating company.

Contact cleaning in conjunction with adhesive rolls is commonly used to clean substrate surfaces in the manufacture of electronic components. For example, we refer to W099/24178, WO2007/034344,

WO2008/041000 and WO2010/035043 which are incorporated herein by reference.

Double-sided surface contact cleaning is also well known in the art. In this process both sides of a single sheet of material are contacted by separate contact rollers which in turn separately contact adhesion rolls.

In known double sided contact cleaning technology the contact rollers are identical to one another in their adhesion force profiles in order that the double sided sheet runs straight through the rollers. This is particularly important where the sheet is a thin sheet of material, for example, under 100μιη thickness as the structural integrity of the thin sheet may be insufficient in itself to ensure that the sheet passes through the contact rollers on either side of the material without bending, folding or creasing. However, existing systems are not capable of efficiently removing small particles from a double-sided film having surfaces with differing adhesion properties. Such double-sided films having surfaces with differing adhesion properties are known as "unbalanced" substrates, wherein the imbalance refers to the differing adhesion forces applied to particles by each side of the double-sided substrate. One of the problems associated with unbalanced films is the tendency of thin films under 100μιη thickness to wrap around a rotating contact cleaning surface or to be drawn closer to one of a pair of contact cleaning surfaces during cleaning and processing, thereby causing processing drawbacks.

It is desirable to be able to clean both surfaces of an unbalanced double- sided contaminated substrate in a manner that ensures maximal cleaning efficiency of the substrate surfaces and is easy to perform and easy to process.

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.

It is an object of at least one aspect of the present invention to provide a contact cleaning surface assembly capable of providing improved cleaning to an unbalanced double-sided contaminated surface.

It is an object of at least one aspect of the present invention to provide a contact cleaning surface assembly capable of removing and/or collecting contaminating material from a double-sided contaminated substrate having unbalanced adhesion forces at its surfaces. It is a yet further object of at least one aspect of the present invention to provide an improved contact cleaning method capable of providing improved cleaning to a contaminated surface.

It is a yet further object of at least one aspect of the present invention to provide an improved contact cleaning method capable of removing and/or collecting contaminating material from a double-sided contaminated substrate having unbalanced adhesion forces at its surfaces.

Summary of the Invention

According to a first aspect of the present invention there is provided a contact cleaning surface assembly comprising:

a first cleaning surface capable of collection and/or removal of small contaminating particles from a first contaminated surface of a

contaminated substrate;

a second cleaning surface capable of collection and/or removal of small contaminating particles from a second contaminated surface of the contaminated substrate;

wherein at least part of the first cleaning surface has different adhesion properties when compared to the adhesion properties of at least part of the second cleaning surface.

A contaminated substrate suitable for cleaning by the contact cleaning surface assembly of the invention is a double-sided contaminated substrate having two surfaces with dissimilar or, unbalanced, adhesion properties. The adhesion properties of each surface of the substrate cause contamination of the substrate due to particles adhering to the substrate surfaces. The differing adhesion properties of each surface of the substrate require cleaning surfaces having reverse matched adhesion properties with the substrate surface to be cleaned such that the cleaning surface is capable of removal and/or collection of particles from the corresponding substrate surface. Thus, the adhesion properties of the first and the second cleaning surface of the assembly are required to be different in order to effectively clean the two substrate surfaces having dissimilar adhesion properties for the contaminant particles.

Reverse matching of adhesion properties shall be taken to mean that the adhesion properties of the cleaning surface are sufficient to overcome the adhesion forces between the particle and the substrate surface to be cleaned and therefore to collect and/or remove the particles from the substrate surface onto the cleaning surface, whilst being insufficient to cause the surface to be cleaned to adhere to the cleaning surface or to cause it to crease as it contacts the cleaning surface.

Preferably the adhesion properties of the first and second cleaning surfaces are provided by one or more of mechanical adhesive forces, chemical adhesive forces, shore hardness and/or electrical adhesive forces.

The mechanical adhesive forces may be provided by surface roughness of the first and/or the second cleaning surface. More specifically, at least a part of the first and/or the second cleaning surface may be microscopically roughened whereby the microscopically roughened surface is capable of enhancing collection and/or removal of small contaminating particles from a contaminated surface by increasing the mechanical adhesive forces of the first and/or the second cleaning surface(s).

The contact cleaning surface assembly may therefore be used to clean surfaces which are contaminated with microscopically sized particles.

In much preferred embodiments, the first and the second cleaning surfaces are differentially microscopically roughened. More specifically, the size and shape of the indentations on the first cleaning surface are different to the size and shape of the indentations on the second cleaning surface. In this way, the first and second cleaning surfaces are provided with different mechanical adhesion properties. Thus, a double-sided contaminated substrate which has mechanically unbalanced adhesive forces associated with its surfaces may be effectively cleaned and processed by the contact cleaning surfaces of the present invention.

The mechanical adhesion properties of the first cleaning surface are reverse matched to the mechanical adhesion properties of a first surface of the contaminated substrate and the mechanical adhesion properties of the second cleaning surface are reverse matched to the mechanical adhesion properties of a second surface of the contaminated substrate. By reverse matching the mechanical adhesion properties of the first cleaning surface with a first surface of the contaminated substrate and the mechanical adhesion properties of the second cleaning surface with a second surface of the contaminated substrate, each cleaning surface is capable of collection and/or removal of contaminant particles from the corresponding substrate surface. Furthermore, by reverse matching the mechanical adhesion properties of each cleaning surface of the assembly with those of the corresponding surface of the substrate to be cleaned, processing of the substrate is made easier as the substrate is less susceptible to wrapping or creasing during processing.

Typically, all or substantially all of the first and/or the second cleaning surface may be microscopically roughened to increase the efficiency of the collection and/or removal of the contaminating particles. More preferably, all of the first cleaning surface and all of the second cleaning surface are differentially microscopically roughened. In this way, all of the first cleaning surface will have different mechanical adhesion forces when compared to all of the second cleaning surface.

The or each cleaning surface which is microscopically roughened may be used to increase and/or maximise surface area contact between the cleaning surface and the small particles causing the contamination.

Although not wishing to be bound by theory this improvement is thought to be due to an increase in van der Waals forces between the contact cleaning surface and the contaminating particles due to the increased surface area contact. The increase in van der Waals forces compared to that of a completely smooth surface as presently used in the prior art has been found to be of the order of an increase of at least about 50%.

To increase the surface area contact, the or each cleaning surface may therefore be roughened with, for example, the aim of providing small indentations on the or each cleaning surface which may be used to capture and/or remove the small contaminating particles. The or each cleaning surface may therefore comprise a plurality of such indentations in, for example, a random or constant pattern. By indentation is meant any type of hollow, notch, recess, cut, depression, dimple, dip, nick and/or pit.

The shape and/or size of the indentions may be substantially uniform or may be substantially non-uniform. In embodiments where the shape and/or size of the indentions are substantially non-uniform, the shape and/or size of the indentions may therefore extend over a range of shapes and/or sizes thereby providing the or each cleaning surface with the capability of maximising the collection of contaminated particles over a range of differently sized contaminating particles. The microscopically roughened cleaning surface(s) may therefore comprise a plurality of small indentations adapted to improve and/or maximise the collection and/or removal of small contaminating particles.

The or each cleaning surface may be microscopically roughened using any suitable mechanical and/or chemical technique. For example, any suitable mechanical means, molding means and/or laser structuring means may be used to microscopically roughen the or each cleaning surface.

The microscopically roughened surface(s) may therefore comprise a series or plurality of indentations with microscopically sized cross-sectional diameters and depths. It is highly preferred that the shape of the indentations may be specifically designed to match the shape of the contaminating particles. This means that the contaminating particles may snugly fit into the indentations therefore allowing the contaminating particles to be removed from a contaminated surface. The contaminating particles may therefore become lodged and/or attached within the indentations during the cleaning process. There is provided, therefore, a method of increasing mechanical adhesion forces between the or each cleaning surface and the contaminating particles such that the force is greater than the force between the contaminating particles and the contaminated surface from which they are originally attached to.

For example, the or each microscopically roughened surface may comprise indentations with a cross-sectional diameter and/or depth ranging from any one of or combination of the following: less than about 100 microns (100,000 nm); less than about 10 microns (10,000 nm); less than about 5 microns (5,000 nm); less than about 1 micron (1 ,000 nm); less than about 0.1 microns (100 nm); less than about 0.01 micron (10 nm); or less than about 0.005 micron (5 nm). Alternatively, the

microscopically roughened surface(s) may comprise indentations with a cross-sectional diameter and/or depth ranging from any one of or combination of the following: about 1 nm to about 100 microns (100,000 nm); about 10 nm to about 100 microns (100,000 nm); about 10 nm to about 10 micron (10,000 nm); about 10 nm to about 1 micron (1 ,000 nm); about 10 nm to about 0.1 microns (100 nm); or about 1 nm to about 0.01 microns (10 nm). As indicated above, the microscopically roughened surface(s) may comprise indentations with a combination of different cross-sectional diameters and/or depths allowing a range of differently sized contaminating material to be collected and/or removed. By cross- sectional diameter is meant the maximum diameter formed by the indentation. By depth is meant the vertical distance between the bottom part of the indentation and the top part of the cleaning surface(s).

In particular embodiments, there may be about 10 to about 100,000 indentations per cm², about 100 to about 10,000 indentations per cm² or about 100 to about 5,000 indentations per cm² of the or each contact cleaning surface.

The small contaminating particles being collected may substantially match the shape and/or dimensions of the indentations and may therefore have a cross- sectional diameter ranging from any one of or combination of the following: less than about 100 microns (100,000 nm); less than about 10 microns (10,000 nm); less than about 5 microns (5,000 nm); less than about 1 micron (1 ,000 nm); less than about 0.1 microns (100 nm); less than about 0.01 micron (10 nm); or less than about 0.005 micron (5 nm). Alternatively, the small particles being collected may have a cross- sectional diameter ranging from any one of or combination of the following: about 1 nm to about 100 microns (100,000 nm); about 10 nm to about 100 microns (100,000 nm); about 10 nm to about 10 microns (10,000 nm); about 10 nm to about 1 micron (1 ,000 nm); about 10 nm to about 0.1 microns (100 nm); or about 1 nm to about 0.01 microns (10 nm).

Conveniently, the indentations may be of a size and shape that about 20%, 30%, 40%, 50%, 60%, 70% or 80% of the volume of the

contaminating particles may fit into the recess formed by the indentations. This means that about 20%, 30%, 40%, 50%, 60%, 70% or 80% of the total surface area of the contaminating particles may be in contact with the or each cleaning surface as they are collected and/or removed from the contaminated surface(s).

The first and/or second cleaning surface(s) may also be electrostatically charged to assist in the collection and/or removal of the contaminating particles from, and in the processing of, an electrostatically unbalanced double-sided substrate.

Preferably, the first and second cleaning surfaces are differentially electrostatically charged. In this way, any imbalance in the adhesion properties of the surfaces of a double-sided contaminated substrate to be cleaned due to electrostatic forces may be reverse matched by the difference in electrostatic charge of the first cleaning surface when compared to the electrostatic charge of the second cleaning surface.

As is well known in the art, materials and/or coatings having different polarities will attract one another whilst materials having similar polarities will repel one another. Whilst electrostatic repulsion occurring between a cleaning surface and a surface to be cleaned is advantageous for processing of the surface to be cleaned in that it is then unlikely to wrap around and/or be creased by contact with the cleaning surface, the same electrostatic repulsion would be disadvantageous for cleaning of the surface due to there being less likelihood of contact occurring between the cleaning surface and the surface to be cleaned.

Reverse matching of the electrostatic adhesion forces of a cleaning surface to those of a surface to be cleaned provides sufficient adhesive force on the cleaning surface to collect and/or remove the contaminating particle(s) from the surface to be cleaned without causing the surface to be cleaned to adhere to the cleaning surface or to cause it to crease as it contacts the cleaning surface.

Thus, the electrostatic adhesion force of the first cleaning surface is reverse matched with the electrostatic adhesion force of the first surface of the double-sided contaminated substrate and the electrostatic adhesion force of the second cleaning surface is reverse matched with the electrostatic adhesion force of the second surface of the double-sided contaminated substrate. In this way, an imbalance in the electrostatic forces between the first and second sides of the double-sided

contaminated substrate is matched by a reverse imbalance between the electrostatic forces of the first and second cleaning surfaces.

The electrostatic forces of each surface of the double-sided contaminated substrate to be cleaned may be provided by one or more of the material of the functional coating applied to one or more surfaces of the substrate and its position in the triboelectric series, static electricity caused by frictional forces acting on the surface of the substrate, London forces, Keesom forces or other similar forces or factors. The present invention provides a cleaning surface assembly wherein each of the cleaning surfaces has an electrostatic charge greater than the electrostatic charge between the surface of the substrate to be cleaned and the contaminant particles to be collected and/or removed from the substrate surface. The present invention is particularly suitable when the double-sided contaminated substrate has unbalanced electrostatic forces between the first and second substrate surfaces.

The first and second cleaning surfaces may each be made from any suitable material. For example, the first and second cleaning surfaces may be made from or comprise elastomer material.

More specifically, the first and second cleaning surfaces may be made from or comprise polyurethane and/or a silicon-based polymer.

The chemical composition of the first and/or second cleaning surface(s) may be modified to modify the chemical adhesive forces of the or each cleaning surface to assist in the collection and/or removal of the contaminating particles from, and in the processing of, a double-sided substrate having unbalanced chemical adhesion properties.

Preferably, the chemical compositions of the first and second cleaning surfaces are differentially chemically modified thereby providing first and second cleaning surfaces having different chemical adhesive forces. In this way, any imbalance in the adhesion properties of the double-sided contaminated substrate to be cleaned due to chemical forces may be reverse matched by the difference in chemical modification of the first cleaning surface when compared to the chemical modification of the second cleaning surface.

The adhesion forces of the first and/or the second cleaning surface due to chemical forces may be changed by modifying the chemical composition of the material forming the first and/or the second cleaning surface. Suitable chemical modifiers include filler materials, for example. In certain embodiments, the filler material comprises a calcium carbonate. Thus, in certain embodiments the first and/or second cleaning surfaces comprise an elastomer containing a filler material whereby the filler material alters the chemical adhesion forces of the first and/or the second cleaning surface.

The first and/or second cleaning surface(s) may also have differing shore hardness to assist in the collection and/or removal of the contaminating particles from the surfaces of an unbalanced double-sided contaminated substrate.

In this way, any imbalance in the adhesion properties of the surfaces of a double-sided contaminated substrate to be cleaned due to shore hardness may be reverse matched by the difference in shore hardness of the first cleaning surface when compared to the shore hardness of the second cleaning surface.

Shore hardness, or the measure of the resistance of a material to permanent indentation, is a term and physical property well known in the art and measured using a durometer.

In embodiments wherein the cleaning surface(s) comprise an elastomer material, factors influencing and modifying shore hardness include the number of chemical bonds in the material, the length of those chemical bonds and the tightness of those chemical bonds. It will be readily understood be the skilled artisan that a greater number of bonds and/or chemical bonds of shorter length and/or chemical bonds with greater chemical tightness are all properties which increase the shore hardness of a surface formed from or comprising an elastomer material. In certain embodiments, the first and second cleaning surfaces form a single pair of opposing cleaning surfaces.

In certain embodiments, the contact cleaning surface assembly further comprises a third cleaning surface capable of collection and/or removal of small contaminating particles from the first contaminated surface of the contaminated substrate. Alternatively or, in addition, the contact cleaning assembly further comprises a fourth cleaning surface capable of collection and/or removal of small contaminating particles from the second contaminated surface of the contaminated substrate.

In such embodiments, the third and fourth cleaning surfaces may form a single pair of opposing cleaning surfaces.

It is much by preference that at least part of the third cleaning surface has different adhesion properties when compared to the adhesion properties of at least part of the fourth cleaning surface. In this way, an unbalanced, double-sided contaminated substrate may be cleaned and processed by reverse matching the adhesion properties of the third cleaning surface with the adhesion properties of a first surface of the substrate and by reverse matching the adhesion properties of the fourth cleaning surface with the adhesion properties of a second surface of the surface.

In particular embodiments, the first and/or second and/or third and/or fourth cleaning surfaces may be in the form of a roller such as a substantially cylindrical roller which may be rotated and/or urged against a surface to be cleaned. The cleaning surfaces may each therefore be placed in contact with and/or urged against a surface to be cleaned using any suitable means.

In certain embodiments, the first and the third cleaning surfaces may be arranged to clean a first surface of the double-sided contaminated substrate and the second and fourth cleaning surfaces may be arranged to clean the second surface of the double-sided contaminated substrate. Advantageously, each of the cleaning surfaces has adhesion forces reverse matched to the surface of the substrate it is arranged to clean. Thus, an imbalance in the adhesion properties of the double-sided substrate is mitigated or obviated by a suitable imbalance in the adhesion properties of the cleaning surfaces of the contact cleaning assembly.

According to a second aspect of the present invention there is provided a method of cleaning a double-sided unbalanced substrate contaminated with small particles, said method comprising:

providing a first cleaning surface capable of collection and/or removal of small contaminating particles from a first contaminated surface of the contaminated substrate said contaminated surface having a first adhesion force profile;

providing a second cleaning surface capable of collection and/or removal of small contaminating particles from a second contaminated surface of the contaminated substrate said contaminated surface having a second adhesion force profile; wherein said first and said second adhesion force profiles are different to one another and wherein at least part of the first cleaning surface has a different adhesion force profile when compared to the adhesion force profile of at least part of the second cleaning surface; contacting and/or urging the first cleaning surface against the first contaminated surface; contacting and/or urging the second cleaning surface against the second contaminated surface; wherein on contacting and/or urging the cleaning surfaces against the contaminated surfaces at least some or substantially all of the small contaminating particles on the contaminated surfaces are capable of being collected and/or removed.

It is much by preference that the adhesion force profile of the first cleaning surface is reverse matched with the adhesion force profile of the first contaminated surface of the contaminated substrate and also that the adhesion force profile of the second cleaning surface is reverse matched with the adhesion force profile of the second contaminated surface of the contaminated substrate. In this way, the contaminated substrate having unbalanced adhesion force profiles between its first and second surfaces is effectively cleaned and processed by the cleaning surfaces.

Typically, all or substantially all of the first cleaning surface has a different adhesion force profile when compared to the adhesion force profile all or substantially all of the second cleaning surface to increase the efficiency of the removal of the contaminating particles.

Preferably the adhesion force profiles of the first and second cleaning surfaces are provided by one or more of mechanical adhesive forces, chemical adhesive forces, shore hardness and/or electrical adhesive forces.

Preferably the adhesion force profiles of the first and second contaminated surfaces are provided by one or more of mechanical adhesive forces, chemical adhesive forces, shore hardness and/or electrical adhesive forces.

Preferably the adhesion force profiles of the first cleaning surface and the first contaminated surface are reversed matched and the adhesion force profiles of the second cleaning surface and the second contaminated surface are reversed matched. That is to say, the adhesion properties of the first cleaning surface are sufficient to overcome the adhesion forces between the particle and the first contaminated substrate surface to be cleaned and therefore to collect and/or remove the particles from the substrate surface onto the cleaning surface and the adhesion properties of the second cleaning surface are sufficient to overcome the adhesion forces between the particle and the second contaminated substrate surface to be cleaned and therefore to collect and/or remove the particles from the substrate surface onto the cleaning surface.

Reverse matching of the adhesion forces of a cleaning surface to those of a surface to be cleaned provides sufficient adhesive force on the cleaning surface to collect and/or remove the contaminating particle(s) from the surface to be cleaned whilst being insufficient to cause the surface to be cleaned to adhere to the cleaning surface or to cause it to crease as it contacts the cleaning surface.

Typically, the cleaning surfaces may be rotated against the surfaces contaminated with small particles with a speed of about 0.1 cm/s to about 5 cm/s.

The first and second cleaning surfaces may be as defined in the first aspect.

According to a third aspect of the present invention there is provided surface cleaning apparatus for cleaning double-sided, unbalanced contaminated substrates, said surface cleaning apparatus comprising: at least one pair of rotatably mounted surface cleaning rollers each capable of removing contaminating small particles from one of the contaminated surfaces of a double-sided contaminated substrate; a pair of rotatably mounted adhesive rollers each separately capable of removing the contaminating small particles collected on one of the rotatably mounted surface cleaning rollers; means capable of urging each surface

contaminated with small particles against one of the rotatably mounted surface cleaning rollers; wherein one of said rollers comprises a first cleaning surface capable of collection and/or removal of small

contaminating particles from a first contaminated surface of the

contaminated substrate; and the other of said cleaning rollers comprises a second cleaning surface capable of collection and/or removal of small contaminating particles from a second contaminated surface of the contaminated substrate; and further wherein at least part of the first cleaning surface of one of the rotatably mounted surface cleaning rollers has different adhesion properties when compared to the adhesion properties of at least part of the second cleaning surface of the other of the rotatably mounted surface cleaning rollers.

A contaminated substrate suitable for cleaning by the surface cleaning apparatus of the invention is a double-sided contaminated substrate having two surfaces with dissimilar adhesion properties. The adhesion properties of each surface of the substrate cause contamination of the substrate due to particles adhering to the substrate surfaces. The differing adhesion properties of each surface of the substrate require cleaning surfaces having reverse matched adhesion properties with the substrate surface to be cleaned such that the cleaning surface is capable of removal and/or collection of particles from the corresponding substrate surface. Thus, the adhesion properties of the first and the second cleaning surface of the apparatus are required to be different in order to effectively clean the two substrate surfaces having dissimilar adhesion properties for the contaminant particles.

Typically, the means capable of urging each surface contaminated with small particles against one of the pair of rotatably mounted surface cleaning rollers may be mounted substantially opposite the rotatably mounted surface cleaning roller.

Motorised means may also be provided for driving the rotatably mounted surface cleaning rollers and the rotatably mounted adhesive rollers.

The rotatably mounted surface cleaning rollers and the rotatably mounted adhesive rollers may rotate in opposite directions.

The apparatus in certain embodiments may comprise two pairs of rotatably mounted surface cleaning rollers and a pair of rotatably mounted adhesive rollers. In such embodiments, each rotatably mounted surface cleaning roller of a pair is located on an opposing side of a substrate to be cleaned to the other rotatably mounted surface cleaning roller of a pair. One of the pair of rotatably mounted adhesive rollers is located on one side of the substrate to be cleaned and is in contact with the first of the rotatably mounted surface cleaning rollers rollers in each of the two pairs, and the other of the pair of rotatably mounted adhesive rollers is located on the opposing side of the substrate to be cleaned and is in contact with the second of the rotatably mounted surface cleaning rollers in each of the two pairs.

Each rotatably mounted adhesive roller may comprise at least one or a plurality of adhesive sheets which may be peeled off and removed when the adhesive sheet has become saturated with contaminated material or the efficiency of the adhesive sheet has reduced.

Each rotatably mounted adhesive roller may therefore be in the form of a pre-sheeted adhesive roll.

Each pair of rotatably mounted surface cleaning rollers may therefore comprise a cleaning surface assembly as defined in the first aspect.

The apparatus may be used in the manufacture of electronic components such as plastic electronics, photovoltaics and flat panel displays.

According to a fourth aspect of the present invention there is provided a method for cleaning contaminated surfaces having unbalanced adhesion force profiles, said method comprising: providing a first rotatably mounted surface cleaning roller capable of removing contaminating small particles from a first contaminated surface of a double-sided substrate; providing a first rotatably mounted adhesive roller capable of removing the

contaminating small particles collected on the first rotatably mounted surface cleaning roller; providing means capable of urging a first surface contaminated with small particles against the first rotatably mounted surface cleaning roller;

wherein at least part of the first surface of the first rotatably mounted surface cleaning roller has a first adhesion force profile capable of reverse matching the adhesion force profile of the first contaminated surface and capable of collection and/or removal of small contaminating particles from the first contaminated surface; and further comprising providing a second rotatably mounted surface cleaning roller capable of removing

contaminating small particles from a second contaminated surface of the double-sided substrate; providing a second rotatably mounted adhesive roller capable of removing the contaminating small particles collected on the second rotatably mounted surface cleaning roller; providing means capable of urging a second surface contaminated with small particles against the second rotatably mounted surface cleaning roller;

wherein at least part of the second surface of the second rotatably mounted surface cleaning roller has a second adhesion force profile capable of reverse matching the adhesion force profile of the second contaminated surface of the double-sided substrate and capable of collection and/or removal of small contaminating particles from the second contaminated surface.

The first and second rotatably mounted surface cleaning rollers may therefore comprise a cleaning surface assembly as defined in the first aspect.

In the first, second, third and fourth aspects of the present invention, the contaminated substrate is preferably a sheet material. More specifically, the contaminated substrate may be a film or foil. Even more specifically, the film is a plastics material such as polyester, polycarbonate, polyvinylchloride (PVC) or the like. Alternatively, the sheet material is a metallic foil.

Preferably the sheet material has a thickness of less than 250μιη. Even more preferably, the sheet material has a thickness of 100μιη or less. Sheet materials having a thickness of 100μιη or less, preferably 50μιη or less, are referred to herein as "thin" sheet materials. The contaminated substrate is preferably a double-sided sheet material having a functional coating applied to at least one surface thereof. The double-sided sheet material may have a functional coating applied to each surface thereof. The sheet material preferably comprises a first functional coating applied to a first surface of the sheet material and a second functional coating applied to a second surface of the sheet material.

Preferably the first and second functional coatings have dissimilar adhesion properties associated therewith.

The contact cleaning surface assembly described herein may therefore be used to clean both surfaces of a double-sided contaminated substrate wherein the surfaces of the substrate differ in their adhesion properties for small particles. Each contact cleaning surface may therefore be selected to have adhesion properties which remove and/or collect particles from one side of the double-sided contaminated substrate the adhesion properties of which side of the substrate will differ from the adhesion properties of the other side of the substrate. In this way, an unbalanced double-sided substrate may be cleaned and effectively processed according to the aspects of the present invention.

The present invention is therefore useful in removing and/or collecting small particles from substrates having two surfaces of differing adhesion properties for those small particles whilst allowing the substrate to be processed without creasing or damage.

Brief Description of the Drawings

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 is a representation of contaminating particles on a first and second cleaning surface of a contact cleaning surface assembly according to an embodiment of the present invention;

Figure 2 is a representation of contaminating particles on a double-sided, unbalanced contaminated substrate capable of being cleaned by a contact cleaning surface assembly according to the present invention;

Figure 3 is a representation of surface cleaning apparatus according to an embodiment of the present invention; and

Figure 4 is a representation of surface cleaning apparatus according to an alternative embodiment of the present invention.

Brief Description

Figure 1 is a representation of a pair of contact cleaning surfaces 10a and 10b according to the present invention. As shown in Figure 1

contaminating particles 12a snugly fit and are lodged into indentations 14a on a first contact cleaning surface 10a. It can be seen that the

indentations 14a have a substantially similar size and shape to the contaminating particles 12a (i.e. they substantially match). There is, therefore, a large contact surface area between the indentations 14a and the contaminating particles 12a. In an exemplary embodiment, the indentations 14a may have a cross-sectional diameter and a depth of less than about 5 microns (5,000nm). These indentations 14a give the first cleaning surface 10a a mechanical adhesion force profile.

Also depicted in Figure 1 contaminating particles 12b snugly fit and are lodged into indentations 14b on a second contact cleaning surface 10b. It can be seen that the indentations 14b have a substantially similar size and shape to the contaminating particles 12b (i.e. they substantially match). There is, therefore, a large contact surface area between the indentations 14b and the contaminating particles 12b. In an exemplary embodiment, the indentations 14b may have a cross-sectional diameter and a depth of between about 10 microns (10,000nm) and about 5 microns (5,000nm). These indentations 14b give the second cleaning surface 10b a

mechanical adhesion force profile. The mechanical adhesion force profile of the first cleaning surface 10a and the mechanical adhesion force profile of the second cleaning surface 10b will be different due to different surface roughness properties.

It will be readily understood that small particles of less than 100 microns (100,000nm) are particularly suitable for collection and/or removal from a contaminated substrate by a cleaning surface of the present invention.

Figure 2 depicts contaminating particles 12a and 12b on a double-sided, unbalanced contaminated thin sheet material 16 capable of being cleaned by a contact cleaning surface assembly according to the present invention. The thin sheet material is a 75μιη polyester film. In alternative

embodiments, the thin film may be polycarbonate or polyvinylchloride or the like of 100 μιη or less thickness.

The imbalance in the film may be due to differences between each of the surfaces of the film in terms of mechanical adhesion forces, for example surface roughness and/or shore hardness, chemical adhesion forces, for example provided by one or more of hydrogen bonds, covalent bonding, ionic bonding, van der Waals forces, dipolar bonds in the material and/or surface coatings of the film, and/or electrostatic forces, provided by pressure and/or friction on the surface and/or the position of the surface material in the triboelectric series. One or each surface of the double-sided film 16 may have a functional coating applied thereto. For example, a double-sided film may have a matt or roughened surface and a smooth, gloss surface, another double- sided film may have a first nanoparticle coating on a first side and a second nanoparticle coating on a second side. Other suitable functional coatings may comprise dry or heat seal adhesives, hard coats, usually formed of a silicon composition, or the like.

Each side 18a, 18b of the double-sided thin film 16 has a mechanical adhesion force profile proportional to its shore hardness and its surface roughness. The shore hardness of the film 16 is measured using a durometer and the surface roughness quantified using microscopy. Each side 18a, 18b of the film 16 has an electrostatic adhesion force and a chemical adhesion force associated therewith. The electrostatic charge associated with the thin film 16 may be measured using a static charge meter and the following protocol. Two test surfaces formed of materials at separate ends of the triboelectric series are selected. The first surface of the film is placed into intimate contact with the first test surface and is lifted therefrom, the electrostatic charge of that first surface of the film is measured. The protocol is repeated for the second surface of the film. The entire protocol is repeated with the second test surface. Each lift is repeated numerous times and a mean value for the electrostatic charge associated with each surface of the film is established.

The adhesion force profiles of each side of a double-sided unbalanced thin film can, therefore, be established.

By providing first 10a and second 10b cleaning surfaces with adhesion profiles reverse matched to each of the surfaces 18a, 18b of the unbalanced thin film 16, problems associated with wrapping or creasing of the film 16 during cleaning and processing are mitigated or obviated.

Figure 3 depicts a surface cleaning apparatus generally denoted by the reference numeral 100. The apparatus 100 has a pair of opposing rotatably mounted surface cleaning rollers 102, 104. Each cleaning roller 102, 104 has a cleaning surface 106, 108 capable of collecting and/or removing contaminating small particles from one of the surfaces of a double-sided contaminated thin film 16 such as that shown in Figure 2. The apparatus 100 further comprises a pair of rotatably mounted adhesive rollers 1 10, 1 12 each being separately capable of removing the

contaminating small particles collected on the cleaning surfaces 106, 108 of one of the rotatably mounted surface cleaning rollers 102, 104. In the embodiment shown, the upper adhesive roller 1 10 is urged against the cleaning surface 106 of cleaning roller 102 by gravity and the lower adhesive roller 1 12 is urged against the cleaning surface 108 of cleaning roller 104 by an urging means (not shown).

The apparatus 100 further comprises an inlet conveyor 1 14 and an exit conveyor 1 16, the inlet conveyor being operable to deliver a thin film to the cleaning surfaces 106, 108 and the exit conveyor 1 16 being operable to transport the thin film away from the cleaning surfaces 106, 108 following the cleaning operation. Guide rollers 120, 122 provide mechanical support for the thin film 16 as it passes through the apparatus 100.

In use, a double-sided thin polycarbonate film 16 of 100μιη thickness and having unbalanced adhesion forces associated with each of its surfaces is placed on inlet conveyor 1 14 and is transported towards the cleaning rollers 102, 104. The mechanical adhesion force profile of each side of the film 16 will have been established using microscopy and a durometer, the chemical adhesion force profile will be ascertained from its chemical composition, and the electrostatic adhesion force profile of each surface will have been measured using the protocol described hereinabove. Thus, the first surface of the film 16 will have a first adhesion force profile and the second surface of the film 16 will have a second adhesion force profile. The adhesion force profile of the first cleaning surface 106 of the first cleaning roller 102 will have been reversed matched to that of the first adhesion force profile and the adhesion force profile of the second cleaning surface 108 of the second cleaning roller 104 will have been reversed matched to that of the second adhesion force profile. Reverse matching the adhesion force profiles is a process whereby the adhesion force between the cleaning surface and the contaminating particles is greater than the adhesion force between the film surface and the particles.

Any imbalance in the adhesion forces between the first film surface and the first cleaning surface 106 and between the second film surface and the second cleaning surface 108 will result in wrapping of the film around one or other of the cleaning rollers. By reverse matching the adhesion force profiles above and below the film, the film is able to be conveyed through the apparatus 100 without wrapping or creasing.

By way of example, a double-sided polycarbonate film of 10Ομιη thickness 1 16 and having a matt (surface roughened) side 1 18a and a gloss

(smooth) side 1 18b may be placed on inlet conveyor 1 14 of apparatus 100. The imbalance in adhesion properties provided by the different coatings will typically be visible through a curling of the sheet material 1 16 from a plane. The inlet conveyor 1 14 transports the film 1 16 towards guide roller 120. Upon leaving the surface of inlet conveyor 1 14, the electrostatic charge on the lower surface 1 18b of the film will change but the electrostatic charge of the upper surface 1 18a of the film 1 16 will remain the same. This change is due to a frictional interaction between the surface of the inlet conveyor 1 14 and the film surface 1 18b.

Furthermore, due to the thin nature of the sheet of film 1 16, the film 1 16 will have a tendency to be drawn, by gravity, towards the surface of guide roller 120. The rotatable guide roller is operable to guide the film 1 16 towards the cleaning rollers 102 and 104. The cleaning surface 106 will have an adhesion profile reverse matched to that of the upper film surface 1 18a in order that contaminating particles on the surface 1 18a will be collected and/or removed onto the cleaning surface 106 in preference to remaining on the surface 1 18a of the film 1 16. The cleaning surface 108 will have an adhesion profile reverse matched to that of the lower film surface 1 18b in order that contaminating particles on the surface 1 18b will be collected and/or removed onto the cleaning surface 108 in preference to remaining on the surface 1 18b of the film 1 16. Because the imbalance in the adhesion profiles of the surfaces of the film is reverse matched by a similar but reversed imbalance between the adhesion profiles of the cleaning surfaces 106, 108 of the cleaning rollers 102, 104, the thin film is prevented from wrapping around one or other of the cleaning rollers 102, 104 or otherwise creasing in apparatus 100.

During operation of the apparatus 100, adhesion roller 1 10 is urged into contact with cleaning surface 106 and is operable to remove the contaminating particles from the cleaning surface 106. Adhesion roller 1 12 is urged into contact with cleaning surface 108 and is operable to remove the contaminating particles from the cleaning surface 108.

The tackiness of the adhesive on adhesive rollers 1 10, 1 12 is preferably modified to order that the adhesive generates as little friction on the cleaning surfaces 106, 108 as possible. Any friction generated, produces electrostatic forces which must be taken into account when the adhesion profiles of the cleaning surfaces 106, 108 are reverse matched with the adhesion profiles of the surfaces of the unbalanced, double-sided contaminated thin film to be cleaned.

The cleaned film 1 16 exiting the pair of rotatable cleaning rollers 102, 104 is fed by guide roller 122 onto exit conveyor 1 16 and thereafter away from apparatus 100.

Thus, in operation of the embodiment shown in Figure 3, a double-sided thin film having unbalanced adhesion profiles associated with its two surfaces, is fed into a pair of opposing cleaning surfaces 106, 108 the adhesion force profiles of which are oppositely and equally unbalanced to those of the film to be cleaned. The adhesion force profile of each cleaning surface is reverse matched with the corresponding surface of the thin film and, therefore, is capable of collecting and/or removing contaminating particles from the film surface. The result being that each surface of the film is cleaned irrespective of the imbalance in adhesion force profiles because the imbalance has been reverse matched by the imbalance in the adhesion force profiles of the two cleaning surfaces.

The adhesion properties of the first and second cleaning surfaces 106, 108 and the film surface 1 18a, 1 18b are provided by one or more of mechanical adhesive forces, chemical adhesive forces, shore hardness and electrical adhesive forces. Each type of adhesion force must be reverse matched between a cleaning surface and a surface of the film in order to ensure the film is not prone to wrapping or creasing in the apparatus. Motorised means (not shown) may be provided for driving the rotatably mounted surface cleaning rollers 102, 104and the rotatably mounted adhesive rollers 1 10, 1 12.

The rotatably mounted surface cleaning rollers 102, 104 and the rotatably mounted adhesive rollers 1 10, 1 12 rotate in opposite directions.

Each rotatably mounted adhesive roller 1 10, 1 12 comprises a plurality of adhesive sheets which may be peeled off and removed when the adhesive sheet has become saturated with contaminated material or the efficiency of the adhesive sheet has reduced.

Each rotatably mounted adhesive roller 1 10, 1 12 is therefore in the form of a pre-sheeted adhesive roll.

In the alternative embodiment of Figure 4, the surface cleaning apparatus 200 comprises twin pairs of cleaning rollers 202a, 204a, 202b, 204b. Each cleaning roller has a cleaning surface 206a, 208a, 206b, 208b capable of collecting and/or removing contaminating particles from the surfaces of the thin film 216. As the film 216 exits the first pair of cleaning rollers 202a, 204a, the film continues to have unbalanced adhesion force profiles associated with each of its surfaces. Furthermore, the thin film has a tendency to be drawn downwards due to gravity as it exits the first pair of cleaning rollers and may also be affected by a differential pressure between the two adhesive rollers 210, 212. Thus, the cleaning surfaces 206b, 208b must be reversed matched with the adhesion force profiles of the surfaces of the unbalanced film as they are when they exit the first pair of cleaning rollers 202a, 204a. The present invention provides an apparatus capable of cleaning both sides of a double-sided thin film of under 100μιη wherein each side of the film has a separate and different adhesion force profile to the opposite side of the film. The adhesion force profile is comprised of one or more of mechanical adhesion forces, for example provided by surface roughness and/or shore hardness, chemical adhesion forces, for example provided by the chemical bonds within the chemical composition of the film material and electrostatic adhesion forces, for example provided by the position of the material of the film surface or its coating in the triboelectric series and/or by static forces due to pressure and/or friction. By matching and slightly exceeding the adhesion force profile of each side of the thin film with the adhesion force profile of a cleaning surface, the tendency of the thin film to wrap or crease during cleaning and processing is mitigated or even obviated.

Claims

1. A contact cleaning surface assembly comprising:

contaminated substrate;

2. A contact cleaning assembly according to claim 1 , wherein the adhesion properties of the first and second cleaning surfaces are provided by one or more of mechanical adhesive forces, chemical adhesive forces, shore hardness and/or electrical adhesive forces.

3. A contact cleaning assembly according to claim 2, wherein the mechanical adhesive forces are provided by surface roughness of the first and/or the second cleaning surface.

4. A contact cleaning assembly according to claim 3, wherein at least a part of the first and/or the second cleaning surface is microscopically roughened whereby the microscopically roughened surface is capable of enhancing collection and/or removal of small contaminating particles from a contaminated surface by increasing the mechanical adhesive forces of the first and/or the second cleaning surface(s).

5. A contact cleaning assembly according to claim 3 or claim 4, wherein the first and the second cleaning surfaces are differentially microscopically roughened.

6. A contact cleaning assembly according to any one of the preceding claims, wherein the first and/or second cleaning surface(s) are

electrostatically charged to assist in the collection and/or removal of the contaminating particles from, and in the processing of, an electrostatically unbalanced double-sided substrate.

7. A contact cleaning assembly according to claim 6, wherein the first and second cleaning surfaces are differentially electrostatically charged.

8. A contact cleaning assembly according to claim 6 or claim 7, wherein the electrostatic adhesion force of the first cleaning surface is reverse matched with the electrostatic adhesion force of the first surface of the double-sided contaminated substrate and the electrostatic adhesion force of the second cleaning surface is reverse matched with the electrostatic adhesion force of the second surface of the double-sided contaminated substrate.

9. A contact cleaning assembly according to any one of the preceding claims, wherein the first and second cleaning surfaces are each made from or comprise elastomer material.

10. A contact cleaning assembly according to any one of the preceding claims, wherein the chemical composition of the first and/or second cleaning surface(s) is modified to modify the chemical adhesive forces of the or each cleaning surface to assist in the collection and/or removal of the contaminating particles from, and in the processing of, a double-sided substrate having unbalanced chemical adhesion properties.

1 1. A contact cleaning assembly according to claim 10, wherein the chemical compositions of the first and second cleaning surfaces are differentially chemically modified thereby providing first and second cleaning surfaces having different chemical adhesive forces.

12. A contact cleaning assembly according to any one of the preceding claims, wherein the first and/or second cleaning surface(s) have different shore hardness to assist in the collection and/or removal of the

contaminating particles from the surfaces of an unbalanced double-sided contaminated substrate.

13. A contact cleaning assembly according to any one of the preceding claims, wherein the first and second cleaning surfaces form a single pair of opposing cleaning surfaces.

14. A contact cleaning assembly according to any one of the preceding claims, further comprising a third cleaning surface capable of collection and/or removal of small contaminating particles from the first contaminated surface of the contaminated substrate.

15. A contact cleaning assembly according to any one of the preceding claims, further comprising a fourth cleaning surface capable of collection and/or removal of small contaminating particles from the second contaminated surface of the contaminated substrate.

16. A contact cleaning assembly according to claim 15 when dependent upon claim 14, wherein the third and fourth cleaning surfaces form a single pair of opposing cleaning surfaces.

17. A contact cleaning assembly according to any one of the preceding claims, wherein the first and/or second and/or third and/or fourth cleaning surfaces are in the form of a roller which may be rotated and/or urged against a surface to be cleaned.

18. A method of cleaning a double-sided unbalanced substrate

contaminated with small particles, said method comprising:

19. A method according to claim 18, wherein the adhesion force profile of the first cleaning surface is reverse matched with the adhesion force profile of the first contaminated surface of the contaminated substrate and also wherein the adhesion force profile of the second cleaning surface is reverse matched with the adhesion force profile of the second

contaminated surface of the contaminated substrate.

20. A method according to claim 18 or claim 19, wherein all or

substantially all of the first cleaning surface has a different adhesion force profile when compared to the adhesion force profile all or substantially all of the second cleaning surface to increase the efficiency of the removal of the contaminating particles.

21 . A method according to any one of claims 18 to 20, wherein the adhesion force profiles of the first and second cleaning surfaces are provided by one or more of mechanical adhesive forces, chemical adhesive forces, shore hardness and/or electrical adhesive forces.

22. A method according to any one of claims 18 to 21 , wherein the cleaning surfaces are rotated against the surfaces contaminated with small particles with a speed of about 0.1 cm/s to about 5 cm/s.

23. A method according to any one of claims 18 to 22, wherein the first and second cleaning surfaces are as defined in any one of claims 1 to 17.

24. A surface cleaning apparatus for cleaning double-sided, unbalanced contaminated substrates, said surface cleaning apparatus comprising: at least one pair of rotatably mounted surface cleaning rollers each capable of removing contaminating small particles from one of the contaminated surfaces of a double-sided contaminated substrate; a pair of rotatably mounted adhesive rollers each separately capable of removing the contaminating small particles collected on one of the rotatably mounted surface cleaning rollers; means capable of urging each surface

contaminating particles from a first contaminated surface of the

25. A surface cleaning apparatus according to claim 24, wherein the first and second cleaning surfaces are as defined in any one of claims 1 to 17.

26. A surface cleaning apparatus according to claim 24 or claim 25, wherein the means capable of urging each surface contaminated with small particles against one of the pair of rotatably mounted surface cleaning rollers are mounted substantially opposite the rotatably mounted surface cleaning roller.

27. A surface cleaning apparatus according to any one of claims 24 to 26, comprising two pairs of rotatably mounted surface cleaning rollers and a pair of rotatably mounted adhesive rollers.

28. A surface cleaning apparatus according to claim 27 wherein each pair of rotatably mounted surface cleaning rollers comprises a cleaning surface assembly as defined in any one of claims 1 to 17.

29. A method for cleaning contaminated surfaces having unbalanced adhesion force profiles, said method comprising: providing a first rotatably mounted surface cleaning roller capable of removing contaminating small particles from a first contaminated surface of a double-sided substrate; providing a first rotatably mounted adhesive roller capable of removing the contaminating small particles collected on the first rotatably mounted surface cleaning roller; providing means capable of urging a first surface contaminated with small particles against the first rotatably mounted surface cleaning roller;

30. A method according to claim 29, wherein the first and second rotatably mounted surface cleaning rollers comprise a cleaning surface as defined in any one of claims 1 to 17.

31 . A contact cleaning surface assembly substantially as hereindescribed with reference to the accompanying Figures.

32. A method of cleaning a double-sided unbalanced substrate contaminated with small particles substantially as hereindescribed with reference to the accompanying Figures.

33. A surface cleaning apparatus substantially as hereindescribed with reference to the accompanying Figures.

34. A method for cleaning contaminated surfaces having unbalanced adhesion force profiles substantially as hereindescribed with reference to the accompanying Figures.