EP2583761B1

EP2583761B1 - Cleaning system

Info

Publication number: EP2583761B1
Application number: EP11795412.3A
Authority: EP
Inventors: Masashi Ohta; Mikio Tsutsumi; Yuka Murakawa
Original assignee: Bando Chemical Industries Ltd
Current assignee: Bando Chemical Industries Ltd
Priority date: 2010-06-17
Filing date: 2011-06-15
Publication date: 2015-04-08
Anticipated expiration: 2031-06-15
Also published as: CN102933323B; TWI406716B; TW201210709A; KR101271040B1; JP5015365B2; EP2583761A4; JPWO2011158504A1; EP2583761A1; WO2011158504A1; CN102933323A; KR20130029392A

Description

TECHNICAL FIELD

The present invention relates to a cleaning system for removing foreign matter (such as dust and dirt) adhering to the surface of an object to be cleaned by means of electrostatic force. In particular, the present invention is more suitably applicable to a thin object to be cleaned (which has a relatively smooth surface, such as a glass substrate, a printed board (e.g. a PCB or a PCBA), a film, a sheet, or a plastic plate).

BACKGROUND ART

There has been conventionally known a cleaning system for removing foreign matter, such as dust and dirt, adhering to the surface of a thin object to be cleaned such as a glass substrate, a bonded film, a printed board of a flat panel display (FPD), in which cleaning system, an adhesive roller is used to remove the foreign matter by utilizing adhesive force thereof (see Patent Document 1, for example).
Such an adhesive roller is incapable of removing fine foreign matter (foreign matter of 1 µm or less in average diameter, for example). Furthermore, it is difficult to completely remove foreign matter, such as dust and dirt, which has once adhered to the surface (an adhesive layer) of the adhesive roller. Therefore, the adhesive roller has poor maintenance performance. Moreover, the adhesive roller is pressed against the object to be cleaned with a certain level of pressure in order to remove foreign matter. Accordingly, in a case where the object to be cleaned is a film, not only the foreign matter is removed but also the film may stick to the surface of the roller.
In view of the above, the inventor has filed a separate patent application, on the basis of the fact that, upon removing foreign matter, such as dust and dirt, from an object to be cleaned, if the surface of a cleaning roller is provided with electric charge by applying a voltage so that the electric charge can adsorb the foreign matter by means of electrostatic force, the cleaning roller can remove the foreign matter by such electrostatic force (see Japanese Patent Application No. 2008-271797 ).
However, in the above invention, the foreign matter, which was removed from the surface of the object to be cleaned with use of the cleaning roller by adsorption force due to such electrostatic force, is sequentially accumulated on the surface (the outer peripheral surface) of the cleaning roller. It is thus necessary to periodically perform maintenance work of removing the foreign matter from the surface of the roller.
The cleaning system utilizing adhesive force of the adhesive roller generally adopts a mechanism in which a transferring roller (an adhesive roller) having adhesive force stronger than that of the cleaning roller (an adhesive roller) is made in contact so that foreign matter is shifted from the cleaning roller to the transferring roller.
Accordingly, there comes an idea of using the transferring roller having such strong adhesive force in the cleaning system.
JP 2010099565 relates to a cleaning system in accordance with the preamble of claim 1. The cleaning system comprises a cleaning roller for rotating while in contact with a surface of a cleaning member. The cleaning member is to be cleaned from foreign matter, such as dust or dirt, adhering to its surface. This is achieved by means of an electrostatic force. The electrostatic force is generated by the cleaning roller being capable of providing on its surface electric charge. Furthermore, the cleaning system comprises a transfer roller. The transfer roller is designed to remove foreign matter adhering to the cleaning roller by means of an electrostatic force.

PRIOR ART DOCUMENT

PATENT DOCUMENT

Patent Document 1: Japanese Unexamined Patent Publication No. 2008-168188

SUMMARY OF THE INVENTION

PROBLEMS TO BE SOLVED BY THE INVENTION

However, use of the transferring roller having such strong adhesive force inhibits stable provision of electric charge that enables adsorption of foreign matter to the surface of the cleaning roller by means of electrostatic force. Accordingly, the cleaning roller cannot adsorb foreign matter continuously for a long period of time without performing maintenance work on the cleaning roller.
It is an object of this invention to provide a cleaning system in which a cleaning roller can adsorb foreign matter continuously for a long period of time without performing maintenance work on the cleaning roller.
When foreign matter is adsorbed by means of electrostatic force (Coulomb force), adsorption force is stronger with a larger amount of electric charge held on the surface of the cleaning roller. However, if the surface of the cleaning roller has an excessive electrification voltage, spark discharge occurs between the cleaning roller and the object to be cleaned as a target object, the electrification state becomes uneven on the surface of the cleaning roller or the object to be cleaned, and the foreign matter is attracted to the uneven electrification, with a result that stable cleaning performance may not be realized. In addition, such spark discharge may damage the target object. Moreover, in a case where the object to be cleaned is an electronic component such as a static-sensitive semiconductor, even the accumulation of electric charge not enough to cause spark discharge brings about electrostatic discharge failure, which is problematic.
In view of the above, in addition to the object mentioned earlier, it is another object of the present invention to provide a cleaning apparatus that can suppress excessive raise of an electrification voltage generated on the surface of the cleaning roller for adsorbing foreign matter by means of electrostatic force, so as to stabilize the electrification voltage.

SOLUTIONS TO THE PROBLEMS

In the invention according to claim 1, a cleaning system includes a cleaning roller for relatively moving by rotating while being in contact with a surface of an object to be cleaned, so as to remove foreign matter, such as dust and dirt, adhering to the surface of the object to be cleaned by means of electrostatic force, wherein the cleaning roller is provided with a transferring roller for rotating while being in contact with a surface of the cleaning roller, the cleaning roller is capable of being provided on the surface thereof with electric charge for adsorbing foreign matter adhering to the surface of the object to be cleaned by means of electrostatic force, the transferring roller is capable of being provided on a surface thereof with electric charge for adsorbing foreign matter adhering to the surface of the cleaning roller by means of electrostatic force, the cleaning roller is grounded via a voltage stabilizing circuit and the transferring roller is connected directly or indirectly with an external power source, and the voltage stabilizing circuit is capable of changing an electrification voltage of the cleaning roller for adsorbing the foreign matter by means of electrostatic force.
In this configuration, the cleaning roller can be provided on the surface thereof with electric charge for adsorbing foreign matter adhering to the surface of the object to be cleaned by means of electrostatic force. Therefore, the foreign matter on the surface of the object to be cleaned is adsorbed to the cleaning roller. Furthermore, the transferring roller can be provided on the surface thereof with electric charge for adsorbing foreign matter adhering to the surface of the cleaning roller by means of electrostatic force. Therefore, the foreign matter having been adsorbed to the cleaning roller is adsorbed to the transferring roller. Consequently, there is no need to perform the maintenance work of periodically removing (cleaning) or periodically replacing the cleaning roller.
In addition, by changing the set voltage value of the voltage stabilizing circuit connected to the cleaning roller, it is possible to suppress excessive raise of an electrification voltage generated on the surface of the cleaning roller for adsorbing foreign matter by means of electrostatic force and thereby to stabilize the electrification voltage. Moreover, an electronic component such as a static-sensitive semiconductor can be protected from electrostatic discharge failure.
In this case, as recited in claim 2, the voltage stabilizing circuit can be a fixed resistor, a variable resistor, or a switchable resistor having a plurality of fixed resistors and switching to one of the fixed resistors to be used so as to change a resistance value.
In this configuration, by changing the resistance value of the fixed resistor, the variable resistor, or the switchable resistor, it is possible to easily configure the voltage stabilizing circuit that can change the electrification voltage of the transferring roller for adsorbing the foreign matter by means of electrostatic force. Even in the case of using the fixed resistor, the resistance value can be changed by replacing the fixed resistor.
More specifically, by changing the resistance value, it is possible to change the electrification voltage of the cleaning roller for adsorbing the foreign matter by means of electrostatic force. Accordingly, even when a voltage is applied to the transferring roller by the external power source, without changing the applied voltage, the cleaning roller can have variable adsorption force applied to the foreign matter adsorbing to the cleaning roller. For example, when the resistance value of the resistor connected to the cleaning roller is decreased as low as possible, decreased is the electric charge for adsorbing foreign matter adhering to the surface of the cleaning roller by means of electrostatic force, so that the cleaning roller can lose the adsorption force applied to the foreign matter adsorbing to the cleaning roller. As a result, the foreign matter having been adsorbed to the cleaning roller is adsorbed to the transferring roller. Consequently, the maintenance work as described earlier can be more simplified.
Therefore, unlike the conventional cleaning system utilizing adhesive force of an adhesive roller, there is no need to perform the maintenance work of periodically removing (cleaning) foreign matter adhering to the surface of the cleaning roller or periodically replacing the cleaning roller to which the foreign matter adheres. It is thus possible to obtain the cleaning system that is excellent in maintenance performance. Moreover, there is no need of sensitive control on the voltage applied to the transferring roller, which results in a compact design of the external power source for applying a voltage to the transferring roller.
As recited in claim 3, the transferring roller desirably is designed for rotating while being in contact with the surface of the cleaning roller, so that a difference in potential is generated between the transferring roller and the cleaning roller in accordance with a difference in surface characteristic (such as electrification ranks) therebetween.
In this configuration, due to contact and separation caused by the rotation of the cleaning roller and the transferring roller, the difference in potential is generated on the transferring roller in accordance with a difference in surface characteristic (such as the electrification ranks) between the transferring roller and the cleaning roller, and the transferring roller is provided with electric charge for adsorbing foreign matter adhering to the surface of the object to be cleaned by means of electrostatic force.
As recited in claim 4, desirably, the transferring roller is provided with a cleaning brush for corotating therewith or rotating reversely thereto, and the cleaning brush is provided with a metal roller for corotating therewith or rotating reversely thereto, and the external power source is connected to the metal roller and is designed for generating differences in potential among the transferring roller, the cleaning brush, and the metal roller.
In this configuration, the foreign matter is removed from the transferring roller by the cleaning brush, and is shifted to the metal roller by means of electrostatic force. Therefore, the foreign matter can be more efficiently removed from the transferring roller. In particular, it is also possible to change the difference in potential that is generated between the metal roller and the transferring roller by the external power source connected to the metal roller. Therefore, the foreign matter can be effectively conveyed to the metal roller.
In this case, as recited in claim 5, the metal roller can be provided near a surface thereof with a cleaning blade having a tip scratcher for scratching foreign matter adhering to the surface of the metal roller.
In this configuration, the foreign matter having been adsorbed to the surface of the metal roller by means of electrostatic force is scratched by the tip scratcher of the cleaning blade. Therefore, the foreign matter can be efficiently removed from the metal roller.
Furthermore, as recited in claim 6, desirably, the cleaning blade is provided nearby with a suction port of an air vacuum means that is capable of sucking foreign matter by means of vacuum pressure, or a foreign matter container for collecting and accumulating foreign matter scratched by the cleaning blade.
In this configuration, the foreign matter having been adsorbed to the surface of the metal roller by means of electrostatic force is scratched by the tip scratcher of the cleaning blade, and the foreign matter is sucked by negative pressure through the suction port of the air vacuum means or is collected in the foreign matter container, with no risk that the periphery of the metal roller gets dirty by the foreign matter. Particularly in the case where the foreign matter container is provided, the foreign matter can be collected in the foreign matter container without providing any additional power source.
As recited in claim 7, a guide roller can be provided opposite to the cleaning roller with the object to be cleaned being interposed therebetween, so that the guide roller designed for enhancing field intensity of the cleaning roller for adsorbing foreign matter adhering to the surface of the object to be cleaned by means of electrostatic force.
In this configuration, the two rollers face each other with the object to be cleaned being interposed therebetween, and the object to be cleaned is supported from above and below at the positions in contact with the cleaning roller and the guide roller. The foreign matter is removed from the surface of the object to be cleaned that is supported stably.
Furthermore, the field intensity of the cleaning roller for adsorbing foreign matter adhering to the surface of the object to be cleaned by means of electrostatic force is enhanced by the guide roller. The electrically charged foreign matter on the object to be cleaned is adsorbed to the cleaning roller in accordance with the electric field thus provided, so as to be removed efficiently.

EFFECTS OF THE INVENTION

According to the present invention configured as described above, it is possible to change the adsorption force applied to the foreign matter adsorbing to the surface of the cleaning roller and the foreign matter can be stably transferred to the transferring roller. Therefore, unlike the conventional cleaning system utilizing adhesive force of an adhesive roller, there is no need to perform the maintenance work of periodically removing (cleaning) foreign matter adhering to the surface of the cleaning roller or periodically replacing the cleaning roller to which the foreign matter adheres. It is thus possible to obtain the cleaning system that is excellent in maintenance performance.
Particularly, in the invention according to claim 1, by changing the set voltage value of the voltage stabilizing circuit connected to the cleaning roller, it is possible to weaken the adsorption force of the cleaning roller, which is applied to the foreign matter adsorbed to the cleaning roller. Therefore, the foreign matter having been adsorbed to the cleaning roller can be adsorbed to the transferring roller.
In addition, by changing the set voltage value of the voltage stabilizing circuit connected to the cleaning roller, it is possible to suppress excessive raise of an electrification voltage generated on the surface of the cleaning roller for adsorbing foreign matter by means of electrostatic force and thereby to stabilize the electrification voltage. Moreover, an electronic component such as a static-sensitive semiconductor can be protected from electrostatic discharge failure.

BRIEF DESCRIPTION OF THE DRAWINGS

Figs. 1(a) and 1(b) are explanatory views on the operation principle of a cleaning system according to a first embodiment of the present invention, respectively.
Fig. 2 is an explanatory view showing an example of the first embodiment.
Fig. 3 is a view showing a first modification of the embodiment shown in Fig. 2.
Fig. 4 is a view showing a second modification of the embodiment shown in Fig. 2.
Fig. 5 is a view showing a third modification of the embodiment shown in Fig. 2.
Fig. 6 is a view showing a fourth modification of the embodiment shown in Fig. 2.
Fig. 7 is a view showing an embodiment in which two sets of cleaning units are aligned with each other.

EMBODIMENTS OF THE INVENTION

Embodiments of the present invention are described below with reference to the drawings.

FIRST EMBODIMENT

Figs. 1(a) and 1(b) are explanatory views on the operation principle of a cleaning system according to a first embodiment of the present invention.
As shown in Fig. 1(a), a cleaning system 1 includes a cleaning roller 11, and a transferring roller 21 that rotates relatively to the cleaning roller 11 while being in contact with the surface of the cleaning roller 11.
The cleaning roller 11 relatively moves by rotating while being in contact with the surface of an object to be cleaned S, so as to remove foreign matter, such as dust and dirt, adhering to the surface of the object to be cleaned S by means of electrostatic force. The cleaning roller 11 can be provided on the outer peripheral surface thereof with electric charge for adsorbing foreign matter adhering to the surface of the object to be cleaned S by means of electrostatic force. The foreign matter is adsorbed by the electrification on the surface (outer peripheral surface) of the cleaning roller.
The transferring roller 21 rotates while being in contact with the surface of the cleaning roller 11, so that a difference in potential is generated between the transferring roller and the cleaning roller 11 in accordance with a difference in surface characteristic (such as electrification ranks) between the transferring roller 21 and the cleaning roller 11. Due to contact and separation caused by the rotation of the cleaning roller 11 and the transferring roller 21, the difference in potential is generated on the transferring roller 21 in accordance with a difference in surface characteristic (such as the electrification ranks) between the transferring roller and the cleaning roller 11, so that the transferring roller is provided with electric charge for adsorbing foreign matter adhering to the surface of the object to be cleaned S by means of electrostatic force.
In this manner, the transferring roller 21 is provided opposite to the object to be cleaned S with respect to the cleaning roller 11 so as to be in contact with the cleaning roller 11. Accordingly, it is possible to transfer (shift), to the transferring roller 21, the foreign matter adhering to the cleaning roller 11 by means of electrostatic force. Therefore, the cleaning roller 11 is made in contact with the object to be cleaned S in the state where the foreign matter adhering to the outer peripheral surface of the cleaning roller 11 is transferred to the transferring roller 21. The foreign matter on the outer peripheral surface of the cleaning roller 11 is thus continuously transferred to the transferring roller 21, so that the cleaning roller 11 can exert the cleaning effect at any time. Therefore, the cleaning roller 11 can continuously adsorb foreign matter for a relatively long period of time. As a result, there is no need to perform the maintenance work of periodically removing foreign matter on the outer peripheral surface of the cleaning roller 11 or replacing the cleaning roller 11, which is advantageous for the improvement in maintenance performance.
The transferring roller 21 has a core metal to which a constant voltage is applied by an external power source 31. The cleaning roller 11 is grounded via a first voltage stabilizing circuit 12, so that the surface of the roller can be provided stably with electric charge for adsorbing foreign matter adhering to the surface of the object to be cleaned S by means of electrostatic force. The first stabilizing circuit 12 is configured by a variable resistor 12a (see Fig. 1(a)). The first stabilizing circuit 12 may be of course replaced with a fixed resistor 12b as shown in Fig. 1(b) (the same applies hereinafter).
As described above, the cleaning roller 11 can be provided on the surface thereof with electric charge for adsorbing foreign matter adhering to the surface of the object to be cleaned S by means of electrostatic force. Therefore, the foreign matter on the surface of the object to be cleaned S is adsorbed to the surface of the cleaning roller 11. Furthermore, the transferring roller 21 can be provided on the surface of the roller with electric charge for adsorbing foreign matter adhering to the surface of the cleaning roller 11 by means of electrostatic force. Therefore, the foreign matter having been adsorbed to the surface of the cleaning roller 11 is adsorbed to the surface of the transferring roller 21, thereby shifting from the cleaning roller 11 to the transferring roller 21. Accordingly, there is no need to perform the maintenance work of periodically removing (cleaning) or periodically replacing the cleaning roller 11. It is therefore possible to obtain the cleaning system that is excellent in maintenance performance.
Furthermore, there is provided the first voltage stabilizing circuit 12 that is connected to the cleaning roller 11. By changing a resistance value of the first voltage stabilizing circuit 12 (the variable resistor 12a), it is possible to change the electrification voltage of the cleaning roller for adsorbing foreign matter by means of electrostatic force. Therefore, the cleaning roller 11 has variable adsorption force applied to the foreign matter adsorbed to the cleaning roller 11. Accordingly, even when a voltage is applied to the transferring roller 21 by the external power source 31, the cleaning roller 11 can have variable adsorption force applied to the foreign matter adsorbing to the cleaning roller 11 without changing the applied voltage. For example, when the resistance value of the variable resistor 12a connected to the cleaning roller 11 is decreased as low as possible, decreased is the electric charge for adsorbing foreign matter adhering to the surface of the cleaning roller 11 by means of electrostatic force, so that the cleaning roller 11 can lose the adsorption force applied to the foreign matter adsorbing to the cleaning roller 11. As a result, the foreign matter having been adsorbed to the cleaning roller 11 is adsorbed to the transferring roller 21. Consequently, the maintenance work as described earlier can be more simplified.
Therefore, unlike the conventional cleaning system utilizing adhesive force of an adhesive roller, there is no need to perform the maintenance work of periodically removing (cleaning) foreign matter adhering to the surface of the cleaning roller or periodically replacing the cleaning roller to which the foreign matter adheres. It is thus possible to obtain the cleaning system that is excellent in maintenance performance. Moreover, there is no need of sensitive control on the voltage applied by the external power source 31 connected to the transferring roller 21, which results in a compact design of the external power source 31.
Described next are the cleaning roller 11 and the transferring roller 21.
The cleaning roller 11 has a core metal (cored bar) 11 a as a conductive shaft member, an inner layer portion 11 b that is provided around the outer periphery of the core metal 11 a and has conductivity, and an outer layer portion 11 c that is provided around the outer periphery of the inner layer portion 11 b, is made of a material having resistance higher than that of the inner layer portion 11 b, and has a thin cylindrical shape, so as to form a bilayer structure.
In the cleaning roller 11 thus configured, the material for the outer layer portion 11c is selected from those which can be provided with electric charge for adsorbing foreign matter, such as dust and dirt, adhering to the surface of the object to be cleaned S by means of electrostatic force.
The outer layer portion 11 c of the cleaning roller 11 is preferably 2 to 500 µm (more preferably 5 to 50 µm) in thickness. This is because, while electric charge is less likely to be provided on the surface of the roller (the surface of the outer layer portion) if the outer layer portion 11 c is less than 2 µm in thickness, it is industrially ineffective to provide the outer layer portion of more than 500 µm in thickness. The core metal 11a can be replaced with a cored bar made of a conductive carbon material, a synthetic resin composite material, or the like. The core metal (cored bar) 11a desirably has a resistance value not more than 10⁵ Ω, between a center portion and an end portion of the core metal.
The inner layer portion 11 b is made of an elastic material having conductivity (such as polyester urethane containing carbon (a conductive material)), and is less than or substantially equal to the outer layer portion 11 c in hardness. The inner layer portion 11 b is not particularly limited as long as having resistance lower than that of the outer layer portion 11 c, while preferably having volume resistivity of approximately 10⁴ to 10¹² Ωcm.
The material for the outer layer portion 11c has hardness (JIS-A) not less than 50° (desirably not less than 50° and less than 100°, more desirably not less than 55° and less than 100°, and further desirably not less than 65° and less than 100°). Furthermore, the outer layer portion 11 c has volume resistivity higher than that of the inner layer portion 11 b. The outer layer portion 11c has volume resistivity desirably not less than 10⁸ Ωcm, and more desirably not less than 10¹⁰ Ωcm.
Preferred examples of the material for the outer layer portion 11 c of the cleaning roller 11 include a urethane resin, and further acrylic mixed urethane and fluorine mixed urethane. Herein, the "acrylic mixed urethane" contains polyester polyurethane or polyether polyurethane as a main component, and indicates (i) a mixture of a thermoplastic urethane resin and a silicon-acrylic copolymer resin, (ii) a mixture of an acrylic resin (such as a graft compound obtained by grafting an aminoethyl group onto the main chain made of methacrylic acid-methyl methacrylate copolymer) and a thermoplastic urethane resin, or (iii) a mixture of an acrylic resin, a urethane resin, and a fluorine-based surface coating agent. On the other hand, the "fluorine mixed urethane" contains polyurethane as a main component, and indicates a mixture of a thermoplastic urethane resin and a urethane-fluorine copolymer.
Similarly to the cleaning roller 11, the transferring roller 21 includes a core metal 21a having conductivity, an inner layer portion 21 b provided around the outer periphery of the core metal 21 a and having a cylindrical shape, and an outer layer portion 21c (an elastic layer portion) provided around the outer periphery of the inner layer portion 21 b. The outer layer portion 21 c can have volume resistivity higher than that of the inner layer portion 21 b. It is noted that the transferring roller 21 may be also configured by the core metal 21a and the cylindrical outer layer portion (the elastic layer portion) provided directly around the core metal. The outer layer portion 21 c of the transferring roller 21 is selected so as to have volume resistivity higher than that of the core metal 21 a as well as to be provided on the outer peripheral surface thereof with electric charge for adsorbing foreign matter adhering to the outer peripheral surface of the cleaning roller 11 by means of electrostatic force.
The transferring roller 21 corotates with the cleaning roller 11 and is electrically charged by contact and separation, so as to generate, between the outer peripheral surface of the transferring roller 21 and the outer peripheral surface of the cleaning roller 11, a difference in potential enough to transfer (shift) the foreign matter adhering to the outer peripheral surface of the cleaning roller 11 to the outer peripheral surface of the transferring roller 21 by means of electrostatic force. More specifically, the transferring roller 21 is configured to have the difference in potential enough to adsorb foreign matter due to the difference in roller surface characteristic (such as the electrification ranks) as compared with the cleaning roller 11, having positive or negative polarity same as that of the electric charge (positive electric charge or negative electric charge) provided to the roller 11 and the absolute value of the electrification voltage being larger than that of the roller 11. In view of the above, the material for the outer layer portion 21 c of the transferring roller 21 is desirably selected so as to have the polarity same as that of the cleaning roller 11 and to have a difference in potential as large as possible in a range of keeping stable adsorption.
The foreign matter, which is transferred to the transferring roller 21 due to the difference in potential generated by contact and separation between the cleaning roller 11 and the transferring roller 21, can be removed from the transferring roller 21 relatively easily, because the transferring roller 21 itself loses adsorption force caused by electrostatic force when the rotation of the transferring roller 21 is stopped.
In addition to the above, as shown in Fig. 2, a cleaning brush 41 can be provided so as to rotate reversely to the corotation with the transferring roller 21, and a metal roller 42 can be provided so as to corotate with the cleaning brush 41. In this case, the external power source 31 is connected to the metal roller 42. As shown in Fig. 3, in this case, the variable resistor can be replaced with a switchable resistor 43 that has a plurality of fixed resistors 43a and a switcher 43b for switching to one of the fixed resistors 43a to be used so as to change a resistance value thereof, which configures a first voltage stabilizing circuit 12A.
Still alternatively, as shown in Fig. 4, it is possible to provide, above the metal roller 42 and near the surface thereof, a cleaning blade 44 having a tip scratcher for scratching foreign matter adhering to the surface of the metal roller 42, as well as to provide, near the cleaning blade 44 and above the metal roller 42, a suction port 45 of an air vacuum means (not shown) that can suck foreign matter by means of negative pressure. Accordingly, the foreign matter scratched by the tip scratcher of the cleaning blade 44 is sucked by the negative pressure through the suction port 45 of the air vacuum means, with no risk that the periphery of the metal roller 42 gets dirty by the foreign matter.
As shown in Fig. 5, it is possible to provide a foreign matter container 46 for collecting and accumulating foreign matter scratched by the cleaning blade 44 located on the surface of the metal roller 42, and it is also possible to provide a foreign matter container for collecting and accumulating foreign matter scattered by the rotating brush.
As shown in Fig. 6, a guide roller 51 can be provided opposite to the cleaning roller 11 with the object to be cleaned S being interposed therebetween. The guide roller 51 enhances field intensity of the cleaning roller for adsorbing foreign matter adhering to the surface of the object to be cleaned by means of electrostatic force.

(Method)

In the cleaning system shown in Fig. 2, the cleaning roller 11 and the transferring roller 21, which were retained by an insulating member (not shown), were made in contact with each other and corotated at a rotation speed of 5 m/min, and the core metal 11a of the cleaning roller 11 was provided with a ground via the variable resistor 12a. Furthermore, the external power source 31 was connected to the metal roller 42 that was provided to the transferring roller 21 with the cleaning brush 41 being interposed therebetween. The cleaning brush 41 was provided so as to rotate reversely to the corotation with the transferring roller 21, and the metal roller 42 was provided so as to corotate with the cleaning brush 41.

In the above state, surface potential of each of the members relative to the change in resistance value of the variable resistor 12a was measured with use of a surface electrometer (Model 341 B manufactured by TREK Inc.).

[Table 1]

Variable resistance value (MΩ)	0	20.3	50.3	97.9	143.6	0	20.3	50.3	97.9	143.6
Potential of external power source (V)	+1000	+1000	+1000	+1000	+1000	-1000	-1000	-1000	-1000	-1000
Potential of metal roller (V)	+1000	+1000	+1000	+1000	+1000	-1000	-1000	-1000	-1000	-1000
Potential of cleaning brush (V)	+768	+830	+864	+884	+903	-759	-824	-852	-882	-894
Potential of transferring roller (V)	+342	+520	+606	+688	+730	-312	-462	-544	-632	-662
Potential of cleaning roller (V)	+8	+148	+263	+368	+446	-5	-194	-324	-487	-565

Found from the measurement results is that the surface potential of the cleaning roller 11 can be adjusted by adjustment of the resistance value of the variable resistor 12a, so as to change the adsorption force applied to foreign matter adsorbing to the cleaning roller 11.
In addition to the above, the present invention can be modified as follows.

(i) As shown in Fig. 7, a cleaning unit U1 (including a cleaning roller 11, a transferring roller 21, a cleaning brush 41, and a metal roller 42) and a cleaning unit U2 (including a cleaning roller 11', a transferring roller 21', a cleaning brush 41', and a metal roller 42') are aligned with each other. In the respective units U1 and U2, the polarity of electric charge provided to the outer peripheral surface of the cleaning roller 11 can be inverted to the polarity of electric charge provided to the outer peripheral surface of the cleaning roller 11'. In this configuration, in the foreign matter adhering to the surface of the object to be cleaned S, the foreign matter having positive electrification can be removed by the cleaning roller 11 (the cleaning unit U1) having negative electrification, while the foreign matter having negative electrification can be removed by the cleaning roller 11' (the cleaning unit U2) having positive electrification. Therefore, it is possible to expand the range of the foreign matter to be removed. Fig. 14 shows a system in which two sets of those shown in Fig. 2 are aligned with each other. It is of course possible to similarly align two sets in any one of the other embodiments, so as to expand the range of the foreign matter to be removed.
(ii) The present invention is applicable to cases where the object to be cleaned is thin, in particular a film, a sheet, a printed board (e.g. a PCB or a PCBA), or the like. However, the present invention is not limited to the above.

DESCRIPTION OF REFERENCE SIGNS

S: Object to be cleaned
11: Cleaning roller
12, 12A: Voltage stabilizing circuit
12a: Variable resistor
12b: Fixed resistor
13, 13A, 13B: First voltage stabilizing circuit
13a, 15a, 16a: Voltage regulator diode
14, 15, 15A, 15B: Second voltage stabilizing circuit
14a, 17a, 13b, 15b, 16b: Variable resistor
14b, 17b, 13c, 15c, 16c: Fixed resistor
16, 16A, 16B: Third voltage stabilizing circuit
17: Fourth voltage stabilizing circuit
21: Transferring roller
31: External power source
41: Cleaning brush
42: Metal roller
43: Switchable resistor
44: Cleaning blade
45: Suction port
46: Foreign matter container
51: Guide roller
61: Polarity switching circuit

Claims

A cleaning system (1) comprising a cleaning roller (11) for relatively moving by rotating while being in contact with a surface of an object to be cleaned (S), so as to remove foreign matter, such as dust and dirt, adhering to the surface of the object to be cleaned by means of electrostatic force, wherein
the cleaning roller (11) is provided with a transferring roller (21) for rotating while being in contact with a surface of the cleaning roller (11),
the cleaning roller (11) is capable of being provided on the surface thereof with electric charge for adsorbing foreign matter adhering to the surface of the object to be cleaned (S) by means of electrostatic force,
the transferring roller (21) is capable of being provided on a surface thereof with electric charge for adsorbing foreign matter adhering to the surface of the cleaning roller (11) by means of electrostatic force, characterized in that,
the cleaning roller (11) is grounded via a voltage stabilizing circuit (12) and the transferring roller (21) is connected directly or indirectly with an external power source (31), and
the voltage stabilizing circuit (12) is capable of changing an electrification voltage of the cleaning roller (11) for adsorbing the foreign matter by means of electrostatic force.
The cleaning system according to claim 1, characterized in that
the voltage stabilizing circuit (12) is a fixed resistor (12b), a variable resistor (12a), or a switchable resistor (43) having a plurality of fixed resistors and switching to one of the fixed resistors to be used so as to change a resistance value.
The cleaning system according to claim 1, characterized in that,
the transferring roller (21) is designed for rotating while being in contact with the surface of the cleaning roller, so as to generate a difference in potential between the transferring roller (21) and the cleaning roller (11) in accordance with a difference in surface electrification between the transferring roller (21) and the cleaning roller (11).
The cleaning system according to claim 1, characterized in that,
the transferring roller (21) is provided with a cleaning brush (41) for corotating therewith or rotating reversely thereto, and the cleaning brush (41) is provided with a metal roller (42) for corotating therewith or rotating reversely thereto, and
the external power source (31) is connected to the metal roller (42) and designed for generating differences in potential among the transferring roller (24), the cleaning brush (41), and the metal roller (42).
The cleaning system according to claim 4, characterized in that,
the metal roller (42) is provided near a surface thereof with a cleaning blade (44) having a tip scratcher for scratching foreign matter adhering to the surface of the metal roller (42).
The cleaning system according to claim 5, characterized in that,
the cleaning blade (44) is provided nearby with a suction port (45) of an air vacuum means that is capable of sucking foreign matter by means of vacuum pressure, or a foreign matter container (46) for collecting and accumulating foreign matter scratched by the cleaning blade (44).
The cleaning system according to claim 1, characterized in that,
a guide roller (51) is provided opposite to the cleaning roller (11) with the object to be cleaned being interposed therebetween, and the guide roller (51) is designed for enhancing field intensity of the cleaning roller (11) for adsorbing foreign matter adhering to the surface of the object to be cleaned (S) by means of electrostatic force.