Wire-less variable gap coater device

Abstract

Systems and methods for coating a thin film with a viscous material, such as a liquid, a paste, or an adhesive, at a desired thickness. In such a system, two films move adjacent to one another, optionally in opposite directions, atop two rollers separated by a known gap that defines a coating thickness, with the material being transferred from one film to the other. The rollers may be maintained in their relative positions by springs and/or linear actuators and positioned using linear encoders. In alternative arrangements, the material to be coated could be low viscosity material such as a polymeric solution. Air knives may be provided near the gap to create an air flow that aids in preventing the free flow of low viscosity materials outside the bounds of the film during coating.

Claims

1. A system, comprising two films that are arranged to move adjacent one another on outer surfaces of respective rollers positioned with respect to one another to define a gap between the films that, in turn, defines a thickness for a layer of a material to be coated on one of the films, wherein a first one of the respective rollers is positioned relative a second one of the respective rollers by a bearing biased by a first pair of parallel springs and wherein the first one of the respective rollers is adjustable in position with respect to the second one of the respective rollers by a pair of linear actuators configured to translate respective arms which support the first pair of parallel springs.

2. The system of claim 1, further comprising a second pair of parallel springs arranged to bias the respective arms away from the first one of the respective rollers.

3. The system of claim 1, further comprising a pair of linear encoders mounted to measure positions of each respective arm.

4. The system of claim 3, wherein an initial position for the system is set as a position at which motion is first detected by the pair of linear encoders when the pair of linear actuators moves the respective arms which adjust the position of the first one of the respective rollers.

5. The system of claim 4, further comprising a limit switch configured to identify a home position of the respective arms.

6. The system of claim 5, wherein the limit switch is an optical, an electrical, or a mechanical limit switch.

7. The system of claim 3, wherein a width of the gap is determined as a distance the pair of linear encoders measure by movement of the respective arms.

8. The system of claim 1, wherein the material is one of a viscous material, a liquid, a paste, an adhesive, a low viscosity material, or a polymeric solution.

9. The system of claim 1, wherein the respective rollers are metal, ceramic, plastic, or rubber.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present invention illustrated by way of example, and not limitation, in the figures of the accompanying drawings, in which:

(2) FIGS. 1A-1C illustrate one embodiment of a wire-less variable gap width system configured in accordance with the present invention in perspective view (FIG. 1A), front view (FIG. 1B), and back view (FIG. 1C).

(3) FIG. 2 illustrates a cross-section view of the system shown in FIG. 1.

(4) FIG. 3 illustrates a detailed view of a gap area between rollers of the system shown in FIG. 1 during the coating of a material onto a film.

(5) FIG. 4 illustrates a detailed view of an area of the system shown in FIG. 1, showing in particular the connection between an arm and a roller thereof.

(6) FIGS. 5A-5C illustrate the use of a well-defined gap of a wire-less variable gap width system configured in accordance with an embodiment of the present invention for mixing of multiple materials when coating a film or other substrate.

(7) FIGS. 6A-6D illustrate a further embodiment of a wire-less variable gap width system configured in accordance with the present invention in which air knives for removal of material are included.

(8) FIG. 7 further illustrates the provision of air knives near a gap between rollers of a wire-less variable gap width system configured in accordance with an embodiment of the present invention.

(9) FIG. 8 illustrates a cut-away view of a pair of air knives near a gap between rollers of a wire-less variable gap width system configured in accordance with an embodiment of the present invention.

DESCRIPTION OF THE INVENTION

(10) Before describing the invention in detail, it is helpful to present an overview. With reference to FIGS. 1A-1C and 2, a wire-less variable gap width system 100 configured in accordance with an embodiment of the present invention includes a frame 10 that supports a spool 12 and a take up reel 14 between sides 16a, 16b of the frame. A film 114 that is carried on spool 12 is passed over one roller 104 of a pair of rollers 102, 104, that are supported longitudinally adjacent one another at one end of frame 10 and is collected on take up reel 14. Not shown in the illustrations are motors or other actuators that are connected to take up reel 14 and spool 12, which motors may advance the take up reel 14 and spool 12 to dispense film 114 prior to, during, and/or following the material deposition operations discussed further below. Rollers 102 and 104 may be supported by pins about which they are free to rotate within frame 10. Alternatively, rollers 102 and 104 may be fixed about such pins, with films 112, 114 sliding over the rollers, but the rollers themselves not moving.

(11) Film 112 which is to be coated with a material passes about roller 102, between roller 102 and 104, adjacent film 114 along a lateral dimension of frame 10 at which rollers 102 and 104 are closest together. Coating of the film 112 occurs in the gap 20 between rollers 102 and 104, or more precisely between films 112 and 114, which are disposed about the outer surfaces to the two rollers.

(12) As shown in FIG. 3, the material 110 to be coated on film 112 is deposited at a point above gap 20 (or, more precisely, upstream in a direction of film 112 travel from gap 20) and the motion of film 112 about roller 102 draws a layer 18 of material 110 onto the outer surface of film 112, with the width of gap 20 determining the thickness of the material layer 18. Film 114 can be advanced about roller 104 as film 112 is advanced about roller 102 in order to remove any residual material 110 from the area of gap 20, e.g., residue due to previous coating operations, to recover unused portions of material 110, or for other purposes (e.g., in connection with a change of materials 110). The material 110 to be coated on film 112 may be a viscous material such as a liquid, a paste, or an adhesive, or it may be a low viscosity material such as a polymeric solution. In various embodiments, the material 110 may be changed between two consecutive coating procedures, with the gap 20 being enlarged during the coating of the second material so as not to displace a previously coated material layer on film 112. The various rollers and spools described herein may be made of metal, ceramic, plastic, rubber, or a combination of such materials and may be coated so as to allow the films 112, 114 to pass freely thereover.

(13) In some embodiments, the material 110 may deposited near gap 20 from a syringe or other reservoir in which the material 110 is maintained. Such a syringe or other reservoir may be kept in a controlled environment in which pressure, temperature, and/or other environmental conditions are maintained according to the needs of material 110. From the syringe or reservoir, the material 110 is deposited upstream of gap 20 to be coated on film 112 (or another substrate), which then passes through gap 20 formed by the pair of cylindrical rollers 102, 104. After passing through the gap 20, a uniform layer 18 of the material 110 will be present on film 112 and the coated film can be provided to further stations for deposition/dispensing of the material or for other purposes. In some cases, after the uniform layer 18 of material 110 has been coated, the coated portion of film 112 can be returned to a position upstream of gap 20 (e.g., in a loop or by linear translation) for recoating with a uniform layer of a second material or to fill in any spaces in layer 18 from the first coating. For example, in various embodiments film 112 can be translated bidirectionally in a controlled manner, so that it can be repositioned while opening the gap 20 between rollers 102, 104, allowing for recoating the same area of film 112 with material 110 (or another material) without contamination to the rollers and reducing or eliminating the amount of film 112 consumed during the coating process. Film 112 may be a transparent film or other substrate, with or without a metal (or other) backing.

(14) Examining system 100 in more detail, FIGS. 1A-1C and 2 illustrate arms 106a, 106b inside of sides 16a, 16b within frame 10. While two, parallel arms 106a, 106b are preferred, in some embodiments only a single arm or, alternatively, more than two arms may be present. In the following description, reference is made to a single arm 106 and is associated components, however, it should be appreciated that the same description applies equally to a second arm and/or additional arms and its/their associated components, where present.

(15) Referring to FIG. 4, arm 106 biases (through springs and an associated bearing, as discussed below) roller 104 along its length so as to maintain consistency in width across the lateral dimension of gap 20. At one end of arm 106 is a guide assembly 130 through which a tapered portion 132 of arm 106 passes. Tapered portion 132 of arm 106 terminates in a notched end 134 having two parallel outer edges 136 and an inner spring anchor 138 in the form of a detent that does not extend the entire length of a recess 140 formed by the two parallel outer edges 136 in the notched end 134.

(16) An H-shaped bracket 108 receives the notched end 134 of arm 106 within recess 142 formed in one side of the bracket. The opposite side of bracket 108 abuts a bearing 144 which acts as an interface between bracket 108 and roller 104. Bearing 108 may be made of metal, ceramic, plastic, rubber, or a combination of such materials and may be coated so as to allow roller 104 to turn freely about its axis.

(17) A spring 118 is helically coiled about an outer perimeter of tapered portion 132 of arm 106 within recess 142 and guide assembly 130 and is compressed between a detent 148 of guide assembly 130 and a cross member 146 of H-shaped bracket 108. As arm 106 moves (under the control of a linear actuator, as described below), the position of the H-shaped bracket 108, and, accordingly, roller 104 changes, thus varying the width of gap 20 between roller 104 and roller 102. A second spring 116 is located within recess 140 in the notched end 134 of arm 106 and is helically coiled about inner spring anchor 138. Spring 116 biases arm 106 against H-shaped bracket 108 and, in turn, roller 104, and is compressed between an inner surface of recess 140 in notched end 134 and cross member 146 of H-shaped bracket 108. Spring 116 thus forces arm 106 away from roller 104 to avoid backlash when the linear actuator begins to move arm 106. Springs 116 and 118 have counterparts for the arm on the opposite side of frame 10.

(18) Returning to FIGS. 1A-1C and 2, linear actuators 124a, 124b (one per arm 106a, 106b) are arranged to move respective arms 106a, 106b longitudinally within frame 10. Moving arms 106a, 106b in this fashion will translate roller 104 within frame 10, thereby adjusting the width of gap 20 between rollers 102, 104. Operation of the linear actuators 124a, 124b is achieved, in one embodiment, using a processor-based controller (not shown). One example of a processor-based controller upon or with which the methods of the present invention may be practiced will typically include a processor communicably coupled to a bus or other communication mechanism for communicating information; a main memory, such as a RAM or other dynamic storage device, coupled to the bus for storing information and instructions to be executed by the processor and for storing temporary variables or other intermediate information during execution of instructions to be executed by the processor; and a ROM or other static storage device coupled to the bus for storing static information and instructions for the processor. A storage device, such as a hard disk or solid-state drive, may also be included and coupled to the bus for storing information and instructions. The subject controller may, in some instances, include a display coupled to the bus for displaying information to a user. In such instances, an input device, including alphanumeric and/or other keys, may also be coupled to the bus for communicating information and command selections to the processor. Other types of user input devices, such as cursor control devices may also be included and coupled to the bus for communicating direction information and command selections to the processor and for controlling cursor movement on the display. The controller may also include a communication interface coupled to the processor, which provides for two-way, wired and/or wireless data communication to/from the controller, for example, via a local area network (LAN). The communication interface sends and receives electrical, electromagnetic, or optical signals which carry digital data streams representing various types of information. For example, the controller may be networked with a remote unit (not shown) to provide data communication to a host computer or other equipment operated by a user. The controller can thus exchange messages and data with the remote unit, including diagnostic information to assist in troubleshooting errors, if needed.

(19) Such a controller may be programmed to operate linear actuators 124a, 124b to move the arms 106a, 106b to achieve a desired gap width 20 for coating a film 114 with a film 18 of material 110 of desired thickness. The controller also may be programmed to advance film 112 and/or film 114 as needed for such a coating process. To achieve the desired level of precision in gap width 20, the linear actuators 124a, 124b may employ piezo translators that include a piezo ceramic that expands in a defined direction upon application of an electric current (e.g., under the control of the controller). The ceramic may be orientated so that when it expands (at the application of a current under the control of the controller), the arm connected to the actuator is displaced along a single axis (e.g., the longitudinal dimension), along the direction of the expansion of the crystal. Generally, a number of piezo translators may be used per actuator and the various piezo translators may be energized at the same time (or nearly so) so that their actions are coordinated with one another. Thus, the piezo translators may be arranged so that they impart longitudinal motion to the arms in the same direction and the translation distance may be proportional to the magnitude of the current applied to the piezo translators. The piezo translator(s) employed in embodiments of the present invention may be any of: longitudinal piezo actuators, in which an electric field in the ceramic is applied parallel to the direction of its polarization; piezoelectric shear actuators, in which the electric field in the ceramic is applied orthogonally to the direction of its polarization; or tube actuators, which are radially polarized and have electrodes are applied to an outer surfaces of the ceramic so that the field parallel to its polarization also runs in a radial direction. Alternatively, the linear actuators 124a, 124b may employ lead screws that are advanced or retracted according to control signals from the controller to move arms 106a, 106b in the longitudinal dimension. Or the linear actuators 124a, 124b may employ worm drives that are activated according to control signals from the controller to move arms 106a, 106b in the longitudinal dimension. The use of the term “actuator” herein is intended to encompass various alternative means for displacing the arms in the longitudinal dimension.

(20) As mentioned, springs 118 act to bias roller 104 towards roller 102, thereby maintaining a constant gap width across the longitudinal dimension of the rollers. Respective springs 116 act to bias the arms 106a, 106b away from the roller 104 to avoid backlash when the associated linear actuator 124a, 124b begins to pull roller 104 away from roller 102, widening gap 20. A linear encoder 120 is mounted on the frame 10 to measure the position of each respective arm 106a, 106b. When the linear actuators 124a, 124b move roller 104, a “zero” position of the system may be set as the position at which such motion is first detected by the linear encoder 120. The width of the gap 20 is then determined by the amount of motion the linear encoder 120 measures after this point. System 100 is also equipped with two optical, or other, limit switches 122a, 122b. The limit switches 122a, 122b serve to identify when each respective arm 106a, 106b has reached its home position. The home position may define a minimum, maximum, or other gap width between rollers 102, 104.

(21) As indicated above, coating of a layer 18 of material 110 onto film 112 occurs in the gap 20 between rollers 102 and 104. The width of this gap 20 determines the thickness of the material layer 18 and is set by positioning roller 104 a desired distance from roller 102 using linear actuators 124a, 124b. Linear actuators 124a, 124b adjust the position of arms 106a, 106b, which in turn set the position of roller 104 (e.g., with respect to roller 102) through the biasing of respective springs 118, one per arm and parallel to one another. With an amount of material 110 deposited upstream of and near gap 20, film 112 is passed over roller 102 and film 114 is passed over roller 104 opposite film 112 (e.g., to remove any material residue from a previous coating, to recover unused material 110 or for other purposes). As film 112 is advanced through gap 20 between the rollers 102, 104, the material 110 forms a layer 18 with thickness equal to the gap width on film 112.

(22) In some embodiments, the layer of material that is coated onto the film 112 may be a mixture of two or more separate materials. FIGS. 5A-5C illustrate one use of a well-defined gap 520 between rollers 502, 504 of a wire-less variable gap width system 500 configured in accordance with an embodiment of the present invention for such mixing of multiple materials 510a, 510b when coating a film 512 or other substrate. The ability to use a gap in such a system for mixing two or more materials just before printing may be of particular importance when the various materials react with one another and dispensing them together on a film from a common dispenser (e.g., a syringe) may end up obstructing or otherwise impairing the operation of the dispenser. By using the gap as a point of mixing, each material is distributed onto the film from its own dispenser and the reaction between the materials (if any) takes place only on the film just before printing. Indeed, such a technique may be employed in other gap-based coating systems that do not utilize other aspects of the above-described wire-less variable gap width system, hence, the provision of a gap-based mixing arrangement should not be construed as being limited to such systems.

(23) As shown in FIG. 5A, system 500 contains two films 512, 514 that each roll over a respective one of a pair of rollers 502, 504 to create a known gap 520 between them. The films and rollers of the system may be made of any of the materials for such items described herein. Film 512 on which a layer of material will be coated is dispensed by an arrangement 550 which, in this example, has a pair of feeder rollers, but this is only for illustration and the details of the dispensing arrangement are not critical to the present invention.

(24) As illustrated in FIG. 5B, upstream (from the point of view of the direction of travel of film 512) of gap 520, amounts of materials 510a and 510b are dispensed onto film 512. The materials 510a and 510b to be coated on film 112 may be dispensed separately, e.g., to avoid reactions between the materials within a common dispenser, and, referring to FIG. 5C, the motion of film 512 about roller 502 draws the two materials together into a single mixture 510c which then forms a layer 518 on the outer surface of film 512, with the width of gap 520 determining the thickness of the layer 518. Film 514 can be advanced about roller 504 as film 512 is advanced about roller 502 in order to remove any residual amounts of the mixture 510c from the area of gap 520, e.g., to prevent blockage of the gap. The materials 510a, 510b used to form the mixture 510c may be any of those discussed above and one or more of the materials may be replenished and/or changed between consecutive coating procedures, with the gap 520 being enlarged during such second coatings so as not to displace a previously coated material layer 518 on film 512.

(25) Further, while maintaining a fixed gap width, the direction of travel of the coated film may be controlled so that the coated film is drawn back through gap 520 with the layer 518 thereon and then passed through gap 520 in the original direction so as to ensure a thorough mixing of the materials that make up layer 518. Such a process may be repeated multiple times to obtain an optimum level of such mixing and to help ensure a uniform layer thickness on film 512. Alternatively, such bidirectional translation of the film 512 through gap 520 may be undertaken while reducing the width of gap 520, e.g., using biased arms controlled by linear actuators to position roller 504 relative to roller 502 as discussed above, so as to produce a layer 518 of a desired thickness.

(26) This ability to mix materials in a gap, and to ensure a robust and reproducible printing process that provides a high-quality layer of material coated on a film or other substrate, is a direct consequence of the method used for the printing process. Other printing techniques, such as inkjet or screen printing, cannot provide such assurances. Further, the present process also ensures that materials such as two components of an epoxy paste will not react with one another in a dispenser prior to printing, thereby prolonging the pot lives of the component materials. Mixing components at a gap, as in the present system, is less prone to clogging than other techniques because the gap can be refreshed simply by moving the non-coated film through the gap to remove any contaminants.

(27) Referring now to FIGS. 6A-6D, 7, and 8 a further embodiment of a wire-less variable gap width system 600 configured in accordance with yet another embodiment of the present invention is illustrated. In these illustrations, components that are the same as those discussed above with respect to wire-less variable gap width system 100 are given similar reference numerals and will not be described further, except in connection with the air knives 602a, 602b included in wire-less variable gap width system 600 for removal of material. As mentioned above, when coating a film 112, it is possible that the gap 20 will become contaminated by unused material 110. Some of the contaminants can be removed using a second film 114, and with relatively viscous materials that technique works well. However, when deposited upstream of a gap 20, low viscosity materials may tend to flow freely, especially as film 112 draws such materials to and through gap 20, and so to stop the low viscosity material from over-running the film, e.g., in a direction orthogonal to the direction of travel of the film while passing through the gap, air knives 602a, 602b may be used. That is, air propelled by air knives 602a, 602b may act as a physical impediment to the flowing of the low viscosity material outside the bounds of the film 112, where the material may contaminate the rollers 102, 104, e.g., on their sides opposite gap 20.

(28) FIG. 7 further illustrates the provision of air knives 602a, 602b near a gap 20 between rollers 102, 104 of a wire-less variable gap width system configured in accordance with an embodiment of the present invention, and FIG. 8 illustrates a cut-away view of a pair of air knives 602a, 602b near such a gap 20. Each air knife 602a, 602b creates an air flow at an angle of 0-180 degrees from a respective side of the propagating material film 112, and preferably at an angle of 70-110 degrees from such side. That is, the angle of the air flow may be directed from 0 to 180 degrees from a respective side of the film, either by rotating the air knife with respect to frame 10 and/or by design of the air flow channel within the air knife, but it has become apparent that an angle of 70-90 degrees will be most effective in preventing the free flow of low viscosity materials.

(29) Air knives 602a, 602b each include a threaded coupling 604 to which an air hose may be attached. For example, threaded coupling 604 may be a check valve to allow airflow only in one direction. In some embodiments, threaded coupling 604 may be a Schrader valve or a Presta valve, either of which may have an associated valve stem 606 to direct air from an air hose or other air supply means to an outlet 608 that is directed towards the area where the edge of the film 112 will pass near gap 20. The air knives may be used in conjunction with any of the embodiments described herein.

(30) Thus, the present invention provides, in various embodiments, systems and methods that enable coating of a thin film with a viscous or other material at a desired thickness at low cost and in a high quality.