Patent Application
20150231663
The present invention relates to an apparatus and method for directly coating a liquid onto a substrate. More particularly, the present invention relates to an apparatus and method for directly coating a liquid onto a substrate where, a programmable traversing dispensing head facilitates controlled dispensing of a liquid wet material with respect to size, shape, position, quantity, width and/or length.
There are many previously known coating techniques but these suffer from a number of disadvantages such as open ducts allowing contamination of the liquid material prior to being deposited. In addition, prior coating techniques comprise bars or rollers coated with liquid over their entire width—meaning that they are unable to control the size of area being coated. Previous coating techniques also suffer from the liquid becoming contaminated with dust or being exposed to light and the surrounding atmosphere prior to being deposited. A further disadvantage of previous coating techniques is that they suffer from the significant problem of liquid spills where the liquid spills over the edge of the substrate being coated.
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 a further object of at least one aspect of the present invention to provide an improved apparatus for directly coating a liquid onto a substrate.
It is a further object of at least one aspect of the present invention to provide an improved method for directly coating a liquid onto a substrate.
According to a first aspect of the present invention there is provided apparatus for directly coating a liquid onto a substrate, said apparatus comprising:
conveying means capable of conveying a substrate to a device capable of directly coating liquid wet material onto a surface of the substrate to form a film of liquid wet material;
a sensing system capable of determining the area to be coated with the liquid wet material; and
conveying the substrate with the film of liquid wet material to a drying device capable of drying the liquid wet material on the substrate.
Generally speaking, the present invention resides in the provision of an apparatus and method capable of directly applying a thin coating of liquid wet material onto a substrate using a programmable traversing dispensing head. The programmable traversing dispensing head facilitates controlled dispensing of the liquid wet material with respect to size, shape, position, quantity, width and/or length. The apparatus of the present invention is also suitable for coating sheets or reel to reel applications.
The liquid wet material is preferably clear but in alternative embodiments the liquid wet material may be coloured e.g. a blue colour.
By directly coating (i.e. depositing) means that only the amount required for coating the substrate is supplied and used. No excess liquid wet material is therefore used. Prior art systems re-circulate liquid wet material fluid which at some time is exposed to the atmosphere. In contrast, the direct depositing in the present invention ensures that the liquid wet material is in an enclosed circulation system which is never exposed to atmosphere except at the point of deposition. There are also no dust or oxidation problems in the present invention due to the present system being in a completely enclosed environment.
The substrate may be provided in separate sheets or alternatively may be supplied in a continuous reel form and then optionally after being coated with liquid wet material and imaging rolled back into a roll form.
The sensing system of the present invention may be programmable which allows accurate deposition of the liquid wet material to occur. This allows the present invention to prevent liquid spills over the edge of a substrate being coated. The sensing system of the present invention allows the size, shape, position, quantity, width and/or length of the liquid deposition to be adjusted and adapted for a range of different requirements. For example, the liquid wet material may be deposited in a range of sizes from 1 cm×1 cm up to 3 m×6 m.
The sensing system may be programmable thereby allowing controlled dispensing of the liquid wet material. The sensing system of the present invention is suitable for coating sheets or for reel to reel applications.
The device capable of depositing liquid wet material may comprise coating head sensors located on either side of a dispensing system. The coating head sensors may locate the edges of the substrate to be coated and limit the period of dispensing from the coating head to ensure that the coating liquid is dispensed only within the boundary of the material to be coated. The dispensing system may also comprise a liquid dispensing tip which is capable of dispensing liquid in a controlled manner. This process may therefore use a Meyer bar method or roller for coating the liquid wet material. The apparatus of the present invention therefore supports the substrate being coated in sheet form on a moving conveyor made of any suitable material such as, for example, film, paper or any other material. Alternatively, the apparatus may operate on a reel to reel principle such that the material forming the conveyor may be rewound and reused. The apparatus may supply liquid wet material using a coating head arrangement comprising a dispensing head which may track across the coating bar. The dispensing head may be activated with pneumatics, electrics or both and dispense a pre-calculated bead of coating liquid on, for example, the tangent point between the substrate and the coating bar. Alternatively, the bead of coating liquid may be dispensed behind the tangent point in the situation where a reversing roller action is used with a roller or Meyer bar. The coating head arrangement may also detect the end of the substrate and thus stop the dispensing of the liquid wet material.
In alternative embodiments the device capable of directly depositing a liquid wet material may comprise a set of application rollers, a set of valves or a combination of both. The application rollers or valves may be located substantially vertical or horizontal to one another depending on whether vertical or horizontal deposition of liquid wet material is required onto a substrate. The device may also comprise a pump capable of feeding liquid wet material to a pressure regulator. There may also be liquid dispensing tips which may be static or may traverse the application rollers or valves. The device may therefore apply liquid wet material vertically or horizontally to a substrate located between the application rollers or valves depending on the orientation of the application rollers or valves.
The speed of the substrate being conveyed may be computer controlled. The computer control may also extend to the control of the size, shape, position, quantity, width and/or length of the liquid wet material being deposited.
The substrate may be any suitable substrate. In particular embodiments the substrate may be a web and may, for example, comprise a dielectric or non-metallic layer (e.g. a film) made from a plastics material such as polyester (e.g. Melinex-Trade Mark), polyimide (e.g. Kapton-Trade Mark) and polycarbonate (e.g. Lexan-Trade Mark). The substrate may be flexible to allow a reel to reel process to occur. On top of the plastics material there may be a further layer which may be in the form of a cladding. The cladding may be made from a conductive material such as copper, silver, gold, ITO, PEDOTT and the like. In embodiments where the substrate is supplied in separate sheet form, the substrate is conveyed to the device capable of depositing a liquid wet material onto the substrate and the drying device using a conveying material (e.g. a conveyor in the form of a belt). The conveying material may be capable of conveying the substrate from one side of the apparatus to the other. The conveying apparatus may comprise a support roller and a cleaning roller. The conveying apparatus may also comprise a take-up roller and a drive roller onto which the conveying material may be driven onto. Therefore, as the drive roller rotates, the conveying material may be rotated from an initial roll, over the support roll and then along the length of the apparatus and over the drive roller and onto the take-up roll. The substrate may therefore be conveyed on the conveying material from one side of the apparatus to the other allowing the deposition of the liquid wet material.
In alternative embodiments, the substrate may be supplied in a roll form, rather than a sheet, therefore forming a reel to reel process. The rolled substrate may initially be passed between a support roller and a cleaning roller. The cleaning roller is used to clean the surface of the unrolled part of the rolled substrate. The adhesive roller removes debris and/or contaminants from the cleaning roller. The cleaned substrate may then be passed to a coating head.
The substrate, in both the sheet and rolled form, may be fed through and between the support roller and the cleaning roller. The support roller may be substantially cylindrical in shape and may be made of any suitable plastics/composite/metal material. The cleaning roller may also be substantially cylindrical in shape and may be made from any suitable rubber or elastomeric type of material which is capable of removing debris and/or contaminants from a substrate surface to be cleaned.
The cleaning roller typically has a lower surface energy towards the contaminating particles than the adhesive roller. This means that the contaminating particles may form a temporary bond with the surface of the cleaning roller and may then be transferred to the adhesive roller which is urged and rotated against the cleaning roller. The adhesive roller removes debris and/or contaminants from the cleaning roller which is being used to clean a substrate surface which may be used in, for example, the manufacturing of electronics, photovoltaics and flat panel displays where the surfaces have to be extremely clean. The adhesive roller therefore cleans the surface of the cleaning roller to improve this process. The adhesive roller may be sheeted meaning that once the performance of the sheeted adhesive roller decreases then the used sheet can be removed exposing a new sheeted adhesive surface.
As the substrate, in both the sheet and rolled form, is fed between the support roller and the cleaning roller the surface intended to have liquid wet material deposited thereon may therefore be cleaned.
In the embodiment where the sheet is conveyed on the conveying material the sheet may be passed under a coating bar which may extend fully across the conveying material and the sheet as it passes underneath. The coating bar is capable of directly applying the liquid wet material. The device capable of depositing a liquid wet material may therefore be seen as a coating apparatus. The coating apparatus may also comprise a coating head which may be situated on a coating head transverse drive. In the embodiment where the substrate is in roll form the part of the roll that is unrolled is also passed under the coating bar.
The liquid wet material may be made up of 100% solids and contain no solvent. Alternatively, the liquid wet material may comprise less than 1% solvent, less than 5% solvent, less than 10% solvent or less than 50% solvent. The solvent may be water or a suitable organic liquid e.g. ethyl acetate.
Typically, the liquid material may be deposited with a thickness according to any of the following: less than or equal to about 150 μm; less than or equal to about 125 μm; less than or equal to about 100 μm; less than or equal to about 75 μm; less than or equal to about 50 μm; less than or equal to about 25 μm; less than or equal to about 10 μm; less than or equal to about 5 μm; less than or equal to about 1 μm; less than or equal to about 0.5 μm or less than or equal to about 0.1 μm. Alternatively, the liquid wet material may be deposited with a thickness ranging from any of the following: about 177 μm to about 0.1 μm; about 125 μm to about 0.1 μm; about 100 μm to about 0.1 μm; about 75 μm to about 0.1 μm; about 50 μm to about 0.1 μm; about 25 μm to about 0.1 μm or about 10 μm to about 0.1 μm. Preferably, the liquid wet material may have a thickness of about 4-5 microns.
By using thin liquid films this allows low intensity radiation (e.g. UV light) or any other suitable drying method to facilitate faster drying.
After the substrate has been coated with wet liquid material the coated substrate in sheet form may then be conveyed by the conveying material to the drying device. The drying device may be any suitable drying device such as a UV radiation source (e.g. a series of UV lamps, LEDs, lasers, etc.), an IR radiation source or any other energy source such as a heat source or hot air.
The apparatus described in the present invention can be fully contained in a self-contained mini-clean room which therefore provides significant cost savings in the coating process as the process need not be carried out in a large expensive clean room.
According to a second aspect of the present invention there is provided a method for directly coating a liquid onto a substrate, said method comprising:
providing conveying means capable of conveying a substrate to a device capable of directly coating liquid wet material onto a surface of a substrate to form a film of liquid wet material;
providing a sensing system capable of determining the area to be coated with the liquid wet material; and
conveying the substrate with the film of liquid wet material to a drying device capable of drying the liquid wet material on the substrate.
The method may use the apparatus as defined in the first aspect.
Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings in which:
Generally speaking, the present invention resides in the provision of an apparatus and method capable of applying a thin coating of liquid wet material using a coating bar or rollers onto a substrate which is capable of being photoimaged or acting as a protective coating.
As the sheet 110 is conveyed on the conveying material 110, the sheet 112 is passed over a supportive roller 126 and under a coating bar 128 which extends across the conveying material 110 and the sheet 112. There is also shown a coating head arrangement 122 which is situated on a coating head transverse drive 124.
Although not shown the apparatus 100 also comprises sensors which detect when a sheet 112 approaches the cleaning roller 118, the speed of the conveyed sheet 112 and when the sheet is approaching the coating bar 128. The system is therefore fully controllable allowing the system to track the location of the sheet 112.
The coating head sensors 150 locate the edges of the sheet 112 to be coated and limit the travel of the coating head arrangement 122 to ensure that the coating liquid is dispensed only within the boundary of the material to be coated. The coating head arrangement 122 therefore accurately dispenses the coating liquid to reduce the volume of liquid exposed and also decrease wastage. The dispensing system 152 comprises a liquid dispensing tip 154 which dispenses liquid in a controlled manner. This process therefore uses a Meyer bar method for coating the liquid wet material prior to curing. Usually, a Meyer bar rotates in a bath of the coating fluid and will likely have a doctor blade or such to calibrate the thickness of coating. To overcome previous problems found in the prior art, the apparatus 100 of the present invention supports the sheet 112 being coated in sheet form on a moving conveyor 110 made of, for example, film, paper or other material. This is on the reel to reel principle such that the material forming the conveyor 110 can be rewound and reused. This has advantages over a continuous belt which has more maintenance issues. It supports the sheet 112 right through the process and avoids any build-up of debris.
There are a number of advantages associated with the apparatus 100 of the present invention. For example, there is very little wastage of the coating liquid which is expensive. In addition, only the fluid being used is applied to the coating bar 128 and exposure to the atmosphere is very brief as it is only applied at the point of application. Moreover, spent fluid is never re-circulated or returned to a bulk storage vessel.
After the sheet 112 has been coated with liquid wet material the coated sheet 112 is then conveyed by the conveying material 110 to a drying source 130 (e.g. a series of UV lamps). The dried sheet 112 can then be collected and removed for further processing.
The coated substrate then passes to a drying source 230 (e.g. a series of UV lamps). The apparatus 200 may also perform a reel to reel continuous process with the cured coated substrate 214 being rolled onto take-up roll 234.
The liquid wet material may be applied to any suitable substrate such as a film which may be in laminated form.
The apparatus as described in the present invention can also be fully contained in a self-contained mini-clean room which therefore provides significant cost savings in the drying process.
Whilst specific embodiments of the present invention have been described above, it will be appreciated that departures from the described embodiments may still fall within the scope of the present invention. For example, any suitable type of imageable substrate may be formed. Moreover, any suitable liquid wet material or combinations thereof may be used. The drying device may use any form of drying which is capable of curing/drying the liquid wet material.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/GB12/52829 | 11/15/2012 | WO | 00 |
