Micro-gravure coating is a kind of reverse inverted gravure coating with a coating thickness of 1~80μm, which is mainly used in shading film, optical film, lithium battery materials, composite tape, protective film, etc. The advantages are thin coating, thin substrate, no offset printing, no wrinkles in the coating, and the coating is uniform, which is recognized by the majority of users.
The principle of micro-concave coating is very ingenious! The development of the micro-concave coating method was based on the increasing market demand for uniform coating of thin layers. This new coating method is simple, reproducible and reliable. Microgravure coating adopts the method of kiss coating, while ordinary gravure coating basically has a back roller, and the function of the back roller is to make the substrate and gravure roller better contact, so that the coating liquid is transferred more. However, due to the pressure generated by the back roller, when the pressure is not appropriate, the substrate is prone to wrinkles and other problems, resulting in uneven coating. Microgravure coating uses kiss coating, and some potential problems are gone.
The picture comes from the Internet
In micro-concave coating, the most important (and the main factor that controls the amount of coating) is the ratio of the linear speed to the rotational speed of the micro-concave roller. The production line is running normally, and the coating roller is stationary, at this time, there is a small amount of coating with the friction of the film surface micro-concave roller to the film surface, with the increase of the micro-concave roller speed, the coating amount will increase, with the increase of the rotation speed, the coating amount will decrease. The test determined that the coating amount would have an arc curve with respect to the rotational speed ratio. The typical micro-concave roll gluing ratio is: (coating roller speed: line speed) when the speed ratio = 1:1, the coating starts; When the speed ratio = 1:1.3, uniform and regular coating; When the speed ratio = 1.3:2.0, the coating amount increases; When the speed ratio = 2.0 or more, the coating amount decreases and instability occurs. The whole working process of micro-gravure coating is accompanied by the equipment composed of unwinding unit, coating unit, oven unit, traction unit, winding unit and control cabinet, and each link is very important.
Advantages and disadvantages of micro-gravure coating
★ ★ Pros
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01 |
Micro-gravure coating can apply a very thin coating to a very thin material, and since there is no back pressure roller, there are no defects such as offset printing and wrinkles on the coating surface. |
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02 |
Since the scraper is in light contact with the anilox roller, the wear of both the scraper and the mesh roller is relatively small. |
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03 |
The micro-concave roller has a small diameter, light weight, and different coating weights, so it is more convenient to replace the micro-concave roller. |
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04 |
Reverse coating can obtain a relatively flat coating with uniform coating volume. |
★ ★ Cons
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01 |
The glue at the bottom of the glue tank cannot be used up, and the amount of slurry below the coating solution in the glue tank cannot be used up, and the phenomenon of waste occurs. |
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02 |
The micro-concave roller needs to be cleaned in time after use, and the concave hole will be blocked if it is not cleaned. |
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03 |
The rubber compound of the glue tank is open and easily contaminated by impurities in the air. |
Causes of horizontal and vertical lines in micro-concave coatings
★ Striated ★
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01 |
The error of the runout of the micro-concave roller itself |
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02 |
Vibrations of motors and other machinery |
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03 |
Micro-concave rollers, couplings, motors, bearings |
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04 |
The tension is uneven |
★ Vertical lines ★
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01 |
The speed ratio is caused by the speed of the car being too fast and the coating roller being too slow |
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02 |
The pressure of the scraper blade is too high, the quality of the blade is poor, the installation is uneven and the angle is so bad |
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03 |
The tension of the substrate is too small |
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04 |
The membrane bread corner is too small |
