The deep printing method is an integral coating application method for adhesive products. It is a process in which adhesive with varying viscosity (about 1500 MPa) can be applied to substrates at a maximum speed of 900 m/min. Coating thickness can range from 1 micron to approximately 50 microns, making it a versatile method. The deep printing method is carried out by a roller, also called a ball applicator, which is engraved from the bottom to control the amount of applied coating. Deep printing is available in various sizes, which, in turn, affects the final finish of the coating.
Application by the method of deep printing offers several approaches, but the two most common methods are Direct Application of Deep Printing and Offset Application of Deep Printing.
What is the deep printing method?
Deep printing typically involves a steel surface engraved with a specific pattern of cells. Adhesive is applied to the surface, and a blade is used to remove any excess adhesive. As the adhesive roller continues its movement, it is subjected to the action of the canvas formed between the applicator ball and the rubber-covered support roller. The rotation of both balls in the same direction and at the same speed as the canvas allows the adhesive to transfer to the canvas.
The dimensions of the etched cellular structure determine the amount of coating transferred to the canvas. Other factors such as rubber thickness, tilt angle, applied pressure, or speed can also alter coating standards.
What is Offset Deep Printing?
Offset Deep Printing is a variation of direct deep coating. In this process, a transfer roll, also known as an «offset» roll, is used to transfer the adhesive coating to the web. The intermediate roll is positioned perfectly between the deep roll and the backing roll, which is now depicted as a rigid, steel-like surface. The web passes through the gap created by the two rolls. Similar to the direct deep printing roll, the size and shape of the cells determine the amount of coating transferred to the offset roll. However, in this method, both rolls rotate in opposite directions at the same speed. Offset deep coating can regulate a range of viscosities.
Is there a difference between Deep Coating and Deep Printing?
There is a difference between applying deep coating and deep printing. Deep printing, also known as rotogravure, is a printing process specifically designed for printing certain patterns. The quality of this process can be judged by the thickness, coverage range, resolution, and clarity of deep printing.
The process begins with applying ink to a cylinder, which is then transferred to the substrate. Deep printing is a method that requires several components, such as:
- Rotogravure cylinder size depends on the product being produced.
- Ink fountain
- Dryer
- Printing roller
- Blade.
The method begins with the formation of a cylinder with images that need to be printed. The embedding process is formed on the surface of the cylinder, while later the cells will transfer it to paper after the doctor blade removes excess ink. The impression roller plays a crucial role in this process as it ensures a uniform and necessary amount of ink on the surface. Cell proportions should be set carefully as inks react to different paper colors. Large cells will form dark and solid colors, while smaller cells will produce dull colors. The ink substrate undergoes a drying process before it pulls for another layer of ink. Rotogravure has a separate block for each color.
This process is extremely useful as it allows printing on thin films such as polyester, nylon, and polyethylene, with a thickness of 10 to 30 micrometers.
Another feature is that it is durable and will not compromise the image quality. Rotogravure also helps manufacturers save costs and allows them to produce a larger volume of products.
This method is actively used in the electrical industry for products such as solar elements, which require uniform coating and high edge clarity.
Development of deep printing cells:
To achieve success with Gravure Coating, the development of cells is crucial. There are two classifications for types of cells:
- Continuous Channel Patterns: These patterns have continuous channels that run at a specific angle on the roller’s surface.
- Individual Patterns: These patterns consist of separate cells on the surface.
Cell formation can be achieved through direct engraving of the cylinder or by applying it to the cylinder using chemicals or lasers.
In direct engraving, the primary form is applied to the roller’s surface to create a cavity. The cavity is applied to the roller using a stylus tip, and each formed cavity creates a cell for deep printing.
Embedding the cylinder can be done chemically or, more commonly, using a laser. In this case, the roller is prepared for the thermal spraying of iron material onto the outer part of the roller, providing a smooth surface. Then, a more powerful laser is used to achieve a favorable pattern.
Direct engraving is often associated with quadrangular, pyramidal, and three-spiral cells. When using a laser, it typically results in a hexagonal shape.
The durability and speed in the deep coating process make it suitable for applying PSA (Pressure-Sensitive Adhesive) on various films such as polyethylene, polypropylene, polyester, as well as aluminum foil used for sealing and packaging various items. Deep coating is also specifically utilized for applying coatings on film materials, such as surface protection tape used to safeguard surfaces from dust, scratches, or any damage.
Deep printing is widely used in the printing industry for newspapers, catalogs, and color sections of magazines. It is most effective in long print runs of black-and-white or color graphics.