Mounting films

What exactly are mounting films?

Mounting films are important multipliers in the form of carrier films in various printing processes. Depending on the printing process, they perform important tasks. If the mounting film is used in offset printing, for example, its task is to precisely align and fix the respective copy templates. To ensure that the printing films can actually be positioned accurately on the respective mounting film, a millimetre film is often also used.

In addition to their use in offset printing, mounting films also serve as an important component in flexographic printing. The special feature here is that the printing inks are not transferred via an intermediate carrier, but by means of so-called flexographic clichés. These are a type of flexible printing plate. The term cliché or flexographic cliché originally comes from newspaper printing and letterpress printing. In these areas of relief printing, clichés are known as printing plates produced photochemically or mechanically.

Important for flexographic printing: flexographic clichés in combination with mounting films

In a slightly modified form, the term is also used in flexographic printing as flexographic cliché. Flexographic printing is one of the direct printing processes. This means that, in terms of functionality, the ink is always transferred directly from the printing plate to the material to be printed. In addition to flexographic printing, gravure and screen printing also use this process.

Whereas rubber used to be the preferred base material for flexographic clichés, modern process technology now relies on clichés made from polyurethane in combination with special mounting films. The latter are usually made from polyethylene terephthalate (PET). Anyone who values particularly high-quality films chooses biaxially oriented film solutions. These are based on particularly heat-resistant BOPET.

Specific properties through the orientation process as a special feature

A biaxially oriented PET mounting film usually offers special mechanical properties that go beyond the classic features. This is made possible by the so-called orientation process. Orientation refers to the longitudinal deformation of the film material. In this process, the deformation exceeds the normal elastic stretching limit. This results in a chain reaction. Through orientation, the material fibres align lengthwise. This in turn makes the material anisotropic: the properties of the material change depending on the direction. By contrast, a material whose properties are always the same regardless of direction is referred to as isotropic.

These advantages are generated by a mounting film made from biaxially oriented PET

Thanks to their specific properties, mounting films made from biaxially oriented PET have become the most commonly used solution for flexographic clichés. The reason for this lies in the specific characteristics of the film material. These are the particularly relevant properties of a mounting film made from biaxially oriented PET or BOPET:

• High mechanical stability
• High thermal stability
• High chemical stability
• High electrical dielectric strength
• Very good tensile strength
• Good electrical insulator
• Very low water absorption of 0.3 percent

Very good tensile strength allows the production of particularly lightweight mounting films

Very good tensile strength is a particularly important criterion. It makes it possible to produce particularly lightweight mounting films and use them optimally in flexographic printing. A typical weight for a mounting film in the context of modern process technology is ten to around 13 g/m². However, films are also available with a thickness of up to three grams per square metre. When selecting a mounting film, however, the greatest care must always be taken. Not all mounting films automatically offer good quality and meet all criteria with regard to the printing process. Premium solutions such as optimont® MF-MW or optimont® MF-SC set the standards here and have already proven themselves many times as top solutions in a wide range of application scenarios.

A high-quality mounting film can be recognized by these criteria

Whether a mounting film meets the respective quality requirements can primarily be measured and evaluated using these four criteria:

• Very good tear resistance
• Dimensional accuracy regardless of the area of application
• Excellent flatness for precise and easy mounting
• Ideally has two different sides

For every requirement – mounting films in different thicknesses for flexible use

Users also do not have to compromise when it comes to the desired thickness. The selection of thicknesses is broad. The range of thicknesses starts at 100 µm and extends to a maximum thickness of 500 µm. The high-quality mounting film optimont® MF-MW, for example, is preferably available in thicknesses of 250 µm, 300 µm and 350 µm. If even higher thickness values are required, the quality film optimont® MF-SC has proven to be an ideal solution.

In this case, thicknesses of up to 500 µm are possible. This is another expression of the diversity and versatility of mounting films. However, certain product specifications regarding possible applications must be taken into account. The top film solutions optimont® MF-MW and optimont® MF-SC are particularly well suited for use in flexographic printing. For offset and screen printing mounting, by contrast, the glass-clear film variant optimont® MF-AS/AC, for example, is better suited.

FAQ