The capillary film, also known as capillary stencil film or cap film, is a type of stencil material used in the screen printing process. It is a thin, flexible sheet made of a photosensitive emulsion coated on a polyester or other film substrate. The capillary film is designed to create stencils for screen printing without the need for traditional liquid emulsions or direct film positives.
Here’s how capillary film works:
Film Selection: Capillary film comes in different thicknesses or “microns” to accommodate various screen mesh counts and ink types. The appropriate film thickness is selected based on the desired stencil thickness and the specific printing requirements.
Preparing the Screen: The screen mesh is cleaned and prepared to ensure it is free from any contaminants that may affect stencil adhesion. It should be dry and tautly stretched on the frame.
Applying the Capillary Film: The capillary film is cut to fit the size of the screen and placed onto the mesh. It is positioned with the photosensitive emulsion side down against the mesh. The film is then gently pressed onto the screen using a squeegee or roller to remove any air bubbles and ensure good contact.
Exposure: The screen with the capillary film is exposed to ultraviolet (UV) light, typically using a UV exposure unit. The light passes through the film’s transparent substrate, but where the design or image is present, the photosensitive emulsion blocks the UV light from reaching the mesh.
Developing: After exposure, the screen is rinsed with water or a developer solution, depending on the specific capillary film product. The developer removes the unexposed emulsion, leaving behind the stencil areas where the UV light was blocked by the design.
Drying and Post-Treatment: Once the stencil is developed, it is allowed to dry completely. Some capillary films may require additional post-treatment steps, such as drying in a controlled environment or applying a post-exposure treatment to further cure the stencil.
Printing: The prepared screen with the capillary film stencil is then ready for use in the screen printing process. Ink is pushed through the open areas of the stencil onto the printing substrate using a squeegee, creating the desired printed image.
Capillary film offers several advantages in screen printing, including faster stencil preparation time, consistent stencil thickness, and simplified cleanup compared to traditional emulsion-based methods. It is commonly used in both manual and automated screen printing operations across various industries.
