Basic Principles and Process of Screen Printing Plate Making

※ The printing plates used in stencil printing are mainly divided into two types: mimeograph stencils and screen printing plates.

· The mimeograph stencil is made by engraving text and images on specially coated wax paper with a stylus, typing with a typewriter, or producing the plate through an electric spark scanning process. It is commonly known as "spirit duplication printing" and is mainly used for reproducing office documents.

· Screen printing plates are classified into photographic screen making and digital direct imaging screen making according to different methods of forming the stencil layer.

· Other non-mainstream methods include infrared screen plate making, etching screen plate making, electroforming screen plate making, etc.

The screen mesh is the basic material for screen printing. It serves as the carrier for the photosensitive emulsion layer and generally features thin structure, high strength, uniform mesh openings, low water absorption, low dimensional expansion and contraction, good resilience, wear resistance, and corrosion resistance.

※ Direct screen plate making method: The direct method is the most widely used screen plate making process.

It features low cost, simple processing procedures, and good print durability. However, it is mostly operated manually, resulting in lower quality and requiring certain technical expertise.

Process flow: Stretching the screen mesh — Screen cleaning treatment — Coating with photosensitive emulsion — Exposure — Developing — Drying — Plate retouching

※ Indirect screen plate making method: The indirect method first creates the stencil on a film coated with photosensitive emulsion, and then transfers it onto the screen mesh.

Process flow: Exposure — Activation treatment — Developing — Image transfer — Adhesive coating — Removal of the film base

※ Direct-indirect combined screen plate making method: In this method, the photosensitive emulsion layer is first attached to the screen frame using water, alcohol, or photosensitive adhesive. After hot-air drying, the base film of the photosensitive film is peeled off, followed by exposure and development treatment to produce the screen printing plate.

Process flow: Attachment of photosensitive film — Drying — Peeling off the film base — Exposure — Developing — Finishing and correction

· The direct-indirect combined method incorporates the characteristics of both the direct and indirect methods. It is relatively simple to operate, and its print durability and image resolution are between those of the two methods.

· Inkjet direct screen plate making is a digital inkjet imaging technology for direct screen plate production. After digital graphic information is processed by the prepress system, it is transferred to the digital inkjet imaging machine. Through program-controlled inkjet heads, opaque dye is sprayed onto the screen coated with photosensitive emulsion. The opaque dye image formed on the screen functions as the positive film in the traditional plate-making process. After conventional exposure, developing, drying and hardening, and finishing processes, the screen printing plate can be produced.

· Laser screen plate making is also a computer-to-screen (CTS) technology, which can directly receive graphic information output from a digital prepress system. It is the fastest screen plate-making method and can produce large-format screen printing plates. However, it is only applicable to metal meshes and is mainly used for textile printing and ceramic printing.