Screen Printing

Roll-to-roll screen printing is a continuous, automated printing technology that precisely transfers inks or functional coatings onto the surface of roll-to-roll materials (such as plastic films, PVA films, etc.) using a screen with an image or coating pattern. Stable, high-speed, repeated printing is possible as the material is fed from one roll to another, and the same screen can be reused. This makes it suitable for mass production and functional coating processes, such as applications in water transfer films, IMD/OMD films, electronic materials, and special functional films.

Roll-to-roll screen printing is widely used in industries requiring continuous, large-area, thick-film, or high-precision pattern transfer. Common applications include:

• Water transfer film production
• IMD / OMD film coating printing
• The piano black coating printed on the backlight decorative parts features high gloss, deep black opacity, and excellent scratch resistance.
• Electronic functional films such as touch panels, conductive films, and sensing elements
• Advanced surface treatments such as optical films, antistatic films, and anti-fog/anti-fingerprint coatings.
• Labels and decorative films

Sage focuses on roll-to-roll screen printing services for water transfer films and IMD/OMD functional films. It is also skilled in precision coatings such as "piano black coating" that have extremely high requirements for film thickness and opacity, providing customers with stable and high-quality production solutions.

The maximum printing width for roll-to-roll screen printing varies depending on the machine specifications and product requirements. Common ranges are as follows:

• Common models used in general industries: width approximately 300mm ~ 800mm
• Large machine tools: up to 1000mm and above

Our roll-to-roll screen printing equipment is optimized for precision functional coating and layer applications. It can handle materials up to 400mm wide and supports a maximum printing unit size of 380mm × 900mm. It can flexibly handle a variety of medium-sized film processes, combining precision and production efficiency.

Roll-to-roll screen printing is a continuous printing method. Theoretically, there is no limit to the length of the material, but the actual printable length mainly depends on:

• Capacity of roll material feeding and taking-up device
• Equipment tension and synchronization control capabilities
• Product requirements for print quality stability

To ensure accuracy and consistency during long-distance continuous operation, our roll-to-roll screen printing machines are set with a minimum upper line length of 30 meters. This standard maintains the stability of the overall printing process and ensures that product quality is not affected by errors or deviations due to changes in the rolling motion.

Functional coating involves selecting coating materials with specific physical properties to achieve the desired performance through precision coating methods, tailored to different product characteristics and application requirements. Among these methods, screen printing technology has become one of the commonly used processes for functional coating due to its high-thickness film transfer capability, applicability to various substrates, clear boundaries, and high-precision positioning.

Functional coatings select coating materials with specific physical properties based on different product characteristics and application requirements. Common types include:

• High-opacity coatings:Piano black and opaque black, for example, have high saturation, high gloss, and opaque properties, and are often used in backlight modules or for decorative purposes.
• Matte coating:Used to reduce surface reflection and improve texture or visual comfort.
• Scratch-resistant coating:Enhance surface abrasion resistance and improve durability
• Anti-fingerprint coating:It has anti-fouling and anti-sticking effects, maintaining a clean appearance.
• Low surface energy coatings:It provides water-repellent and oil-repellent functions and is commonly found in electronic thin films.
• Adhesive or intermediate coating:Enhance interlayer adhesion and improve the stability of subsequent processing.

Sage focuses on the development and mass production of piano black coating and light-blocking coating. Combined with roll-to-roll screen printing technology, it can stably achieve thick film coating and precise pattern control, making it suitable for mid-to-high-end thin film decoration applications.

In roll-to-roll screen printing, coating thickness control primarily relies on the coordination between screen design and material formulation. Control methods include:

• Screen mesh count and emulsion thickness:A lower mesh count results in a thicker emulsion layer and a higher coating weight; conversely, a higher mesh count results in a thinner coating.
• Scraper pressure and angle:Affects ink release and coating uniformity
• Coating or ink viscosity:Formula adjustments can affect coating stacking and leveling effects.
• Pattern design and screen aperture ratio:Directly determines the actual transfer area and coating distribution

In practice, our company selects appropriate screen structure and printing parameters according to product requirements to ensure consistent coating thickness each time, which helps improve the yield and appearance quality of finished products.

Roll-to-roll screen printing, operating at high speeds and continuously, demands extremely high precision in image registration. To ensure accurate registration of each layer, our company primarily controls registration accuracy through the following methods:

• Mechanical precision design:The machine adopts a high-rigidity and high-precision tension control and conveyor system to ensure that the substrate does not snake or deviate during operation.
• Alignment sensing system:Equipped with photoelectric or CCD vision alignment devices, it can detect the positioning point in real time and make fine adjustments and corrections.
• Screen tension and repeatability control:High-precision plate-making technology and fixed screen tension are used to reduce registration errors caused by screen deformation.
• Material stability requirements:It is used in conjunction with thin film substrates with low heat shrinkage and high dimensional stability to avoid displacement caused by material deformation.

Sage's roll-to-roll screen printing equipment features an automatic calibration module and conducts rigorous alignment tests on functional layers (such as light-blocking layers and light-guiding structures) to ensure consistent product quality for each batch.

Screen printing is a printing method that transfers ink from the image area of a screen onto the surface of a substrate. Its basic principle is as follows:

• Plate-making stage:Photosensitive emulsion is coated onto the screen, and after exposure, "image and text areas" and "non-image and text closed areas" are formed.
• Printing stage:The ink is poured onto the screen and then squeezed through the mesh by a squeegee from the image area to the surface of the substrate below.
• Curing stage:After the transfer is completed, the ink will undergo drying or UV curing processes to form a stable layer.

This technology features thick ink layers, strong adhesion, and wide applicability to various materials, making it particularly suitable for non-absorbent materials such as plastic films, glass, and metals. It can also support functional coating applications, such as light-blocking coatings, conductive layers, or protective layers.

Screen printing can be used with various ink types, and the selection should be based on the substrate properties and application requirements. The following are common ink types:

• Solvent-based inks
  Suitable for non-absorbent materials such as plastic films, metals, and glass. It exhibits excellent adhesion and weather resistance, and is widely used in industrial applications such as IMD, OMD, and water transfer printing films.
• UV curing ink
  It can be cured instantly under ultraviolet light, has a fast printing speed and good wear resistance, and is suitable for fine patterns or functional coating applications.
• Water-based inks
  It meets environmental protection requirements and is mainly used in applications with high environmental standards, such as printing on paper or some PVA films. However, it has weak adhesion to non-absorbent materials and must be used with a treatment layer or additives.
• Conductive ink / Special function ink
  Layers used for creating circuits or with special functions (such as piano black, light-blocking layers, scratch-resistant layers, etc.) must possess high stability and special functionality.

In screen printing applications, Sage selects inks that comply with environmental regulations, have low VOC emissions, and possess good processability, based on functional coating requirements. Sage can also collaborate with customers to develop special formulations.

When selecting inks, the material and properties of the substrate are the most important considerations. It is essential to ensure good adhesion and compatibility between the ink and the substrate to achieve stable and high-quality printing results. The following is an explanation based on common substrate classifications:

• Plastic films (such as PET, OPP, PVC, PE)
  Solvent-based inks (such as polyurethane (PU) inks) are recommended, as they have strong adhesion and are durable, making them suitable for printing on functional films and multi-layer structures.
• PVA film (water transfer film)
  Water-based inks or alcohol-based solvent-based inks must be used, which have good water decomposability and low residue, facilitating subsequent water transfer printing processes.
• Paper materials
  Water-based inks or general solvent-based inks can be used, depending on product requirements and environmental protection requirements.
• Metal foil (such as aluminum foil)
  It needs to be used with a special solvent-based ink with strong adhesion to ensure that the ink adheres firmly and does not peel off.

When making a selection, it is also necessary to consider the printing process, product application, and environmental regulations to ensure that the ink is safe and meets performance requirements.

Mesh count refers to the number of wires per square inch of a screen, and it has a direct impact on print quality.

• The higher the mesh count, the smaller the mesh openings, which allows for the printing of more delicate and intricate patterns and details, making it suitable for high-resolution designs and small-font printing.
• The lower the mesh count, the larger the mesh size, which is suitable for printing thick coatings or large areas of solid color, but the details are rougher.

Choosing the appropriate screen count depends on the detail requirements of the printed pattern and the characteristics of the ink or coating. Only by matching it with the appropriate ink viscosity can the best printing effect and quality stability be achieved.

The ink thickness in screen printing is typically between 5 and 25 micrometers (μm), and the specific thickness may vary depending on the following factors:

• Types of printing materials (such as plastic film, paper, etc.)
• The required functionality (such as special coatings for light blocking, scratch resistance, and conductivity).
• Ink type and viscosity
• Mesh count and printing speed

Generally, functional coatings (such as piano black coating) require thicker ink layers to achieve the desired visual and physical effects. Roll-to-roll screen printing equipment can precisely control the ink coating thickness, ensuring uniformity and compliance with specifications.