News

Knowledge

Company News

Application Mind Map

Test Report

Technical Article

Industry News

Detailed Explanation of the Coating Method for UV Paper Varnish (Part 2)

Release time:

2024-12-28 07:29

Detailed Explanation of the Coating Method for UV Paper Varnish (Part 2)
Detailed Explanation of the Coating Method for UV Paper Varnish (Part 2)

UV coating on paper primarily relies on free radicals generated by photoinitiators under ultraviolet light irradiation. These free radicals initiate polymerization reactions involving the unsaturated groups in prepolymers and monomers, causing the UV coating to rapidly transform from a liquid into a solid. This process typically takes only 0.1 to 0.3 seconds, which is why UV curing is highly efficient and energy-saving.

In the last issue, we analyzed the three-roller and gripper-type methods for UV coating on paper, each of which has its own advantages and application scenarios. In this issue, we’ll continue our analysis by examining the anilox coating and gravure coating methods used in UV paper coating.

I. Gravure Coating

Relief coating is a process that uses a relief printing press to apply a glossy finish. It leverages the pressure rollers and printing plates of the relief printing press to transfer varnish onto the surface of paper through the raised areas of the printing plate, thereby achieving a glossy effect.

1. Principle

The principle behind relief coating is based on relief printing technology. In relief printing, the text and image areas on the printing plate are raised, while the non-image areas are recessed. When the impression cylinder comes into contact with the printing plate, the varnish is evenly applied to the raised portions of the plate. As the impression cylinder rotates, the varnish from the raised areas is transferred onto the surface of the paper, creating the desired gloss effect.

2. Advantages

(1) Excellent print quality: Relief coating ensures that the varnish is evenly and accurately transferred onto the paper surface, resulting in high-quality printing effects. This varnishing method enhances the color saturation and gloss of printed materials, making them more visually appealing and attractive.

(2) Suitable for intricate patterns and text: Due to the high precision of letterpress printing, letterpress coating is particularly well-suited for printed materials that require fine patterns and text to be highlighted with varnish. It ensures that the detailed elements of patterns and text receive adequate varnishing, thereby enhancing the overall visual effect.

3. Applicable Scenarios

Flexographic coating is widely used in printed materials that require high-quality glossing, such as book and magazine covers, photo albums, and brochures. These printed materials typically have high demands for color accuracy and glossiness; therefore, flexographic coating can meet these requirements and enhance the overall quality of the products.

II. Gravure Coating

Rotogravure coating is an efficient printing and varnishing process widely used for printed materials such as packaging materials and advertising posters that require uniform, large-area varnishing.

1. Principle

Gravure coating is carried out using a gravure printing machine. In a gravure printing machine, the surface of the printing plate features numerous tiny recesses arranged according to the desired print patterns and text. The varnish is stored in these recesses on the printing plate; then, a doctor blade scrapes away any excess varnish from the surface of the plate, leaving only the varnish contained within the recesses. When the printing plate comes into contact with the paper, the varnish from the recesses is transferred onto the paper surface, creating the desired gloss effect.

2. Advantages

(1) Uniform Coating: Because the varnish is precisely stored in the recesses of the printing plate and accurately controlled by a doctor blade, gravure coating ensures an even distribution of the coating on the paper surface. This uniformity is particularly important for printed materials that undergo large-area varnishing, as it helps prevent issues such as uneven coating or missed areas.

(2) Suitable for large-area varnishing: Gravure coating can quickly and efficiently handle large-area varnishing tasks. Because the recessed pits on the printing plate allow precise control over the distribution of the varnish, gravure coating ensures that the coating thickness and gloss level remain consistent across the entire surface of the printed material.

3. Applicable Scenarios

Gravure coating is particularly suitable for the following scenarios:

(1) Packaging Materials: Packaging materials typically need to have an attractive appearance and high-quality gloss. Gravure coating can deliver a uniform coating and brilliant luster, making packaging materials more visually appealing and enticing.

(2) Advertising Posters: Advertising posters need to have a strong visual impact to capture people’s attention. Gravure coating ensures that the coating on the poster’s surface is uniform and brilliant, making the poster even more eye-catching.

III. Conclusion

Through an in-depth analysis of the gravure and flexographic coating methods used in UV coating of paper, we have gained a deeper understanding of the unique advantages and wide-ranging applications of these two coating techniques in the printing industry. Flexographic coating, with its high print quality and suitability for varnishing fine patterns and text, has become the preferred choice for high-quality printed materials such as book covers and art albums. Meanwhile, gravure coating, thanks to its uniform coating layer and ability to handle large-area varnishing, demonstrates strong competitiveness in fields like packaging materials and advertising posters.

Disclaimer: The above content is sourced from the internet and is for reference only. If any infringement occurs, please contact us, and we will remove it promptly. 

Share to:

Previous page

Detailed Explanation of the Coating Method for UV Paper Varnish (Part 3)

Detailed Explanation of the Coating Method for UV Paper Varnish (Part 1)

Next page

Related News

Detailed Explanation of the Coating Method for UV Paper Varnish (Part 1)

As an efficient surface treatment material for printed materials, UV coating for paper has gained widespread adoption in the printing industry due to its outstanding characteristics, including superior gloss, excellent abrasion resistance, environmental friendliness, and rapid curing. This article will explore in detail the application methods of UV coating for paper, analyzing this crucial process step—from its underlying principles and selection of appropriate techniques to practical applications.

A New Option for Paper Coating: UV Coating

In the printing industry, gloss coatings for paper are an indispensable material. They not only enhance the glossiness, abrasion resistance, and water resistance of printed materials but also significantly improve their visual appeal and service life. Among the many types of paper gloss coatings, UV paper gloss coatings stand out with their unique advantages, making them a new favorite choice for numerous printing companies.

Solutions to Common Issues in UV Coatings (Part 2)

UV coatings have found widespread applications in various fields—including wood processing, automobile manufacturing, and electronics—thanks to their advantages such as rapid curing, energy efficiency, environmental friendliness, and excellent coating performance. However, during actual use, UV coatings can also encounter certain issues, including significant variations in the gloss of the topcoat, sticky paint that doesn't dry properly, strong odors after UV curing, undercutting, oil bleeding, and yellowing of the coating film. These problems not only affect the aesthetic quality of the product but may also negatively impact its performance and service life. Therefore, it is particularly important to address these common issues effectively when using UV coatings.