What is UV ink?

Date: Aug 21 2024 From: Star Color

1. Definition of UV Ink
UV ink, also known as UV curable ink, is a special type of ink that can quickly cure into a film under ultraviolet (UV) irradiation. Its uniqueness lies in the fact that its drying process does not rely on traditional solvent evaporation or thermal curing methods, but rather achieves rapid curing of ink through chemical reactions induced by ultraviolet radiation.

Specifically, the composition of UV ink mainly includes polymeric prepolymers, photoinitiators, photosensitive monomers (also known as reactive diluents), coloring pigments, and possibly added fillers and additives. Among them, polymeric prepolymers are the main film-forming substances of ink, which determine the basic properties of the cured ink film; The photoinitiator is the "trigger" of the entire curing process, which generates free radicals after absorbing ultraviolet light energy, and then triggers the crosslinking polymerization reaction of polymeric prepolymers and photosensitive monomers; The photosensitive monomer acts as a reaction medium, participates in the curing process, and regulates the viscosity of the ink; Coloring pigments give ink color, but also affect the ink's hiding power, light resistance, heat resistance, and other properties; Fillers and additives are used to improve the physical properties of ink, such as fluidity and stability.

During the curing process of UV ink, when the ink is exposed to ultraviolet light, the photoinitiator rapidly absorbs light energy and converts it into free radicals. These free radicals then trigger chain polymerization reactions between polymeric prepolymers and photosensitive monomers, forming highly cross-linked three-dimensional network structures. This reaction process is very rapid, usually taking only a few seconds to a few minutes to complete, thus achieving rapid solidification of the ink.

ultraviolet spectrogram

The development process of UV ink:
In the 1960s, scientists first discovered UV curable ink, paving the way for the development of the UV ink industry.
In the 1970s, UV ink began to be widely used in the printing industry, especially in the packaging and printed circuit board industries.
In the 1980s, the UV ink industry entered a stage of rapid development, with the market constantly expanding and application areas gradually expanding.
In the 1990s, significant breakthroughs were made in the production technology of UV ink, resulting in continuous improvement in product quality and enhanced market competitiveness.
Since the beginning of the 21st century, the UV ink industry has continued to innovate, with product quality and technological level constantly improving. Its application areas have further expanded to multiple industries such as electronics, packaging, plastics, glass, ceramics, etc. UV ink has become a mature ink technology and is widely used worldwide.

2. The principle of UV ink
The principle of UV ink is to induce photochemical reactions in ink through the radiation of ultraviolet light sources, thereby achieving the purpose of ink curing. There are two main chemical reactions during its drying process:
Photochemical reaction: When UV ink is exposed to ultraviolet light, the photopolymerization initiator (photoinitiator) in the ink absorbs the energy of ultraviolet light, transitions from the ground state to the excited state, and forms free radicals or ions. This step is the starting point of the curing process and also the key to the entire reaction.

Chain reaction: The free radicals generated by photochemical reactions are highly active and can trigger chain polymerization reactions of unsaturated multifunctional prepolymers, multifunctional crosslinking agents, reactive diluents, etc. in UV inks. During this process, free radicals constantly react with surrounding molecules, generating new free radicals and forming continuously growing polymer chains. These chain like molecules crosslink with each other to form a three-dimensional network structure, thereby achieving the solidification of ink.

As the chain reaction progresses, the polymer compounds in UV ink gradually crosslink into a network structure, forming a strong cured film. This layer of film has the advantages of good adhesion, wear resistance, chemical resistance, and vivid color.
It should be noted that the curing process of UV ink is influenced by various factors, including the wavelength, intensity, irradiation time, and ink formulation of ultraviolet light. Among them, the wavelength of ultraviolet light has a particularly significant impact on the curing effect. Generally speaking, UV ink is most sensitive to near ultraviolet light with wavelengths between 300-400nm, especially in the wavelength range of 350-420nm. The pigments in the ink have the highest transmittance, resulting in the best curing effect.

Zhongzhixing UV Flexo Ink

3. Formula for UV ink
UV ink is mainly composed of the following key components: polymeric prepolymers, photoinitiators, photosensitive monomers (also known as reactive diluents), coloring pigments, as well as possible fillers and various additives.

3.1. Aggregated Prepolymer
Definition and Function: Polymeric prepolymers are the most basic formula components of UV ink and also film-forming substances. It plays a decisive role in the performance of cured ink film, such as hardness, friction resistance, adhesion, light resistance, chemical resistance, and water resistance.

Type: Polymeric prepolymers mainly include methacryloyl, unsaturated polyester resin, polyether acrylic resin, etc. These resins contain unsaturated double bonds in their internal chemical structure, which are the main components that form the cured film.
Classification criteria: Aggregated prepolymers are usually classified based on their skeletal structure, and different skeletal structures determine their performance differences after curing.

3.2. Photoinitiator
Definition and Function: Photoinitiator is a key component in UV ink, which absorbs UV energy, generates free radicals or ions, and triggers polymerization reactions. The choice of photoinitiator directly affects the curing speed and curing effect of ink.
Type: Photoinitiators are divided into two types: hydrogen abstraction type and cleavage type. Hydrogen abstraction type photoinitiators utilize different alkyl and aryl groups to extract hydrogen atoms, stimulating them to transform into excited state complexes; Cracking type photoinitiators act by stimulating direct decomposition into free radicals.

Selection principle: When choosing a photoinitiator, it is necessary to consider factors such as high light absorption efficiency in the UV range, good relative stability, and low cost.

3.3. Photosensitive monomer (active diluent)
Definition and Function: Photosensitive monomers, also known as reactive diluents, are a type of functional monomer. It not only provides viscosity for UV ink, but also participates in curing reactions, improves curing speed, and becomes a part of the cured film.

Type: Photosensitive monomers mainly include monofunctional compounds and bifunctional or multifunctional compounds. The former is like styrene, while the latter is like acrylic compounds of polyols.
Selection principle: When selecting photosensitive monomers, it is necessary to follow the principles of low viscosity, good dilution effect, fast curing, and no odor in the coating.

3.4. coloring pigment
Definition and Function: Coloring pigments are essential components in UV ink, which impart color to the ink and affect its properties such as coverage, light resistance, and heat resistance.
Type: Commonly used color pigments for UV ink include benzidine yellow, Hansha yellow, phthalocyanine blue, phthalocyanine green, permanent red, and red powder; Color reducing pigments include titanium dioxide, high pigment carbon black, etc.
Influence: The addition of pigments will change the rheological properties of the ink and affect the gloss of the printing film. Meanwhile, the absorption, reflection, or scattering of UV light by pigments can also reduce the curing and drying speed of ink.

3.5. Fillers and additives
Filler: Filler is mainly used in ink to increase the solid content, improve the rheological properties of ink, and reduce the price of ink. Common fillers include calcium carbonate, aluminum hydroxide, silica, etc. However, the addition of fillers may also hinder the ink's absorption of UV light and reduce the ink's drying rate.

Additives: In order to improve the printing and quality adaptability of UV ink, multiple additives need to be added. These additives include polymerization inhibitors (to prevent ink cross-linking during storage), defoamers (to eliminate bubbles generated during ink manufacturing and use), leveling agents (to improve the leveling of the ink layer), and so on.

UV ink printing speed is very fast

4. Classification of UV Ink
There are various classification methods for UV ink, and here we mainly discuss the classification based on printing technology. UV ink can be classified into the following types based on printing technology, each with its specific application scenarios and advantages. Here is a detailed explanation of these types:

4.1. UV offset printing ink
Application scenario: UV offset printing ink is widely used for printing books, magazines, packaging and other printed materials. It is suitable for high-speed continuous printing and can maintain bright colors and stable printing quality.
characteristic: Fast curing speed: Through UV irradiation, UV offset printing ink can quickly cure in a short period of time, improving production efficiency.
Vibrant colors: Ink colors are full and can present high-definition printing effects.
Environmental protection and energy saving: No heating is required during the curing process, and almost no volatile organic compounds (VOCs) are produced, which meets environmental protection requirements.

4.2. UV screen printing ink
Application scenario: UV screen printing ink is mainly used for screen printing, suitable for printing small, raised patterns, such as glass bottles, ceramics, etc.
characteristic: Strong adhesion: UV screen printing ink can firmly adhere to the surface of the substrate and is not easy to peel off.
Good toughness: The printed pattern has good toughness and can adapt to various shapes and curved substrates.
Fast curing: Rapid curing is also achieved through UV irradiation.

4.3. UV flexographic ink
Application scenarios: UV flexographic ink is suitable for printing on absorbent/non absorbent substrate surfaces, flat/rough substrate surfaces, and thin/thick substrate surfaces. It has been widely used in packaging printing fields such as flexible packaging, paper boxes, labels, and corrugated boxes.
characteristic: Good printing adaptability: able to adapt to the printing needs of different materials and surfaces.
Low cost: Compared with other printing technologies, UV flexographic ink has certain cost advantages.
Energy saving and environmental protection: The curing process does not require a large amount of energy and meets environmental protection requirements.

Paper bag UV flexographic printing

4.4. UV inkjet ink
Application scenario: UV inkjet ink is mainly used in inkjet printers, suitable for various digital printing needs, such as personalized customization, short form printing, etc.
characteristic: High precision: Inkjet technology can achieve high-precision printing effects.
Rapid curing: Ink can be quickly cured through UV irradiation, improving production efficiency.
Wide applicability: Suitable for various printing materials, including paper, plastic, metal, etc.

4.5. UV gravure ink
Application scenario: UV gravure ink is suitable for gravure printing, mainly used for printing materials such as plastic film, paper, plastic bags, etc.
characteristic: Strong adhesion: Ink can firmly adhere to the surface of the substrate and is not easily peeled off.
Good wear resistance: The printed patterns have good wear resistance and can adapt to various usage scenarios.
High resolution: gravure printing technology can achieve high-resolution printing effects, making patterns more delicate.

5. The Development and Prospects of UV Ink
With the growth of the global economy and the increase in consumer spending, the demand for UV ink market continues to grow. According to the report, the UV ink market is showing a growth trend worldwide, with a global market size of 20.629 billion US dollars in 2023 and expected to reach 40.581 billion US dollars by 2029.

The application fields of UV ink are constantly expanding, covering multiple industries such as printing, packaging, advertising, and electronic products. Especially in the packaging and advertising industries, UV ink is widely welcomed for its high glossiness, good adhesion, and environmental performance.

With the increasing demand for personalized customization, UV printing technology can achieve highly personalized design and printing, meet the customization needs of different industries and customers, and further promote the development of the UV ink market.

With the continuous advancement of technology, the formula and production process of UV ink are constantly innovating and improving. The development of new monomers, resins, and additives enables UV inks to have superior performance, such as faster curing speed, higher wear and chemical resistance, and better printing results.

The popularization of digital printing technology has also promoted the development of UV digital printing systems, further improving the printing speed and accuracy of UV ink.

With the increasing awareness of environmental protection, the demand for environmental performance in the UV ink market is also constantly improving. New UV ink products often have the characteristics of low volatile organic compound (VOCs) emissions, low energy consumption, and low pollution to meet environmental regulations and consumer demand for green products.

The UV ink industry is in a stage of rapid development, with high technological barriers but significant profit margins. With the growth of market demand and continuous technological advancement, the industry will usher in more development opportunities.

Zhongzhixing UV Ink

Especially in the fields of digital printing, personalized customization, and environmentally friendly ink, UV ink will show greater development potential.

Huizhou Zhongzhixing Color Technology Co., Ltd. is an enterprise dedicated to the research and production of water-based ink, flexographic, gravure, and UV environmentally friendly ink. With outstanding technological research and development capabilities and forward-looking market insights, the company has always been at the forefront of the industry, providing high-quality ink products for the printing industry.

Zhongzhixing Color has a professional R&D team and advanced production equipment, dedicated to the research and innovation of UV ink technology. The company continuously introduces advanced technology and management experience from both domestic and foreign sources to improve product performance and quality, in order to meet the constantly changing demands of the market.

With the increasingly strict environmental regulations and the growing demand for high-quality printed materials in the market, the UV ink market has broad prospects. Zhongzhixing Color will continue to adhere to the development concept of "innovation, environmental protection, and efficiency", increase research and development investment, improve product performance and quality, and provide customers with higher quality ink products and services. At the same time, the company will actively expand its international market and promote the green and sustainable development of the UV ink industry.