A Complete Analysis Of Inks: From Basics To Applications

 

 

1. Introduction
2. Printing substrates for UV inks
3.Printing methods for UV print inks
4.Drying methods for offset inks
5.Technical specifications of inks

 

1.Introduction

Ink is an indispensable material in the printing process. Its performance and application directly affect the quality and effect of printed products. Understanding the basic information of ink, including printing substrate, printing method, drying method and technical indicators, is very important for printing industry practitioners and researchers in related fields.

 

2.Printing substrates for UV inks

Cardboard: It has a large thickness and good stiffness and is often used for packaging box printing. Cardboard printing requires the ink to have good adhesion to adapt to subsequent die-cutting, folding and other processing technologies.
Plastics
Polyethylene (PE): The surface is smooth and the chemical stability is good, but the printability is poor, and the surface needs to be pre-treated, such as corona treatment. Inks for PE plastics need to have good flexibility and chemical resistance to ensure that the ink does not fall off or fade during the use of plastic products.

Polypropylene (PP): Similar to PE, it also requires surface treatment. PP plastic is often used for printing plastic films, such as food packaging films. The ink on PP film must meet hygiene standards and have good scratch resistance.

Polyvinyl chloride (PVC): widely used, can be used for printing plastic products such as stationery and toys. When printing ink on PVC, it is necessary to consider the compatibility with PVC materials to avoid problems such as ink bleeding.

Glass
Ordinary glass: commonly found in daily glass products, such as glass cups and glass bottles. The ink for printing ordinary glass must have good water resistance and chemical corrosion resistance to meet the needs of cleaning and containing items.

Borosilicate glass: has good thermal and chemical stability, and is often used in laboratory instruments and high-end glass products. In addition to general adhesion properties, the ink for printing borosilicate glass must also be able to withstand certain high temperature treatment.

Tempered glass: high strength and good safety. When printing on tempered glass, the ink needs to withstand the high temperature and stress changes during the tempering process to ensure the integrity and stability of the printed pattern.

Metal
Tinplate: commonly used in food can packaging. The ink used to print tinplate must have good corrosion resistance and boiling resistance to ensure that the ink will not contaminate the food during storage, while the pattern remains clear.

Aluminum plate: widely used in beverage cans, decorative materials, etc. The ink printed on the aluminum plate needs to have good adhesion and weather resistance to adapt to different usage environments.

 

3.Printing methods for inks

 

Lithographic printing
Lithographic printing uses the principle that oil and water are immiscible. The image and text part is oil-loving and the blank part is hydrophilic. This printing method is suitable for printed products with large printing volume and high precision requirements, such as newspapers, magazines, etc. Lithographic printing ink needs to have good fluidity and transferability to ensure that the ink can be evenly transferred to the printing plate and paper during the printing process.

 

Letterpress printing
The image and text part of letterpress printing is higher than the blank part, and the ink is transferred to the substrate during printing. Letterpress printing is often used to print business cards, greeting cards, etc. Letterpress printing ink needs to have high viscosity and good transferability to ensure the clarity and three-dimensional sense of the printed pattern.

 

Gravure printing
The image and text part of gravure printing is lower than the blank part, and the ink is filled in the pit for printing. Gravure printing is suitable for high-quality, long-run printing, such as plastic film printing, cigarette package printing, etc. Gravure printing ink needs to have low viscosity and good drying performance to ensure that the ink can dry quickly during high-speed printing without smudging.

 

Screen printing
Screen printing uses a scraper to squeeze the ink through the mesh of the image and text part and transfer it to the substrate. Screen printing has strong adaptability and can be printed on substrates of various shapes and materials, such as ceramics, fabrics, etc. Screen printing ink needs to have appropriate viscosity and thixotropy to ensure that the ink can pass through the mesh smoothly and form a uniform ink layer on the substrate.

 

4.Drying methods for inks

 

Natural drying
Natural drying relies on the natural volatilization and oxidation of the solvent in the ink to achieve drying. This drying method is simple and low-cost, but the drying speed is slow, and it is suitable for printed products with low drying speed requirements, such as some hand-printed works. Naturally drying inks need to choose solvents with moderate volatility to ensure the stability of the ink performance during the drying process.

 

Heating drying
Heating drying accelerates the volatilization and chemical reaction of the solvent in the ink by heating the printed product, thereby achieving rapid drying. Common heating methods include hot air drying and infrared drying. Heating drying is suitable for mass-produced printed products, such as packaging printing. When heating and drying, pay attention to controlling the heating temperature and time to avoid deformation of the printed product or damage to the ink performance.

 

Ultraviolet drying
Ultraviolet drying uses ultraviolet rays to irradiate the ink, so that the photoinitiator in the ink decomposes to produce free radicals, which triggers the polymerization reaction of monomers and prepolymers, thereby achieving rapid drying. Ultraviolet drying is fast and efficient, and is suitable for printing processes with extremely high drying speed requirements, such as UV printing. UV drying inks need to contain specific photoinitiators and photosensitive monomers to ensure rapid curing under ultraviolet irradiation.

 

Electron beam drying
Electron beam drying is similar to ultraviolet drying, and the polymerization reaction of ink is triggered by electron beam irradiation. Electron beam drying has higher energy, can cure ink in a shorter time, and has a wider adaptability to ink. However, the cost of electron beam drying equipment is relatively high, and it is currently mainly used in some high-end printing fields.

 

5.Technical specifications of inks

 

Color
Color is one of the most important technical indicators of ink, which directly affects the visual effect of printed products. The color of the ink needs to match the standard color card or the color required by the customer, and is accurately measured and controlled by instruments such as colorimeter.

 

Fineness
Fineness refers to the size of the pigment particles in the ink, which affects the fluidity and printing quality of the ink. The smaller the fineness, the finer the printing effect of the ink and the clearer the pattern. The fineness of the ink is generally measured by a scraper fineness meter.

 

Viscosity
Viscosity reflects the viscosity of the ink and has an important influence on the transfer and printing uniformity of the ink. Different printing methods require inks of different viscosities. For example, the viscosity of lithographic inks is relatively high, while the viscosity of gravure inks is low. Viscosity is generally measured by a viscometer.

 

Drying speed
Drying speed is related to printing production efficiency and the quality of printed products. Too fast drying speed may lead to poor ink transfer, while too slow drying speed will affect production efficiency and may also cause problems such as smearing. The drying speed needs to be adjusted according to factors such as printing method, drying method and printing substrate.

 

Adhesion fastness
Adhesion fastness refers to the bonding strength between ink and printed substrate. Good adhesion fastness is the key to ensure that the ink does not fall off or fade during the use of printed products. Adhesion fastness is generally tested by methods such as the cross-sectional test.