Exploration on Improving the Quality of Matte Color Inkjet Paper

With the rapid development of science and technology, integrated circuits, computers, and digital imaging technologies have made rapid progress in recent years. With the popularity of printers and the decline in their own prices, color ink-jet printing papers have gradually entered millions of households. Printer manufacturers continue to improve and improve the quality of inkjet printers, and correspondingly require higher quality print quality. There are many kinds of inkjet paper, which can be divided into no-adhesive paper and coated paper. At present, the existing adhesive-free paper is difficult to meet the needs of high-precision printing, the need for technological breakthroughs and innovation, in the coming period of time, with Paper for inkjet printing will be dominated by coated paper.

The color inkjet paper of the coating machine has good print quality and can meet the needs of high-precision printing. The currently coated color ink-jet printing paper can be coated with different substrates, such as metal, plastic sheet, paper, PE, etc. Membrane paper and many other substrates, according to the surface gloss of the coating, can be divided into high-light inkjet paper, matte color inkjet paper. These two types of paper are the most common coated inkjet papers on the market, and the market price has fallen a lot, but the market demand is large and the increase rate is fast. This article only discusses how to produce high-quality matte color inkjet paper.

1 Subglare inkjet paper manufacturing process

At present, many companies at home and abroad are producing subglossed inkjet paper. The production method is to coat the raw paper with a coating composed of solid particles, adhesives, cationic fixing agents, whitening agents, etc., which can be dip-coated or blade-coated. , After drying and other steps.

Paper → Coating → Drying → Post-processing

Common paint formulations:

Silica 100 parts

50-80 parts of polyvinyl alcohol

Cationic fixing agent 20-30 copies

Brightener a little

Other additives

Solid powder content 15%-30%

Coating weight 5-12 g/m2

2 base paper quality

In the market, the coated base paper is usually coated with 70-200 g/m2. The quality of the base paper has great influence on the processing of inkjet paper. The base paper is the carrier of the coating, and its quality will directly affect the color. The quality of the paper. In order to obtain good coating effect, raw paper is required;

(1) Good whiteness

(2) good uniformity, smooth and smooth paper;

(3) High tightness and small water absorption distortion;

(4) High stiffness and low expansion rate

(5) Good strength

(6) Low water absorption.

3 Water color fastness

The color fastness of the sub gloss paper is very important. In everyday use, it will inevitably encounter the flooding of printed images. In order to ensure that the image is not immersed in water, the solid carrier must be modified into a cation, which is advantageous for the anionic ink to be fixed on the cation carrier so that the water solubility of the dye is reduced, and dye displacement and color bleeding do not occur. The use of cationic fixing agents is also an important factor in ensuring the accuracy of inkjet printing.

There are many types of cationic fixing agents, and polymer cationic polymers are generally used. In order to achieve better water resistance, the amount of cationic fixing agent should account for 20-30% of the solids mass, and the specific amount should be based on the solids ratio. The quality of the solids on the surface and the unit surface depends. Larger than the surface, the more cationic fixing agent, the amount of solids in the unit flat surface, the cationic fixing agent can add less. There are several series of fixing agents produced by the Hangzhou Green Additives Research Institute. For PF-30, SF-20, NF-30, etc., the cationic printing agent is used to reduce the cationicity.

4 coating strength

After the coating is dried, it is evenly fixed on the surface of the paper. When the coating is immersed in water, the adhesive will melt or swell, such as polyvinyl alcohol, which can be easily wiped off due to the reduced adhesion of the adhesive on the paper surface. Therefore, addition of polyvinyl alcohol in the coating, but also need to add cross-linking agent, common cross-linking agents such as formaldehyde, formaldehyde resin, glyoxal, glutaraldehyde, cross-linking agent aldehyde and polyvinyl alcohol hydroxyl Cross-linking reactions occur, forming a network structure and improving water resistance. The aldol condensation reaction is more suitable for the acidity value being around pH 4.5-5.0. It is best to add some other water-resistant, wear-resistant, structural strength, good adhesive strength, many types of adhesive, such as styrene butadiene latex, acrylic latex, styrene-acrylic latex, vinyl acetate latex, water-based polyurethane, etc., should use non-ionic or cationic milk .

5 Whiteness

The whiteness of coated inkjet paper plays an important role in improving the vividness or brightness of the print. The paper color is different from the display, and the color is expressed by light reflection. To achieve high brightness, in addition to reducing the color of dyes, it is also necessary to manufacture high brightness white paper products.

To achieve high whiteness, attention should be paid to the following aspects:

(1) Improve the whiteness and flatness of the base paper:

(2) The use of high white solids, such as the whiteness of silica;

(3) Select a suitable brightener.

The whiteness of brighteners is related to their dispersion state and carrier. It is very important to choose how to use brighteners that meet the coating cation system. The whitening agent BF-1 newly researched by Hangzhou Green Additive Research Institute is a cationic fixing agent with whitening agent.

6 color light reduction

Most ink-jet printing inks use water-soluble dyes, usually with sulfonic acid groups, such as:

When the ink dye is combined with the cationic fixing agent on the coating, the power supply capacity of the sulfonic acid group and the carboxylic acid group on the dye molecule structure will be changed, so that the energy level of the conjugated electron cloud on the dye molecule will change slightly, and the color of the dye will be changed. .

On the other hand, the molecular weight of the dye is large and the hydrophilicity is not equal. Therefore, it is very important to choose the fixing agent rationally. When using the fixing agent we produce, it is recommended that several fixing agents be used in combination to facilitate the realism of color shade.

Such as PF-30:SF-20=1:3-6

This helps to manage the color balance of various dyes.

7 Others

In addition to the above points, there is a need for improvement in the flatness of the coating, the light resistance of the dye, the printing accuracy, the production cost, and the like.

The quality improvement of color ink-jet printing paper is a long-term development process, and it needs to closely follow the pace of printer development. It needs raw paper production, chemical additives, and coating production companies to work together to solve various technical problems. Produce higher quality coated inkjet paper.

Source: "Shanghai Paper"