Study of Color Business Printing Paper (Part 2)

Study 3 Color ink-jet paper

Survey data show that in recent years, with the advancement of color inkjet printing paper manufacturing technology, quality color inkjet printing paper is getting higher and higher, and the price is falling, making color inkjet printing technology for business and home office The main methods of document and image output accounted for 70% of the color business printing market, and continued to grow at more than 40% growth rate. The quality of color ink-jet printing paper is mainly determined by the performance of the ink-absorbing layer, especially the paper-grade color ink-jet printing paper, which requires the vividness, saturation, detail level, sharpness and color of the printed image. Both reduction and color fastness can reach the level of color photo paper. In order to achieve high-quality image effects, color ink-jet printing paper should have the following characteristics: It can absorb ink evenly and quickly, without bleed, smudging, and blemishes; ink dots have a high degree of roundness and sharp edges. High dot density, high image resolution, good color fastness, good water resistance, light resistance, abrasion resistance, and preservation of image and text; good color reproduction, high saturation, high color density and Color intensity.

3.1 The research status of color inkjet paper at home and abroad

The study of color ink-jet printing papers abroad started earlier, and related reports and patents were relatively numerous. The research content mainly focuses on the inkjet materials, Xu cloth technology, Xu composition and printed images. For example, Hyun-Kook and Margaret et al. have conducted more in-depth research on color ink-jet printing papers. Their research suggests that (1) conventional coating pigments replace a part of alumina and silica to reduce production costs; (2) gas-phase oxidation Effects of Si on the structure and print quality of the Xu layer; (3) Effects of silica and alumina on the structure and print quality of the Xu layer; (4) Effects of the chemical properties and particle size of the pigment on the structure of the Xu layer and Xu Layer structure on the print quality and so on. (5) Study of metal oxides in glossy inkjet paper coatings. In addition, Rich YR et al. studied that the addition of cationic additives has a greater influence on the properties of the material, and increases the viscosity, yield stress, and elastic modulus of the coating. Cawthorne J. et al. studied the use of modified china clay and silica to produce matt inkjet paper. Boylan JR studied polyvinyl alcohol for ink-jet printing paper adhesive research. Jopson RN study the modification and application of adhesives blade coating production of inkjet printing paper. A.Hladnik used a self-developed print test form to measure print image quality, and used the main component analysis method (PCA) to conduct research on the quality evaluation of inkjet paper. Jonckherree E. and Mabire have made studies to improve the water resistance of matt and glossy inkjet paper; Katri Vikman has studied the fastness properties of coated inkjet paper; Henry Wilhelm's color photographs and traditional flushes for inkjet printing. The lightfastness of the color photos was explored and so on.

However, it is only in recent years that domestic research has focused on coating inkjet paper. At present, the main institutions engaged in the research of color ink jet printing paper mainly include Hunan Paper Research Institute, South China University of Technology, Shandong Institute of Light Industry, Northwest University of Science and Technology, Nanjing Forestry University and Tianjin Yuanda Materials Co., Ltd., etc. The research content mainly includes the analysis of color ink-jet printing paper, the properties of the coating layer, the coating composition, and the specialty chemicals. Most of them focus on silica coating pigments, application of coating chemicals, etc., and there are fewer experimental studies conducted. Existing research includes: research on the layer structure and sheet properties of high-gloss color ink-jet printing papers, research on ink-jet printing paper coatings, and color inkjet on the Beijing Pulp and Paper Research Institute and the Hunan Paper Research Institute. Development and research of printing paper.

3.2 color inkjet paper coating research

Studies have shown that the microscopic and macroscopic pore structures of coatings have a great influence on the print quality of color ink jet paper because most of the ink composition is water (2%-5% of dyes or pigments, 2%-5% of the surface Active Agents and Additives, 30% Humectant, 65% Water. The coating must be quickly absorbed by the ink in order to fix the ink and prevent water from penetrating into the paper base so as not to affect the print quality. In traditional coating pigments such as kaolin, calcium carbonate, and titanium dioxide, pores that are favorable for liquid absorption (.2-0.4um) have a small effective volume fraction and are favorable for the pores of liquid flow (0.OZ-0.04um). Due to its narrow diameter, it is not suitable for use as a pigment for color inkjet paper coating. Due to the large oil absorption of silicon and aluminum oxides (20. g silicon oxide oil absorption 200-350 g), large BET surface area (250-600 m2/g), and the formation of a high porosity similar to the sponge-like In the network structure, when the ink contacts the silicon-containing layer, the porous layer quickly absorbs the ink solvent, while the dye and the colorant are fixed on the surface of the coating, showing a good optical printing density, so it is more suitable for spraying. Ink paper coating pigment.

According to the coating ink-absorbing mechanism, the ink-absorbing coating of color ink-jet printing paper can be classified into a swelling type and a void type, or a resin type and a pigment type. The swellable ink-receptive coating is mainly composed of some macromolecules capable of absorbing water and swell, such as gelatin, polyvinyl alcohol, polyvinylpyrrolidone, PT-propyl cellulose, and the like, and the resin undergoes slight swelling after receiving the ink. , Stick ink, absorb ink, but the ink drying speed is slow, poor water resistance; and void type ink-absorbing coating is composed of a pigment with a microporous structure or can form a porous structure of the material, such as amorphous oxidation Silicon, alumina, etc., form an internal pore structure to achieve fast absorption and color fixation of the ink droplets. The ink has a fast drying speed and good water resistance.

Silicon oxide is currently the most widely used void-type ink-absorbing coating pigment. The silica pigment has strong ink absorption, high brightness, high opacity, large specific volume, and good oil and water absorption. Porous silica pigments can be classified as colloidal (nanometer) silicon, fumed silica, precipitated silicon, and gel silicon or silica gel. Table 1 summarizes the physical properties of various silica pigments. Colloidal silica is non-porous stable dispersion in water. These particles are composed of dense phase silicon elements, and the size is between 1Onm1 and 100nm. The porosity in the pigment is mainly derived from the stacking of colloidal silica particles, the surface area is from the spherical particle outer surface area. Composition, and therefore related to particle diameter.

Due to polymerization or aggregation, a continuous, rigid and porous three-dimensional network structure is formed

Similar to traditional materials, there are many kinds of adhesives used for color ink-jet paper coatings. Commonly used are polyvinyl alcohol (PVA), polyvinyl acetate vinegar (PVAC), casein, soy polymers, and sulfomethyl groups. Cellulose (CMC), mercaptobutylene latex, modified starch, etc. Compared with latex and natural adhesives, PVA has the highest strength of brownies. Moreover, PVA has good film-forming properties. Because it is a water-soluble synthetic latex, it can regulate PVA properties as needed, for example, although PVA is hydrophilic. Sex, but can also be made of hydrophobic PVA o PVA can form easily deformable film at room temperature, and the wear resistance of the film is better. In addition, PVA has good compatibility and can be blended with other hydrocolloids, adhesives, pigments and excipients without affecting the performance of other substances.

In addition to dispersants, dyes, defoamers and other additives, solid May 2006

Table 1 Characteristics of Some Silicon Nitride Materials

┌───────┬────────────┐│ │ non-porous silicon oxide nano-particle shape (spherical) sub ││ │ dispersion stability, prevent settling │├──── method smoke ───┼────────────┤│ silicon (fumed silica) │ non-porous particle shape (spherical shape) poly ││ │ set weak, easily shear dispersion │├─── ───┼──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────── ─ ┤ │ silica gel │ due to polymerization or aggregation, forming a continuous │ │ , rigid and porous three-dimensional │ │ │ mesh structure │ └ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ tincture.

In order to ensure that the image color has a certain degree of fastness, in particular, the image does not appear blurred or color diffusion after the water-jet image of the inkjet image is dried again. Usually, a cationic polymer fixing agent is added to the coating. Cationic fixing agents are used because the inks used in color ink jet printing papers are usually composed of anionic dyes, water and other special auxiliaries such as wetting agents and the like. When the anionic dye contacts the cationic polymer in the x-layer, a water-insoluble complex is formed, thereby fixing the ink on the surface of the x-layer pigment particles, preventing the ink from penetrating and spreading, and also improving the printing. The color density of the image. When configuring the paint, the use of several fixing agents at the same time is beneficial to the true color performance.

Commonly used cationic fixing agents are polyethyleneimine, Poly-DADMAC or polyvinylamine, and the amount of the cationic fixing agent used is 113 parts. The cations attract anionic dye molecules to very high specific surface area silica pigments and are trapped there, preventing lateral movement of the dye molecules. This lateral movement can cause bleed-through of the printed image, or reduce the optical density and speed up the penetration of the paper. Studies have shown that cationic dye fixing agents can also improve water resistance.

3.3 Color inkjet paper coating structure features

The coating structure determines the performance of the Xu layer, which in turn determines the performance index of the Xu cloth. Color inkjet printing paper is a kind of Xubu paper with special functions, which not only has the properties of conventional coated paper but also has big differences. The most prominent features are good absorption performance and high gloss. The layered structure of color ink jet printing paper includes two kinds of outer pore structure and cracked structure.

The outer pore structure is the presence of uniformly distributed pores or pits on the surface of the coating. The surface has pore structures consistent with the interior, including both closed and open surfaces. The pores of the coating include inter-pigment pores and pigments. Internal pores. This x-layer structure is shown in Figure 1 under scanning electron microscope (SEM).

The cracked structure is named because the surface of the coating structure has a crack structure resembling the surface pattern of the tortoiseshell shell. There are two possible reasons for this structure: First, the molecular weight and surface charge of the cracked structure are controlled by the adhesive modification, thereby affecting the structure. The surface tension causes it to microcrack during drying. The second is that the coating is dried below the glass transition temperature (Tg) of the polymer added. The polymer is broken due to the surface tension and cannot form a complete film. The formed groove is such a shell-like crack. structure. Figure 2 depicts the characteristics of this coating structure.

3.4 Quality Requirements for Color Inkjet Paper

Color inkjet printing paper is a new type of recording paper, because it has developed rapidly and there is no uniform quality standard. However, depending on the actual usage, the ink absorption, glossiness, roundness of ink droplets, contact angle, print density, etc. are the most important indicators of the gap type color inkjet paper, which determine the drying speed and image of the ink, respectively. The brightness, print resolution, and color intensity of the image all affect the print effect of the image. Color density is a measure of print image quality