Most ink-jet printing inks are made with dyes using water and other high-boiling hydrophilic solvents as dye carriers. The chemical properties and formulation components of inkjet printing inks not only determine the ink droplet ejection performance and the security of the printing system, but also affect the quality of the printed image. The physical properties of inkjet-receiving matrices are key to achieving the ultimate inkjet performance. Therefore, gloss, air permeability, opacity, surface energy, dimensional stability, strength, whiteness, and thickness are all important parameters that determine print quality, and are also factors that manufacturers need to consider when manufacturing ink-jet printing paper. Porous inked coatings will provide fast drying performance, but generally have poorer image quality than non-porous media that require longer drying times.
The uncoated paper surface is rough and has hydrophilic fibers that promote the diffusion and penetration of ink droplets, resulting in low quality images or textual content. Therefore, surface sizing is often required to improve the density and bleeding of pigments. . The surface coating of the coated paper improves the surface structure and performance of the base paper, and can provide a better ink receiving layer, thereby achieving high printing quality and image stability.
The most common inorganic pigments currently used for ink coating are SiO2, kaolin, Al2O3 and CaCO3. With the development of nanotechnology, very fine particles can be produced. Inkjet coatings containing nano-sized particles have received great attention from raw material suppliers and paper manufacturers to achieve bright, image-like print quality.
In this study, three types of pigment particles, colloidal SiO2, sintered SiO2 and smoke SiO2, were investigated and their application in ink jet coating formulations was investigated.
1 raw materials and methods
1.1 Raw materials
Commercial samples were used for both colloidal SiO2 and smoke SiO2. Nalco N2329 was used for the colloidal SiO2 and Cabot 019 was used for the smoke SiO2. Sintered SiO2 is an experimental Nalco sample. Celvol 203 polyvinyl alcohol (PVA) was used as an adhesive in all tests.
The base paper used for the coating test contains no sizing agent. The physical properties were: quantitative 156.9 g/m2, smoothness 5.26 μm, brightness 92.5%, gloss (75°) 12.0.
1.2 Coating research
1.2.1 Preparation
The paint formulation used had a pigment to adhesive ratio of 80/20. The coating was prepared using the following methods: using a variety of Mayer rods and an air-drying or cylindrical laboratory coater (CLC) operating at 3000 r/min and drying with an infrared dryer. The amount of coating was determined on a specific area of ​​the sample using a Labwave 9000 microwave moisture analyzer.
1.2.2 Calendering
Calendering was performed using a hot/soft nip calender at approximately 3.10 MPa (450 psi) and 80°C conditions, and each paper was calendered through 3 nips prior to gloss measurement.
1.2.3 Determination of Gloss
The gloss was measured using a Gardner multi-angle gloss meter at a 75° angle. Measure 10 points on each sheet, calculate the average, and report the results.
1.3 Printing Research
Samples were printed on Canon S450 and Epson Stylus Color 900 (thermal and piezo type, respectively) presses. All samples had the same coating weight (16~18g/m2).
1.3.1 Determination
The experimental glossiness, the ink density, and the experimental values ​​of the four colors of blue, red, yellow, and black (CMYK) were measured. Calculate the average of at least 5 data points and report the results. The instrument used is as follows:
60° print gloss - Gardner Nova gloss meter
Printing Density - X-Rite 408
Experimental value - Data color SpectroFlash
1.3.2 Image Analysis
Samples were printed on the Epson Pro 5000 and HP Design Jet 20PS presses. Images were taken with a CCD camera and analyzed with Image Pro-Plus software.
1.3.3 Coating Porosity Study
Coatings were prepared on a Mellinex 534 non-porous stent. Optically determine the coating thickness and calculate the porosity of the coating. (to be continued)
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