Analyze printer ink and paper (on)
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Printing ink
The ink color is provided by two types of materials, one is a dye and the other is a pigment.
1. Dye
Dyes are characterized by a transparent color that changes the color of the transmitted light by selectively absorbing certain spectral components of the incident light. Therefore, the dye ink can be used not only for printing color photos, but also for printing transparent light boxes. Traditional color photographs and transparent positive films are dyed to form a color.
The raw materials of many kinds of dyes are insoluble in water, so some special solvents are needed to dissolve them first and then diluted with water. Some of these solvent-dissolving solvents are detrimental to the material from which the ink head is made. When the sample is injected into the ink head, the ink head is quickly damaged. The reason for this is that the solvent causes damage to the ink head.
The durability of the ink is basically determined by the original material of the dye. Magenta in EPSON dye inks is a less durable color. Use it to print color cards on matt paper and find that if you are exposed to the air, you don't need to see the light, as long as the color will fade a lot in a month, the gray scale will turn green. Some manufacturers' EPSON inks are even more terrible. After printing this evening, if they don't cover the film in time, they will fade the next morning.
Ink should be used on different printers to add other things to change its viscosity, surface tension, and possibly thermal expansion coefficient or boiling point, so that different printers can be sprayed smoothly. These additives should also be safe for the ink head. Solvents and additives used on different printers make different printers have different selectivity for paper. As everyone knows, the EPSON dye ink printer picks paper, but if it is replaced with ink, it can be used like an HP printer.
Most inks are not formulated with one dye during the formulation of compatible inks from different manufacturers. The phenomenon is that most of the inks sold on the market have higher color saturation than the original ink. We usually use two or three inks to mix the colors close to the original ink.
2. Pigment
Pigment inks used to be made from mineral pigments. Current pigments may also have non-mineral materials. In general, it is made from solid pigments and then emulsified to make ink. Its main feature is that it is more durable, and the thicker the particles, the more durable it is. It is not very transparent. It can also be seen from the bottle of ink, it is a bit like milk. Therefore it cannot be used to print transparent sheets. Because of its opacity, its composite color: red, green, and blue have lower saturation.
No oily ink is used in small printers. Only large outdoor jets are used with oily inks. This ink is similar to printing inks, but printing inks usually use transparent dyes, while outdoor jets use inks formulated with pigments. The nozzles of outdoor jets are very large and are not easily clogged. This ink uses an organic solvent and a film former, like a paint. The surface requirements for the material are very low. It is both water and light resistant, and the quality is not very good.
Ink color matching problem
The similarity of ink color has three main parameters: hue, color saturation and concentration. We usually use several inks to formulate its parameters to match the original ink.
More difficult to deal with is another factor
Since the human eye also causes illusion to the human observation, the matching of the primary colors of yellow, magenta, and cyan does not indicate that the color mixed with these inks is consistent with the original ink. The reason is that the color looks the same, and its absorption spectrum may be different. Therefore, the absorption spectra produced by the two types of dyes are definitely different, and the colors may not be the same. Mainly in the red, green and blue colors are not the same. Therefore, when selecting the original ink, it is necessary to take care of the matching degree of the three mixed colors. If the 6 colors match well, the rest of the problem is not big. Because in the printing software, the color is mainly based on these six colors to construct other colors by additive color.
Printing paper and matching with ink
Let's first discuss reflective printing paper. The main purpose of the coating of the printing paper is to absorb the ink faster and prevent lateral diffusion of the ink. Ordinary offset paper has good ink absorption capacity, but it can't prevent the lateral diffusion of ink, so the image clarity is not high, and the color saturation is even lower.
We may usually notice that the surface of the plaster or whitewashed wall is also very absorbing, and the dot spread is relatively small. So we use something like gypsum powder to make the coating, the quality of the print will be better. Coated paper is just such a thing. Of course it may not be coated with gypsum powder. It is made of some white fine powder mixed with some adhesive, and there are many small holes in the middle to absorb the ink. When the ink drops up, it spreads both in depth and horizontally. Compared with offset paper, it spreads less in the horizontal direction, so the sharpness and color saturation are better. In addition, its pores are relatively large, no matter what kind of ink can absorb. However, after the evaporation of the ink, these pores become a clear channel for air to enter, so the photos printed on the coated paper fade faster. Pictures printed with HP printers will fade by more than 30% in one year. The coating of the coated paper is still not strong, and the powder is dropped by a single stroke, and it cannot be protected by the film.
Another disadvantage of coated paper is that the diffuse reflection from the rough surface makes the maximum density of the photo not very high, usually only 1.6, and sometimes 2.0 with special black ink. However, because the coating is opaque, the level of the dark part is not good.
The printing paper developed with the coated paper as the basic technology is called powder coated paper by many people. Although the degree of dot spread is different, their defects are common.
High-gloss photographic paper for printing is very different from coated paper, especially for high-gloss photographic papers used in traditional printers such as Hewlett-Packard and NOVAJET. If we use a little water droplet on it, the coating on the surface will become sticky. But it is transparent, and it makes us feel like a kind of animal glue. However, the current coatings are probably made of high molecular organic compounds, and will not use the bovine bone glue or pig skin glue used in the film. When a drop of ink is dripped onto it, we will notice that the coating swells up after it absorbs water. It is obvious that this "glue" absorbs moisture and dye molecules into its own microstructure to soften itself. A good coating is not a fast ink absorption, but a slower ink absorption, and the surface tension of the coating is also relatively large, so that the ink droplets do not infiltrate like water droplets on the lotus leaf when they are not sucked into the "glue". Then slowly inhale the "glue", and after the water evaporates, the "glue" shrinks and the dye is tightly wrapped. The thick coating paper has strong ink absorption capacity and small horizontal diffusion. The printing paper can be printed with a relatively large amount of ink. The printed photos are clear and sharp, the density of the dark parts is large, and the layers are crystal clear and very beautiful. We have bought a paper that has been coated twice, and the printing effect is very good. Our recently tailored canvases are coated twice.