Grasp the ink layer thickness to improve the quality of the print

If the ink layer on the paper is too thick, the gloss of the print will be good. The screen dark tone will be blurred, the color will darken, and the layers will be dull; the ink layer will be too thin, the print will be dull, the color will be shallow, the layer will be gray, and India The weather is as old and worn as years, and it is old; the ink layer is moderate, the color is close to the original, and the layers are clear, and the bright areas reflect the light level. If it is a snow scene, it can be seen that the snow is flying; the dark tone area presents the subtle layers such as creases. If it is a stage, it can be seen that the curtain was broken. Ink color shines, fragrant ink, put it down.

The thickness of the ink layer printed on the paper is very difficult to calculate by the weighing method. Generally, the photometric method is used, that is, the density value printed on the paper ink film is measured by a reflection density meter. The greater the density value, the greater the ink layer. Thick, for black ink printing samples, the measured density value is the thickness of the ink layer. However, when measuring the ink layer thickness of a color ink, it is necessary to install a color filter that complements the color ink in the densitometer. For example, to determine the density of yellow (Y) ink, install a blue (B) filter in a densitometer, measure the density of magenta (M) ink, install a green (G) filter, and measure the amount of blue (C) ink. Density, install red (R) filter. Experiments show that the field reflection density of prints gradually increases with the increase of the ink layer thickness of the printed matter. When the ink layer thickness increases to a certain value, the ink's on-site reflection density also reaches the maximum saturation value, even if the ink continues to increase. Layer thickness, solid reflection density will not increase. After a lot of experiments have shown that the density of reflection of various inks changes with the thickness of the ink layer. However, different colors of ink are printed on the same paper, and the maximum value of the maximum reflection density obtained is different. For example, black, cyan (C), magenta (M), and yellow inks are printed on coated paper respectively. When the thickness of the ink layer reaches 1.1 μm, the thickness of the ink layer is increased, and the field reflection density no longer increases. The maximum reflection density value is 1.8-2.0 for black ink, 1.45-1.7 for cyan ink, 1.25-1.5 for magenta ink, and 0.9-1.05 for yellow ink.

What about a small printer without a densitometer? The majority of the printers are proofs printed on the basis of a printed sample. Both the ink in the actual area and the ink in the dot area are the same. The ink color tones and proofs are basically the same as the proofs. The thickness of the printed ink is slightly more than the proofs. Thicker, if using offset paper, the ink layer should be thicker when printed. Because, the reflection density value of the ink, as the ink dries, this phenomenon is called the dry density phenomenon. Taking black ink as an example, when the coated paper was printed, the field reflection density was 1.9. After three days, the field reflection density was 1.55. When the offset paper was printed, the field reflection density was 1.35. After three days, the field reflection was measured. The density is 1.16.

The technical parameters of the paper are one of the important factors affecting the printing quality. For example, if the thickness of the same batch of paper is different, if the thickness of the paper is different, the depth of the print will also be uneven.

● Paper smoothness. The surface roughness of the paper is different from that of macroscopic unevenness and microscopic unevenness. The macroscopic unevenness of non-coating paper means that the height difference between two points 300-400μm is within 25μm, and the microscopic unevenness refers to the difference in height between irregular two points directly close to each other. Within 3-5 μm, the surface of the super-calendered coated paper is microscopically uneven and its micro-unevenness is 0.1-0.5 μm. Such as the smoothness of the paper, only suitable for printing a monochrome text version, if you print color images, you should use a high degree of smoothness of the paper to print, in order to achieve a certain thickness of the ink layer, printing a rich variety of products.

● Paper sizing. Lithographic printing paper should be exposed to the printing plate dampening solution. If the sizing degree is poor, the water resistance is not satisfactory. The degree of binding between the coating layer of the paper and the base paper and the gloss of the paper itself are easily damaged, resulting in hair loss and loss. Powder, even a paper-cutting failure. Only by printing a color image print with a high degree of sizing can reach a certain ink thickness.

● Scalability. The paper's flexibility refers to the paper's dimensional stability. In multi-color printing, paper with high flexibility can easily cause overprinting. Strictly speaking, large stretch paper should not be used for multicolor printing.

● Whiteness. The whiteness of the paper is measured using a reflectance photometer (whiteness meter). The whiteness of the completely reflecting diffuser is usually defined as 100%. Compared with a paper sample, the reflectance is small, and the whiteness is poor. With high-white paper for color printing, ink thickness requirements can be achieved, bright and colorful. However, books printed on paper with high degree of whiteness have a strong contrast between black and white, which can easily cause visual fatigue. Therefore, the whiteness of newsprint is set at 45%-52%, the whiteness of offset printing paper is 55%-75%, the whiteness of offset paper is 77%-87%, the whiteness of offset paper is 80%-85%, and A is white. Card whiteness is not less than 92%.

● gloss. Glossiness is one of the optical properties of paper. Papers such as letterpress papers, newsprint papers, and offset papers are not required to measure gloss, but glossiness is required for coated paper and cast coated paper (such as self-adhesive paper). Glossy paper can print products with moderate thickness, bright colors, and rich layers.

According to information: Different paper, due to the paper's whiteness, gloss and other technical parameters are different, although the ink layer thickness is the same at the time of printing, but the field reflection density is different, for example, a certain ink layer thickness, senior coated paper reflection density 1 .5, the offset density of offset paper is 1.2, and the general newsprint has a reflection density of only 1.0 or less. In other words, if the same paper quality, reflective density, corresponding to the thickness of the ink layer or the ink layer is thin (of course, the ink's field reflection density reaches a maximum, and then continue to increase the thickness of the ink layer, the field reflection density does not increase) . If the paper is not the same, the field reflection density value is the same, but the ink layer thickness is different. Because of this, there are printing monographs suggesting that the printing factory selects several types of paper (eg, coated paper, offset paper, newsprint) to represent most of its production paper, and determines the ideal solid color reflection density value with the plate-making factory. , Used as the proofing paper for electric parting plate making, the printing factory controls the ink layer thickness of the proof draft in the actual printing is much easier, the color reproduction is closer to the proof draft. Now, the proofing paper of the plate-making factory generally uses 157 g double-sided coated paper. When it is actually printed, there are various kinds of paper, such as coated paper, offset paper and white paper. Inconvenience to the printing factory, the correct thickness of the ink layer is difficult to grasp.