When printing tinplates, they usually use two printing methods: four-color printing or spot color printing. The characteristics and differences between the two are described in detail below:
Four-color printing is a lithographic method that uses CMYK, namely cyan, magenta, yellow, black (ink or dye) four colors to achieve color overprinting. It adds black to the original three color-reduction methods. In theory, four-color printing can obtain thousands of colors, and combinations of C, M, Y, and K colors are not repeated. Monochrome: Y, M, C and K; two colors: Y+M, Y+C, Y+K, M+C, M+K, C+K; three colors: Y+M+C, M+C+K, Y+C+K, Y+M+K; four colors: Y+M+C+K, a total of fifteen colors. In color printing, the size of the "mesh" is used to indicate the depth of the color.
In theory, "spots" can be divided into 22 levels, and 279,840 colors can be obtained according to the arrangement formula. In fact, due to the deformation error of the "mesh" during the printing process and the limitation of the visual recognition threshold, the color that can be obtained by four-color printing is much less than theoretical.
From the printing effect point of view, the four-color printing surface is rough, not full enough, the dot is relatively obvious, the copying color is heavy, the tone is large, the layering is not real, and the three-dimensional feeling is not strong.
The spot color printing is the process of printing by the ink distributor according to the Pantone color spot color card. The Pantone color card is an international standard color card. It is the authority of the color, covering printing, textile, plastic, drawing, Color communication systems in areas such as digital technology.
The inks prepared by the spot color printing are obtained according to the principle of color reduction and color mixing, and the color brightness is low and the saturation is high: the spot color of the ink color is usually printed in the field, and the ink is appropriately increased. When the thickness of the ink layer of the printing plate is large, the sensitivity of the change of the thickness of the ink layer to the color change is lowered, so that it is easier to obtain a uniform and thick printing effect of the ink color. Therefore, the color of the spot color printing effect is more full and vivid, so in the printing cost, the spot color printing is higher than the four color printing.
It is generally recommended to use spot colors in the case of large-area color printing of tinplate boxes, because large-area four-color printing will have obvious color difference and uneven color depth. If a product has a color-level image in the picture, In addition, there is a large-area background color, and the color-level picture portion can be printed in four colors, and the large-area background color can be printed in a spot color. The advantage of this is that the four-color printing part can correctly restore the picture by controlling the density of the ground, and the background color part can obtain the uniform and thick visual effect of the ink by appropriately increasing the amount of ink.