Talking about the gloss of printed products
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The appearance of the product is the result of a complex interaction between light and the object, the optical properties of the object, and the human sensation. Appearance is one of the most important business attributes of a product. Printed matter must not only have a beautiful design, but also convey information about the product to consumers. Improving gloss is one of the ways to improve the quality of printed matter. Below we discuss the relationship between gloss, gloss and print quality.
First, gloss, gloss
Gloss refers to the property of the surface of a object to selectively reflect, as a result of a different degree of bright spots on the surface or an image of an object that overlaps the surface. Gloss is a numerical representation of the gloss of the surface of an object.
Simply speaking, gloss is the reflection phenomenon on the surface of an object, which is caused by the reflection of light on the surface of the object. Generally, the gloss is divided into three types: metallic luster, pearl luster, silk luster and the like. Generally, for glossy flat specimens such as printed matter, it is suitable to use specular gloss and open angle contrast gloss.
Second, the relationship between print and gloss
The surface of the object can be divided into two types according to the reflection state of the light: one is the ideal mirror surface, which can reflect all the incident light, and the light is directionally reflected from the specular reflection angle; the other is the complete diffuse reflector, the incident light Reflecting in all directions with the same brightness; the third is a semi-glossy surface between the two, neither the ideal mirror nor the complete diffuse surface, the surface of most objects in nature belongs to this surface The surface of the print is also a semi-gloss surface.
When light hits the surface of the printed product, a part of the light enters the ink layer, is selectively absorbed by the ink, and then reflects the ink layer through the substrate. The color of the reflected light is the color of the printed product; The ink layer has already been reflected (called surface reflection), and this part of the light is not dyed, and the reflected light is white light. The gloss of the printed product mainly refers to the visual effect produced by this part of white light.
Obviously, the gloss of the surface of the printed ink layer should not be too high, because the gloss is too high, and too much white light will affect the color effect of the printed product. Assuming that the illumination light is incident at an angle of 45°, since the surface reflected light is mainly directional reflection, when the observer's line of sight is perpendicular to the printed matter, the reflected light does not easily enter the observer's eyes, and the pattern and color on the printed matter cannot be accurately perceived. .
When the main part of the incident light passes through the ink layer, the part of the color light that is selectively absorbed by the ink and then reflected is called the main color light. If the surface of the printing ink layer is rough and dull, and the surface reflected light is diffused and reflected in various aspects, the color of the printed matter observed is the mixed light of the primary color light and the surface reflected light. Since the white light reflected by the surface is added to the main color light, the color saturation of the printed matter is lowered.
Another optical phenomenon, internal reflection, also affects the color of the ink layer of the print. When the light entering the ink layer is reflected from the surface of the paper to the inner surface of the ink, there is also reflection on the inner surface of the ink layer, and this portion of the light is reflected between the paper and the inner surface of the ink layer a plurality of times, which is called multiple internal reflection. The inner surface of the ink layer and the surface of the ink layer reflect light in a similar state. When the surface gloss of the ink layer is low, the inner surface is also diffusely reflected to light. The number of multiple internal reflections between the inner surface of the ink layer and the paper is increased, and the absorption of light by the ink is increased, so that the brightness of the printed matter is lowered. Therefore, the surface of the ink layer has high gloss, the color has high saturation and high brightness, and the printed matter is bright and full. On the contrary, the prints are dull and dry.
Third, factors affecting the gloss of printed matter
The glossiness of the surface of the printed matter is mainly determined by the smoothness of the surface of the printed ink layer. The state of the surface of the ink layer is related to the type of paper and ink. In addition, a reasonable printing color sequence has a certain influence on the gloss of the printed product.
Paper with a rough surface, because of its loose fibrous structure, the surface of the ink film is never smooth. Therefore, in order to smooth the surface of the ink layer, the premise is that the paper has high smoothness, high paper tightness, and low absorptivity, so that a sufficiently thick ink can be smoothed on the surface of the paper to obtain a smooth ink film surface. Otherwise, the binder in the ink will be partially absorbed or completely absorbed by the paper, and the binder is not enough to completely enclose the pigment particles, and it is impossible to form a smooth ink film surface. In general, coated paper has a higher gloss than non-coated paper prints.
Another factor that affects gloss is the ink itself. For example, the bright-light fast-drying offset ink has better fluidity during the printing transfer process. When the ink is printed on the paper, a small amount of low-viscosity kerosene in the ink penetrates into the paper, leaving the high-viscosity resin to be gel-fixed quickly, which not only adapts to high speed. The printing requirements, and the graphic ink layer is thick and the gloss is good.
Choosing the right printing color sequence can also play a role in improving the gloss of the printing. For example, when the absorptivity of the printing paper is too high, the full color ink can be printed as the first color. The full color refers to the full color distributed over the entire graphic area. For example, printing warm color pictures, yellow ink and magenta ink are full colors; when printing cold color pictures, yellow ink and green ink are full colors. For atypical warm or cool colors. Because of the wide distribution of yellow ink, yellow ink can be considered as a constant full color. Printing the full color as the first color is equivalent to first giving the paper a ground color, so that the ink is less absorbed by the ink material after the printing, so that they can spread on the surface of the paper, so that the gloss of the printed product is increased.
Because yellow is a weak color. That is, it is not as good as magenta, cyan, and black ink on white paper. Sometimes it is difficult to judge the amount of ink when printing, and yellow ink is inconvenient for first color printing. In order to improve the gloss, the yellow ink can be printed as the last color, so that the yellow ink of the full version acts as a bright oil to improve the gloss of the printed product.
After four-color ink overprinting, the addition of varnish or composite plastic film has a very obvious effect on improving the gloss of the print.
Improve the gloss of printed matter, not only to improve its saturation and brightness, but also to get the luster of the picture - the dazzling effect of white light, like the charm of the gem is mainly the glittering luster. A beautiful print is placed on the shelf, and people can move their footsteps by enjoying the beautiful color of it, which shows its luster. If people stay in the specular direction of a certain part of the picture, the visual experience will be a piece of white, and there is no beauty at all.
The gloss of the printed matter is not as high as possible. When selecting a process for improving the gloss, attention should be paid to the type of the printed matter and the size of the printed matter, and the use of the printed product cannot be impaired for improving the gloss.
A large area, especially a non-supplemented substrate, often cannot form a flat surface when placed. If the gloss is too high, the observer will observe a large number of glare-reflecting white light regardless of the angle from which the image is viewed. Can not give people the full effect of the printed surface. The images and text became fragmented and the effect was terrible.
In order to attract the attention of consumers, it is not only novel, eye-catching, and pleasant to be designed, but also to introduce consumers to the brand, performance, and origin of the product. The pattern, form, color and text content should give consumers the feeling of impacting information at the same time, so that they will receive the best results. Let the consumer dangle their heads to avoid the sparkling white light in order to see the entire contents printed on the package. Obviously it is not advisable. The use of gloss to improve the color quality of printed matter should be done without damaging the use of the printed product.