Analysis of printing ink gloss
We are a big printing company in Shenzhen China . We offer all book publications, hardcover book printing, papercover book printing, hardcover notebook, sprial book printing, saddle stiching book printing, booklet printing,packaging box, calendars, all kinds of PVC, product brochures, notes, Children's book, stickers, all kinds of special paper color printing products, game cardand so on.
For more information please visit
http://www.joyful-printing.com. ENG only
http://www.joyful-printing.net
http://www.joyful-printing.org
email: info@joyful-printing.net
Gloss and color are collectively referred to as color. Because the color is more intuitive and has a direct impact on many mental factors such as people's mental state and mood, people's research on color started earlier. This research work is basically mature and is obtained in daily life. A wide range of applications. Gloss is the same as color, and it can also respond to people's psychology, especially in the evaluation of print quality.
The so-called gloss of printed products refers to the contrast between the brightness of the printed matter and the brightness distribution of the printed products under certain background and illumination conditions. The optical properties associated with gloss mainly include surface reflected light and internally reflected light.
1. Surface reflected light, the surface reflected light consists of surface regular reflected light and surface diffused light.
Positive reflected light: Light that conforms to the law of reflection is called regular reflected light. The intensity of the specular reflected light is mainly related to the state of the light-receiving surface of the object, in addition to the reflectivity of the substance. In general, the smoother and smoother the surface, the stronger the reflected light. Positive reflected light is a special kind of information reflected by an object, which has special significance for the study of gloss. Previous gloss studies have placed considerable emphasis on specularly reflected light, such as the measurement of gloss on generally smooth surface objects. In the industrial standards of Japan and the United States, specular gloss directly related to specular reflected light is mostly used. The specular reflected light is basically reflected on the surface of the object, so the object absorbs little of this part of the light, and its spectral composition is basically the same as that of the original incident light.
Surface diffused light: The actual mirror surface is not the ideal mirror surface, thus producing a diffuse light. At this time, it can be considered that the light intensity of many small specular reflections is superimposed, and when the brightness of the diffusing surface is a constant, it is called a cosine diffuser.
2. Internally reflected light, after the light is refracted into the object, it is re-entered into the original medium by the internal reflection of the object. This part of the light is called internal reflected light. The internally reflected light is absorbed by the material, so that its spectral composition changes. If the incident light is white, the internal reflected light will become colored light and the color of the object will appear.
The mattness of the imprint is one of the quality marks of the printed matter. If it is lustrous, it can increase the vividness of the printed imprint color; enhance the stereoscopic effect of the image, especially the reproduction of the physical photograph, with a luster and more realistic. There are many factors that affect the gloss of the imprint, which are summarized in the following aspects.
First, the nature of the paper
The structural state of the paper has a decisive influence on the gloss of the print, which is the most basic condition. The three indicators of surface smoothness, gloss and ink absorption of paper have an impact on the gloss of printed products.
1. The effect of the smoothness of the surface of the paper on the gloss of the print. In order to make the printed product mirror-reflective, the color is bright and the gloss is good, and it must be printed on a smooth paper. Paper having a rough surface is difficult to make the print shiny. Even if the flatness is good, capillary pores are formed between the paint particles of the paper, and the permeability of the binder is large, and a product having high gloss is still not obtained. The surface smoothness of various papers is different, and the smoothness has a great influence on the gloss of the finished product. The paper with high smoothness has good contact speed with the ink, which can ensure the complete reproduction of the dots and make the finished product have better gloss. Because the gloss of the ink film on the paper depends on whether the incident light can be specularly reflected. Only the paper with high smoothness can be specularly reflected after the ink film is leveled. On the contrary, the paper with poor smoothness and rough surface, the imprinted ink film is uneven, and only diffuse reflection can be formed on the light, and the finished product is not glossy. Therefore, in order to obtain a better finished gloss, a fine and high-grade product should first be printed with a smooth paper.
2. The effect of paper absorbency on gloss. The ink absorption of paper actually refers to the absorption performance of paper on the ink binder. The absorption of paper is one of the main conditions for determining the amount of penetration. If the properties of the ink are certain, the absorption of the paper is large, and the pigment of the ink layer is thick and overlapping. The gloss is reduced or even dull. The coarser the paper, the larger the fiber gap and the stronger the absorption capacity of the binder. When the binder is not dried, most of the fibers are absorbed by the fibers, and a part of the binder and ink particles adhere to the surface of the paper, losing the proper leveling property, and failing to form a smooth ink film layer. The product is dull. For coated paper (coated paper), there are two main reasons that affect the ink absorption: one is the variety and material used in the paint. The lower the ratio of adhesive to pigment, the higher the paper's absorbency for the ink. When the concentration of the coating is low, the adhesive and water in the coating easily penetrate into the thick paper, which reduces the amount of the adhesive in the coating, thereby increasing the absorption of the ink. Second, the pigment variety and particle fineness in the paint are also related to ink absorption. The finer the particles of the pigment, the less the glue in the coating is easily transferred to the paper base. The pigment particles are coarse, the particle gap is large, and the absorption of the ink is also large, and it is difficult to obtain a desired gloss effect in the finished product.
3. The effect of the gloss of the paper on the gloss of the print. The gloss of the paper itself has a considerable effect on the gloss of the finished product. The gloss of the surface of the coated paper depends mainly on the glossing material used in the papermaking process and the processing precision of the paper. The light-increasing materials are aluminum stearate, paraffin wax, insect wax, etc., and the finishing method is super calendering. The paper processed by the above method has a smooth plane, and itself forms a specular reflection (unidirectional reflection) property to light, and a higher transparency ink is printed, and the finished gloss effect is better.
4. The effect of paper strength on the gloss of the print. The paper has low strength, heavy powder and hair loss. When printing, the adhesion between ink and paper is not high, and the gloss of the printed product is low or even dull.
5. The effect of the pH of the paper on the gloss of the print. The pH of the paper affects the drying speed of the ink film, and the drying speed of the ink film affects the gloss of the printed product. The alkaline paper can accelerate the drying of the ink film, thereby relatively reducing the penetration time and the amount of penetration of the binder, so that the gloss of the printed product is better; the acid paper is the second.
Second, the nature of the ink
1. The leveling property of the ink. In the printing process, the leveling property of the ink is good, the gloss is good; the leveling property is poor, the drawing is easy, and the gloss is poor.
2. The fluidity of the ink, the fluidity of the ink is large, the size of the blot is enlarged, the dot size is increased, the ink layer is thin, the gloss is poor, the fluidity of the ink is small, the penetration can be reduced, the ink film is easily flattened, and the gloss of the printed product is improved. high. However, the ink fluidity is too small, and the ink is not easily transferred, which is not conducive to printing. Therefore, in order to obtain better gloss, it is necessary to control the fluidity of the ink, increase the viscosity or reduce the fluidity. All printing conditions must be considered. Otherwise, simply emphasizing the gloss of the print will cause other quality problems.
3. The fineness of the ink, the coarseness of the ink particles, the troubles such as stacking in the printing, the printing is also rough, the diffuse reflection occurs, and the gloss is poor. On the contrary, the gloss is good, and attention should be paid when selecting inks (especially gold ink and silver ink).
4. The viscosity of the ink, the viscosity should not be too large or too small, too much to separate the blanket and the surface of the printed product, drawing; too small, the size of the print is enlarged, the ink layer is thin, affecting the gloss. Greater China Graphic Arts Network
5. The dry form of the ink, the same amount of ink is in different dry forms, and the gloss is different. Generally, the oxidized conjunctiva is dried at a higher gloss than the osmotic drying, because the oxidized conjunctiva is dried on the surface of the ink print, and the osmosis is dry. The ink prints have less surface binder. When the ink is transferred to the paper, the solvent portion of the binder penetrates into the paper at a faster rate, and the coating and the paper fibers absorb the binder. The coarser the paper, the absorption capacity of the binder is also The stronger it is. The binder is mostly absorbed by the paper fibers in the absence of oxidized conjunctiva drying, and a small portion of the binder and pigment particles adhere to the surface of the paper, thereby making the product dull.
6. The amount of drier added to the ink. In addition to the drying properties of the ink itself, the amount of drier added to the ink is also a factor in determining the gloss of the print. As the drier increases, the drying speed can be increased accordingly, and the penetration time of the ink layer can be reduced. For example, the cobalt drier is mainly used to promote the oxidized conjunctiva, and it is appropriately selected, the drying is fast, the surface conjunctiva is smooth, and the gloss is increased. The disappearance of gloss is often caused by excessive drying time, the absorption of ink by the paper and the penetration of ink into the paper, resulting in the separation of the binder and the pigment. Some of the binder in the ink penetrates into the capillary pores of the paper, so that the binder is The proportion on the paper surface is reduced, and if the penetration phase is terminated as early as possible, the gloss of the ink layer after drying can be improved. On the contrary, the surface of the ink film is diffused and dull.
7. The transparency of the ink, the ink with high transparency forms the ink film color layer, part of the incident light is reflected by the surface of the ink film, and the other part reaches the surface of the paper, and then reflects out to form two color filters. This complex reflection mechanism is rich. The color effect, the color ink film formed by the opaque pigment, the gloss is only the surface reflection, and the gloss effect is certainly not as good as the transparent ink.
8. The gloss of the binder, the main components of the ink are binders and pigments. The gloss of the binder is a major factor in whether the ink footprint produces gloss. The early ink binders were made from vegetable oils such as linseed oil, tung oil and eucalyptus oil. The smoothness of the surface after blotting the conjunctiva was not high, and only the fatty film surface was formed, which formed diffuse reflection on the incident light. difference. Now the ink is made of resin as the main component, the smoothness of the surface after imprinting the conjunctiva is high, and the diffuse reflection of incident light is reduced, so the gloss of the imprint is several times higher than that of the grease ink.
9. The viscosity of the ink is the adsorption force between the binder and the pigment. The viscosity of the ink is related to the adsorption between the binder and the pigment. Increasing the viscosity increases the adsorption between the two, so that the paper is bonded to the binder. The absorption is correspondingly reduced, the amount of permeation is reduced, and the gloss is better, so that an appropriate increase in viscosity in the ink can increase the gloss of the print.
10. The thickness of the ink layer, the total thickness of the ink layers on the surface of the printed sheet has a great relationship with the gloss. Generally, the monochromatic prints rarely appear luster. If the overprint is printed on the top, the gloss will appear, so the thickness of each ink layer is correct. Gloss has an effect. For example, if the ink layer is thicker, it can lay a foundation for the improvement of glossiness, and if the number of times of coloring is large, the paper surface can be filled, and the gloss can be improved.
11. The emulsification of the ink, the emulsified ink must be dried after the water has evaporated, so that the drying is delayed, and many small holes are formed on the surface of the ink layer, thereby reducing the gloss of the print.
Third, printing pressure
Pressure is the key to good transfer of the blot. The pressure is too large, the blot is enlarged, and the gloss is weak. If the pressure is too small, the print is not clear, which will cause the print to be dull. Therefore, under the premise of ensuring that the ink on the blanket can be correctly transferred to the printing material during offset printing, the minimum pressure should be used as much as possible to print the glossy printed product.
Under the same paper and ink conditions, due to problems in the operation process, the gloss of the finished products is often large after printing. The following methods can be used to improve the gloss of printed products without considering the post-press glazing treatment:
1. Improve the acid wetting solution. China has been using acidic wetting liquid for decades, mainly chromic acid and phosphoric acid. Although it is diluted, the PH value is still between 3.5 and 5.6. The stronger the acidity, the greater the decomposition force and corrosive force of the ink binder and pigment, resulting in rough surface of the blotting film and reduced gloss. The research and development of dampening fluid has made breakthroughs in recent years. For example, the “Lide Wetting Powder” in Shanghai can be said to be effective. Nowadays, China's offset dampening liquid has entered a new stage, but some printing The factory is still using the old formula.
2. Reduce the emulsification of the ink. The excessive emulsification of the ink in the offset printing is caused by the large amount of water in the operation. The ink layer is thick, but the ink molecules become oil-in-water. After drying, the gloss is extremely poor, and a series of other malfunction. Water and ink is the most taboo in offset printing. To change this situation, in addition to the quality and technical education of the operator, it is recommended to use “Lide Wet Powder” because the agent has good wetting performance. Even if the plate has a small moisture, it is not easy to get dirty. It is good for operation and makes the finished product shiny.
3. Adhesives are appropriately added to the ink. By adding an appropriate auxiliary agent to the ink, the printing suitability of the ink can be adjusted for smooth printing. Most of the adjuvants have an adverse effect on the gloss of the finished product. For example: anti-adhesive agent, the main raw material is six-grain powder. After adding ink, the surface of the imprinted film layer becomes rough due to the precipitation of corn flour, and the gloss of the finished product is poor. Another example is the addition of No. 6 thin tempering ink, which not only increases the fluidity, but also increases the permeability of the imprint on the paper, and also reduces the dryness, which is unfavorable for the gloss of the imprint. Therefore, the amount of the auxiliary agent added to the ink should not exceed 5%. If the gloss effect is considered, it should be placed less or not. However, fluorocarbon surfactants are different in that they prevent surface defects such as orange peel and wrinkles in the ink layer, and at the same time improve the gloss of the printed surface.
4. Use dry oil properly. For advanced bright and fast drying inks, they have sufficient drying ability under normal temperature and humidity conditions. In case of the following conditions, dry oil should be added: first, in the case of low temperature and humidity in winter; second, in the case where anti-adhesive, detacking agent, thin ink, etc. must be added to the ink, Dry oil. In the process operation, the correct use of dry oil is very beneficial for the gloss of the finished product. This is because it takes a certain time for the paper to absorb the binder. In this process, the binder is condensed as soon as possible until the conjunctiva is dry, which is the key to the gloss of the finished product.
5. Pay attention to dusting. Spraying powder, like the ink, will also cause agglomeration, especially in bags or drums with poor sealing. After the dust is sprayed, it will condense into larger particles and spray onto the wet ink mark to make the surface of the ink layer rough and reduce. The original luster, so pay attention to moisture. In addition, the mechanism of the powder spraying device has a heating device, which should be inspected when the powder is used, and whether the heating device is malfunctioning.
6. Adjust the machine correctly. Whether the thickness of the imprinted ink layer reaches the standard also has an effect on the gloss. For example, the pressure regulation is poor, the dot enlargement rate is high, the thickness of the ink layer is not up to standard, and the gloss of the finished product is slightly poor. Therefore, it is necessary to adjust the pressure so that the expansion rate of the dot is controlled at about 15%, and the ink layer of the printed product is thick, the layer is pulled open, and the gloss is also available.
7. Jiafan Lishui (No. 0 oil). The oil has a large viscosity and is thick in itself, and can adjust the ink concentration to thicken the thin ink and increase the gloss of the printed product.
8. Add a bright paste. The bright paste is processed from raw materials with high gloss, which can increase the gloss of the ink, but the dosage should not be too large, otherwise the drying speed of the ink will be lowered, the sticking and drawing phenomenon will occur, and the gloss will be affected.
9. Add a lightening agent. When some inks are too dark to meet the requirements of spot color printing, they need to be lighter, which not only makes the ink lighter, but also improves the gloss of the print.
10. Add 19# resin oil. When the ink fluidity and transfer performance are not good, the 19# resin oil can be directly transferred, which not only improves the gloss of the ink, but also does not affect the multicolor overprinting.