What's the difference between photographic paper and coated paper? Is it the same?

Photographic paper and coated paper are not the same kind of paper.

1, different definitions

Photographic paper refers to a kind of paper used when printing photos.

Coated paper is also called printed coated paper. The surface of the base paper is coated with a layer of white paint, and the base paper is made of super calendering. It is divided into single-sided paper and double-sided paper, and the paper surface is divided into light splitting and cloth grain.

2. Different characteristics

Photographic paper is characterized by bright colors and long-term color retention.

Coated paper is characterized by smooth surface, high whiteness, good ink absorption and ink adhesion.

Extended data:

Technical requirements for printing coated paper:

Due to process defects, some domestic coated paper is prone to degumming and shrinkage variation in different degrees, especially single-sided coated paper, which is prone to curl defects and affects overprinter accuracy. If the process of printing coated paper is not properly operated, it is easy to be dirty (over-bottomed), powdery, slow to dry, star color, insufficient brightness and so on. Therefore, we should pay attention to the following questions.

1. Before each batch of coated paper is put into use, it is necessary to test and analyze a series of problems related to printing adaptability, such as smoothness, pH value, absorbability, dryness, flexibility and surface bonding strength, and then take corresponding technological measures according to the characteristics of the paper, such as adjusting the viscosity, fluidity, dryness and anti-sticking measures of the ink, so as to realize standardized and scientific production and prevent printing defects.

2. It is necessary to adjust the pad printing process and printing pressure to ensure that the ink layer is uniform and bright. The printing pressure of coated paper should be uniform and appropriate. Excessive pressure can easily lead to poor powder dropping, unclear dot printing and increased plate wear.

On the other hand, it is easy to cause weak dot printing, and blindly increase the ink layer to make up for the page smudge caused by insufficient pressure. In that case, it is easy to produce bad consequences such as sticky dirt, slow drying and poor overprint. Therefore, when printing coated paper, the pressure should be uniform and appropriate. The lining should be made of neutral hard materials.

3. Printing trademarks and packaging products with coated paper, usually with light color as the background color, is formed by overprinting. Improper printing color technology is also likely to cause some problems and affect the quality. Therefore, when preparing the background color ink, heat-resistant and light-resistant ink should be selected as far as possible, and thinner should be prepared with bright paste, so that the background color can be printed at the end to prevent the ink layer from being damaged by friction when the background color is printed first.

4. Due to the smooth surface of coated paper and poor ink absorption ability, we should try our best to be "deep ink and thin ink" when printing large-format field plates. That is, if the ink color is deepened properly, the ink layer will be thinned correspondingly during printing, so as to meet the requirements of printing hue, reduce the chance of overprinting and prevent overlapping colors from being printed.

In addition, due to the poor adhesion of paper, the printed ink layer is sometimes easy to change color due to powder dropping. Therefore, 19 resin oil can be used as blending oil for the first printing color. In order to make the overlapping ink layers bright, some bright oil and dry oil can be added to the ink appropriately.

5. Due to a large amount of paint, coated paper often encounters the phenomenon of powder shedding and black shadow in the printing process. In this case, you should pay attention to check whether the mounting process is proper, such as whether the printing plate is heavily padded, because if the paper pressure is too high, it is easy to crush the coating powder on the surface of the coated paper, resulting in powder removal and black spots.

In addition, check whether the viscosity of the ink is appropriate. If the ink layer is too thick and sticky, it is also one of the reasons for the accumulation of pages. In this case, we should consider using auxiliary materials to adjust the ink, and the above quality problems can be better controlled.

6. It is necessary to control the anti-sticking technology of coated paper printing. Coated paper has weak ink absorption and smooth back, and it is easy to get dirty when printing a large amount of ink or multicolor overprinter on one page. Therefore, anti-sticking measures should be taken to overcome it. For example, an appropriate amount of anti-sticking agent is stirred evenly with bright oil to make it liquid, and then mixed evenly with ink, so that a good anti-sticking effect can be obtained in printing.

However, the dosage of anti-sticking agent should be controlled reasonably, and should not exceed 4%, so as to avoid the disadvantages of ink emulsification, printing ink layer frosting, ink layer gloss decline and so on.

Baidu encyclopedia-photo paper

Baidu encyclopedia-coated paper