How much is the packaging offset? (81-87)

81. What is the principle of plate making in the positive PS version?

The positive Ps version uses a photodegradable diazonium compound as the light-sensitive material, which is printed on the positive plate as the original plate. When the blank part is exposed to ultraviolet rays, the sensitizer decomposes and releases nitrogen. When the remaining material is developed with a dilute alkaline solution, it reacts with water molecules and bases in turn to form water-soluble substances and is washed away by water. Alumina membrane of water, as a non-graphic part of the printing plate. The graphic part is blocked by the image on the positive picture. The sensitizer does not decompose and it cannot react with dilute alkaline solutions and dissolve in water. The unsensitized diazo compound sensitizer left on the Ps plate has good lipophilicity and forms the basis of the graphic part of the plate.

82. What is the principle of plate making in the negative PS version?

The negative PS type plate uses a photopolymerizable azide compound as a light-sensitive material, which is negatively printed using a negative film negative. When the photosensitizer in the graphic part of the printing plate is irradiated with ultraviolet rays, it crosslinks into a network structure and hardens, and is firmly adsorbed on the surface of the printing plate, becoming a graphic basis for lipophilicity. The non-exposed portions of the photosensitive material that have not been exposed can be removed by the developer, exposing the aluminum oxide film on the aluminum plate to form a hydrophilic blank.

83. What are the pros and cons of using negative and positive PS versions?

The positive PS version is better than the negative PS model in that the negative is better than the negative. The negative is easier to check before printing, and it is easy to use hand-made imprints. Cover the film with shading paper. The process is easy to operate.

The advantages of the negative Ps version are: the sensitizer becomes soluble from soluble to light, and there are fewer dirty spots after printing. It is easier to remove dirt; the photosensitive layer remaining on the plate is not affected by light and acid. Alkali resistance is good, and the printing plate is more resistant to printing forces. For some simple packaging and printing products, simply use the device to shoot negatives film can be used for printing, reducing the trouble of copying the factory.

Negative PS version is rarely used in our country, and most of the production use positive PS version.

84. What are the different effects of improper exposure time on the level reduction of positive PS type and negative PS type?

When the exposure is excessive, for the positive PS version, since it belongs to the PS decomposition type, the edges of the graphic part will be decomposed due to more light infiltration, resulting in smaller dots and a small loss of small dots. The overall tone becomes lighter. For the negative PS version, the situation is the opposite. The edge of the blank part is cross-linked due to more light infiltration, which can easily cause dot gain, dark tone and paste, and the overall tone becomes darker.

When the exposure is insufficient, for the positive PS version. The blank part fails to fully see the light decomposition, which will cause dark tone and paste, more dirty spots, and even the entire blank part is dirty. For the negative Ps version, the photo-texturing part fails to fully see the light cross-linking, and the dots are likely to be smaller and the smaller dots are lost. The plate is poor in acid and alkali resistance, and its resistance to printing is reduced.

85. What is the printing process of the positive PS version?

The general process flow of the positive PS version printing plate is: one version of the exposure and one version of the development; and one version of the revised one (the baking version and the ink extraction). Baking and ink extraction can be selected according to production needs.

86. What are the main factors affecting the quality of printing in common production?

1PS version quality.

2 print quality of the original negative film.

3 print shop environment.

4 Slate performance (including exposure status and pumping performance).

5 development conditions.

6 process operation method.

87. What is the quality of the PS version?

The effect of the PS plate on the quality of the printing plate is mainly related to the quality of the plate base and the quality of the photosensitive coating. Plate base quality includes material properties and surface finish quality. It affects the stability of the plate size and the printing force and wetting properties of the plate. The quality of the photosensitive coating includes the thickness of the coating. Uniformity and photosensitivity. It affects the resolution of the printing plate, the accuracy of the reproduction of outlets, and the virtual reality of outlets. (to be continued)