Diazo-based photosensitive materials are now used the most, direct and straight-law method.

Diazo-type photosensitive adhesive is generally: PVA + PVAC + aromatic diazonium salt (diazo resin, composite hydrazine resin). The diazo resin and the composite diazo resin are the same as the double nitrogen salt, but the performance is more stable. In particular, composite diazo resins have a higher cross-link density and thus have better resolving power and resistance.

Diazo type photosensitive adhesives appeared in the 1970s and have been rapidly developed and popularized. The domestically developed units include the China Institute of Printing Science and Technology, such as water-resistant photosensitive adhesives, solvent-resistant photosensitive adhesives, high-resolution dot-sensitive adhesives, and circular-retardant adhesives. There are many manufacturers of such products, such as DSI-type screen-sensitive adhesive (solvent-resistant type) and DS-II-type screen-sensitive adhesive (water resistant type) produced by Beijing Taipingqiao Printing Materials Factory. The solvent-resistant photosensitive adhesive (DSI) is resistant to organic solvents and is suitable for the screen printing of oil-soluble printing inks (inks) in electronics, instruments, plastics, enamels, glass and leather industries. The resolution is 100 lines/inch, and the resistance force is more than 40,000 times. It is developed with water, free of contamination, and can be reused after the screen is removed. The adhesive can be applied to a screen printing plate with a film thickness of 10 μm. The printing conditions are as follows: the light source is 3 kW, and the exposure time is 1.5 to 2 minutes. Water-resistant photosensitive adhesive (DSII) is highly resistant to water, suitable for textile printing, ceramics, paper screen printing and other industries water-soluble printing ink (ink) screen printing plate. The resolution is high, the edge is clear, the minimum line width of printing can reach 50μm; the thickness of the plate can be up to 8～12μm; the resistance force can be up to 4～100,000; the water can be used for development and no pollution; the screen can be repeated after the film is removed. use. The printing conditions were a light source of 3 kW and exposure for 1.5 to 2 minutes.

4. Iron salt photosensitive adhesive. The basic composition of this glue is: gelatin or PVA (film former), acrylamide and N,N' methylenebisacrylamide (crosslinker), ferric ammonium citrate (sensitizer) and lauryl Sodium (dispersant).

After the trivalent iron salt in gelatin is exposed, it will produce ferrous ions in proportion to the exposure. At this time, the photosensitive layer is immersed in the initiator (H-2O-2), and ferrous ions decompose hydrogen peroxide to produce hydroxyl radicals:

Fe+=H2O2[FY](Fe-HO)2++·OH

· OH will initiate acrylamide polymerization, but this polymerization is only a linear polymer, can not obtain a good image, N, N 'methylene bis acrylamide added, can be copolymerized with the former and cross-linking, Become a body structure, improve the resistance of the film. In free radical initiated polymerization, graft polymerization with gelatin is also included.

The performance of this adhesive is stable, making it easy to make sensitized dry film. Because the depth of hardening is proportional to the exposure, it is suitable for transfer (ie, indirect) film printing.

5.SBQ emulsion. SBQ photopolymer is a patented product of Murakami Screen Co., Ltd. of Japan. SBQ is a photopolymer derived from a styrylpyridinium salt compound group. Its greatest advantage is the ability to crosslink directly with the emulsion polymer (PVA).

This new type of photosensitive adhesive is a liquid type and can be used directly. Its characteristics are long life, not affected by heat; high sensitivity, can shorten the printing time; high resolution, suitable for high-precision silk screen; coating job is good.

Using the PVA (polyvinyl alcohol)-SBQ, a 50 μm thick emulsion layer plate can be produced by direct indirect plate making. When a thicker film is required, special water-soluble photosensitive resins can be applied. If a direct plate process is used, a 400 μm thick emulsion layer plate can be produced. In addition, if a thick-film photosensitive resin is used, a screen printing plate having a total thickness of 2000 μm of the screen and the plate film can be produced by the direct method. Toxicological tests demonstrate that styrylpyridine is harmless and therefore safe to use.

6. Screen printing photosensitive film. Photosensitive film, also known as film film, film paper, is made of plastic transparent film as the base, coated with a certain thickness of the sensitized emulsion. Sensitive film is mainly used in indirect method and straight-line method plate, the product color is generally red, blue, green three. Photosensitive films are usually divided into four sizes, 1 to 4 sizes, depending on the thickness of the photosensitive layer to which they are applied. The domestic photosensitive film is divided into two kinds of pink and blue translucent films from the appearance, its performance is the same, but the exposure time required for pink is slightly longer. The following examples of photosensitive films produced by Wuxi Paper Products Co., Ltd. are described as follows:

No. 11 photosensitive film. Photosensitive film adhesive layer thickness of 0.01 ~ 0.014mm, mainly used for printing about 0.1mm fine line screen printing plate.

No. 22 photosensitive film. Photosensitive adhesive layer thickness of 0.018 ~ 0.022mm, mainly for the line screen printing plate greater than 0.1mm.

No. 33 photosensitive film. Photosensitive adhesive layer thickness of 0.035 ~ 0.04mm, mainly used for printed circuit boards, three-dimensional surface plate, signs, such as the screen printing plate.

No. 44 photosensitive film. The thickness of the photosensitive layer is 0.05-0.06mm, which is mainly used for the screen printing of the thicker ink film.

Various types of photosensitive films, used in the production of screen printing plate process is basically the same, only the fourth photosensitive film sensitized film, on the back of the screen need to re-brush two sensitized solution to ensure thorough sensitization.

The finished product of the photosensitive film is available in single sheet and reel, and can be cut as needed.

Murakami Screen Co., Ltd. Japan produced a variety of straight between the film film (MS film), is also the domestic screen printing manufacturers often use photosensitive film. The utility model has the advantages of simple printing plate, uniform thickness, smooth film surface, high resolution, and can be used for screen printing plates with high precision requirements.