Printed version of the three major family of photosensitive plastic (a)

In recent years, the screen printing industry has developed rapidly. Some people say that it has become an industry that is not easily satisfied by market demand. Its changes are changing with each passing day, constantly expanding into new areas of application while quickly introducing new products. Although there have been many changes in screen printing, the method of screen printing has not changed. The basis of the plate making and the chemical principle cannot be separated from the photosensitive adhesive. Therefore, in recent years, the photosensitive adhesive has also been continuously developed.

Photoresist general properties:

Photoresist is composed of three basic ingredients: sensitizer, water and solids content. The sensitizer works on ultraviolet light. The combination of polyvinyl alcohol (PVA) solids with a photosensitizer produces a solid material that is insoluble in water.

Photosensitive adhesive structure:

There are three major families of photosensitive adhesives today: diazo photosensitive adhesives, double-sensitized photosensitive adhesives, and pure photopolymer sensitive adhesives.

(1) Diazo Photoschicht

The diazo sensitizer is a polyvinyl alcohol (PVA) and polyvinyl acetate (PVAC) emulsion that uses only a diazo sensitizer (photosensitive resin).

The diazonium salt is mixed with the basic emulsion before use.

General examples of PVA and PVAC

※ There is no structure of diazo polymer in this diagram, it shows only a simplified example. PVA-chain

In the cross-linking of PVA chains, cross-linking with diazo increases the molecular weight of the PVA material. The exposed part is changed, has water resistance, and remains as a stencil overlay. The unexposed portion maintains its water-solubility, and after being washed with water, it can pass through ink or color paste to form an image.

Diazo cross-linked emulsions (photosensitive adhesives) are primarily used for general screen printing applications using solvent-based inks.

(2) Dual Cure Photosensitive Adhesive (Dual Cure)

Double photosensitizer is a type of photosensitizer (photosensitizer), usually diazo and photopolymer. The dual sensitizers are mixed with a diazonium salt but have to be additionally linked to the photopolymer. The main component of the photopolymer in the photoresist contains acrylate chemistry and a photoinitiator. The component acts as a polyvinyl alcohol and a diazo resin at various sensitizations to various ultraviolet light source wavelengths. The photocuring technique in the photopolymer system is illustrated below by way of example. This example is only a simplified illustration.

1.........>1 release agent

1 ※+M.........>1M ※ Cross-link reaction

1M+M.........>1MM※ diffusion

1MM ※.........>1MMR end

Character description:

1 = release agent (photoinitiator)

1 ※ = free radical

M=Acrylic Chemicals

R = final stage

Repeated description: Crosslinking of the photopolymer increases the molecular weight of the material, and thus produces a durable and correct reproduction method required by the original. Because the chemical composition is a double-sensitizer product, very accurate reproductions can be made.

Double photosensitizers have a wide range of applications for screen printing: screen printing plates made with dual photosensitizers are suitable for solvent screen printing inks, water-based screen printing inks, solvent/water-based screen printing inks and other etchings. Inks and colorants, and can ensure excellent reproduction quality and high stability of batch printing.

(3) Pure Photopolymer Photopolymer

This is the third type of photopolymer, which consists of 100% of photopolymer. Pure photopolymer photosensitive adhesives are currently marketed under the trademark Chroma/Tech PL by Chromaline. The photoresist does not contain diazo as a sensitizer appendage. It is pre-sensitized without mixing