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Raw Materials and Properties of Photosensitive Resin

Release time:

2024-10-29 17:13

Raw Materials and Properties of Photosensitive Resin
Raw Materials and Properties of Photosensitive Resin

Photosensitive resin, also known as light-curable resin, is an oligomer that undergoes rapid physical and chemical changes upon exposure to light, enabling it to crosslink and solidify within a relatively short period. It consists of resin monomers and prepolymers, among other components, and contains reactive functional groups. Under irradiation with ultraviolet or visible light, these functional groups are triggered by a photoinitiator to initiate a polymerization reaction, ultimately forming an insoluble coating film.

I. Basic raw materials for photosensitive resins

Photosensitive resins are primarily composed of polymer monomers and prepolymers, with the addition of auxiliary ingredients such as photoinitiators (also known as photosensitizers). Together, these raw materials determine the curing speed, mechanical properties, thermal resistance, and other critical performance characteristics of photosensitive resins.

1. Polymer monomer

Polymer monomers are the basic building blocks of photosensitive resins, and they form polymer chains through polymerization reactions. Common polymer monomers include acrylates, vinyl compounds, and epoxies. Under ultraviolet light irradiation, these monomers undergo polymerization reactions initiated by photoinitiators, forming long-chain polymers. These polymer chains interweave with one another to create the resin’s skeletal structure, endowing the resin with strength and toughness.

2. Prepolymer

A prepolymer is a polymer with a low molecular weight that exhibits a certain degree of reactivity. It can further polymerize or crosslink in subsequent reactions, ultimately forming a high-molecular-weight polymer. Prepolymers typically possess specific reactive end groups or side groups; these functional groups enable the prepolymers to undergo chemical reactions with other components during the second-stage reaction. In photosensitive resins, prepolymers serve as the primary film-forming substances, enhancing the material's strength and toughness. The molecular weight of prepolymers usually ranges from 1,000 to 5,000, and their types and contents significantly influence the performance of photosensitive resins.

3. Photoinitiator

Photoinitiators are key components of photosensitive resins. After absorbing light energy, they generate active free radicals or cations, which in turn initiate polymerization reactions by generating active species such as free radicals and cations, thereby triggering monomer polymerization, crosslinking, and curing. Common photoinitiators include benzoin and its derivatives, acetophenone derivatives, and triaryl sulfonium salts. The selection and dosage of photoinitiators significantly influence the curing speed and degree of the photosensitive resin.

4. Reactive diluent

An active diluent is a low-molecular-weight compound containing reactive functional groups that can participate in polymerization reactions and become part of the cured film. They help reduce the viscosity of photosensitive resins and improve the flowability and wettability of the coating film. Based on the number of reactive functional groups per molecule, active diluents can be classified into monofunctional active diluents, bifunctional active diluents, and polyfunctional active diluents. Common examples of active diluents include styrene, butyl acrylate, and the bifunctional compound 1,6-hexanediol diacrylate.

II. Characteristics of Photopolymer Resin Raw Materials

The properties of photosensitive resin raw materials directly affect their performance after curing, including mechanical properties, heat resistance, and chemical corrosion resistance.

1. Properties of polymer monomers

The type and structure of polymer monomers significantly influence the curing speed and degree of photopolymer resins. For example, acrylate monomers exhibit high reactivity and can complete the curing reaction in a relatively short time; in contrast, epoxy monomers offer superior thermal stability and chemical resistance.

2. Characteristics of the prepolymers

The molecular weight of the prepolymer, as well as the types and content of functional groups, all influence the curing speed and mechanical properties of the photosensitive resin. Generally speaking, the greater the molecular weight of the prepolymer, the higher the strength of the cured material; increasing the types and content of functional groups also enhances both the strength and toughness of the material.

3. Properties of Photoinitiators

The characteristics of a photoinitiator—such as its absorption spectrum, quantum yield, and half-life—determine its ability to initiate polymerization reactions. The better the match between its absorption spectrum and the light source, the higher the photoinitiation efficiency; the higher the quantum yield, the greater the number of active radicals or cations generated per absorbed photon; and the longer the half-life, the better the photoinitiator’s stability under illumination.

4. Properties of Reactive Diluents

The type and content of reactive diluents significantly influence the viscosity, curing speed, and degree of cure of photosensitive resins. By selecting appropriate reactive diluents, the viscosity of the photosensitive resin can be adjusted to make it easier to coat and level. Meanwhile, the incorporation of reactive diluents can also enhance the cross-linking density and mechanical properties of the cured product.

III. Summary

As a high-performance material, photosensitive resin holds broad application prospects in fields such as coatings, inks, 3D printing, and electronic packaging. With continuous technological advancements and an ever-expanding market, the demand for photosensitive resin will keep growing and continue to play a vital role in future development. By continuously optimizing preparation processes and refining modification technologies to enhance product performance and reduce costs, photosensitive resin will find wider applications and greater adoption across more industries.

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