Photoinitiator TPO manufacturers believe that photoinitiator, also known as photosensitizer or photocuring agent, is a kind of ultraviolet (250 ~ 420 nm) or visible (400 ~ 800 nm) region to absorb a certain wavelength of energy, and produce free radicals, cations and other compounds. Thus, monomer polymerization, cross-linking and curing are initiated.
Photoinitiator TPO manufacturers believe that photoinitiator is the key component of the photocuring system, related to the formula system under the light, oligomer and thinner can quickly change from liquid to solid, that is, crosslinking curing. Its basic functional characteristics are: the initiator molecule has a certain light absorption capacity in the ultraviolet (200 ~ 400 nm) or visible (400 ~ 800 nm) region. After direct or indirect absorption of light energy, the initiator molecule jumps from the ground state to the active excited state, resulting in an active fragment that can initiate monomer polymerization. These fragments can be free radicals, cations, anions or ionic radicals.
Photoinitiator TPO manufacturers believe that according to the different active fragments produced, photoinitiator can be divided into free radical polymerization photoinitiator and cationic polymerization photoinitiator, among which free radical polymerization photoinitiator is widely used, followed by cationic photoinitiator. Anionic
Photoinitiators are rarely studied and no commercial application has been reported so far.
Photoinitiator TPO manufacturers believe that in many practical photocuring systems, the formation of active fragments involves chemical interactions between the photoinitiator and other auxiliary components to promote the formation of active fragments and improve the initiation efficiency. These auxiliary components may be referred to as coinitiators sensitizers or photosensitizers depending on their specific functions. Initiator is an important part of the bimolecular photoinitiation system. If it is consumed by chemical reactions in the photoinitiation process, it is often called sensitizer. Photosensitizers can also act with photoinitiators to promote photopolymerization, but only the physical interaction of energy transfer occurs between them. The action principle is that the photosensitizer molecule absorbs light energy of large wavelength and transitions to an excited state. Energy is transferred from the excited photosensitizer molecule to the initiator molecule through intermolecular physics. In this way, initiator molecules that cannot absorb long-wave light energy indirectly transition from the ground state to the excited state, resulting in fragments with polymerization initiation activity. This process is also known as photosensitization. In the whole process, the photosensitizer is not consumed, just as a carrier of energy in the system repeatedly run.
Photoinitiator TPO manufacturers believe that the more the absorption peak of photoinitiator overlaps with the main emission band of the light source, the higher the effective radiation enhancement degree of photoinitiator, and the better the effect of improving the curing speed of ink. The peak value of UV-LED is narrow and the radiation energy is concentrated in the narrow UV spectrum, so UV curing can only be concentrated in the narrow UV spectrum range. At present, the wavelengths of UV-LED curing light sources are mainly 365nm, 375nm, 385nm, 395nm and 405nm, and the emission bandwidth of each wavelength light source is about 10nm. However, most of the photoinitiators in the market have strong absorption at 300-370nm, but the optical absorption performance is poor in the range of more than 370nm, resulting in the emission spectrum of the light source in the UV-LED curing system and the traditional photoinitiator is different.
Wuxi Volksky New Materials Co.,Ltd.
