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A photopolymer or light-activated resin is a polymer that changes its properties when exposed to light, often in the ultraviolet or visible region of the electromagnetic spectrum.[1] These changes are often manifested structurally, for example hardening of the material occurs as a result of cross-linking when exposed to light. An example is shown below depicting a mixture of monomers, oligomers, and photoinitiators that conform into a hardened polymeric material through a process called curing.[2][3]
A wide variety of technologically useful applications rely on photopolymers; for example, some enamels and varnishes depend on photopolymer formulation for proper hardening upon exposure to light. In some instances, an enamel can cure in a fraction of a second when exposed to light, as opposed to thermally cured enamels which can require half an hour or longer.[4] Curable materials are widely used for medical, printing, and photoresist technologies.
Changes in structural and chemical properties can be induced internally by chromophores that the polymer subunit already possesses, or externally by addition of photosensitive molecules. Typically a photopolymer consists of a mixture of multifunctional monomers and oligomers in order to achieve the desired physical properties, and therefore a wide variety of monomers and oligomers have been developed that can polymerize in the presence of light either through internal or external initiation. Photopolymers undergo a process called curing, where oligomers are cross-linked upon exposure to light, forming what is known as a network polymer. The result of photo-curing is the formation of a thermoset network of polymers. One of the advantages of photo-curing is that it can be done selectively using high energy light sources, for example lasers, however, most systems are not readily activated by light, and in this case a photoinitiator is required. Photoinitiators are compounds that upon radiation of light decompose into reactive species that activate polymerization of specific functional groups on the oligomers.[5] An example of a mixture that undergoes cross-linking when exposed to light is shown below. The mixture consists of monomeric styrene and oligomeric acrylates.[6]
intro scheme for photopolymerization
Most commonly, photopolymerized systems are typically cured through UV radiation, since ultraviolet light is more energetic. However, the development of dye-based photoinitiator systems have allowed for the use of visible light, having the potential advantages of being simpler and safer to handle.[7] UV curing in industrial processes has greatly expanded over the past several decades. Many traditional thermally cured and solvent-based technologies can be replaced by photopolymerization technologies. The advantages of photopolymerization over thermally cured polymerization include higher rates of polymerization and environmental benefits from elimination of volatile organic solvents.[1]
There are two general routes for photoinitiation: free radical and ionic.[1][4] The general process involves doping a batch of neat polymer with small amounts of photoinitiator, followed by selective radiation of light, resulting in a highly cross-linked product. Many of these reactions do not require solvent which eliminates termination path via reaction of initiators with solvent and impurities, in addition to decreasing the overall cost.[8]
^ abcCrivello JV, Reichmanis E (2014). "Photopolymer Materials and Processes for Advanced Technologies". Chem. Mater.26 (1): 533–48. doi:10.1021/cm402262g.
^Phillips R (1984). "Photopolymerization". J. Photochem.25 (1): 79–82. doi:10.1016/0047-2670(84)85016-9.
^Burton, Jeff. "A Primer on UV-Curable Inkjet Inks". Specialty Graphic Imaging Association.
^ abCite error: The named reference Light-associated reactions of synthetic polymers was invoked but never defined (see the help page).
^Cite error: The named reference Photoinitiators for Polymer Synthesis: Scope, Reactivity and Efficiency was invoked but never defined (see the help page).
A photopolymer or light-activated resin is a polymer that changes its properties when exposed to light, often in the ultraviolet or visible region of the...
create raised surface printing plates from a negative and a photopolymer plate. Photopolymer plates are light sensitive. On one side the surface is cured...
surface of a vat filled with a liquid photopolymer. The beam is focused onto the surface of the liquid photopolymer, creating each layer of the desired...
be carved from a potato or other semi-rigid food item. Furthermore, photopolymer stamps are gaining popularity. They are most often produced in a set...
using photopolymer plates. After engraving, the photopolymer is exposed through the imaged black layer and washed out in the traditional photopolymer process...
Stereolithography (SLA) → a laser-cured photopolymer for materials such as thermoplastic-like photopolymers. Selective Laser Sintering (SLS) → a laser-sintered...
bonds in acrylates. Polymerization occurs when photopolymers are exposed to light when photopolymers contain chromophores, otherwise, the addition of...
of poly(phthalaldehyde)". Journal of Photopolymer Science and Technology. 6 (4): 491. doi:10.2494/photopolymer.6.491. B. Zoecklein, K. Fugelsang, B....
process can differ depending on whether solid sheets of photopolymer or liquid photopolymer are used, but the principle is still the same. The plate...
radiation (UV or visible). Synthetic photoinitiators are key components in photopolymers (for example, photo-curable coatings, adhesives and dental restoratives)...
ultraviolet light is focused onto the surface of a vat filled with liquid photopolymer. The light beam, moving under computer control, draws each layer of the...
technique that can store information at high density inside crystals or photopolymers. The ability to store large amounts of information in some kind of medium...
Computer-to-plate (CTP) is an imaging technology used in modern printing processes. In this technology, an image created in a desktop publishing (DTP)...
substrate. There are two main types of printing plate materials: photopolymer and steel. Photopolymer plates are the most popular, as they are easy to use. These...
density, high strain recovery, biocompatibility, and biodegradability. Photopolymers or light activated polymers (LAP) are another type of SMP that are activated...
Light is projected onto the plate as a negative image to expose it. Photopolymer plates are either washed in hot water or under other chemicals according...
adhesives, photopolymer resins, custom printer ink cartridges, Gas pipe sealants, and soak off nail polishes. Chemence is a supplier of photopolymer and commercial...
system spray photopolymer materials onto a build tray in ultra-thin layers (between 16 and 30 μm) until the part is completed. Each photopolymer layer is...
so-called voxel. Voxels are thus the smallest, single volumes of cured photopolymer. They represent the basic building blocks of 3D-printed objects. Other...
bath and is gradually etched in baths which are increasingly acidic. Photopolymer plates, usually used for relief and letterpress printing, can be used...
Resolution Limit From EUV Photoelectron Spread J. Torok et al., J. Photopolymer Sci. & Tech., 27, 611 (2014). "Low Energy Electrons Set the Limits for...
entire body panels of cars. Advances in 3D printing technology, using photopolymers that do not melt during the injection moulding of some lower-temperature...
Desktop Metal purchased EnvisionTEC, a German company that specializes in photopolymer printing. On March 15, Desktop Metal announced its new line Desktop Health...
materials, depending on the needs of the printing method, usually Thermal, Photopolymer or Silver-Halogen (violet) plates are used. They usually have a processing...
Holographic data storage stores information optically inside crystals or photopolymers. Holographic storage can utilize the whole volume of the storage medium...
newspapers. Dry offset printing A printing process which uses a metal backed photopolymer relief plate, similar to a letterpress plate, but, unlike letterpress...
Shen, Z.X.; Chew, S. (1999-01-01). "Curing characteristics of acrylic photopolymer used in stereolithography process". Rapid Prototyping Journal. 5 (1):...
the film is taken to the plate maker, where the film is laid on top of photopolymer plate material. A vacuum is then drawn to ensure tight contact between...
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