Printing photopolymer

Letterpress. This is the oldest printing process stiU in use. It continues to be replaced by newer printing processes. Printing is conducted from a raised image area of the printing plate. Inks in the printing process are transferred directly from a raised area to a substrate. The printing plates contain a thick layer of photopolymer (often a mixture with polymer such as poly(vinyl alcohol) deposited over a plastic or aluminum base. 

Printing is conducted with a printing plate similar to letterpress. However, the chemistry of the photopolymer is somewhat different in order to... 

Flexographic Printing Plates. There are three primary types of flexographic printing plates molded mbber, soHd-sheet photopolymer, and hquid photopolymer. 

Photopolymerization reactions are widely used for printing and photoresist appHcations (55). Spectral sensitization of cationic polymerization has utilized electron transfer from heteroaromatics, ketones, or dyes to initiators like iodonium or sulfonium salts (60). However, sensitized free-radical polymerization has been the main technology of choice (55). Spectral sensitizers over the wavelength region 300—700 nm are effective. AcryUc monomer polymerization, for example, is sensitized by xanthene, thiazine, acridine, cyanine, and merocyanine dyes. The required free-radical formation via these dyes may be achieved by hydrogen atom-transfer, electron-transfer, or exciplex formation with other initiator components of the photopolymer system. 

Typical of the temporary or manufacturing aid coating systems is the RISTON dry film photoresist for printed circuit (PC) board fabrication. This was the first of these systems developed. The RISTON product stmcture and the basic steps in its use are shown in Figure 2. It consists of a photopolymer sheet laminated between a Mylar cover sheet and a polyolefin separation sheet. It is manufactured as a continuous web (see Coating PROCESSES, survey), and is suppHed in roUs of varying width and photopolymer composition. 

Figure 14.13. An engine block printed by processing photopolymers. (http //www.2objet. com/Misc/Gallery/tabid/70/AlbumID/393-3/Default.aspx).

Napadensky, E. 2005. Ink-jet 3d printing of photopolymers materials An emerging rapid prototyping technology. Proceedings—RadTech Europe 05 UV/EB 2 193-197. 

This review will highlight the interrelationships between basic photopolymer science and practical applications of this technology. Each application of photopolymer technology can be described in terms of three primary descriptors the mode of exposure, the mechanism of the photopolymer reaction employed and the visualization method used. Using this foundation, the widely diverse applications of photopolymer technology to electronic materials, printing materials, optical and electro-optical materials, the fabrication of devices and polymeric materials, adhesives and coating materials will be discussed. 

Photo/Thermal Reactions. The fifth basic class of photopolymer chemistry that can be used in commercial applications is based more on physical changes in a polymer-based matrix than on chemical reactions. A recent application of this technology is the laser ablation (77) of an organic coating on a flat support to directly produce a printing plate. The availability of newer high energy lasers will allow more applications to be based on the photo/thermal mechanism. 

Electronic Materials. Applications of photopolymer technology to electronic products is probably one of the largest imaging categories in terms of sales and total number of patents and publications. A wide variety of products have been developed for the production of printed wiring boards (PWB) and the manufacture of integrated circuits (IC). 

Manufacture of Printed Wiring Boards. Printed wiring boards, or printed circuit boards, are usually thin flat panels than contain one or multiple layers of thin copper patterns that interconnect the various electronic components (e.g. integrated circuit chips, connectors, resistors) that are attached to the boards. These panels are present in almost every consumer electronic product and automobile sold today. The various photopolymer products used to manufacture the printed wiring boards include film resists, electroless plating resists (23), liquid resists, electrodeposited resists (24), solder masks (25), laser exposed photoresists (26), flexible photoimageable permanent coatings (27) and polyimide interlayer insulator films (28). Another new use of photopolymer chemistry is the selective formation of conductive patterns in polymers (29). 

Printing Materials. The application of photopolymer technology to a wide variety of imaging applications in the printing industry is a quite important. Most printing plates and pre-press proofing products used today are based on, or utilize some element of, photopolymer chemistry. 

Other Printing Applications. There are a number of lower volume applications of photopolymer chemistry to the printing industry. Some of these include the production of tactile images (raised Braille patterns) (47) and screen stencil resists... 

Fabrication of Devices and Materials. Many of the previously discussed applications of photopolymer technology have utilized photopolymer materials to manufacture a part that is then incorporated into commercial products (e.g. film resists used to manufacture printed circuit boards). One area that has been increasing very rapidly in the past 5-6 years has been the use of photopolymer chemistry to fabricate devices and materials that are used directly in the final product. This development has been made possible, in part, by the design of new photopolymer chemistry that can produce polymerized materials with enhanced physical properties. 

Synthesis and Properties of Photopolymer Printing Plates for a Printing Master Plate by Modification of Polyvinyl Alcohol... 

A number of photopolymer printing plates are already known. Their basic structures are to combine one of the general purpose resins such as cellulose (1), polyamide (2J, polyester, poly urethane (3j, polyvinyl alcohol (4), synthetic rubber (5) and the like with photopolymerizing vinyl monomer, photopolymerization initiator and so on. Any one of the plates of such structures can be used as a press plate, but they can not be used as an original plate for duplicate plate owing to their insufficient hardness, toughness and the similar negative properties. 

Therefore, metal plates have been conventionally used. We have performed the research and development of a photopolymer printing plate for a master plate with a new basic structure by combining an oligomer of urea structure having a polyvinyl base with polyvinyl alcohol, photopolymerization initiator and other ingredients. The result shows that the newly developed plate (6) is so good that it has replaced metal plates and has been stably used at leading newspaper companies in Japan where several millions of newspapers are daily issued. 

Figure 4. Structure of photopolymer printing plate for duplicate plate. ( ) The plate of the present development (hereafter referred to as the Photopolymer Plate).

The Photopolymer Plate of over 85° Shore D hardness can stand temperatures over 160°C, and it could be successfully used as a master plate for making thermoformed matrix of phenol group resin to be used for thermoformed polymer printing plates such as rubber plates and the like under conditions of 30 kg/cm2 pressure... 

Figure 19. Thermoformed rubber printing plate and matrix by the Photopolymer...

The Photopolymer Plate, a water developable photopolymer relief printing master plate made by modification of polyvinyl alcohol with urea group oligomer having a functional polyvinyl base, for making paper mold and matrix for printing master plates, has characteristics which are very close to those of the conventionally etched metal relief printing plates and has some superior points to them. 

Because of these advantages, the Photopolymer Plate has been accepted by most of the leading Japanese newspaper companies and it is attracting more people in different field of the printing industry. 

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