DPL UV LED system for security printing

Case study – how LED UV curing system working in security printing process

What is security printing?

Security printing is the field of the printing industry that deals with the printing of items such as banknoteschequespassportstamper-evident labels, product authenticationstock certificatespostage stamps and identity cards. The main goal of security printing is to prevent forgery, tampering, or counterfeiting. More recently many of the techniques used to protect these high-value documents have become more available to commercial printers whether they are using the more traditional offset and flexographic presses or the newer digital platforms. Businesses are protecting their lesser-value documents such as transcripts, coupons and prescription pads by incorporating some of the features listed below to ensure that they cannot be forged or that alteration of the data cannot occur undetected.

 

One of the key technology of security printing is – Hologram.

hologram may be embedded either via hot-stamping foil, wherein an extremely thin layer of only a few micrometers of depth is bonded into the paper or a plastic substrate by means of a hot-melt adhesive (called a size coat) and heat from a metal die, or it may be directly embossed as holographic paper, or onto the laminate of a card itself. When incorporated with a custom design pattern or logo, hologram hot stamping foils become security foils that protect credit cards, passports, bank notes and value documents from counterfeiting. Holograms help in curtailing forging, and duplication of products hence are very essential for security purposes. Once stamped on a product, they cannot be removed or forged, enhancing the product at the same time. Also from a security perspective, if stamped, a hologram is a superior security device as it is virtually impossible to remove from its substrate.

 

LED UV curing and hologram embossing process?

Normally hologram embossing process is a hot and press process. Film pass through nip rollers (steel roll+rubber roll or steel roll+ steel roller which has high temp and high pressure, so the hologram image on one of the rollers will be embossed into the surface of film. The problem for most film is high temp in this process, for example a stamping foil need pass more than 190C in embossing process, meanwhile PET film’s TG temp is about 150C. It means film is stretched in this process, which also damage registered mark in the film as well.

 

LED UV embossing is one of the lasted technology to solve “registered problem” caused by hot hologram embosser. Compared with normal traditional mercury UV lamp, LED lamp curing temp is only 60-70C even at the same energy output. On the other way, LED curing system’s single wavelength also provide the possibility to improve hologram brightness and sharp edge effect.

 

More details, welcome to DPL International service team, we are happy to share our experience on security printing process with you.

 

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