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2022/9/17

TOYOBO develops laser printable film ‘Lesire’ that can create specific colors

'Lesire' is TOYOBO CO., LTD's laser printing technology for package labels that produces specific colors on the irradiated area by laser light in a specific wavelength range. It is the first ever direct printing solution in which conventional laser devices can be adopted for this purpose in the packaging industry (based on our own investigation as of December 20th, 2021). The new technology saves costs and time when compared to thermal transfer printing and IJ printing, the traditional technologies widely used for printing expiry dates and production lots on packages of consumable items. Also, there is no longer a need for ink removal as part of the material recycling process.

Printing without the use of inks and coating agents

Hot stamp printing (with ink ribbons), thermal transfer printing (with thermal ribbons), and non-contact printing (e.g. IJ printing and laser marking) are commonly used for printing variable information such as expiry date, production lot, and identification code on package labels in the food, cosmetic and other industries. There is also a risk that the ink might rub off after printing due to friction. Additionally, the process involves continuous replacement of consumables, such as ink ribbons and laser-sensitive ink coating agents. Moreover, it is necessary to clean the ink and coating agent in the waste film recycling process. So, we could deal with this material recycling challenge with a much more environmentally sustainable approach.

“It’s important to go environmental-friendly!”, expressed Tomoyuki Hashida from the Packaging Business Management Division when talking about the background of the development of Lesire. “Instead of sticking labels on the product packages, we need to reduce packaging materials and simplify complicated processes by printing directly on the package. Considering simplifying the recycling process of packaging materials, we came up with the idea of printing directly on the package without using ink or coating agents. Based on the continuous discussion with Shintaro Ishimaru from our Inuyama Films Technology Center, we officially started the development of laser printing.”

Color development in response to laser

in the wavelength range of

approximately 355 - 1064nm

Lasers penetrate through conventional plastic films while Lesire reacts with UV laser (wavelength 355 nm), YAG laser and fiber laser (wavelength 1064 nm) to generate heat. This serves to produce color in a mechanism in which the resin of the film itself produces color, as opposed to using a layer structure in which laser-sensitive ink or coating agent is applied to the film. Therefore, there is no need for pretreatment to apply laser-sensitive ink to the printing area. All we have to do is to install a laser irradiation device. Furthermore, as consumables (i.e ink ) are not involved, there is no need to replace ink ribbons.

Currently, transparent type and milky white type are available for both polypropylene and polyester, the most common materials for package labels. With YAG laser*, fiber laser, and UV laser, we can print on Lesire using a general irradiation device. At the current stage, it has been confirmed that the quality of UV laser print is the highest, although its device is relatively expensive amongst all conventional equipment.

*A solid-state laser using a crystal composed of yttrium aluminum garnet as a medium.

“Colors are developed by lasers in the wavelength range of 355 to 1,064 nm. Currently, this makes CO2 lasers (wavelength 10,600 nm) incompatible with our technology. The printing speed depends on the performance of the device and the printing specifications. Mr. Ishimaru also revealed that heat resistance of the film has to be increased using their exclusive film-forming technologies for PP Lesire with a low heat resistance, which prevents the base material from shrinking due to the heat of laser irradiation. The transparent-type printing is in golden ink while the milky white-type print is in a grayish color. These colors are opaque and provide an alternative to foil stamping (gold ink). “It’s been difficult to create the golden color well with conventional ink printing methods. Additionally, foil stamping is expensive and time consuming. Lesire makes it possible to create “foil-like design” as has never been before. Regarding color variety, our clients have already expressed interest in developing other colors in the future. “Definitely, it’s what we would love to work on” commented Mr. Ishimaru. One more thing that needs to be evaluated is the effect of the colored resin on recycled materials.

The laser printing area is extremely small with respect to the film area. But we still need to verify whether or not the colored resin will be dispersed in the recycling process and affect the color.

Application to internal components

as an industrial use, not only to

packaging labels

The use of Lesire is not only limited to secondary packaging such as external labels for food and cosmetics- it also has potential in many other applications.

“For instance, the packaging can be become much simpler and more practical when Lesire is used in primary packaging with direct contact with the product. The milky white-type OPP has heat-sealing properties, so I am convinced that it can also be used as a sealant,” added Mr. Hashida. Mr. Ishimaru, on the other hand, revealed that the technology has great value in terms of industrial use. “From automobiles to smartphones, we need serial numbers and other design printing on different industrial components. So, the technology might, all in all, help to solve a string of problems in the future!”

Samples of Lesire have been available since early December last year and the feedback from the market has been great. Inquiries were received not only from converters but also from user companies and laser equipment manufacturers.

“It was a surprise for us to have received inquiries from laser device manufacturers. Personally, I also hope that this will be an opportunity for us to initiate collaborations with equipment manufacturers,” commented Mr. Ishimaru.

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