The challenge of achieving the high-speed continuous printing of high-quality images
Canon has made significant achievements not only in the area of consumer inkjet printers, but also large-format and other business inkjet printers. However, the newly developed DreamLabo 5000 marks Canon's entry into a new field. What conditions had to be met for it to succeed as a product?
- Ikeda
- Ensuring both high image quality and high productivity was essential because it is a commercial photo printer for the retail photo industry.*1 The high image quality enables photo output on par with conventional silver-halide photos as well as the printing of high-definition text. High productivity ensures that printing is fast and that the equipment runs non-stop.
- Yamada
- Although we've accumulated "FINE"*2 technology over many years, printing high-quality images at high speeds is not easy. It was a level of technology that Canon was venturing into for the first time.
How long and how large was the development project?
- Teshigawara
- I can't go into specific figures, but the period and scale of the project was of a level that doesn't even compare with projects for consumer products that I have worked on before. Creating something this new requires considerable power.
What was the greatest issue you imagined you would face in development?
- Teshigawara
- Of course, this project involved the development of a print head that would enable "one-pass printing." We used roll paper to increase productivity and adopted "one-pass printing," which requires only a single pass of the printing paper. This meant that a major issue was the need for an unprecedented wide-type print head that remains in a fixed position during paper feed to realize continuous high-quality photo printing.
The DreamLabo 5000 print head
- Hirosawa
- To be more precise, the specifications called for a print head with a higher nozzle density that enabled a maximum print width of 305 mm. In conventional inkjet printers, the print head moves back and forth during printing so there are various ways you can go about improving print quality, but in the DreamLabo 5000 the print head is fixed. Because print quality is determined by the performance of the head itself, we faced some tough challenges during development.
I see. So does that mean you had trouble drawing out, or supporting high performance in virtually every aspect related to the print head? Such as achieving a stable paper feed and ensuring the high-speed processing of print data?
- Watanabe
- Exactly. The number of sensors and motors, and the volume of circuitry and wiring in the machine differs from Canon's consumer-model inkjet printers by an order of two digits. The total area of the control board we made to check the mechatronics portion of the prototype was around the size of four and a half tatami mats (7.425m2) (laughs).
- Teshigawara
- To be honest, when I got a look at that, I thought the development would fall apart (laughs). It definitely wasn't a size that would fit inside the main unit. That was a hurdle we weren't expecting.
Mr. Watanabe, were you confident that you could fit something so large inside the main unit?
- Watanabe
- It wasn't a matter of having confidence or not. It just needed to be done. It was much later that I heard of the doubts the other team members had regarding whether or not development was even possible, and I think they were careful in trying not to lower the spirits of us in the electrical design team (laughs).
- *1 Retail photo industry
Over-the-counter and Web-based print-service business targeting the production of photo prints, photo albums and other photo materials - *2 FINE (Full-photolithography Inkjet Nozzle Engineering)
Canon's proprietary core technology for inkjet printing
How the high-performance wide print head was developed
Now I would like to ask you about the print head, the core of this development. To what degree did you increase the nozzle density?
- Hirosawa
- The number of head nozzles for each color was increased to around 100 times the number in Canon's consumer printers, and there is one print head for each of the seven colors.
That's amazing. Was it because chip production technology has advanced so much that you were able to increase the density that much without fundamentally changing the existing principle of FINE or the drive format?
- Hirosawa
- I think you could say that. It was the culmination of ten years of FINE development and production. Also, a major issue with regard to print head production technology was ensuring the uniform ejection of ink droplets. We couldn't allow any variation between the nozzles or between the chips. When we affixed the chips to the print heads, we needed to make sure that there were no deviations. If we weren't able to produce these with the required level of precision, we wouldn't have been able achieve the image quality to match the specifications.
- Teshigawara
- Actually, even with such a high-performance print head, it wouldn't be possible to realize excellent printing results without establishing the necessary conditions during the operation of the print head.
What do you mean?
- Teshigawara
- In order to stably eject a certain amount of ink with a certain amount of force, you need to ensure an optimal temperature within the print head and a proper level of humidity around the print head. To achieve this, it's necessary to adjust the temperature of ink supplied to the print head and the quality of the air in the print head.
- Nakao
- It was mentioned just a little while ago about all the sensors and motors there are, and how there's a massive amount of wiring compared with a normal printer, but this is the result of all the efforts we made at every stage to maintain the right conditions for the head when printing. Even in the firmware that controls the printer as a whole, a substantial amount of development was focused on the control system for optimizing the print head environment.
DreamLabo enables the printing of small and complex text without allowing them to become illegible. Were some special steps taken with the print head to enable this?
- Hirosawa
- We didn't do anything special to the nozzles or the head. We made it so that the satellite droplets, the smaller droplets that separate from the main droplet of ink that is ejected from the nozzle, lands on the same impact point as the main droplet.
- Teshigawara
- Normally, with inkjet printing, which uses liquid ink, you get satellite droplets apart from the main droplets each time ink is ejected. It's unavoidable due to the printing principle involved. Until now, the location where satellite droplets landed was just a little off from where the main droplets landed, which led to misshapen dots. With the DreamLabo 5000, we've virtually eliminated this obstacle to image quality. That's why it's capable of clearly printing text as small as 3 points in size.
How did you overcome this obstacle?
- Hirosawa
- We comprehensively considered interrelated factors, such as the differences in timing and direction of the main droplets and satellite droplets, the distance between the head and the paper, and the composition of the ink, and adjusted these to ensure that the droplets create true round dots.
