Canon : Canon Technology | The Minds Behind the Magic

Hirobe: One weak point of electrophotographic printing is that the difference in surface glossiness between areas where toner has been applied and those where it hasn´t (the paper itself). In concrete terms, the areas where there is toner are quite glossy compared with the surface of the paper itself. If you took a look at it you would see what I mean. With offset printing, though, there is almost no difference.

Hirobe: The amount of gloss is determined by the surface of the paper. Did you know that if you look at a piece of paper under magnification, the surface is uneven? The amount of toner that accumulates on the paper and fixes to it differs greatly depending on how rough the paper is. The amount of gloss changes depending on such factors.
With our traditional toner, the level of gloss changed dramatically depending on the paper type. In order to keep the gloss at an optimum level regardless of the type of paper, we had the toner team create toner suited to all kinds of printing media. Then, by altering the conditions for fixing according to the type of paper, we were finally able to achieve beautiful uniform coloration.

Fujikawa: I can´t even remember how many attempts it took to reach that point. (Laughs.)

Hirobe: The development of the new toner that Fujikawa was in charge of and the fixing unit that Kameda was overseeing led to a new system, which was when a commercial press first became feasible. In my opinion, we were able to develop this technology because the combination of fixing and toner worked so well.

Coated paper (high gloss)
= glossy finish

High-quality paper (low gloss)
= matte finish

Achieving natural-looking output adjusted to the glossiness of the paper

Fujikawa: Attaining a broad color gamut was extremely difficult.
In industries such as publishing, the range of color reproduction (color gamut) needs to be wider than for other applications. If the range of color in printed material output by the imagePRESS series were narrower than that of a printing press, then the product´s added value would have been lost.
In addition, we controlled the melting characteristics of the toner to deliver the optimum gloss for the paper being printed on.

Fujikawa: For example, with the imagePRESS, the color of the toner is one thing while the fixed colors are a different matter. After passing through the fixing unit, a single color has to be this color, while a color created by mixing four colors together has to be properly combined to get the correct color. That balance is important.

Fujikawa: The V stands for "vivid."
Beautiful coloration and vivid colors. For a toner, those qualities are an absolute must.

Hirobe "...we added new controls in the form of technology to stabilize the color page by page." (Hirobe)

Hirobe: I think this is also one of the selling points of this product. What we needed to achieve was a high level of stability.
For example, with professionally printed matter, if you print 100 copies of something and the hundredth copy is a little darker or lighter than the rest, that´s unacceptable. That´s why we developed the imagePRESS so that the color would not change at all for runs of up to a few thousand copies, the range that this product is best suited for.
We made possible the output of high-resolution printed matter, but the technology for maintaining the quality over a long print run was difficult. In order to address that problem, we added new controls in the form of technology to stabilize color page by page.

Kameda: Let me put it this way. Let´s say we want to keep producing the color red at the same density; if we think it has gotten a little lighter, we darken it. The technology manages the color for every sheet just that way, from inside the press.

Hirobe: There are many, many factors involved, so I can't cover all of them, but the hardware side of the development team does everything it can to improve performance, like choosing toner that won´t be affected by environmental factors such as temperature and humidity, and incorporating technology to prevent toner degradation.
When colors shifted even after we´d made adjustments, each and every time we checked the color density and used the feedback to achieve stable performance.

Kameda: The method of applying heat to the toner was really difficult.
Previously, heat was applied to the paper by means of a roller with a heater in the center, which melted the toner and fixed it to the paper. With that method, though, when the paper is pushed between the fixing roller and the pressure roller to even out the toner, the pattern breaks up, which distorts the image.
With the imagePRESS series, we adopted the belt fixing method in order to apply heat uniformly over a wider area and melt the toner cleanly without blurring, producing the finish we wanted.
In belt fixing systems, heat is applied for a long time so that the toner fixes neatly without smudging.

Hirobe: Yes, especially between image development, which I was looking after, and the fixing system that Kameda was in charge of. We continue to argue even now. (Laughs.)

Kameda: Let´s say, for example, the fixing team chooses a toner that melts easily. Then the image development team upstream starts complaining, saying that it makes controlling the image harder. Every time a problem occurs, there´s a whole lot of "OK, what do we do?" and "We´ll do this, so you should do that." (Laughs.)

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