Controlling the paper feed on a micron scale!
In order to realize high image quality by drawing out the high performance of the print head, the paper also needs to be fed with great precision, doesn't it?
- Ikeda
- Yes, that's right. The paper generally passes under the head at a fixed speed. The technology that ensures a constant paper-feed speed, regardless of differences in paper thickness and surface conditions, is not easy to achieve. Furthermore, errors can occur during feeding, resulting in slight deviations in the timing of ink ejection. If all seven ink colors are printed without addressing these errors, image quality will be reduced. To address this, we added a mechanism that measures the fixed distance of errors and makes adjustments by increasing and decreasing the ink ejection speed.
Is that a specialized paper-reading sensor and a device for detecting errors?
- Watanabe
- That's right. It's capable of detecting not only feed errors, but also the stretching and shrinking of paper. It senses errors on a scale of microns and enables paper feeding and ink discharge to be adjusted.
Despite using soft materials such as paper and ink, it adjusts on a micron scale? That's amazing precision.
- Watanabe
- In order to realize consistently high image quality for the DreamLabo 5000, we decided that it was necessary to go to that level.
If that's the case, development of specialized roll paper must have been important too.
- Kamo
- To achieve color reproducibility and high-speed printing, the ink absorbing speed of the ink-receiving layer was increased more than ever to produce high-speed output. In addition, by fixing only the dye component of ink close to the surface of the ink receiving layer, we were able to realize stable, high image quality.
Fixing dye ink (inkjet system) to paper
So, does this mean that there's an upper limit to the amount of ink that can be absorbed by the ink-receiving layer and anything more than that overflows onto the paper?
- Kamo
- That's right. The mechanism of ink absorbing is that ink is absorbed into cavities on the surface of the ink receiving layer. Therefore, if the ink supplied exceeds the cavity volume of the ink receiving layer, the oversupplied ink will spill onto the surface.
However, the specialized paper used by the DreamLabo 5000 is designed with an ink-receiving layer that best matches the printing system. Therefore, high-quality images are achieved at all time without problems such as ink overflowing.
- Teshigawara
- It sounds simple and easy when hearing about the finished product, but ink formulation is important in order to get the best performance out of the media, which is why we made so many prototypes. Eventually, we settled on a design that balanced the two, but we were asked many times to make the ink ejection stronger as it relates to both media and ink (laughs).
- Yamada
- Image quality is directly affected by the performance of the paper regardless of the printing method, but it's particularly pronounced in inkjet printing. Even with a high performance print head and mechanical system, if the paper is no good, image quality will be degraded.
I've heard that high-quality output also boasts excellent durability.
- Kamo
- Yes. Because dye is fixed near the surface of ink receiving layer, it's susceptible to oxidation and light degradation. To handle this, we've also incorporated a formula including anti-oxidant agents and light stabilizer in the ink receiving layer. This makes possible highly durable output that can be stored in an album for approximately 300 years.*1
- *1 Estimates regarding album storage, light resistance and gas resistance (ozone gas) are calculated by Canon in accordance with the indoor thermal stability, indoor light stability and indoor ozone stability testing methods of the Digital Color Photo Print Stability Evaluation (JEITA CP-3901), published by the Standard of Japan Electronics and Information Technology Industries Association
Seven-color ink system with a color gamut surpassing silver halide photography
The DreamLabo's seven-color ink system comprises seven colors, including black, cyan, magenta and yellow, as well as three lighter-color inks—photo cyan, photo magenta and gray. A number of conventional printers use twelve colors; why did you decide on using seven this time?
- Yamada
- We decided that this was the best number of colors to realize a balance between high speed and high image quality. The three light-color inks are for reproducing light and bright colors and are not required if image quality is not of importance. As everyone knows, it takes four colors—black, cyan, magenta and yellow—to reproduce color images. However, image quality decreases when using only four colors to print at high speeds, falling to a level below that deemed acceptable for a commercial photo printer. On the other hand, what would happen if more than seven colors were used? Admittedly, image quality would improve but, accordingly, the composition and control of the main unit would become more complex and would thus affect the sale price. As a result of considering the situation from various perspectives in this way, we decided that seven colors would be best for the DreamLabo 5000.
I can imagine the effect that photo cyan and photo magenta would have on reproducing light and bright colors, but gray doesn't really make sense. What effect does it have?
- Teshigawara
- One effect is that it makes possible monochrome photos with richer gradation. Because printer users include professionals and semi-professional photographers, we felt that it was necessary to ensure the image quality of monochrome images. Another effect is that the use of gray ink enables more stable color reproduction compared with gray produced by combining the four standard ink colors. The combined gray can sometimes appear to have a slight red or blue tinge due to a color cast by the four colors during image processing.
- Yamada
- Based on the principles of color production, I think inkjet printers can reproduce a wider range of colors than silver halide photos can. When we measured the color expression in photos output by the DreamLabo 5000, we found that the machine delivered a level of color representation surpassing that of conventional silver halide photos, *2 which are the type of photos generally printed at stores. Moreover, in addition to a feeling of transparency, FINE technology is characterized by its ability to express depth in dark areas.
To elaborate a little, the advantage of silver halide photography is its ability to reproduce the similar depth and color that are in human memory. During development, we also carried out color processing while considering this area. As a result, we were able to reproduce vibrant colors in both bright and dark areas.
The use of gray ink enables stable color reproduction with less color cast
- *2 As researched by Canon
