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Color PxP-EQ Toner

Color PxP-EQ Toner achieved coexistence of Eco-friendliness and Quality from the two aspects of energy saving (low-temperature fixing) and high-definition (color gamut extension).

Another key to energy saving is to lower the fusion point of a toner

An important key to achieve QSU (Quick Start-Up) of a multifunction copier, to make it ready to use quickly from “sleep mode,” lies in a fixing technology to conduct heat efficiently and to lower the fusion point of the toner. The fuser roller, a bottleneck for quick start-up, needs to be heated to a high temperature to melt the toner. If toner can be melted at a lower temperature, less heat is required.

The Aficio MP C5502/C4502/C3502/C3002 color multifunction copier, which achieved unprecedented energy saving performance, features color PxP-EQ toner, which can be fixed at 30 degrees C lower than the first generation color PxP toner released in 2004 (Figuer 1).

Evolution of lowering fusion point of color PxP toner
Figure 1: Evolution of lowering fusion point of color PxP toner

Ricoh, since starting development, has remained tenacious to challenge polymerization of polyester resins, which might melt at a lower temperature instead of styrene acryl resins that were common as materials in polymerized toners. This was considered difficult at the time. With our efforts, Ricoh PxP polymerized toner was born in 2004. Since then, Ricoh has successively directed its energy towards the pursuit of fixing performance and reliability.

Mixing multiple resins led to success in significantly lowering fusion point

The EQ of Color PxP-EQ toner stands for Eco-friendliness (E) and Quality (Q). We have achieved superiority in two aspects of energy saving (low-temperature fixing) and high-definition (color-gamut extension).

First, it is very important not to spoil storage stability when lowering the fusion point of a toner while achieving fixing at a lower temperature. Simply making the toner melt at a low temperature results in deteriorated toner quality when the toner is stored in a warehouse or is transported in a vehicle. To satisfy the contradictory properties of low-temperature fixability and high storage stability, we blended multiple new polyester resins designed to act advantageously on the respective properties in the Color PxP-EQ toner. In contrast with usual resins (toner), which soften gradually as temperature rises, the color PxP-EQ toner is designed not to change states until it reaches a fixing temperature. It is, however, designed to soften the moment it reaches fixing temperature and is fixed at once. Using these iterations, we achieved a top-class low fusion point toner while maintaining storage stability.

Functions required for a toner
Figure 2: Functions required for a toner

Improved ductility of toner achieved image quality; more natural and easy to read

In the Color PxP-EQ toner, we have improved the ductility (spreading ease) of the toner to achieve a more natural and reader-friendly image quality. With conventional toner, since it was difficult to spread toner uniformly on the uneven surface of paper fiber (Figure 3 (a)), it was necessary to increase the mass of deposit per unit area of toner (Figure 3 (b)). This resulted in the increased consumption of toner. Other problems include the level difference (swelling) resulting from the thickness of toner between portions with and without images, and parts of an image shinier than necessary. In the color PxP-EQ toner, the easy ductile toner made uniform image formation possible with a small mass of deposit per unit area, as shown in Figure 3 (c); with it we have achieved natural legible typography.

Particle diameter and ductility of toner
Figure 3: Particle diameter and ductility of toner

During the development, when ductility was enriched we found that the dots were crushed at the edge of an image at the time of fixing, and the toner extended even into the unnesessary portion and the ooze enlarged. However, by reducing toner particle size uniformly to about 5μm and sufficiently controlling precision, we were able to maintain the resolution. Additionally, this extended the color reproduction area by 10% (Figure 4) compared with conventional toners. Also, it enabled high speed, high definition printing without worrying about the type or thickness of paper.

Extension of color reproduction area
Figure 4: Extension of color reproduction area