Electrophotographic Toner Acid Value Control for Streak Prevention

The patent applies parameter changes by precisely controlling the molecular weights of the polyester resins (resin (i) with Mw 30,000-100,000 and resin (ii) with Mw 8,000-12,000) and their acid values (A, B, and C satisfying B>A>C). These parameter specifications ensure the toner maintains stable image quality even after prolonged storage at high humidity, preventing streak-form defects while preserving normal toner processing characteristics.

The patent employs composite materials by formulating the toner with a specific combination of crystalline polyester resin and non-crystalline polyester resins in defined proportions (resin (i) 10-40 parts, resin (ii) 30-70 parts, resin (iii) 10-40 parts by mass). This composite structure creates synergistic effects that enhance both the toner's stability during storage and its image-forming performance, resolving the contradiction between reliability and storage duration.

The patent applies preliminary action by pre-formulating the toner with specifically designed polyester resin combinations and controlled molecular weight distributions before storage. This preliminary structuring of the toner composition creates inherent stability that prevents photoreceptor surface contamination even when stored at high humidity for extended periods, allowing storage flexibility without suffering from streak-form defects.

The patent effectively makes the toner resistant to degradation by designing it to behave as if it were stable and reusable under harsh storage conditions. The specific resin formulation (with controlled acid values and molecular weights) prevents the toner from becoming contaminated or degraded during storage, thereby maintaining photoreceptor surface cleanliness and preventing streak-form image defects even after long-term high humidity exposure.

The patent applies local quality by creating a differentiated structure where crystalline polyester resin (resin (iii)) is embedded within a matrix of non-crystalline polyester resins (resin (i) and resin (ii))). The crystalline resin provides low-temperature fixability at the molecular level, while the non-crystalline resins with higher acid values (A and B) form a stable outer structure that prevents surface exposure. This local differentiation of resin functions and positions resolves the contradiction between low-temperature fixability and composition stability.

The patent applies the nested doll principle by structuring the toner composition with crystalline polyester resin (resin (iii)) nested within or surrounded by non-crystalline polyester resins (resin (i) and resin (ii))). This nested arrangement allows the crystalline resin to provide its low-temperature fixability function while being protected by the outer non-crystalline resin layers, preventing surface exposure and maintaining composition stability. The hierarchical nesting of different resin types resolves the contradiction between functional performance and compositional stability.