Electrostatic Toner with Silane-Modified Polyester Coating
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Solution Overview
Problem
Electrophotographic toners experience changes in packed bulk density and gradation reproducibility when stored at high temperatures for extended periods, leading to reduced image quality due to the burial of external additives within the toner particles, which affects their charging and packing characteristics.
Innovation Solution
The use of toner particles comprising a polyester resin and a styrene-(meth)acrylic resin, with external additives of poly[alkyl (meth)acrylate] particles, where the poly[alkyl (meth)acrylate] particles are present in specific amounts and ratios relative to the toner particles, and the styrene-(meth)acrylic resin is deposited on the toner particle surfaces in specific proportions to maintain distance and prevent burial, thereby controlling the packed bulk density and gradation reproducibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If toner is stored at high temperature for extended periods, then storage stability is improved, but external additives become buried within toner particles causing deterioration of charging characteristics and image quality
Solution Approach 1:
A silane-modified polyester resin coating layer is applied as an intermediary between the toner particle core and the external additive particles. This coating layer acts as a barrier that prevents the external additives from being buried into the toner particles during high-temperature storage, thereby maintaining charging characteristics while allowing long-term storage. The coating layer has specific glass transition temperature and flexibility to accommodate thermal expansion without cracking.
Solution Approach 2:
The invention controls specific parameters of the coating layer including glass transition temperature (Tg: 40-80°C), thickness (1-10 nm), and composition (silane-modified polyester resin with specific molecular weight and hydroxyl value). By optimizing these parameters, the coating layer maintains its protective function during high-temperature storage while preserving the electrical properties needed for charging.
2Reliability
If external additive amount is increased to improve charging characteristics, then charging performance is improved, but packed bulk density becomes unstable and additives are more prone to burial
Solution Approach 1:
The silane-modified polyester resin coating layer serves as a protective intermediary that allows higher amounts of external additives to be applied without causing burial. The coating layer anchors the external additives to the toner particle surface, maintaining stable packed bulk density even with increased additive content, while preserving improved charging characteristics.
Solution Approach 2:
The invention creates a composite structure consisting of the toner particle core, the silane-modified polyester resin coating layer, and the external additive particles. This composite structure combines the electrical properties of the external additives with the protective and adhesive properties of the silane-modified resin coating, achieving both stable packed bulk density and reliable charging characteristics.
3Shape
If styrene-(meth)acrylic resin content on toner surface is increased to control particle morphology, then particle surface properties are improved, but external additive burial is accelerated at high temperature
Solution Approach 1:
The silane-modified polyester resin coating layer is positioned as an intermediary between the styrene-(meth)acrylic resin-containing toner core and the external additives. This coating layer prevents direct interaction between the external additives and the thermoplastic styrene-(meth)acrylic resin surface, which would otherwise cause additive burial during high-temperature storage. The coating layer maintains particle surface properties while protecting against additive migration.
Data Source
AI summary
An electrostatic-image developing toner includes a toner particle including a polyester resin and a styrene-(meth)acrylic resin, and an external additive including a poly[alkyl (meth)acrylate] particle. The amount of the poly[alkyl (meth)acrylate] particles is about 0.05 parts by mass or more and about 1.0 parts by mass or less relative to 100 parts by mass of the toner particle. The ratio D50P/D50T of the number-average diameter D50P of the poly[alkyl (meth)acrylate] particles to the number-average diameter D50T of the toner particles satisfies 0.03≦D50P/D50T≦0.15. The proportion of the styrene-(meth)acrylic resin in a resin component deposited on the surface of the toner particle is about 5 atom % or more and about 30 atom % or less as determined by X-ray photoelectron spectroscopy (XPS).