Toner with Controlled Viscoelasticity for Low-Temperature Fixing
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Solution Overview
Problem
Existing toners for electrostatic latent images face challenges in achieving stable continuous printing at low temperatures with minimal fluctuation in gloss levels between the front and rear surfaces, and between sheets, due to issues with viscoelasticity and hot offsetting during the low-temperature fixing process.
Innovation Solution
A toner composition including a particulate toner with a binder resin containing a styrene-acrylic resin, a crystalline polyester resin, and a mold release agent, where the storage and loss moduli are within specific ranges to ensure compatibility between low-temperature fixing characteristics and stability of image gloss, achieved by controlling the molecular weights and acid values of the resin components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a crystalline resin is added to reduce viscoelasticity for low-temperature fixing, then the fixing temperature can be reduced, but the toner exhibits hot offsetting due to excessive viscoelasticity reduction
Solution Approach 1:
The patent changes the molecular weight parameters of the resin components to achieve optimal viscoelasticity. Specifically, it uses a crystalline resin with weight average molecular weight of 10,000 to 50,000 and a specific polydispersity index range, along with controlling the molecular weight distribution of the amorphous resin, to balance low-temperature fixing capability with hot offsetting resistance.
Solution Approach 2:
The patent creates a composite binder resin system combining amorphous resin with controlled molecular weight distribution and crystalline resin with specific molecular weight range. This composite structure allows the amorphous resin to provide low-temperature fluidity while the crystalline resin with controlled parameters prevents excessive viscoelasticity reduction that causes hot offsetting.
2Temperature
If the storage modulus is reduced to improve low-temperature fixing characteristics, then the toner becomes more fusible, but the gloss level fluctuation increases due to excessive softening
Solution Approach 1:
The patent precisely controls the storage modulus parameters by adjusting the molecular weight and polydispersity index of the amorphous resin and the molecular weight range of the crystalline resin. This parameter optimization ensures the toner has sufficient fusibility at low temperatures while maintaining gloss level uniformity by preventing excessive softening.
3Stability of the object's composition
If two immiscible amorphous resins are used to absorb excess heat, then fluidity is maintained, but sufficient sharp-melt characteristics cannot be ensured
Solution Approach 1:
The patent uses a composite resin system where amorphous resin with controlled molecular weight distribution (polydispersity index 1.05 to 1.30) is combined with crystalline resin having specific molecular weight (10,000 to 50,000). This composite structure enables heat absorption stability while achieving sufficient sharp-melt characteristics at low temperatures, overcoming the limitation of using only immiscible amorphous resins.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The toner ensures stable continuous printing with reduced viscoelastic fluctuations and prevents hot offsetting, maintaining uniform gloss levels across the printed images, even at low temperatures.
Implementation Method 1
the fused toner has a low storage modulus and a low loss modulus and the viscoelasticity of the toner is specified only at a certain temperature. Hence, a subtle change in temperature near the fixing temperature will lead to a significant variation in viscoelasticity, resulting in hot offsetting.
Implementation Method 2
the resin B present in an immiscible state in the resin A phase absorbs excess heat at high temperatures at which excess heat is readily applied to the fused toner.
Data Source
AI summary
A toner for developing electrostatic latent images contains a particulate toner which at least includes a colorant, a binder resin, a mold release agent, and a crystalline polyester resin. The binder resin contains a styrene-acrylic resin. The toner has a storage modulus G′, a difference (X) between the maximum value and the minimum value of the storage modulus G′, and a difference (Y) between the maximum value and the minimum value of a loss modulus G″ within the range of 140 to 180° C. satisfying relationships expressed by Conditional expressions (1) 1.0×102≦G′≦1.0×103, (2) 0≦X≦3.0×102, and (3) 0≦Y≦6.0×102.