Toner Set Surface Roughness Ratio for Image Clarity
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Solution Overview
Problem
The challenge in achieving high image quality and stability in color printing, particularly in electrophotographic methods, is exacerbated by the low chargeability of black toner due to its low electrical resistance, leading to charge quantity imbalances with color toner, resulting in image blurring and unevenness, especially when printing black and color images side by side.
Innovation Solution
A toner set comprising black and color toners with controlled surface roughness ratios, where the color toner has a surface roughness of 10-30 nm and the black toner has a lower surface roughness, enhancing charge quantity equivalence and electrostatic adhesive force, thereby improving image clarity and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If carbon black or iron oxide is used as colorant in black toner, then the black toner can be produced with standard materials, but the chargeability of the black toner becomes low due to relatively low electrical resistance
Solution Approach 1:
The patent changes the surface roughness parameter of the black toner to be smaller than that of the color toner. This parameter change compensates for the low electrical resistance of carbon black/iron oxide by creating a surface morphology that enhances charge retention and electrostatic adhesive force, thereby improving chargeability stability without changing the colorant materials.
Solution Approach 2:
The patent applies different surface roughness qualities to different toner types: the black toner is given a smoother surface while the color toner has a rougher surface. This local quality differentiation allows each toner type to optimize its electrostatic properties for its specific material characteristics, particularly compensating for the low chargeability of black toner materials.
2Quantity of substance
If the surface roughness of color toner is increased to improve chargeability, then the electrostatic adhesive force improves, but the image quality deteriorates due to blurring and unevenness at color boundaries
Solution Approach 1:
The patent applies different surface roughness qualities to different toner types: the black toner is given a smoother surface (Sa < 30 nm) while the color toner has a rougher surface (Sa ≥ 30 nm). This local quality differentiation allows the color toner to maintain sufficient chargeability while the black toner's smoother surface prevents excessive charge that would cause blurring, thus resolving the contradiction between charge quantity and image clarity.
3Quantity of substance
If the surface roughness ratio between color toner and black toner is controlled within 1.05-5.00, then the charge quantity equivalence is achieved, but the image quality becomes unstable in long-term continuous printing
Solution Approach 1:
The patent narrows and optimizes the surface roughness parameter ranges: black toner Sa is controlled at 5-30 nm and color toner Sa at 10-50 nm, with a ratio of 1.10-3.00. These refined parameter changes ensure both charge quantity equivalence and stable electrostatic adhesive force throughout long-term continuous printing, preventing image quality degradation over time.
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
This approach effectively reduces image unevenness and blurring at color boundaries, maintaining image quality over long-term continuous printing by ensuring equivalent charge quantities between black and color toners, thus stabilizing the electrostatic adhesive force and preventing toner shifting during the printing process.
Implementation Method 1
an electrophotographic method includes: a charging step of charging an electrostatic latent image-bearing member
Implementation Method 2
the toner is moved by an electrostatic force and held
Implementation Method 3
a fixing step of passing the recording material carrying the toner image through a nip portion formed of a pressurizing member and a rotatable image-heating member to fix the toner image with heat and pressure
Data Source
AI summary
A toner set capable of eliminating unclearness in a color boundary of an image in which a color image and a black image are printed side by side. The toner set includes at least: a black toner for forming a black image; and a color toner for forming a color toner image. The black toner is a toner comprising a black toner particle containing a black colorant formed of carbon black or iron oxide, a binder resin, and a releasing agent, and an external additive. The color toner is a toner comprising a color toner particle containing a color organic colorant, a binder resin, and a releasing agent. A ratio in surface roughness (Sa) between the toners is 1.30≤ surface roughness Sa(C) of color toner/surface roughness Sa(Bk) of black toner ≤4.00. The surface roughness Sa(C) of the color toner is 10 nm to 30 nm.