Ballpoint Pen Ink Composition Suppressing Dripping via Viscosity Control
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Solution Overview
Problem
Existing oil-based ballpoint pen inks struggle with excessive dripping, stringiness, and line skipping, leading to poor writing quality and instability in ink flow.
Innovation Solution
An oil-based ink composition optimized with a resin component and solvent content, where the solvent and water content is 40 mass% or more, and the resin component is 0.5 mass% or less, with specific weight reduction rates and viscosity ratios to minimize dripping and enhance writing smoothness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the ink viscosity is reduced to improve writing smoothness, then the writing feeling becomes smoother, but the dripping phenomenon is not sufficiently suppressed
Solution Approach 1:
The patent applies parameter changes by precisely controlling the ink viscosity within 1-200 mPa·s at 25°C and shear rate 200-2000 s⁻¹, and by regulating the resin content (0.1-5 mass%) and solvent content (40-80 mass%). This optimized parameter range resolves the contradiction by achieving both smooth writing and reduced dripping through balanced formulation rather than extreme values
Solution Approach 2:
The patent uses composite materials by combining specific resin components (such as polyvinyl butyral, polyvinyl acetate, or cellulose derivatives) with solvents (alcohols, esters, or hydrocarbons) and colorants in controlled ratios. This composite ink formulation creates a synergistic effect where the resin provides viscosity control and the solvent system ensures proper flow characteristics, simultaneously achieving smooth writing and minimizing dripping
2Object-generated harmful factors
If resin species are combined to collect excess ink around the tip, then the stringiness is enhanced and dripping is reduced, but excess ink accumulates near the caulking and causes large dripping on the drawn line
Solution Approach 1:
The patent resolves this contradiction by changing the parameter of resin content to a controlled range of 0.1-5 mass%, preventing excessive resin accumulation. Additionally, the ink viscosity is optimized to 1-200 mPa·s to ensure proper ink distribution. This balanced parameter control prevents both insufficient dripping suppression and excessive ink accumulation near the caulking that would degrade line quality
Solution Approach 2:
The patent applies partial action by using a moderate resin content (0.1-5 mass%) rather than high concentrations. This partial resin inclusion provides sufficient stringiness to collect excess ink and reduce dripping, while avoiding the harmful effect of excessive ink accumulation near the caulking. The solution uses just enough resin to achieve the desired effect without over-correcting
3Ease of operation
If the ink viscosity is designed to be low for smooth writing, then the writing feeling improves, but the initial writing property becomes faint and line skipping occurs
Solution Approach 1:
The patent resolves this contradiction through parameter changes by optimizing ink viscosity to a specific range of 1-200 mPa·s at 25°C and shear rate 200-2000 s⁻¹. This controlled viscosity range ensures the ink flows smoothly for comfortable writing while maintaining sufficient concentration and adhesion for strong initial writing properties and preventing line skipping. The patent also controls resin content (0.1-5 mass%) and solvent content (40-80 mass%) to support this balanced performance
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 ink composition effectively suppresses dripping, ensures smooth writing, maintains initial writing quality, prevents ink stretch, and improves line skipping, thereby securing stable ink flow and reducing bleed-through.
Implementation Method 1
an ink storage tube communicates with a tip holding a tip ball via a joint
Implementation Method 2
the tip has a spring therein that constantly presses the tip ball so that the close contact state is released when writing is performed
Implementation Method 3
a solvent containing 60 wt.% or more of an organic solvent having a vapor pressure of 0.2 mmHg (25°C) or less
Data Source
Figure 1
AI summary
Provided are an oil-based ink composition for a ballpoint pen and an oil-based ballpoint pen, which is excellent in the effect of suppression of dripping phenomenon, have good initial property (not faint at the time of writing), have a quick drying property, have no ink stretch at the time of rubbing because of dripping, have improved line skipping, and thus can secure a stable ink flow amount regardless of the ink flow amount design of the tip, and can also improve the bleed-through property because of the suppression of the dripping and the quick drying property. The oil-based ink composition for a ballpoint pen is an oil-based ink composition for a ballpoint pen including at least a colorant, a resin component, a solvent, and water, wherein a content of the solvent and water is 40 mass% or more with respect to a total amount of the ink composition, when a resin having a mass-average molecular weight of 40,000 or more is contained as the resin component, a content of the resin component is 0.5 mass% or less with respect to the total amount of the ink composition, a weight reduction rate A when the ink composition is allowed to stand in an open state for 2 hours under an environment of 50°C and a relative humidity of 35±5%RH is 25% or more, and a ratio A/B of the weight reduction rate A to a weight reduction rate B when the ink composition is allowed to stand in an open state for 2 hours under an environment of 50°C and a relative humidity of 85±5%RH is 0.8 to 1.2. The oil-based ballpoint pen is equipped with the oil-based ink composition for a ballpoint pen.