What is the core difference between a Rollerball Pens and a ballpoint pen?

Rollerball Pens mainly use water-based ink or neutral ink, which is based on water as the solvent, with dyes and a small amount of surfactants added, and the ink viscosity is low. This ink has stronger permeability and can be quickly absorbed by paper fibers, but may cause slight bleeding on thin paper. Ballpoint pens use oil-based ink, which is made of mineral oil or synthetic oil as a solvent and mixed with high-concentration pigments. It has extremely high viscosity and a paste-like texture. The ink liquefies due to the heat generated by rolling friction, dries faster and is not easy to smudge.
The tip of the Rollerball Pens is usually made of tungsten carbide or ceramic, with a diameter of 0.5-0.7 mm. Because water-based ink has strong fluidity, only slight pressure is needed to form a continuous ink mark when writing, and the lines are even and delicate, which is suitable for long-term writing. The ball of the ballpoint pen has a larger diameter, and it needs to apply more pressure to bring out the ink with high-viscosity ink. Long-term use can easily cause hand fatigue, and the edge of the line may accumulate ink. "Ink accumulation" phenomenon.
Roller-ball pens have high requirements for the smoothness of the paper surface. The ink may break on rough or coated paper, and the water-based ink is easy to evaporate and dry when exposed to the air. The pen cap should be tightly closed after use. Its advantage is that the color expression is strong, and a rich color range can be achieved by mixing dyes, which is suitable for note-taking or artistic creation. With the strong adhesion of the ink, the ballpoint pen can write on carbon paper, thermal paper and even plastic surfaces. The sealed structure enables it to stably produce ink at extreme temperatures or inverted states, which is more suitable for bill filling, field recording and other scenes.
Oil-based ballpoint pen ink has stronger light resistance and oxidation resistance, and the written content can be preserved for more than ten years, which meets the archive management standards. The water-based ink of the ballpoint pen is easy to fade under ultraviolet light. Although the neutral ink has improved, it is still weaker than the durability of oil-based ink. From an environmental perspective, Rollerball Penss usually adopt a replaceable refill design to reduce plastic consumption; ballpoint pens are relatively more stressful on the environment because the ink is difficult to degrade after solidification.