Ink set, inkjet recording method, ink medium set, and printing medium

An ink composition forming a first image, and used with an ink composition applied to the first image to form a second image,

• wherein the ink composition forming the first image comprises a first colorant, a first surfactant, a first hydrophobic organic solvent, and water,
• the ink composition forming the second image comprises a second colorant, a second surfactant, a second hydrophobic organic solvent, and water,
• the first and second surfactants are each independently a silicone-based surfactant represented by formula (1):
• wherein in the formula (1), R1 and R2 each independently represents a hydrogen atom, a hydroxy group, an alkyl group having 1 to 6 carbon atoms, or an alkoxy group having 1 to 3 carbon atoms, a is an integer of 1 to 80, x and y are each independently an integer of 1 to 4, m and n are each independently an integer of 1 to 50, o and p are each independently an integer of 0 to 40, a sum of m and n is 2 to 100, and a sum of o and p is 0 to 80,
• the first and second hydrophobic organic solvents each have a water-octanol partition coefficient of 2.00 or more and less than 3.50, and
• when a content of the first surfactant in the ink composition forming the first image is designated as A1 (% by mass), a content of the first hydrophobic organic solvent in the ink composition forming the first image is designated as A2 (% by mass), a content of the second surfactant in the ink composition forming the second image is designated as B1 (% by mass), and a content of the second hydrophobic organic solvent in the ink composition forming the second image is designated as B2 (% by mass), a condition expressed by equation (2) is satisfied:
• 0.05≤[0.5×(B1−A1)+(B2−A2)]≤0.70 (2).

An ink composition forming a second image, and used with an ink composition forming a first image having the second image formed thereon,

• wherein the ink composition forming the first image comprises a first colorant, a first surfactant, a first hydrophobic organic solvent, and water,
• the ink composition forming the second image comprises a second colorant, a second surfactant, a second hydrophobic organic solvent, and water,
• the first and second surfactants are each independently a silicone-based surfactant represented by formula (1):
• wherein in the formula (1), R1 and R2 each independently represents a hydrogen atom, a hydroxy group, an alkyl group having 1 to 6 carbon atoms, or an alkoxy group having 1 to 3 carbon atoms, a is an integer of 1 to 80, x and y are each independently an integer of 1 to 4, m and n are each independently an integer of 1 to 50, o and p are each independently an integer of 0 to 40, a sum of m and n is 2 to 100, and a sum of o and p is 0 to 80,
• the first and second hydrophobic organic solvents each have a water-octanol partition coefficient of 2.00 or more and less than 3.50, and
• when a content of the first surfactant in the ink composition forming the first image is designated as A1 (% by mass), a content of the first hydrophobic organic solvent in the ink composition forming the first image is designated as A2 (% by mass), a content of the second surfactant in the ink composition forming the second image is designated as B1 (% by mass), and a content of the second hydrophobic organic solvent in the ink composition forming the second image is designated as B2 (% by mass), a condition expressed by equation (2) is satisfied:
• 0.05≤[0.5×(B1−A1)+(B2−A2)]≤0.70 (2).