Overcoating liquid, ink set, image forming method, and image forming apparatus

• US 9,783,700 B2
• Filed: 02/27/2015
• Issued: 10/10/2017
• Est. Priority Date: 03/11/2014
• Status: Active Grant

• Current Assignee: Ricoh Company Limited
• Original Assignee: Ricoh Company Limited
• Inventors: Tamai, Takashi, Namba, Michihiko, Gotoh, Akihiko
• Primary Examiner(s): NILAND, PATRICK DENNIS
• Application Number:
  US14/633,328
• Publication Number:
  US 20150259567A1
• Time in Patent Office: 956 Days
• CPC Class Codes: B41M 7/0018 using ink-fixing material, e.g. mordant, precipitating agent, after printing, e.g. by ink-jet printing, coating or spraying
• CPC Class Codes: B41M 7/0036 using protective coatings or layers dried without curing
• CPC Class Codes: C09D 11/322 Pigment inks
• CPC Class Codes: C09D 11/40 Ink-sets specially adapted for multi-colour inkjet printing
• CPC Class Codes: C09D 11/54 Inks based on two liquids, one liquid being the ink, the other liquid being a reaction solution, a fixer or a treatment solution for the ink
• CPC Class Codes: C09D 175/04 Polyurethanes

Abstract

An overcoating liquid contains a hydrodispersible polyurethane; a compound represented by Chemical formula 1: C₆F₁₃—CH₂CH₂O(CH₂CH₂O)_nH, where n represents an integer of from 1 to 40; a compound represented by Chemical formula 2: HOR₁R₃C—(CH₂)_n—CR₂R₄OH, where R₁ and R₂ each, independently represent alkyl groups having three to six carbon atoms, R₃ and R₄ each, independently represent methyl groups or ethyl groups, and n represents an integer of from 1 to 6; and water, wherein the overcoating liquid is applied to the surface of a recording medium onto which inkjet ink is already discharged.

Claims

1. An overcoating liquid comprising:

a hydrodispersible polyurethane that includes at least one of polyacrylate-urethane and polycarbonate-urethane;

a compound represented by Chemical formula 1;

C₆F₁₃—

CH₂CH₂O(CH₂CH₂O)_nH, where n represents an integer of from 1 to 40;

a compound represented by Chemical formula 2;

HOR₁R₃C—

(CH₂)_n—

CR₂R₄OH, where R₁ and R₂ each, independently represent alkyl groups having three to six carbon atoms, R₃ and R₄ each, independently represent methyl groups or ethyl groups, and n represents an integer of from 1 to 6; and

water,

wherein the overcoating liquid is applied to a surface of a recording medium on which inkjet ink is already discharged.

2. The overcoating liquid according to claim 1, wherein the compound represented by Chemical formula 1 accounts for 0.05% by weight to 1% by weight.

3. The overcoating liquid according to claim 1, wherein the compound represented by Chemical formula 2 is 2,4,7,9-tetramethyl-4,7-decane diol.

4. The overcoating liquid according to claim 1, wherein the compound represented by Chemical formula 2 accounts for 0.2% by weight to 1% by weight.

5. The overcoating liquid according to claim 1, further comprising polyethylene wax.

6. The overcoating liquid according to claim 5, wherein a mass ratio of the polyethylene wax to the hydrodispersible polyurethane ranges from 0.1 to 1.

8. An image forming method comprising:

discharging inkjet ink to a recording medium comprising a substrate; and

applying the overcoating liquid of claim 1 to a surface of the recording medium on which the inkjet ink is already discharged,

wherein the inkjet ink comprises a hydrodispersible colorant, a wetting agent, a surfactant, a permeating agent, and water.

9. The image forming method according to claim 8, further comprising heat-fixing the overcoating liquid on the recording medium.

10. The image forming method according to claim 8, wherein a coated layer is formed on one or both sides of the substrate and a transfer amount of pure water ranges from 1 mL/m² to 10 mL/m² when a contact time of a surface on which the coated layer is formed is 100 ms.

11. An image forming apparatus comprising:

a discharging device to discharge inkjet ink to a recording medium;

the overcoating liquid of claim 1;

an application device to apply the overcoating liquid to a surface of the recording medium on which the inkjet ink is already discharged,

wherein the inkjet ink comprises a hydrodispersible colorant, a wetting agent, a surfactant, a permeating agent, and water.

7. An inkset comprising:

an inkjet ink comprising;

a hydrodispersible colorant,

a surfactant,

a hydrosoluble organic solvent, and

water; and

an overcoating liquid comprising;

a hydrodispersible polyurethane that includes at least one of polyacrylate-urethane and polycarbonate-urethane;

a compound represented by Chemical formula 1;

C₆F₁₃—

CH₂CH₂O(CH₂CH₂O)_nH, where n represents an integer of from 1 to 40;

a compound represented by Chemical formula 2;

HOR₁R₃C—

(CH₂)_n—

CR₂R₄OH, where R₁ and R₂ each, independently represent alkyl groups having three to six carbon atoms, R₃ and R₄ each, independently represent methyl groups or ethyl groups, and n represents an integer of from 1 to 6; and

water,

wherein the overcoating liquid is applied to a surface of a recording medium on which the inkjet ink is already discharged.