The present application is based on, and claims priority from JP Application Serial Number 2019-166070, filed Sep. 12, 2019, the disclosure of which is hereby incorporated by reference herein in its entirety.

BACKGROUND

1. Technical Field

The present disclosure relates to a radiation-curable ink jet composition and an ink jet method.

2. Related Art

An ink jet recording method can record high definition images with a relatively simple apparatus and has been rapidly developed in various fields. In such circumstances, improvement in various characteristics has been variously investigated. For example, JP-A-2012-116934 discloses a radiation-curable ink jet ink composition containing 20 mass % or more and 50 mass % or less of a vinyl ether group-containing (meth)acrylate and 5 mass % or more and 15 mass % or less of N-vinylcaprolactam for the purpose of providing a radiation-curable ink jet ink composition showing excellent scratch resistance, adhesion, and alcohol resistance and a recorded matter and an ink jet recording method using the ink composition.

In addition, JP-A-2012-162688 discloses a photocurable ink jet ink composition containing 40 mass % or more and 75 mass % or less of a vinyl ether group-containing (meth)acrylate, 1 mass % or more and 20 mass % or less of a urethane (meth)acrylate oligomer, and a photopolymerization initiator for the purpose of providing a photocurable ink jet ink that can provide printed matter having excellent film characteristics, in particular, stretchability, while having low viscosity and high reactivity.

However, although N-vinylcaprolactam that is used in JP-A-2012-116934 shows excellent adhesion and scratch resistance of a coating film, since the boiling point is low, handling at ordinary temperature is difficult. In addition, since it tends to increase the viscosity of ink, there is a problem that a lot of use for ink jet ink is difficult. In addition, since the urethane acrylate oligomers that are used in JP-A-2012-162688 tend to increase the viscosity of ink, a lot of use for ink jet ink is difficult. In addition, since they are multifunctional, there is a problem that they are inferior in stretchability of a coating film. Inks having these problems tend to be unsuitable for, in particular, sign application. Accordingly, there is a demand for a radiation-curable ink jet composition hardly increasing the viscosity of ink and having excellent stretchability.

SUMMARY

The present disclosure is a radiation-curable ink jet composition including a monofunctional (meth)acrylate monomer and vinyl methyl oxazolidinone.

In the radiation-curable ink jet composition, the content of the vinyl methyl oxazolidinone may be 5 to 40 mass % based on the total amount of the radiation-curable ink jet composition.

In the radiation-curable ink jet composition, the content of the monofunctional (meth)acrylate monomer may be 10 to 50 mass % based on the total amount of the radiation-curable ink jet composition.

The radiation-curable ink jet composition may include a vinyl ether group-containing (meth)acrylate represented by the following formula (1):
H2C═CR1—CO—OR2—O—CH═CH—R3
(where, R1is a hydrogen atom or a methyl group, R2is a divalent C2-C20 organic residue, and R3is a hydrogen atom or a monovalent C1-C11 organic residue).

In the radiation-curable ink jet composition, the content of the vinyl ether group-containing (meth)acrylate may be 10 to 50 mass % based on the total amount of the radiation-curable ink jet composition.

The radiation-curable ink jet composition may include, as the monofunctional (meth)acrylate monomer, at least any of a monofunctional alicyclic (meth)acrylate, a monofunctional (meth)acrylate having a cyclic ether structure, or a monofunctional (meth)acrylate having a crosslinked condensed ring structure.

The radiation-curable ink jet composition may include a multifunctional (meth)acrylate, and the content of the multifunctional (meth)acrylate may be 2 to 20 mass % based on the total amount of the radiation-curable ink jet composition.

The radiation-curable ink jet composition may include a urethane acrylate oligomer, and the content of the urethane acrylate oligomer may be 1 to 10 mass % based on the total amount of the radiation-curable ink jet composition.

The radiation-curable ink jet composition may include a 2,2,6,6-tetramethylpiperidinyl-1-oxyl derivative as a polymerization inhibitor.

The radiation-curable ink jet composition may include an acylphosphine oxide-based polymerization initiator as a photopolymerization initiator.

The radiation-curable ink jet composition may include a fluorescent whitener.

In addition, the ink jet method of the present disclosure includes a discharging step of discharging the radiation-curable ink jet composition by a liquid jet head to adhere the composition to a recording medium and an irradiation step of irradiating the radiation-curable ink jet composition adhered to the recording medium with radioactive rays.

