RADIATION-CURABLE INK JET COMPOSITION AND RECORDING METHOD

Abstract

A radiation-curable ink jet composition contains polymerizable compounds including a monofunctional monomer and a multifunctional monomer. The amount of the monofunctional monomer is 90 mass % or more relative to the total amount of the polymerizable compounds. The weighted mean of glass transition temperatures of homopolymers of the polymerizable compounds with the content mass ratio of each of the polymerizable compounds taken as a weight is 42 C. or higher. The weighted means of SP values of the polymerizable compounds with the content mass ratio of each of the polymerizable compounds taken as a weight is from 9.5 to 10.0.

Claims

1. A radiation-curable ink jet composition comprising: polymerizable compounds including a monofunctional monomer and a multifunctional monomer, wherein an amount of the monofunctional monomer is 90 mass % or more relative to a total amount of the polymerizable compounds, a weighted mean of glass transition temperatures of homopolymers of the polymerizable compounds with a content mass ratio of each of the polymerizable compounds taken as a weight is 42 C. or higher, and a weighted means of SP values of the polymerizable compounds with the content mass ratio of each of the polymerizable compounds taken as a weight is from 9.5 to 10.0.

2. The radiation-curable ink jet composition according to claim 1, wherein the weighted mean of glass transition temperatures is 48 C. or higher.

3. The radiation-curable ink jet composition according to claim 1, wherein an amount of the multifunctional monomer is 0.01 mass % or more and 10 mass % or less relative to the total amount of the polymerizable compounds.

4. The radiation-curable ink jet composition according to claim 1, wherein the multifunctional monomer includes a vinyl ether group-containing (meth)acrylic acid ester represented by formula (1):
CH.sub.2CR.sup.1COOR.sup.2OCHCHR.sup.3 . . . (1) wherein R.sup.1 is a hydrogen atom or a methyl group, R.sup.2 is a divalent organic residue having 2 to 20 carbon atoms, and R.sup.3 is a hydrogen atom or a monovalent organic residue having 1 to 11 carbon atoms.

5. A recording method comprising: a discharging step of discharging the radiation-curable ink jet composition according to claim 1 from an ink jet head and attaching the radiation-curable ink jet composition to a recording medium; and an irradiating step of irradiating the ink jet composition attached to the recording medium with radiation.

6. A recorded article comprising: a cured product of the radiation-curable ink jet composition according to claim 1; and a recording medium to which the cured product is attached.

Description

EXAMPLES

[0112] The present disclosure will be described below in more detail by way of Examples. The present disclosure is not limited by Examples below.

1. Preparation of Ink Jet Composition

[0113] First, a colorant, a dispersant, and part of each monomer were weighed and placed in a pigment dispersion tank, and ceramic beads having a diameter of 1 mm were placed in the tank. The mixture was stirred to form a pigment dispersion in which the colorant was dispersed in the monomers. Next, the remaining monomers, a polymerization initiator, and a polymerization inhibitor were placed in a mixture tank, which was a stainless steel container, so as to obtain the composition described in Table 1. The mixture was mixed and stirred to complete dissolution. Subsequently, the pigment dispersion formed as described above was placed in the mixture tank, and the mixture was further mixed and stirred at normal temperature for 1 hour and then filtered through a 5 m membrane filter to obtain a radiation-curable ink jet composition in Example. The value for each component shown in Examples in Table is on a mass % basis.

TABLE-US-00001 TABLE 1 Tg SP Example Comparative Example ( C.) value 1 2 3 4 5 6 7 1 2 3 4 Composition Monofunctional PEA 22 9.99 36.2 38.2 38.4 36.7 38.2 36.0 35.2 40.2 35.7 42.0 33.2 (mass%) monomer NVC 90 10.65 25.0 0.0 0.0 0.0 0.0 0.0 10.0 0.0 0.0 0.0 10.0 ACMO 145 11.55 8.0 14.0 11.0 0.0 12.0 12.0 12.0 17.0 0.0 15.0 15.0 IBXA 94 7.24 8.0 22.0 14.8 0.0 24.0 23.0 12.0 15.0 28.0 0.0 5.0 DCPA 110 10.53 0.0 10.0 10.0 36.7 8.0 7.6 8.0 0.0 14.0 25.2 0.0 TBCHA 38 7.78 7.0 0.0 10.0 8.8 0.0 0.0 5.0 10.0 4.5 0.0 10.0 Multifunctional VEEA 39 9.41 1.0 1.0 1.0 3.0 3.0 5.0 3.0 3.0 3.0 3.0 12.0 monomer Oligomer CN991 27 11.57 2.0 2.0 2.0 2.0 2.0 3.6 2.0 2.0 2.0 2.0 2.0 Polymerization Irg.819 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 initiator TPO 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 Polymerization MEHQ 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 inhibitor Slip agent BYK-UN3500 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 Pigment Carbon black 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 Dispersant solsperse 36000 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 Physical Proportion (mass %) of 96.6 96.6 96.6 94.3 94.3 90.1 94.3 94.3 94.3 94.3 83.9 properties monofunctional monomers in polymerizable compounds Weighted mean ( C.) of glass 42.7 51.0 42.6 42.8 48.2 48.6 48.6 40.6 42.8 48.1 42.6 transition temperatures Weighted mean of SP values 9.9 9.6 9.6 10.0 9.5 9.6 9.8 9.6 9.1 10.4 9.9 Evaluation PP adhesion A A A A A A A A A D D items PET adhesion A A A A A A A A D A D Rub fastness B A B B A A A C B A A Flexibility A A A A A A A A A A D

[0114] The abbreviations and the components of products used in Table 1 are as described below.

[0115] Monofunctional Monomer [0116] PEA (trade name Viscoat #192 available from Osaka Organic Chemical Industry Ltd., phenoxyethyl acrylate) [0117] NVC (available from ISP Japan, Ltd., N-vinylcaprolactam) [0118] ACMO (available from KJ Chemicals Corporation, acryloylmorpholine) [0119] IBXA (available from Osaka Organic Chemical Industry Ltd., isobornyl acrylate) [0120] DCPA (available from Hitachi Chemical Co., Ltd., dicyclopentenyl acrylate) [0121] TBCHA (trade name SR217, available from Sartomer Company, Inc., tert-butylcyclohexanol acrylate)

Multifunctional Monomer

[0122] VEEA (available from Nippon Shokubai Co., Ltd., 2-(2-vinyloxyethoxy) ethyl acrylate)

Oligomer

[0123] CN991 (available from Sartomer, bifunctional urethane acrylate oligomer)

Polymerization Initiator

[0124] Irg. 819 (trade name IRGACURE 819 available from BASF SE, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide) [0125] TPO (trade name IRGACURE TPO available from BASF SE, 2,4,6-trimethylbenzoyl diphenylphosphine oxide)

Polymerization Inhibitor

[0126] MEHQ (trade name p-methoxyphenol available from Kanto Chemical Co., Inc., hydroquinone monomethyl ether)

Slip Agent

[0127] BYK-UV 3500 (available from BYK Additives & Instruments, acryloyl group-containing polyether-modified polydimethylsiloxane)

Colorant (Pigment)

[0128] Carbon black (trade name MA-100 available from Mitsubishi Chemical Corporation)

Dispersant

[0129] Solsperse 36000 (available from The Lubrizol Corporation, polymer dispersant)

2. Evaluation Method

2.1. Evaluation of Flexibility

[0130] Each radiation-curable ink jet composition was applied to a PVC film (JT 5829 R available from Mactac) by using a bar coater such that the thickness of the composition was 10 m. Next, the composition was cured by using a metal halide lamp (available from Eye Graphics Co., Ltd.) at an energy of 400 mJ/cm.sup.2 to form a coating film. The release paper of the PVC film on which the coating film was formed was released and cut into a strip shape having a width of 1 cm and a length of 8 cm to prepare test pieces. The flexibility and elongation of each test piece were measured by using a tensile tester (TENSILON available from ORIENTEC Co., LTD). The elongation was the value at the time when the test piece was cracked when pulled at 5 mm/min. The value was calculated from {(length at crackinglength before stretching)/length before stretching100}. The evaluation criteria are as described below.

Evaluation Criteria

[0131] A: 300% or more
B: 250% or more and less than 300%
C: 200% or more and less than 250%
D: Less than 200%

2.2. Evaluation of PP Adhesion

[0132] Each radiation-curable ink jet composition was applied to a polypropylene board (available from Coroplast, Inc.) by using a bar coater such that the thickness of the composition was 10 m. Next, the composition was cured by using a metal halide lamp (available from Eye Graphics Co., Ltd.) at an energy of 400 mJ/cm.sup.2 to form a coating film. The obtained coating film was evaluated in the cross-cut test in accordance with JIS K5600-5-6.

[0133] More specifically, a 1010 grid pattern was formed by making cross-cuts at intervals of 1 mm using a cutter with the blade of the cutting tool placed on the coating film at right angles. A transparent adhesive tape (25 mm wide) having a length of about 75 mm was attached to the grid, and the tape was rubbed with a finger sufficiently so as to allow the cured film to be seen through the tape. Next, the tape was assuredly released from the cured film at an angle near 60 in 0.5 to 1.0 seconds within 5 minutes after the tape was attached, and the grid condition was visually observed. The evaluation criteria are as described below.

Evaluation Criteria

[0134] A: No peeling of the cured film was observed in the grid.

[0135] B: Peeling of the cured film was observed in less than 10% of the grid.

[0136] C: Peeling of the cured film was observed in 10% or more and less than 50% of the grid.

[0137] D: Peeling of the cured film was observed in 50% or more of the grid.

2.3. Evaluation of PET Adhesion

[0138] The adhesion to a polyethylene terephthalate film was evaluated in the same manner except that a polyethylene terephthalate film (available from Toray Industries, Inc.) was used as a recording medium instead of a polypropylene board (available from Coroplast, Inc.).

Evaluation Criteria

[0139] A: No peeling of the cured film was observed in the grid.

[0140] B: Peeling of the cured film was observed in less than 10% of the grid.

[0141] C: Peeling of the cured film was observed in 10% or more and less than 50% of the grid.

[0142] D: Peeling of the cured film was observed in 50% or more of the grid.

2.4. Evaluation of Rub Fastness

[0143] The cured coating film obtained in the evaluation of flexibility was evaluated in the micro-scratch test in accordance with JIS R3255. The withstand load indicating rub fastness was measured by using a nano-layer scratch tester (CSR-5000 available from Nanotec Corporation). The withstand load was the load under which the stylus reached the medium surface in creating micro-scratches under load. The measurement was performed under the conditions: stylus diameter 15 m, amplitude 100 m, and scratch speed 10 m/sec. The evaluation criteria are as described below.

Evaluation Criteria

[0144] A: 30 mN/cm.sup.2 or more

[0145] B: 25 mN/cm.sup.2 or more and less than 30 mN/cm.sup.2

[0146] C: 20 mN/cm.sup.2 or more and less than 25 mN/cm.sup.2

[0147] D: Less than 20 mN/cm.sup.2

3. Evaluation Results

[0148] Table 1 shows the components of the radiation-curable ink jet compositions used in Examples and the evaluation results. As shown in Table 1, the flexibility, adhesion, and rub fastness are good and all rated B or higher for the radiation-curable ink jet compositions of Example 1 to Example 7 in which the amount of monofunctional monomers is 90 mass % or more relative to the total amount of polymerizable compounds, the weighted mean of glass transition temperatures of homopolymers of the polymerizable compounds with the content mass ratio of each of the polymerizable compounds taken as a weight is 42 C. or higher, and the weighted means of SP values of the polymerizable compounds with the content mass ratio of each of the polymerizable compounds taken as a weight is from 9.5 to 10.0.

[0149] Specifically, as Examples are compared with Comparative Example 1, the rub fastness is found to be further improved when the weighted mean of glass transition temperatures of homopolymers of the polymerizable compounds is 42 C. or higher. As Examples are compared with Comparative Examples 2 and 3, the adhesion is found to be improved when the weighted mean of SP values of the polymerizable compounds with the content mass ratio of each of the polymerizable compounds taken as a weight is in the range from 9.5 to 10.0. As Examples are compared with Comparative Example 4, the flexibility and adhesion are found to be improved when the proportion of monofunctional monomers in the total polymerizable compounds is 90 mass % or more.