Actinic-ray-curable ink set for ink-jet recording

Abstract

To provide an actinic-ray-curable ink set for ink-jet recording which is excellent in thick-film curability even when a UV-LED lamp is used as a light source, and has uniform curing sensitivity across different colors. The present invention relates to an actinic-ray-curable ink set for ink-jet recording, characterized in that a cyan ink contains a phthalocyanine pigment, a radical polymerizable compound, and less than 10% by mass of a photopolymerization initiator based on the total amount of the cyan ink, a magenta ink contains a quinacridone-based pigment, a radical polymerizable compound, and less than 5% by mass of a photopolymerization initiator based on the total amount of the magenta ink, a yellow ink contains an azo pigment, a radical polymerizable compound, and less than 10% by mass of a photopolymerization initiator based on the total amount of the yellow ink, and a black ink contains a carbon black, a radical polymerizable compound, and less than 12% by mass of a photopolymerization initiator based on the total amount of the black ink.

Claims

1. An actinic-ray-curable ink set for ink-jet recording, comprising a cyan ink, a magenta ink, a yellow ink, and a black ink, the cyan ink comprising a phthalocyanine pigment, a radical polymerizable compound, and 3 to 10% by mass of a photopolymerization initiator based on the total amount of the cyan ink, wherein an acylphosphine oxide-based photopolymerization initiator in the photopolymerization initiator in the cyan ink comprises bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide and 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide at a mass ratio of 0.1 to 0.4; the magenta ink comprising a quinacridone-based pigment, a radical polymerizable compound, and 1 to 5% by mass of a photopolymerization initiator based on the total amount of the magenta ink, wherein an acylphosphine oxide-based photopolymerization initiator in the photopolymerization initiator in the magenta ink comprises bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide and 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide at a mass ratio of 0.4 to 0.8; the yellow ink comprising an azo pigment, a radical polymerizable compound, and 3 to 10% by mass of a photopolymerization initiator based on the total amount of the yellow ink, wherein an acylphosphine oxide-based photopolymerization initiator in the photopolymerization initiator in the yellow ink comprises bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide and 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide at a mass ratio of 0.1 to 0.4; and the black ink comprising a carbon black, a radical polymerizable compound, and 5 to 12% by mass of a photopolymerization initiator based on the total amount of the black ink, wherein an acylphosphine oxide-based photopolymerization initiator in the photopolymerization initiator in the black ink comprises bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide and 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide at a mass ratio of 0.1 to 0.4.

Description

EXAMPLES

(1) The present invention will be described in detail below with reference to examples.

Preparation Example of High Concentration Pigment Dispersion

Preparation Example of Cyan Pigment Dispersion (1)

(2) 10 parts by mass of FASTOGEN BLUE TGR-G (phthalocyanine pigment CI pigment blue 15:4 from DIC Corporation), 4.5 parts by mass of Solsperse 32000 (polymer pigment dispersant from Lubrizol), and 85.5 parts by mass of LIGHT ACRYLATE PO-A (phenoxyethyl acrylate from Kyoeisha Chemical Co., Ltd.) were mixed with stirring by a stirrer for 1 hour, and then the mixture was treated by a bead mill for 2 hours to prepare a cyan pigment dispersion (1).

Preparation Example of Magenta Pigment Dispersion (2)

(3) 10 parts by mass of FASTOGEN SUPER MAGENTA RTS (magenta pigment CI pigment red 122 from DIC Corporation), 4.5 parts by mass of Solsperse 32000 (polymer pigment dispersant from Lubrizol), and 85.5 parts by mass of LIGHT ACRYLATE PO-A (phenoxyethyl acrylate form Kyoeisha Chemical Co., Ltd.) were mixed with stirring by a stirrer for 1 hour, and then the mixture was treated by a bead mill for 2 hours to prepare a magenta pigment dispersion (2).

Preparation Example of Yellow Pigment Dispersion (3)

(4) 10 parts by mass of LEVASCREEN YELLOW GO1 (CI pigment yellow 150 from LANXESS), 6 parts by mass of Solsperse 32000 (polymer pigment dispersant from Lubrizol Japan), and 84 parts by mass of LIGHT ACRYLATE PO-A (phenoxyethyl acrylate from Kyoeisha Chemical Co., Ltd.) were mixed with stirring by a stirrer for 1 hour and then the mixture was treated by a beads mill for 2 hours to prepare a yellow pigment dispersion (3).

Preparation Example of Black Pigment Dispersion (4)

(5) 10 parts by mass of carbon black #960 (carbon black from Mitsubishi Chemical Corporation), 4.5 parts by mass of Solsperse 32000 (polymer pigment dispersant from Lubrizol), and 85.5 parts by mass of LIGHT ACRYLATE PO-A (phenoxyethyl acrylate from Kyoeisha Chemical Co., Ltd.) were mixed with stirring by a stirrer for 1 hour, and then the mixture was treated by a beads mill for 2 hours to prepare a black pigment dispersion (4).

Preparation Example of Inks

(6) Actinic-ray-curable inks for ink-jet recording were produced according to compositions shown in Tables 1 and 2. Specifically, MIRAMER M3130, MIRAMER M240, IBXA, V-CAP, LIGHT ACRYLATE POA, and KF-54 were put into a container and mixed with stirring, and then Irgacure 819, Irgacure TPO, and DETX were added and the mixture was mixed and dissolved with heat at 60 C. for 30 minutes. After dissolution of powder compounds was confirmed, each of the pigment dispersions prepared in the preparation examples of high concentration pigment dispersions described above was added and the mixture was mixed with stirring for 10 minutes to produce cyan inks (C1 to C3), magenta inks (M1 to M4), yellow inks (Y1 to Y3), and black inks (K1 to K3).

(7) The abbreviations in Tables 1 and 2 represent the following compounds. M3130: ethylene oxide (EO)-modified trimethylolpropane triacrylate from MIWON M240: ethylene oxide (EO)-modified bisphenol A diacrylate from MIWON IBXA: isobornyl acrylate from Osaka Organic Chemical Industry Ltd. V-CAP: N-vinyl-2-caprolactam from ISP POA: phenoxyethyl acrylate from Kyoeisha Chemical Co., Ltd. KF-54: polysiloxane from Shin-Etsu Chemical Co., Ltd. Irgacure 819: bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide from BASF Irgacure TPO: 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide from BASF DETX-S: diethylthioxanthone from Nippon Kayaku Co. Ltd. [Irgacure 819/Irgacure TPO]: weight ratio of bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide to 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide
[Surface Curability]

(8) The actinic-ray-curable inks for ink-jet recording produced in the preparation examples of inks were each applied on a polycarbonate plate (LEXAN, thickness: 1 mm from AGC Inc.) using a spin coater into a thickness of 10 m, and then was irradiated with light using an LED irradiation device equipped with a stage moving unit (emission wavelength: 385 nm, peak intensity: 500 mW/cm.sup.2) manufactured by Hamamatsu Photonics K. K. so that one irradiation energy was 30 J/m.sup.2, and the integrated value of the quantity of the irradiation energy until tack-free was achieved was determined.

(9) [Balance of Surface Curability across Different Ink Colors]

(10) The integrated values of the quantity of the irradiation energy for inks which are calculated in the method described in the evaluation method in [Surface Curability] were compared in each of the ink sets having the compositions shown in Table 3 to 7. An ink set in which the inks of four colors had the same integrated value (30 mJ/cm.sup.2number of irradiations) of the quantity of the irradiation energy was evaluated as o, and an ink set in which one or more color inks among the four color inks had a different integrated value (30 mJ/cm.sup.2number of irradiations) of the quantity of the irradiation energy was evaluated as .

(11) [Thick-Film Curability]

(12) The actinic-ray-curable inks for ink-jet recording prepared in the preparation examples of inks were each applied on a polycarbonate plate (LEXAN, thickness: 1 mm form AGC Inc.) using a spin coater into a thickness of 10 m and a thickness of 15 m, and then were irradiated with light using an LED irradiation device equipped with a stage moving unit (light emitting wavelength: 385 nm, peak intensity: 500 mW/cm.sup.2) manufactured by Hamamatsu Photonics K. K. until tack-free was achieved. Cuts of 1010=100 squares were made in the resulting cured coating film with a cutter knife, a piece of cellophane tape from NICHIBAN CO. LTD. was adhered, and was rubbed 10 times with a nail. The tape was peeled vigorously at a rate of about 1 cm/sec, and the number of remaining squares of the coating film was checked. A coating film in which a large number of squares remained on the surface of the polycarbonate plate, which is considered to have excellent adhesiveness, was evaluated as a coating film that sufficiently cured down to the depths of the coating film having a large thickness.

(13) Evaluation Criteria

(14) o: Number of squares of coating film remaining on polycarbonate plate surface is 80 or more.

(15) : Number of squares of coating film remaining on polycarbonate plate surface is 50 to 79.

(16) x: Number of squares of coating film remaining on polycarbonate plate surface is less than 50.

(17) TABLE-US-00001 TABLE 1 Cyan ink Magenta ink C-1 C-2 C-3 M-1 M-2 M-3 M-4 Pigment dispersion (1) (1) (1) (2) (2) (2) (2) (parts by mass) 20.0 20.0 20.0 40.0 40.0 40.0 40.0 M3130 4.5 4.5 4.5 4.5 4.5 4.5 4.5 (parts by mass) M240 4.0 4.0 4.0 4.0 4.0 4.0 4.0 (parts by mass) IBXA 12.0 12.0 12.0 12.0 12.0 12.0 12.0 (parts by mass) V-CAP 12.0 12.0 12.0 12.0 12.0 12.0 12.0 (parts by mass) POA 39.8 39.8 36.8 23.5 23.3 23.3 20.3 (parts by mass) KF-54 0.2 0.2 0.2 0.2 0.2 0.2 0.2 (parts by mass) Irgacure 819 1.5 2.0 2.0 1.0 1.5 0.8 2.0 (parts by mass) Irgacure TPO 5.0 4.5 7.0 1.8 1.5 2.2 4.0 (parts by mass) DETX 1.0 1.0 1.5 1.0 1.0 1.0 1.0 (parts by mass) Photopolymerization 7.5 7.5 10.5 3.8 4.0 4.0 7.0 initiator (parts by mass) Irgacure 819/Irgacure 0.30 0.44 0.29 0.56 1.00 0.36 0.50 TPO (mass ratio) Surface curability 120 120 90 120 120 120 90 mJ/cm.sup.2 Thick-film Thickness curability 10 m Thickness x x 15 m

(18) TABLE-US-00002 TABLE 2 Yellow ink Black ink Y-1 Y-2 Y-3 K-1 K-2 K-3 Pigment dispersion (3) (3) (3) (4) (4) (4) (parts by mass) 30.0 30.0 30.0 20.0 20.0 20.0 M3130 4.5 4.5 4.5 4.5 4.5 4.5 (parts by mass) M240 4.0 4.0 4.0 4.0 4.0 4.0 (parts by mass) IBXA 12.0 12.0 12.0 12.0 12.0 12.0 (parts by mass) V-CAP 12.0 12.0 12.0 12.0 12.0 12.0 (parts by mass) POA 28.3 28.3 26.3 36.2 36.2 34.3 (parts by mass) KF-54 0.2 0.2 0.2 0.2 0.2 0.2 (parts by mass) Irgacure 819 1.8 2.5 2.0 1.9 3.0 2.5 (parts by mass) Irgacure TPO 5.4 4.7 7.0 7.0 5.9 8.0 (parts by mass) DETX 1.8 1.8 2.0 2.2 2.2 2.5 (parts by mass) Photopolymerization 9.0 9.0 11.0 11.1 11.1 13.0 initiator (parts by mass) Irgacure 819/ 0.33 0.53 0.29 0.27 0.51 0.31 Irgacure TPO (mass ratio) Surface curability 120 120 90 120 120 90 mJ/cm.sup.2 Thick- Thickness film 10 m cura- Thickness x x bility 15 m

Example 1

(19) An ink set in which the amount of a photopolymerization initiator was less than 10% by mass for a cyan ink and a yellow ink, and less than 5% by mass for a magenta ink, and less than 12% by mass for a black ink, and the Irgacure 819/Irgacure TPO ratio was 0.1 to 0.4 for the cyan ink, the yellow ink, and the black ink, and 0.4 to 0.8 for the magenta ink had a good balance in curability across different colored inks, and was superior in thick-film curability. Table 3 shows the results.

(20) TABLE-US-00003 TABLE 3 Example 1 C-1 M-1 Y-1 K-1 Photopolymerization initiator 7.5 3.8 9.0 11.1 (parts by mass) Irgacure 819/Irgacure TPO 0.30 0.56 0.33 0.27 (mass ratio) Surface curability mJ/cm.sup.2 120 120 120 120 Balance of surface curability across different colored inks Thick-film Thickness curability 10 m Thickness 15 m

Example 2

(21) An ink set in which the amount of a photopolymerization initiator used was less than 10% by mass for a cyan ink and a yellow ink, less than 5% by mass for a magenta ink, and less than 12% by mass for a black ink, and the Irgacure 819/Irgacure TPO ratio exceeded 0.4 for the cyan ink, the yellow ink, and the black ink, and exceeded 0.8 for the magenta ink showed a little reduction in thick-film curability, but had a good balance in curability across different colored inks, and was superior in thick-film curability. Table 4 shows the results.

(22) TABLE-US-00004 TABLE 4 Example 2 C-2 M-2 Y-2 K-2 Photopolymerization initiator 7.5 4.0 9.0 11.1 (parts by mass) Irgacure 819/Irgacure TPO 0.44 1.00 0.53 0.51 (mass ratio) Surface curability mJ/cm.sup.2 120 120 120 120 Blance in surface curability across different colored inks Thick-film Thickness curability 10 m Thickness 15 m

Example 3

(23) An ink set in which the amount of a photopolymerization initiator was less than 10% by mass for a cyan ink and a yellow ink, less than 5% by mass for a magenta ink, and less than 12% by mass for a black ink, and the Irgacure 819/Irgacure TPO ratio exceeded 0.4 for the cyan ink, the yellow ink, and the black ink, and was less than 0.4 for the magenta ink showed a little reduction in thick-film curability, but had a good balance in curability across different colored inks, and was superior in thick-film curability. Table 5 shows the results.

(24) TABLE-US-00005 TABLE 5 Example 3 C-2 M-3 Y-2 K-2 Photopolymerization initiator 7.5 4.0 9.0 11.1 (parts by mass) Irgacure 819/Irgacure TPO 0.44 0.36 0.53 0.51 (mass ratio) Surface curability mJ/cm.sup.2 120 120 120 120 Balance in surface curability across different colored inks Thick-film Thickness curability 10 m Thickness 15 m

Comparative Example 1

(25) An ink set in which the amount of a photopolymerization initiator was less than 10% by mass for a cyan ink and a yellow ink, 5% by mass or more for a magenta ink, and less than 12% by mass for a black ink, and the Irgacure 819/Irgacure TPO ratio exceeded 0.4 for the cyan ink, the yellow ink, and the black ink, and was 0.4 to 0.8 for the magenta ink had high curability only in the magenta ink and lacked the balance in curability. Table 6 shows the results.

(26) TABLE-US-00006 TABLE 6 Comparative Example 1 C-1 M-4 Y-1 K-1 Photopolymerization initiator 7.5 7.0 9.0 11.1 (parts by mass) Irgacure 819/Irgacure TPO 0.30 0.50 0.33 0.27 (mass ratio) Surface curability mJ/cm.sup.2 120 90 120 120 Balance in surface curability across x different colored inks Thick-film Thickness curability 10 m Thickness x 15 m

Comparative Example 2

(27) An ink set in which the amount of a photopolymerization initiator was 10% by mass or more for a cyan ink and a yellow ink, 5% by mass or more for a magenta ink, and 12% by mass or more for a black ink, and the Irgacure 819/Irgacure TPO ratio was 0.1 to 0.4 for the cyan ink, the yellow ink, and the black ink, 0.4 to 0.8 for the magenta ink, which ink set had an amount of the photopolymerization initiator added in each ink exceeding the amount defined for each color in the present invention, was inferior in the thick-film curability. Table 7 shows the results.

(28) TABLE-US-00007 TABLE 7 Comparative Example 2 C-3 M-4 Y-3 K-3 Photopolymerization initiator 10.5 7.0 11.0 13.0 (parts by mass) Irgacure 819/Irgacure TPO 0.29 0.50 0.29 0.31 (mass ratio) Surface curability mJ/cm.sup.2 90 90 90 90 Balance in surface curability across different colors Thick-film Thickness curability 10 m Thickness x x x x 15 m