JPH06220376A - Ink composition for ink jet recording - Google Patents

Abstract

PURPOSE:To obtain a high-quality image on a recording medium under a low transfer pressure by improving the peelability from a transfer medium to the recording medium in a transfer type ink jet printer. CONSTITUTION:This ink composition is used for an ink jet recording method having at least a heating means 7 and comprises at least water, a colorant, a resin dissolved and/or dispersed in water, a surfactant and an oil-in-water type emulsion.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink composition for a transfer type ink jet printer, which forms an ink image on a transfer medium and then transfers it to the recording medium to obtain the ink image on the recording medium.

[0002]

2. Description of the Related Art As a conventional ink for ink jet recording of a type in which ink droplets are ejected onto a recording medium to write an ink image, a composition example of a water-based recording ink containing water, a colorant and a water-soluble resin is known. JP-A-2-276874, JP-A-2-255875, and the like, for the purpose of improving ejection stability from nozzles, fixability on a recording medium, and storage stability of ink. There is.

Further, Japanese Patent Publication No. 62-1426 and Japanese Patent Laid-Open No. 4-18462 aim at fixing of an ink image on a recording medium, prevention of ink bleeding and flow.
An ink composition example comprising water, a pigment and a water-insoluble synthetic resin emulsion is described.

JP-A-62-164773 discloses a boiling point of 1 for the purpose of stability, prevention of drying, and stability of re-discharge property.
It contains an emulsion having an oily substance at 70 ° C. or higher as a dispersed phase.

Further, as an example of the ink for the transfer type printer, the applicant of the present invention has disclosed an ink composition example of water, a dye and a polyhydric alcohol in JP-A-62-92849 and US Pat. No. 4,538,156. Have been described. In the conventional example of this transfer type recording method, ink droplets are once ejected onto a transfer medium so that most of the water in the ink droplets is evaporated and the concentrated ink is transferred onto a recording medium such as paper. In addition to achieving high print quality without being affected by differences in recording media, it also made it possible to improve the drying properties of ink images.

[0006]

However, when an ink composition for ink jet recording of a type in which ink is directly ejected onto a recording medium to write a recorded image is used in a transfer type ink jet printer, the ink image is concentrated. Regarding the relationship between the state and the transfer pressure, the transfer pressure tends to increase as the ink image is concentrated, and in order to transfer at a low pressure, the ink concentration is within a range in which good transfer can be performed without image deletion. In, it is necessary to make it as low as possible. However, the state of ink concentration differs depending on the location from ink ejection to transfer. Also in the print pattern, the concentration state varies depending on the amount of ink per unit area. For this reason, it is necessary to set the pressure according to the maximum concentrated state of the ink, and an excessive pressure is required.

Further, even if an oil-in-water emulsion is contained as a transfer aid, there is no component that enhances the internal cohesive force of the concentrated ink, so that cohesive failure is likely to occur and an ink image can be transferred onto a recording medium. High pressure was needed.

The present invention solves these problems, and an object of the present invention is to reliably transfer the ink on the transfer medium to the recording medium at a low pressure regardless of the condensed state of the ink and to achieve high quality. It is an object of the present invention to provide a novel transfer type ink jet recording ink composition that realizes an image.

[0009]

The ink composition for ink jet recording of the present invention is an ink composition for use in an ink jet recording method having at least a heating means, which is at least dissolved in water, a coloring material, and / or water. It is characterized in that it contains a dispersed resin, a surfactant, and an oil-in-water emulsion, and the oil-in-water emulsion is a liquid-liquid emulsion.

[0010]

When the ink composition for ink jet recording of the present invention contains a surfactant in the ink, a high quality ink image can be formed on the transfer medium without repelling or flowing of the ink. Further, since the ink image is heated by the heating means to form the peeling layer of the oil component between the ink and the transfer medium and transfer it to the recording medium, high image quality can be realized by applying low pressure.

[0011]

EXAMPLES First, examples of the constitution of the ink jet recording ink of the present invention will be described in detail. The inkjet recording ink of the present invention is characterized by containing at least water, a coloring material, a resin dissolved and / or dispersed in water, a surfactant, and an oil-in-water emulsion.

Conventionally, water has been mainly used as an ink solvent because of its low viscosity, excellent safety, easy handling, low cost, and no odor. Ion exchange as ink material,
Pure water or ultrapure water that has undergone a purification process such as distillation is desirable.

Further, a hydrophilic high-boiling point low-volatile solvent is added in order to impart the effects of nozzle clogging resistance, moisture retention and dispersion stability. As the hydrophilic high-boiling point low-volatile solvent used in the present invention, glycerin, ethylene glycol, diethylene glycol, triethylene glycol,
Glycols such as propylene glycol, polyethylene glycol, and thiodiglycol, or their monoethers, diethers, and esters, such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol mono Ethyl ether, diethylene glycol monobutyl ether, etc. are used, and in addition, N-methyl-2pyrrolidone, 1.3-dimethylimidazolidinone, monoethanolamine, N, N-dimethylethanolamine, N, N-diethylethanolamine,
Printing with a water-soluble organic solvent such as a nitrogen-containing organic solvent such as diethanolamine, N-n-butyldiethanolamine, triisopropanolamine, triethanolamine,
It can be added within the range where bleeding does not occur. The amount used is preferably 0.5 to 10% by weight, and one kind or a mixture of two or more kinds is used, but it is not limited thereto.

For the purpose of improving the drying property and fixing property with respect to water as the main solvent, ethanol, propanol,
Highly volatile monohydric alcohols such as isopropanol and butanol, and relatively low volatility alcohols such as hexanol, heptanol and octanol can be added in small amounts.

In the release layer of the oil component of the present invention, when the ink is heated, the stable structure such as micelles of the oil-in-water emulsion in the ink composition is destroyed, and the oil component is present between the solid ink component and the transfer medium. Formed by bleeding. The release layer improves the releasability of the ink image from the transfer medium and improves the transferability. As a result, the transfer pressure can be reduced.

In the oil-in-water emulsion which can be used in the present invention, it is preferable that the solid content of the ink containing a resin as a main component and the oil component of the oil-in-water emulsion are incompatible, and the solubility parameter (hereinafter referred to as SP value). The closer the value is, the better the compatibility is. Therefore, if a material having a large difference from the SP value of the resin is selected, the oil component can be exuded between the solid content of the ink and the transfer medium when the ink is concentrated and dried. it can. The addition amount is required to be 0.01 to 8 wt% in order to secure sufficient releasability.

The oil-in-water emulsion is preferably a liquid-liquid emulsion, in which the dispersed phase is a water-insoluble liquid component and the continuous phase is water. Further, a surfactant can be used if necessary to form an oil-in-water emulsion.

As the water-insoluble component of the dispersed phase, dimethyl silicone oil, methyl silicone oil, methylphenyl silicone oil, methyl hydrogen silicone oil, polyether modified silicone oil, silicone polyester copolymer, amino modified silicone oil,
Fluorosilicone oil, castor oil, oleic acid, linolenic acid, conjugated linoleic acid, soybean fatty acid, nuka fatty acid, coconut oil fatty acid, fatty acid triglyceride, higher fatty acid, soybean oil, coconut oil, linseed oil, tall oil, rapeseed oil, cottonseed oil, olive oil , Squalane, lanolin, hydrogenated oil, hydrocarbon-based organic solvents such as paraffin chloride, decalin, tetralin, kerosene, liquid paraffin, isoper, petroleum,
Toluene, xylene, polyoxyethylene nonylphenyl ether, polyoxyethylene higher alcohol ether, polyoxyethylene oleyl ether, sorbitan monolaurate, lauryl alcohol, myristyl alcohol, octanol, decanol, propyl caproate, hexyl caproate, ethyl caprylate , Methyl oleate, and the like, but are not limited thereto.

Further, as the surfactant which can be used in the present invention, the dispersion stabilization of the oil-in-water emulsion for forming the release layer, and the ink of the ink on the transfer medium such as a rubber material having a low surface tension are used. In order to prevent repulsion and flow, and to fix the ink image, the following may be mentioned for the purpose of lowering the surface tension of the ink.

Water-soluble anionic, cationic, amphoteric,
One or more nonionic surfactants are added. The amount added is 0.0 to ensure sufficient wettability.
1 to 10 wt%, preferably 0.1 to 8 wt% is necessary.

For example, as the anionic surfactant, higher fatty acid salt, higher alkyl dicarboxylic acid salt, higher alcohol sulfuric acid ester salt, higher alkyl sulfonate, alkyl benzene sulfonate, alkyl naphthalene sulfonate, naphthalene sulfonic acid salt ( Na, K, Li, C
a) Formalin polycondensation product, condensate of higher fatty acid and amino acid, dialkylsulfosuccinate ester salt, alkylsulfosuccinate salt, naphthenate salt, etc., alkyl ether carboxylate salt, acylated peptide, α-olefin sulfonate salt, N -Acyl methyl taurine, alkyl ether sulfate, secondary higher alcohol ethoxy sulfate,
Polyoxyethylene alkyl phenyl ether sulfate,
Examples thereof include, but are not limited to, monoglycerate, alkyl ether phosphate ester salt, and alkyl phosphate ester salt.

Examples of cationic surfactants include, but are not limited to, aliphatic amine salts, quaternary ammonium salts, sulfonium salts and phosphonium salts.

Amphoteric surfactants include, but are not limited to, carboxybetaine type, aminocarboxylic acid salts, lecithin and the like.

Fluorine-based nonionic surfactants,
Silicone type, acrylic acid copolymer, polyoxyethylene alkyl ether, polyoxyethylene alkylphenyl ether, polyoxyethylene secondary alcohol ether, polyoxyethylene sterol ether, polyoxyethylene lanolin derivative, ethylene oxide derivative of alkylphenol formalin condensate , Polyoxyethylene polyoxypropylene block polymer, polyoxyethylene polyoxypropylene alkyl ether, polyoxyethylene compound fatty acid ester type, polyethylene oxide condensation type polyethylene glycol fatty acid ester, fatty acid monoglyceride, polyglycerin fatty acid ester, sorbitan fatty acid ester, propylene glycol Fatty acid ester, sucrose fatty acid ester, fatty acid alkanolamide, Polyoxyethylene fatty acid amide, polyoxyethylene alkylamine alkylamine oxides but not limited thereto.

The mixing ratio of the disperse phase component and the surfactant is preferably 10: 0.1 to 5: 1 by weight. Within the above range, the release layer can be easily formed when the ink is heated. As a result, since the transferability is improved by forming the peeling layer, the ink on the transfer medium can be surely transferred to the recording medium at a low pressure regardless of the ink concentration state. When the amount of the surfactant used is less than the above range, the dispersion stability of the emulsion itself cannot be obtained,
When the amount is more than the above range, when added to the ink, the foaming property becomes large, which causes defective ejection of the ink.

The oil-in-water emulsion can be produced by a known method such as an emulsion polymerization method using a general agitator such as a low shear agitator or a pipeline mixer.

The resin dissolved and / or dispersed in water which can be used in the present invention preferably has a tackiness upon concentration. The tackiness due to the concentration of the resin can impart an adhesive effect and a cross-linking effect when transferred to a recording medium. Further, when the ink containing the resin is concentrated, the internal cohesive force is increased, so that cohesive failure on the transfer medium is eliminated, and it becomes easy to prevent transfer residue due to interruption of the ink in the middle, resulting in In addition, it is possible to reliably transfer the ink on the transfer medium to the recording medium at a low pressure regardless of the ink concentration state.

As the resin dispersed in water, a resin having a heat softening temperature or a heat melting temperature of 50 ° C. to 150 ° C. is used, and preferably 60 ° C. to 100 ° C. is used. A mixture of two or more species can be used. The addition amount is the weight ratio of the colorant and the resin,
It is preferable to set it to 0.1: 1 to 1: 0.2. However, as the addition amount is increased, the ink viscosity is also increased. Therefore, it is preferable to suppress the addition amount to about 30% by weight with respect to the entire ink.

Examples of the resin dispersed in water include polyacrylic acid, polymethacrylic acid, polyethylacrylic acid, styrene-butadiene copolymer, butadiene copolymer, acrylonitrile-butadiene copolymer and chloroprene copolymer. Polymer, crosslinked acrylic resin, crosslinked styrene resin,
Fluorine resin, vinylidene fluoride, benzoguanamine resin, phenol resin, polyolefin resin, cellulose, styrene-acrylic acid copolymer, styrene-methacrylic acid copolymer, polystyrene, styrene-acrylamide copolymer, n-isobutyl acrylate, acrylonitrile , Vinyl acetate, acrylamide, silicone resin, polyvinyl acetal, polyamide, rosin resin, polyethylene, polycarbonate, vinylidene chloride resin, polyvinyl alcohol, cellulose resin, epoxy resin, vinyl acetate resin, ethylene-vinyl acetate copolymer, vinyl acetate -Acrylic copolymer, vinyl chloride resin, polyurethane, rosin ester, microgel,
Examples thereof include, but are not limited to, microemulsions.

Further, as the resin dispersed in low molecular weight water, the following may be mentioned. For example, polyethylene wax, montan wax, alcohol wax, synthetic oxidation wax, α-olefin-maleic anhydride copolymer, animal and vegetable wax such as carnauba wax, lanolin, paraffin wax, microcrystalline wax and the like can be used.

The above-mentioned resins were dispersed in the ink in the form of fine colored resin particles integrated with the coloring material, in the form of only the resin dispersed in the ink as fine particles, and in a stable dispersion in water. It is preferably added in the form of resin emulsion particles.

Examples of the resin dissolved in water include polyalkyl oxides such as polyethylene oxide, polyvinyl pyrrolidone, polyvinyl alcohol, polyvinyl butyral, polyacrylic acid, glue, gelatin, casein, albumin, gum arabic, alginic acid, methyl cellulose, carboxy. There are methyl cellulose, hydroxyethyl cellulose, polyvinyl ether, starch, polyethylene glycol, polyvinyl methyl ether and the like.

The resin dissolved in water as described above has tackiness in the concentrated or dried state in which the water is removed, and the internal cohesive force of the concentrated ink is increased. It is desirable to be able to bind additional components such as colorants and thermoplastic resins in the ink.

As the coloring material, pigments, water-soluble dyes, disperse dyes, and water-insoluble dyes (when kneaded with resin) are used, and those having a good affinity with water as a main solvent, dispersants, etc. Any combination can be used as long as it can be uniformly dispersed.

Pigments that can be used in the present ink include organic pigments and inorganic pigments. For black and white, for example, carbon black (C.I., such as furnace black, lamp black, acetylene black and channel black) can be used. ．Pigment black 7) type or copper,
Examples include metals such as iron (CI Pigment Black 11) and titanium oxide, and organic pigments such as aniline black (CI Pigment Black 1). For color, C.I. I. Pigment Yellow 1 (Fast Yellow G), 3, 1
2 (this as yellow AAA), 13, 14, 17, 24, 3
4, 35, 37, 42 (yellow iron oxide), 53, 55, 8
1, 83 (This As Yellow HR), 95, 97, 98, 10
0, 101, 104, 108, 109, 110, 11
7, 120, 138, 153, C.I. I. Pigment Orange 5, 13, 16, 17, 3
6, 43, 51, C.I. I. Pigment Red 1, 2, 3, 5, 17, 22
(Brilliant First Scarlet), 23, 31, 38, 48: 2
(Permanentlet 2B (Ba)), 48: 2 (Permanentlet 2B (C)
a)), 48: 3 (permanentlet 2B (Sr)), 48: 4 (permanentlet 2B (Mn)), 49: 1, 52: 2, 53: 1, 57: 1
(Brilliant Carmine 6B), 60: 1, 63: 1, 63: 2, 64: 1, 81 (Rotamine 6G rake), 83, 88, 101
(Bengara), 104, 105, 106, 108 (cadmium let), 112, 114, 122 (quinacridone magenta),
123, 146, 149, 166, 168, 170, 1
72, 177, 178, 179, 185, 190, 19
3, 209, 219, C.I. I. Pigmen Violet 1 (Rotamine Lake), 3,
5: 1, 16, 19 (quinacridlet), 23, 38, C.I. I. Pigment Blue 1, 2, 15 (Phthalocyanine Blue
R), 15: 1, 15: 2, 15: 3 (phthalocyanine blue G), 1
5: 4, 15: 6 (phthalocyanine blue E), 16, 17: 127
(Dark blue), 28 (court blue), 29 (marine blue), 56,
60, 63, C.I. I. Pigment Green 1, 4, 7, 8, 10, 1
In addition, processed pigments such as graft carbon having a pigment surface treated with a resin or the like can be used. The addition amount thereof is preferably 1 to 30% by polymerization, and further 1.
5-12% polymerization is preferred. A pigment having a particle size of 25 μm or less is used, and a pigment having particles of 1 μm or less is preferably used.

In order to uniformly disperse these coloring materials, if necessary, a dispersant is added in an amount of 0.01 to 1 wt% with respect to the pigment.
Can be added, and it is desirable that they be dispersed by a ball mill or the like.

As the water-soluble dye used in the present ink, a direct dye, an acid dye, a basic dye, an edible dye and the like are used. I. Direct Black 9, 17, 19, 22, 3
2, 51, 56, 62, 69, 77, 80, 91, 9
4, 97, 108, 112, 113, 114, 117,
118, 121, 122, 125, 132, 146, 1
54, 166, 168, 173, 199, C.I. I. Direct Red 2, 4, 9, 23, 26, 3
1, 39, 62, 63, 72, 75, 76, 79, 8
0, 81, 83, 84, 89, 92, 95, 111, 1
73, 184, 207, 211, 212, 214, 21
8, 221, 223, 224, 225, 226, 22
7, 232, 233, 240, 241, 242, 24
3, 247, C.I. I. Direct violet 7, 9, 47, 48,
51, 66, 90, 93, 94, 95, 98, 100,
101, C.I. I. Direct Yellow 8, 9, 11, 12, 2
7, 28, 29, 33, 35, 39, 41, 44, 5
0, 53, 58, 59, 68, 86, 87, 93, 9
5, 96, 98, 100, 106, 108, 109, 1
10, 130, 132, 142, 144, 161, 16
3, C.I. I. Direct Blue 1, 10, 15, 22, 2
5, 55, 67, 68, 71, 76, 77, 78, 8
0, 84, 86, 87, 90, 98, 106, 108,
109, 151, 156, 158, 159, 160, 1
68, 189, 192, 193, 194, 199, 20
0, 201, 202, 203, 207, 211, 21
3, 214, 218, 225, 229, 236, 23
7, 244, 248, 249, 251, 252, 26
4, 270, 280, 288, 289, 291, C.I. I. Acid Black 7, 24, 29, 48, 5
2: 1, 172, C.I. I. Acid Red 35, 42, 52, 57, 6
2, 80, 82, 111, 114, 118, 119, 1
27, 128, 131, 143, 151, 154, 15
8, 249, 254, 257, 261, 263, 26
6, 289, 299, 301, 305, 336, 33
7, 361, 396, 397, C.I. I. Acid Violet 5, 34, 43, 47,
48, 90, 103, 126, C.I. I. Acid Yellow 17, 19, 23, 25, 3
9, 40, 42, 44, 49, 50, 61, 64, 7
6, 79, 110, 127, 135, 143, 151,
159, 169, 174, 190, 195, 196, 1
97, 199, 218, 219, 222, 227, C.I. I. Acid Blue 9, 25, 40, 41, 62,
72, 76, 78, 80, 82, 92, 106, 11
2, 113, 120, 127: 1, 129, 138, 1
43, 175, 181, 205, 207, 220, 22
1, 230, 232, 247, 258, 260, 26
4, 271, 277, 278, 279, 280, 28
8, 290, 326, C.I. I. Reactive Black 4, 5, 8, 14, 2
1, 23, 26, 31, 32, 34, C.I. I. Reactive Red 3, 13, 17, 19, 2
1, 22, 23, 24, 29, 35, 37, 40, 4
1, 43, 45, 49, 55, C.I. I. Reactive Violet 1, 3, 4, 5,
6, 7, 8, 9, 16, 17, 22, 23, 24, 2
6, 27, 33, 34, C.I. I. Reactive Yellow 2, 3, 13, 14, 1
5, 17, 18, 23, 24, 25, 26, 27, 2
9, 35, 37, 41, 42, C.I. I. Reactive Blue 2, 3, 5, 8, 10, 1
3, 14, 15, 17, 18, 19, 21, 25, 2
6, 27, 28, 29, 38, C.I. I. Basic Black 8, C.I. I. Basic Red 12, 13, 14, 15, 1
8, 22, 23, 24, 25, 27, 29, 35, 3
6, 38, 39, 45, 46, C.I. I. Basic Violet 1, 2, 3, 7, 1
0, 15, 16, 20, 21, 25, 27, 28, 3
5, 37, 39, 40, 48, C.I. I. Basic Yellow 1, 2, 4, 11, 13,
14, 15, 19, 21, 23, 24, 25, 28, 2
9, 32, 36, 39, 40, C.I. I. Basic Blue 1, 3, 5, 7, 9, 22,
26, 41, 45, 46, 47, 54, 57, 60, 6
2, 65, 66, 69, 71, C.I. I. Food black and the like are used, but not limited to these.

The disperse dyes and water-insoluble dyes which are used by being dispersed in the present ink or mixed or dissolved in a resin include C.I. I. Solvent Black 3, 5, 22, C.I. I. Solvent Yellow 19, 44, 98, 104,
105, 112, 113, 114 C.I. I. Solvent Red 8, 24, 71, 109, 1
52, 155, 176, 177, 179 C.I. I. Solvent Blue 2, 11, 25, 78, 9
4, 95, C.I. I. Solvent Green 26, C.I. I. Solvent Orange 5, 40, 45, 72, 6
3, 68, 78 C.I. I. Solvent Violet 13, 31, 32, 3
3, C.I. I. Disperse Yellow 3, 5, 56, 60, 6
4, 160 C.I. I. Day Super Red 4, 5, 60, 72, 7
3, 91, C.I. I. Desperce Blue 3, 7, 56, 60, 7
9, 198 C.I. I. Disperse oranges 13, 30 and the like are used, but not limited to these.

The amount of these dyes to be added is determined depending on the type of dye, the type of solvent component, the properties required for the ink, etc., but is generally 0.2 with respect to the total weight of the ink.
The range of 10 to 10% by weight, preferably 0.5 to 5% by weight is good.

In addition, if necessary, a pH adjusting agent such as potassium dihydrogen phosphate or disodium hydrogen phosphate, an antifungal agent,
Benzoic acid, dichlorophen, hexachlorophen, sorbic acid, p-hydroxybenzoic acid ester, ethylenediaminetetraacetic acid (EDTA) and the like may be included for the purpose of antiseptic and rust prevention. Furthermore, for the purpose of preventing nozzle drying, urea, thiourea, ethylene urea, etc. can be added.

The ink was manufactured by the following procedure, but the invention is not limited to this. An aqueous dispersion of a colorant and a dispersant is dispersed in a ball mill, and it is confirmed by microscopic observation that the colorant particles are in a monodispersed state, and the resin and interface are dissolved and / or dispersed in water there. Activator,
An oil-in-water emulsion and a hydrophilic high-boiling point low-volatile solvent are added, and the mixture is stirred for further 30 minutes and completely mixed. After that, additives such as preservatives were added to confirm complete dissolution, and the dispersion was filtered through a membrane filter having a pore size of 10 μm to remove dust and coarse particles to obtain a recording ink. Finally, performing the filtration operation once again is effective in preventing the inclusion of impurities.

Table 1 shows the composition of the ink composition of the present invention made of the above materials prepared by the above-mentioned production method.

[0043]

[Table 1]

The oil-in-water emulsions of Examples 1 to 3 were
A commercially available product was used as it was, and in Example 4, squalane was mixed in the dispersed phase and sodium dioctylsulfosuccinate was mixed in the surfactant in a mixing ratio by weight ratio (dispersed phase: surfactant = 10: 0.
In 1), a mixture of 100 parts by weight of the mixture and 150 parts by weight of water was stirred at high speed with a homomixer, and Example 5 was the same as Example 4 except that Adecut EMCO360 was used as the dispersed phase and polyoxyethylene alkyl ether was used as the surfactant. What was stirred at high speed with a homomixer was used.

The physical property values of the above ink examples are adjusted within the following ranges.

The ink viscosity is 50 m in order to ensure stable ejection from the head and stable ink supply to the head.
Pa · sec or less is desirable, and more preferably 25 mPa · sec or less.

The contact angle between the ink and the transfer medium is preferably 60 degrees or less in order to prevent repulsion and flow of the ink on the transfer medium and form a high quality ink image. Further, the surface tension of the ink is set to 4 in order to ensure wettability with the transfer medium.
It is preferably 5 dyne / cm or less, more preferably 35 dyne / cm or less.

The composition of the ink comparative example composition of the present invention is shown in Table 1.
Shown in. The method for producing each ink comparative example composition is shown below.

Ink Comparative Example 1 An ink composition was prepared by removing the resin dissolved and / or dispersed in water from the composition of Example 1 in the same manner as in Example 1 to prepare an ink.

Ink Comparative Example 2 An ink composition prepared by removing the oil-in-water emulsion from the composition of Example 1 was prepared in the same manner as in Example 1 to obtain an ink.

Next, a printing test was conducted using the above-mentioned inks in a transfer type ink jet recording apparatus described below.

FIG. 1 is a perspective view showing a characteristic structure of a transfer type ink jet recording apparatus used in the present invention. Figure 2
FIG.

This transfer type ink jet printer has a heating means 7 on the outside and an ink jet type recording head 2 from the upstream side in the rotation direction around the transfer medium 1 which is rotated in the direction of arrow A by a driving means (not shown). , Heating means 7
A halogen lamp 73, a reflecting mirror 74, a pressure roller 3 as a transfer means, and a cleaner 4 if necessary.
And are arranged in sequence.

The recording head 2 is an ink jet recording head of a type using a piezoelectric element, and a plurality of nozzles are arranged so as to face the transfer medium 1. An ink tank (not shown) is connected to the recording head 2, and ink is supplied as needed.

The transfer medium 1 is formed by laminating an elastic layer 12 made of silicone rubber around a metal tube 11.
A rubber material is suitable for the elastic layer 12, and among them, a material having a good mold release property for easily peeling an ink image and having heat resistance and durability is preferable, such as silicone rubber, fluororesin,
Fluorosilicone rubber and the like, or modified products thereof are preferable. Also, as other materials, chloroprene rubber,
Nitrile rubber, ethylene propylene rubber, natural rubber, styrene rubber, isoprene rubber, butadiene rubber, ethylene / propylene / butadiene polymer, nitrile butadiene rubber and the like can also be used.

Further, the elastic layer 12 may be formed by applying various good release agent to the surface layer (ink image bearing surface) of the various rubber materials. As the coating agent, silicone coating and fluorine coating are preferable.

The pressure roller 3 is a metal roller made of aluminum, and the pressure application mechanism 30 presses the ink image 5 through the recording medium 6 in the transfer area facing the transfer medium 1, and transfers and fixes the ink image 5 on the recording medium 6. After that, the pressure release mechanism 31 is configured to release the pressure.

The cleaner 4 is made of felt,
The transfer medium 1 is contacted with a predetermined pressure by a contact mechanism (not shown).

The heating means 7 is a rod-shaped halogen lamp 73.
And a reflector 74, and is arranged downstream of the recording head 2 and upstream of the pressure roller 3 in the rotational direction of the transfer medium.

Next, the operation will be described. First, the ink image writing process will be described. FIG. 3 is a diagram showing how an ink image is written. In the ink image writing step, the pressure roller 3 is controlled to be pressed against the surface of the transfer medium 1. The recording head 2 used in this embodiment is of a type that scans in the direction of arrow B along a carriage shaft 20 parallel to the rotation axis of the transfer medium 1. Ink droplets are selectively ejected from the nozzles of the recording head 2 onto the print area L in accordance with a recording signal, and a desired ink image 5 is formed in a band shape.

Next, the ink image 5 formed by the recording head 2 on the transfer medium 1 is heated by the heating means 7.
The heating means 7 is controlled by a temperature detector (not shown) so as to be within a predetermined temperature range. Ink image 5 on transfer medium 1
Is heated to increase the solid content concentration and forms a peeling layer between the transfer medium 1 and the ink solid content. This is because the ink composition contains an oil-in-water emulsion. The operation of forming the release layer will be described in detail later.

In the ink image formed by the above-mentioned ink image writing step, there is a difference in the ink concentration state depending on the place of the transfer medium 1 until it is heated by the heating means and the print pattern. That is, there is a time difference in the movement of the recording head 2 along the carriage between the first position and the last position where the recording head 2 ejects the ink droplets. In addition, when the print pattern, in other words, when the ink amount per unit area forms a large-area image (hereinafter referred to as solid) and when one dot is formed, the ink is naturally concentrated depending on the presence or absence of ink dot overlap. There is a difference. However, by using the ink of the present invention and heating after the ink image writing step, the peeling layer is formed, so that the peeling layer can have a substantially uniform peeling property regardless of the elapsed time or the printing pattern, and thus the low pressure is applied. Can be transferred with. Here, the low pressure means 1 kg in order to downsize the apparatus, reduce the cost of components such as the transfer medium 1 and the pressure roller 3, and further improve the durability of the elastic layer on the surface of the transfer medium.
Weight / cm or less is preferable, more preferably 0.6 kg
Weight / cm or less is desirable.

Next, the behavior of the ink image 5 from image formation to transfer fixing will be described in detail. 4, FIG.
6 and 7 are schematic diagrams showing the behavior of the ink image 5.

At the time of ejection from the recording head 2, the ink is
Among its constituents, the proportion of water is high, and the coloring material,
The resin is also in a good dissolved or dispersed state and kept in a low viscosity state. Therefore, good ejection characteristics (maximum ejection frequency, ejection speed, ink amount of ejected ink droplets, stability thereof, and the like) can be obtained. That is, the ink is adjusted to have an optimum viscosity according to the characteristics of the recording head 2.

The ink flying as an ink droplet forms an ink image 5 on the transfer medium 1 as shown in FIG. At this time, due to the effect of the surfactant appropriately added to the ink, the ink image 5 is appropriately wet on the transfer medium 1 so as to obtain a desired dot diameter.

Since the surface of the elastic layer 11 of the transfer medium 1 is heated by the heating means 7, the evaporation of the water 51 in the ink is promoted (FIG. 5). Along with this, the components that have been dispersed or dissolved until then are aggregated, and most or all of the ink image 5 is solid particles 5 composed of a colorant and a resin.
It will be formed by 2 aggregates. At the same time, when the ink image 5 is heated by the heating means 7, the peeling layer 53 is formed between the aggregate of the solid content particles 52 and the elastic layer 11. It is considered that the peeling layer 53 is generated when the dispersion system of the oil-in-water emulsion collapses as the moisture 51 in the ink evaporates. In order to break the dispersion system of the oil-in-water emulsion, heating is more efficient than applying mechanical force. The oil component in the ink has a boiling point higher than that of water and has a property of being hard to evaporate by heating. Therefore, in the above heating step, it is possible to concentrate the ink image and simultaneously form a peeling layer of the oil component of the oil-in-water emulsion. This release layer 53
Has a low pressure transfer effect by being interposed between the ink image 5 and the elastic layer 11.

As the transfer medium 1 rotates, the ink image 5
Are conveyed to the transfer area facing the pressure roller 3. Here, the transfer medium 1 bearing the ink image 5 is pressed by the pressure roller 3 via the recording medium 6. This state is shown in FIG. Here, since the outer layer of the transfer medium 1 is the elastic layer 11, the elastic layer 11 and the recording medium 6 exhibit a substantially uniform pressure distribution in the rotational axis direction of the transfer medium 1 in the pressed state. Therefore, a good contact state is obtained. At this time, since the ink image 5 has an adhesive property in a concentrated state, the ink image 5 comes into contact with the recording medium 6 to generate an adhesive force between the recording medium 6 and the ink image 5. (This adhesive force is indicated by F1 in the figure.) As the ink image, one having an appropriate adhesive force by being in an appropriate concentrated state is selected.
The cohesive force of the ink image is indicated by F2 in the figure. Further, since the peeling layer 53 formed by heating is interposed between the ink image 5 and the elastic layer 11, the solid content of the ink is easily separated, so that the transfer pressure can be reduced. Therefore, the adhesive force between the ink image 5 and the surface of the elastic layer 11 is very low (this adhesive force is indicated by F3 in the figure).

Therefore, at the time of transfer, the adhesive force (F1) between the ink image 5 and the recording medium 6 and the cohesive force (F) of the ink image 5
2), the adhesive force between the ink image 5 and the surface of the elastic layer 11 (F
Among the three forces of 3), the adhesive force (F3) between the ink image 5 and the surface of the elastic layer 11 is the lowest. For this reason,
The ink image 5 is interfacially separated from the surface of the elastic layer 11 as shown in FIG.
0% transfer.

The above description applies not only to the one-dot ink image 5 but also to the ink image as an aggregate in which a plurality of dots are adjacently connected to each other. That is, since the cohesive forces act on each other in the adjacent dot areas, the ink image 5 as the aggregate is formed.
, The aggregates are interfacially separated as a single mass and transferred to the recording medium 6. Therefore, a high-quality image can be obtained on the recording medium 6 regardless of any output pattern and the time elapsed from printing.

Generally, it is difficult for an image forming apparatus utilizing transfer to faithfully transfer an image on a transfer medium onto a recording paper (eg, bond paper) having large irregularities. This is largely because it is difficult to bring the image on the transfer medium into contact with the concave portion of the recording paper. However, according to the present invention, as described above, the ink image 5 having the appropriate adhesive force and the cohesive force is separated at the interface, so that a partial area of the ink image 5 does not come into contact with the recording medium 6. Even if the area exists, another area comes into contact with the recording medium 6,
That is, if there is a region where the adhesive force with the recording medium 6 can be obtained, good transfer can be performed without image loss.

Further, conventionally, the ink image 5 is easy to wet on the transfer medium in which the interface energy of the transfer medium is large and a faithful image can be formed, but a high pressure is required at the time of transfer.
Alternatively, cohesive failure occurs during transfer, but by forming the release layer 53, good transfer characteristics can be obtained even for transfer media with poor releasability, so it is possible to expand the selection range of transfer media compared to the past. Has the effect that Figure 8
Then, the recording head 2 is a line-shaped recording head that has nozzles over the entire printing area L and does not perform scanning, and writes one page of ink image by one rotation of the transfer medium 1. The ink image formed on the transfer medium 1 is
Although it is heated by the heating means, when the above-mentioned writing step is performed, normally, the ink concentration state differs depending on the print pattern, and the peelability differs during transfer. Good peelability can be obtained regardless of the pattern.

In FIG. 9, while the recording head 2 having a plurality of nozzles along the axial direction of the transfer medium 1 is moved in the rotational axis direction of the transfer medium 1 (direction C in the figure), the transfer drum 1 is moved to a predetermined position. This is a method in which a belt-shaped ink image is formed by rotating at a constant speed for a number of times. In this ink image writing method, there is a difference between the time until the ink image is heated by the heating means and the ink concentration state due to the print pattern, depending on the location where the transfer medium 1 is ejected. Since the oil component of the oil-in-water emulsion contained therein forms the peeling layer, good peelability can be obtained.

The results of a printing test of the ink composition of the present invention and the ink composition of the comparative example using the above-mentioned transfer type ink jet recording apparatus are shown below.

The evaluation items evaluated the relationship between the transfer pressure and the transfer efficiency when transferring the ink image.

The respective evaluation conditions and judgment criteria are as follows.

Relationship between Transfer Pressure and Transfer Efficiency 1. Time from printing to transfer Printing start part: 10 seconds Printing end part: 2 seconds 2. Transfer pressure 0.6 kg weight / cm 1.0 kg weight / cm 1.5 kg weight / cm 3. Print pattern Solid 1 dot continuous line Dotted line every other dot 4. Transfer efficiency ◯: Transfer efficiency is 100% and no image deformation occurs. Δ: Transfer efficiency is 95 to 100% and image transfer occurs partially. X: Transfer efficiency is less than 95% and clear density. Change, void,
Table 2 shows the results of evaluation by a transfer type inkjet recording device using each of the ink examples 1 to 5 and the ink comparative examples 1 and 2 based on the above evaluation method in which image deformation occurs.

[0077]

[Table 2]

As shown in the above table, when the ink composition of the present invention is used, a high-quality ink image free from repulsion and flow on the transfer medium can be formed, and further from low printing pressure to printing. Transfer efficiency 1 regardless of time and print pattern
I was able to achieve 00%. Further, among those to which the oil-in-water emulsion was added, those obtained by emulsion polymerization of silicone oil were the most excellent in releasability, and a sharp image without transfer residue was obtained.

On the other hand, the ink of Comparative Example 1 containing no resin component cannot increase the internal cohesive force of the concentrated ink, and thus causes cohesive failure and is difficult to transfer. Further, in the ink of Comparative Example 2 in which the oil-in-water emulsion was not added, the release layer could not be formed,
Since the adhesive force between the transfer medium and the ink image is greater than the adhesive force between the ink image and the recording medium, the releasability is poor and transfer residue occurs, or transfer is not possible unless the transfer pressure is high.

From the above results, when the ink composition of the present invention contains the resin dissolved and / or dispersed in water, the internal cohesive force of the concentrated ink can be increased. As a result of the synergistic effect of the effect that transfer is possible without causing cohesive failure and the effect of forming the release layer by containing the oil-in-water emulsion and improving the releasability of the ink image from the transfer medium. ,
The ink on the transfer medium can be reliably transferred at a low pressure regardless of the ink concentration state. Furthermore, it is possible to obtain a clear image ink image having a sharp edge without generating a transfer residual ink image by applying a low pressure even on a transfer medium having a poor peeling property. It is a thing.

Further, the ink composition for ink jet recording of the present invention can be applied to a two-color printer, a multi-color printer and a full-color printer because it is possible to superpose a plurality of inks on a transfer medium. is there.

[0082]

INDUSTRIAL APPLICABILITY As described above, the ink composition for ink jet recording according to the present invention has the inside of the ink in which the resin formed by being dissolved and / or dispersed in the water added to the ink by the heating means is concentrated. The effect that the cohesive force can be increased and transfer is possible without causing cohesive failure, etc., and the inclusion of the oil-in-water emulsion forms a release layer and improves the releasability of the ink image from the transfer medium. As a result of the synergistic effect of the effect, it is possible to provide an inkjet recording liquid that can obtain high-quality printing on a recording medium by applying a low pressure, regardless of the difference between the time from ink ejection to transfer and the concentration state caused by the printing pattern. Has the effect.

[Brief description of drawings]

FIG. 1 is a perspective view showing a configuration of a transfer type inkjet recording device used for evaluation of the present invention.

FIG. 2 is a cross-sectional view showing a configuration of a transfer type inkjet recording device used for evaluation of the present invention.

FIG. 3 is a perspective view showing an ink image writing process used for evaluation of the present invention.

FIG. 4 is a schematic diagram showing the behavior of an ink image in the inkjet printer of the present invention.

FIG. 5 is a schematic diagram showing the behavior of an ink image in the inkjet printer of the present invention.

FIG. 6 is a schematic diagram showing the behavior of an ink image in the inkjet printer of the present invention.

FIG. 7 is a schematic diagram showing the behavior of an ink image in the inkjet printer of the present invention.

FIG. 8 is a perspective view showing another ink image writing step used in the evaluation of the present invention.

FIG. 9 is a perspective view showing still another ink image writing step used in the evaluation of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Transfer medium 2 ... Recording head 3 ... Pressure roller 5 ... Ink image 6 ... Recording medium 7 ... Heating means

Claims (2)

[Claims] 1. An ink composition used in an inkjet recording method having at least a heating means, which comprises at least water, a coloring material, and a resin dissolved and / or dispersed in water,
An ink composition for ink jet recording, comprising a surfactant and an oil-in-water emulsion. 2. The ink composition for inkjet recording according to claim 1, wherein the oil-in-water emulsion is a liquid-liquid emulsion.