JP4512341B2 - Inkjet ink - Google Patents

Description

  INDUSTRIAL APPLICABILITY The present invention is excellent in image saturation (color tone sharpness), ink-jet ink excellent in scratch resistance and ink storage stability, an ink cartridge containing the ink, and recording by discharging the ink. The present invention relates to an ink jet recording apparatus, an image forming method using the recording apparatus, and an image formed product produced by the method.

  The inkjet recording method is easy to make full color because the process is simpler than other recording methods, and there is an advantage that a high-resolution image can be obtained even with an apparatus having a simple configuration. As ink-jet inks, dye-based inks in which various water-soluble dyes are dissolved in water or a mixture of water and an organic solvent are used. Dye-based inks have excellent color tone, but are resistant to light. There was a disadvantage that was inferior in nature. On the other hand, pigment-based inks in which carbon black and various organic pigments are dispersed are actively studied because they are superior in light resistance compared to dye-based inks.

Ink using organic pigments and carbon black, a method of mechanically pulverizing and dispersing organic pigments and carbon black with the aid of a dispersant is used, but organic pigments and carbon black are made very fine, If the ink is not stably dispersed in the medium, not only good transparency, definition and color developability can be obtained, but also ink jet ink may cause nozzle clogging. However, in general, the degree of atomization by mechanical pulverization / dispersion of the pigment is practically limited, and the atomized pigment ink tends to cause problems such as secondary aggregation and storage stability.

  In order to improve nozzle clogging and color gamut, it is necessary to reduce the average particle diameter of the pigment, but styrene-acrylic copolymers and styrene-maleic acid copolymers (for example, patent documents) which are currently widely used. 1), an ink using a polymer dispersant such as sodium naphthalene sulfonate formalin condensate (for example, see Patent Document 2), polyethylene glycol alkyl phenyl ether (for example, see Patent Document 3), polyethylene glycol alkyl. In any of the inks using a surfactant such as phenyl ether sulfate (for example, see Patent Document 4) and polyethylene glycol alkylphenyl ether phosphate (for example, see Patent Document 5), the average particle size of the pigment is It was large and inferior in color tone sharpness, ejection stability and liquid stability.

  Conventionally, for an image output apparatus based on an ink jet method, a color image reproduction process using four colors obtained by adding black (K) to three colors of yellow (Y), magenta (M), and cyan (C). Has been done. However, there is a limit to the color reproduction range in the mixed color of four colors of yellow (Y), magenta (M), cyan (C), and black (K) as described above. In particular, color reproduction with high saturation of each of the secondary colors Red (R), Green (G), and Blue (B) is expressed by a mixed color of Y, M, C, and K, and the saturation is high. There was not enough color reproducibility.

  In order to compensate for these disadvantages, images are formed with 7 color inks of R, B, and G inks in addition to Y, M, C, and K inks. The color blur is improved (for example, refer to Patent Documents 6 and 7). However, increasing the number of inks to 7 or more colors and increasing the number of heads at the same time increases the cost of the image output device, increases the size, and increases the maintenance load on the head. . Furthermore, the load on image processing for converting an image signal into an output signal is increased. Such a load is not preferable because it leads to a decrease in recording speed.

  When a pigment is used as an ink colorant, the lightness and saturation of the printed portion are lower than when a dye is used, and the color reproducibility is generally inferior. Particularly problematic is the secondary color described above, and the brightness and saturation are greatly reduced. In order to improve such problems with pigment inks, techniques using Y, M, C, K pigment inks, green (G) pigment inks, and orange (Or) pigment inks have been disclosed (for example, Patent Documents). 8). However, color reproducibility, especially red reproducibility, is not sufficient.

  Further, it has been proposed to identify and use a dispersant and an additive that can efficiently produce a fine particle size pigment dispersion that can be suitably used for ink jet recording ink in a short time (see, for example, Patent Document 9). ). However, the particle size is about 100 to 200 nm, and in order to provide a pigment ink excellent in image saturation (color tone sharpness) and ejection stability, the particle size needs to be 10 to 50 nm. There is. Dispersions up to now have been difficult to disperse to 10 to 50 nm due to problems such as viscosity.

  As described above, the degree of atomization by mechanical pulverization / dispersion of the pigment generally has practical limits, and the particle size generally means the average particle size of particles of various sizes. In general, large-size particles having an unfavorable average particle size or more are also included, but it is not preferable when the large-size particles have a high content. In addition, pigment particles atomized by mechanical pulverization / dispersion increase the specific surface area and activate the surface due to the newly created fine cross-section by grinding operation, etc., so secondary aggregation and storage There have been no pigment inks that are likely to cause problems such as stability, have excellent image saturation (color tone sharpness), ejection stability, and favorable storage stability.

Basically, when the average particle size is reduced, the surface area per unit volume of the particle is increased, and the contact area between particles in the ink is likely to be increased, or the ink viscosity is increased and clogging is likely to occur. On the other hand, when it becomes large, dispersion tends to be unstable, and there is a tendency to lead to aggregation and sedimentation of the pigment.
In addition, when the average particle size is small, a clear image can be easily obtained, but there is a tendency that the scratch resistance to the printed object after printing is halved. In order to enhance the fixing property of the ink, it has already been proposed that the aqueous pigment-based ink itself contains a resin emulsion. For example, an ink containing wax emulsion, resin emulsion, latex, inorganic or organic ultrafine particles and having a minimum film forming temperature of 40 ° C. or higher is disclosed. Examples of resin emulsions that can be used are vinyl acetate-based, acrylic-based, styrene-based, olefin-based single or copolymer emulsions, and the minimum film-forming temperature is 40 ° C. or more (Patent Document 10). reference). That is, there is no particular limitation on the resin composition as long as the minimum film-forming temperature constraint is satisfied. Further, there is no description or suggestion about the superiority or inferiority of the effect depending on the type of resin, and the performance and effect of the ink shown in the examples are the same and excellent regardless of the type of resin. However, this is a disclosure in a range where the particle diameter of the pigment is as large as 1.0 μm or less. When the particle diameter of the pigment is 10 to 50 nm, the scratch resistance, ink storage stability, image saturation (color tone sharpness) is disclosed. No resin emulsion satisfying the above has been found yet.
Patent Documents 11 and 12 describe water-based pigment ink compositions for ink-jet printing composed of four essential components of pigments, water-based dispersion media, pigment dispersants, and emulsion particles mainly composed of polyurethane resins. . However, this is intended to improve the water resistance of the printed material so that the pigment does not fall off from the printed material during washing. The polyurethane resin emulsion particles also have a particle size of 0.3 μm (300 nm) or less. Specifically, it is described that it is preferably 0.06 μm (60 nm), 0.08 μm (80 nm), 0.1 μm (100 nm), 0.06 μm (60 nm), 0.075 μm ( 75 nm) and 0.08 μm (80 nm).

JP-A-56-147863 Japanese Patent Laid-Open No. 61-083267 JP-A-5-105837 JP-A-10-168367 Japanese Patent Laid-Open No. 10-88050 JP-A-8-244254 JP 10-44473 A WO99 / 05230 Publication JP 2001-192583 A Japanese Patent No. 2867491 JP 2003-96342 A JP 2003-213164 A

  The present invention has been made in view of the above problems, and is a pigment-based inkjet ink (inkjet ink composition) that has excellent image saturation (color tone sharpness), ejection stability, and storage stability. In addition, it is compatible with both scratch resistance, which is a problem with pigment-based inks, and image saturation (sharpness of color tone). An object of the present invention is to provide a pigment-based ink-jet ink (ink-jet ink composition) having no change in characteristics.

  As a result of intensive studies, the inventors of the present invention have the physical properties of ink-jet ink, and by blending a specific emulsion, the image has excellent color saturation (color tone sharpness), ejection stability, and storage. The present inventors have found that a pigment-based ink-jet ink excellent in stability can be obtained, and that the present invention has been completed. Furthermore, the physical properties of the ink-jet ink and specific materials include polyurethane-based resins, specific surfactants, and specific materials. It has been found that a pigment-based ink-jet ink can be obtained by blending an organic solvent, which is excellent in scratch resistance and excellent in ink storage stability and image saturation (color tone sharpness), and completes the present invention. It came to. Therefore, as will be understood from the following description, the present invention can be divided into the invention of the group (I) and the invention of the group (II).

That is, the said subject is achieved by this invention (1)-(8).
(1) "at least water, a water-soluble organic solvents, pigments, emulsion particles, and dispersing agents including, an inkjet ink, the pigment particles has an average particle size (D50) of the 100nm or less, and the pigment The particle size standard deviation in the particle size distribution of the particles is ½ or less of the average particle size, the emulsion particles are urethane emulsion particles having an average particle size of 50 nm or less, and the dispersant is represented by the following general formula (1). The water-soluble organic solvent content is more than 10% by weight and less than 50% by weight, and the pigment content is more than 1% by weight and less than 20% by weight. , and the said content of the emulsion particles is more than 1 wt%, less than 20 wt%, especially the weight of the dispersant is 0.3 to 2 with respect to the pigment 1 Inkjet ink to;

(ｎは３０以上５０以下の整数を表わす。)」、
（２）「当該インクの表面張力が２０ｍＮ／ｍ以上、５０ｍＮ／ｍ以下であることを特徴とする前記第（１）項に記載のインクジェット用インク」、
（３）「当該インクの粘度が１０ｍｐａ・ｓ以下であることを特徴とする前記第（１）項又は第（２）項に記載のインクジェット用インク」

(n represents an integer of 30 to 50)
( 2 ) “The ink for ink-jet recording as described in (1) above, wherein the surface tension of the ink is 20 mN / m or more and 50 mN / m or less”,
( 3 ) "Inkjet ink according to item (1) or (2), wherein the viscosity of the ink is 10 mpa · s or less"

Moreover, the said subject is achieved by this invention ( 4 )-( 16 ).
(4) "the paragraph (1), second (3) section jet recording ink according to any one characterized in that it comprises a further field surfactant",
( 5 ) "Ink for inkjet recording according to any one of items (1) to (4), wherein the urethane emulsion particles are anionic self-emulsifying type",
( 6 ) "Ink for inkjet recording according to any one of items (1) to (5), wherein the urethane emulsion particles are of a polycarbonate type",
( 7 ) "Ink for inkjet recording according to any one of items (1) to (6), wherein the urethane-based emulsion particles have a glass transition point of 0 to -50 ° C",
( 8 ) "Ink for inkjet recording according to any one of items (1) to (7), wherein the urethane emulsion particles have an average particle size of 150 nm or less",
( 9 ) "Ink for inkjet recording according to any one of items (1) to (8), wherein the minimum film-forming temperature of the urethane emulsion particles is 25 ° C or lower",
( 10 ) "Ink for inkjet recording according to any one of items ( 4) to (9 ), wherein the surfactant is nonionic",
( 11 ) "The inkjet recording ink according to item ( 10 ), wherein the nonionic surfactant has an HLB value in the range of 8.5 to 20,"
( 12 ) "Ink for inkjet recording according to item ( 10) or (11 ), wherein the hydrophilic group of the nonionic surfactant is a polyoxyethylene group",
( 13 ) "Inkjet recording according to any one of items ( 4) to ( 13 ), wherein the content of the surfactant is 0.1 wt% or more and 10 wt% or less. For ink ",
( 14 ) Any one of ( 1) to (13 ) above, wherein the water-soluble organic solvent contains at least 2-ethyl-1,3-hexanediol (hereinafter abbreviated as EHD) Ink-jet recording ink described in "
( 15 ) "Ink for inkjet recording according to item ( 14 ), wherein the EHD content is 0.1 wt% or more and 4.0 wt% or less",
( 16 ) "Ink for inkjet recording according to any one of items ( 1) to (15 ), wherein pH is 7 to 10,"

Moreover, the said subject is achieved by this invention ( 17 )-( 28 ).
( 17 ) "The inkjet ink according to any one of items (1) to ( 16), wherein the dispersant is POE (n = 40) β-naphthyl ether",
( 18 ) "Ink for inkjet recording according to any one of items ( 1) to (17 ), wherein the pigment is a self-dispersing pigment",
( 19 ) "Ink for inkjet recording according to any one of items (1) to ( 18 ), wherein the pigment is a capsule pigment",
( 20 ) "Ink for inkjet recording according to any one of items (1) to ( 19 ), wherein a black pigment among the pigments is carbon black",
( 21 ) "Among the pigments, magenta pigments are Pig. Red 5, 7, 12, 48 (Ca), 48 (Mn), 57 (Ca), 57: 1, 112, 122, 123, 146, 168, 176. , 184, 185, 202, Pig. Violet 19, and the inkjet recording ink according to any one of (1) to ( 19 ),
( 22 ) "Of the pigments, the cyan pigment is at least one of Pig. Blue 1, 2, 3, 15, 15: 3, 15: 4, 16, 22, 60, 63, 66. The inkjet recording ink according to any one of (1) to ( 19 ),
( 23 ) “Of these pigments, the yellow pigment is Pig. Yellow 1, 2, 3, 12, 13, 14, 16, 17, 73, 74, 75, 83, 93, 95, 97, 98, 114, 120, 128. 129, 138, 150, 151, 154, 155, 174, 180. The ink-jet recording according to any one of items (1) to ( 19 ), characterized in that it is at least one of the following. ink",
( 24 ) "Ink cartridge characterized by containing ink jet ink according to any one of (1) to ( 23 )",
( 25 ) "Inkjet recording apparatus comprising a head for recording by ejecting the inkjet ink according to any one of (1) to ( 23 )",
( 26 ) "Image forming method characterized by printing using the ink jet recording apparatus according to item ( 25 )",
( 27 ) "Image formed product printed by the image forming method according to item ( 26 )",
( 28 ) "Image-formed product according to item ( 27 ), wherein the image support is paper"

As is clear from the detailed and specific description including the following examples, the ink-jet inks of the present invention of the group (I) are conventional in terms of image sharpness (saturation) and ejection stability. It is better. In addition, the storage stability is remarkably improved. Furthermore, according to the present invention of the group (I), each of the ink cartridge, the inkjet printing apparatus and the image forming method to which the pigment ink composition of the present invention is applied has excellent image sharpness (saturation). An image formation can be provided.
Further, the ink-jet ink of the present invention of the group (II) is superior to conventional ones in scratch resistance, ink storage stability, and image saturation (color tone sharpness). Further, according to the present invention of the group (II), the ink cartridge, the ink jet printing apparatus and the image forming method to which the pigment ink composition of the present invention is applied, respectively, are scratch resistant, ink storability, image coloring It is possible to provide an image formed product excellent in degree (sharpness of color tone).

Hereinafter, the present invention will be described in more detail.
[Invention of Group (I)]
(1) in the group (I) above: “Contains at least water, a water-soluble organic solvent, a pigment and a dispersant, the average particle diameter (D50) of the pigment particles is 100 nm or less, and the particle diameter in the particle size distribution of the pigment particles According to the inkjet ink characterized in that the standard deviation is 1/2 or less of the average particle size, the average particle size (D50) of the pigment particles is 100 nm or less, and the particle size standard in the particle size distribution of the pigment particles Since the deviation is ½ or less of the average particle diameter, the ink for ink-jet recording is provided, in which the saturation of the formed image is improved and a clear image can be formed.

In addition, according to the ink for ink jet recording of (2) above, the ink for ink jet recording is provided that further includes emulsion particles to improve the saturation of the formed image and enable clear image formation.
In addition, according to the inkjet recording ink of (3), since the average particle diameter of the emulsion particles is 50 nm or less, the saturation of the formed image is improved, and an inkjet recording ink capable of forming a clear image is provided. Is done.

  In addition, according to the ink for ink jet recording of the above (4), since the content of the emulsion particles is 1% by weight or more and 20% by weight or less, the saturation of the formed image is improved and a clear image can be formed. Ink jet recording ink is provided.

  In addition, according to the ink jet recording ink of the above (5), since the pigment content is 1% by weight or more and 20% by weight or less, the saturation of the formed image is improved and a clear image can be formed. A recording ink is provided.

  In addition, according to the ink for ink jet recording of (6), since the content of the water-soluble organic solvent is 10% by weight or more and 50% by weight or less, the saturation of the formed image is improved, and a clear image is formed. An ink for ink jet recording is provided.

  In addition, according to the ink for ink jet recording of (7), since the surface tension of the ink is 20 mN / m or more and 50 mN / m or less, the saturation of the formed image is improved, and the ink jet capable of forming a clear image. A recording ink is provided.

  Further, in the ink for ink jet recording of the above (25), since the weight reference of the dispersant is 0.3 or more and 2 or less with respect to the pigment 1, the color saturation of the formed image is improved, and the ink jet capable of forming a clear image. A recording ink is provided.

The ink-jet ink (ink-jet recording ink composition) of the present invention of the group (I) contains at least water, a water-soluble organic solvent, a pigment and a dispersant, and the average particle diameter (D50) of the pigment particles is 100 nm or less. The particle diameter standard deviation in the particle size distribution of the pigment particles is ½ or less of the average particle diameter.
The average particle diameter (D50) of the pigment particles is preferably 100 nm or less, and the particle diameter standard deviation in the particle size distribution of the pigment particles is preferably in the range of 1/2 or less of the average particle diameter. This makes it possible to prevent irregular reflection of the pigment particles in the print image portion and provide a print image having a uniform density.
On the other hand, when the average particle size of the pigment particles is 100 nm or more and the particle size standard deviation is ½ or more of the average particle size, the pigment particles in the printed image portion cause irregular reflection, resulting in a decrease in image saturation and non-uniform density.

More preferably, the average particle diameter (D50) of the pigment particles is 50 nm or less, and the particle diameter standard deviation in the particle size distribution of the pigment particles is 1/4 or less of the average particle diameter. The reason is based on the fact that it has an effect of preventing irregular reflection of pigment particles in the printed image portion.
In the present invention of the group (I), the storage stability of the pigment-based ink is further improved. The reason for this is not clear, but as is clear from the examples shown later, when the amount of dispersion used is 0.3 or more and 2 or less with respect to the pigment 1 on a weight basis, the effect becomes significant. In particular, when the dispersant represented by the general formula (1) is used, the effect is further improved.
In addition, the average particle diameter in the present invention of the group (I) and the group (II) is a measured value D50 particle size standard deviation of the particle size analyzer UPA150 manufactured by Nikkiso Co., Ltd. is manufactured by Nikkiso Co., Ltd. This is a measured value sd of the particle size analyzer UPA150.

Examples of the pigment used in the present invention of the group (I) (same as in the present invention of the group (II)) include carbon black produced by the furnace method or the channel method.
Examples of the yellow pigment include Pigment Yellow 1, Pigment Yellow 2, Pigment Yellow 3, Pigment Yellow 12, Pigment Yellow 13, Pigment Yellow 14, Pigment Yellow 16, Pigment Yellow 17, Pigment Yellow 73, Pigment Yellow 74, Pigment Yellow 75, Pigment Yellow 83, Pigment Yellow 93, Pigment Yellow 95, Pigment Yellow 97, Pigment Yellow 98, Pigment Yellow 114, Pigment Yellow 120, Pigment Yellow 128, Pigment Yellow 129, Pigment Yellow 138, Pigment Yellow 150, Pigment Yellow 151, Pigment Yellow 154 Pigment Yellow 155, Pigment Yellow 174, Pigme Door yellow 180, and the like.

  Examples of magenta pigments include Pigment Red 5, Pigment Red 7, Pigment Red 12, Pigment Red 48 (Ca), Pigment Red 48 (Mn), Pigment Red 57 (Ca), Pigment Red 57: 1, Pigment Red 112, and Pigment Red. 122, Pigment Red 123, Pigment Red 168, Pigment Red 176, Pigment Red 184, Pigment Red 185, Pigment Red 202, Pigment Violet 19, and the like.

Examples of cyan pigments include Pigment Blue 1, Pigment Blue 2, Pigment Blue 3, Pigment Blue 15, Pigment Blue 15: 3, Pigment Blue 15: 4, Pigment Blue 16, Pigment Blue 22, Pigment Blue 60, Pigment Blue 63, Pigment Blue 66, Bat Blue 4, Bat Blue 60 and the like.
By using Pigment Yellow 138 as the yellow pigment, Pigment Red 122 as the magenta pigment, and Pigment Blue 15 as the cyan pigment, it is possible to obtain a well-balanced ink having excellent color tone and light resistance.

The weight standard of the dispersant with respect to the pigment of the inkjet ink of the present invention of the group (I) is preferably 0.3 or more and 2 or less, more preferably 0.5 to 2 with respect to the pigment 1. By setting it in the range of 0.5 to 2, an ink liquid having a small average particle diameter and a small standard deviation in the particle size distribution can be provided. An image is formed.
If the dispersant for the pigment is less than 0.3, the average particle size is large, and satisfactory chroma cannot be obtained due to the ink liquid having a large standard deviation in the particle size distribution. When it is larger than 2, the viscosity of the ink is too high, and printing by the inkjet method tends to be difficult.

  Any dispersant may be used for the ink-jet ink of the present invention. By using the following general formula (1), an ink-jet ink having a small average particle diameter and a small standard deviation in the particle size distribution can be obtained. .

(ｎは２０以上１００以下の整数を表わす。)

(n represents an integer of 20 to 100.)

  In the dispersant represented by the general formula (1), n is preferably 20 or more and 100 or less, more preferably 30 or more and 50 or less. If n is less than 20, the dispersion stability tends to decrease, the average particle size is large, and satisfactory saturation cannot be obtained due to the ink liquid having a large standard deviation in the particle size distribution. On the other hand, when n is larger than 100, the viscosity of the ink increases, and printing by the ink jet method tends to be difficult. POE (n = 40) β naphthyl ether is more preferred.

It is preferable that emulsion particles are contained in the ink-jet ink of the present invention of the group (I). This is because by adding emulsion particles, irregular reflection of the pigment particles in the print image portion can be prevented and a print image having a uniform density can be provided.
The particles of the emulsion of the present invention of the group (I) refer to emulsion particles in which the continuous phase is water and the dispersed phase is the following components.

Components of the dispersed phase include acrylic, vinyl acetate, styrene-butadiene, vinyl chloride, acrylic-styrene, butadiene, styrene, crosslinked acrylic, crosslinked styrene, benzoguanamine, phenol, silicon, epoxy, urethane Type, paraffin type, fluorine type and the like. Of these, urethane is particularly preferably used from the viewpoint of improving the saturation of the formed image and ink dispersion stability when it is contained in the ink jet ink.
The average particle size of the emulsion particles of the present invention in the group (I) is preferably 50 nm or less, more preferably 40 nm or less. If the average particle size of the emulsion particles exceeds 50 nm, transparency and saturation of ink jet ink will be reduced, and emulsion particles in the printed image will cause irregular reflection, resulting in reduced image saturation and uneven density. It becomes.

  The content of the emulsion particles of the present invention in the group (I) is preferably 1% by weight or more and 20% by weight or less, more preferably 5% by weight or more and 10% by weight or less. If the content of the emulsion particles is less than 1% by weight, the effect of preventing the irregular reflection of the emulsion particles is insufficient, and if it is more than 20% by weight, the viscosity of the ink tends to be too high and printing by the inkjet method tends to be difficult. There is.

  The content of the pigment of the present invention in the group (I) is preferably 1% by weight or more and 20% by weight or less, more preferably 5% by weight or more and 10% by weight or less. When the pigment content is less than 1% by weight, the coloring power at the time of printing is insufficient, and when it is more than 20% by weight, the viscosity of the ink tends to be too high and printing by the inkjet method tends to be difficult. is there.

  The content of the water-soluble organic solvent of the present invention in the group (I) is preferably 10% by weight or more and 50% by weight or less, more preferably 20% by weight or more and 40% by weight or less. When the content of the water-soluble organic solvent is less than 10% by weight, the effect of preventing the irregular reflection of the water-soluble organic solvent is insufficient. When the content is more than 50% by weight, the viscosity of the ink is too high and printing by the ink jet system is possible. Tend to be difficult. The water-soluble organic solvent referred to in the present invention in the group (I) has a boiling point of 180 ° C. or higher.

  When the water-soluble organic solvent is contained in the ink for ink jet recording, the water retention and wettability of the ink composition can be ensured. There is no increase in viscosity and excellent storage stability can be realized. Further, an ink for ink jet recording that maintains the fluidity of the dried material for a long time can be realized even when left in an open state at the nozzle tip of an ink jet printer. Furthermore, nozzle clogging does not occur during printing or when restarting after printing interruption, and high ejection stability can be obtained.

Examples of the water-soluble organic solvent used in the present invention of the group (I) are as follows, but are not limited thereto.
For example, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, polypropylene glycol, 1,5-pentanediol, 1,6-hexanediol, glycerin, 1,2,6-hexanetriol, 2-ethyl-1 , 3-hexanediol, ethyl-1,2,4-butanetriol, polyhydric alcohols such as 1,2,3-butanetriol, petriol, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, Polyhydric alcohol alkyl ethers such as diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, and propylene glycol monoethyl ether Polyhydric alcohol aryl ethers such as tellurium, ethylene glycol monophenyl ether, ethylene glycol monobenzyl ether; 2-pyrrolidone, N-methyl-2-pyrrolidone, N-hydroxyethyl-2-pyrrolidone, 1,3-dimethyl Nitrogen-containing heterocyclic compounds such as imidazolidinone, ε-caprolactam, γ-butyrolactone; amides such as formamide, N-methylformamide, N, N-dimethylformamide; monoethanolamine, diethanolamine, triethanolamine, monoethylamine, Examples thereof include amines such as diethylamine and triethylamine, sulfur-containing compounds such as dimethyl sulfoxide, sulfolane and thiodiethanol, propylene carbonate, and ethylene carbonate. These water-soluble organic solvents can be used alone or in combination of two or more.
Among the water-soluble organic solvents, particularly containing diethylene glycol, triethylene glycol and / or glycerin prevents clogging due to drying of the ink, that is, prevention of poor jetting characteristics due to water evaporation, and improves the saturation of the formed image of the present invention. An excellent effect can be obtained.

The surface tension of the ink-jet ink of the invention of the group (I) is preferably 20 mN / m or more and 50 mN / m or less, more preferably 25 mN / m or more and 45 mN / m or less.
If the surface tension of the inkjet ink is less than 20 mN / m or more than 50 mN / m, not only the wettability between the ink and the paper surface and the penetration rate into the paper are deteriorated, but also the saturation of the formed image is inferior and clear. Image formation cannot be obtained. In addition, the surface tension of the ink-jet ink in the present invention of the group (I) and the group (II) shows a value measured with the KRUSS K-10ST type in an environment of 23 ° C. and 55% RH.

  When the viscosity of the inkjet ink of the present invention of the group (I) is larger than 10 mpa · s, it tends to be difficult to print with an inkjet printer having low ejection energy. The viscosity of the ink for inkjet recording in the present invention is a value measured with a RE-80L type manufactured by Toki Sangyo Co., Ltd. in an environment of 23 ° C. and 55% RH.

An ink cartridge containing the ink for ink jet recording of the present invention can be formed, and the ink is ejected from the orifice according to a recording signal in the ink jet apparatus containing the ink cartridge, and an image is formed on the recording material. An image formed product can be obtained.
In addition, as a means for printing using the ink for inkjet recording of the present invention, a printing system using the above-described inkjet printer (inkjet printer) having a continuous jet type or on-demand type recording head can be cited. Note that examples of the on-demand type include a piezo method, a thermal ink jet method, and an electrostatic method.
As these ink cartridge formation, ink jet apparatus formation, and image formation method, known techniques relating to this technical field such as those described in Japanese Patent Application Laid-Open No. 2000-198958 can be appropriately employed.

  In the present invention, the recording medium is preferably used regardless of whether the recording medium has an absorptivity with respect to an ink composition such as paper or a recording medium substantially non-absorbable with respect to the ink composition. Specific examples of the recording medium to which the ink jet recording method according to the present invention can be applied include plastic sheets based on polyethylene terephthalate, polycarbonate, polypropylene, polyethylene, polysulfone, ABS resin, polyvinyl chloride, brass, iron, aluminum, SUS, a metal surface such as copper or a non-metallic base material, a recording medium that has been subjected to a metal coating process by vapor deposition or the like, a recording medium that has been subjected to water-repellent treatment using paper as a base material, and an inorganic material are fired at a high temperature And a recording medium made of a so-called ceramic material. Of these, paper is most preferable from the viewpoint of economy and the naturalness of images.

[Invention of Group (II)]
According to the invention, according to (9) “ink jet recording ink comprising at least a pigment, water, a water-soluble organic solvent, a surfactant, and a polyurethane resin” in the group (II) above , Ink jet ink physical properties and specific materials include polyurethane resins, specific surfactants, and specific organic solvents, resulting in excellent scratch resistance, ink storability and image saturation (clear color tone) A pigment-based ink for ink jet recording is also provided.

That is, in the present invention of the group (II), the practicable emulsion resin is a polyurethane resin, and when used as an ink preparation raw material or after preparation of the ink composition of the present invention, an O / W type It exists as an emulsion.
In the polyurethane resin emulsion, a relatively hydrophilic ordinary polyurethane resin is emulsified using an emulsifier externally, and a functional group that functions as an emulsifier is introduced into the resin itself by means such as copolymerization. Self-emulsifying emulsions. Either can be implemented, but care is required because there is a slight difference in the dispersion stability of the pigment and emulsion particles depending on the combination of the components of the ink composition.
In various combinations with pigments and dispersants, it is an anionic self-emulsifying polyurethane emulsion resin that is always excellent in dispersion stability.
In this case, the polyurethane resin is preferably a polycarbonate resin rather than a polyester resin in terms of pigment fixing and dispersion stability. This is also true in the present invention of the (I) group.

  The glass transition point of the polyurethane resin is preferably in the range of 0 to -50 ° C. More preferably, it is in the range of −10 to −40 ° C. The reason is not clear, but when the glass transition point exceeds 0 ° C., the film-forming property of the polyurethane resin is glassy and hard, but the pigment particles and the polyurethane resin land on the object to be printed at the same time. On the other hand, when the glass transition point is 0 ° C. or less, the film-forming property of the polyurethane resin is rubbery and soft, but it has excellent scratch resistance. From the above points, at the same addition amount, the effect of scratch resistance is larger when the glass transition point is in the range of 0 to -50 ° C. The glass transition point of the resin in the present invention of the group (I) and the group (II) is based on either DSC (differential scanning calorimeter) or TMA (thermomechanical analysis) measurement method. is there.

  The average particle diameter (D50) of the polyurethane resin is preferably 150 nm or less. More preferably, it is 100 nm or less. If it exceeds 150 nm, there may be a problem that ink is not ejected while the ink jet printer is operating while printing is continued. Printing can be resumed by cleaning the ink flow path including the nozzle holes of the ink jet printer, but this impedes practicality.

The polyurethane resin preferably has a minimum film forming temperature of room temperature or lower, more preferably 25 ° C. or lower.
If the film formation of the resin emulsion particles is performed at room temperature or lower, particularly 25 ° C. or lower, the binding of the paper fibers described above automatically proceeds without particularly performing treatment such as heating or drying of the image-formed recording medium. This is preferable.
Here, the “minimum film-forming temperature” means that the water-based emulsion particles obtained by dispersing the resin emulsion particles in water are cast thinly on a metal plate such as aluminum and become transparent when the temperature is raised. The lowest temperature at which a continuous film is formed. In the temperature range below the minimum film-forming temperature, a white powder is formed.
“Film-forming” means that when polymer particles are dispersed in water to form a polymer emulsion, a polymer film is formed when the water component, which is a continuous layer of the polymer emulsion, is evaporated. means. This polymer film plays a role of firmly fixing the pigment in the ink composition to the surface of the recording medium. Thus, it is considered that an image excellent in abrasion resistance and water resistance can be realized.

  The content of the polyurethane resin is preferably 0.1% by weight or more and 20% by weight or less, more preferably 1.0% by weight or more and 10.0% by weight or less. If the content of the emulsion particles is less than 0.1% by weight, the amount of polyurethane resin covering the pigment after landing on the object to be printed is insufficient, the scratch resistance effect is small, and if it is more than 20% by weight, the ink The viscosity of the ink tends to be too high and printing by the ink jet method tends to be difficult. The polyurethane resin is preferably added so that the viscosity of the ink is in the range of 2 to 20 mpa · s, and more preferably in the range of 5 to 10 mpa · s. In addition, the viscosity of the ink for ink jet recording in the present invention of the group (I) and the group (II) shows a value measured with a Toki Sangyo RE-80L type in an environment of 23 ° C. and 55% RH. .

The water-soluble organic solvent referred to in the present invention in the group (II) is a solvent having a boiling point of 180 ° C. or higher, like the water-soluble organic solvent referred to in the present invention in the group (I).
When the water-soluble organic solvent is contained in the ink for ink jet recording, the water retention and wettability of the ink composition can be ensured. There is no increase in viscosity and excellent storage stability can be realized. Also, an ink for ink jet recording can be realized that maintains the fluidity of the dried material for a long time even when left in an open state at the nozzle tip of an ink jet printer or the like. Furthermore, nozzle clogging does not occur during printing or when restarting after printing interruption, and high ejection stability can be obtained.

Examples of the water-soluble organic solvent used in the present invention of the group (II) are the same as the water-soluble organic solvent used in the present invention of the group (I), and these water-soluble organic solvents are: These can be used alone or in admixture of two or more.
Among the water-soluble organic solvents, particularly containing diethylene glycol, triethylene glycol and / or glycerin prevents clogging due to drying of the ink, that is, prevention of poor jetting characteristics due to water evaporation, and improves the saturation of the formed image of the present invention. An excellent effect can be obtained.

  Preferably, it contains 2-ethyl-1,3-hexanediol (EHD) to increase the ink permeability and at the same time eliminate the bleeding by keeping the pigment on the surface, resulting in a high image density and little show-through. A printed image can be obtained. The content of EHD is preferably 0.1% by weight or more and 4.0% by weight or less, more preferably 0.5% by weight or more and 3.0% by weight or less. If it is less than 0.1% by weight, the effect is small, and if it exceeds 4.0% by weight, the solubility itself is low, and the reliability deteriorates.

  Nonionic surfactants used in the present invention of the group (II) include polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene glycol ester, polyoxyethylene polyoxypropylene decyl ether or Nonionic surfactants such as acetylene-based surfactants, silicon-based surfactants, and fluorine-based surfactants may be used.

In the present invention of the group (II), the following surfactants may be used in combination as long as the ink properties are not affected.
Specifically, nonionic surfactants include BT series (Nikko Chemicals) Nonipol series (Sanyo Kasei), D-, P-series (Takemoto Yushi) Surfynol series (Air Products) Olphin series (Nisshin) Chemistry) EMALEX DAPE series (Japan emulsion), silicone surfactants (Toray Dow Corning, etc.), fluorosurfactants (Neos, Sumitomo 3M, Dupont, Daikin), etc.

  These surfactants are added to reduce the surface tension of the ink and increase the permeability of the ink to the paper, thereby increasing the dryness of the printed image. The amount of the surfactant added is the surface tension of the ink. Is usually adjusted to 50 mN / m or less, preferably 40 mN / m or less, and the content is preferably 0.1 wt% or more and 10.0 wt% or less, more preferably 1.0 wt%. As mentioned above, it is 5.0 weight% or less. If the addition amount of the surfactant is less than 0.1% by weight, the dynamic surface tension is high and the drying property is poor. Conversely, if the addition amount is more than 10.0% by weight, the surfactant is deposited during storage. Occurs.

The HLB value can be measured and calculated by various methods, and there are slight differences depending on the method. Therefore, in this invention, it defined as what is described in FIG.
Here, inorganic and organic in the formula illustrated in FIG. 1 are inorganic and organic in the constituent atoms, molecules, groups, or bonding parts of each part of the organic compound submitted by Fujita in 1941. Are assigned to each other and added. As the HLB value increased, the permeation decreased, and it was found that the permeation amount was 8.5 to 20 and was almost as small as when no surfactant was added. More preferably, it is 10-16. This is because when a surfactant with a small HLB value (high hydrophobicity) is added, the familiarity with the surface of paper that has been subjected to hydrophobic treatment in advance usually becomes better, and the penetration of ink into the paper increases. It is considered.
HLB is calculated | required by following Formula.
HLB value = (inorganic / organic) × 10

  It is preferable that the hydrophilic group of the nonionic surfactant of the present invention in the group (II) is a polyoxyethylene group. The reason is not clearly understood, but it is preferably a polyoxyethylene group from the viewpoint that the charge on the pigment surface can be suitably maintained and the foaming property of the ink can be reduced.

  The average particle diameter (D50) of the pigment particles is preferably 100 nm or less. This is because by making the pigment particle diameter equal to or smaller than the specific particle diameter, irregular reflection of the pigment particles in the print image portion can be prevented and a print image having a uniform density can be provided. On the other hand, when the average particle diameter of the pigment particles exceeds 100 nm, the pigment particles in the printed image portion cause irregular reflection, resulting in a decrease in image saturation and uneven density. The average particle diameter (D50) of the pigment particles is more preferably 50 nm or less. The reason is based on the fact that it has an effect of preventing irregular reflection of pigment particles in the printed image portion. The average particle size of the pigment particles in the present invention is a value measured with Nikkiso Microtrac UPA in an environment of 23 ° C. and 55% RH.

  The pH of the ink for ink jet recording of the invention of the group (II) is preferably 7 or more and 10 or less. If the pH of the ink for ink jet recording is less than 7 or greater than 10, not only is the ink easily aggregated but also the formed image is inferior in saturation and a clear image cannot be formed. Moreover, since the pH stable area | region of the polyurethane resin to add is 7-10 vicinity, it is necessary to adjust there. In addition, pH of the ink for inkjet recording in this invention shows the value measured by Toa Denpa Kogyo HM-50V type in the environment of 23 degreeC and 55% RH.

  One form of the pigment used in the present invention of the group (II) is characterized by being dispersed with a dispersant. By adding the dispersant, the pigment is dispersed, the average particle diameter (D50) of the pigment particles can be reduced, and the standard deviation of the particle diameter can be reduced, and a printed image with clear and uniform image density can be provided.

  The weight standard of the dispersant with respect to the pigment of the inkjet recording ink of the present invention of the group (II) is preferably 0.3 or more and 2 or less, more preferably 0.5 to 2.0 with respect to the pigment 1. By setting it in the range of 0.3 to 2.0, an ink liquid having a small average particle diameter and a small standard deviation in the particle size distribution can be provided. If the dispersant for the pigment is less than 0.3, the average particle size is large, and satisfactory chroma cannot be obtained because of the ink liquid having a large standard deviation in the particle size distribution. If it is greater than 2.0, the ink viscosity tends to be too high, and printing by the inkjet method tends to be difficult.

  The dispersant for the ink jet recording ink of the present invention of the group (II) may be a known one, but by using the general formula (1), the average particle size is small and the standard deviation in the particle size distribution is small. Recording ink can be obtained.

(ｎは２０以上１００以下の整数を表わす。)

(n represents an integer of 20 to 100.)

  In the dispersant represented by the general formula (1), n is preferably 20 or more and 100 or less, more preferably 30 or more and 50 or less. When n is less than 20, the dispersion stability tends to be lowered, the average particle size is large, and satisfactory saturation cannot be obtained due to the ink standard having a large standard deviation in the particle size distribution. On the other hand, when n is larger than 100, the viscosity of the ink increases, and printing by the ink jet method tends to be difficult. POE (n = 40) β naphthyl ether is more preferred.

Another form of the pigment used in the present invention is a self-dispersing pigment. In order to make the pigment into a self-dispersing pigment, a chemical treatment is performed on the pigment surface, and a necessary amount of functional groups capable of stably dispersing each pigment particle in water by an electrostatic repulsive force may be chemically bonded.
Examples of methods for producing these self-dispersing pigments are described in US Pat. No. 5,571,311, US Pat. No. 5,630,868, US Pat. No. 5,707,432, JEJohnson, Imaging Science and Technology's 50th Annual Coference (1997), Yuan Yu, Imaging Science. and Technology's 53th Annual Conference (2000), Polyfile, 1248 (1996). By using a self-dispersing pigment, it is possible to provide a printed image with a clear image and uniform density.

Another form of the pigment used in the present invention is a capsule-type pigment. In order to make the pigment into a capsule-type pigment, a microencapsulated pigment dispersion can be prepared by coating the pigment with an anionic group-containing organic polymer compound, which is disclosed in JP-A-9-151342.
Examples of the resin containing the colorant include a resin in which a water-insoluble colorant is confined in a resin microcapsule, and a resin emulsion in which a water-insoluble colorant dissolved or dispersed in an oily solvent is dispersed in an aqueous medium. In particular, a microencapsulated resin that is confined is preferable. By using the capsule-type pigment, it is possible to provide a printed image with a clear image and uniform density.

  As the pigment used in the present invention of the (II) group, the black pigment includes carbon black produced by the furnace method or the channel method as in the case of the pigment used in the present invention of the (I) group.

  Examples of magenta pigments include Pigment Red 5, Pigment Red 7, Pigment Red 12, Pigment Red 48 (Ca), Pigment Red 48 (Mn), Pigment Red 57 (Ca), Pigment Red 57: 1, Pigment Red 112, and Pigment Red. 122, Pigment Red 123, Pigment Red 168, Pigment Red 176, Pigment Red 184, Pigment Red 185, Pigment Red 202, Pigment Violet 19, and the like.

  Examples of cyan pigments include Pigment Blue 1, Pigment Blue 2, Pigment Blue 3, Pigment Blue 15, Pigment Blue 15: 3, Pigment Blue 15: 4, Pigment Blue 16, Pigment Blue 22, Pigment Blue 60, Pigment Blue 63, Pigment Blue 66, Bat Blue 4, Bat Blue 60 and the like.

  Examples of the yellow pigment include Pigment Yellow 1, Pigment Yellow 2, Pigment Yellow 3, Pigment Yellow 12, Pigment Yellow 13, Pigment Yellow 14, Pigment Yellow 16, Pigment Yellow 17, Pigment Yellow 73, Pigment Yellow 74, Pigment Yellow 75, Pigment Yellow 83, Pigment Yellow 93, Pigment Yellow 95, Pigment Yellow 97, Pigment Yellow 98, Pigment Yellow 114, Pigment Yellow 120, Pigment Yellow 128, Pigment Yellow 129, Pigment Yellow 138, Pigment Yellow 150, Pigment Yellow 151, Pigment Yellow 154 Pigment Yellow 155, Pigment Yellow 174, Pigme Door yellow 180, and the like.

In the case of the pigment used in the invention of the second group (II) and the ink for ink jet recording of the invention, an ink cartridge containing the ink can be formed, and the ink can be applied to the ink by the ink jet apparatus containing the ink cartridge. In accordance with the recording signal, it is ejected from the orifice, image formation is performed on the recording material, and an image formed product can be obtained.
In addition, as a means for printing using the ink for inkjet recording of the present invention, a printing system using the above-described inkjet printer (inkjet printer) having a continuous jet type or on-demand type recording head can be cited. Note that examples of the on-demand type include a piezo method, a thermal ink jet method, and an electrostatic method.
As these ink cartridge formation, ink jet apparatus formation, and image formation method, known techniques relating to this technical field such as those described in Japanese Patent Application Laid-Open No. 2000-198958 can be appropriately employed.

  In the present invention, the recording medium is preferably used regardless of whether the recording medium has an absorptivity for an ink composition such as paper or the like and a recording medium substantially non-absorbable for the ink composition. Specific examples of the recording medium to which the ink jet recording method according to the present invention can be applied include plastic sheets based on polyethylene terephthalate, polycarbonate, polypropylene, polyethylene, polysulfone, ABS resin, polyvinyl chloride, brass, iron, aluminum, SUS, a metal surface such as copper or a non-metallic base material, a recording medium that has been subjected to a metal coating process by vapor deposition or the like, a recording medium that has been subjected to water-repellent treatment using paper as a base material, and an inorganic material are fired at a high temperature And a recording medium made of a so-called ceramic material. Of these, paper is most preferable from the viewpoint of economy and the naturalness of images.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail based on an Example, this invention is not limited to a present Example. In addition, the number of parts in an Example represents a weight part.

[Invention of Group (I)]
Ink jet ink was prepared according to the formulations of Reference Examples 1 to 3, Examples 1 and 2 , Comparative Examples 1 to 14, and Reference Examples 4 and 5 in Table 1 below. Filtration was performed to obtain ink jet recording inks (a) to (u) of the present invention.
In the table, glycerin is abbreviated as Gly, diethylene glycol as DEG, polyoxyethylene (3) alkyl (C13) ether sodium acetate as ECTD, and proxel LV (S) 20% solution (preservative) as LV.

分散剤比率＝分散剤重量÷顔料重量とする。

Dispersant ratio = dispersant weight ÷ pigment weight.

In Table 1 above, the formulations of pigment types α to δ, dispersants (1) to (4), and emulsions A to D are as follows.
Pigment type α: Pigment Red 122 (Dainippon Ink, FASTOGEN SUPER MAGENTA RG)
Pigment type β: Pigment Blue 15: 3 (manufactured by Toyo Ink Manufacturing Co., Ltd., LIONOL BLUE FG-7351)
Pigment type γ: Pigment Yellow 138 (Toyo Ink Mfg. Co., Ltd., LIONOLGEN YELLOW 1010)
Pigment type δ: Pigment Red 122 (manufactured by Clariant, HOTTAPERM RED EB02)

The above inks (a) to (u) are filled in a black cartridge of an ink-jet printer EM-930C manufactured by EPSON, then vacuum degassed, and the ejection stability and the printed image are X-rite density using the ink-jet printer EM-930C manufactured by EPSON. Measured with a meter.
At that time, Xerox 4024 paper (size 32 s, air permeability 21 s) manufactured by Xerox Corporation was used as a recording medium.
The sharpness (saturation) of an image refers to the distance from the origin on the chromaticity diagram when the solid image of the image sample is measured with an Xrite densitometer and plotted on the chromaticity diagram. More specifically, regarding the a value and b value on the chromaticity diagram,

を言う。

Say.

Regarding ejection stability, after printing a printed matter, the printer was left in a 40 ° C. environment for one month with the printer head capped. Whether or not the discharge state of the printer after being left restored to the initial discharge state was evaluated by the following number of cleaning operations (the same applies to the invention of the group (II)).
Evaluation criteria ○: Recovered by one operation.
Δ: Recovered by 2 to 3 operations.
X: No recovery was observed even after three or more operations.

Ink storage stability Each ink was placed in a polyethylene container and sealed, and after storing at 70 ° C. for 3 weeks, the particle size, surface tension and viscosity were measured and evaluated according to the rate of change from the initial physical properties as follows.
○: Within 10% △: Within 30% ×: Over 50%

Next, the evaluation results in Table 4 will be examined.
(1) Excellent results were obtained in all evaluations in Reference Examples 1 to 3 (inks a to c) without addition of emulsion and Examples 1 to 2 (inks d to e) with addition of emulsion. Further, the inks of Comparative Examples 1 to 14 and Reference Examples 4 to 5 were inferior in at least one evaluation.
(2) About Comparative Examples 1 to 14 (Inks f to s) In Comparative Example 1 (ink f), the saturation is low and the storage stability is not sufficient. This cause is thought to be due to the addition of no dispersant.
In Comparative Example 2 (ink g), the saturation is low. The cause is considered to be that the amount of the dispersant added is insufficient, the average particle diameter is around 100 nm, and the surface active effect of the dispersant is small.
In Comparative Example 3 (ink h), the saturation is low and the storage stability is not sufficient. This is because the added amount of dispersant is too high, and the viscosity of the ink is too high, which has some influence on the atomization state of the pigment due to mechanical grinding and dispersion, and it becomes difficult to print by the ink jet method. It is considered that the printed image cannot be obtained.
In Comparative Example 4 (ink i), the saturation is low. This is considered to be because the pigment particles do not become fine because the dispersant of the substance of n = 10 in the general formula (1) is used.
In Comparative Example 5 (ink j), the saturation is low and the storage stability is not sufficient. The cause is considered to be that the pigment particles do not become fine because the dispersant of the substance of n = 130 in the general formula (1) is used.
In Comparative Example 6 (ink k), the saturation is low. This is considered because the pigment particles do not become fine because the dispersant of the substance of n = 40 in the general formula (1) is not used.
In Comparative Example 7 (ink 1), the saturation is low. This is considered because the emulsion particles to be added do not use urethane, so that the effect of preventing irregular reflection of the pigment particles in the print image portion is small and a print image having a uniform density cannot be provided.
In Comparative Example 8 (ink m), the saturation is low and the storage stability is not sufficient. This is because the emulsion particles to be added have a D50 of 50 nm or more, which causes a decrease in transparency and saturation when ink jet ink is contained, and emulsion particles in the printed image portion cause irregular reflection, resulting in image saturation. This is considered to be caused by a decrease and non-uniform density.
In Comparative Example 9 (ink n), the saturation is low. This is because the emulsion particles are added in an amount of 1% by weight or less, and the effect of preventing irregular reflection of the emulsion particles is considered insufficient.
In Comparative Example 10 (ink o), the saturation is low and the storage stability is not sufficient. This is because the amount of the emulsion particles added is 20% by weight or more, and the viscosity of the ink is too high, making it difficult to print by the ink jet method, and it becomes impossible to obtain a stable printed image. Conceivable.
In Comparative Example 11 (ink p), the saturation is low and the storage stability is not sufficient. This is considered to be caused by insufficient coloring power when printing because the amount of pigment added is 1% by weight or less.
In Comparative Example 12 (ink q), the saturation is low and the storage stability is not sufficient. This is considered to be caused by the fact that the added amount of the pigment is 20% by weight or more, so that the viscosity of the ink is too high and printing by the ink jet system becomes difficult, and a stable printed image cannot be obtained. It is done.
In Comparative Example 13 (ink r), the saturation is low and the storage stability is not sufficient. This is because the amount of water-soluble organic solvent added is 10% by weight or less, so that the irregular reflection effect of the water-soluble organic solvent is insufficient and a stable print image cannot be obtained due to clogging after nozzle drying. It is thought to do.
In Comparative Example 14 (ink s), the saturation is low. This is because the amount of the water-soluble organic solvent added is 20% by weight or more, so that the viscosity of the ink is too high, making it difficult to print by the inkjet method, and a stable printed image cannot be obtained.

(3) Reference Examples 4 to 5 (Inks t to u) In Reference Example 4 (ink t), the saturation is low. This is considered because the emulsion particles to be added do not use urethane, so that the effect of preventing irregular reflection of the pigment particles in the print image portion is small and a print image having a uniform density cannot be provided.
Reference Example 5 (Ink u) has low saturation. This is because the emulsion particles to be added have a D50 of 50 nm or more, which causes a decrease in transparency and saturation when ink jet ink is contained, and emulsion particles in the printed image portion cause irregular reflection, resulting in image saturation. It is considered that the concentration is lowered and the concentration becomes nonuniform.

[Invention of Group (II)]
Ink jet recording inks were prepared according to the formulations of Examples 3 to 7 , Reference Examples 6 to 22 and Comparative Example 15 shown in Table 5 below, stirred for 1 hour, and then filtered through a membrane filter having a pore size of 1.2 μm. Recording inks (a) to (w) were obtained.
In the table, glycerin is abbreviated as Gly, diethylene glycol is abbreviated as DEG, proxel LV (S) 20% solution (preservative) is abbreviated as LV, and 2-ethyl-1,3-hexanediol is abbreviated as EHD.

The ink formulation is
(1) Gly, DEG
(2) EHD
(3) Surfactant (4) LV
(5) Add in the order of distilled water, stir for about 30 minutes, add pigment dispersion, stir for 30 minutes, adjust pH (around 7-10), add polyurethane resin, stir for 30 minutes, inkjet Create ink for use.

分散剤比率＝分散剤重量÷顔料重量とする。

Dispersant ratio = dispersant weight ÷ pigment weight.

  In Table 5 above, the pigment types (α) to (ζ), surfactants (A) to (E) agent physical properties, emulsions (a) to (g) and dispersants (1) to (4) are formulated. Hereafter, it is as Tables 6-9.

After filling the above ink (a) to (w) into a black cartridge of an EPSON EM-930C modified machine manufactured by EPSON, vacuum deaeration, and using an EPSON EM-930C modified machine, discharge stability and print image can be obtained. It measured with the X-rite densitometer.
At that time, Xerox 4024 paper (size 32 s, air permeability 21 s) manufactured by Xerox Corporation was used as a recording medium.
The sharpness (saturation) of an image refers to the distance from the origin on the chromaticity diagram when the solid image of the image sample is measured with an Xrite densitometer and plotted on the chromaticity diagram. More specifically, regarding the a value and b value on the chromaticity diagram,

を言う。

Say.

Image Sharpness (Saturation) Evaluation For pigment type α type, chromaticity of 60 or higher is indicated by ○, 60 to 55 is indicated by Δ, and the following is indicated by ×.
In the pigment type β type, the saturation is 50 or more, ◯, 50 to 45 is Δ, and the following is ×.
For the pigment type γ type, chromaticity of 58 or more is indicated by ◯, 58 to 53 are indicated by Δ, and the following are indicated by ×.
In the pigment type δ type, a saturation of 75 or more is indicated by ◯, 75 to 70 is indicated by Δ, and the following is indicated by ×.
For the pigment type ε type, chromaticity of 48 or more is indicated by ◯, 48 to 43 are indicated by Δ, and the following is indicated by ×.
In the pigment type ζ type, a saturation of 55 or more is indicated by “◯”, a 55-50 is indicated by “Δ”, and the following is indicated by “x”.

Regarding ejection stability, after printing a printed matter, the printer was left in a 40 ° C. environment for one month with the printer head capped. Whether the discharge state of the printer after being left is restored to the initial discharge state was evaluated by the following number of cleaning operations.
○: Recovered by one operation.
Δ: Recovered by 2 to 3 operations.
X: No recovery was observed even after three or more operations.

Ink storage stability Each ink was placed in a polyethylene container and sealed, and after storing at 70 ° C. for 3 weeks, the particle size, surface tension and viscosity were measured and evaluated according to the rate of change from the initial physical properties as follows.
○: Within 10% △: Within 30% ×: Over 50%

Eraser Friction Test A commercially available sand eraser was rubbed 10 times with a weight of 750 g, and the peeled state of the image before and after the friction was observed. The determination was performed as follows.
○: No peeling.
(Triangle | delta): Peeling is recognized partially and visibility also falls.
X: Most part peeled.

Next, the evaluation results in Table 10 will be examined.
(1) Examples 3 to 7 (Inks a to e) were superior in all evaluations.
(2) Reference Examples 6 to 22 (Inks f to v) were inferior in at least one evaluation. In Comparative Example 15 (ink w), all evaluations were inferior.
(3) In Comparative Example 15, it was confirmed that the scratch resistance and the ink storage stability were deteriorated. This is due to the absence of polyurethane resin.
(4) In Reference Example 6 , deterioration of ink storage stability was confirmed. This is because the polyurethane resin is not an anionic self-emulsifying type.
(5) In Reference Example 7 , deterioration of ink storage stability was confirmed. This is because the polyurethane resin is not a polycarbonate type.
(6) In Reference Example 8 , the deterioration of the scratch resistance was confirmed. This is because the glass transition point of the polyurethane resin is not in the range of 0 to -50 ° C.
(7) In Reference Example 9 , deterioration of ink storage stability and ejection stability was confirmed. This is because the average particle size of the polyurethane resin is 150 nm or more.
(8) In Reference Example 10 , the deterioration of scratch resistance was confirmed. This is because the minimum film forming temperature of the polyurethane resin is 25 ° C. or higher.
(9) In Reference Example 11 , deterioration of ejection stability was confirmed. This is because the content of the polyurethane resin is 20% by weight or more.
(10) In Reference Example 12 , deterioration of ink storage stability was confirmed. This is because the surfactant is not nonionic.
(11) In Reference Example 13 , deterioration of ink storage stability was confirmed. This is because the HLB value of the surfactant is not in the range of 8.5-20.
(12) In Reference Example 14 , deterioration of ink storage stability was confirmed. This is because the hydrophilic group of the surfactant is not a polyoxyethylene group.
(13) In Reference Example 15 , it was confirmed that image sharpness, ink storage stability, ejection stability, and scratch resistance were deteriorated. This is because the surfactant content is 10% by weight or more.
(14) In Reference Example 16 , it was confirmed that image sharpness deteriorated. This is because 2-ethyl-1,3-hexanediol is not included as a water-soluble organic solvent.
(15) In Reference Example 17 , deterioration of ejection stability was confirmed. This is because the average particle diameter of the pigment is 100 nm or more.
(16) In Reference Example 18 , it was confirmed that image sharpness, ink storage stability, ejection stability, and scratch resistance were deteriorated. This is because the pigment is not dispersed with the dispersant.
(17) In Reference Example 19 , deterioration of ejection stability was confirmed. This is because the weight reference of the dispersant is 2 or more with respect to the pigment 1.
(18) In Reference Examples 20 and 21 , deterioration of ink storage stability was confirmed. This is because the compound is not a compound represented by the following general formula (1) as a dispersant.

(ｎは３０以上５０以下の整数を表わす。)
（１９）参考例２２では、インク保存性の悪化が確認された。この原因は、分散剤がＰＯＥ（ｎ＝４０）βナフチルエーテルでないことによる。

(n represents an integer of 30 to 50.)
(19) In Reference Example 22 , deterioration of ink storage stability was confirmed. This is because the dispersant is not POE (n = 40) β naphthyl ether.

It is explanatory drawing of HLB.

Claims (28)

At least water, a water-soluble organic solvents, pigments, emulsion particles, and a dispersant ink including ink jet, the pigment particles has an average particle size (D50) of the 100nm or less, and the particle size distribution of the pigment particles The standard deviation in particle size is 1/2 or less of the average particle size, the emulsion particles are urethane emulsion particles having an average particle size of 50 nm or less, and the dispersant is a compound represented by the following general formula (1). The water-soluble organic solvent content is more than 10 wt% and less than 50 wt%, the pigment content is more than 1 wt% and less than 20 wt%, more than 1 wt% content of the emulsion particles is less than 20 wt%, wherein the weight of the dispersant is 0.3 to 2 with respect to the pigment 1 Ink jet ink.

(n represents an integer of 30 to 50.) The ink for ink jet recording according to claim 1, wherein the surface tension of the ink is 20 mN / m or more and 50 mN / m or less. The inkjet ink according to claim 1 or 2 the viscosity of the ink is equal to or less than 10 MPa · s. Jet recording ink according to any one of claims 1 to 3, characterized in that it comprises a further field surfactant. The ink for inkjet recording according to any one of claims 1 to 4, wherein the urethane emulsion particles are of an anionic self-emulsifying type. The ink for inkjet recording according to any one of claims 1 to 5, wherein the urethane emulsion particles are of a polycarbonate type. The ink for inkjet recording according to any one of claims 1 to 6 , wherein the urethane emulsion particles have a glass transition point of 0 to -50 ° C. The ink for inkjet recording according to any one of claims 1 to 7 , wherein the urethane emulsion particles have an average particle size of 150 nm or less. The ink for inkjet recording according to any one of claims 1 to 7 , wherein a minimum film-forming temperature of the urethane emulsion particles is 25 ° C or lower. The ink for inkjet recording according to any one of claims 4 to 9 , wherein the surfactant is nonionic. The ink for inkjet recording according to claim 10 , wherein the nonionic surfactant has an HLB value in the range of 8.5 to 20. The ink for inkjet recording according to claim 10 or 11 , wherein the hydrophilic group of the nonionic surfactant is a polyoxyethylene group. The ink for inkjet recording according to any one of claims 4 to 13 , wherein the content of the surfactant is 0.1 wt% or more and 10 wt% or less. The ink for inkjet recording according to any one of claims 1 to 13 , comprising at least 2-ethyl-1,3-hexanediol (hereinafter abbreviated as EHD) as the water-soluble organic solvent. The ink for inkjet recording according to claim 14 , wherein the content of the EHD is 0.1 wt% or more and 4.0 wt% or less. jet recording ink according to any one of claims 1 to 15 p H is characterized in that it is a 7-10. The inkjet ink according to any one of claims 1 to 16, wherein the dispersant is a POE (n = 40) β-naphthyl ether. The ink for inkjet recording according to any one of claims 1 to 17 , wherein the pigment is a self-dispersing pigment. The ink for inkjet recording according to any one of claims 1 to 18 , wherein the pigment is a capsule-type pigment. The ink for inkjet recording according to any one of claims 1 to 19 , wherein the black pigment among the pigments is carbon black. Among the pigments, magenta pigments are Pig. Red 5, 7, 12, 48 (Ca), 48 (Mn), 57 (Ca), 57: 1, 112, 122, 123, 146, 168, 176, 184, 185, 202, Pig. The ink for inkjet recording according to any one of claims 1 to 19 , wherein there is at least one kind of violet 19 . Among the pigments, cyan pigments are Pig. The inkjet recording according to any one of claims 1 to 19 , wherein the ink jet recording is at least one of Blue 1, 2, 3, 15, 15: 3, 15: 4, 16, 22, 60, 63, 66. For ink. Among the pigments, the yellow pigment is Pig. Yellow 1, 2, 3, 12, 13, 14, 16, 17, 73, 74, 75, 83, 93, 95, 97, 98, 114, 120, 128, 129, 138, 150, 151, 154, 155, The ink for inkjet recording according to any one of claims 1 to 19 , wherein the ink is at least one of 174 and 180. An ink cartridge containing the ink-jet ink according to any one of claims 1 to 23 . 24. An ink jet recording apparatus comprising: a head for recording by ejecting the ink for ink jet according to any one of claims 1 to 23 . An image forming method for printing using the ink jet recording apparatus according to claim 25 . 27. An image formed product printed by the image forming method according to claim 26 . 28. The image-formed product according to claim 27 , wherein the image support is paper.

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