JP2008239705A - Ink set, recording method using the same, and recorded matter - Google Patents

Abstract

[PROBLEMS] To provide excellent color developability for various recording media (plain paper, matte paper, glossy paper, printing paper, etc.), and particularly excellent gloss feeling and gloss uniformity for glossy recording media. A pigment ink set capable of obtaining an excellent image, having high ink storage stability and high reliability such as clogging, and particularly suitable for use in an ink jet recording method, and a recording method and recorded matter using the same To provide.
An ink set comprising a dark ink composition and a light ink composition having the same color but different color densities, wherein the dark ink composition and the light ink composition are both colored. An ink set comprising a colorant coated with a water-insoluble polymer as a material, and a recording method and recorded matter using the ink set.
[Selection figure] None

Description

  The present invention relates to an ink set. More specifically, it has excellent color developability for various recording media (plain paper, matte paper, glossy paper, printing paper, etc.), and particularly excellent gloss and gloss uniformity for glossy recording media. A pigment ink set suitable for use in an ink jet recording method, a recording method using the same, and a recording method. Related to things.

  The ink jet recording method is a printing method in which printing is performed by causing ink droplets to fly and adhere to a recording medium such as paper. Due to recent advances in inkjet recording technology, the inkjet recording method has been used for high-definition image recording (printing), which has been the field of photography and offset printing. High-quality recording has been demanded not only for paper and dedicated paper for ink jet recording (matte and glossy) but also for recording media such as printing paper.

As an ink used for ink jet recording, an ink composition is generally known that includes a coloring material that is a colorant, water, a water-soluble organic solvent, a surfactant, and the like.
As the colorant, dyes or pigments are used. In particular, water-soluble dyes are often used for color inks because of high color saturation, transparency, and high solubility in water. However, such dyes generally have insufficient light resistance and gas resistance, and because they are water-soluble, there are also problems with water resistance. The recorded matter has a drawback that the recorded image has poor storage stability.

  On the other hand, a colorant insoluble in water is advantageous in terms of water resistance. Among pigments that are insoluble in water, in particular, pigments are color materials excellent in light resistance, gas resistance, and water resistance, and therefore, pigment inks that take advantage of these color material properties have been developed. An aqueous pigment ink in which a pigment is dispersed with a surfactant or a polymer dispersant, an aqueous pigment ink using a self-dispersing pigment with a water-dispersible functional group added to the pigment surface, or a pigment coated with a water-dispersible resin An aqueous pigment ink using colored fine particles has been proposed.

  In such a pigment ink, pigment particles (including pigment-containing colored fine particles) are stably dispersed in the ink liquid. The process of drying the ink after the ink has adhered to a recording medium such as paper. As the moisture and volatile solvents evaporate, the stable dispersion system collapses and the pigments tend to aggregate. When the aggregated pigment is deposited on a recording medium such as paper, the smoothness of the surface is lost, the glossiness is deteriorated, the uniformity of the printed image is deteriorated, and there is a problem that a high-quality image cannot be obtained. Further, the reflected light of the deposited pigment makes it possible to see a color with a hue different from the original hue (bronze phenomenon), and there is a problem that an image with a uniform desired hue cannot be obtained.

  Such a change in hue due to the deposition of the coloring material may occur when a dye is used at a high concentration. In order to prevent this, a branched water-soluble polymer is contained in the ink to prevent the ink from being changed. There has been proposed a method for inhibiting the change in hue by inhibiting crystallization or association of dye molecules accompanying drying (see Patent Document 1).

As for the image quality of the pigment ink, the particle diameter of the pigment dispersed in the ink is limited for the purpose of improving glossiness and dispersibility (see Patent Document 2), and the pigment and pigment derivative are used. Including at the same time (see Patent Document 3), for the purpose of improving bleeding and color development, the polymer fine particles are contained (see Patent Document 4), the inorganic fine particles are contained (see Patent Document 5), For the purpose of improving the printing density on plain paper and the glossiness on inkjet paper, an ink containing a water-insoluble vinyl polymer dispersion containing a pigment (see Patent Document 6) has been proposed.
JP-A-8-337748 JP 2002-356737 A JP 2002-294134 A JP 2001-123098 A JP-A-11-209671 JP 2004-75988 A

However, although the method disclosed in Patent Document 1 is effective in suppressing the color material deposition of dye ink, it is insufficient in pigment ink, and the dispersion stability may be deteriorated by including a water-soluble polymer. In addition, there are problems in terms of reliability, such as an increase in ink viscosity.
In addition, when an image is formed as an ink set by combining known pigment inks, even if there is good print quality with a single ink, the pigment at that location aggregates when a mixed color is formed with different inks. There has been a problem that problems such as a decrease in gloss and a deterioration in gloss uniformity of a printed image have not been solved.
Even in the case of an ink set using dark ink and light ink, if different dispersants are used in dark ink and light ink, the pigments aggregate in the mixed portion of the dark ink and light ink, resulting in glossiness. There are problems such as degradation of the print quality and gloss uniformity of the printed image.

  The present invention has been made in view of the above problems, and its object is to have excellent color developability for various recording media (plain paper, matte paper, glossy paper, printing paper, etc.). In particular, it is possible to obtain an image excellent in glossiness and gloss uniformity with respect to a glossy recording medium, and has high ink storage stability and high reliability such as clogging. It is an object to provide a pigment ink set suitable for use in a system, a recording method using the same, and a recorded matter.

  As a result of intensive studies, the inventors have found an ink set containing a dark ink composition and a light ink composition that have the same color but different color densities, and the ink set includes the dark ink composition and the light ink composition. Have found that the above-mentioned problems can be solved by an ink set comprising a pigment coated with a water-insoluble polymer as a colorant. The present invention is based on such knowledge, and the configuration of the present invention is as follows.

1. An ink set comprising a dark ink composition and a light ink composition having the same color but different color densities, wherein both the dark ink composition and the light ink composition are water-insoluble as a coloring material. An ink set comprising a colorant coated with a polymer.

2. The water-insoluble polymer is a polymer obtained by polymerization by a solution polymerization method using at least a polymerizable unsaturated monomer and a polymerization initiator, and the colorant coated with the water-insoluble polymer is the water-insoluble polymer. 2. The ink set according to 1 above, which is a colorant obtained by a phase inversion emulsification method in which at least a colorant and water are added and mixed after being dissolved in an organic solvent, and the organic solvent is removed and dispersed in an aqueous system.

3. The ink set according to 1 or 2, wherein the colorant is a pigment.

4). The ink set according to any one of 1 to 3, wherein the colorant is in a range of colorant: water-insoluble polymer = 1: 0.2 to 1: 1 as a weight ratio.

5. The ink set according to any one of 1 to 4, wherein in the dark ink composition and the light ink composition, the volume average particle diameter of pigment particles in the ink composition is 50 to 150 nm.

6). The ink set according to any one of 1 to 5, further comprising at least a polyhydric alcohol, a solid wetting agent, and a butyl ether of glycol as a water-soluble organic compound.

7. The dark ink composition includes at least a yellow ink composition, a magenta ink composition, and a cyan ink composition, and the light ink composition includes at least a light magenta ink composition and a light cyan ink composition. The ink set as described in any one of -6.

8). A recording method for performing printing by attaching the ink set according to any one of 1 to 7 to a recording medium.

9. 8. An ink jet recording method, wherein printing is performed by discharging the ink droplets according to any one of 1 to 7 and attaching the droplets to a recording medium.

10. A recorded matter recorded by the recording method according to 8 or 9 above.

  According to the present invention, it has excellent color developability for various recording media (plain paper, matte paper, glossy paper, printing paper, etc.), and particularly has excellent gloss and gloss for glossy recording media. Pigment ink set capable of obtaining an image having excellent uniformity and having high ink storage stability and high reliability such as clogging, and particularly suitable for use in an ink jet recording method, and a recording method using the same A record is provided.

Hereinafter, the ink set of the present invention will be described in detail based on preferred embodiments thereof.
A preferred embodiment of the ink set of the present invention is an ink set having at least a yellow ink, a magenta ink, a cyan ink, a light magenta ink, and a light cyan ink,
The light magenta ink and the light cyan ink both contain a colorant coated with a water-insoluble polymer as a colorant,
The water-insoluble polymer in the light magenta ink and the water-insoluble polymer in the light cyan ink are the same or have any of the following similar relationships (i) to (iii).
(I) The types of monomers are exactly the same, but the composition ratio (content ratio) of each monomer is different. (Ii) A monomer that is a main component of a polymer [a monomer that is a constituent unit of a water-insoluble vinyl polymer, Monomer with a content (raw material basis) of 10% by weight or more] is due to the difference in salt type, the number of repeating oxyalkylene units, the chain length of an alkyl group, or the difference between an acryloyl group and a methacryloyl group. (Iii) Monomer that is the main component of the polymer [a monomer that is a constituent unit of the water-insoluble vinyl polymer, and its content (raw material basis) is 10 wt. % Or more of the monomer] is the difference in the type of salt, the difference in the number of repeating oxyalkylene units, the difference in the chain length of the alkyl group, or the acryloyl group and methacrylo In difference in group, that the composition ratio of the monomers to be the main component (content ratio) are different

  Next, each component of the ink set will be described in detail.

[Ink set]
The ink set of the present invention is an ink set containing a dark ink composition and a light ink composition having the same color but different color densities, wherein the dark ink composition and the light ink composition are Both are characterized by containing a colorant coated with a water-insoluble polymer as a coloring material.
Here, “the same color but different color density” means that the same type of colorant is used, and the concentration (weight ratio) of the colorant in each of the dark and light ink compositions. Means different.

The ink set of the present invention may contain one pair of dark and light inks having the same color but different color densities, or may contain two or more pairs.
Here, when the same color and relatively large weight of the colorant are defined as a dark ink composition and a small colorant as a light ink composition, in the ink set of the present invention, the dark ink composition is cyan. It is an ink composition and / or a magenta ink composition, and the light ink composition is preferably a light cyan ink composition and / or a light magenta ink composition. That is, as the dark and light ink composition, it is preferable to use a pair of a cyan ink composition and a light cyan ink composition, a pair of a magenta ink composition and a light magenta ink composition, or both of them. . A pair of a yellow ink composition and a light yellow ink composition, or a pair of a black ink composition and a light black ink composition may be used. In the ink set of the present invention, the dark ink composition includes at least a yellow ink composition, a magenta ink composition, and a cyan ink composition, and the light ink composition includes a light magenta ink composition and a light cyan composition. What contains at least an ink composition is preferable.

The water-insoluble polymer used in the dark and light ink constituted in the ink set of the present invention may be the same and / or any one of the following similar relationships (i) to (iii).
(I) The types of monomers are exactly the same, but the composition ratio (content ratio) of each monomer is different. (Ii) A monomer that is a main component of a polymer [a monomer that is a constituent unit of a water-insoluble vinyl polymer, Monomer with a content (raw material basis) of 10% by weight or more] is due to the difference in salt type, the number of repeating oxyalkylene units, the chain length of an alkyl group, or the difference between an acryloyl group and a methacryloyl group. (Iii) Monomer that is the main component of the polymer [a monomer that is a constituent unit of the water-insoluble vinyl polymer, and its content (raw material basis) is 10 wt. % Or more of the monomer] is the difference in the type of salt, the difference in the number of repeating oxyalkylene units, the difference in the chain length of the alkyl group, or the acryloyl group and methacrylo In difference in group, that the composition ratio of the monomers to be the main component (content ratio) are different

[Colorant]
As the colorant used in the colorant coated with the water-insoluble polymer used in the present invention, existing dyes and pigments described in “Dye Handbook” (publisher: Maruzen Co., Ltd.) and the like can be used.
The colorant used in the present invention is preferably a water-insoluble colorant, and a more preferred colorant is a pigment. As the pigment that can be used in the present invention, any of known inorganic pigments and organic pigments can be used, and pigments such as Pigment Yellow, Pigment Red, Pigment Violet, Pigment Blue, and Pigment Black described in the Color Index. In addition, phthalocyanine-based, azo-based, anthraquinone-based, azomethine-based, condensed ring-based pigments can be exemplified. Further, organic pigments such as yellow No. 4, 5, 205, 401; orange 228, 405; blue No. 1, 404, etc., titanium oxide, zinc oxide, zirconium oxide, iron oxide, ultramarine blue, bitumen, Examples thereof include inorganic pigments such as chrome oxide. For example, C.I. I. Pigment Yellow 1, 3, 12, 13, 14, 17, 24, 34, 35, 37, 42, 53, 55, 74, 81, 83, 95, 97, 98, 100, 101, 104, 108, 109, 110, 117, 120, 128, 138, 150, 153, 155, 174, 180, 198, C.I. I. Pigment Red 1,3,5,8,9,16,17,19,22,38,57: 1,90,112,122,123,127,146,184,202,209, C.I. I. Pigment Bio Red 1,3,5: 1, 16, 19, 23, 38, C.I. I. Pigment Blue 1, 2, 15, 15: 1, 15: 2, 15: 3, 15: 4, 16, C.I. I. Pigment Black 1, 7, etc., and an ink composition can also be formed using a plurality of pigments.

The pigment content in the ink composition constituting the ink set of the present invention is preferably contained in the range of 0.01 to 8% by weight from the viewpoint of color developability and clogging. Further, when the same color and the relatively large weight of the colorant are defined as the dark ink composition and the small colorant as the light ink composition, the pigment content in the dark ink composition is 1.5 to 8 wt. % Is more preferable, and the pigment content in the light ink composition is more preferably 0.01 to 3% by weight.
When the content is 0.01% by weight or more, color development can be satisfied in the light ink composition, and when the content is 8% by weight or less, the glossiness of the printed image, clogging property, ink storage property, etc. Reliability can be satisfied.

[Colorant coated with water-insoluble polymer]
The water-insoluble polymer used in the colorant coated with the water-insoluble polymer used in the present invention is a polymer obtained by polymerization by a solution polymerization method using at least a polymerizable unsaturated monomer and a polymerization initiator. An insoluble polymer refers to a polymer having a solubility in 100 g of water at 25 ° C. of less than 1 g after neutralization.

  Examples of the polymerizable unsaturated monomer include vinyl aromatic hydrocarbons, methacrylic acid esters, methacrylamide, alkyl-substituted methacrylamide, maleic anhydride, vinyl cyanide compounds, methyl vinyl ketone, and vinyl acetate. Specifically, styrene, α-methylstyrene, vinyl toluene, 4-t-butyl styrene, chlorostyrene, vinyl anisole, vinyl naphthalene, methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n- There are amyl methacrylate, isoamyl methacrylate, n-hexyl methacrylate, 2-ethylhexyl methacrylate, octyl methacrylate, decyl methacrylate, dodecyl methacrylate, octadecyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, benzyl methacrylate, glycidyl methacrylate, acrylonitrile, methacrylonitrile, etc. Use alone or in combination of two or more It is also possible.

Further, the water-insoluble polymer preferably contains a monomer having a hydrophilic group and a monomer having a salt-forming group in order to impart gloss to the printed image.
Examples of the monomer having a hydrophilic group include polyethylene glycol monomethacrylate, polypropylene glycol monomethacrylate, and ethylene glycol / propylene glycol monomethacrylate. These can be used alone or in admixture of two or more. In particular, polyethylene glycol (2-30) monomethacrylate, polyethylene glycol (1-15) / propylene glycol (1-15) monomethacrylate, polypropylene glycol (2-30) methacrylate, methoxypolyethylene glycol (2-30) methacrylate, methoxy The gloss of printed images is further improved by using monomer components that constitute branched chains such as polytetramethylene glycol (2-30) methacrylate and methoxy (ethylene glycol / propylene glycol copolymer) (1-30) methacrylate. To do.

Monomers having a salt-forming group include acrylic acid, methacrylic acid, styrene carboxylic acid, maleic acid, etc., and each can be used alone or in combination of two or more.
Furthermore, a macromonomer such as a styrene macromonomer or a silicone macromonomer having a polysynthetic functional group at one end, or other monomers can be used in combination.

  The colorant coated with the water-insoluble polymer is obtained by a phase inversion emulsification method. That is, the above water-insoluble polymer is dissolved in an organic solvent such as methanol, ethanol, isopropanol, n-butanol, acetone, methyl ethyl ketone, dibutyl ether, a colorant is added to the resulting solution, and then a neutralizing agent and water are added. By adding, kneading and dispersing, an oil-in-water type dispersion is prepared, and an organic solvent is removed from the obtained dispersion to obtain an aqueous dispersion. For the kneading and dispersing treatment, for example, a ball mill, a roll mill, a bead mill, a high-pressure homogenizer, a high-speed stirring type disperser, or the like can be used.

  The neutralizing agent is preferably a tertiary amine such as ethylamine or trimethylamine, lithium hydroxide, sodium hydroxide, potassium hydroxide, ammonia or the like, and the pH of the resulting aqueous dispersion is preferably 6-10.

  The water-insoluble polymer to be coated is preferably a polymer having a weight average molecular weight of about 10,000 to 150,000 from the viewpoint of stably dispersing a colorant, particularly a pigment. The weight average molecular weight can be measured by a molecular weight analysis method by gel permeation chromatography (GPC).

  Further, the ratio of the colorant to the water-insoluble polymer is in the ratio of colorant: water-insoluble polymer = 1: 0.2 to 1: 1, so that the dispersion stability, the storage stability of the ink, and the nozzle are clogged. From the viewpoint of prevention and the like, and from the viewpoint of glossiness on glossy media. Specifically, if the water-insoluble polymer is less than 20% with respect to the colorant, stable dispersion cannot be achieved and aggregation of the colorant occurs. If the water-insoluble polymer is more than 100% with respect to the colorant, the bronze phenomenon becomes small. This is because the coloring is lowered and the gloss on the Mitsuzawa Media is also deteriorated.

  Further, from the viewpoint of coloring and glossiness on glossy media, the volume average particle diameter of the colorant in the ink is preferably in the range of 50 to 150 nm. These volume average particle diameters can be obtained by particle diameter measurement using a Microtrac UPA150 (manufactured by Microtrac) or a particle size distribution analyzer LPA3100 (manufactured by Otsuka Electronics Co., Ltd.).

  The colorant covered with the water-insoluble polymer of the present invention may have a shape in which a part of the colorant is exposed without being completely covered with the water-insoluble polymer.

[Ink composition]
An ink composition suitable for the ink jet recording method of the present invention, which contains water and a water-soluble organic compound. Water is the main solvent, and it is preferable to use pure water or ultrapure water such as ion exchange water, ultrafiltration water, reverse osmosis water, and distilled water. In particular, it is preferable to use water sterilized by ultraviolet irradiation or addition of hydrogen peroxide in order to prevent the generation of mold and bacteria and enable long-term storage of the ink composition.

Examples of the water-soluble organic compound include glycerin, 1,2,6-hexanetriol, ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, pentaethylene glycol, dipropylene glycol, 2-butene-1, 4-diol, 2-ethyl-1,3-hexanediol, 2-methyl-2,4-pentanediol, 1,2-octanediol, 1,2-hexanediol, 1,2-pentanediol, 4-methyl-1 Polyhydric alcohols such as 1,2-pentanediol, trimethylolethane, methylolpropane, glucose, mannose, fructose, ribose, xylose, arabinose, galactose, aldonic acid, glucitol, (Sorbit), maltose Sugars such as cellobiose, lactose, sucrose, trehalose, maltotriose, so-called solid wetting agents such as sugar alcohols, hyaluronic acids, ureas, etc., alkyls having 1 to 4 carbon atoms such as ethanol, methanol, butanol, propanol, isopropanol Alcohols, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol monomethyl ether acetate, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono-n-propyl ether, ethylene glycol mono-iso-propyl ether , Diethylene glycol mono-iso-propyl ether, ethylene glycol mono n-butyl ether, ethylene glycol mono-t-butyl ether, diethylene glycol mono-t-butyl ether, 1-methyl-1-methoxybutanol, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol mono-t-butyl ether, propylene glycol mono Glycols such as n-propyl ether, propylene glycol mono-iso-propyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol mono-n-propyl ether, dipropylene glycol mono-iso-propyl ether Ethers, 2-pyrrolidone, N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidino , Formamide, acetamide, dimethyl sulfoxide, sorbitol, sorbitan,
Examples include acetin, diacetin, triacetin, sulfolane and the like, and one or more of these can be used, and these water-soluble organic compounds have appropriate physical property values of the ink composition (
From the viewpoints of ensuring viscosity, etc., printing quality, and reliability, the ink composition preferably contains 10 to 50% by weight.

Furthermore, in the present invention, as a water-soluble organic compound, at least a polyhydric alcohol, a solid wetting agent, and a butyl ether of glycol are used in combination to improve reliability such as print quality, ejection stability, and clogging recovery. An excellent ink composition can be provided. This is because polyhydric alcohols and solid wetting agents are suitable for controlling water retention (moisturizing properties) and penetrability of the ink composition into recording media such as plain paper, and glycol butyl ethers are suitable for ejection stability and recording. It is suitable for controlling the permeability of the ink composition to the media.
An ink composition having high reliability such as ejection stability and clogging recovery can be provided.

As a particularly preferred water-soluble organic compound, the polyhydric alcohol is a combination of two or more selected from glycerin, diethylene glycol, triethylene glycol, 1,5-pentanediol and 1,2-hexanediol, and the solid wetting agent is Trimethylolethane, trimethylolpropane or urea, and butyl glycols include diethylene glycol monobutyl ether or triethylene glycol monobutyl ether.

[Other additives]
Further, it may contain a surface tension adjusting agent in order to control the wettability of the ink to the recording medium, to impart uniform glossiness, to obtain the penetrability into the recording medium and the printing stability in the ink jet recording method. preferable. As the surface tension adjusting agent, acetylene glycol surfactants and polyether-modified siloxanes are preferable.
Examples of acetylene glycol surfactants include Surfynol 420, 440, 4
65, 485, 104, STG (product of Air Products), Olfin PD-001,
SPC, E1004, E1010 (Nissin Chemical Industry Co., Ltd. product), acetylenol E00,
E40, E100, LH (Kawaken Fine Chemical Co., Ltd. product) and the like. Polyether-modified siloxanes include BYK-346, 347, 348, UV3530 (
Big Chemie product). A plurality of these may be used in the ink composition, and the surface tension is preferably adjusted to 20 to 40 mN / m, and 0.1 to 3 in the ink.
. Contains 0% by weight.

Furthermore, the ink composition of the present invention preferably contains a pH adjuster.
As the pH adjuster, it is possible to use alkali metal hydroxides such as lithium hydroxide, potassium hydroxide and sodium hydroxide, amines such as ammonia, triethanolamine, tripropanolamine, diethanolamine and monoethanolamine. Although it is possible, it preferably contains at least one pH adjusting agent selected from alkali metal hydroxides, ammonia, triethanolamine, and tripropanolamine, and is preferably adjusted to pH 6-10. If the pH is out of this range, the material constituting the ink jet printer will be adversely affected, and the clogging recoverability will deteriorate.

Further, an antifoaming agent, an antioxidant, an ultraviolet absorber, an antiseptic / antifungal agent and the like can be added as necessary.

  The ink set of the invention can be suitably used for writing instruments such as pens, stamps and the like, but can be more suitably used as an ink set for inkjet recording. In the present invention, the ink jet recording system means a system in which an ink composition is ejected as droplets from a fine nozzle and the droplets are attached to a recording medium. This will be specifically described below.

  As a first method, there is an electrostatic suction method, which applies a strong electric field between the nozzle and the acceleration electrode placed in front of the nozzle, and continuously ejects ink from the nozzle in the form of droplets. This is a method in which a print information signal is applied to the deflection electrode while the ink droplet is flying between the deflection electrodes for recording, or a method in which the ink droplet is ejected in response to the print information signal without being deflected.

  The second method is a method in which ink droplets are forcibly ejected by applying pressure to the ink liquid with a small pump and mechanically vibrating the nozzle with a crystal resonator or the like. The ejected ink droplet is charged simultaneously with the ejection, and a printing information signal is given to the deflection electrode and recorded while the ink droplet flies between the deflection electrodes.

  The third method is a method using a piezoelectric element, in which a pressure and a print information signal are simultaneously applied to an ink liquid by a piezoelectric element to eject and record ink droplets.

  The fourth method is a method in which the ink liquid is rapidly expanded in volume by the action of heat energy, and the ink liquid is heated and foamed with a microelectrode in accordance with a print information signal to eject and record ink droplets.

  Any of the above methods can be used in the ink jet recording method using the ink set of the present invention.

  The recorded matter of the present invention is recorded at least using the above ink set. By using the ink set of the present invention, this recorded matter is provided as a recorded matter having excellent gloss and gloss. In particular, it is provided as a recorded matter having excellent color developability when recorded on plain paper and excellent glossy images with less gloss unevenness when recorded on dedicated glossy paper.

<Example>
EXAMPLES Hereinafter, although this invention is demonstrated further in detail using an Example, this invention is not limited to these Examples.

[Adjustment of colorant dispersion]
A colorant dispersion having dispersed particles of a colorant coated with a water-insoluble polymer was prepared by the following method.

(Synthesis of water-insoluble polymers 1 and 2)
In a reaction vessel sufficiently substituted with nitrogen gas using 20 parts by weight of an organic solvent (methyl ethyl ketone), 0.03 part by weight of a polymerization chain transfer agent (2-mercaptoethanol), a polymerization initiator, and each monomer shown in Table 1. The mixture was polymerized with stirring at 75 ° C., and 0.9 part by weight of 2,2′-azobis (2,4-dimethylvaleronitrile) dissolved in 40 parts by weight of methyl ethyl ketone was added to 100 parts by weight of the monomer component. The polymer solution was obtained by aging for 1 hour.

(Pigment dispersion Y1)
5 parts obtained by drying the polymer solution obtained as water-insoluble polymer 1 under reduced pressure was dissolved in 15 parts of methyl ethyl ketone, and the polymer was neutralized with an aqueous sodium hydroxide solution. Furthermore, C.I. I. 15 parts of Pigment Yellow 74 was added and kneaded with a disperser while adding water.
After 100 parts of ion-exchanged water was added to the kneaded mixture and stirred, methyl ethyl ketone was removed at 60 ° C. under reduced pressure, and a part of the water was further removed, whereby a yellow pigment having a solid content concentration of 20% by weight was removed. An aqueous dispersion was obtained. (Pigment: Water-insoluble polymer = 1: 0.3)

(Pigment dispersion Y2)
9 parts obtained by drying the polymer solution obtained as the water-insoluble polymer 2 under reduced pressure were dissolved in 45 parts of methyl ethyl ketone, and the polymer was neutralized with an aqueous sodium hydroxide solution. Furthermore, C.I. I. 18 parts of Pigment Yellow 74 was added and kneaded with a disperser while adding water.
After 120 parts of ion-exchanged water was added to the kneaded mixture and stirred, methyl ethyl ketone was removed at 60 ° C. under reduced pressure, and a part of the water was further removed, whereby a yellow pigment having a solid content concentration of 20% by weight was removed. An aqueous dispersion was obtained. (Pigment: Water-insoluble polymer = 1: 0.5)

(Pigment dispersion M1)
In the pigment dispersion Y1, C.I. I. Instead of CI Pigment Yellow 74, C.I. I. A dispersion M1 was obtained in the same manner as the dispersion Y1, except that CI Pigment Red 122 was used.

(Pigment dispersion M2)
In the pigment dispersion Y2, C.I. I. Instead of CI Pigment Yellow 74, C.I. I. A dispersion M2 was obtained in the same manner as the dispersion Y2, except that Pigment Red 122 was used and the ratio of pigment: water-insoluble polymer was changed to 1: 0.2.

(Pigment dispersion C1)
In the pigment dispersion Y1, C.I. I. Instead of CI Pigment Yellow 74, C.I. I. A dispersion C1 was obtained in the same manner as the pigment dispersion Y1, except that CI Pigment Blue 15: 3 was used.

(Pigment dispersion C2)
In the pigment dispersion Y2, C.I. I. Instead of CI Pigment Yellow 74, C.I. I. A dispersion C2 was obtained in the same manner as the dispersion Y2, except that CI Pigment Blue 15: 3 was used and the ratio of pigment: water-insoluble polymer = 1: 0.8 was changed.

[Preparation of ink]
Each component was mixed in the ratio shown in Table 2, stirred at room temperature for 2 hours, and then filtered through a membrane filter having a pore size of 8 μm to prepare each ink. However, the addition amounts shown in Table 2 are all expressed as weight percent concentrations, and the numbers in parentheses in the colorant dispersion represent the solid content concentration of the colorant. The “remaining amount” of ion-exchanged water means adding ion-exchanged water so that the total amount of ink becomes 100 parts.

  Using the inks prepared in Table 2, the following evaluations were performed on the ink sets shown in Table 3.

(Test 1) Average particle diameter Using a particle size distribution meter (UPA-150 manufactured by Microtrac), each ink was diluted 1000 times with pure water, and the particle size distribution of the diluted solution was measured. Asked. The results are shown in Table 2.

(Test 2) Gloss unevenness (gloss uniformity)
For ink sets 1 to 8, 150 color patch patterns are printed on photographic paper <Glossy> (trade name: manufactured by Seiko Epson Corporation) using an inkjet printer PM-4000PX (trade name: manufactured by Seiko Epson Corporation). Then, after being allowed to stand at 25 ° C. for 24 hours, the 20-degree specular gloss (Gs20) was measured using a gloss meter GM-268 (manufactured by Konica Minolta), and the difference between the maximum and minimum gloss values was calculated. . (However, the non-printing part (printing duty is 0% part) was excluded from the evaluation.)
The ink usage rate (ink generation rate) of dark and light inks in the same color is shown in FIG. Further, FIG. 1A shows the ink usage rate (ink generation rate) when only dark ink is used (ink set 6).

A: The difference between the maximum value and the minimum value of Gs20 is less than 20.
B: The difference between the maximum value and the minimum value of Gs20 is 20 or more and less than 40.
C: The difference between the maximum value and the minimum value of Gs20 is 40 or more.

(Test 3) Glossiness For ink sets 1 to 8, 100% and 40% DUTY patch patterns were printed on photographic paper <Glossy> (trade name: manufactured by Seiko Epson Corporation) using the printer, 25 After being left at 24 ° C. for 24 hours, a 20-degree specular gloss (Gs20) was measured using a gloss meter GM-268 (manufactured by Konica Minolta), and an average gloss value was calculated.
Note that the ink usage rates when only dark and light inks and dark inks in the same color are used are shown in FIGS. 1B and 1A, respectively, similarly to the gloss unevenness test.

A; 70 ≦ Gs20
B; 40 ≦ Gs20 <70
C; Gs20 <40

(Test 4) Color developability For ink sets 1 to 8, a solid pattern with a print duty of 100% was created on Xerox-4024 using the printer, and left at 25 ° C. for 24 hours. Colorimetry was performed using Spectrolino (trade name: manufactured by Gretag), and the determination was made based on the following criteria.
A: OD value 1.2 or more B; OD value 1.0 to less than 1.2 C; OD value less than 1.0

(Test 5) Ink Storage Stability The ink was placed in an aluminum pack at 50 ° C. for 2 weeks with 50 g of ink. The presence or absence of foreign matter (floating matter or sediment) after standing, and those that do not produce foreign matter are further evaluated for changes in physical properties (viscosity, surface tension, pH, particle size) based on the following criteria: did.
A: In all ink compositions of the ink set, there is no generation of foreign matters and no change in physical properties.
B: At least one ink composition in the ink set does not generate foreign matter, but the physical properties slightly change.
C: At least one ink composition in the ink set generates foreign matter or changes its physical properties remarkably.

(Test 6) Ejection stability In the case of printing in test 2, whether or not ink dot dropout or flight bending occurs from the start of printing to the ink end, and if it occurs, printer cleaning is performed as a return operation to normal printing. The number of times it was necessary was evaluated and judged based on the following criteria.
A: No occurrence or cleaning once B: Cleaning 2-4 times C: Cleaning 5 times or more

(Test 7) About the clogging recoverable ink sets 1 to 8, using the printer, each ink composition was filled into the head, and after confirming that the ink was normally discharged from the nozzle, the ink cartridge was The printer head was left for 1 week in an environment of 40 ° C. with no printer head capped. After being allowed to stand, the number of cleanings required until the ink composition was normally ejected from the nozzles again was examined, and the determination was made based on the following criteria.
A: Within 2 cleanings B: 3-5 cleanings C: 6 cleanings or more

The above results are shown in Table 4, respectively.

  As is apparent from Table 4, according to the ink set of the present invention, it is possible to obtain an excellent plain paper color developability and an excellent gloss image with less gloss unevenness on the dedicated glossy paper. In addition, the ink set is excellent in storage stability and suitable for use in an ink jet recording system.

  The present invention is not limited to the above-described embodiment, but can be applied to uses such as ink for writing instruments and ink for offset printing.

FIG. 1A is a graph showing the ink usage rate (ink generation rate) when only dark ink is used in the gloss unevenness test in the example, and FIG. 1B is the ink usage rate of dark and light inks in the same color. It is a graph which shows (ink generation rate).

Claims (10)

  An ink set comprising a dark ink composition and a light ink composition having the same color but different color densities, wherein both the dark ink composition and the light ink composition are water-insoluble as a coloring material. An ink set comprising a colorant coated with a polymer.   The water-insoluble polymer is a polymer obtained by polymerization by a solution polymerization method using at least a polymerizable unsaturated monomer and a polymerization initiator, and the colorant coated with the water-insoluble polymer is the water-insoluble polymer. The ink set according to claim 1, which is a colorant obtained by a phase inversion emulsification method in which at least a colorant and water are added and mixed after being dissolved in an organic solvent, and the organic solvent is removed and dispersed in an aqueous system.   The ink set according to claim 1, wherein the colorant is a pigment.   The ink set according to any one of claims 1 to 3, wherein the colorant has a weight ratio of colorant: water-insoluble polymer = 1: 0.2 to 1: 1.   The ink set according to any one of claims 1 to 4, wherein in the dark ink composition and the light ink composition, the volume average particle diameter of pigment particles in the ink composition is 50 to 150 nm.   Furthermore, the ink set as described in any one of Claims 1-5 which uses together at least polyhydric alcohols, a solid wetting agent, and the butyl ether of glycol as a water-soluble organic compound.   The dark ink composition includes at least a yellow ink composition, a magenta ink composition, and a cyan ink composition, and the light ink composition includes at least a light magenta ink composition and a light cyan ink composition. The ink set according to any one of 1 to 6.   A recording method for performing printing by attaching the ink set according to claim 1 to a recording medium.   8. An ink jet recording method, wherein printing is performed by ejecting the ink droplets according to any one of claims 1 to 7 and attaching the droplets to a recording medium.   A recorded matter recorded by the recording method according to claim 8.