JP2010168586A - Ink set and recording method using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink set that has a wide color reproduction range, a high chroma, is not prominent in graininess by dot expression, obtains a recorded image having a gloss feeling, especially, exceedingly suppresses graininess by dot expression in application to a medium having a coated layer and obtains a recorded image having exceedingly excellent color development in application to plain paper. <P>SOLUTION: The ink set includes at least yellow ink (Y), magenta ink (M), cyan ink (C) and red ink (R). The L<SP>*</SP>value of the 1,000-fold diluted aqueous solution of each ink in the Lab display system defined by CIE is in the following range. (Y): ≥89 and ≤94, (M): ≥76 and <83, (C): ≥74 and ≤87, (R): ≥62 and <67.5. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an ink set including at least three inks of yellow, magenta, and cyan, and red ink as a special color ink other than these, and more particularly, has a wide color reproduction range, high saturation, and dot Glossy recorded images can be obtained without noticeable graininess, especially when applied to media with a coating layer. In particular, the present invention relates to an ink set capable of obtaining a recorded image with extremely excellent color developability, a recording method, a recording system, and a recorded matter using the ink set.

  Pigment inks are generally superior in image robustness of printed matter compared to dye inks, and are used in various applications that take advantage of their characteristics, such as wide-format color inkjet recording inks for sign and display markets. Yes. In this color ink jet recording, usually, a three-color ink set including three pigment inks of yellow (Y), magenta (M) and cyan (C), which are three subtractive primary colors, or black (K ) Is used to express various hues.

  However, the three-color or four-color ink set has a problem that the color reproduction range is narrow and the saturation of a secondary color or higher printing portion (mixed color portion) is lowered, which is comparable to silver salt photography or plate-making printing. However, it has not reached a level that can provide high-quality printed matter.

  In order to increase the saturation problem, a method of increasing the pigment concentration of each YMC color ink or a method of increasing the amount of YMC ink to be printed on the recording medium is adopted. However, any of these methods has a drawback that glossiness is lowered and a photographic texture cannot be obtained even when glossy paper is used as a recording medium. In addition, in order to efficiently expand saturation with only three primary color (YMC) inks, it is necessary to select a pigment type for YMC ink that has ideal spectral characteristics suitable for subtractive color mixing, and is also light resistant. The number of pigment types that are excellent in properties, gas resistance, etc. is limited, and among these limited pigment types, even if trying to increase the saturation by increasing the pigment concentration as described above, There is a risk that the hues of the three primary colors may change or the nozzles of the ink jet printer may be clogged, which is not effective.

  In addition, as a pigment ink set having a wide color reproduction range, Japanese Patent Application Laid-Open No. 2000-351928 discloses at least one of orange, green and violet containing specific pigments in addition to YMC three-color pigment inks. A color ink-jet ink set for color printing with color is disclosed (Patent Document 1), but this ink set cannot be said to have a sufficiently wide reproduction range of saturation, and does not cause a decrease in glossiness. Saturation could not be increased. In particular, when the image is represented by dots, the saturation of vermilion cannot be increased without causing noticeable graininess (a state in which dots can be visually recognized with the naked eye). Further, WO99 / 05230 discloses an ink set including two color pigment inks of orange and green in addition to the four color pigment inks of YMCK (Patent Document 2). Is excellent in the reproducibility of colors with high brightness and low saturation, such as pastel colors, but for the other colors, as in the ink set, the saturation reproduction range is inadequate and glossy. Saturation could not be increased without incurring a drop in

  Further, a recorded image formed using a conventional pigment ink set has a problem that a hue of the recorded image changes when the light source to be illuminated changes, that is, a so-called metamerism. This metamerism is particularly prominent in composite black and gray hue portions formed with YMC three-color inks, and contributes to a reduction in image quality.

In order to solve such problems in the conventional ink set, in addition to the specific pigment inks of three colors of YMC, red and red for the purpose of providing a printed matter having high chroma and high gloss without particularly noticeable graininess. Various ink sets have been proposed, such as an ink set provided with a specific special color pigment ink of violet, but the effect has not yet reached a sufficient level. The reason is that the effect to be improved differs depending on the type of recording medium to which the ink set is applied. For example, when the ink set is applied to a medium (recording medium) having a coating layer such as photographic paper at a low resolution, there is a problem that graininess due to dot expression at the time of recording becomes particularly noticeable. In addition, when the ink set is applied to plain paper (a recording medium in which fibers are exposed on the recording surface), the dark portion (L ^* value defined in the CIELAB color space on the recording medium is around 40) There is a problem that the color developability is particularly lowered.

  In addition, depending on the image formed on the plain paper, there may be a case where the dark portion cannot be sufficiently developed at a specific hue angle, and the quality of the image may be deteriorated. For this reason, there has been a demand for the development of an ink set that suppresses the conspicuousness of graininess and is excellent in color development in a dark portion having a specific hue angle on plain paper.

JP 2000-351928 A WO99 / 05230 Publication

  Accordingly, an object of the present invention is to provide a glossy recorded image with a wide color reproduction range, high saturation, and no noticeable graininess due to dot expression, and particularly for media having a coating layer. It is an object of the present invention to provide an ink set that can extremely suppress the graininess due to dot expression when applied, and can obtain a recorded image with extremely excellent color developability when applied to plain paper.

  Another object of the present invention is to provide an ink set capable of obtaining a high-quality image with reduced metamerism, in addition to the above-described excellent performance, which is excellent in coloring in a dark portion of a specific hue angle on plain paper. There is to do.

  Another object of the present invention is to provide a highly reliable ink set as an ink set for ink jet recording.

  Another object of the present invention is to provide a glossy recorded image with a wide color reproduction range, high saturation, and no noticeable graininess due to dot expression. It is an object of the present invention to provide a recording method and a recording system capable of extremely suppressing the graininess due to dot expression when applied to a medium having the recording medium and obtaining a recorded image with extremely excellent color development when applied to plain paper.

  Another object of the present invention is to provide a wide color reproduction range, high saturation, inconspicuous graininess due to dot expression, and glossiness, particularly when using a medium having a coating layer. An object of the present invention is to provide a recorded matter having a recorded image in which the graininess due to expression is extremely suppressed and the color developability is excellent when plain paper is used.

As a result of earnest research, the inventor has a red ink as a special color ink in addition to a three-color system of yellow ink, magenta ink, and cyan ink, and the L ^* value in CIE-Lab of each ink under a predetermined condition. The present inventors have found that an ink set having a value within a specific range can achieve the above-mentioned purpose.

The present invention has been made based on the above knowledge, and is an ink set including at least a yellow ink (Y), a magenta ink (M), a cyan ink (C), and a red ink (R). The present invention provides an ink set in which the L ^* value in the Lab display system defined by CIE of a double-diluted (weight basis, the same applies hereinafter) aqueous solution is within the following range.
(Y); 89 to 94, (M); 76 to 83, (C); 74 to 87, (R); 62 to 67.5

  Since the ink set of the present invention is composed of the above-described configuration, it is possible to obtain a glossy recorded image with a wide color reproduction range, high saturation, and no noticeable graininess due to dot expression. In particular, when applied to a medium having a coating layer, graininess due to dot expression can be extremely suppressed, and when applied to plain paper, a recorded image with extremely excellent color development can be obtained.

  In the present invention, the yellow ink is C.I. I. Pigment Yellow 74 is contained in an amount of 2.0 to 4.0% by weight, and the magenta ink is C.I. I. Pigment Violet 19 is contained in an amount of 1.7 to 3.0% by weight, and the cyan ink is C.I. I. Pigment Blue 15: 3 is contained in an amount of 0.5 to 2.5% by weight, and the red ink is C.I. I. The ink set containing 1.8 to 2.4% by weight of Pigment Red 264 is provided. According to this ink set, in addition to the above-described excellent performance, it is possible to obtain a high-quality image that is excellent in color development in a dark portion having a specific hue angle on plain paper and has reduced metamerism.

  The present invention also provides a recording method for forming an image using the ink set. According to this recording method, it is possible to obtain a glossy recorded image with a wide color reproduction range, high saturation, and no noticeable graininess due to dot expression, and is particularly applicable to media having a coating layer. In this case, the graininess due to dot expression can be extremely suppressed, and when applied to plain paper, a recorded image with extremely excellent color development can be obtained.

  The present invention also provides a recording system for forming an image using the ink set. According to this recording system, it is possible to obtain a glossy recorded image with a wide color reproduction range, high saturation, and no noticeable graininess due to dot expression, especially for media having a coating layer. In this case, the graininess due to dot expression can be extremely suppressed, and when applied to plain paper, a recorded image with extremely excellent color development can be obtained.

  The present invention also provides a recorded matter in which an image is formed using the ink set. This recorded material has a wide color reproduction range, high saturation, inconspicuous graininess due to dot expression, and glossiness, especially when using media with a coating layer, the graininess due to dot expression is extremely high. It has a recorded image that is suppressed and has excellent color developability when plain paper is used.

[Ink set]
Hereinafter, the ink set of the present invention will be described based on preferred embodiments thereof.

In the ink set of the present invention, as described above, the L ^* value in the Lab display system defined by CIE (Commission Internationale d'Eclairage; International Illumination Commission) of 1000 times diluted aqueous solution of each ink is yellow ink (Y); 89 to 94, magenta ink (M); 76 to less than 83, cyan ink (C); 74 to 87, red ink (R); 62 to less than 67.5. Furthermore, it is preferable that it exists in the following range at the point which can improve the effect of this invention.
(Y); L ^* : 89-93, especially 90-93, especially 90-92, especially 91-92
(M); L ^* : 77-82, especially 78-82, especially 79-82, especially 81-82.
(C); L ^* : 75-86, especially 76-85, especially 77-83, especially 79-81
(R); L ^* : 63-67, especially 64-67, especially 65-67, especially 66-67

Here, the L ^* value can be obtained, for example, by using a U3300 manufactured by Hitachi, Ltd., with a D65 light source and a viewing angle of 2 degrees (hereinafter the same applies to other inks).

Moreover, it is preferable that the a ^* value and b ^* value in the Lab display system defined by the CIE of a 1000-fold diluted aqueous solution of each of the inks used in the ink set of the present invention are in the following ranges.
(Y); a ^* : −14 to −8, b ^* : 102 to 115
(M); a ^* : 31 to 51, b ^* : −17 to −10
(C); a ^* : -40 to -24, b ^* : -37 to -22
(R); a ^* : 42-62, b ^* : 1-10

Similarly to the L ^* value, the a ^* value and the b ^* value can also be obtained, for example, by measuring using U3300 manufactured by Hitachi, Ltd. (hereinafter the same applies to other inks).

  The colorant (colorant) contained in each ink provided in the ink set of the present invention is preferably a pigment from the viewpoint of excellent image fastness of recorded matter. Moreover, as a pigment, an inorganic pigment and an organic pigment can be used, and each can be used individually or in mixture of multiple types. As the inorganic pigment, for example, carbon black produced by a known method such as a contact method, a furnace method, or a thermal method can be used in addition to titanium oxide and iron oxide. Examples of the organic pigment include azo pigments (including azo lakes, insoluble azo pigments, condensed azo pigments, chelate azo pigments), polycyclic pigments (for example, phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments, Dioxazine pigments, thioindigo pigments, isoindolinone pigments, quinofullerone pigments, etc.), dye chelates (for example, basic dye-type chelates, acidic dye-type chelates), nitro pigments, nitroso pigments, aniline black, and the like can be used. Specifically, as will be described below, a desired pigment is used according to each color ink.

Examples of the yellow ink used in the present invention include C.I. I. Preferred are pigment yellow 74 containing 2.0 to 4.0% by weight, particularly 2.5 to 3.5% by weight, especially 2.7 to 3.3% by weight. The yellow ink is not limited to this, and the type and content of the color material are not particularly limited as long as it has a predetermined L ^* value. I. Pigment Yellow 1, 2, 3, 12, 13, 14, 16, 17, 73, 74, 75, 83, 93, 95, 97, 98, 109, 110, 114, 128, 129, 138, 139, 147, One, two or more of 150, 151, 154, 155, 180, 185, etc. may be used in an appropriate amount so that the ink falls within a predetermined L ^* value range. The components other than the color material in the yellow ink will be described later together with each ink.

Examples of the magenta ink used in the present invention include C.I. I. The pigment violet 19 preferably contains 1.7 to 3.0% by weight, particularly 1.7 to 2.5% by weight, particularly 1.8 to 2.3% by weight. In particular, this C.I. I. It is preferable to use the pigment violet 19 because a high-quality image with reduced metamerism can be obtained. The magenta ink is not limited to this, and the type and content of the color material are not particularly limited as long as it has a predetermined L ^* value. I. Pigment Red 5, 7, 12, 48 (Ca), 48 (Mn), 57 (Ca), 57: 1, 112, 122, 123, 168, 184, 202, 209; I. One or two or more types such as pigment violet 19 may be used in an appropriate amount so that the ink falls within a predetermined L ^* value range. Further, components other than the color material in the magenta ink will be described later together with each ink.

  Further, as the magenta ink, when the Y value in the XYZ display system defined by the CIE, which is calculated from the ultraviolet visible transmittance of the 1000-fold diluted aqueous solution, is 55, the Z value is 83 or less. For example, metamerism is excellent even at low resolution, graininess can be further suppressed, and an image with further excellent color reproducibility can be obtained.

Examples of the cyan ink used in the present invention include C.I. I. Preferred are pigment blue 15: 3 containing 0.5 to 2.5% by weight, particularly 1.0 to 2.0% by weight, especially 1.2 to 1.8% by weight. The cyan ink is not limited to this, and the type and content of the color material are not particularly limited as long as it has a predetermined L ^* value. I. Pigment Blue 1, 2, 3, 15: 3, 15: 4, 15:34, 16, 22, 60; I. One type or two or more types such as Vat Blue 4 and 60 may be used in an appropriate amount so that the ink falls within a predetermined L ^* value range. Further, components other than the color material in the cyan ink will be described later together with each ink.

Examples of the red ink used in the present invention include C.I. I. The pigment red 264 preferably contains 1.8 to 2.4% by weight, particularly 1.8 to 2.2% by weight, particularly 1.9 to 2.1% by weight. In particular, this C.I. I. It is preferable to use CI Pigment Red 264 because a recorded image having excellent hue in a dark portion having a hue angle of 20 to 30 degrees can be obtained. The red ink is not limited to this, and the type and content of the color material are not particularly limited as long as it has a predetermined L ^* value. I. Pigment Orange 5, 43 and 62 and C.I. I. CI Pigment Red 17, 49: 2, 112, 149, 177, 178, 188, 255, 264, etc. are used in an appropriate amount so that the ink falls within a predetermined L ^* value range. It may be what you did. The components other than the color material in the red ink will be described later together with each ink.

  Since the ink set of the present invention includes such a red ink, it is possible to reproduce a low brightness and high saturation color as compared with the case of forming an image by mixing two colors of yellow ink and magenta ink. An image with a wide reproduction range can be obtained.

The ink set of the present invention includes at least each of the inks described above, that is, each of yellow, magenta, cyan, and red inks. Further, L ^* in the Lab display system defined by the CIE of a 1000-fold diluted aqueous solution ^. Having a violet ink (Vi) with a value in the range of 40 to 58 can reproduce colors with low brightness and high saturation, compared to the case of forming an image by mixing two colors of cyan ink and magenta ink. Therefore, it is preferable in that an image having a wider color reproduction range can be obtained.

The L ^* value relating to the violet ink is preferably in the range of 42 to 55, particularly 45 to 52, from the viewpoint of further improving the above effect.

Moreover, it is preferable that the a ^* value and b ^* value in the Lab display system defined by the CIE of a 1000-fold diluted aqueous solution of violet ink are in the following ranges.
(Vi); a ^* : 56 to 76, b ^* : −75 to −56

Examples of violet ink include C.I. I. The pigment violet 23 preferably contains 1.0 to 3.0% by weight, particularly 1.5 to 2.5% by weight, particularly 1.7 to 2.3% by weight. The violet ink is not limited to this. I. Pigment blue 60 and C.I. I. One or two or more of pigment violet 3, 19, 23, 32, 36, and 38 may be used in an appropriate amount so that the ink falls within a suitable L ^* value range. Further, components other than the color material in the violet ink will be described later together with each ink.

  The ink set of the present invention includes at least each of the above-described inks, that is, each of yellow, magenta, cyan, and red inks, and further includes a violet ink as necessary. Can also be provided.

  As the black ink, for example, carbon black (CI pigment black 7) such as furnace black, lamp black, acetylene black and channel black, inorganic pigments such as iron oxide pigments; aniline black (C And pigments containing organic pigments such as I. Pigment Black 1). Among these pigments, it is particularly preferable to use carbon black, and examples of preferable carbon black include No. 1 manufactured by Mitsubishi Chemical Corporation. 2300, no. 900, MCF88, no. 33, no. 40, no. 52, MA7, MA8, MA100, no. Raven5750, Raven5250, Raven5000, Raven3500, Raven1255, Raven700, etc. manufactured by Colombia, etc. Regal 400R, Regal 400R, Regal 1660R, Mul 1, Mon 700, Mon 80, Mon ch 700, Mon , Monarch 1100, Monarch 1300, Monarch 1400, etc., such as Color Black FW1, Color Black FW2, Color Black FW2V, Color Black FW18, Color Black FW200, Color Black FW200, Color Black FW200, Color Black FW200 ack S160, Color Black S170, Printex 35, Printex U, Printex V, Printex 140U, Special Black 6, Special Black 5, Special Black 4A, Spec.

In the present invention, in particular, the black ink contains 3.0% by weight or less of carbon black [hereinafter also referred to as photo black ink (PK). Is preferable in that it is particularly excellent in suppressing graininess of images and gloss of mixed colors when applied to a medium having a coating layer as a recording medium, and containing more than 3.0% by weight of carbon black [Hereinafter also referred to as matte black ink (MK). Is preferable in that the color developability of an image when applied to plain paper as a recording medium is particularly excellent.
These black inks can be used either alone or both. However, it is desirable that both the photo black ink and the matte black ink are provided in terms of obtaining both of these functions.

  The content of carbon black in the photo black ink is preferably 0.1 to 3.0% by weight, more preferably 1.0 to 2.0% by weight, particularly preferably 1.2 to 1.8% by weight. is there. In addition to carbon black, as a photo black ink, C.I. I. Pigment Blue 15: 3 and other cyan pigments containing 1.0% by weight or less, particularly 0.25% by weight or less, in a trace amount are preferable in terms of obtaining a complementary color effect on a recorded image.

The photo black ink preferably has an L ^* value in the Lab display system defined by the CIE of a 1000-fold diluted aqueous solution in the range of 42 to 67, particularly 48 to 60, and the a ^* value is − It is preferable that it exists in the range of 2.75--2.40, and it is preferable that the b ^* value exists in the range of 9-14.

  On the other hand, the carbon black content in the matte black ink is preferably 4.0 to 9.0% by weight, more preferably 5.0 to 8.0% by weight, and particularly preferably 6.0 to 7.0% by weight. %.

The mat black ink preferably has an L ^* value in the Lab display system defined by the CIE of a 1000-fold diluted aqueous solution in the range of 0.1 to 16, particularly 2 to 10, and the a ^* value is the same. The b ^* value is preferably in the range of 1-18.

  Furthermore, the ink set of the present invention is not limited to the above-described ink, and includes other types such as a dark magenta ink having a higher color material density than the magenta ink and a dark cyan ink having a color material density higher than the cyan ink. You may provide 1 type, or 2 or more types of ink.

Each of the inks included in the ink set of the present invention preferably uses a pigment as a coloring material and contains a dispersant for dispersing the pigment. As the dispersant, those similar to those in this type of pigment ink can be used without particular limitation, and examples thereof include a cationic dispersant, an anionic dispersant, a nonionic dispersant, and a surfactant. Examples of anionic dispersants include polyacrylic acid, polymethacrylic acid, acrylic acid-acrylonitrile copolymer, vinyl acetate-acrylic acid ester copolymer, acrylic acid-acrylic acid alkyl ester copolymer, styrene-acrylic acid. Copolymer, styrene-methacrylic acid copolymer, styrene-acrylic acid-alkyl acrylate copolymer, styrene-methacrylic acid-alkyl acrylate copolymer, styrene-α-methylstyrene-acrylic acid copolymer Styrene-α-methylstyrene-acrylic acid-alkyl acrylate copolymer, styrene-maleic acid copolymer, vinyl naphthalene-maleic acid copolymer, vinyl acetate-ethylene copolymer, vinyl acetate-fatty acid vinyl ethylene Copolymer, vinyl acetate-maleic ester Examples include copolymers, vinyl acetate-crotonic acid copolymers, vinyl acetate-acrylic acid copolymers, and the like. Examples of anionic surfactants include sodium dodecylbenzenesulfonate, sodium laurate, ammonium salt of polyoxyethylene alkyl ether sulfate, and examples of nonionic surfactants include polyoxyethylene alkyl. Examples include ether, polyoxyethylene alkyl ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene alkylphenyl ether, polyoxyethylene alkylamine, polyoxyethylene alkylamide, and the like, and one or more of these are used. In particular, it is preferable to use a styrene- (meth) acrylic acid copolymer from the viewpoint of enhancing the dispersion stability of the pigment.
The dispersant is usually contained in each ink in an amount of 140% by weight or less in terms of solid content based on the weight of the pigment.

  In particular, in color inks such as yellow ink, magenta ink, cyan ink, red ink, and violet ink, the dispersant is preferably 20 to 80% by weight in terms of solid content, based on the weight of the pigment, Preferably, 40 wt% is contained.

On the other hand, with regard to the black ink, the mat black ink may or may not contain the dispersant, but in particular, the dispersant is not used (0% by weight), and the self-dispersion as a coloring material. It is preferable to use a type of pigment from the viewpoint of improving the color developability of the recorded image. Incidentally, the self-dispersing pigment has a functional group (dispersibility imparting) of one or more selected from the group consisting of —COOH, —CHO, —OH, —SO ₃ H and salts thereof on the surface of the pigment. The pigment is treated so as to have a group) and can be uniformly dispersed in the water-based ink without adding a dispersant separately. The term “dispersed” as used herein refers to a state in which a self-dispersing pigment is stably present in water without a dispersant, and not only in a dispersed state but also in a dissolved state. Shall be included.

  In the photo black ink, the dispersant is preferably 60 to 120% by weight, most preferably 100% by weight in terms of solid content, based on the weight of the pigment, in terms of improving the gloss of the recorded image. included.

  Further, the content of the dispersant with respect to each ink amount is preferably 0.1 to 10% by weight, more preferably 0.3 to 6% by weight in terms of solid content.

In addition, each ink provided in the ink set of the present invention contains a high-boiling organic solvent from the viewpoint of preventing the ink from drying and clogging at the head of the inkjet printer when used for inkjet recording. preferable. Examples of the high boiling point organic solvent include ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, polypropylene glycol, propylene glycol, butylene glycol, 1,2,6-hexanetriol, thioglycol, hexylene glycol, glycerin, and trimethylol. Polyhydric alcohols such as ethane and trimethylolpropane; ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, tri Multivalent such as ethylene glycol monobutyl ether Alkyl ethers of alcohol; urea, 2-pyrrolidone, N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, organic alkalis such as triethanolamine, saccharides such as sugar alcohol, etc. These 1 type (s) or 2 or more types are used. In particular, it is preferable to add an organic alkali such as triethanolamine in order to stabilize the dispersibility of the coloring material and improve the gloss of the recorded image.
The high boiling point organic solvent is preferably contained in the respective inks in an amount of 0.1 to 30% by weight, more preferably 0.5 to 20% by weight.

Moreover, each ink with which the ink set of the present invention is provided can contain a penetration enhancer from the viewpoint of increasing the wettability to the recording medium and increasing the permeability of the ink. Examples of the penetration enhancer include alcohols such as methanol, ethanol, iso-propyl alcohol; ethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, propylene glycol monobutyl ether, dipropylene glycol mono Examples include lower alkyl ethers of polyhydric alcohols such as butyl ether; diols such as 1,2-pentanediol and 1,2-hexanediol, and one or more of these are used. In particular, it is preferable to use diethylene glycol monobutyl ether, triethylene glycol monobutyl ether or 1,2-hexanediol.
The penetration enhancer is preferably contained in the ink in an amount of 1 to 20% by weight, more preferably 1 to 10% by weight.

  Further, each of the inks included in the ink set of the present invention is an anionic surfactant and a nonionic surfactant from the viewpoint of increasing the wettability to the recording medium and increasing the permeability of the ink, similarly to the penetration accelerator. Various surfactants such as a cationic surfactant and an amphoteric surfactant can also be used, and it is particularly preferable to use an acetylene glycol compound or a silicone compound. Commercially available compounds can be used as the acetylene glycol compounds, such as Olphine Y, Surfynol 82, 440, 465, 485, STG, E1010 (all trade names, Air Products and -Chemicals) etc. are mentioned, These 1 type (s) or 2 or more types are used. In particular, Surfynol 465 is preferably used. Moreover, as this silicone type compound, polysiloxane type compounds, such as BYK348 (made by Big Chemie Japan), can be used as a commercial item. The acetylene glycol compound and / or the silicone compound is preferably contained in the ink in an amount of 0.01 to 5% by weight, more preferably 0.1 to 0.5% by weight.

  Moreover, each ink with which the ink set of this invention is provided can contain the low boiling-point organic solvent from a viewpoint of shortening the drying time of an ink. Examples of the low boiling point organic solvent include methanol, ethanol, n-propyl alcohol, iso-propyl alcohol, n-butanol, sec-butanol, tert-butanol, iso-butanol, n-pentanol and the like. These 1 type (s) or 2 or more types are used. In particular, monohydric alcohol is preferable.

  Each ink provided in the ink set of the present invention contains components such as the pigment, dispersant, high boiling point organic solvent, penetration enhancer, acetylene glycol-based compound and / or silicone-based compound described above, and usually contains water as a balance. It contains. It is preferable to use pure water or ultrapure water such as ion exchange water, ultrafiltration water, reverse osmosis water, or distilled water. In particular, water obtained by sterilizing these waters by ultraviolet irradiation or addition of hydrogen peroxide is preferable because generation of mold and bacteria is prevented over a long period of time.

  Each ink provided in the ink set of the present invention further includes a fixing agent such as a water-soluble rosin, an antifungal agent or preservative such as sodium benzoate, an antioxidant or an ultraviolet absorber such as an allophanate, if necessary. Additives such as chelating agents, oxygen absorbers, and pH adjusting agents can be contained, and one or more of these can be used.

  Each ink included in the ink set of the present invention can be prepared in the same manner as the conventional pigment ink using a conventionally known apparatus, for example, a ball mill, a sand mill, an attritor, a basket mill, a roll mill or the like. In the preparation, it is preferable to remove coarse particles using a membrane filter, a mesh filter or the like.

When the ink set of the present invention is applied to a medium having a coating layer as a recording medium for forming an image (image formation), the L ^* value (CIELAB color) of Duty 20% on the medium of each ink It is preferable that the L ^* value defined in space is within the following range.
(Y); 85-95, (M); 70-80, (C); 70-80, (R); 62-72
The L ^* value of Duty 20% can be measured using “SPM-50” manufactured by Gretag Co., Ltd. with a light source D50 and a viewing angle of 2 degrees (the same applies hereinafter).

  In the present specification, the “media having a coating layer” means all of the surfaces on which an image is formed (recorded surface) using the ink set described above and covered with at least the coating layer. As the media having this coating layer, those having an 85 degree gloss of 120 or less are usually used. Here, the 85 degree glossiness is measured by using “PG1M” manufactured by Nippon Denshoku Industries Co., Ltd. In the measurement, the measuring apparatus is adjusted in advance so that the 85 ° glossiness of the standard glossy plate is 100.

As media having a coating layer, specular tone media having a glossiness of 85 to 70 to 120, for example, when a fluorescent lamp is applied from a distance of 1 m or more, the contour of the fluorescent lamp can be visually confirmed. Examples of such media include a resin coating layer, and a typical example thereof is “PGPP (Premium Glossy Photo Paper)” manufactured by Seiko Epson Corporation having an 85 degree gloss of 81.
Other examples of media having a coating layer include semi-glossy media having an 85 ° glossiness of 10 to 70, and matte media having an 85 ° glossiness of 10 or less.

Further, in this specification, “Duty” is defined by the following formula and indicates a unit of the calculated value D.
D = [number of actual printing dots / (vertical resolution × horizontal resolution)] × 100
Duty 100% means the maximum ink weight of a single color for a pixel.

In the ink set of the present invention, the L ^* value of Duty 20% on the medium having the magenta ink coating layer is 1 of the L ^* value of Duty 20% on the medium having the red ink coating layer. A combination of magenta ink and red ink is preferably used in a range of 0.0 to 1.2 times.

In the ink set of the present invention, the L ^* value of Duty 20% on the medium having the cyan ink coating layer is also 1 of the L ^* value of Duty 20% on the medium having the red ink coating layer. A combination of a cyan ink and a red ink is preferable so that the ratio is 0 to 1.2 times.

When the ink set of the present invention is provided with violet ink, it is preferable that the L ^* value of Duty 20% on the medium having the coating layer of the ink is in the range of (Vi); 47-57.

In this case, Duty20% of the L ^* value on media having a coating layer of magenta ink, the Duty20% of the L ^* value on media having a coating layer of violet ink 1.4 to 1. A combination of magenta ink and violet ink that is 6 times greater is preferred.

Also, if similar, Duty20% of the L ^* value on media having a coating layer of cyan inks, 1.4 of Duty20% of the L ^* value on media having a coating layer of violet ink A combination of magenta ink and violet ink, which is 1.6 times, is preferable.

  The ink set of the present invention is not particularly limited in its application, but is an inkjet which is a recording method in which ink droplets are ejected from nozzles and adhered to a recording medium to form images such as characters and figures. It is preferably used in a recording method, and particularly preferably used in an on-demand ink jet recording method. As an on-demand type ink jet recording method, for example, a piezoelectric element recording method that performs recording using a piezoelectric element disposed in a printer head, or a thermal energy generated by a heater of a heating resistance element disposed in the printer head is used. And a thermal jet recording method for recording, and can be suitably used for any ink jet recording method.

  The ink set of the present invention is highly reliable as an ink set for ink jet recording when used in the ink jet recording method as described above. In particular, each ink in the ink set is used as a nozzle of an ink jet printer. By setting the pigment concentration to such a level that does not cause clogging of the ink, the ink set for ink jet recording has higher reliability even though the color reproducibility is wide.

〔Recording method〕
Next, the recording method of the present invention will be described.
The present invention provides a recording method for forming an image using the above-described ink set, that is, a yellow ink (Y), a magenta ink (M), a cyan ink (C), and a red ink having the above-described predetermined L ^* values. This is a method of forming an image using an ink set having at least (R), and a recording method using the ink set of the above-described embodiment is particularly suitable. The recording method of the present invention is carried out in the same manner as a normal ink jet recording method except that the ink set is used.

As the recording method of the present invention, in particular, when one color (single color) of YMC is formed on a recording medium by ejecting a plurality of ink droplets, the ink corresponding to the color is used. When forming an image and forming a mixed color portion of secondary color or higher (color that cannot be formed by YMC ink alone), at least two of YMC ink and R ink, or at least two of YMC ink and R ink In addition, the ink jet recording method for forming the mixed color portion by using the violet ink (Vi) having the predetermined L ^* value described above, or the photo black ink (PK) or the matte black ink (MK) in addition to these inks is suitably provided. To do.

The recording method of the present invention includes a perceptual chromaticity index a ^* and b ^* defined in a CIELAB color space on a recording medium of a recording image to be formed when a mixed color portion of secondary colors or more is formed. Depending on the range, it is preferable to use each ink in the following combinations because a high-quality image with reduced metamerism can be obtained.

That is, the chromaticity index a ^* and b ^* are in the range of a ^* = about −50 to about 50 and b ^* = about −50 to about 50, that is, between white and black. In the case of forming a mixed color portion of one color (for example, gray color), at least three inks of yellow, magenta, and cyan, and red ink and / or violet ink are used. Further, ink other than these inks, for example, photo black ink, matte black ink, etc. may be further provided and used as appropriate.

  When forming a mixed color portion of one color of a hue group between white and black as described above, the amount of ink applied per unit area of the red ink and / or violet ink is the ink used for forming the mixed color portion. Preferably it is 10 to 90 weight% with respect to the total implantation amount, More preferably, it is 30 to 50 weight%.

The perceptual chromaticity indices a ^* and b ^* are in the range of a ^* = about −40 to about 90 and b ^* = about −40 to about 100, that is, yellow color and magenta color, respectively. In the case of forming a mixed color portion of one color (for example, orange or red) of the hue group between, at least two inks of yellow and magenta and red ink are used. In this case, the ink placement amount per unit area of the red ink is preferably 10 to 90% by weight, and more preferably 30 to 50% by weight, with respect to the total amount of ink used for forming the mixed color portion. It is.

The perceptual chromaticity indices a ^* and b ^* are in the range of a ^* = about −50 to about 100 and b ^* = about −10 to about −80, that is, magenta and cyan. In the case of forming a mixed color portion of one color (for example, violet color or blue) of the hue group between the two, at least two inks of magenta and cyan and violet ink are used. In this case, the amount of ink applied per unit area of the violet ink is preferably 10 to 90% by weight, more preferably 30 to 50% by weight, based on the total amount of ink used for forming the mixed color portion. It is.

  In the recording method of the present invention, when forming a monochrome image, yellow ink, magenta ink, and red ink are used individually, and when forming a mixed color portion of secondary or higher colors, yellow ink and magenta ink are used. Mixing yellow ink, magenta ink, and red ink, or mixing yellow ink, magenta ink, red ink, and matte black ink can improve color reproducibility. It is preferable in that it is particularly excellent.

At this time, the maximum duty of the ink used alone can be appropriately selected according to the type of the recording medium to be applied, but is preferably 60 to 120%, and the maximum ink amount is 7 to 16 mg / inch ² . It is preferable to do. Further, the maximum duty of the ink used by mixing is preferably 80 to 130%, and the maximum ink amount is preferably 9 to 18 mg / inch ² .

  In the recording method of the present invention, when a monochrome image is formed, magenta ink, cyan ink, and violet ink are used individually, and when forming a mixed color portion of secondary colors or more, magenta ink, It is preferable to use a mixture of cyan ink and violet ink because it is particularly excellent in suppressing metamerism.

In this case as well, the maximum duty of the ink used alone can be appropriately selected according to the type of the recording medium to be applied, but is preferably 60 to 120%, and the maximum ink amount is 7 to 16 mg / inch. ² is preferable. Further, the maximum duty of the ink used by mixing is preferably 80 to 130%, and the maximum ink amount is preferably 9 to 18 mg / inch ² .

  In addition, the recording method of the present invention can be applied to a recording medium usually used in an ink jet recording method or the like, but as described below, in particular, a medium having a coating layer, plain paper (on a recording surface) This is useful when applied to a recording medium in which fibers are exposed.

  That is, when the recording method of the present invention is applied to a medium having a coating layer, the conspicuous graininess due to dot expression when an image is formed can be extremely suppressed, and a high quality image can be obtained. Can do.

In the recording method of the present invention, when applied to a medium having a coating layer, the L ^* value of Duty 20% on the medium of each ink in the ink set is set within the following range. It is preferable.
(Y); 85-95, (M); 70-80, (C); 70-80, (R); 62-72

In the recording method of the present invention, when applied to a medium having a coating layer, the L ^* value of Duty 20% on the medium having a magenta ink coating layer has a red ink coating layer. It is preferably performed so as to be 1.0 to 1.2 times the L ^* value of Duty 20% on the medium.

In the recording method of the present invention, when applied to a medium having a coating layer, the L ^* value of Duty 20% on the medium having a cyan ink coating layer also has a red ink coating layer. It is preferably performed so as to be 1.0 to 1.2 times the L ^* value of Duty 20% on the medium.

Furthermore, in the recording method of the present invention, when applied to a medium having a coating layer, a violet ink is further used, and the L ^* value of Duty 20% on the medium having the coating layer of the ink is (Vi ); It is preferable to carry out so that it may become in the range of 47-57.

If similar, when using violet ink, Duty20% of the L ^* value on media having a coating layer of magenta ink, the Duty20% of the L ^* value on media having a coating layer of violet ink It is preferable to carry out so that it may become 1.4 to 1.6 times.

In the same case, when violet ink is used, the L ^* value of Duty 20% on a medium having a cyan ink coating layer is equal to the L ^* value of Duty 20% on a medium having a violet ink coating layer ^. It is preferable to carry out so that it may become 1.4 to 1.6 times the value.

  On the other hand, when the recording method of the present invention is applied to plain paper (a recording medium in which fibers are exposed on the recording surface), a relatively small amount of ink is applied when forming an image of a mixed color portion. Thus, since a highly colored image can be formed, deformation of paper wrinkles and the like, and coloring on the back side of paper can be suppressed. In addition, according to the recording method of the present invention using the ink set described above, a recorded image with excellent color developability can be obtained on plain paper, and color development with high saturation and low brightness (dark part), which has not been obtained conventionally, is possible. Become.

  As the plain paper, for example, “XeroxP”, “Xerox 4024” (trade name, manufactured by Xerox), high-quality plain paper (manufactured by Seiko Epson) and the like are suitable.

In the recording method of the present invention, it is preferable to form an image so that the ink weight of 100% duty is 7 to 13 mg / inch ² , particularly 7 to 10 mg / inch ² .

[Recording system]
The present invention is a recording system that forms an image using the above-described ink set, and in particular, a recording apparatus such as an ink jet printer that uses the ink set of the above-described embodiment and other recording systems are suitable.

[Recorded material]
The present invention is a recorded matter in which an image is formed using the ink set described above, and in particular, one using the ink set of the above-described embodiment is preferable.

[Modification]
The present invention suitably provides each of the embodiments described above, but is not limited to these embodiments, and various modifications can be made without departing from the spirit of the present invention.

  Hereinafter, the present invention will be described more specifically with reference to examples and test examples of the present invention. However, the present invention is not limited to the examples.

[Ink set of Example]
A yellow ink, a magenta ink, a cyan ink, a red ink, a violet ink, a photo black ink, and a matte black ink having the following compositions were respectively prepared according to conventional methods. That is, after the colorant component was dispersed together with the dispersant component, other components were added and mixed, and the insoluble component having a certain size or more was filtered to prepare an ink. The obtained inks were combined to form an ink set of Example.

<Yellow ink>
C. I. Pigment Yellow 74 3.0% by weight
Dispersant (styrene-acrylic acid copolymer) 1.2% by weight
Glycerin 15.0% by weight
1,2-hexanediol 10.0% by weight
Triethanolamine 0.9% by weight
BYK348 (silicone surfactant) 0.3% by weight
Ion exchange water
Total 100.0% by weight

<Magenta ink>
C. I. Pigment Violet 19 2.0% by weight
Dispersant (styrene-acrylic acid copolymer) 0.8% by weight
Glycerin 15.0% by weight
1,2-hexanediol 10.0% by weight
Triethanolamine 0.9% by weight
BYK348 (silicone surfactant) 0.3% by weight
Ion exchange water
Total 100.0% by weight

<Cyan ink>
C. I. Pigment Blue 15: 3 1.5% by weight
Dispersant (styrene-acrylic acid copolymer) 0.6% by weight
Glycerin 15.0% by weight
1,2-hexanediol 10.0% by weight
Triethanolamine 0.9% by weight
BYK348 (silicone surfactant) 0.3% by weight
Ion exchange water
Total 100.0% by weight

<Red ink>
C. I. Pigment Red 264 2.0% by weight
Dispersant (styrene-acrylic acid copolymer) 1.0% by weight
Glycerin 15.0% by weight
1,2-hexanediol 10.0% by weight
Triethanolamine 0.9% by weight
BYK348 (silicone surfactant) 0.3% by weight
Ion exchange water
Total 100.0% by weight

<Violet ink>
C. I. Pigment Violet 23 2.0% by weight
Dispersant (styrene-acrylic acid copolymer) 0.8% by weight
Glycerin 15.0% by weight
1,2-hexanediol 10.0% by weight
Triethanolamine 0.9% by weight
BYK348 (silicone surfactant) 0.3% by weight
Ion exchange water
Total 100.0% by weight

<Photo black ink>
C. I. Pigment Black 7 1.5% by weight
Dispersant (styrene-acrylic acid copolymer) 1.5% by weight
Glycerin 15.0% by weight
1,2-hexanediol 10.0% by weight
Triethanolamine 0.9% by weight
BYK348 (silicone surfactant) 0.3% by weight
Ion exchange water
Total 100.0% by weight

<Matte black ink>
C. I. Pigment Black 7 (self-dispersing type) 6.0% by weight
Glycerin 15.0% by weight
1,2-hexanediol 10.0% by weight
Triethanolamine 0.9% by weight
BYK348 (silicone surfactant) 0.3% by weight
Ion exchange water
Total 100.0% by weight

[Ink set of reference example]
Each ink was prepared and obtained in the same manner as in the ink set of Example, except that it was changed to yellow ink, magenta ink, cyan ink, red ink, violet ink, photo black ink, and matte black ink, respectively. Each ink was combined to obtain an ink set of a reference example.

<Yellow ink>
C. I. Pigment Yellow 74 3.0% by weight
Dispersant (styrene-acrylic acid copolymer) 1.0% by weight
Glycerin 15.0% by weight
Ethylene glycol 5.0% by weight
2-pyrrolidone 2.0% by weight
1,2-hexanediol 5.0% by weight
Olfine E1010 0.5% by weight
Ion exchange water
Total 100.0% by weight

<Magenta ink>
C. I. Pigment Red 202 1.5% by weight
Dispersant (styrene-acrylic acid copolymer) 0.5% by weight
Glycerin 15.0% by weight
Ethylene glycol 5.0% by weight
2-pyrrolidone 2.0% by weight
1,2-hexanediol 5.0% by weight
Olfine E1010 0.5% by weight
Ion exchange water
Total 100.0% by weight

<Cyan ink>
C. I. Pigment Blue 15: 3 1.5% by weight
Dispersant (styrene-acrylic acid copolymer) 0.5% by weight
Glycerin 15.0% by weight
Ethylene glycol 5.0% by weight
2-pyrrolidone 2.0% by weight
1,2-hexanediol 5.0% by weight
Olfine E1010 0.5% by weight
Ion exchange water
Total 100.0% by weight

<Red ink>
C. I. Pigment Red 178 2.0% by weight
Dispersant (styrene-acrylic acid copolymer) 0.7% by weight
Glycerin 15.0% by weight
Ethylene glycol 5.0% by weight
2-pyrrolidone 2.0% by weight
1,2-hexanediol 5.0% by weight
Olfine E1010 0.5% by weight
Ion exchange water
Total 100.0% by weight

<Violet ink>
C. I. Pigment Violet 23 2.0% by weight
Dispersant (styrene-acrylic acid copolymer) 0.7% by weight
Glycerin 15.0% by weight
Ethylene glycol 5.0% by weight
2-pyrrolidone 2.0% by weight
1,2-hexanediol 5.0% by weight
Olfine E1010 0.5% by weight
Ion exchange water
Total 100.0% by weight

<Photo black ink>
C. I. Pigment Black 7 1.5% by weight
Dispersant (styrene-acrylic acid copolymer) 1.5% by weight
Glycerin 15.0% by weight
Ethylene glycol 5.0% by weight
2-pyrrolidone 2.0% by weight
1,2-hexanediol 5.0% by weight
Olfine E1010 0.5% by weight
Ion exchange water
Total 100.0% by weight

<Matte black ink>
C. I. Pigment Black 7 (self-dispersing type) 6.0% by weight
Glycerin 15.0% by weight
Ethylene glycol 5.0% by weight
2-pyrrolidone 2.0% by weight
1,2-hexanediol 5.0% by weight
Olfine E1010 0.5% by weight
Ion exchange water
Total 100.0% by weight

(Measurement of L ^* value of 1000 times diluted aqueous ink solution)
The L ^* value in the Lab display system defined by the CIE of a 1000-fold diluted aqueous solution of each color ink used in each ink set of Examples and Reference Examples was measured as follows using U3300 manufactured by Hitachi, Ltd.
In other words, prepare a 4mL capacity cell with 1cm length x 1cm width x 4cm height, divide it into a cell on the sample side and a cell on the reference side, add pure water to both cells, and measure the baseline. , Set it up. While the cell on the reference side was left as it was, a 1000-fold weight diluted aqueous solution of ink was put in the cell on the sample side instead of pure water. A 1000-fold diluted aqueous solution of the ink was prepared by transferring 1.00 g of each ink in each of the ink sets of Examples and Reference Examples to a 1 L beaker and immediately adding pure water to make a total of 1 kg.
Then, the sample side cell and the reference side cell are set in the measurement section, the slit width of the light source lamp is set to 2.0 nm, the scan speed of the measurement interval is set to 600 nm / min, and the transmittance is 0.0 to 100. The L ^* value was measured under the conditions of 0% T, 380 to 800 nm, D65 light source, viewing angle 2 °, photovoltaic voltage 200V, and switching the light source lamp to D2 lamp and WI lamp by switching 340 nm. The L ^* value of the 1000-fold diluted aqueous solution of each ink obtained is shown below.
Example ink set (Y); 91.30, (M); 81.08, (C); 79.84, (R); 66.59, (Vi); 49.01, (PB); 54.40, (MB); 4.55
Ink set of reference example (Y); 91.30, (M); 84.18, (C); 79.84, (R); 70.89, (Vi); 49.01, (PB); 54.40, (MB); 4.55

[Test Example 1] Application to media having a coating layer PGPP (PM photograph) as a media having a coating layer by using an ink jet printer PM900C (manufactured by Seiko Epson Corporation) using each ink set of Examples and Reference Examples. Paper) (manufactured by Seiko Epson Corporation) was printed at a duty of 10 to 100% (single color) and 10 to 120% (when a plurality of inks were arbitrarily mixed). At the time of printing, when forming a mixed color portion of a secondary color or higher, the mixed color portion was formed by at least two kinds of YMC inks and R and Vi inks. Further, in this case, each ink was used in the above-described preferred combination according to the range of the perceptual chromaticity index a ^* and b ^* . Specifically, when the chromaticity index a ^* and b ^* form a color mixture portion where a ^* = about −50 to about 50 and b ^* = about −50 to about 50, respectively. , YMC ink, R, Vi ink, and PK ink were used to print a picture image of the Japanese Standards Association SCID sample “bicycle” at 1440 × 720 dpi.

  Similarly, a recorded matter was obtained on PM photographic paper using PM900C at 1440 × 720 dpi according to the following ink weight tables (Tables 1 and 2). Color inks 1 and 2 in the following Tables 1 and 2 indicate any two of yellow ink, magenta ink, cyan ink, red ink, and violet ink, and ink 3 in Table 2 below is red. One of ink, violet ink, and photo black ink is shown.

In this case, (L ^* value of the image by the ink other than black) Duty20% monochromatic L ^* values on PM photographic paper were as follows (Measurement of the L ^* value; Gretag Co. " SPM-50 "and measured with a light source D50 and a viewing angle of 2 degrees).

-L ^* value of Duty 20% on PM photographic paper with ink set of example;
(Y); 90.07, (M); 74.34, (C); 74.41, (R); 63.30, (Vi); 52.17
-L ^* value of Duty 20% on PM photographic paper with ink set of reference example;
(Y); 90.07, (M); 75.01, (C); 74.41, (R); 67.63, (Vi); 52.17

(Evaluation of gamut volume)
The gamut volume of the obtained recorded matter was measured. Measurements gamut volume, using a Gretag Co. Guretasu Macbeth SPM50, by D50 light source, no filter, measured at a viewing angle 2 °, CIE in a defined L ^* a ^* b ^* color system, L ^* = The volume when the volume of a cube consisting of 1, a ^* = 1, b ^* = 1 is taken as 1 was determined. As a result, both of the print images obtained by the ink sets of the example and the reference example were about 650,000 or more and were images having a wide color reproduction range.

(Evaluation of graininess)
The portion of the recorded matter (excluding the case where the ink 3 is photo black) obtained with each ink set of Example and Reference Example having a duty of 20% or less has an L ^* value of 50 or more, and it is difficult to confirm the graininess in both cases. It was an excellent quality image.

(Glossiness evaluation)
A fluorescent lamp was applied to the obtained printed part from a distance of about 2 m, and it was visually determined whether the outline of the fluorescent lamp could be confirmed. As a result, both the printed images obtained by the ink sets of the example and the reference example can recognize the illumination shape and have excellent gloss.

[Test Example 2] Application to plain paper (YMR saturation and brightness evaluation)
Using each ink set of Examples and Reference Examples, yellow ink, magenta ink at 720 × 720 dpi on plain paper (“XeroxP”, manufactured by Xerox Corporation) by an inkjet printer PM900C (manufactured by Seiko Epson Corporation) When each red ink is used in a single color, the maximum duty is 66% (maximum ink amount: 7.2 mg / inch ² ). On the other hand, when yellow ink, magenta ink, red ink, and matte black ink are used in mixed colors. Printed at a maximum duty of 86% (maximum ink amount: 10.5 mg / inch ² ) to obtain a recorded matter. In the case of printing, when forming a mixed color portion of a secondary color or higher, the mixed color portion was formed in the same manner as in Test Example 1. Specifically, the following ink weight tables (Tables 3 and 4) were used.

  The obtained recorded matter was measured using a “Gretag Macbeth SPM-50” (manufactured by Gretag) with a D50 light source, no filter, and a viewing angle of 2 degrees, and a Lab display system value defined by CIE was obtained. From this value, the image of the recorded matter obtained by the ink set of the example is superior in saturation at a hue angle of 0 to 20 degrees as compared with the image of the recorded matter obtained by the ink set of the reference example. It was also found that a color image with high saturation and low brightness can be obtained.

(Saturation and brightness evaluation of MCVi)
Using each ink set of Examples and Reference Examples, magenta ink, cyan ink, 720 × 720 dpi on plain paper (“XeroxP”, manufactured by Xerox Co., Ltd.) by an inkjet printer PM900C (manufactured by Seiko Epson) When the violet ink is used in a single color, the maximum duty is 66% (maximum ink amount: 7.2 mg / inch ² ). On the other hand, when magenta ink, cyan ink, and violet ink are used in mixed colors, the maximum duty is 86. % (Maximum ink amount: 10.5 mg / inch ² ) was printed to obtain a recorded matter. In the case of printing, when forming a mixed color portion of a secondary color or higher, the mixed color portion was formed in the same manner as in Test Example 1. Specifically, the ink weight table for each color (Tables 3 and 4) was followed.

  The obtained recorded matter was measured using a “Gretag Macbeth SPM-50” (manufactured by Gretag) with a D50 light source, no filter, and a viewing angle of 2 degrees, and a Lab display system value defined by CIE was obtained. From this value, it was found that the recorded matter obtained using the ink set of the example had an image excellent in color developability equivalent to the recorded matter obtained using the ink set of the reference example. .

[Test Example 3] Application to media with coating layer (Part 2)
Using each ink set of Examples and Reference Examples, 720 × with respect to PGPP (PM photographic paper) (manufactured by Seiko Epson) as a medium having a coating layer by an ink jet printer PM900C (manufactured by Seiko Epson). When yellow ink, magenta ink, and red ink are each used at 720 dpi, the maximum duty is 100% (maximum ink amount: 13 mg / inch ² ). On the other hand, when yellow ink and magenta ink are used in mixed colors Printed as a maximum duty of 120% (maximum ink amount: 16 mg / inch ² ) to obtain a recorded matter. In the case of printing, when forming a mixed color portion of a secondary color or higher, the mixed color portion was formed in the same manner as in Test Example 1.

(Evaluation of metamerism)
The obtained recorded matter was measured with “Gretag Macbeth SPM-50” (manufactured by Gretag Co., Ltd.) without a filter and at a viewing angle of 2 degrees with two types of D50 light source and A light source. System values were obtained. From this value, the image of the recorded matter obtained with the ink set of the example has a color development with an L ^* value of 53 or less at a hue angle of 20 to 30 degrees, and the recorded matter obtained with the ink set of the reference example. It was found that a high-quality image with reduced metamerism can be obtained compared to the above image.

[Test Example 4] Application to media with coating layer (Part 3)
Using each ink set of Examples and Reference Examples, 720 × with respect to PGPP (PM photographic paper) (manufactured by Seiko Epson) as a medium having a coating layer by an ink jet printer PM900C (manufactured by Seiko Epson). When yellow ink, magenta ink, and red ink are used in a single color at 720 dpi, the maximum duty is 100% (maximum ink amount: 13 mg / inch ² ), while yellow ink, magenta ink, and red ink are used in mixed colors. In this case, printing was performed with a maximum duty of 120% (maximum ink amount: 16 mg / inch ² ) to obtain a recorded matter. In the case of printing, when forming a mixed color portion of a secondary color or higher, the mixed color portion was formed in the same manner as in Test Example 1.

(Evaluation of color development and metamerism)
The obtained recorded matter was measured with “Gretag Macbeth SPM-50” (manufactured by Gretag Co., Ltd.) without a filter and at a viewing angle of 2 degrees with two types of D50 light source and A light source. System values were obtained. From this value, the image of the recorded matter obtained with the ink set of the example has a color development with an L ^* value of 53 or less at a hue angle of 20 to 30 degrees, and the recorded matter obtained with the ink set of the reference example. It was found that a high-quality image with reduced metamerism can be obtained compared to the above image.

Claims (13)

An ink set including at least a yellow ink (Y), a magenta ink (M), a cyan ink (C), and a red ink (R), wherein L in a Lab display system defined by CIE of a 1000-fold diluted aqueous solution of each ink ^* value, Ri near within the scope of the following,
The yellow ink contains 2.0 to 4.0 wt% pigment, the magenta ink contains 1.7 to 3.0 wt% pigment, and the cyan ink contains 0.5 to 2.5 wt% pigment. The red ink contains 1.8 to 2.4% by weight of a pigment;
Ink set.
(Y); 89 to 94, (M); 76 to 83, (C); 74 to 87, (R); 62 to 67.5   The yellow ink is C.I. I. Pigment Yellow 74 is contained in an amount of 2.0 to 4.0% by weight, and the magenta ink is C.I. I. Pigment Violet 19 is contained in an amount of 1.7 to 3.0% by weight, and the cyan ink is C.I. I. Pigment Blue 15: 3 is contained in an amount of 0.5 to 2.5% by weight, and the red ink is C.I. I. The ink set according to claim 1, comprising 1.8 to 2.4% by weight of Pigment Red 264. The ink set according to claim 1, further comprising a violet ink (Vi) having an L ^* value in a range of 40 or more and 58 or less in a Lab display system defined by CIE of a 1000-fold diluted aqueous solution.   The violet ink is C.I. I. The ink set according to claim 3, comprising 1.0 to 3.0% by weight of pigment violet 23.   The ink set according to any one of claims 1 to 4, wherein each of the inks contains 20 to 80 wt% of a dispersant for dispersing the pigment together with the pigment as a colorant.   The ink set according to any one of claims 1 to 5, further comprising a photo black ink (PK) containing 3.0% by weight or less of carbon black.   The ink set according to claim 6, wherein the photo black ink includes a pigment as a coloring material and a dispersant for dispersing the pigment in an amount of 60 to 120% by weight based on the pigment.   The ink set according to any one of claims 1 to 7, further comprising a matte black ink (MK) containing more than 3.0% by weight of carbon black.   The ink set according to claim 8, wherein the matte black ink includes a self-dispersing pigment as a coloring material and does not include a dispersant.   The ink set according to claim 1, wherein each ink contains 0.1 to 30% by weight of a high boiling point organic solvent.   The ink set according to claim 1, wherein each of the inks contains 1 to 20% by weight of a penetration accelerator.   The ink set according to any one of claims 1 to 11, wherein each of the inks contains 0.1 to 5% by weight of an acetylene glycol compound and / or a silicone compound.   A recording method for forming an image using the ink set according to claim 1.