JP2004231692A - Ink set for ink-jet recording, ink and liquid set and method for ink-jet recording using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink set for ink-jet recording having excellent color reproducibility of an image such as a photograph and preparing a document having the image density balanced with an image and a letter when a multicolor document is prepared. <P>SOLUTION: The ink set for ink-jet recording is composed of a combination of a black ink with a color ink of ≥3 colors of cyan, magenta and yellow. The number-average particle diameter (nm) and the number of particles (particles/μl) contained in 1 μl of each ink after jetting satisfy formulas <1> to <5>. <1> is 10≤BD and CD≤150. <2> is 6×10<SP>4</SP>≤BN(0.5)≤6×10<SP>5</SP>. <3> is 6×10<SP>3</SP>≤CN(0.5)≤6×10<SP>5</SP>. <4> is CN(0.5)≤BN(0.5). <5> is BN(5)≤50 and CN(5)≤50 [wherein, B denotes the black ink; C denotes the color ink; BD and CD denote each the particle diameter; BN(0.5) and CN(0.5) denote each the number of particles having ≥0.5 μm particle diameter; and BN(5) and CN(5) denote each the number of particles having ≥5 μm particle diameter]. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【０１２４】
［実施例１、２及び比較例１〜３］
分散液１〜１６を使用し、分散液以外の下記の溶媒成分を３０分間攪拌混合した。その後、攪拌中の溶媒に分散液をゆっくり添加し、そのままさらに３０分間攪拌混合し、インクを作製した。分散液１〜４を用いたインクセットを実施例１、分散液５〜８を用いたインクセットを実施例２、分散液９〜１２を用いたインクセットを比較例１、分散液１３〜１６を用いたインクセットを比較例２、分散液１７〜２０を用いたインクセットを比較例３とした。
【０１２５】
・分散液：５０重量部
・エチレングリコール（溶解性パラメータ１７．８）：１２重量部
・イソプロピルアルコール（溶解性パラメータ１１．６）：３重量部
・サーフィノール４６５（日信化学社製）：０．０５重量部
・脱イオン水：３５重量部
【０１２６】
［試験例１］
実施例１、２及び比較例１〜３で作製したインクセットを用い、富士ゼロックスで試作したフルカラーインクジェットプリンター（６００ｓｐｉ）により２ｃｍ帯の単色（ブラック、シアン、マゼンタ、イエロー）、２次色（レッド、グリーン、ブルー）、３次色（プロセスブラック）パッチの印字を行った。使用した用紙は、代表的な普通紙として、ＦＸ−Ｌ紙（富士ゼロックス社製）を用いた。
【０１２７】
評価は、印字された１次色、２次色および３次色からなるソリッド画像について、光学濃度の測定、色ムラ発生有無の観察を行い、さらにカラーインクについてはＧａｍｕｔ値を求めて色再現範囲を確認した。
なお、各色のインク中の噴射前後の数平均粒子径が０．５μｍ以上および５μｍ以上の粒子数と、インク中の粒度分布を測定した。すなわち、作製直後のインクと、プリンターより噴射されたインクをビーカに回収した噴射後のインクについて、粒子径が０．５μｍ以上の粒子数を、Ａｃｃｕｓｉｚｅｒ（ＰＡＲＴＩＣＬＥ ＳＩＺＩＮＧ ＳＹＳＴＥＭＳ社製）により測定し、粒度分布を、マイクロトラックＵＰＡ（Ｌｅｅｄｓ ＆ Ｎｏｒｔｈｒｕｐ社製）により測定した。Ａｃｃｕｓｉｚｅｒの測定条件は、インク２μｌを５０ｍｌの脱イオン水に希釈して測定し、粒子数は１μｌに換算した。マイクロトラックＵＰＡの測定条件は、インク粘度を溶媒粘度として、インク原液を測定した。
【０１２８】
また、色再現範囲については、シアン、マゼンタ、イエロー、レッド、グリーン、ブルーの各ソリッド画像について、色相をＸ−Ｒｉｔｅ９３８（Ｘ−Ｒｉｔｅ社製）で測定し、得られたａ^＊値、ｂ^＊値を２次元平面に作図してできる六角形の面積（Ｇａｍｕｔ）を求めることにより評価した。これらの結果を表２に示す。
【０１２９】
【表２】

【０１３０】
実施例１、２のインクを用いて印字したものは、比較例１〜３のインクと比べて、高い光学濃度が得られ、２次色／３次色の発色性も良好で、色ムラ発生は無く、また、Ｇａｕｍｔ値も大きく、良好な色再現範囲を得ることができた。
【０１３１】
［実験例３、４］
表３の組成に従い、分散液以外の溶媒組成成分及び脱イオン水１０重量部を３０分間攪拌混合した。その後、攪拌中の溶媒に各分散液５０重量部をゆっくり添加した。さらに脱イオン水を加え、全量を１００重量部とし、このまま３０分間攪拌混合しインクを作製した。
【０１３２】
［試験例２］
作製直後の初期のインク、プリンターより噴射されたインクをビーカに回収した噴射後インク、６０℃１００時間保管したインク、それぞれのインクの粒子径０．５μｍ以上の粒子数、数平均粒度を測定し、インクジェット記録用インクセットの保存安定性を調べた。結果を表３に示す。
【０１３３】
【表３】

【０１３４】
以下は、本発明のインク及び液体セットに関する実施例、その比較例及び試験例である。
［第１インクの作製］
・エチレングリコール：１２重量部
・エタノール：４重量部
・尿素：５重量部
・ラウリル硫酸エステルナトリウム塩：０．０５重量部
上記組成と脱イオン水で合計５０重量部とし、３０分間撹拌した。その後、分散液１〜４、９〜１２をそれぞれ５０重量部添加し、さらに撹拌を３０分間続けた。２μｍのメンブランフィルターを通過させて、インクを作製した。分散液１〜４を使用した第１インクセットをインクＡ、Ｂ、Ｃ、Ｄ、分散液９〜１２を使用した第一インクセットをインクＥ、Ｆ、Ｇ、Ｈとした。
【０１３５】
［試験例３］
作製直後のインクＡ〜Ｈと、プリンターで噴射されたインクをビーカに回収した噴射後のインクＡ〜Ｈとについて、粒子径０．５μｍ以上の粒子数と、インクの粒度分布を上記試験例１と同様にして測定した。インクＡ〜Ｈの粒子径０．５μｍ以上の粒子数及び変化倍率、粒度及び変化率を表４に示す。
【０１３６】
【表４】

【０１３７】
（第二液体の作製：着色剤を含有する場合）
［第二液体１］
・ダイレクトイエロー１４４（１０％水溶液）：２０重量部
・エチレングリコール（溶解性パラメータ１７．８）：２０重量部
・２−（２エトキシエトキシ）エタノール（溶解性パラメータ１０．９）：５重量部
・尿素：５重量部
・塩化ベンザルコニウム：１重量部
上記組成と脱イオン水で全量を１００重量部とし、３０分間撹拌した。その後、１μｍのメンブランフィルターを通過させて、第二液体１を作製した。
【０１３８】
［第二液体２］
・ダイレクトイエロー１４４（１０％水溶液）：２０重量部
・エチレングリコール（溶解性パラメータ１７．８）：２０重量部
・２−（２エトキシエトキシ）エタノール（溶解性パラメータ１０．９）：５重量部
・尿素：５重量部
・塩化ベンザルコニウム：５重量部
上記組成と脱イオン水で全量を１００重量部とし、３０分間撹拌した。その後、１μｍのメンブランフィルターを通過させようとしたが、フィルターが詰まり、濾過できなかった。濾紙上には粒状物が観察された。
【０１３９】
［第二液体３］
・ダイレクトイエロー１４４（１０％水溶液）：２０重量部
・エチレングリコール（溶解性パラメータ１７．８）：２０重量部
・２−（２エトキシエトキシ）エタノール（溶解性パラメータ１０．９）：５重量部
・尿素：５重量部
・硫酸マグネシウム：０．８重量部
上記組成を用い、第二液体１と同様にして、第二液体３を作製した。
【０１４０】
［実施例５、６、比較例４、５による試験例４］
（印字テスト）
富士ゼロックス社で試作したフルカラーインクジェットプリンター（６００ｓｐｉ）を用いて、表５に示すそれぞれの第１インク及び第二液体を、２ｃｍ四方のパッチにそれぞれ接するように印字した。用紙は、代表的な普通紙としてＦＸ−Ｌ紙（富士ゼロックス社製）を用いた。評価項目は接した印字物の混色を１０人の被験者により、下記基準で官能評価した。
○：全く混色していない
△：混色が発生しているが、気にならない
×：混色が発生し、許容できない
結果を表５に示す。
【０１４１】
【表５】

【０１４２】
表５に示される結果から明らかなように、本発明のインク及び液体セットを用いたもの（実施例５、６）は、比較例４，５のものに比べて、混色の発生がなかった。
【０１４３】
（第二液体の作製：着色剤を含有しない場合）
［第二液体４］
・エチレングリコール（溶解性パラメータ１７．８）：２５重量部
・尿素：５重量部
・サーフィノール４６５：１重量部
・塩化ベンザルコニウム：５重量部
上記組成と脱イオン水で全量を１００重量部とし、３０分間撹拌した。その後、１μｍのメンブランフィルターを通過させて第二液体４を作製した。
【０１４４】
［実施例７、８、９、比較例６、７、８による試験例５］
（印字テスト）
富士ゼロックス社で試作したフルカラーインクジェットプリンター（６６０ｓｐｉ）を用いて、第二液体４を、表６に示す第１インクの噴射直前に、第１インク印字予定部に印字した。その直後に第１インク及びベースインクとして液体１を１０ｃｍ四方のパッチに接するように印字した。第二液体の印字は、表６に示すように、第１インクの単位面積当たりのドット数に対して、１／１０、３／１０、５／１０のドット数で行った。用紙は、代表的な普通紙としてＦＸ−Ｌ紙（富士ゼロックス社製）を用いた。評価項目は、接した印字物の混色の下記基準による１０人の被験者による官能評価及び下記基準による用紙カクル（しわ）高さとした。
○：全く混色していない
△：混色が発生しているが、気にならない
×：混色が発生し、許容できない
○：０〜４ｍｍ未満
×：４〜８ｍｍ未満
××：８ｍｍ以上
これらの結果を表６に示す。
【０１４５】
【表６】

【０１４６】
表６に示された結果から明らかなように、本発明のインク及び液体セットを用いた実施例７、８、９のものは、比較例６、７、８に比べて、混色がなく、カクルの発生も防止することができた。
【０１４７】
以上、説明したように、本発明のインクジェット記録用インクセットは、従来のインクセットよりも２次色、３次色の色の再現性が良く、また、画像と文字との画像濃度のバランスも良好である。さらに、従来のインクセットと同様に、顔料分散型インクでありながら、高い光学濃度を有し、加えて保存安定性も優れている。また、本発明のインクジェット記録用インクセットは、印字に際して第二液体とセットで用いることにより、隣接した着色剤の混色防止を達成することができる。
【０１４８】
本発明のインクジェット記録用インクセット、または、インク及び液体セットは、レポート用紙、コピー用紙、ボンド紙、上質紙等の普通紙上において鮮明で高解像度の高耐水性フルカラー画像を形成することができ、しかも、カール・カクルの用紙品質低下も防止することができる。本発明のインクジェット記録用インクセットは、熱インクジェット方式、或いはピエゾ方式、超音波、電界等を利用したインクジェット記録のためのインクとして好適である。特に、普通紙上に高耐水性フルカラー画像を鮮明にかつ安定に再現し得るインクとして好適である。
【０１４９】
【発明の効果】
以上に説明したように本発明によれば、すなわち、本発明は、ノズル詰まりを防止でき、色ムラが無く、更に、各色のインクを組み合わせて多色のドキュメントを作成する場合においても、写真等の画像の色再現性に優れ、且つ、画像と文字との画像濃度のバランスの取れたドキュメントの作成が可能なインクジェット記録用インクセット、インク及び液体セット、および、これらを用いたインクジェット記録方法を提供することができる。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an aqueous ink set for inkjet recording, an ink and a liquid set, and an inkjet recording method using the same.
[0002]
[Prior art]
A so-called inkjet printer that discharges liquid or molten solid ink from a nozzle, slit, or porous film, and records on paper, cloth, film, and the like has various advantages such as small size, low cost, and quietness. In particular, a black single-color printer is commercially available as a printer capable of obtaining good printing quality on so-called plain paper such as report paper and copy paper. With the spread of the ink jet printer, various studies have been made on the improvement of ink sets for ink jet recording.
[0003]
Regarding the ink used in the ink jet printer, (1) a uniform image with high resolution, high density and no bleeding or fogging on paper is obtained, and (2) clogging due to ink drying at the nozzle tip occurs. (3) good ink quick-drying properties on paper, (4) good image solidity, and (5) good long-term storage stability. , And many proposals have been made to satisfy these requirements.
[0004]
Conventionally used ink jet recording ink sets are mainly inks using water-based dyes, but because the dyes are water-soluble, there are problems with water resistance and light resistance, and regarding the storage stability of images, Not always satisfactory. On the other hand, an ink using a pigment as a coloring material is very promising because it can achieve an improvement in water resistance and light resistance, and therefore many proposals have been made and put to practical use.
[0005]
However, although pigment ink has high water fastness, it tends to aggregate during long-term storage or high-temperature storage, and storage stability is a problem. In a pigment ink, the optical density and the dispersion stability are in an opposite relationship. This reciprocal relationship is due to the strength of the cohesive force of the pigment, and although high optical density can be obtained by aggregating the pigment on paper after printing, the dispersion stability is poor due to the strong cohesive force. .
[0006]
Examples of color ink sets for inkjet using pigments that have been proposed so far include, for example, a pigment ink set containing a specific pigment and an anionic surfactant containing an ethylene oxide group as essential components (see Patent Document 1). A pigment ink set that includes a specific pigment and an acetylene glycol compound as essential components and has an impurity concentration of a certain amount or less (see Patent Document 2). However, in the ink sets proposed in the former and the latter, the characteristics of both optical density and dispersion stability were not fully compatible with all the inks of each color.
[0007]
On the other hand, methods of obtaining a high optical density include (1) increasing the pigment concentration in the ink, (2) increasing the hydrophobicity of the dispersant, (3) decreasing the amount of the dispersant added, and (4) oil absorption of the pigment. And the like. However, the method shown in (1) deteriorates storage stability due to aggregation of the pigment and deteriorates head clogging, and the methods shown in (2) to (4) show storage stability, particularly storage stability at high temperatures. It has drawbacks such as severe deterioration of properties.
For this reason, in order to secure dispersion stability, it is necessary to adopt a method reverse to the methods shown in the above (1) to (4), and it is difficult to achieve both high optical density and dispersion stability. Met.
[0008]
In order to solve such a problem, in a pigment-dispersed ink containing a pigment, an aqueous polymer, a water-soluble organic solvent, and water, the number of particles present in the ink before and after the ink is ejected from the nozzle of the inkjet head is reduced. It has been proposed to perform control within a certain range (see Patent Document 3). According to this proposal, it is reported that the above-mentioned problem is solved by controlling the number of particles contained in the ink before and after the ejection and the number average particle diameter within a certain range.
[0009]
On the other hand, when creating various documents using an actual inkjet recording apparatus, for example, in addition to creating a monochromatic document such as a monochrome print using only black ink, a plurality of colors of ink are used. There are also many opportunities to create multicolor documents.
In this case, when a multi-color document is created by using a combination of inks of the respective colors having the above-described configurations, the color reproducibility of an image such as a photograph on the document becomes poor, or On the other hand, the image density of the character may seem relatively light, and the color balance of the entire document may be poor.
[0010]
[Patent Document 1]
JP-A-2002-88291
[Patent Document 2]
JP 2002-226738 A
[Patent Document 3]
JP 2000-204305 A
[0011]
[Problems to be solved by the invention]
An object of the present invention is to solve the above-mentioned problems of the related art. That is, the present invention can prevent nozzle clogging, has no color unevenness, and is excellent in color reproducibility of images such as photographs even when a multi-color document is created by combining inks of each color. It is an object of the present invention to provide an ink jet recording ink set, an ink and a liquid set, and an ink jet recording method using the same, which can create a document having a well-balanced image density between the image and the character.
[0012]
[Means for Solving the Problems]
When a multi-color document is created using a combination of the inks of each color described in Patent Document 3, the color reproducibility of an image such as a photograph on the document and the image density of characters are reduced. We examined the causes of incompatibilities and the jumble of the whole document. In doing so, the present inventors first considered the optical density and color reproducibility required for each color in the case of a document.
[0013]
First, when creating a multi-colored document, the optical density and color generally required for black printed with black ink and the color printed using a single color ink or a combination of color inks of each color are used. Reproducibility is different.
This is because it is difficult to define quantitatively for a document that has a good balance between image density and color reproducibility of the entire document, but is generally difficult to define. Is required to be higher than the image density of the entire image portion, and the image portion is required to have both a certain image density and high color reproducibility.
[0014]
On the other hand, black printed with black ink is very often used for printing characters. In this case, since it is necessary that each character can be clearly recognized for each character by eyes, it is extremely important that black printed by black ink has a high optical density.
[0015]
Of course, it is necessary for the color color to have a high optical density, but it is not required to have the same level as the black color printed by the black ink. This is because color is used less frequently for printing characters than black, which is printed with black ink, and color inks are overlaid rather than printed using only one color ink. This is because they are very often used for printing images of a multicolor configuration such as photographs and graphics.
That is, the color ink is required to have a characteristic that can achieve a good balance between color reproducibility and optical density.
[0016]
However, as a result of extensive studies by the present inventors, when a multi-color document is created by using a combination of inks of the respective colors described in Patent Document 3, the density of characters printed in black on the appearance may be reduced. (1) When the characters printed in black are thin with respect to the image portion and the impact of the character portion on the document is felt weak, or (2) ) In some cases, the color reproducibility of the image portion was poor. Further, in the cases shown in (1) and (2), since the printing quality of the other image portion and the character portion constituting the document is relatively good, the space between the character portion and the image portion is relatively small. In many cases, a gap occurs in the printing quality, giving a visually jerky impression as a whole document.
[0017]
On the other hand, it is considered that the optical density at the time of printing increases due to the presence of particles having a number average particle diameter of 0.5 μm or more contained in the ink on the paper. The present inventor has paid attention to this point and has studied the causes of the above-mentioned phenomena (1) and (2). As a result, the present inventors have found that such a phenomenon occurs when the number of particles having a number average particle diameter of 0.5 μm or more contained in the ejected ink is larger in the color ink than in the black ink. I found that.
[0018]
This is based on the following findings. That is, while black ink is often used only for printing of the primary color (black), color ink is used not only for printing of the primary color but also for secondary colors and tertiary colors. More than one kind of color ink is often used in an overlapping manner. On the other hand, as the number of particles having a number average particle diameter of 0.5 μm or more in the ink applied on paper increases, the optical density can be further increased. However, in the case of secondary and tertiary colors, more particles are formed by agglomeration on paper than in the case of the primary color, so that the color is reproducible in proportion to the increase in optical density. Tends to decrease.
[0019]
Accordingly, when the number of particles having an average particle diameter of 0.5 μm or more contained in the ejected ink is larger in the black ink and the color ink than in the black ink, the optical density of black is sufficiently secured. Although the color reproducibility of the secondary and tertiary colors is reduced, or the color reproducibility of the secondary and tertiary colors is good, the black image density However, it is relatively lighter than an image portion formed in a color color, resulting in a weaker impact on a character portion. The present inventors have devised the following present invention based on the above findings.
[0020]
That is, the present invention
<1> A combination of a black ink and three or more color inks including three colors of cyan, magenta and yellow, wherein the black ink and the color ink are a pigment, an aqueous polymer, and a water-soluble organic solvent. And an ink set for inkjet recording containing at least water.
The black ink and the color ink include particles after being ejected from a nozzle of an inkjet head, and the number average particle diameter and the number of particles contained in the ejected black ink and color ink are represented by the following formula (1). (7) An ink set for inkjet recording, characterized by satisfying (7).
・ Formula (1) 10 ≦ BD ≦ 150
Formula (2) 10 ≦ CD ≦ 150
・ Formula (3) 6 × 10⁴≦ BN (0.5) ≦ 6 × 10⁵
・ Formula (4) 6 × 10³≦ CN (0.5) ≦ 6 × 10⁵
・ Formula (5) CN (0.5) ≦ BN (0.5)
・ Formula (6) BN (5) ≦ 50
・ Formula (7) CN (5) ≦ 50
[However, in the formulas (1) to (7), BD is the number average particle diameter (nm) of the particles contained in the black ink after the ejection, and CD is the number of particles contained in the color ink after the ejection. The average particle diameter (nm) and BN (0.5) are the number of particles (particles / μl) having a number average particle diameter of 0.5 μm or more contained in the black ink after jetting, and the CN (0.5) is The number of particles having a number average particle size of 0.5 μm or more (particles / μl) contained in the color ink after ejection, and BN (5) is the number of particles having a number average particle size of 5 μm or more contained in the black ink after ejection ( Particles / μl) and CN (5) represent the number (particles / μl) of particles having a number average particle diameter of 5 μm or more contained in the color ink after jetting. ]
[0021]
<2> The ink set for inkjet recording according to <1>, and at least a water-soluble organic solvent and / or a surfactant having a solubility parameter of 9 to 11, and water are used, and the ink set for inkjet recording is used. And a second liquid used in combination for printing.
[0022]
<3> A recording medium using the ink of each color constituting the ink set for inkjet recording according to <1>, or the ink and the second liquid constituting each of the ink and liquid set according to <2>. In an ink jet recording method of printing an image on,
An ink jet recording method comprising: printing by applying the inks of the respective colors, or the inks of the respective colors and the second liquid, in the form of droplets by applying energy onto the recording medium. It is.
[0023]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail in the order of an ink set for ink jet recording, an ink and liquid set, and an ink jet recording method.
[0024]
(Ink set for inkjet recording)
The ink set for ink jet recording of the present invention (hereinafter sometimes abbreviated as “ink set”) comprises a combination of a black ink and three or more types of color inks including three colors of cyan, magenta and yellow. The black ink and the color ink, the pigment, an aqueous polymer, a water-soluble organic solvent and water in an inkjet recording ink set including at least, after the black ink and the color ink is ejected from the nozzle of the inkjet head The number average particle diameter and the number of particles containing particles and contained in the black ink and the color ink after ejection satisfy the following expressions (1) to (7).
・ Formula (1) 10 ≦ BD ≦ 150
Formula (2) 10 ≦ CD ≦ 150
・ Formula (3) 6 × 10⁴≦ BN (0.5) ≦ 6 × 10⁵
・ Formula (4) 6 × 10³≦ CN (0.5) ≦ 6 × 10⁵
・ Formula (5) CN (0.5) ≦ BN (0.5)
・ Formula (6) BN (5) ≦ 50
・ Formula (7) CN (5) ≦ 50
[0025]
In the formulas (1) to (7), BD is the number average particle diameter (nm) of the particles contained in the black ink after the ejection, and CD is the number average particle number of the particles contained in the color ink after the ejection. The particle diameter (nm) and BN (0.5) are the number of particles (particles / μl) having a number average particle diameter of 0.5 μm or more contained in the black ink after the ejection, and CN (0.5) is the The number of particles having a number average particle diameter of 0.5 μm or more (particles / μl) contained in the subsequent color ink and the number of particles having a number average particle diameter of 5 μm or more (particles) / Μl) and CN (5) represent the number of particles (particles / μl) having a number average particle diameter of 5 μm or more contained in the color ink after the ejection.
[0026]
The ink of each color constituting the ink set for color inkjet recording of the present invention is not particularly limited as long as it is at least composed of black ink and three kinds of color inks including three colors of cyan, magenta and yellow. Although not limited, in addition to the above three colors, color inks of colors other than these three colors may be further used as the color ink.
[0027]
The components constituting the inks of each color are not particularly limited as long as they include a pigment, an aqueous polymer, a water-soluble organic solvent and water, but if necessary, a surfactant, a pH adjuster, a hydrotrope, a chelating agent Agents, clathrates, oxidants, antioxidants, reducing agents, enzymes, germicides, defoamers, abrasives, and other additives.
[0028]
Further, each color ink containing the above components contains particles after being ejected from the nozzle of the inkjet head. However, the particles mean pigment particles and / or polymer colloid particles (so-called polymer emulsion) present in the ink. It should be noted that such particles may be contained in the ink before the ejection, and the following description will be made on the assumption that the ink is also contained in the ink before the ejection.
[0029]
The number average particle diameter of the particles contained in the ink of each color after the ejection needs to be in the range of 10 nm to 150 nm as shown in Expressions (1) and (2), and in the range of 10 nm to 100 nm. It is preferable that
If the number average particle diameter of the particles exceeds 150 nm, it may cause clogging of the head channel during storage. When the number average particle diameter of the particles is less than 10 nm, it is necessary to reduce the primary particle diameter of the components constituting the particles and to improve the dispersibility, but this is not practical.
[0030]
The change rate of the number average particle diameter of the particles contained in the ink before and after the ejection from the inkjet head is based on the number average particle diameter of the particles contained in the ink before the ejection, and Preferably increases in the range of 0% to 50%. On the other hand, particles having a number average particle diameter of 0.5 μm or more (hereinafter, may be abbreviated as “coarse particles”) contained in the ink after ejection have grown by agglomeration of the particles contained in the ink before ejection. It is. Therefore, when the rate of change in the number average particle diameter of the particles contained in the ink before and after the ejection exceeds 50%, the number of coarse particles contained in the ink after the ejection is 6 × 10⁵In some cases, the number of ink droplets may exceed the number of ink droplets / μl, making it impossible to eject ink from the nozzles.
[0031]
The number average particle diameter can be measured by any method such as a centrifugal sedimentation method, a laser diffraction method (light scattering method), an ESA method, a capillary method, and an electron microscope method which are generally commercially available. Above all, measurement by Microtrac UPA 9340 (manufactured by Leeds & Northrup) using the dynamic light scattering method is preferable. In the present invention, the number average particle diameter was determined by measuring the ink stock solution using the Microtrack UPA 9340 (manufactured by Leeds & Northrup) with the ink viscosity as the solvent viscosity.
[0032]
In addition, the number of particles having a number average particle diameter of 0.5 μm or more contained in the ejected ink is 6 × 10 5 in the black ink as shown in the equations (3) and (4).⁴Pieces / μl to 6 × 10⁵Pieces / μl, and 6 × 10³Pieces / μl to 6 × 10⁵It is necessary to be in the range of pcs / μl.
In the black ink and the color ink, the number of particles having a number average particle diameter of 0.5 μm or more contained in the ejected ink is 6 × 10⁵When the number of pieces / μl is exceeded, clogging of the head occurs, and discharge becomes impossible. In the present invention, the increase in coarse particles generated only by injection is governed by the HLB of the aqueous polymer used, and the details will be described later.
[0033]
On the other hand, the number of particles having a number average particle diameter of 0.5 μm or more contained in the ink after ejection is 6 × 10⁴Or less than 6 × 10³If the number is less than the number of particles / μl, the optical density of black printed using black ink or color (especially primary color) printed using color ink is too low.
[0034]
As can be seen by comparing Equations (3) and (4), the lower limit of the value of CN (0.5) is one digit smaller than the lower limit of the value of BN (0.5). This is because color colors printed using color inks are rarely used for characters requiring high optical density, and are also used as secondary colors and tertiary colors whose optical density is higher than the primary color. The reason that black ink printed using black ink is often used only for primary colors and is frequently used for characters that require high optical density, while black ink is often used. It is due to.
[0035]
Further, the number of particles having a number average particle diameter of 0.5 μm or more contained in the black ink and the color ink after the ejection satisfies the relations of Expressions (3) and (4) for the reason described above. , Equation (5).
That is, the number of particles having a number average particle size of 0.5 μm or more contained in the color ink after ejection; CN (0.5) is the number of particles having a number average particle size of 0.5 μm or more contained in the black ink after ejection. Number: It must be the same as or smaller than BN (0.5).
When the values of CN (0.5) and BN (0.5) satisfy the relationship of the above-described expression (5), even when a multi-color document is created by combining the inks of the respective colors, the This makes it possible to create a document having excellent color reproducibility and a well-balanced image density between images and characters.
[0036]
If the values of CN (0.5) and BN (0.5) cannot satisfy the relationship of Expression (5), the color reproducibility of the image portion deteriorates when a multi-color document is created. Alternatively, the image density of the character may be felt to be relatively light relative to the image portion, the color balance of the entire document may be poor, and the whole document may be visually jerky.
[0037]
Note that in order to create a document in which the color balance of the entire document is balanced at a higher level, the ratio of the value of BN (0.5) to the value of CN (0.5); BN (0.5) /CN(0.5) is preferably in the range of 1 to 10, more preferably in the range of 3 to 8.
[0038]
The number of particles having a particle diameter of 0.5 μm or more contained in the ink of each color before ejection is not particularly limited, but it is desirable to minimize the number of particles in order to ensure storage stability. Specifically, irrespective of black ink or color ink, 6 × 10⁴Is preferably 3 × 10 or less⁴More preferably, the number is not more than the number.
[0039]
The number of particles having a number average particle diameter of 0.5 μm or less contained in each color ink before ejection is 6 × 10⁴If the number is less than or equal to the number, it is confirmed that the coarse particles immediately after the injection do not cause clogging of the head flow path. This is because the jet stress is applied at the head end, so that there is almost no stress on the head flow path. Further, since the ejection force is applied to the ink, it is considered that the adhesion of the particles is prevented. However, the number of particles having a number average particle diameter of 0.5 μm or more contained in the ink before ejection is 6 × 10⁴If the number of particles is more than the number of particles, it becomes impossible to prevent the adhesion of the particles by the spraying force, and the ejection becomes impossible. In addition, when these particles are stored for a long period of time, they become a core of aggregation and may impair the storage stability.
[0040]
In addition, in each color ink, the number of particles having a number average particle diameter of 0.5 μm or more present in 1 μl of the ink desirably changes three times or more after ejection compared to before ejection. If it is less than three times, the increase in optical density may not be visually distinguished. In addition, the change rate of the number of particles having a number average particle diameter of 0.5 μm or more before and after the ejection is 0.5 to 1. It is preferably within a range of 5 times, preferably within a range of 0.7 to 1.2 times, and more preferably around 1 time.
[0041]
Furthermore, it is preferable that the increase in the number of particles having a number average particle diameter of 0.5 μm or more in 1 μl of the ink is suppressed as much as possible even when the ink of each color is stored in a high-temperature environment at 60 ° C. for 100 hours. Note that storage in a high-temperature environment of 60 ° C. for 100 hours corresponds to storage for two years at room temperature, and is an index of storage stability.
The number of particles having a number average particle diameter of 0.5 μm or more present in 1 μl of the ink after storage in a high temperature environment at 60 ° C. for 100 hours is 6 × 10 for both black ink and color ink.⁴It is desirable that the number is not more than the number.
[0042]
The number of particles having a number average particle diameter of 0.5 μm or more present in 1 μl of the ink after storage in a high temperature environment is 6 × 10⁴If the number exceeds the limit, the ink internal flow path may be clogged, and ejection may not be possible. This increase in coarse particles is governed by the number of particles of 0.5 μm or more present in 1 μl of the ink in the initial state and the solubility parameter of the organic solvent used in the ink. The solubility parameter of the organic solvent will be described later.
[0043]
Further, the number of particles having a number average particle diameter of 5 μm or less contained in the ink of each color after the ejection needs to be 50 particles / μl or less as shown in the equations (6) and (7). If the number of particles having a number average particle diameter of 5 μm or less contained in the ink of each color after ejection exceeds 50 particles / μl, clogging of the head is induced and ejection becomes impossible.
[0044]
The number of particles having a number average particle diameter of 5 μm or less contained in the ink of each color before ejection is preferably 50 particles / μl or less. If the number of particles having a number average particle diameter of 5 μm or less contained in each color ink before ejection exceeds 50 particles / μl, clogging of the head may be induced and ejection may not be possible.
[0045]
The number of particles having a number average particle diameter of 0.5 μm or more and 5 μm or more as described above can be measured with an Accusizer manufactured by PARTICLE SINGING SYSTEMS, USA. In the present invention, 2 μl of each color ink was diluted in 50 ml of water, and the number of particles was measured using the Accusizer.
[0046]
In the present invention, the term “ejection” means that the ink of each color is ejected in the form of droplets, and the ejection method is not particularly limited, and a known method can be used.
The ejection method includes a thermal inkjet method in which the ink is heated by a heater and the ink is ejected by thermal expansion due to boiling of the ink, a piezo inkjet method in which the ink is ejected by expansion and contraction of a piezo element, and a method in which an ultrasonic wave is applied to the ink to apply the ink. Can be used. Of course, any ejection method other than those listed above may be used as long as the method can eject ink. However, thermal inkjet systems and piezo inkjet systems are desirable as systems capable of ensuring sufficient ejection stability.
[0047]
Next, the materials constituting the inks of the respective colors will be described in detail with respect to pigments, aqueous polymers, aqueous organic solvents, water, and other additives.
[0048]
-Pigment-
The pigment used in each color ink constituting the ink set for ink jet recording of the present invention is not particularly limited, and examples thereof include zinc white, titanium white, chromium oxide, iron oxide, alumina white, cadmium yellow, zinc sulfide, and zinc chromate. , Yellow lead, barium sulfate, basic lead sulfate, calcium carbonate, lead white, inorganic pigments such as ultramarine blue, calcium silicate, manganese purple, cobalt purple, dark blue, carbon black, etc., Madalake, cochineal lake, naphthol green B, naphthol green Y , Naphthol Yellow S, Permanent Red 4R, Hansa Alu, Benzidine Yellow, Risor Red, Lake Red C, Lake Red D, Brilliant Carmine 6B, Bordeaux 10B, Phthalocyanine Blue, Phthalocyanine Green, Sky Blue, Rhodamine Lake, Chill violet lake, quinoline yellow lake, peacock blue lake, thioindigo maroon, alizarin lake, quinacridone red, berylene red, aniline black, dioxazine violet, organic fluorescent pigments, organic pigments such as isoindolinone yellow, cobalt oxide, γ-oxidation A magnetic substance such as iron, metallic iron powder, barium ferrite, or a ferrite, or a superparamagnetic substance, a plastic pigment, a metallic luster pigment, or the like can be selected according to the hue to be used. In addition, one or more known dyes can be used as a mixture with the pigment.
[0049]
The pigment used in the ink set for inkjet recording of the present invention is a trade name and C.I. I. Pigment numbers are exemplified, but the present invention is not limited to these.
[0050]
Examples of the black pigment include carbon black pigments such as furnace black, lamp black, acetylene black, and channel black. Raven 1255, Raven 1080 (all manufactured by Columbia), Regal 400R, Regal 330R, Regal 660R, Mogul L, Black Pearls L, Black Pearls 1300, Monarch 700, Monarch 800, Monarch 880, Monarch 900, Monarch 1000, Monarch 1100, Monarch 1300, Monarch 1400 (all manufactured by Cabot Corporation), Color Black FW1, Color Black FW2, Color Black FW2V, Color Black Boll, Color 200, Color Bock, Color Wo Brock, Color Wo Brock 18, Color W Black Boll No. S170, Printex35, PrintexU, PrintexV, printx140U, Printex140V, Special Black 6, Special Black 5, Special Black 4A, Special Black 4 (all manufactured by Degussa). 25, no. 33, no. 40, no. 47, no. 52, no. 900, No. 2300, MCF-88, MA600, MA7, MA8, MA100 (all manufactured by Mitsubishi Chemical Corporation) and the like. The carbon black preferably has a primary particle diameter of 10 to 30 nm.
[0051]
Examples of the cyan pigment include C.I. I. Pigment Blue-1, C.I. I. Pigment Blue-2, C.I. I. Pigmet Blue-3, C.I. I. Pigment Blue-15: 3, C.I. I. Pigment Blue-15: 34, C.I. I. Pigment Blue-16, C.I. I. Pigment Blue-22, C.I. I. Pigment Blue-60 and the like.
Examples of the magenta pigment include C.I. I. Pigment Red 5, C.I. I. Pigment Red 7, C.I. I. Pigment Red 12, C.I. I. Pigment Red 48, C.I. I. Pigment Red 48: 1, C.I. I. Pigment Red 57, C.I. I. Pigment Red 112, C.I. I. Pigment Red 122, C.I. I. Pigment Red 123, C.I. I. Pigment Red 146, C.I. I. Pigment Red 168, C.I. I. Pigment Red 184, C.I. I. Pigment Red 202 and the like.
[0052]
As the yellow pigment, C.I. I. Pigment Yellow-1, C.I. I. Pigment Yellow-2, C.I. I. Pigment Yellow-3, C.I. I. Pigment Yellow-12, C.I. I. Pigment Yellow-13, C.I. I. Pigment Yellow-14, C.I. I. Pigment Yellow-16, C.I. I. Pigment Yellow-17, C.I. I. Pigment Yellow-73, C.I. I. Pigment Yellow-74, C.I. I. Pigment Yellow-75, C.I. I. Pigment Yellow-83, C.I. I. Pigment Yellow-93, C.I. I. Pigment Yellow-95, C.I. I. Pigment Yellow-97, C.I. I. Pigment Yellow-98, C.I. I. Pigment Yellow-114, C.I. I. Pigment Yellow-128, C.I. I. Pigment Yellow-129, C.I. I. Pigment Yellow-151, C.I. I. Pigment Yellow-154 and the like.
[0053]
These pigments may be used alone or in a combination of two or more. In addition to these pigments, pigments newly synthesized for the present invention may be used. The content of these pigments is preferably in the range of 0.3 to 20% by weight, more preferably 0.5 to 8% by weight, based on the total ink amount.
[0054]
The pigment may be used after the surface treatment is performed in advance. For example, surface treatment with alcohols such as ethanol and propanol, surfactant treatment, pigment derivative treatment for replacing acidic and basic groups, pigment coating reaction treatment for coating the pigment surface with other substances, condensation reaction and graft reaction Surface chemical reaction treatment for introducing a substituent, coupling reaction treatment for surface treatment with a silane coupling agent, titanate coupling agent, zirconate coupling agent, aluminate coupling agent, etc., plasma reaction treatment, CVD Processing and the like can be performed.
[0055]
In addition, a pigment that can be self-dispersed in water can also be used. The pigment that can be self-dispersed in water can be prepared by any known method for introducing a hydrophilic functional group on the surface of the pigment, or any method newly invented. Examples of such a method include, for example, oxidation treatment with an oxidizing agent such as nitric acid, permanganate, dichromate, hypochlorite, ammonium persulfate, hydrogen peroxide, ozone, and treatment with a coupling agent. , Polymer grafting treatment, plasma treatment and the like.
Further, a commercially available hydrophilic treatment pigment can also be used. Examples of commercially available hydrophilic treated pigments which can be used in the present invention and are self-dispersible in water include MICROJET BLACK CW-1 (manufactured by Orient Chemical Industries), CAB-O-JET200, and CAB-O-JET300 (Cabot Corporation). Manufactured).
[0056]
The water-solubilizing group contained in the surface-modified pigment may be nonionic, cationic, or anionic, but sulfonic acid, carboxylic acid, hydroxyl group, and phosphoric acid are preferred. In the case of sulfonic acid, carboxylic acid, and phosphoric acid, they can be used as they are in the form of a free acid, but in order to enhance water solubility, it is preferable to use them in the form of a salt with a basic compound.
[0057]
Examples of the compound forming a salt include alkali metals such as sodium, potassium and lithium, aliphatic amines such as monomethylamine, dimethylamine and triethylamine, monomethanolamine, monoethanolamine, diethanolamine, triethanolamine and diisopropanolamine. Alcohol amines, ammonia, etc. can be used. Among these, basic compounds of alkali metals such as sodium, potassium and lithium are preferably used. This is presumably because the basic compound of the alkali metal is a strong electrolyte and has a large effect of promoting the dissociation of the acidic group.
[0058]
The pigment may be used after being washed and purified as necessary. Commercially available pigments contain large amounts of organic and inorganic impurities. In particular, impurities such as water-insoluble or hardly water-soluble, hardly dispersible polyvalent metal cations, Si-based, and P-based impurities can cause clogging of ink nozzles and kogation. The pigment is washed and refined as necessary for the purpose of removing these pigments, because the pigment adversely affects storage stability, recording reliability and the like. Examples of the removal method include furnace filtration, centrifugal sedimentation, separation membrane method, ion exchange resin treatment method, reverse osmosis method, activated carbon method, zeolite method, water washing, and solvent extraction.
[0059]
Although not particularly limited, inorganic impurities in the ink are desirably 500 ppm or less, more preferably 300 ppm or less, in order to prevent nozzle clogging. Calcium, iron, silicon, and magnesium may cause clogging in particular, so that the content of each is preferably 30 ppm or less, preferably 20 ppm or less, more preferably 10 ppm or less. The cation concentration in these inks can be measured by an atomic absorption method or an induction plasma emission analysis method.
[0060]
-Aqueous polymer-
The aqueous polymer used in the ink of each color constituting the ink set for inkjet recording of the present invention preferably has an HLB (Hydrophile-Lyophile Balance: hydrophilic lipophilic balance) of 11 to 15. If the HLB of the aqueous polymer is less than 11, the hydrophobicity becomes so strong that the aqueous polymer associates only by storage, and may become a thickened gel. On the other hand, if the HLB is more than 15, the hydrophilicity becomes strong, the association does not occur even when the jet is applied, and a high optical density increase may not be obtained.
[0061]
The HLB of the aqueous polymer can be arbitrarily changed by changing the ratio of the hydrophilic part to the hydrophobic part or by changing the hydrophilic group type and the hydrophobic group type. Various methods have been proposed for measuring and calculating HLB, and there are some differences between the methods. In the present invention, a value calculated based on the method defined by the following equation (8) proposed by Davies in 1957 is used.
Formula (8) HLBx = 7 + Σ (number of hydrophilic groups) + Σ (number of hydrophobic groups)
[0062]
In the aqueous polymer used for the inks of each color constituting the ink set for inkjet recording of the present invention, it is desirable that a molecule whose terminal group is a hydrophobic group at both ends is contained in 10% to 60% in all the polymers. Molecules whose terminal groups are both hydrophobic at both ends are likely to associate with each other, especially when subjected to injection stress. If the number of molecules having a hydrophobic group at both ends is less than 10% in the whole polymer, it may not be sufficient for thickening even if it associates at the time of jetting, and the optical density may not increase. On the other hand, if it exceeds 60%, the association is promoted and gelled without spraying, so that storage stability may not be ensured in some cases. For the terminal group of the aqueous polymer, a hydrophobic group / hydrophilic group can be selected depending on the type of the polymerization initiator.
[0063]
The ratio of the hydrophobic groups at both ends was defined as follows. When the initiator is a hydrophobic group, one end is always a hydrophobic group. On the opposite terminal side, the ratio of the hydrophobic group was determined as the ratio of the hydrophobic groups at both terminals present in the entire polymer from the blending molar ratio of the hydrophilic group and the hydrophobic group during polymer polymerization. When the initiator is a hydrophilic group, one end is always a hydrophilic group. For this reason, both ends do not become hydrophobic groups. Therefore, by using a hydrophobic group as the initiator and changing the ratio of the hydrophilic group / hydrophobic group at the time of polymerization, the ratio of the hydrophobic group at the molecular end can be changed.
[0064]
The aqueous polymer used for the inks of each color constituting the ink set for inkjet recording of the present invention means an aqueous polymer colloid (polymer emulsion) and a water-soluble polymer. As the polymer colloid, for example, acrylic resin emulsion, vinyl acetate resin emulsion, urethane resin emulsion, acryl-styrene resin emulsion, butadiene resin emulsion, styrene resin emulsion, polyester resin emulsion, silicone resin emulsion, Fluorine-based resin emulsions, acrylic silicone-based resin emulsions, and the like are included.
[0065]
Examples of the water-soluble polymer include (1) a hydrophobic part that binds to the pigment particle surface and SO₃A homopolymer of a hydrophilic monomer component comprising a hydrophilic portion having an H group or a salt thereof, (2) a hydrophobic monomer component and SO₃A copolymer with a hydrophilic monomer component having an H group or a salt thereof, (3) a homopolymer of a hydrophobic monomer component or a copolymer of two or more hydrophobic monomer components is subjected to hydrophilic treatment by sulfonation. Or a salt thereof, (4) a hydrophobic part and H₃PO₄A homopolymer of a hydrophilic monomer component comprising a hydrophilic portion having a group or a salt thereof, (5) a hydrophobic monomer component and H₃PO₄A copolymer with a hydrophilic monomer component having a group or a salt thereof, (6) a homopolymer of a hydrophilic monomer component comprising a hydrophobic part and a hydrophilic part having a COOH group or a salt thereof, and (7) a hydrophobic monomer component. It is a copolymer with a hydrophilic monomer component having a COOH group or a salt thereof. In addition, other components can be copolymerized with these as required. These may be used alone or in combination of two or more.
[0066]
The copolymer may have any structure such as random, graft, block and the like. Further, these salts represent onium compounds such as alkali metals, alcoholamines such as monoethanolamine and diethanolamine triethanolamine, ammonium ions, sulfonium ions, oxonium ions, stibonium ions, stannonium, and iodonium. However, the present invention is not limited to these.
[0067]
SO₃Examples of the hydrophilic monomer component having an H group include styrene sulfonic acid derivatives, styrene sulfonic acid derivatives, benzene sulfonic acid derivatives, benzene sulfonic acid derivatives, naphthalene sulfonic acid derivatives, naphthalene sulfonic acid derivatives, toluene sulfonic acid derivatives, and toluene sulfonic acid derivatives. , A vinyl sulfonic acid derivative, a vinyl sulfonic acid derivative, and the like. Among them, vinyl sulfonic acid derivatives, vinyl sulfonic acid derivatives, naphthalene sulfonic acid derivatives, naphthalene sulfonic acid derivatives, styrene sulfonic acid derivatives, and styrene sulfonic acid derivatives are preferable.
[0068]
H₃PO₄Examples of the hydrophilic monomer component having a group include a higher alkyl phosphate ester salt and a phosphate ester salt of a higher alcohol ethylene oxide adduct. Examples of the hydrophilic monomer component having a COOH group include α, β-ethylenically unsaturated carboxylic acid and its aliphatic alcohol ester, acrylic acid, acrylic acid derivative, methacrylic acid, methacrylic acid derivative, maleic acid, maleic acid derivative, itacone Acids, itaconic acid derivatives, fumaric acid, fumaric acid derivatives and the like. Among these, acrylic acid, acrylic acid derivatives, methacrylic acid, and methacrylic acid derivatives are preferred.
[0069]
Hydrophobic monomer components include styrene, styrene derivatives, vinyl toluene, vinyl toluene derivatives, vinyl naphthalene, vinyl naphthalene derivatives, butadiene, butadiene derivatives, isoprene, isoprene derivatives, ethylene, ethylene derivatives, propylene, propylene derivatives, alkyl acrylates Examples include esters and alkyl esters of methacrylic acid. Among these, styrene, styrene derivatives, alkyl acrylates and alkyl methacrylates are preferred, and the C number of the alkyl group is preferably in the range of 1 to 10, more preferably 1 to 6.
[0070]
Other components include acrylamide, acrylamide derivatives, dimethylaminoethyl methacrylate, ethoxyethyl methacrylate, butoxyethyl methacrylate, ethoxytriethylene methacrylate, vinylpyrrolidone, vinylpyridine, alkyl ethers and polyoxyethylene such as methoxypolyethylene glycol methacrylate and polyethylene glycol methacrylate. And a component containing a hydroxyl group such as hydroxymethyl methacrylate, hydroxyethyl methacrylate, and vinyl alcohol.
[0071]
In addition to the above, an aqueous polymer can be obtained by addition-polymerizing a hydrophilic monomer component using a condensation polymer of an unsaturated carboxylic acid and an alcohol or glycol (polyester-based condensation polymer) as a hydrophobic component. In addition, water-soluble polymers such as carboxylic acid group-modified polyvinyl alcohol and carboxymethyl cellulose can be used, and are not limited to those described above.
[0072]
COOH group or a salt thereof, SO₃H group or a salt thereof, H₃PO₄The monomer component having a group or a salt thereof is preferably in the range of 0.1 mol% to 100 mol%, more preferably in the range of 30 mol% to 100 mol%, based on the whole polymer. In the case of a polymer having a COOH group or a salt thereof, the corresponding acid value is preferably from 100 to 800, and more preferably from 150 to 800. SO₃H group or a salt thereof, H₃PO₄In the case of a polymer having a group or a salt thereof, the range is preferably 100 to 500.
[0073]
The molecular weight of the aqueous polymer is preferably a weight average molecular weight of 3,000 to 20,000 from the relationship with the viscosity of each color ink. As a method for measuring the weight average molecular weight, a value in terms of polyethylene glycol measured by a light scattering method, an X-ray small angle scattering method, a sedimentation equilibrium method, a diffusion method, an ultracentrifugation method, or various kinds of chromatography, for example, a GPC method can be used.
[0074]
Further, the content of the aqueous polymer in each color ink is preferably in the range of 0.002% to 10% by weight, more preferably 0.003 to 8% by weight, based on the total amount of the ink. If the content is less than 0.002% by weight, the effect of addition cannot be obtained, and if it exceeds 10% by weight, an increase in the viscosity of the ink and a remarkable decrease in the optical density due to the penetrating action occur.
[0075]
These aqueous polymers may be used alone or in combination of two or more. When used as a pigment dispersant, the effect is maximized and is most preferable. When these aqueous polymers are used as a dispersant, the preferred ratio of the dispersant to the pigment varies depending on the particle size, specific surface area, surface structure and the like of the pigment, but generally, the pigment: aqueous polymer = 10: 8 to weight ratio. The ratio is preferably set to 10: 0.5.
[0076]
The disperser to be used may be any commercially available one. For example, colloid mill, flow jet mill, slasher mill, high speed disperser, ball mill, attritor, sand mill, sand grinder, ultra fine mill, Eiger motor mill, dyno mill, pearl mill, agitator mill, kobol mill, three rolls, two rolls Examples thereof include a roll, an extruder, a kneader, a microfluidizer, a laboratory homogenizer, and an ultrasonic homogenizer. These may be used alone or in combination of two or more.
[0077]
In order to prevent the contamination of inorganic impurities, it is preferable to use a dispersion method that does not use a dispersion medium, and a microfluidizer or an ultrasonic homogenizer is suitable. Further, in order to enhance the dispersing effect, it is preferable to degas and defoam the aqueous solution used for dispersion. The pH at the time of dispersion is preferably 9 or less.
[0078]
-Aqueous organic solvent-
As the water-soluble organic solvent used for the inks of each color constituting the ink set for inkjet recording of the present invention, polyhydric alcohols and derivatives thereof such as alkyl ethers may be used to prevent solidification of the ink. Can be. For example, glycerin, polyethylene glycol, polypropylene glycol, diethylene glycol, (2 (2 butoxyethoxy) ethanol), diethylene glycol phenyl ether, propylene glycol, propylene glycol monomethyl ether, butylene glycol, triethylene glycol, thiodiglycol, hexylene glycol, ethylene Glycol methyl ether, diethylene glycol methyl ether, pentanediol, hexanetriol, trimethylolpropane and the like can be mentioned, and these may be used alone or in combination of two or more.
[0079]
Examples of the water-soluble organic solvent include alcohols such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, hexyl alcohol, and benzyl alcohol; amides such as dimethylformamide and dimethylacetamide; acetone; Ketones such as acetone alcohol, keto alcohols, triethanolamine, diethanolamine, pyrrolidone, N-methyl-2-pyrrolidone, high-boiling nitrogen-containing solvents such as 1,3-dimethyl-2-imidazolidinone, dimethyl sulfoxide, Sulfur-containing solvents such as diethylsulfoxide, sulfolane, and thiodiethanol; sugars such as glucose, maltose, amylose (dextrin), cellulose, and sodium alginate; It can be use, but is not limited thereto.
[0080]
These water-soluble organic solvents can be used alone or in combination of two or more. However, in order to ensure long-term dispersion stability, a water-soluble organic solvent having a solubility parameter of 11 or less should not be contained in the ink. It is particularly desirable that the content of the water-soluble organic solvent having a solubility parameter of 11 to 15 relative to the total ink weight be 5% by weight or less. The content of the water-soluble organic solvent having a solubility parameter of 15 or more based on the total weight of the ink is preferably 1 to 50% by weight. A water-soluble organic solvent having a solubility parameter of less than 11 may be adsorbed on the pigment surface and impair the long-term storage stability. When the content of the water-soluble organic solvent having a solubility parameter of 11 to 15 with respect to the total weight of the ink exceeds 5% by weight, the adsorption to the pigment is promoted and the long-term storage stability may be deteriorated. If the content of the water-soluble organic solvent having a solubility parameter of more than 15 relative to the total weight of the ink is less than 1% by weight, the moisturizing effect cannot be obtained. is there.
[0081]
The solubility parameter is calculated using any method such as calculation from heat of evaporation, calculation from refractive index, calculation from Kauributanol value, calculation from surface tension, or calculation from chemical composition. You may.
The solubility parameter (δ) is a value calculated by the calculation of Fedors obtained from the evaporation energy (Δei) and the molar volume (Δvi) of the atom or atomic group of the chemical structure as shown in the following formula (9). .
Equation (9) δ = (ΣΔei / ΣΔvi)^1/2
[0082]
−Water−
Water used in each color ink constituting the ink set for ink jet recording of the present invention may be ion-exchanged water, ultrapure water, distilled water, or ultrafiltration water, particularly in order to prevent impurities from being mixed. preferable.
[0083]
-Other additives-
The inks of each color constituting the ink set for ink jet recording of the present invention have various known interfaces for the purpose of controlling the ejection stability by adjusting the surface tension and controlling the permeability (drying time) during printing. Activators can also be added. As the surfactant, any of nonionic, anionic, cationic and amphoteric surfactants may be used, but a nonionic surfactant is particularly preferable in order to keep the conductivity low.
[0084]
Examples of the nonionic surfactant include polyoxyethylene nonyl phenyl ether, polyoxyethylene octyl phenyl ether, polyoxyethylene dodecyl phenyl ether, polyoxyethylene alkyl ether, polyoxyethylene fatty acid ester, sorbitan fatty acid ester, polyoxyethylene / Polyoxypropylene block copolymer, polyoxyethylene sorbitan fatty acid ester, fatty acid alkylolamide, acetylene glycol derivative (Sufinol) and the like can be mentioned.
[0085]
Examples of the anionic surfactant include alkyl benzene sulfonate, alkyl naphthalene sulfonate, formalin condensate of alkyl naphthalene sulfonate, higher fatty acid salt, higher fatty acid ester sulfate, higher fatty acid ester sulfonate, Higher alcohol ether sulfates and sulfonates, higher alkylsulfonamides alkylcarboxylates, sulfosuccinates, ester salts thereof, alkyl phosphites, alkyl phosphates, alkyl phosphates and esters, higher Alcohol phosphate salts and the like.
[0086]
Examples of the cationic surfactant include primary, secondary, and tertiary amine salts and quaternary ammonium salts, and examples of the amphoteric surfactant include betaine, sulfobetaine, and sulfate betaine. In addition, silicon-based surfactants such as polysiloxane polyoxyethylene adducts, fluorine-based surfactants such as perfluoroalkylcarboxylic acid, perfluoroalkylsulfonic acid, and oxyethylene perfluoroalkylether, and natural or biosurfactant lecithin , Spiculisporic acid, rhamnolipid, saponin, cholate and the like.
[0087]
These surfactants may be used alone or in combination of two or more. The content of these surfactants is preferably in the range of 0.001 to 7% by weight, more preferably 0.001 to 5% by weight, based on the total amount of the ink. If the amount is less than 0.001% by weight, the effect of addition may not be obtained. If the amount exceeds 7% by weight, the penetrating effect on paper may be too high to cause deterioration of image quality, which is not preferable.
[0088]
In addition, as an additive, it may contain a carboxylate such as sodium butyrate and sodium salicylate, an aromatic sulfonate such as sodium toluenesulfonate, a lower alcohol such as ethyl alcohol, urea, and acetamide as a hydrotrope. it can.
[0089]
As a chelating agent, ethylenediaminetetraacetic acid (EDTA), iminodiacetic acid (IDA), ethylenediamine-di (o-hydroxyphenylacetic acid) (EDDHA), nitrilotriacetic acid (NTA), dihydroxyethylglycine (DHEG), trans -1,2-cyclohexanediaminetetraacetic acid (CyDTA), diethylenetriamine-N, N, N ', N ", N",-pentaacetic acid (DTPA), glycol etherdiamine-N, N, N', N ' -Tetraacetic acid (GEDTA) and the like.
[0090]
Examples of the inclusion compound include urea, thiourea, desoxycholic acid, bis- (N, N′-tetramethylenebenzidine), cyclophan, cyclodextrin, etc., preferably containing urea and cyclodextrin. can do.
[0091]
Further, if necessary, the pH of each color ink constituting the ink set for ink jet recording of the present invention can be adjusted. The pH of the ink is preferably 7 to 10. If the pH is more than 10, adverse effects such as corrosion, dissolution, and peeling of the head material may be caused. For adjusting the pH, sodium hydroxide, potassium hydroxide, lithium hydroxide, sodium sulfate, acetate, lactate, benzoate, triethanolamine, ammonia, 2-amino-2-methyl-1-propanol ( AMP), ammonium phosphate, sodium phosphate, lithium phosphate and the like, and organic or inorganic acids such as acetic acid, hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, propionic acid, and P-toluenesulfonic acid. In addition, other general pH buffers and good buffers can be used, but are not limited thereto. In addition, an oxidizing agent, an antioxidant, a reducing agent, an enzyme, a bactericide, an antifoaming agent, an abrasive, and other additives can be added as necessary.
[0092]
The surface tension of the ink of each color constituting the ink set for ink jet recording of the present invention is preferably in the range of 35 to 55 mN / m at 20 ° C. If it is less than 35 mN / m, bleeding on paper becomes remarkable and stable jetting may not be obtained, which is not preferable. On the other hand, if it exceeds 55 mN / m, the ink does not sufficiently penetrate into the paper, which may lead to a prolonged drying time, which is not preferable.
[0093]
The viscosity of each color ink constituting the ink set for ink jet recording of the present invention at 20 ° C. is preferably in the range of 1 to 8 mPa · s, and more preferably 2 to 4 mPa · s. If the pressure is higher than 8 mPa · s, the ejection may become unstable, which is not desirable. If the pressure is 1 mPa · s or less, the storage stability may deteriorate, which is not desirable.
[0094]
The ink conductivity of each color constituting the ink set for inkjet recording of the present invention is preferably not more than 0.5 S / m, and is preferably from 0.005 to 0.4 S / m, because if it is high, the ink stability impairs dispersion stability. The range of m is more preferred. In a light-colored ink corresponding to a photographic image, the ink conductivity may be low because the ink is diluted, and is preferably 0.005 to 0.2 S / m.
[0095]
(Ink and liquid set)
The “ink set for ink jet recording” of the present invention described above can be used as an “ink and liquid set” in combination with a “second liquid” described in detail below at the time of printing. By using the “ink and liquid set” of the present invention, in full-color ink jet recording, color mixing of pigment inks can be prevented and an image can be clearly reproduced on plain paper. Hereinafter, the ink of the “ink set for inkjet recording” of the present invention used in the “ink and liquid set” of the present invention may be abbreviated as “first ink”.
[0096]
The second liquid used in combination with the first ink contains at least a water-soluble organic solvent having a solubility parameter of 9 to 11 and / or a surfactant, and water, and further improves the effect of preventing color mixing. For this purpose, it may contain a polyvalent metal salt and / or a cationic compound. In addition, this second liquid may contain a water-soluble organic solvent having a solubility parameter of more than 11, a coloring agent, a pH adjuster, a polymer, a hydrotrope, a chelating agent, an inclusion compound, an oxidizing agent, an oxidizing agent, if necessary. Inhibitors, reducing agents, enzymes, bactericides, defoamers, abrasives, and other additives can be added. When a colorant is contained, it is used substantially as an ink.
[0097]
The second liquid preferably contains a component consisting of a water-soluble organic solvent and / or a surfactant having a solubility parameter of 9 to 11 and water, in an amount of 1 to 10% by weight based on the total weight. In general, when a pigment-dispersed ink comes in contact with a solvent or surfactant having a low solubility parameter, the dispersant on the pigment surface is replaced by the solvent / surfactant and inhibits the dispersion stability. , And usually does not have a color mixing prevention function. However, in the present invention, since the first ink forms an aggregate or an aggregate by jetting, the aggregation or association by contact with the liquid is promoted in a short time, and the effect of preventing color mixing is exhibited. When a colorant is used for the second liquid, a low solubility parameter and high compatibility with a surfactant are required, and a dye ink is preferable as the colorant.
[0098]
Further, it is preferable that the second liquid further contains a polyvalent metal salt and / or a cation compound.
In general, when a cationic compound or a polyvalent metal salt is added to an ink, if the coloring agent is anionic, even a dye is easily precipitated. If a sufficient effect of preventing color mixing is to be obtained, a problem of dye precipitation occurs, and it is difficult to achieve both. However, since the first ink forms an aggregate or an aggregate by ejection, a small amount of the electrolyte exerts a sufficient effect. These additives can be added in any amounts as long as the reliability is not reduced.
[0099]
As the water-soluble organic solvent used for the second liquid, polyhydric alcohols and their derivatives such as alkyl ethers can be used to prevent solidification of the ink. Examples of these include glycerin, polyethylene glycol, polypropylene glycol, diethylene glycol, (2 (2 butoxyethoxy) ethanol, diethylene glycol phenyl ether, propylene glycol, propylene glycol monomethyl ether, butylene glycol, triethylene glycol, thiodiglycol, and hexylene. Glycol, ethylene glycol methyl ether, diethylene glycol methyl ether, pentanediol, hexanetriol, trimethylolpropane and the like.
[0100]
Further, as other components, alcohols such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, hexyl alcohol, and benzyl alcohol, amides such as dimethylformamide and dimethylacetamide, acetone, diacetone High-boiling nitrogen-containing solvents such as ketones such as alcohols, ketone alcohols, triethanolamine, diethanolamine, pyrrolidone, N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, dimethylsulfoxide, and diethyl Sulfur-containing solvents such as sulfoxide, sulfolane, thiodiethanol, etc., sugars such as glucose, maltose, amylose (dextrin), cellulose, sodium alginate and derivatives thereof, gum arabic, etc. It can be used.
[0101]
The water-soluble organic solvent used for the second liquid may be used alone or as a mixture of two or more. The content of these water-soluble organic solvents with respect to the total amount of the second liquid is preferably 1 to 50% by weight. If it is less than 1% by weight, the moisturizing effect cannot be obtained, and if it exceeds 50% by weight, the ink may not be ejected due to an increase in ink viscosity. The content of the water-soluble organic solvent having a solubility parameter of 9 to 11 based on the total liquid weight is preferably 1 to 10% by weight. If the amount is less than 1% by weight, the effect of promoting coagulation cannot be obtained. If the amount exceeds 10% by weight, the permeability to paper increases, and curling may occur. In the case of a liquid containing a colorant, penetration into the back surface of the paper is conspicuous, which may cause a problem of a decrease in optical density and strikethrough.
[0102]
The surfactant used for the second liquid may be a nonionic, anionic, cationic or amphoteric surfactant, but the second liquid may contain a cationic compound. It is preferable to use When the composition contains an anionic colorant, a nonionic surfactant is particularly preferred for preventing precipitation.
[0103]
As the cationic compound that can be contained in the second liquid, compounds such as the following cationic dyes, cationic aqueous polymers, primary, secondary, and tertiary amine salts, and quaternary ammonium salts can be used.
As the cationic aqueous polymer, a copolymer of a hydrophilic monomer component having an amino group or a quaternary amino group and a hydrophobic monomer component or a salt thereof is preferable. In addition, other components can be copolymerized as necessary. The copolymer may have any structure such as random, graft, block and the like.
[0104]
Examples of the hydrophilic monomer having an amino group and a quaternary amino group include N, N-dimethylaminoethyl methacrylamide, N, N-dimethylaminoethylacrylamide, N, N-dimethylacrylamide, N, N-dimethylmethacrylamide, N , N-dimethylaminopropyl methacrylamide and the like. For quaternization, methyl chloride, methyl iodide, dimethyl sulfate, benzyl chloride, epichlorohydrin and the like can be used.
[0105]
Hydrophobic monomer components include styrene, styrene derivatives, vinyl toluene, vinyl toluene derivatives, vinyl naphthalene, vinyl naphthalene derivatives, butadiene, butadiene derivatives, isoprene, isoprene derivatives, ethylene, ethylene derivatives, propylene, propylene derivatives, alkyl acrylates Examples include esters and alkyl esters of methacrylic acid. Of these, styrene, styrene derivatives, alkyl acrylates and alkyl methacrylates are preferred. The C number of the alkyl group is preferably 1 to 10, and more preferably 1 to 6.
[0106]
As the other components described above, acrylamide, acrylamide derivatives, dimethylaminoethyl methacrylate, ethoxyethyl methacrylate, butoxyethyl methacrylate, ethoxytriethylene methacrylate, vinylpyrrolidone, vinylpyridine, alkyl ether and methoxypolyethylene glycol methacrylate, polyethylene glycol methacrylate and the like Examples include a component containing polyoxyethylene, a component containing a hydroxyl group such as hydroxymethyl methacrylate, hydroxyethyl methacrylate, and vinyl alcohol.
[0107]
The weight average molecular weight of the cationic aqueous polymer is preferably from 1,000 to 20,000, more preferably from 1,000 to 5,000, from the viewpoint of liquid viscosity. As a method for measuring the weight average molecular weight, a value in terms of polyethylene glycol measured by a light scattering method, an X-ray small angle scattering method, a sedimentation equilibrium method, a diffusion method, an ultracentrifugation method, or various kinds of chromatography, for example, a GPC method can be used.
[0108]
The content of the cationic aqueous polymer is preferably in the range of 0.002 to 10% by weight based on the total amount of the second liquid. When the content is less than 0.002% by weight, there is no effect of addition, and when the content exceeds 10% by weight, an increase in liquid viscosity or a remarkable decrease in optical density due to a penetrating action may occur, which is not preferable. When the second liquid contains an anionic colorant, the content of the cationic aqueous polymer is set to 0.002 to 3% by weight based on the total amount of the liquid in order to prevent precipitation of the colorant. Is preferably, and more preferably 0.003 to 1% by weight. When the content is less than 0.002% by weight, there is no effect of addition, and when the content exceeds 3% by weight, aggregation and precipitation of the colorant may be induced. In addition, these cationic aqueous polymers may be used as a dispersant for a pigment.
[0109]
Examples of the primary, secondary and tertiary amine salts and quaternary ammonium salt compounds include, for example, dodecyltrimethylammonium chloride, dodecylbenzyltrimethylchloride, dodecyldimethylbenzylammonium chloride, stearyltrimethylammonium chloride, benzyltributylammonium chloride , Benzalkonium chloride, cetyltrimethylammonium chloride and the like, ethylene oxide adducts of higher alkylamines as amine salts, for example, dihydroxyethylstearylamine, and pyridium salt-type compounds, for example, cetylpyridium chloride, cetylpyridium bromide Examples of the imidazoline-type cationic compound include 2-heptadeniser-hydroxyethylimidazoline and the like. Further, a so-called cationic surfactant may be diverted. The addition amount of these compounds is preferably 0.002 to 7% by weight based on the total amount of the second liquid. If the addition amount is less than 0.002% by weight, the effect of addition cannot be obtained, and if it exceeds 7% by weight, the jetting reliability may be lowered, which is not preferable.
[0110]
When the second liquid contains an anionic colorant, the content is preferably 0.002 to 3% by weight, more preferably 0.003 to 1% by weight, based on the total amount of the second liquid. If it is less than 0.002% by weight, the effect of addition may not be obtained, and if it exceeds 3% by weight, aggregation and precipitation of the colorant may be induced.
[0111]
As the polyvalent metal salt that the second liquid can contain, Ca (NO₃)₂, CaCl₂, Ca (CH₃COO)₂, Al (NO₃)₃, Nd (NO₃)₃, Y (NO₃)₃, Cu (NO₃)₂, Zn (NO₃)₂, CuCl₂, ZnCl₂, COCl₂, Co (NO₃)₂, NiCl₂, MgBr₂, Mg (NO₃)₂, ZnBr₂, NH₄Cl, Ni (NO₃)₂And the like. The amount of the polyvalent metal salt added to the second liquid is preferably 0.01 to 10% by weight based on the total amount of the second liquid. If the amount is less than 0.01% by weight, the effect of addition may not be obtained. If the amount exceeds 10% by weight, the clogging property may be significantly deteriorated.
[0112]
When the second liquid contains the anionic colorant, the content is preferably 0.01 to 3% by weight, more preferably 0.01 to 1% by weight, based on the total amount of the second liquid. If the content is less than 0.01% by weight, the effect of addition may not be obtained. If the content exceeds 3% by weight, aggregation and precipitation of the colorant may be induced.
[0113]
In addition, as the water used for the second liquid, it is preferable to use ion-exchanged water, ultrapure water, distilled water, and ultrafiltration water, in particular, in order to prevent contamination of impurities. When the second liquid contains a colorant, the second liquid can be selected from the pigments and the water-soluble dyes described with respect to the ink set for inkjet recording, and the water-soluble dye is preferable.
[0114]
As the water-soluble dye, direct dyes and acid dyes can be used. I. Direct Black-2, -4, -9, -11, -17, -19, -22, -32, -80, -151, -154, -168, -171, -194; I. Direct Blue-1, -2, -6, -8, -22, -34, -70, -71, -76, -78, -86, -112, -142, -165, -199, -200, -201, -202, -203, -207, -218, -236, -287; I. Direct Red-1, -2, -4, -8, -9, -11, -13, -15, -20, -28, -31, -33, -37, -39, -51, -59, -62, -63, -73, -75, -80, -81, -83, -87, -90, -94, -95, -99, -101, -110, -189; I. Direct Yellow-1, -2, -4, -8, -11, -12, -26, -27, -28, -33, -34, -41, -44, -48, -58, -86, -87, -88, -135, -142, -144; I. Food black-1 and -2; I. Acid Black-1, -2, -7, -16, -24, -26, -28, -31, -48, -52, -63, -107, -112, -118, -119, -121, -156, -172, -194, -208; I. Acid Blue-1, -7, -9, -15, -22, -23, -27, -29, -40, -43, -55, -59, -62, -78, -80, -81, -83, -90, -102, -104, -111, -185, -249, -254; I. Acid Red-1, -4, -8, -13, -14, -15, -18, -21, -26, -35, -37-110, -144, -180, -249, -257; C . I. Acid Yellow-1, -3, -4, -7, -11, -12, -13, -14, -18, -19, -23, -25, -34, -38, -41, -42, -44, -53, -55, -61, -71, -76, -78, -79-, 122 and the like.
[0115]
Examples of the cationic dye include C.I. I. Basic yellow-1, -11, -13, -19, -25, -33, -36; I. Basic red-1, -2, -9, -12, -13, -38, -39, -92; I. Basic Blue-1, -3, -5, -9, -19, -24, -25, -26, -28 and the like.
[0116]
The content of these dyes is preferably about 0.3 to 15% by weight, more preferably about 1 to 10% by weight, based on the total amount of the second liquid. These dyes can be used alone or in combination of two or more, or may be adjusted to custom colors such as red, blue, and green in addition to the four primary colors of cyan, magenta, yellow, and black.
[0117]
When the second liquid contains a colorant, it can be used substantially as an ink, and can be printed adjacent to the first ink to prevent color mixing with each other. When the second liquid does not contain a coloring agent, it can be used independently of the first ink. As a printing method, it can be ejected to the printing portion of the first ink before and / or after printing the first ink. At this time, the ratio between the drop amount of the first ink and the drop amount of the second liquid is preferably in the range of 10: 2 to 10: 0.1, and more preferably in the range of 10: 2 to 10: 0.5. More preferred. The drop amount of the first ink is usually a fixed amount because of the relationship with the optical density. Therefore, if the ratio exceeds 10: 2, the amount of liquid on the paper becomes large, and wrinkles such as curl and cuckling of the paper in the printing portion become conspicuous, which may degrade the quality. In addition, a problem of delay in drying time may occur. On the other hand, if the ratio is less than 10: 0.1, the effect of preventing bleeding may not be obtained.
[0118]
(Inkjet recording method)
Next, the ink jet recording method of the present invention will be described. The ink jet recording method of the present invention uses an ink of each color constituting an ink set for ink jet recording as described above, or an ink and a second liquid of each color constituting an ink and liquid set, on a recording medium. An image is recorded. At this time, the inks of the respective colors, or the inks of the respective colors and the second liquid are given a certain energy to form droplets, and printing is performed by applying the droplets on the recording medium. Do.
[0119]
The method of applying energy is not particularly limited, but a method of applying thermal energy and a method of applying mechanical energy can be suitably used, and specifically, a thermal inkjet method and a piezo method can be used.
[0120]
In the ink jet recording method of the present invention, for example, a method of heating the recording paper and the ink of each color at 50 ° C. to 200 ° C. before and after printing at 50 ° C. to 200 ° C. to promote print fixing (thermal type method) may be used. In addition to the method of printing directly on plain paper, glossy paper, special paper, cloth, film, OHP, etc., printing on an intermediate drum or belt, etc., and adjusting the ink image on the intermediate, paper, cloth, A method of transferring and recording on a film or the like can also be adopted. Further, as the inkjet device used in the inkjet recording method of the present invention, any known inkjet device may be used as long as the above conditions are satisfied.
[0121]
【Example】
Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.
[0122]
[Preparation of dispersion]
While mixing and stirring 60 parts by weight of a dispersant having the composition shown in the following Table 1 (10% aqueous solution of polymer solid content) and 210 parts by weight of ion-exchanged water, 30 parts by weight of the pigment shown in Table 1 were added and stirred for 30 minutes. Thereafter, the mixture was dispersed with an ultrasonic homogenizer (300 W, 400 μA) for 30 minutes. Furthermore, after performing centrifugation (8000 rpm, 15 minutes) using a centrifugal separator, the mixture was passed through a 1 μm membrane filter to obtain a dispersion.
[0123]
[Table 1]

[0124]
[Examples 1 and 2 and Comparative Examples 1 to 3]
Using the dispersions 1 to 16, the following solvent components other than the dispersions were stirred and mixed for 30 minutes. Thereafter, the dispersion was slowly added to the stirring solvent, and the mixture was further stirred and mixed for 30 minutes to prepare an ink. Example 1 is an ink set using dispersions 1 to 4, Example 2 is an ink set using dispersions 5 to 8, Comparative Example 1 is an ink set using dispersions 9 to 12, and dispersions 13 to 16. Was used as Comparative Example 2 and an ink set using Dispersions 17 to 20 was used as Comparative Example 3.
[0125]
-Dispersion: 50 parts by weight
Ethylene glycol (solubility parameter 17.8): 12 parts by weight
-Isopropyl alcohol (solubility parameter 11.6): 3 parts by weight
・ Surfinol 465 (manufactured by Nissin Chemical Co.): 0.05 parts by weight
・ Deionized water: 35 parts by weight
[0126]
[Test Example 1]
Using the ink sets prepared in Examples 1 and 2 and Comparative Examples 1 to 3, a 2 cm band single color (black, cyan, magenta, yellow) and a secondary color (red) were produced by a full-color inkjet printer (600 spi) prototyped by Fuji Xerox. , Green and blue) and a tertiary color (process black) patch was printed. FX-L paper (manufactured by Fuji Xerox Co., Ltd.) was used as a representative plain paper.
[0127]
The evaluation was carried out by measuring the optical density and observing the occurrence of color unevenness on the printed solid image composed of the primary color, the secondary color and the tertiary color, and determining the Gamut value of the color ink to obtain a color reproduction range. It was confirmed.
In addition, the number of particles having a number average particle diameter of 0.5 μm or more and 5 μm or more before and after ejection in the ink of each color and the particle size distribution in the ink were measured. That is, the number of particles having a particle diameter of 0.5 μm or more was measured with an Accusizer (manufactured by PARTICLE SIZING SYSTEMS) for the ink immediately after the preparation and the ink after ejection collected from the printer into a beaker. The distribution was measured by Microtrac UPA (Leeds & Northrup). Accusizer measurement conditions were measured by diluting 2 μl of the ink with 50 ml of deionized water, and the number of particles was converted to 1 μl. The measurement conditions of the Microtrac UPA were such that the ink stock solution was measured using the ink viscosity as the solvent viscosity.
[0128]
Regarding the color reproduction range, the hue of each solid image of cyan, magenta, yellow, red, green, and blue was measured with an X-Rite 938 (manufactured by X-Rite), and a was obtained.^*Value, b^*The values were evaluated by calculating the area (Gamut) of a hexagon formed by plotting the values on a two-dimensional plane. Table 2 shows the results.
[0129]
[Table 2]

[0130]
The inks printed with the inks of Examples 1 and 2 have higher optical densities than the inks of Comparative Examples 1 to 3, have good secondary / tertiary color development, and have color unevenness. No Gamut value was large, and a good color reproduction range could be obtained.
[0131]
[Experimental Examples 3 and 4]
According to the composition shown in Table 3, the solvent composition components other than the dispersion and 10 parts by weight of deionized water were stirred and mixed for 30 minutes. Thereafter, 50 parts by weight of each dispersion was slowly added to the stirring solvent. Further, deionized water was added to make the total amount 100 parts by weight, and the mixture was stirred and mixed for 30 minutes to prepare an ink.
[0132]
[Test Example 2]
The initial ink immediately after the preparation, the post-ejection ink obtained by collecting the ink jetted from the printer into a beaker, the ink stored at 60 ° C. for 100 hours, the number of particles having a particle diameter of 0.5 μm or more, and the number average particle size of each ink were measured. The storage stability of the ink set for inkjet recording was examined. Table 3 shows the results.
[0133]
[Table 3]

[0134]
The following are examples of the ink and liquid set of the present invention, comparative examples and test examples.
[Preparation of first ink]
・ Ethylene glycol: 12 parts by weight
・ Ethanol: 4 parts by weight
・ Urea: 5 parts by weight
・ Lauryl sulfate sodium salt: 0.05 parts by weight
The above composition and deionized water were added to make up to 50 parts by weight, and the mixture was stirred for 30 minutes. Thereafter, 50 parts by weight of each of the dispersions 1 to 4 and 9 to 12 were added, and stirring was further continued for 30 minutes. The ink was passed through a 2 μm membrane filter to prepare an ink. The first ink set using the dispersions 1 to 4 was inks A, B, C, and D, and the first ink set using the dispersions 9 to 12 was inks E, F, G, and H.
[0135]
[Test Example 3]
With respect to the inks A to H immediately after the preparation and the inks A to H after the ejection of the ink ejected by the printer into the beaker, the number of particles having a particle diameter of 0.5 μm or more and the particle size distribution of the ink were measured in the above Test Example 1. The measurement was performed in the same manner as described above. Table 4 shows the number of particles having a particle size of 0.5 μm or more, the change magnification, the particle size, and the change rate of the inks A to H.
[0136]
[Table 4]

[0137]
(Preparation of the second liquid: when containing a colorant)
[Second liquid 1]
・ Direct Yellow 144 (10% aqueous solution): 20 parts by weight
Ethylene glycol (solubility parameter 17.8): 20 parts by weight
-2- (2ethoxyethoxy) ethanol (solubility parameter 10.9): 5 parts by weight
・ Urea: 5 parts by weight
・ Benzalkonium chloride: 1 part by weight
The total amount was adjusted to 100 parts by weight with the above composition and deionized water, and the mixture was stirred for 30 minutes. Thereafter, the mixture was passed through a 1 μm membrane filter to prepare a second liquid 1.
[0138]
[Second liquid 2]
・ Direct Yellow 144 (10% aqueous solution): 20 parts by weight
Ethylene glycol (solubility parameter 17.8): 20 parts by weight
-2- (2ethoxyethoxy) ethanol (solubility parameter 10.9): 5 parts by weight
・ Urea: 5 parts by weight
-Benzalkonium chloride: 5 parts by weight
The total amount was adjusted to 100 parts by weight with the above composition and deionized water, and the mixture was stirred for 30 minutes. Thereafter, an attempt was made to pass through a 1 μm membrane filter, but the filter was clogged and could not be filtered. Granules were observed on the filter paper.
[0139]
[Second liquid 3]
・ Direct Yellow 144 (10% aqueous solution): 20 parts by weight
Ethylene glycol (solubility parameter 17.8): 20 parts by weight
-2- (2ethoxyethoxy) ethanol (solubility parameter 10.9): 5 parts by weight
・ Urea: 5 parts by weight
・ Magnesium sulfate: 0.8 parts by weight
Using the above composition, a second liquid 3 was prepared in the same manner as the second liquid 1.
[0140]
[Test Example 4 by Examples 5, 6 and Comparative Examples 4 and 5]
(Print test)
Using a full-color inkjet printer (600 spi) prototyped by Fuji Xerox, each of the first ink and the second liquid shown in Table 5 was printed so as to be in contact with a 2 cm square patch. FX-L paper (manufactured by Fuji Xerox Co., Ltd.) was used as typical plain paper. For the evaluation items, the color mixing of the printed matter in contact with each other was sensory evaluated by ten subjects according to the following criteria.
：: No color mixing
Δ: Color mixture occurred, but not bothersome
×: Color mixing occurs and is unacceptable
Table 5 shows the results.
[0141]
[Table 5]

[0142]
As is clear from the results shown in Table 5, the inks and the liquid sets of the present invention (Examples 5 and 6) did not cause color mixture as compared with those of Comparative Examples 4 and 5.
[0143]
(Preparation of the second liquid: when no colorant is contained)
[Second liquid 4]
Ethylene glycol (solubility parameter 17.8): 25 parts by weight
・ Urea: 5 parts by weight
・ Surfinol 465: 1 part by weight
-Benzalkonium chloride: 5 parts by weight
The total amount was adjusted to 100 parts by weight with the above composition and deionized water, and the mixture was stirred for 30 minutes. Thereafter, the solution was passed through a 1 μm membrane filter to prepare a second liquid 4.
[0144]
[Test Example 5 by Examples 7, 8, 9 and Comparative Examples 6, 7, 8]
(Print test)
Using a full-color inkjet printer (660 spi) prototyped by Fuji Xerox, the second liquid 4 was printed on the first ink print scheduled portion immediately before the ejection of the first ink shown in Table 6. Immediately thereafter, liquid 1 was printed as a first ink and a base ink so as to be in contact with a 10 cm square patch. As shown in Table 6, printing of the second liquid was performed with 1/10, 3/10, and 5/10 of the number of dots per unit area of the first ink. FX-L paper (manufactured by Fuji Xerox Co., Ltd.) was used as typical plain paper. The evaluation items were a sensory evaluation by ten subjects according to the following criteria for color mixing of the printed matter in contact with the paper, and a paper cuckle (wrinkle) height according to the following criteria.
：: No color mixing
Δ: Color mixture occurred, but not bothersome
×: Color mixing occurs and is unacceptable
○: 0 to less than 4 mm
×: less than 4 to 8 mm
XX: 8 mm or more
Table 6 shows the results.
[0145]
[Table 6]

[0146]
As is evident from the results shown in Table 6, the inks of Examples 7, 8, and 9 using the ink and liquid set of the present invention had no color mixing and had less ink droplets than Comparative Examples 6, 7, and 8. Was also able to be prevented.
[0147]
As described above, the ink set for ink jet recording of the present invention has better reproducibility of secondary colors and tertiary colors than the conventional ink set, and also has a good image density balance between images and characters. Good. Further, as with the conventional ink set, it is a pigment-dispersed ink, but has a high optical density and excellent storage stability. Further, the ink set for ink jet recording of the present invention can achieve the prevention of color mixing between adjacent colorants by using the ink set for printing with the second liquid.
[0148]
The ink set for ink jet recording of the present invention, or the ink and liquid set, can form a clear, high-resolution, high water-resistant full-color image on plain paper such as report paper, copy paper, bond paper, and high-quality paper, In addition, it is possible to prevent curl / cuckle from deteriorating the sheet quality. The ink set for ink jet recording of the present invention is suitable as an ink for ink jet recording using a thermal ink jet method, a piezo method, ultrasonic waves, an electric field, or the like. In particular, it is suitable as an ink capable of clearly and stably reproducing a highly water-resistant full-color image on plain paper.
[0149]
【The invention's effect】
As described above, according to the present invention, that is, the present invention can prevent nozzle clogging, have no color unevenness, and even when creating a multi-color document by combining inks of each color, a photograph or the like can be obtained. An ink jet recording ink set, an ink and liquid set, and an ink jet recording method using the same, which are capable of producing a document excellent in color reproducibility of an image and having a well-balanced image density between an image and a character. Can be provided.

Claims (3)

A black ink and a combination of three or more types of color inks including three colors of cyan, magenta and yellow, wherein the black ink and the color ink contain a pigment, an aqueous polymer, a water-soluble organic solvent and water. In the ink set for inkjet recording including at least,
The black ink and the color ink include particles after being ejected from the nozzle of the inkjet head, and the number average particle diameter and the number of particles contained in the ejected black ink and color ink are represented by the following formula (1). (7) An ink set for inkjet recording, which satisfies (7).
・ Formula (1) 10 ≦ BD ≦ 150
Formula (2) 10 ≦ CD ≦ 150
Formula (3) 6 × 10 ⁴ ≦ BN (0.5) ≦ 6 × 10 ⁵
Formula (4) 6 × 10 ³ ≦ CN (0.5) ≦ 6 × 10 ⁵
・ Formula (5) CN (0.5) ≦ BN (0.5)
・ Formula (6) BN (5) ≦ 50
・ Formula (7) CN (5) ≦ 50
[However, in the formulas (1) to (7), BD is the number average particle diameter (nm) of the particles contained in the black ink after the ejection, and CD is the number of particles contained in the color ink after the ejection. The average particle diameter (nm) and BN (0.5) are the number of particles (particles / μl) having a number average particle diameter of 0.5 μm or more contained in the black ink after jetting, and the CN (0.5) is The number of particles having a number average particle size of 0.5 μm or more (particles / μl) contained in the color ink after ejection, and BN (5) is the number of particles having a number average particle size of 5 μm or more contained in the black ink after ejection ( Particles / μl) and CN (5) represent the number (particles / μl) of particles having a number average particle diameter of 5 μm or more contained in the color ink after jetting. ] An ink jet recording ink set according to claim 1, which is used in combination with a water-soluble organic solvent and / or a surfactant having a solubility parameter of 9 to 11, and water when printing using the ink jet recording ink set. And a second liquid to be used. An image on a recording medium using the ink of each color constituting the ink set for inkjet recording according to claim 1 or the ink and the second liquid constituting the ink and liquid set according to claim 2 In the ink jet recording method for printing
An ink jet recording method comprising: printing by applying the inks of the respective colors, or the inks of the respective colors and the second liquid, in the form of droplets by applying energy onto the recording medium. .