JP4158303B2 - Water-based pigment ink for inkjet recording - Google Patents

Description

【００４４】
試験例
上記各実施例及び比較例で得られたインキを用いて、その物性の測定及び以下の評価を行なった。その結果を表２に示す。
【００４５】
［粘度］
２５℃におけるインキの粘度をＥ型粘度計（トキメック社製）を用いて測定した。
【００４６】
［表面張力］
２５℃におけるインキの表面張力を自動表面張力計（商品名：ＣＢＶＰ−Ａ３型、協和界面科学社製）で測定した。
【００４７】
［長期保存性試験］
インキを−３０℃及び７０℃の温度環境下でそれぞれ７日間密封放置後、常温（２５℃）に戻し、そのときのインキの物性（粘度、表面張力）及び分散安定性を測定して、最初の各測定値と比較した。そして、インキの物性と分散安定性の両方に変化がなかったものを○、いずれか一方でも変化があったものは×とした。
【００４８】
なお、インキの物性（粘度、表面張力）の測定は、上記の各測定方法と同様にして行なった。また、分散安定性は、分散カーボン粒子の粒度分布を粒度分布測定器（商品名：コールターカウンターＴＡ−ＩＩ型、米国コールター社製）で測定した。
【００４９】
以下の評価においては、４色一体型プリントヘッドを搭載したピエゾ方式インクジェット記録装置、試験紙は普通紙（商品名：ゼロックス４０２４、ゼロックス社製）を用い、インキの吐出量は５０ｐｌとした。
【００５０】
［連続印字性試験］
連続吐出記録印字を行ない、３００時間以上安定吐出印字ができたものを○、３００時間未満で不吐出現象を示したものを×とした。
【００５１】
［発色性試験］
カーボンブラック顔料のインキ中の分散安定性、及びベタ印字部の光学反射濃度で評価した。
【００５２】
分散安定性は、インキを上記長期保存性試験と同様の環境下におき、同様の方法で測定して粒度分布の変化がないものを合格とした。また、光学反射濃度はマクベス反射濃度計（商品名：ＲＤ−９１８型、マクベス社製）で測定し、反射濃度１．２以上を合格とした。そして、分散安定性と反射濃度の両方を満足したものを○、いずれか一方でも満足しないものは×とした。
【００５３】
［滲み試験］
ベタ印字及び文字印字端部における滲み（フェザーリング現象を含む）を目視で官能評価した。いずれの印字端部にも滲みがないものを○、いずれか一つでも滲みがあれば×とした。
【００５４】
［乾燥性試験］
ベタ印字完了５秒経過後、印字部を濾紙で擦り、インクの濾紙への付着の有無調べた。インクの付着がなければ○、付着があれば×とした。
【００５５】
【表２】

【００５６】
表２に示されるように、ジエチレングリコールモノブチルエーテル又はピロリドン類を添加していない比較例は、実施例に比べて長期保存性、連続印字性、発色性、滲み、乾燥性等の評価項目のいずれかが劣っていることが分かる。
【００５７】
【発明の効果】
以上説明したように、本発明によれば、被印字媒体に対して充分な画像（印字）濃度を得ることができ、発色性、印字信頼性、耐水性、耐光性及び長期保存性に優れたインクジェット記録用水性顔料インキを得ることができる。
【００５８】
本発明のインクジェット記録用水性顔料インキは、普通紙に記録した場合でも優れた発色性を示し、また、モノクロ及びフルカラー記録のような多重記録でも滲みがなく、定着性も充分である。さらに、インクジェット用記録ヘッドの目詰まりが少なく、吐出安定性にも優れており、ピエゾ及びサーマル方式のインクジェット記録方式全般に好適に用いられる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an aqueous pigment ink used in an ink jet recording type recording apparatus.
[0002]
[Prior art]
The ink jet recording method is one of the image recording techniques which have recently been improved in importance due to excellent recording stability and easy full color image recording.
[0003]
Ink jet recording inks are generally classified into water-based inks using purified water as a main solvent and oil-based inks using an organic solvent as a main solvent.
[0004]
In general, the basic performance required for ink jet recording inks is as follows: (1) sufficient image (printing) density is obtained for the printing medium; (2) the recorded image is clear and clear. (3) Fast drying on the printing medium, (4) Good water resistance and light resistance, (5) Excellent long-term storage, (6) Inkjet There is no inconvenience such as clogging at the nozzle tip of the recording head (hereinafter abbreviated as “head”), blurring of the recorded image when continuous printing is performed, or when recording is started after being left for a long time. (8) There is no problem in the safety of the user, (9) There is no problem even if it comes into contact with the members constituting the recording means at the time of use, etc. Can be mentioned.
[0005]
Water-based inks are generally inferior in water resistance compared to oil-based inks, but because the solvent is water, it is excellent in safety, and carbon black with excellent water resistance and light resistance has come to be used. The mainstream of the ink jet recording method.
[0006]
Since carbon black is generally not highly dispersible, when carbon black is used in an aqueous pigment ink for inkjet recording, a polymer compound such as a surfactant or a water-soluble resin is used as a dispersant to obtain a uniform dispersion system. As added.
[0007]
On the other hand, self-dispersing carbon black that can be dispersed stably without using a dispersant by introducing a water-soluble group on the surface of carbon has also been developed (Japanese Patent Application Laid-Open No. 5-186704, Japanese Patent Application Laid-Open 8-3498).
[0008]
[Problems to be solved by the invention]
However, the conventional water-based pigment ink for ink jet recording has the following problems.
[0009]
B) In the method of adding a surfactant as a dispersant and maintaining the dispersion stability of the pigment, the surface tension of the ink is reduced, the permeability to the inside of the recording paper is improved, and the drying property is improved. There is a problem that the color developability is remarkably lowered because the recording paper penetrates deeply into the recording paper. Furthermore, the ink to which the surfactant is added has a problem that it easily foams, has poor ink ejection stability, and significantly impairs printing reliability.
[0010]
B) The method of adding a polymer compound such as a water-soluble resin as a dispersant is effective for the dispersibility of the pigment, but the ink for inkjet recording needs to have low viscosity and Newtonian fluid properties. If the ink viscosity is increased or the resin is dissolved, the drive frequency response will be reduced, or the initial ejection characteristics will be easily impaired when reprinting after printing is stopped. There was a problem.
[0011]
Further, even a method using the above-described dispersant cannot provide a sufficiently satisfactory dispersibility, and in particular, there is a problem that the ink in which carbon black is dispersed is inferior in long-term storage.
[0012]
C) Even in a method using self-dispersing carbon black without using a dispersant, there is a problem that a failure is likely to occur at the time of reprinting after printing is stopped.
[0013]
Accordingly, an object of the present invention is to provide a water-based pigment for ink-jet recording which improves the drawbacks of the conventional ink-jet recording ink and satisfies the following conditions.
[0014]
1) A sufficient image (printing) density can be obtained for a printing medium.
2) The recorded image is clear and clear (good color developability).
3) There is no inconvenience such as blurring of recorded images when continuous printing is performed or when recording is started after being left for a long time (excellent printing reliability).
4) Good water resistance and light resistance.
5) Excellent long-term storage stability.
[0015]
[Means for Solving the Problems]
As a result of intensive studies to achieve the above object, the present inventors have used diethylene glycol monobutyl ether, N-methyl-2-pyrrolidone, and 2-pyrrolidone as a water-soluble organic solvent for recording on plain paper. However, water-based pigments for inkjet recording exhibit excellent color developability, have no bleeding even in multiple recording such as monochrome and full-color recording, have sufficient drying properties, have less clogging of the head, and have excellent ejection stability. The present inventors have found that an ink can be obtained and have completed the present invention.
[0016]
That is, the aqueous pigment ink for inkjet recording of the present invention is a self-dispersing carbon black dispersion as the carbon black pigment dispersion in the aqueous pigment ink for inkjet recording containing a carbon black pigment dispersion, a water-soluble organic solvent, and water. And diethylene glycol monobutyl ether, N-methyl-2-pyrrolidone and 2-pyrrolidone as the water-soluble organic solvent, and the content of diethylene glycol monobutyl ether in the aqueous pigment ink for inkjet recording is 1 to 10% by mass, N -Methyl-2-pyrrolidone content is 5 to 15% by mass, and 2-pyrrolidone content is 10 to 30% by mass .
[0017]
In this invention, it is preferable that content of the said carbon black pigment dispersion is 1-10 mass% in carbon black pigment solid content.
[0018]
The self-dispersing carbon black dispersion preferably has a surface tension of 60 mN / m or more and a viscosity of 20 mPa · s or less.
[0019]
Further, the aqueous pigment ink for inkjet recording of the present invention preferably has a surface tension of 40 to 50 mN / m and a viscosity of 1.5 to 10 mPa · s.
[0020]
According to the present invention, an aqueous pigment ink for ink-jet recording having the characteristics 1) to 5) above can be obtained.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Self-dispersing carbon black is obtained by chemically bonding a hydrophilic group to a carbon surface to modify the surface of the carbon black and improving its dispersibility. Such hydrophilic functional groups are dissociated in water, so that when dispersed, a stable dispersion state can be maintained without adding a surfactant or a polymer compound, and the surface tension of the dispersion is almost equal to that of water. Equivalent value is shown.
[0022]
As the self-dispersing carbon black used in the present invention, for example, a carbon black surface chemically bonded with, for example, a sulfone group or a carboxyl group is used.
[0023]
The carbon black pigment dispersion is preferably an ultra fine particle aqueous pigment dispersion in which primary dispersed particles have a particle distribution with an average particle size of 0.05 to 0.2 μm and a maximum particle size of 1 μm or less. When the average particle size is less than 0.05 μm, the blackness is lowered, and when it exceeds 0.2 μm, the dispersion stability is lowered, which is not preferable. Moreover, when the maximum particle diameter exceeds 1 μm, the particles are aggregated and precipitated, which is not preferable.
[0024]
Furthermore, the self-dispersing carbon black pigment dispersion used in the present invention preferably has a surface tension of 60 mN / m or more and a viscosity of 20 mPa · s or less. By using a self-dispersing carbon black pigment dispersion liquid whose surface tension and viscosity are in the above numerical ranges, the physical properties of the aqueous pigment ink for inkjet recording can be easily within the numerical ranges described below.
[0025]
The self-dispersing carbon black pigment dispersion used in the present invention may be any liquid that satisfies the above physical properties. For example, commercially available products include CAB-O-JET200, CAB-O-JET300 (above Cabot Corporation). And MICROJET C-TYPE (manufactured by Orient Chemical Co., Ltd.).
[0026]
The content ratio of the carbon black pigment dispersion in the aqueous pigment ink for inkjet recording of the present invention is 1 to 10% by mass, preferably 4 to 6% by mass, based on the solid content of the carbon black pigment. If the content ratio of the carbon black pigment dispersion (as the solid content of the carbon black pigment) is less than 1% by mass, a sufficient image (printing) density cannot be obtained. Since it is inferior to reliability etc., it is not preferable.
[0027]
The water-based pigment ink for inkjet recording of the present invention is used by mixing water as a main solvent and a water-soluble organic solvent as an auxiliary solvent.
[0028]
The water used in the present invention is preferably purified water having a purity higher than that of ion-exchanged water so as not to be affected by heavy metals.
[0029]
On the other hand, in the present invention, the selection of the water-soluble organic solvent is extremely important, and it is preferable to use butyl glycols and pyrrolidones listed below in combination.
[0030]
-Butyl glycols: diethylene glycol monobutyl ether, diethylene glycol monoisobutyl ether, triethylene glycol monobutyl ether, ethylene glycol monobutyl ether, ethylene glycol dibutyl ether, and the like.
-Pyrrolidones: N-methyl-2-pyrrolidone, 2-pyrrolidone and the like.
[0031]
In the present invention, butyl glycols act as a control and adjustment material for surface tension and ink viscosity, and are effective in preventing drying. Pyrrolidones are effective for the dispersion stability of carbon black pigment particles, and are effective for imparting permeability to plain paper and preventing drying. Therefore, by using these in combination, excellent color developability, printing reliability, long-term storage stability, and the like can be obtained.
[0032]
In the present invention, it is particularly preferable to use diethylene glycol monobutyl ether as butyl glycols and N-methyl-2-pyrrolidone and 2-pyrrolidone as pyrrolidones. In this case, the content of diethylene glycol monobutyl ether in the aqueous pigment ink for inkjet recording is 1 to 10% by mass, the content of N-methyl-2-pyrrolidone is 5 to 15% by mass, and the content of 2-pyrrolidone is 10 to 30%. It is preferable that it is mass%.
[0033]
In addition to the above, the following water-soluble organic solvents may be used in appropriate combination. However, if the addition amount of the following water-soluble organic solvent exceeds 2%, the physical properties (viscosity, surface tension, pH, etc.) of the ink will be affected, so that the quality required by the purpose and application will be achieved. It is preferable to add.
[0034]
Alcohols: methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, butyl alcohol, cyclohexanol, benzyl alcohol, etc.
-Glycols: ethylene glycol, diethylene glycol, propylene glycol, polyethylene glycol, glycerin and the like.
-Glycol ethers: ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, triethylene glycol monomethyl ether, ethylene glycol monobutyl ether, and the like.
Alkanolamines: ethanolamine, diethanolamine, triethanolamine, N-methylethanolamine, N-ethyldiethanolamine and the like.
[0035]
In the present invention, the content ratio of the entire water-soluble organic solvent in the aqueous pigment ink for inkjet recording is preferably 10 to 45% by mass.
[0036]
The aqueous pigment ink for inkjet recording of the present invention can be obtained by uniformly dispersing and dissolving the above raw materials, followed by filtration.
[0037]
The water-based pigment ink for ink-jet recording of the present invention exhibits excellent color developability even when recorded on plain paper, and does not bleed even in multiple recording such as monochrome and full-color recording and has sufficient fixability. In addition, the inkjet recording head is less clogged and has excellent ejection stability.
[0038]
In the present invention, the surface tension of the aqueous pigment ink for inkjet recording is particularly preferably 40 to 50 mN / m and the viscosity is 1.5 to 10 mPa · s, and the surface tension and viscosity are within the above numerical ranges. It exhibits the most excellent characteristics.
[0039]
In addition to the above, an antifoaming agent, an antiseptic, an antifungal agent, and the like may be appropriately added to the aqueous pigment ink for inkjet recording of the present invention.
[0040]
【Example】
Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples. In the following Examples and Comparative Examples,% indicates mass%.
[0041]
Examples Each raw material was mixed at the blending ratio shown in Table 1, and a liquid that was sufficiently uniformly dispersed and dissolved at room temperature was filtered under pressure using a cartridge filter (pore size: 1 μm). An ink was obtained. As the carbon black dispersion, in Examples 1, 3, and 4, CAB-O-JET300 (solid content 16%, surface tension 73 mN / m, viscosity 4 mPa · s, manufactured by Cabot Corporation, the same shall apply hereinafter) was used. In Examples 2 and 5, MICROJET C-TYPE (solid content 20%, surface tension 69 mN / m, viscosity 3 mPa · s, manufactured by Orient Chemical Industries, the same applies hereinafter) was used.
[0042]
Comparative Examples Each raw material was mixed at a blending ratio shown in Table 1, and each aqueous pigment ink of Comparative Examples 1 to 5 was obtained in the same manner as in the Examples. As the carbon black dispersion, CAB-O-JET300 was used in Comparative Examples 1, 3, and 4, and MICROJET C-TYPE was used in Comparative Examples 2 and 5.
[0043]
[Table 1]

[0044]
Test Example Using the inks obtained in the above Examples and Comparative Examples, the physical properties were measured and the following evaluations were performed. The results are shown in Table 2.
[0045]
[viscosity]
The viscosity of the ink at 25 ° C. was measured using an E-type viscometer (manufactured by Tokimec).
[0046]
[surface tension]
The surface tension of the ink at 25 ° C. was measured with an automatic surface tension meter (trade name: CBVP-A3 type, manufactured by Kyowa Interface Science Co., Ltd.).
[0047]
[Long-term storage test]
After the ink was sealed for 7 days in a temperature environment of −30 ° C. and 70 ° C., respectively, it was returned to room temperature (25 ° C.), and the physical properties (viscosity, surface tension) and dispersion stability of the ink at that time were measured. The measured values were compared. A sample in which both the physical properties and the dispersion stability of the ink did not change was evaluated as ◯, and a sample in which either one was changed was evaluated as ×.
[0048]
In addition, the physical properties (viscosity and surface tension) of the ink were measured in the same manner as the above measurement methods. The dispersion stability was measured by measuring the particle size distribution of the dispersed carbon particles with a particle size distribution analyzer (trade name: Coulter Counter TA-II, manufactured by Coulter USA).
[0049]
In the following evaluation, a piezo-type inkjet recording apparatus equipped with a four-color integrated print head, plain paper (trade name: Xerox 4024, manufactured by Xerox Co., Ltd.) was used as the test paper, and the ink discharge amount was 50 pl.
[0050]
[Continuous printability test]
Continuous discharge recording printing was performed, and those that were able to perform stable discharge printing for 300 hours or more were marked with ◯, and those that showed a non-ejection phenomenon in less than 300 hours were marked with x.
[0051]
[Color development test]
The dispersion stability of the carbon black pigment in the ink and the optical reflection density of the solid print portion were evaluated.
[0052]
For dispersion stability, the ink was placed in the same environment as in the long-term storage stability test, and the ink was measured without any change in particle size distribution, and passed. The optical reflection density was measured with a Macbeth reflection densitometer (trade name: RD-918, manufactured by Macbeth Co.), and a reflection density of 1.2 or higher was regarded as acceptable. A sample satisfying both the dispersion stability and the reflection density was marked with “◯”, and a sample satisfying both of the values was marked “x”.
[0053]
[Bleeding test]
Sensory evaluation was visually performed on the solid print and the blur (including the feathering phenomenon) at the end of the character print. The case where there was no bleeding at any of the printed edge portions was marked with ◯, and if there was any bleeding, it was marked with ×.
[0054]
[Dryability test]
5 seconds after the completion of solid printing, the printed portion was rubbed with filter paper, and the presence or absence of ink adhering to the filter paper was examined. If there was no ink adhesion, it was marked as ◯, and if there was adhesion, it was marked as x.
[0055]
[Table 2]

[0056]
As shown in Table 2, the comparative example in which diethylene glycol monobutyl ether or pyrrolidones are not added is one of the evaluation items such as long-term storability, continuous printability, color developability, bleeding, and drying properties as compared with the examples. It turns out that is inferior.
[0057]
【The invention's effect】
As described above, according to the present invention, a sufficient image (printing) density can be obtained with respect to a printing medium, and color development, printing reliability, water resistance, light resistance and long-term storage stability are excellent. An aqueous pigment ink for ink jet recording can be obtained.
[0058]
The water-based pigment ink for ink-jet recording of the present invention exhibits excellent color developability even when recorded on plain paper, and does not bleed even in multiple recording such as monochrome and full-color recording and has sufficient fixability. Further, the ink jet recording head is less clogged and has excellent ejection stability, and is suitably used for piezo and thermal ink jet recording systems in general.

Claims (4)

In the water-based pigment ink for inkjet recording containing a carbon black pigment dispersion, a water-soluble organic solvent and water, a self-dispersing carbon black dispersion is used as the carbon black pigment dispersion.
Using diethylene glycol monobutyl ether, N-methyl-2-pyrrolidone and 2-pyrrolidone as the water-soluble organic solvent,
The content of diethylene glycol monobutyl ether in the aqueous pigment ink for inkjet recording is 1 to 10% by mass, the content of N-methyl-2-pyrrolidone is 5 to 15% by mass, and the content of 2-pyrrolidone is 10 to 30% by mass. An aqueous pigment ink for ink-jet recording , which is characterized by The water-based pigment ink for inkjet recording according to claim 1, wherein the content of the carbon black pigment dispersion is 1 to 10% by mass in terms of solid content of the carbon black pigment. The aqueous pigment ink for inkjet recording according to claim 1 or 2, wherein the self-dispersing carbon black dispersion has a surface tension of 60 mN / m or more and a viscosity of 20 mPa · s or less. The water-based pigment ink for inkjet recording according to any one of claims 1 to 3 , having a surface tension of 40 to 50 mN / m and a viscosity of 1.5 to 10 mPa · s.