JP5480459B2 - Inkjet ink - Google Patents

Description

  The present invention relates to an inkjet ink comprising a specific linear block copolymer and used in an inkjet recording system having high image saturation and excellent ejection stability.

  Conventionally, inks used in ink jet recording systems have been mainly used in which various water-soluble dyes are dissolved in water alone or in a solvent composed of water and a water-soluble solvent, and various additives are added as necessary ( For example, see Patent Documents 1, 2, and 3).

  However, when printing is performed using such a dye-based ink, the water resistance of the recorded image on the recording material is poor, and if the water is spilled, the problem of bleeding of the dye in the recorded portion easily occurs, Since the light resistance is poor, there is a problem that when the recording portion is exposed to light, a change in color tone or a decrease in density occurs.

  In order to improve the above-mentioned problems of dye-based inks, it is disclosed that so-called pigment-based inks using carbon black or various organic pigments instead of dyes as colorants are applied to inkjet recording systems (for example, Patent Documents 4 and 5). , 6, 7 and 8).

When printing is performed using pigment-based ink, the ink dried on the recording material is a pigment as a colorant. Good properties.
In addition, since pigments are less reactive to light than dyes, the light resistance of pigment-based inks is superior to that of dye-based inks.

  Such pigment-based inks are generally produced by adding various additives as necessary to a pigment dispersion prepared by dispersing a mixture of a pigment, a liquid medium and a dispersant using a dispersing machine such as a ball mill or a sand mill. However, the pigment dispersion used in the ink for ink jet recording usually has a particle size level of 200 nm or less in order to prevent nozzle clogging in a printing apparatus (ink jet printer), sharpness of a printed image, secondary color reproducibility, and transparency. It is necessary to finely disperse the pigment particles in the pigment dispersion. Furthermore, it is known that if the particles are made fine to a level of 50 nm or less, an image having high saturation and high transparency close to that of a dye ink can be formed.

  However, in order to finely disperse and disperse the pigment to a level of 50 nm or less, it is necessary to use a large amount of a dispersant that is adsorbed on the total pigment surface area that increases as the finely divided dispersion is used. As a result, the ink liquid easily bubbles, and as a result, it becomes difficult to discharge with an ink jet printer, causing image blurring, clogging, and the like.

Several ink compositions containing a modified polysiloxane compound are known.
For example, a compound having an oxyalkylene group at the end of a linear polyalkylsiloxane (so-called terminal-modified type) is used as an antifoaming agent (see Patent Document 9), and a polyalkylene is used as the side chain of the linear polydimethylsiloxane. An example of improving the frequency response by using a compound having an oxide group (so-called pendant type) and increasing the drying speed of the ink (Patent Document 10). An oxyalkylene group is added to the end of the linear polydimethylsiloxane. Example (Patent Document 11) in which an ink having no image blurring and excellent drying properties is provided by using a compound having a so-called end-modified compound (Patent Document 11), a polyalkylene oxide group as a side chain of a linear polyalkylsiloxane Ink pool on the surface of the nozzle plate by using a compound (so-called pendant type) An example in which the number of nozzle failures can be reduced (Patent Document 12), and by using a compound (so-called pendant type) having a polyalkylene oxide group as a side chain of a linear polyalkylsiloxane. There is an example (see Patent Document 13) in which ink with little image blurring and bleeding and excellent ejection stability is provided.

However, all of these have a structure having an oxyalkylene group at the terminal (so-called terminal-modified type) with respect to the linear polyalkylsiloxane main skeleton, or a polyalkylene oxide in the side chain with respect to the linear polyalkylsiloxane main skeleton. This is a structure having a group (so-called pendant type), and is completely different from the linear block copolymer in which dimethylpolysiloxane and polyalkylene oxide are alternately and repeatedly bonded in the present invention.
Therefore, the present invention is not an invention that achieves both the effect of improving the saturation of an image and the effect of suppressing the bubbling of the ink and improving the discharge performance of the printer, which are the subject of the present invention.

JP-A-63-51485 JP-A 63-56575 Japanese Patent Laid-Open No. 1-198671 Japanese Patent Laid-Open No. 57-10660 Japanese Patent Laid-Open No. 57-10661 JP-A-2-255875 JP 2004-2715 A JP 2004-169008 A Japanese Patent Publication No. 1-30872 Japanese Patent No. 3120347 Japanese Patent Laid-Open No. 10-310732 Japanese Patent Laid-Open No. 10-279871 JP 2004-131644 A

  The present invention has been made in view of the above problems, and improves the saturation of an image formed with a pigment-based ink-jet ink, suppresses foaming of the ink, puts the ink in a practical range, and It is an object of the present invention to provide an ink-jet ink that can be used for printing with an ink-jet printer with good ejection stability.

  In order to solve the above-described problems, the pigment-based inkjet ink according to the present invention contains a linear block copolymer in which dimethylpolysiloxane and polyalkylene oxide are alternately and repeatedly bonded, thereby suppressing ink bubbling. Thus, the ejection stability of the ink jet printer can be improved, and the saturation of the image can be increased.

That is, the said subject is solved by the structure of following (1)-(22).
(1) “ Pigment-based ink - jet ink comprising a linear block copolymer in which pigment, water, water-soluble organic solvent, dimethylpolysiloxane and polyalkylene oxide are alternately and repeatedly bonded”;
(2) The pigment-based inkjet ink according to item (1), wherein the polyalkylene oxide part of the block copolymer is a copolymer of ethylene oxide and propylene oxide;
(3) The pigment-based inkjet according to (1) or (2) above, wherein the block copolymer is contained in an amount of 0.01 to 3% by weight, preferably 0.1 to 3% by weight. ink";
(4) “The pigment-based inkjet ink according to any one of (1) to (3) above, wherein the pigment has an average particle diameter of 10 to 200 nm”;
(5) “ Pigment-based inkjet ink according to any one of (1) to (4) above, comprising 1 to 15% by weight of the pigment ”;
(6) “ Pigment-based inkjet ink according to any one of (1) to (5) above, wherein the pigment is dispersed with a surfactant”;
(7) “ Pigment-based inkjet ink according to item (6), wherein the surfactant is a nonionic surfactant”;
(8) The pigment-based inkjet ink according to item (7), wherein the surfactant is a compound represented by the following general formula (I);

（式中、Ｒ_１は炭素数１〜２０のアルキル基、アリル基、アラルキル基を表わし、ｌは０〜７の整数を表わし、ｍは２０〜２００の整数を表わす。）」；
（９）「前記界面活性剤が、ＰＯＥ（ｎ＝４０）βナフチルエーテルであることを特徴とする前記第（８）項に記載の顔料系インクジェット用インク」；
（１０）「アルカンジオールをさらに含んでなることを特徴とする前記第（１）乃至（９）項のいずれかに記載の顔料系インクジェット用インク」；
（１１）「前記アルカンジオールが２−エチル−１．３−ヘキサンジオールであることを特徴とする前記第（１０）項に記載の顔料系インクジェット用インク」；
（１２）「前記アルカンジオールを０．２〜１５重量％含んでなることを特徴とする前記第（１０）又は（１１）項に記載の顔料系インクジェット用インク」；
（１３）「アセチレングリコール系界面活性剤をさらに含んでなることを特徴とする前記第（１）乃至（１２）項のいずれかに記載の顔料系インクジェット用インク」；
（１４）「前記第（１）乃至（１３）項のいずれかに記載の顔料系インクジェット用インクを含有することを特徴とするインクカートリッジ」；
（１５）「画像形成装置に着脱可能であることを特徴とする前記第（１４）項に記載のインクカートリッジ」；
（１６）「前記第（１）乃至（１３）項のいずれかに記載の顔料系インクジェット用インクを用いて受容体に画像が形成されていることを特徴とする画像形成体」；
（１７）「前記第（１）乃至（１３）項のいずれかに記載の顔料系インクジェット用インクを用いて受容体に画像を形成することを特徴とする画像形成方法」；
（１８）「前記画像形成装置がインクジェットプリンターであることを特徴とする前記第（１５）項に記載のインクカートリッジ」；
（１９）「インクジェットプリンターから受容体に前記第（１）乃至（１３）項のいずれかに記載の顔料系インクジェット用インクを吐出させることを特徴とする前記第（１７）項に記載の画像形成方法」；
（２０）「前記インクジェットプリンターが、ピエゾ方式のインクジェットプリンターであることを特徴とする前記第（１９）項に記載の画像形成方法」；
（２１）「前記インクジェットプリンターが、サーマル方式のインクジェットプリンターであることを特徴とする前記第（１９）項に記載の画像形成方法」；
（２２）「前記受容体が紙であることを特徴とする前記第（１６）項に記載の画像形成体」

(Wherein R ₁ represents an alkyl group having 1 to 20 carbon atoms, an allyl group, or an aralkyl group, l represents an integer of 0 to 7, and m represents an integer of 20 to 200).
(9) “The pigment-based inkjet ink according to (8) above, wherein the surfactant is POE (n = 40) β-naphthyl ether”;
(10) “ Pigment-based inkjet ink according to any one of (1) to (9) above, further comprising alkanediol”;
(11) “ Pigment-based inkjet ink according to item (10), wherein the alkanediol is 2-ethyl-1.3-hexanediol”;
(12) “ Pigment-based inkjet ink according to item (10) or (11) above, comprising 0.2 to 15% by weight of the alkanediol”;
(13) “ Pigment inkjet ink according to any one of (1) to (12) above, further comprising an acetylene glycol surfactant”;
(14) "Ink cartridge comprising the pigment-based inkjet ink according to any one of (1) to (13)";
(15) “Ink cartridge according to item (14), which is detachable from the image forming apparatus”;
(16) "An image forming body in which an image is formed on a receptor using the pigment-based inkjet ink according to any one of (1) to (13)";
(17) "An image forming method comprising forming an image on a receptor using the pigment-based inkjet ink according to any one of (1) to (13)";
(18) "The ink cartridge according to item (15), wherein the image forming apparatus is an ink jet printer";
(19) The image formation according to (17), wherein the pigment-based inkjet ink according to any one of (1) to (13) is ejected from an inkjet printer to a receiver. Method";
(20) “The image forming method according to (19), wherein the ink jet printer is a piezo ink jet printer”;
(21) “The image forming method according to (19), wherein the ink jet printer is a thermal ink jet printer”;
(22) “The image forming body according to item (16), wherein the receptor is paper”

  As will be apparent from the following detailed and specific description, it can be seen that the ink jet ink of the present invention has high image saturation and excellent ejection stability. This provides an extremely excellent effect of providing pigment-based inkjet inks with high image saturation and high image saturation, high bubbling suppression effect and high image saturation, and excessive ink wetting on the nozzle surface. In addition, pigment-based inkjet ink with higher image saturation is provided without causing problems such as bending of the flying direction of ink during ink ejection, ink storage stability is good, and image saturation is high. The nozzles are less clogged and the ink ejection stability is excellent.

As described above, according to the items (1) to (3), it is possible to provide a pigment-based inkjet ink that suppresses foaming of ink and has high image saturation.
The polyalkylene oxide portion of the block copolymer may be polyethylene oxide, propylene oxide, or a copolymer thereof, but in the present invention, it was the copolymerization of ethylene oxide and propylene oxide that was more effective in suppressing foaming.

The content of the block copolymer is preferably 0.01 to 3% by weight, more preferably 0.1 to 2% by weight. When the content is less than 0.01% by weight, the effect of suppressing foaming is low and the image saturation is also low. When the content is more than 3% by weight, ink wetting on the nozzle surface increases, and the ink flying direction is bent during ink ejection. Such problems occur.
Some of the block copolymers are commercially available and can be used. For example, there are silicone surfactants FZ-2203, FZ-2207, FZ-2208 and the like marketed by Nippon Unicar Co., Ltd.

According to the item (4), as described above, a pigment-based inkjet ink having higher image saturation is provided.
That is, the average particle diameter of the pigment is preferably 10 to 200 nm, more preferably 20 to 100 nm.
When the average particle diameter is smaller than 10 nm, dispersion for a long time is required, and the storage stability of the ink also deteriorates. When the average particle diameter exceeds 200 nm, not only the image saturation is lowered, but also nozzle clogging is increased, and ink ejection stability is deteriorated.
In addition, the average particle diameter of the pigment in this invention has shown the value measured by Nikkiso Co., Ltd. Microtrac UPA.

According to the item (5), as described above, a pigment-based inkjet ink having better ejection stability is provided.
The content of the pigment is preferably 1 to 15% by weight, more preferably 3 to 12% by weight.
When the pigment content is less than 1% by weight, the image density is low, and when it is more than 15% by weight, nozzle clogging increases and ink ejection stability deteriorates.

According to the above items (6) to (9), as described above, a pigment-based ink-jet ink is provided that is more suppressed in foaming of ink and has high image saturation.
In order to disperse the pigment with the surfactant, the pigment powder, water and the surfactant are premixed and then dispersed by a known method using a dispersing machine such as a sand mill or a dyno mill.
Water, a water-soluble organic solvent, and, if necessary, a surfactant, a preservative, and the like are added to the pigment dispersion thus obtained to prepare an inkjet ink.

  As the surfactant, an anionic, nonionic, cationic or amphoteric surfactant can be used.

  Anionic surfactants include fatty acid salts, alkyl sulfate salts, alkyl aryl sulfonates, alkyl naphthalene sulfonates, dialkyl sulfonates, dialkyl sulfosuccinates, alkyl diaryl ether disulfonates, alkyl phosphates, Examples include polyoxyethylene alkyl ether sulfate, polyoxyethylene alkyl aryl ether sulfate, naphthalenesulfonic acid formalin condensate, polyoxyethylene alkyl phosphate ester salt, glycerol borate fatty acid ester, polyoxyethylene glycerol fatty acid ester, etc. The

  Nonionic surfactants include polyoxyethylene alkyl ether, polyoxyethylene alkyl aryl ether, polyoxyethylene oxypropylene block copolymer, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene sorbitol fatty acid ester, glycerin fatty acid ester And polyoxyethylene fatty acid ester, polyoxyethylene alkylamine, fluorine-based, silicon-based and the like.

Examples of the cationic surfactant include alkylamine salts, quaternary ammonium salts, alkylpyridinium salts, alkylimidazolium salts and the like.
Examples of amphoteric surfactants include alkylbetaines, alkylamine oxides, phosphadylcholines, and the like.

  Among these, nonionic surfactants are more preferably used, and particularly the compounds of the above general formula (I), among which POE (n = 40) β naphthyl ether can be particularly preferably used.

According to the items (10) to (13), there is provided a pigment-based ink-jet ink in which foaming of ink is further suppressed and image saturation is high.
The content of alkanediol is preferably 0.2 to 15% by weight, more preferably 0.3 to 10% by weight.

When the content of alkanediol is less than 0.2% by weight, image saturation is lowered, and when it is more than 15% by weight, the storage stability of the ink is deteriorated.
The alkanediol is not particularly limited, but preferably 1,2-hexanediol, 1,2-heptanediol, 1,3-heptanediol, 2-methyl-1,3-hexanediol, 2- And butyl-2-ethyl-propanediol, 2-ethyl-1,3-hexanediol, and the like.
Among these, 2-ethyl-1,3-hexanediol is preferable because the image saturation becomes higher.
It is preferable to include an acetylene glycol surfactant since the image saturation is further increased.

  The content of the acetylene glycol surfactant is preferably 0.1 to 12% by weight, more preferably 0.1 to 5% by weight. The acetylene glycol surfactant is not particularly limited, but preferably 2,4,7,9-tetramethyl-5-decyne-4,7-diol, 3,6-dimethyl-4-octyne. In addition to 3,6-diol and 3,5-dimethyl-1-hexyn-3-ol, commercially available products include Surfynol 104, 82, 465, 485, or TG (obtained from Air Products and Chemicals. Inc.) Yes), Olphine STG, Olphine E1010 (above, Nissin Chemical Co., Ltd. trade name) and the like.

The ink-jet ink of the present invention comprises a pigment as a colorant.
As the pigment, either an inorganic pigment or an organic pigment can be used.
Specific examples of the inorganic pigment include carbon black produced by a known method such as a contact method, a furnace method, and a thermal method in addition to titanium oxide and iron oxide.
Specific examples of the organic pigment include an azo pigment, a phthalocyanine pigment, a perylene pigment, an anthraquinone pigment, a quinacridone pigment, a dioxazine pigment, a thioindigo pigment, an isoindolinone pigment, a quinophthalone pigment, a nitro pigment, a nitroso pigment, and aniline black.

  Specific examples of the pigment include carbon black, No. manufactured by Mitsubishi Chemical Corporation. 2300, no. 2200B, no. 900, no. 33, no. 40, no. 45, no. 45L, no. 52, HCF88, MA7, MA8, MA100, etc. are Raven 5750, Raven 5250, Raven 5000, Raven 3500, Raven 1255, Raven 700, etc. manufactured by Colombia. , Monarch 880, Monarch 900, Monarch 1000, Monarch 1100, Monarch 1300, Monarch 1400, etc. are manufactured by Degussa Color Black FW1, FW2, FW2V, FW18, FW200, S150, S160, U, S160, U V, 140U, Special Black 6, 5, 4, 4A, NIPEX 150, NIPEX 160, NIPEX 170, NIPEX 180, and the like.

  Specific examples of pigments used in yellow ink include C.I. I. Pigment Yellow 1, 2, 3, 12, 13, 14, 16, 17, 73, 74, 75, 83, 93, 95, 97, 98, 109, 110, 114, 120, 128, 129, 138, 150, 151, 154, 155, 174, 180, 185 and the like.

  Specific examples of pigments used in magenta ink include C.I. I. Pigment Red 5, 7, 12, 48 (Ca), 48 (Mn), 57 (Ca), 57: 1, 112, 122, 123, 146, 168, 176, 184, 185, 202, 209, Pigment Violet 19 Etc.

  Specific examples of pigments used for cyan ink include C.I. I. Pigment blue 1, 2, 3, 15, 15: 3, 15: 4, 16, 22, 60, 63, 66, and the like.

  In the present invention, the pigment may be a so-called self-dispersing pigment (surface-treated pigment) having a water dispersibility-imparting group on its surface and capable of stably maintaining a dispersed state even without a dispersant, or the entire pigment surface. A so-called capsule type pigment (water-dispersible polymer-containing pigment) that can be coated with a polymer and can stably maintain a dispersed state without a dispersant, or a pigment dispersed with a dispersant may be used.

In the present invention, the pigment is preferably added to the ink as a pigment dispersion dispersed by a surfactant.
As the surfactant, a nonionic surfactant is preferable, and a compound represented by the following general formula (I) is more preferable.

（式中、Ｒ_１は炭素数１〜２０のアルキル基、アリル基、アラルキル基を表わし、ｌは０〜７の整数を表わし、ｍは３０〜６０の整数を表わす。）

(In the formula, R ₁ represents an alkyl group having 1 to 20 carbon atoms, an allyl group, or an aralkyl group, l represents an integer of 0 to 7, and m represents an integer of 30 to 60.)

In the inkjet ink of the present invention, the water can be pure water such as ion exchange water, ultrafiltration water, reverse osmosis water, distilled water, or ultrapure water.
In addition, the use of water sterilized by ultraviolet irradiation or addition of hydrogen peroxide is preferable because generation of mold and bacteria can be prevented when the ink is stored for a long period of time.

  Examples of the water-soluble organic solvent contained in the inkjet ink in the present invention include carbon such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, and tert-butyl alcohol. 1 to 4 alkyl alcohols; amides such as dimethylformamide and dimethylacetamide; ketones or ketone alcohols such as acetone, methyl ethyl ketone and diacetone alcohol; ethers such as tetrahydrofuran and dioxane; ethylene glycol, propylene glycol, 1, 2-propanediol, 1,2-butanediol, 1,3-butanediol, 3-methyl-1,3-butanediol, 1,4-butanediol, diethylene glycol, triethyl Polyhydric alcohols such as ethylene glycol, 1,2,6-hexanetriol, thiodiglycol, hexylene glycol and glycerin; polyalkylene glycols such as polyethylene glycol and polypropylene glycol; ethylene glycol monomethyl (or ethyl) ether, diethylene glycol Lower alkyl ethers of polyhydric alcohols such as methyl (or ethyl) ether and triethylene glycol monomethyl (or ethyl) ether; alkanolamines such as monoethanolamine, diethanolamine and triethanolamine; N-methyl-2-pyrrolidone; Examples include 2-pyrrolidone and 1,3-dimethyl-2-imidazolidinone.

Among the water-soluble organic solvents, polyhydric alcohols such as diethylene glycol or lower alkyl ethers of polyhydric alcohols such as triethylene glycol monomethyl (or ethyl) ether are preferable.
In addition, the content of the water-soluble organic solvent in the ink jet ink is preferably 50% by weight or less in consideration of environmental properties and the like.

  In addition to the water-soluble organic solvent, a pH adjuster, preservative, resin, and the like may be used as necessary for the inkjet ink in the present invention.

  Examples of the means for printing using the inkjet ink of the present invention include a printing method using an inkjet printer (inkjet printer) having a continuous jet type or on-demand type recording head. Note that examples of the on-demand type include a piezo method, a thermal ink jet method, and an electrostatic method.

  Further, the present invention relates to the configuration of an ink cartridge containing the ink composition of the present invention, the configuration of an ink jet printing apparatus that performs recording by discharging the ink composition of the present invention, and the image forming method in the printing apparatus. By referring to known techniques in the technical field, such as those disclosed in Japanese Patent Application Laid-Open No. 2000-198958, it can be easily implemented.

EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples at all. In addition, the number of parts in an Example represents a weight part.
Example 1
150 parts of Pigment Red 122 (Ciba Specialty Chemicals, Irgaphora Magenta DMQ)
POE (n = 40) β naphthyl ether 56 parts Distilled water 794 parts After premixing the above mixture, it is circulated for 20 hours in a disk type bead mill (Shinmaru Enterprises KDL type, media: 0.3 mmφ zirconia ball used) Dispersion was performed to obtain a pigment dispersion (A) having an average particle diameter of 63.5 nm.
Using the pigment dispersion (A) obtained by the above method, an ink liquid was prepared according to the following ink formulation 1, stirred for 30 minutes, filtered through a membrane filter having a pore size of 0.8 μm, and vacuum degassed. Inkjet ink (a) was obtained.

Ink formula 1
Pigment dispersion (A) 40.0 parts Glycerin 7.5 parts Diethylene glycol 22.5 parts Block copolymer 0.1 part (Nippon Unicar FZ-2203)
29.9 parts distilled water

Example 2
A pigment dispersion (B) having an average particle size of 68.8 nm was obtained in the same manner as in Example 1 except that Pigment Red 122 was changed to the following material in Example 1 and the dispersion time was 23 hours.
Pigment Blue 15: 3 150 parts (Toyo Ink Co., Ltd., LIONOL BLUE FG-7351)
The pigment dispersion (B) obtained by the above method is used in place of the pigment dispersion (A) of the ink formulation 1 to prepare an ink solution, stirred for 30 minutes, and then filtered with a membrane filter having a pore size of 0.8 μm. Filtration and vacuum degassing gave ink-jet ink (b) of the present invention.

Example 3
A pigment dispersion (C) having an average particle diameter of 12.4 nm was obtained in the same manner as in Example 1 except that Pigment Red 122 was changed to the following material in Example 1 and the dispersion time was changed to 14 hours.
150 parts of Pigment Yellow 74 (Daihin Seika Co., Ltd., Yellow No. 43)
The pigment dispersion (C) obtained by the above method was used in place of the pigment dispersion (A) of the ink formulation 1 to prepare an ink solution. After stirring for 30 minutes, a membrane filter having a pore size of 0.8 μm was used. Filtration and vacuum degassing yielded an inkjet ink (c) of the present invention.

Example 4
Example 1 is the same as Example 1 except that the amount of the block copolymer (FZ-2203 manufactured by Nihon Unicar Co., Ltd.) used in the ink formulation 1 is 0.01 parts and the amount of distilled water used is 29.99 parts. Thus, an inkjet ink (d) of the present invention was obtained.

Example 5
In Example 1, except that the amount of the block copolymer (FZ-2203 manufactured by Nihon Unicar Co., Ltd.) in the ink formulation 1 was 3 parts and the amount of distilled water was 27 parts, the same procedure as in Example 1 was repeated. An ink jet ink (e) of the invention was obtained.

Example 6
In the same manner as in Example 1 except that 3 parts of 2-ethyl-1,3-hexanediol was further added to the ink formulation 1 in Example 1 and the amount of distilled water used was 26.9 parts. Ink jet ink (f) was obtained.

Example 7
Example 1 is the same as Example 1 except that 0.1 part of acetylene glycol surfactant (Olphine STG manufactured by Nissin Chemical Co., Ltd.) is further added to Ink Formula 1 and the amount of distilled water used is 29.8 parts. Similarly, an inkjet ink (g) of the present invention was obtained.

Example 8
In Example 1, 3 parts of 2-ethyl-1,3-hexanediol and 0.1 part of acetylene glycol surfactant (Olfin STG manufactured by Nissin Chemical Co., Ltd.) were added to ink formulation 1, and the amount of distilled water used. The inkjet ink (h) of the present invention was obtained in the same manner as in Example 1 except that 26.8 parts was used.

Comparative Example 1
Inkjet recording was conducted in the same manner as in Example 1 except that the amount of the block copolymer (FZ-2203 manufactured by Nihon Unicar Co., Ltd.) used in the ink formulation 1 was 0 part and the amount of distilled water was 30 parts. Ink (i) was obtained.

Comparative Example 2
Inkjet ink jet recording was carried out in the same manner as in Example 2 except that the amount of the block copolymer (FZ-2203 manufactured by Nihon Unicar Co., Ltd.) in ink formulation 1 was 0 part and the amount of distilled water was 30 parts. Ink (j) was obtained.

Comparative Example 3
Inkjet inkjet recording was conducted in the same manner as in Example 3 except that the amount of the block copolymer (FZ-2203 manufactured by Nihon Unicar Co., Ltd.) in ink formulation 1 was 0 part and the amount of distilled water was 30 parts. Ink (k) was obtained.

Comparative Example 4
In Example 1, except that a pendant polymer (BYK347 manufactured by Big Chemie Japan) was used in place of the block copolymer (FZ-2203 manufactured by Nihon Unicar Co., Ltd.) in the ink formulation 1, the same as in Example 1 was used. Ink (l) was obtained.

Comparative Example 5
In Example 1, except that a terminal-modified polymer (L-700, manufactured by Nihon Unicar) was used instead of the block copolymer (FZ-2203, manufactured by Nihon Unicar) in the ink formulation 1, in the same manner as in Example 1, Ink jet ink (m) was obtained.

The inkjet inks (a) to (m) thus obtained were printed on plain paper (X-4024) with a piezoelectric inkjet printer EM-930C manufactured by EPSON and a thermal inkjet printer Desk Jet 880C manufactured by HP. ), But good print images were obtained in all cases. The printed image with EM-930C was measured with an Xrite densitometer, and the image saturation was calculated. The results are shown in Table 1.
In Table 1, the saturation of an image refers to the distance from the origin on the chromaticity diagram when the solid image of the image sample is measured with an Xrite densitometer and plotted on the chromaticity diagram. More specifically, about a value and b value on the chromaticity diagram

をいう。
次に、面積率７０％のベタ画像テストパターンをインクジェットプリンターＥＭ−９３０Ｃ及びインクジェットプリンターＤｅｓｋ Ｊｅｔ ８８０ＣでＡ４サイズの普通紙に連続で２００枚印字し、印字終了後、ノズルチェックパターンを印字して目詰まり（不吐出）を起こしているノズルの数を数えた。その結果を表１に示す。

Say.
Next, 200 sheets of a solid image test pattern with an area ratio of 70% were continuously printed on A4 size plain paper with the ink jet printer EM-930C and the ink jet printer Desk Jet 880C. The number of nozzles causing clogging (non-ejection) was counted. The results are shown in Table 1.

Claims (15)

A pigment-based inkjet ink comprising 0.1 to 3% by weight of a linear block copolymer in which pigment, water, water-soluble organic solvent, dimethylpolysiloxane and polyalkylene oxide are alternately and repeatedly bonded. 2. The pigment-based inkjet ink according to claim 1, wherein the polyalkylene oxide portion of the block copolymer is a copolymer of ethylene oxide and propylene oxide. The pigment-based inkjet ink according to claim 1 or 2, wherein the pigment has an average particle size of 10 to 200 nm. 4. The pigment-based inkjet ink according to claim 1, comprising 1 to 15% by weight of the pigment . The pigment-based inkjet ink according to any one of claims 1 to 4, wherein the pigment is dispersed with a surfactant. The pigment-based inkjet ink according to claim 5, wherein the surfactant is a nonionic surfactant. The pigment-based inkjet ink according to claim 6, wherein the surfactant is a compound represented by the following general formula (I).

(In the formula, R ₁ represents an alkyl group having 1 to 20 carbon atoms, an allyl group or an aralkyl group, l represents an integer of 0 to 7, and m represents an integer of 20 to 200.) The pigment-based inkjet ink according to claim 7, wherein the surfactant is POE (n = 40) β-naphthyl ether. The pigment-based inkjet ink according to claim 1, further comprising alkanediol. The pigment-based inkjet ink according to claim 9, wherein the alkanediol is 2-ethyl-1.3-hexanediol. The pigment-based inkjet ink according to claim 9 or 10, comprising 0.2 to 15% by weight of the alkanediol. The pigment-based inkjet ink according to any one of claims 1 to 11, further comprising an acetylene glycol-based surfactant. An ink cartridge comprising the pigment-based inkjet ink according to claim 1. An image forming method comprising forming an image on a receptor using the pigment-based inkjet ink according to claim 1. The image forming method according to claim 14, wherein the pigment-based ink - jet ink according to claim 1 is ejected from an ink-jet printer to a receiver.