JP2956948B2 - Ink jet recording liquid - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording liquid suitable for an ink jet system in which liquid droplets are ejected from an orifice of a recording head to perform recording, and more particularly, to an excellent ink characteristic having little sedimentation and liquid separation. It has excellent mechanical properties such as dischargeability, continuous stability, non-clogging property, good drying resistance at the discharge orifice, fixing property,
The present invention relates to an ink jet recording liquid having excellent print characteristics such as print density and print quality.

[0002]

2. Description of the Related Art Conventionally, writing instruments (sign pens, water-based ball pens, etc.) for recording on a recording material such as paper have various dyes and pigments dissolved in water or other organic solvents as ink. Dispersed ones are used. Further, in a so-called ink jet recording method in which ink in a head is ejected from fine nozzles by electrostatic printing force caused by the vibration or heat of a pressure oscillator or high voltage and electrostatic printing force is applied to perform recording, various dyes, Pigments dissolved or dispersed in water or other organic solvents are used.

However, compared to stationery inks such as general felt-tip pens and water-based ball pens, the recording liquid used in the ink jet recording system performs recording by generating ink droplets from extremely fine nozzles. Therefore, more precise conditions are required for many characteristics.

[0004] In other words, the recording liquid for ink-jet recording includes: 1. proper physical properties (viscosity, particle diameter, surface tension, specific conductivity,
Density). 2. It is stable for long-term storage, and solids do not precipitate or do not adhere to the vicinity of the nozzle when not in use for a long time or when printing is suspended.

[0005] 3. The printed image has sufficiently high contrast and sharpness. 4. The printed image has excellent water resistance and fixability. 5. Able to print with contrast without the need for specific fixing process for plain paper. It is necessary to satisfy such conditions.

At present, as ink for ink jet recording,
Basically, an aqueous ink containing a dye, water and a water-miscible organic solvent as a solvent is mainly used, but the physical properties of the recording liquid largely depend on the intrinsic properties of the dye.

Therefore, when ink-jet recording is performed using a recording liquid containing a water-soluble dye, the resulting recorded image is affected by the physical properties of the water-soluble dye, and thus has poor water and light fastness. There was a drawback that it would be inferior. Further, the storage stability of the recording liquid itself containing such a water-soluble dye is not so high.

In the recorded print, the water-soluble dye easily bleeds on the paper, and only a low contrast and unclear image can be obtained. Therefore, recently, an attempt has been made to apply a pigment-based recording liquid to an ink jet recording system in place of such a dye-based ink. This pigment-based recording liquid has an advantage that the light resistance and water resistance of the obtained recorded image are extremely good as compared with the image obtained by the dye-based recording liquid.

[0009]

However, since the pigment is insoluble in the recording liquid medium, a high level of technique is required for finely dispersing it in the recording liquid, and the dispersion stability is maintained for a long period of time. It was very difficult.

An object of the present invention is to provide an ink jet recording resin and an ink jet recording ink (hereinafter, referred to as a recording liquid) which do not cause nozzle clogging for a long period of time and maintain good ejection stability. Another object is to provide a safe and low-odor recording solution for the human body.

It is still another object of the present invention to provide a recording liquid which is excellent in print fixability, print density, print quality and the like, and provides clear and contrast images without bleeding on plain paper.

[0012]

[Means for solving the problems]

That is, the ink jet recording liquid of the present invention comprises an aqueous pigment-dispersed ink jet recording liquid containing a pigment and an emulsifier, wherein the medium is an aqueous medium. Alkyl sulfide terminal group having a molecular weight of 500 to
An inkjet recording liquid characterized by being a 40,000 oligomer emulsifier.

Preferably, the emulsifier is represented by the following general formula (1) and / or (2)

[0015]

Embedded image

[0016]

Embedded image Here, R ₁ is an alkyl group having 5 to 20 carbon atoms (that is, all groups represented by the general formula C _n H _{2n + 1} ).

R ₂ , R ₃ , R ₅ : hydrogen or an alkyl group having 1 to 5 carbon atoms (general formula C _n H _{2n + 1} ), or a carboxyl group, a carboxylate ester group or an ammonium base, amine base or alkali of a carboxylic acid Metal base or alkaline earth metal base

R₄: Hydrogen, halogen or alkyl group having 1 to 4 carbon atoms
(General formula C_nH_{2n + 1}) X: cyano group, -COOCH₃Group, -OCOCH₃Or -OCOC₂H₅  Y: hydrogen, ammonium group, amine base, alkali metal
Or alkaline earth metal

And b / (a + b) is in the range of 0.45 to 0.95.

[0020]

Also preferably, the pigment has a DBP adsorption amount of 7
This is an ink jet recording liquid characterized by using carbon black having characteristics of 0 to 200 [DBPml / 100 g] and PH of 2 to 6.

To explain the present invention in detail, a conventional aqueous pigment dispersion using a polymer dispersant has a considerably high viscosity, and the viscosity of such a conventional aqueous pigment dispersion is
When the viscosity is reduced to obtain a viscosity suitable for ink jet recording (1 to 30 CPS), pigment particles aggregate and sediment, making it impossible to use the ink for ink jet recording.

The inventors of the present invention have conducted intensive studies to obtain a finely dispersed and highly stable aqueous pigment dispersion suitable for an ink jet recording liquid. It has been found that when an oligomer emulsifier having a terminal group having a molecular weight of 500 to 4000 and a pigment are mixed and milled, the pigment is very finely dispersed and its storage stability is extremely high.

In the step of mixing and grinding the pigment and the oligomer-emulsifier, which will be described later, an alkyl group, which is a hydrophobic portion of the dispersant, is used to stabilize the crystal energy of the pigment, The hydrophilic portion is adsorbed to the outside of the pigment particles, that is, dissolved in the aqueous medium, so that the hydrophilic portions on the pigment surface repel each other, so that the pigment does not accumulate, and the It is considered that these are dispersed stably.

The oligomer emulsifier used as an emulsifier in the present invention is mainly an oligomer polymer of a monomer having an addition-polymerizable vinyl group and a mercaptan having a long-chain alkyl group. ) And / or (2)

[0026]

Embedded image

[0027]

Embedded image

R ₁ is an alkyl group having 5 to 20 carbon atoms (that is, all groups represented by the general formula CnH ₂ n + ₁ ).

R ₂ , R ₃ , R ₅ : hydrogen or an alkyl group having 1 to 5 carbon atoms (general formula C _n H _{2n + 1} ), or a carboxyl group, a carboxylate group or an ammonium base of a carboxylic acid, an amine base, or an alkali Metal base or alkaline earth metal base

R₄: Hydrogen, halogen or alkyl group having 1 to 4 carbon atoms
(General formula C_nH_{2n + 1}) X: cyano group, -COOCH₃Group, -OCOCH₃Or -OCOC₂H₅  Y: hydrogen, ammonium group, amine base, alkali metal
Or alkaline earth metal

[0031] These can be used alone or in combination of two or more.

Examples of the hydrophobic moiety include alkyl mercaptans having an alkyl group having 5 to 20 carbon atoms. Specific examples include n-butyl mercaptan, n-hexyl mercaptan octyl mercaptan, decarmercaptan, dodecyl mercaptan, and tetradecane mercaptan. Is introduced into the polymer terminal using an alkyl mercaptan. Particularly preferred are octyl mercaptan and dodecyl mercaptan.

On the other hand, as the monomer unit for introducing a hydrophilic moiety, a monomer having a carboxyl group, specifically, acrylic acid, methacrylic acid, crotonic acid, itaconic acid, itaconic acid monoester, maleic acid, maleic acid And α-β-unsaturated monomers such as monoester, fumaric acid and fumaric acid monoester, and monomers such as acrylonitrile, methylacrylonitrile, ethylacrylonitrile, vinyl acetate, styrene and styrene derivatives.

It can be used in the range of b / (a + b) = 0.45 to 0.95, particularly preferably in the range of 0.5 to 0.8. When the above ratio is less than 0.45, hydrophilicity is lacking, and dispersibility of the pigment is deteriorated.

In the present invention, it is necessary to form a salt of the oligomer for the purpose of solubilizing the oligomer in an aqueous liquid. Examples of such salts include ammonium salts, aliphatic amines or amine salts such as alcohol amines, and alkali metal salts or alkaline earth metal salts such as Na or K.

The oligomer emulsifier used in the present invention preferably has a molecular weight of 500-4000. If the molecular weight is too high exceeding 4000, the viscosity of the dispersion tends to increase,
In some cases, stable ejection cannot be obtained as ink for inkjet recording. If the molecular weight is too low, less than 500, the dispersion stability of the pigment tends to be poor, and the long-term storage stability is poor.

The oligomer-emulsifier having an alkyl sulfide terminal group used in the present invention can be prepared by any known polymerization method, such as bulk polymerization, suspension polymerization, emulsion polymerization, solution polymerization under high pressure, and the like. The polymerization is carried out by a usual radical polymerization method, but solution polymerization and bulk polymerization are preferred because those having a relatively small molecular weight are easily obtained.

For example, in a low-boiling alcohol solvent having a temperature of 100 ° C. or lower (eg, methanol, ethanol, propanol)
Solution polymerization using a persulfate or a peroxide and, if necessary, a reducing agent in the presence of an alkyl mercaptan, and adding an alkali metal hydroxide such as potassium hydroxide and water. After adjusting the pH to 5 to 9, the alcohol solvent and the residual monomer are removed under reduced pressure.

In the polymerization, the monomer mixture, the polymerization initiator, and the alkyl mercaptan may be charged all at once from the beginning of the polymerization, or only a part may be charged at the beginning and the remaining mixture may be charged with the progress of the polymerization reaction. It may be dropped.

The pigment is used as a colorant, and various known pigments can be used. Specific examples thereof include azo pigments, condensed polyazo pigments, phthalocyanine pigments, quinacdrine pigments, and anthraquinone pigments. Organic pigments such as dioxazine pigments, indigo pigments, isoindolenone pigments, thioindigo pigments, perinone pigments, perylene pigments; inorganic pigments such as titanium oxide, iron oxide, and carbon black; and fluorescent pigments Is mentioned.

Further, as the above-mentioned pigments, those subjected to a grafting treatment or a surface treatment can of course be used.

Particularly, carbon black can be typically used as a black recording liquid, but the viscosity of the dispersion liquid tends to increase.
Also, it has been difficult to maintain the dispersed particle size over a long period of time. However, when an oligomer emulsifier having an alkyl sulfide terminal group is used, the amount of DBP adsorbed is 70 to 200 [DBP ml / mg], and carbon black having a pH of 2 to 6 is dispersed. It was found that the viscosity of the liquid was low, and there was no liquid separation or sedimentation over a long period of time, and the initial dispersion particle size was maintained.

The preferred concentration of the pigment in the ink is determined by its influence on the coloring power and ink viscosity, but it can be used in the range of 2 to 30% by weight based on the total weight of the ink.
The preferred concentration of the oligomer-emulsifier varies depending on the type of the pigment, but can be used in the range of 2 to 40% by weight, more preferably 3 to 30% by weight, based on the weight of the pigment.
The storage stability is poor at the weight end, and if it exceeds 40% by weight,
Bubbling is likely to occur, and stable ejection cannot be obtained.

The recording liquid used in the present invention may contain, in addition to the above essential components, various conventionally known additives such as a water-soluble organic solvent, a pH adjuster, a defoamer, a preservative, a surface tension adjuster, Surfactants, salts, synthetic and natural resins, various dyes and the like can be used in combination.

Examples of the pH adjuster include various organic amines such as diethanolamine and triethanolamine; inorganic alkali agents such as alkali metal hydroxides such as sodium hydroxide, lithium hydroxide and potassium hydroxide; Organic acids and mineral acids.

As synthetic and natural resins, water-soluble resins and emulsion resins can be used.
Proteins such as gelatin, albumin and casein, natural gums such as gum arabic and tragacanth, glucosides such as saponin, methylcellulose, carboxycellulose
, Cellulose derivatives such as hydroxymethylcellulose, ligninsulfonate, natural polymers such as shellac,
Polyacrylate, styrene-acrylic acid copolymer salt,

Salts of vinyl naphthalene-acrylic acid copolymer, salts of styrene-maleic acid copolymer, salts of vinyl naphthalene-maleic acid copolymer, sodium salts of β-naphthalene sulfonic acid formalin condensate, phosphates And the like, nonionic polymers such as anionic polymers such as polyvinyl alcohol, polyvinyl pyrrolidone, and polyethylene glycol.

Examples of the emulsion resin include synthetic resin emulsions such as a vinyl acetate emulsion, an acrylic ester / methacrylic ester emulsion, a styrene emulsion, a urethane emulsion and an ethylene vinyl acetate emulsion.

Examples of the surfactant include anionic surfactants such as fatty acid salts, higher alcohol sulfate salts, liquid fatty oil sulfate salts, alkyl allyl sulfonates, and polyoxyethylene alkyl ethers. And non-ionic surfactants such as polyoxyethylene alkyl esters, sorbitan alkyl esters, and polyoxyethylene sorbitan alkyl esters.

The water-soluble organic solvent used by mixing with water includes, for example, methyl alcohol, ethyl alcohol, n-propyl alcohol and isopropyl alcohol.
, N-butyl alcohol, sec-butyl alcohol, tert
-1 carbon atoms such as butyl alcohol and isobutyl alcohol
-4 alkyl alcohols; amides such as dimethylformamide dimethylacetamide;

Ketone or keto alcohols such as acetone and diacetone alcohol; ethers such as tetrahydrofuran and dioxane; polyalkylene glycols such as polyethylene glycol and polypropylene glycol; ethylene glycol Alkylene groups such as propylene glycol, butylene glycol, triethylene glycol, 1,2,6-hexanetriol, thiodiglycol, hexylene glycol, diethylene glycol; Alkylene glycols containing 5 carbon atoms;

Glycerin; polyhydric alcohols such as ethylene glycol methyl (or ethyl) ether, diethylene glycol methyl (or ethyl) ether, and triethylene glycol monomethyl (or ethyl) ether
Lower alkyl ethers such as N-methyl-2-pyrrolidone and 1,3-dimethyl-2-imidazolidin.

Of these many water-soluble organic solvents,
Polyalkyl alcohols such as diethylene glycol; lower alkyl ethers of polyhydric alcohols such as triethylene glycol monomethyl (or ethyl) ether; and ethanol.
Preferred are aliphatic monohydric alcohols such as alcohols, and they may be used in combination.

The content of these water-soluble organic solvents is from 10 to 80
%, More preferably in the range of 20 to 60% by weight. When the content is less than 10% by weight, clogging at the tip of the discharge nozzle is liable to occur, and the discharge is always stable even when the driving condition changes. Cannot be obtained.

If it exceeds 80% by weight, the print quality tends to be impaired. The water content ranges from 10 to 80% by weight, preferably from 20 to 70% by weight.

Further, a known antifungal agent such as dioxin or sodium tehydroacetate can be used for long-term storage of the ink and for suppressing the generation of bacteria and mold.

Various methods can be employed for adjusting the recording liquid. For example, the above components are blended, and the mixture is ball milled.
A method of mixing and grinding using a roll mill, a speed line mill, a homogenizer, a homomixer, a sand grounder, or the like can be employed, and further, coarse particles of the pigment are removed by a method such as filtration or centrifugation. Thereby, it can be easily obtained.

The pigment dispersion step is carried out in a state where the pigment concentration is as high as possible. After the dispersion treatment, if necessary, a resin and a medium are further adjusted to adjust the viscosity of the recording liquid. The particle size of the recording agent is adjusted to about 1 to 20 cps, preferably about 2 to 10 cps, and 1 to 20 times, preferably 1 to 10 times the primary particle diameter of the pigment.

If pigment particles, especially large particles having a large particle diameter of 3 μm or more, are present in the ink, some change occurs in the ink dispersion system when energy is applied to the ink on the ejection head, and the orifice and the Foreign matter is easily deposited on the wall surface and settles easily. On the other hand, fine pigment particles, especially ink of fine particles of 0.5 μm or less,
, The dispersion system is stable, and even if the particles adhere to the wall surface, precipitation of foreign matter is unlikely to occur, and stable ejection can be obtained over a long period of time.

In the recording liquid thus prepared, even when stored for a long period of time in a low viscosity region, pigment particles are not collected or settled.

Then, this recording liquid is obtained by: (1) a wide range of recording liquid discharge conditions (the driving voltage of the piezoelectric element,
It has liquid physical properties (viscosity, particle diameter, surface tension, specific conductivity, etc.) matching the drive frequency, the shape and material of the discharge orifice, the discharge orifice diameter, and the like.

(2) It is stable for long-term storage and does not cause clogging of the ink jet device. (3) The formed recording image has a clear color tone and a high density. (4) It has excellent fixability to plain paper, and even when printed on plain paper, the periphery of dots is smooth and does not blur.

(5) The formed recorded image is excellent in water resistance and weather resistance.

[0064]

According to the present invention, a resin for an ink jet recording liquid suitable for an ink jet system for performing recording by flying droplets from an orifice of a recording head and an ink jet recording liquid using the same are obtained.

More specifically, it has excellent ink properties with little sedimentation and liquid separation properties, excellent mechanical properties such as dischargeability, continuous stability and non-clogging properties, and has good drying resistance at the discharge orifice. It is an invention to obtain an ink jet recording liquid having excellent printing characteristics such as fixability, print density and print quality.

Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited by these examples.
The quantities used in the following examples are based on weight unless otherwise specified.

Synthesis Example of Oligomer-Emulsifier Example 1 630 g of acrylic acid, 455 g of acrylonitrile, 160 g of n-octyl mercaptan and 177 g of methanol were added to a reactor having a stirrer, a reflux condenser, a dropping device and an N ₂ introduction pipe. ₍₂ ) After performing the substitution, heat to 35 ° C., add 67 g of a 0.6% methanol solution of ammonium persulfate to start the polymerization reaction, and 600 g of a 0.6% solution of ammonium persulfate in methanol.
Was added dropwise over 6 hours, and the reaction was continued until the conversion exceeded 99.5%.

The resulting methanol solution was dried under reduced pressure at 100 ° C. and 10 mmHg, and then neutralized and dissolved in an aqueous solution of potassium hydroxide to obtain 47.5 mol% of acrylic acid having a nonvolatile content of 40%, a pH of 7.0 and a molecular weight of about 1200. A potassium salt of a copolymer of 46.5 mol% of acrylonitrile and 6.0 mol% of n-octyl mercaptan was obtained.

Example 2 In the same reactor as in Example 1, 663 g of itaconic acid, 260 g of acrylonitrile, 78 g of n-dodecylmercaptan and 540 g of isopropanol were added, and after N ₂ substitution, the mixture was heated to 40 ° C.
Thereafter, 40 g of a 1% solution of lauroyl peroxide in isopropyl alcohol was added to initiate the polymerization reaction, and 360 g of a 1% solution of lauroyl peroxide in isopropyl alcohol was added dropwise over 6 hours to carry out the reaction.

By performing the same processing as in Example 1, the nonvolatile component
A sodium salt of a copolymer of 40%, pH 6.5, 49.1 mol% of itaconic acid having a molecular weight of 3,800, 47.2 mol% of acrylonitrile, and 3.7 mol% of n-dodecyl mercaptan was obtained.

Example 3 In the same manner as in Example 1, a copolymer was obtained from the following raw materials. Acrylonitrile 144 g Acrylic acid 780 g n-octyl mercaptan 164 g Isopropanol 690 g Lauroyl peroxide 10 g

The obtained copolymer was treated in the same manner as in Example 1 to obtain a copolymer having a nonvolatile content of 40%, a pH of 7.0, a molecular weight of 800, 73.8 mol% of acrylic acid, acrylonitrile of 18.5 mol%, and a copolymer of n-octyl mercaptan of 7.7 mol%. The combined potassium salt was obtained.

Example 4 Vinyl acetate 413 g Maleic anhydride 706 g n-Dodecyl mercaptan 121 g Isopropanol 820 g Ammonium persulfate 4.5 g

A potassium salt of a copolymer having a nonvolatile content of 40%, a pH of 7.5, a molecular weight of about 2,000, 57.0 mol% of maleic acid, vinyl acetate 38.2 mol%, and n-dodecyl mercaptan 4.8 mol% was obtained.

Example 5 374 g of styrene 823 g of maleic anhydride 88 g of n-octyl mercaptan 88 g of isopropanol 10 g of lauroyl peroxide

A potassium salt of a copolymer having a nonvolatile content of 40%, a pH of 7.0, a molecular weight of about 1,000, 66.7 mol% of maleic acid, 28.5 mol% of styrene, and 4.8 mol% of n-dodecyl mercaptan was obtained.

Example-1 0.8 parts by weight of the aqueous solution of the potassium salt of the copolymer obtained in Synthesis Example-1 8 parts by weight of carbon black (DBP adsorption amount: 115 [DBPml / 100 g], PH; 5, primary particle diameter) : 29mμ) Triethylene glycol 12 parts by weight Glycerin 4 parts by weight Sodium tetrahydroacetate 0.1 parts by weight Water 75.1 parts by weight

The above-mentioned components were used in a gorin homogenizer.
(Mount Gorling Co., Ltd.), and filtered through a 1200 mesh wire net to obtain a black recording liquid. The viscosity of the obtained ink is about 2 cps at 20 ° C. and the average particle diameter is 0.12 μm
And it was about 4.1 times the primary particle diameter.

Example 2 1.6 parts by weight of the aqueous solution of the copolymer sodium salt obtained in Synthesis Example 2 8 parts by weight of carbon black used in Example 1 15 parts by weight of triethylene glycol 15 parts by weight of ethanol 5 parts by weight Parts Sodium tehydroacetate 0.1 parts by weight Water 70.3 parts by weight

The above components were dispersed in the same manner as in Example 1,
A black recording liquid was obtained. The viscosity of the obtained ink was about 3 cps at 20 ° C., the average particle diameter was 0.16 μm, and was about 5.5 times the primary particle diameter.

Example 3 5 parts by weight of the aqueous solution of the potassium salt of the copolymer obtained in Synthesis Example-3 8 parts by weight of copper phthalocyanine blue (primary particle diameter: 70 mμ) 10 parts by weight of triethylene glycol 10 parts by weight formamide 10 parts by weight FC-128 (manufactured by Sumitomo Threes Co., Ltd., fluorine surfactant) 0.01 part by weight Sodium tehydroacetate 0.1 part by weight Water 66.89 parts by weight

After the above components were dispersed in a ball mill, the components were again dispersed in a Gorin homogenizer and filtered through a 1200 mesh wire net to obtain a blue recording liquid. The viscosity of the obtained ink is about 4 cps at 20 ° C. and the average particle diameter is 0.12 μm
And it was about three times the primary particle diameter.

Example-4 2.2 parts by weight of aqueous solution of the copolymer potassium salt obtained in Synthesis Example-4 9 parts by weight of carbon black used in Example-1 12 parts by weight of triethylene glycol 3 parts by weight of glycerin Tehydro 0.1 parts by weight of sodium acetate 73.7 parts by weight of water

The above components were dispersed in the same manner as in Example 1,
A black recording liquid was obtained. The viscosity of the obtained ink is about 3 cps
The average particle size was 0.12 μm, which was about 4.1 times the primary particle size.

Example-5 7.5 parts by weight of the aqueous solution of the potassium salt of the copolymer obtained in Synthesis Example-5 Magenta, (CIPigment Red81) ... (primary particle diameter: 90 mμ) 10 parts by weight Diethylene glycol 15 parts by weight Isopropyl alcohol -8 parts by weight Sodium tetrahydroacetate 0.1 parts by weight Water 59.4 parts by weight

The above components were dispersed in the same manner as in Example 3;
A red recording liquid was obtained. The viscosity of the obtained ink is about 2 cps
The average particle diameter was 0.18 μm, which was about twice the primary particle diameter.

Comparative Synthesis Example 1 The following was added to the same reactor as in Synthesis Example 1, except that styrene 338 g maleic anhydride 172 g diacetone alcohol 669 g butanol 350 g benzoyl peroxide 18 g

After N ₂ substitution, the mixture was heated and polymerized at 80 ° C. for 8 hours, dried under reduced pressure, and neutralized and dissolved in an aqueous potassium hydroxide solution to obtain a nonvolatile content of 20%, pH 6.5, A potassium salt of a copolymer of 64.9 mol% of styrene and 35.1 mol% of maleic acid having a molecular weight of about 15,000 was obtained.

Comparative Example-1 1.8 parts by weight of the aqueous solution of the potassium copolymer of Comparative Example 1 9 parts by weight of carbon black used in Example 1 12 parts by weight of triethylene glycol 12 parts by weight of glycerin 4 parts by weight of tehydro 0.1 parts by weight of sodium acetate 73.1 parts by weight of water

After the above-mentioned components were dispersed with a Gorin homogenizer, the mixture was filtered through a 1200-mesh wire gauze. The viscosity of the unfiltered ink was about 11 cps, the average particle size was 2.8 μm, and was about 97 times the primary particle size.

Comparative Example-2 50 parts by weight of the aqueous solution of the copolymer potassium of Comparative Synthesis Example-1 Magenta (CIPigment Red81) ... (primary particle diameter: 90 mμ) 10 parts by weight Diethylene glycol 15 parts by weight Isopropyl alcohol -8 parts by weight Sodium tetrahydroacetate 0.1 parts by weight Water 17 parts by weight

After dispersing the above components in a ball mill,
The mixture was dispersed again with a Gorin homogenizer and filtered through a 1200 mesh wire net to obtain a red recording liquid. The viscosity of the obtained ink was about 37 cps, the average particle diameter was 0.65 μm, and was about 7.2 times the primary particle diameter.

Comparative Synthetic Example-2 The following was added to the same reactor as in Synthetic Example-1, and styrene 390 g maleic anhydride 122 g isopropyl alcohol 420 g lauroyl peroxide 51 g

After performing N ₂ substitution, the mixture was heated at 80 ° C. for 10 minutes.
After conducting the polymerization reaction for a period of time, the mixture was dried under reduced pressure, neutralized and dissolved in an aqueous potassium hydroxide solution, and had a nonvolatile content of 40%, a pH of 7.0, 75.2 mol% of styrene having a molecular weight of about 2,000, and 24.8 mol% of maleic acid.
A potassium salt of the copolymer was obtained.

Comparative Example 3 2.3 parts by weight of the aqueous potassium copolymer solution of Comparative Synthesis Example 2 9 parts by weight of carbon black used in Example 1 12 parts by weight of triethylene glycol 12 parts by weight of glycerin 4 parts by weight of sodium tetrahydroacetate 0.1 parts by weight Water 72.6 parts by weight

The above components were dispersed in the same manner as in Example 1,
A black recording liquid was obtained. The viscosity of the obtained ink is about 6 cps
The average particle diameter is 0.39 μm, about 13.4 of the primary particle diameter
It was twice.

Using the inks of Examples 1 to 5 and Comparative Examples 1 to 3, the storage stability of the recording liquid and the on-demand type recording head (the orifice diameter of the discharge nozzle of 25 μm) for discharging the ink by the piezo vibrator were set. With the use of a recording apparatus having the same, the mechanical suitability (dischargeability) as an ink for inkjet recording and the printing quality were examined. The results are summarized in Table 1.

The test methods, evaluation methods, and terms used in the present invention are described below. 1. Measurement of average molecular weight The molecular weight was measured under the following conditions by mounting a column (3 GMHs, manufactured by Tosoh Corporation) on a gel permeation chromatography (GPC). The sample was dissolved in THF (tetrahydrofuran) at a concentration of 0.2 wt%, and 1 ml at 20 ° C.
/ Min flow rate.

When measuring the molecular weight of a sample, the measurement conditions in which the molecular weight of the sample is included in a range in which the logarithm of the molecular weight and the count number are linear in a calibration curve prepared from several types of monodisperse polystyrene standard samples are linear. Selected. Further, the molecular weight was represented by a number average molecular weight (Mn).

2. Measurement of Viscosity of Recording Solution The viscosity was measured using a Rheomat 30 viscometer manufactured by Contraves.

3. Measurement of Primary Particle Diameter of Pigment and Particle Diameter of Dispersion The primary particle diameter of the pigment is an average particle diameter calculated from the primary diameter and the number of the pigment particles by an electron micrograph. The particle size of the dispersion is `` DLS-700 '' manufactured by Otsuka Electronics Co., Ltd.
c Light Scattering Spectrophotometer). 1 ≦ particle size of pigment dispersion ÷ primary particle size of pigment agent ≦ 10

4. Preservation of Ink The ink was sealed in a glass container, stored at -5 ° C and 70 ° C for 6 months, and examined for changes. (Evaluation) ；: No liquid separation of the recording liquid and no sedimentation of the recording agent were observed. ；: Some separation of the recording liquid was observed, but no sedimentation of the recording agent was observed, and the recording liquid returned to its original state by weak shaking. C: Separation of the recording liquid and sedimentation of the recording agent were observed, and they did not return to the original state with only slight shaking.

5. Discharge stability 5,000 sheets were continuously discharged in an atmosphere at room temperature of 5 ° C. and 40 ° C., respectively, and the recording stability was examined. (Evaluation) A: Stable ejection continued. X: Weakness occurred in discharge.

6. Restartability The recording device is placed in a constant temperature and humidity condition of 20 ° C. and 60% RH in a windless state. After a continuous operation for 1 hour, the operation is stopped, and the recording head is left open for 15 minutes with the recording head completely open. Then, the print quality at the time of restart was confirmed. (Evaluation) ；: Good printing is obtained from the beginning. ；: Initial printing is disturbed, but restored. ×: Printing is not possible.

7. Print Density A test piece was printed on a commercially available copy paper (P paper manufactured by Xerox Corporation) and measured with a Macbeth densitometer.

8. Print Quality In the above paper, the spread of dot diameter (bleeding) and the breakage of dots (roundness) when one-dot printing was performed were evaluated with an optical microscope. (Evaluation) ；: Less bleeding and higher roundness. ；: Less bleeding but low roundness. ×: Much blurring and low roundness.

9. Print fixability Stain when the print test piece was rubbed with the copy paper was visually determined. (Evaluation) A: There is no stain. ×: The periphery of the printed portion is stained

[0108]

[Table 1]

[0109]

The ink jet recording liquid of the present invention has excellent ink properties with little sedimentation and liquid separation properties, and has excellent mechanical properties such as dischargeability, continuous stability and non-clogging properties. Good drying resistance, fixability,
It has excellent printing characteristics such as printing density and printing quality.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁶ , DB name) C09D 11/00-11/20

Claims (1)

(57) [Claims] 1. An aqueous pigment-dispersed inkjet recording liquid containing a pigment and an emulsifier, wherein the medium is an aqueous medium, wherein the emulsifier has a terminal group of an alkyl sulfide of a monomer having an amino-free addition-polymerizable vinyl group. An inkjet recording liquid, which is an oligomer emulsifier having a molecular weight of 500 to 4,000.