JP2007217695A - Ink for inkjet recording - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink for inkjet recording, enabling high density recording and having excellent uniformity in solid recorded part, scratch resistance, marker resistance and water resistance to any paper including plain paper. <P>SOLUTION: The ink for inkjet recording contains dispersed pigments comprising two kinds of pigments having different peaks in particle diameter distributions determined by dynamic scattering method and obtained by mixing a pigment having a peak diameter of ≥150 nm and ≤300 nm in the particle diameter distribution after the dispersion treatment with a pigment having a peak diameter of ≤80 nm in the particle diameter distribution after the dispersion treatment and an average particle diameter smaller than the peak particle diameter at a weight ratio of 1:(1-5). More particularly, the invention provides an ink containing a pigment having a peak diameter of ≥150 nm and ≤200 nm in particle diameter distribution and a pigment having an average particle diameter of ≥65 nm and ≤75 nm, an ink containing a pigment having an average particle diameter of ≥100 nm and a pigment having an average particle diameter of ≤60 nm, and an ink having a pigment content of 1-20 wt.% based on the total weight. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an ink for ink jet recording, and relates to an ink for ink jet recording which is excellent in solid uniformity while being capable of high density recording and excellent in abrasion resistance, marker resistance and water resistance.

  The ink jet recording method has an advantage that a multicolor image can be obtained at high speed with less noise during recording.

  As a conventional ink for inkjet recording, a dye-based ink in which various water-soluble dyes are dissolved in water or a mixed liquid of water and an organic solvent has been used. However, recorded images with dye-based inks are not sufficient in fastness such as light resistance and water resistance.

  Therefore, a pigment-based ink in which a pigment is dispersed as a coloring material has been developed. However, in the case of dye-based inks, the dye develops color by being dyed on the recording material, so the surface condition of the recording material has little effect on the image density. However, the surface state of the recording material has a great influence on the image density.

  Therefore, depending on the type of recording material, the pigment-based ink has a markedly deteriorated image density and the image quality is impaired. In particular, plain paper such as copy paper and bond paper is not uniform, unlike the ink-jet dedicated paper, so that the image density of the pigment-based ink is lowered.

  In view of this, a technique has been proposed in which a pigment having a high concentration is added to these pigment-based inks in order to improve the decrease in image density. For example, Patent Document 1 describes a water-based black ink containing carbon black and a dye. According to this ink, stable discharge can be always performed even when the driving conditions fluctuate or used for a long time. There are advantages that the recorded image has excellent fastness and the density of the recorded image is high.

Further, as another approach for obtaining a high optical density, a technique using a pigment having a large particle diameter has been proposed. For example, Patent Document 2 finds that the presence of particles having a particle diameter of 0.5 μm or more in the ink on paper increases the optical density, and the number of particles of 0.5 μm or more is 6 ×. It is described that stable ejection is possible if the particle size is 10 4 to 6 × 10 5 particles / μl and the number of particles of 5 μm or more is 50 particles / μl or less.
JP-A-4-57861 JP 2000-204305 A

  However, in the case of the water-based black ink to which the conventional dye is added, since the water-soluble dye is used, there is a concern that the pigment dispersion system becomes unstable, and in the worst case, the dispersion system may be broken. The Further, by using a water-soluble dye, a completely water-resistant recorded matter cannot be obtained, resulting in inconvenience that water resistance is poor.

  In addition, in the case of the conventional ink using a pigment having a large particle diameter, the optical density increases, but on the other hand, color unevenness occurs, and inconveniences such as poor abrasion resistance and marker resistance occur.

  The present invention has been made in view of such circumstances, and in all papers including plain paper, it is excellent in solid uniformity while being capable of high-density recording, and has excellent abrasion resistance, marker resistance, and water resistance. An object of the present invention is to provide an excellent ink jet recording ink.

  The ink for ink jet recording of the present invention for solving the above problems is an ink for ink jet recording in which a pigment is dispersed, and has two kinds of peaks having different peaks in particle size distribution measured by a dynamic scattering method. A pigment having a peak part of the particle size distribution after dispersion treatment of 150 nm or more and 300 nm or less, and a peak part of the particle size distribution after dispersion treatment of 80 nm or less and an average particle diameter of Smaller pigments are mixed in a weight ratio of 1: 1 to 1: 5. Thereby, while high density recording is possible, it is excellent in solid uniformity and excellent in abrasion resistance, marker resistance and water resistance.

  The ink for inkjet recording of the present invention comprises two types of pigments, a pigment having a particle size distribution peak after dispersion treatment of 150 nm to 300 nm, preferably 150 nm to 200 nm, and a particle size distribution peak after dispersion treatment. Part is 80 nm or less, preferably 65 nm or more and 75 nm or less. High density recording is possible by using a pigment having a particle size value of 150 nm or more at the peak part of the particle size distribution, and high density recording is possible by using a pigment having a particle size value of 80 nm or less at the peak part of the particle size distribution. While possible, solid uniformity can be secured. In addition, pigments having a particle size distribution peak value of 80 nm or less enter the voids between the paper fibers, thereby improving the abrasion resistance and marker resistance.

  The ink for inkjet recording of the present invention uses two types of pigments, a pigment having an average particle diameter of 100 nm or more and a pigment having an average particle diameter of 60 nm or less. Within this range, the printing density, uniformity, abrasion resistance and marker resistance are excellent in a well-balanced manner.

  In the ink for ink jet recording of the present invention, in the particle size distribution measured by the dynamic scattering method, the particle size values of the peak portions of the two kinds of pigments used are both 300 nm or less. Within this range, the dispersion stability is excellent.

  The ink for inkjet recording of the present invention contains a pigment in the range of 1 to 20% by weight based on the total weight. When the content is 1% by weight or less, the concentration cannot be ensured, and when it is 20% by weight or more, structural viscosity is generated in the viscosity characteristics of the ink composition, and the ejection stability cannot be secured. With a content in the above range, the printing density and ejection stability are excellent.

  The pigment that can be used in the ink for ink jet recording of the present invention is not particularly limited. For example, the following pigments are preferably used.

  As the pigment used in the black ink, carbon black conventionally used in ink-jet ink compositions can be used. Specific examples include furnace black, lamp black, acetylene black, and channel black.

  Examples of pigments used for cyan ink include C.I. I. Pigment Blue 1, 2, 15, 15: 1, 15: 2, 15: 3, 15: 4, 15: 6, 16, 17: 1, 56, 60, 63 and the like.

  Examples of pigments used in magenta ink include C.I. I. PigmentRed 1, 2, 3, 5, 7, 17, 22, 23, 31, 38, 48: 2 (Ba), 48: 2 (Ca), 48: 3 (Sr), 48: 4 (Mn), 49: 1, 52: 2, 53: 1, 57: 1, 60: 1, 63: 1, 63: 2, 64: 1, 81, 83, 88, 101, 104, 105, 106, 108, 112, 114, 122, 123, 146, 149, 166, 168, 170, 172, 177, 178, 179, 185, 190, 193, 209, and 219.

  Examples of pigments used in yellow ink include C.I. I. Pigment Yellow 1, 3, 12, 13, 14, 17, 24, 34, 35, 37, 42, 53, 55, 81, 83, 95, 97, 98, 100, 101, 104, 108, 109, 110, 117, 120, 128, 138, 153 and the like. These pigments may be subjected to a surface treatment or the like in order to improve the wettability of the pigment.

  In addition to the above pigments, for example, black organic pigments such as aniline black (CI Pigment Black 1), C.I. I. Pigment Orange 1, 2, 5, 7, 13, 14, 15, 16, 34, 36, 38, C.I. I. PigmentViolet 1, 2, 19, 32, C.I. I. PigmentGreen 1, 4, 36 and C.I. I. Pigment Brown 3, 5, 25, 26, etc. can also be used.

  The content of the pigment used in the inkjet recording ink is determined in order to satisfy the color, density, or preferable ink physical properties required for the printed matter, and varies depending on the specific gravity and bulk density of the pigment. Although not limited, it is preferably 1 to 20% by weight, more preferably 1 to 15% by weight, based on the total weight of the ink composition. If the pigment content is less than 1% by weight, the printing density may not be ensured. If the pigment content exceeds 20% by weight, structural viscosity is generated in the viscosity characteristics of the ink composition, and ejection stability can be ensured. It may disappear.

  The dispersant used for the ink jet recording ink is an alkali-soluble water-soluble resin, and the weight average molecular weight is preferably 1000 to 30000, more preferably 3000 to 15000. Specifically, styrene, styrene derivatives, vinyl naphthalene, vinyl naphthalene derivatives, hydrophobic monomers such as aliphatic alcohol esters of α, β-ethylenically unsaturated carboxylic acids, or acrylic acid, acrylic acid derivatives, maleic acid A block copolymer consisting of two or more monomers selected from the group consisting of maleic acid derivatives, itaconic acid, itaconic acid derivatives, fumaric acid, fumaric acid derivatives, graft copolymers, or random copolymers, or These salts are mentioned. These resins are alkali-soluble resins that are soluble in an aqueous solution in which a base is dissolved. Furthermore, homopolymers composed of hydrophilic monomers and salts thereof may be used. In addition, water-soluble resins such as polyvinyl alcohol, carboxymethyl cellulose, and naphthalenesulfonic acid formaldehyde condensate can also be used. However, when an alkali-soluble resin is used, the viscosity of the dispersion can be reduced and the dispersion is easier.

  These dispersants are preferably used in an amount of 0.1 to 5% by weight based on the total amount of ink for inkjet recording. When the content of the resin dispersant is less than 0.1% by weight, the dispersion stability of the pigment over time when the ink composition is allowed to stand may deteriorate. When the content exceeds 5% by weight, the ink composition is dried. The redispersibility required in some cases may not be obtained.

  In order to improve the solubility of the dispersant and obtain long-term storage stability, it is preferable to adjust the entire ink to neutral or alkaline so that the salt in the dispersant is easily ion-dissociated, and the pH is 7 It is preferable to use in the range of -10.

  Examples of the pH adjusting agent include various organic amines such as diethanolamine and triethanolamine and inorganic bases such as alkali metal hydroxides such as sodium hydroxide, potassium hydroxide and lithium hydroxide.

  The optimum base species varies depending on the type of the selected pigment and dispersant, but is preferably non-volatile and stable and has high water retention. The amount of base used is basically the amount calculated from the acid value of the dispersant, and is used as the amount of base necessary to neutralize it. For the purpose of improving the dispersibility of the pigment, adjusting the pH of the ink, adjusting the recording performance, and improving the moisture retention, an amount of base exceeding the equivalent of acid may be used.

  The embodiment of the ink used in the present invention described above is one in which a pigment such as carbon black is uniformly dispersed in the ink by a dispersant, but the ink that can be used in the present invention is not limited to this. That is, in the present invention, carbon black of a type in which the surface active group is oxidized or other surface treatment and does not require a dispersant can also be suitably used. Since the surface of the carbon black subjected to the treatment as described above is rich in carboxyl groups and sulfonic acid groups, it can be self-dispersed in the ink without using a dispersant. Examples of such carbon black include carbon black having a sulfone group bonded to the surface and capable of being dispersed in water without a dispersant (for example, trade name: CABOJET (CAB-O-JET) 200, CABOT (CABOT)). ), Carbon black having a carboxyl group bonded to the surface and capable of being dispersed in water without a dispersant (for example, trade name: CABOJET (CAB-O-JET) 300, manufactured by CABOT) And trade name: BONJETBLACKCW-1, manufactured by Orient Chemical Co., Ltd.).

  The aqueous medium used for the ink jet recording ink is mainly water, but it is preferable to use a water-soluble organic solvent added to water. Examples of the water-soluble organic solvent include alkyl alcohols having 1 to 4 carbon atoms such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, tert-butyl alcohol, and dimethylformamide. Amides such as dimethylacetamide, ketones or ketone alcohols such as acetone and diacetone alcohol, ethers such as tetrahydrofuran and dioxane, polyalkylene glycols such as polyethylene glycol and polypropylene glycol, ethylene glycol, propylene glycol, butylene glycol, Triethylene glycol, 1,2,6-hexanetriol, thiodiglycol, hexylene glycol, diethylene glycol Alkylene glycols in which any alkylene group contains 2 to 6 carbon atoms, glycerin, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol methyl ether, diethylene glycol ethyl ether, triethylene glycol monomethyl ether and triethylene glycol monoethyl ether And lower alkyl ethers of polyhydric alcohols such as N-methyl-2-pyrrolidone, 2-pyrrolidone and 1,3-dimethyl-2-imidazolidinone.

  Of these many water-soluble organic solvents, polyhydric alcohols such as diethylene glycol and lower alkyl ethers of polyhydric alcohols such as triethylene glycol monomethyl ether and triethylene glycol monoethyl ether are preferred.

  In the case of adopting a bubble jet (registered trademark) method utilizing the force of bubbles generated by boiling of the ink for ink jet recording, ethanol, isopropyl alcohol, or polyhydric alcohol is used in order to obtain the ejection stability of the ink for ink jet recording. It is effective to add the lower alkyl ethers. By adding these solvents, it is possible to more stably foam the inkjet recording ink on the thin film resistor.

  The content of the water-soluble organic solvent in the ink for ink jet recording is in the range of 5 to 60% by weight, preferably in the range of 10 to 50% by weight based on the total weight of the ink. By making the content within the above range, it is possible to ensure the ejection stability of the pigment ink. If the content of the water-soluble organic solvent is too large, drying may be poor.

  In addition to the above components, the ink for ink jet recording may be supplemented with a surfactant, an antifoaming agent, a preservative, and the like in order to obtain a recording liquid having desired physical properties as required. .

  Furthermore, urea, thiourea, ethyleneurea or derivatives thereof may be added as an anti-drying agent for the nozzle.

  As the surfactant, specifically, as an anionic surfactant, higher fatty acid salt, alkyl sulfate, alkyl ether sulfate, alkyl ester sulfate, alkyl aryl ether sulfate, alkyl sulfonate, sulfosuccinate, Examples include alkyl allyl and alkyl naphthalene sulfonates, alkyl phosphates, polyoxyethylene alkyl ether phosphates and alkyl aryl ether phosphates.

  Examples of the cationic surfactant include alkylamine salts, dialkylamine salts, tetraalkylammonium salts, benzalkonium salts, alkylpyridinium salts and imidazolinium salts.

  Examples of amphoteric surfactants include dimethylalkyl lauryl betaine, alkyl glycine, alkyl di (aminoethyl) glycine and imidazolinium betaine.

  Nonionic surfactants include polyoxyethylene alkyl ether, polyoxyethylene alkyl allyl ether, polyoxyethylene polyoxypropylene glycol, glycerin ester, sorbitan ester, sucrose ester, glycerin ester polyoxyethylene ether, sorbitan ester Polyoxyethylene ether, polyoxyethylene ether of sorbitol ester, fatty acid alkanolamide, polyoxyethylene fatty acid amide, amine oxide, polyoxyethylene alkylamine, and the like can be used.

  Specific examples of the antifoaming agent include ethyl alcohol and isopropyl alcohol.

  Specific examples of fungicides, antiseptics and rust inhibitors include benzoic acid, dichlorophene, hexachlorophene, sorbic acid, p-hydroxybenzoic acid ester, ethylenediaminetetraacetic acid (EDTA), sodium dehydroacetate, 1,2-benziso. And thiazoline-3-one and 3,4-isothiazoline-3-one.

  Various physical properties of the ink for ink jet recording can be appropriately controlled. According to a preferred embodiment of the present invention, the viscosity of the ink for ink jet recording is 25 mPa · sec or less, preferably 10 mPa · sec or less (25 ° C.). It is. When the viscosity is within this range, the inkjet recording ink can be stably ejected from the ejection head. The surface tension of the ink for ink jet recording can be appropriately controlled, but is preferably in the range of 20 to 50 mN / m (25 ° C.).

  As a method for preparing the pigment used in the ink jet recording ink, it can be produced by simultaneously adding a pigment and a dispersant to an aqueous medium and performing a dispersion treatment. The dispersion treatment is not particularly limited. For example, first, a dispersant, an alkali neutralizer (pH adjuster) and a dissolution aid are made into a uniform solution with an aqueous medium, and then a pigment is added to the solution. Premixing is performed to add and shake the dispersant component, and further, dispersion is performed by a disperser, and centrifugation is performed as necessary to obtain a desired dispersion. Finally, in order to prepare the ink for ink jet recording, each of the above components is added to two kinds of such dispersions prepared so as to have different peaks in particle distribution, and stirred to obtain an ink. The disperser may be any commonly used disperser, and examples thereof include a ball mill, a roll mill, and a sand mill.

  The ink for ink jet recording in the embodiment of the present invention has a peak of 2 when the particle size distribution is measured by the dynamic scattering method after mixing two types of pigments after dispersion treatment for each color ink for ink jet recording. It is composed of two existing pigment inks.

  The pigment having the peak of the particle size distribution after the dispersion treatment at a desired position can be adjusted by appropriately selecting the size of the grinding media of the disperser. A pigment having a peak of particle size distribution at a desired position can also be obtained by increasing the filling rate of the pulverizing media or increasing the pulverization time. Further, after pulverizing the pigment, it may be classified into a pigment having a peak of particle size distribution at a desired position using a filter or a centrifugal separator. Alternatively, a pigment having a peak of particle size distribution at a desired position can also be prepared by combining these methods.

  According to the present invention, it is possible to provide an ink for inkjet recording that is excellent in solid uniformity and excellent in abrasion resistance, marker resistance, and water resistance while being capable of high density recording on any paper including plain paper. Can do.

EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist.
(Preparation of each color pigment dispersion)
(A) Preparation of black dispersion 1 4 parts by weight of styrene-acrylic acid copolymer resin (weight average molecular weight = 7500; acid value = 200)
2.7 parts by weight of triethanolamine 0.4 part by weight of isopropyl alcohol 72.9 parts by weight of ion-exchanged water The above components were completely dissolved under heating at 70 ° C.

Next, 20 parts by weight of carbon black (MA100; manufactured by Mitsubishi Chemical Corporation) is added to the above solution, and after premixing, the particle size of the peak part of the particle size distribution of carbon black is measured with a ball mill (manufactured by Fritsch). Dispersion was carried out until the value reached 150 nm (average particle diameter 130 nm) (zirconium bead filling factor = 50%; media diameter = 0.5 mm), and passed through a 0.6 μm filter to obtain a black dispersion liquid 1. Microtrac UPA (manufactured by Nikkiso Co., Ltd.) was used for particle size measurement.
(B) Preparation of Black Dispersion 2 Dispersion was performed under the same composition and conditions as in the preparation of Black Dispersion 1, and the particle size value of the peak part of the particle size distribution of carbon black was 75 nm (average particle size 50 nm). A black dispersion 2 was obtained.
(C) Preparation of Cyan Dispersion 1 4 parts by weight of styrene-acrylic acid copolymer resin (weight average molecular weight = 7500; acid value = 200)
2.7 parts by weight of triethanolamine 0.4 part by weight of isopropyl alcohol 72.9 parts by weight of ion-exchanged water The above components were completely dissolved under heating at 70 ° C.

Next, 20 parts by weight of a phthalocyanine blue pigment (Lionol Blue FG-7330; manufactured by Toyo Ink Co., Ltd.) was added to the above solution, and after premixing, the phthalocyanine blue pigment was mixed with a ball mill (manufactured by Fritsch). Dispersion was performed until the particle size value at the peak of the particle size distribution reached 200 nm (average particle size 150 nm) (zirconium bead filling rate = 50%; media size = 0.5 mm), passed through a 0.6 μm filter, and cyan. Dispersion 1 was obtained.
(D) Preparation of Cyan Dispersion 2 Dispersion was carried out under the same composition and the same conditions as in the preparation of Cyan Dispersion 1, and the particle size value of the peak part of the particle size distribution of the phthalocyanine blue pigment was 65 nm (average particle size 40 nm). Cyan dispersion 2 was obtained.
(E) Preparation of Cyan Dispersion 3 Dispersion was carried out under the same composition and the same conditions as in the preparation of Cyan Dispersion 1, and the particle size value of the peak part of the particle size distribution of the phthalocyanine blue pigment was 100 nm (average particle size of 80 nm). ) Was obtained.
(F) Preparation of magenta dispersion 1 4 parts by weight of styrene-acrylic acid copolymer resin (weight average molecular weight = 7500; acid value = 200)
2.7 parts by weight of triethanolamine 0.4 part by weight of isopropyl alcohol 72.9 parts by weight of ion-exchanged water The above components were completely dissolved under heating at 70 ° C.

Next, 20 parts by weight of quinacridone-based red pigment (Fastgen Super Magenta RE-O3; manufactured by Dainippon Ink Chemical Co., Ltd.) is added to the solution, premixed, and then quinacridone-based using a ball mill (manufactured by Fritsch). Dispersion is performed until the particle size value of the peak portion of the particle size distribution of the red pigment reaches 180 nm (average particle size 150 nm) (zirconium bead filling ratio = 50%: media diameter = 0.5 mm), and a 0.6 μm filter is formed. Through this, a magenta dispersion 1 was obtained.
(G) Preparation of Magenta Dispersion 2 Dispersion was carried out under the same composition and conditions as in the preparation of the magenta dispersion 1, and the particle size value of the peak part of the particle size distribution of the quinacridone red pigment was 65 nm (average particle size 45 nm). ) Magenta dispersion 2 was obtained.
(H) Preparation of yellow dispersion 1 4 parts by weight of styrene-acrylic acid copolymer resin (weight average molecular weight = 7500; acid value = 200)
2.7 parts by weight of triethanolamine 0.4 part by weight of isopropyl alcohol 72.9 parts by weight of ion-exchanged water The above components were completely dissolved under heating at 70 ° C.

Next, 20 parts by weight of a disazo yellow pigment (Shimura Fast Yellow 4306; manufactured by Dainippon Ink & Chemicals, Inc.) is added to the above solution, premixing is performed, and then the disazo yellow pigment is mixed with a ball mill (manufactured by Fritsch). Dispersion is performed until the particle size value at the peak part of the particle size distribution reaches 160 nm (average particle size 100 nm) (zirconium bead filling rate = 50%; media size = 0.5 mm), and the filter is passed through a 0.6 μm filter. Dispersion 1 was obtained.
(I) Preparation of Yellow Dispersion 2 Dispersion was performed under the same composition and conditions as in the preparation of Yellow Dispersion 1 above, and the particle size value of the peak part of the particle size distribution of the disazo yellow pigment was 75 nm (average particle size 55 nm). ) Was obtained.
(J) Preparation of Yellow Dispersion 3 Dispersion was carried out under the same composition and the same conditions as in the preparation of Yellow Dispersion 1, and the particle size value of the peak part of the particle size distribution of the disazo yellow pigment was 90 nm (average particle size 90 nm). ) Was obtained.
(Example 1)
An ink for inkjet recording was prepared by adding the following components.
Black dispersion 1 15 parts by weight Black dispersion 2 15 parts by weight Glycerin 10 parts by weight Diethylene glycol 10 parts by weight Polyethylene glycol # 400 5 parts by weight 2-pyrrolidone 10 parts by weight Ion-exchanged water 35 parts by weight (Example 2)
An ink for inkjet recording was prepared by adding the following components.
Cyan dispersion 1 5 parts by weight Cyan dispersion 2 25 parts by weight Glycerin 10 parts by weight Diethylene glycol 10 parts by weight Polyethylene glycol # 400 5 parts by weight 2-pyrrolidone 10 parts by weight Ion-exchanged water 35 parts by weight (Example 3)
An ink for ink jet recording was prepared by calorilating the following components.
10 parts by weight of the magenta dispersion 1 20 parts by weight of the magenta dispersion 2 10 parts by weight of glycerin 10 parts by weight of diethylene glycol 10 parts by weight of polyethylene glycol # 400 5 parts by weight of 2-pyrrolidone 10 parts by weight of ion-exchanged water 35 parts by weight (Example 4)
An ink for inkjet recording was prepared by adding the following components.
7.5 parts by weight of the yellow dispersion 1 22.5 parts by weight of the yellow dispersion 2 10 parts by weight of glycerin 10 parts by weight of polyethylene glycol 10 parts by weight of polyethylene glycol # 400 5 parts by weight of 2-pyrrolidone 10 parts by weight of ion-exchanged water 35 parts by weight (comparative example) 1)
An ink for inkjet recording was prepared by adding the following components.
Cyan dispersion 1 5 parts by weight Cyan dispersion 3 25 parts by weight Glycerin 10 parts by weight Diethylene glycol 10 parts by weight Polyethylene glycol # 400 5 parts by weight 2-pyrrolidone 10 parts by weight Ion-exchanged water 35 parts by weight (Comparative Example 2)
An ink for inkjet recording was prepared by adding the following components.
Cyan dispersion 3 5 parts by weight Cyan dispersion 2 25 parts by weight Glycerin 10 parts by weight Diethylene glycol 10 parts by weight Polyethylene glycol # 400 5 parts by weight 2-pyrrolidone 10 parts by weight Ion-exchanged water 35 parts by weight (Comparative Example 3)
An ink for inkjet recording was prepared by adding the following components.
20 parts by weight of the magenta dispersion 1 10 parts by weight of the magenta dispersion 2 10 parts by weight of glycerin 10 parts by weight of diethylene glycol 10 parts by weight of polyethylene glycol # 400 5 parts by weight of 2-pyrrolidone 10 parts by weight of ion-exchanged water 35 parts by weight (Comparative Example 4)
An ink for inkjet recording was prepared by adding the following components.
Black dispersion 1 30 parts by weight Glycerin 10 parts by weight Diethylene glycol 10 parts by weight Polyethylene glycol # 400 5 parts by weight 2-pyrrolidone 10 parts by weight Ion-exchanged water 35 parts by weight (Comparative Example 5)
An ink for inkjet recording was prepared by adding the following components.
Black dispersion 2 30 parts by weight Glycerin 10 parts by weight Diethylene glycol 10 parts by weight Polyethylene glycol # 400 5 parts by weight 2-pyrrolidone 10 parts by weight Ion-exchanged water 35 parts by weight (Comparative Example 6)
An ink for inkjet recording was prepared by adding the following components.
Yellow dispersion 3 30 parts by weight Glycerin 10 parts by weight Diethylene glycol 10 parts by weight Polyethylene glycol # 400 5 parts by weight 2-Pyrrolidone 10 parts by weight Ion-exchanged water 35 parts by weight Each color ink jet recording ink obtained as described above was used. The recording was made on PPC paper (manufactured by Sharp Corporation). As the ink jet recording apparatus, a modified machine of an ink jet printer AJ2000 (manufactured by Sharp Corporation) was used.

The recorded image was evaluated by the following method. The results are shown in Table 1.
(Evaluation 1) Image density A solid image of 2 cm × 2 cm was formed using ink jet recording inks of each color, and after standing for 1 hour, the recording density at the center of the solid image was determined by X-Rite 938 (manufactured by Nihon Hakusho Kaisha Co., Ltd.). The density of the black is 1.3 or more: ○, the density is 1.2 or more and less than 1.3: Δ, the density is less than 1.2 Things were represented by: x. Regarding the color, those having a density of 0.65 or more are indicated by: ◯, those having a density of 0.60 or more and less than 0.65: Δ, and those having a density of less than 0.60: ×.
(Evaluation 2) Solid Uniformity A solid image of 2 cm × 2 cm was formed using ink jet recording inks of each color, and after standing for 1 hour, the recording density of a total of five points at the center and four corners of the solid image was determined as X-Rite 938 ( When the difference between the maximum value and the minimum value of the measured value is less than 0.05: ○, 0.05 or more and less than 0.1 In the case: Δ, in the case of 0.1 or more: ×.
(Evaluation 3) Abrasion resistance A solid image of 2 cm × 2 cm was formed using ink jet recording ink of each color, and left for 1 hour, then rubbed with a finger and an eraser. If the finger, eraser and paper were not soiled: ○, If dirty, it was marked as x.
(Evaluation 4) Marker resistance Characters were printed using ink-jet recording inks of each color, and after standing for 1 hour, the printed characters were rubbed with a marker pen. If there was no blur: ○, if there was blur: × .

表１の実施例１〜４より、顔料を分散させてなるインクジェット記録用インクにおいて、分散した該顔料の粒子径分布を測定した場合、ピークが２つ存在するインク、すなわち、本発明に係るインクを用いた場合は、高濃度記録が可能でありながらベタ均一性に優れ、かつ耐擦性および耐マーカー性に優れた画像を得ることが判った。

From Examples 1 to 4 in Table 1, in the ink for inkjet recording in which the pigment is dispersed, when the particle size distribution of the dispersed pigment is measured, the ink having two peaks, that is, the ink according to the present invention. It was found that an image having excellent solid uniformity and excellent abrasion resistance and marker resistance can be obtained in the case of using.

  On the other hand, when only the pigment having a single particle size distribution of Comparative Examples 4, 5 and 6 is used, all of high density recording, solid uniformity, abrasion resistance and marker resistance are satisfied. No image was obtained.

  It can be used for high density recording using any paper including plain paper as ink for inkjet recording.

Claims (4)

An ink for inkjet recording in which a pigment is dispersed,
Two types of pigments having different peaks in the particle size distribution measured by the dynamic scattering method are used,
A pigment having a peak part of the particle size distribution after the dispersion treatment of 150 nm or more and 300 nm or less;
A pigment having a peak portion of the particle size distribution after the dispersion treatment of 80 nm or less and an average particle size smaller than the peak particle size
An ink for ink jet recording, which is mixed in a weight ratio of 1: 1 to 1: 5. 2. A pigment having a particle size distribution peak after dispersion treatment of 150 nm to 300 nm and a pigment having a particle size distribution peak of 65 nm to 75 nm after dispersion treatment are used as the two types of pigments. 2. Ink for ink jet recording described in 1. The ink for inkjet recording according to claim 1 or 2, wherein a pigment having an average particle diameter of 100 nm or more and a pigment having an average particle diameter of 60 nm or less are used as the two kinds of pigments. The ink for inkjet recording according to any one of claims 1 to 3, wherein the pigment is contained in an amount of 1 to 20% by weight based on the total weight.