JPH11209671A - Inkjet recording ink - Google Patents

Abstract

(57) [Problem] To provide an ink jet recording ink capable of realizing high print density. SOLUTION: The ink for ink jet recording of the present invention contains a pigment, a dispersant, monodispersed fine particles, and a water-soluble medium, and when the ink is printed on a recording member, a portion of the printed portion is printed. It is characterized in that the fine particles are used in such a particle size and amount that the coverage of the fine particles with respect to the area is 50% or more.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink for ink jet recording, and more particularly to an ink for ink jet recording having improved print density in a pigment dispersion ink.

[0002]

2. Description of the Related Art As a conventional technique relating to mixing fine particles into an ink for ink jet recording, for example, the technique described in Japanese Patent Application Laid-Open No. 8-319442 is known.

The above publication discloses a dye dispersed with an anionic surfactant for the purpose of providing an ink jet ink composition capable of forming a clear image with a small amount of ink bleeding on a recording member. An inkjet ink composition comprising at least a pigment and substantially colorless fine particles is disclosed. However, the ink composition described in the publication has a small bleeding of the ink on the recording member and can form a clear image.
It was not yet satisfactory in terms of print density. Further, the publication only describes the use of substantially colorless fine particles, and the use of fine particles which are monodispersed on a recording member and the coverage of the fine particles on the recording member are described. Nothing is described.

Accordingly, it is an object of the present invention to provide an ink jet recording ink capable of realizing a high print density.

[0005]

Means for Solving the Problems As a result of intensive studies, the present inventors have used fine particles which are monodispersed on a recording member, and when ink is printed on the recording member, the area of the printed portion is reduced. It has been found that by selecting the fine particles so that the coverage of the fine particles is equal to or more than a specific value, an ink for inkjet recording that can achieve the above object can be obtained.

The present invention has been made on the basis of the above findings, and provides an ink jet recording ink containing a pigment, a dispersant, monodispersed fine particles, and a water-soluble medium.
When the ink is printed on a recording member, the fine particles are used in a particle size and a compounding amount such that the coverage of the fine particles with respect to the area of the printed portion is 50% or more. The above object has been attained by providing an ink jet recording ink.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The ink jet recording ink of the present invention contains a pigment, a dispersant, monodisperse fine particles, and a water-soluble medium as essential components. The ink jet recording ink according to the present invention has a particle diameter and a compounding ratio such that, when the ink is printed on a recording member, the coverage of the fine particles with respect to the area of the printed portion is 50% or more. It is characterized by being used in an amount.

The fine particles monodispersed on the recording member will be described in detail. In the present invention, as described above, the fine particles have a coverage of 50% or more, preferably 80% or more, and more preferably 90% or more. It is used in a particle size and a compounding amount such that By using the fine particles so as to have such a coverage, a high printing density of the ink can be realized. If the coverage of the fine particles is less than 50%,
The desired high print density cannot be obtained. The method of measuring the coverage will be described in detail in Examples described later. Further, in the present specification, “monodispersion” refers to a state in which fine particles do not aggregate.

The conditions of the fine particles selected to keep the coverage of the fine particles within the above-mentioned predetermined range depend on the kind, particle size or blending amount of the fine particles. The particle size is 1 to 50 nm, the compounding amount is 1 to 10% by weight based on the total amount of the ink, and the polymer fine particles have a particle size of 100 to 300 nm, and the compounding amount is 1 to 20% by weight based on the total amount of the ink. Is preferred. Here, the above-mentioned particle size is an average particle size of primary particles, and is a CPS Disc Centrif of Central Science Trading Co., Ltd.
uge (trade name).

As a material constituting the fine particles, fine particles which have a performance capable of being monodispersed and are substantially insoluble in water are used. For example, a polymer or an inorganic compound may be used alone or in combination of two or more. Can be. By including the fine particles, the printing density of the ink is further improved.

The polymer constituting the polymer fine particles does not swell with water or a water-soluble organic solvent, or even if swollen, the particle size after swelling is 1 to 1.2 times the particle size before swelling. It is preferable to use such a polymer. Examples of such a polymer include melamine-based resins such as benzoguanamine and benzoguanamine-melamine and methacrylate-based resins, silicon-based resins, fluorine-based resins, and polyamide-based resins, among which melamine resins are preferred.

The particle size of the polymer fine particles is 100 to 30.
It is preferably 0 nm, particularly 100 to 150 nm, and the amount of the fine particles is preferably 1 to 20% by weight, particularly preferably 1 to 5% by weight, based on the whole ink. By setting the particle size and the content in such a range, it becomes easy to set the coverage of the polymer fine particles on the recording member within a predetermined range.

The fine particles comprising the inorganic compound include:
For example, silicon oxide, titanium oxide, aluminum oxide, and the like, and at least one selected from these,
Particularly, silicon oxide such as colloidal silica is preferably used. Here, as the fine particles, those having both hydrophilic and hydrophobic surfaces can be used.
Those having a hydrophilic surface are more preferable in terms of ease of compounding.

The particle diameter of the fine particles made of the inorganic compound is 1
It is preferably from 50 to 50 nm, particularly preferably from 30 to 50 nm, and the compounding amount of the fine particles is preferably from 1 to 10% by weight, particularly preferably from 1 to 5% by weight, based on the whole ink. By setting the particle size and the content in such a manner, it becomes easy to set the coverage of the fine particles made of the inorganic compound on the recording member within a predetermined range.

Next, an essential component other than the above-mentioned fine particles, that is, a pigment, which is blended in the ink jet recording ink of the present invention,
The dispersant and the water-soluble medium will be described in detail in order. The pigment is not particularly limited, and various inorganic pigments, organic pigments, and the like are used. In the present specification, "pigment"
The term “insoluble or hardly soluble in water and organic solvents” (Chemical Encyclopedia, edited by Kyoritsu Shuppan Co., Ltd.).

Specific examples of the pigment are not particularly limited. For example, it is preferable to use an azo pigment, a phthalocyanine pigment, an anthraquinone pigment, and a carbon black pigment.

The average primary particle size of the pigment is preferably from 10 to 150 nm from the viewpoints of long-term storage stability, environmental stability, abrasion resistance and filterability at the preparation stage. In particular, when carbon black is used as the pigment, it is preferable that the average particle size of the primary particles is 10 to 100 nm from the viewpoint of the structure structure unique to carbon.
More preferably, it is 10 to 80 nm, and 10 to 60 nm.
More preferably, it is nm.

In particular, the above-mentioned carbon black has a BE
Preferably T specific surface area of 20 to 500 m ² / g, and further preferably from 50 to 500 m ² / g.

The pigment is preferably incorporated in the ink for inkjet recording of the present invention in an amount of 1 to 10% by weight, more preferably 3 to 7% by weight, and still more preferably 3 to 7% by weight.
5% by weight is blended. If the amount of the pigment is less than 1% by weight, not only a good dispersion liquid cannot be obtained in the ink preparation stage, but also the printing density is low and the efficiency in the ink preparation stage may be poor, If it exceeds 10% by weight, the effect is saturated in terms of print density, so it is preferable to be within the above range.

As the above-mentioned dispersant, those which can improve the dispersibility of the above-mentioned pigment in the ink are used. Examples of the dispersant include, but are not particularly limited to, a polymer dispersion obtained by subjecting a sulfonated product obtained by sulfonating aromatic compounds including a polynuclear aromatic compound to formalin condensation and then neutralizing the sulfonated product. When the agent is used, even when printing is performed on a non-penetrable recording member such as a plastic sheet, which has conventionally been difficult to enhance the fixing property, the coloring material becomes fine particles, and extremely high fixing property can be exhibited. This is preferable because a printed image having high scratch resistance can be obtained.

Examples of the polynuclear aromatic compound include the following:
Anthracene, phenanthrene, pyrene, acenaphthene, indene, fluorancene, chrysene, benzofluorancene, benzopyrene, perylene and benzoperylene and their mono-, di- or trialkyl-substituted products;
Compounds and derivatives thereof in which two or more aromatic rings or heterocycles share two or more carbon atoms to form a condensed ring, such as mono- or dialkylnaphthalene, and b) fluorene, diphenyl And compounds in which two or more aromatic or heterocyclic rings are bonded directly or via an alkylene group, such as dibenzofuran, and derivatives thereof.

As such a polymer dispersant, a commercially available product such as Demol C (trade name) manufactured by Kao Corporation can be used. Further, the polymer dispersant preferably has a weight average molecular weight of 2,000 to 50,000.

The dispersant is preferably incorporated in the ink for ink jet recording of the present invention in an amount of 0.1 to 10% by weight, more preferably 0.5 to 5% by weight, and still more preferably 1 to 4% by weight. Be blended. If the amount of the dispersant is less than 1% by weight, depending on the type of the pigment, the ink cannot be prepared at the preparation stage, or even if it can be prepared, the ink has long-term storage stability, Environmental stability and abrasion resistance may not be exhibited, and if it exceeds 10% by weight, in particular, adsorption of the dispersant to the pigment may be hindered.

The above-mentioned water-soluble medium is used as a liquid medium, for example, water (preferably purified water).
Or a water-soluble solvent. Examples of the water-soluble solvent include glycols such as ethylene glycol, propylene glycol, and diethylene glycol; ethers of polyhydric alcohols such as diethylene glycol monobutyl ether; acetates; and one or more thiodiglycols. . The amount of the water-soluble medium (the total amount of water and the water-soluble solvent) is 80 to 96% by weight, preferably 90 to 96% by weight in terms of dispersion efficiency.
%, More preferably 91 to 96% by weight.

The ink jet recording ink of the present invention may further contain optional components, if necessary, in addition to the above essential components. Such optional components include, for example, wetting agents or humectants such as polyalkylene glycol, 2-pyrrolidinone, glycerin, alkyl glycine (eg, methyl glycine), anionic surfactants such as alkyl sulfosuccinates, and other surfactants Agents (nonionic, cationic, zwitterionic surfactants), pH adjusters such as 2-aminoethanol, defoamers such as silicone compounds, fungicides such as chloromethylphenol compounds, E
Chelating agents such as DTA, oxygen absorbers such as sulfites, 2,
UV absorbers such as 4-dihydroxybenzophenone,
Antioxidants such as 2,6-di-t-butylphenol and the like can be mentioned. These optional components are preferably 1 to 5% by weight (particularly 2
~ 3% by weight).

The method of preparing the ink for ink jet recording of the present invention is not particularly limited, but is preferably prepared by the method described below. That is, first, (1) the above-mentioned fine particles, the above-mentioned pigment, the above-mentioned dispersant, the above-mentioned water-soluble medium and, if necessary, the above-mentioned optional components are stirred with a dissolver to prepare a preliminary dispersion, and then (2) the preliminary dispersion Is dispersed in a wet medium mill such as a dyno mill to obtain a pigment dispersion, and (3) the above ink is obtained by diluting the pigment dispersion with at least water, preferably purified water (ion-exchanged water). Can be

As a recording member to be recorded by using the ink for ink jet recording of the present invention, paper dedicated to ink jet, glossy paper for ink jet, ink jet co-paper, copy paper, recycled paper and the like are used.

[0028]

EXAMPLES The effectiveness of the ink jet recording ink of the present invention will be illustrated below with reference to examples. However, the scope of the present invention is not limited to such an embodiment.
In the following examples, “parts” means “parts by weight” unless otherwise specified.

Example 1 The following components were mixed with 70 parts of purified water in the following mixing ratio, and a dissolver (a high-speed / high-shear-force dissolver, manufactured by Shinmaru Enterprises) was used.
(Temperature: 30 ° C., Time: 15 minutes, number of revolutions: 6000 rpm) to prepare a preliminary dispersion. 12.5 parts of carbon black [BET specific surface area: 260 m ² / g, average particle diameter of primary particles: 15 nm] ・ 7.5 parts of formalin condensate of polynuclear aromatic compound sulfonate [Demol manufactured by Kao Corporation] C (trade name), weight average molecular weight: about 5000] 5 parts of diethylene glycol Next, the above preliminary dispersion was dispersed under the following dispersion conditions.・ Mill: Dynomill ・ Beads: Yttria-stabilized zirconia beads (0.5
mmφ) ・ Dispersion time: 2 hr / kg (2 per kg of preliminary dispersion)
(Dispersion of time) Dispersion temperature: 60 ° C. ± 5 ° C. The pigment dispersion obtained by dispersion is returned to the above-mentioned dissolver, stirred, and then dispersed again by the above dyno mill to prepare a pigment dispersion. did. Then
A dispersant, fine particles, a water-soluble medium and various additives are added to the above-mentioned pigment dispersion so that the blending amount in the obtained ink 100 parts is as shown below, and the pigment dispersion is stirred using a dissolver. Diluted. Further, the mixture was filtered through a 1.2-micron filter to prepare an ink for inkjet recording. Table 1 shows the types, particle diameters and amounts of the fine particles used here. -3 parts of the carbon black-1.9 parts of the formalin condensate-5 parts of the fine particles-1.1 parts of diethylene glycol-5 parts of polyethylene glycol (weight average molecular weight 4000)-5 parts of 2-pyrrolidinone-water remaining

Example 2 An ink jet recording ink was prepared in the same manner as in Example 1 except that the fine particles in Example 1 were replaced with the fine particles shown in Table 1.

Comparative Example Table 1 shows the fine particles in Example 1.
An ink-jet recording ink was prepared in the same manner as in Example 1 except that the fine particles were replaced with the fine particles shown.

[Evaluation of Performance] In order to evaluate the performance of the inks obtained in Examples and Comparative Examples, printing was performed by the following method, and the coverage of fine particles and the print density were measured. Table 1 shows the results.

<Fine particle coverage> Inkjet co-paper (manufactured by Canon) having a Beck smoothness of 20 seconds as a recording member
Using Canon inkjet printer BJC-
By 430J, 18cm × 2 at a discharge amount 18 g / m ²
Solid printing was performed on an area of 5 cm. The coverage of the fine particles with respect to the area of the printed portion was determined from an electron microscope at any five points in the printing area, and the coverage was determined using the average value of the measurement points.

<Print Density> After the solid print printed on the recording member was air-dried, its optical density was measured with a Macbeth densitometer RD918 (manufactured by Macbeth).

[0035]

[Table 1]

As is clear from the results shown in Table 1, when the ink is printed on the recording member, the fine particles are selected such that the coverage of the fine particles with respect to the area of the printed portion becomes a specific value or more. It can be seen that the ink for inkjet recording (Examples 1 and 2) has a higher print density than the ink of the comparative example. Although not shown in the table, as a result of observation with an electron microscope, fine particles were monodispersed in the print image formed using the ink jet recording ink of the example.

[0037]

According to the present invention, an ink for ink jet recording capable of obtaining a printed matter having a high print density can be obtained.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yoshiaki Tsujii 2606 Akabane, Kaigamachi, Haga-gun, Tochigi Pref.

Claims (3)

[Claims] 1. An ink jet recording ink comprising a pigment, a dispersant, monodispersed fine particles, and a water-soluble medium, wherein when the ink is printed on a recording member, the ink is applied to the area of the printed portion. An ink jet recording ink characterized in that the fine particles are used in a particle size and a compounding amount such that the coverage of the fine particles is 50% or more. 2. The ink for ink-jet recording according to claim 1, wherein the fine particles are made of an inorganic compound having a particle size of 1 to 50 nm, and the compounding amount of the fine particles is 1 to 10% by weight based on the total amount of the ink. 3. The ink jet recording ink according to claim 1, wherein the fine particles are composed of polymer fine particles having a particle diameter of 100 to 300 nm, and the compounding amount of the fine particles is 1 to 20% by weight based on the total amount of the ink.