JP2003238855A - Ink for inkjet recording and method for forming image - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink for inkjet recording, improved in the prevention of clogging at an inkjet head, and capable of giving an image with high density and reduced in nonuniformity, and a method for forming an image. <P>SOLUTION: The ink for inkjet recording contains colored fine particles comprising a resin A containing a coloring material, or a resin A containing a coloring material and coated with a resin B, an aqueous solvent and water, wherein the initial dissolution of the coloring material of the colored fine particles into a solvent for the coloring material is 10% or less, the intermediate dissolution of the coloring material of the colored fine particles into a solvent for the coloring material is 50% or less, and the resin A comprises two or more resins different in weight-average molecular weight. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inkjet ink and an image forming method, and more specifically, to an inkjet ink and an image in which clogging of an inkjet head is improved, high image density is obtained, and image unevenness is reduced. The present invention relates to a forming method.

[0002]

2. Description of the Related Art Ink jet recording is a technique for ejecting minute droplets of ink by various operating principles and adhering them to a recording medium to record images, characters, etc. It has an advantage that it can be easily colored.

In addition, due to recent technological advances, ink jet printing using dye ink is accelerating its widespread use with the high image quality approaching that of silver halide photography and the cost reduction of the apparatus.

The dye is soluble in a solvent, and the dye molecule is colored in a molecular state or a cluster state. Therefore,
Since the environment of each molecule is similar, its absorption spectrum is sharp, and it exhibits high purity and vivid color. Furthermore, since there is no granular pattern due to particles, and since scattered light or reflected light does not occur, it is possible to obtain an inkjet image with high transparency and clear hue, and from the high reliability against clogging in printers. , Most commonly used.

On the other hand, however, when the molecules are destroyed by a photochemical reaction or the like, the decrease in the number of molecules is reflected in the coloring density as it is, so that the light resistance is poor. An ink jet recorded image using a dye ink has high image quality, but since it is an aqueous solution of a dye, it easily bleeds on a recording medium, and it is unavoidable that the use is limited and the recording quality is deteriorated. Further, as compared with an ink using a pigment described later, there is a problem that it is difficult to obtain a high density due to the penetration of the coloring material into the recording medium.

In contrast to dye inks, pigment inks using pigments having good light resistance as colorants are used as inks for applications requiring an image resistant to fading by light. However, since the pigment is present as pigment particles as compared with the dye, it is more susceptible to light scattering and gives an image with no sense of transparency, so there is a drawback that the dye does not match the color reproducibility.

As a measure for solving the problems of the water-based ink using the water-soluble dye as described above, an emulsion,
The addition of resin fine particles such as latex has been studied for a long time. Japanese Patent Application Laid-Open No. 55-18418 proposes a recording agent for ink jet recording to which a latex which is "a kind of colloidal solution in which components such as rubber and resin are dispersed in water in the form of fine particles by an emulsifier" is added. is there. In order to improve light fastness by adding latex as in the patent proposal or to have a bleeding prevention effect,
It is very difficult to secure dispersion stability and discharge stability because more latex than the amount of dye used is required, and to obtain an image comparable to a photographic image in terms of graininess and glossiness. The current situation is that it has not arrived.

A proposal for coloring a water-dispersible resin with an oil-soluble dye or a hydrophobic dye in order to solve the problems of low image density and light fastness of a water-based ink using the above-mentioned water-soluble dye is proposed as an ink jet recording ink. Has been done. For example, JP-A-55-139471, JP-A-58-58
45272, JP-A-3-250069, JP-A-8-
253720, JP-A-8-92513, JP-A-8-
An ink using emulsion-polymerized particles dyed with an oil-soluble dye or dispersed polymerized particles is proposed in 183920, JP 2001-11347 A, and the like. In a water-based ink using such colored fine particles, the presence of a dye on the particle surface or outside the particle reduces the effect, and it is difficult to improve various properties such as dispersion stability, ejection stability, and image density. In the images printed with these inks, it became clear that unevenness is likely to become apparent.

On the other hand, with respect to the pigment, attempts have been made to coat the surface of the pigment with a film-forming resin other than a dispersant in order to improve dispersion stability, ejection stability and glossiness. For example, JP-A-8-269374 and JP-A-9-15134.
2, JP-A-10-88045, and JP-A-10-292.
143 etc. describe an example in which a pigment is coated with a resin. However, it is not easy to completely coat the fine particle pigments, and the present situation is that a coated pigment that surpasses the performance of conventional pigment dispersions has not yet appeared.

In the case of water-based inks, the dynamic surface tension of inks such as triethylene glycol monobutyl ether is lowered as a method of increasing the penetration speed of the inks into the ink jet recording medium and improving the blur resistance and glossiness of the image. Although a method of using a solvent having a function of making it known is used, in an aqueous ink containing colored fine particles in which the above coloring material is encapsulated by a resin, a solvent such as triethylene glycol monobutyl ether is used. , Because it penetrates into the resin that constitutes the colored fine particles and elutes the contained coloring material into the aqueous ink medium, the image density is reduced, the inkjet head is clogged, and fusion occurs on the recording medium surface. Causing a decrease in the permeation rate of the water-based ink into the recording medium, causing ink overflow and uneven printed images. , The amount of the solvent having a function of reducing the dynamic surface tension of the ink, such as triethylene glycol monobutyl ether, there is naturally limited.

As described above, the colored fine particle-containing water-based ink using the oil-soluble dye or pigment overcomes the problems of the conventional water-based ink using the water-soluble dye or pigment dispersion,
Although it has the potential to achieve high recording quality, it leaves various problems and further improvement is required.

[0012]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object thereof is to improve clogging of an inkjet head, obtain a high image density, and reduce image unevenness. Another object of the present invention is to provide an inkjet ink and an image forming method.

[0013]

The above objects of the present invention have been achieved by the following constitutions.

1. An inkjet ink containing colored fine particles made of a resin A containing a coloring material or colored fine particles obtained by further coating the surface of a resin A containing a coloring material with a resin B, an aqueous solvent and water. The initial elution ratio of the coloring material to the dissolving agent is 10% or less, and the resin A
Is two or more resins having different weight average molecular weights.

2. An inkjet ink containing colored fine particles made of a resin A containing a coloring material or colored fine particles obtained by further coating the surface of a resin A containing a coloring material with a resin B, an aqueous solvent and water. The medium-term dissolution rate of the coloring material to the dissolving agent is 50% or less, and the resin A
Is two or more resins having different weight average molecular weights.

3. An inkjet ink containing colored fine particles made of a resin A containing a coloring material or colored fine particles obtained by further coating the surface of a resin A containing a coloring material with a resin B, an aqueous solvent and water. The initial elution ratio of the coloring material to the dissolving agent is 10% or less, the medium-term elution ratio of the coloring material to the coloring material dissolving agent of the coloring fine particles is 50% or less, and the resin A has two or more different weight average molecular weights. An inkjet ink, which is a resin.

4. Of the two or more resins having different weight average molecular weights, the solubility parameter of the resin having the smallest weight average molecular weight is ps (J / cm ³ ) ^1/2 and the solubility parameter of the resin having the largest weight average molecular weight is pl (J / cm
³ ) ^1/2 , solubility parameter of coloring material is pc (J / cm ³ )
^The ink-jet ink according to any one of items 1 to 3, wherein when the ^ratio is ^1/2 , the conditions of the formulas (1) and (2) are satisfied.

5. At least 1 sort (s) of the said aqueous solvent is polyhydric alcohol ether or polyhydric alcohol, The inkjet ink of any one of said 1-4 characterized by the above-mentioned.

6. 6. The inkjet ink according to any one of items 1 to 5, wherein the colored fine particles have a core-shell structure in which the surface of a resin A containing a coloring material is further covered with a resin B.

7. The volume average particle diameter of the colored fine particles is
The inkjet ink according to any one of items 1 to 6, which has a thickness of 10 to 200 nm.

8. Surface tension of 25 or more, 50 mN / m
Any one of the above items 1 to 7, characterized in that
Ink jet ink according to the item.

9. pH is 6.0 or more and 11.0 or less, The ink-jet ink according to any one of items 1 to 8 above.

10. An image forming method characterized in that the inkjet ink according to any one of the above items 1 to 9 is ejected as a droplet from an inkjet head based on a digital signal, and the droplet is attached to an inkjet recording medium.

The inventors of the present invention have found that the coloring fine particles of the resin A containing the coloring material or the coloring fine particles obtained by further coating the surface of the resin A containing the coloring material with the resin B, an aqueous solvent and water are used. As for the ink, as a result of earnestly studying improvement of clogging of the inkjet head, improvement of image density, and reduction of image unevenness, as a result, the initial elution ratio of the coloring material to the coloring material dissolving agent of the colored fine particles is 10% or less, and As the resin A coexisting with the colorant, two or more resins having different weight average molecular weights are used, or the resin having a medium-term elution rate of the coloring material to the colorant dissolving agent of 50% or less and coexisting with the colorant As A, 2 having different weight average molecular weights
It has been found that this can be achieved by using three or more resins, and in particular, an image obtained by using a polyhydric alcohol ether or a polyhydric alcohol as a solvent having a function of lowering the dynamic surface tension of the ink. It has been found that it has a remarkable effect in reducing the density, clogging of the inkjet head, ink overflow and unevenness of the printed image. Further, the above effect is obtained in two or more resins having different weight average molecular weights. , The solubility parameter of the resin having the smallest weight average molecular weight is ps (J / cm ³ ) ^1/2 , and the solubility parameter of the resin having the largest weight average molecular weight is pl.
(J / cm ³ ) ^1/2 , the solubility parameter of the coloring material is pc (J
/ Cm ³ ) ^1/2 , it was found that the object of the present invention can be achieved by setting each relationship to a specific condition.

The technical improvement mechanism by the constitution defined in the present invention is not clear in detail, but the solubility of the coloring material in the resin is such that the smaller the molecular weight of the resin used is, or the solubility with the coloring material. It is speculated that the smaller the difference in the parameter, the higher it becomes. Therefore, most of the coloring materials are dissolved in the resin having a small molecular weight, and conversely, the resin having a high molecular weight hinders the permeation of the ink solvent. In addition, when the solubility parameter is set to the condition defined in the present invention, a larger effect is obtained because the resin having a larger molecular weight is distributed to the outside of the resin having a smaller molecular weight in which the coloring material is dissolved in a larger amount. I presume that it has been obtained.

Further, the volume average particle diameter of the colored fine particles is 10
To 200 nm, the coloring fine particles have a core-shell structure in which the surface of the resin containing the coloring material is further coated with the resin, or the surface tension and pH of the inkjet ink (hereinafter, also referred to as the ink of the present invention) are specified. It has been found that the effect of the present invention can be further exerted by defining the above range, and the present invention has been achieved.

The details of the present invention will be described below. In the invention according to claim 1, an inkjet ink containing colored fine particles made of a resin A containing a coloring material or colored fine particles obtained by further coating the surface of a resin A containing a coloring material with a resin B, an aqueous solvent and water. The initial elution ratio of the coloring material to the coloring material dissolving agent of the colored fine particles is 10% or less, and the resin A is two or more resins having different weight average molecular weights. In the invention according to, the medium-term dissolution rate of the coloring material in the coloring material dissolving agent is 50%.
The characteristic feature is that the resin A is two or more resins having different weight average molecular weights.

The colorant-dissolving agent in the present invention is a solvent which dissolves 1 to 200 g / L of colorant at 20 ° C., and various solvents from hydrophobic solvent to hydrophilic solvent can be used. A solvent that dissolves the coloring material in an amount of 30 to 100 g / L is preferable. Although a suitable coloring material dissolving agent differs depending on the coloring material, it is generally preferable that the solubility parameter (SP value) is close to that of the coloring material. Examples of the dye include ethyl acetate, dichloromethane, dichloroethane, chloroform, toluene, tetrahydrofuran, methanol, acetone and the like. From the SP value of the dye used, a hydrophobic solvent is preferable, and ethyl acetate is particularly preferable. When the coloring material is a pigment, concentrated sulfuric acid, diluted sulfuric acid, Lewis acid such as trifluoroacetic acid, or dimethyl sulfoxide in the presence of an inorganic or organic base, N, N-dimethylformamide or the like is preferable. Particularly preferred is sulfuric acid.

In the case of a hydrophobic solvent that is phase-separated from water, it is easy to measure the dye elution rate from the absorbance, but in the case of a water-soluble solvent, a separation operation is required. For example, a general method for separating a solvent and a dispersed solid content such as filtration, salting-out, aciding-out, centrifugation, and extraction can be used.

The initial dissolution rate and the medium-term dissolution rate according to the present invention are defined as follows. The elution rate of the color material with respect to the color material dissolving agent, among the solvents satisfying the conditions of the color material dissolving agent,
If the value when any one is used is within the range, it is regarded as the present invention. To measure the elution rate of the coloring material, the ink and the coloring material dissolving agent should be 1:
The mixing is performed in the range of 1 to 1:39. It is preferable to perform the measurement at 1:19 for the convenience of spectral absorption measurement. The elution rate of the coloring material is determined by measuring the absorbance every 30 seconds from the time of mixing and measuring the spectral absorption, and plotting the ratio at each time with the concentration when all dyes are dissolved in the solubilizer being 100%. . In this measurement, the measurement liquid should not be strongly stirred and shaken, and when stirring is performed, it is performed at a rotation speed of 100 rpm or less by a magnetic stirrer.

The initial elution rate of the coloring material with respect to the coloring material dissolving agent defined in claim 1 is obtained by mixing the ink and the coloring material dissolving agent based on the slope of the dissolution rate data obtained according to the above measuring method. The initial elution rate is preferably 8% or less, more preferably 0.1 to 5%, after 30 seconds.

The medium-term elution ratio of the color material to the color material dissolving agent defined in claim 2 is the mixture of the ink and the color material dissolving agent based on the slope of the elution rate data obtained according to the above measuring method. After 2 minutes, the value of the elution rate after 2 minutes is indicated, and the medium-term elution rate is preferably 40% or less, more preferably 0.1 to 30%.

In the present invention, there is no particular limitation as to the method for obtaining an ink jet ink having the respective elution ratios defined in claims 1 and 2, but in the present invention, the resin has a weight average molecular weight of It is preferable to use two or more different resins, or to use a resin having the characteristics defined in claim 4, and particularly to use a resin having the above-mentioned characteristics as the resin constituting the core.

The present invention is characterized in that the resin A coexisting with the coloring material used for the colored fine particles is composed of two or more resins having different weight average molecular weights, and more preferably gel permeation chromatography. It has two or more peaks, and more preferably the largest weight average molecular weight is 2.5 times the smallest weight average molecular weight in the two or more peaks, when measured by a graphic method. The above is preferable.

In the invention according to claim 6, it is preferable that the colored fine particles have a core-shell structure in which the surface of the resin A containing the coloring material is further coated with the resin B.

Further, in the invention according to claim 4, in the resin A consisting of two or more resins having different weight average molecular weights, the solubility parameter of the resin having the smallest weight average molecular weight is ps (J / cm ³ ) ^{1 / 2} , the solubility parameter of the resin with the highest weight average molecular weight is pl (J / c
m ³ ) ^1/2 , the solubility parameter of the coloring material is pc (J / c
When m ³ ) ^1/2 , it is preferable to satisfy the conditions of the following formulas (1) and (2).

Formula (1) ps ≦ pl Formula (2) | ps-pc | ≦ | pl-pc | In the above formula (2), | ps-pc | is preferably 3.6 or less, more preferably It is 0 or more and 2.0 or less.

The solubility parameter referred to in the present invention is a value obtained by the solubility parameter of Hildebrand which is often used in evaluating the solubility of the non-electrolyte in the organic solvent. This solubility parameter is described, for example, in J. H. Hildebrand, J. et al. M.
Prausnitz. R. L. Scott's "Regu
lar and Related Solution
s ", Van Nostrand-Reinhold,
See Princeton (1970), "Polymer Data Handbook Basic Edition", The Polymer Society of Japan. The values of the solubility parameters of various solvents are A. F. M. Barton, "H
andbook of Solrbility Par
ameters and other cohesio
n Parameters ”, CRC Press, B
oca Raton / Florida (1983),
"Polymer Data Handbook Basic Edition" is described in The Polymer Society of Japan.

The solubility parameter of a substance is defined by SP = (δE / V) ^1/2 , where δE is the cohesive energy per mole and V is the molar volume.

The solubility parameter can be determined by several methods such as a method of determining from solubility or a latent heat of vaporization method, a vapor pressure method, a swelling method, a surface tension method, a thermal swelling coefficient method, and a refractive index method.

In the present invention, any solubility parameter obtained by the following method is used.
The unit is represented by (J / cm ³ ) ^1/2 in the present invention.

The solubility parameter can be determined from the solubility in a solvent of which various SP values are known. This method of obtaining the solubility parameter by the solubility in the solvent is effective when the structure of the dye or the like is unknown.

When the coloring material according to the present invention is a dye, various solvents having known SP values such as ethanol, acetone, methyl ethyl ketone, ethyl acetate, etc. are used, and the solute is determined from the SP value of the solvent having the highest solubility. Dye S as
The dissolution method for determining the P value is used. In the documents listed below,
Δd (dispersion force term), δp (polarity term), δh, which are the components of the SP value of each solvent of the group with the highest solubility
(Hydrogen bond term) is plotted separately for each term,
The central value is calculated for each term. The SP value of the dye can be obtained by using the center value as the value of each term of the SP value of the dye. C. M. Hansen, J .; Paint
Technol. , 39 (505) 104 (196
7), C.I. M. Hansen, J .; Paint Te
chnol. , 39 (511) 505 (1967) On the other hand, in the case of a pigment having a low solubility in a solvent, the S
Although it is difficult to obtain the P value accurately, the above-mentioned document shows the measurement using the suspended state. That is, the closer the solvent is to the pigment, the better the wetting of the pigment. Therefore, after mixing the solvent and the pigment, shake the solvent well to produce a solvent in a good suspended state (not settling) such as ethanol, acetone, methyl ethyl ketone, ethyl acetate, etc. (A plurality of solvents may be used), and δd (dispersion force term), δp (polarity term), and δh (hydrogen bond term) of each solvent in good suspension state are divided for each term. Plot each δd (dispersive force term), δ
The central value of each of the p (polar term) and δh (hydrogen bond term) is calculated, and the calculated central value of each term is the SP of the desired pigment.
The SP value of the pigment can be obtained by setting each term of the value. Further, the solubility parameter can be obtained by calculation when the structure is known.

Small proposed a method of calculating the SP value by relating the chemical composition to the SP value and dividing the sum of the molar attraction constants ΔF in the molecule by the molar volume V. In this method, ΔF can be assigned to each atomic group and therefore can be easily calculated.

S = (ΣΔF) / V However, in the Small equation, since only the cohesive energy generated from the dispersive force is included, in order to further improve the accuracy of the above calculation method, Rheineck, Hoy, Kre
velen, Fedors and others have proposed different modified ΔF. In addition, Hansen proposed three-dimensionally decomposed parameters. Although the numerical value varies slightly depending on each correction parameter, the error when viewed as the difference between the two types of color materials defined in the present invention is small. When the structure is known, the solubility parameter obtained by calculation using the above-mentioned correction parameter can be used. The calculation program used in the present invention is Project Leader in a molecular calculation package called CACHE manufactured by Fujitsu Limited.

The solubility parameter calculated by any of these methods is used in the present invention. For example, when the solubility parameter value is obtained from the solubility in a solvent, the solubility parameter value of the solvent to be used may be slightly different depending on the obtaining method, and the SP value of the coloring material is slightly different accordingly. come. However, since the difference in the value is not so large, the difference in SP value between the color materials may be the smallest. Therefore, in the case of a dye or pigment of known structure,
The calculation method described above is preferably used.

Next, resin A that can be used in the present invention
(Also referred to as the polymer according to the present invention) will be described.

In the colored fine particles according to the present invention, as the resin A coexisting with the coloring material, it is preferable to use two or more resins having different weight average molecular weights, and use the polymer under the condition defined in claim 4, and the number thereof. 500 as the average molecular weight
It is preferably from 100 to 100,000, and particularly from 3000 to 60,000 from the viewpoint of the strength of the coating film after printing, its durability and the formability of the suspension.

Various Tg values can be used for the polymer of the present invention, but it is preferable to use at least one of the polymers having a Tg of 10 ° C. or higher.

In the present invention, as the resin A according to the present invention, generally known polymers can be used, but particularly preferable polymers are those containing an acetal group as a main functional group and a carbonic acid ester group. The polymer contained, the polymer having a hydroxyl group, and the polymer having an ester group, and particularly the polymer constituting the outermost shell portion preferably has a hydroxyl group. The above polymer may have a substituent,
The substituent may have a linear, branched or cyclic structure. Further, the polymer having the above functional group,
Although various products are commercially available, they can be synthesized by a conventional method. Further, these copolymers can also be obtained, for example, by introducing an epoxy group into one polymer molecule and then polycondensing it with another polymer or performing graft polymerization using light or radiation.

As a polymer containing an acetal as a main functional group, a polyvinyl butyral resin can be preferably mentioned. For example, Denki Kagaku Kogyo Co., Ltd. # 2000-L, # 3000-1, # 3000-
2, # 3000-4, # 3000-K, # 4000-
1, # 4000-2, # 5000-A, # 6000-
C, # 6000-EP, or BL made by Sekisui Chemical Co., Ltd.
-1, BL-1H, BL-2, BL-2H, BL-5,
BL-10, BL-S, BL-SH, BX-10, BX
-L, BM-1, BM-2, BM-5, BM-S, BM
-SH, BH-3, BH-6, BH-S, BX-1, B
X-3, BX-5, KS-10, KS-1, KS-3,
KS-5 and the like.

Polyvinyl butyral resin is obtained as a derivative of PVA (polyvinyl alcohol), but the acetalization of the hydroxyl group of the original PVA is 80 mol at maximum.
%, Usually from 50 mol% to 80 mol%
It is a degree. It should be noted that the acetal referred to here is 1 in a narrow sense.
It does not refer to the 1-diethoxyethane group, but refers to compounds in general with orthoaldehyde. The hydroxyl group is not particularly defined, but in the polymer constituting the outermost shell portion, the hydroxyl group-containing monomer is preferably 5 to 50 mol%, more preferably 10 to 30 mol%.
Is. The content of acetyl groups is not particularly limited, but is preferably 10 mol% or less. A polymer containing acetal as a main functional group means at least 30 mol% of oxygen atoms contained in the polymer.
The above means that an acetal group is formed.

Besides, as a polymer containing acetal as a main functional group, Iupital series manufactured by Mitsubishi Engineering Plastics Co., Ltd. can be used.

Examples of the polymer containing carbonic acid ester as a main functional group include polycarbonate resins. For example, there are Iupilon series and Novarex series manufactured by Mitsubishi Engineering Plastics Co., Ltd. The Iupilon series is made from bisphenol A as a raw material, and various molecular weights can be used although the value varies depending on the measuring method. The Novarex series has a molecular weight of 20,000 and a glass transition point of 150.
A material having a temperature in the vicinity of ° C can be used, but the material is not limited to these.

The polymer containing a carbonic acid ester group as a main functional group means that at least 30 mol% or more of oxygen atoms contained in the polymer contribute to the formation of a carbonic acid ester group.

Examples of the polymer containing a hydroxyl group as a main functional group include PVA. Although the solubility of PVA in organic solvents is low in many cases, the solubility of PVA in organic solvents increases if the saponification value is low. Highly water-soluble PVA can also be used by adding it to the aqueous phase, removing the organic solvent, and adsorbing it to the polymer suspension.

Commercially available PVA can be used. For example, Kuraray's Poval PVA-102 and PVA can be used.
VA-117, PVA-CSA, PVA-617, PV
In addition to A-505, special grade PVA for sizing agents,
As PVA for hot melt molding and other functional polymers, K
L-506, C-118, R-1130, M-205,
MP-203, HL-12E, SK-5102, etc. can be used. The degree of saponification is generally 50 mol% or more, but it is 40 mol as in LM-10HD.
Even if it is about 1%, it is possible to use it.
Other than PVA, those having a hydroxyl group as a main functional group can be used, but those having at least 20 mol% or more of oxygen atoms contained in the polymer forming a hydroxyl group can be used.

Examples of the polymer containing an ester group as a main functional group include methacrylic resin. Asahi Kasei Delpet series 560F, 60N,
80N, LP-1, SR8500, SR6500, etc. can be used. The polymer containing an ester group as a main functional group means that at least 30 mol% or more of oxygen atoms contained in the polymer form an ester group.

One of these polymers is used or two of them are used.
You may mix and use 1 or more types. Further, other polymers and inorganic fillers may be contained as long as these polymers are contained in a mass ratio of 50% or more.

Although it is preferable to use a copolymer of these polymers, for example, a polymer containing a hydroxyl group,
As a method of copolymerizing various polymers, it can be obtained by reacting a hydroxyl group with a monomer having an epoxy group such as glycidyl methacrylate and then copolymerizing it with a methacrylic acid ester monomer by suspension polymerization.

Further, the resin B according to the present invention can be appropriately selected and used from the above-mentioned polymers.

In the ink-jet ink of the present invention, the polymer used for the colored fine particles is preferably contained in the ink in an amount of 0.5 to 50% by mass, and 0.5 to 50% by mass is preferable.
It is more preferable that the content is ˜30% by mass. If the blending amount of the above polymer is less than 0.5% by mass, the ability to protect the coloring material is insufficient, and if it exceeds 50% by mass, the storage stability of the suspension as an ink is lowered, or the nozzle tip portion is deteriorated. Since there is a case where clogging of the printer head may occur due to thickening of the ink and aggregation of the suspension due to the evaporation of the ink, it is preferably within the above range.

Next, the aqueous solvent according to the present invention will be described. The aqueous solvent that can be used in the present invention is not particularly limited, but it is preferable to use the compound represented by the following general formula (1).

General Formula (1) AB In the formula, A represents a group containing a hydrophilic substituent, and B represents a hydrophobic group.

The group represented by A here is a group containing a hydrophilic substituent, and as the hydrophilic substituent, a hydroxy group, a carboxyl group, a sulfoxide group, a sulfone group, a sulfonic acid group, and 2-keto-1. -Pyrrolidinyl group and the like.
Of these, a hydroxy group is preferable.

B represents a hydrophobic group, preferably an aliphatic or aromatic hydrocarbon group having 3 to 10 carbon atoms.
Further, B is preferably an aliphatic group having 4 to 8 carbon atoms.

The compound represented by the general formula (1) has a structure similar to that of a general surfactant. A general surfactant has a characteristic of forming micelles in an aqueous solution at a low concentration.

The compound represented by the general formula (1) preferably does not have such micelle forming ability. This is because, when it has a micelle forming ability, it has a drawback that the viscosity of the ink remarkably increases when the concentration exceeds 1% because the interaction between molecules is strong.

As the aqueous solvent that can be used in the present invention, a water-soluble organic solvent is preferable, and specifically, alcohols (for example, methanol, ethanol, propanol, isopropanol, butanol, isobutanol, secondary butanol, tert-butanol) are used. Libutanol, pentanol, hexanol, cyclohexanol, benzyl alcohol, etc., polyhydric alcohols (eg, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, butylene glycol, hexanediol) , Pentanediol, glycerin, hexanetriol, thiodiglycol, etc.), polyhydric alcohol ethers (eg ethylene glycol Monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol monophenyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, diethylene glycol dimethyl ether, propylene glycol monomethyl ether, propylene glycol monobutyl ether, ethylene glycol Monomethyl ether acetate, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether, triethylene glycol dimethyl ether, dipropylene glycol monopropyl ether, tripropylene glycol dime Ether, etc.), amines (e.g., ethanolamine, diethanolamine, triethanolamine, N- methyldiethanolamine, N- ethyldiethanolamine, morpholine, N- ethylmorpholine, ethylenediamine,
Diethylenediamine, triethylenetetramine, tetraethylenepentamine, polyethyleneimine, pentamethyldiethylenetriamine, tetramethylpropylenediamine, etc.), amides (eg, formamide, N, N-)
Dimethylformamide, N, N-dimethylacetamide, etc.), heterocycles (eg, 2-pyrrolidone, N-methyl-2-pyrrolidone, N-cyclohexyl-2-pyrrolidone, 2-oxazolidone, 1,3-dimethyl-2-). Imidazolidinone etc.), sulfoxides (eg dimethyl sulfoxide etc.), sulfones (eg sulfolane etc.), sulfonates (eg 1-butanesulfonic acid sodium salt etc.), urea, acetonitrile, acetone and the like. However, in the invention according to claim 5, at least one of the aqueous solvents is preferably a polyhydric alcohol ether or a polyhydric alcohol,
More preferably, as the polyhydric alcohol ethers,
Ethylene glycol monobutyl ether (butyl cellosolve), diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, ethylene glycol monophenyl ether, and polyhydric alcohols are 1,2-hexanediol, or 1,2-hexanediol.
-Pentanediol, particularly preferably triethylene glycol monobutyl ether or 1,2-hexanediol.

Next, the colored fine particles according to the present invention will be described in detail below. Colored fine particles according to the present invention,
It can be prepared by various methods. For example, a method of dissolving an oil-soluble coloring material in a monomer, emulsifying it in water, and then encapsulating the coloring material in a polymer by polymerization, dissolving the polymer and the coloring material in an organic solvent, and then emulsifying in water and then using an organic solvent. How to remove, add porous polymer particles to the colorant solution,
Examples thereof include a method of adsorbing and impregnating fine particles with a coloring material, and a shelling method of coating these colored fine particles with a polymer can also be used.

The polymer shell may be provided by adding a water-soluble polymer dispersant to an aqueous suspension of the core and adsorbing it, by gradually dropping a monomer and depositing it on the surface of the core simultaneously with polymerization, or by using an organic solvent. There is a method in which the polymer dissolved in is gradually dropped and adsorbed on the core surface simultaneously with precipitation. A method of forming the core shell in one step is also conceivable. For example, a method in which a core polymer and a dye together with a shell polymer are heated and dissolved, and then suspended and polymerized in water, or emulsion polymerization is performed while gradually dropping the liquid into water containing an active agent micelle. There are ways. Alternatively, there is a method in which a dye is dissolved or dispersed in a monomer that can be a core and a monomer that can be a shell after polymerization, and suspension polymerization or emulsion polymerization is performed.

The colored fine particles according to the present invention are not particularly limited to shelled ones and shelled ones. However, in view of the effect of the invention, in the invention according to claim 6, the colored fine particles are It is preferable that the surface of the resin A containing the coloring material is further covered with the resin B to have a core-shell structure. In that case, the amount of polymer used in the shell is preferably 5% by mass or more and 95% by mass or less of the total amount of polymer. When the amount is less than 5% by mass, the thickness of the shell is insufficient and a part of the core containing a large amount of coloring material is likely to appear on the particle surface. On the other hand, if the shell polymer is too much, the amount of the core polymer is relatively decreased, and the function of protecting the color material is likely to be deteriorated. More preferably, it is 10% by mass or more and 90% by mass or less.

The coloring material is 20% by mass with respect to the total amount of polymer.
It is preferably not less than 1000% by mass. When the amount of the coloring material is too small compared to the polymer, the image density after ejection does not increase, and when the ratio of the coloring material is high, the polymer protecting ability cannot be sufficiently obtained.

(Evaluation of core-shell formation) In the present invention, it is important to evaluate whether or not a core-shell structure is actually formed. In the present invention, the particle size of each particle is very small, 150 nm or less, so the analysis method is limited from the viewpoint of resolution. A transmission electron microscope (TEM), a time-of-flight secondary ion mass spectrometer (TOF-SIMS), or the like can be applied as an analysis method that meets such a purpose. TE
When observing the colored fine particles core-shelled by M,
The dispersion can be coated on a carbon support film, dried, and observed. Since the TEM observation image is usually monochrome, it is necessary to dye the colored fine particles in order to evaluate whether or not it is core-shelled. The colored fine particles of only the core are dyed, and the TEM observation is performed, and comparison is made with the one provided with the shell. Further, the fine particles provided with the shell and the fine particles not provided with the shell are mixed and dyed, and it is confirmed whether or not the ratio of the fine particles having different degrees of dyeing coincides with the presence or absence of the shell. In TOF-SIMS, it is confirmed that the dye in the vicinity of the surface is reduced by providing the shell on the particle surface as compared with the case where only the core is used. When the coloring material has an element that is not contained in the polymer of the core shell, it is possible to confirm whether or not a shell having a small coloring material content is provided by using the element as a probe. In the absence of such elements, the colorant content in the shell can be compared with that without the shell using an appropriate dye. By embedding core-shell particles in an epoxy resin, making an ultrathin section with a microtome, and dyeing, core-shell formation can be observed more clearly. When the polymer or dye has an element that can serve as a probe, the composition of the core-shell and the amount of the dye distributed to the core and the shell can be estimated by TEM.

In the invention according to claim 7, the colored fine particles preferably have a volume average particle size of 10 to 200 nm, preferably 20 to 120 nm, and particularly preferably 20.
It is preferable that the volume-average particle diameter defined by the present invention can exert the effects of the present invention at all.

The volume average particle size can be measured by a commercially available particle size measuring device using, for example, a light scattering method, an electrophoresis method, a laser Doppler method, etc. , Shimadzu laser diffraction particle size analyzer SLAD1100, particle size analyzer (HOR
IBA LA-920), Zetasizer 1000 manufactured by Malvern Instruments Ltd., and the like.

Next, the coloring material according to the present invention will be described. In the present invention, various dyes or pigments known in the ink jet can be used as the coloring material encapsulated by the polymer, but in the present invention, it is preferable to use a dye as the coloring material. The dye that can be used is not particularly limited, and examples thereof include oily dyes, disperse dyes, direct dyes, acid dyes, and basic dyes. In the present invention, it is preferable to use oily dyes.

As the hue, yellow, magenta, cyan, black, blue, green and red are preferably used, and yellow, magenta, cyan and black dyes are particularly preferable. The oil-soluble dyes also include dyes that exhibit oil-solubility by forming a salt of a water-soluble dye with a long-chain base. The oily dye is not limited to the following, but a particularly preferred specific example is, for example, Valifast manufactured by Orient Chemical Industry Co., Ltd.
Yellow 4120, Valifast Yel
low 3150, Valifast Yellow
3108, Valifast Yellow 2310
N, Valifast Yellow 1101, Va
liftast Red 3320, Valifast
Red 3304, Valifast Red 130
6, Valifast Blue 2610, Vali
fast Blue 2606, Valifast B
lue 1603, Oil Yellow GG-S,
Oil Yellow 3G, Oil Yellow 1
29, Oil Yellow107, Oil Yell
ow 105, Oil Scarlet 308, Oi
l Red RR, Oil Red OG, Oil R
ed 5B, OilPink 312, Oil Blu
e BOS, Oil Blue 613, Oil Bl
ue 2N, Oil Black BY, Oil Bl
ack BS, Oil Black 860, Oil
Black 5970, Oil Black 590
6, Oil Black 5905, Kayase Yellow SF-G, Kay manufactured by Nippon Kayaku Co., Ltd.
aset Yellow K-CL, Kayaset
Yellow GN, Kayaset Yellow
AG, Kayset Yellow 2G, Kay
asset Red SF-4G, Kayase Re
d K-BL, Kayaset Red A-BR, K
ayasetMagenta312, Kayaset
Blue K-FL, FS manufactured by Arimoto Chemical Industry Co., Ltd.
Yellow 1015, FS Magenta 14
04, FS Cyan 1522, FS Blue 1
504, C.I. I. Solvent Yellow 8
8 、 Solvent Yellow 83 、 Solve
nt Yellow 82, Solvent Yell
ow 79, Solvent Yellow 56, S
solvent Yellow 29, Solvent
Yellow 19, Solvent Yellow
16, Solvent Yellow 14, Solv
ent Yellow 04, Solvent Yel
low 03, Solvent Yellow 02,
Solvent Yellow 01, C.I. I. Sol
Vent Red 84: 1, C.I. I. Solvent
Red 84, C.I. I. SolventRed 21
8, C.I. I. Solvent Red 132, C.I.
I. Solvent Red 73, C.I. I. Solv
ent Red 72, C.I. I. Solvent Re
d 51, C.I. I. Solvent Red 43,
C. I. Solvent Red 27, C.I. I. So
lvent Red 24, Solvent Red
18, Solvent Red 01, Solvent
Blue 70, Solvent Blue 67, S
solvent Blue44, Solvent Blu
e 40, Solvent Blue 35, Solv
ent Blue 11, Solvent Blue
02, Solvent Blue 01, Solve
nt Black 43, C.I. I. Solvent B
rack 70, C.I. I. Solvent Black
34, C.I. I. Solvent Black 29,
C. I. Solvent Black 27, C.I. I.
Solvent Black 22, C.I. I. Solv
ent Black 7, C.I. I. Solvent B
rack 3, C.I. I. Solvent Violet
3, C.I. I. Solvent Green 3 and 7
Etc.

Further, JP-A-9-277693 and 10
Metal complex dyes as shown in Nos. -20559 and 10-30061 are also preferably used, and a preferable structure is represented by the following general formula (2).

In the general formula (2) M (Dye) _l (A) _m , M represents a metal ion, and Dye represents a dye capable of forming a coordinate bond with a metal. A represents a ligand other than the dye, 1 represents 1 to 3 and m represents 0, 1, 2, 3. When m is 0, 1 represents 2 or 3, and in that case, Dye may be the same or different. Examples of the metal ion represented by M include Al, Co, Cr, Cu, Fe, Mn, Mo and N.
Examples include ions of i, Sn, Ti, Pt, Pd, Zr, and Zn. Ni, Cu, Cr, from the color tone and various durability,
Ions of Co, Zn and Fe are particularly preferable. More preferably, it is Ni ion.

Various dye structures are conceivable as the dye represented by Dye and capable of forming a coordination bond with the metal, but a conjugated methine dye, an azomethine dye, and a dye having a coordination group in the azo dye skeleton are preferable.

The disperse dye is not limited to the following, but particularly preferable specific examples include C.I. I. Disperse Yellow 5, 42, 54, 64, 79, 8
2, 83, 93, 99, 100, 119, 122, 12
4, 126, 160, 184: 1, 186, 198, 1
99, 204, 224 and 237; C.I. I. Disperse Orange 13, 29, 31: 1, 33, 49, 54,
55, 66, 73, 118, 119 and 163;
I. Disperse Red 54, 60, 72, 73, 8
6, 88, 91, 92, 93, 111, 126, 12
7, 134, 135, 143, 145, 152, 15
3, 154, 159, 164, 167: 1, 177, 1
81, 204, 206, 207, 221, 239, 24
0, 258, 277, 278, 283, 311, 32
3, 343, 348, 356 and 362; I. Disperse Violet 33; C.I. I. Disperse Blue 56, 60, 73, 87, 113, 128, 143,
148, 154, 158, 165, 165: 1, 16
5: 2, 176, 183, 185, 197, 198, 2
01, 214, 224, 225, 257, 266, 26
7, 287, 354, 358, 365 and 368; and C.I. I. Examples include Disperse Green 6: 1 and 9.

The pigment is not limited to the following, but as a particularly preferred specific example, the carbon black pigment may be No. 1 manufactured by Mitsubishi Kasei. 2300, No. 90
0, MCF-88, No. 33, No. 40, No. Four
5, No. 52, MA7, MA8, MA100, No. 52.
2200B, Columbia Raven 700, Ra
ven 5750, Raven 5250, Raven
5000, Raven3500, Raven 125
5, Cabot's Regal 400R, Regal
330R, Regal 660R, Mogul L,
Monarch 700, Monarch 800, Mo
narch 880, Monarch 900, Mona
rch 1000, Monarch 1100, Mon
arch 1300, Monarch 1400, Degussa's Color Black FW1, Color
Black FW2, Color Black FW2
V, Color Black FW18, Color
Black FW200, Color Black S
150, Color Black S160, Colo
r Black S170, Printex 35, P
printexU, Printex V, Printex
140U, Printex 140V, Specia
l Black 6, Special Black
5, Special Black 4A, Specia
l Black 4, Maxsorb G-40, Maxsorb G-15, Maxsorb G-08 and the like manufactured by Kansai Thermochemical Co., Inc. can be used.

As the yellow pigment, C.I. I. Pigm
ent Yellow 1, C.I. I. Pigment
Yellow 2, C.I. I. Pigment Yell
ow3, C.I. I. Pigment Yellow 1
2, C.I. I. Pigment Yellow 13, C.I.
I. Pigment Yellow 14, C.I. I. P
igment Yellow 16, C.I. I. Pigm
ent Yellow 17, C.I. I. Pigment
Yellow 73, C.I. I. Pigment Ye
low 74, C.I. I. Pigment Yellow
w 75, C.I. I. Pigment Yellow 8
3, C.I. I. Pigment Yellow 93,
C. I. Pigment Yellow 95, C.I.
I. Pigment Yellow 97, C.I. I. P
igment Yellow 98, C.I. I. Pigm
ent Yellow 114, C.I. I. Pigmen
tYellow 128, C.I. I. Pigment Y
ellow 129, C.I. I. Pigment Yel
low 151, C.I. I. Pigment Yellow
w 154, magenta pigments include C.I. I. Pigm
ent Red 5, C.I. I. Pigment Red
7, C.I. I. Pigment Red 12, C.I.
I. Pigment Red 48 (Ca), C.I. I.
Pigment Red 48 (Mn), C.I. I. Pi
gment Red 57 (Ca), C.I. I. Pigm
ent Red 57: 1, C.I. I. Pigment
Red 112, C.I. I. Pigment Red 1
23, C.I. I. Pigment Red 168, C.I.
I. Pigment Red 184, C.I. I. Pig
ment Red 202, and cyan pigments include C.I.
I. Pigment Blue 1, C.I. I. Pigm
ent Blue 2, C.I. I. Pigment Bl
ue 3, C.I. I. Pigment Blue 15:
3, C.I. I. Pigment Blue 15:34,
C. I. Pigment Blue 16, C.I. I. P
igmentBlue 22, C.I. I. Pigment
Blue 60, C.I. I. VatBlue 4, C.I.
I. The coloring material contained in the colored fine particles according to the present invention, such as Vat Blue 60, is contained in the ink in an amount of 1 to 3
It is preferably blended in an amount of 0% by mass, more preferably 1.5 to 25% by mass. If the blending amount of the coloring material is less than 1% by mass, the print density is insufficient, and if it exceeds 30% by mass, the stability of the suspension with time deteriorates.
Since the particle size tends to increase due to agglomeration and the like, it is preferably within the above range.

The ink-jet ink of the present invention comprises a suspension of a polymer in which water is used as a medium and in which the above-mentioned coloring material is encapsulated. In addition to the above-mentioned aqueous solvent, the suspension includes various conventionally known additives such as, for example, A dispersant, a silicone-based antifoaming agent, a chloromethylphenol-based antifungal agent and / or a chelating agent such as EDTA, and an oxygen absorbent such as sulfite may be contained.

The dispersant is not particularly limited, but when the HLB value is 8 to 18, the effect as a dispersant is exhibited and the effect of suppressing the increase in the particle size of the suspension is obtained. preferable.

Commercially available products can also be used as the dispersant. Examples of such a commercially available product include dispersants DEMOL SNB, MS, N, SSL, ST, P manufactured by Kao Corporation.
(Product name).

The amount of the dispersant blended is not particularly limited, but 0.01 to 10% by mass is preferably blended in the ink-jet ink of the present invention. The compounding amount of the compound is 0.
If the amount is less than 01% by mass, it is difficult to reduce the particle size of the suspension. If the amount is more than 10% by mass, the particle size of the suspension may be increased or the suspension stability may be deteriorated to cause gelation. It is preferable that

The defoaming agent is not particularly limited, and commercially available products can be used. Examples of such commercially available products include KF96, 6 manufactured by Shin-Etsu Silicone Co., Ltd.
6, 69, KS68, 604, 607A, 602, 60
3, KM73, 73A, 73E, 72, 72A, 72
C, 72F, 82F, 70, 71, 75, 80, 83
A, 85, 89, 90, 68-1F, 68-2F (brand name) etc. are mentioned. The compounding amount of these compounds is not particularly limited, but it is 0.
It is preferable that 001 to 2 mass% is blended. If the compounding amount of the compound is less than 0.001% by mass, bubbles are likely to be generated during ink preparation, and it is difficult to remove small bubbles in the ink, and if it exceeds 2% by mass, the generation of bubbles is suppressed. ,
At the time of printing, repellency may occur in the ink and the print quality may deteriorate, so the range is preferably within the above range.

Next, a method for producing the ink-jet ink of the present invention will be described. The inkjet ink of the present invention can be manufactured by various emulsification methods.

As described above, in the invention according to claim 7, the volume average particle diameter of the colored fine particles is preferably 10 to 200 nm, but there is no particular limitation as a method for achieving the average particle diameter defined above. However, it can be achieved, for example, by appropriately selecting or combining the types and amounts of the dispersants described above, or the emulsification methods shown below.

Various methods can be used as the emulsification method. Examples of these are summarized, for example, in the description on page 86 of “Progress of Functional Emulsifiers / Emulsification Technologies and Their Application and Development”. In the present invention, it is particularly preferable to use an emulsifying / dispersing device using ultrasonic waves, high-speed rotary shearing, and high pressure.

In ultrasonic dispersion, so-called batch type and continuous type can be used. The batch type is
It is suitable for preparing a relatively small amount of sample, and the continuous method is suitable for preparing a large amount of sample. In the continuous system, for example, UH-60
It is possible to use a device such as 0SR (manufactured by SMT Co., Ltd.). In the case of such a continuous system, the irradiation time of ultrasonic waves can be obtained by the formula: volume of dispersion chamber / flow velocity × number of circulations. When there are a plurality of ultrasonic irradiation devices, the total irradiation time can be calculated. The ultrasonic wave irradiation time is actually required to be 3 seconds or longer, and if the emulsification is completed within that time, the ultrasonic wave emulsification dispersion device is not required. Further, if it is necessary for 10000 seconds or more, the load of the process is heavy, and it is necessary to shorten the emulsification / dispersion time by reselection of the emulsifier in practice. Therefore, 10,000 seconds or more is not necessary. More preferably, 10 seconds or more, 20
It is within 00 seconds.

Examples of the emulsification / dispersion apparatus using high-speed rotary shearing include a disper mixer as described on pages 255-256 of “Advancement of functional emulsifier / emulsification technology and its application development” and a page 251. A homomixer as described above, an ultramixer as described on page 256, or the like can be used. These types can be used properly depending on the liquid viscosity at the time of emulsion dispersion. In these emulsifying dispersers using high-speed rotary shearing, the rotation speed of the stirring blade is important. Since the clearance with the stator is usually about 0.5 mm and cannot be extremely narrowed, the shearing force mainly depends on the peripheral speed of the stirring blade. When the peripheral speed is 5 m / sec or more and 150 m / sec or less, it can be used in the emulsification / dispersion of the present invention. This is because when the peripheral speed is slow, it is often impossible to reduce the particle size even if the emulsification time is extended, and it is necessary to extremely improve the performance of the motor in order to achieve 150 m / sec. More preferably, it is 20 to 100 m / sec.

For emulsification and dispersion by high pressure, LAB2000
(Made by SMT) can be used, but the emulsification /
Dispersion capacity depends on the pressure applied to the sample. The pressure is preferably 10 MPa or more and 500 MPa or less. In addition, the desired particle size can be obtained by emulsifying and dispersing several times as necessary. If the pressure is too low, the desired particle size cannot be achieved in many cases, no matter how many times emulsification and dispersion are performed, and in order to set the pressure to 500 MPa, a large load is applied to the device, which is not practical. More preferably, it is 50 MPa or more and 200 MPa or less.

These emulsifying / dispersing devices may be used alone, or may be used in combination as required. A colloid mill, a flow jet mixer, etc., alone cannot achieve the object of the present invention, but by combining with the above-mentioned device, the effect of the present invention can be enhanced by enabling emulsification / dispersion in a single time. .

Further, the ink of the present invention can be produced by so-called phase inversion emulsification, in addition to using the above apparatus. Here, the phase inversion emulsification is to dissolve the above polymer together with the above dye in an organic solvent such as ester or ketone,
If necessary, a neutralizing agent is added to ionize the carboxyl groups in the polymer, and then an aqueous phase is added, and then the organic solvent is distilled off to invert the phase into an aqueous system.

After completion of the phase inversion, the system is heated under reduced pressure to remove the ester and ketone solvents and a predetermined amount of water to obtain the colored fine particles of the present invention having a desired concentration. An ink containing is obtained.

Next, another preferred embodiment of the inkjet ink of the present invention will be described.

In the invention according to claim 8, the surface tension of the ink jet ink is preferably 25 or more and 50 mN / m, more preferably 30 to 40 m.
N / m. As a means for adjusting the surface tension of the inkjet ink of the present invention, it is preferable to use various surfactants and to appropriately adjust the type and the addition amount thereof.

In a ninth aspect of the present invention, the pH of the inkjet ink is preferably 6.0 or more and 11.0 or less, and more preferably 8.0 or more and 1 or less.
It is 0.0 or less. Examples of the pH adjuster used in the inkjet ink of the present invention include various organic amines such as monoethanolamine, diethanolamine and triethanolamine, and alkali metal hydroxides such as sodium hydroxide, lithium hydroxide and potassium hydroxide. Examples thereof include inorganic alkaline agents such as substances, organic acids, and mineral acids.

In the ink-jet ink of the present invention, one kind or two or more kinds of anionic surfactant, nonionic surfactant and cationic surfactant can be used. Each surfactant that can be used in the present invention is not particularly limited, but examples thereof include anionic surfactants such as dialkylsulfosuccinates, alkylnaphthalenesulfonates, fatty acid salts, polyoxyethylene alkyl ethers, and polyoxyethylene alkyl ethers. Examples thereof include nonionic surfactants such as oxyethylene alkyl allyl ethers, acetylene glycols, polyoxyethylene / polyoxypropylene block copolymers, and cationic surfactants such as alkylamine salts and quaternary ammonium salts. In particular, an anionic surfactant and a nonionic surfactant can be preferably used.

In the present invention, a polymeric surfactant can also be used, and examples thereof include styrene-acrylic acid-acrylic acid alkyl ester copolymers, styrene-acrylic acid copolymers, styrene-maleic acid-acrylics. Acid alkyl ester copolymer, styrene-maleic acid copolymer, styrene-methacrylic acid-acrylic acid alkyl ester copolymer, styrene-methacrylic acid copolymer, styrene-maleic acid half ester copolymer, vinylnaphthalene-acrylic Examples thereof include acid copolymers and vinylnaphthalene-maleic acid copolymers.

The ink-jet ink of the present invention may contain a water-soluble polymer or water-insoluble polymer dispersion.

A natural polymer is a preferable example of the water-soluble polymer, and specific examples thereof include glue and
Proteins such as gelatin, casein, or albumin, natural gums such as gum arabic, or gum tragacanth, glucosides such as savonine, alginic acid and propylene glycol alginate, triethanolamine alginate, or alginate derivatives such as ammonium alginate, methylcellulose, Examples thereof include cellulose derivatives such as carboxymethyl cellulose, hydroxyethyl cellulose, or ethyl hydroxyl cellulose.

Further, as a preferable example of the water-soluble polymer, a synthetic polymer may be mentioned, and polyvinyl alcohols, polyvinyl pyrrolidones, polyacrylic acid, acrylic acid-acrylonitrile copolymers, potassium acrylate-acrylonitrile copolymers. Acrylic resins such as vinyl acetate-acrylic acid ester copolymers or acrylic acid-acrylic acid ester copolymers, styrene-acrylic acid copolymers, styrene-methacrylic acid copolymers, styrene-methacrylic acid-acrylic acid Ester copolymer, styrene-
Styrene acrylic acid resin such as α-methylstyrene-acrylic acid copolymer or styrene-α-methylstyrene-acrylic acid-acrylic acid ester copolymer, styrene-maleic acid copolymer, styrene-maleic anhydride copolymer Copolymer, vinylnaphthalene-acrylic acid copolymer, vinylnaphthalene-maleic acid copolymer, and vinyl acetate-ethylene copolymer, vinyl acetate-fatty acid vinylethylene copolymer, vinyl acetate-maleic acid ester copolymer, acetic acid Examples thereof include vinyl acetate-based copolymers such as vinyl-crotonic acid copolymers and vinyl acetate-acrylic acid copolymers and salts thereof. Among these, polyvinylpyrrolidones are particularly preferable.

The molecular weight of the water-soluble polymer is preferably 1,000 or more and 200,000 or less. Furthermore, 3,000 or more and 20,000 or less are more preferable. If it is less than 1,000, the effect of suppressing the growth and aggregation of the colored fine particles is reduced, and if it exceeds 200,000, problems such as an increase in viscosity and poor dissolution tend to occur.

The amount of the water-soluble polymer added is 1 with respect to the dye.
It is preferably 0% by mass or more and 1,000% by mass or less. Furthermore, 50 mass% or more and 200 mass% or less are more preferable.
If it is less than 10% by mass, the effect of suppressing the growth and aggregation of the colored fine particles is reduced, and if it exceeds 1000% by mass, problems such as viscosity increase and poor dissolution tend to occur.

Further, as a water-insoluble polymer dispersion liquid (hereinafter also referred to as latex) which can be used in the present invention,
Although not particularly limited, for example, styrene-butadiene copolymer, polystyrene, acrylonitrile-butadiene copolymer, acrylic ester copolymer, polyurethane,
Examples thereof include silicone-acrylic copolymers and latices such as acrylic modified fluorinated grease. Latex, even if the polymer particles are dispersed using an emulsifier,
It may also be dispersed without using an emulsifier. A surfactant is often used as an emulsifier, but a polymer having a water-soluble group such as a sulfonic acid group or a carboxylic acid group (for example, a polymer having a solubilizing group graft-bonded thereto or a monomer having a solubilizing group It is also preferable to use a polymer obtained from a monomer and a monomer having an insoluble portion.

In the ink of the present invention, it is particularly preferable to use soap-free latex. Soap-free latex is a latex that does not use an emulsifier, and a polymer having a water-soluble group such as a sulfonic acid group and a carboxylic acid group (for example, a polymer having a solubilizing group graft-bonded thereto, a solubilizing group Polymer obtained from a monomer having an insoluble portion and a monomer having an insoluble portion) is used as an emulsifier.

In recent years, as latex polymer particles, in addition to latex in which polymer particles having a uniform particle size are dispersed, core particles having different compositions at the central portion and the outer edge portion
Although there is a latex in which shell-type polymer particles are dispersed, this type of latex can also be preferably used.

In the ink of the present invention, the average particle size of the polymer particles in the latex is 10 nm or more and 300 nm or less, and more preferably 10 nm or more and 100 nm or less. If the average particle size of the latex exceeds 300 nm, the glossiness of the image deteriorates, and if it is less than 10 nm, the water resistance and scratch resistance become insufficient. The average particle size of the polymer particles in the latex can be determined by a commercially available particle size measuring device using a light scattering method, an electrophoresis method, or a laser Doppler method.

In the ink of the present invention, the latex content is 0.1% by mass based on the total mass of the ink as a solid content.
As described above, it is added so as to be 20% by mass or less, but it is particularly preferable that the solid content of the latex is 0.5% by mass or more and 10% by mass or less. If the solid content of the latex is less than 0.1% by mass, it is difficult to exert a sufficient effect on water resistance, and if it exceeds 20% by mass, the viscosity of the ink increases with the passage of time and the dispersion of colored fine particles occurs. In many cases, problems occur in terms of ink storability such that the particle size tends to increase.

In the ink of the present invention, in addition to the above description, if necessary, the ejection stability, the compatibility with the print head or the ink cartridge, the storage stability, the image storability, and other purposes of improving various performances are satisfied. , Various known additives, for example, viscosity modifier, resistivity modifier, film-forming agent, ultraviolet absorber, antioxidant, anti-fading agent, anti-rust agent, rust inhibitor, etc. may be appropriately selected and used. For example, liquid paraffin, dioctyl phthalate, tricresyl phosphate, oil droplet fine particles such as silicone oil, and JP-A-57-74.
193, 57-87988 and 62-2614.
UV absorbers described in JP-A-76-74192.
No. 57-89789, No. 60-72785, No. 61-146591, No. 1-95091 and No. 3-13376, and anti-fading agents, No. 59-42993, 59-52689, 62
Examples thereof include fluorescent whitening agents described in JP-A-280069, JP-A-61-242871 and JP-A-4-219266.

The recording medium used in the present invention includes plain paper, coated paper, swelling type inkjet recording paper provided with an ink receiving layer which absorbs an ink liquid and swells, and voids having a porous ink receiving layer. Type inkjet recording paper,
Further, a substrate using a resin support such as a polyethylene terephthalate film can be used instead of the base paper, but in the present invention, it is preferable to use a void type porous ink jet recording medium, and by this combination, the present invention can be used. Most effective.

As the porous ink jet recording medium,
Specifically, mention may be made of void-type inkjet recording paper or void-type inkjet film, which are recording media provided with a void layer having an ink absorbing ability, and the void layer is mainly hydrophilic. It is formed by soft agglomeration of the binder and the inorganic fine particles.

Various methods for forming a void layer are known as a method for forming voids in a film. For example, a uniform coating solution containing two or more kinds of polymers is coated on a support and dried in a drying process. A method of phase-separating these polymers with each other to form voids, a coating liquid containing solid fine particles and a hydrophilic or hydrophobic binder is applied on a support, and after drying,
A method of immersing an inkjet recording paper in water or a liquid containing a suitable organic solvent to dissolve solid fine particles to form voids, a coating liquid containing a compound having a property of foaming during film formation, and a drying process. A method of foaming this compound to form voids in the film, a method of applying a coating liquid containing porous solid fine particles and a hydrophilic binder onto a support to form voids in the porous fine particles or between the fine particles. ,
A method of forming voids between solid fine particles by applying a coating liquid containing solid fine particles and / or fine particle oil droplets and a hydrophilic binder having a volume equal to or more than the hydrophilic binder to a solid fine particle. However, when using the ink of the present invention, good results are obtained even if they are provided by any method.

In a tenth aspect of the present invention, it is a preferable mode that the ink of the present invention is ejected as a droplet from the ink jet head based on the digital signal and is attached to the ink jet recording medium.

The ink jet head that can be used in the image forming method of the present invention may be either an on-demand type or a continuous type. In addition, as a discharge method, an electro-mechanical conversion method (for example, a single cavity type, a double cavity type, a bender type, a piston type, a shear mode type, a shared wall type, etc.), an electric-heat conversion method (for example, a thermal type Specific examples include an inkjet type, a bubble jet (R) type, an electrostatic suction type (for example, an electric field control type, a slit jet type, etc.), and a discharge type (for example, a spark jet type). However, any ejection method may be used.

[0120]

The present invention will be specifically described below with reference to examples, but the present invention is not limited thereto.

<< Preparation of Colored Fine Particle Dispersion >> Colored fine particle dispersions 1 to 16 shown in Table 1 were prepared. An example of the preparation is shown below.

<Preparation of Core-Shell Type Colored Fine Particles: Preparation of Colored Fine Particle Dispersion 1 (Preparation Method 1)> 2.5 g of polyvinyl butyral (BL-1, manufactured by Sekisui Chemical Co., Ltd., weight average molecular weight 43,000, solubility) Parameter 10.0), 2.5g
Polyvinyl butyral (BM-5 manufactured by Sekisui Chemical Co., Ltd.,
Weight average molecular weight 120,000, solubility parameter 10.0),
5.0 g of Dye 1 (solubility parameter 9.9) and 50
g of ethyl acetate was placed in a separable flask, the inside of the flask was replaced with nitrogen gas, and the mixture was stirred to completely dissolve the above polyvinyl butyral and Dye 1. Then, 100 g of an aqueous solution containing 2.0 g of sodium dodecyl sulfonate
Was added dropwise and stirred, and then emulsified for 300 seconds using an ultrasonic disperser (UH-150 type manufactured by SMT Co., Ltd.). Then, ethyl acetate was removed under reduced pressure to obtain a colored fine particle dispersion containing core type colored fine particles impregnated with the dye.

Then, in the shell forming step, the inside of the flask containing the above dispersion liquid was replaced with nitrogen gas, and then 0.15 g of potassium persulfate was added to the dispersion liquid to dissolve it.
After heating with a heater to 70 ℃, styrene /
Core-shell type colored fine particles containing Dye 1 after reacting for 7 hours while dropping 2 g of a mixed liquid of 2-hydroxyethyl methacrylate (molar ratio 4/1) for 7 hours and then purifying with an ultrafiltration device. Dispersion liquid 1 was obtained. The average particle diameter of the colored fine particles contained in this colored fine particle dispersion liquid 1 is
It was 87 nm.

<Preparation of Core Type Colored Fine Particles: Preparation of Colored Fine Particle Dispersion 2 (Preparation Method 2)> 2.5 g of polyvinyl butyral (BL-1, manufactured by Sekisui Chemical Co., Ltd., weight average molecular weight 43,000, solubility) Parameter 10.0), 2.5 g of polyvinyl butyral (BM-5 manufactured by Sekisui Chemical Co., Ltd., weight average molecular weight 120,000, solubility parameter 10.0),
0 g of Dye 1 (solubility parameter 9.9) and 50 g of ethyl acetate were placed in a separable flask, the inside of the flask was replaced with nitrogen gas, and the mixture was stirred to completely dissolve the above polyvinyl butyral and Dye 1. Then, 100 g of an aqueous solution containing 2.0 g of sodium dodecyl sulfonate was added dropwise and stirred, and then an ultrasonic disperser (UH-150 type) was used.
It was emulsified for 300 seconds using SMT Co., Ltd. Then, ethyl acetate was removed under reduced pressure to obtain a colored fine particle dispersion liquid 2 containing core type colored fine particles impregnated with a dye.

<Preparation of Other Colored Fine Particle Dispersion Liquids> Coloring fine particle dispersion liquids other than those described above were also colored using the coloring materials shown in Table 1 and each polymer at the time of core formation, in accordance with the above-mentioned preparation example. Fine particle dispersions 3 to 16 were prepared.

Table 1 shows the constitution of each colored fine particle dispersion liquid obtained as described above.

[0127]

[Table 1]

[0128]

[Chemical 1]

Details of the compound abbreviations shown in Table 1 are as follows. Dye 2: FS Blue 1505 (manufactured by Arimoto Chemical Co., Ltd.) P-1: Styrene / butyl acrylate / 2-hydroxyethyl methacrylate copolymer (monomer molar ratio:
72/22/6, weight average molecular weight: 32,000, solubility parameter: 10.4) P-2: styrene / butyl acrylate / 2-hydroxyethyl methacrylate copolymer (monomer molar ratio:
75/10/15, weight average molecular weight: 32,000, solubility parameter: 10.9) P-3: styrene / butyl acrylate / 2-hydroxyethyl methacrylate copolymer (monomer molar ratio:
75/10/15, weight average molecular weight: 78,000, solubility parameter: 10.9) P-4: styrene / butyl acrylate / 2-hydroxyethyl methacrylate copolymer (monomer molar ratio:
72/22/6, weight average molecular weight: 78,000, solubility parameter: 10.4) P-5: Styrene / 2-hydroxyethyl methacrylate copolymer (monomer molar ratio 4/1) P-6: Styrene / 2-hydroxyethyl methacrylate copolymer (monomer molar ratio 3/1) P-7: styrene / butyl acrylate copolymer (monomer molar ratio: 75/25, weight average molecular weight: 6.0)
10,000, solubility parameter: 10.4) P-8: styrene / butyl acrylate / 2-hydroxyethyl methacrylate copolymer (monomer molar ratio:
75/5/20, weight average molecular weight: 68,000, solubility parameter: 11.1) BH-3: polyvinyl butyral (Sekisui Chemical Co., Ltd.,
Weight average molecular weight: 240,000, solubility parameter: 10.
0) BX-L: polyvinyl butyral (manufactured by Sekisui Chemical Co., Ltd.,
Weight average molecular weight: 43,000, solubility parameter: 10.
3) BL-S: polyvinyl butyral (manufactured by Sekisui Chemical Co., Ltd.,
Weight average molecular weight: 50,000, solubility parameter: 9.
5) << Measurement of Characteristic Value of Colored Fine Particle Dispersion >> (Calculation of Solubility Parameters | ps-pc |, | pl-pc |) Dyes, Low-Molecular Polymers and Polymers Used in Preparation of Each Colored Fine Particle Dispersion | Ps-pc | and | pl-pc | were calculated from the solubility parameter values of the polymer.

(Measurement of Average Particle Size of Colored Fine Particles) Each colored fine particle dispersion was diluted 1000 times with a 0.1% aqueous solution of Perex OT-P, and then a laser particle size analysis system manufactured by Otsuka Electronics was used. And the average particle size (volume average particle size) was measured.

(Measurement of Initial Elution Rate and Medium-Term Elution Rate of Colored Fine Particles to Coloring Material Dissolving Agent) Each colored fine particle dispersion was diluted 4 times with pure water, and 20 times the amount of ethyl acetate of the solution was added. While rotating the magnetic stirrer at a slow speed of 50 rpm, the absorbance of the ethyl acetate phase was monitored every 30 seconds by using MCPD-2000 manufactured by Otsuka Electronics Co., Ltd., and the time when the increase in the absorbance was not observed. After mixing the colored fine particle solution with ethyl acetate, the absorbance ratio after 30 seconds was determined as the initial dissolution rate, and then the absorbance ratio after 2 minutes was determined as the medium-term dissolution rate.

Table 2 shows the respective characteristic values obtained as described above.

[0133]

[Table 2]

<< Preparation of Ink >> Inks 1 to 21 were prepared using the colored fine particle dispersions prepared above. In the preparation of each ink, pure water and Solvent 1 or Solvent 2 shown in Table 3 were added to each colored fine particle dispersion, and the concentration of the dye in the ink was appropriately adjusted to 2% by mass. For the pH, an aqueous solution of sodium hydroxide or an aqueous solution of acetic acid is used, and for the surface tension, Surfynol 465 is used as a surfactant.
The addition amount (manufactured by Nissin Chemical Industry Co., Ltd.) was adjusted so that the respective values were as shown in Table 3. Each of the inks prepared as described above was filtered through a 2 μm membrane filter to remove dust and coarse particles, and the inks 1 to 2 shown in Table 3 were removed.
1 was prepared.

Details of each compound shown in Table 3 are as follows. Solvent 1: ethylene glycol / glycerin / triethylene glycol monobutyl ether = 10/5/5 (numerical values represent mass% based on the total mass of the ink) Solvent 2: ethylene glycol / glycerin / 1,2-hexanediol = 11/6 / 5 (numerical values represent% by mass relative to the total mass of the ink) <Measurement of pH and surface tension> The pH and surface tension were measured by a conventional method.

<< Formation and Evaluation of Inkjet Image >> (Image Formation) After storing each of the inks prepared above in an inkjet cartridge, a color inkjet printer PM-800 (manufactured by Epson) was used to print Konica Photojet Paper Photolike QP glossy paper (Konica (Manufactured by the company) to make an image. As the image, a wedge image (3 cm × 3 cm patch image) obtained by dividing the output density from 0% to 100% into 16 steps and a solid image having a density of 1.0 were output, and the following evaluations were performed.

(Evaluation of resistance to clogging of head) 20 ° C.
In a 30% RH environment, a color inkjet printer PM-800 (manufactured by Epson) was equipped with a piezo-type head with a nozzle hole diameter of 20 microns, and 12 picoliters per drop were ejected for 1 week without cleaning. The state of discharge was continuously observed, and the state was observed and evaluated according to the following criteria.

◯: Normal emission from all nozzles Δ: 1 to 3 nozzles are clogged but recovered by suction cleaning from the nozzle surface x: 4 or more nozzles are clogged and cannot be recovered by suction cleaning Among the output images obtained, one or more nozzles were clogged (measurement of image density), a wedge image (patch image of 3 cm x 3 cm) having an output density of 100% was measured with an optical densitometer (manufactured by X-Rite). X-R
The density was measured using ITE938, the maximum reflection density value (Dmax) was measured, and the image density was determined according to the conditions described below.

⊚: The obtained maximum reflection density is 1.80 or more. ◯: The obtained maximum reflection density is 1.65 to less than 1.80. Δ: The obtained maximum reflection density is 1. .50 to less than 1.65 x: The obtained maximum reflection density is less than 1.50 (evaluation of image unevenness) of the output solid image having a density of 1.0 after printing due to the difference in ink absorption speed. The image quality unevenness was visually observed, and the image unevenness was determined according to the conditions described below.

⊚: No unevenness is observed in the printed image. ◯: No unevenness is observed in the printed image. Δ: Some unevenness is observed in the printed image, but it is in a practically acceptable range. X: Clearly printed image. Table 3 shows the respective evaluation results obtained by the above, in which unevenness was observed and it was not practical.

[0141]

[Table 3]

As is clear from Table 3, the comparative example was inferior in all the evaluation items such as the head clogging resistance, the image density, and the image unevenness.
On the other hand, any of the inks using the colored fine particles whose initial elution rate or middle-term elution rate of the coloring material with respect to the coloring material dissolving agent satisfy the conditions specified in the present invention are It can be seen that the clogging resistance is good, the image density is high, and the occurrence of image unevenness is small. Among them,
In particular, the level using the polymer and dye satisfying the conditions of the formulas (1) and (2), the surface tension is 25 to 50 mN / m.
It was possible to confirm that the effect was further enhanced at the level of 1) and the level of pH in the range of 6.0 to 11.0.

[0143]

According to the present invention, it is possible to provide an inkjet ink in which clogging of an inkjet head is improved, a high image density is obtained, and image unevenness is reduced, and an image forming method.

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 2C056 EA04 FC01                 2H086 BA52 BA59 BA60                 4J039 AD06 AD07 AE06 BC09 BC13                       BC14 BC15 BE01 BE03 BE04                       BE07 BE08 BE12 BE28 BE30                       CA06 EA41 EA48 GA24

Claims (10)

[Claims] 1. An inkjet ink containing colored fine particles of a resin A containing a coloring material or colored fine particles obtained by further coating the surface of a resin A containing a coloring material with a resin B, an aqueous solvent and water. An inkjet ink, wherein the initial elution ratio of the coloring material to the coloring material dissolving agent of the colored fine particles is 10% or less, and the resin A is two or more resins having different weight average molecular weights. 2. An inkjet ink containing colored fine particles of a resin A containing a coloring material or colored fine particles obtained by further coating the surface of a resin A containing a coloring material with a resin B, an aqueous solvent and water. An inkjet ink, wherein the medium-term elution ratio of the coloring material to the coloring material dissolving agent is 50% or less, and the resin A is two or more resins having different weight average molecular weights. 3. An ink jet ink containing colored fine particles made of a resin A containing a coloring material or colored fine particles obtained by further coating the surface of a resin A containing a coloring material with a resin B, an aqueous solvent and water. The initial elution ratio of the coloring material to the coloring material dissolving agent of the coloring fine particles is 10% or less, the medium-term elution ratio of the coloring material to the coloring material dissolving agent of the coloring fine particles is 50% or less, and the resin A has a weight average molecular weight of An inkjet ink comprising two or more different resins. 4. Of the two or more resins having different weight average molecular weights, the resin having the smallest weight average molecular weight has a solubility parameter of ps (J / cm ³ ) ^1/2 and the resin having the largest weight average molecular weight. The solubility parameter of pl (J / c
m ³ ) ^1/2 , the solubility parameter of the coloring material is pc (J / c
The inkjet ink according to any one of claims 1 to 3, wherein when m ³ ) ^1/2 , the conditions of the following formulas (1) and (2) are satisfied. Formula (1) ps ≦ pl Formula (2) | ps-pc | ≦ | pl-pc | 5. The inkjet ink according to claim 1, wherein at least one kind of the aqueous solvent is a polyhydric alcohol ether or a polyhydric alcohol. 6. The inkjet according to any one of claims 1 to 5, wherein the colored fine particles have a core-shell structure in which the surface of a resin A containing a coloring material is further coated with a resin B. ink. 7. The volume average particle diameter of the colored fine particles is 1
It is 0-200 nm, The inkjet ink of any one of Claims 1-6 characterized by the above-mentioned. 8. The inkjet ink according to claim 1, wherein the surface tension is 25 or more and 50 mN / m or less. 9. The inkjet ink according to any one of claims 1 to 8, which has a pH of 6.0 or more and 11.0 or less. 10. An image forming method, wherein the inkjet ink according to any one of claims 1 to 9 is ejected as a droplet from an inkjet head based on a digital signal, and the droplet is attached to an inkjet recording medium. .