JPH0953038A - Ink jet recording ink - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an ink jet recording ink which is excellent in recording quality and stability to settling and has improved recorded image stability and printer operation stability by dispersing specific copolyester resin particles colored with a hydrophobic dye in a dispersion medium mainly comprising water. SOLUTION: This ink is a dispersion, in a dispersion medium mainly comprising water, of fine particles of a copolyester resin which is formed from a polycarboxylic acid component contg. 80mol% or higher cyclohexanedicarboxylic acid and a polyhydric alcohol component comprising 50-70mol% aliph. diol and 30-50mol% tricyclodecanedimethanol, contains 100-500eq/ton trialkanolamine carboxylate groups as ionic groups, has a glass transition point of 40 deg.C or higher and a softening point of 100 deg.C or lower, and has been colored with a hydrophobic dye. The ink satisfies the relations: α=0.2-0.5 and α<2> .(ρ-1)/η.100<=0.5 [wherein α is the wt. average particle size (μm) of the resin particles; ρ is their specific gravity; and η is the viscosity (mPa.s) of the dispersion medium at 20 deg.C] and has a pH of 7-10 and a lowest film-forming temp. of 40 deg.C or higher.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inkjet recording ink suitable for an inkjet recording apparatus that records an image by ejecting ink droplets onto a recording medium.

[0002]

2. Description of the Related Art Conventionally, as an ink jet recording ink, an ink in which a dye is dissolved in water and an organic solvent or the like is further added as a mainstream has been dominated.

However, in these inks, since the dye is water-soluble, bleeding occurs in the recording dots on the paper, and there are problems such as spread of the image and deterioration of contrast.

Therefore, as a method for solving these problems,
A colored resin particle type ink has been proposed in which colored particles that are difficult to penetrate into paper are dispersed in a dispersion medium, and a colored portion formed of the particles is formed on the paper. When such a colored resin particle type ink is used, since the coloring component is not water-soluble, there is a beard-like bleeding prevention effect that occurs along the paper fiber, and among the ink droplets ejected on the recording paper, only the aqueous medium is used. However, since the colored resin particles penetrate into the recording paper and remain on the fibers of the recording paper and are deposited, there is an advantage that the printing density can be easily obtained as compared with the dye ink. Such characteristics are more effective as the particle size of the particles is larger.

However, when the particle size of the colored resin particles is large, sedimentation due to the weight of the particles is likely to occur, which causes problems in ink storage stability and ink ejection reliability.
That is, when particles settle in the ink jet recording head, density problems occur in a printed image, and further, there are serious problems such as ejection failure due to nozzle clogging. Reliability cannot be neglected because reliability is an essential property for ink as well as print quality.

Since the stability of the particles against sedimentation is determined by the particle size and specific gravity of the colored resin particles and the viscosity of the dispersion medium, the ink obtained by dispersing such colored resin particles achieves both print quality and reliability. In addition to the particle size of the colored resin particles, the set values of the specific gravity and the viscosity of the dispersion medium are very important.

Many inks of such colored resin particle type have been proposed in the past.

JP-A-54-58504 proposes an ink in which a mixture of a hydrophobic dye solution and vinyl polymer fine particles is oil-in-water dispersed. It is disclosed in the text that the vinyl polymer fine particles are swelled in the solvent of the dye solution by being mixed with the hydrophobic dye solution and further colored by the dye. Polymers preferably used are mainly (meth) acrylic acid ester-based copolymer fine particles, and it is described that a glass transition temperature of 30 ° C. or lower is a suitable condition. As the effect of the invention, the development of water resistance by using a hydrophobic dye as a recording agent is particularly emphasized, but the effect on recording quality is not particularly described. Although there is a specific description regarding the ink viscosity, there is only a vague description such as 0.1 μm or less in the text regarding the particle size. Even in the examples, there is no description about the specific particle diameter and the specific gravity of the resin. Some composition ratios of the vinyl polymer are illustrated, and it is possible to infer the specific gravity of the resin, but it is not possible to specify the specific composition of the vinyl polymer used in the examples. Therefore, it must be said that it is insufficient to specify the relationship between the particle size, the specific gravity and the viscosity regarding the sedimentation stability of the particles. in addition,
It is obvious that fine particles swollen with a solvent at such a low glass transition temperature have film-forming properties when dried at room temperature, and when such an ink is used, nozzle clogging may frequently occur. It is easily analogized.

Japanese Unexamined Patent Publication No. 55-139471 discloses a colored resin particle-dispersed ink jet ink in which an aqueous vinyl polymer latex is dispersed and dyed at a high temperature and the latex particles are impregnated with a disperse dye. . Water resistance is emphasized as the effect of the invention,
In this patent proposal also, no particular effect on recording quality is described. The viscosity is specifically described, and the particle size is preferably 0.01 to 1.0 in the text.
It is stated that a μm, particularly preferably 0.02 to 0.5 μm, is preferably used. In the examples, the particle size is 0.
The use of latex with a specific composition ratio of 02-0.09 μm is described. Although there is no clear description regarding the resin specific gravity, it is approximately 1.0 from the composition ratio of the disclosed resin components.
It is inferred to be about 1.1.

JP-A-58-2366 proposes an ink jet recording ink comprising a hydrophobic dye-containing vinyl polymer latex, an organic solvent having an HLB of 9.5 or less, and an aqueous medium. In this patent, dot quality improvement is mentioned as an effect of the invention, but the essential particle size is not disclosed in the examples at all, and in addition, there is no description regarding specific gravity.

JP-A-62-172076 proposes an ink jet recording ink comprising a dispersion of a water-insoluble polymer containing an oil-soluble dye (a nonionic stabilizer is bound to the polymer). As effects of the invention, reduction of feathering (a phenomenon in which ink spreads like a beard along the fibers of recording paper), improvement of resolution, and water resistance are clearly described. It is also disclosed that by suppressing the particle diameter to 0.5 μm or less, stable ejection can be performed without nozzle clogging.

In the examples, colored resin particles in the range of 0.2 to 0.5 μm are described with specific composition ratios.
Although there is no specific description regarding the specific gravity of the resin, it can be estimated from the composition ratio, although it is about 1.0 to 1.1. However, there is no specific description about the viscosity, and it cannot be said that the sedimentation stability of particles is sufficiently described.

Japanese Patent Laid-Open No. 4-185672 discloses an ink comprising colored resin particles and an aqueous medium, wherein a water-soluble compound is dissolved in the aqueous medium so that the difference in specific gravity between the colored resin particles and the aqueous medium is 0.04 or less. There is a proposal regarding the ink for inkjet recording.

Here, there is a concrete description regarding the concern about the sedimentation of the colored resin particles and the specific gravity difference between the particles and the dispersion medium for the purpose of preventing sedimentation, and it is suggested that these are related to Stokes' theorem. ing. However, according to Stokes's theorem, although the sedimentation of particles is described by three parameters of specific gravity difference, particle size, and viscosity (assuming that they are used on the earth), a description of particle size and viscosity is given. However, it cannot be said that the specific action for preventing the sedimentation of particles is clearly explained in such a proposal that captures only the difference in specific gravity. In addition, it is said that inorganic salts are preferably used as the water-soluble compound, but when such inorganic salts are dissolved in an aqueous medium to such an extent that their specific gravity changes effectively, the ionic strength in the system increases. , The stability of the dispersion system decreases. Therefore, aggregation of colored resin particles is expected to occur, and it is difficult to maintain stability itself as a dispersion before the particles settle.

JP-A-4-185673 and JP-A-4-1-1
No. 85674 discloses that an effective specific gravity is lowered by swelling colored resin particles with a solvent in an ink composed of colored resin particles and an aqueous medium, and the difference in specific gravity between the colored resin particles and the aqueous medium is 0.04 or less. It is suggested to. Concerning the concern about the sedimentation of the colored resin particles and the specific description regarding the specific gravity difference between the particles and the dispersion medium for the purpose of preventing sedimentation, it is similar to the above-mentioned patent proposal, but the description regarding the particle diameter and the viscosity is insufficient. . In addition, when the resin particles swollen with the solvent are used, it is difficult to avoid the nozzle clogging when the ink is dried in the vicinity of the ejection port of the ink nozzle, as described above.

The resin fine particles exemplified in the prior inventions described so far are all limited to vinyl polymers. The solubility of hydrophobic dyes such as oil dyes and disperse dyes in vinyl polymers is low, and it is difficult to perform high-density coloring.

With the recent trend toward higher resolution of ink jet printers, the miniaturization of ink droplets has led to a demand for higher optical density of the recording density. With vinyl polymers such as those found in the conventional invention, this requirement is met. It's difficult.

JP-A-6-340835 proposes an ink-jet ink having polyester particles containing an ionic group as a dispersoid. It is said that by using a polyester resin as a resin particle material, coloring with a hydrophobic dye at high density and high robustness is possible, and the effects of improving water resistance and improving recording quality are also described. Regarding the particle size, there is a description in the text that the particle size is 0.01 to 1.0 μm, more preferably 0.1 to 0.5 μm.
15 μm colored polyester particles are illustrated. Polyester resin is known to have a higher specific gravity than vinyl-based resin, and there is a great concern about the sedimentation of particles, but in this patent proposal, there is no description about the specific gravity of resin particles, and It cannot be said that the relationship is sufficiently described.

[0019]

As described above, although many proposals have heretofore been made regarding an ink jet recording solution ink using colored resin particles as a recording agent, the print quality and the stability against particle sedimentation have been proposed. There are no patent proposals that clearly define the relationship among the three parameters required for satisfying both: particle size, specific gravity, and viscosity of the dispersion medium. Further, the concrete means for realizing the colored resin particles satisfying the physical properties defined by the three parameters and also satisfying other various properties required for the ink jet recording ink are also included in the prior invention. Is not disclosed.

The present invention is a colored resin particle type which satisfies both high recording quality and stability against sedimentation of particles, and further satisfies the stability of recorded images such as water resistance and light resistance and the reliability of printer operation. An object is to provide an inkjet recording ink.

[0021]

SUMMARY OF THE INVENTION In view of the above situation, the inventors of the present invention have conducted intensive research and, as a result, have arrived at the next invention. That is, the present invention is an ink for inkjet recording comprising a dispersion medium containing at least water as a main component, and colored resin particles dispersed in a fine particle form in the dispersion medium, wherein the colored resin particles are dyes. From polyhydric carboxylic acids containing 80 mol% or more of cyclohexanedicarboxylic acid, 50 to 70 mol% of an aliphatic diol, and 30 to 50 mol% of tricyclodecane dimethanol. The group of the trialkanolamine salt of carboxylic acid obtained as the ionic group is 1
The weight average particle diameter of the colored resin particles is α μm, the specific gravity is ρ, and the dispersion medium is 2
When the viscosity at 0 ° C. is ηmPa · sec, α = 0.
^{2 to} 0.5 and α ² · (ρ−1) /η·100≦0.5, wherein the copolymer polyester resin fine particles are insoluble or insoluble in water. An inkjet recording ink characterized by being colored with a sparingly soluble hydrophobic dye, the inkjet recording ink having a pH in the range of 7 to 10, and having a minimum film forming temperature of 40 ° C. or higher. And the polyester resin has a softening temperature of 100 ° C. or lower.

The ink jet recording ink of the present invention comprises
Colored resin particles are dispersed in a dispersion medium containing water as the main component, and the weight average particle diameter of the colored resin particles, the specific gravity, and the viscosity of the dispersion medium are set in the optimum range, so that all paper It satisfies all the characteristics such as the bleeding prevention effect by seeds, the ejection stability from the inkjet head, and the dispersion stability of the ink.

Furthermore, by using the ink jet recording ink of the present invention, it is possible to increase the resolution of a printed image. The reason why the resolution of the printed image can be increased is not clear, but it is presumed that the use of the ink of the present invention makes the ink dots uniform and a synergistic effect with the bleeding prevention effect and the like.

In the present invention, when the weight average particle diameter of the colored resin particles is α μm, the specific gravity is ρ, and the viscosity of the dispersion medium at 20 ° C. is ηmPa · sec, α = 0.2 to 0.5 and α It is essential that ^ 2 · (ρ−1) /η·100≦0.5. When the particle size α exceeds 0.5 μm, ejection stability from the inkjet head may be insufficient. On the other hand, if the particle diameter α is 0.2 μm or less, sufficient recording quality cannot be obtained on recording paper of poor quality such as recycled paper. When the value given by α ^ 2 · (ρ−1) / η · 100 exceeds 0.5, the sedimentation stability of the particles becomes insufficient.

Means for specifically realizing such characteristics will be described below. The main constituent components of the ink used in the present invention are a colored resin particle component and a dispersion medium containing water as a dispersion medium as a main component.

The colored resin particle of the present invention comprises at least a resin component, a colorant, and an additive which is appropriately added to improve its properties.

The copolyester resin used in the present invention is obtained by condensation of polyvalent carboxylic acids and polyhydric alcohols, and is a polycarboxylic acid containing 80 mol% or more of cyclohexanedicarboxylic acid and 50 to 50 7
Obtained from polyhydric alcohols containing 0 mol% of aliphatic diol and 30 to 50 mol% of tricyclodecane dimethanol, and the group of trialkanolamine salt of carboxylic acid as an ionic group is in the range of 100 to 500 eq./ton. It is composed of a copolyester resin contained as a component.

Such a copolyester resin has an alicyclic monomer as a main constituent, and is a substance which has both a low specific gravity and a high glass transition temperature and is excellent in hydrolysis resistance in a weak alkaline region. is there.

Such polyester resin has 10 groups of trialkanolamine salt of carboxylic acid as ionic groups.
It is essential to contain it in the range of 0 to 500 eq./ton. The ionic group has a function of imparting dispersion stability to the polyester resin fine particles, and when the content of the ionic group is less than the predetermined amount, sufficient water dispersibility may not be obtained, and the ionic group may be ionic. If the content of the group is too large, the polyester resin may become water-soluble and the desired water dispersion may not be obtained.

The ionic group consisting of a trialkanolamine salt of a carboxylic acid can be obtained by introducing a carboxyl group into a polyester resin and then neutralizing it with a trialkanolamine. Preference is given to using triethanolamine as trialkanolamine. When an alkali metal hydroxide is used as a base for neutralization, it causes unnecessary hydrolysis of the copolyester resin and impairs the stability of the dispersion. Further, when other organic amines such as ammonia and alkylamines are used, an amine odor remains, limiting the environment in which the printer is used.

The glass transition temperature of the polyester resin in the present invention is preferably 40 ° C. or higher, more preferably 50 ° C. or higher, and even more preferably 60 ° C. or higher. The film temperature decreases, and nozzle clogging easily occurs.

The softening temperature of the polyester resin in the present invention is preferably 100 ° C. or lower. If the softening temperature exceeds the range, the fixability of the ink will be poor.

Pigments, oil-soluble dyes and disperse dyes are used as the colorant for the resin particles, and those which are excellent in coloring and dyeing properties to the resin and which are insoluble in water as a dispersion medium are preferred.

In the present invention, among these coloring materials, it is preferable that the coloring material is colored with a hydrophobic dye which is insoluble or hardly soluble in water. Specific examples thereof include C.I. I. Solvent Black 3, 5, 22, C.I. I. Solvent Yellow 19,
44, 98, 104, 105, 112, 113, 11
4, C.I. I. Solvent Red 8, 24, 71, 10
9, 152, 155, 176, 177, 179, C.I.
I. Solvent Blue 2, 11, 25, 78, 94, 9
5, C.I. I. Solvent Green 26, C.I. I. Solvent Orange 5, 40, 45, 72, 63, 68, 7
8, C.I. I. Solvent Violet 13, 31, 3
2, 33, C.I. I. Disperse Yellow 3, 5, 56,
60, 64, 160, C.I. I. Disperse red 4,
5, 60, 72, 73, 91, C.I. I. Disperse Blue 3, 7, 56, 60, 79, 198, C.I. I. Disperse oranges 13, 30, etc. are used.

The amount of these dyes added is determined depending on the type of resin, the properties required for the ink, etc., but generally 1 to 20% by weight, preferably 2 to 15% by weight based on the resin component. % Range is good.

Since the ionic group-containing polyester resin of the present invention has a self-emulsifying property, fine particles can be prepared by a phase inversion self-emulsifying method.

The fine particle dispersion of the polyester resin is prepared by previously mixing the ionic group-containing polyester resin and the water-soluble organic compound and then adding water, or by collectively adding the ionic group-containing polyester resin, the water-soluble organic compound and water. It can be obtained by a method of mixing and heating.

As the water-soluble organic compound, ethanol, isopropanol, butanol, ethylene glycol, propylene glycol, methyl cellosolve, ethyl cellosolve, butyl cellosolve, tertiary butyl cellosolve, acetone, methyl ethyl ketone, Tetrahydrofuran, dioxane and the like can be used. The water-soluble organic compound is preferably one that can be removed by azeotropic distillation after the ionic group-containing polyester resin is dispersed in water.

As a preferred method for obtaining an aqueous dispersion of a colored polyester resin in the present invention, a polyester resin having a predetermined amount of a carboxyl group is first polymerized, and the polyester resin, dye, water-soluble organic compound and trialkanolamine are sufficiently added. An example is a method of mixing and dissolving, then adding water to disperse the water, and removing the water-soluble organic compound by azeotropic distillation or the like as necessary. Further, a colored aqueous dispersion can be obtained in the same manner by adding a dye into the system and treating at a high temperature after obtaining an aqueous dispersion of a polyester resin.

The water dispersion means a state generally called an emulsion or colloidal dispersion. The ionic group dissociates in the aqueous medium,
An electric double layer is formed at the interface between the polyester resin and water. When the polyester resin is present as fine microparticles in the aqueous system, an electrostatic repulsive force is generated between the microparticles due to the action of the electric double layer, and the microparticles are stably dispersed in the aqueous medium.

The particle size of the polyester resin fine particles can be controlled by the ionic group content, the ratio of the polyester resin and the water-soluble organic compound at the time of emulsification, the stirring conditions, the temperature and other emulsification conditions.

Water serving as the main dispersion medium of the present ink is preferably pure water or ultrapure water that has undergone a purification process such as ion exchange and distillation.

Further, to the ink of the present invention, a hydrophilic high-boiling point low-volatile solvent is added in order to further impart the effects of moisturizing property and dispersion stability. Examples of the hydrophilic high-boiling point low-volatile solvent used in the present invention include glycerin, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol,
Hexylene glycol, polyethylene glycol, high boiling and low volatility polyhydric alcohols such as polypropylene glycol are used, or their mono-etherified products, di-etherified products, esterified products such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, Ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, etc. are used, and other N-methyl-2pyrrolidone, 1.3-dimethylimidazolidinone, monoethanolamine, N, N-dimethylethanolamine, N , N-diethylethanolamine, diethanolamine, N-n-butyldiethanolamine, triisopropanolamine It is possible to add a water-soluble organic solvents such as nitrogen-containing organic solvents such as triethanolamine print stream, to the extent that bleeding does not occur. 3 as the addition amount
It is preferably 0% by weight or less, more preferably 15% by weight or less.

In addition, the drying property with respect to water, which is the main dispersion medium,
Highly volatile monohydric alcohols such as ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, iso-butanol, and tert-butanol can be added for the purpose of improving the permeability. . The preferable addition amount is 10% by weight or less, more preferably 5% by weight or less.

Examples of the water-soluble polymer that can be dissolved in the aqueous dispersion medium of the present ink include polyalkyl oxides such as polyethylene oxide, polyvinylpyrrolidone, polyvinyl alcohol, polyvinyl butyral,
Alkali-soluble acrylic resin, glue, gelatin, casein, albumin, gum arabic, alginic acid, methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, polyvinyl ether, polyvinyl methyl ether, polyethylene glycol, α-cyclodextrin, glucose, xylose, Examples include monosaccharides such as sucrose, maltose, arabinose, maltitol and starch, disaccharides, polysaccharides and glycosides. The amount of these water-soluble polymers added is preferably 20% by weight or less, more preferably 10% by weight or less.

Further, as a surfactant which can be added for controlling the surface tension of the dispersion medium or for imparting dispersion stability of the colored resin particles, for example, anionic surfactants include higher fatty acid salts and higher alkyldicarboxylic acids. Acid salt, higher alcohol sulfate ester salt, higher alkyl sulfonate, alkyl benzene sulfonate, alkyl naphthalene sulfonate, salt of naphthalene sulfonic acid (Na,
K, Li, Ca) formalin polycondensate, condensate of higher fatty acid and amino acid, dialkyl sulfosuccinate ester salt, alkyl sulfosuccinate, naphthenate, etc., alkyl ether carboxylate, acylated peptide, α-olefin sulfonic acid Salt, N-acyl methyl taurine, alkyl ether sulfate, secondary higher alcohol ethoxy sulfate, monoglycer sulfate, alkyl ether phosphate ester salt, alkyl phosphate ester salt, polyoxyethylene alkyl ether sulfate ammonium salt, polyoxyethylene alkyl ether sulfate Sodium salt, polyoxyethylene alkylphenyl ether sulfate ammonium salt, polyoxyethylene alkylphenyl ether sulfate sodium salt, polyoxyethylene alkyl sulfate monoethanolamine , Polyoxyethylene alkyl ether phosphate salts, polyoxyethylene alkyl ether phosphate potassium salt, polyoxyethylene alkyl ether phosphate diethanolamine, sodium alkylnaphthalenesulfonate, sodium laurylsulfate.

As the nonionic surfactant, a fluorine-based surfactant, a silicone-based surfactant, polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monostearate, polyoxyethylene alkylphenyl ether, sorbitan monostearate. ,
There are acetylene glycol, ethylene oxide adduct of acetylene glycol, propylethanolamide, polyoxyethylene alkyl ether, polyoxyethylene alkylphenyl ether, and the like.

If the amount added is too large, the foaming property becomes large, and there is a risk of impairing the ejection stability.
The amount is preferably wt% or less, more preferably 1 wt% or less.

Further, urea, thiourea, ethylene urea and the like can be added for the purpose of preventing nozzle drying.

The weight concentration of the colored resin particles in the ink is 5
The range is ˜50 wt%, preferably 10-40 wt%, more preferably 15-30 wt%.

The pH of the ink is preferably adjusted within the range of 7-10. Furthermore, the minimum film formation temperature of ink is 40
It is preferably at least ° C.

The ink viscosity is 25 m in order to ensure stable ejection from the head and stable ink supply to the head.
Pa · sec or less is desirable, and more preferably 15 mPa · sec or less. Further, the surface tension of the ink is preferably 30 to 60 mN / m in order to satisfy the water repellency of the nozzle and the spreading and wetting on the recording medium.

[0053]

The ink for ink-jet recording of the present invention comprises colored resin particles dispersed in a dispersion medium containing water as a main component, and has a wide range from plain paper, high-quality paper, etc. to recycled paper with poor paper quality. Has a high anti-bleeding effect on the paper types, and at the same time, the weight average particle diameter of the colored resin particles, the specific gravity, and the viscosity of the dispersion medium required to satisfy the ejection stability from the inkjet head and the sedimentation stability of the dispersed particles. The above three parameters are related to each other so as to be in the optimum range.

As described above, the relationship between the sedimentation velocity of particles and these three parameters is widely known as the Stokes' relational expression. The Stokes' relational expression describes that unless the specific gravity difference between the dispersion medium and the dispersoid is 0, the particles settle or float. Since the Stokes relational expression is a relational expression that is derived by ignoring the Brownian motion of particles, in reality, if the difference in specific gravity is within a certain value, the sedimentation or levitation of particles is disturbed by Brownian motion and Does not happen. The problem is that it is unreasonable to uniquely determine such a difference in specific gravity, and should be defined in the relationship between the particle size of particles and the viscosity of the dispersion medium.
The present invention is significant in clarifying this point in the Stokes relational expression that describes the relationship among particle diameter, specific gravity, and dispersion medium viscosity.

Of the colored resin fine particles, many of which are solid at room temperature or have no film-forming property have a high specific gravity, and when the particle size is increased, stability against sedimentation during stationary storage is obtained. It becomes a problem. In addition, colored fine particles with low specific gravity (for example, polymers with a large amount of aliphatic components, resin particles swollen with a low specific gravity solvent, or oil droplets in which a dye is dissolved) are not sufficiently colored, or are produced by drying at room temperature. Since the film is formed, there is a problem that clogging easily occurs in the recording system. A polyester resin can achieve a sufficient coloring density, but generally has a high specific gravity, and it is difficult to satisfy the relationship among the particle diameter, the specific gravity, and the medium viscosity limited in the present invention.

However, the alicyclic monomer introduced into the polyester of the present invention as an essential component, that is, cyclohexanedicarboxylic acid tricyclodecane dimethanol, maintains the glass transition temperature of the polyester resin,
It has the effect of reducing the specific gravity of the polyester resin. As a result, the stability of the fine particles against sedimentation is improved, the clogging prevention in the inkjet head when using this colored dispersion as an ink, and high recording quality. It is a product that has the function of achieving both. When the requirements of the present invention are met,
It is possible to reduce the specific gravity without deteriorating the high dyeing property of the polyester resin, and further, the glass transition temperature of the polyester resin is not lowered, and therefore, the dry film-forming property at around room temperature is not exhibited. Therefore, both high recording quality and stationary storage reliability are achieved, and the effect of preventing clogging due to drying in the recording system is also high.

The present invention will be more specifically described with reference to the following examples, but the present invention is not limited to the examples shown here.

[0058]

BEST MODE FOR CARRYING OUT THE INVENTION

<< Polymerization of Polyester Resin >> In an autoclave equipped with a thermometer and a stirrer, cyclohexanedicarboxylic acid 156.4 parts by weight ethylene glycol 111.6 parts by weight tricyclodecane dimethanol 78.4 parts by weight tetrabutoxy 0.1 part by weight of titanate was charged and heated at 150 to 220 ° C. for 180 minutes to carry out an esterification reaction. Next, after raising the temperature to 240 ° C., the system pressure is gradually reduced to 30 mm after 10 minutes, and the pressure is adjusted to 10 mmHg.
The reaction was continued for 20 minutes. After that, the atmosphere in the autoclave was replaced with nitrogen gas and the pressure was adjusted to atmospheric pressure. 200 to 220 ℃
15.4 parts by weight of trimellitic anhydride was added and the reaction was carried out for 60 minutes to obtain a copolyester resin (A1). The obtained copolyester resin had an average molecular weight of 3,300, an acid value of 360 eq./ton, and a glass transition temperature of 70 ° C. Further, the composition ratio by NMR analysis was as shown in Table 1.

[0059]

[Table 1]

Polymerization was performed in the same manner except that the raw materials were changed, and Table 1
Was obtained.

In Table 1, CHDA cyclohexanedicarboxylic acid TPA terephthalic acid IPA isophthalic acid SIP 5-sodium sulfoisophthalic acid TMA trimellitic acid EG ethylene glycol NPG neopentyl glycol TCDL tricyclodecane dimethanol Tg glass transition temperature. In addition to the polyester resin A4, the content of elemental sulfur was determined by fluorescent X-ray analysis and converted into sodium sulfonate group equivalent.

<< Preparation of Colored Polyester Aqueous Dispersion >> Polyester resin (A1) 2 was placed in a four-necked 10-liter separable flask equipped with a thermometer, a condenser, and a stirring blade.
00 parts by weight, 100 parts by weight of methyl ethyl ketone, 50 parts by weight of tetrahydrofuran, and oil black HBB (CI Solvent Black) as a black dye.
3) 20 parts by weight of [Orient Chemical Co., Ltd.], 9 parts by weight of triethanolamine as a base (300e in terms of resin)
q./ton) was charged and dissolved at 70 ° C. Next, 500 parts by weight of ion-exchanged water at 70 ° C. was added to disperse the water. Further, it was distilled in a distillation flask until the distillate temperature reached 103 ° C. to obtain a colored polyester resin fine particle water dispersion.

<< Ink formation >> The obtained colored polyester resin fine particle aqueous dispersion, surfactant and water-soluble organic solvent were added to water and mixed with stirring, and after confirming by a microscope observation that a monodispersed state was obtained. Then, other additives such as a water-soluble polymer and a preservative were added thereto and further stirred sufficiently to completely dissolve them. The dispersion liquid is filtered with a membrane filter under pressure to remove dust and coarse particles, and a prototype ink (K
1) was obtained. Colored polyester resin fine particles of the obtained ink, average particle diameter, dispersion medium viscosity, minimum film forming temperature (MF
T) and pH are shown in Table 2.

[0064]

[Table 2]

All the inks used for evaluation were 20
The surface tension was adjusted to 30 to 60 mN / m at 0 ° C., and the weight concentration of the colored resin in the ink was adjusted to 20%. The viscosity was measured using RFS-II manufactured by Rheometrics at a temperature of 20 ° C. and a shear rate of 500 s −1. For the measurement of particle size distribution, an electrophoretic light scattering device ELS-8 manufactured by Otsuka Electronics Co., Ltd.
00 was used.

<Evaluation> The ink obtained is used as an ink jet printer MJ-700V2 manufactured by Seiko Epson Corporation.
The ink was used as C ink, and 1) bleeding of printed matter, 2) ejection stability, 3) sedimentation stability, 4) high resolution printing, and 5) storage stability were evaluated. The results are shown in Table 2. Shown in The evaluation methods and criteria for each evaluation item are as follows.

1) Bleed of printed matter a. Recycled paper with non-uniform and large fibers in the paper, b.
The following level judgment was performed using two types of copy paper, which were papers having relatively uniform fibers. ◯: Almost no bleeding due to paper fibers, and the edges of the printed matter are clear. B: Bleeding occurs along the fibers of the paper. X: Bleeding occurs considerably along the fibers of the paper, and the printed matter is difficult to read.

2) Ejection Stability The ink ejection from the ink jet recording head was evaluated by continuous operation of the printer during actual printing. The evaluation was performed by the following level judgment. ⊚: It is possible to eject with all nozzles in actual printing operation for 5 hours or more continuously. ◯: It is possible to eject with all the nozzles in the actual printing operation for two hours or more continuously. X: There are nozzles that cannot be ejected in the continuous printing operation for 2 hours.

3) Sedimentation Stability After printing on plain paper, the apparatus was left with ink filled for a certain period of time, and printing was performed again to compare the densities of the printed matters before and after the standing. The evaluation was performed by the following level judgment. ◯: Even if left for one week, the printed matter does not change in density before and after being left. X: When left for 1 week, the printed matter changes in density.

Table 1 shows the above evaluation results.

4) High-resolution printing A screened pattern is printed on plain paper at 720 dpi.
The presence or absence of print unevenness in the print image was observed. The evaluation was performed by the following level judgment. ◯: No print unevenness occurs in the print pattern. X: Print unevenness occurs in the print pattern.

5) Storage stability The obtained ink was sealed in an ink pack, allowed to stand in an environment of 70 ° C. for 2 weeks and then opened, and the change in pH was examined. A: The change range of pH is within ± 0.5. ◯: The range of pH change is within ± 1.0. X: The range of change in pH exceeds ± 1.0.

Hereinafter, using polyester resin A1, colored polyester fine particle water dispersions having different particle diameters were obtained by changing the amount of triethanolamine added during the preparation of the colored polyester resin fine particle water dispersion. The ink viscosity was adjusted by changing the addition amounts of the solvent and the water-soluble polymer to obtain trial inks K2 to K8. The following evaluation was performed in the same manner. Table 2 shows the results.

Using polyester resins A2 to A4, colored polyester resin fine particle water dispersions were prepared in the same manner as described below.
Further, it was made into ink in the same manner and evaluated in the same manner. The results are shown in Table 3. When polyester A4 was used, triethanolamine was not used when the colored polyester resin fine particle water dispersion was prepared.

[0075]

[Table 3]

From the above results, the ink jet recording ink of the present invention contains a dispersion medium and colored resin particles dispersed in the dispersion medium in the form of fine particles, and the colored resin particles are colored with a dye. And polyhydric carboxylic acids containing 80 mol% or more of cyclohexanedicarboxylic acid, 50 to 70 mol% of aliphatic diol and 30 to 5
It is obtained from a polyhydric alcohol containing 0 mol% of tricyclodecane dimethanol, and the group of trialkanolamine salt of carboxylic acid as an ionic group is 100 to 500 eq./to.
When the coloring resin particle diameter is α μm, the specific gravity is ρ, and the viscosity of the dispersion medium is ηmPa · second, α = 0.2 to 0.5.
By doing so, it is possible to secure a good printed image without bleeding on all paper types and stable ejection from the inkjet head, and further satisfy the following expression α2 · (ρ−1) /η·100≦0.5. Therefore, sedimentation stability can be secured.

Further, by using the ink jet recording ink of the present invention, it is possible to increase the resolution of the printed image.

[0078]

According to the present invention, when the colored resin particle ink is used in an ink jet printer, the particle diameter and specific gravity of the resin, and the viscosity of the dispersion medium, which are most important in terms of printing quality and reliability, are determined. It can be set within an appropriate range. Therefore, it is possible to obtain print quality without bleeding on all types of paper, and it is possible to ensure ejection stability from the inkjet head and ink sedimentation stability, and it is also possible to increase the resolution of the printed image. Become.

Moreover, the use of the ink-jet ink of the present invention is characterized in that the colored resin is deposited on the paper fibers, so that an image having a higher print density can be obtained as compared with the dye ink.

Front page continuation (72) Inventor Goji Maeda 2-1-1 Katata, Otsu-shi, Shiga Toyobo Co., Ltd. Research Institute (72) Inventor Tetsuo Shimomura 2-1-1 Katata, Otsu, Shiga Prefecture Toyobo Co., Ltd. Corporate Research Institute (72) Inventor Yozo Yamada 2-1-1 Katata, Otsu City, Shiga Prefecture Toyobo Co., Ltd.

Claims (5)

[Claims] 1. A dispersion medium containing at least water as a main component,
An ink for inkjet recording comprising colored resin particles finely dispersed in the dispersion medium, wherein the colored resin particles are colored with a dye, and 80 mol% or more of cyclohexanedicarboxylic acid And a polyhydric alcohol containing 50 to 70 mol% of an aliphatic diol and 30 to 50 mol% of tricyclodecane dimethanol, the alkanoic acid being a trialkanolamine salt of a carboxylic acid. Base 1
It is composed of a copolyester resin contained in the range of 0 to 500 eq./ton, the weight average particle diameter of the colored resin particles is α μm, the specific gravity is ρ, and the viscosity of the dispersion medium at 20 ° C. is ηmPa.
An ink for inkjet recording, characterized in that, when expressed in seconds, α = 0.2 to 0.5 and α ² · (ρ−1) /η·100≦0.5. 2. The copolyester resin fine particles,
The ink for inkjet recording according to claim 1, which is colored with a hydrophobic dye which is insoluble or hardly soluble in water. 3. The ink for inkjet recording according to claim 1, wherein the pH is in the range of 7 to 10. 4. The ink for ink jet recording according to claim 1, which has a minimum film forming temperature of 40 ° C. or higher. 5. The softening temperature of the polyester resin is 10.
The inkjet recording ink according to claim 1, which has a temperature of 0 ° C. or lower.