JPH07258591A - Ink for ink jet printer - Google Patents

Abstract

PURPOSE:To obtain an ink for an ink jet printer which does not bolt on recording paper and can give an excellent image density by giving a specified surface tension to an ink comprising a water-base dispersion prepared by finely dispersing fine resin particles colored with a dye or a pigment in an aqueous medium. CONSTITUTION:The ink is prepared by giving a surface tension of 25-40dyn to an ink comprising a water-base dispersion prepared by finely dispersing in an aqueous medium fine resin particles of a polyester resin (e.g. a resin made from dimethyl terephthalate, dimethyl isophthalate, dimethyl 5- sodiosulfoisophthalate, ethylene glycol and neopentyl glycol) colored with a dye or a pigment and desirably containing 20-1000eq/ton ionic groups. Desirably, the diameter of the fine resin particle is 0.1-1.0mum, and its content is 10-50wt.%. The content of the dye should be 2-20wt.% based on the fine resin particles.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an output device, and more particularly to an ink for an ink jet printer.

[0002]

2. Description of the Related Art As an output device of information equipment such as a computer, a dot matrix printer, a thermal transfer printer,
There are various methods such as laser printers, among them, recently,
Inkjet systems are attracting attention as a system with low running cost, high definition, and easy colorization. As an ink for an inkjet printer, a dye aqueous solution has been used so far, but when the ink ejected from the nozzle adheres to the recording paper, the ink bleeds on the recording paper and is more likely than the ink particles formed when the ink is ejected. There were problems such as large dots and water resistance of the recorded image.

Conventionally, in such ink jet inks, many ideas have been proposed in order to solve these problems. a) A water-soluble dye is dissolved in a mixed solvent of water and an organic solvent so that the concentration of the dye is 5 wt% or less and the additive of the organic solvent is in the range of 3 to 30% (JP-A-62-124166).
B) Ink to which a specific diether compound is added (JP-A-62-32159) c) A water-soluble direct dye from which surface-active substances are removed by an adsorption resin, or an acid dye (JP-A-60-32159) -49070) d) Dye and emulsion for film formation added to ink
18462) e) A method using emulsion-polymerized or dispersion-polymerized particles dyed with a dye (JP-A-3-250069) has been proposed.

[0004]

The above-mentioned inks (a)-
(d) reduces the ink bleeding on the recording paper to some extent, but it was impossible to completely prevent the ink bleeding due to the capillary phenomenon on the recording paper fibers. On the other hand, in the above method e), bleeding does not occur because the dyed polymer particles are used, but the particles obtained by this method have poor stability of the particles and the dye precipitates when left for a long time. It will settle or float on the particle surface. Further, since it is difficult to dye with high density, sufficient image density cannot be obtained.

[0005]

DISCLOSURE OF THE INVENTION The present invention provides an ink for an ink jet printer which can prevent ink from bleeding on a recording paper and obtain an extremely good image density. That is, the present invention, the fine resin particles,
An ink for an ink jet printer characterized by being finely dispersed in an aqueous medium, wherein the surface tension of the ink is 25 dyn or more and 40 dyn or less. The fine resin particles of the present invention are preferably 2
A polyester resin containing an ionic group in the range of 0 to 1000 eq / ton is preferable. Furthermore, the particle size is 0.1
To 1.0 μm, and the content of the particles in the dispersion is 10 to 50 Wt. %, And the content of the dye in the particles is 2 to 20 Wt. %
Of 0.1 to 10 Wt.
% Ethylene glycol or glycerin or polyhydric alcohols are preferable.

The present invention has solved the problem of obtaining high image density by using polyester, which is easy to dye, as fine particles. Further, since the polyester is an emulsion, it has an effect of reducing bleeding when it adheres to the recording paper. The ink of the present invention has a surface tension of 25 dyn or more by adding a substance that lowers the surface tension such as a surfactant.
It is indispensable that the range is 40dyn or less. Within this range, water, which is the dispersion medium of the ink, is easily absorbed by the recording paper, and has the effect of significantly reducing ink bleeding. Further, when the surface tension of the ink is 25 dyn or less, dripping of ink occurs on the print head nozzles, which makes it difficult to perform good printing. The polyester fine particles used in the present invention are preferably in an emulsion state, but more preferably have a particle size of 1 micron or less. Further, the polyester resin used in the polyester microparticles of the present invention includes polyvalent carboxylic acids and polyvalent alcohols.
Consists of Examples of the polyvalent carboxylic acids used for the polyester resin include terephthalic acid, isophthalic acid, orthophthalic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, diphenic acid, sulfoterephthalic acid and 5- Sulfoisophthalic acid, 4-sulfophthalic acid, 4-sulfonaphthalene-2,7dicarboxylic acid, 5 [4-sulfophenoxy] isophthalic acid, sulfoterephthalic acid, and / or aromatic dicarboxylic acids such as metal salts and ammonium salts thereof, aromatic oxycarboxylic acids such as p-oxybenzoic acid p- (hydroxyethoxy) benzoic acid, succinic acid, adipic acid, azelaic acid,
Sebacic acid, unsaturated dicarboxylic acids such as dodecanedicarboxylic acid, fumaric acid, maleic acid, itaconic acid, hexahydrophthalic acid, tetrahydrophthalic acid, and other unsaturated aliphatic, and alicyclic dicarboxylic acids, Other examples of the polyvalent carboxylic acid include trivalent or higher polyvalent carboxylic acids such as trimellitic acid, trimesic acid and pyromellitic acid.

Examples of the polyvalent alcohols used in the polyester resin include aliphatic polyvalent alcohols, alicyclic polyvalent alcohols, aromatic polyvalent alcohols and the like.
Examples of the aliphatic polyhydric alcohols include ethylene glycol
, Propylene glycol, 1,3-propanedioe
2,3-butanediol, 1,4-butanediol
1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, diethylene glycol
, Dipropylene glycol, 2,2,4-trimethyl-1,3-pentanediol, polyethylene glycol
Examples include aliphatic diols such as propylene, polypropylene glycol and polytetramethylene glycol, triols such as trimethylolethane, trimethylolpropane, glycerin, pentaerythritol and tetraols. it can.

The alicyclic polyvalent alcohols are 1,4-
Cyclohexanediol, 1,4-cyclohexanedimethanol, spiroglycol, hydrogenated bisphenol A, ethylene oxide adduct and propylene oxide adduct of hydrogenated bisphenol A, tricyclodecanediol, Examples thereof include tricyclodecane dimethanol. As aromatic polyhydric alcohols, paraxylene glycol, metaxylene glycol, orthoxylene glycol, 1,4-phenylene glycol, and ethylene oxide adduct of 1,4-phenylene glycol. , Bisphenol A, ethylene oxide adduct of bisphenol A, propylene oxide adduct and the like.

Further, as a polyester polyol, ε
Examples thereof include lactone-based polyester polyols obtained by ring-opening polymerization of lactones such as caprolactone. In addition to these, a monofunctional monomer may be introduced into the polyester for the purpose of blocking polar groups at the ends of the polyester polymer. Examples of monofunctional monomers include benzoic acid, chlorobenzoic acid, bromobenzoic acid, parahydroxybenzoic acid, sulfobenzoic acid monoammonium salt, sulfobenzoic acid monosodium salt, cyclohexylaminocarbonylbenzoic acid, n-dodecylaminocarbonylbenzoic acid. Acid, tert-butylbenzoic acid, naphthalenecarboxylic acid, 4-methylbenzoic acid, 3-methylbenzoic acid, salicylic acid, thiosalicylic acid, phenylacetic acid, acetic acid, propionic acid, butyric acid, isobutyric acid, octanecarboxylic acid, lauric acid, stearyl acid , And monocarboxylic acids such as lower alkyl esters thereof, or aliphatic alcohols
Mono alcohols such as alcohol, aromatic alcohol and alicyclic alcohol can be used.

In the present invention, if necessary, an unsaturated monomer is used, and other components are appropriately selected depending on the glass transition temperature of the polyester resin, the compatibility with the monomer, and the like.

As the ionic group to be introduced into the polyester, a mono- or dicarboxylic acid having an alkali metal sulfonate or ammonium sulfonate can be preferably used. For example, an alkali metal carboxylate or an ammonium carboxylate can be used. Having a monomer, a sulfuric acid group, a phosphoric acid group, a phosphonic acid group, a phosphinic acid group or an anionic group such as an ammonium salt or a metal salt thereof, or a cationic group such as a primary to tertiary amine group. You can use a quantity etc.

When an alkali metal carboxylate or ammonium carboxylate is introduced, a polyvalent carboxylic acid such as trimellitic acid is introduced into the system at the final stage of polymerization of polyester to add a carboxyl group to the polymer terminal. Then, a method of exchanging it with a carboxylate group by neutralizing it with ammonia, sodium hydroxide or the like can be used. Further, by containing a mono- or dicarboxylic acid having an alkali metal sulfonate or ammonium sulfonate, these ionic groups can be introduced into the polyester resin. As salts, ammonium-based ions, Li, Na,
Examples thereof include salts of K, Mg, Ca, Cu, Fe and the like, and particularly preferred are K salt or Na salt. In the present invention, 5-
It is preferable to use sodium sulfoisophthalic acid or metasodium sulfobenzoic acid. Alternatively, a carboxylate group and a sulfonate group may be used.

More specific examples of the polyester resin in the present invention are shown below. a) a polyester resin obtained from polycarboxylic acids containing 80 mol% or more of an aromatic monomer, and b) 0 to 90 mol% of ethylene glycol and 100 to 10 mol% of propylene glycol, or a) A polyester resin obtained from polyvalent carboxylic acids containing 80 mol% or more of an aromatic monomer, and b) 2,3-butanediol 5-80 mol% and ethylene glycol 20-95 mol%, or a ) Polyvalent carboxylic acids containing 80 mol% or more of aromatic monomers, b) 70 to 95 mol% of C2 to C4 aliphatic glycols, and c) mono- or polyvalent compounds having a tricyclodecane skeleton. Polyester resin obtained from 5 to 30 mol% of alcohols, or a) polyvalent carboxylic acid containing 80 mol% or more of an aromatic monomer, and b) C2 to C4 aliphatic glycols 70-95 mol%, c) hydroxymethyl Polyester resins obtained from Rishikurodekan 5 to 30 mol%, or,

A) polyvalent carboxylic acids containing 80 mol% or more of an aromatic monomer, b) 70 to 95 mol% of C2 to C4 aliphatic glycols, and c) tricyclodecane dimethanoe. 5 to 30 mol% of a polyester resin, or a) polyvalent carboxylic acids containing 80 mol% or more of an aromatic monomer, and b) 70 to 95 mol of C2 to C4 aliphatic glycols. %, C) a polyester resin obtained from 5 to 30 mol% of a mono- or polyvalent alcohol having a cyclohexane skeleton, or a) a polyvalent carboxylic acid containing 80 mol% or more of an aromatic monomer, and b Polyester resin obtained from 70 to 95 mol% of C2 to C4 aliphatic glycols, c) 5 to 30 mol% of cyclohexanediol, or a) Polyester resin containing 80 mol% or more of an aromatic monomer. Carboxylic acids, and b) C2-C4 aliphatic system A polyester resin obtained from 70 to 95 mol% of glycols, c) 5 to 30 mol% of hydrogenated biphenol, or

A) polycarboxylic acids containing 80 mol% or more of an aromatic monomer, b) 70 to 95 mol% of C2 to C4 aliphatic glycols, and c) hydrogenated bisphenol A5 From 30 to 30 mol%, or a) a polyvalent carboxylic acid containing 80 mol% or more of an aromatic monomer containing 1 to 20 mol% of a mono- or divalent carboxylic acid having a naphthalene skeleton, b) C2 to C4 aliphatic glycols 70 to 100 mol
%, C) Polyvalent alcohol containing 0 to 30 mol% of alicyclic monomer
Examples thereof include polyester resins obtained from Furthermore, "a) an aromatic monomer" shown here.
Is preferably terephthalic acid or isophthalic acid. The ratio of terephthalic acid and isophthalic acid is terephthalic acid content / isophthalic acid content = 90-40 / 10
60 [mol%] is preferable, and further terephthalic acid content / isophthalic acid content = 80 to 50/20 to 50 [mol]
%], And more preferably terephthalic acid content / isophthalic acid content = 85-60 / 15-40 [mol%].

When an ionic group-containing monomer is introduced into a polyester resin to give an ionic group to the polyester resin, the polyester resin exhibits water dispersibility. As the ionic group-containing monomer, a mono- or dicarboxylic acid having the above-mentioned alkali metal sulfonate or ammonium sulfonate can be preferably used. For example, a monomer having an alkali metal carboxylate or ammonium carboxylate can be used. Anionic group such as a monomer, a sulfate group, a phosphoric acid group, a phosphonic acid group, a phosphinic acid group or an ammonium salt or a metal salt thereof, or a first
A cationic group monomer such as a primary to tertiary amine group can be used. When an alkali metal carboxylate or ammonium carboxylate is introduced, a polyvalent carboxylic acid such as trimellitic acid is introduced into the system at the final stage of polymerization of polyester to add a carboxyl group to the polymer terminal, It is possible to use a method of neutralizing this with ammonia, sodium hydroxide or the like to exchange it for a carboxylate group.

The content of these ionic groups is 10 to 1000 meq / 1000 g, preferably 20 to 500 meq / 1000 g, and more preferably 50, based on the polyester resin, including the groups of sulfonic acid groups and / or salts thereof. ~ 200 meq / 1000 g. When the content of the ionic group is less than the predetermined amount, sufficient water dispersibility cannot be obtained. The content of the (colored) fine particles in the ink of the invention is 10 to 50 Wt. % Range is preferred. Content is 10 Wt. % Or less, the required image density cannot be obtained, and the content is 50 Wt. When it exceeds%, the viscosity of the ink (dispersion) increases, and there is a great possibility that ejection of the ink from the nozzle becomes difficult. The content of the dye with respect to the resin fine particles is preferably 2 to 20 Wt. % Range. 2 Wt. % Or less, good image density cannot be obtained, and 20 Wt. When it is at least%, the dispersion tends to be unstable. As the dye, it is preferable to use "a dye insoluble in water at room temperature". These are generally classified as disperse dyes or oil-soluble dyes. More specific examples are: C.I. I. Disperse Yellow 198 C.I. I. Disperse Yellow 42 C.I. I. Solvent Yellow 162 C.I. I. Disperse Red 92 C.I. I. Disperse Red 60 C.I. I. Solvent Red 49 C.I. I. Disperse Violet 26 C.I. I. Disperse Violet 35 C.I. I. Disperse Blue 60 C.I. I. Disperse Blue 49 C.I. I. Disperse Blue 87 C.I. I. Solvent Blue 25 C.I. I. Solvent Blue 35 C.I. I. Solvent Blue 38 C.I. I. Solvent Blue 70 C.I. I. There are Solvent Black 3 and the like. These are particularly excellent in light fastness, sublimation fastness, hue and saturation, and are preferable as three primary colors for process color. In addition, known dyes and pigments may be used in combination for fine adjustment of hue.

The average particle diameter of the fine particle dispersion in the present invention is essential to be 1.0 μm or less, preferably 0.5 μm or less. If the particle system of the fine particle dispersion exceeds this range, the dispersion stability may deteriorate.
The average particle size is preferably at least 0.1 μm or more. If the particle system of the fine particle dispersion exceeds this range, ink bleeding may increase.

A fine particle dispersion of such polyester resin can be obtained by the method described below. That is, when it contains an ionic group, the polyester resin of the present invention exhibits water dispersibility. Water dispersibility means a state generally called emulsion or colloidal dispersion. The ionic group dissociates in the aqueous medium and forms an electric double layer at the interface between the polyester resin and water. When the polyester resin is present as fine microparticles in the water 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 water system.

The aqueous dispersion of the ionic group-containing polyester resin is prepared by mixing the ionic group-containing polyester resin and the water-soluble organic compound in advance and then adding water, and the ionic group-containing polyester resin, the water-soluble organic compound and water. Can be obtained by a method of mixing and heating all at once. At that time, a surfactant or the like can be used together. As the water-soluble organic compound, ethanol, isopropanol,
Butanol, ethylene glycol, propylene glycol
, Methyl cellosolve, ethyl cellosolve, 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.

The polyester resin of the present invention has good light fastness even when it is finely divided by a dye. As a method for incorporating the dye into the polyester resin, a high temperature dispersion dyeing method can be used. The method of directly kneading the dye base material into the resin is not preferable in consideration of the damage of the dye due to heating. Since the polyester resin of the present invention exhibits good stable dispersibility in water due to the action of ionic groups, it is possible to perform high-density dyeing while maintaining the particulate state. Further, a dye may be added when the polyester resin is dissolved in a solvent during emulsification. The inkjet printer ink of the present invention contains 10 to 50 wt% of fine polyester particles dispersed in water.
In addition to the fine polyester particles, the ink for an inkjet printer of the present invention may optionally contain a dispersant and a dispersion stabilizing aid such as a surfactant or a polymer dispersion stabilizer. Further, ethylene glycol, glycerin, and various polyhydric alcohols may be added to improve the wettability of the particles. Further, various chelating agents may be added to block the metal ions mixed in the ink. Further, in order to improve the storage stability of the ink, various germicides, fungicides, ultraviolet absorbers, antioxidants and the like may be added.

[0022]

Example 1 (Synthesis of Polyester Resin) In an autoclave equipped with a thermometer and a stirrer, 140 parts by weight of dimethyl terephthalate, 140 parts by weight of dimethyl isophthalate, and 5 sodium sulfoisophthalic acid. Dimethyl ester 1
1 part by weight, 102 parts by weight of ethylene glycol and 172 parts by weight of neopentyl glycol were charged and heated at 180 to 230 ° C. for 120 minutes to carry out a transesterification reaction. Then, the reaction system was heated to 240 ° C., and the reaction was continued for 60 minutes at a system pressure of 1 to 10 mmHg, and as a result, a copolyester resin was obtained. Next, 150 parts by weight of the obtained polyester resin, 150 parts by weight of methyl ethyl ketone, 150 parts by weight of tetrahydrofuran, dye C.I. I. After dissolving 15 parts by weight of Solvent Blue 70 concrete at 80 ° C., 600 parts of water at 75 ° C. was added to obtain an aqueous microdispersion of a copolyester resin having a particle diameter of about 0.15 μm. Further, the obtained water-based microdispersion was put into a distillation flask and distilled until the distillate temperature reached 100 ° C. After cooling, water was added to make the solid content concentration 20%. The obtained water-based microdispersion has a surface tension of about 60 dyn. Therefore, in order to lower the surface tension, ethylene glycol was further added so that the ethylene glycol concentration becomes 10% of water as the dispersion medium. I chose The surface tension was measured and found to be 40 dyn.

The aqueous microdispersion thus obtained was used as an ink jet printer (IO-735 manufactured by SHARP).
It was used as the ink of X). The paper used was unprocessed for inkjet.
As a result, no ink bleeding was observed when the ink according to the present invention was used. The density of the obtained image was extremely high and the image was clear. Further, the produced water-based microdispersion exhibited extremely good stability without causing precipitation or dye precipitation even when left at room temperature for 3 months or more.

[0024]

Comparative Example 1 As a comparative example, a dispersion of styrene was produced. A styrene polymer was produced by emulsion polymerization to obtain a monodisperse having an average particle size of about 0.1 μm. Then, the styrene dispersion thus obtained was treated with C.I. I. Solvent
Blue 70 was dyed with a dye liquor in which a surfactant (Mignol 802, manufactured by Yatsusha Yushi Kogyo Co., Ltd.) was dispersed. The temperature at this time was 130 ° C., and the dyeing time was 2 hours. The dispersion thus produced had a low minute concentration, and further, the stability of the dispersion was poor, and precipitation of the dye was observed when the dispersion was left at room temperature for 3 months or more.

[0025]

Comparative Example 2 Further, as a comparative example, ink bleeding was observed using a water-soluble dye that is usually used in inkjet inks. The water-soluble dye used was C.I. I. Acid Blue 1 was dissolved in water to prepare an ink. As a result, when the special paper was used, the result was good, but when the plain paper was used, the present invention was different from the present invention, and was greatly blurred. Also, the light resistance was compared. Each ink printed out is UV fade meter (carbon arc) 20 at 63 ℃
The color difference before and after the time irradiation was measured. As a result, the ink according to the present invention had a ΔE of 1 to 3, whereas the ink containing the water-soluble dye had a large ΔE of 8 to 40, and the color fading was large.

[0026]

[Comparative Example 3] In order to investigate the difference in surface tension, the ink of the water-based microdispersion prepared in Example 1 in which ethylene glycol was not added (surface tension 65 dyn) and the ink in which ethylene glycol was added (surface tension 40 dyn ) Was prepared.
Each ink is SHARP printer IO-7
Printed at 35X. At this time, two dots of yellow and black ink were printed alternately, and the degree of ink bleeding at the boundary was observed. The ink with ethylene glycol added to reduce the surface tension showed little ink bleeding. . On the other hand, in the ink having a high surface tension without adding ethylene glycol, the yellow and black inks were mixed at the boundary.

[0027]

It has been found that the ink having a specific surface tension containing the fine resin particles of the present invention can provide a clear image with less bleeding.

Claims (6)

[Claims] 1. An ink for an ink jet printer, which is an aqueous dispersion in which fine resin particles colored with a dye or a pigment are finely dispersed in an aqueous medium, and the surface tension of the ink is 25 dyn or more and 40 dyn or less. An ink for an inkjet printer, which is 2. The fine resin particles are 20 to 1000 eq /
The ink for an inkjet printer according to claim 1, which is composed of a polyester resin containing an ionic group in a ton range. 3. The particle size of the fine resin particles is from 0.1 μm to 1.
The ink for an ink jet printer according to claim 1, which is in a range of 0 μm. 4. The content of fine resin particles is 10 to 50 wt%.
The ink for an inkjet printer according to claim 1, which is in the range of. 5. The dye content of the fine resin particles is 2
The ink for an ink jet printer according to claim 1, which is in the range of 20 wt% to 20 wt%. 6. The ink according to claim 1, wherein the aqueous dispersion contains ethylene glycol, glycerin, or a polyhydric alcohol in a range of 0.1 to 10 wt%.