JP2000313125A - Ink cartridge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a high concentration layer excellent in water resistance and weatherability by providing a pigment ink containing pigment particles charged with one polarity in an aqueous vehicle, and an ink holder containing at least a functional group chargeable with same polarity as the pigment ink. SOLUTION: An ink dispersed with anions or cations is prepared as an aqueous vehicle and polyurethane foam having an anion and cation group containing a functional group, e.g. -COOH, is prepared as an ink holder. Since the carbon black and the ink holder in an ink are charged with the same polarity of minus or plus, electrostatic repulsion takes place between them and pigment is fed to a print section while being dispersed uniformly into the vehicle without being attracted to the ink holder. Consequently, ink is discharged without causing any clogging and a situation where ink is not discharged despite a large residual quantity can be eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art Conventionally, as a colorant for such an aqueous ink, a dye ink in which a dye is dissolved and a pigment ink in which a pigment is dispersed are known. Generally, the former has a high recording density and the latter has a higher recording density. The image is characterized by high fastness such as water fastness and light fastness. Ink jet inks using pigments such as carbon black are particularly excellent in fastness such as water resistance and weather resistance. Examples of ink jet pigment inks having improved dispersion stability of carbon black include, for example, JP-A-64-31881 and JP-A-64-60.
No. 74 describes an ink using carbon black which has been oxidized with nitric acid or the like to have a pH of 5.0 or less. Also, Japanese Patent No. 2714240 (Japanese Unexamined Patent Application Publication No.
No. 373) discloses that the image density of a printed matter is inferior to that of a dye ink, so that when the pigment concentration in the ink is increased to increase the image density, the dispersion stability and the ejection stability at the tip of the ejection nozzle are lacking and used. When this is interrupted, the solidification occurs at the tip of the nozzle.To solve this problem, a water-soluble resin is added and used for dispersion.In particular, if the average molecular weight of the water-soluble resin is too low, it adheres around the carbon black particles and disperses The weight average molecular weight must be 3,000 or more because the particle size cannot be made sufficient to stably disperse the body. If the average molecular weight of the water-soluble resin is too high, the viscosity of the aqueous medium increases. Weight average molecular weight 30
It is described that those having a molecular weight of 000 or less are employed.

[0003] When a dispersant resin is incorporated for the purpose of stabilizing the dispersion of the pigment, the pigment may not be completely and uniformly coated with the minimum necessary amount of the dispersant resin. The self-dispersion type in which a functional group contributing to dispersion is directly bonded to the surface of the pigment is clearly superior to the coating of the pigment with a dispersant resin because the pigment may be eluted in a medium. JP-A-10-195360 describes that -COOM, -SO
_{3 M, -PO 3 HM, -PO} 3 M 2, -SO 2 NH 2, -SO
Represented by ₂ and colorant containing self-dispersing carbon black having a hydrophilic group such as NHCOR are bonded directly or through another atomic group, the general formula _{H (CH 2) mC ((} CH 2) nOH) 3 Water for inkjet recording with improved long-term storage stability, nozzle clogging prevention, intermittent ejection stability, and ejection durability by containing a humectant and an aqueous medium composed of water and a water-soluble organic solvent. Although an ink jet recording apparatus using pigment ink is described, this ink jet recording apparatus does not use an ink jet cartridge containing a foam.

On the other hand, in order to uniformly supply ink to a jet nozzle, it has been conventionally known to store a foam inside an ink jet cartridge and impregnate the foam with an aqueous ink. 2729
No. 7 discloses that when a polyurethane foam obtained by foaming polyoxyethylene and organic diisocyanate as all polyol components is used for an ink holder placed in an ink container of an ink jet system, the ink can be quickly and dead-spaced. It is described that the material is not suitable for filling.
Japanese Patent Application Laid-Open No. 6-64,087 discloses an ink cartridge provided with a resistance coating having positive water absorption resistance change characteristics in which carbon black is dispersed in a water-absorbent resin containing hydroxyacrylate or hydroxymethacrylate as a main component. JP-A-5-38816 discloses that instead of ester-based urethane foam which causes a problem such as decomposition of a foam due to deterioration of the foam itself due to the ink and lowering of the surface tension of the ink, polyether-based polyols and A urethane foam obtained by foaming and reacting with a polyisocyanate, wherein a urethane foam ink carrier using a polymer polyol grafted with styrene and / or acrylonitrile in an amount of 20% (weight ratio) or more of all polyol components is used as an ink. Described to be stored inside the cartridge It has been.

Japanese Patent Application Laid-Open No. 6-15840 discloses that the ratio of ethylene oxide (EO) to propylene oxide (PO) in a polyether polyol is 20: 80-5.
0:50, Inserting an ink carrier made of urethane foam manufactured from 2 to 5 parts by weight of a water blowing agent per 100 parts by weight of polyether polyol and having a volume swelling ratio to the ink of 5 to 60% into the ink cartridge. Describes that the gap between the inner wall of the cartridge and the ink holder is eliminated, and JP-A-6-99585 discloses that it is difficult to uniformly fill the entire cartridge with a plastic foam ink holder. In the case where a high-density plastic foam is applied particularly near the ink discharge port in consideration of the drawback, the other ink tank (cartridge) is filled with an uncompressed plastic foam (see Japanese Patent Application Laid-Open No. 4-173343). Plastic foams with different compression densities, or The case may be) to be filled into the ink tank,
In the compressed part of the urethane foam or melamine formaldehyde foam having fine interconnected pores,
It is described that filling is performed by forming a slit directed in the compression direction.

Japanese Patent Application Laid-Open No. Hei 6-107836 discloses that a thermosetting melamine condensate is an open-celled and fine-celled plastic home. There is a risk of breakage, and pores with extremely large cell diameters are likely to be formed in the foam body compared to other cell diameters, and if there are pores in the ink holder, the properties will be lost. The polyester type urethane foam has a cell diameter (cell average diameter of 100 to 300) suitable for use as an ink carrier having substantially the same degree as a melamine condensate foam.
μm) can be obtained, but is easily hydrolyzed, easily eluted during the ink composition, and is unsuitable. Polyether type urethane foam has a small cell diameter due to low viscosity of the raw material. It is difficult to obtain a foam body, and even if a prepolymer method is used as a method for obtaining a polyether type urethane foam having a small cell diameter, open-cell cells (so-called open cells) are used.
It is described that it is not possible to obtain a urethane foam having the following properties.Moreover, the gap between the meshes is reduced by compressing the urethane foam and filling the cartridge in order to further develop a capillary phenomenon for holding ink. In this case, when heated and compressed, deformation is caused semi-permanently, and heat is hardly transmitted uniformly to the urethane foam which is heat insulating. In order to avoid inconvenience, an ink carrier of a polyether type polyurethane foam obtained by mixing a polyether polyol, an isocyanate, a foam stabilizer, a catalyst, and the like as main raw materials, and having a viscosity of 1,500 to
Japanese Patent Application Laid-Open Publication No. HEI 9-26139 discloses that a polyether polyol of 30,000 CP is used, and a main raw material is simultaneously introduced into a mixing head, and a foam for an ink carrier having a cell diameter of 80 to 400 μm mixed and foamed is used. No. 7,242,761 discloses that, as a foam stabilizer at the time of foaming a polyurethane ink carrier, an organopolysiloxane having a drawback of dissolving into the ink and lowering the surface tension of the ink is used. It is described that an organopolysiloxane having at least one of a group, an epoxy group and an isocyanate group is used.

Japanese Patent Application Laid-Open No. 7-286056 discloses that a hydroxyl value of 8 is used in order to suppress a decrease in surface tension of an ink over time.
0 and 460 of polyether polyol were added to 85 parts each.
1 part by weight of a 15 wt.% Aqueous solution, 1.0 part by weight of a foam stabilizer having a surface tension of 31 dyne / cm, and other polyol components comprising a foaming agent and a catalyst are reacted with TDI (isocyanate index = 110) It is described that the obtained polyurethane foam is subjected to a reticulation treatment to obtain an ink carrier using a foam having a three-dimensional network structure. Japanese Patent Application Laid-Open No. 7-32613 describes that a polyether having a molecular weight of 2,000 is used. 100 parts by weight of a polyol,
1 part by weight of a triethylamine catalyst, 1 part by weight of a silicone foam stabilizer, and a predetermined amount of an allohanate-modified TDI adjusted to an NCO content of 29.0% by weight (isocyanate index = 10
0) In addition, an ink that can be easily reused by filling a hot-melt polyurethane foam obtained by foaming into a container made of polystyrene and pulverizing and re-melting the ink including the ink holder without dismantling. It is described as a storage container.

[0008] In any case, such an ink carrier of a foam is formed of a resin material, and thus includes a portion having a hydrophobic structure and a portion having a hydrophilic structure. Further, the dispersant for stabilizing the dispersion of the pigment for ink also structurally has a hydrophobic portion and a hydrophilic portion. When such a pigment ink is impregnated into the ink holder of the foam, the hydrophobic portion of the dispersant is oriented to the hydrophobic portion of the foam resin, and as a result, the dispersant drops off from the pigment. .
JP-A-10-140062 discloses a self-dispersion type carbon black in which at least one kind of hydrophilic group is bonded directly or via another atomic group to the surface of carbon black in order to prevent such ink deterioration. And impregnating it with a hydrophobic foam.
However, hydrophobic foams may repel impregnation of hydrophilic pigment inks.

In addition, when a pigment ink containing carbon black is filled in a cartridge using a polyurethane foam as an ink holder and used, a sufficient amount of the ink still remains, but the ink does not come out any more, In some cases, the concentration cannot be obtained sufficiently.These problems are that the carbon black concentration in the ink discharged from the cartridge is lower than the original ink concentration, and that the carbon black particles are not polyurethane. It was found that this was due to adsorption to the foam, which resulted in the vehicle being preferentially ejected from the cartridge.

[0010]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-mentioned problems and to obtain a high-density image excellent in water resistance and weather resistance. Another object of the present invention is to provide an ink cartridge capable of stably supplying ink to the end without causing clogging in the cartridge.

[0011]

The object of the present invention is to provide (1) a pigment ink containing pigment particles charged to one polarity in an aqueous vehicle, and a functional group capable of being charged to the same polarity as the pigment particles. And (2) that the pigment particles are carbon black in which a group selected from the following functional group is chemically bonded. The ink cartridge according to the above (1), which is characterized in that:

[0012]

Embedded image (R represents H or an alkyl group, and X represents an inorganic or organic anion.) ", (3)" (1) or (2) wherein the ink carrier is a polyether-based urethane foam. The ink cartridge according to the item (2)).

[0013]

The present invention will be described below in more detail with reference to examples. First, by the following method, the pigment ink used in the present invention,
A polyurethane foam and a cartridge were produced. [Pigment ink] Anion dispersion ink 1, anion dispersion ink 2, and cation dispersion ink 3 were prepared according to the following formulation.

Ink 1 Sulfone group-containing carbon 5 parts by weight (CAB-O-JET200, manufactured by Cabot) Diethylene glycol 15 parts by weight Glycerin 5 parts by weight 2-pyrrolidone 2 parts by weight Water 73 parts by weight

Ink 2 Carboxyl group-containing carbon 5 parts by weight (CAB-O-JET300, manufactured by Cabot) Diethylene glycol 15 parts by weight Glycerin 5 parts by weight 2-pyrrolidone 2 parts by weight Water 73 parts by weight

Ink 3 Quaternary amine group-containing carbon 5 parts by weight (IJX-55, manufactured by Cabot) Diethylene glycol 15 parts by weight Glycerin 5 parts by weight 2-pyrrolidone 2 parts by weight Water 73 parts by weight

[Polyurethane Foam] A polyurethane foam 1 having an anion and a polyurethane foam 2 having a cationic group were prepared according to the following formulation.
For the polyurethane foam, remove the cell membrane by a conventional method
It was a foam with a three-dimensional network structure.

Polyurethane foam 1 polyol 61.5 parts by weight (acrylic acid graft copolymer polyol) tolylene diisocyanate 35 parts by weight Polyether siloxane 1 part by weight Water 2 parts by weight Triethylenediamine 0.3 parts by weight Tin octylate 0.2 parts by weight Department

Polyurethane foam 2 polyol 61.5 parts by weight (diethylaminoethyl methacrylate graft copolymer polyol) tolylene diisocyanate 35 parts by weight polyethersiloxane 1 part by weight water 2 parts by weight triethylenediamine 0.3 parts by weight tin octylate 0.2 Parts by weight

[Production of Cartridge] Ricoh IPSi was prepared by combining a pigment ink and a polyurethane foam.
A cartridge was prepared by filling an empty case for OJET300 with 52 g of ink, and the image density, the carbon content of the extracted ink, and the amount of ink remaining in the cartridge at the time when printing became impossible were examined. (The ink remaining amount detection function was cut in advance and used so that printing was not disabled by the remaining amount detection.) The results are shown in Table 1.

[0021]

[Table 1]

In Examples 1 and 2, the carbon black and the ink carrier in the ink are both negatively charged, and in Example 3, both are positively charged, so that they are attracted by electrostatic repulsion. Without this, the carbon black concentration in the ink supplied to the printing unit was equivalent to the original ink concentration, and a sufficient image density was obtained. On the other hand, in Comparative Examples 1 and 2, the carbon black and the ink carrier are charged to opposite polarities, so that the carbon black particles are electrostatically adsorbed on the ink carrier and the ink supplied to the printing unit is not charged. The density of carbon black was extremely reduced to obtain only a low-density image, and the ink was not discharged from the cartridge even though the ink still remained sufficiently.

[0023]

As is apparent from the above detailed and concrete description, in the cartridge of the present invention, since the pigment particles and the ink carrier are both charged to the same polarity, the electrostatic repulsion force between the both is provided. Works and the pigment is supplied to the printing unit in a state of being uniformly dispersed in the vehicle without being adsorbed on the ink carrier, so that the ink is discharged without clogging,
As in the prior art, there is no possibility that the discharge is stopped despite the large remaining amount (claim 1). Also, the print density is high.
Further, in the ink containing the carbon black having a functional group of the present invention, the chargeability of the carbon black is high and stable, so the repulsive force with the ink carrier is stronger, and the dispersion stability of the carbon black itself is also improved. Is high,
The effect of the present invention becomes more remarkable (claim 2). Further, by using the ink holding member of the present invention, an excellent effect that the deterioration due to the aqueous ink is small, the durability is excellent, the cost is low, and the appropriate hydrostatic pressure can be easily maintained regardless of the remaining amount of the ink. I do.

Claims (3)

[Claims] 1. An ink comprising: a pigment ink containing pigment particles charged to one polarity in an aqueous vehicle; and an ink carrier containing at least a functional group capable of being charged to the same polarity as the pigment particles. cartridge. 2. The ink cartridge according to claim 1, wherein the pigment particles are carbon black to which a group selected from the following functional group is chemically bonded. Embedded image (R represents H or an alkyl group, and X represents an inorganic or organic anion.) 3. The ink cartridge according to claim 1, wherein the ink holding member is a polyether-based urethane foam.