JP3050044B2 - Recording ink - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording ink comprising a pigment dispersed therein.

[0002]

2. Description of the Related Art Conventionally, a recording ink used for printing by an ink jet recording system mainly uses a solvent mainly composed of water and an organic solvent and uses a dye as a coloring material (hereinafter referred to as a dye ink). ). As shown in JP-A-61-2770 and JP-A-2-49078, the dye is generally a metal salt, and is ionized when dissolved in water. Has a high electrical conductivity. Also, due to the properties of the dye, lightfastness,
The water resistance was not satisfactory.

In order to solve these light and water resistances,
Inks (pigment inks) using pigments such as carbon black and diazo yellow instead of dyes as coloring materials are also disclosed in JP-B-1-15542, JP-A-2-255875, JP-A-2-276876, and the like. Have been. These pigment inks use a pigment dispersant (hereinafter simply referred to as a dispersant) to disperse the pigment in a solvent. Many of the substances used for the dispersing agent are conductive, which increases the electrical conductivity of the pigment ink.

[0004] Incidentally, as one of conventionally known ink jet recording systems, there is one disclosed in Japanese Patent Application Laid-Open No. 2-150355, and a schematic configuration thereof will be described below. As shown in FIG.
Is an epoxy-based adhesive bonding a piezoelectric ceramic plate 2 having a plurality of grooves and side walls 11 separating the grooves and having been polarized in the direction of arrow 5 and a cover plate 3 made of a ceramic material or a resin material. By bonding via the bonding layer 4 made of an agent or the like, the groove becomes a plurality of ink liquid chambers 12 spaced from each other in the lateral direction. Ink chamber 12
Has an elongated shape with a rectangular cross section, and the side wall 11 extends over the entire length of the ink liquid chamber 12. Electrodes 13 for applying a driving voltage are formed on both surfaces from the upper portion of the side wall 11 near the adhesive layer 4 to the center of the side wall 11. Each ink chamber 12 is supplied from an ink supply source (not shown).
Then, ink is supplied through an ink supply port (not shown) and a manifold (not shown) provided in the cover plate 3.

Next, FIG. 2 is a sectional view showing an ink ejecting apparatus.
The operation will be described below. In the ink jet head 1, for example, the ink liquid chamber 12 according to desired print data
When b is selected, a positive drive voltage is rapidly applied to the electrodes 13e and 13f, and the electrodes 13d and 13g are grounded. As a result, a driving electric field in the direction of arrow 14b acts on the side wall 11b, and a driving electric field in the direction of arrow 14c acts on the side wall 11c. At this time, since the driving electric field directions 14b and 14c are orthogonal to the polarization direction 5, the side walls 11b and 11c
Is rapidly deformed toward the inside of the ink liquid chamber 12b due to the piezoelectric thickness-shear effect. Due to this deformation, the volume of the ink liquid chamber 12b is reduced, the ink pressure in the ink liquid chamber 12b is rapidly increased, and a pressure wave is generated.
An ink droplet is ejected from a nozzle (not shown) communicating with the ink jet head. When the application of the driving voltage is stopped, the side walls 11b
11c return to the position before deformation (see FIG. 1), the ink pressure in the ink liquid chamber 12b decreases, and ink is supplied from the ink supply source into the ink liquid chamber 12b through the ink supply port and the manifold. You.

[0006]

In the ink jet head 1 of the recording system as described above, since the electrode 13 is provided on the inner wall of the ink liquid chamber 12, the electrode 13 is in contact with the ink. Since ink is supplied to all the ink liquid chambers 12 from the manifold, the inks in all the ink liquid chambers 12 are connected. For this reason, when the electric conductivity of the ink is high, if a different polarity of potential is applied to the side wall 11, a short circuit may occur through the ink, and the electrode 13 may be electrochemically deteriorated to deteriorate the printing quality. There is. In order to solve such a problem, it is conceivable to attach a protective film to the electrode 13 to prevent short circuit and corrosion, but it is extremely difficult to completely insulate the electrode 13 from the ink.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and has as its object to provide a recording ink capable of continuously performing stable printing.

[0008]

According to the first aspect of the present invention , an electrode is disposed in an ink flow path.
Injecting ink by applying voltage to the electrodes
In a recording ink that is used in a jetting device and has a pigment dispersed in a solvent, water or an organic solvent is used as the solvent.
Nonionic surfactant with dispersant
Agent, using either a polymer or a water-soluble resin,
The electric conductivity is not more than 1.0 mS / cm.

[0009]

In the recording ink of the present invention having the above structure , either water or an organic solvent is used as the solvent.
Non-ionic surfactants, high molecular weight polymers,
Or a water-soluble resin, and has an electric conductivity of 1.0
By controlling the ink flow rate to mS / cm or less,
In the ink ejecting apparatus in which is disposed, printing can be performed continuously and stably.

[0010]

Embodiments of the present invention will be described below.

The recording ink of the present invention is obtained by dispersing a pigment as a colorant. And as a main solvent of the recording ink, it is low viscosity, excellent in safety,
Water is mainly used due to its easy handling, low cost and no odor.

For the purpose of improving the drying and fixing properties after printing, highly volatile alcohols such as ethanol, isopropanol and butanol, and low volatile alcohols such as hexanol, heptanol and octanol are added to water as a main solvent. It may be added.

For the purpose of improving clogging prevention of a finely opened nozzle, polyhydric alcohols such as ethylene glycol, diethylene glycol, propylene glycol and glycerin, N-methyl-2-pyrrolidone,
A high-boiling solvent such as a nitrogen-containing organic solvent such as 1,3-dimethylimidazolidinone may be added to the main solvent. However,
The solvent needs to be non-conductive.

The pigment that can be used in the recording ink of the present invention is not particularly limited. For example, for black and white, pigments such as furnace black, lamp black, acetylene black, channel black, and the like; Examples include metals such as copper, iron and titanium oxide, and organic pigments such as altonitroaniline black.
For color, Toluidine Red, Permanent Carmine FB, Fast Yellow AAA, Disazo Orange PMP, Lake Red C, Brilliant Carmine 6
B, phthalocyanine blue, quinacridone red, dioxane violet, pictoria pure blue, alkali blue toner, first yellow 10G, disazo yellow AAMX, disazo yellow AAOT, disazo yellow AOAA, yellow iron oxide, disazo yellow HR, orthonitroaniline orange, dinitroaniline orange, balkan Orange, toluidine red, chlorinated para red, brilliant first scarlet, naphthol red 23, pyrazolone red, barium red 2
B, calcium red 2B, strontium red 2
B, Manganese Red 2B, Barium Lisome Red, Pigment Scar Red 3B Lake, Lake Bordeaux 10
B, Ansosine 3B lake, Ansosine 5B lake, Rhodamine 6G lake, Eosin lake, Bengala, Faftor red FGR, Rhodamine B lake, Methyl bio red lake, Dioxazine bio red, Basic blue 5B lake, Basic blue 6G lake,
Fast Sky Blue, Alkaline Blue R Toner, Peacock Blue Lake, Navy Blue, Ultramarine, Reflex Blue 2G, Reflex Blue R, Brilliant Green Lake, Diamond Green Thioflavin Lake, Phthalocyanine Green G, Green Gold, Phthalocyanine Green Y, Iron Oxide Powder, rust, zinc white, titanium oxide, calcium carbonate, clay, barium sulfate, alumina, alumina white, aluminum powder, bronze powder,
Daylight fluorescent pigment, pearl pigment, naphthol carmine F
B, Naphthol Red M, Permanent Carmine FB,
Processed pigments such as Fastero G, Disazo Yellow AAA, Dioxane Violet Red, and Alkaline Blue G toner, and other grafted carbon whose pigment surface is treated with a resin or the like can be used. These may be used in combination of two or more.

It is desirable to use a nonionic surfactant, a polymer or a water-soluble resin as the dispersant. It is not desirable to use a cationic surfactant or an anionic surfactant that increases the conductivity. As nonionic surfactants, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene alkyl ethers,
Polyoxyethylene alkyl phenyl ether, polyoxyethylene, polyoxypropylene glycol, polyoxypropylene alkyl ether and the like can be used.

As the high molecular weight polymer, those having a functional group (for example, carbonyl group, amino group, etc.) having an affinity for the pigment can be used. Examples of the water-soluble resin that can be used include a cellulose resin, an acrylic resin, a silicone resin, and a vinyl resin. These water-soluble resins can also be added as a fixing agent for fixing the pigment to the recording material.

In addition, if necessary, lower alkanolamines such as ethanolamine, diethanolamine, triethanolamine and propanolamine having low conductivity can be used as a pH adjuster. The use of metal hydroxides is undesirable because of their high electrical conductivity.

As described above, the solvent, the pigment, the dispersant, and other components have been exemplified, but the present invention is not limited to this example.

Hereinafter, specific examples of the present invention and comparative examples will be described.

Example 1 Carbon black (PRINTEX 90) 5% Water-soluble resin (polyvinylpyrrolidone K-15) 2% Glycerin 10% Ion-exchanged water 83% The electrical conductivity of this ink was 0.38 mS / cm. PRINTEX90 used here is Deguss
The carbon black and water-soluble resin polyvinylpyrrolidone K-15 manufactured by A Company were polyvinylpyrrolidone manufactured by GAF and having an average molecular weight of 10,000.

The manufacture of the ink was performed as described below.
A water-soluble resin, polyvinylpyrrolidone, is dissolved in a solvent consisting of ion-exchanged water and glycerin.
Add TEX90 and perform dispersion using a bead mill. The ink of the present invention is obtained through the above steps. The following Examples and Comparative Examples were similarly manufactured, but the manufacturing method is not limited to this method.

Example 2 Carbon black (MA-77) 5% Water-soluble resin (polyvinylpyrrolidone K-15) 2% Glycerin 10% Deionized water 83% The electrical conductivity of this ink was 0.89 mS / cm. . MA-77 used here is carbon black manufactured by Mitsubishi Kasei.

Example 3 Carbon black (MA-77) 5% Nonionic surfactant (Emulgen A-90) 3% Glycerin 10% Deionized water 82% The electric conductivity of this ink was 0.48 mS / cm. Was. Here, Emulgen A-90 used is a nonionic surfactant manufactured by Kao Corporation.

Example 4 Pigment (KERed 309) 5% Nonionic surfactant (Emulgen A-90) 3% Glycerin 10% Deionized water 82% The electrical conductivity of this ink is 0.35 mS / cm.
KERed 309 used here is an organic pigment for color toner manufactured by Dainippon Ink and Chemicals, Inc.

Example 5 Pigment (KETYELLOW403) 5% Nonionic surfactant (Emulgen A-90) 3% Glycerin 10% Deionized water 82% The electrical conductivity of this ink is 0.38 mS / cm.
KETYELLOW403 used here is an organic pigment for color toner manufactured by Dainippon Ink and Chemicals, Inc.

Example 6 Pigment (KETBLUEEx-1) 5% Nonionic surfactant (Emulgen A-90) 3% Glycerin 10% Deionized water 82% The electrical conductivity of this ink is 0.36 mS / cm.
KETBLUEEx-1 used here is an organic pigment for color toner manufactured by Dainippon Ink and Chemicals, Inc.

Comparative Example 1 Carbon black (PRINTEX 90) 5% Anionic surfactant (Demol EP) 3% Glycerin 10% Deionized water 82% The electric conductivity of this ink is 1.5 mS / cm. This comparative example is an example in which a highly conductive anionic surfactant was used as a dispersant in Example 1. Demol EP used here is an anionic surfactant manufactured by Kao Corporation.

Comparative Example 2 Carbon black (MA-77) 5% Anionic surfactant (Demol P) 3% Glycerin 10% Deionized water 82% The electrical conductivity of this ink is 2.2 mS / cm. This comparative example is an example in which a highly conductive anionic surfactant was used as a dispersant in Example 2. Demol P used here is an anionic surfactant manufactured by Kao Corporation.

Comparative Example 3 Carbon black (MA-77) 5% Cationic surfactant (Cotamine 24P) 3% Glycerin 10% Deionized water 82% The electrical conductivity of this ink is 2.5 mS / cm. This comparative example is an example in which a highly conductive cationic surfactant was used as a dispersant in Example 2. Cotamine 24P used here is a cationic surfactant manufactured by Kao Corporation.

Comparative Example 4 Pigment (KERed 309) 5% Anionic surfactant (Demol P) 3% Glycerin 10% Ion-exchanged water 82% The electrical conductivity of this ink is 2.1 mS / cm. This comparative example is an example in which a highly conductive anionic surfactant was used as a dispersant in Example 4.

Comparative Example 5 Pigment (KETYELLOW403) 5% Anionic surfactant (Demol P) 3% Glycerin 10% Ion-exchanged water 82% The electrical conductivity of this ink is 2.2 mS / cm. This comparative example is an example in which a highly conductive anionic surfactant was used as a dispersant in Example 5.

Comparative Example 6 Pigment (KETBLUEEx-1) 5% Anionic surfactant (Demol P) 3% Glycerin 10% Deionized water 82% The electrical conductivity of this ink is 2.2 mS / cm. This comparative example is an example in which a highly conductive anionic surfactant was used as a dispersant in Example 6.

When printing was performed using the inks of Examples 1 to 6 described above using the ink jet head 1 shown in FIGS. 1 and 2, stable printing could be continuously performed for 50 hours or more. In particular, Examples 1 and 3 to 6 performed stable printing over a longer time (100 hours or more) than Example 2. The inks of Examples 1 to 6 all have an electric conductivity of less than 1.0 mS / cm, and the inks of Examples 1 and 3 to 6 have an electric conductivity of 0.5 mS / c.
m.

On the other hand, when the inks of Comparative Examples 1 to 6 were used in the same ink jet head 1 as in the embodiment, the number of ink liquid chambers 12 that did not eject ink gradually increased, and high-quality, stable printing was performed. Could not. Each of the inks of Comparative Examples 1 to 6 has an electric conductivity of 1.0 mS / c.
m. When these ink jet heads 1 were disassembled, the electrodes 13 were sometimes deteriorated.

As described above, the inks of Examples 1 to 6 have an electric conductivity of 1.0 mS / cm or less.
Even when used in the ink jet head 1 in which the electrodes 13 are formed in the ink liquid chamber 12, stable printing can be performed for a long time. In particular, the electric conductivity is 0.5 mS / c.
m or less, stable printing can be performed for a longer period.

In Examples 1 to 6 and Comparative Examples 1 to 6, the pigment was dispersed using a bead mill.
Sand mill, attritor, roll mill, agitator,
The pigment may be dispersed using a Henschel mixer, a colloid mill, an ultrasonic homogenizer, an ultra-high pressure homogenizer, a pearl mill, or the like.

In this embodiment, ion-exchanged water is used as the solvent, but pure water may be used. Alternatively, a low-volatile organic solvent may be used as the solvent. For example, propylene glycol solvents, aliphatic hydrocarbons, dibasic acid esters and the like are desirable. Specifically, propylene glycol-based solvents include propylene glycol, dipropylene glycol, tripropylene glycol, propylene glycol monomethyl ether, dipropylene glycol monomethyl ether, tripropylene glycol monomethyl ether, propylene glycol-n-butyl ether,
Dipropylene glycol-n-butyl ether, tripropylene glycol-n-butyl ether, propylene glycol methyl ether acetate, propylene glycol diacetate, polypropylene glycol, and aliphatic hydrocarbons such as IP Solvent of Idemitsu Petrochemical Co., Ltd.
Nippon Petrochemical's Isosol, Exxon's Isopar, Shell Petrochemical's Shellsol, and dibasic acid esters include DuPont's DBE and Zeneca's Imzol R.

[0038]

As apparent from the above description, according to the recording ink of the present invention , water or water is used as the solvent.
Non-ionic solvent as a dispersant
Surfactant, polymer or water-soluble resin
Since the electric conductivity is 1.0 mS / cm or less,
Even in an ink ejecting apparatus in which an electrode is provided in the ink flow path, printing can be performed continuously and stably.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating an inkjet head.

FIG. 2 is an explanatory diagram showing an operation of the inkjet head.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ink jet head 12 Ink liquid chamber 13 Electrode

Claims (1)

(57) [Claims] An electrode is arranged in an ink flow path, and a voltage is applied to the electrode.
Ejecting apparatus that ejects ink by applying ink
In a recording ink obtained by dispersing a pigment in a solvent, either water or an organic solvent is used as a solvent, and a nonionic surfactant, a high-molecular polymer or the like is used as a dispersant.
Or a water-soluble resin, having an electric conductivity of 1.0 mS / cm or less.