JP2003206420A - Ink for inkjet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink for inkjet, hardly changing the pH with time even when a self-dispersing pigment is used, and having excellent jetting stability even when the ink is used in a nonthermal energy type printer having inferior jetting energy. <P>SOLUTION: This ink for the inkjet contains at least the self-dispersing pigment, water, a water-soluble organic solvent and a buffer, and has ≤200 mPa.s viscosity after drying for 7 days at 23°C in 50%RH humidity. The recording is carried out by acting the nonthermal energy thereon to form an ink droplet. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inkjet ink for a non-thermal energy type printer, which has a small pH fluctuation and an excellent ejection stability.

[0002]

2. Description of the Related Art An ink jet recording system has an advantage that a full-color image can be easily obtained because the process is simpler than other recording systems, and a high-resolution image can be obtained even with an apparatus having a simple structure. As an inkjet ink, a dye-based ink in which various water-soluble dyes are dissolved in water or a mixed liquid of water and an organic solvent is used, but the dye-based ink has excellent color tone sharpness but light resistance. There was a defect that it was inferior in properties and water resistance. On the other hand, pigment-based inks in which carbon black and various organic pigments are dispersed are excellent in light resistance and water resistance as compared with dye-based inks, and thus are being actively researched. However, the pigment-based ink tends to cause nozzle clogging as compared with the dye-based ink. Usually, the pigment in the pigment-based ink is dispersed by using a dispersant such as a polymer dispersant and a surfactant dispersant. In recent years, the pigment is aimed at improving the stability of the dispersion system and eliminating clogging of the inkjet head. Self-dispersion pigments have been developed which have an ionic functional group such as a sulfone group or a carboxyl group on the surface and can be dispersed by electrostatic repulsion without a dispersant. However, it has been newly found that the ink using the self-dispersion pigment has a tendency of lowering the pH with time as compared with the ink using the conventional pigment. When the pH is lowered, not only the pigment is easily aggregated, but also members such as heads that come into contact with ink are damaged.
There is a risk of damage.

As a method for suppressing the decrease in pH, boric acid-potassium chloride-sodium hydroxide system and glycine-sodium chloride described in JP-A-64-6074, JP-A-4-189876 and the like are known. -Sodium hydroxide system, potassium dihydrogen phosphate-sodium hydrogen phosphate system, sodium carbonate-sodium hydrogen carbonate system, potassium hydrogen phthalate-sodium hydroxide, sodium citrate-sodium hydroxide, potassium dihydrogen citrate- There is a method of adding a buffering agent such as sodium tetraborate, acetic acid-sodium acetate, sodium dihydrogen phosphate-citric acid, but when the above-mentioned buffering agent is added to the ink using the self-dispersion pigment, the pigment aggregates, Especially with non-thermal energy type printers such as piezo type, clogging easily occurs over time, so pH even with time using dispersed pigment
Ink jet ink having excellent ejection stability has not yet been obtained even when used in a non-thermal energy type printer that has a small fluctuation in ejection energy and inferior ejection energy.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and is a non-thermal energy type printer in which the fluctuation of pH with time is small even when a self-dispersion pigment is used and ejection energy is inferior. It is an object of the present invention to provide an inkjet ink having excellent ejection stability even when used for.

[0005]

As a result of intensive studies, the present inventors have found that there is an extremely high correlation between clogging and the viscosity after drying ink, and the viscosity after drying ink is controlled. The inventors have found that the above problems can be solved by doing so and have reached the present invention.

That is, the above-mentioned problem is (1) of the present invention, "after containing at least a self-dispersible pigment, water, a water-soluble organic solvent, and a buffer, and drying at a temperature of 23 ° C and a humidity of 50% RH for 7 days. An ink jet ink characterized by having a viscosity of 200 mPa.s or less and applying non-thermal energy to form ink droplets for recording, (2) "pH of the ink is 6.5 or more 11 The inkjet ink according to item (1) above, characterized in that the pH is 6.5 or more and 11 or less after the ink is stored in a sealed state at 70 ° C. for 3 weeks. The inkjet ink according to item (2) above, (4) "the viscosity of the ink is 10 mPa.s or less," (1) to (3) above. ) In any one of Ink for Kujetto ", (5)
“As the buffer, 3-[(1,1-dimethyl-2-
At least one of hydroxyethyl) amino] -2-hydroxypropanesulfonic acid, 2-cyclohexylaminoethanesulfonic acid, N-cyclohexyl-2-hydroxy-3-aminopropanesulfonic acid, and 3-cyclohexylaminopropanesulfonic acid is used. The inkjet ink according to any one of the items (1) to (4) above, (6) "The amount of the buffer added is 0.1% or more and 2% or less. (7) The ink jet ink according to any one of (1) to (5) above, wherein "(7)" self-dispersing carbon black is used as the self-dispersing pigment. (1) The ink jet ink according to any one of (6), (8) "The average particle size of the self-dispersion pigment is 20 nm. Inkjet ink according to any one of (1) to (7) above, wherein the pigment concentration is 1 nm or more and 10% or more. The ink-jet ink according to any one of items (1) to (8) above, (10) "the amount of the water-soluble organic solvent added is 10% or more and 50% or less" The ink-jet ink according to any one of items (1) to (9) above.

Further, the above object is achieved by (11) of the present invention, "An ink cartridge containing the ink according to any one of the above items (1) to (10)". .

Further, the above-mentioned problems are (12) of the present invention, wherein the ink according to any one of (1) to (10) above is ejected and non-thermal energy is applied to form ink droplets. And an ink jet device characterized by having a recording type head.

Further, the above object is to form ink droplets by applying non-thermal energy to the ink by using the ink according to any one of the items (1) to (10) of (13) of the present invention. , An image forming method characterized by printing with an inkjet printer of a recording type.

Further, the above object is to form an ink droplet by applying non-thermal energy to the ink by using the ink according to any one of (14) to "(1) to (10) of the present invention. , An image formed by printing with an ink jet printer of a recording type.

The present invention will be described in more detail below. The inkjet ink of the present invention contains at least a self-dispersion pigment, water, a water-soluble organic solvent, and a buffer, and has a temperature of 23.
Viscosity after drying for 7 days at 50 ℃ and humidity of 50% RH is 20
0 mPa. An inkjet ink for recording by forming non-thermal energy to form ink droplets, which is characterized by being s or less.

The viscosity after drying is 200 mPa.s. By setting it to s or less, even when used in a printer of a non-thermal energy system, which discharge energy is weaker than that of a thermal energy system, clogging is less likely to occur because the viscosity of the ink is small even if the nozzle tip of the inkjet is dried after being left for a long time, It is possible to provide an ink having excellent ejection stability.

The viscosity after drying in the present invention means that 10 g of ink is placed in a petri dish having a diameter of 9 cm and a depth of 2 cm, and allowed to stand for 7 days in a windless environment at a temperature of 23 ° C. and a humidity of 50% RH, after which Toki Sangyo Co., Ltd. Rotor 1 with company viscometer RU
It is the value measured at a rotation speed of 255 rpm using 34 ° R24.

The pH of the ink and the ink in the sealed state are 70
The pH after storage at 3 ° C for 3 weeks is preferably 6.5 or more and 11 or less. Storage conditions at 70 ° C. for 3 weeks correspond to an accelerated test that reproduces a state at room temperature for about 2 years. PH of the ink or pH after the ink is stored in a sealed state at 70 ° C for 3 weeks
Is less than 6.5 or greater than 11, not only the self-dispersion pigment is likely to aggregate, but also a member such as a head, which is in contact with ink, may be attacked and damaged.

The viscosity of the ink of the present invention is 10 mP
a. s or less is preferable. The ink viscosity is 10 mPa.s. s
If it is higher, not only it becomes difficult to print with a non-thermal energy type head whose ejection energy is weak, but also the dry viscosity tends to increase.

The buffer used in the present invention is 3-
[(1,1-Dimethyl-2-hydroxyethyl) amino] -2-hydroxypropanesulfonic acid, 2-cyclohexylaminoethanesulfonic acid, N-cyclohexyl-2-hydroxy-3-aminopropanesulfonic acid, 3
It is preferable to use at least one of -cyclohexylaminopropanesulfonic acid. These buffers have a smaller increase in viscosity of the self-dispersion pigment ink after the ink is dried than other buffers, and are less likely to cause clogging.

The amount of the buffer added is 0.1% or more and 2% or more.
The following is preferable, and 0.2% or more and 1% or less is more preferable. If the added amount of the buffering agent is less than 0.1%, the effect of suppressing the change in pH is small, and if it is more than 2%, the viscosity after ink drying tends to increase.

As the pigment used in the present invention, a self-dispersing pigment having an ionic substituent chemically bonded thereto is preferably used as described above. Examples of the base black pigment before the introduction of the ionic substituent include carbon black produced by the furnace method or the channel method.

As the base yellow pigment, pigment yellow 1, pigment yellow 2, pigment yellow 3, pigment yellow 12, pigment yellow 13, pigment yellow 14, pigment yellow 1
6, Pigment Yellow 17, Pigment Yellow 7
3, Pigment Yellow 74, Pigment Yellow 7
5, Pigment Yellow 83, Pigment Yellow 9
3, Pigment Yellow 95, Pigment Yellow 9
7, Pigment Yellow 98, Pigment Yellow 11
4, Pigment Yellow 120, Pigment Yellow 1
28, Pigment Yellow 129, Pigment Yellow 138, Pigment Yellow 150, Pigment Yellow 151, Pigment Yellow 154, Pigment Yellow 155, Pigment Yellow 180 and the like.

Pigment Red 5, Pigment Red 7, and Pigment Red 1 are used as base magenta pigments.
2, Pigment Red 48 (Ca), Pigment Red 48 (Mn), Pigment Red 57 (Ca), Pigment Red 57: 1, Pigment Red 112, Pigment Red 122, Pigment Red 123, Pigment Red 168, Pigment Red 184, Pigment Red 202, Pigment Violet 19, and the like.

The base cyan pigments include Pigment Blue 1, Pigment Blue 2, Pigment Blue 3,
Pigment Blue 15, Pigment Blue 15: 3, Pigment Blue 15: 4, Pigment Blue 16, Pigment Blue 22, Pigment Blue 60, Vat Blue 4, Vat Blue 60 and the like. Among the above pigments, the self-dispersion pigment is most preferably self-dispersion carbon black.

The average particle size of the self-dispersion pigment is 20 nm.
Or more and 200 nm or less, preferably 50 nm or more and 150 n
It is more preferably m or less. If the average particle size is less than 20 nm, the coloring power when printing is insufficient and the average particle size is 200 nm.
If it is larger, the dispersion stability tends to decrease. In addition,
The average particle diameter in the present invention is a value measured by Microtrac UPA manufactured by Nikkiso Co., Ltd.

The pigment concentration of the self-dispersion pigment in the ink is preferably 1% or more and 10% or less. If the pigment concentration is less than 1%, the coloring power when printing is insufficient and the pigment concentration is 1
If it is more than 0%, not only the dispersion stability is lowered but also the viscosity after drying tends to be high.

As an additive to the ink, in addition to water, a water-soluble organic solvent such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, isobutyl alcohol, etc., ethylene glycol, diethylene glycol. Polyhydric alcohols such as triethylene glycol, propylene glycol, 1,2-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol and glycerin, the above polyhydric alcohols and the above alcohols Dehydrocondensation of monoether and diether derivatives, pyrrolidone derivatives such as N-methylpyrrolidone and 2-pyrrolidone, ketones such as acetone and methylethylketone, monoethanolamine, diethanolamine and triethanolamine Alkanolamine, preservatives, and the like.

The amount of the water-soluble organic solvent added is preferably 10% or more and 50% or less. If the amount of the water-soluble organic solvent is less than 10%, the viscosity after drying will be high, and if it is more than 50%, not only the viscosity of the ink will be high, but also the character quality when printed tends to be deteriorated.

An ink cartridge containing the ink-jet ink of the present invention can be formed, and non-thermal energy is applied to the ink in accordance with a recording signal in the ink-jet apparatus containing the ink cartridge to eject the ink from the orifice. An image can be obtained by forming an image on a recording material.

The present invention can be applied to, for example, an ink jet device as shown in FIG. As shown in FIG. 1, the inkjet device (1) has a mechanism for conveying a sheet (3) by a paper feed motor (2) and a carriage motor (4) for causing a carriage (5) to face a platen (6). While reciprocating, a mechanism that drives a print head (7) mounted on a carriage (5) to control ink ejection and dot formation, a paper feed motor (2), and a carriage motor (4) ), A print head (7), and a control circuit (9) that controls the exchange of signals with the operation panel (8).

The mechanism for conveying the paper (3) as a recording medium is equipped with a gear train for transmitting the rotation of the paper feed motor (2) not only to the platen (6) but also to a paper conveying roller (not shown). The mechanism for reciprocating the carriage (5) includes a slide shaft (10) which is installed in parallel with the shaft of the platen (6) and slidably holds the carriage (5), and a carriage motor (4). Endless drive belt between (11)
And a position detection sensor (13) for detecting the origin position of the carriage (5).

Although the control system is not shown,
The control circuit provided in the inkjet device is, for example, a P-RO that stores a well-known CPU, program, and the like.
It is configured as an arithmetic and logic operation circuit centering on M, RAM, a character generator (CG) that stores a dot matrix of characters, etc. In addition to this, it is also an I / F dedicated to interface with an external motor etc. A circuit, a head drive circuit that is connected to this I / F dedicated circuit and drives the print head (7), a motor drive circuit that also drives the paper feed motor (2) and the carriage motor (4), and the like.

[0030]

The present invention will be described in more detail based on the following examples, but the invention is not intended to be limited to these examples. The parts in the examples represent parts by weight.
Inks were prepared according to the formulations of Examples 1 to 4 and Comparative Examples 1 to 3 in Table 1 below. After stirring for 2 hours, the pH was adjusted to the value shown in Table 1 with a 5% aqueous lithium hydroxide solution, and the pore size was 0.8 μm. Inks (a) to (g) were obtained by filtering with a membrane filter of No. 3.

[0031]

[Table 1]

Pigment dispersion A: CAB, manufactured by Cabot Co.
O-JET300 (self-dispersed black pigment, solid content 15
%, Average particle size 106 nm) Pigment dispersion B: Cabot's IJX-266 (self-dispersing magenta pigment, solid content 14.3%, average particle size 10)
9.5 nm) Pigment dispersion C: Cabot, IJX-346B (self-dispersion black pigment, solid content 15%, average particle diameter 56n)
m) Buffering agent α: 3-[(1,1-dimethyl-2-hydroxyethyl) amino] -2-hydroxypropanesulfonic acid buffering agent β: 2-Cyclohexylaminoethanesulfonic acid buffering agent γ: N-cyclohexyl-2 -Hydroxy-3-
Aminopropanesulfonic acid buffer δ: 3-cyclohexylaminopropanesulfonic acid buffer ε: Potassium dihydrogen phosphate-disodium hydrogen phosphate buffer ζ: Piperazine-N, N′-bis (2-hydroxypropane-3-) Sulfonic acid)

The viscosities of the above inks (a) to (g), the viscosities after the inks were dried at a temperature of 23 ° C. and a humidity of 50% RH for 7 days, and the inks were stored in a sealed state at 70 ° C. for 3 weeks. Was measured. Further, the inks (a) to (g)
Inkjet printer EM-900 manufactured by EPSON
After filling the black cartridge C of C with vacuum deaeration, printing was carried out with an inkjet printer EM-900C manufactured by EPSON Co., and after leaving the cartridge at room temperature for 1 week, reprinting was carried out to evaluate the ejection stability. The results are shown in Table 2.

[0034]

[Table 2] Ejection stability ○: No clogging of the head and missing printing ×: There is clogging of the head and missing printing

[0035]

EFFECTS OF THE INVENTION As is clear from the detailed and specific description above, the inkjet ink of the present invention has a small pH variation and excellent ejection stability, and is suitable for use in a non-thermal energy type printer. Is what you can do.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an inkjet device of the present invention.

[Explanation of symbols]

1 Inkjet device 2 Paper feed motor 3 sheets 4 Carriage motor 5 carriage 6 Platen 7 print head 8 Operation panel 9 Control circuit 10 Sliding shaft 11 drive belt 12 pulley 13 Position detection sensor 14 color ink cartridges 15 partition boards 16 Black ink cartridge

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 2C056 EA04 FC01                 2H086 BA03 BA52 BA53 BA55 BA59                       BA60 BA61                 4J039 BA04 BC07 BC54 BE01 BE12                       BE30 CA03 EA41 EA44 GA24

Claims (9)

[Claims] 1. A self-dispersion pigment, water, a water-soluble organic solvent, and a buffer are contained at a temperature of 23 ° C. and a humidity of 50% RH.
Viscosity after drying for 7 days at 200 mPa.s. An ink for inkjet recording, which is less than or equal to s and forms a droplet by applying non-thermal energy to perform recording. 2. The viscosity of the ink is 10 mPa.s. The inkjet ink according to claim 1, wherein the inkjet ink is s or less. 3. As the buffer, 3-[(1,1-dimethyl-2-hydroxyethyl) amino] -2-hydroxypropanesulfonic acid, 2-cyclohexylaminoethanesulfonic acid, N-cyclohexyl-2-hydroxy The inkjet ink according to claim 1, wherein at least one of -3-aminopropanesulfonic acid and 3-cyclohexylaminopropanesulfonic acid is used. 4. The inkjet ink according to claim 1, wherein self-dispersion carbon black is used as the self-dispersion pigment. 5. The average particle size of the self-dispersion pigment is 20 nm.
The inkjet ink according to any one of claims 1 to 4, which has a thickness of 200 nm or more. 6. An ink cartridge containing the ink according to any one of claims 1 to 5. 7. An ink jet device comprising a head of a system for ejecting the ink according to any one of claims 1 to 5 and applying non-thermal energy to form ink droplets for recording. . 8. An image forming method using the ink according to claim 1, wherein non-thermal energy is applied to form ink droplets and printing is performed by an inkjet printer of a recording type. Method. 9. An image formed by using the ink according to any one of claims 1 to 5, which is printed by an ink jet printer of a type in which non-thermal energy is applied to form an ink droplet and recording is performed. Formation.