JPH0517714A - Ink for ink-jet recording, ink-jet recording method using the ink and apparatus using the ink - Google Patents

Abstract

PURPOSE:To obtain the subject ink having stable physical properties and composition even in a high-temperature environment or after a long-term storage by adding an ammonium salt in addition to a colorant, water, a polar organic solvent and urea. CONSTITUTION:The objective ink is produced by compounding (A) preferably about 0.1-15wt.% of a colorant composed of preferably a water-soluble dye, (B) water, (C) preferably 2-30wt.% of a polar organic solvent preferably containing a polyhydric alcohol, (D) preferably 0.5-20wt.% of urea and (E) preferably 0.5-10wt.% of an ammonium salt (preferably ammonium chloride, ammonium sulfide, ammonium phosphate, ammonium acetate, etc.).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording ink, an ink jet recording method using the ink and an apparatus using the ink, and more specifically, an ink jet recording ink containing urea and an ink jet recording method using the ink. And a device using such an ink.

[0002]

2. Description of the Related Art Conventionally, when an aqueous ink is used as an ink for inkjet recording, problems such as clogging due to evaporation of water from a recording head have occurred. On the other hand, JP-A-56-2363 and JP-A-57-743
In Japanese Patent Laid-Open No. 72-72, etc., an aqueous ink has been proposed in which urea having a high water retention effect is added to prevent clogging and solidification at low temperature.

[0003]

However, with the widespread use of ink jet recording methods, the inks used have come to be used under more severe conditions, and there are some new problems that were not a problem in the past. Has occurred. That is, the conventionally known urea-containing ink causes a problem in stability of the physical properties and composition of the ink under a high temperature environment or a long-term storage state. Specifically, when the ink containing urea is stored at a high temperature or for a long period of time, the pH increases and the urea decreases, which causes a decrease in the clogging prevention effect of the ink containing urea and a decrease in the ejection stability. The printing will be disturbed. In particular, when high-density recording is performed by using thermal energy as disclosed in Japanese Patent Publication No. 61-5911 and Japanese Patent Publication No. 61-59914, the temperature inside the recording head increases due to an increase in heating elements. Rises,
Since the physical properties and composition of the ink change remarkably, problems occur not only in the disturbance of printing but also in the durability of the recording head of the apparatus. Therefore, an object of the present invention is to provide an ink for inkjet recording, which achieves stability of the physical properties and composition of the ink containing urea, under high temperature environment or under long-term storage condition, and further to provide such ink. An object of the present invention is to provide an inkjet recording method and a device using such an ink, which does not cause printing disturbance due to a decrease in clogging prevention effect and a decrease in ejection stability when used.

[0004]

[Means and Means for Solving the Problems]
It is achieved by the present invention described below. That is, the present invention is an inkjet recording ink containing a coloring material, water, a water-soluble organic solvent, and urea, the inkjet recording ink characterized by containing an ammonium salt, and using the ink, and thermal energy And an apparatus using such an ink.

[0005]

The present inventors have earnestly studied the improvement of conventional inkjet recording ink containing urea and the inkjet recording method using the same, and as a result, by adding ammonium salt to the urea-containing ink, urea The present invention has been completed by finding that the problems of the prior art can be solved by suppressing the decomposition. In conventional urea-containing inks, an increase in pH or a decrease in urea content is measured as a result of high temperature or long-term storage. Presumably, this is due to the phenomenon that urea in an aqueous solution is hydrolyzed to ammonia and carbon dioxide when stored at high temperature or for a long period of time, so that the pH of the ink increases and the urea content decreases. Furthermore, as a result of increasing the pH of the ink in this way,
When the ink is used in an inkjet recording method that uses thermal energy, it is thought that the constituent members of the recording head of various devices and the insulating organic protective film will be damaged, and the adverse effect of shortening the durability of the head itself will occur. To be Therefore, the present inventors believe that the decomposition of urea can be suppressed by adding an ammonium salt to the urea-containing ink, and actually, the ammonium salt is added to the urea-containing ink to store it in a high temperature environment or for long-term storage. As a result of conducting and examining, it was confirmed that an increase in pH and a decrease in urea content could be suppressed, and the present invention was completed.

[0006]

Preferred Embodiments Specific examples of the coloring material used in the present invention include direct dyes, acid dyes, food dyes, basic dyes, reactive dyes, disperse dyes, soluble vat dyes, reactive disperse dyes, oil dyes and the like. And various pigments such as carbon black. Of these, water-soluble dyes are particularly preferable in terms of ink performance. The content of these coloring materials is not particularly limited, but is generally preferably in the range of about 0.1 to 15% by weight based on the total weight of the ink.

Further, as the water-soluble organic solvent used in the present invention, any water-soluble organic solvent can be used as long as it has been used in conventionally known inks. Specifically, methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol,
C1-C5 alkyl alcohols such as sec-butyl alcohol, tert-butyl alcohol, isobutyl alcohol, n-pentanol; amides such as dimethylformamide, dimethylacetamide; ketones or keto alcohols such as acetone and diacetone alcohol. Kind;
Ethers such as tetrahydrofuran and dioxane; oxyethylene or oxypropylene addition polymers such as diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, polyethylene glycol, polypropylene glycol; ethylene glycol, propylene glycol, trimethylene Alkylene glycols having an alkylene group of 2 to 6 carbon atoms such as glycol, butylene glycol, 1,2,6-hexanetriol, and hexylene glycol; thiodiglycol; glycerin; ethylene glycol monomethyl (or ethyl) ether; Diethylene glycol monomethyl (or ethyl)
Lower alkyl ethers of polyhydric alcohols such as ethers and triethylene glycol monomethyl (or ethyl) ethers; lower dialkyl ethers of polyhydric alcohols such as triethylene glycol dimethyl (or ethyl) ether and tetraethylene glycol dimethyl (or ethyl) ether Examples: sulfolane, N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone and the like. The content of the water-soluble organic solvent as described above is generally in the range of 1 to 49%, preferably 2 to 30% by weight based on the total weight of the ink. The water-soluble organic solvent as described above can be used alone or as a mixture, but the most preferable liquid medium composition in the case of having a medium together is at least one water-soluble high-boiling point organic solvent such as diethylene glycol or triethylene. It contains a polyhydric alcohol such as glycol or glycerin.

The amount of urea added to the ink of the present invention is preferably in the range of 0.5 to 20% by weight, more preferably 1 to 15% by weight, based on the total weight of the ink. When the amount of urea added is small, the water retention effect is weak and it is not practical. On the other hand, if the addition amount is larger than this, the orifice is easily clogged at a high temperature, which is not preferable.

As the ammonium salt which characterizes the ink jet recording ink of the present invention, a salt composed of ammonia and an organic acid, an inorganic acid or the like, and a water-soluble salt is preferably used. Further, those that are more soluble than water-insoluble ammonium salts are preferred, and specifically, ammonium chloride, ammonium sulfide, ammonium phosphate,
Ammonium acetate and the like are preferably used from the viewpoint of dissolution stability. The addition amount of these ammonium salts is preferably 0.5 to 10% by weight, more preferably 1 to 8% by weight, based on the total weight of the ink. If the addition amount is too small, the effect of suppressing the decomposition of urea is insufficient, and if it is too large, problems such as nozzle clogging may occur, which is not preferable.

Further, various conventionally known general additives, dispersants, surfactants, surface tension adjusting agents, fluorescent whitening agents and the like can be used in combination with the ink jet recording ink of the present invention. Specifically, viscosity adjusting agents such as polyvinyl alcohol, celluloses and water-soluble resins; various cationic, anionic or nonionic surfactants; surface tension adjusting agents such as diethanolamine and triethanolamine; pH adjustment by buffer solution Agents; antifungal agents and the like can be mentioned.

The ink jet recording method of the present invention uses the above ink jet recording ink of the present invention to perform recording by an ink jet method using heat energy. As a result, even though the ink contains urea,
Even if the temperature inside the recording head of various devices rises due to the heating element, it is possible to suppress the increase in pH and the decrease in the urea content, and the discharge and printing are stable, and the durability of the recording head is also improved. It is about the same as when using ink without
The effectiveness was confirmed. Further, this tendency becomes more apparent when high-density recording is performed, that is, as the degree of integration of the heating elements increases, and the effect was exhibited at 300 dpi, and the remarkable effect was obtained at 360 dpi. In addition, as described above, the ink of the present invention,
It is particularly preferably used in the inkjet recording method of the present invention in which droplets are discharged by the action of heat energy for recording, but it goes without saying that it can also be used for general writing instruments. As a method and apparatus suitable for performing recording using the ink of the present invention, a method and apparatus for applying thermal energy corresponding to a recording signal to the ink in the chamber of the recording head and generating droplets by the thermal energy are provided. Can be mentioned. These will be described below.

An example of the structure of the head, which is the main part of the apparatus, is shown in FIGS. 1, 2 and 3. The head 13 is made by bonding glass, ceramics or a plastic plate having a groove 14 through which ink is passed, and a heating head 15 (a head is shown in the drawing, but not limited to this) used for thermal recording. Obtained. The heating head 15 includes a protective film 16 made of silicon oxide and an aluminum electrode 17.
-1, 17-2, a heat generating resistor layer 18 formed of nichrome or the like, a heat storage layer 19, and a substrate 20 having good heat dissipation such as alumina.
Is made up of.

The ink 21 is a discharge orifice (fine hole) 2
2, the meniscus 23 is formed by a pressure (not shown). Now, when an electric signal is applied to the electrodes 17-1 and 17-2, the area indicated by n of the heat generation head 15 rapidly generates heat, and bubbles are generated in the ink 21 in contact with the area, and the meniscus 23 is generated by the pressure. Are ejected, the ink 21 is ejected, and becomes a recording droplet 24 from the orifice 22 and flies toward the recording material 25. FIG. 3 shows an external view of a multi-head in which many heads shown in FIG. 1 are arranged. The multi-head is manufactured by closely contacting a glass plate 27 having a multi-groove 26 and a heating head 28 similar to that described in FIG. 1 shows the head 13 along the ink flow path.
2 is a cross-sectional view of FIG. 2, and FIG. 2 is a cross-sectional view taken along the line AB of FIG.

FIG. 4 shows an example of an ink jet recording apparatus incorporating such a head. In FIG. 4, reference numeral 61 denotes a blade as a wiping member, one end of which is held by a blade holding member to become a fixed end, which is in the form of a cantilever. The blade 61 is arranged at a position adjacent to the recording area of the recording head, and in the case of this example, is held in a protruding form in the moving path of the recording head. Reference numeral 62 denotes a cap, which is disposed at a home position adjacent to the blade 61, and has a configuration in which it moves in a direction perpendicular to the moving direction of the recording head and contacts the ejection port surface to perform capping. Further, 63 is an ink absorber provided adjacent to the blade 61, and like the blade 61,
The recording head is held in a protruding form in the moving path of the recording head.
The blade 61, the cap 62, and the absorber 63 constitute a discharge recovery unit 64, and the blade 61 and the absorber 6
By the means 3, water, dust and the like are removed from the ink ejection port surface.

Reference numeral 65 denotes a recording head which has an ejection energy generating means and ejects ink to a recording material facing the ejection port surface where the ejection ports are arranged for recording, and 66 denotes a recording head in which the recording head 65 is mounted. A carriage for moving 65. The carriage 66 is slidably engaged with the guide shaft 67, and a part of the carriage 66 is connected (not shown) to a belt 69 driven by a motor 68. As a result, the carriage 66 can move along the guide shaft 67, and the recording head 65 can move the recording area and its adjacent area. Reference numeral 51 is a paper feed section for inserting a recording material, and 52 is a paper feed roller driven by a motor (not shown). With these configurations, the recording material is fed to a position facing the ejection port surface of the recording head, and is ejected to a paper ejection unit provided with a paper ejection roller 53 as the recording progresses.

In the above structure, when the recording head 65 returns to the home position after recording is completed, the cap 62 of the head recovery section 64 is retracted from the movement path of the recording head 65, but the blade 61 is projected into the movement path. There is. As a result, the ejection port surface of the recording head 65 is wiped. When the cap 62 comes into contact with the ejection surface of the recording head 65 to perform capping, the cap 62 moves so as to project into the movement path of the recording head. Recording head 6
When 5 moves from the home position to the recording start position, the cap 62 and the blade 61 are at the same position as the above-described position at the time of wiping. As a result, the ejection opening surface of the recording head 65 is wiped even during this movement.

The above-described movement of the recording head to the home position is not limited to the completion of recording and the recovery of ejection, and the home adjacent to the recording area at a predetermined interval while the recording head moves in the recording area for recording. The wiper is moved to the position, and the wiping is performed along with the move. FIG. 5 is a diagram showing an example of an ink cartridge in which the ink is supplied to the head via an ink supply member, for example, a tube. Here, 40 is an ink containing portion containing the supply ink, for example, an ink bag, and a rubber stopper 42 is provided at the tip thereof. By inserting a needle (not shown) into this stopper 42, the ink in the ink bag 40 can be supplied to the head. An ink absorber 44 receives the waste ink. It is preferable for the present invention that the surface of the ink containing portion that comes into contact with the ink is made of polyolefin, especially polyethylene.

The ink jet recording apparatus used in the present invention is not limited to the one in which the head and the ink cartridge are separately provided as described above, but is also suitable for the one in which they are integrated as shown in FIG. Used. In FIG. 6, reference numeral 70 denotes a recording unit, in which an ink containing portion containing ink, for example, an ink absorber is contained, and the ink in the ink absorber has a head portion having a plurality of orifices. The ink is ejected from 71 as an ink droplet. As the material of the ink absorber,
The use of polyurethane is preferred for the present invention.
Reference numeral 72 denotes an atmosphere communication port for communicating the inside of the recording unit with the atmosphere. The recording unit 70 is used in place of the recording head shown in FIG.
It is removable with respect to 6.

[0019]

EXAMPLES Next, the present invention will be described more specifically with reference to Examples and Comparative Examples. In addition, unless otherwise specified, "parts" and "%" in the text are based on weight. Examples 1 to 5 Each of the composition components shown in Table 1 consisting of a coloring material, water, a water-soluble organic solvent, urea, and an ammonium salt were mixed in a beaker and stirred at 25 ° C for 4 hours. The mixture is pressure filtered through a membrane filter with a pore size of 0.22 μm,
Ink for inkjet recording of Examples 1 to 5 of the present invention.

[Table 1] Table 1

Comparative Examples 1 to 5 The compositions shown in Table 2 below were prepared in the same manner as in Examples 1 to 4 to obtain comparative ink jet recording inks.

[Evaluation Method and Evaluation Criteria] Example 1 above
5 to Comparative Examples 1 to 5, suppression of increase in pH, suppression of decrease in urea content, ink ejection stability, printing stability, etc. were measured by the following methods, and the effectiveness of the inkjet recording ink of the present invention was confirmed. The sex was evaluated. Table 3 shows the evaluation results of Examples 1 to 5 and Comparative Examples 1 to 5 thus obtained. Evaluation methods

(1) pH measurement The pH of the ink is measured immediately before the temperature is raised from room temperature to 60 ° C. and after the temperature is returned from room temperature to room temperature for 24 hours. ,
HORIBA pH meter (pH METER F-
The measurement was carried out in 11) and the evaluation was made according to the following criteria. ◯: When the pH change is within 5%. X: When the pH change is 5% or more.

(2) Urea content In the ink immediately before raising the temperature from room temperature to 60 ° C. and after leaving it at room temperature for 24 hours at room temperature from 60 ° C. The urea content was measured by liquid chromatography (detector: shode
x R1 SE-51, column: Tosoh G100
It was measured with 0 PW (column No. PW16D0015 with a guard column) and evaluated according to the following criteria. ◯: When the change in the urea content is within 5%. X: When the change in the urea content is 5% or more.

(3) Ejection stability Ink jet printer BJ-130 for recording by returning the ink from an environment of 60 ° C. to room temperature and leaving it at room temperature for 24 hours to generate droplets by using thermal energy.
(Brand name: manufactured by Canon Inc.), and printed alphanumeric characters on 100 sheets of commercially available high-quality paper.
The following criteria evaluated. ⊚: Characters are not disturbed. ◯: Characters are occasionally distorted, but hardly distorted. Δ: Characters are distorted but can be read. X: Characters are very disturbed and difficult to read.

(4) Ink odor The odor of the ink taken out from the environment of 60 ° C. was smelled, and the presence or absence of ammonia odor generated by decomposition of urea was evaluated according to the following criteria. ◯: No ammonia odor. X: There is an ammonia odor.

[Table 3]

[0026]

As described above, the ink jet recording ink of the present invention can stabilize the physical properties and composition of the ink because the decomposition of urea is suppressed in a high temperature environment or in a long-term storage state. Becomes Further, when the ink composition of the present invention is used in a high-density recording head using heat energy, the above-mentioned effects can greatly improve the durability. Furthermore, the ink jet recording ink of the present invention,
When used in the inkjet recording system, good effects such as stabilization of ink droplet shape on recording paper, ejection stabilization, high density, water resistance, light resistance, weather resistance, and storage stability can be obtained. It is possible to describe the obtained image with high image quality and high definition.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a head portion of an inkjet recording apparatus.

FIG. 2 is a cross-sectional view of a head portion of an inkjet recording device.

3 is an external perspective view of a head in which the head shown in FIG.

FIG. 4 is a perspective view showing an example of an inkjet recording apparatus.

FIG. 5 is a vertical sectional view of an ink cartridge.

FIG. 6 is a perspective view of a recording unit.

[Explanation of symbols]

61: Wiping member 62: Cap 63: Ink absorber 64: Discharge recovery unit 65: recording head 66: Carriage

Claims (10)

[Claims] 1. An inkjet recording ink containing a coloring material, water, a water-soluble organic solvent, and urea, which contains an ammonium salt. 2. An inkjet recording method for recording on a recording material by ejecting ink droplets from an orifice according to a recording signal, wherein the ink is the ink according to claim 1. . 3. The ink jet recording method according to claim 2, wherein thermal energy is applied to the ink to eject ink droplets. 4. A recording unit comprising an ink containing portion containing ink and a head portion for ejecting the ink as ink droplets, wherein the ink is the ink according to claim 1. unit. 5. The recording unit according to claim 4, wherein the head portion includes a head that applies thermal energy to the ink to eject ink droplets. 6. An ink cartridge provided with an ink containing portion containing ink, wherein the ink is the ink according to claim 1. 7. An ink according to claim 1, wherein the ink is an ink jet recording apparatus including a recording unit having an ink containing portion containing the ink and a head portion for ejecting the ink as an ink droplet. An ink jet recording apparatus characterized by the above. 8. The ink jet recording apparatus according to claim 7, wherein the head portion includes a head that applies thermal energy to the ink to eject ink droplets. 9. An ink jet recording apparatus comprising a recording head for ejecting ink droplets, an ink cartridge having an ink accommodating portion for accommodating ink, and an ink supply portion for supplying ink from the ink cartridge to the recording head. An ink jet recording apparatus, wherein the ink is the ink according to claim 1. 10. The ink jet recording apparatus according to claim 9, wherein the recording head is a head that causes thermal energy to act on ink to eject ink droplets.