JPH09300637A - Cleaning fluid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to remove fixed ink formed at a delivering port without applying external force by a method wherein the cleaning fluid used for cleaning the nozzle of an ink jet printer is prepared by including at least one kind of polar solvents and at least one kind of surfactants. SOLUTION: This fixed ink cleaning fluid is prepared by mixing one or more different polar solvents such as dimethylsulfoxide, methyl ethyl ketone, ethanol or the like and one or more different nonionic surfactant such as polyether-based, silicone-based, fluorine-based surfactant or the like. The concrete cleaning method with this cleaning fluid is as follows: A cleaning cap 19, in which the prepared cleaning fluid is filled, is mounted to a stopped nozzle 3. Though the fixed ink is present on the delivering plate 14 of the nozzle 3, the delivering through which is stopped, the fixed ink dipped in the cleaning fluid 20 can easily be removed through dissolution and separation.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a nozzle cleaning liquid.

[0002]

2. Description of the Related Art Ink jet printers create charged ink particles by ejecting ink under pressure from a nozzle to which vibration is applied to create charged ink particles, and the ink particles are directed by an electrostatic deflection system. Character information is recorded by controlling. The principle is shown in FIG.

The ink in the ink bottle 8 is supplied by the supply pump 7.
Is sucked and pressurized by. The pressure is controlled by the pressure regulating valve 1. As an example of the pressure, the pressure is adjusted to 2.9 kgf / cm ² . The ink whose pressure is controlled is supplied to the nozzle 3.
The nozzle 3 is provided with an electrostrictive element 2, and by applying an electric signal to the electrostrictive element 2, vibration can be applied to the ink. Frequency 68.2 as an example of an electric signal
kHz 200V is applied. A discharge port 18 is provided at the tip of the nozzle. The diameter of the discharge port 18 is, for example, 65 μm. Ink jetted with vibration 18
Ink particles 10 are formed in the charging electrode 4 by being ejected from. At this time, it is possible to apply a charge to the ink particles 10 formed by applying a voltage to the charging electrode 4. 200 V is applied as an example of the voltage. Nozzle 3
The ink particles 10 ejected from pass through between the deflection electrodes 9. A voltage is applied to the deflection electrode 9. As an example, a voltage of 5.4 kV is applied. The ink particles 10 passing between the deflection electrodes 9 are deflected by electrostatic force and
Fly over to form letters. The ink not involved in the characters is first stored in the gutter 11, and further collected by the collection pump 6 and returned to the ink container 8. The feature of the inkjet printer is that ink is ejected to print. Therefore, it is possible to perform printing by separating the nozzle from the object to be printed, and it is possible to print on the uneven surface or the curved surface of the object to be printed. In addition, since the charge amount can be electrically changed, the character information can be easily changed. Taking advantage of these features, it is often printed on steel, paper, aluminum, plastic, glass, etc. Conventionally, methyl ethyl ketone, methanol, or ethanol has been mainly used as a solvent in order to use a resin having an adhesive force to these as a material of the ink. Water may be used as a solvent for printing on printed matter or food that does not require strong adhesive force. In particular, in order to reduce the influence on the working environment, the main solvent tends to shift from methyl ethyl ketone to ethanol and water. Also,
As the dye that gives color to the ink, a dye that is soluble in these solvents and a pigment that has the property of being insoluble in the medium but dispersed in the medium are used. Conventionally, dyes having a metal such as chromium have been mainly used because they are soluble in a medium and have excellent light resistance. However, it becomes difficult to use chromium or the like due to environmental issues, and pigments having excellent light resistance tend to be used instead.

Since all of these solvents have a vapor pressure at atmospheric pressure to some extent, they are ejected from the nozzle 3 as ink particles 10 as shown in FIG.
When it comes into contact with the atmosphere while being collected in the ink container 8 via the, a part of it is vaporized into the atmosphere as vapor.
As a result, the composition ratio of the solvent in the recovered ink decreases from the initial state. Therefore, the ink concentration and the ink viscosity increase. In the inkjet printer, when ejected from the nozzles 3 as described above, the ink is deformed by the vibration given from the electrostrictive element 2 to form the ink particles 10. Therefore, when the viscosity of the ink increases, the deformation of the ink is hindered, and the ink particles 10 may not be rapidly formed due to the vibration applied from the electrostrictive element 2. In order to prevent this, it has a function of supplying the evaporated solvent by a mechanism not shown in the figure. Therefore, a liquid level sensor for managing the liquid level of the ink is provided.

The ink is pressurized by the supply pump 7 and ejected from the nozzle 3. The detailed structure is shown in FIG. A nozzle tube 12 is attached to the nozzle 3. A discharge plate 14 is provided at the tip of the nozzle tube 12. Discharge plate 1
As an example of the material No. 4, a hard material such as ruby, ceramic or the like is used to prevent abrasion by ink. The discharge plate 14 is provided with a discharge port 18. The pressurized ink is ejected from the ejection port 18 through the inside of the nozzle tube 12 to form the ink column 13. Since ultrasonic waves are applied to this ink by the electrostrictive element 2 as already described, the ink column 13 ejected from the ejection port 18 of the nozzle 3 forms the ink particles 10 by the vibration of the ink.

FIG. 3 shows changes in the surface condition of the ejection plate 14 during ink ejection. In the stopped state, nothing is attached to the surface of the discharge plate 14. (A). When the pressurized ink is ejected from the ejection port 18, the inside of the nozzle 3 is about 2.9 kgf / c.
Although the pressure is m ^2, the pressure outside the discharge port 18 is atmospheric pressure,
Due to the rapid expansion due to the pressure difference, the ink not only advances straight to form the ink column 13, but also the ink is scattered 17 and adheres to the surface of the ejection plate 14 to form the adhered ink 15. (B). Further, the attached ink 15 is the ink column 1.
It is also formed when the ink oozes out from 3.
Further, the ink adheres to the ejection port even when the ejection of the ink is stopped. These adhering inks 15 eventually solidify to become fixed inks 16. (C). This fixed ink 1
6 is re-dissolved by the ink scattering 17 when the ink is ejected again, and returns to the attached ink 15. (D). Further, when the apparatus is stopped, the cleaning cap 19 shown in FIG. 6 is filled with a solvent so that the adhered ink 15 does not solidify when the discharge is stopped.
Measures were taken to prevent the surface of the discharge plate 14 from drying. Also,
There is also a method in which a solvent is caused to flow through the ink path of the nozzle 3 when the apparatus is stopped, and the path is washed to remove the adhered ink 16.

[0007]

The fixed ink 16 at the tip of the nozzle affects the straightness of the ink column 13. For example, when the ink column 13 comes into contact with the fixed ink 16, the ejection direction is bent and the unprinted ink particles 10 are not printed.
Does not enter the gutter 11 and the ink overflows from the gutter 11. The state is shown in FIG. Also,
The direction of ink is extremely short, for example from several Hz to several tens of H
When disturbed at the z-interval, this disorder disturbs the formation of the ink particles 10 from the ink column 13 in the charging electrode, and the charging for the purpose of printing is not normally performed. as a result,
Ink particles fly to places other than the target, and the printing is disturbed.

In the prior art, these structures are fixed ink 1
Since the problem caused by the interference between the ink 6 and the ink column 13 was not taken into consideration, the means for preventing the formation of the fixed ink 16 was insufficient. In the prior art, this fixed ink 1
The formation of No. 6 was prevented by re-dissolving the fixed ink 16 due to the ink scattering 17 at the time of ejection and washing with the solvent at the time of stop. This technique is based on the assumption that the fixed ink 16 is redissolved by the ink itself and the solvent. That is, it was necessary to dissolve all the materials constituting the ink. Since dyes have been used as pigments in the conventional main ink, all the ink constituent materials are dissolved in the solvent. However, as described above, a new problem arises as the dye is changed from the dye to the pigment due to environmental problems. That is, since the pigment does not dissolve in the solvent but only disperses, there occurs a phenomenon that the pigment component of the fixed ink is not redissolved. This phenomenon is shown in FIG.

In the stopped state, nothing is attached to the surface of the discharge plate 14. (A). Pressurized ink is ejection port 1
When discharging from 8, the inside of the nozzle 3 is about 2.9 kgf / cm ²
However, since the outside of the ejection port 18 is at atmospheric pressure, the ink not only advances straight to form the ink column 13 due to the rapid expansion due to the pressure difference, but also the ink is scattered 17 and the ejection plate 14 is ejected. Also adheres to the surface of the ink to form the adhered ink 15. (B). Further, the attached ink 15 is the ink column 13.
It is also formed when ink oozes out from the ink. Further, the ink adheres to the ejection port even when the ejection of the ink is stopped. These adhering inks 15 eventually solidify to become fixed inks 16. (C). When the ink was re-ejected, the conventional dye ink was redissolved by the ink splatter 17. However, since the pigment component is not dissolved in the pigment ink by the ink and the solvent, the fixed ink 16
Is not completely redissolved, and new fixed ink 16a is formed from the adhered ink. (D). The size of the fixed ink 16 is about 0.1 mm, but when the fixed ink 16 grows in this way, the fixed ink 16 and the ink column 13 come into contact with each other, and the ejection direction is bent as described above. Further, the fixed ink is oxidized with time, and the chemical bond with the surface of the adhered substance is promoted based on the oxidized portion, so that the removal becomes more difficult.

When the degree of adhesion is light, the ink column 13 removes a part of the fixed ink 16 and ejects it without being bent, but when the adhesion is remarkable, it is not removed and becomes a bent state. Therefore, if this bend occurs,
It was necessary to remove the nozzle 3 from the apparatus and perform disassembly cleaning. Since the pigment of the fixed ink 16 does not dissolve in the solvent, in order to disperse and remove the pigment, ultrasonic vibration was performed in a state of being immersed in the solvent, and the pigment was redispersed for cleaning. Therefore, there is a problem in workability that the device is removed from the device and washed. Further, as a means for removing the adhered matter on the discharge plate 14 without removing it from the apparatus, there is a method of impregnating absorbent cotton or absorbent paper with a solvent and rubbing the surface of the discharge plate 14 with tweezers itself. It was taken. However, since the discharge plate 14 is made of a hard and brittle material such as ruby or ceramic, there is a problem that a part of the discharge plate 14 is chipped by the rubbing operation. Further, since the target object to be removed has a small area, there is a problem that it is uncertain whether or not it has been removed even when the work is performed.

It has also been tried to process the surface condition of the discharge plate 14 so that ink does not adhere to it. For example, it is possible to form a surface that repels liquid by chemically bonding a resin containing fluorine atoms in the molecule to the surface of the ejection plate 14. The surface having a contact angle with water of 30 degrees and a contact angle with a solvent of 5 degrees in the initial state has a contact angle with water of 135 degrees and a contact angle with a solvent of 70 degrees. It can be increased every time. Therefore, it has been attempted to prevent the ink from adhering to the surface of the ejection plate 14 and to prevent the adhered ink 16 from being generated by performing such a treatment on the surface. However, when the ink is ejected, the ink is scattered 17 and the ink adheres to the ejection plate 14. Since the ejection plate 14 repels the ink by the above processing, the attached ink 15 becomes island-shaped droplets,
It is not possible to create a state that does not completely adhere. As a result, the adhered ink 15 becomes the adhered ink 16, which does not contribute to solving the problem. Further, since the surface subjected to this treatment has a property of being hard to be wetted by the solvent, it becomes difficult to permeate the solvent between the fixed matter and the ejection plate 14 when the fixed ink 16 is removed, and as a result, the solvent is removed. The problem of difficulty also arises. Therefore, with this method, the result is that the fixation of ink cannot be prevented. That is, in pigment-based inks, how to remove the fixed ink is an important issue.

An object of the present invention is to provide a cleaning liquid capable of removing the fixed ink 16 formed on the ejection port 14 without applying an external force.

[0013]

The object is achieved by using, as the main cleaning liquid, a cleaning liquid containing at least one kind of polar medium and at least one kind of surfactant.

Removal of deposits from the surface is accomplished by the entry of media between the surface and the deposits. When this medium is entered, the force acting between the surface and the deposit is cut, and the deposit is removed from the surface.

Since the ink 16 adhered to the ejection plate 14 is oxidized with time, an oxygen functional group is formed in its molecular structure. When a substance dissolves or swells, substances that are similar in molecular structure have the property of being easily adapted. Therefore, in order to dissolve and swell the ink that has been oxidized, it is necessary to use a medium having a similar molecular structure. When oxygen is contained in the molecule, the oxygen tends to be negatively polarized. Therefore, it has polarity. That is, it becomes easy to remove the fixed ink by using a medium having polarity. The medium having polarity is not limited to a medium having an oxygen atom, and a medium containing a nitrogen atom or the like also has a polarity.

In order to allow the medium to enter between the surface and the deposit, it is necessary to improve the permeability of the medium. This permeability is achieved by reducing the surface tension of the medium.
The means is effective by adding a surfactant. Further, the surfactant has an action of reducing the adhesive force between the surface and the adhered substance, and thus facilitates its removal. Surfactants are roughly classified into ionic and nonionic. Any of the above can be used for the above purpose, but if an ionic substance is mixed in some inks for inkjet printers, problems such as precipitation of constituent substances may occur, so non-ionic interfaces Activators are more preferred.

By applying the cleaning liquid containing the polar medium and the surfactant to the nozzle after the ink ejection is stopped, the cleaning liquid enters between the surface and the ink adhered to the surface and the adhered matter is removed. . Further, by sealing with a cleaning cap filled with the cleaning liquid when the apparatus is left standing still, the cleaning liquid further advances and the adhered substances can be easily removed.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 is a diagram showing the principle of an ink jet printer. The ink in the ink container 8 is suction-pressed by the supply pump 7. The pressure is controlled by the pressure regulating valve 1. As an example of the pressure, the pressure is adjusted to 2.9 kgf / cm ² .
The ink whose pressure is controlled is supplied to the nozzle 3. The nozzle 3 is provided with an electrostrictive element 2, and the electrostrictive element 2
By applying an electric signal to the ink, vibration can be applied to the ink. Frequency of 68.2 kHz as an example of an electric signal
z 200V is applied. An orifice is provided at the tip of the nozzle. The diameter of the orifice is 65 as an example.
μm. The vibrated ink is ejected from the orifice and forms ink particles 10 in the charging electrode 4. At this time, it is possible to apply a charge to the ink particles 10 formed by applying a voltage to the charging electrode 4.
200 V is applied as an example of the voltage. The ink particles 10 ejected from the nozzle 3 pass between the deflection electrodes 9. A voltage is applied to the deflection electrode 9. For example, 5.
A voltage of 4 kV is applied. The ink particles 10 passing between the deflecting electrodes 9 are deflected by electrostatic force and fly to the printing object 5 to form characters. The ink not involved in the characters is first stored in the gutter 11, and further collected by the collection pump 6 and returned to the ink container 8.

The ink is pressurized by the supply pump 7 and ejected from the nozzle 3. The structure is shown in FIG. Nozzle 3
Is provided with a nozzle tube 12. A discharge plate 14 is provided at the tip of the nozzle tube 12. Discharge plate 1
As an example of the material No. 4, a hard material such as ruby, ceramic or the like is used to prevent abrasion by ink. The discharge plate 14 is provided with a discharge port 18. The pressurized ink passes through the inside of the nozzle pipe 12 and
To form an ink column 13. Since the ultrasonic wave is applied to this ink by the electrostrictive element 2 as described above, the ink column 1 ejected from the ejection port 18 of the nozzle 3
3 forms ink particles 10 by vibration of the ink.

FIG. 4 shows changes in the surface condition of the ejection plate 14 with the pigment ink. In the stopped state, nothing is attached to the surface of the discharge plate 14. (A). When the pressurized ink is ejected from the ejection port 18, the inside of the nozzle 3 is about 2.9 kg.
Although the pressure is f / cm ² , the outside of the ejection port 18 is atmospheric pressure, and due to the rapid expansion due to the pressure difference, the ink not only advances straight to form the ink column 13 but also scatters the ink 17. And also adheres to the surface of the ejection plate 14
To form (B). The attached ink 15 is also formed by the ink bleeding from the ink column 13. Further, the ink adheres to the ejection port even when the ejection of the ink is stopped. These adhering inks 15 eventually solidify to become fixed inks 16. (C). When the ink was re-ejected, the conventional dye ink was redissolved by the ink splatter 17. However, in the pigment ink, since the pigment component is not dissolved in the ink and the solvent, the fixed ink 16 is not completely redissolved, and new fixed ink 16a is formed from the attached ink. (D).

An example of a cleaning liquid for removing this fixed ink is shown below. Various polar media are used as a medium constituting the cleaning liquid for the purpose of dissolving and swelling the deposits. For example, methyl ethyl ketone or ethanol, which is the main solvent of ink, is one of the polar media. However, since it is difficult to dissolve the oxidized component with these solvents, a medium having more polarity is used. As an example, dimethyl sulfoxide can be used. It has oxygen and sulfur atoms in the molecule and has high polarity and solubility. Similarly, dimethylformamide, N-methylpyrrolidone, and the like also have a nitrogen atom in their molecular structure, and have polarity and high dissolving power. These media are used alone or as a mixed medium. In the case of a medium having a melting point near room temperature such as dimethyl sulfoxide, it can be mixed with methyl ethyl ketone having a low melting point to improve workability at room temperature. The present invention is not limited to these substances.

The nonionic surfactants added to these media include polyether-based, silicon-based and fluorine-based surfactants. Polyether type surfactants are polyoxyethylene lauryl ether type, polyoxyethylene cetyl ether type, polyoxyethylene stearyl ether,
Examples thereof include polyoxyethylene derivatives such as polyoxyethylene oleyl ether, polyoxyethylene higher alcohol ether, polyoxyethylene octylphenyl ether, and polyoxyethylene nonylphenyl ether. Further, examples of the silicone type include those obtained by subjecting dimethylpolysiloxane, which is the main chain, to epoxy modification, polyether modification, alcohol modification, epoxy / polyether modification, and alkylaralkylpolyether modification. Fluorine is perfluoroalkyl betaine,
Examples thereof include perfluoroalkylamine oxide and perfluoroalkylethylene oxide. The present invention is not limited to these substances. The addition amount of these varies depending on the types of the polar medium and the surfactant, but is usually appropriate in the range of 0.05% to 0.5%.

An example of a cleaning method using this cleaning liquid is shown in FIG.
It will be explained in. A cleaning cap 19 is attached to the tip of the nozzle 3 that has stopped discharging. The cleaning cap 20 is filled with the cleaning liquid 20. There is adhered ink on the ejection plate 14 of the nozzle whose ejection has stopped, but it is dissolved and peeled off by being immersed in the cleaning liquid 20 in this way.

The effect of this cleaning with pigment ink is as follows. The main composition of the pigment ink used for evaluation is shown below.

Solvent Methyl ethyl ketone resin PVC resin Pigment carbon black (average pigment particle size: 0.2 μm) When this ink is repeatedly ejected and stopped (left standing for 1 hour) 10 times, a sticky substance is formed at the tip of the nozzle. . In this state, when methyl ethyl ketone is used as a cleaning solvent in the cap cleaning shown in FIG. 6 and left for 8 hours, the dissolved resin component is mainly removed, but the adhered pigment (carbon black) remains. This pigment is a particle of about 0.2 μm in the ink solution state, but when adsorbed on the nozzle surface, the pigments aggregate with each other to form a mass of several μm. Therefore, it is difficult to recognize the red color of the ruby that forms the nozzle discharge port. When the above discharge-stop is further repeated, this aggregate further grows. In this state, it is not removed by contact with methyl ethyl ketone, so it is removed by rubbing it with tweezers by adding it to absorbent cotton. Next, when the discharge-stop was repeated 10 times in the same manner and the cap cleaning of FIG. 6 was performed and left for 8 hours with the cleaning liquid of the present development, the pigment adhering to the surface was removed.

[0027]

According to the present invention, the ink adhered to the ink ejection port can be removed without using external force, and the ejection of the ink column at the time of ejecting the ink can be stabilized. It is possible to prevent instability, and it is also possible to prevent print disturbance due to unstable ejection.

[Brief description of drawings]

FIG. 1 is a perspective view of a printing apparatus using a nozzle cleaning liquid according to an exemplary embodiment of the present invention.

FIG. 2 is a perspective view of the tip of a printing apparatus using the nozzle cleaning liquid according to the embodiment of the invention.

FIG. 3 is a cross-sectional view showing changes in the ejection port during the dye ink ejection-stop cycle.

FIG. 4 is a cross-sectional view showing a change in an ejection port during a pigment ink ejection-stop cycle.

FIG. 5 is an explanatory diagram showing the ejection direction when the ink column is bent.

FIG. 6 is an explanatory diagram showing an example of a cleaning method using a nozzle cleaning liquid according to an embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Pressure regulating valve, 2 ... Electrostrictive element, 3 ... Nozzle, 4 ... Charging electrode, 5 ... Printed object, 6 ... Recovery pump, 7 ... Supply pump,
8 ... Ink bottle, 9 ... Deflection electrode, 10, 10a ... Ink particles, 11 ... Gutter.

Claims (1)

[Claims] 1. A cleaning liquid used for cleaning a nozzle of an ink jet printer for printing with ink particles formed by ejecting ink from a nozzle contains at least one kind of polar medium and at least one kind of surfactant. A characteristic cleaning solution.