JP2708538B2 - Cleaning solution and cleaning method using the same - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a cleaning liquid and a cleaning method using the cleaning liquid.

[Conventional technology]

In the ink jet printer, a method of supplying an aqueous solution of sodium hydroxide as described in JP-A-62-117751 is known in order to prevent nozzle clogging.

On the other hand, dimethyl sulfoxide is known as a solvent or a release agent for dyes and pigments.

[Problems to be solved by the invention]

The supply of the aqueous sodium hydroxide solution in the above-described ink jet printer is intended to prevent the deposition and deposition of alkali-soluble components due to a decrease in the pH of the ink. Has no effect.

Also, meditytyl sulfoxide is widely used as a solvent or release agent because of its high solubility. However, its high melting point (18.4 ° C) makes the storage environment temperature or use environment temperature impractical. Atsuta.

SUMMARY OF THE INVENTION An object of the present invention is to provide a cleaning solution which dissolves the deteriorating components of ink well and has a practical storage environment temperature or usage environment temperature, and a cleaning method using the cleaning solution.

[Means for solving the problem]

The cleaning liquid of the present invention is characterized in that an ink solvent and dimethyl sulfoxide are mixed, and in the cleaning method, the cleaning liquid is caused to act on the object to be cleaned, or the cleaning liquid is used for the object to be cleaned and ultrasonic waves are applied. The object to be cleaned is washed while the object is washed.

[Action]

In ink jet printing, the deteriorated ink produced during operation is mainly a substance having a polar group, which is generated by oxidation or hydrolysis of components. On the other hand, dimethyl sulfoxide is a polar aprotic solvent and dissolves the above-mentioned ink degraded products. It is also compatible with other polar and non-polar solvents. The freezing point of the mixed solvent of the dimethyl sulfoxide and the ink solvent is lower than the freezing point of the dimethyl sulfoxide due to the principle of lowering the freezing point of the solvent.

It is a cleaning solution that has a high detergency and is practical for storage or use at an ambient temperature, and is a cleaning method.

〔Example〕

 Hereinafter, examples of the present invention will be specifically described.

FIG. 4 is an external view of an ink jet printer having a nozzle to be cleaned by a cleaning liquid according to the present invention.
The figure shows an example of the ink flow path.

In the ink jet printer, the ink 22 in the ink bolt 7 is supplied to the nozzle 3 by the pump 6, and an electric charge corresponding to a character signal is given from the charging electrode 14 to the ink particles 12 ejected from the nozzle 3. The charged ink particles 12 are turned into deflection electrodes 11
When passing through the gap, the flight direction is bent by the Coulomb force, and the printing object 10 adheres. Unnecessary ink particles 12 for recording to which no charge is given go straight and are captured by the gutter 9,
Then, the ink bolt 7
Is returned to.

In addition, 1 is a recording head unit, 2 is a nozzle case,
4 is a nozzle excitation element, 5 is a pressure regulating valve, 13 is a character signal generation circuit, and 15 is a control unit.

The main components of the ink 22 are a dye, a pigment, and a solvent that dissolves these. FIG. 2 shows an example of the molecular structure of the dye,
FIG. 3 shows an example of the molecular structure of the resin. As a solvent for dissolving these, a hydrocarbon-based, alcohol-based, ketone-based, ester-based or ether-based solvent can be used alone or in a mixture. As an example,
By volume composition ratio, methyl ethyl ketone 90%, methanol 10
% Of the mixed solvent is used.

In the ink jet printer, the ink 22 not involved in printing is mixed with air and stirred when it is returned from the gutter 9 to the ink bolt 7 by the recovery pump 8.
The flow rate of the recovery pump 8 is, for example, 1 / min. For this reason, air oxidation occurs in the ink components, and the molecules in the components become carbonyl groups (CO) carboxy groups (-COOH),
It will have a hydroxy group (-OH). Further, if a substance having a catalytic action such as acid or alkali which promotes hydrolysis is mixed in the surrounding air, it is taken into the ink to cause hydrolysis. As an example, in the dye of FIG. 2, the reaction of -NHCOCH ₃ → -NH ₃ + CH ₃ CO ₂ H -OCOCH ₃ → -OH + CH ₃ CO ₂ H occurs, and the amide group (-NHCO-) and the ester group ( −
OCO-), respectively, comprising an amino group and (-NH ₂₎ and hydroxy group (-OH). Since all of these functional groups have strong polarities, dyes and resins having these functional groups in the molecular structure are hardly soluble or insoluble in the above-mentioned solvents. Adheres inside.
This is called a deteriorated ink.

On the other hand, the diameter of the nozzle 3 is, for example, about 30 μm in diameter. If the deposit adheres to the nozzle 3, the flow of the ink is disturbed and the ejection direction changes, or the nozzle 3 is clogged. Since the deposited precipitate is hardly soluble or insoluble in the ink solvent as described above, it is difficult to remove it even by washing with the ink solvent.

Dimethyl sulfoxide is a polar aprotic solvent and can easily dissolve the above-mentioned molecule having a polar functional group, and is suitable as a washing solution. However, since dimethyl sulfoxide has a high melting point of 18.4 ° C., there is a problem that the dimethyl sulfoxide solidifies when stored or used at an environmental temperature lower than this.

 Next, the cleaning liquid according to the present invention will be described.

The cleaning liquid according to the present invention is adjusted by mixing the ink solvent with dimethyl sulfoxide so that the freezing point does not solidify at ordinary storage environment temperature and use environment temperature. As the ink solvent, a mixture of 90% methyl ethyl ketone and 10% ethanol in volume composition ratio is used, but the composition and composition ratio are not limited.

FIG. 1 shows the change characteristic of the freezing point with respect to the change in the dimethyl sulfoxide concentration of the cleaning solution, and it can be seen that the freezing point temperature decreases as the concentration decreases. For example, when the concentration of dimethyl sulfoxide becomes 60%, the freezing point temperature becomes −10 ° C. or less, which is a practical environmental temperature specification.

It is clear that a solvent other than the ink solvent may be mixed in order to lower the freezing point temperature of dimethyl sulfoxide, but when used as a cleaning liquid for cleaning the nozzles of an ink jet printer, the cleaning liquid may be used. It may remain in the ink flow path and adversely affect the ink.
Therefore, in order to avoid adverse effects when mixed into the ink, it is desirable that the ink solvent itself or a component contained in the ink solvent.

The cleaning liquid having the characteristics shown in FIG. 1 has a volume composition ratio of 60% dimethyl sulfoxide, 36% methyl ethyl ketone, and 4% methanol, but has a volume composition ratio of 55 to 65% dimethyl sulfoxide and 30% methyl ethyl ketone. A good cleaning solution can be obtained in the range of 4040% and methanol in the range of 11010%.

Dimethyl sulfoxide 59%, methyl ethyl ketone 41
% Of the mixed solution is also a preferable washing solution, but in the case of this mixed solution, the volume composition ratio is 55 to 65% of dimethyl sulfoxide.
%, And methyl ethyl ketone in the range of 35 to 45% can provide a cleaning solution having good characteristics.

A mixture of 76% dimethyl sulfoxide and 24% methanol is also effective as a similar washing solution, but in the case of this mixture, the volume composition ratio is 70-80% dimethyl sulfoxide,
A washing solution with good characteristics can be obtained in the range of 20 to 30% of methanol.

It goes without saying that the composition and volume composition ratio of the cleaning liquid change depending on the set environmental temperature specification.

These cleaning liquids are effective as cleaning liquids for ink jet printers, but can also be used for cleaning other liquids.

6 and 7 show an example of a nozzle cleaning method for the ink jet printer using the cleaning liquid according to the present invention.

In this cleaning method, the inside of the nozzle
Then, the nozzle cap 16 covers the nozzle 3 so that the cleaning liquid 17 penetrates through the nozzle hole to dissolve the deteriorated ink adhered to the inner surface.
This is a method of ejecting ink or a solvent from the nozzle by ejecting the ink or the solvent from the nozzle. According to this method, it is not necessary to remove the nozzle 3 from the recording head unit 1, and the nozzle 3 can be cleaned by a simple operation.

This method is also effective as a method for preventing the adhesion of the deteriorated ink. That is, when the operation of the ink jet printer is stopped, the nozzle cap filled with the cleaning liquid 17 is used.
By covering the nozzle 3 with 16 and allowing the cleaning liquid 17 to penetrate into the nozzle hole, it is possible to prevent the deteriorated ink from depositing and adhering.

When the ultrasonic dispersing force is applied to the dissolving power of the cleaning liquid 17,
Even more effective cleaning can be performed.

FIG. 8 shows an example of a cleaning method for cleaning the nozzle 3 while applying ultrasonic waves. In this cleaning method, the cleaning liquid 17 is placed in a cleaning container 19, the tip of the nozzle 3 removed from the recording head unit 1 is immersed in the cleaning liquid 17, and the cleaning container 19 is placed in a cleaning chamber 20a of an ultrasonic cleaning machine 20 together with water 21. In this method, the deteriorated ink adhered to the inside of the nozzle is dissolved while applying the ultrasonic wave 23, and then the ink or the solvent is ejected from the nozzle 3 to discharge them out of the nozzle. According to this cleaning method, the dispersing force due to the ultrasonic wave is added to the dissolving power by the cleaning liquid 17, so that it is also possible to remove the degraded ink that is firmly attached.

Nozzle excitation element 4 and resin layer 18 integrated with nozzle 3
If there is a possibility that the cleaning liquid 17 will dissolve, swell, or peel off, the amount of the cleaning liquid 17 is adjusted so that only the tip of the nozzle 3 is immersed in the cleaning liquid 17.

When dimethyl sulfoxide is added to the ink, the deterioration of the ink can be reduced.

FIG. 9 shows the ink containing dimethyl sulfoxide,
4 shows the relationship between the dimethyl sulfoxide concentration and the degree of ink deterioration. Here, the deterioration degree of the ink is a comparison value of the absorbance of a liquid obtained by dissolving the filtration residue of the ink, which has been subjected to the deterioration test under a predetermined condition, with dimethyl sulfoxide.

The deterioration test conditions are such that air having a humidity of 60% at 20 ° C. is blown into 10 ml of the ink to be evaluated at a rate of 1 / min for 8 hours, and the ink solvent component evaporated at this time is always replenished.

The deteriorated ink generated in this deterioration test is manufactured by Millipore.
The mixture is filtered through a 0.5 μm polytetrafluoroethylene filter, and an ink solvent is allowed to act on the filter to remove components soluble in the ink solvent from the filter, whereby an ink degraded product is obtained as a residue on the filter.
The filter is immersed in 10 ml of dimethyl sulfoxide to form a solution in which the residue is completely dissolved, and the absorbance at a wavelength of 540 nm is determined. According to Lambert-Beer's law, the absorbance is proportional to the concentration of the dissolved substance, and thus the absorbance is proportional to the concentration of the deteriorated ink. Therefore, the degree of deterioration of the ink can be compared numerically by comparing the absorbance. FIG. 9 shows the absorbance of the ink without added dimethyl sulfoxide as 1.0.

In the example of FIG. 9, dimethyl sulfoxide was added to ink 1
By adding 0.1ml per ink, the degree of ink deterioration is 1/5 ~
Reduce to 1/6. Therefore, when an ink to which 0.1 ml of dimethyl sulfoxide is added per ink is used in an ink jet printer, the amount of ink deteriorating substances adhered to the nozzles is reduced to 1/5 to 1/6.

〔The invention's effect〕

ADVANTAGE OF THE INVENTION According to this invention, the washing | cleaning method which uses the washing | cleaning liquid which has a large washing | cleaning effect which can be generally stored and used at environmental temperature, and which uses this washing | cleaning liquid can be provided.

[Brief description of the drawings]

The drawings show an embodiment of the present invention. FIG. 1 is a diagram showing a change characteristic of a freezing point with respect to a change in dimethyl sulfoxide concentration of a cleaning solution, FIG. 2 is a molecular structure diagram of a dye, and FIG. FIG. 4 is an external view of an ink jet printer,
FIG. 5 is an ink flow path diagram, FIGS. 6 and 7 are perspective views showing a nozzle cleaning method and a longitudinal side view in which main parts are enlarged, and FIG. 8 is a longitudinal side view showing another nozzle cleaning method. FIG. 9 is a characteristic diagram showing the relationship between the amount of ink added with dimethyl sulfoxide and the amount of residue. Reference numeral 1 denotes a recording head unit, 3 denotes a nozzle, 16 denotes a nozzle cap, 17 denotes a cleaning liquid, and 22 denotes ink.

Claims (11)

(57) [Claims] 1. A cleaning liquid comprising a mixture of an ink solvent and dimethyl sulfoxide. 2. The cleaning solution according to claim 1, wherein the freezing point is adjusted to be lower than the storage environment temperature. 3. The cleaning solution according to claim 1, wherein the freezing point is adjusted to -10 ° C. or lower. 4. A dimethyl sulfoxide having a volume composition ratio of 55 to 55.
65%, methyl ethyl ketone 30-40%, methanol 1-10
% Cleaning solution. 5. A dimethyl sulfoxide having a volume composition ratio of 60.
5. The cleaning liquid according to claim 4, wherein the cleaning liquid is 36%, methyl ethyl ketone 36%, and methanol 4%. 6. A dimethyl sulfoxide having a volume composition ratio of 55 to 55.
A cleaning solution comprising 65% and methyl ethyl ketone 35-45%. 7. A dimethyl sulfoxide having a volume composition ratio of 59.
7. The cleaning liquid according to claim 6, wherein the cleaning liquid is 0.1% and methyl ethyl ketone is 41%. 8. A dimethyl sulfoxide having a volume composition ratio of 70 to 70.
A cleaning liquid characterized by being 80% and methanol being 20 to 30%. 9. A dimethyl sulfoxide having a volume composition ratio of 76.
9. The cleaning liquid according to claim 8, wherein the cleaning liquid is 0.1% and methanol is 24%. 10. A method for cleaning a nozzle of an ink jet printer, wherein a nozzle cap filled with a cleaning liquid in which an ink solvent and dimethyl sulfoxide are mixed is covered on a nozzle for ink jet printing to clean the nozzle. 11. A cleaning method, comprising: placing an object to be cleaned in a cleaning container containing a cleaning liquid in which an ink solvent and dimethyl sulfoxide are mixed; and washing the object to be cleaned while applying ultrasonic waves.