JP2002060665A - Ink jet printer and ink for ink jet printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dye ink which hardly coagulates even when mixed with a pigment ink at the time of ink switching in an ink jet printer capable of alternately using a pigment ink and a dye ink; and a highly reliable ink jet printer. SOLUTION: The ink jet printer can alternately use a dye ink containing an acidic dye having a sulfo or sulfonate group and an alkaline pigment ink containing an acrylic acid copolymer as a dispersant by switching from one to another at any time. The difference in pH between the dye ink and the pigment ink is set at 1.5 or smaller.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet printer which uses a pigment ink and a dye ink by switching between them in order to obtain desired recording information, and an ink for the ink jet printer.

[0002]

2. Description of the Related Art Conventionally, dye ink and pigment ink have been used for recording by an ink jet printer.

[0003] Recording using the dye ink is suitable for outputting a vivid recording result or the like. However, since the dye ink is dissolved at the molecular level, it has poor light fastness and is easily discolored. For this reason, it is not suitable for recording posters and the like that are stuck outdoors for a long time. In that respect, since pigment ink is dispersed as relatively large particles, it compensates for the above-mentioned disadvantage, and recording using pigment ink is
It can be said that it is also suitable for recording of a recorded material that is exposed to an outdoor environment for a long time.

As described above, it is necessary to switch the ink to be loaded in the same ink jet printer depending on the use of the recording result.

[0005] When a relatively large recording result such as a poster is obtained, an ink jet printer to be used becomes large. Such large-sized inkjet printers do not use small cassette-type ink tanks with integrated ejection nozzles, because they require frequent replacement in order to obtain large-format recording. In many cases, only the large ink tank having no nozzle is replaced and replaced.

In such an ink jet printer in which only the ink tank is replaced, when switching processing is performed between the pigment ink and the dye ink, a tank filled with a cleaning liquid is loaded in a predetermined tank holding unit instead of the ink tank, The cleaning liquid is supplied to the ink supply path from the tank to the discharge nozzle (head) by the pump repeatedly to clean the tube and the discharge nozzle.

[0007]

However, such cleaning of the ink jet printer is often insufficiently performed, which sometimes causes defective ink ejection and nozzle clogging. In other words, if the residual concentration in the ink supply path is high, when the pigment ink and the dye ink are mixed, the acid dye and the acrylic acid copolymer-based dispersant of the pigment ink react, and Since the ionic dissociation of the carboxyl group is reduced and molecularized, the affinity between the pigment itself and the dispersant is reduced. Then, the pigment particles aggregate and grow, eventually causing problems such as clogging of the nozzles of the discharge nozzles.

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above-described circumstances, and provides an ink jet printer in which a pigment ink and a dye ink can be used alternately.
It is an object of the present invention to develop a dye ink that hardly aggregates even when a pigment ink and a dye ink are mixed, and to provide a highly reliable inkjet printer.

[0009]

According to a first aspect of the present invention, there is provided an ink jet printer comprising: a dye ink containing an acid dye having a sulfone group or a salt thereof; An ink-jet printer using an alkaline pigment ink having a coalescing agent as a dispersant as needed, wherein the difference between the pH of the dye ink and the pH of the pigment ink is 1.5 or less. The inkjet printer according to claim 2, wherein the dye ink and the pigment ink are organic amines in excess of the dye ink. By adding a kind or inorganic alkali, the difference between the pH of the dye ink and the pH of the pigment ink is reduced by 1.5.
It is characterized by being adjusted within.

According to these inventions, when an excess of an organic amine or an inorganic alkali is added to the dye ink to bring the pH closer to the pigment ink and the pH difference is adjusted to 1.5 or less, the pigment ink is removed. By bringing the pH for preventing aggregation closer to that of the pigment ink, the aggregation of the pigment is prevented, the cause of ink ejection failure of the inkjet printer and the cause of nozzle clogging are eliminated, and a highly reliable inkjet printer can be provided.

According to a third aspect of the present invention, there is provided an ink jet printer ink comprising a dye ink containing an acid dye having a sulfone group or a salt thereof and an acrylic acid copolymer, which are used interchangeably in the same ink jet printer. Pigment ink and two types of ink for inkjet printers, wherein the relationship between the dye ink and the pigment ink is characterized in that the pH difference is adjusted to be within 1.5, The ink for an inkjet printer according to claim 4 is the ink for an inkjet printer according to claim 3, wherein the dye ink and the pigment ink are:
By adding excess organic amines or inorganic alkalis to the dye ink, the pH of the dye ink is increased.
And the pH of the pigment ink is adjusted to be within 1.5.

According to these inventions, an excess amount of organic amines or inorganic alkali is attached to the dye ink to bring the pH closer to the pigment ink, thereby preventing aggregation of the pigment and discharging the ink of the ink jet printer. It is possible to eliminate the cause of the defect and the nozzle clogging.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG.

As shown in FIG. 1, the ink jet printer 1 of the present invention is supported by a pair of stands 3, 3 extending vertically and having a plurality of casters 2, 2,. An auxiliary frame 4 is provided between the stands 3 and 3 to connect a substantially central portion of the stands 3 and 3 in the vertical direction.

A flat platen 5 is disposed in front of the printer main body 1 so as to face upward. The platen 5 has a recording paper (not shown) conveyed to the platen 5 portion. A large number of suction holes 5a are provided for sucking and bringing the platen 5 into close contact with the platen 5.
Also, behind the platen 5 of the printer body 1,
Two carriage shafts 6, 6 extending in parallel to the longitudinal direction of the platen 5 are provided, and a carriage 7 is mounted on the carriage shafts 6, 6 along the carriage shafts 6, 6. Reciprocally mounted. The carriage 7 is connected to a carriage drive belt 8 located between the carriage shafts 6 and 6. The carriage 7 is driven by a drive device (not shown) to move the carriage 7 to the carriage shaft 6. 6 is driven back and forth.

The platen 5 of the carriage 7
The ink jet head 9 is attached at a position facing the recording nozzle 10 so that the ink ejection nozzle 10 faces the recording surface of the platen 5. And the discharge nozzle 1
A piezoelectric element (not shown), which is a piezoelectric element for ejecting ink from the discharge nozzle 10 at the tip of each ink supply path, is provided on the outer periphery of the ink supply path (not shown) in the area 0.

Further, in each of the ink jet heads 9, an inlet (not shown) for adjusting pressure is formed on the back side of the discharge nozzle 10. Inside the inlet, ink is stored and a certain amount of air is sealed at the upper side. This air absorbs the wave fluctuation of the ink generated in the ink jet head 9 due to the reciprocating movement of the carriage 7. And attenuate. That is, it has a role like a damper. A head solenoid valve (not shown) is provided above the inlet. When the head solenoid valve is opened, air in the inlet flows out, and the amount of air in the inkjet head 9 is constant. It is supposed to be.

A tank holding portion 11 is formed on one rear side of the printer main body 1. The tank holding portion 11 is provided with any type of ink such as pigment ink or dye ink during recording. The ink tanks 12a for each of the four colors of yellow (Y), magenta (M), cyan (C), and black (BK) are held, and the types of ink used for recording are pigment ink and dye. When switching between the ink and the ink, the tank holding unit 1 is used.
1, an air tank 12b or a cleaning liquid tank 12c is held.

A tube 13 is provided between each of the tanks 12 and the ink-jet head 9 and communicates from each of the tanks 12 to each of the ink-jet heads 9 via the carriage 7. These tubes 13
Are disposed one by one with respect to one tank 12, and a needle (not shown) for connecting to the tank 12 is attached to an end on the tank 12 side.

The ink tank 12a, the air tank 12b, and the cleaning liquid tank 12c held by the tank holding section 11 are provided with automatic pressurizing means (not shown) such as a pressurizing pump for pressurizing the inside of each tank 12. ) Can be connected by a pressurizing air passage (not shown) in the tank 12 via a pressure relay section (not shown). The automatic pressurizing means supplies air into the ink tank 12 through the pressurizing air passage, and the ink supply path including the tube 13 and the ink jet head 9 from each tank 12 to the discharge nozzle 10. To increase the internal pressure.

Further, a pressure measuring means (not shown) such as a pressure measuring device for measuring a pressing force of the automatic pressurizing means is connected to the pressure relay section. A pressure release valve (not shown) is connected to release air to the outside to reduce the pressure to atmospheric pressure. The automatic pressurizing means automatically keeps the internal pressure of the tank 12 at a set value based on the measurement value of the pressure measuring means, while the pressurizing air passage of each tank 12 A tank solenoid valve (not shown) is connected in the middle of the process. When the tank is opened (off), air from the pressurizing means 14 is supplied into the tank 12, and when closed (on), the tank is closed. It is assumed that no air is supplied into the interior 12. The head solenoid valve, the tank solenoid valve, and the pressure release valve are configured to be opened and closed at predetermined timings at the time of recording and at the time of ink replacement, respectively, by control means described later.

The control means, when connected to at least an input device (not shown), includes a CPU, a ROM having an appropriate capacity,
It has a memory formed by a RAM or the like, and is electrically connected to each unit of the inkjet printer 1 using an I / O interface. In the present embodiment, the CPU is connected to the inkjet head 9 based on the recording information, an automatic pressurizing unit, a paper transport motor for transporting the paper, and a carriage drive motor for driving the carriage 4, and controls the drive. For example, a proximity switch for detecting the operation reference position of the carriage 4 or an origin position sensor including a non-contact sensor such as an optical sensor is electrically connected.

Further, one side (the left side in FIG. 1 in the present embodiment) of the platen 2 of the ink jet printer 1 is a home position of the ink jet head 9, and a position corresponding to the home position is When the ink jet head 5 is not in use, it covers the discharge nozzle 10 to prevent drying and adhesion of foreign matter.
A cap device 14 for collecting ink, cleaning liquid, and the like discharged from the discharge nozzle 10 by suction into a liquid collecting tank (not shown) is provided.

The ink jet printer according to the present embodiment having the above-described structure is composed of a dye ink containing an acid dye having a sulfone group or a salt thereof and a pigment ink containing an acrylic acid copolymer as a dispersant. A type of ink for an ink jet printer is used. Describing the pigment ink and the dye ink, the relationship between the dye ink and the pigment ink used in the ink jet printer of the present embodiment is adjusted so that the pH difference is within 1.5.

That is, in the present embodiment, the pH of the dye ink is brought close to the pH of the pigment ink. The reason is as follows.

In a pigment ink using a polyacrylic acid copolymer as a dispersing agent, the carboxyl group in the dispersing agent is weak acid and has a small dissociation constant. Has been adjusted. On the other hand, an acidic ink using an acidic dye having a sulfone group or a salt thereof and having a large dissociation constant is neutralized with an alkali to form an ion pair, and the pH is originally near neutral. When these are mixed, the above-mentioned dispersant tends to be converted from ions to molecules. That is, the pigment is easily aggregated.
Therefore, in order to prevent this aggregation, an excessive amount of alkali is added to the dye ink to prevent rapid aggregation.

Then, the inventor attaches excess organic amines or inorganic alkali to the dye ink to bring the pH closer to the pigment ink, and when the pH difference is within 1.5, the aggregation of the pigment is reduced. The following experiment found that the effect of prevention was great.

The data shown below are examples of the composition of the yellow (Y) dye ink and pigment ink.

Dye ink composition Dye 5-nitro-o-toluenesulfonic acid self-condensate 2-7% Water 50-60% Diethylene glycol 30-40% Triethanolamine 1-3% Pigment ink composition Pigment Linole yellow pigment 4- 10% Dispersant Acrylic acid copolymer resin 1-2% Water 30-60% Diethylene glycol 30-60% Caustic soda <0.1% pH 9.5 To the dye ink thus composed, triethanolamine is further added. A dye ink added to adjust the pH to 7,
Similarly, three kinds of dye inks having a pH of 8 and a dye ink having a pH of 9 are prepared, and the respective volume ratios of the dye ink and the pigment ink are mixed at a ratio of 100: 1, and heated to 50 ° C. Immediately after the test, the sample was left for 14 days, the state of aggregation at this time was observed, and an experiment for measuring the particle size with a particle size distribution meter was performed.

[0030]

[Table 1]

As a result, as shown in Table 1, in the experiment using the dye ink adjusted to pH 9, the pigment particle size was determined to be the initial pigment particle size (200 nm) immediately after the mixing of the dye ink and the pigment ink. After 7 days, the pigment particle size was only agglomerated to about 250 nm, and hardly changed from the initial pigment particle size.
After 14 days, the result was that the pigment particle size was 700 nm.

In an experiment using a dye ink also adjusted to pH 8, the pigment particle size was determined to be the initial pigment particle size (200 n) immediately after mixing the dye ink and the pigment ink.
m), it aggregated to about 500 nm after 7 days, and again to 700 nm after 14 days. The particle diameter of about 700 nm is a particle diameter that does not hinder the ejection of the ink nozzle.

On the other hand, in an experiment using a dye ink adjusted to pH 7, the pigment particle size already changed to 500 nm immediately after the mixing of the dye ink and the pigment ink.
Aggregated to 3000 nm after 14 days, 3
000 nm was measured. In this experiment, 300
Measurement was impossible at 0 nm or more.

As described above, when the dye inks adjusted to pH 9 and pH 8 were used, the effect of alleviating agglomeration could be recognized after 7 days of standing and 14 days of standing, and the pH was adjusted to 7. When a dye ink was used, such an effect of alleviating aggregation was not able to be obtained.

Thus, when the pH difference between the pigment ink and the dye ink is within 1.5, that is, by bringing the pH of the dye ink close to that of the pigment ink, the difference is within 1.5. It was clarified that the effect of preventing the aggregation of the pigment particle size was great in the case of This has made it possible to greatly reduce the risk of replacing the pigment ink with the dye ink.

That is, by using a pigment ink having a pH difference of 1.5 or less from the pH of the pigment ink, the dye ink and the pigment ink can be exchanged with each other and used in the same inkjet printer. In addition, even if cleaning cannot be performed to completely remove the ink used at first, it is possible to reduce the aggregation of the pigment to a level that does not substantially cause a problem regarding the aggregation. This is not limited to the case of the above-described yellow ink, but also applies to inks of other compositions (including cases where the colors are different).

The pH of the dye ink is adjusted to the pH of the pigment ink.
It is not preferable to make the melting point higher than H, because it has an adverse effect on the dissolution characteristics of the dye ink and the like, and when a glass material is used for the inkjet head nozzle, the melting of the glass is promoted.

It should be noted that the present invention is not limited to the above-described embodiment, but can be variously modified as needed. For example, the organic amines or inorganic alkalis to be further added to change the pH of the dye ink are not limited to the above-mentioned triethanolamine. For example, monotriethanolamine, ditriethanolamine, ammonium hydroxide, water Such materials as sodium oxide and potassium hydroxide may be used.

[0039]

As described above, according to the present invention,
Aggregation of the pigment can be suppressed in the ink for an ink jet printer, and therefore, in the ink jet printer, problems such as non-ejection of the ink can be solved.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a configuration of an ink jet printer using the ink for an ink jet printer of the present invention.

[Explanation of symbols]

 Reference Signs List 1 printer 2 caster 3 stand 4 auxiliary frame 5 platen 5a hole 6 carriage shaft 7 carriage 8 carriage drive belt 9 inkjet head 10 discharge nozzle 11 tank holding unit 12 tank 12a ink tank 12b air tank 12c cleaning liquid tank 13 tube 14 cap device

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2C056 EA26 EB15 EB34 EC18 EC32 EC65 FA04 FA10 FC02 JA13 JC13 JC20 KA08 KB03 KB04 KB05 KB08 KB11 KB15 KB21 KB35 2H086 BA55 BA57 BA60 4J039 AD09 BC33 BC54 BC79 BE01 BE04 BE22 DA07 EA41 EA41

Claims (4)

[Claims] An ink jet printer using a dye ink containing an acid dye having a sulfone group or a salt thereof and an alkaline pigment ink using an acrylic acid copolymer as a dispersant as needed. An ink-jet printer using a dye ink and a pigment ink in which the difference between the pH of the dye ink and the pH of the pigment ink is within 1.5. 2. The dye ink and the pigment ink are prepared by adding an excess of an organic amine or an inorganic alkali to the dye ink so that the difference between the pH of the dye ink and the pH of the pigment ink is 1. 2. The ink jet printer according to claim 1, wherein the adjustment is made within five. 3. Two types of ink jets, which are used interchangeably for the same ink jet printer, a dye ink containing an acid dye having a sulfone group or a salt thereof and a pigment ink containing an acrylic acid copolymer as a dispersant. Ink for a printer, wherein the relationship between the dye ink and the pigment ink is adjusted so that the pH difference is within 1.5. 4. The dye ink and the pigment ink are prepared by adding an excessive amount of organic amines or inorganic alkalis to the dye ink so that the difference between the pH of the dye ink and the pH of the pigment ink is 1. 4. The ink for an ink jet printer according to claim 3, wherein the ink is adjusted within 5 or less.