JP2001150794A - Ink for ink jet printer and printing mechanism of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide ink for ink jet printer, which is capable of printing on an ordinary paper as well as a recycled paper and which will not generate clogging, and a printing mechanism for the ink. SOLUTION: 1. An aqueous ink contains an ultraviolet ray curing type resin prepolymer, a reaction initiator and a dye. 2. The ink is constituted of an ultraviolet ray curing type resin prepolymer, a non-aqueous dye and a reaction initiator. 3. The prepolymer and the reaction initiator are injected out of different nozzles to use them 4. The prepolymer is provided with a dye adsorbing site. 5. The aqueous ink is cured by the amount of UV less than 100 mj/cm2. 6. The aqueous ink contains a fluorine base compound.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink for an ink jet printer and a printing mechanism thereof.

[0002]

2. Description of the Related Art Ink jet printers for printing by ejecting liquid ink from head nozzles are considered to be the mainstream of color printers in the future since they are composed of compact and relatively inexpensive components.

At present, inks for ink jet printers are aqueous inks in which a dye is dissolved as a colorant in an aqueous solvent, and dyes are dissolved in a wax solvent which solidifies at room temperature.
There is a solid ink which is ejected from a head and printed when heated and melted.

[0004] In addition, in ordinary water-based inks, glycerin or the like having a water-retaining function is used because the ink staying in the head nozzles is clogged by drying.

On the other hand, the ultraviolet curable ink for an ink jet printer is described in Japanese Patent Application Laid-Open No. 63-235382, but has little specific content.

[0006]

The prior art has the following problems.

[0007] 1. When the water-based ink is used for color printing, for example, when printing the first color and drying the first color, and then printing the second color, when the second color dot overlaps the first color dot, the second color is printed. There is a problem that the dye as the color material of the first color dot is redissolved and bleeds due to the water content of the color color ink, thereby deteriorating the print quality. For this reason,
It has been difficult to perform color printing on plain paper or recycled paper by the inkjet method. On the other hand, the wax-based solid ink can avoid the above-described problem of bleeding, but has a thick print dot due to the nature of the ink, and has a thickness of 10 to 20%.
Since the material is of the order of microns and is made of a soft material such as wax, print dots are easily scraped off even with a weak frictional force. That is, there is a problem in reliability after printing due to low abrasion resistance. In general, an ink containing an organic solvent is not preferable because it emits a solvent odor.

[0008] 2. Conventionally, ink for inkjet has been
If the residence time in the head nozzle portion is long, nozzles are clogged due to deposition of the coloring material due to drying, which has been a problem. As a countermeasure for this, various additives have been considered, but since these are originally required to have an action of preventing drying, they have deteriorated the ink quick-drying property after printing.

3. In an ink containing a photocurable resin,
In order to increase the sensitivity of photocuring and improve the curability significantly, it is generally possible to respond by increasing the amount of the reaction initiator or the reaction accelerator, but on the other hand, the dark reaction during storage tends to proceed, so the storage stability Had a problem.

[0010] 4. Further, in the ink containing a photocurable resin, when the resin is cured, the resin and the dye as a coloring material are separated from each other, and the effect of preventing the bleeding described in 1 above may be reduced.

5. In an ink containing a photocurable resin,
In general, when exposure to light exceeding 100 mJ / cm ² is performed during curing by irradiation with ultraviolet light, the color of the dye having an azo group proceeds. Therefore, when a dye having an azo group is used, 10
It has been found that it is necessary to cure at least the outermost surface only at an exposure dose of 0 mJ / cm2 or less.

6. Conventionally, in general inks for water-based inkjet printers, especially in the case of inks using organic pigments as coloring materials, once the ink dries in the head nozzle, the pigment particles aggregate and re-disperse even when water is supplied. Was difficult.

An object of the present invention is to solve the above problems, and an object of the present invention is to provide an ink for an ink jet printer having the following contents and an ink jet recording apparatus therefor.

1. In color printing, an ink is provided which has an effect of preventing the dye from bleeding even if water (ink by printing the second and subsequent colors) adheres again after printing, while being an aqueous ink containing a dye as a coloring material.

2. By using a prepolymer of an ultraviolet curable resin instead of conventional water as a base solution of the ink, an ink that is difficult to dry in a head nozzle even without adding a drying inhibitor is provided.

3. Ink-jet recording for forming print dots by separately storing the resin component and the reaction initiator to improve the storage stability of the ink when using ink containing a photo-curable resin, and ejecting it from separate head nozzles Provide equipment.

4. In an ink containing a photocurable resin,
Provided is an ink using a resin to which dye molecules are easily adsorbed so that a dye component and a resin component are not separated when the resin component is cured.

5. In an ink containing a photocurable resin,
Provided is an ink in which a dye as a coloring material does not fade when irradiated with ultraviolet light.

6. Provided is an ink that can prevent aggregation of a pigment due to drying in a head nozzle, particularly when an organic pigment is used as a coloring material in a general ink for an aqueous inkjet printer.

[0020]

The ink for an ink jet printer according to the present invention is an ink for an ink jet printer having a property of being cured by irradiation of ultraviolet rays, and comprises water and two or more functional groups in a monomer structure. It comprises at least a water-soluble photocurable resin prepolymer, a water-soluble or water-insoluble photopolymerization initiator, and a water-soluble dye.

An ink-jet ink according to another aspect of the present invention is an ink-jet printer ink having a property of being cured by irradiation with ultraviolet rays, and comprises a photocurable resin prepolymer or monomer or a mixture thereof. And a base solution substantially free of water, wherein the base solution contains at least a water-insoluble dye and a photopolymerization initiator, and the ink has a viscosity of 3%.
It is less than 0 cps.

In the ink for an ink jet printer according to the present invention, the photocurable resin preferably has a water-soluble dye adsorption site. As the dye, an azo dye can be used. According to a preferred embodiment of the present invention, the ink has an ultraviolet irradiation dose of 100 mJ / cm ^2.
The surface is hardened at least below.

According to another aspect of the present invention, there is provided an aqueous ink for an ink jet printer comprising a fluorine compound in a colloidal state.

Further, according to another aspect of the present invention, there is provided an ultraviolet irradiation-curable ink jet recording method, which comprises jetting a solution 1 and a solution 2 on a printing paper to form print dots. The solution 1 comprises a dye and either a photocurable resin or a photopolymerization initiator, and the solution 2 comprises a photocurable resin or a photopolymerization initiator. When one of the solution 1 and the solution 2 contains a photocurable resin, the other contains a photopolymerization initiator.

According to the present invention, there is provided an ink jet recording apparatus for performing the above ink jet recording method. The apparatus comprises an ink jet recording means for jetting a solution 1 onto printing paper and an ink jet recording means for jetting a solution 2 onto printing paper. And means for irradiating ultraviolet rays.

[0026]

EXAMPLES Example 1 Inks having compositions (weight ratios) as shown in Table 1 were prepared. Two kinds of inks were prepared, one using cyan color and the other using aagenta color.

Table 1 Photocurable resin prepolymer * 1 20.0% Reaction initiator * 2 0.06% Dye * 3 1.5% Water 68.44% Glycerin (anti-drying agent) 10.0% * 1 Unidick SI-929 (water-soluble, manufactured by Dainippon Ink and Chemicals, Inc.) * 2 Darocure 1173 (manufactured by Merck) * 3 Cyan or magenta color First, the cyan ink prepared was used.

After printing on plain paper using an ink jet head using a piezoelectric material, ultraviolet light was irradiated from an optical fiber provided beside the head. Irradiation with ultraviolet light was about 5 seconds and about 100 mJ / cm ² .

At this point, the blue ink has hardened to such a degree that sufficient hardness can be felt when touched with a fingertip.

Subsequently, magenta printing was performed so as to partially overlap the cyan printing. Subsequently, ultraviolet rays were irradiated for about 5 seconds to confirm the curing of the magenta ink.

As a result of observing the overlapping portion of the two kinds of inks with an optical microscope, the dye of the first color cyan ink was
There was no trace of the occurrence of bleeding due to the re-dissolution due to the color-grain printing, confirming the effect of the present invention.

Example 2 An ink having a composition (weight ratio) as shown in Table 2 was prepared.

Table 2 Photocurable resin monomer * 1 93.5% Reaction initiator and accelerator * 2 5.0% Dye (blue) * 3 1.5% * 1 KAYARAD-TPGDA and KAYARAD-PEG400DA (Izu 1: 1 mixture of Nippon Kayaku Co., Ltd. * 2 3: 1 mixture of KAYARAD-DTEX and EPA (both from Nippon Kayaku Co., Ltd.) * 3 Oil-soluble dyes As described above, the present ink is based on a solution of a photocurable resin monomer and does not contain water at all. At this time, the viscosity becomes 30 cps (20 degrees Celsius) or less, and printing is possible even with a head using a piezoelectric element.
This ink was put in the head and left for 2 months. Two months later, printing was performed as it was, but no clogging of the nozzle occurred, and if a low-volatile monomer was used for the ink base, drying in the head was simple with a simple ink composition, unlike water. It was confirmed that it was possible to make it difficult to occur.

On the other hand, with regard to printing, it was also confirmed that the curability was good and bleeding hardly occurred as in Example 1.

(Example 3) An ink having a composition obtained by removing the reaction initiator from the ink composition shown in Table 1 was prepared. On the other hand, only the reaction initiator was dissolved in water only,
The concentration was adjusted to double the concentration. However, in this case, Darocure 2529 (manufactured by Merck) was used as a reaction initiator.

Next, these were jetted to the same point from separate ink jet head nozzles arranged in parallel and immediately irradiated with ultraviolet rays of about 60 mJ / cm 2.

According to this mechanism, the ink was allowed to react by increasing the amount of the reaction initiator, so that the ink was easily cured (ultraviolet irradiation time of about 3 seconds).

On the other hand, in this ink, since the reaction initiator is separated from the resin component, it is obvious that the curing of the resin component did not proceed at all during storage.

For comparison, an ink was prepared by mixing a reaction initiator twice as much as the composition shown in Table 1 with a resin, and stored at room temperature (in a dark place) for two months. As a result, a microgel of resin was generated due to a dark reaction. As a result, the effects of the present invention were confirmed.

Example 4 An ink composition (weight ratio) shown in Table 3 was prepared.

Table 3 Photocurable resin prepolymer * 1 41.0% Reaction initiator * 2 1.5% Dye (blue) * 3 1.5% Water 46.0% Glycerin (anti-drying agent) 10.0 % * 1 RW101A (manufactured by Sekisui Fine Chemical Co., Ltd.) * 2 RW101B (manufactured by Sekisui Fine Chemical Co., Ltd.) * 3 Blue5P (manufactured by Nippon Kayaku Co., Ltd.) It is a prepolymer in the structure. As a result of printing with the ink having the composition shown in Table 3, the compatibility between the dye and the resin at the time of curing was extremely good, no phase separation occurred, and the bleeding resistance was improved.

This result is not limited to the case where the above-mentioned resin is used, but is not particularly limited as long as it is a photocurable resin having a functional group to which a general water-soluble dye is easily adsorbed.

Example 5 An ink composition similar to that of Example 1 was used, but an azo dye having low light resistance was used as the dye. Curing of the resin was completed by exposure within 100 mJ / cm ² . There was no fading of the dye before and after UV irradiation.

Similarly, the ink composition was the same as in Example 2, except that an azo oil-soluble dye was used as the dye. The curing of the resin was completed by exposure to about 50 mJ / cm ² . Also in this case, there was no fading of the dye. That is, since the inks prepared in Examples 1 and 2 were cured with a low ultraviolet exposure amount of 100 mJ / cm ² or less, it was confirmed that the inks were photocurable inks that can also use azo dyes.

Example 6 An aqueous emulsion of a fluorinated surfactant (Fomblin EM, manufactured by Montecatini Co., Ltd.) was added to an aqueous ink jet printer ink in which a black pigment (carbon particles) was dispersed with a nonionic surfactant. Was added 3%. When this ink was left in the print head nozzle for two months and then printed as it was, no clogging of the nozzle was confirmed.
In addition, no particular effect was observed on the printing quality of the fluorine-based aqueous emulsion.

For comparison, the same test was carried out for the same ink to which no fluorine-based aqueous emulsion was added, and nozzle clogging occurred.

[0047]

As described above, the following effects were confirmed by the present invention.

In other words, with regard to the ink for a photocurable ink jet printer and its printing mechanism, plain paper and recycled paper can be used as a printing medium because the ink coloring material does not bleed. (Especially effective for color printing.) Clogging of ink can be prevented. Even in the case of the photocurable ink, the curable resin and the reaction initiator are separately stored, and are ejected from different nozzles and printed, so that the curability and storage stability of the ink are improved. Phase separation of dye / resin hardly occurs. No fading of the dye occurs.

In addition, by adding a fluorine-based compound, a general aqueous ink for an ink jet printer
In particular, in the case of an ink using an organic pigment, an effect of preventing clogging of a head nozzle was obtained.

Claims (8)

[Claims] 1. An ultraviolet irradiation-curable ink jet recording method for jetting a solution 1 and a solution 2 onto a printing paper and irradiating ultraviolet rays to form printing dots, thereby performing printing. 1 comprises a dye and either a photocurable resin or a photopolymerization initiator; solution 2 comprises either a photocurable resin or a photopolymerization initiator; and solution 1 An ink-jet recording method, wherein one of the solution and the solution 2 comprises a photocurable resin and the other comprises a photopolymerization initiator. 2. The photocurable resin is a water-soluble photocurable resin prepolymer having a monomer structure and containing two or more functional groups, wherein the photopolymerization initiator is water-soluble or water-insoluble.
The recording method according to claim 1, wherein the dye is a water-soluble dye. 3. The recording method according to claim 1, wherein the photocurable resin is a photocurable resin oligomer or monomer or a mixture thereof, and the dye is a water-insoluble dye. 4. The recording method according to claim 1, wherein the photocurable resin has a water-soluble dye adsorption site. 5. The method according to claim 1, wherein the ultraviolet irradiation is performed with an ultraviolet irradiation amount of 100 mJ.
The recording method according to any one of claims 1 to 4, wherein the recording method is performed so that the surface is hardened at least at / cm ² or less. 6. The method according to claim 1, wherein said dye is an azo dye.
6. The recording method according to any one of 5. 7. The recording method according to claim 1, wherein said solution 1 or 2 contains a fluorine compound in a colloidal state. 8. An ink jet recording apparatus for performing the recording method according to any one of claims 1 to 7, wherein the ink jet recording means jets a solution 1 onto printing paper, and jets a solution 2 onto printing paper. An ink-jet recording apparatus comprising: an ink-jet recording unit that performs irradiation; and a unit that irradiates ultraviolet rays.