JP2003213185A - Ink set for inkjet recording and inkjet recording method using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink set for inkjet recording which can decrease the uneveness of shade and can realize a high definition without needing a large- scale apparatus and without extending the time for printing in inkjet recording using a plurality of colored inks curable by energizing; and an inkjet recording method using the same. <P>SOLUTION: This ink set for inkjet recording comprises a plurality of colored inks curable by energizing, each ink containing an aqueous medium, a colorant, a water-soluble resin, a water-soluble monomer solidifiable by energizing, and a polymerization initiator. At least one of the colored inks has a curing reaction sensitivity different from those of the other colored inks. The inkjet recording method uses the ink set. <P>COPYRIGHT: (C)2003,JPO

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 set used for ink jet recording using a plurality of colors of ink, and an ink jet recording method.

[0002]

2. Description of the Related Art Ink for an ink jet recording apparatus for printing by ejecting liquid ink from a head nozzle, an aqueous ink in which a dye is dissolved as a coloring material in an aqueous solvent, and a dye in a wax solvent which solidifies at room temperature. Then
There is solid ink that is ejected from a head in a heated and melted state and printed.

As for the ultraviolet-curable ink for inkjet printing, there is one using a water-soluble dye as described in JP-A-5-186725, which is used for printing on plain paper or recycled paper. Is made easy.

Further, in JP-A-07-224241, at least a pigment, a water-soluble resin,
A water-soluble monomer that solidifies by application of energy, and an ink characterized by containing a photopolymerization initiator, an inkjet recording method characterized by applying this ink is proposed, regardless of the recording material, An ink capable of recording with weather resistance and good print quality, an ink jet recording method and a recording apparatus using the ink have been proposed.

[0005]

An ink-jet recording method in which ink-jet recording is carried out using an ultraviolet-curable ink for inkjet printing, and then cured and fixed by irradiation of ultraviolet rays, is performed depending on the time until the irradiation of ultraviolet rays after ink-jet recording. The shape of fixed dots, the degree of mixing of color dots, and the amount of dyes, pigments, and solvents permeated into the recording medium change when recording on a recording medium having ink absorbability.

This is, for example, an ink jet recording apparatus for bidirectional serial recording, in which four color inks of cyan, magenta, yellow and black are ejected from different recording heads to form an image on a recording medium. In the case of a recording apparatus in which ink is cured and fixed by ultraviolet irradiation, it is an important parameter that influences image quality.

For example, when rapid curing and fixing is performed by irradiating ultraviolet rays immediately after applying each color ink, a large amount of dye or pigment remains on the surface of the recording medium, so that the reflection density is high and a clear image without dot bleeding can be obtained. On the other hand, since the ink dye permeates into the recording medium or there is not enough time for the ink colors to mix with each other, the ink color applied on the surface of the recording medium or on the surface layer of the absorption layer inside the recording medium. The ink color layer is clearly formed in the order of, and there is an adverse effect that the tint unevenness of the color is clearly generated due to the bidirectional ink application order (difference in the arrangement order of the heads with respect to the main scanning movement direction). .

Further, for example, when a sufficient time is elapsed from the application of each color ink and then ultraviolet rays are irradiated to cure and fix the ink slowly, the formation of the ink color layer in the recording medium receiving layer becomes ambiguous depending on the application order of the ink colors. Although the difference in color tone in both directions is alleviated, conversely, the dye or pigment sinks deep inside the recording medium and a sufficient reflection density cannot be obtained. Defects such as deterioration occur.

On the other hand, depending on the content of the image to be recorded, whether the time for curing and fixing should be shortened or longer should be changed.

For example, when expressing characters such as text and fine lines, high density and high definition recording expression is required. Therefore, rapid curing and fixing by irradiation of ultraviolet rays immediately after ink application has a higher reflection density. , A clear image expression without dot bleeding is possible, high definition as high as characters is not required to express figures and tables, and there is no uniformity of solid areas or color unevenness rather than density. Since it is sometimes required, it may be more effective to irradiate ultraviolet rays and slowly cure and fix the ink after a sufficient time from the application of ink, because color unevenness in both directions can be reduced.

In such a case, in the black ink which is often used for expressing characters and fine lines, it is preferable to perform a rapid solidification fixing by irradiating ultraviolet rays immediately after coating each color ink. , Magenta, and yellow inks), it is preferable to irradiate ultraviolet rays and perform solidification and fixing after a proper time from the application of the respective color inks, because uneven color tone in both directions can be reduced. However, it is possible to change the time from application to ultraviolet irradiation with black ink and color ink. For example, an ultraviolet irradiation device is individually provided between the recording head applying black ink and the recording head applying color ink. In the case of arranging, the device configuration becomes large, or only one ultraviolet irradiation device is provided, and the black ink and color ink application processes are separately performed, and the ultraviolet irradiation is performed for each process. There is a problem that it takes time.

It is an object of the present invention to reduce unevenness in tint and high definition in ink jet recording using a plurality of color inks which are cured by application of energy, without increasing the apparatus structure and extending the time required for printing. To provide an inkjet recording ink set and an inkjet recording method capable of achieving high performance.

More specifically, even if energy is applied at the same timing under the same energy application conditions without changing the time from the application of ink to the application of energy such as UV irradiation, the curing varies depending on the ink color. The purpose is to increase the speed, and in ink jet recording that performs bidirectional serial recording using an ink that is cured by applying energy, it reduces uneven color tone in both directions and is expressed with black ink. The purpose is to clearly record the characters and fine lines that appear.

[0014]

The present invention provides an ink jet recording ink set having a plurality of colors of ink jet recording ink which are cured by application of energy.
Each ink contains a coloring material, a water-soluble monomer that solidifies upon application of energy, and a polymerization initiator, and among these inks, the curing reaction sensitivity of at least one color ink is
An ink set for inkjet recording, which is different from the curing reaction sensitivity of inks of other colors.

An ink jet recording ink set is
For example, it refers to a combination of a plurality of inkjet recording inks such as black ink, cyan ink, magenta ink, and yellow ink. In actual use,
The ink is contained in a container, but its form is not limited,
For example, each color ink may be contained in a separate container, or a multi-color ink cartridge having a structure in which these separate containers are integrated may be used.

In the above ink set, a black ink and a color ink are used as the ink for ink jet recording of the plurality of colors, and the curing reaction sensitivity of the black ink as the at least one color ink is as the ink of the other color. From the viewpoint of practical use, a form different from the curing reaction sensitivity of the color ink is preferable.

The ink used in the present invention is cured by application of energy due to the presence of the water-soluble monomer which is solidified by application of energy. The curing reaction sensitivity means the degree of curing of the ink under the same energy application conditions. The state where no curing reaction occurs is 0% cured state and the completely cured state is 100% cured state. At this time, the cured state of the at least one color ink is 100%.
It is preferable that the ink of the other color is in a cured state range of 10% to 50% under the energy application condition.

Alternatively, the amount of applied energy (J) necessary and sufficient for the ink of at least one color to be completely cured.
/ Cm ² ) is different from the amount of applied energy (J / cm ² ) necessary and sufficient for the inks of the other colors to completely cure, and the higher of these applied energy amounts is 100%.
It is also preferable that the lower one is in the range of 10% to 50%.

The amount of applied energy means the amount of energy applied to cure the ink when a certain amount of ink adheres to the recording material per unit area, and the unit is, for example, J / cm ² . Shown.

In the ink set of the present invention, it is preferable that the energy is ultraviolet rays, heat and / or electron rays.

In order to change the curing reaction sensitivity depending on the ink, there are the following forms of ink set.

In the first embodiment, in order to make the curing reaction sensitivities of the at least one color ink and the other color ink different, the at least one color ink and the other color ink contain the water-soluble monomer. It is an inkjet recording ink set having different contents.

In the second embodiment, in order to make the curing reaction sensitivity of the at least one color ink and the other color ink different, the polymerization initiator of the at least one color ink and the other color ink is used. It is an inkjet recording ink set having different contents.

In a third embodiment, the coloring material contains a dye and a pigment, and the at least one color ink and the other color ink have different curing reaction sensitivities in order to have different curing reaction sensitivities of the at least one color ink and the other color ink. This is an inkjet recording ink set in which the content ratio of the dye and the pigment is different depending on the color ink.

In the ink set of the present invention, it is preferable that each of the inks contains a monomer having a polyfunctional group as the water-soluble monomer.

It is also preferable that the pH of each ink is 5-10.

It is also preferable that each of the inks contains 50% by mass or more of water.

The viscosity of each ink is 1.0 × 1.
It is also preferable that it is 0 ⁻² Pa · s or less.

It is also preferable that the concentration of the water-soluble monomer in each of the inks is 1 to 40% by mass.

The present invention is also an ink jet recording method characterized by using the above ink set in an ink jet recording method in which ink droplets ejected by an ink jet method are adhered to a recording material to perform recording.

In the ink jet recording method of the present invention, it is preferable that the ink jet method is a method in which thermal energy is applied to the ink.

Further, it is preferable to have a step of applying ultraviolet rays, heat and / or electron beams to the ink attached to the recording material.

[0033]

BEST MODE FOR CARRYING OUT THE INVENTION [Monomer] In the present invention, examples of the monomer which is solidified by applying energy include UV-polymerizable monomers, 1) high solubility in water, 2) low viscosity, and 3) photopolymerization. 4) It is required to have properties such as excellent physical properties of the cured film, and radically polymerizable acrylic monomers can be preferably used.

Radical polymerizable acrylic monomers
Include N, N-dimethylaminoethyl methacrylate,
CH₂= C (CH₃) -COO-CH₂CH₂N (C
H₃)₂: N, N-dimethylaminoethyl acrylate,
CH₂= CH-COO-CH₂CH₂N (CH₃)₂: N,
N-dimethylaminopropyl methacrylate, CH₂=
C (CH₃) -COO-CH₂CH₂CH₂N (CH₃)₂:
N, N-dimethylaminopropyl acrylate, CH₂
= CH-COO-CH₂CH₂CH₂N (CH₃)₂: N,
N-dimethylaminoacrylamide, CH₂= CH-C
ON (CH₃)₂: N, N-dimethylaminomethacrylic
Amide, CH₂= C (CH₃) -CON (CH₃)₂: N,
N-dimethylaminoethylacrylamide, CH₂= C
H-CONHC₂H _FourN (CH₃)₂: N, N-Dimethyla
Minoethylmethacrylamide, CH₂= C (CH₃) −
CONHC₂H_FourN (CH₃)₂: N, N-dimethylamino
Propylacrylamide, CH₂= CH-CONH-C₃
H₆N (CH₃)₂: N, N-dimethylaminopropylme
Taacrylamide, CH₂= C (CH₃) -CONH-C
₃H₆N (CH₃)₂: And these quaternized substances,
And the like are particularly preferable because they have excellent dyeing properties for coloring materials. Multi-valued
Alcohol (meth) acrylate, polyhydric alcohol
Glycidyl ether (meth) acrylic acid ester
And polyethylene glycol (meth) acrylate
Tellurium, an ethylene oxide addition compound of polyhydric alcohol
(Meth) acrylic acid ester, polybasic acid anhydride and hydroxyl group
Containing (meth) acrylic acid ester, etc., it
Known UV-curable monomers and oligomers are used.
Be done. Among these substances, the compatibility with ink and hydrophilic
A high substance is appropriately selected and used.

The amount of the water-soluble monomer used is preferably in the range of 1 to 40% with respect to the total mass of the ink.

[Polymerization Initiator] As the polymerization initiator, a photopolymerization initiator can be used when the applied energy is light such as ultraviolet rays.

As the method of using the photopolymerization initiator, one kind of photoinitiator may be used, two or more kinds of photoinitiators may be used, and a photoinitiator and a sensitizer may be used. The main photoinitiator and sensitizer may be selected, combined and blended in proportion to the monomer used and the apparatus used.

The main photoinitiators and sensitizers include, for example, acetophenone, 2,2-diethoxyacetophenone, p-dimethylaminoacetophene, p-dimethylaminopropiophenone and benzophenone as photoinitiators. , 2-chlorobenzophenone, pp'-dichlorobenzophene, pp'-bisdiethylaminobenzophenone, Michler's ketone, benzyl, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin n-propyl ether, benzoin isobutyl ether, benzoin n. -Butyl ether, benzyl dimethyl ketal, tetramethyl thiuram monosulfide, thioxanthone,
2-chlorothioxanthone, 2-methylthioxanthone, azobisisobutyronitrile, benzoin peroxide, di-tert-butyl peroxide, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenyl -1-on, 1- (4-
Isopropylphenyl) -2-hydroxy-2-methylpropan-1-one, methylbenzoyl formate,
Is mentioned. The amount used is usually 0.1 to 1 with respect to the total amount of the water-soluble monomer that is solidified by energy application.
0 mass% is preferable.

In the cationic polymerization type, aromatic diazonium salt, aromatic halonium salt, aromatic sulfonium salt,
A photoinitiator such as a metallocene compound is used. Specific examples thereof include triphenylsulfone hexafluorophosphate and diphenyliodonium hexafluoroantimonate. Further, in the case of a cationic polymerization type, in order to make the curing more complete, 80 to 170
It is desirable to heat in the range of 100 ° C, particularly preferably in the range of 100 to 150 ° C. The heating time varies depending on the conditions, but is usually between 5 and 30 minutes.

As the sensitizer, for example, 1) amine-based: aliphatic amine, amine containing aromatic group,
Piperidine 2) Urea: Allyl-based, o-Tolylthiourea 3) Sulfur compound: Sodium diethyldithiophosphate, soluble salt of aromatic sulfinic acid 4) Nitrile-based compound: N, N-disubstituted p-aminobenzonitrile 5) Phosphorus compound: 6) Nitrogen compound: Michler's ketone, N nitrisohydroxylamine derivative, oxazolidine compound, tetrahydro-1,3-oxazine compound, formaldehyde or condensate of acetaldehyde and diamine 7) Chlorine compound: Carbon tetrachloride, hexachloroethane 8) Polymerized amine of reaction product of epoxy resin and amine, triethanolamine triacrylate.

[Coloring Material] The coloring material used in the present invention includes a water-soluble dye dissolved in an aqueous liquid medium and a pigment dispersion prepared by dispersing an inorganic pigment or an organic pigment in the aqueous liquid medium with a dispersant. Any of these is applicable, but when the printed matter is irradiated with ultraviolet rays after recording, it is preferable to use a dye or pigment stable to light.

In the present invention, the dye used is
Various known dyes can be used. Examples include azo dyes as direct dyes, phthalocyanine dyes, azo dyes as acid dyes, anthraquinone dyes, metal complexes of reactive dyes, and polyvalent metal salts.

When the pigment is used in the present invention, all the conventionally known organic and inorganic pigments can be used. For example, azo pigments such as azo lakes, insoluble azo pigments, condensed azo pigments and chelate azo pigments, and phthalocyanine pigments, perylene and perylene pigments, antothequinone pigments, quinacridone pigments, dioxazine pigments, thioisidigo pigments, isoindolinone pigments, polycyclic rings such as quinophthaloni pigments. Formula pigments, dye lakes such as basic dye type lakes and acid dye type lakes, organic pigments such as nitro pigments, nitroso pigments, aniline black, daylight fluorescent pigments, titanium oxide, iron oxides and carbon blacks Inorganic pigments can be used. Further, any pigment not listed in the color index may be used as long as it can be dispersed in water.

Further, it is preferable that the particle size distribution of the dispersion is such that the average particle size is in the range of 25 nm to 350 nm.

In the present invention, when the pigment and the dye are used in combination, the pigment: dye (mass ratio) is generally 8: 2.
It is preferably in the range of 2: 8. More preferably,
The range is from 7: 3 to 3: 7 (pigment: dye).

[Dispersant] A water-soluble resin (dispersion resin) can be contained in the ink as a dispersant in order to disperse the ink pigment. The water-soluble resin is soluble in an aqueous solution in which an amine or a base is dissolved and has a mass average molecular weight of 300.
The range of 0 to 30,000 is preferable. Further, it is preferably in the range of 5000 to 15000, for example, styrene-acrylic acid copolymer, styrene-acrylic acid-acrylic acid alkyl ester copolymer,
Styrene-maleic acid copolymer, styrene-maleic acid-acrylic acid alkyl ester copolymer, styrene-methacrylic acid copolymer, styrene-methacrylic acid-acrylic acid alkyl ester copolymer, styrene-maleic acid half ester copolymer Coalesce, vinylnaphthalene-acrylic acid copolymer, vinylnaphthalene-maleic acid copolymer,
A styrene-maleic anhydride-maleic acid half ester copolymer or salts thereof can be used.

[Ink pH] Furthermore, it is preferable that the ink used in the present invention is adjusted so that the entire ink is weakly acidic, neutral or alkaline, which improves the solubility of the water-soluble resin described above. It is desirable because the ink can have excellent long-term storage stability. PH of ink
May cause corrosion of various members used in the ink jet recording apparatus, so that it is preferably 5 to 10
It is desirable that the pH range is set to.

Examples of the pH adjusting agent include various organic amines such as diethanolamine and triethanolamine, inorganic alkali agents such as hydroxides of alkali metals such as sodium hydroxide, lithium hydroxide and potassium hydroxide, and organic acids. And mineral acids.

[Aqueous Liquid Medium] A suitable aqueous liquid medium in the ink used in the present invention is a mixed solvent of water and a water-soluble organic solvent, and water is ion-exchanged water rather than general water containing various ions. It is preferred to use (deionized water). The ink preferably used in the present invention is a water-based ink, and the content of water is preferably 50% by mass or more of the total mass of the ink.

Examples of the water-soluble organic solvent used as a mixture with water include, for example, methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, tert-butyl alcohol and iso. -Alkyl alcohols having 1 to 4 carbon atoms such as butyl alcohol; amides such as dimethylformamide and dimethylacetamide;
Keto alcohols such as acetone and diacetone alcohols; ethers such as tetrahydrofuran and dioxane;
Polyalkylene glycols such as polyethylene glycol and polypropylene glycol; ethylene glycol,
Propylene glycol, butylene glycol, triethylene glycol, 1,2,6-hexanetriol, thiodiglycol, hexylene glycol, diethylene glycol and other alkylene groups containing 2 to 6 carbon atoms; glycerin: ethylene glycol Lower alkyl ethers of polyhydric alcohols such as monomethyl (or ethyl) ether, diethylene glycol methyl (or ethyl) ether, triethylene glycol monomethyl (or ethyl) ether; N-methyl-2-pyrrolidone, 1,3-dimethyl-2 -Imidazolidinone and the like.

An organic amine can be used as the water-soluble organic solvent. The organic amine is added to the ink used in the present invention to neutralize the dispersant and adjust the pH of the ink in the neutral to basic range.
It is preferable that the content be contained by mass%.

The above-mentioned water-soluble organic solvent other than the organic amine is appropriately selected and contained in an appropriate amount as desired. Among them, polyhydric alcohols such as diethylene glycol, triethylene glycol monomethyl (or ethyl) ether, etc. Lower alkyl ethers of polyhydric alcohols are preferred.

Further, from the viewpoint of ejection stability, it is preferable to add 3% by mass or more of aliphatic monohydric alcohol such as ethanol or isopropyl alcohol to the ink. It is considered that the addition of these solvents makes it possible to more stably foam the ink thin film on the heating resistor.

[Other Components in Ink] In addition to the above components, the ink used in the present invention contains a surfactant and a defoaming agent in order to obtain an ink having desired physical properties, if necessary. , A preservative and the like can be further added.

[Inkjet Recording Method] In the inkjet recording method using the ink set of the present invention, a recording image is formed by applying two or more colors of ink to a recording material from a recording head having a plurality of ink ejection ports. An inkjet recording method for forming a recording image, which comprises ejecting an ink droplet from an ejection port of the recording head in accordance with an image recording signal to apply the ink droplet to a predetermined position of the recording material to form a recording image; Curing the ink applied on the recording material.

An ultraviolet (UV) irradiation lamp can be used as a means for curing the ink. Since the UV irradiation lamp may generate heat and deform the recording material, it is preferable that the UV irradiation lamp is provided with a cooling mechanism such as a cold mirror, a cold filter, and work cooling.

Next, one example of a recording apparatus that can be used in the above-mentioned ink jet recording method of the present invention will be described.
FIG. 1 is a simplified perspective view of an inkjet printer to which the present invention is applied. The drive of the stepping motor 6 controlled by the control unit 9 is propagated to the paper feed roller 3, and the recording paper 4 is fed in the sub operation direction (arrow C in the figure). Reference numeral 8 denotes a paper pressing roller, and the recording paper 4 is fed in the sub-operation direction (arrow C in the figure) while being supported by the paper feed roller 3 and the paper pressing roller 8 while maintaining its flatness. 13 is a head carriage,
By mounting the detachable head units 2a and 2b and driving the DC motor 12 controlled by the control unit 10,
It reciprocates in the main operation direction (arrows A and B in the figure) along a carriage roller 5 provided in parallel with a platen plate 7 provided to improve the flatness of the recording paper. The recording heads 11a and 11b are fixed to the head unit 2a at regular intervals in the moving direction of the head carriage 13 (arrow A), and ink tanks 1a and 1b filled with black and cyan inks can be attached and detached. Has become. On the other hand, recording heads 11c and 11d are fixed to the head unit 2b at fixed intervals in the moving direction of the head carriage 13 (arrow A), and ink tanks 1c and 1d filled with magenta and yellow inks are attached and detached. It is possible.

A simplified diagram of the recording head 11a is shown in FIG.
An electrothermal converter 26 and electrodes (not shown) for supplying electric power thereto are formed on the substrate 25. The nozzles 24 (ink passages) are provided in the same number corresponding to the electrothermal converters 26, and communicate with the ejection ports 27 and the common liquid chamber 23. Black ink is supplied to the recording head 11a from the above-mentioned ink tank 1a in the direction of arrow E in the figure, and is supplied to the common liquid chamber 23 while removing impurities such as dust by the filter 22. The black ink supplied to the common liquid chamber 23 is discharged from the nozzle 2 by the capillary phenomenon.
4 is supplied to the inside of the nozzle 4, and a meniscus is formed and held near the discharge port 27 at the tip of the nozzle. In this state, by energizing the electrothermal converter, the ink is heated on the electrothermal converter and fires, and the firing energy ejects an ink droplet in the direction of arrow D in the drawing.

Similarly, the recording heads 11b, 11c, and 11d are supplied with cyan, magenta, and yellow inks, respectively, and ink droplets can be ejected from the ejection ports of the nozzles by the energy of the firing of the ink.

Reference numeral 14 denotes an ultraviolet irradiation lamp, which is arranged at both ends of the head carriage 13.

In recording, first, while the recording paper 4 is stopped, while the head carriage 13 moves at a constant speed in the direction of arrow A, yellow ink is applied from the recording head 11d and magenta ink is applied from the recording head 11c. Then, the cyan ink is ejected from the recording head 11b and the black ink is ejected from the recording head 11a, and the color inks are applied onto the recording medium by overlapping ejection.

Subsequently, among the ultraviolet irradiation lamps 14 arranged at both ends of the head carriage 13, the ultraviolet irradiation lamps 14 arranged at the rear of the main scanning are irradiated to cure the ink applied on the recording medium. When the recording of one line is completed in this way, the recording paper 4 is stepped by a certain amount in the direction of arrow C, and this time the head carriage 13 moves in the opposite direction of arrow A (arrow B) at a constant speed. The black ink is ejected from the recording head 11a, the cyan ink is ejected from the recording head 11b, the magenta ink is ejected from the recording head 11c, and the yellow ink is ejected from the recording head 11d. Of the ultraviolet irradiation lamps 14 arranged at both ends of the head carriage 13, the ultraviolet irradiation lamps 14 arranged at the rear of the main scanning are irradiated to cure the ink applied on the recording medium. . By repeating these steps a plurality of times, it is possible to perform color recording on the full surface of the recording paper 4.

As a recording method, printing is carried out by a printing method in which image data recording for one line is completed by superposing a plurality of passes such as two passes and four passes.

[0064]

Example (Example 1) First, a solution A1 and a solution B1 having the following compositions (mass ratios) were prepared. Solution B1 was prepared in each of four colors of black, cyan, magenta, and yellow.

(Solution A1) UV-polymerizable monomer * 1 55.6% by mass photopolymerization initiator * 2 2.8% by mass water-soluble organic solvent * 3 41.6% by mass * 1 Shin-Nakamura Kagaku Co., Ltd., trade name: NK ester A-40
0.

* 2 Ciba Geigy, trade name: Irgacure 651.

* 3 Inpropyl alcohol (IPA)
/ Diethylene glycol (DEG).

(Solution B1) Dye ink 10% solution * 4 93.0% by mass Surfactant * 5 7.0% by mass * 4 Aqueous solution in which dyes of the following colors are dissolved in water (dye solid content 10% by mass) .

Black: Food Black Cyan: Project Cyan Magenta: Acid Red Yellow: Direct Yellow * 5 manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., trade name Neugen ET15
An aqueous solution of 0 dissolved in water at a ratio of 10% by mass.

Solution A1 and solution B1 were separately stirred for about 10 minutes, and each had a viscosity of 5 cp (0.005 Pa).
・ S) has been adjusted. Finally solution A1 and solution B1
An ink was prepared by mixing the above. The mixing ratio of the solution A1 and the solution B1 was 1:10 for the black ink and 1:10 for the color inks (cyan, magenta, yellow).

As a result, in the ink of Example 1, the mixing ratio of the UV-polymerizable monomer and the photopolymerization initiator in the ink was changed between the black ink and the color ink, and the UV-curing reaction sensitivity was changed. That is, in the black ink, since the mixing ratio of the UV polymerization monomer and the photopolymerization initiator is high, the reaction sensitivity due to the ultraviolet irradiation is high, and in the color ink, the mixing ratio of the UV polymerization monomer and the photopolymerization initiator is lower than that of the black ink. The reaction sensitivity due to external irradiation is low. Therefore, even if the black ink is completely cured by the UV irradiation immediately after the ink application, the color ink is not cured under the same UV irradiation condition, and the UV is irradiated multiple times by multiple passes. The condition is adjusted so that it will be completely cured only by being treated.

This is because if the color inks are cured by ultraviolet light immediately after the inks are applied, the ink dyes penetrate into the inside of the recording medium, and it is not possible to obtain a sufficient time for the ink colors to mix with each other. Or, because the ink color layers are clearly formed in the order of the ink colors applied on the surface of the absorption layer inside the recording medium, it depends on the bidirectional ink application order (the difference in the order in which the heads are arranged with respect to the main scanning movement direction). This is because the tint unevenness of the color is clearly seen, and the ink dye permeates into the inside of the recording medium to allow a sufficient time for the ink colors to mix with each other.

As described above, in the first embodiment, the curing reaction sensitivities of the black ink and the color ink under the same UV irradiation condition are made different, and the reaction sensitivity of the black ink is increased to cause the bleeding of dots and the inside of the recording medium. By curing the dye before it sinks, letters and fine lines are clearly expressed in high density, and with color inks, the reaction sensitivity is lowered to allow the dyes to penetrate into the recording medium and mix each color ink multiple times. By slowly curing it by irradiating ultraviolet rays, it is difficult to clearly form the ink color layer according to the ink application order inside the recording medium, and uneven color tint due to the bidirectional ink application order is reduced. There is.

Example 2 Inks having the compositions (mass ratios) shown in Table 1 were prepared in four colors of black, cyan, magenta and yellow.

[0075]

[Table 1]

* 1 Shin-Nakamura Chemical Co., Ltd., trade name: NK ester A-400 * 2 Aqueous solution in which dyes of the following colors are dissolved in water (solid content of dye: 10% by mass) Cyan: Project cyan Magenta: Acid red yellow: Direct Yellow Black: Food Black * 3 color pigment dispersed in an aqueous solution of a water-soluble resin (10% by weight of pigment in the aqueous solution) * 4 Ciba-Geigy product name: Irgacure 65
1.

First, the UV-curable monomer and the photopolymerization initiator were mixed in a mass ratio of 1: 0.05, and the mixture was stirred for about 10 minutes. Further, 1.5 times the mass of the monomer was added to isopropyl alcohol. Stir for 5 minutes to increase viscosity to 5c
It was adjusted to ps (0.005 Pa · s) (referred to as solution A2).

Next, dye ink (dye / water): pigment ink (pigment / water-soluble resin / water) = 10: 0, 8: 2, 5:
They are mixed so as to be 5, 2: 8 and 0:10 (solution B2).

Solution B2: Monomer = 10: 1, Solution A2 and Solution B2 were mixed and stirred for 30 minutes to obtain an ultraviolet curable ink.

The column of ultraviolet intensity in Table 1 is a value showing the amount of ultraviolet energy required for curing each ink, which requires a larger amount of energy for curing the ink as the proportion of the pigment increases. I understand.

In the second embodiment, using the results described above, the curing reaction sensitivity under the same ultraviolet irradiation conditions is made different by changing the mixing ratio of the dye and the pigment in the black ink and the color ink.

That is, with the black ink of this example, Composition 1 in Table 1 was used, and an ink was prepared using only the dye color material.

The irradiation intensity of the ultraviolet irradiation lamp is set so that the energy irradiation of 0.1 J / cm ² can be performed in one pass irradiation. Immediately after the application of ink for one pass, dot bleeding or recording medium By curing the dye before it sinks inside, letters and fine lines can be clearly expressed in high density.

On the other hand, the color ink used in this example uses the composition 2 in Table 1 and is mixed with 63.7% of the dye solvent and 15.9% of the pigment solvent to prepare an ink, thereby improving the ultraviolet response sensitivity. I am lowering. Since the irradiation intensity of the ultraviolet irradiation lamp of this embodiment is set so that the energy irradiation of 0.1 J / cm ² can be performed by one-pass irradiation as described above, the color ink of this embodiment has about 3 passes. It is completely cured only after a considerable amount of UV irradiation. The dye permeates inside the recording medium, and while each color ink mixes, it cures slowly with UV irradiation equivalent to 3 passes, so it is difficult to form a clear ink color layer according to the ink application order inside the recording medium. The unevenness of color due to the order of ink application is reduced.

[0085]

INDUSTRIAL APPLICABILITY According to the present invention, in ink jet recording using a plurality of color inks which are cured by application of energy, the tint unevenness is reduced and the high definition is achieved without increasing the apparatus structure and extending the time required for printing. An ink set for inkjet recording and an inkjet recording method that can realize the property are provided.

[Brief description of drawings]

FIG. 1 is a simplified perspective view showing an example of an ink jet recording apparatus using an ink set.

FIG. 2 is a simplified diagram showing an example of an inkjet recording head.

[Explanation of symbols]

1a-f ink tank 2a, 2b head unit 3 roller 4 recording paper 5 Carriage roller 6 stepping motor 7 Platen board 8 Paper holding roller 9 Sub-scanning motor controller 10 Main scanning motor controller 11a-f recording head 12 DC motor 13 head carriage 14 UV irradiation lamp A, B main operation direction C Sub operation direction 22 filters 23 Common liquid chamber 24 nozzles 25 substrates 26 Electrothermal converter 27 outlet D Ink drop ejection direction E Ink flow direction

Continued front page    F-term (reference) 2C056 EA13 EC14 FA03 FA11 FC02                       HA44                 2H086 BA05 BA59 BA60 BA61 BA62                 4J039 AD10 AD12 AD21 BC20 BE01                       BE02 BE12 BE26 CA03 EA03                       EA04 EA06 EA08 GA24

Claims (16)

[Claims] 1. An ink jet recording ink set having a plurality of colors of ink for ink jet recording that is cured by application of energy, each ink comprising a coloring material, a water-soluble monomer that solidifies by application of energy, and a polymerization initiator. An ink set for ink-jet recording, comprising at least one color ink of the inks having a curing reaction sensitivity different from that of other color inks. 2. A black ink and a color ink as the inks for inkjet recording of the plurality of colors, wherein the curing reaction sensitivity of the black ink as the at least one color ink is the same as that of the color ink as the other color ink. The ink set for inkjet recording according to claim 1, which has a different curing reaction sensitivity. 3. A state where the ink is not cured is 0% cured, and a state where the ink is completely cured is 100%.
The ink of another color is in a range of 10% to 50% in a cured state under an energy application condition in which the cured state of the at least one color ink is 100% when the cured state is set. Inkjet recording ink set. 4. An amount of applied energy (J / c) necessary and sufficient for the ink of at least one color to be completely cured.
m ² ) and the amount of applied energy (J / cm ² ) necessary and sufficient for the inks of the other colors to completely cure are different,
The ink set for ink jet recording according to claim 1 or 2, wherein the higher one of these applied energy amounts is in the range of 10% to 50% when the higher one is 100%. 5. The energy is ultraviolet light, heat and / or
Alternatively, the inkjet recording ink set according to any one of claims 1 to 4, which is an electron beam. 6. The content of the water-soluble monomer is different between the at least one color ink and the other color ink in order to make the curing reaction sensitivities of the at least one color ink and the other color ink different from each other. The ink set for inkjet recording according to claim 1. 7. The content of the polymerization initiator is different between the at least one color ink and the other color ink in order to make the curing reaction sensitivity of the at least one color ink and the other color ink different. The ink set for inkjet recording according to claim 1. 8. The coloring material contains a dye and a pigment, and the at least one color ink and the other color ink are different from each other in order to make the curing reaction sensitivity of the at least one color ink and the other color ink different from each other. 6. The ink set for inkjet recording according to claim 1, wherein the content ratio of the dye and the pigment is different. 9. The ink according to claim 1, wherein the water-soluble monomer includes a monomer having a polyfunctional group.
9. The ink set for inkjet recording according to any one of items 8 to 8. 10. The pH of each ink is 5 to 1
The ink set for inkjet recording according to claim 1, wherein the ink set is 0. 11. Each of the inks comprises 50% by mass.
The ink set for inkjet recording according to any one of claims 1 to 9, which contains the above water. 12. The viscosity of each ink is 1.0.
The inkjet recording ink set according to any one of claims 1 to 9, which has a pressure of × 10 ^-2 Pa · s or less. 13. The concentration of the water-soluble monomer in each of the inks is 1 to 40% by mass.
The ink set for inkjet recording according to any one of 1. 14. An ink jet recording method for recording by recording ink droplets ejected by an ink jet method on a recording material, wherein the ink set according to any one of claims 1 to 13 is used. Inkjet recording method. 15. The ink jet recording method according to claim 14, wherein the ink jet method is a method in which thermal energy is applied to the ink. 16. The ink jet recording method according to claim 14, further comprising the step of applying ultraviolet rays, heat and / or an electron beam to the ink attached to the recording material.