JP2008183820A - Ink-jet recording method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink-jet recording method which suppresses reaction obstruction by oxygen at the time of polymerizing a light polymerizable substance. <P>SOLUTION: The ink-jet recording method is characterized in that after the ink shown in the following (1) is given to a recording medium, a reaction accelerator composition shown in the following (2) is given, and, then, irradiated with an active energy beam. (1) The ink contains photo-polymerizable substance having water-soluble double bond and a color material, photo-polymerization initiator. (2) The reaction accelerator composition containing water-soluble curing reaction accelerator. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a novel inkjet recording method. More specifically, the present invention relates to an ink jet recording method in which recording is performed by sequentially applying an ink and a curing reaction accelerator composition to a recording medium and then curing with an active energy ray.

  Active energy ray curing technology having excellent features such as solvent-free system, high energy efficiency, and quick-drying has attracted widespread attention due to the growing interest in environmental problems in recent years. In particular, UV curing technology has been developed through the development of small, high-power UV lamps and research and development of many UV-curable resins, including (meth) acrylates and vinyl ethers. Adhesives, paints, inks, printing, The market is expanding in a wide range of fields such as recording materials and electrical and electronic parts, but after applying an ultraviolet curable composition obtained by adding a polymerization initiator to this curable resin to a recording medium, ultraviolet rays are emitted in the air. When irradiated, the curing reaction of the surface layer may be inhibited by oxygen in the air, and unreacted resin may remain. Due to this so-called oxygen inhibition, there is a problem that it is difficult to obtain good results in physical properties related to surface hardness such as scratch resistance.

  In order to cope with this oxygen inhibition, additives such as amine compounds and phosphorus compounds disclosed in JP-A No. 64-79213 have been devised from the viewpoint of materials. While this additive has a relatively high effect, it has a problem that the addition amount is limited due to a decrease in water resistance and solvent resistance of the cured product and yellowing. In addition, developments have been made to improve water resistance and solvent resistance after curing by adding an unsaturated group to the amine compound, but its own curability is insufficient and the molecular weight is low. Therefore, it has not yet reached a sufficient stage, for example, it is difficult to achieve both inhibition of oxygen inhibition and physical properties of the coating film.

  In the past, as shown in JP-A-49-9, a polymerization reaction system that is insensitive to oxygen inhibition, such as a polyene-polythiol system, has been studied. When used, it is necessary to add it to the ink, and in the present situation that water-soluble thiols having a low viscosity are hardly developed, it is difficult to use.

  On the other hand, from the viewpoint of the process, a method of performing ultraviolet irradiation in an inert gas or vacuum is employed. This is performed, for example, by a method of exchanging nitrogen gas in the entire atmosphere, but it is necessary to provide equipment for uniformly supplying the inert gas into the atmosphere, and the required amount of the inert gas is increased. Therefore, there is a drawback that it takes considerable cost for installation and running.

  As another method, after a UV curable resin is applied, a film such as a polyester film is layered on the coating film, the air is shut off, and the film is peeled off after being cured with UV rays. Deterioration of the yield due to the cost of the film and the air from the edges, poor curing of the part where the air is caught when the films are stacked, and the problem of dust adhering due to the generation of static electricity when peeling the film is there.

On the other hand, in the case of an ink containing an ultraviolet curable resin, when the sensitivity of ultraviolet curing is to be increased and the curability is to be remarkably improved, generally, an increase in the amount of a polymerization initiator or a reaction accelerator can be dealt with. Viscosity is severely limited when used in, and the disadvantage that the necessary and sufficient amount of polymerization initiator and reaction accelerator cannot be added to the ink, and conversely the dark reaction is likely to proceed even though the necessary and sufficient amount can be added. Therefore, there is a drawback that a problem occurs in storage stability, which is a big problem similar to oxygen inhibition.
JP-A 64-79213 Japanese Patent Laid-Open No. 49-9

  Accordingly, an object of the present invention is to provide an ink jet recording method that suppresses reaction inhibition by oxygen during polymerization of a photopolymerizable substance. Another object of the present invention is to provide an ink jet recording method using an ink with suppressed dark reaction and improved storage stability. Another object of the present invention is to provide an ink jet recording apparatus for applying the ink or reaction accelerator composition and curing the active energy ray.

  The above object is achieved by the present invention described below. That is, the present invention provides an ink jet recording method in which an ink containing at least a photopolymerizable substance having a water-soluble double bond, a color material, and a photopolymerization initiator is ejected to the recording medium, and the ink is applied to the recording medium. Thereafter, an ink jet recording method comprising applying a reaction accelerator composition containing a curing reaction accelerator and then irradiating an active energy ray.

  Further, the present invention is an ink jet recording method in which an ink container and a reaction accelerator composition container are prepared separately, and the stability of the ink during storage is achieved.

  In addition, according to the present invention, there is provided an ink jet recording apparatus for performing the above ink jet recording method. This apparatus includes an ink container, ink jet recording means for ejecting the ink onto a recording medium, and a reaction accelerator composition. An object storage unit, an inkjet recording means for discharging the reaction accelerator composition onto a recording medium, and a means for irradiating active energy rays.

  As described above, according to the present invention, at least a photopolymerizable substance having a water-soluble double bond, a colorant, and an ink containing a photopolymerization initiator according to the present invention are applied to a recording medium and then cured. By applying a composition containing a reaction accelerator and then irradiating active energy rays, inhibition of reaction by oxygen during polymerization of the polymerizable substance can be suppressed, and an image having a highly cured surface can be obtained quickly. . At this time, both curing performance and coating film performance can be achieved by using a curing reaction accelerator that is not a conventional amine compound that also functions as a plasticizer for the cured resin. At this time, the difference in curing performance between the inks of the respective colors is improved. In addition, due to these facts, improvement in transportability or loadability is also expected.

  Furthermore, since the ink container and the reaction accelerator composition container are prepared separately, the present invention compares the progress of the dark reaction during storage of the ink with the case where the curing reaction accelerator is added directly. Can be suppressed.

  Next, the present invention will be described in detail with reference to preferred embodiments. In the following description, the active energy ray is radically polymerized by ultraviolet rays that are particularly preferably used, and the explanation proceeds with a typical example of an ultraviolet curable composition that cures. However, the active energy rays used for curing in the present invention are ultraviolet rays. It is not limited to.

  In order to solve the above-described problems of the prior art, the present inventors ejected an ink containing at least a photopolymerizable substance having a water-soluble double bond, a coloring material, and a photopolymerization initiator to a recording medium, and then After applying a transparent composition containing a curing reaction accelerator, it was found that the ink surface layer was cured satisfactorily by irradiating with ultraviolet rays, and the present invention was achieved.

  That is, in the present invention, a transparent or translucent reaction accelerator is formed after formation of an ultraviolet curable image by ink jet recording with an ink containing at least an aqueous photopolymerizable substance, an aqueous photopolymerization initiator, and an aqueous color material. By separately applying the composition (without being restricted by viscosity and dark reaction suppression when added to the ink), the situation where the ink surface layer is shielded from oxygen in the air is created to suppress oxygen inhibition. Moreover, since the curing reaction is literally promoted, the surface hardness is high, and a cured product having good scratch resistance and the like can be reached.

Next, the constituent materials of [1] ink and [2] reaction accelerator composition according to the present invention having the above-described excellent actions and effects, and [3] recording apparatus will be specifically described.
[1] Ink The ink according to the present invention contains at least water, a water-soluble polymerizable substance that undergoes radical polymerization by ultraviolet rays, a water-soluble photopolymerization initiator that generates radicals by the action of ultraviolet rays, and an aqueous colorant. To do.

<Water-soluble polymerizable substance that undergoes radical polymerization by ultraviolet rays>
First, a polymerizable substance that undergoes radical polymerization with ultraviolet rays used in the present invention will be described. Examples of such polymerizable substances include hydrophilic polyfunctional polymerizable compounds exemplified in the following (1) to (4). These compounds have high hydrophilicity, are water-soluble, have a polymerizability, have a high polymerization rate, and have a low viscosity per se. The viscosity is much lower than that of the existing compounds.

[Polyfunctional polymerizable substance that undergoes radical polymerization by ultraviolet rays]
As a general polyfunctional polymerizable substance that undergoes radical polymerization by ultraviolet rays, for (meth) acrylate, for example, polyester (meth) acrylate, polyurethane (meth) acrylate, epoxy (meth) acrylate, polyether (meth) acrylate, It is classified into oligo (meth) acrylate, alkyd (meth) acrylate, polyol (meth) acrylate and the like. Specifically, for example, 1,6-hexanediol di (meth) acrylate, triethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, tripropylene glycol di (meth) acrylate, neopentyl glycol di ( (Meth) acrylate, ethylene oxide modified bisphenol A di (meth) acrylate, propylene oxide modified bisphenol A di (meth) acrylate, trimethylolpropane tri (meth) acrylate, ethylene oxide modified trimethylolpropane tri (meth) acrylate, propylene oxide modified Trimethylolpropane tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, ditrimethylolpropane tetra (meth) acrylate , Dipentaerythritol hexa (meth) acrylate, urethane acrylate, ester acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol di (meth) acrylate, 3- (meth) acryloyloxyglycerin mono (meth) acrylate, dipentaerythritol tetra Examples include (meth) acrylate and dipentaerythritol penta (meth) acrylate, but are not necessarily limited thereto.

Among the above-mentioned photopolymerizable substances, water-soluble substances are preferably used in the present invention from the group of compounds having the following structures.
Polyethylene oxide / propylene oxide derivative (PA group for convenience)
Glycerin derivatives (PB group for convenience)
Trimethylolpropane derivative (PC group for convenience)
Pentaerythritol derivatives (PD group for convenience)
The derivatives are preferably the respective acrylates or methacrylates. These are specifically represented by the following general formula.
(1) Polyethylene oxide / propylene oxide derivatives: PA group

上記に示す一般式からなる重合性物質群において、具体的には例えば、下記式で表される重合性物質ＰＡ−１を用いることができる。

In the polymerizable substance group consisting of the general formula shown above, specifically, for example, a polymerizable substance PA-1 represented by the following formula can be used.

（２）グリセリン誘導体：ＰＢ群

(2) Glycerin derivatives: PB group

上記に示す一般式からなる重合性物質群において、具体的には例えば、下記式で表される重合性物質ＰＢ−１を用いることができる。

In the polymerizable substance group consisting of the general formula shown above, specifically, for example, a polymerizable substance PB-1 represented by the following formula can be used.

（３）トリメチロールプロパン誘導体：ＰＣ群

(3) Trimethylolpropane derivatives: PC group

上記に示す一般式からなる重合性物質群において、具体的には例えば、下記式で表される重合性物質ＰＣ−１を用いることができる。

In the polymerizable substance group consisting of the general formula shown above, specifically, for example, polymerizable substance PC-1 represented by the following formula can be used.

（４）ペンタエリスリトール誘導体：ＰＤ群

(4) Pentaerythritol derivatives: PD group

上記に示す一般式からなる重合性物質群において、具体的には例えば、下記式で表される重合性物質ＰＤ−１を用いることができる。

In the polymerizable substance group consisting of the general formula shown above, specifically, for example, polymerizable substance PD-1 represented by the following formula can be used.

［上記一般式（１）〜（４）中、ＸはＨ又はＣＨ₃である。ｉ１＋ｋ１は８乃至２４の整数、ｊ１は０乃至６の整数、ｉ２、ｊ２、及びｋ２は１以上の整数、ｌ２、ｍ２、及びｎ２は０又は１である。ｉ３、ｊ３、及びｋ３は１以上の整数、ｌ３、ｍ３、及びｎ３は０又は１である。Ｒ₁はカルボキシル基を持つ置換又は未置換のアルキル基である。ｉ４、ｊ４、ｋ４、及びｌ４は１以上の整数である。］
＜光の作用によってラジカルを生成する水溶性光重合開始剤＞
本発明にかかる光の作用によってラジカルを生成する水溶性光重合開始剤について説明する。一例は、例えば、吸収波長が４００ｎｍ前後以下までの光重合開始剤が挙げられる。この光重合開始剤は、例えば、長波長領域に官能性、即ち、紫外線を受けてラジカルを生成する感受性を持つ物質である後記一般式（１）〜（４）で表される光重合開始剤が挙げられる。

[In the general formula (1) ~ (4), X is H or CH _3. i1 + k1 is an integer of 8 to 24, j1 is an integer of 0 to 6, i2, j2, and k2 are integers of 1 or more, and l2, m2, and n2 are 0 or 1. i3, j3, and k3 are integers of 1 or more, and l3, m3, and n3 are 0 or 1. R ₁ is a substituted or unsubstituted alkyl group having a carboxyl group. i4, j4, k4, and l4 are integers of 1 or more. ]
<Water-soluble photopolymerization initiator that generates radicals by the action of light>
The water-soluble photopolymerization initiator that generates radicals by the action of light according to the present invention will be described. An example is a photopolymerization initiator having an absorption wavelength of about 400 nm or less. This photopolymerization initiator is, for example, a photopolymerization initiator represented by the following general formulas (1) to (4), which is a substance having a functionality in a long wavelength region, that is, a sensitivity to generate a radical upon receiving ultraviolet rays. Is mentioned.

  As the water-soluble photopolymerization initiator that generates radicals by the action of light, a hydrogen abstraction type or α-cleavage type photopolymerization initiator is generally used. Specifically, acetophenone, 2,2-diethoxyacetophenone, p-dimethylaminoacetophene, p-dimethylaminopropiophenone, benzophenone, 2-chlorobenzophenone, p, p'-dichlorobenzophene, p, p'- 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, tetramethylthiuram monosulfide, thioxanthone, 2 -Chlorothioxanthone, 2-methylthioxanthone, azobisisobutyronitrile, benzoin peroxide, di-tert-butyl Oxide, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-1-one, 1- (4-isopropylphenyl) -2-hydroxy-2-methylpropan-1-one, methylbenzoylpho Examples include, but are not necessarily limited to these.

Among the above photopolymerization initiators, a compound group having the following structure is preferably used in the present invention.
Thioxanthone derivatives (for convenience, TX group)
Acridone derivatives (for convenience, AC group)
Benzophenone derivatives (for convenience, BP group)
(4) α-Hydroxyphenyl ketone derivative (for convenience, IC group)
These are specifically represented by the following general formula.
(1) Thioxanthone derivatives: TX group

上記に示す一般式からなる重合開始剤において、具体的には例えば、下記式で表される重合開始剤ＴＸ−１、ＴＸ−２を用いることができる。

In the polymerization initiator having the general formula shown above, specifically, for example, polymerization initiators TX-1 and TX-2 represented by the following formulas can be used.

（２）アクリドン誘導体：ＡＣ群

(2) Acridone derivatives: AC group

上記に示す一般式からなる重合開始剤において、具体的には例えば、下記式で表される重合開始剤ＡＣ−１を用いることができる。

In the polymerization initiator having the general formula shown above, specifically, for example, a polymerization initiator AC-1 represented by the following formula can be used.

（３）ベンゾフェノン誘導体（便宜上ＢＰ群とする）

(3) Benzophenone derivative (referred to as BP group for convenience)

上記に示す一般式からなる重合開始剤において、具体的には例えば、下記式で表される重合開始剤ＢＰ−１を用いることができる。

In the polymerization initiator having the general formula shown above, specifically, for example, a polymerization initiator BP-1 represented by the following formula can be used.

（４）α−ヒドロキシフェニルケトン誘導体：ＩＣ群

(4) α-hydroxyphenyl ketone derivatives: IC group

上記に示す一般式からなる重合開始剤において、具体的には例えば、下記式で表される重合開始剤ＩＣ−１を用いることができる。

In the polymerization initiator consisting of the general formula shown above, specifically, for example, a polymerization initiator IC-1 represented by the following formula can be used.

［上記一般式（１）中、Ｒ₁は、−（ＣＨ₂）_x− （ｘは０又は１）、−Ｏ−（ＣＨ₂）y− （ｙは１又は２）、又は置換若しくは未置換のフェニレン基である。又Ｒ₁がフェニレン基の場合には、ベンゼン環中の水素原子の少なくとも１つが、例えば、カルボキシル基若しくはその塩、スルホン酸若しくはその塩、炭素数１〜４の直鎖状若しくは分岐鎖状のアルキル基、ハロゲン原子（フッ素、塩素、臭素等）、炭素数１〜４のアルコキシル基、フェノキシ基等のアリールオキシ基等から選ばれる１つ又は２つ以上の基や原子で置換されていてもよい。Ｍは、水素原子若しくはアルカリ金属（例えば、Ｌｉ、Ｎａ、Ｋ等）を表わす。更に、Ｒ₂及びＲ₃は各々独立に、水素原子、又は置換若しくは未置換のアルキル基を表わす。ここでアルキル基の例は、例えば、炭素数１〜１０程度、特には、炭素数１〜３程度の直鎖状又は分岐鎖状のアルキル基が挙げられる。又、これらのアルキル基の置換基の例は、例えば、ハロゲン原子（フッ素原子、塩素原子、シュウ素原子等）、水酸基、アルコキシル基（炭素数１〜３程度）等が挙げられる。又、ｉ１は１乃至１０の整数である。これらの親水性原子団で置換されたチオキサントンは、水溶性、アニオン系水性顔料分散体との共溶性があり、有機顔料自身の吸収の影響が少ないので、顔料系組成物において感度の高い触媒として作用する。

[In the general formula (1), R ₁ represents — (CH ₂ ) _x — (x is 0 or 1), —O— (CH ₂ ) y — (y is 1 or 2), or substituted or unsubstituted. The phenylene group. When R ₁ is a phenylene group, at least one hydrogen atom in the benzene ring is, for example, a carboxyl group or a salt thereof, a sulfonic acid or a salt thereof, a linear or branched chain having 1 to 4 carbon atoms. Even if it is substituted with one or more groups or atoms selected from alkyl groups, halogen atoms (fluorine, chlorine, bromine, etc.), C1-C4 alkoxyl groups, aryloxy groups such as phenoxy groups, etc. Good. M represents a hydrogen atom or an alkali metal (for example, Li, Na, K, etc.). Furthermore, R ₂ and R ₃ each independently represents a hydrogen atom or a substituted or unsubstituted alkyl group. Examples of the alkyl group include, for example, a linear or branched alkyl group having about 1 to 10 carbon atoms, particularly about 1 to 3 carbon atoms. Examples of substituents for these alkyl groups include, for example, halogen atoms (fluorine atoms, chlorine atoms, oxalic atoms, etc.), hydroxyl groups, alkoxyl groups (about 1 to 3 carbon atoms), and the like. I1 is an integer of 1 to 10. Thioxanthone substituted with these hydrophilic atomic groups is water-soluble and co-soluble with an anionic aqueous pigment dispersion, and is less affected by the absorption of the organic pigment itself. Therefore, it is a highly sensitive catalyst in pigment-based compositions. Works.

In the general formulas (2) and (3), R ₄ and R ₅ are each independently, for example, a hydrogen atom, a carboxyl group or a salt thereof, a sulfonic acid or a salt thereof, a linear or branched chain having 1 to 4 carbon atoms. An alkyl group, a halogen atom (fluorine, chlorine, bromine, etc.), an alkoxyl group having 1 to 4 carbon atoms, an aryloxy group such as a phenoxy group, etc., i2 is an integer of 1 to 10, and i3 is 1 to 10 Is an integer.

In the general formula (4), i4 is an integer of 2 to 5, and j4 is an integer of 0 to 5. The compound represented by the general formula (4) is a water-soluble derivative of Irgacure (registered trademark) 2959 (trade name: manufactured by Ciba Specialty Chemicals) and is nonionic, but has a wavelength range that is sensitive to ultraviolet rays. In the shorter wavelength region than the photopolymerization initiator represented by the general formula (1) mentioned above. ]
<Aqueous pigment dispersion>
Examples of the pigment that can be used in the ink of the present invention include carbon black and organic pigments. The content (% by mass) of the pigment in the ink is preferably 0.1% by mass or more and 10.0% by mass or less based on the total mass of the ink.

Examples of the carbon black include furnace black, lamp black, acetylene black, channel black and the like, and those having the following characteristics are preferable. Primary particle size 15 nm to 40 nm, specific surface area by BET method 50 m ² / g to 300 m ² / g, DBP oil absorption 40 ml / 100 g 150 ml / 100 g, volatile content 0.5% to 10% The pH value is preferably 2 or more and 9 or less. In the present invention, the following carbon black can be used as a commercial product having the above-described characteristics. No. 2300, no. 900, MCF88, No. 33, no. 40, no. 45, no. 52, MA7, MA8, no. 2200B (manufactured by Mitsubishi Chemical). RAVEN (registered trademark) 1255 (made in Colombia). REGAL (registered trademark) 400R, 330R, 660R, MOGUL L (manufactured by Cabot). Color Black FW1, FW18, S170, S150, Printex (registered trademark) 35, U (manufactured by Degussa) and the like.

  Specifically, the following can be used as the organic pigment. Water-insoluble azo pigments such as toluidine red, toluidine maroon, Hansa yellow, benzidine yellow and pyrazolone red. Water-soluble azo pigments such as Ritolol Red, Helio Bordeaux, Pigment Scarlet, and Permanent Red 2B. Derivatives from vat dyes such as alizarin, indanthrone and thioindigo maroon. Phthalocyanine pigments such as phthalocyanine blue and phthalocyanine green. Quinacridone pigments such as quinacridone red and quinacridone magenta; and perylene pigments such as perylene red and perylene scarlet. Isoindolinone pigments such as isoindolinone yellow and isoindolinone orange. Imidazolone pigments such as benzimidazolone yellow, benzimidazolone orange, and benzimidazolone red. Pilanthrone pigments such as pyranthrone red and pyranthrone orange. Indigo pigment. Thioindigo pigment. Condensed azo pigment. Flavanthrone yellow, acylamide yellow, quinophthalone yellow, nickel azo yellow, copper azomethine yellow, perinone orange, anthrone orange, dianthraquinonyl red, dioxazine violet, etc.

  In addition, when the organic pigment is represented by a color index (CI) number, the following can be used.

  C. I. Pigment Yellow: 1, 2, 3, 12, 13, 14, 16, 17, 55, 73, 74, 75, 83, 93, 95, 97, 98, 109, 110, 114, 128, 138, 139, 150 151, 154, 155, 180, etc.

  C. I. Pigment Red: 5, 7, 12, 48 (Ca), 48 (Mn), 57: 1, 57 (Sr), 57: 2, 122, 123, 168, 184, 202, 238 and the like.

  C. I. Pigment Blue: 1, 2, 3, 16, 22, 60, 15: 2, 15: 3, etc.

  The average particle diameter of the pigment is preferably 25 nm or more and 200 nm or less. If the average particle diameter of the pigment is within the above-mentioned range, it depends on the use of the recorded material, but it is sufficiently smaller than the wavelength of visible light, so that a recorded material that can be said to be sufficiently transparent is obtained if there is little light scattering. Can do.

<Diluted solvent>
As the solvent for diluting the aqueous photopolymerizable substance and the aqueous photopolymerization initiator according to the present invention, water is mainly used, but other than this, an aqueous polymerization-reactive low-viscosity monomer can be used. The advantage of using these substances, rather than ordinary solvents, is that these substances do not remain as plasticizers in the solid after reaction cured with UV light, so that the effect on solid physical properties is reduced. is there. Reactive diluent solvent components selected for such purposes include, for example, acryloylmorpholine, N-vinyl-2-pyrrolidone, acrylamide, methylenebisacrylamide, monosaccharide monoacrylate, oligoethylene oxide monoacrylate, And a compound such as a monoacrylic acid ester of a dibasic acid.

<Additives>
In addition to the above, any additive may be used for the ink. For example, a pH adjuster, a leveling agent, a viscosity adjuster, an antioxidant, a hindered amine light stabilizer (HALS), an antiseptic, an antifungal agent and the like can be mentioned. The content (% by mass) of these additives is usually preferably 0.1% by mass or more and 5% by mass or less based on the total mass of the ink.

<Material composition in ink>
In the ink according to the present invention, it is preferable to adjust the concentration of the photopolymerization initiator and the photopolymerizable substance in the ink in accordance with the absorption characteristics of the contained colorant. As described above, the blending amount is such that the amount of water is in the range of 40 to 90%, preferably 60 to 75%, based on mass. Furthermore, the content of the photopolymerizable substance in the ink is in the range of 1% to 30%, preferably in the range of 5 to 20%, based on the mass, with respect to the total amount of the ink. The photopolymerization initiator depends on the content of the photopolymerizable substance, but is generally in the range of 0.1 to 7%, preferably 0.3 to 5% on the mass basis with respect to the total amount of the ink.

  When a pigment is used as the ink coloring material, the concentration of the pure pigment in the ink is generally in the range of 0.3 to 10% by mass with respect to the total amount of the ink. The coloring power of the pigment depends on the dispersion state of the pigment particles, but if it is in the range of about 0.3 to 1%, it becomes a range used as a light-colored ink. On the other hand, if it is more than that, it gives a density used for general color coloring. The concentration of the pigment dispersion also depends on the viscosity and flow characteristics required by the recording apparatus. In the case of an on-demand inkjet apparatus, there is no nonlinearity in a wide range of viscosity, and the upper limit is 15 mPa · s. In the case where the ink dots are fine high density and high drive frequency nozzles, the upper limit is 10 mPa · s.

[2] Reaction accelerator composition The reaction accelerator composition according to the present invention contains at least one curing reaction accelerator having a proton donating group based on a nitrogen atom or a sulfur atom.

<Proton donating curing reaction accelerator>
The proton-donating curing reaction accelerator according to the present invention will be described. An example is a proton-donating curing reaction accelerator based on, for example, a nitrogen atom or a sulfur atom. Examples of the proton-donating curing reaction accelerator include curing reaction accelerators (1) to (4) represented by the following general formula, which is a substance having hydrogen that can be donated to the photopolymerization initiator radical. In the present invention, it is preferable to select and use at least one of these appropriately.
(1) A compound having a proton-donating group based on an N atom and water-soluble (for convenience, N group)
(2) A compound that has two or more polymerizable unsaturated bonds in one molecule and a proton-donating group based on an N atom, and is water-soluble. (For convenience, the AN group is used.)
(3) A compound having both a polymerizable unsaturated bond and a proton donating group based on an S atom in one molecule, and being water-soluble. (As group for convenience, AS group)
(4) A compound having a proton-donating group based on two or more S atoms in one molecule and water-soluble. These are represented by the following general formula (referred to as S group for convenience).

  Compounds having proton-donating groups based on N atoms and water-soluble: Group N

上記に示す一般式からなる硬化反応促進剤において、具体的には例えば、下記式で表される硬化反応促進剤Ｎ−１を用いることができる。

In the curing reaction accelerator having the general formula shown above, specifically, for example, a curing reaction accelerator N-1 represented by the following formula can be used.

［上記一般式（１）中、Ｒ₁、Ｒ₂、Ｒ₃は親水基を有する原子団であり、典型的にはエチレンオキシド鎖を含む原子団である。］
（２）１分子中に重合性不飽和結合を２個以上とＮ原子に基づくプロトン供与性基を併せ持ち、且つ水溶性である化合物：ＡＮ群

[In the general formula (1), R ₁ , R ₂ , and R ₃ are atomic groups having a hydrophilic group, and are typically atomic groups including an ethylene oxide chain. ]
(2) Compounds having two or more polymerizable unsaturated bonds in one molecule and a proton-donating group based on an N atom and water-soluble: AN group

上記に示す一般式からなる硬化反応促進剤において、具体的には例えば、下記式で表される硬化反応促進剤ＡＮ−１、ＡＮ−２を用いることができる。

In the curing reaction accelerator having the general formula shown above, specifically, for example, curing reaction accelerators AN-1 and AN-2 represented by the following formulas can be used.

［上記一般式（２）中、Ｒ₁、Ｒ₂、Ｒ₃、Ｒ₄、Ｒ₅は繰り返し単位が２〜６であるエチレンオキシド鎖又は炭素原子の数が２〜６の水酸基で置換されている脂肪族アルキルである。］
（３）１分子中に重合性不飽和結合とＳ原子に基づくプロトン供与性基を併せ持ち、且つ水溶性である化合物：ＡＳ群

[In the general formula (2), R ₁ , R ₂ , R ₃ , R ₄ and R ₅ are substituted with an ethylene oxide chain having 2 to 6 repeating units or a hydroxyl group having 2 to 6 carbon atoms. Aliphatic alkyl. ]
(3) A compound having both a polymerizable unsaturated bond and a proton donating group based on an S atom in one molecule and water-soluble: AS group

上記に示す一般式からなる硬化反応促進剤において、具体的には例えば、下記式で表される硬化反応促進剤ＡＳ−１を用いることができる。

In the curing reaction accelerator having the general formula shown above, specifically, for example, a curing reaction accelerator AS-1 represented by the following formula can be used.

［上記一般式（３）中、Ｒ₁は親水基を有する原子団であり、典型的にはエチレンオキシド鎖を含む原子団である。］
（４）１分子中に２つ以上のＳ原子に基づくプロトン供与性基を持ち、且つ水溶性である化合物：Ｓ群

[In the general formula (3), R ₁ is an atomic group having a hydrophilic group, and is typically an atomic group including an ethylene oxide chain. ]
(4) Compound having a proton-donating group based on two or more S atoms in one molecule and water-soluble: S group

上記に示す一般式からなる硬化反応促進剤において、具体的には例えば、下記式で表される硬化反応促進剤Ｓ−１を用いることができる。

In the curing reaction accelerator having the general formula shown above, specifically, for example, a curing reaction accelerator S-1 represented by the following formula can be used.

［上記一般式（４）中、Ｒ₁は親水基を有する原子団であり、典型的にはエチレンオキシド鎖を含む原子団である。］
＜硬化反応促進剤組成物における材料構成＞
本発明にかかる硬化反応促進剤組成物は、インクジェット方式で記録媒体に付与することを鑑みて、配合量は、硬化反応促進剤水溶液の粘度が１５ｍＰａ・ｓ以下であり、可能な限り水分量が少なくなるように調整することが好ましい。

[In the above general formula (4), R ₁ is an atomic group having a hydrophilic group, typically an atomic group containing an ethylene oxide chain. ]
<Material structure in curing reaction accelerator composition>
In view of the fact that the curing reaction accelerator composition according to the present invention is applied to a recording medium by an inkjet method, the blending amount is such that the viscosity of the aqueous solution of the curing reaction accelerator is 15 mPa · s or less, and the water content is as much as possible. It is preferable to adjust so that it may decrease.

[3] Recording Device Next, a recording device for applying the above-described ink and reaction accelerator composition to a recording medium and curing with ultraviolet rays will be described.

<Inkjet recording apparatus>
A recording apparatus suitable for recording using the ink and the reaction accelerator composition according to the present invention described above provides, for example, thermal energy corresponding to a recording signal to the ink in the chamber of the recording head. A recording apparatus that ejects ink may be used.

  Specifically, it has a configuration as shown in the schematic diagram of the front side of the recording apparatus in FIG. For example, an ink cartridge unit 1 that contains the ink of the present invention, a head unit 2 that performs recording, a lamp unit 3 that performs ultraviolet irradiation for curing, a driving unit 4 that drives the head unit and the lamp unit, and a recording medium to be recorded Is a recording apparatus provided with a paper discharge unit 5 that conveys. The head unit 2 uses a multi-head in which a large number of heads are arranged. In addition to these, a wiping unit (not shown), a capping unit, a paper feeding unit, and a drive motor unit are also provided.

  In FIG. 1, a nozzle unit for ejecting ink is arranged symmetrically for each color in a head unit 2, and the head unit 2 and the lamp unit 3 are integrally scanned left and right to apply ink to a recording medium. Thereafter, UV irradiation is performed immediately (details of the lamp will be described later).

  In this case, the ink cartridge unit 1 is provided with four colors of black (Bk), cyan (C), magenta (M), and yellow (Y). In order to record a higher-definition image, light cyan ( LC and light magenta (LM) may be added. A tank for storing the ink of the present invention is capable of blocking light.

  In the present invention, in addition to the recording system described above, a lamp is disposed on the front surface of the paper discharge unit, a paper feed / discharge is performed by wrapping around a rotating drum, and a drying unit is provided separately. Can be selected as appropriate.

<Light irradiation lamp>
Hereinafter, an ultraviolet irradiation lamp used for curing a water-soluble ultraviolet curable polymerizable material particularly suitable in the present invention will be described. However, the active energy ray irradiation section used in the present invention is not limited to the ultraviolet lamp. The ultraviolet irradiation lamp is preferably a so-called low-pressure mercury lamp, high-pressure mercury lamp, mercury lamp coated with a phosphor, or the like whose mercury vapor pressure is 1 Pa to 10 Pa during lighting. The emission spectrum of these mercury lamps in the ultraviolet region is in the range of 184 nm to 450 nm, which is suitable for efficiently reacting the water-soluble photopolymerizable substance in the black or colored ink. In addition, a small power supply can be used for mounting the power supply in the recording apparatus, which is also suitable in that sense. As the mercury lamp, for example, a metal halide lamp, a high-pressure mercury lamp, an ultrahigh-pressure mercury lamp, a xenon flash lamp, a deep ultraviolet lamp, a lamp that uses a microwave to excite a mercury lamp from the outside without using an electrode, an ultraviolet laser, and the like are in practical use. Since the emission wavelength region of these lamps includes the above range, it is basically applicable if the power source size, input intensity, lamp shape, etc. are allowed. The light source is selected according to the sensitivity of the water-soluble photopolymerization initiator used.

Irradiation intensity of ultraviolet light that may be used to cure the ink is preferably 500 mW / cm ² or more 5,000 MW / cm ² or less in wavelength region effective to cure. If the irradiation intensity is insufficient, the ink adhesion to the recording medium may not be sufficiently obtained. In addition, fastness such as water resistance may not be sufficiently obtained.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. The present invention is not limited by the following examples unless it exceeds the gist. In the text, “part” or “%” is based on mass unless otherwise specified.

Ink Ink01 and reaction accelerator composition Pro01 used in Example 1 were prepared in the following manner. For Ink01, each constituent material was mixed and stirred, and then filtered through a 0.5 μm membrane filter.
[Ink01]
Photopolymerizable material PA-1 15 parts Photopolymerizable initiator TX-1 2 parts Pigment dispersion (four colors Bk, C, M and Y below) 6.5 parts Monomer diluent Acryloylmorpholine 5 parts pH adjuster 0.5 part ion-exchanged water balance [Pro01]
Curing reaction accelerator N-1 50 parts Ion exchange water Remainder Pigments Bk, C, M, and Y used in Example 1 are as follows.
Pigment Bk: Carbon black pigment (C.I Pigment Black 7 / Columbia Carbon)
Pigment C: Copper phthalocyanine pigment (C.I Pigment Blue 15: 3 / manufactured by Clariant)
Pigment M: Gimethyl quinacridone pigment (CI Pigment Red 122 / Clariant)
Pigment Y: benzimidazolone pigment (C.I Pigment Yellow 180 / manufactured by Clariant)
Using these pigments, the following composition was dispersed in a sand mill (not shown) for 5 hours, and then filtered through a 0.5 μm membrane filter to obtain a pigment dispersion liquid.

Pigment (Bk, C, M, Y) 30 parts Water-soluble polymer: Styrene-acrylic copolymer (molecular weight 10,000, acid value 200) 10 parts Ion-exchanged water balance

Ink Ink02 and reaction accelerator composition Pro02 used in Example 2 were prepared in the same manner as in Example 1 except that the photopolymerizable substance, the photopolymerization initiator, and the curing reaction accelerator were as follows.
[Ink02] Photopolymerizable substance PB-1, photopolymerizable initiator TX-1
[Pro02] Curing reaction accelerator N-1

Ink Ink03 and reaction accelerator composition Pro03 used in Example 3 were prepared in the same manner as in Example 1 except that the photopolymerizable substance, the photopolymerization initiator, and the curing reaction accelerator were as follows.
[Ink03] Photopolymerizable substance PB-1, photopolymerizable initiator AC-1
[Pro03] Curing reaction accelerator N-1

Ink Ink04 and reaction accelerator composition Pro04 used in Example 4 were prepared in the same manner as in Example 1 except that the photopolymerizable substance, the photopolymerization initiator, and the curing reaction accelerator were as follows.
[Ink04] Photopolymerizable substance PB-1, Photopolymerizable initiator BP-1
[Pro04] Curing reaction accelerator N-1

Ink Ink05 and reaction accelerator composition Pro05 used in Example 5 were prepared in the same manner as in Example 1 except that the photopolymerizable substance, the photopolymerization initiator, and the curing reaction accelerator were as follows.
[Ink05] Photopolymerizable substance PB-1, photopolymerizable initiator IC-1
[Pro05] Curing reaction accelerator N-1

Ink 06 and reaction accelerator composition Pro06 used in Example 6 were prepared in the same manner as in Example 1 except that the photopolymerizable substance, the photopolymerization initiator, and the curing reaction accelerator were as follows.
[Ink06] Photopolymerizable substance PC-1, photopolymerizable initiator IC-1
[Pro06] Curing reaction accelerator N-1

Ink Ink07 and reaction accelerator composition Pro07 used in Example 7 were prepared in the same manner as in Example 1 except that the photopolymerizable material, the photopolymerization initiator, and the curing reaction accelerator were as follows.
[Ink07] Photopolymerizable substance PD-1, photopolymerizable initiator IC-1
[Pro07] Curing reaction accelerator N-1

Ink 08 and reaction accelerator composition Pro08 used in Example 8 were prepared in the same manner as in Example 1 except that the photopolymerizable substance, the photopolymerization initiator, and the curing reaction accelerator were as follows.
[Ink08] polyfunctional photopolymerizable substance PB-1, photopolymerizable initiator TX-1
[Pro08] Curing reaction accelerator AN-1

Ink 09 and reaction accelerator composition Pro09 used in Example 9 were prepared in the same manner as in Example 1 except that the photopolymerizable substance, the photopolymerization initiator, and the curing reaction accelerator were as follows.
[Ink09] polyfunctional photopolymerizable substance PB-1, photopolymerizable initiator TX-1
[Pro09] Curing reaction accelerator AS-1

Ink Ink10 and reaction accelerator composition Pro10 used in Example 10 were prepared in the same manner as in Example 1 except that the photopolymerizable substance, the photopolymerization initiator, and the curing reaction accelerator were as follows.
[Ink10] Photopolymerizable substance PB-1, photopolymerizable initiator TX-1
[Pro10] Curing reaction accelerator S-1

Ink Ink11 and reaction accelerator composition Pro11 used in Example 11 were prepared in the same manner as in Example 1 except that the photopolymerizable substance, the photopolymerization initiator, and the curing reaction accelerator were as follows.
[Ink11] Photopolymerizable substance PB-1, photopolymerizable initiator TX-2
[Pro11] Curing reaction accelerator S-1
(Comparative Example 1)
The ink CompInk01 used in Comparative Example 1 was the same as Ink08, and was prepared in the same manner as in Example 1 except that the photopolymerizable substance and the photopolymerization initiator were as follows. In addition, here, since the case where a reaction accelerator composition is not used is shown as a comparative example, the one corresponding to CompPro01 is not used.
[CompInk01] photopolymerizable substance PB-1, photopolymerizable initiator TX-2
<Recording test>
Recording evaluation was performed using the above various inks and the reaction accelerator composition. The ink jet recording apparatus used here was the same as that shown in FIG. The recording head had a recording density of 1200 dpi, and the driving condition was a driving frequency of 10 kHz. When a 1200 dpi head was used, the discharge amount per dot was 6.0 pl. The center emission wavelength of the lamp is 365 nm, and the intensity at the irradiation position is 300 mW / cm ² . These recording conditions are the same throughout the examples and comparative examples.

  In Examples 1 to 11 and Comparative Example 1, this ink jet recording apparatus was used to produce color images of Bk, C, M, Y (black, cyan, magenta, yellow) and R, G, B (red, green, blue). ) Were formed. The recording medium used for the evaluation is a white film of polyethylene terephthalate having an A4 size and a uniform and clean surface.

<Evaluation 1>
The fixing properties, scratch resistance, and water resistance of the recording samples of Examples 1 to 11 and Comparative Example 1 and Comparative Example 2 described later were evaluated as follows.

(1) Fixability 10 seconds after recording, when the Sylbon paper was pulled with the Sylbon paper (Sylbon is a registered trademark) on the recorded paper and a weight of 40 g / cm ² overlaid on the recording surface, It was visually observed whether or not the recording portion was smudged by rubbing the recording portion on the non-recording portion (white background portion) and the Sylbon paper of the recording medium, and evaluated according to the following criteria.
A: Dirt due to rubbing is not seen.
B: There is almost no dirt due to rubbing.
C: The dirt part by a blur is conspicuous.

(2) Scratch resistance When the sample was left for 24 hours, when the Sylbon paper was placed on the recorded paper and the weight of 40 g / cm ² was placed on the recording surface, the Sylbon paper was pulled. Whether or not the recording part (white background part) and the Sylbon paper were stained by rubbing of the recording part was visually observed and evaluated according to the following criteria.
A: Dirt due to rubbing is not seen.
B: There is almost no dirt due to rubbing.
C: The dirt part by a blur is conspicuous.

(3) Water resistance About 1 g of water was dropped with a dropper with respect to the above sample left for 24 hours, and the presence or absence of ink bleeding was visually observed, and the result was evaluated according to the following criteria.
A: There is almost no ink bleeding.
B: Slight ink bleeding occurs.
C: Ink bleeding is noticeable.

(Comparative Example 2)
The ink CompInk02 used in Comparative Example 2 was prepared in the same manner as in Example 1 using the same photopolymerizable substance and photopolymerization initiator as Ink11, and the mixing ratio was ink: reaction accelerator composition = 1: 1. In this case, only the curing reaction accelerator in an amount contained in the reaction accelerator composition is directly added to the ink. In this case, since the difference in storage stability by adding the curing reaction accelerator to the ink is shown as a comparative example, the one corresponding to CompPro02 is not used.
[CompInk02] Photopolymerizable substance PB-1, photopolymerizable initiator TX-2, curing reaction accelerator S-1
<Evaluation 2>
The storage stability of the inks of Examples 1 to 11 and Comparative Examples 1 and 2 produced under the above conditions was evaluated as follows.

(4) Storage stability The ink was filled in an ink tank and the cured state of the ink when stored in a dark place for 1 week was visually observed, and the result was evaluated according to the following criteria.
A: The ink is not cured and has sufficient fluidity in the tank.
B: There are some hardened parts, but there are many parts that have fluidity in the tank.
C: Most part is cured and no fluidity is observed.

  The evaluation results regarding Examples 1 to 11 and Comparative Examples 1 and 2 are shown in Table 1.

1 is a schematic front view of a preferred inkjet recording apparatus used in the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ink cartridge part which accommodates the ink of this invention 2 Recording head part which mounts an ink cartridge and performs recording 3 Lamp part which performs light irradiation for hardening 4 Recording head part and drive part which drives lamp part 5 Recording medium Paper discharge unit

Claims (7)

An ink jet recording method comprising: applying an ink shown in (1) below to a recording medium, applying a reaction accelerator composition shown in (2) below, and then irradiating an active energy ray.
(1) An ink containing at least a photopolymerizable substance having a water-soluble double bond, a coloring material, and a photopolymerization initiator.
(2) A reaction accelerator composition containing a water-soluble curing reaction accelerator. The inkjet recording method according to claim 1, wherein the photopolymerizable substance is at least one selected from the group of water-soluble polymerizable compounds represented by the following general formula.
(1) Polyethylene oxide / propylene oxide derivatives

(2) Glycerin derivative

(3) Trimethylolpropane derivative

(4) Pentaerythritol derivative

[In the above general formula, X is H or CH ₃ . i1 + k1 is an integer of 8 to 24, j1 is an integer of 0 to 6, i2, j2, and k2 are integers of 1 or more, and l2, m2, and n2 are 0 or 1. i3, j3, and k3 are integers of 1 or more, and l3, m3, and n3 are 0 or 1. R ₁ is a substituted or unsubstituted alkyl group having a carboxyl group. i4, j4, k4, and l4 are integers of 1 or more. ] The inkjet recording method according to claim 1, wherein the photopolymerization initiator is any one of water-soluble compounds represented by the following general formula.
(1) Thioxanthone derivative

(2) Acridone derivatives

(3) Benzophenone derivatives

(4) α-Hydroxyphenyl ketone derivative

[In the above general formula, R ₁ represents — (CH ₂ ) _x — (x is 0 or 1), —O— (CH ₂ ) _y — (y is 1 or 2), or a substituted or unsubstituted phenylene group. It is. M is a hydrogen atom or an alkali metal, and R ₂ and R ₃ are each independently a hydrogen atom or a substituted or unsubstituted alkyl group. i1 is an integer of 1 to 10. R ₄ and R ₅ are each independently a hydrogen atom, a carboxyl group or a salt thereof, a sulfonic acid or a salt thereof, a linear or branched alkyl group having 1 to 4 carbon atoms, a halogen atom, or a carbon number of 1 or more. It is selected from 4 or less alkoxyl groups and aryloxy groups. i2 is an integer from 1 to 10, i3 is an integer from 1 to 10, i4 is an integer from 2 to 5, and j4 is an integer from 0 to 5. ] The inkjet recording method according to claim 1, wherein the curing reaction accelerator is at least one selected from the group of compounds represented by the following (1) to (4).
(1) A compound having a proton-donating group based on an N atom and water-soluble.
(2) A compound that has two or more polymerizable unsaturated bonds in one molecule and a proton-donating group based on an N atom, and is water-soluble.
(3) A compound having both a polymerizable unsaturated bond and a proton donating group based on an S atom in one molecule, and being water-soluble.
(4) A compound having a proton-donating group based on two or more S atoms in one molecule and water-soluble. The inkjet according to claim 4, wherein the compound having two or more polymerizable unsaturated bonds in one molecule and a proton-donating group based on an N atom and water-soluble is a compound represented by the following general formula: Recording method.

[In the above general formula, R ₁ , R ₂ , R ₃ , R ₄ and R ₅ are each independently substituted with an ethylene oxide chain having 2 to 6 repeating units or a hydroxyl group having 2 to 6 carbon atoms. Is an aliphatic alkyl. ] The ink jet recording method according to claim 4, wherein the compound having both a polymerizable unsaturated bond and a proton donating group based on an S atom in one molecule and having water solubility is a compound represented by the following general formula.

[In the above general formula, R ₁ is an atomic group having a hydrophilic group, typically an atomic group containing an ethylene oxide chain. ] The inkjet recording method according to claim 4, wherein the compound having a proton-donating group based on two or more S atoms in one molecule and water-soluble is a compound represented by the following general formula.

[In the above general formula, R ₁ is an atomic group having a hydrophilic group, typically an atomic group containing an ethylene oxide chain. ]

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