JP2014237741A - Aqueous ink set, ink cartridge set, recording device, and recording method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aqueous ink set in which the deformation of a recording medium is inhibited.SOLUTION: An aqueous ink set has a plurality of photocuring aqueous inks comprising a colorant, a photopolymerizable compound, a photopolymerization initiator, and water, and the plurality of aqueous inks have different colors and also have differences in temperature after photocuring being 40°C or less.

Description

  The present invention relates to a water-based ink set, an ink cartridge set, a recording apparatus, and a recording method.

  Patent Document 1 discloses a coating step of applying a flocculant, a water-soluble organic solvent, a saccharide, and water on a recording medium, a colorant, an amphiphilic photopolymerizable compound, and a photopolymerization initiator. , A polar solvent, and a water-based photocurable ink composition containing at least water, and discharging the ink composition onto a recording medium after the coating process by discharging the ink composition from a recording head; and the discharging process An inkjet recording method including a curing step of curing a later aqueous photocurable ink composition by irradiation with light is disclosed.

  Patent Document 2 discloses an ink application process in which an ink composition containing a pigment having a specific volume average particle diameter, a polymerizable compound, and water is applied on a recording medium by an inkjet method under specific application conditions; A treatment liquid application step for applying a treatment liquid containing a flocculant for aggregating the components in the ink composition onto the recording medium; and a drying step for removing at least a part of the water under a drying condition in which a specific amount of water is removed. And a polymerization step of irradiating the ink composition from which the water has been removed with active energy rays.

  Patent Document 3 discloses an inkjet ink containing a coloring material, an organic solvent, water and a polymer compound, wherein the water content is a specific amount, and at least one SP value of the organic solvent and The content is in a specific range, and the polymer compound has a plurality of side chains in the hydrophilic main chain, and is a polymer compound that can be cross-linked between the side chains by irradiation with active energy rays. An ink-jet ink characterized by this is disclosed.

  In Patent Document 4, an actinic ray curable ink containing a photoinitiator, a photopolymerizable compound and a pigment, and a dispersant having an acid value larger than an amine value is jetted onto a recording material from an inkjet recording head, An image forming method for printing on a recording material, wherein the actinic ray curable ink is landed and then cured by a light source having a specific intensity is disclosed.

JP 2011-218571 A JP 2011-178029 A JP 2007-91910 A JP 2005-224971 A

  An object of the present invention is to provide an aqueous ink set in which deformation of a recording medium is suppressed.

The above problems are improved by the following means. That is,
The invention according to claim 1
A plurality of photocurable water-based inks containing a colorant, a photopolymerizable compound, a photopolymerization initiator, and water;
The plurality of water-based inks are water-based ink sets having different colors from each other and having a temperature difference of 40 ° C. or less after photocuring.

The invention according to claim 2
The water-based ink set according to claim 1, wherein the water-based ink further contains a light absorbing exothermic agent.

The invention according to claim 3
It is an ink cartridge set which accommodated each water-based ink of the water-based ink set of Claim 1 or Claim 2.

The invention according to claim 4
A discharge device for discharging each water-based ink of the water-based ink set according to claim 1 or 2,
A light irradiation device for irradiating the discharged water-based ink with light;
Is a recording apparatus.

The invention according to claim 5
Discharging each water-based ink of the water-based ink set according to claim 1 or 2,
Irradiating each discharged water-based ink with light;
Is a recording method.

  According to the first aspect of the present invention, the deformation of the recording medium is suppressed as compared with the case where the temperature difference exceeds 40 ° C.

  According to the invention which concerns on Claim 2, compared with the case where a light absorption exothermic agent is not used, it is easy to control the said temperature difference within 40 degreeC.

  According to the invention of claim 3, the deformation of the recording medium is suppressed as compared with the case where the temperature difference in the water-based ink set exceeds 40 ° C.

  According to the fourth aspect of the present invention, the deformation of the recording medium is suppressed as compared with the case where the temperature difference in the water-based ink set exceeds 40 ° C.

  According to the fifth aspect of the present invention, the deformation of the recording medium is suppressed compared to the case where the temperature difference in the water-based ink set exceeds 40 ° C.

1 is a schematic configuration diagram illustrating an ink jet recording apparatus according to an embodiment. FIG. 2 is a partial plan view showing the periphery of a recording head in the ink jet recording apparatus according to the embodiment.

  Hereinafter, embodiments of the water-based ink set, ink cartridge set, recording apparatus, and recording method of the present invention will be described in detail.

[Water-based ink set]
A water-based ink set according to the present embodiment (hereinafter sometimes referred to as “ink set”) is a photocurable water-based ink including a colorant, a photopolymerizable compound, a photopolymerization initiator, and water. (Hereinafter sometimes referred to as “ink”). The plurality of water-based inks are different in color from each other and have a temperature difference of 40 ° C. or less after photocuring.
In addition, the water-based ink which comprises the water-based ink set of this embodiment is hardened | cured when irradiated with light. Specifically, for example, by ejecting ink onto the surface of a recording medium or the like to form an ink layer, and irradiating the ink layer with light, the photopolymerizable compound contained in the ink is polymerized to form the ink layer. The ink layer is cured and an image is obtained. That is, a plurality of inks constituting the ink set of the present embodiment are respectively ejected onto a recording medium, and after the ink layer is formed and irradiated with light, the ink layer is cured and a cured layer is formed. An image composed of a plurality of hardened layers having different colors can be obtained.

Here, the “temperature difference after photocuring” is defined as follows. Specifically, when light is applied to ink (for example, ink contained in an ink layer formed on the surface of a recording medium or the like), the temperature of the ink rises as the ink cures, and the ink reaches the maximum temperature. The temperature drops. The maximum temperature is defined as “temperature after photocuring”.
In addition, each of the plurality of inks constituting the ink set (for example, inks contained in a plurality of ink layers formed on the surface of a recording medium or the like) is irradiated with light under the same conditions. The difference in “temperature after photocuring” is defined as “temperature difference after photocuring”. For example, in the case of an ink set having three or more inks having different colors, the difference between the highest “temperature after photocuring” and the lowest “temperature after photocuring” is “temperature difference after photocuring”. is there.

The “temperature difference after photocuring” is measured as follows, for example. Specifically, for example, each ink constituting the ink set is first ejected onto the surface of the recording medium, and an ink layer corresponding to each ink (for example, a film thickness of 18.22 using a wire bar of ROD No. 8). 3 μm layer). Thereafter, light is irradiated to all the ink layers from one light source (for example, a metal halide lamp) under the same irradiation conditions (for example, the integrated irradiation amount is ² J / cm ² ), and a cured film corresponding to each ink ( 1 minute after the light irradiation, the ink layer is formed so that no trace remains even if the surface is touched with a finger. That is, for example, the above-mentioned ink layers are irradiated with light of an irradiation amount necessary for all the ink layers to become cured films, thereby forming the cured films. And the said maximum temperature in the surface temperature of each cured film is measured, for example using a radiation temperature sensor, and the difference of the said maximum temperature between each cured film is calculated | required.

As described above, the water-based ink set of the present embodiment includes a plurality of water-based inks having different colors. Then, when the “temperature after photocuring” is measured and compared for each of the plurality of water-based inks, the difference between the highest and the lowest (ie, “temperature difference after photocuring”). ) Is within 40 ° C.
Since the water-based ink set of the present embodiment has the above configuration, the deformation of the recording medium is suppressed as compared with the case where the temperature difference exceeds 40 ° C. The reason is not clear, but is presumed as follows.

When the ink used in this embodiment is irradiated with light, the polymerization reaction of the photopolymerizable compound is started by the active species (for example, radicals) generated by the light absorption of the photopolymerization initiator, and the polymerization reaction proceeds. It is believed that the ink is cured. The polymerization reaction of this photopolymerizable compound is often an exothermic reaction, and in that case, it is considered that the temperature of the ink rises as the ink cures due to the heat released by the polymerization reaction.
The heat generated in the ink is used to vaporize water contained in the ink, or is released from the surface of the ink to the outside (for example, a recording medium in contact with the ink layer or in the air). It is considered that the temperature of the ink decreases after reaching the maximum temperature.

  On the other hand, when a colorant is included in the ink as in the present embodiment, the colorant absorbs the light irradiated for photocuring the ink, and the energy is converted into heat and released. The temperature may increase further. That is, in an ink containing a colorant, as the ink is cured by light irradiation, both heat due to the polymerization reaction of the photopolymerizable compound and heat due to the colorant that absorbs light are released. It is thought that the temperature of the ink rises. Hereinafter, the heat released by the colorant that has absorbed light may be referred to as “colorant release heat”.

  Then, as in the present embodiment, in an ink set having a plurality of water-based inks having different colors, the color tone differs between at least one of the plurality of inks by at least one of the type and content of the colorant. ing. Therefore, even if each ink is irradiated with light from one light source (that is, the conditions such as the wavelength and the intensity are the same), the “temperature after photocuring” is different because the total amount of the released heat is different. There may be cases. Further, in an ink set having a plurality of inks having different types and contents of the colorant, for example, the same types and contents of the photopolymerizable compound and the photoinitiator are used between the plurality of inks in order to align the curing conditions. Even so, the total amount of heat released may be different.

When an image is formed on a recording medium using an ink set having a plurality of water-based inks whose “temperatures after photocuring” are greatly different from each other, the recording medium may be deformed for the following reason.
Specifically, for example, when a permeable recording medium such as plain paper is used, if the “temperature after photocuring” of a plurality of inks is greatly different from each other, the amount of water vaporized when the ink is cured also varies between the inks. Are very different from each other. Therefore, the amount of remaining water greatly differs between the plurality of cured layers corresponding to each ink. In a region where a hardened layer with a large amount of remaining water is formed, a relatively large amount of water may penetrate into the recording medium as compared with a region where a hardened layer with a small amount of remaining water is formed. . As described above, it is estimated that the deformation of the recording medium occurs due to the difference in the amount of the penetrated water depending on the position of the recording medium.
Further, for example, when a non-permeable recording medium such as a resin sheet represented by an OHP (OverHead Projector) sheet is used, if the “temperature after photocuring” is greatly different, the temperature depends on the position of the recording medium. It is thought that there will be a difference. In the high temperature region of the recording medium, the degree of expansion of the recording medium due to heat is considered to be relatively large compared to the low temperature region. Thus, it is estimated that the deformation of the recording medium occurs due to the difference in the degree of expansion depending on the position of the recording medium.

  On the other hand, as described above, the ink set of the present embodiment includes a plurality of water-based inks having different colors, and the “temperature difference after photocuring” is within 40 ° C. Therefore, compared with the case where the “temperature difference after photocuring” exceeds 40 ° C., the temperature difference is small between the plurality of curing layers constituting the image, and the difference in the amount of remaining water is small. It is presumed that the deformation of is suppressed.

In the present embodiment, the method of setting the “temperature difference after photocuring” within the above range is not particularly limited. For example, a method of changing the content of the photopolymerization initiator to adjust the photopolymerization initiator, Examples include a method of adjusting by changing the type, a method of adjusting by changing the content of the photopolymerizable compound, a method of adjusting by changing the type of the photopolymerizable compound, and the like.
In the case of using a sensitizer (photopolymerization initiation aid) together with the photopolymerization initiator, the “temperature difference after photocuring” may be adjusted by changing the content of the sensitizer. You may adjust by changing the kind of sensitizer.
Moreover, you may adjust a "temperature difference after photocuring" by adding a light absorption exothermic agent as components other than a photoinitiator or a photopolymerizable compound.
In addition, although these methods may be used alone, the “temperature difference after photocuring” may be within the above range by combining them.

  Here, the “photopolymerization initiator” means a component that generates an active species that initiates polymerization of a photopolymerizable compound by light absorption. “Sensitizer” means a component that, when used alone, does not initiate polymerization of a photopolymerizable compound even when irradiated with light, but promotes initiation of polymerization of a photopolymerizable compound when used in combination with a photopolymerization initiator. To do. The “light absorption exothermic agent” means a component that does not contribute to the polymerization reaction of the photopolymerizable compound but emits heat by absorbing light.

In the present embodiment, as described above, the plurality of inks having different colors include a plurality of inks using different types of colorants, a plurality of inks having different colorant contents, the types of colorants, and A plurality of inks having different contents are exemplified.
A combination of a plurality of inks having different colors is not particularly limited, and examples thereof include a combination of two or more inks among black ink, cyan ink, magenta ink, and yellow ink.

In particular, for example, a black UV curable ink using a black pigment as a colorant and a magenta UV curable ink (a color other than black) using a magenta color pigment (a pigment other than black) as a colorant. In the ink set including the ultraviolet curable ink, the amount of the “colorant emission heat” may be greatly different between the inks. Specifically, it is considered that the black pigment absorbs more ultraviolet rays irradiated to cure the ink and emits more heat than the magenta color pigment.
In an ink set having the above color combination, if the types and contents of the photopolymerizable compound and the photoinitiator are the same among the inks, the difference in the amount of colorant emission heat causes the above-mentioned “temperature after photocuring”. It is conceivable that the “difference” becomes large.
However, in the present embodiment, the above-described method realizes an ink set having the above-described color combination while keeping the “temperature difference after photocuring” within the above range. That is, in the present embodiment, for example, for an ink using a magenta color pigment with little colorant emission heat, the content of the photopolymerization initiator is relatively increased, or a light absorption exothermic agent is added separately, The amount of heat released by components other than the colorant is made larger than that of the black ink. As a result, the difference in the amount of colorant emission heat is offset, and the “temperature difference after photocuring” becomes small, and an ink set within the above range can be obtained.

  In the present embodiment, the “temperature difference after photocuring” is within 40 ° C., preferably within 30 ° C., and more preferably within 20 ° C.

Next, components and physical properties constituting the water-based ink of the water-based ink set according to the present embodiment will be described in detail.
The water-based ink is a photocurable water-based ink, and a typical example thereof is an ultraviolet curable water-based ink. The water-based ink may be an active energy ray (active energy light) curable water-based ink other than ultraviolet light (ultraviolet light).

  The water-based ink includes a colorant, a photopolymerizable compound, a photopolymerization initiator, and water. The water-based ink may contain a light absorption exothermic agent, a water-soluble organic solvent, a surfactant, and other additives as necessary.

<Colorant>
Examples of the colorant include pigments. Examples of the pigment include organic pigments and inorganic pigments.

  Specific examples of black pigments (black pigments) include Raven7000, Raven5750, Raven5250, Raven5000 ULTRAII, Raven3500, Raven2000, Raven1500, Raven1250, Raven1200, Raven1190, Raven1190, Raven1190, Raven1190 ), Regal 400R, Regal 330R, Regal 660R, Mogu L, Black Pearls L, Monarch 700, Monarch 800, Monarch 880, Monarch 900, Monarch 1000, Monarch 1100, Monarch 1300, Mo arch 1400 (above Cabot), Color Black FW1, Color Black FW2, Color Black FW2V, Color Black 18, Color Black FW200, Color Black S150, Color Black S150, Color Black S160, Color Black S160, Color Black S160, Color Black S150, Color Black , Printex 140V, Special Black 6, Special Black 5, Special Black 4A, Special Black 4 (manufactured by Degussa), No. 25, no. 33, no. 40, no. 47, no. 52, no. 900, no. 2300, MCF-88, MA600, MA7, MA8, MA100 (manufactured by Mitsubishi Chemical Corporation) and the like, but are not limited thereto.

Specific examples of the cyan pigment include C.I. I. Pigment Blue-1, -2, -3, -15, -15: 1, -15: 2, -15: 3, -15: 4, -16, -22, -60, and the like. It is not limited.
Specific examples of the magenta color pigment include C.I. I. Pigment Red-5, -7, -12, -48, -48: 1, -57, -112, -122, -123, -146, -168, -177, -184, -202, C.I. I. Pigment Violet-19 etc. are mentioned, However, It is not limited to these.
Specific examples of yellow pigments include C.I. I. Pigment Yellow-1, -2, -3, -12, -13, -14, -16, -17, -73, -74, -75, -83, -93, -95, -97, -98, -114, -128, -129, -138, -151, -154, -180, and the like, but are not limited thereto.

  Here, when a pigment is used as the colorant, it is desirable to use a pigment dispersant together. Examples of the pigment dispersant used include a polymer dispersant, an anionic surfactant, a cationic surfactant, an amphoteric surfactant, and a nonionic surfactant.

  As the polymer dispersant, a polymer having a hydrophilic structure portion and a hydrophobic structure portion is preferably used. As the polymer having a hydrophilic structure part and a hydrophobic structure part, for example, a condensation polymer and an addition polymer are used. Examples of the condensation polymer include known polyester dispersants. Examples of the addition polymer include addition polymers of monomers having an α, β-ethylenically unsaturated group. Desired polymer dispersion by copolymerizing a monomer having an α, β-ethylenically unsaturated group having a hydrophilic group and a monomer having an α, β-ethylenically unsaturated group having a hydrophobic group An agent is obtained. A homopolymer of a monomer having an α, β-ethylenically unsaturated group having a hydrophilic group is also used.

  Monomers having an α, β-ethylenically unsaturated group having a hydrophilic group include monomers having a carboxyl group, a sulfonic acid group, a hydroxyl group, a phosphoric acid group, such as acrylic acid, methacrylic acid, and crotonic acid. , Itaconic acid, itaconic acid monoester, maleic acid, maleic acid monoester, fumaric acid, fumaric acid monoester, vinyl sulfonic acid, styrene sulfonic acid, sulfonated vinyl naphthalene, vinyl alcohol, acrylamide, methacryloxyethyl phosphate, bismethacrylic acid Examples include roxyethyl phosphate, methacrylooxyethyl phenyl acid phosphate, ethylene glycol dimethacrylate, and diethylene glycol dimethacrylate.

  Examples of the monomer having an α, β-ethylenically unsaturated group having a hydrophobic group include styrene derivatives such as styrene, α-methylstyrene, vinyltoluene, vinylcyclohexane, vinylnaphthalene, vinylnaphthalene derivatives, alkyl acrylate esters, Examples include methacrylic acid alkyl esters, methacrylic acid phenyl esters, methacrylic acid cycloalkyl esters, crotonic acid alkyl esters, itaconic acid dialkyl esters, maleic acid dialkyl esters, and the like.

  Examples of desirable copolymers as the polymer dispersant include styrene-styrene sulfonic acid copolymer, styrene-maleic acid copolymer, styrene-methacrylic acid copolymer, styrene-acrylic acid copolymer, vinyl naphthalene- Maleic acid copolymer, vinyl naphthalene-methacrylic acid copolymer, vinyl naphthalene-acrylic acid copolymer, alkyl acrylate ester-acrylic acid copolymer, alkyl methacrylate ester-methacrylic acid copolymer, styrene-methacrylic acid Examples include alkyl ester-methacrylic acid copolymer, styrene-acrylic acid alkyl ester-acrylic acid copolymer, styrene-methacrylic acid phenyl ester-methacrylic acid copolymer, and styrene-methacrylic acid cyclohexyl ester-methacrylic acid copolymer. It is done. Moreover, you may copolymerize the monomer which has a polyoxyethylene group and a hydroxyl group with these polymers.

  The weight average molecular weight of the polymer dispersant is preferably, for example, 2000 or more and 50000 or less.

  These polymer dispersants may be used alone or in combination of two or more. The content of the polymer dispersant varies greatly depending on the pigment and cannot be generally stated, but it is preferably 0.1% by mass or more and 100% by mass or less based on the pigment.

Examples of the pigment include pigments that are self-dispersed in water (hereinafter referred to as self-dispersing pigments).
The self-dispersing pigment refers to a pigment that has a water-solubilizing group on the pigment surface and disperses in water without the presence of a polymer dispersant. The self-dispersing pigment can be obtained, for example, by subjecting the pigment to surface modification treatment such as acid / base treatment, coupling agent treatment, polymer graft treatment, plasma treatment, oxidation / reduction treatment, and the like.

  As self-dispersing pigments, in addition to pigments that have been surface-modified to the above pigments, Cab-o-jet-200, Cab-o-jet-300, Cab-o-jet-400 manufactured by Cabot Corporation. IJX-157, IJX-253, IJX-266, IJX-273, IJX-444, IJX-55, Cab-o-jet-250C, Cab-o-jet-260M, Cab-o-jet-270Y, Cab -O-jet-450C, Cab-o-jet-465M, Cab-o-jet-470Y, Cab-o-jet-480M, Microjet Black CW-1, CW-2 manufactured by Orient Chemical Co., etc. Examples include dispersed pigments.

  The self-dispersing pigment is desirably a pigment having at least sulfonic acid, sulfonate, carboxylic acid, or carboxylate as a functional group on the surface thereof. More desirably, the pigment has at least a carboxylic acid or a carboxylate as a functional group on the surface.

Here, examples of the pigment include a pigment coated with a resin. This is called a microcapsule pigment, and there are commercially available microcapsule pigments such as those manufactured by DIC Chemical Industry Co., Ltd. and Toyo Ink Co., Ltd. In addition, it is not restricted to a commercially available microcapsule pigment, You may use the microcapsule pigment produced according to the objective.
Examples of the pigment also include a resin dispersion type pigment in which a polymer compound is physically adsorbed or chemically bonded to the pigment.
In addition to black, cyan, magenta, and yellow, the pigments include specific color pigments such as red, green, blue, brown, and white, metallic luster pigments such as gold and silver, and colorless or light-colored constitutions. Examples include pigments and plastic pigments.
Examples of the pigment include particles in which silica, alumina, polymer beads or the like are used as a core, and a dye or pigment is fixed on the surface thereof, an insoluble lake of the dye, a colored emulsion, a colored latex, or the like.

  As colorants, in addition to pigments, other hydrophilic anionic dyes, direct dyes, cationic dyes, reactive dyes, polymer dyes and oil-soluble dyes, wax powders and resin powders colored with dyes And emulsions, fluorescent dyes and fluorescent pigments.

The volume average particle diameter of the colorant is, for example, 10 nm or more and 1000 nm or less.
The volume average particle diameter of the colorant refers to the particle diameter of the colorant itself, or the particle diameter to which the additive has adhered when an additive such as a dispersant is attached to the colorant. The volume average particle diameter is measured by a Microtrac UPA particle size analyzer UPA-UT151 (manufactured by Microtrac). The measurement was performed by putting the ink diluted 1000 times into a measurement cell. As input values at the time of measurement, the viscosity of the ink diluent was used as the viscosity, and the refractive index of the particle was used as the particle refractive index.

  The content (concentration) of the colorant is, for example, preferably 1% by mass to 25% by mass and more preferably 2% by mass to 20% by mass with respect to the ink.

  Among the colorants, the combination having a large difference in the amount of the “colorant release heat” includes, for example, a combination of the black pigment and the magenta color pigment, a combination of the black pigment and the cyan pigment, The combination of the said black pigment and the said yellow pigment is mentioned. More specifically, the combination having a large difference in the amount of the “colorant emission heat” includes, for example, a combination of the black pigment and the magenta color pigment. The specific pigment is a carbon that is a black pigment. C. black and magenta pigments I. And a combination with Pigment Red-122.

<Photopolymerizable compound>
Examples of the photopolymerizable compound include a compound having a polymerizable group that undergoes radical polymerization by ultraviolet rays, and may be a monomer, an oligomer, or a mixture containing these. Examples of the polymerizable group include a group having an ethylenically unsaturated double bond, and specifically include, for example, an acryloyl group, a methacryloyl group, a vinyl group, a vinyl ether group, a maleic anhydride group, and an N-substituted group. And maleimide groups. The photopolymerizable compound may be a cationic polymerizable compound.

  The photopolymerizable compound may be a water-soluble photopolymerizable compound or a water-insoluble photopolymerizable compound. In the photopolymerizable compound, water-soluble means that the amount of the target substance dissolved in 100 parts by mass of water at 25 ° C. is 5 parts by mass or more (preferably 10 parts by mass or more). On the other hand, water-insoluble means that the amount of the target substance dissolved in 100 parts by mass of water at 25 ° C. is less than 5 parts by mass.

Examples of water-soluble photopolymerizable compounds include well-known photopolymerizable compounds, and specifically include acryloyl morphophorin (ACMO), hydroxyethyl acrylate (HEAA), diacetone acrylate, N-vinyl-2. -Pyrrolidone, N-vinyl-formamide, vinyl naphthalenesulfonic acid, hydroxyethyl (meth) acrylate, methoxypolyethylene glycol methacrylate, methoxypolyethylene glycol acrylate, ester of succinic anhydride and 2-hydroxyethyl (meth) acrylate, orthophthalic anhydride Examples thereof include radical polymerizable monomers such as esters of acid and 2-hydroxyethyl (meth) acrylate.
Examples of the water-soluble photopolymerizable monomer also include radical polymerizable monomers such as (meth) acrylic acid ester of polyhydric alcohol and (meth) acrylic acid ester of glycidyl ether derived from polyhydric alcohol.
Examples of the water-soluble photopolymerizable compound include oligomers obtained by polymerizing a water-soluble photopolymerizable monomer at a desired degree of polymerization.

Examples of the water-insoluble photopolymerizable compound include known water-insoluble photopolymerizable substances. Specifically, examples of the water-insoluble photopolymerizable substance include alcohols, polyhydric alcohols, and amino alcohols. Radical polymerizable monomers such as methacrylic acid esters of alcohols or polyhydric alcohols; acrylic aliphatic amides; acrylic alicyclic amides; acrylic aromatic amides.
Examples of water-insoluble photopolymerizable compounds include oligomers in which water-insoluble photopolymerizable monomers are polymerized at the desired degree of polymerization; addition of acryloyl group or methacryloyl group to epoxy skeleton, urethane skeleton, polyester skeleton or polyether skeleton And oligomers of acrylates (epoxy acrylate, urethane acrylate, polyester acrylate, polyether acrylate, urethane methacrylate, polyester methacrylate, etc.).

  The water-insoluble photopolymerizable compound is emulsified (emulsified) by a known method and dispersed in the aqueous ink. The water-insoluble photopolymerizable substance may be a self-emulsifying type (self-emulsifying type) or may be emulsified (emulsified) with a dispersant.

  A photopolymerizable compound may be used individually by 1 type and may be used together 2 or more types.

  The content (concentration) of the photopolymerizable compound is, for example, preferably from 5% by mass to 50% by mass, more preferably from 10% by mass to 30% by mass, and from 15% by mass to 25% by mass with respect to the ink. Further preferred.

<Photopolymerization initiator>
As a photoinitiator, a water-soluble photoinitiator may be sufficient and a water-insoluble photoinitiator may be sufficient. In the photopolymerization initiator, water-soluble means that the amount of the target substance dissolved in 100 parts by mass of water at 25 ° C. is 0.1 parts by mass or more. On the other hand, water-insoluble means that the amount of the target substance dissolved in 100 parts by mass of water at 25 ° C. is less than 0.1 parts by mass.

  Examples of water-soluble photopolymerization initiators include hydroxyacetophenones (1-phenyl-2-hydroxy-2-methyl-1-propanone, 1-hydroxy-cyclohexyl-phenyl-ketone, 1- [4- (2-hydroxyethoxy). ) -Phenyl] -2-hydroxy-2-methyl-1-propanone), aminoacetophenones (2-methyl-1- (4-methylthiophenyl) -2-morpholinopropan-1-one, 2-benzyl- Well-known photopolymerization initiators such as 2-dimethylamino-1- (4-morpholinophenyl) -butan-1-one), thioxanthone ammonium salt, and benzophenone ammonium salt.

  Examples of water-insoluble photopolymerization initiators include benzoin compounds (benzoin ethyl ether, benzoin isopropyl ether, etc.), benzophenone, acylphosphine oxide compounds (bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide, bis (2 , 6-dimethoxybenzoyl) -2,4,4-trimethylpentylphosphine oxide, 2,4,6-trimethylbenzoylphenylethoxyphosphine oxide, 2,4,6-trimethylbenzoyldiphenylphosphine oxide), thioxanthone compound (isopropylthioxanthone, 2,4-diethylthioxanthone, etc.) and known photopolymerization initiators such as anthraquinone compounds (ethyl anthraquinone, etc.).

  The water-insoluble photopolymerization initiator may be emulsified (emulsified) by a known method using a dispersant or the like and dispersed in an aqueous ink, or dissolved or dispersed in a water-soluble organic solvent. It may be dispersed in ink.

  The content of the photopolymerization initiator is, for example, preferably 0.1% by mass to 20% by mass, more preferably 0.1% by mass to 10% by mass, and more preferably 1% by mass to 10% by mass with respect to the ink. Is more preferable.

Here, a sensitizer (polymerization initiation assistant) may be used in combination with the photopolymerization initiator. Sensitizers (polymerization initiation aids) include aliphatic amines, amines containing aromatic groups (ethyl 2-dimethylaminobenzoate, ethyl 4- (dimethylamino) benzoate, isoamyl 4-dimethylaminobenzoate, etc. Tertiary amine-containing compounds), amine-containing compounds such as piperidine and triethanolamine; urea-containing compounds such as allylurea and o-tolylthiourea; sulfur-containing compounds such as sodium diethyldithiophosphate and soluble sulfinic acid salts; N Nitrile-containing compounds such as N, di-substituted p-aminobenzonitrile; phosphorus-containing compounds such as tri-n-butylphosphine and netyldiethyldithiophosphide; Michler's ketone, N-nitrisohydroxylamine derivative, oxazolidine compound, tetrahydro-1,3- Oxazine compounds, aldehydes (form Aldehyde or acetaldehyde) and condensation products such as a nitrogen-containing compound of the diamines: Polymer amines of the reaction product of an epoxy resin and an amine; triethanol amine triacrylate, and the like.
Examples of the content of the sensitizer include 0.01% by mass to 20% by mass with respect to the ink.

In this embodiment, as the kind of photopolymerization initiator that changes the content of the photopolymerization initiator and easily sets the “temperature difference after photocuring” within the above range, for example, an acylphosphine oxide compound (bis (2 , 4,6-trimethylbenzoyl) -phenylphosphine oxide, bis (2,6-dimethoxybenzoyl) -2,4,4-trimethylpentylphosphine oxide, 2,4,6-trimethylbenzoylphenylethoxyphosphine oxide, 2,4 , 6-trimethylbenzoyldiphenylphosphine oxide), thioxanthone compounds (2,4-diethylthioxanthone, isopropylthioxanthone, etc.), hydroxyacetophenones (1-phenyl-2-hydroxy-2-methyl-1-propanone, 1-hydroxy-cyclohexane) Sill - phenyl - ketone, 1- [4- (2-hydroxyethoxy) - phenyl] -2-hydroxy-2-methyl-1-propanone and the like).
Further, for example, in an ink set including a black ultraviolet curable ink and an ultraviolet curable ink other than black (for example, a magenta ultraviolet curable ink), the content of an ultraviolet polymerization initiator (a sensitizer is used in combination). In the case where the total amount of the content of the ultraviolet polymerization initiator and the content of the sensitizer is adjusted so that the “difference in temperature after photocuring” is within the above range, the method of adjusting as follows: Is mentioned. Specifically, for example, the content of the ultraviolet polymerization initiator contained in the black ultraviolet curable ink is 0.5 times or more of the content of the ultraviolet polymerization initiator contained in the ultraviolet curable ink other than black. The method of adjusting to the range below 0.98 times is mentioned.

<Water>
As water, ion-exchanged water, ultrapure water, distilled water, and ultrafiltered water are particularly preferable from the viewpoint of preventing contamination of impurities or generation of microorganisms.

  The water content is, for example, preferably 10% by mass to 95% by mass and more preferably 30% by mass to 90% by mass with respect to the ink.

<Light absorption exothermic agent>
As described above, the light-absorbing exothermic agent is not particularly limited as long as it is a compound that absorbs light and emits heat, but it is desirable that it does not cause a chemical change in the process.
The light absorption exothermic agent may be a compound in which the photopolymerization initiator absorbs light having a wavelength that initiates the polymerization reaction of the photopolymerizable compound and releases heat, and absorbs light of other wavelengths. It may be a compound that releases heat. For example, when an ultraviolet polymerization initiator is used as a photopolymerization initiator, an ultraviolet absorber that absorbs ultraviolet rays in a wavelength region where the ultraviolet polymerization initiator initiates polymerization may be used as a light absorption exothermic agent. Absorbing ultraviolet absorbers may be used as light absorbing exothermic agents. Even when an ultraviolet polymerization initiator is used, a compound that absorbs light other than ultraviolet light (for example, infrared light) (for example, an infrared absorbent) may be used as the light-absorbing exothermic agent.
In addition, when the wavelength of the light for initiating the polymerization reaction is different from the wavelength of the light absorbed by the light-absorbing heat generating agent, two or more types of light sources may be used when curing the ink, A light source that emits light (for example, a lamp having a wide wavelength region) may be used. Specifically, for example, when an ultraviolet absorber that absorbs ultraviolet rays in the different wavelength regions is used, the ultraviolet polymerization initiator and the ultraviolet absorber are irradiated with light from separate light sources (for example, light emitting diodes having a narrow wavelength region). Alternatively, both may be irradiated with a single light source (for example, a metal halide lamp) having a wide wavelength region.

The light absorbing exothermic agent may be a water-soluble light absorbing exothermic agent or a water-insoluble light absorbing exothermic agent. Here, in the light absorption exothermic agent, water-soluble means that the amount of the target substance dissolved in 100 parts by mass of water at 25 ° C. is 0.1 parts by mass or more. On the other hand, water-insoluble means that the amount of the target substance dissolved in 100 parts by mass of water at 25 ° C. is less than 0.1 parts by mass.
When a water-insoluble light-absorbing heat-generating agent is used, it may be emulsified (emulsified) by a well-known method using a dispersant or the like and dispersed in an aqueous ink, or dissolved or dispersed in a water-soluble organic solvent. Then, it may be dispersed in the ink.

As a light absorption exothermic agent, an ultraviolet absorber, an infrared absorber, etc. are mentioned, for example.
Examples of the ultraviolet absorber include benzophenone-based, benzotriazole-based, salicylic acid ester-based, oxalic acid amide-based, and nickel complex-based ultraviolet absorbers.

  Examples of the benzophenone-based ultraviolet absorber include 2-hydroxy-4-methoxybenzophenone-5-sulfonic acid, 2-hydroxy-4-methoxy-2′-carboxybenzophenone, 2,4-dihydroxybenzophenone, and 2-hydroxy-4. -Methoxybenzophenone (oxybenzone), 2,2'-dihydroxy-4-methoxybenzophenone, 2-hydroxy-4-octyloxybenzophenone, 4-dodecyloxy-2-hydroxybenzophenone, 2,2 ', 4,4'-tetrahydroxy Examples include benzophenone, 2,2′-dihydroxy-4,4′-dimethoxybenzophenone, 1,4-bis (4-benzoyl-3-hydroxyphenyl) -butane and the like.

  Examples of the benzotriazole ultraviolet absorber include 2- (2-hydroxy-5-methylphenyl) -2H-benzotriazole, 2- (2-hydroxy-3,5-di-t-butylphenyl) -2H-. Benzotriazole, 2- (3-tert-butyl-2-hydroxy-5-methylphenyl) -2H-benzotriazole, 2- (3,5-di-tert-pentyl-2-hydroxyphenyl) -2H-benzotriazole 2- (2-hydroxy-4-octyloxyphenyl) -2H-benzotriazole, 2- (2-hydroxy-5-t-octylphenyl) -2H-benzotriazole, 5-chloro-2- (3,5 -Di-t-butyl-2-hydroxyphenyl) -2H-benzotriazole, 5-chloro-2- (3,5-di-sec-butyl-2- Hydroxyphenyl) -2H- benzotriazole, 2 (3-t- butyl-2-hydroxy-5-methylphenyl) -5-chloro 2H-benzotriazole.

Examples of the salicylic acid ester ultraviolet absorber include phenyl salicylic acid ester, p-octylphenyl salicylic acid ester, pt-butylphenyl salicylic acid ester, and the like.
Examples of the oxalic acid amide UV absorber include 2-ethoxy-2′-ethyl oxalic bisanilide, 2-ethoxy-5-t-butyl-2′-ethyl oxalic bisanilide, and the like. Is mentioned.
Examples of the nickel complex ultraviolet absorber include [2,2′-thiobis (4-t-octylphenolate)]-2-ethylhexylamine nickel salt (II), [2,2′-thiobis (4-t -Octylphenolate)]-n-butylamine nickel salt (II) and the like.

Further, as an ultraviolet absorber, octyl methoxycinnamate, t-butylmethoxydibenzoylmethane, TINUVIN 1130 (methyl 3- (3- (2H-benzotriazol-2-yl) -5-t-butyl-4-hydroxyphenyl) ) Propionate / polyethylene glycol 300 reaction product), hydroxyphenyl triazine UV absorber (for example, 2,4-bis (2-hydroxy-4-butoxyphenyl) -6- (2,4-dibutoxyphenyl)- 1,3,5-triazine, 2- (4,6-bis (2,4-dimethylphenyl) -1,3,5-triazin-2-yl) -5-hydroxyphenyl, and derivatives thereof), Diethylaminohydroxybenzoyl excyl benzoate, zinc oxide, titanium oxide, ethylhexyl triazone, etc. It is below.
You may use the said ultraviolet absorber individually or in mixture of 2 or more types.
Among the above ultraviolet absorbers, benzophenone-based ultraviolet absorbers are preferable.

Examples of infrared absorbers include cyanine compounds, diimonium compounds, aminium compounds, and the like.
Specific examples of the infrared absorber include “KAYASORB IRG-140” manufactured by Nippon Kayaku Co., Ltd., “KAYASORB IRG-022” manufactured by Nippon Kayaku Co., Ltd., “KAYASORB CY-40MC” manufactured by Nippon Kayaku Co., Ltd., “NIR- “IM1” manufactured by Nagase Chemtech, “NIR-AM1” manufactured by Nagase Chemtech, etc.
You may use the said infrared absorber individually or in mixture of 2 or more types.
Moreover, you may use combining the said ultraviolet absorber and the said infrared absorber.

The content of the light-absorbing exothermic agent is adjusted according to the combination of colorants contained in each of the plurality of inks constituting the ink set (difference in colorant emission heat).
For example, a plurality of inks constituting an ink set include black ultraviolet curable ink (for example, black ink using carbon black as a colorant as a colorant) and non-black ultraviolet curable ink (for example, magenta as a colorant. In combination with CI pigment Red-122, which is a color pigment), and when a benzophenone-based UV absorber is used as the UV absorber, the content of the UV absorber is as follows: Such a range is mentioned. Specifically, for example, the difference between the content of the ultraviolet absorber contained in the ink other than black and the content of the ultraviolet absorber contained in the black ink is 0.05% by mass or more and 5% by mass or less. A range is mentioned. That is, when the black ink does not use the ultraviolet absorbent, the content of the ultraviolet absorbent contained in the ink other than black is in the range of 0.05% by mass or more and 5% by mass or less.

<Water-soluble organic solvent>
Examples of the water-soluble organic solvent include polyhydric alcohols, polyhydric alcohol derivatives, nitrogen-containing solvents, alcohols, and sulfur-containing solvents. Other examples of the water-soluble organic solvent include propylene carbonate and ethylene carbonate. In the water-soluble organic solvent, water-soluble means that the amount of the target substance dissolved in 100 parts by mass of water at 25 ° C. is 1 part by mass or more.

  Polyhydric alcohols include ethylene glycol, diethylene glycol, propylene glycol, butylene glycol, triethylene glycol, 1,5-pentanediol, 1,2-hexanediol, 1,2,6-hexanetriol, glycerin, trimethylol Sugar alcohols such as propane and xylitol; sugars such as xylose, glucose and galactose;

  Polyhydric alcohol derivatives include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, propylene glycol monobutyl ether, dipropylene glycol monobutyl ether, diglycerin. And ethylene oxide adducts.

Examples of the nitrogen-containing solvent include pyrrolidone, N-methyl-2-pyrrolidone, cyclohexyl pyrrolidone, triethanolamine and the like.
Examples of alcohols include ethanol, isopropyl alcohol, butyl alcohol, and benzyl alcohol.
Examples of the sulfur-containing solvent include thiodiethanol, thiodiglycerol, sulfolane, dimethyl sulfoxide and the like.

  Here, examples of the water-soluble organic solvent also include morpholine compounds having a morpholine skeleton. When a water-insoluble photopolymerization initiator (particularly a thioxanthone compound (isopropylthioxanthone, 2,4-diethylthioxanthone, etc.)) is applied as a photopolymerization initiator, The water-insoluble photopolymerization initiator is preferable because the solubility or dispersibility of the water-insoluble photopolymerization initiator is easily increased.

  Examples of the morpholine compound include morpholine compounds represented by the following general formula (MO).

In the general formula (MO), Rm ¹ represents a methyl group, a hydroxyl group, a carboxyl group, an amino group, or a halogen. Rm ² represents a single bond, a substituted or unsubstituted alkylene group, a carbonyl group, an ester group, or a group composed of a combination of these. When Rm ² represents a single bond, the morpholine compound represented by the general formula (MO) is a compound in which Rm ² is absent and Rm ¹ is directly bonded to the morpholine skeleton.
Here, the alkylene group represented by Rm ² may be either linear or branched, and examples thereof include an alkylene group having 1 to 5 carbon atoms (preferably 1 to 3 carbon atoms). Examples of the linear alkylene group include a methylene group, an ethylene group, an n-propylene group, an n-butylene group, and an n-pentylene group. Examples of the branched alkylene group include an isopropylene group, an isobutylene group, a sec-butylene group, and a tert-butylene group.
Examples of the substituent that can be substituted on the alkylene group represented by Rm ² include a hydroxyl group, a carboxyl group, an amino group, and a halogen atom.

  Hereinafter, although the specific example of the morpholine compound shown by general formula (MO) is illustrated, it is not restricted to this.

Examples of the compound having a morpholine skeleton other than the morpholine compound represented by the general formula (MO) include dimethylmorpholine.
Examples of the water-soluble organic solvent include alkoxy alcohols in addition to compounds having a morpholine skeleton.
Examples of the alkoxy alcohol include 2- (2-butoxyethoxy) ethanol, 2- (2- (2-butoxyethoxy) ethoxy) ethanol, diethylene glycol monopropyl ether, diethylene glycol hexyl ether, diethylene glycol monoethyl ether, and the like.

  The water-soluble organic solvent may be used alone or in combination of two or more.

  1 mass% or more and 60 mass% or less are preferable with respect to water, and, as for content of a water-soluble organic solvent, 1 mass% or more and 40 mass% or less are more preferable.

<Surfactant>
Examples of the surfactant include an anionic surfactant, a nonionic surfactant, a cationic surfactant, an amphoteric surfactant, and the like, and preferably an anionic surfactant and a nonionic surfactant.

Examples of the anionic surfactant include alkylbenzene sulfonate, alkylphenyl sulfonate, alkylnaphthalene sulfonate, higher fatty acid salt, sulfate of higher fatty acid ester, sulfonate of higher fatty acid ester, sulfuric acid of higher alcohol ether. Examples thereof include ester salts and sulfonates, higher alkyl sulfosuccinates, polyoxyethylene alkyl ether carboxylates, polyoxyethylene alkyl ether sulfates, alkyl phosphates, polyoxyethylene alkyl ether phosphates, and the like.
Among these, as anionic surfactants, dodecylbenzenesulfonate, isopropylnaphthalenesulfonate, monobutylphenylphenol monosulfonate, monobutylbiphenylsulfonate, monobutylbiphenylsulfonate, dibutylphenylphenol A disulfonate is preferable.

Nonionic surfactants include polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers, polyoxyethylene fatty acid esters, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene sorbitol fatty acid esters, glycerin fatty acid esters, poly Oxyethylene glycerin fatty acid ester, polyglycerin fatty acid ester, sucrose fatty acid ester, polyoxyethylene alkylamine, polyoxyethylene fatty acid amide, alkyl alkanolamide, polyethylene glycol polypropylene glycol block copolymer, acetylene glycol, polyoxyethylene adduct of acetylene glycol Etc.
Among these, nonionic surfactants include polyoxyethylene nonylphenyl ether, polyoxyethylene octylphenyl ether, polyoxyethylene dodecylphenyl ether, polyoxyethylene alkyl ether, polyoxyethylene fatty acid ester, sorbitan fatty acid ester, polyoxyethylene Oxyethylene sorbitan fatty acid ester, fatty acid alkylol amide, polyethylene glycol polypropylene glycol block copolymer, acetylene glycol, and polyoxyethylene adduct of acetylene glycol are preferable.

  Other nonionic surfactants include silicone surfactants such as polysiloxane oxyethylene adducts; fluorine surfactants such as perfluoroalkyl carboxylates, perfluoroalkyl sulfonates, and oxyethylene perfluoroalkyl ethers; And biosurfactants such as spicrispolic acid, rhamnolipid, and lysolecithin.

  The hydrophilic / hydrophobic balance (HLB) of the surfactant is preferably in the range of 3 to 20, for example, in consideration of solubility.

  The surfactant may be used alone or in combination of two or more.

  The content of the surfactant is preferably from 0.1% by weight to 10% by weight, more preferably from 0.1% by weight to 5% by weight, and more preferably from 0.2% by weight to 3% by weight with respect to the ink. Further preferred.

<Other additives>
Other additives include ink ejection improvers (polyethyleneimine, polyamines, polyvinylpyrrolidone, polyethylene glycol, ethylcellulose, carboxymethylcellulose, etc.), conductivity / pH adjusters (potassium hydroxide, sodium hydroxide, lithium hydroxide, etc.) Alkali metal compounds), reactive diluents, penetrants, pH buffers, antioxidants, fungicides, viscosity adjusters, conductive agents, chelating agents, ultraviolet absorbers, infrared absorbers, etc. Can be mentioned.

<Physical properties of water-based ink>
Examples of the surface tension of the water-based ink include a range of 20 mN / m to 45 mN / m.
Here, as the surface tension, a value measured in an environment of 23 ° C. and 55% RH using a Wilhelmy type surface tension meter CBVP-Z (manufactured by Kyowa Interface Science Co., Ltd.) was adopted.

Examples of the viscosity of the water-based ink include a range of 1.5 mPa · s to 30 mPa · s. Here, as the viscosity, a value measured under the conditions of a cone plate type TV-20L (manufactured by Toki Sangyo Co., Ltd.) as a measuring device, a measurement temperature of 23 ° C., and a shear rate of 750 s ⁻¹ was adopted.

[Recording apparatus and recording method]
Next, a recording apparatus and a recording method using the water-based ink set according to the present embodiment will be described.
The recording apparatus according to the present embodiment irradiates light to each of the ejected water-based inks, the ejection device that ejects each water-based ink (photocurable water-based ink) of the water-based ink set according to the present embodiment. And at least a light irradiation device.
Here, the light irradiating apparatus is a light irradiating apparatus that irradiates each water-based ink with light so that a temperature difference between the water-based inks after photocuring is within 40 ° C. Specifically, for example, when at least one of the inks constituting the ink set contains a light absorbing exothermic agent, the “temperature difference after photocuring” is adjusted to the above range, and photopolymerization starts. A light irradiation device that irradiates both the light absorbed by the agent and the light absorbed by the light absorption exothermic agent is used. That is, when one light irradiation device is a device that irradiates both the light absorbed by the photopolymerization initiator and the light absorbed by the light absorption exothermic agent, the one light irradiation device may be used. In addition, when the wavelength of the light absorbed by the photopolymerization initiator and the wavelength of the light absorbed by the light absorption exothermic agent are different, the light irradiation device that irradiates the light absorbed by the photopolymerization initiator and the light absorption exothermic agent absorbs the light. A light irradiating device that irradiates light to be used may be used in combination.

In the recording apparatus according to the present embodiment, a step of ejecting each water-based ink (photo-curable water-based ink) of the water-based ink set according to the present embodiment, and irradiating the discharged water-based ink with light. And a recording method comprising the steps of:
Here, in the step of irradiating each ejected water-based ink with light, the water-based ink is irradiated so that the temperature difference after photocuring is within 40 ° C. Specifically, for example, when at least one of the inks constituting the ink set contains a light absorbing exothermic agent, the “temperature difference after photocuring” is adjusted to the above range, and photopolymerization starts. Both the light absorbed by the agent and the light absorbed by the light absorption exothermic agent are irradiated. When the wavelength region of light absorbed by the photopolymerization initiator overlaps with the wavelength region of light absorbed by the light-absorbing heat generating agent, each aqueous ink may be irradiated with light having a wavelength in the overlapping region.

  In the recording apparatus according to the present embodiment, each water-based ink (photocurable water-based ink) of the water-based ink set according to the present embodiment is accommodated, and an ink cartridge set that is made into a cartridge so as to be attached to and detached from the recording apparatus. You may have.

  Hereinafter, an example of the recording apparatus according to the present embodiment will be described with reference to the drawings. However, the present invention is not limited to this. The main parts shown in the figure will be described, and the description of the other parts will be omitted.

  FIG. 1 is a schematic configuration diagram illustrating an ink jet recording apparatus according to the present embodiment. FIG. 2 is a partial plan view showing the periphery of the recording head in the ink jet recording apparatus according to the present embodiment.

  For example, as illustrated in FIG. 1, the inkjet recording apparatus 12 according to the present embodiment includes a paper feed container 16 at a lower portion in a housing 14, and the paper P ( An example of the recording medium) has a mechanism for taking out one sheet at a time by the take-out roll 18. The taken paper P is transported by a plurality of transport roller pairs 20 constituting the transport path 22.

  Above the paper supply container 16, an endless conveyance belt 28 supported while tension is applied to the driving roll 24 and the driven roll 26 is disposed. A recording head 30 (an example of a discharge device) is disposed above the conveyor belt 28 and faces a flat portion of the conveyor belt 28. A region where the recording head 30 faces the flat portion of the conveying belt 28 is an ejection region where ink droplets are ejected from the recording head 30 onto the paper P. The paper P transported by the transport roller pair 20 is held by the transport belt 28 and reaches the discharge area, is in a state of facing the recording head 30, and ink droplets discharged from the recording head 30 according to image information. Adheres to the surface of the paper P.

  Here, each color recording head 30 is connected to each color ink cartridge 30A attached to and detached from the ink jet recording apparatus 12 through a supply pipe (not shown), and each color ink is supplied to the recording head 30 by the ink cartridge 30A. Supplied.

For example, as shown in FIG. 2, the recording head 30 has a length in a direction in which an effective recording area (arrangement area of nozzles that eject ink) intersects the width of the paper P (for example, intersects (for example, intersects) with the paper P). This is a long recording head.
The recording head 30 is not limited to this, and is a recording head that is shorter than the width of the paper P, and is a recording head that moves in the width direction of the paper P and discharges ink (so-called carriage method). There may be.

  The recording head 30 may be a so-called thermal system that ejects ink droplets by heat, or a so-called piezoelectric system that ejects ink droplets by pressure.

  As the recording head 30, for example, four recording heads corresponding to four colors of yellow (Y), magenta (M), cyan (C), and black (K) are arranged in an array along the transport direction. ing. Of course, the recording head 30 is not limited to the form in which the four recording heads 30 corresponding to each of the above four colors are arranged, and four or more corresponding to each of four or more colors including other intermediate colors depending on the purpose. The recording head 30 may be arranged.

  A charging roll 32 is disposed on the upstream side of the recording head 30 (upstream side in the transport direction of the paper P). The charging roll 32 is driven while sandwiching the conveyance belt 28 and the paper P with the driven roll 26, generates a potential difference with the grounded driven roll 26, and charges the paper P to the conveyance belt 28. Adsorb electrostatically.

  An ultraviolet irradiation device 50 (an example of a light irradiation device) is disposed above the conveying belt 28 on the downstream side of the recording head 30 (downstream in the conveyance direction of the paper P).

  The ultraviolet irradiation device 50 irradiates the ink attached to the paper P on the transport belt 28 with ultraviolet rays.

For example, as illustrated in FIG. 2, the ultraviolet irradiation device 50 has an effective ultraviolet irradiation region (arrangement region of a light source that emits ultraviolet rays) that is a width of a recordable region by the recording head 30 (crossing (for example, orthogonal) with the conveyance direction of the paper P). This is a long-sized ultraviolet irradiation device.
The ultraviolet irradiation device 50 is not limited to this, and is an ultraviolet irradiation device that is shorter than the width of the recordable region by the recording head 30, and moves in the width direction of the recording region by the recording head 30 to irradiate ultraviolet rays. It is also possible to use an ultraviolet irradiation device of the type (so-called carriage type).

As a light source of the ultraviolet irradiation device 50, a mercury lamp (for example, low pressure, medium pressure, high pressure mercury lamp having an operating pressure of several hundred Pa to 1 MPa), metal halide lamp, xenon lamp, cold cathode tube, hot cathode tube, light emitting diode ( LED), semiconductor laser (LD, VCSEL), laser wavelength conversion light source, and the like.
Among these, as a light source of the ultraviolet irradiation device 50, a light emitting diode having a high irradiation energy density with a small change in the state when ink is cured (a change in water content and temperature), that is, a change in curing conditions is small. LED) or semiconductor laser (LD, VCSEL) is preferable.

  A peeling plate 34 is disposed on the downstream side of the ultraviolet irradiation device 50 (on the downstream side in the conveyance direction of the paper P), and the paper P is peeled from the conveyance belt 28. The peeled paper P is transported by a plurality of discharge roller pairs 38 constituting a discharge path 36 on the downstream side of the peeling plate 34 (downstream in the transport direction of the paper P), and is discharged on the top of the housing 14. It is discharged into the container 40.

Next, the operation of the recording apparatus 12 according to this embodiment will be described.
In the recording apparatus 12 according to the present embodiment, the paper P is picked up one by one from the paper supply container 16 by the pick-up roll 18 and is transported to the transport belt 28 via the transport-in path 22.
Next, the sheet P is electrostatically attracted to the conveyance belt 28 by the charging roll 32, and is conveyed below the recording head 30 by the rotation of the conveyance belt 28.
Next, ink is ejected from the recording head 30 onto the paper P, and a target image is recorded.

  Next, the ultraviolet light is irradiated to the ink attached to the paper P by the ultraviolet irradiation device 50, the curing reaction (polymerization reaction) of the ultraviolet polymerizable compound in the ink proceeds, and the ink (image by the ink) is cured. To be fixed on the paper P.

Here, the ultraviolet irradiation conditions of the ultraviolet irradiation device 50 vary depending on the type of the ultraviolet polymerizable compound contained in the ink, but for example, the curing reaction of the ultraviolet polymerizable compound in the ink ejected onto the paper P ( The conditions are preferably such that the polymerization reaction proceeds and cures.
Specifically, as the ultraviolet irradiation conditions, for example, the wavelength region (center wavelength) is 375 nm to 450 nm and the irradiation intensity is 10 mW / cm ^{2 to} 5000 mW / cm ² (desirably 50 mW / cm ^{2 to} 500 mW / cm ^2). The irradiation time is preferably from 0.1 milliseconds to 10 seconds (desirably from 10 milliseconds to 100 milliseconds).

  Next, the paper P on which the ink (image by ink) is fixed (formed) is discharged to the paper discharge container 40 via the discharge path 36.

  In this way, in the recording apparatus 12 according to the present embodiment, the paper P on which ink (image by ink) is fixed (formed) is obtained.

  In the recording apparatus 12 according to the present embodiment, the method of directly ejecting ink droplets onto the surface of the paper P by the recording head 30 has been described. However, the present invention is not limited to this. A method of transferring ink droplets on the intermediate transfer member onto the paper P after ejection is also possible.

  In the recording apparatus 12 according to the present embodiment, the method of fixing (forming) ink (an image using ink) on a sheet as the paper P has been described. However, a roll paper is used as the paper P using a continuous book machine. Alternatively, a method of fixing (forming) ink (image by ink) may be used.

Further, in the recording apparatus 12 according to the present embodiment, the embodiment including one ultraviolet irradiation device 50 has been described. However, in accordance with the components contained in the photocurable water-based ink, a plurality of light irradiation devices are used in combination. There may be.
Further, in the recording apparatus 12 according to the present embodiment, the embodiment including the ultraviolet irradiation device 50 has been described. However, depending on the type of the photocurable water-based ink, active energy rays (active energy light) other than ultraviolet (ultraviolet light) are used. ) May be provided.

  Further, it is needless to say that this embodiment is not limitedly interpreted and is realized within a range that satisfies the requirements of the present invention.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples.

[Preparation of ink]
<Water-based ink 1>
-Cyan pigment aqueous dispersion: 20 parts by mass (colorant, manufactured by Cabot, product name: Cab-o-jet 250C, pigment concentration: 10% by mass, water content: 90% by mass)
-Urethane acrylate oligomer aqueous emulsion: 50 parts by mass (photopolymerizable compound, manufactured by Arakawa Chemical Industries, Ltd., product name: beam set EM-92, ultraviolet polymerizable compound component 40% by mass, water content: 60% by mass)
Polyethylene glycol diacrylate # 400: 10 parts by mass (photopolymerizable compound, manufactured by Shin-Nakamura Chemical Co., Ltd., product name: A-400)
-Glycerin (water-soluble organic solvent): 4 parts by mass-Surfactant (Product name: Surfynol 440, manufactured by Nissin Chemical Co., Ltd.): 3 parts by mass-Kayacure DETX-S (manufactured by Nippon Kayaku Co., Ltd.): 1.5 masses Parts (UV polymerization initiator: thioxanthone compound: 2,4-diethylthioxanthone)
・ Kayacure EPA (manufactured by Nippon Kayaku Co., Ltd.): 1 part by mass (UV polymerization initiation assistant, tertiary amine compound: ethyl 4-dimethylaminobenzoate)
・ 2-hydroxy-4-methoxybenzophenone-5-sulfonic acid: 0.3 part by mass (ultraviolet absorber)

After mixing the materials having the above composition, the mixture was filtered through a 5 μm filter to obtain a cyan ultraviolet curable aqueous ink.
Note that Kayacure DETX-S (2,4-diethylthioxanthone) has an absorption peak at 385 nm.

<Water-based ink 2 to water-based ink 20>
Aqueous ink 2 to aqueous ink 10 were obtained in the same manner as aqueous ink 1 except that the addition amount of the composition of the material to be mixed was changed to Table 1 below.
Aqueous ink 11 to aqueous ink 20 were obtained in the same manner as aqueous ink 1 except that the addition amount of the composition of the material to be mixed was changed to Table 2 below.
In Tables 1 and 2 below, “cyan pigment aqueous dispersion (pigment concentration 10% by mass)”, “urethane acrylate oligomer aqueous emulsion (curable component 40% by mass)”, “polyethylene glycol diacrylate # 400”, “Glycerin”, “surfactant”, “ultraviolet polymerization initiator”, “ultraviolet polymerization initiation aid”, and “ultraviolet absorber” mean the same materials used in the preparation of the water-based ink 1.

In Tables 1 and 2 below, “glycidyl ether (meth) acrylate” is a photopolymerizable compound, and “black pigment aqueous dispersion (pigment concentration 10% by mass)” is “black pigment aqueous dispersion”. (Colorant, manufactured by Cabot Corporation, product name: Cab-o-jet 200Bk, pigment concentration: 10% by mass, water content: 90% by mass) "means" magenta pigment aqueous dispersion (pigment concentration: 10% by mass) ""Means a magenta pigment aqueous dispersion (colorant, manufactured by Cabot, product name: Cab-o-jet 260M, pigment concentration: 10% by mass, water content: 90% by mass)" “Dispersion (pigment concentration: 10% by mass)” is “yellow pigment aqueous dispersion (colorant, manufactured by Cabot, product name: Cab-o-jet 270Y, pigment concentration: 10% by mass, water content: 90% by mass)” The Taste.
Moreover, the unit of the number which shows the addition amount in following Table 1 and Table 2 is a "mass part", and a blank shows that it is 0 mass part.

<Temperature after photocuring of ink>
About the obtained ink, the temperature after photocuring was measured as follows, and the results are shown in Tables 1 and 2.
Specifically, a 18.3 μm thick aqueous ink layer (solid coating pattern) is formed on an OHP (overhead projector) film placed on a slide bench by a wire bar (ROD No. 8), and then a metal halide. The cured film was obtained by adjusting the output of the lamp (maximum irradiation wavelength 365 nm) and the irradiation time (OHP feed rate) so that the integrated dose was ² J / cm ² .
The temperature of the ink after photocuring was measured by installing a radiation temperature sensor (FT-H30 manufactured by Keyence Co., Ltd.) so that the distance from the end of the light source to the cured film was within 20 mm, and the surface temperature was measured. The maximum temperature within the range was defined as “temperature after photocuring”.

[Production and evaluation of ink set]
The obtained water-based inks were combined as shown in Tables 3 to 5 to prepare ink sets.
The obtained ink set was evaluated as follows. The evaluation results are shown in Tables 3 to 5.

-Evaluation of surface condition of cured film-
Using the obtained ink set, each ink was applied to a recording medium placed on a slide bench with a wire bar (ROD No. 8), and each aqueous ink layer having a thickness of 18.3 μm (4-color solid coating) was used. After the pattern is formed, the output of the metal halide lamp (maximum irradiation wavelength 365 nm) and the irradiation time (feed speed of the recording medium) are adjusted, and irradiation is performed so that the integrated irradiation amount satisfies the curing conditions shown in Tables 3 to 5. Thus, a cured film was obtained.
In the evaluation of the surface state, an OHP (overhead projector) film was used as the recording medium.

The curing conditions shown in Tables 3 to 5 are as follows.
Curing condition (1): Integrated dose ² J / cm ²
Curing condition (2): Integrated dose 1.5 J / cm ²
Curing condition (3): cumulative dose 3 J / cm ²

About the obtained cured film, the surface of the cured film was touched with a finger immediately after ultraviolet irradiation (within 3 seconds after completion of ultraviolet irradiation) and 1 minute after ultraviolet irradiation, and it was visually confirmed whether or not a trace remained. The evaluation criteria are as follows.
G1: There is no finger touch mark immediately after G2: There is a finger touch mark immediately after, but there is no finger touch mark when touched after 1 minute G3: There is a finger touch mark even after 1 minute

-Evaluation of deformation of recording media-
Using the obtained ink set, a cured film was obtained in the same manner as in the evaluation of the surface state.
In the evaluation of deformation of the recording medium, as the recording medium, an OHP (overhead projector) film (10 cm × 20 cm) which is a non-permeable recording medium and a permeable paper (Nippon Paper Industries NPi) which is a permeable recording medium are used. Forms 70 and 10 cm × 20 cm) were used, and images of four-color solid coating patterns (images of 2 cm × 20 cm per color) were formed for each.

The recording medium on which the image was formed was placed on a horizontal plane, the difference in height was measured, and the result was defined as “amount of deformation of the recording medium”. The evaluation criteria are as follows.
G1: deformation amount of the recording medium is 5 mm or less G2: deformation amount of the recording medium is 10 mm or less G3: deformation amount of the recording medium exceeds 10 mm

  From the above results, it can be seen that in this example, deformation of the recording medium is suppressed as compared with the comparative example.

DESCRIPTION OF SYMBOLS 12 Inkjet recording device 14 Housing | casing 16 Paper supply container 18 Take-out roll 20 Conveying roller pair 24 Drive roll 26 Followed roll 28 Conveying belt 30 Recording head 30A Ink cartridge 32 Charging roll 34 Release plate 36 Discharge path 38 Discharge roller pair 40 Discharge container 50 UV irradiation device P Paper

Claims (5)

A plurality of photocurable water-based inks containing a colorant, a photopolymerizable compound, a photopolymerization initiator, and water;
The plurality of water-based inks are different from each other in color, and the water-based ink set has a temperature difference within 40 ° C. after photocuring.   The water-based ink set according to claim 1, wherein the water-based ink further contains a light absorption exothermic agent.   An ink cartridge set containing each water-based ink of the water-based ink set according to claim 1. A discharge device for discharging each water-based ink of the water-based ink set according to claim 1 or 2,
A light irradiation device for irradiating the discharged water-based ink with light;
A recording apparatus comprising: Discharging each water-based ink of the water-based ink set according to claim 1 or 2,
Irradiating each discharged water-based ink with light;
A recording method.