JP2019151772A - Active ray curable inkjet ink and image formation method - Google Patents

Abstract

To provide an active ray curable inkjet ink that has a gelator, the active ray curable inkjet ink having excellent pinning properties and capable of preventing the occurrence of image blocking due to storage of printed matter, and an image formation method.SOLUTION: An active ray curable inkjet ink has a pigment, a photopolymerizable compound, a photopolymerization initiator and a gelator, the active ray curable inkjet ink having at least one of a polyester resin or a chlorinated polyolefin resin.SELECTED DRAWING: None

Description

  The present invention relates to an actinic ray curable inkjet ink and an image forming method, and in particular, in an actinic ray curable inkjet ink containing a gelling agent, has excellent pinning properties and suppresses occurrence of image blocking due to storage of printed matter. The present invention relates to an actinic ray curable inkjet ink and the like.

The ink jet recording system is used in various printing fields because it can form an image easily and inexpensively. As one of the ink-jet inks, an ink containing a photopolymerizable compound that cures when irradiated with actinic rays (hereinafter, also simply referred to as “actinic ray curable ink”) is known.
In recent years, actinic ray curable ink does not require a step of drying a solvent or water and can be transferred to a post-processing step in a short time after image formation.
When the ink jet ink contains a gelling agent, the ink gels due to crystallization of the gelling agent when it is landed on the recording medium and cooled. It is known that high-quality images can be obtained. (For example, refer to Patent Document 1).
A method of containing a polyester resin in an ultraviolet curable ink for a printing plate (for example, see Patent Document 2) or a method of adding a polymer component such as a styrene polymer to an inkjet ink containing a specific photopolymerizable monomer (for example, Patent Document 3) is disclosed for the purpose of improving adhesion to a plastic substrate.

When the printed matter formed with actinic ray curable ink is stored in a stacked state, a phenomenon in which an image and a recording medium, or images are fused, so-called blocking may occur. In particular, in an image printed with an ink containing a gelling agent, it has been found that the gelling agent once melts when placed at a high temperature, and then cooled, thereby causing blocking. In particular, in the case of discrete dots, peeling off from the recording medium results in a lack of image, and the quality is greatly reduced.
In Patent Documents 1 to 3, there is no description about blocking in ink containing a gelling agent, and a method for solving the above problem has not been known.

JP 2007-63553 A Japanese Patent No. 5540862 Japanese Patent No. 5994393

  The present invention has been made in view of the above-described problems and circumstances, and a solution to the problem is that, in an actinic ray curable ink-jet ink containing a gelling agent, it has excellent pinning properties and image blocking due to storage of printed matter. It is to provide an actinic ray curable inkjet ink and an image forming method capable of suppressing the occurrence of the above.

In order to solve the above-mentioned problems, the present inventor has an actinic ray curable type that can suppress the occurrence of pinning and image blocking by containing a specific resin in the process of examining the cause of the above-mentioned problem. The present inventors have found that an ink jet and image forming method can be provided, and have reached the present invention.
That is, the said subject which concerns on this invention is solved by the following means.

1. An actinic ray curable inkjet ink containing a pigment, a photopolymerizable compound, a photopolymerization initiator and a gelling agent,
An actinic ray curable inkjet ink comprising at least one of a polyester resin and a chlorinated polyolefin resin.

  2. Item 1 is characterized in that the resin is at least one of a polyester resin having a number average molecular weight in the range of 2000 to 20000 or a chlorinated polyolefin resin having a weight average molecular weight in the range of 10,000 to 100,000. The actinic ray curable inkjet ink described in 1.

  3. 3. The actinic ray curable ink jet according to item 1 or 2, wherein the total content of the resin is in the range of 1.0 to 20.0% by mass relative to the total mass of the ink. ink.

  4). The actinic ray curable inkjet ink according to any one of items 1 to 3, wherein the resin is a chlorinated polyolefin resin having a weight average molecular weight of 10,000 to 50,000.

5. The gelling agent contains at least one of compounds having a structure represented by the following general formula (G1) or (G2), according to any one of the first to fourth items, Actinic ray curable inkjet ink.
General formula (G1): R < ₁₁ > -CO-R < ₁₂ >
General formula (G2): R < ₁₃ > -COO-R < ₁₄ >
[In formula, R < ₁₁ > -R < ₁₄ > represents the alkyl group which contains the linear part within a C12-C26 range, and may also contain a branch each independently. ]

  6). The content of the gelling agent is in the range of 1.0 to 7.0% by mass with respect to the total mass of the ink, as described in any one of items 1 to 5. Actinic ray curable inkjet ink.

  7). The polyfunctional (meth) acrylate containing 2 to 20 ethylene oxide groups or propylene oxide groups as the photopolymerizable compound is contained, any one of items 1 to 6 The actinic ray curable inkjet ink described in 1.

  8). The content of the polyfunctional (meth) acrylate containing the ethylene oxide group or the propylene oxide group in the range of 2 to 20 is in the range of 25.0 to 80.0% by mass with respect to the total mass of the ink. 8. The actinic ray curable ink-jet ink according to item 7, wherein

9. An image forming method using the actinic ray curable inkjet ink according to any one of items 1 to 8,
A step of landing droplets of the actinic ray curable inkjet ink on a recording medium by an inkjet method;
And irradiating the droplets landed on the recording medium with an actinic ray to form an image.

The actinic ray curable inkjet ink containing the gelling agent and having excellent pinning property and capable of suppressing the occurrence of blocking of an image due to storage of a printed material by the above means of the present invention, and An image forming method can be provided.
The expression mechanism or action mechanism of the effect of the present invention is not clear, but is presumed as follows.
The resin according to the present invention has relatively high hydrophobicity in the ink composition and low affinity with the gelling agent. Therefore, after the ink ejected from the head has landed on the base material, it is cooled from the base material side and gelled. In the process of crystallizing the agent, the resin tends to exist near the ink surface at a high concentration.
In particular, as a photopolymerizable compound, a polyfunctional compound containing an ethylene oxide group (hereinafter also referred to as “EO group”) or a propylene oxide group (hereinafter also referred to as “PO group”) having high affinity with a gelling agent. The tendency becomes more remarkable by containing many (meth) acrylates.
Furthermore, in the case of discrete dots, it is considered that the resin component tends to gather near the apex where the distance from the substrate is long. After that, the printed matter cured with actinic rays is placed in a high temperature state, and even if the gelling agent crystals inside the ink are remelted, it is difficult to be exposed due to the presence of resin near the ink surface. It is considered that the occurrence of blocking is suppressed without the image and the recording medium or the images being fused later.

The actinic radiation curable inkjet ink of the present invention is an actinic radiation curable inkjet ink containing a pigment, a photopolymerizable compound, a photopolymerization initiator, and a gelling agent, and is at least one of a polyester resin or a chlorinated polyolefin resin. One of the resins is contained.
This feature is a technical feature common to or corresponding to each of the following embodiments.

  As an embodiment of the present invention, the resin is at least one of a polyester resin having a number average molecular weight in the range of 2000 to 20000 or a chlorinated polyolefin resin having a weight average molecular weight in the range of 10,000 to 100,000. Is preferable in terms of good solubility in ink. In particular, a chlorinated polyolefin resin having a weight average molecular weight in the range of 10,000 to 50,000 is preferable.

  Moreover, it is preferable that the total content of the resin is in the range of 1.0 to 20.0% by mass with respect to the total mass of the ink because the effect of suppressing the occurrence of blocking is more exhibited. .

It is preferable that the gelling agent contains at least one of the compounds having the structure represented by the general formula (G1) or (G2) from the viewpoint that the pinning property can be further improved.
Further, the content of the gelling agent is in the range of 1.0 to 7.0% by mass with respect to the total mass of the ink, so that the gloss of the image can be suppressed and the pinning property can be improved. Is preferable.

When the photopolymerizable compound contains a polyfunctional (meth) acrylate containing 2 to 20 ethylene oxide groups or propylene oxide groups, the resin is likely to be present at a high concentration in the vicinity of the ink surface. This is preferable in that the occurrence of blocking can be reliably suppressed.
In addition, the content of the polyfunctional (meth) acrylate containing 2 to 20 ethylene oxide groups or propylene oxide groups in the range of 25.0 to 80.0% by mass with respect to the total mass of the ink. It is preferable that there is more an effect of suppressing the occurrence of blocking.

  The image forming method of the present invention is an image forming method using the actinic radiation curable inkjet ink, the step of landing droplets of the actinic radiation curable inkjet ink on a recording medium by an inkjet method, and the recording And irradiating the droplets landed on the medium with an actinic ray to form an image. Thereby, it is excellent in pinning property and generation | occurrence | production of the blocking of the image by preservation | save of printed matter can be suppressed.

  Hereinafter, the present invention, its components, and modes and modes for carrying out the present invention will be described. In addition, in this application, "-" is used in the meaning which includes the numerical value described before and behind that as a lower limit and an upper limit.

1. Actinic ray curable inkjet ink The actinic ray curable inkjet ink of the present invention (hereinafter also simply referred to as “inkjet ink” or “ink”) contains a pigment, a photopolymerizable compound, a photopolymerization initiator, and a gelling agent. An actinic radiation curable inkjet ink that contains at least one of a polyester resin and a chlorinated polyolefin resin.

1-1. Resin according to the present invention The ink according to the present invention contains at least one of a polyester resin and a chlorinated polyolefin resin.
The resin is at least one of a polyester resin having a number average molecular weight in the range of 2000 to 20000 or a chlorinated polyolefin resin having a weight average molecular weight in the range of 10,000 to 100,000. It is preferable at the point which is favorable.

The number average molecular weight and weight average molecular weight in the present invention mean values measured under the following conditions by GPC (Gel Permeation Chromatography).
-Equipment: GPC-8020 (manufactured by Tosoh Corporation)
Column: TSK G2000HXL and G4000HXL (manufactured by Tosoh Corporation)
・ Temperature: 40 ℃
・ Solvent: THF (tetrahydrofuran)
Flow rate: 1.0 mL / min 1 mL of a polymer having a concentration of 0.5% by mass is injected, and a molecular weight calibration curve prepared from a monodisperse polystyrene standard sample is used to calculate the weight from the molecular weight distribution of the polymer measured under the above conditions. The number average molecular weight Mn and the weight average molecular weight Mw of the coalescence are calculated.

The resin preferably has good solubility in the photopolymerizable compound according to the present invention. For this reason, those having a cross-linked structure are unsuitable and are preferably chain-like. Even in the case of a chain, those having an excessively high molecular weight are not preferable because they are remarkably impaired in dissolution in ink, and from this viewpoint, the average molecular weight of the resin is determined as described above.
Further, regarding the solubility, it is preferable that the polymer is not very rigid and the crystallinity is not too high. In addition, it is advantageous that it can be procured practically at low cost. Further, those having an arbitrary acid value or hydroxy value (also referred to as hydroxyl value) can be used depending on solubility and other required properties.
The polyester resin and the chlorinated polyolefin resin are not particularly limited, and can be appropriately selected from known polymers.

1-1-1. Polyester resin A polyester resin can be obtained using a polyhydric alcohol component and a polyvalent carboxylic acid component such as a polyvalent carboxylic acid, a polyvalent carboxylic acid anhydride, or a polyvalent carboxylic acid ester.
Examples of the polyhydric alcohol component include divalent alcohols (diols), specifically alkylene glycols having 2 to 36 carbon atoms (ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1 , 4-butylene glycol, 1,6-hexanediol, etc.), alkylene ether glycols in the range of 4 to 36 carbon atoms (diethylene glycol, triethylene glycol, dipropylene glycol, polyethylene glycol, polypropylene glycol, polybutylene glycol, etc.), An alicyclic diol (1,4-cyclohexanedimethanol, hydrogenated bisphenol A, etc.) within the range of 6 to 36 carbon atoms, an alkylene oxide (ethylene oxide (hereinafter referred to as “ethylene oxide”) within the range of 2 to 4 carbon atoms of the alicyclic diol. , Abbreviated as EO. , Propylene oxide (hereinafter abbreviated as PO), butylene oxide (hereinafter abbreviated as BO)) adduct (range of 1 to 30 moles added) or bisphenols (bisphenol A, bisphenol F, bisphenol S, etc.) ) Of alkylene oxide (EO, PO, BO, etc.) within the range of 2 to 4 carbon atoms (range of added mole number of 2 to 30) and the like. These may be used individually by 1 type and may use 2 or more types together.

  Examples of the polyvalent carboxylic acid component include divalent carboxylic acids (dicarboxylic acids), specifically, alkane dicarboxylic acids having a carbon number of 4 to 36 (succinic acid, apidic acid, sebacic acid, etc.), and alkenyl succinic acids. (Such as dodecenyl succinic acid), alicyclic dicarboxylic acids (dimer acid (dimerized linoleic acid), etc.) within the range of 4 to 36 carbon atoms, alkene dicarboxylic acids (maleic acid, fumaric acid within the range of 4 to 36 carbon atoms) , Citraconic acid, mesaconic acid, etc.), or aromatic dicarboxylic acids (phthalic acid, isophthalic acid, terephthalic acid or derivatives thereof, naphthalenedicarboxylic acid, etc.) having 8 to 36 carbon atoms. These may be used individually by 1 type and may use 2 or more types together.

The polyester resin preferably has good solubility in the photopolymerizable compound according to the present invention. Therefore, those having a crosslinked structure cannot be used, and a chain shape is preferable. Even if it is chain-like, the polyester resin having an excessively large average molecular weight is not preferable because it can significantly reduce workability when dissolved in ink, and the number average molecular weight is preferably in the range of 1000 to 50000, 2000 A range of ˜20,000 is more preferable.
Furthermore, it is also important for the solubility that the polyester resin is not very rigid and the crystallinity is not too high. In addition, it is also important that the polyester resin is practically inexpensive and can be procured easily. Also, those having any acid value or hydroxy value can be used depending on solubility and other conveniences.

  Commercially available products may be used as the polyester resin. Examples of the commercially available products include trade name: Byron 802 (manufactured by Toyobo Co., Ltd., number average molecular weight: 3000), trade name: Byron GK810 (Toyobo Co., Ltd.). Product number: Byron 650 (manufactured by Toyobo Co., Ltd., number average molecular weight: 23000), product name: Elitel UE-3320 (manufactured by Unitika Ltd., number average molecular weight: 1800), product name: Elitel UE-3380 (manufactured by Unitika Ltd., number average molecular weight: 8000), trade name: Elitel UE-3250 (produced by Unitika Ltd., number average molecular weight: 18000) and the like. These may be used individually by 1 type and may use 2 or more types together.

The polyester resin precipitates when the active energy ray-curable composition is dropped into a solvent such as methanol. Therefore, the polyester resin can be isolated by filtration or the like. When analyzed by infrared spectroscopy, the polyester resin is 1700 cm. It can be confirmed as an absorption peak derived from an ester bond in the vicinity of ^-1 . Other components can be confirmed to be the same as the polyester resin by mass spectrometry gas chromatogram method or the like.

  The content of the polyester resin is preferably in the range of 1.0 to 20% by mass with respect to the total ink mass in terms of more effectively suppressing the occurrence of blocking.

1-1-2. Chlorinated polyolefin resin Examples of the chlorinated polyolefin resin include chlorinated polyethylene, chlorinated polypropylene, and chlorinated polybutylene.
The chlorinated polyolefin resin preferably has good solubility in the photopolymerizable compound according to the present invention. Therefore, those having a crosslinked structure cannot be used, and a chain shape is preferable. Even if it is chain-like, an excessively large average molecular weight of the chlorinated polyolefin resin is not preferable because the workability is remarkably impaired when dissolved in the ink, and the weight average molecular weight is in the range of 5,000 to 200,000. It is preferable that it is in the range of 10,000 to 100,000, and more preferably in the range of 10,000 to 50,000.
Furthermore, regarding solubility, it is also important that the chlorinated polyolefin resin is not very rigid and the crystallinity is not too high. In addition, it is also important that it can be procured practically at low cost.

  Commercially available products may be used as the chlorinated polyolefin resin. Examples of the commercially available products include trade name: Supercron L-206 (manufactured by Nippon Paper Industries Co., Ltd., weight average molecular weight: 9000), trade name: Super. Cron 370M (made by Nippon Paper Industries Co., Ltd., weight average molecular weight: 10,000), trade name: Super Clone 814HS (made by Nippon Paper Industries Co., Ltd., weight average molecular weight: 20000), trade name: HARDREN 14-LWP (manufactured by Toyobo Co., Ltd., number average molecular weight) : 40000), trade name: HARDREN DX-530P (manufactured by Toyobo Co., Ltd., number average molecular weight: 100000), trade name: HARDREN 15-LP (manufactured by Toyobo Co., Ltd., number average molecular weight: 150000), trade name: HARDREN 13- LP (manufactured by Toyobo Co., Ltd., number average molecular weight: 200000) and the like. These may be used individually by 1 type and may use 2 or more types together.

  The content of the chlorinated polyolefin resin is preferably in the range of 1.0 to 20% by mass with respect to the total ink mass in terms of more effectively suppressing the occurrence of blocking.

1-2. Pigments Examples of pigments include:
C. I. Pigment Yellow 1, 2, 3, 12, 13, 14, 16, 17, 73, 74, 75, 81, 83, 87, 93, 95, 97, 98, 109, 114, 120, 128, 129, 138, 150, 151, 154, 155, 180, 185, 213
C. I. Pigment Red 5, 7, 12, 22, 38, 48: 1, 48: 2, 48: 4, 49: 1, 53: 1, 57: 1, 63: 1, 101, 112, 122, 123, 144, 146, 168, 184, 185, 202
C. I. Pigment Violet 19, 23, 37
C. I. Pigment Violet 19 / Pigment Red 202
C. I. Pigment Blue 1, 2, 3, 15: 1, 15: 2, 15: 3, 15: 4, 18, 22, 27, 29, 60
C. I. Pigment Green 7,36
C. I. Pigment Orange 36, 43, 64, 71
C. I. Pigment White 6, 18, 21
C. I. Pigment Black 7

  The pigment may be subjected to a surface treatment for imparting acidic groups (acid treatment), a surface treatment for covering the entire pigment with a resin, or such a surface treatment may not be performed. May be.

The average particle diameter of the pigment particles is preferably in the range of 0.08 to 0.5 μm from the viewpoint of further improving the dischargeability from the inkjet head, and the maximum particle diameter of the pigment particles is 0.3 to 10 μm. It is preferable to be within the range.
The average particle diameter of the pigment particles means a value obtained by a dynamic light scattering method using Data Sizer Nano ZSP, manufactured by Malvern. The ink containing the pigment has a high concentration and does not transmit light with this measuring instrument. Therefore, the ink is diluted 200 times before measurement. The measurement temperature is room temperature (25 ° C.).

  The pigment content is preferably in the range of 1.0 to 10.0% by mass and more preferably in the range of 2.0 to 5.5% by mass with respect to the total mass of the ink.

1-3. Photopolymerizable compound The photopolymerizable compound is a compound that crosslinks or polymerizes when irradiated with actinic rays.
Examples of actinic rays include ultraviolet rays, electron beams, α rays, γ rays and X rays. From the viewpoint of safety and from the viewpoint that polymerization and crosslinking can be generated even with a lower energy amount, ultraviolet rays or electron beams are preferable.

  The photopolymerizable compound can be a radical polymerizable compound or a cationic polymerizable compound. A radical polymerizable compound is preferable from the viewpoint that it is easy to cause polymerization and crosslinking and can be selected from various compounds according to the image to be formed.

  The radical polymerizable compound is a compound having an ethylenically unsaturated bond capable of radical polymerization. The radical polymerizable compound may be any of a monomer, a polymerizable oligomer, a prepolymer, or a mixture thereof. Only one kind of radically polymerizable compound may be contained in the ink, or two or more kinds thereof may be contained.

  Examples of the compound having an ethylenically unsaturated bond capable of radical polymerization include an unsaturated carboxylic acid and a salt thereof, an unsaturated carboxylic acid ester, an unsaturated carboxylic acid urethane compound, an unsaturated carboxylic acid amide compound and an anhydride thereof, and acrylonitrile. , Styrene, unsaturated polyester, unsaturated polyether, unsaturated polyamide, unsaturated urethane, and the like. Examples of the unsaturated carboxylic acid include (meth) acrylic acid, itaconic acid, crotonic acid, isocrotonic acid, maleic acid and the like. Among these, unsaturated carboxylic acid esters are preferable, and (meth) acrylates are more preferable. “(Meth) acrylate” means acrylate or methacrylate. The (meth) acrylate may be monofunctional, bifunctional, trifunctional or higher.

  Examples of monofunctional (meth) acrylates include isoamyl (meth) acrylate, stearyl (meth) acrylate, lauryl (meth) acrylate, octyl (meth) acrylate, decyl (meth) acrylate, isomustyl (meth) acrylate, and isostearyl. (Meth) acrylate, 2-ethylhexyl-diglycol (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 2- (meth) acryloyloxyethyl hexahydrophthalic acid, butoxyethyl (meth) acrylate, ethoxydiethylene glycol (meta ) Acrylate, methoxydiethylene glycol (meth) acrylate, methoxypolyethylene glycol (meth) acrylate, methoxypropylene glycol (meth) acrylate, pheno Siethyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, isobornyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate 2- (meth) acryloyloxyethyl succinic acid, 2- (meth) acryloyloxyethyl phthalic acid, 2- (meth) acryloyloxyethyl-2-hydroxyethyl-phthalic acid and t-butylcyclohexyl (meth) An acrylate etc. are mentioned.

  Examples of the bifunctional (meth) acrylate include diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, dipropylene glycol di ( (Meth) acrylate, tripropylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, 1,9-nonane Diol (meth) acrylate, neopentyl glycol di (meth) acrylate, dimethylol-tricyclodecane di (meth) acrylate, bisphenol A PO adduct di (meth) acrylate, Rokishipibarin acid neopentyl glycol di (meth) acrylate, polytetramethylene glycol di (meth) acrylate, and and modified products thereof.

Examples of the tri- or higher functional (meth) acrylate include trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, and ditrimethylolpropane. Examples include tetra (meth) acrylate, glycerin propoxytri (meth) acrylate, pentaerythritol ethoxytetra (meth) acrylate, and modified products thereof.
Examples of the oligomer include an oligomer having a (meth) acryloyl group including a polyester acrylate oligomer, and modified products thereof.

Examples of the modified product include an ethylene oxide-modified (EO-modified) acrylate having an ethylene oxide group inserted therein, and a propylene oxide-modified (PO-modified) acrylate having a propylene oxide group inserted therein. Specific examples thereof include 3PO-modified trimethylolpropane triacrylate, 9EO-modified trimethylolpropane triacrylate, and EO-modified trimethylolpropane trimethacrylate.
The photopolymerizable compound according to the present invention contains a polyfunctional (meth) acrylate containing 2 to 20 ethylene oxide groups or propylene oxide groups, so that the resin is present at a high concentration in the vicinity of the ink surface. This is preferable in that it is easy to control and the occurrence of blocking can be reliably suppressed.

The photopolymerizable compound preferably includes a (meth) acrylate compound having a molecular weight in the range of 200 to 1500 and a ClogP value in the range of 4.0 to 7.0.
The photopolymerizable compound more preferably has two or more (meth) acrylate groups.
The molecular weight of the photopolymerizable compound is in the range of 200 to 1500 as described above, and more preferably in the range of 240 to 800.

The content of the photopolymerizable compound may be in a range in which the ink irradiated with actinic rays is sufficiently cured, and is preferably in the range of 1 to 97% by mass with respect to the total mass of the ink, 30 to More preferably, it is within the range of 95% by mass.
Furthermore, the polyfunctional (meth) acrylate containing 2 to 20 ethylene oxide groups or propylene oxide groups in the range of 25.0 to 80.0% by mass with respect to the total mass of the ink. In particular, the effect of suppressing the occurrence of blocking is more preferable.

1-4. Photopolymerization initiator The photopolymerization initiator is a photoradical initiator when the photopolymerizable compound is a radical polymerizable compound, and a photoacid generator when the photopolymerizable compound is a cationic polymerizable compound. is there.
As for a photoinitiator, only 1 type may be contained in the ink and 2 or more types may be contained in it. The photopolymerization initiator may be a combination of both a photo radical initiator and a photo acid generator.

  The photo radical initiator can be a cleavage type radical initiator or a hydrogen abstraction type radical initiator.

  Examples of cleavage type radical initiators include diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, benzyldimethyl ketal, 1- (4-isopropylphenyl) -2-hydroxy-2- Methylpropan-1-one, 4- (2-hydroxyethoxy) phenyl- (2-hydroxy-2-propyl) ketone, 1-hydroxycyclohexyl-phenylketone, 2-methyl-2-morpholino (4-thiomethylphenyl) An acetophenone-based initiator including propan-1-one and 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone, a benzoin-based initiator including benzoin, benzoin methyl ether and benzoin isopropyl ether; 2,4,6-trimethylbenzoindipheni Acylphosphine oxide initiator containing a phosphine oxide, benzyl and methyl phenylglyoxylate ester.

  Examples of hydrogen abstraction type radical initiators include benzophenone, methyl-4-phenylbenzophenone o-benzoylbenzoate, 4,4'-dichlorobenzophenone, hydroxybenzophenone, 4-benzoyl-4'-methyl-diphenyl sulfide, acrylated Benzophenone-based initiators, including benzophenone, 3,3 ', 4,4'-tetra (t-butylperoxycarbonyl) benzophenone and 3,3'-dimethyl-4-methoxybenzophenone, 2-isopropylthioxanthone, 2,4- Thioxanthone initiators including dimethylthioxanthone, 2,4-diethylthioxanthone and 2,4-dichlorothioxanthone, aminobenzophenone initiators including Michler's ketone and 4,4'-diethylaminobenzophenone, 10 Butyl-2-chloro acridone, 2-ethyl anthraquinone, include 9,10-phenanthrenequinone and camphorquinone.

  Examples of the photoacid generator include the compounds described in Organic Electronics Materials Research Group, “Organic Materials for Imaging”, Bunshin Publishing (1993), pages 187-192.

  Content of a photoinitiator should just be a range which can fully harden a photopolymerizable compound, for example, can be in the range of 0.01-10 mass% with respect to the total mass of an ink.

1-5. Gelling agent The gelling agent has a function of temporarily fixing (pinning) ink droplets landed on a recording medium in a gel state. When ink containing a gelling agent is pinned in a gel state, wetting and spreading of the ink is suppressed and adjacent dots are less likely to be the same, so a higher definition image can be formed.

  The gelling agent is preferably crystallized at a temperature below the gelation temperature of the ink. The gelation temperature refers to a temperature at which the viscosity of the ink changes abruptly when the gelled solderized or liquefied ink is cooled and the gelling agent undergoes a phase transition from sol to gel. Specifically, the sol or liquefied ink is cooled while measuring the viscosity with a viscoelasticity measuring device (for example, MCR300, manufactured by Anton Paar), and the temperature at which the viscosity rapidly increases is measured. The gelation temperature of

  When the gelling agent is crystallized in the ink, a structure in which the photopolymerizable compound is included in the three-dimensional space formed by the gelling agent that has been crystallized in a plate shape may be formed (such a structure). Hereafter referred to as the “cardhouse structure”). When the card house structure is formed, since the liquid photopolymerizable compound is held in the space, the ink droplets are less likely to spread and the pinning property of the ink is further increased. When the pinning property of the ink is increased, the ink droplets that have landed on the recording medium are less likely to coalesce, and a higher definition image can be formed.

  In order to form the card house structure, it is preferable that the photopolymerizable compound dissolved in the ink and the gelling agent are compatible.

  Examples of gelling agents suitable for the formation of card house structures include aliphatic ketones, aliphatic esters, petroleum waxes, vegetable waxes, animal waxes, mineral waxes, hardened castor oil, modified waxes, higher fatty acids, Higher alcohols, hydroxystearic acid, fatty acid amides including N-substituted fatty acid amides and special fatty acid amides, higher amines, esters of sucrose fatty acids, synthetic waxes, dibenzylidene sorbitol, dimer acids and dimer diols are included. Of these, aliphatic ketones, aliphatic esters, higher fatty acids, and higher alcohols having a hydrocarbon group in the range of 9 to 25 carbon atoms are preferred from the viewpoint of further improving pinning properties. Only one type of gelling agent may be included in the ink, or two or more types may be included.

  Examples of aliphatic ketones include dilignoseryl ketone, dibehenyl ketone, distearyl ketone, dieicosyl ketone, dipalmityl ketone, dilauryl ketone, dimyristyl ketone, myristyl palmityl ketone and palmityl stearyl ketone. It is.

Examples of aliphatic esters include fatty acid esters of monoalcohols such as behenyl behenate, icosyl icosanoate, oleyl palmitate; glycerin fatty acid ester, sorbitan fatty acid ester, propylene glycol fatty acid ester, ethylene glycol fatty acid ester and polyoxyethylene fatty acid ester And fatty acid esters of polyhydric alcohols.
Examples of commercially available aliphatic esters include EMALEX series, manufactured by Nippon Emulsion Co., Ltd. ("EMALEX" is a registered trademark of the company), Riquemar series and Poem series, Riken Vitamin Co., Ltd. ("Riquemar" and "Poem" Both are registered trademarks of the company.

  Examples of higher fatty acids include behenic acid, arachidic acid, stearic acid, palmitic acid, myristic acid, lauric acid, oleic acid, and erucic acid.

  Examples of higher alcohols include stearyl alcohol and behenyl alcohol.

  Among these, aliphatic ketones represented by the following general formula (G1) and aliphatic esters represented by the following general formula (G2) are particularly preferable.

General formula (G1): R < ₁₁ > -CO-R < ₁₂ >
In General Formula (G1), R ₁₁ and R ₁₂ each independently represent an alkyl group that includes a straight chain portion having ₁₂ to 26 carbon atoms and may include a branch.

General formula (G2): R < ₁₃ > -COO-R < ₁₄ >
In General Formula (G2), R ₁₃ and R ₁₄ each independently represent an alkyl group that includes a straight chain portion having 12 to 26 carbon atoms and may include a branch.

  In General Formulas (G1) and (G2), since the linear or branched hydrocarbon group has 12 or more carbon atoms, the aliphatic ketone represented by General Formula (G1) or General Formula (G2) The crystallinity of the aliphatic ester represented by the formula is further increased, and more sufficient space is generated in the card house structure. For this reason, the photopolymerizable compound can be easily contained in the space, and the pinning property of the ink becomes higher. Since the linear or branched hydrocarbon group has 26 or less carbon atoms, the melting point of the aliphatic ketone represented by the general formula (G1) or the aliphatic ester represented by the general formula (G2) is low. The ink does not rise excessively, and it is not necessary to heat the ink excessively when ejecting the ink.

From the viewpoint of increasing the gelation temperature of the ink, causing the ink to gel more rapidly after landing, and increasing the compatibility with a specific low molecular weight compound, at least one of R ₁₁ and R ₁₂ or R ₁₃ and R Preferably, at least one of ₁₄ is a saturated hydrocarbon group having 14 to 23 carbon atoms; both R ₁₁ and R ₁₂ or both R ₁₃ and R ₁₄ are saturated with 14 to 23 carbon atoms. More preferably, it is a hydrocarbon group.

Examples of the aliphatic ketone represented by the general formula (G1) include dilignoseryl ketone (carbon number: 23 to 24), dibehenyl ketone (carbon number: 21 to 22), distearyl ketone (carbon number: 17 To 18), dieicosyl ketone (carbon number: 19 to 20), dipalmityl ketone (carbon number: 15 to 16), dimyristyl ketone (carbon number: 13 to 14), dilauryl ketone (carbon number: 11). -12), lauryl myristyl ketone (carbon number: 11-14), lauryl palmityl ketone (carbon number: 11-16), myristyl palmityl ketone (carbon number: 13-16), myristyl stearyl ketone (carbon number: 13) -18), myristyl behenyl ketone (carbon number: 13-22), palmityl stearyl ketone (carbon number: 15-18), valmityl behenyl ketone (carbon number: 5 to 22) and stearyl behenyl ketone (carbon number: 17-22) are included. The number of carbons in the parenthesis represents the number of carbons of each of the two hydrocarbon groups separated by the carbonyl group.
Examples of commercially available products of the aliphatic ketone represented by the general formula (G1) include 18-Pentriacontanon, manufactured by Alfa Aeser, Hentriacontan-16-on, manufactured by Alfa Aeser, and Kao wax T-1, manufactured by Kao Corporation. included.

Examples of the aliphatic ester represented by the general formula (G2) include behenyl behenate (carbon number: 21 to 22), icosyl icosanoate (carbon number: 19 to 20), stearyl stearate (carbon number: 17 to 18), palmitic acid stearate (carbon number: 17 to 16), lauryl stearate (carbon number: 17 to 12), cetyl palmitate (carbon number: 15 to 6), stearyl palmitate (carbon number: 15 to 18) , Myristyl myristate (carbon number: 13-14), cetyl myristate (carbon number: 13-16), octyldodecyl myristate (carbon number: 13-20), stearyl oleate (carbon number: 17-18), Stearyl erucate (carbon number: 21-18), stearyl linoleate (carbon number: 17-18), behenyl oleate (carbon number: 18-22) and Arachidyl linoleic acid (carbon number: 17 to 20) are included. The number of carbons in the parenthesis represents the number of carbons of each of the two hydrocarbon groups separated by the ester group.
Examples of commercially available products of the aliphatic ester represented by the general formula (G2) include Unistar M-2222SL and Spalm acetyl, manufactured by NOF Corporation (“Unistar” is a registered trademark of the company), Exepearl SS and Exepearl MY-M, Made by Kao Corporation (“EXPEARL” is a registered trademark of the company), EMALEX CC-18 and EMALEX CC-10, manufactured by Nippon Emulsion Co., Ltd. (“EMALEX” is a registered trademark of the company), Amreps PC, manufactured by Higher Alcohol Industry Co., Ltd. "Is a registered trademark of the company).

The content of the gelling agent is preferably in the range of 1.0 to 10.0% by mass with respect to the total mass of the ink. By setting the content of the gelling agent to 1.0% by mass or more, the pinning property of the ink can be sufficiently enhanced and a higher definition image can be formed. Further, by enhancing the pinning property of the ink, it is possible to suppress insufficient color development due to the ink entering the inside of the recording medium, particularly when an image is formed on the water-absorbing recording medium. By setting the content of the gelling agent to 10.0% by mass or less, precipitation of the gelling agent from the surface of the formed image can be suppressed, and the ejection property of the ink from the inkjet head is hardly impaired.
The content of the gelling agent is more preferably in the range of 1.0 to 7.0% by mass, and in the range of 2.0 to 5.0% by mass with respect to the total mass of the ink. More preferably, it is most preferably in the range of 2.5 to 4.0% by mass.

1-6. Other components The actinic ray curable ink jet ink of the present invention is a polymer dispersant, a pigment derivative, a photopolymerization initiator auxiliary agent, a polymerization inhibitor, a surfactant, etc., as long as the effects of the present invention are obtained. An ingredient may be further included. One of these components may be included in the ink, or two or more of these components may be included.

1-6-1. Polymer Dispersant The polymer dispersant is not particularly limited as long as it is a polymer that contributes to pigment dispersion. For example, a polymer dispersant having a plurality of repeating units connected in the molecule and having a weight average molecular weight (Mw) of 1000 or more. Can be used.

  Examples of polymer dispersants include hydroxy group-containing carboxylic acid esters, salts of long-chain polyaminoamides and high-molecular-weight acid esters, salts of high-molecular-weight polycarboxylic acids, salts of long-chain polyaminoamides and polar acid esters, and high-molecular-weight unsaturateds. Acid ester, polymer copolymer, modified polyurethane, modified polyacrylate, polyether ester type anionic activator, naphthalene sulfonic acid formalin condensate salt, aromatic sulfonic acid formalin condensate salt, polyoxyethylene alkyl phosphate ester, Examples include polyoxyethylene nonylphenyl ether and stearylamine acetate.

Further, as the polymer dispersant, for example, a comb-type block copolymer having a basic group may be used.
Comb block copolymer in basic block-containing comb block copolymer is a linear polymer that forms the main chain and graft polymerization to each structural unit derived from the monomer that forms the main chain And another type of polymer.
As the side chain, a long-chain polyoxyalkyl group (EO-PO copolymer group) is preferable. Examples of the comb block copolymer include those in which the main chain is a polymer of an acrylate ester and the side chain is a long-chain polyoxyalkyl group (EO-PO copolymer group).
The basic group in the comb block copolymer having a basic group is preferably a quaternary, tertiary, secondary or primary amine group.

  The weight average molecular weight of the polymer dispersant is preferably in the range of 1000 to 50000, and more preferably in the range of 5000 to 30000. The weight average molecular weight of the polymer dispersant can be determined in terms of polystyrene by gel permeation chromatography (GPC method).

  Examples of commercially available polymer dispersants containing a basic group include DISPERBYK-109, 161, 168, 180, 2013, 2155, BYKJET-9150 and BYKJET-9151 manufactured by BYK; Efka-4431 manufactured by BASF. , PX4701; PB-821, 822, and 824 manufactured by Ajinomoto Fine-Techno; Solsperse 24000GR, 32000, 39000, 71000, and J-200 manufactured by Lubrizol. “DISPERBYK” and “BYKJET” are registered trademarks of BYK, “Efka” is a registered trademark of BASF, and “Solsperse” is a registered trademark of Lubrizol.

The content of the polymer dispersant is preferably in the range of 30 to 70% by mass with respect to the total mass of the pigment. When the content of the polymer dispersant is 30% by mass or more with respect to the pigment, not only the aggregation of the pigment can be made more difficult to occur, but also the interaction between the pigment and the gelling agent is effectively suppressed, Gloss fluctuation and dot diameter fluctuation under high temperature storage can be further suppressed. When the content of the polymer dispersant is more than 70% by mass with respect to the pigment, the excess polymer dispersant that does not contribute to the pigment dispersion causes gelation inhibition, and the initial gloss value and the initial dot diameter become large. End up.
The content of the polymer dispersant is more preferably in the range of 35 to 65% by mass with respect to the total mass of the pigment.
Only one type of polymer dispersant may be included in the inkjet ink of the present invention, or two or more types of polymer dispersants may be included.

  The dispersion of the pigment and the polymer dispersant can be performed by, for example, a ball mill, a sand mill, an attritor, a roll mill, an agitator, a Henschel mixer, a colloid mill, an ultrasonic homogenizer, a pearl mill, a wet jet mill, or a paint shaker.

1-6-2. Pigment derivative A pigment derivative may be contained for the purpose of improving the dispersibility of the pigment. The pigment derivative is preferably obtained by introducing an acidic group such as a sulfonic acid group or a carboxy group into the pigment.

  The content of acidic groups in the pigment derivative is 0.5 mol or more, preferably 1 mol or more with respect to 1 mol of the pigment skeleton of the pigment derivative.

  The basic structure of the pigment derivative is not particularly limited, but may be the same as the basic structure of the pigment used in combination.

  The pigment derivative having a sulfonic acid group or a carboxy group can be synthesized by a known method. The pigment may be surface-modified with a chemical such as concentrated sulfuric acid to introduce a sulfonic acid group or a carboxy group, or a raw material having a sulfonic acid group or a carboxy group may be synthesized as a starting material.

The content of the pigment derivative may be in the range of 2 to 10% by mass with respect to the total mass of the pigment. When the content of the pigment derivative is 2% by mass or more, since the pigment is sufficiently dispersed, the discharge stability is likely to increase. When the content of the pigment derivative is 10% by mass or less, aggregation of the pigment derivative is suppressed, and the discharge stability is hardly impaired. Moreover, it is easy to suppress that the amount of gelling agents which can be crystallized decreases, and the pinning effect is easily obtained.
The content of the pigment derivative is more preferably in the range of 2 to 4% by mass with respect to the total mass of the pigment.

  The pigment derivative has a structure in common with the pigment and easily forms a π-π bond with the pigment; the sulfonic acid group or carboxy group easily forms an acid-base bond with the acidic group of the polymer dispersant. Therefore, by further adding the pigment derivative, the polymer dispersant can be indirectly adsorbed on the surface of the pigment particle via the pigment derivative, so that the dispersibility of the pigment particle can be further enhanced.

1-6-3. Photopolymerization initiator assistant Examples of photopolymerization initiator assistants include tertiary amine compounds including aromatic tertiary amine compounds. Examples of aromatic tertiary amine compounds include N, N-dimethylaniline, N, N-diethylaniline, N, N-dimethyl-p-toluidine, N, N-dimethylamino-p-benzoic acid ethyl ester, N, N-dimethylamino-p-benzoic acid isoamyl ethyl ester, N, N-dihydroxyethylaniline, triethylamine and N, N-dimethylhexylamine are included.

1-6-4. Polymerization inhibitors Examples of polymerization inhibitors include (alkyl) phenol, hydroquinone, catechol, resorcin, p-methoxyphenol, t-butylcatechol, t-butylhydroquinone, pyrogallol, 1,1-picrylhydrazyl, phenothiazine, p-benzoquinone, nitrosobenzene, 2,5-di-t-butyl-p-benzoquinone, dithiobenzoyl disulfide, picric acid, cuperone, aluminum N-nitrosophenylhydroxyamine, tri-p-nitrophenylmethyl, N- (3 Oxyanilino-1,3-dimethylbutylidene) aniline oxide, dibutylcresol, cyclohexanone oxime cresol, guaiacol, o-isopropylphenol, butyraloxime, methyl ethyl ketoxime and cyclohexanone Contains oximes.

1-6-5. Surfactants Examples of surfactants include anionic surfactants such as dialkyl sulfosuccinates, alkyl naphthalene sulfonates and fatty acid salts, polyoxyethylene alkyl ethers, polyoxyethylene alkyl allyl ethers, acetylene glycols And nonionic surfactants such as polyoxyethylene / polyoxypropylene block copolymers, cationic surfactants such as alkylamine salts and quaternary ammonium salts, and silicone-based and fluorine-based surfactants. .

  Examples of silicone surfactants include polyether-modified polysiloxane compounds, specifically, KF-351A, KF-352A, KF-642 and X-22-4272, manufactured by Shin-Etsu Chemical Co., Ltd., BYK307, BYK345, BYK347 and BYK348, manufactured by Big Chemie ("BYK" is a registered trademark of the company), TSF4452, manufactured by Momentive Performance Materials, Inc. are included.

  The fluorosurfactant means a compound in which a part or all of the fluorosurfactant is substituted with fluorine in place of hydrogen bonded to carbon of the hydrophobic group of a normal surfactant. Examples of fluorosurfactants include Megafac F, manufactured by DIC ("Megafac" is a registered trademark of the company), Surflon, manufactured by AGC Seikagaku ("Surflon" is a registered trademark of the company), Fluorad FC, 3M (“Fluorad” is a registered trademark of the company), Monfluor, manufactured by Imperial Chemical Industry, Zonyls, manufactured by Ei Dupont de Nemours & Company, Licowet VPF, manufactured by Lebevelke Hoechst, And FTERGENT, manufactured by Neos ("FTERGENT" is a registered trademark of the same company).

  The amount of the surfactant can be arbitrarily set as long as the effect of the present invention is obtained. The amount of the surfactant can be, for example, 0.001% by mass or more and less than 1.0% by mass with respect to the total mass of the ink.

1-7. Physical properties of actinic radiation curable ink jet ink From the viewpoint of further improving the dischargeability from the ink jet head, the viscosity of the ink at 80 ° C. is preferably within the range of 7 to 11 mPa · s, and within the range of 8 to 10 mPa · s. It is more preferable that Further, from the viewpoint of sufficiently gelling the ink when it has landed and cooled to room temperature, the viscosity of the ink at 25 ° C. is preferably 1000 mPa · s or more.

  The gelation temperature of the ink is preferably in the range of 50 to 60 ° C. When the gelation temperature of the ink is 50 ° C. or higher, the ink gels quickly after landing on the recording medium, and therefore the pinning property is further improved. When the gelation temperature of the ink is 60 ° C. or less, the ink is less likely to gel when the ink is ejected from the ink jet head whose ink temperature is usually about 80 ° C., so that the ink can be ejected more stably.

The viscosity of the ink at 60 ° C., the viscosity at 25 ° C., and the gelation temperature can be determined by measuring the temperature change of the dynamic viscoelasticity of the ink with a rheometer.
Specifically, the viscosity and the gelation temperature can be measured by the following methods. While the ink is heated to 100 ° C. and the viscosity is measured with a cone plate type rheometer (MCR300 manufactured by Anton Paar), the shear rate is 1000 (1 / s) and the cooling rate is 0.1 ° C./s up to 20 ° C. The ink is cooled to obtain a temperature change curve of viscosity. The viscosity at 90 ° C. and the viscosity at 25 ° C. are determined by reading the viscosity at 90 ° C. and 25 ° C. in the temperature change curve of the viscosity, respectively. The gelation temperature is determined as the temperature at which the viscosity becomes 200 mPa · s in the temperature change curve of the viscosity.

2. Preparation of actinic ray curable inkjet ink The actinic ray curable inkjet ink of the present invention can be obtained, for example, by mixing the aforementioned components under heating. It is preferable to further filter the obtained liquid mixture with a predetermined filter.

  Specifically, the actinic ray curable inkjet ink includes (i) a step of obtaining a pigment dispersion by dispersing a pigment and a polymer dispersant in a photopolymerizable compound, and (ii) the obtained pigment dispersion. And a photopolymerizable compound, a photopolymerization initiator, a gelling agent, and a resin of the present invention are mixed to obtain an actinic ray curable inkjet ink.

  As described above, the amount of the polymer dispersant added in the step (i) is preferably in the range of 30 to 70% by mass with respect to the pigment, and is preferably in the range of 35 to 65% by mass. More preferred.

The photopolymerizable compound added in the step (ii) may be the same as or different from the photopolymerizable compound added in the step (i).
The dispersion of the pigment and the polymer dispersant can be performed by, for example, a ball mill, a sand mill, an attritor, a roll mill, an agitator, a Henschel mixer, a colloid mill, an ultrasonic homogenizer, a pearl mill, a wet jet mill, or a paint shaker.

3. Image Forming Method The image forming method of the present invention comprises (I) a step of ejecting the actinic ray curable ink jet ink of the present invention from a nozzle of an ink jet head to land on a recording medium, and (II) an ink landed on the recording medium. Irradiating actinic rays to cure the ink.

3-1. Step (I) In step (I), ink droplets are ejected from an ink jet head and landed on the recording medium at a position corresponding to the image to be formed.

  The ejection method from the ink jet head may be either an on-demand method or a continuous method. On-demand inkjet heads include electro-mechanical conversion systems such as single cavity type, double cavity type, bender type, piston type, shear mode type and shared wall type, as well as thermal inkjet type and bubble jet. Any of electric-thermal conversion methods such as Canon Inc. (registered trademark) type may be used.

  By discharging the ink droplets from the inkjet head in a heated state, the discharge stability can be improved. The temperature of the ink when ejected is preferably in the range of 35 to 100 ° C., and more preferably in the range of 60 to 90 ° C. in order to further improve the ejection stability. In particular, it is preferable to emit at an ink temperature such that the viscosity of the ink is in the range of 7 to 15 mPa · s, more preferably in the range of 8 to 13 mPa · s.

The sol-gel phase transition type ink has an ink temperature of (gelation temperature +10) ° C. to (gelation) when the ink is filled in the ink jet head in order to improve the ink dischargeability from the ink jet head. The temperature is preferably set to +30) ° C.
When the temperature of the ink in the ink jet head is (gelation temperature + 10) ° C. or more, it is possible to prevent the ink from being gelled in the ink jet head or the nozzle surface, thereby reducing the ink discharge performance. On the other hand, when the temperature of the ink in the ink jet head is (gelation temperature + 30) ° C. or lower, the ink becomes too hot, and the ink component does not deteriorate.

  The method for heating the ink is not particularly limited. For example, at least one of an ink tank constituting the head carriage, an ink supply system such as a supply pipe and an anterior chamber ink tank just before the head, a pipe with a filter, and a piezo head is heated by a panel heater, a ribbon heater, or warm water. be able to.

  The amount of ink droplets to be ejected is preferably in the range of 1 to 20 pL from the viewpoint of recording speed and image quality.

  The recording medium is not particularly limited, but is made of plastic such as polyester, polyvinyl chloride, polyethylene, polyurethane, polypropylene, acrylic resin, polycarbonate, polystyrene, acrylonitrile-butadiene-styrene copolymer, polyethylene terephthalate, and polybutadiene terephthalate. Non-absorbent recording media (plastic substrate), non-absorbing inorganic recording media such as metals and glass, and absorbent paper (for example, coated paper for printing and coated paper B for printing) can be used. .

3-2. Step (II) In step (II), the ink landed on the recording medium in step (I) is irradiated with actinic rays to form an image formed by curing the ink.

  The actinic rays can be selected from, for example, electron beams, ultraviolet rays, α rays, γ rays, X-rays, and the like, and are preferably ultraviolet rays. Irradiation with ultraviolet rays can be performed under the condition of a wavelength of 395 nm using, for example, a water-cooled LED manufactured by Phoseon Technology. By using the LED as the light source, it is possible to suppress ink curing failure due to melting of the ink by the radiant heat of the light source.

In the irradiation of ultraviolet rays, the peak illuminance on the image surface of ultraviolet rays having a wavelength in the range of 370 to 410 nm is preferably in the range of 0.5 to ¹⁰ W / cm ² , more preferably in the range of 1 to 5 W / cm ² . To do so. From the viewpoint of suppressing the radiant heat from being applied to the ink, the amount of light applied to the image is preferably less than 350 mJ / cm ² .

  Irradiation with actinic rays is preferably performed between 0.001 and 1.0 seconds after ink landing. In order to form a high-definition image, it is performed between 0.001 and 0.5 seconds. More preferred.

  Irradiation with actinic rays may be performed in two stages. First, the ink may be temporarily cured by irradiation with an actinic ray between 0.001 and 2.0 seconds after the ink has landed, and after the completion of all printing, the ink may be further irradiated with actinic light to be fully cured. . By dividing the irradiation of actinic rays into two stages, the shrinkage of the recording material that occurs during ink curing is less likely to occur.

EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.
[Example 1]
1. Ink material 1-1. Pigment (Black pigment)
C. I. Pigment Black 7 (manufactured by Mitsubishi Chemical Corporation, MA7) was used.

1-2. Photopolymerizable compound The photopolymerizable compound shown in Table I was used.

1-3. A photopolymerization initiator IRGACURE 819 (manufactured by BASF, acylphosphine oxide) was used.

1-4. Gelling agents Gelling agents shown in Table II were used.

1-5. Resins according to the present invention Resins shown in Tables III to IV were used.

1-6. Other components 1-6-1. Polymer dispersing agent BYKJET-9151 (manufactured by BYK) was used.
1-6-2. Polymerization inhibitor Irgastab UV-10 (manufactured by BASF) was used.

1-6-3. Surfactant KF-352 (manufactured by Shin-Etsu Chemical Co., Ltd.) was used.

2. Preparation and evaluation of ink <Preparation of ink U-1>
(Preparation of pigment dispersion)
The following components and 120 g of zirconia beads having a diameter of 0.5 mmφ were placed in a 200 mL plastic bottle, the lid was tightened, and dispersed for 4 hours with a vibration mill (Red Devil 4500L, manufactured by Nishimura Seisakusho). After dispersion, the beads were separated and the dispersion was taken out to obtain pigment dispersion 1.
Pigment: C.I. I. Pigment Black 7 (Mitsubishi Chemical Corporation, MA7)
: 20.0 parts by mass Photopolymerizable compound: M-2: 71.9 parts by mass Polymer dispersant: BYKJET-9151 (manufactured by BYK): 8.0 parts by mass Polymerization inhibitor: Irgastab UV-10 (BASF) Made)
: 0.1 parts by mass

(Preparation of ink)
The following additives were sequentially mixed, heated to 80 ° C. and stirred, and then the resulting liquid was filtered with a # 3000 metal mesh filter under heating and cooled to prepare ink U-1.
Photopolymerizable compound: M-2: 32.8% by mass
Photopolymerizable compound: M-3: 40.0% by mass
Photopolymerization initiator: IRGACURE 819 (manufactured by BASF)
: 3.0% by mass
Polymerization inhibitor: Irgastab UV-10 (manufactured by BASF)
: 0.1% by mass
Surfactant: KF-352 (manufactured by Shin-Etsu Chemical Co., Ltd.): 0.1% by mass
Resin according to the present invention: R-1: 10.0% by mass
Pigment dispersion 1 (above): 10.0% by mass
Gelling agent: G-1: 4.0% by mass

<Preparation of actinic ray curable inks U-2 to U-29>
The actinic ray curable ink U-2 was prepared in the same manner as in the preparation of the actinic ray curable ink U-1, except that various additives and addition amounts were changed as shown in Table V-1 and Table V-2. -U-29 was prepared.

3. 3. Evaluation method and evaluation results 3-1. Evaluation Method When an image was formed using the obtained ink, the dot diameter and blocking resistance were evaluated by the following methods, respectively.
(Printing method of actinic ray curable ink)
The obtained ink was introduced into an inkjet head HA1024 type (manufactured by Konica Minolta) of a line type ink jet recording apparatus (manufactured by Konica Minolta). The temperature of the inkjet head was set to 80 ° C. Resolution 720 × 720 dpi, ink droplet 8 pL. After ejecting ink under the condition of a voltage of 16 V and landing on the recording medium, the ink droplet is cured by irradiating the landed ink droplet with ultraviolet light having an energy of 250 mJ / cm ² with an LED lamp, A solid image and a dot image each having a size of 50 mm × 50 mm were formed. An OK top coat (manufactured by Oji Paper Co., Ltd.) was used as the recording medium.

(Dot diameter: Pinning)
The dot image was observed under a condition of 100 times with a microscope, and an average size value of 10 droplets was obtained. The dot diameter was determined to be good if it was in the range of 50 to 70 μm. If the dot diameter was within the range of 55 to 65 μm, it was determined to be even better.

(Blocking resistance)
After printing the solid image and the dot image, an OK topcoat (made by Oji Paper Co., Ltd.) that is not printed on the image is superimposed on the image, and this is sandwiched between two 10 cm square glass plates. A load of 10 g / cm ² was applied, and the mixture was left under environmental conditions of 60 ° C. and 10% RH for 24 hours. Thereafter, it was left at room temperature (25 ° C.) for 2 hours, and the adhesiveness, ink adhesion on the back surface, and image quality when peeled off were visually observed and evaluated according to the following evaluation criteria.
"Evaluation criteria"
◎: No change ○: Slightly sticky, no ink attached, no change in image quality ○ △: Slightly sticky, no ink attached, slightly reduced image quality △: Sticky, slightly ink There is adhesion, and the image quality deteriorates. X: The ink is peeled off from the image, and there is clear ink adhesion.

(Evaluation results)
The evaluation results of the obtained inks U-1 to U-29 are shown in Table V-1 and Table V-2. In Table V-1 and Table V-2, the unit of numerical values in the ink composition is “mass%”.
As shown in Table V-1 and Table V-2, the inks U-1 to U-26 containing the resin according to the present invention are all excellent in pinning properties and the occurrence of blocking is suppressed. I understand.
In particular, it can be seen that blocking is further suppressed by using a chlorinated polyolefin resin as the resin (contrast between inks U-1 to U-5 and U-6 to U-11).
Further, the content of the polyfunctional (meth) acrylate containing 2 to 20 ethylene oxide groups or propylene oxide groups as the photopolymerizable compound is 25.0 to 80.0 masses relative to the total mass of the ink. %, It is understood that blocking is further suppressed (contrast of ink U-8 with U-19 and U-20).
Moreover, it turns out by using the compound which has a structure represented by the said general formula (G1) or (G2) as a gelatinizer that pinning property is favorable and suppresses blocking more (ink U-8, Comparison between U-23, U-24 and U-25, U-26).
On the other hand, it can be seen that the inks U-27 to U-29 which do not contain the resin according to the present invention (all are comparative examples) cannot suppress blocking, and the image quality deteriorates.

[Example 2: Example of other pigment seed ink]
In the preparation of the pigment dispersion 1, the pigment type is C.I. I. When the ink was prepared and evaluated in the same manner as in Example 1 except that Pigment Black 7 was changed to the following pigment types, the same evaluation results as in Example 1 were obtained.
(Other pigment types)
・ C. I. Pigment Yellow 185 (BASF, D1155)
・ C. I. Pigment Violet 19 / Pigment Red 202 (manufactured by Clariant, E7B)
・ C. I. Pigment Blue 15: 4 (BASF, D7110F)
・ C. I. Pigment Green 7 (manufactured by Clariant, GNX01)
・ C. I. Pigment Orange 71 (BASF, D2905)
・ C. I. Pigment Violet 23 (manufactured by Clariant, P-RL)
・ C. I. Pigment White 6 (manufactured by Sakai Chemical Industry Co., Ltd., TCR-52)

Claims (9)

An actinic ray curable inkjet ink containing a pigment, a photopolymerizable compound, a photopolymerization initiator and a gelling agent,
An actinic ray curable inkjet ink comprising at least one of a polyester resin and a chlorinated polyolefin resin.   The resin is at least one of a polyester resin having a number average molecular weight in the range of 2,000 to 20,000 and a chlorinated polyolefin resin having a weight average molecular weight in the range of 10,000 to 100,000. The actinic ray curable inkjet ink described in 1.   The actinic ray curable inkjet according to claim 1 or 2, wherein the total content of the resin is in the range of 1.0 to 20.0 mass% with respect to the total mass of the ink. ink.   The actinic ray curable inkjet ink according to any one of claims 1 to 3, wherein the resin is a chlorinated polyolefin resin having a weight average molecular weight of 10,000 to 50,000. 5. The gelling agent according to claim 1, wherein the gelling agent contains at least one of compounds having a structure represented by the following general formula (G1) or (G2). Actinic ray curable inkjet ink.
General formula (G1): R < ₁₁ > -CO-R < ₁₂ >
General formula (G2): R < ₁₃ > -COO-R < ₁₄ >
[In formula, R < ₁₁ > -R < ₁₄ > represents the alkyl group which contains the linear part within a C12-C26 range, and may also contain a branch each independently. ]   The content of the gelling agent is in the range of 1.0 to 7.0% by mass with respect to the total mass of the ink, according to any one of claims 1 to 5. Actinic ray curable inkjet ink.   7. The polyfunctional (meth) acrylate containing 2 to 20 ethylene oxide groups or propylene oxide groups as the photopolymerizable compound is contained. 7. The actinic ray curable inkjet ink described in 1.   The content of the polyfunctional (meth) acrylate containing the ethylene oxide group or the propylene oxide group in the range of 2 to 20 is in the range of 25.0 to 80.0% by mass with respect to the total mass of the ink. The actinic ray curable inkjet ink according to claim 7. An image forming method using the actinic ray curable inkjet ink according to any one of claims 1 to 8,
A step of landing droplets of the actinic ray curable inkjet ink on a recording medium by an inkjet method;
And irradiating the droplets landed on the recording medium with an actinic ray to form an image.