JP5189400B2 - Active energy ray curable ink - Google Patents

Description

  The present invention relates to an active energy ray-curable ink that can increase the separation stability of an ink at a high temperature and prevent the ink from dripping without impairing the stability to a change in viscosity due to a high temperature.

Conventionally, emulsion ink has been used as ink for stencil printing to form an image with ink that has passed through the perforated part by using stencil paper that has been perforated by heat-sensitive digital engraving, but the emulsion ink is dried. However, when there is a lot of solid parts on the printed matter, there is a problem that the printed matter is turned over, that is, when the printed matter that has just been printed is stacked, the ink of the adjacent printed matter adheres and stains the printed matter.
Therefore, ultraviolet curable inks have been used instead of conventional emulsion inks. Since this ultraviolet curable ink is cured immediately upon irradiation with ultraviolet rays, when printing is performed using the ultraviolet curable ink, the ink is more ink than a commonly used W / O (water-in-oil) emulsion ink. It has the advantages of good dryness and no set-off.

Conventionally, various proposals have been made as technologies relating to the ultraviolet curable ink for stencil printing. For example, an ultraviolet curable ink using an ultraviolet curable resin as a main component and using organic bentonite as an extender has been proposed (see Patent Document 1). However, the ink using the UV curable resin like the proposed ink has a large temperature dependency, and therefore the viscosity change with respect to the temperature of the ink is large, the image is blurred at a low temperature, and the printing paper is at a high temperature. Is a problem. In addition, the ink using organic bentonite as an extender pigment like this proposed ink has a problem in that each component is separated when stored at a high temperature.
For the viscosity change with respect to the temperature, an emulsion-type ultraviolet curable ink has been proposed (see Patent Document 2). However, in this proposal, by emulsifying the ink, the change in viscosity with respect to temperature can be made comparable to that of conventional emulsion inks for stencil printing, but when stored at a high temperature, the water content of the ink evaporates on the printing press. As a result, the ink is separated as a result of the change in viscosity.
In addition, the ultraviolet curable ink has a problem that ink dripping occurs on a printing machine at a temperature at which it is normally used, and a good printed matter cannot be obtained when it is used again. Further, the ink dripping has a problem that it becomes more prominent when the ink is stored at a high temperature.

  Therefore, it is desirable to develop an active energy ray-curable ink for stencil printing that can improve the separation stability of the ink at a high temperature and prevent the ink from dripping without impairing the stability to the viscosity change due to the high temperature. This is the current situation.

Japanese Patent No. 2660000 JP-A-9-20876

  This invention is made | formed in view of this present condition, and makes it a subject to solve the said problem in the past and to achieve the following objectives. That is, an object of the present invention is to provide an active energy ray-curable ink that can improve the separation stability of the ink at a high temperature and prevent the ink from dripping without impairing the stability to the viscosity change due to the high temperature. And

Means for solving the problems are as follows. That is,
<1> An active energy ray-curable ink comprising hydrophilic silica having a primary particle size of 100 nm or less.
<2> The active energy ray-curable ink according to <1>, wherein the specific surface area of the hydrophilic silica is 280 m ² / g or less.
<3> The active energy ray-curable ink according to any one of <1> to <2>, wherein the hydrophilic silica has a primary particle diameter of 28 nm or less and a specific surface area of 190 m ² / g or less.
<4> The active energy ray-curable ink according to any one of <1> to <3>, which contains a monomer having an ethylene oxide unit represented by the following structural formula (1).
_{- (CH 2 CH 2 O)} - ··· structural formula (1)
<5> The active energy ray-curable ink according to <4>, wherein the number of ethylene oxide units represented by the structural formula (1) is 6 or more and 19 or less.
<6> The content of the monomer having an ethylene oxide unit represented by the structural formula (1) is 0.02% by mass to 20% by mass with respect to the total mass of the ink. <4> to <5> The active energy ray-curable ink according to any one of the above.
<7> The active energy ray-curable ink according to any one of <1> to <6>, wherein the water content is 5% by mass or less with respect to the total mass of the ink.
<8> Active energy ray curing according to any one of <1> to <7>, which is used for stencil printing in which an image is formed with ink that has passed through the perforated part using a stencil sheet perforated by heat-sensitive digital plate making Mold ink.
<9> When the monomer having an ethylene oxide unit is contained, the active energy ray-curable ink according to any one of <1> to <8>, wherein the monomer having the ethylene oxide unit is a methacrylate monomer.

  ADVANTAGE OF THE INVENTION According to this invention, the active energy ray hardening type which can solve the problem in the past, can improve the separation stability at the time of high temperature of ink, and can prevent ink dripping, without impairing the stability to the viscosity change by high temperature Ink can be provided.

(Active energy ray curable ink)
The active energy ray-curable ink of the present invention (hereinafter sometimes simply referred to as “ink”) includes an extender pigment, an active energy ray-curable polymerizable component, a colorant, a dispersant, and a polymerization initiator. If necessary, it contains other components such as polymerization inhibitors, vegetable oils, antioxidants, synergists, and the like.

Here, active energy ray curing means that the polymerizable component is polymerized and cured by irradiation with active energy rays, and this can be confirmed, for example, by touching ink after irradiation with active energy rays. . Examples of the active energy rays include ultraviolet rays and electron beams.
The ink of the present invention may be composed of a material that is solidified by radical polymerization, or may be composed of a material that is solidified by cationic polymerization.

<External pigment>
At least one of the extender pigments is hydrophilic silica, and further includes hydrophobic silica and extender pigments other than the hydrophilic silica and hydrophobic silica as necessary.

-Hydrophilic silica-
The hydrophilic silica is silica having an OH group on the surface of the molecule.
The hydrophilic silica is not particularly limited and may be appropriately selected depending on the intended purpose. For example, Aerosil 50, Aerosil 90G, Aerosil 130, Aerosil 200, Aerosil 300, Aerosil 380, Aerosil TT600, Aerosil COK84 (any Also manufactured by Nippon Aerosil Co., Ltd.).
The said hydrophilic silica may be used individually by 1 type, and may use 2 or more types together.
By containing the hydrophilic silica in the ink, the separation stability of the ink at a high temperature can be enhanced.

There is no restriction | limiting in particular as a primary particle diameter of the said hydrophilic silica, Although it can select suitably according to the objective, 100 nm or less is preferable and 28 nm or less is more preferable. When the primary particle size is 100 nm or less, film strength can be imparted, ink dripping on a printing machine at a commonly used temperature can be further prevented, and the ink was stored at a high temperature. Ink dripping on the printing press at the time can be further prevented.
Here, the “primary particles” mean particles that are in contact with each other at their faces or edges and cannot be further dispersed. The “primary particle diameter” can be measured by a transmission electron microscope (TEM).
The “normally used temperature” is 10 to 30 ° C., and the “high temperature when stored at high temperature” is 50 to 70 ° C.

As the specific surface area of the hydrophilic silica is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 280 meters ² / g or less, more preferably ^{250m 2 / g, 70~190m 2 /} g Is more preferable. When the specific surface area is 280 m ² / g or less, it is possible to prevent ink dripping on a printing machine at a temperature usually used. Moreover, it is preferable that the specific surface area is 70 m ² / g or more in that the separation stability at high temperature is increased.
Here, the “specific surface area” means a surface area per 1 g. The “specific surface area” can be measured by the BET method.
When the primary particle size is 28 nm or less and the specific surface area is 190 m ² / g or less, the separation stability of the ink at a high temperature is further increased, and the ink is used on a printing machine at a normally used temperature. Dripping can be prevented and clogging of the plate can be prevented.

There is no restriction | limiting in particular as content of the said hydrophilic silica, Although it can select suitably according to the objective, 0.5-20 mass% is preferable with respect to the total mass of ink, and 1-10 mass%. Is more preferable. When the content is less than 0.5% by mass, the yield value of the ink cannot be increased and ink dripping may not be prevented. When the content exceeds 20% by mass, the yield value is too high. This may impair ink fluidity.
The “yield value” here means “the value of the minimum shearing force necessary to cause flow”. If the yield value of the ink is high, the shape becomes stable when the ink is left in a state where no external force is applied, and ink dripping can be prevented.

-Hydrophobic silica-
The hydrophobic silica is silica obtained by replacing (hydrophobizing) about 80% of OH groups on the surface of the hydrophilic silica with a hydrophobic group such as a methyl group.
The hydrophobic silica is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include Aerosil R972, R974, R202, R805, R812, R812S, RX200, and RY200 (all manufactured by Nippon Aerosil Co., Ltd.). Is mentioned.
In addition, the said hydrophobic silica may be used individually by 1 type, and may use 2 or more types together.
Thus, by using the hydrophilic silica and the hydrophobic silica in combination, it is possible to impart a plastic viscosity to the ink without impairing the temperature characteristics of the hydrophilic silica. Stability can be increased.

There is no restriction | limiting in particular as a specific surface area of the said hydrophobic silica, Although it can select suitably according to the objective, 70-300 m < ² > / g is preferable, 70-200 m < ² > / g is more preferable, 70-150 m < ² >. / G is more preferable.

  There is no restriction | limiting in particular as content of the said hydrophobic silica, Although it can select suitably according to the objective, 0.5-20 mass% is preferable with respect to the total mass of ink, and 1-10 mass% Is more preferable. If the content is less than 0.5% by mass, the plastic viscosity may be too low, and if it exceeds 20% by mass, the plastic viscosity may be too high and the fluidity of the ink may be impaired.

-Body pigments other than hydrophilic silica and hydrophobic silica-
The extender pigment other than the hydrophilic silica and the hydrophobic silica is not particularly limited and may be appropriately selected depending on the intended purpose. For example, organic bentonite, white clay, talc, clay, calcium carbonate, barium sulfate, titanium oxide Inorganic fine particles such as alumina white, diatomaceous earth, kaolin, mica, aluminum hydroxide; polyacrylate, polyurethane, polyester, polyethylene, polypropylene, polyvinyl chloride, polyvinylidene chloride, polystyrene, polysiloxane, phenol resin, epoxy Organic fine particles such as resins; or fine particles made of a copolymer thereof;
The extender pigments other than the hydrophilic silica and the hydrophobic silica may be used alone or in combination of two or more.

  There is no restriction | limiting in particular as content of extender pigments other than the said hydrophilic silica and hydrophobic silica, Although it can select suitably according to the objective, 0.1-50 mass% with respect to the total mass of ink. Is preferable, 1-15 mass% is more preferable, and 2-5 mass% is especially preferable.

<Polymerizable component>
At least one of the active energy ray-curable polymerizable components is a monomer having a unit represented by the following structural formula (1) in the molecule, and further contains other polymerizable components as necessary. . The unit represented by the structural formula (1) is an ethylene oxide (EO) unit.
_{- (CH 2 CH 2 O)} - ··· structural formula (1)

-Monomer having ethylene oxide unit-
The monomer having an ethylene oxide unit is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, and (ethylene oxide unit). Number: 5-20), ethylene oxide-modified trimethylol tri (meth) acrylate (number of ethylene oxide units: 3-20), and the like. The monomer having an ethylene oxide unit is preferably a methacrylate monomer from the viewpoint of safety such as skin irritation and skin sensitivity.

As the monomer having an ethylene oxide unit, a commercially available product can be used. For example, Aronics series (M-102, M-113, M-120, M-210, M-240, M, manufactured by Toagosei Co., Ltd.) -243, M-245, M-260, M-350, M-360); manufactured by Sartomer (SR504, CD614, CD9087, CD550, CD552, SR230, SR259, SR268, SR273, SR344, SR349, CD560, CD561 CD564, SR601, SR602, SR610, CD9043, SR9045, SR9029, SR205, SR209, SR210, SR231, SR252, SR348, SR480, CD540, CD541, CD542, SR603, SR9036, SR41 SR454, SR499, SR502, SR9035, SR494); New Frontier Series (PHE-2, PHE-4, CEA, NP-4, N-177E, ME-3, ME-4S, EH-2 manufactured by Daiichi Kogyo Co., Ltd.) , PE-200, PE-300, PE-400, PE-600, BPE-4, BPE-10, BPE-20, HBPE-4, MPEM-400, MPEM-1000, TEGDMA, PEM-1000, BPEM-10 ); Light ester series (BC, MTG, 130MA, 041MA, 2EG, 3EG, 4EG, 9EG, 14EG, BP-2EM, BP-4EM, BP-6EM, light acrylate series EC-A, MTG-) A, EHDG-A, 130A, P-200A, NP-4EA, NP-8E , 3EG-A, 4EG-A, 9EG-A, 14EG-A, BP-4EA, BP-10EA, TMP-3EO-A, TMP-6EO-3A); Ebercryl series (PEG300DA, PEG400DA) manufactured by Daicel Cytex , 11, 160, TMPEOTA, 40); Bremer series (PE-90, PE-200, PE-350, AE-90, AE-200, AE-400, 50PEP-300, 70PEP-350B) manufactured by NOF Corporation. , AEP series, 55PET-400, 30PET-800, 55PET-800, AET series, PME-100, PME-200, PME-350, PME-400, PME-550, PME-1000, PME-4000, AME-400 , AEE-100, 50POEP-80 0B, 50AOEP-800B, PLE-200, ALE-200, ALE-800, PSE-200, PSE-400, PSE-1300, ASEP series, PKEP series, AKEP series, ANE, 43ANEP-500, 70ANEP-550, 75ANEP -600, AAE-300, PDE-100, PDE-100, PDE-150, PDE-200, PDE-400, PDE-600, PDE-1000, ADE-200, ADE-400, PDE series, 50 ADET-1800, 30PDC-800B, 30PDC-950B, 20PDC-1300B, 40PDC-1700B, 30ADC-900B, PDBE-200, PDBE-250, PDBE-450, PDBE-1300, ADBE-200, DBE-250, ADBE-450, PDBEP series, ADBEP series, 43PDBPE-800B); and the like.
When the monomer having the ethylene oxide unit is contained in the ink, ink dripping on the printing press when the ink is stored at high temperature can be further prevented, and viscosity stability at high temperature storage is further improved. Can do.
The monomer having an ethylene oxide unit preferably does not have a benzene structure or a bisphenol A skeleton in the molecular structure.

  There is no restriction | limiting in particular as the number of the ethylene oxide units in the monomer which has the said ethylene oxide unit, Although it can select suitably according to the objective, 6-19 are preferable, 6-14 are more preferable, 7-10 are Further preferred. When the number of the ethylene oxide units is 6 or more, it is preferable in that the ink dripping on the printing press when the ink is stored at a high temperature can be further prevented. When the number of the ethylene oxide units is 19 or less, it is preferable in that ink dripping on a printing machine at a commonly used temperature can be further prevented.

The content of the monomer having an ethylene oxide unit is preferably 0.02% by mass or more and 20% by mass or less, more preferably 0.2% by mass or more and 10% by mass or less, based on the total mass of the ink. 2 mass% or more and 5 mass% or less are especially preferable. It is preferable that the content is 0.02% by mass or more and 20% by mass or less in terms of improving the viscosity stability during high-temperature storage.
The monomer having an ethylene oxide unit is preferably water-soluble, and is preferably used in combination with a monomer insoluble in water. The monomer having an ethylene oxide unit is particularly preferably used in combination with a caprolactone-modified monomer such as caprolactone-modified dipentaerythritol hexaacrylate or caprolactone-modified hydroxypivalate ester neopentyl glycol.

  The ink contains a monomer having a unit represented by the structural formula (1) in the molecule, and the specific structure is polymerized from the ink by, for example, centrifugation or Soxhlet extraction. After extracting the sexual components and concentrating the extract, instrumental analysis such as gas chromatography, liquid chromatography, FT-IR (Fourier transform infrared spectrophotometer), NMR (nuclear magnetic resonance apparatus), elemental analysis, mass spectrometry, etc. Therefore, analysis can be made by the structural formula and composition ratio.

-Other polymerizable components-
The active energy ray-curable polymerizable component may contain other polymerizable component that does not have a unit represented by the structural formula (1) in the molecule.
Examples of the other polymerizable component include urethane-based, epoxy-based, polyester-based, and polyol-based monomers and oligomers modified with acrylic acid or methacrylic acid.

Examples of the monomer in the other polymerizable component include monofunctional or polyfunctional acrylate-based and methacrylate-based monomers (hereinafter referred to as “(meth) acrylate” when both are included). Among these, methacrylate monomers are preferable from the viewpoint of safety such as skin irritation and skin sensitivity.
Specifically, examples of the monofunctional (meth) acrylate monomer include dicyclopentylethyl (meth) acrylate, isobornyl (meth) acrylate, phenol ethylene oxide-modified (meth) acrylate, and the like. Examples of the bifunctional (meth) acrylate monomer include tripropylene glycol di (meth) acrylate, caprolactone-modified hydroxypivalate ester neopentyl glycol, 1,6-hexanediol di (meth) acrylate, bisphenol A diglycidyl ether di ( (Meth) acrylate, polypropylene glycol di (meth) acrylate (the number of propylene oxide units is 3 to 14), polytetramethylene glycol di (meth) acrylate (PO: 3 to 14), 1,4-butanediol di (meth) Examples thereof include acrylate and neopentyl glycol di (meth) acrylate. Examples of the trifunctional (meth) acrylate monomer include trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, propylene oxide modified glycerol tri (meth) acrylate, propylene oxide (PO) modified trimethylolpropane tri ( And (meth) acrylate (the number of propylene oxide units is 1 to 6). Examples of tetrafunctional or higher functional (meth) acrylate monomers include pentaerythritol tetra (meth) acrylate, ditrimethylolpropane tetra (meth) acrylate, pentaerythritol ethoxytetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, and caprolactone. Modified dipentaerythritol hexa (meth) acrylate, etc. are mentioned.

Commercially available products can be used as the monomers in the other polymerizable components. Besides the above-described monomers, Toagosei, Sartomer, Kyoeisha Chemical, Nippon Kayaku, Daiichi Kogyo Seiyaku, Daicel CYTEC Monomers commercially available from Nippon Oil & Fat Co., Ltd., Shin Nakamura Chemical Co., Ltd., BASF Co., Ltd., Nippon Synthetic Chemical Co., Ltd., Asahi Denka Co., Ltd., Arakawa Chemical Co., Ltd., etc. can be used.
The monomer in the other polymerizable component preferably has no benzene structure or bisphenol A skeleton in the molecular structure.

Examples of the oligomer include epoxy acrylate, epoxy oil acrylate, urethane acrylate, unsaturated polyester, polyester acrylate, and vinyl acrylate.
The said other polymerizable component may be used individually by 1 type, and may use 2 or more types together.

  The viscosity of the other polymerizable component is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 1.5 Pa · s or less at 25 ° C. in order to reduce the change in viscosity with respect to temperature. 0.3 Pa · s or less is more preferable. However, from the viewpoint of preventing problems in image quality due to poor fluidity of ink, it is preferably 0.02 Pa · s or more, and more preferably 0.1 Pa · s or more.

<Colorant>
There is no restriction | limiting in particular as said coloring agent, Insoluble coloring agents, such as a well-known pigment and disperse dye of various colors, can be used.
Examples of the colorant include carbon blacks such as acetylene black, channel black, and furnace black; metal powders such as aluminum powder and bronze powder; inorganic pigments such as petals, yellow lead, ultramarine blue, chromium oxide, and titanium oxide; Azo pigments such as insoluble azo pigments, azo lake pigments, condensed azo pigments; phthalocyanine pigments such as metal-free phthalocyanine pigments and copper phthalocyanine pigments; anthraquinone pigments, quinacridone pigments, isoindolinone pigments, isoindoline pigments, dioxane Gin dyes, selenium dyes, perylene dyes, perinone dyes, thioindigo dyes, quinophthalone dyes, condensed polycyclic pigments such as metal complexes; acid or basic dye lakes and other organic pigments; diazo dyes, anthraquinones Oil-soluble dyes such as dyes; fluorescent pigments It is.

  As the fluorescent pigment, a so-called synthetic resin solid solution obtained by dissolving or dyeing a fluorescent dye that develops various hues after bulk polymerization of a synthetic resin or by pulverizing and refining the obtained colored bulk resin The type is preferable, and examples of the synthetic resin carrying a dye include melamine resin, urea resin, sulfonamide resin, alkyd resin, and polyvinyl chloride resin.

Moreover, a commercial item can be used as said coloring agent, for example, as a commercial item of the said carbon black, MA-100, MA-100S, MA-7, MA-70, MA-77, MA-11. , # 1000, # 40, # 44 (all manufactured by Mitsubishi Chemical Corporation), Raven1100, Raven1080, Raven1255, Raven760, Raven410 (all manufactured by Colombian Carbon), MOGUL-L, MOGUL-E, PEARLS-E ( All of them are manufactured by Cabot Corporation).
In addition, the said coloring agent may be used individually by 1 type, and may use 2 or more types together.

  The colorant is present in a dispersed state in the ink. There is no restriction | limiting in particular as an average particle diameter of the said colorant disperse | distributed in the said ink, Although it can select suitably according to the objective, 0.1-10 micrometers is preferable and 0.1-1.0 micrometer is preferable. More preferred. If the average particle size is less than 0.1 μm, the pigment may permeate the paper immediately after printing, and a desired effect on the image density may not be obtained. If it exceeds 10 μm, the ink stability is poor. Sometimes.

  There is no restriction | limiting in particular as content of the said coloring agent, Although it can select suitably according to the objective, Usually, 2-15 mass% is preferable with respect to the total mass of ink.

<Colorant dispersant>
The colorant dispersant is a component having a function of dispersing the colorant and extender pigment.
The colorant dispersant is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include sorbitan fatty acid esters such as sorbitan sesquiolate, polyglycerin fatty acid esters such as hexaglycerin polyricinoleate, polyoxyethylene, and the like. Nonionic surfactants such as glycerin fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene alkyl ether, polyoxyethylene alkylamine fatty acid amide; alkylamine polymer compound; aluminum chelate compound; styrene-anhydrous malee Acid copolymer polymer compound; Polycarboxylic acid ester type polymer compound; Aliphatic polyvalent carboxylic acid; Amine salt of polymer polyester; Ester type anionic surfactant; Long chain amino acid of high molecular weight polycarboxylic acid Salts: Long-chain polyaminoamides and polymeric acid polyester salts; Polyamide compounds; Phosphate ester surfactants; Alkyl sulfocarboxylates; Sulfonates; α-Olefin sulfonates; Dioctyl sulfosuccinates; An alkylolamine salt; a resin having an insoluble colorant-dispersing ability such as an alkyd resin;

In addition, as the colorant dispersant, a commercially available product can be used. S27000, S28000, S31845, S31850, S32000, S32550, S34750, S39000, S41090, S53095, etc.); Ajinomoto Fine Techno Co., Ltd. Plain Act AL-M, Ajisper series (PB711, PM821, PB821, PB811, PN411, PA111, etc.) ; Nikko Chemicals TMGS-15, TMGO-15, Decaglyn series (1-L, 1-M, 1-O, etc.), TL-10, TP-10, T -10, TI-10, BL-21, BC-15TX, BC-23, BC-30TX, BC-40TX, BS-20, BO-10TX, TAMNS-10, TAMNS-15, TAMNO-5, TAMNO-15 , TDMNS-8, OTP-100, OTP-75;
In addition, the said colorant dispersing agent may be used individually by 1 type, and may use 2 or more types together.

  There is no restriction | limiting in particular as content of the said coloring agent dispersing agent, Although it can select suitably according to the objective, 40 mass% or less is preferable with respect to the total mass of a coloring agent and an extender, and 2-35. The mass% is more preferable.

<Polymerization initiator>
There is no restriction | limiting in particular as said polymerization initiator, According to the objective, it can select suitably. Examples of the radical polymerization initiator include a photo-opening type and a hydrogen abstraction type, and examples thereof include benzophenone, acetophenone, 4,4′-bisdiethylaminobenzophenone, benzoin, and benzoin ethyl ether.

As the polymerization initiator, commercially available products can be used. For example, IRGACURE series (651, 184, 907, 369, 379, 819) of Ciba Specialty Chemicals, DAROCUR series (MBF, TPO, 1173); Kayacure series (MBS, DETX-S, ITX, CTX) manufactured by Nippon Kayaku Co., Ltd .;
In addition, the said polymerization initiator may be used individually by 1 type according to a light source, and may use 2 or more types together.

The polymerization initiator may be used in combination with a sensitizer or a polymerization accelerator, and examples thereof include aliphatic amines such as n-butylamine, triethylamine, and p-dimethylamine ethyl benzoate, and aromatic amines. Specific examples thereof include DAROCUR EDB, DAROCUR EHA (all manufactured by Ciba Specialty Chemical Co.), KAYACURE EPA, KAYAKURE DMBI (all manufactured by Nippon Kayaku Co., Ltd.), and the like.
The content of the polymerization initiator, sensitizer and polymerization accelerator is not particularly limited and can be appropriately selected depending on the purpose within a range not impairing the effects of the present invention. In each case, 1 to 25% by mass is preferable, and 1 to 15% by mass is more preferable.

<Other ingredients>
The other components in the ink of the present invention are not particularly limited and can be appropriately selected depending on the purpose within a range not impairing the effects of the present invention. For example, polymerization inhibitors, vegetable oils, antioxidants, Synergists, and the like.

-Polymerization inhibitor-
In the ink of the present invention, a polymerization inhibitor may be used for the purpose of storage stability of the ink and prevention of gelation due to a dark reaction.
There is no restriction | limiting in particular as said polymerization inhibitor, According to the objective, it can select suitably, For example, hydroquinone, p-benzoquinone, t-butylhydroquinone, p-methoxyphenol (MEHQ), etc. are mentioned.
There is no restriction | limiting in particular as content of the said polymerization inhibitor, Although it can select suitably according to the objective, Usually, it is 100-5,000 ppm with respect to the total mass of ink, and 100-500 ppm is preferable. .

-Vegetable oil-
If necessary, the ink of the present invention may use vegetable oil as long as it does not impair the curing properties.
The vegetable oil is not particularly limited and may be appropriately selected depending on the intended purpose.For example, soybean oil, rapeseed oil, corn oil, sesame oil, tall oil, cottonseed oil, sunflower oil, safflower oil, walnut oil, Examples include poppy oil and linseed oil.
In addition, as the vegetable oil, esterified vegetable oil can also be used. Examples of the ester include methyl ester, butyl ester, isopropyl ester, and propyl ester. Among these, in consideration of ink drying after printing, it is preferable to use what is generally referred to as drying oil and semi-drying oil having an iodine value of 100 or more. However, when the ink sticking on the printing press after standing for a long time becomes a problem, a vegetable oil having an iodine value of 100 or less may be used.
In addition, the said vegetable oil may be used individually by 1 type, and may use 2 or more types together.

  When dry oil and semi-dry oil having a high iodine value are used as the vegetable oil, an oxidation reaction occurs with oxygen in the air, whereby the drying (solidification) of the oil proceeds, and thus the ink containing the vegetable oil. Will also solidify. When solidification of the ink occurs, problems such as clogging of the screen and deterioration of image rise occur. Therefore, when using a vegetable oil having a high iodine value (containing many unsaturated bonds), In order to prevent oxidation of fatty acids (linolenic acid, linoleic acid, oleic acid, etc.), it is preferable to contain an antioxidant described later.

  There is no restriction | limiting in particular as content of the said vegetable oil, Although it can select suitably according to the objective, 5-70 mass% is preferable with respect to the total mass of ink, and 30-50 mass% is more preferable.

-Antioxidant-
The antioxidant is not particularly limited and may be appropriately selected from known ones according to the purpose. Examples thereof include amine compounds such as diphenylphenylenediamine and isopropylphenylphenylenediamine, tocopherol, dibutylmethylphenol, and the like. Phenol compounds, sulfur compounds such as mercaptomethylbenzimidazole, dibutylhydroxytoluene, propyl gallate, butylhydroxyanisole, and the like.
In addition, the said antioxidant may be used individually by 1 type, and may use 2 or more types together.

There is no restriction | limiting in particular as content of the said antioxidant, Although it can select suitably according to the objective, 2 mass% or less is preferable with respect to the oil in ink, 0.1-1.0 mass% Is more preferable.
When the antioxidant is added with a very small amount of antioxidant with respect to the content of the vegetable oil, an appropriate antioxidant effect may not be expected, and conversely, a large amount of oxidation with respect to the content of the vegetable oil. If an inhibitor is added all at once, it may act as an oxidation accelerator. Therefore, it is preferable to add a synergist described later in order to suppress plant oxidation even with a small amount of antioxidant.

-Synergist-
The synergist itself has little antioxidant action, but is used in combination with an antioxidant to enhance the antioxidant action of the antioxidant. The synergist is usually a polyfunctional compound which is an acidic substance and has several hydroxyl groups or carboxyl groups.
The synergist is not particularly limited and may be appropriately selected depending on the intended purpose. For example, methionine, ascorbic acid, threonine, leucine, milk protein hydrolyzate, norvaline, ascorbyl palmitate, phenylalanine, cystine, tryptophan , Proline, alanine, glutamic acid, valine, pepsin digestion of pancreatic protein, asparagine, arginine, barbituric acid, asphenamine, ninhydrin, propanidin, histidine, norleucine, glycerophosphate, casein trypsin hydrolyzate, casein hydrochloride hydrolyzate Etc.
In addition, the said synergist may be used individually by 1 type, and may use 2 or more types together.

  There is no restriction | limiting in particular as content of the said synergist, Although it can select suitably according to the objective, 50-150 mass% is preferable with respect to the total mass of antioxidant.

<Emulsion form>
In addition, the ink of this invention is good also as a form of an emulsion by adding water, an emulsifier (HLB: 3-10), etc.
When a small amount of water is added to the ink, ink breakage is improved, and paper discharge errors during printing are improved.
There is no restriction | limiting in particular as content of the said water, Although it can select suitably according to the objective, When considering the separation stability at the time of high temperature, it is 20 mass% or less with respect to the total mass of an ink. Is preferable, 5 mass% or less is more preferable, and it is still more preferable not to contain water. When the content exceeds 20% by mass, the separation stability of the ink may be lowered on the printing press. When the content is 5% by mass or less, the separation stability of the ink at a high temperature can be further increased.
There is no restriction | limiting in particular as content of the said emulsifier, Although it can select suitably according to the objective, It is preferable not to contain. When a water-soluble monomer is used as a monomer other than the monomer having an ethylene oxide unit, it is preferable in that it can be formed into an emulsion without adding an emulsifier to the ink.

<Method for producing active energy ray-curable ink>
The production method of the active energy ray-curable ink of the present invention is not particularly limited and can be appropriately selected from known methods according to the purpose. For example, by mixing each component by a conventional method, Examples thereof include a method of producing by performing dispersion treatment using a dispersing machine such as a three-roll mill.
When the ink is used for a stencil printing system, the viscosity of the ink can be adjusted by stirring conditions. The viscosity is not particularly limited as long as it is suitable for the system, but the viscosity at a shear rate of 20 s ⁻¹ is preferably 2 to 40 Pa · s, more preferably 10 to 30 Pa · s. preferable. Further, from the viewpoint of rolling up the paper after printing, the plastic viscosity of the ink approximated by the following Casson approximation is preferably 2.0 Pa · s or less, more preferably 1.0 Pa · s or less, and 5 Pa · s or less is more preferable. Further, the yield value of the ink approximated by the following Casson approximation is preferably 25 to 250 Pa or less, and more preferably 25 to 100 Pa or less.
In the above equation, τ represents shear stress. τ ₀ represents a yield value. Eta represents the plastic viscosity. D represents the shear rate.

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

(Examples 2 , 3, 7-16, 18-24, Reference Examples 1, 4-6, 17, and Comparative Examples 1-5)
-Preparation of active energy ray curable ink-
In accordance with the formulations shown in Tables 1 to 3, the colorant, the colorant dispersant, the extender pigment, the polymerizable component and the polymerization initiator are mixed and subjected to a dispersion treatment using a three roll mill (manufactured by Inoue Seisakusho Co., Ltd.) The active energy ray-curable inks of Examples 2, 3, 7 to 16, 18 to 24 , Reference Examples 1, 4 to 6, 17, and Comparative Examples 1 to 5 were prepared.

(1) to (3) in Tables 1 to 3 represent (1) Mitsubishi Chemical Corporation, (2) Lubrizol Corporation, and (3) Ciba Specialty Japan, respectively.
Details of extender pigments and polymerizable components in Tables 1 to 3 are as shown in Tables 4 and 5.

[Evaluation]
Using active energy ray-curable inks of Examples 2, 3, 7 to 16, 18 to 24 , Reference Examples 1, 4 to 6, 17, and Comparative Examples 1 to 5, separation at high temperatures is performed according to the following contents. The stability, film strength, sag on two rolls, high temperature storage sag, high temperature storage viscosity stability and clogging were evaluated. Each evaluation result is shown in Tables 6-8.
The sagability on a printing machine at a temperature that is normally used can be evaluated by the evaluation of the sagability on the two-roll. It is possible to evaluate the sagging property of the prepared ink on a printing machine at a temperature at which it is usually used.

<Evaluation of separation stability at high temperature>
Using the active energy ray-curable inks of Examples 2, 3, 7 to 16, 18 to 24 , Reference Examples 1, 4 to 6, 17, and Comparative Examples 1 to 5, each ink was put in a glass bottle and sealed. In this state, the ink was allowed to stand at 60 ° C. for one month, and then the ink separation state was visually observed and evaluated based on the following three evaluation criteria.
-Evaluation criteria-
○: Separation is hardly observed.
(Triangle | delta): Although isolation | separation is seen a little, it is a level which is satisfactory practically.
X: Remarkable separation was observed and there was a problem in practical use.

<Evaluation of film strength>
Using the active energy ray-curable inks of Examples 2, 3, 7 to 16, 18 to 24 , Reference Examples 1, 4 to 6, 17, and Comparative Examples 1 to 5, a stencil printing machine ("Saterio A650"; after printing the image using Ltd. Ricoh), rubbed over the printed matter of an image with a cloth was visually evaluated based on the cleanliness of the fabric to the evaluation criteria for the following three levels.
-Evaluation criteria-
○: Dirt is hardly seen.
Δ: Slight dirt is observed, but it is at a level that causes no practical problems.
X: Remarkable dirt is seen and there is a problem in practical use.

<Evaluation of sag on two rolls>
Using the active energy ray-curable inks of Examples 2, 3, 7 to 16, 18 to 24 , Reference Examples 1, 4 to 6, 17, and Comparative Examples 1 to 5, the ink in the printing machine at 23 ° C. The shape of the ink on the roll for kneading (consisting of two rolls) was visually evaluated based on the following four-stage evaluation criteria.
-Evaluation criteria-
A: No change is observed.
○: Some changes are observed, but there is no practical problem.
Δ: Although the shape of the ink reservoir changes from the kneaded state, it is at a level that causes no problem in practical use.
X: The ink is flattened and has fluidity, which is problematic in practice.

<High temperature storage sag>
Example 2,3,7～16,18 24, Reference Examples 1,4～6,17, and with the active energy beam-curable ink of Comparative Example 1-5, 1 month storage samples of the 60 ° C. The fluidity was visually evaluated based on the following three evaluation criteria. In addition, the temperature of the sample at the time of evaluation is 23 degreeC.
-Evaluation criteria-
○: Fluidity is not observed.
(Triangle | delta): Although the tendency of fluidity | liquidity is seen, it is a level which is satisfactory practically.
X: Fluidity and practical problems.

<High temperature storage viscosity stability>
Using the active energy ray-curable inks of Examples 2, 3, 7 to 16, 18 to 24 , Reference Examples 1, 4 to 6, 17, and Comparative Examples 1 to 5, the viscosity of the sample before storage, and this The viscosity after storing the sample at 60 ° C. for 1 month was measured with a stress rheometer (CSR-10 manufactured by Borin). Specifically, using a cone having a diameter of 2 cm and an angle of 2 degrees, a flow curve with a stress of 12.5 to 150 Pa was measured at a measurement temperature of 23 ° C., and Casson plastic viscosity and Casson yield were obtained according to the following Casson approximation formula. The value was calculated, and the viscosity at the shear rate of 10 s ⁻¹ was obtained from the calculation and used as the viscosity of the sample.
In the above equation, τ represents shear stress. τ ₀ represents a yield value. Eta represents the plastic viscosity. D represents the shear rate.

Then, the amount of change in the viscosity of the sample after storage with respect to the sample before storage was evaluated based on the following four evaluation criteria.
-Evaluation criteria-
A: Increase in viscosity of less than 20%, or decrease in viscosity of less than 15% B: Increase in viscosity of 20% or more, or decrease in viscosity of 15% or more, but at a level that is not problematic in practice.
(Triangle | delta): Although it is a viscosity rise of 40% or more, it is a level which is satisfactory practically.
X: Viscosity increase of 60% or more, which is problematic in practical use.

<Clogged plate>
Using the active energy ray-curable inks of Examples 2, 3, 7 to 16, 18 to 24 , Reference Examples 1, 4 to 6, 17, and Comparative Examples 1 to 5, Satellite A650 manufactured by Ricoh Co. , Ltd. was used. After printing 1000 sheets, the surface of the plate was visually evaluated based on the following three evaluation criteria.
-Evaluation criteria-
○: There is no sign of clogging.
(Triangle | delta): Although the sign of clogging is observed slightly, it is a level which is satisfactory practically.
X: Clogging is observed and there is a problem in practical use.

The results shown in Tables 6 to 8 showed the following.
By comparing Examples 2, 3 and Reference Examples 1, 4 to 6 with Comparative Examples 1, 2, and 4, it is shown that when hydrophilic silica is added as an extender, the separation stability at high temperatures is increased. It was done.
By comparing Examples 2, 3 and Reference Examples 1, 4 to 6 with Comparative Examples 3 and 5, when the primary particle diameter of hydrophilic silica is 100 nm or less, film strength can be imparted, It has been shown that sagging on a two-roll (sag on a printing machine at a commonly used temperature) can be further prevented, and sagging of ink exposed to high temperatures can be further prevented.
By comparing Reference Example 4 with Reference Examples 5 and 6, it is shown that if the specific surface area of the hydrophilic silica is 280 m ² / g or less, the sagging property on the two rolls can be further prevented. It was done.
By comparing Examples 2 and 3 with Reference Examples 1, 4 and 17, when the primary particle diameter of hydrophilic silica is 28 nm or less and the specific surface area is 190 m ² / g or less, It was shown that the separation stability can be further increased, the sagability on the two rolls can be further prevented, and clogging can be further prevented.

By comparing Examples 7 to 10, 18, 20 to 24 with Example 3 and containing a monomer having an ethylene oxide unit as a polymerizable component, the dripping property of ink exposed to high temperature is further prevented. It was shown that the viscosity stability during high temperature storage can be further improved.
By comparing Examples 8, 12, 13, and 19 with Examples 11 and 14, when the number of ethylene oxide units is 6 or more and 19 or less, the sagging property on the two rolls can be further prevented. It was shown that the dripping property of ink exposed to high temperature can be further prevented.
By comparing Examples 22 and 23 with Examples 7 and 24, the content of the monomer having an ethylene oxide unit is 0.02% by mass or more and 20% by mass or less with respect to the total mass of the ink. It was shown that the viscosity stability during high temperature storage can be further improved.

  By comparing Example 15 and Example 16, when the water content is 5% by mass or less with respect to the total mass of the ink, separation stability at high temperatures can be further improved. Indicated.

  The active energy ray curable ink of the present invention can increase the separation stability of the ink at a high temperature and prevent the ink from dripping without impairing the stability to the viscosity change due to the high temperature. It is very useful as an ink for use in a printing press used in offices where there is no ink.

Claims (7)

Ri der primary particle diameter of 28 nm or less, the active energy beam-curable ink having a specific surface area, characterized in that it contains a 190 m 2 / ^g or less der Ru hydrophilic silica. The active energy ray-curable ink according to claim 1, comprising a monomer having an ethylene oxide unit represented by the following structural formula (1).
-(CH ₂ CH ₂ O) − ... Structural formula (1) The active energy ray-curable ink according to claim 2, wherein the number of ethylene oxide units represented by the structural formula (1) is 6 or more and 19 or less. The content of the monomer having an ethylene oxide unit represented by the structural formula (1) is 0.02% by mass or more and 20% by mass or less with respect to the total mass of the ink. Active energy ray curable ink. The active energy ray-curable ink according to any one of claims 1 to 4, wherein the water content is 5% by mass or less based on the total mass of the ink. 6. The active energy ray-curable ink according to claim 1, wherein the active energy ray-curable ink is used for stencil printing in which an image is formed with ink that has passed through the perforated portion by using a stencil sheet perforated by heat-sensitive digital plate making. The active energy ray-curable ink according to any one of claims 1 to 6, wherein when the monomer having an ethylene oxide unit is contained, the monomer having the ethylene oxide unit is a methacrylate monomer.