Photocurable ejection ink

Abstract

To provide a photohardenable ink for discharging capable of favorably performing printing or forming while maintaining discharging properties.SOLUTION: The photohardenable ink for discharging includes a radically polymerizable compound, a photoinitiator, and a thixotropic agent, where the first viscosity measured with a rate of share of 10,000 s-1 is 1,000 mPa s or less, and the second viscosity measured with a rate of share of 10-1 s-1 after applying a share force by a rate of share of 10,000 s-1 for 30 sec. is 10,000 mPa s or more.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a photocurable ink for ejection. [Background technology]

[0002] Ink used in devices such as inkjet printers and dispensers that eject ink and make it fly and land at an appropriate position must have a viscosity that is similar to that at the time of ejection and the time of landing.

[0003] For example, Patent Document 1 discloses an ultraviolet-curable composition that is discharged by an inkjet method in order to improve the discharge stability of the ink, and that contains a polymerizable compound, a metal powder, and a thixotropy inhibitor, and is cured at a shear rate of 1000 s -1 Viscosity η1 [mPa·s] at 1000s -1 After applying shear stress at a shear rate of 10 s for 10 min, the shear rate was reduced to 10 s -1 The present invention discloses an ultraviolet-curable composition characterized in that the viscosity η2 [mPa·s] of the composition satisfies the relationship η2-η1≦3 with respect to the viscosity η2 [mPa·s] measured in the above-mentioned state. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-88820 Summary of the Invention [Problem to be solved by the invention]

[0005] In inkjet printing and additive manufacturing (e.g., a method of manufacturing a three-dimensional object by layering ink with a dispenser), it is preferable that the ink that lands at the printing position has high viscosity and does not wet and spread, in order to improve the quality of printing and modeling (e.g., by suppressing ink bleeding) and to improve the modeling speed (e.g., by increasing the thickness of ink layered at one time and accelerating the layering speed).

[0006] However, as shown in Patent Document 1 and other documents, it is not possible to make the viscosity of ink when ejected significantly different from the viscosity of ink when it lands, so in order to increase the viscosity when it lands, it is necessary to increase the viscosity when it is ejected as well. However, ink with a high viscosity when ejected is prone to clogging inside the ejection device and at the ejection orifice. In particular, ink with a viscosity of 10,000 mPa·s or higher when it lands is preferable for the production of three-dimensional objects, but it is nearly impossible to eject ink with such a viscosity normally.

[0007] That is, there is a trade-off between ink ejection performance and printing or modeling performance (for example, printing quality, modeling quality, or modeling speed).

[0008] In view of the above, an object of the present invention is to provide a photocurable ink for ejection that can be suitably used for printing or modeling while maintaining ejection properties. [Means for solving the problem]

[0009] The photocurable ejection ink according to a first aspect of the present invention comprises: Contains a radical polymerizable compound, a photoinitiator, and a thixotropic agent, Shear rate 10000s -1 the first viscosity measured by is 1000 mPa s or less, Shear rate 10000s -1 After applying shear force at 10 for 30 seconds, the shear rate was increased to 10 -1 s -1 The second viscosity measured in this state is 10,000 mPa s or more. It is characterized by:

[0010] With the above configuration, the viscosity of the ink can be made low when ejected and high when it lands, so that ink ejection performance and printability or modeling performance can be compatible.

[0011] The radical polymerizable compound may be an acrylate monomer.

[0012] With the above configuration, the viscosity of the ink can be made low when ejected and high when it lands, so that ink ejection performance and printability or modeling performance can be compatible.

[0013] The thixotropic agent may be fine particles of silicon dioxide.

[0014] With the above configuration, the viscosity of the ink can be made low when ejected and high when it lands, so that ink ejection performance and printability or modeling performance can be compatible.

[0015] The radical polymerizable compound has a solubility parameter of less than 10, and The thixotropic agent is a microparticle having a hydrophilic surface. This may also be the case.

[0016] With the above configuration, the viscosity of the ink can be made low when ejected and high when it lands, so that ink ejection performance and printability or modeling performance can be compatible.

[0017] The microparticles having a hydrophilic surface are silicon dioxide microparticles whose surfaces are untreated. This may also be the case.

[0018] The above-mentioned configuration allows the viscosity of the ink to be low when ejected and high when it lands, thereby achieving both ink ejection performance and printability or shaping performance. In addition, silicon dioxide particles with untreated surfaces are inexpensive, making them economical.

[0019] The radical polymerizable compound has a solubility parameter of 10 or more, and The thixotropic agent is a microparticle having a hydrophobic surface. This may also be the case.

[0020] With the above configuration, the viscosity of the ink can be made low when ejected and high when it lands, so that ink ejection performance and printability or modeling performance can be compatible. [Effects of the Invention]

[0021] According to the present invention, printing or modeling can be performed favorably while maintaining ink ejection properties. DETAILED DESCRIPTION OF THE INVENTION

[0022] A photocurable ink for ejection according to one embodiment of the present invention contains a radically polymerizable compound, a photoinitiator, and a thixotropic agent. As will be described later, the thixotropy of the ink is controlled by the thixotropic agent so that the ink can be easily ejected from an ejection port such as a nozzle and the ink is prevented from spreading after landing.

[0023] (discharge device) The ink is used by any ejection device capable of ejecting the ink, particularly an ejection device that ejects the ink to print the ink onto a printing target (for example, a printing medium such as paper, a raw material roll such as cloth, or a building material such as a glass plate or a wooden board), or to form a three-dimensional object by layering the ink.

[0024] The ejection device may be any device that can eject the ink from the ejection port and land it at a specific position, and may be, for example, an inkjet printer equipped with an ejection mechanism (e.g., a print head) of an inkjet type (e.g., a continuous type, an on-demand type (piezo type, or thermal type)), or a dispenser equipped with an ejection mechanism (e.g., a syringe) of another liquid fixed amount ejection type (e.g., a lead screw type, an air pressure type, etc.).

[0025] The ejection device preferably includes a mechanism for applying shear force to the ink by vibration, stirring, compression, etc., to prevent clogging of the ink from its storage unit (e.g., a tank, cartridge, etc.) to the ejection orifice (particularly at the ejection orifice). Examples of such mechanisms for applying shear force include those described in JP-A Nos. 2005-212412, 2008-149594, and 8-216425.

[0026] (Radical polymerizable compound) The radical polymerizable compound is not particularly limited as long as it is a compound having radical polymerizability, but acrylates are preferred in terms of polymerizability, durability of the cured product, solubility of initiators and sensitizers, etc. In particular, acrylate monomers are preferred as radical polymerizable compounds.

[0027] Examples of acrylates include monofunctional acrylates such as phenol EO modified acrylate, nonylphenol EO modified acrylate, and ethoxydiethylene glycol acrylate; Bifunctional acrylates such as hexanediol diacrylate, hexanediol EO-modified diacrylate, hydroxypivalic acid neopentyl glycol diacrylate, neopentyl glycol PO-modified diacrylate, tripropylene glycol diacrylate, dipropylene glycol diacrylate, bisphenol A EO-modified diacrylate, polyethylene glycol diacrylate, and polypropylene glycol diacrylate, Examples of the polyfunctional acrylate include trimethylolpropane triacrylate, trimethylolpropane EO-modified triacrylate, trimethylolpropane PO-modified triacrylate, glycerin propoxy triacrylate, pentaerythritol triacrylate, pentaerythritol EO-modified tetraacrylate, ditrimethylolpropane tetraacrylate, and dipentaerythritol hexaacrylate.

[0028] These radical polymerizable compounds may be used alone or in combination of two or more.

[0029] Among these, bifunctional acrylates are preferred in terms of mechanical properties such as durability and rigidity of the resulting shaped article, and a combination of PO-modified neopentyl glycol PO-modified diacrylate and bisphenol A EO-modified diacrylate is more preferred.

[0030] Examples of monofunctional acrylates that can be used include phenol EO-modified (n=2) acrylate (trade name: Miramer M142), phenol EO-modified (n=4) acrylate (trade name: Miramer M144), nonylphenol EO-modified (n=8) acrylate (trade name: Miramer M166), and ethoxydiethylene glycol acrylate (trade name: Miramer M170), all of which are manufactured by Bigen Specialty Chemical Co., Ltd.

[0031] Examples of bifunctional acrylates include hexanediol diacrylate (trade name: Miramer M200), hexanediol EO-modified diacrylate (trade name: Miramer M202), hydroxypivalic acid neopentyl glycol diacrylate (trade name: Miramer M210), neopentyl glycol PO-modified (n=2) diacrylate (trade name: Miramer M216), tripropylene glycol diacrylate (trade name: Miramer M220), dipropylene glycol diacrylate (trade name: Miramer M222), bisphenol A EO-modified (n=4) diacrylate (trade name: Miramer M240), bisphenol A EO-modified (n=10) diacrylate (trade name: Miramer M2100), and polyethylene glycol (molecular weight 400) diacrylate (abbreviated name: PEG400DA, trade name: Miramer M2100), all of which are manufactured by Bigen Specialty Chemical Co., Ltd. M280), polyethylene glycol (molecular weight 300) diacrylate (abbreviated name: PEG300DA, trade name: Miramer M284), polypropylene glycol diacrylate (trade name: Miramer M2040), etc. can be used.

[0032] Examples of polyfunctional acrylates include trimethylolpropane triacrylate (trade name: Miramer M300), trimethylolpropane EO-modified (n=3) triacrylate (trade name: Miramer M3130), trimethylolpropane EO-modified (n=6) triacrylate (trade name: Miramer M3160), trimethylolpropane EO-modified (n=9) triacrylate (trade name: Miramer M3190), trimethylolpropane PO-modified (n=3) triacrylate (trade name: Miramer M360), glycerin propoxy triacrylate (trade name: Miramer M320), pentaerythritol triacrylate (trade name: Miramer M340), pentaerythritol EO-modified tetraacrylate (trade name: Miramer M4004), and ditrimethylolpropane tetraacrylate (trade name: Miramer M360), all of which are manufactured by Bigen Specialty Chemical Co., Ltd. M410), dipentaerythritol hexaacrylate (trade name: Miramer M600), etc. can be used.

[0033] The content of the radical polymerizable compound in the ink is not particularly limited, but is preferably 70 to 99% by mass, more preferably 75 to 90% by mass, and particularly preferably 80 to 85% by mass.

[0034] (Photoinitiator / sensitizer) The photoinitiator is not particularly limited as long as it generates radicals and cures the radically polymerizable compound when irradiated with light of a specific wavelength (for example, ultraviolet light).

[0035] For example, the initiator may be an aminoalkylphenone initiator, a phosphine oxide initiator, etc. The initiator may be used alone or in combination of two or more types.

[0036] Among the aminoalkylphenone initiators, α-aminoalkylphenone initiators are preferred, and 2-benzyl-2-(dimethylamino)-4′-morpholinobutyrophenone is more preferred.

[0037] Examples of the aminoalkylphenone initiator that can be used include 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one (trade name: Omnirad907 (formerly BASF product name: Irgacure907)), 2-benzyl-2-(dimethylamino)-4'-morpholinobutyrophenone (trade name: Omnirad369 (formerly BASF product name: Irgacure369)), and 2-dimethylamino-2-(4-methylbenzyl)-1-(4-morpholin-4-yl-phenyl)-butan-1-one (trade name: Omnirad379EG (formerly BASF product name: Irgacure379EG)), all of which are manufactured by IGM Resins.

[0038] The phosphine oxide initiator is preferably an acylphosphine oxide photopolymerization initiator, and 2,4,6-trimethylbenzoyl-diphenylphosphine oxide and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide are more preferred.

[0039] Examples of phosphine oxide initiators that can be used include 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (trade name: Omnirad TPO H (formerly BASF's trade name: Irgacure TPO)) and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (trade name: Omnirad819 (formerly BASF's trade name: Irgacure819)), both manufactured by IGM Resins.

[0040] In addition to the initiator, a sensitizer may be blended into the ink. The sensitizer imparts photosensitivity to a wavelength region to which the initiator has no photosensitivity, or increases the photosensitivity of the initiator.

[0041] For example, the sensitizer may be a thioxanthone-based sensitizer, 2-isopropylthioxanthone, 2,4-diethylthioxanthen-9-one, etc. The sensitizer may be used alone or in combination of two or more kinds.

[0042] Examples of thioxanthone sensitizers include thioxanthone, 2,4-diethyl-9H-thioxanthen-9-one, and 2-isopropylthioxanthone.

[0043] Examples of thioxanthone-based sensitizers that can be used include thioxanthone manufactured by Tokyo Chemical Industry Co., Ltd., 2,4-diethyl-9H-thioxanthen-9-one manufactured by Wako Pure Chemical Industries Co., Ltd., and 2-isopropylthioxanthone manufactured by Tokyo Chemical Industry Co., Ltd.

[0044] If only aminoalkylphenone initiators and thioxanthone sensitizers, or only phosphine oxide initiators and thioxanthone sensitizers, are used as initiators and sensitizers in the ink, there is a limit to the amount of each initiator that can be dissolved, which may result in an insufficient amount of initiator, resulting in insufficient internal curing of the ink. However, if an aminoalkylphenone initiator, a phosphine oxide initiator, and a thioxanthone sensitizer are used in combination in the ink, the total amount of initiator dissolved in the ink can be increased, and the ink can contain a sufficient amount of initiator that generates a sufficient amount of radicals for curing when exposed to light with a wavelength that easily penetrates the ink (for example, light with a wavelength of 405 nm), thereby improving the internal curing of the ink.

[0045] The total content of initiator and sensitizer in the ink is not particularly limited, but is preferably 1 to 25% by mass, more preferably 5 to 20% by mass, and particularly preferably 10 to 15% by mass. A content of the curing agent within this range is preferred in terms of the reactivity of the radical polymerizable compound.

[0046] (thixotropic agent) The thixotropic agent is not particularly limited as long as it is a compound that imparts the desired thixotropy to the ink, but fine particles of silicon dioxide are preferred in terms of compatibility with radical polymerizable compounds (especially acrylate monomers).

[0047] Examples of such silicon dioxide particles include fumed silica such as hydrophilic fumed silica and hydrophobic fumed silica, silica such as mesoporous silica, and alumina.

[0048] Furthermore, when the thixotropic agent is composed of fine particles, it is desirable to appropriately select the surface affinity based on the Hildebrand solubility parameter (SP value) of the radical polymerizable compound. The SP value of the radical polymerizable compound or a mixture thereof can be calculated according to conventional methods.

[0049] When the SP value of the radical polymerizable compound is less than about 10 (e.g., 9.5 or less, 9 or less), the thixotropic agent is preferably a fine particle having a hydrophilic surface. For example, such a fine particle can be hydrophilic fumed silica. As the hydrophilic fumed silica, Aerosil A255, Aerosil A300, Aerosil A380, etc. manufactured by Aerosil Co., Ltd. can be used. Furthermore, as the fine particle having a hydrophilic surface, silicon dioxide fine particles with an untreated surface can also be used.

[0050] When the SP value of the radical polymerizable compound is about 10 or more (e.g., 10.5 or more, 11 or more), the thixotropic agent is preferably a fine particle having a hydrophobic surface. For example, such a fine particle can be hydrophobic fumed silica. Examples of hydrophobic fumed silica that can be used include Aerosil R972, Aerosil R974, and Aerosil R104 manufactured by Aerosil Co., Ltd.

[0051] When the thixotropic agent is in the form of fine particles, the particle size is arbitrary as long as it can impart thixotropy to the ink and enable ejection. 50 It is preferable that the D50 is 0.1 to 0.5 μm. For example, this D50 can be measured by a laser diffraction / scattering particle size distribution measuring device LA960 (manufactured by HORIBA).

[0052] The content of the thixotropic agent in the ink is not particularly limited, but the content of the thixotropic agent consisting of fine particles with hydrophilic surfaces is preferably 2 to 12 mass%, and more preferably 4 to 8 mass%, and the content of the thixotropic agent consisting of fine particles with hydrophobic surfaces is preferably 4 to 16 mass%, and more preferably 6 to 12 mass%.

[0053] (thixotropy) The thixotropy of the ink is controlled by the thixotropic agent described above so that the ink can be easily ejected from an ejection port such as a nozzle and the ink is prevented from spreading after landing.

[0054] In particular, the thixotropy of this ink is -1 The viscosity of this ink measured at a shear rate of 10,000 s -1 After applying shear force at 10 for 30 seconds, the shear rate was increased to 10 -1 s -1 When the viscosity of the ink measured under these conditions is defined as the second viscosity, it is preferable that the second viscosity is adjusted to be higher than the first viscosity.

[0055] The first viscosity is preferably 1000 mPa·s or less, 500 mPa·s or less, or 100 mPa·s or less.

[0056] The second viscosity is preferably 10,000 mPa·s or more, 50,000 mPa·s or more, or 100,000 mPa·s or more.

[0057] The viscosity recovery time of the ink is preferably shorter than the time it takes for the ink to be cured by light irradiation after landing. For example, the recovery time is preferably 10 seconds or less, 5 seconds or less, or 2 seconds or less. The shorter the recovery time, the more the ink can be prevented from wetting and spreading before light irradiation. This further reduces ink bleeding and defective modeling of three-dimensional objects.

[0058] The ink viscosity was measured at a temperature of 25°C and a shear rate of 10 -1 (1 / s) and shear rate 104 The viscosity (mPa·s) was measured after a sufficient time had passed and the ink had stabilized at a shear rate of 1 / s. A rheometer (manufactured by Anton Paar, product name: MCR302) or the like can be used to measure the viscosity. The recovery time of the ink viscosity was measured by subjecting the ink to a low shear rate (10 -1 (1 / s)), and then the shear rate was suddenly increased to a high shear rate (10 4 The shear rate was increased to 1 / s and sheared for 30 seconds, and then the shear rate was decreased to a low shear rate, and the time it took for the ink viscosity to recover to 80% of the viscosity at the initial low shear rate was measured. The viscosity recovery time can be measured using a rheometer (manufactured by Anton Paar, product name: MCR302) or the like.

[0059] (Other ingredients) The ink may contain other components within the scope of the present invention. Examples of other components include fillers, colorants, dispersants, initiators, plasticizers, surfactants, surface conditioners, leveling agents, antifoaming agents, antioxidants, charge-imparting agents, bactericides, preservatives, deodorizers, charge control agents, wetting agents, antiskinning agents, fragrances, pigment derivatives, and solvents. Some of these components may have a slight effect on the thixotropy of the ink, but such effects can be offset by appropriately adjusting the content of the thixotropic agent described above.

[0060] Examples of fillers include titanium oxide, zinc oxide (ZnO), zinc dioxide (ZnO2), antimony trioxide, indium tin oxide, aluminum oxide, and barium titanate.

[0061] As the coloring material, known dyes and pigments can be used, including inorganic pigments and organic pigments.

[0062] Examples of inorganic pigments include titanium oxide, zinc oxide, zinc oxide, tripon, iron oxide, aluminum oxide, silicon dioxide, kaolinite, montmorillonite, talc, barium sulfate, calcium carbonate, cadmium red, red iron oxide, molybdenum red, chrome vermilion, molybdate orange, yellow lead, chrome yellow, cadmium yellow, yellow iron oxide, titanium yellow, chromium oxide, pyridian, cobalt green, titanium cobalt green, cobalt chrome green, ultramarine blue, Prussian blue, cobalt blue, cerulean blue, manganese violet, cobalt violet, and mica.

[0063] Examples of organic pigments include azo pigments, azomethine pigments, polyazo pigments, phthalocyanine pigments, quinacridone pigments, anthraquinone pigments, indigo pigments, thioindigo pigments, quinophthalone pigments, benzimidazolone pigments, isoindoline pigments, isoindolinone pigments, and carbon black.

[0064] When the ink is a cyan ink, CI Pigment Blue 1, 2, 3, 15:3, 15:4, 15:34, 16, 22, 60, etc. can be blended as a coloring material.

[0065] When the ink is to be used as a magenta ink, CI Pigment Red 5, 7, 12, 48(Ca), 48(Mn), 57(Ca), 57:1, 112, 122, 123, 168, 184, 202, 209, CI Pigment Violet 19, etc. may be blended as colorants.

[0066] When the ink is to be a yellow ink, CI Pigment Yellow 1, 2, 3, 12, 13, 14C, 16, 17, 73, 74, 75, 83, 93, 95, 97, 98, 109, 110, 114, 120, 128, 129, 130, 138, 150, 151, 154, 155, 180, 185, or the like can be blended as a colorant.

[0067] When using this ink as a black ink, it is possible to blend HCF, MCF, RCF, LFF, SCF manufactured by Mitsubishi Chemical Corporation, Monarch and Regal manufactured by Cabot Corporation, Color Black, Special Black, and Printex manufactured by Degussa-Huls, Toka Black manufactured by Tokai Carbon Co., Ltd., and Raven manufactured by Columbia Corporation.

[0068] The content of the coloring material in the optical ink is not particularly limited, but when a coloring material is used, it is preferably 1 to 20% by mass, and more preferably 1 to 10% by mass in the ink.

[0069] When a pigment is used as the coloring material, the ink may contain a dispersant to disperse the pigment.

[0070] Examples of dispersants include low molecular weight dispersants and polymeric dispersants, and more specifically, examples include nonionic, cationic, and anionic surfactants, polyester polymeric dispersants, acrylic polymeric dispersants, and polyurethane polymeric dispersants.

[0071] The present ink can be prepared by, but not limited to, a method for producing the ink, for example, by mixing and stirring various initiators, a radical polymerizable compound, and other components that may be added as needed.

[0072] Examples of mixers include lead screw type feeders, three-one motors, magnetic stirrers, dispersers, homogenizers, container-driven media mills such as ball mills, centrifugal mills and planetary ball mills, high-speed rotary mills such as sand mills, media stirring mills such as stirred tank mills, bead mills, high-pressure injection mills and dispersers.

[0073] (Effects of this ink) Conventionally, in inkjet printing and additive manufacturing (for example, a method of manufacturing a three-dimensional object by layering ink with a dispenser), it is preferable that the ink that lands at the printing position has high viscosity and does not wet and spread in order to improve the quality of printing and modeling (for example, by suppressing ink bleeding) and the speed of modeling (for example, by increasing the thickness of ink layered at one time and accelerating the layering speed), but such high-viscosity ink is prone to ink clogging, and depending on the viscosity, it has even been impossible to eject it. In other words, there has been a trade-off between the ejection ability of the ink and the printability or modeling ability.

[0074] However, according to the present invention, the thixotropy of the ink is suitably adjusted, so that when the ink is ejected, which applies high shear force, the viscosity is low enough to allow ejection, and when the ink is landed, which applies no shear force (or only very low shear force), the viscosity is high enough to prevent the ink from spreading or wetting, thereby achieving both ink ejectability and printability or modeling properties. As a result, this ink allows for suitable printing or modeling while maintaining ejectability.

[0075] (Example) EXAMPLES The present invention will be described below based on examples, but the present invention is not limited to these examples. Performance tests of various ink samples were carried out by the following methods.

[0076] (thixotropy test) (1-1) Viscosity / shear rate Using a rheometer (manufactured by Anton Paar, product name: MCR302), the temperature was 25°C and the shear rate was 10 -1 (1 / s) and shear rate 10 4 The viscosity (mPa·s) was measured after sufficient time had passed and the viscosity stabilized at (1 / s). (1-2) Recovery time The ink was subjected to a low shear rate (10 ) at 25°C for 10 seconds while measuring the viscosity (mPa·s) over time using a rheometer (manufactured by Anton Paar, product name: MCR302). -1 (1 / s)), and then the shear rate was suddenly increased to a high shear rate (104 The shear rate was increased to 1 / s (1 / s) and sheared for 30 seconds, after which the shear rate was decreased to a low shear rate, and the time it took for the viscosity of the ink to recover to 80% of the viscosity at the initial low shear rate was measured.

[0077] Example 1 1.5 parts of 2-benzyl-2-(dimethylamino)-4'-morpholinobutyrophenone (manufactured by BASF, trade name: Irgacure 369) as an aminoalkylphenone initiator, 1.5 parts of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (manufactured by BASF, trade name: TPO) and 1.5 parts of bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (manufactured by IGM Resins, trade name: Omnir) as phosphine oxide initiators, ad819) 2.5 parts, 2,4-diethylthioxanthen-9-one (LAMBSON, trade name: DETX) 1.0 part as a thioxanthone-based sensitizer, functionalized amine coagent (DSM, trade name: AgiSyn008) 2.0 parts as an amine-based initiator aid, neopentyl glycol PO-modified diacrylate (abbreviated name: NPG(PO)2DA) (Bigen Specialty Chemical Co., Ltd., trade name: Miramer) as a radical polymerizable compound. M216, abbreviated name: PONPGDA M216, viscosity 30 mPa·s (25°C), acid value 0.3 mg KOH / g, hydroxyl value 20 mg KOH / g, molecular weight 328, refractive index 1.447) 52.93 parts and bisphenol A EO-modified (n = 10) diacrylate (manufactured by Bigen Specialty Chemical Co., Ltd., trade name: Miramer M2100, abbreviated name: BPE10A M2100, viscosity 700 mPa·s (25°C), acid value 0.2 mg KOH / g, hydroxyl value 20 mg KOH / g, molecular weight 770, refractive index 1.516) 30.0 parts, as a thixotropic agent, fumed silica (surface-untreated silica, manufactured by Evonik, trade name: Aerosil A300) 5.0 parts, as a surface preparation agent, fully cross-linked silicone polyether acrylate (Evonik Resources 0.07 parts of TEGO RAD2100 (trade name: short-chain siloxane skeleton / long-chain organically modified highly crosslinked additive) manufactured by Evonik Resource Efficiency GmbH was added and mixed to obtain ink E1.

[0078] Example 2 Ink E2 was obtained in the same manner as in Example 1, except that only 8.0 parts of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide and 2.0 parts of 2,4-diethylthioxanthen-9-one, which are phosphine oxide initiators, were used as initiators, 74.9 parts of neopentyl glycol PO-modified diacrylate was used as the radical polymerizable compound, the content of the thixotropic agent was 15.00 parts, and the content of the surface conditioner was 0.10 parts.

[0079] Example 3 Ink E3 was obtained in the same manner as in Example 1, except that the content of the thioxanthone-based sensitizer was 2.0 parts, 100 parts of phenoxyethyl acrylate (manufactured by MIWON, trade name: Miramer M140) and 10.0 parts of pentaerythritol triacrylate (manufactured by MIWON, trade name: Miramer M340) were used as the radical polymerizable compounds, and 8.0 parts of fumed silica (surface-treated silica, manufactured by Evonik, trade name: Aerosil R974) was used as the thixotropic agent.

[0080] (Comparative Example 1) Ink CE1 was obtained in the same manner as in Example 3, except that the content of phenoxyethyl acrylate was 108 parts and no thixotropic agent was added.

[0081] (Comparative Example 2) Ink CE2 was obtained in the same manner as in Example 3, except that the content of phenoxyethyl acrylate was 68.93 and 8.0 parts of fumed silica (surface-untreated silica, manufactured by Evonik, trade name: Aerosil A300) was used as the thixotropic agent.

[0082] The viscosity measurement results for the resulting inks E1, E2, E3, CE1, and CE2 at shear rates of 1 (1 / s) and 1000 (1 / s) are shown in Table 1. The calculated SP values ​​of the acrylates in inks E1 and E2 were less than 10, while the calculated SP values ​​of the acrylates in inks E3, CE1, and CE2 were 10 or more. From Table 1, it can be seen that for inks E1, E2, and E3, the viscosity was 10 at low shear rates. 5The viscosity of inks E1, E2, and E3, which was around mPa·s, decreases as the shear rate increases, dropping to several hundred mPa·s, indicating that inks E1, E2, and E3 exhibit thixotropy. Furthermore, while ink E3 exhibits thixotropy, inks CE1 and CE2 do not, suggesting that when the solubility parameter of a radical polymerizable compound is 10 or higher, the thixotropic agent must have a hydrophobic surface.

[0083] [Table 1] *Comparative Example 1 Ink CE1 did not exhibit thixotropy, so recovery time could not be measured.

[0084] The present invention allows various embodiments and modifications without departing from the broad spirit and scope of the present invention. Furthermore, the above-described embodiments are intended to explain the present invention and do not limit the scope of the present invention. That is, the scope of the present invention is defined by the claims, not the embodiments. Various modifications made within the scope of the claims and the meaning of the invention equivalent thereto are considered to be within the scope of the present invention.

Claims

1. A photocurable ejection ink containing a radical polymerizable compound, a photoinitiator, and a thixotropic agent, When the solubility parameter of the radical polymerizable compound is less than 10, the thixotropic agent is a fine particle having a hydrophilic surface, when the solubility parameter of the radical polymerizable compound is 10 or more, the thixotropic agent is a fine particle having a hydrophobic surface; The ink was subjected to a shear rate of 10,000 s －１ the first viscosity measured by is 1000 mPa s or less, The ink was subjected to a shear rate of 10,000 s －１ After applying shear force for 30 seconds, the shear rate was increased to 10 －１ s －１ The second viscosity measured in this state is 10,000 mPa s or more, The ink was heated at a temperature of 25° C. for 10 seconds at a shear rate of 10 －１ s －１ Then, the shear rate was increased to 10,000 s －１ and sheared for 30 seconds, then the shear rate was increased to 10 －１ s －１ The viscosity of the ink then first decreases at a shear rate of 10 －１ s －１ The time required for the viscosity to recover to 80% of the original value when sheared is 10 seconds or less. Photocurable ejection ink.

2. The ink of claim 1 , wherein the radical polymerizable compound is an acrylate monomer.

3. 3. The ink according to claim 1, wherein the thixotropic agent is fine particles of silicon dioxide.

4. The solubility parameter of the radical polymerizable compound is less than 10, the thixotropic agent is a fine particle having a hydrophilic surface, The microparticles having a hydrophilic surface are silicon dioxide microparticles whose surfaces are untreated. The ink of claim 1.

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