JP2021021008A - Photohardenable ink for discharging - Google Patents

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

The present invention relates to a photocurable ejection ink.

The ink used in a device such as an inkjet printer or a dispenser that ejects ink to fly to an appropriate position and land on it must have a viscosity at the time of ejection and a viscosity at the time of impact that do not differ significantly.

For example, Patent Document 1 is an ultraviolet curable composition ejected by an inkjet method in order to improve the ejection stability of an ink, which comprises a polymerizable compound, a metal powder, and a thixophilic inhibitor. viscosity η1 [mPa · s] at a shear rate of 1000 s ^-1, after continuously applied shear stress for 10 minutes at a shear rate of 1000 s ^-1, viscosity is determined by measuring in a state in which the shear rate was ^{10s -1} .eta.2 [ mPa · s] discloses an ultraviolet curable composition characterized by satisfying the relationship of η2-η1 ≦ 3.

JP-A-2017-88820

In inkjet printing and additive manufacturing (for example, a method of laminating ink with a dispenser to produce a three-dimensional model), the quality of printing and modeling can be improved (for example, ink bleeding can be suppressed), and modeling can be performed. In order to improve the speed (for example, increase the thickness of the ink to be laminated at one time and increase the stacking speed), it is preferable that the ink landed at the printing position has a high viscosity and does not spread wet.

However, conventionally, as shown in Patent Document 1 and the like, the viscosity of the ink at the time of ejection and the viscosity of the ink at the time of impact cannot be significantly different. Therefore, in order to increase the viscosity at the time of impact, at the time of ejection. It is necessary to increase the viscosity, but ink having a high viscosity at the time of ejection tends to cause ink clogging in the ejection device or at the ejection port. In particular, for the production of a three-dimensional model, an ink having a viscosity at the time of landing of 10,000 mPa · s or more is preferable, but it is almost impossible to normally eject an ink having such a viscosity.

That is, there was a trade-off relationship between ink ejection property and printability or formability (for example, print quality, formability, or formability).

In view of the above, it is an object of the present invention to provide a photocurable ejection ink capable of printing or modeling while maintaining ejection properties.

The photocurable ejection ink according to the first aspect of the present invention is
It contains a radically polymerizable compound, a photoinitiator, and a thixotropic agent.
The first viscosity measured at a shear rate of 10000 s ^-1 is 1000 mPa · s or less.
The second viscosity measured at a shear rate of 10 ^-1 s ^-1 after continuing to apply a shearing force for 30 seconds at a shear rate of 10000 s ^-1 is 10000 mPa · s or more.
It is characterized by that.

With the above configuration, the viscosity of the ink can be lowered at the time of ejection and increased at the time of impact, so that both the ejection property of the ink and the printability or the formability can be achieved at the same time.

The radically polymerizable compound may be an acrylate monomer.

With the above configuration, the viscosity of the ink can be lowered at the time of ejection and increased at the time of impact, so that both the ejection property of the ink and the printability or the formability can be achieved at the same time.

The thixotropy may be fine particles of silicon dioxide.

With the above configuration, the viscosity of the ink can be lowered at the time of ejection and increased at the time of landing, so that both the ejection property of the ink and the printability or the formability can be achieved at the same time.

The solubility parameter of the radically polymerizable compound is less than 10 and
The thixotropic agent is a fine particle having a hydrophilic surface.
It may be that.

With the above configuration, the viscosity of the ink can be lowered at the time of ejection and increased at the time of impact, so that both the ejection property of the ink and the printability or the formability can be achieved at the same time.

The fine particles having a hydrophilic surface are fine particles of silicon dioxide whose surface is untreated.
It may be that.

With the above configuration, the viscosity of the ink can be lowered at the time of ejection and increased at the time of landing, so that both the ejection property of the ink and the printability or the formability can be achieved at the same time. Further, since the fine particles of silicon dioxide whose surface is untreated are inexpensive, they are excellent in economy.

The solubility parameter of the radically polymerizable compound is 10 or more, and
The thixotropic agent is a fine particle having a hydrophobic surface.
It may be that.

With the above configuration, the viscosity of the ink can be lowered at the time of ejection and increased at the time of landing, so that both the ejection property of the ink and the printability or the formability can be achieved at the same time.

According to the present invention, printing or modeling can be preferably performed while maintaining the ejection property of ink.

The photocurable ejection ink according to one embodiment of the present invention contains a radically polymerizable compound, a photoinitiator, and a thixo agent. The thixotropic property of the ink is controlled by the thixotropy so that the ink can be easily ejected from the ejection port such as a nozzle and the wet spread of the ink after landing is suppressed, as will be described later. There is.

(Discharge device)
This ink is used for printing this ink on any ejection device capable of ejecting this ink, particularly on a printing object (for example, a printing medium such as paper, a raw material roll such as cloth, a building material such as a glass plate or a wooden board). Or, it is used by an ejection device that ejects the present ink in order to laminate the present ink to form a three-dimensional model.

The ejection device is arbitrary as long as the ink can be ejected from the ejection port and landed at a specific position. For example, an inkjet method (for example, a continuous type, an on-demand type (piezo method, or a piezo method)) is used. , Thermal method), etc.) may be an inkjet printer equipped with a discharge mechanism (for example, printhead, etc.), or another liquid quantitative discharge method (for example, lead screw method, pneumatic method, etc.) discharge mechanism (for example, syringe). Etc.) may be provided.

The ejection device vibrates, stirs, and stirs the ink so that the ink does not become clogged from the storage part (for example, tank, cartridge, etc.) where it is stored to the ejection port (particularly at the ejection port). Alternatively, it is preferable to provide a mechanism for applying a shearing force by compression or the like. As a mechanism for imparting such a shearing force, for example, those described in JP-A-2005-212912, JP-A-2008-149594, JP-A-8-216425 and the like can be adopted.

(Radical polymerizable compound)
The radically polymerizable compound is not particularly limited as long as it is a radically polymerizable compound, but acrylate is preferable in terms of polymerizable property, durability of the cured product, solubility of the initiator / sensitizer, and the like. In particular, as the radically polymerizable compound, an acrylate monomer is preferable.

Examples of the acrylate include monofunctional acrylates such as phenol EO modified acrylate, nonylphenol EO modified acrylate, and ethoxydiethylene glycol acrylate.
Hexadiol diacrylate, hexanediol EO modified diacrylate, neopentyl glycol diacrylate hydroxypivalate, neopentyl glycol PO modified diacrylate, tripropylene glycol diacrylate, dipropylene glycol diacrylate, bisphenol A EO modified diacrylate, polyethylene glycol Bifunctional acrylates such as diacrylates and polypropylene glycol diacrylates,
Trimethylolpropane triacrylate, trimethylolpropane EO modified triacrylate, trimethylolpropane PO modified triacrylate, glycerin propoxytriacrylate, pentaerythritol triacrylate, pentaerythritol EO modified tetraacrylate, ditrimethylolpropane tetraacrylate, dipentaerythritol hexaacrylate Polyfunctional acrylates such as, and the like.

These radically polymerizable compounds can be used alone or in combination of two or more.

Among these, a bifunctional acrylate is preferable, and a combination of PO-modified neopentyl glycol PO-modified diacrylate and bisphenol AEO-modified diacrylate is more preferable in terms of mechanical properties such as durability and rigidity of the obtained modeled product.

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

Examples of the bifunctional acrylate include hexanediol diacrylate (trade name: Miramer M200), hexanediol EO-modified diacrylate (trade name: Miramer M202), and neopentyl glycol diacrylate of hydroxypivalate manufactured by Bigen Specialty Chemical Co., Ltd. Product Name: Miramer M210), Neopentyl Glycol PO Modified (n = 2) Diacrylate (Product Name: Miramer M216), Tripropylene Glycol Diacrylate (Product Name: Miramer M220), Dipropylene Glycol Diacrylate (Product 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), polyethylene glycol (molecular weight 400) diacrylate ( Abbreviated name: PEG400DA, trade name: Miramer M280), polyethylene glycol (molecular weight 300) diacrylate (abbreviation name: PEG300DA, trade name: Miramer M284), polypropylene glycol diacrylate (trade name: Miramer M2040) and the like can be used. ..

Examples of the polyfunctional acrylate include trimethylolpropane triacrylate (trade name: Miramer M300), trimethylolpropane EO-modified (n = 3) triacrylate (trade name: Miramer M3130), and trimethylol, manufactured by Bigen Specialty Chemical Co., Ltd. Propane 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 (Product name: Miramer M360), glycerin propoxytriacrylate (trade name: Miramer M320), pentaerythritol triacrylate (trade name: Miramer M340), pentaerythritol EO-modified tetraacrylate (trade name: Miramer M4004), dimethylolpropanetetra Acrylate (trade name: Miramer M410), dipentaerythritol hexaacrylate (trade name: Miramer M600) and the like can be used.

The content of the radically 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.

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

For example, examples of the initiator include an aminoalkylphenone-based initiator and a phosphine oxide-based initiator. The initiator can be used alone or in combination of two or more.

Among the aminoalkylphenone-based initiators, α-aminoalkylphenone-based initiators are preferable, and 2-benzyl-2- (dimethylamino) -4'-morpholinobtyrophenone is more preferable.

The aminoalkylphenone-based initiator is, for example, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropan-1-one (trade name: Omnirad907 (former product of BASF) manufactured by IGM Resins). Name: Irgacure907)), 2-Benzyl-2- (dimethylamino) -4'-morpholinobtyrophenone (trade name: Omnirad369 (former trade name of BASF): Irgacure369)), 2-dimethylamino-2- (4-methyl) Benzyl) -1- (4-morpholin-4-yl-phenyl) -butane-1-one (trade name: Omnirad379EG (former trade name of BASF): Irgacure379EG), and the like can be used.

The phosphine oxide-based initiator is preferably an acylphosphine oxide-based photopolymerization initiator, and 2,4,6-trimethylbenzoyl-diphenylphosphine oxide and biz (2,4,6-trimethylbenzoyl) phenylphosphine oxide are used. More preferred.

The phosphine oxide-based initiator is, for example, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (trade name: Omnirad TPO H (former trade name: BASF)), Biz (2,) manufactured by IGM Regins. 4,6-trimethylbenzoyl) phenylphosphine oxide (trade name: Omnirad819 (former trade name of BASF): Irgacure819) can be used.

Further, in addition to the initiator, a sensitizer may be added to the ink. The sensitizer imparts photosensitivity to a wavelength region in which the initiator does not have photosensitivity, or increases the photosensitivity of the initiator.

For example, examples of the sensitizer include thioxanthone-based sensitizers, 2-isopropylthioxanthone, 2,4-diethylthioxanthene-9-one and the like. The sensitizer may be used alone or in combination of two or more.

Examples of the thioxanthone-based sensitizer include thioxanthone, 2,4-diethyl-9H-thioxanthene-9-one, 2-isopropylthioxanthone and the like.

The thioxanthone-based sensitizers are, for example, thioxanthone manufactured by Tokyo Chemical Industry Co., Ltd., 2,4-diethyl-9H-thioxanthene-9-one manufactured by Wako Pure Chemical Industry Co., Ltd., and 2-isopropyl manufactured by Tokyo Chemical Industry Co., Ltd. Thioxanthone can be used.

If only the aminoalkylphenone-based initiator and the thioxanthone-based sensitizer are used as the initiator / sensitizer to be blended in the ink, or if only the phosphine oxide-based initiator and the thioxanthone-based sensitizer are used, the respective initiators are used. There is a limit to the amount of dissolved initiator, and the amount of initiator may be insufficient, resulting in insufficient internal curing of the ink. However, when an aminoalkylphenone-based initiator, a phosphine oxide-based initiator, and a thioxanthone-based sensitizer are used in combination in an ink, the total amount of the initiators dissolved in the ink can be increased, and the ink can easily penetrate. The internal curability of the ink can be improved by containing an initiator that generates a sufficient amount of radicals for curing with light having a wavelength (for example, light having a wavelength of 405 nm) in a sufficient amount for curing.

The total content of the initiator and the sensitizer in the ink is not particularly limited, but is preferably 1% by mass to 25% by mass, preferably 5% by mass to 20% by mass, and particularly preferably 10% by mass to 15% by mass. .. When the content of the curing agent is in this range, it is preferable in terms of the reactivity of the radically polymerizable compound.

(Thixotropic agent)
The thixotropy is not particularly limited as long as it is a compound that imparts desired thixotropy to the ink, but fine particles of silicon dioxide are preferable in terms of compatibility with a radically polymerizable compound (particularly, an acrylate monomer).

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

When the thixotropy consists of fine particles, it is desirable that the affinity of the surface thereof be appropriately selected based on the solubility parameter (SP value) of Hildebrand, a radically polymerizable compound. The SP value of the radically polymerizable compound or a mixture thereof can be calculated according to a conventional method.

When the SP value of the radically polymerizable compound is less than about 10 (for example, 9.5 or less and 9 or less), the thixotropic agent is preferably fine particles having a hydrophilic surface. For example, examples of such fine particles include hydrophilic fumed silica. As the hydrophilic fumed silica, Aerosil A255, Aerosil A300, Aerosil A380 and the like manufactured by Aerosil Co., Ltd. can be used. Further, as the fine particles having a hydrophilic surface, fine particles of silicon dioxide having an untreated surface can also be used.

When the SP value of the radically polymerizable compound is about 10 or more (for example, 10.5 or more and 11 or more), the thixotropic agent is preferably fine particles having a hydrophobic surface. For example, such fine particles include hydrophobic fumed silica. As the hydrophobic fumed silica, Aerosil R972, Aerosil R974, Aerosil R104 and the like manufactured by Aerosil Co., Ltd. can be used.

When the thixotropy is fine particles, the particle size is arbitrary as long as it imparts thixotropic properties to the ink and can be ejected, but it is measured according to the laser diffraction method, and D ₅₀ is 0.1 to 0.5 μm. Is preferable. For example, this D50 can be measured by a laser diffraction / scattering type particle size distribution measuring device LA960 (manufactured by HORIBA).

The content of the thixotropic agent in this ink is not particularly limited, but the content of the thixotropic agent composed of fine particles having a hydrophilic surface is preferably 2 to 12% by mass, particularly preferably 4 to 8% by mass. The content of the thixotropic agent composed of fine particles having a hydrophobic surface is preferably 4 to 16% by mass, particularly preferably 6 to 12% by mass.

(Thixotropic)
The thixotropy of the ink is controlled by the above-mentioned thixotropic agent so that the ink can be easily ejected from a ejection port such as a nozzle and the wet spread of the ink after landing is suppressed.

In particular, thixotropy of the inks, a first viscosity The viscosity of this ink was measured at a shear rate of 10000s ^-1, after continued applying shearing force 30 seconds minutes at a shear rate of 10000s ^-1, shear rate ^{of 10 -1} When the viscosity of the present ink measured in the state of s ^-1 is set to the second viscosity, it is preferable that the second viscosity is adjusted to be higher than the first viscosity.

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

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

The recovery time of the viscosity of the ink is preferably shorter than the time from the impact of the ink to the curing by light irradiation. 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 it is possible to prevent the ink from spreading wet before light irradiation. As a result, it is possible to further suppress the occurrence of ink bleeding and the molding defect of the three-dimensional modeled object.

The viscosity of the ink was measured at a temperature of 25 ° C. at a shear rate of 10 ^-1 (1 / s) and a shear rate of 10 ⁴ (1 / s) after sufficient time had elapsed and stabilized (mPa ·. s) was measured. A rheometer (manufactured by Antonio Par, trade name: MCR302) or the like can be used for measuring the viscosity. The recovery time of the viscosity of the ink is such that the viscosity (mPa · s) is measured over time, and the ink is sheared at a temperature of 25 ° C. for 10 seconds at a low shear rate (10 ^-1 (1 / s)). then, suddenly the shear rate for 30 seconds sheared is raised to a high shear rate ^{(10 4 (1 / s)} ), then lowering the shear rate to low shear rate, the initial low shear rate viscosity of the ink after the The time required for the viscosity to recover to 80% of the viscosity was measured. A rheometer (manufactured by Antonio Par, trade name: MCR302) or the like can be used for measuring the viscosity recovery time.

(Other ingredients)
The present ink may contain other components as long as the present invention is not impaired. Other ingredients include fillers, colorants, dispersants, initiators, plasticizers, surfactants, surface conditioners, leveling agents, defoamers, antioxidants, charge-imparting agents, bactericides, preservatives, etc. Examples thereof include deodorants, charge regulators, wetting agents, anti-skinning agents, fragrances, pigment derivatives, solvents and the like. It should be noted that some of these components may have a slight effect on the thixotropy of the ink, but such an effect can be offset by appropriately adjusting the content of the thixotropic agent described above.

Examples of the filler include titanium oxide, zinc oxide (ZnO), zinc dioxide (ZnO ₂ ), antimony trioxide, indium tin oxide, aluminum oxide, barium titanate and the like.

Known dyes and pigments can be used as the coloring material. Examples of pigments include inorganic pigments and organic pigments.

Examples of inorganic pigments include titanium oxide, zinc oxide, zinc oxide, trypon, iron oxide, aluminum oxide, silicon dioxide, kaolinite, montmorillonite, talc, barium sulfate, calcium carbonate, cadmium red, bengara, molybdenum red, and chrome bar. Million, Molybdate Orange, Chrome Yellow, Chrome Yellow, Cadmium Yellow, Yellow Iron Oxide, Titanium Yellow, Chromium Oxide, Pyridian, Cobalt Green, Titanium Cobalt Green, Cobalt Chrome Green, Ultramarine Blue, Ultramarine Blue, Navy Blue, Cobalt Blue, Cerulean Examples include blue, manganese violet, cobalt violet, and mica.

Examples of organic pigments include azo-based, azomethine-based, polyazo-based, phthalocyanine-based, quinacridone-based, anthracinone-based, indigo-based, thioindigo-based, quinophthalone-based, benzimidazolone-based, isoindoline-based, isoindolinone-based, and carbon. Examples include black.

When this ink is cyan ink, C.I. I. Pigment Blue 1, 2, 3, 15: 3, 15: 4, 15:34, 16, 22, 60 and the like can be blended.

When this ink is used as magenta ink, C.I. I. Pigment Red 5, 7, 12, 48 (Ca), 48 (Mn), 57 (Ca), 57: 1, 112, 122, 123, 168, 184, 202, 209, C.I. I. Pigment Violet 19 and the like can be blended.

When this ink is yellow ink, C.I. I. 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 and the like can be blended.

When this ink is used as black ink, Mitsubishi Chemical's HCF, MCF, RCF, LFF, SCF, Cabot's Monarch, Regal, Degussa Huls' color black, Special Black, Printex, Tokai Talker Black made by Carbon, Raven made by Colombia, etc. can be blended.

The content of the coloring material in the light ink is not particularly limited, but when the coloring material is used, it is preferably 1 to 20% by mass, more preferably 1 to 10% by mass in the present ink.

When a pigment is used as the coloring material, a dispersant can be contained in the ink in order to disperse the pigment.

Examples of the dispersant include low molecular weight dispersants and high molecular weight dispersants, and more specifically, nonionic, cationic, anionic surfactants, polyester polymer dispersants, and acrylic polymer dispersions. Agents, polyurethane polymer dispersants and the like.

The ink can be prepared, for example, by mixing and stirring various initiators, radically polymerizable compounds, and other components to be added if necessary, although not limited by the production method.

Mixers include lead screw type feeders, three-one motors, magnetic stirrers, dispersers, homogenizers, ball mills, centrifugal mills, container drive medium mills such as planetary ball mills, high-speed rotary mills such as sand mills, and media such as stirring tank type mills. Examples include a stirring mill, a bead mill, a high pressure injection mill, and a disper.

(Effect of this ink)
Conventionally, in inkjet printing and additional manufacturing (for example, a method of laminating ink with a dispenser to manufacture a three-dimensional model), the quality of printing and modeling is improved (for example, ink bleeding is suppressed). In order to improve the molding speed (for example, increase the thickness of the ink to be laminated at one time and increase the lamination speed), it is preferable that the ink landed at the printing position has high viscosity and does not spread wet. Such high-viscosity ink is prone to ink clogging, and depending on the viscosity, it is impossible to eject the ink. That is, there was a trade-off relationship between ink ejection property and printability or formability.

However, according to the present invention, the chicosis of the ink is preferably adjusted, and when a high shearing force is applied to the ink, the viscosity is low enough to allow ejection, and the shearing force is not applied to the ink (or Since the viscosity is so high that the ink hardly gets wet and spreads at the time of landing (only an extremely low shearing force is added), it is possible to achieve both ink ejection property and printability or formability. Therefore, according to this ink, printing or modeling can be preferably performed while maintaining the ejection property.

(Example)
Hereinafter, the present invention will be described based on examples, but the present invention is not limited to these examples. Performance tests of various ink samples were performed by the following methods.

(Thixotropic test)
(1-1) Viscosity / Shear Rate Using a rheometer (manufactured by Antonio Par, trade name: MCR302), a shear rate of 10 ^-1 (1 / s) and a shear rate of 10 ⁴ (1 / s) at a temperature of 25 ° C. The viscosity (mPa · s) after sufficient time had passed and stabilized at 1 / s) was measured.
(1-2) Recovery time Using a rheometer (manufactured by Anton Par, trade name: MCR302), the viscosity (mPa · s) is measured over time, and the ink is applied at a temperature of 25 ° C. for 10 seconds. sheared at a low shear rate ^{(10 -1 (1 / s)} ), then 30 seconds shear sharply raising the shear rate to high shear rates ^{(10 4 (1 / s)} ), then the shear rate The shear rate was reduced 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 then measured.

(Example 1)
2-benzyl-2- (dimethylamino) -4'-morpholinobtyrophenone (manufactured by BASF, trade name: Irgacure 369) 1.5 parts as an aminoalkylphenone-based initiator, 2,4 as a phosphine oxide-based initiator , 6-trimethylbenzoyl-diphenylphosphine oxide (manufactured by BASF, trade name: TPO) 1.5 parts and Biz (2,4,6-trimethylbenzoyl) phenylphosphin oxide (manufactured by IGM Resins, trade name: Omnirad819) 2.5 parts, 2,4-diethylthioxanthene-9-one (manufactured by LAMBSON, trade name: DETX) 1.0 part as a thioxanthone-based sensitizer, functionalized amine jointly as an amine-based initiator Agent (manufactured by DSM, trade name: AgiSyn008) 2.0 parts, as a radically polymerizable compound, neopentyl glycol PO-modified diacrylate (abbreviation name: NPG (PO) 2DA) (manufactured by Bigen Specialty Chemical Co., Ltd., trade name) : Miramer M216, abbreviated name: PONPGDA M216, viscosity 30 mPa · s (25 ° C), acid value 0.3 mgKOH / g, hydroxyl value 20 mgKOH / g, molecular weight 328, refractive index 1.447) 52.93 parts and bisphenol AEO Modified (n = 10) diacrylate (manufactured by Bigen Specialty Chemical Co., Ltd., trade name: Miramer M2100, abbreviation name: BPE10A M2100, viscosity 700 mPa · s (25 ° C.), acid value 0.2 mgKOH / g, hydroxyl value 20 mgKOH / g, molecular weight 770, viscosity 1.516) 30.0 parts, as a thixo agent, fumed silica (surface untreated silica, manufactured by Evonik, trade name: Aerozil A300) 5.0 parts, complete as a surface preparation agent Add and mix 0.07 part of crosslinked silicone polyether acrylate (manufactured by Evonik Resources Efficiency GmbH, trade name: TEGO RAD2100, short chain siloxane skeleton / long chain organic modified hypercrosslinked additive). , Ink E1 was obtained.

(Example 2)
Radical polymerization using only 8.0 parts of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide and 2.0 parts of 2,4-diethylthioxanthene-9-one of the phosphine oxide-based initiator as the initiator. As the sex compound, only 74.9 parts of neopentyl glycol PO-modified diacrylate was used, and the content of the thixotropic agent was 15.00 parts and the content of the surface conditioner was 0.10 parts, and the same as in Example 1. Obtained ink E2.

(Example 3)
The content of the thioxanthone-based sensitizer was 2.0 parts, and as the radically polymerizable compound, 100 parts of phenoxyethyl acrylate (manufactured by MIWON, trade name: Silica M140) and pentaerythritol triacrylate (manufactured by MIWON, trade name: Only 10.0 parts of Miramer M340) was used, and 8.0 parts of fumed silica (surface-treated silica, manufactured by Evonik, trade name: Aerosil R974) was used as the thixo agent, and the ink E3 was the same as in Example 1. Got

(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.

(Comparative Example 2)
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 a thixotropic agent in the same manner as in Example 3. Ink CE2 was obtained.

Table 1 shows the measurement results of the viscosities of the obtained inks E1, E2, E3, CE1 and CE2 with respect to the shear rates 1 (1 / s) and 1000 (1 / s). The calculated SP value of the acrylate in the inks E1 and E2 is less than 10, and the calculated SP value of the acrylate in the inks E3, CE1 and CE2 is 10 or more. Decreased from Table 1, the ink E1, E2, E3, a viscosity at low shear rate was about ¹⁰ 5 mPa · s is the shear rate is increased to decrease the viscosity, until several hundred mPa · s It can be seen that these inks E1, E2, and E3 exhibit thixotropic properties. Further, although the ink E3 exhibits thixotropic property, the inks CE1 and CE2 do not exhibit such thixotropic property. Therefore, when the solubility parameter of the radically polymerizable compound is 10 or more, the thixotropic agent needs to have a hydrophobic surface. Conceivable.

＊比較例１のインクＣＥ１は、チキソ性を示さなかったので、回復時間は測定できなかった。

* Since the ink CE1 of Comparative Example 1 did not show thixotropic property, the recovery time could not be measured.

The present invention allows for various embodiments and modifications without departing from the broad spirit and scope of the present invention. Moreover, the above-described embodiment is for explaining the present invention, and does not limit the scope of the present invention. That is, the scope of the present invention is indicated by the scope of claims, not by the embodiment. Then, various modifications made within the scope of the claims and the equivalent meaning of the invention are considered to be within the scope of the present invention.

Claims (6)

It contains a radically polymerizable compound, a photoinitiator, and a thixotropic agent.
The first viscosity measured at a shear rate of 10000 s ^-1 is 1000 mPa · s or less.
The second viscosity measured at a shear rate of 10 ^-1 s ^-1 after continuing to apply a shear force for 30 seconds at a shear rate of 10000 s ^-1 is 10000 mPa · s or more.
Photo-curable ejection ink. The ink according to claim 1, wherein the radically polymerizable compound is an acrylate monomer. The ink according to claim 1 or 2, wherein the thixotropy is fine particles of silicon dioxide. The solubility parameter of the radically polymerizable compound is less than 10 and
The thixotropic agent is a fine particle having a hydrophilic surface.
The ink according to any one of claims 1 to 3. The fine particles having a hydrophilic surface are fine particles of silicon dioxide whose surface is untreated.
The ink according to claim 4. The solubility parameter of the radically polymerizable compound is 10 or more, and
The thixotropic agent is a fine particle having a hydrophobic surface.
The ink according to any one of claims 1 to 3.