Curable clear ink composition, ink set, storing container, printing method, method for producing printed matter, and cured material

Abstract

To provide a curable clear ink composition capable of forming a clear coat layer having excellent smoothness, productivity and discharge stability, and forming a cured material having excellent adhesiveness and curing ability.SOLUTION: A curable clear ink composition comprising a surfactant, 10 mass% or more and 30 mass% or less of a monofunctional polymerizable compound having a static surface tension of 33 mN / m or less at 25°C, an oligomer having a weight average molecular weight (Mw) of 1,000 or more, and 8 mass% or more and 12 mass% or less of an acylphosphine oxide polymerization initiator.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a curable clear ink composition, an ink set, a storage container, a printing method, and a cured product. [Background technology]

[0002] Inkjet ink compositions that can be cured by exposure to actinic rays such as ultraviolet rays (actinic ray-curable inkjet ink compositions) are an excellent method in that they can be printed on a variety of substrates because they have a shorter drying time than water-based or solvent-based inks, do not emit evaporative substances that are harmful to the environment, and images are less likely to bleed.

[0003] Actinic ray-curable inkjet ink compositions mainly include color inks (mainly cyan, magenta, yellow, and black) required for forming images, white ink required for enhancing the color development of images when printing on transparent media, and clear ink for surface protection and controlling the glossiness of images.

[0004] The qualities required for the clear ink include productivity for high-speed printing, smoothness, hardness, and adhesion of the clear coat layer during multi-pass printing.

[0005] Therefore, in order to address the issues of having excellent image quality and gloss, providing a good surface condition, and preventing blocking resistance and uneven gloss in the clear ink coating layer, a clear ink has been proposed that contains, for example, an acylphosphine oxide polymerization initiator in a weight ratio of more than 1 to 10 times the weight of the color ink, and also contains a surfactant (see, for example, Patent Document 1). Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide a curable clear ink composition that provides a clear coat layer with excellent smoothness, productivity, and ejection stability, and that can yield a cured product with excellent adhesion and curability. [Means for solving the problem]

[0007] The curable clear ink composition of the present invention, which is a means for solving the above problems, contains a surfactant, 10% by mass or more and 30% by mass or less of a monofunctional polymerizable compound having a static surface tension of 33 mN / m or less at 25°C, an oligomer having a weight-average molecular weight (Mw) of 1,000 or more, and 8% by mass or more and 12% by mass or less of an acylphosphine oxide polymerization initiator. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a curable clear ink composition that provides a clear coat layer with excellent smoothness, productivity, and ejection stability, and that gives a cured product with excellent adhesion and curability. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram showing an example of an image forming apparatus equipped with an inkjet ejection means. [Figure 2] FIG. 2 is a schematic diagram showing an example of another image forming device (a device for forming a three-dimensional image). [Figure 3] FIG. 3 is a schematic diagram illustrating an example of a method for performing three-dimensional modeling using a curable clear ink composition. DETAILED DESCRIPTION OF THE INVENTION

[0010] (Curable clear ink composition) The curable clear ink composition of the present invention contains a surfactant, 10% by mass or more and 30% by mass or less of a monofunctional polymerizable compound having a static surface tension of 33 mN / m or less at 25°C, an oligomer having a weight-average molecular weight (Mw) of 1,000 or more, and 8% by mass or more and 12% by mass or less of an acylphosphine oxide polymerization initiator, and may further contain other components as necessary.

[0011] In conventional techniques, when a clear ink contains 12% by mass or more of an acylphosphine oxide polymerization initiator, the ejection stability is insufficient when the ink is ejected at high frequency, and a clear ink that has excellent smoothness of the clear coat layer and excellent ejection stability when ejected at high frequency has not yet been obtained.

[0012] Therefore, in the present invention, by containing a surfactant, 10% by mass or more and 30% by mass or less of a monofunctional polymerizable compound having a static surface tension of 33 mN / m or less at 25°C, an oligomer having a weight-average molecular weight (Mw) of 1,000 or more, and 8% by mass or more and 12% by mass or less of an acylphosphine oxide polymerization initiator, it is possible to provide a curable clear ink composition that provides a clear coat layer with excellent smoothness, productivity, and ejection stability, and that produces a cured product with excellent adhesion and curability.

[0013] The curable clear ink composition of the present invention may be a heat-curable clear ink composition or an active energy ray-curable clear ink composition, with an active energy ray-curable clear ink composition being more preferred.

[0014] <Polymerizable compound> The curable clear ink composition of the present invention contains a polymerizable compound. The polymerizable compound essentially contains a monofunctional polymerizable compound, and the content of the monofunctional polymerizable compound is preferably 50% by mass or more and 90% by mass or less, and more preferably 70% by mass or more and 90% by mass or less, relative to the total amount of the curable clear ink composition.

[0015] Examples of the monofunctional polymerizable compound include a monofunctional polymerizable compound having a static surface tension of 33 mN / m or less at 25°C, and a monofunctional polymerizable compound having a static surface tension of more than 33 mN / m at 25°C.

[0016] -Monofunctional polymerizable compounds with a static surface tension of 33 mN / m or less at 25°C The monofunctional polymerizable compound having a static surface tension of 33 mN / m or less at 25°C is not particularly limited and can be appropriately selected depending on the purpose. Examples thereof include isobornyl(meth)acrylate (static surface tension at 25°C: 33 mN / m), lauryl(meth)acrylate (static surface tension at 25°C: 29 mN / m), isodecyl(meth)acrylate (static surface tension at 25°C: 28 mN / m), isooctyl(meth)acrylate (static surface tension at 25°C: 29 mN / m), and the like. acrylate (static surface tension at 25°C: 28 mN / m), n-octyl (meth)acrylate (static surface tension at 25°C: 28 mN / m), isobutyl (meth)acrylate (static surface tension at 25°C: 25 mN / m), isononyl (meth)acrylate (static surface tension at 25°C: 28 mN / m), octyl / decyl (meth)acrylate (static surface tension at 25°C: 29 mN / m), etc. These may be used alone or in combination of two or more. Of these, isobornyl (meth)acrylate is preferred from the viewpoint of increasing the hardness of the coating film. The content of the monofunctional polymerizable compound having a static surface tension of 33 mN / m or less at 25°C is from 10% to 30% by mass, and preferably from 15% to 25% by mass, relative to the total amount of the curable clear ink composition. A content of from 10% to 30% by mass has the advantages of excellent ejection stability and coating hardness. The static surface tension can be measured, for example, by a static surface tension measuring device.

[0017] - A monofunctional polymerizable compound having a static surface tension of more than 33 mN / m at 25°C The monofunctional polymerizable compound having a static surface tension of more than 33 mN / m at 25°C is not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include (meth)acryloylmorpholine (static surface tension at 25°C: 44 mN / m), N-vinylcaprolactam (static surface tension at 25°C: 40 mN / m), phenoxyethyl (meth)acrylate (static surface tension at 25°C: 40 mN / m), and cyclic trimethylolpropane formal (meth)acrylate (static surface tension at 25°C: 36 mN / m). These may be used alone or in combination of two or more. The content of the monofunctional polymerizable compound having a static surface tension of more than 33 mN / m at 25° C. is preferably 50% by mass or more and 70% by mass or less relative to the total amount of the curable clear ink composition. The static surface tension can be measured, for example, by a static surface tension measuring device.

[0018] -Other polymerizable monomers- The curable clear ink composition of the present invention may contain other polymerizable monomers in addition to the monofunctional polymerizable compound having a static surface tension of 33 mN / m or less at 25°C and the monofunctional polymerizable compound having a static surface tension of more than 33 mN / m at 25°C. As other polymerizable monomers, known polymerizable monomers typified by (meth)acrylic acid esters can be used, for example, methyl (meth)acrylate, ethyl (meth)acrylate, allyl (meth)acrylate, glycidyl (meth)acrylate, 2-(dimethylamino)ethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-butoxyethyl (meth)acrylate, ethyl carbitol (meth)acrylate, cyclohexyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, 2-(2-vinyloxyethoxy)ethyl (meth)acrylate, 2-phenoxyethyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, ethylene glycol di(meth)acrylate, diene Examples of such diacrylates include ethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, tetrapropylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, ethoxylated neopentyl glycol di(meth)acrylate, propoxylated neopentyl glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, and 1,9-nonanediol di(meth)acrylate. These may be used alone or in combination of two or more.

[0019] The curable clear ink composition of the present invention contains an oligomer having a weight-average molecular weight (Mw) of 1,000 or more. The inclusion of an oligomer having a weight-average molecular weight (Mw) of 1,000 or more has the advantage of providing a coating film with excellent adhesion and hardness. The oligomer is a polymerizable oligomer having an ethylenically unsaturated double bond, and examples thereof include aromatic urethane oligomers, aliphatic urethane oligomers, epoxy acrylate oligomers, polyester acrylate oligomers, and other special oligomers.As the oligomer having a weight-average molecular weight (Mw) of 1,000 or more, commercially available products can be used. Examples of such commercially available products include UV-2000B, UV-2750B, UV-3000B, UV-3010B, UV-3200B, UV-3300B, UV-3700B, UV-6640B, UV-8630B, UV-7000B, UV-7610B, UV-1700B, UV-7630B, UV-6300B, UV-6640B, UV-7550B, UV-7600B, UV-7605B, UV-7610B, and UV-7630B manufactured by Nippon Chemical Synthetic Co., Ltd. B, UV-7640B, UV-7650B, UT-5449, UT-5454, CN902, CN902J75, CN929, CN940, CN944, CN944B85, CN959, CN961E75, CN961H81, CN962, CN963, CN963A80, CN963B80, CN963E75, CN963E80, CN963J85, CN964, CN965, CN965A80, CN966, CN966A80, CN966B85, CN966H90, CN966J75, CN968, CN969, CN970, C manufactured by Sartomer Corporation N970A60, CN970E60, CN971, CN971A80, CN971J75, CN972, CN973, CN973A80, CN973H85, CN973J75, CN975, CN977, CN977C70, CN978, CN980, CN981, CN981 A75, CN981B88, CN982, CN982A75, CN982B88, CN982E75, CN983, CN984, CN985, CN985B88, CN986, CN989, CN991, CN992, CN994, CN996, CN997, CN999, CN90 01, CN9002, CN9004, CN9005, CN9006, CN9007, CN9008, CN9009, CN9010, CN9011, CN9013, CN9018, CN9019, CN9024, CN9025, CN9026, CN9028, CN9029, CN9030, CN9060, CN9165, CN9167, CN9178, CN9290, CN9782, CN9783, CN9788, CN9893, EBECRYL210, EBECRYL220, EBECRYL230, EBECRYL270 manufactured by Daicel-Cytec,Examples of such acrylic resins include KRM8200, EBECRYL5129, EBECRYL8210, EBECRYL8301, EBECRYL8804, EBECRYL8807, EBECRYL9260, KRM7735, KRM8296, KRM8452, EBECRYL4858, EBECRYL8402, EBECRYL9270, EBECRYL8311, and EBECRYL8701. These may be used alone or in combination of two or more. Among these, CN963, CN964, CN965, and CN996 manufactured by Sartomer Corporation are preferred.

[0020] The content of the oligomer is preferably 0.1% by mass or more and 15% by mass or less, and more preferably 1% by mass or more and 10% by mass or less, relative to the total amount of the curable clear ink composition.

[0021] <Surfactant> In the present invention, the surfactant is a compound having surface activity, excluding so-called "pigment dispersants," and examples thereof include amphoteric surfactants, nonionic surfactants, anionic surfactants, fluorine-containing surfactants, polysiloxane surfactants, etc. Among these, polysiloxane surfactants are preferred because of their high surface activity.

[0022] Examples of the polysiloxane surfactant include compounds having a hydrophilic group or a hydrophilic polymer chain on the side chain of a compound (silicone-based compound) having a polysiloxane structure such as polydimethylsiloxane, and compounds having a hydrophilic group or a hydrophilic polymer chain on the end of a compound (silicone-based compound) having a polysiloxane structure such as polydimethylsiloxane. Note that the polysiloxane surfactant may be any compound having a polysiloxane structure in its structure, and includes polysiloxane-based surfactants.

[0023] Examples of the hydrophilic group or the hydrophilic polymer chain include a polyether group (polyethylene oxide, polypropylene oxide, copolymers thereof, etc.), polyglycerin (C3H6O(CH2CH(OH)CHO) n-H, etc.), pyrrolidone, betaine (C3H6N + (C2H4)2-CH2COO ― etc.), sulfates (C3H6O(C2H4O) n -SO3Na etc.), phosphates (C3H6O(C2H4O) n -P(=O)OHONa, etc.), quaternary salts (C3H6N + (C2H4)3Cl - In the above chemical formula, n represents an integer of 1 or more. Among these, it is preferable that the compound has a polyether group. Other suitable examples include vinyl copolymers having silicone compound chains such as polydimethylsiloxane in their side chains, which are obtained by copolymerizing polydimethylsiloxane or the like having a polymerizable vinyl group at the end with other copolymerizable monomers (it is preferable to use a hydrophilic monomer such as (meth)acrylic acid or a salt thereof as at least a part of the monomer). Among these, compounds having a polysiloxane structure and a hydrophilic polymer chain are preferred, and it is more preferred that the hydrophilic polymer chain contains a polyether group. It is particularly preferred that the polysiloxane surfactant is a nonionic surfactant having a methylpolysiloxane structure as the hydrophobic group and a polyoxyethylene structure as the hydrophilic group.

[0024] Examples of the polysiloxane surfactant include polyether-modified silicone compounds and polyoxyalkylene group-containing silicone compounds.

[0025] Commercially available products can be used as the polysiloxane surfactant. Examples of the commercially available products include TEGO WET270 (manufactured by Evonik), BYK3150, BYK3151 (manufactured by BYK-Chemie Co., Ltd.), Silface SAG005, Silface SAG008 (all manufactured by Nissin Chemical Industry Co., Ltd.), FZ2110, FZ2166, SH-3772M, L7001, SH-3773M (all manufactured by Toray-Dow Co., Ltd.), KF-945, KF-6017, KF-353 (all manufactured by Shin-Etsu Chemical Co., Ltd.), and FormBan MS-575 (manufactured by Ultra Additives Inc.).

[0026] The content of the surfactant is preferably 0.01% by mass or more and 1% by mass or less, and more preferably 0.05% by mass or more and 0.2% by mass or less, relative to the total amount of the curable clear ink composition.

[0027] <Polymerization initiator> The curable clear ink composition of the present invention may contain a polymerization initiator. The polymerization initiator may also be simply referred to as an initiator. Polymerization initiators include thermal polymerization initiators and photopolymerization initiators. The photopolymerization initiator may be any one that can generate active species such as radicals or cations by the energy of active energy rays and initiate polymerization of a polymerizable compound (monomer or oligomer). As the photopolymerization initiator, known radical polymerization initiators, cationic polymerization initiators, base generators, etc. can be used alone or in combination of two or more, and among these, radical polymerization initiators are preferred. Examples of the radical polymerization initiator include aromatic ketones, acylphosphine oxide compounds, aromatic onium salt compounds, organic peroxides, thio compounds (thioxanthone compounds, thiophenyl group-containing compounds, etc.), hexaarylbiimidazole compounds, ketoxime ester compounds, borate compounds, azinium compounds, metallocene compounds, active ester compounds, compounds having a carbon-halogen bond, and alkylamine compounds. Among these, acylphosphine oxide polymerization initiators are particularly preferred. As the acylphosphine oxide polymerization initiator, commercially available products can be used, and examples of such commercially available products include Omnirad 819 and Omnirad TPO manufactured by IGM. The content of the acylphosphine oxide polymerization initiator is 8% by mass or more and 12% by mass or less based on the total amount of the curable composition. When the content of the acylphosphine oxide polymerization initiator is 8% by mass or more and 12% by mass or less, there is an advantage that both curability and discharge stability can be achieved when using an LED light source.

[0028] In addition to the polymerization initiator, a polymerization accelerator (sensitizer) can also be used in combination. The polymerization accelerator is not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include amine compounds such as trimethylamine, methyldimethanolamine, triethanolamine, p-diethylaminoacetophenone, ethyl p-dimethylaminobenzoate, 2-ethylhexyl p-dimethylaminobenzoate, and N,N-dimethylbenzylamine 4,4'-bis(diethylamino)benzophenone. The content of the polymerization accelerator is not particularly limited and may be appropriately determined depending on the polymerization initiator used and its content.

[0029] The curable clear ink composition of the present invention does not substantially contain a colorant and may be colorless and transparent, in which case it is suitable, for example, as an overcoat layer for protecting an image.

[0030] <Other ingredients> The curable clear ink composition of the present invention may contain other components as needed. The other components are not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include organic solvents, polymerization inhibitors, leveling agents, antifoaming agents, fluorescent brightening agents, penetration promoters, wetting agents (moisturizing agents), fixing agents, viscosity stabilizers, antifungal agents, preservatives, antioxidants, UV absorbers, chelating agents, pH adjusters, and thickeners.

[0031] - Organic solvents - The curable clear ink composition of the present invention may contain an organic solvent, but preferably does not contain one if possible. A composition that does not contain organic solvents, particularly volatile organic solvents (VOC (Volatile Organic Compounds)-free) increases the safety of the area where the composition is handled and also makes it possible to prevent environmental pollution. Note that "organic solvent" refers to common non-reactive organic solvents such as ether, ketone, xylene, ethyl acetate, cyclohexanone, and toluene, and should be distinguished from reactive monomers. Furthermore, "free of" organic solvents means that the composition is substantially free of organic solvents, and preferably contains less than 0.1% by mass.

[0032] Regarding the components in the curable clear ink composition, low-molecular-weight components such as polymerizable monomers and polymerization initiators can be identified using gas chromatography-mass spectrometry or other methods, and polymer components can be isolated by precipitation separation in a poor solvent such as methanol, allowing the main skeleton and chlorine atom content to be identified using infrared spectroscopy or elemental analysis.

[0033] <Preparation of Curable Clear Ink Composition> The curable clear ink composition of the present invention can be prepared using the various components described above. The preparation means and conditions are not particularly limited. For example, the curable clear ink composition can be prepared by adding a polymerizable compound, pigment, dispersant, etc. to a dispersing machine such as a ball mill, Kitty mill, disc mill, pin mill, or Dyno mill, dispersing the components to prepare a pigment dispersion, and then mixing a polymerizable compound, polymerization initiator, polymerization inhibitor, surfactant, etc. into the pigment dispersion.

[0034] <Viscosity> The viscosity of the curable clear ink composition of the present invention can be adjusted appropriately depending on the application and means of application, and is not particularly limited. For example, when using an ejection means that ejects the curable clear ink composition from a nozzle, the viscosity in the range of 20°C to 65°C, desirably the viscosity at 25°C, is 60 mPa·s or less, preferably 3 mPa·s or more and 40 mPa·s or less, more preferably 5 mPa·s or more and 30 mPa·s or less, even more preferably 5 mPa·s or more and 15 mPa·s or less, and particularly preferably 6 mPa·s or more and 12 mPa·s or less. It is particularly preferable that the viscosity range is satisfied without including the organic solvent. The viscosity can be measured using a cone-plate type rotational viscometer, VISCOMETER TVE-22L, manufactured by Toki Sangyo Co., Ltd., with a cone rotor (1°34' x R24), at a rotation speed of 50 rpm, and by appropriately setting the temperature of the constant temperature circulating water in the range of 20°C to 65°C. A VISCOMATE VM-150III can be used to adjust the temperature of the circulating water.

[0035] <Curing means> The curing method for curing the curable clear ink composition of the present invention includes heat curing and curing with active energy rays, and among these, curing with active energy rays is preferred. The active energy rays used to cure the curable clear ink composition are not particularly limited, and include ultraviolet rays, electron beams, α-rays, β-rays, γ-rays, X-rays, and other rays that can provide the energy necessary to promote the polymerization reaction of the polymerizable components in the composition. When a particularly high-energy light source is used, the polymerization reaction can proceed without the use of a polymerization initiator. Furthermore, in the case of ultraviolet irradiation, mercury-free irradiation is strongly desired from the perspective of environmental protection, and replacement with GaN-based semiconductor ultraviolet light-emitting devices is extremely useful from both an industrial and environmental perspective. Furthermore, ultraviolet light-emitting diodes (UV-LEDs) and ultraviolet laser diodes (UV-LDs) are preferred as ultraviolet light sources due to their compact size, long life, high efficiency, and low cost. It is more preferable to use light-emitting diodes with a wavelength of 350 nm to 450 nm (particularly, a wavelength of 350 nm to 400 nm).

[0036] (ink set) The ink set of the present invention comprises a clear ink comprising the curable clear ink composition of the present invention and color inks, thereby enabling the ink set to achieve excellent smoothness of the clear coat layer on color images. The color ink is not particularly limited except that it is substantially free of N-vinyl compounds and surfactants, and known color inks can be used depending on the purpose. As the color ink, at least one of cyan ink, magenta ink, yellow ink, and black ink is used.

[0037] <Application> The use of the curable clear ink composition of the present invention is not particularly limited as long as it is in a field in which active energy ray-curable materials are generally used, and can be appropriately selected depending on the purpose. Examples include molding resins, paints, adhesives, insulating materials, mold release agents, coating materials, sealants, various resists, and various optical materials.

[0038] The curable clear ink composition of the present invention can be used as an ink to form two-dimensional characters, images, and decorative coatings on various substrates. It can also be used as a three-dimensional modeling material for forming three-dimensional images (three-dimensional objects). This three-dimensional modeling material can be used, for example, as a binder between powder particles in a powder additive manufacturing process, which involves repeatedly curing and stacking powder layers to create a three-dimensional object. It can also be used as a three-dimensional constructing material (model material) or a support member (support material) in an additive manufacturing process (stereolithography) such as those shown in FIGS. 2 and 3. FIG. 2 illustrates a method for three-dimensional modeling in which an active energy ray-curable composition of the present invention is dispensed into a predetermined area, cured by irradiation with active energy rays, and then sequentially stacked to form a three-dimensional object (described in detail below). FIG. 3 illustrates a method for three-dimensional modeling in which a storage pool (reservoir) 1 containing an active energy ray-curable composition 5 of the present invention is irradiated with active energy rays 4 to form a cured layer 6 of a predetermined shape on a movable stage 3, and these layers are then sequentially stacked to form a three-dimensional object. As a three-dimensional modeling device for forming a three-dimensional object using the curable clear ink composition of the present invention, a known device can be used, and is not particularly limited. Examples of the three-dimensional modeling device include a device that includes a means for storing, supplying, and discharging the composition, and an active energy ray irradiation means. The present invention also includes a molded article obtained by processing a cured product obtained by curing the curable composition or a structure formed on a substrate with the cured product. The molded article is, for example, obtained by subjecting a cured product or structure formed in a sheet or film form to molding processing such as heat stretching or punching, and is suitable for applications requiring surface decoration followed by molding, such as meters and operation panels for automobiles, office automation equipment, electrical and electronic devices, and cameras. The substrate is not particularly limited and can be appropriately selected depending on the purpose. Examples include paper, thread, fiber, fabric, leather, metal, plastic, glass, wood, ceramics, and composite materials thereof, with plastic substrates being preferred from the viewpoint of processability.

[0039] <Containment Container> The storage container of the present invention refers to a container in which the curable clear ink composition of the present invention is stored, and is suitable for use in the above-mentioned applications. For example, when the curable clear ink composition of the present invention is used as an ink, the container storing the ink can be used as an ink cartridge or ink bottle, which eliminates the need to directly touch the ink during tasks such as ink transport and ink replacement, preventing staining of fingers and clothing. It is also possible to prevent foreign matter such as dust from getting mixed into the ink. The shape, size, material, etc. of the container itself are not particularly limited as long as they are suitable for the application and usage, but it is desirable that the material be a light-blocking material that does not transmit light, or that the container be covered with a light-blocking sheet or the like.

[0040] (Printing method) In the printing method of the present invention, the curable clear ink composition of the present invention is ejected in droplets having a size of 10 pL or more and 20 pL or less to print an image. In the printing method, it is preferable that the same portion of the print image is printed by scanning it eight or less times. The leveling time from when the ejected curable clear ink composition lands on the substrate until when it is irradiated with active energy rays is preferably 15 seconds or more and 120 seconds or less. In the present invention, the clear ink composition has a composition that allows it to be ejected in large droplets, making it possible to print in eight passes, and the clear ink composition can be leveled without UV irradiation for the time required for eight passes. This provides the productivity required for high-speed printing, as well as the smoothness, hardness, and adhesion of the clear coat layer during multi-pass printing.

[0041] <Image forming method, image forming device> The image forming method according to the present invention may use actinic energy rays, or may involve heating, etc. To cure the curable clear ink composition of the present invention with actinic energy rays, an irradiation step of irradiating with actinic energy rays is included, and the image forming apparatus of the present invention includes an irradiation means for irradiating with actinic energy rays and a storage section for storing the curable clear ink composition of the present invention, and the storage section may store the container. Furthermore, the apparatus may include a discharge step and a discharge means for discharging the curable clear ink composition of the present invention. The discharge method is not particularly limited, and examples include a continuous spray type and an on-demand type. On-demand types include a piezo type, a thermal type, and an electrostatic type.

[0042] FIG. 1 shows an example of an image forming apparatus equipped with an inkjet ejection unit. Each color printing unit 23a, 23b, 23c, and 23d, each equipped with an ink cartridge and ejection head for yellow, magenta, cyan, and black actinic energy ray-curable ink, ejects ink onto a recording medium 22 supplied from a supply roll 21. The ink is then cured by irradiating it with actinic energy rays from light sources 24a, 24b, 24c, and 24d, forming a color image. The recording medium 22 is then transported to a processing unit 25 and a print take-up roll 26. Each printing unit 23a, 23b, 23c, and 23d may be provided with a heating mechanism to liquefy the ink at the ink ejection section. If necessary, a mechanism for cooling the recording medium to approximately room temperature, either by contact or non-contact, may also be provided. In addition, the inkjet recording method can be either a serial method in which the head is moved to eject ink onto a recording medium that moves intermittently according to the width of the ejection head, or a line method in which the recording medium is moved continuously and ink is ejected onto the recording medium from a head held at a fixed position. The recording medium 22 is not particularly limited, but examples thereof include paper, film, metal, and composite materials thereof, and may be in the form of a sheet. The recording medium 22 may be configured to allow only single-sided printing, or may be configured to allow double-sided printing. Furthermore, the active energy rays from the light sources 24a, 24b, and 24c may be weakened or omitted, and after printing multiple colors, the active energy rays may be irradiated from the light source 24d, which can save energy and reduce costs. Recorded materials that can be recorded with the ink used in the present invention include not only those printed on smooth surfaces such as ordinary paper or resin film, but also those printed on uneven printing surfaces and those printed on printing surfaces made of various materials such as metal or ceramic. Furthermore, by layering two-dimensional images, it is possible to form images with a partial three-dimensional effect (images consisting of two and three dimensions) or three-dimensional objects.

[0043] FIG. 2 is a schematic diagram showing another example of an image-forming apparatus (a device for forming a three-dimensional solid image) according to the present invention. The image-forming apparatus 39 in FIG. 2 uses a head unit (movable in the AB direction) with an array of inkjet heads. The first curable composition is ejected from the ejection head unit 30 for the object to be formed, and the second curable composition is ejected from the ejection head unit 30 for the object to be formed, and the first curable composition is ejected from the ejection head unit 30 for the support material to be formed. The first curable composition is then solidified by irradiating the first curable composition with active energy rays to form a first object layer. This process is repeated multiple times while lowering a vertically movable stage 38 in accordance with the number of layers to be formed, thereby laminating the support layer and the object layer to produce a three-dimensional object 35. Thereafter, the support layer 36 is removed as necessary. Although FIG. 2 shows only one ejection head unit 30 for the object to be formed, two or more may be provided. [Example]

[0044] Examples of the present invention will be described below, but the present invention is not limited to these examples in any way.

[0045] (Color ink manufacturing examples 1-2) Magenta inks 1 and 2 were prepared as color inks by mixing the compositions and contents shown in Table 1 below.

[0046] [Table 1]

[0047] (Examples 1 to 11 and Comparative Examples 1 to 7) The materials shown in Tables 2 to 5 were added in order with stirring, and then stirred for 2 hours to prepare the curable clear ink compositions of Examples 1 to 11 and Comparative Examples 1 to 7. Next, the obtained curable clear ink composition was printed under the printing conditions shown in Tables 2 to 5 to obtain a cured product.

[0048] Next, the obtained curable clear ink compositions and cured products were evaluated for the smoothness, hardness, adhesion, ejection stability, curability, and productivity of the clear coat layer as follows. The results are shown in Tables 2 to 5.

[0049] <Smoothness of clear coat layer> Each curable clear ink composition was ejected using a GEN5 head manufactured by Ricoh Co., Ltd. to an average thickness of approximately 20 μm. After a waiting period of 60 seconds from ink landing to UV irradiation using a UV-LED irradiator manufactured by Phoseon, UV light was irradiated to form a clear coat layer, which was then visually observed and evaluated for smoothness according to the following criteria. [Evaluation criteria] A: No visible irregularities, no practical problems B: Visually, there are irregularities, but there are no practical problems. C: Visually observed unevenness, at a level that is problematic for practical use

[0050] <Hardness> The pencil hardness of the resulting cured product was measured in accordance with JIS K5600-5-4 scratch hardness (pencil method), and the "hardness" was evaluated based on the following evaluation criteria. [Evaluation criteria] A: Pencil hardness H or higher B: Pencil hardness B or higher and F or lower C: Pencil hardness 2B or less

[0051] <Adhesion> The adhesion was evaluated according to the cross-cut method specified in JIS K5600-5-6, using the following evaluation criteria. [Evaluation criteria] A: Rank 0-1 B: Rank 2~3 C: Rank 4~5

[0052] <Discharge stability> Using an inkjet ejection device equipped with a GEN5 head manufactured by Ricoh Co., Ltd., each composition was continuously ejected for one minute at a frequency of 28 kHz under conditions where the flying speed of the composition was 7 m / s ± 1 m / s, and the number of nozzles that failed to eject was counted, and the ejection stability was evaluated based on the following criteria. [Evaluation criteria] S: The number of non-ejecting nozzles is 0 A: The number of non-ejecting nozzles is 1 or more but less than 4 B: The number of non-ejecting nozzles is 4 or more but less than 10 C: The number of non-ejecting nozzles is 10 or more

[0053] <Curability> It was made on a polyethylene terephthalate (PET) film using a wire bar #8. The uniform film of each composition was measured using a Phoseon FJ800 (wavelength 395 nm). and illuminance 1W / cm 2 When UV light is irradiated, the accumulated light intensity at which the tackiness is no longer felt by the fingers is calculated. Therefore, the curability was evaluated based on the following criteria. [Evaluation criteria] A: The cumulative light intensity is 800mJ / cm 2 less than B: Accumulated light intensity 800mJ / cm 2 More than 1,200mJ / cm 2 less than C: Accumulated light intensity 1,200mJ / cm 2 End

[0054] <Productivity> Using a printer equipped with a Ricoh GEN5 head, an image with an average clear coat layer thickness of 20 μm or more was printed at an ink ejection frequency of 28 kHz and a resolution of 600 dpi x 600 dpi. Productivity was evaluated based on the printing speed, according to the following criteria. A grade of B or higher is considered practically usable. [Evaluation criteria] S: Printing speed is 12m 2 / h or more A:Printing speed is 10m 2 / h or more 12m 2 / h or less B: Printing speed is 10m 2 / h or less

[0055] [Table 2]

[0056] [Table 3]

[0057] [Table 4]

[0058] [Table 5] *In Table 5, "-" for "Smoothness," "Hardness," and "Adhesion" for Comparative Example 7 means that they could not be measured.

[0059] (Examples 12 to 13) The materials shown in Table 6 were added in order with stirring, and then stirred for 2 hours to prepare the curable clear ink compositions of Examples 12 and 13. As shown in Table 6, the color inks and the curable clear ink compositions were combined to form the ink sets of Examples 12 and 13. The ink sets of Examples 12 and 13 were used to evaluate the smoothness, hardness, adhesion, ejection stability, curability, and productivity of the clear coat layer. The smoothness of the clear coat layer on a color image formed using the color inks of the ink set was also evaluated as follows. The results are shown in Table 6.

[0060] <Smoothness of clear coat layer on color image> Using a GEN5 head manufactured by Ricoh Co., Ltd., color inks were ejected to an average thickness of approximately 10 μm, and then a UV-LED irradiator manufactured by Poseon was used to irradiate with UV to form a color ink layer. Each curable clear ink composition was then ejected to an average thickness of approximately 20 μm, and after a waiting period of 60 seconds from ink landing to UV irradiation using the UV-LED irradiator manufactured by Poseon, UV was irradiated to form a clear coat layer. The clear coat layer was visually observed, and the smoothness of the clear coat layer on the color image was evaluated based on the following criteria. [Evaluation criteria] A: No visible irregularities, no practical problems B: Visually, there are irregularities, but there are no practical problems.

[0061] [Table 6]

[0062] Details of the materials used in the color ink production examples, examples, and comparative examples in Tables 1 to 6 are as follows.

[0063] -Monofunctional polymerizable compounds with a static surface tension of 33 mN / m or less at 25°C Isobornyl acrylate ("IBXA" manufactured by Osaka Organic Chemical Industry Ltd., static surface tension at 25°C: 33 mN / m)

[0064] -Monofunctional polymerizable compounds with a static surface tension of more than 33 mN / m at 25°C Acryloylmorpholine (KJ Chemicals Co., Ltd., "ACMO," static surface tension at 25°C: 44 mN / m) Phenoxyethyl acrylate (Osaka Organic Chemical Industry Ltd., "PEA", static surface tension at 25°C: 40 mN / m) Cyclic trimethylolpropane formal acrylate (manufactured by Osaka Organic Chemical Industry Ltd., "CTFA", static surface tension at 25°C: 36 mN / m)

[0065] -Oligomer- CN963 (urethane acrylate oligomer, manufactured by Sartomer, weight average molecular weight (Mw) = 1,400)

[0066] -Polymerization inhibitor- TBH (tert-butylhydroquinone, manufactured by Tokyo Chemical Industry Co., Ltd.) MEHQ (4-methoxyphenol: methoquinone, manufactured by Seiko Chemical Co., Ltd.)

[0067] -Acylphosphine oxide polymerization initiator- Omnirad 819 (phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, manufactured by IGM) Omnirad TPO (2,4,6-trimethylbenzoyl-diphenyl phosphine oxide, manufactured by IGM)

[0068] -Polymerization initiators other than acylphosphine oxides- Omnirad 379 (IGM) DAIDO UV Cure DETX (manufactured by Daido Chemical Industry Co., Ltd.)

[0069] -Surfactants- F-556 (fluorine-based surfactant, manufactured by DIC Corporation) TEGO WET270 (polyether-modified siloxane copolymer, manufactured by Evonik Japan)

[0070] -N-vinyl compounds- V-CAP (Ashland)

[0071] -Pigments- Pigment Red 122 ("Hostapalm" Pink EB transp., Clariant)

[0072] -Dispersant- BYK9151 (BYK)

[0073] The present invention includes, for example, the following aspects. <1> A surfactant, a monofunctional polymerizable compound having a static surface tension of 33 mN / m or less at 25°C in an amount of 10% by mass or more and 30% by mass or less; an oligomer having a weight average molecular weight (Mw) of 1,000 or more; an acylphosphine oxide polymerization initiator in an amount of 8% by mass or more and 12% by mass or less; The curable clear ink composition is characterized by comprising: <2> The above-mentioned material is substantially free of coloring materials. <1> 1. The curable clear ink composition according to claim 1. <3> The surfactant is a polysiloxane surfactant. <1> from <2> 1. The curable clear ink composition according to claim 1, wherein the curable clear ink composition is a curable clear ink composition according to any one of claims 1 to 10. <4> The surfactant content is 0.05% by mass or more and 0.2% by mass or less. <1> from <3> 1. The curable clear ink composition according to claim 1, wherein the curable clear ink composition is a curable clear ink composition according to any one of claims 1 to 10. <5> The monofunctional polymerizable compound having a static surface tension of 33 mN / m or less at 25°C is at least one selected from isobornyl (meth)acrylate, lauryl (meth)acrylate, isodecyl (meth)acrylate, isooctyl (meth)acrylate, n-decyl (meth)acrylate, n-octyl (meth)acrylate, isobutyl (meth)acrylate, and isononyl (meth)acrylate. <1> from <4> 1. The curable clear ink composition according to claim 1, wherein the curable clear ink composition is a curable clear ink composition according to any one of claims 1 to 10. <6> The monofunctional polymerizable compound having a static surface tension of 33 mN / m or less at 25°C is isobornyl (meth)acrylate. <5> 1. The curable clear ink composition according to claim 1. <7> The active energy ray-curable clear ink composition <1> from <6> 1. The curable clear ink composition according to claim 1, wherein the curable clear ink composition is a curable clear ink composition according to any one of claims 1 to 10. <8> The inkjet ink <1> from <7> 1. The curable clear ink composition according to claim 1, wherein the curable clear ink composition is a curable clear ink composition according to any one of claims 1 to 10. <9> The aforementioned <1> from <8> 1. A storage container comprising the curable clear ink composition according to any one of the above items stored in the container. <10> The aforementioned <1> from <8> and a color ink. <11> The color ink is substantially free of N-vinyl compounds and surfactants. <10> The ink set is described in <12> The aforementioned <1> from <8> The curable clear ink composition according to any one of the above items is ejected in droplets having a size of 10 pL or more and 20 pL or less to print an image. <13> The same part of the print image is scanned 8 times or less. <12> This is a printing method described in <14> The leveling time from when the ejected curable clear ink composition lands on the substrate until when it is irradiated with active energy rays is 15 seconds or more and 120 seconds or less. <12> from <13> 1. A printing method according to claim 1, wherein <15> The aforementioned <12> from <14> 1. A printed matter obtained by printing using any one of the printing methods described above. <16> The aforementioned <1> from <8> a storage section that stores the curable clear ink composition according to any one of the above items; an application means for applying the composition; a curing means for curing the composition; The present invention relates to a two-dimensional or three-dimensional image forming device. <17> The curing means is a light emitting diode light source having a wavelength of 350 nm or more and 450 nm or less. <16> 2. A two-dimensional or three-dimensional image forming apparatus according to claim 1. <18> The aforementioned <1> from <8> an application step of applying the curable clear ink composition according to any one of the above items; a curing step of curing the composition; A two-dimensional or three-dimensional image forming method comprising: <19> In the curing step, the light is irradiated from a light emitting diode light source having a wavelength of 350 nm or more and 450 nm or less. <18> The two-dimensional or three-dimensional image forming method according to the present invention is <20> The aforementioned <1> from <8> 1. A cured product formed using the curable clear ink composition according to any one of claims 1 to 8. <21> The aforementioned <20> 1. A molded article characterized by being obtained by stretching the cured product described in 1. <22> On the substrate <20> 1. A decorated body characterized by being surface-decorated with the cured product described in 1.

[0074] The aforementioned <1> from <8> The curable clear ink composition according to any one of the preceding claims. <9> The storage container according to <10> from <11> The ink set according to any one of <12> from <14> The printing method according to any one of the <15> The printed matter described in <16> from <17> The two-dimensional or three-dimensional image forming apparatus according to any one of the preceding claims. <18> from <19> The two-dimensional or three-dimensional image forming apparatus according to any one of the preceding claims, <20> The cured product according to <21> The molded article according to the above, <22> According to the decorative body described in the above, the various problems in the prior art can be solved and the object of the present invention can be achieved. [Explanation of symbols]

[0075] 1. Storage pool (container) 3 Movable stage 4. Active energy rays 5. Active energy ray-curable composition 6 Hardened layer 21 Supply Roll 22 Recording Media 23a, 23b, 23c, 23d Printing units 24a, 24b, 24c, 24d light source 25 processing units 26 Printed material winding roll 30. Discharge head unit for modeling 31, 32 Support ejection head unit 33, 34 Ultraviolet irradiation means 35 Three-dimensional sculpture 36 Support layer section 37 Object support substrate [Prior art documents] [Patent documents]

[0076] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-067770

Claims

1. A surfactant, a monofunctional polymerizable compound having a static surface tension of 33 mN / m or less at 25°C in an amount of 10% by mass or more and 30% by mass or less; an oligomer having a weight average molecular weight (Mw) of 1,000 or more; A curable clear ink composition comprising: an acylphosphine oxide polymerization initiator in an amount of 8% by mass or more and 12% by mass or less.

2. The curable clear ink composition according to claim 1 , which is substantially free of coloring materials.

3. The curable clear ink composition according to claim 1 , wherein the surfactant is a polysiloxane surfactant.

4. The curable clear ink composition according to claim 1 , wherein the content of the surfactant is 0.05% by mass or more and 0.2% by mass or less.

5. 5. The curable clear ink composition according to claim 1, wherein the monofunctional polymerizable compound having a static surface tension of 33 mN / m or less at 25°C is at least one selected from isobornyl (meth)acrylate, lauryl (meth)acrylate, isodecyl (meth)acrylate, isooctyl (meth)acrylate, n-decyl (meth)acrylate, n-octyl (meth)acrylate, isobutyl (meth)acrylate, and isononyl (meth)acrylate.

6. The curable clear ink composition according to claim 5, wherein the monofunctional polymerizable compound having a static surface tension of 33 mN / m or less at 25°C is isobornyl (meth)acrylate.

7. The curable clear ink composition according to any one of claims 1 to 6, which is an actinic energy ray-curable clear ink composition.

8. The curable clear ink composition according to any one of claims 1 to 7, which is for inkjet printing.

9. A storage container, comprising the curable clear ink composition according to claim 1 stored therein.

10. An ink set comprising a clear ink comprising the curable clear ink composition according to any one of claims 1 to 8, and a color ink.

11. 11. The ink set according to claim 10, wherein the color inks are substantially free of N-vinyl compounds and surfactants.

12. A printing method comprising ejecting the curable clear ink composition according to claim 1 in droplets having a size of 10 pL or more and 20 pL or less to print an image.

13. The printing method according to claim 12, wherein the same portion of the print image is scanned eight times or less.

14. 14. The printing method according to claim 12, wherein a leveling time from when the ejected curable clear ink composition lands on the substrate until when the active energy ray is irradiated is 15 seconds or more and 120 seconds or less.

15. A printed matter obtained by printing using the printing method according to any one of claims 12 to 14.

16. A cured product formed using the curable clear ink composition according to claim 1 .

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