Active energy ray curable inkjet inks and printed materials

Abstract

To provide an inkjet ink and a light-shielding film that have high light-shielding properties over a wide wavelength range, while also exhibiting excellent ejection stability and curing properties. [Solution] An active energy ray-curable inkjet ink comprising a pigment, a polymerizable compound, and a photopolymerization initiator, wherein the pigment comprises carbon black and an inorganic pigment other than carbon black. The active energy ray-curable inkjet ink wherein the inorganic pigment other than carbon black comprises titanium black.

Description

[Technical Field]

[0001] This invention relates to an active energy ray curable inkjet ink and printed materials. [Background technology]

[0002] In recent years, inkjet technology has expanded beyond mere printing applications to include the creation of various functional coatings. The inkjet method enables the formation of highly accurate and uniform coatings, and its ability to utilize inks with diverse materials and functions has led to a wide range of applications in industrial fields. For example, attempts are being made to create functional coatings using inkjet technology in displays, electronic devices, and even building materials.

[0003] Light-shielding coatings play an important role in improving the performance of electronic devices and building materials by utilizing their light-blocking properties. Patent document 1 discloses a black paint containing metal oxides and carbon black, which is used to eliminate optical defects when applied to camera lenses and the like. In recent years, there has been a demand for the formation of fine patterns to improve product quality and for inkjet printing of light-shielding paints to automate manufacturing.

[0004] Patent Document 2 discloses an inkjet ink using titanium black as a pigment with light-shielding properties, and states that a light-shielding film with high light-shielding properties can be created by inkjet coating. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Patent No. 5937448 [Patent Document 2] Patent No. 6882499 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] As described above, a technique for forming a light-shielding film having high light-shielding properties by an inkjet method using a specific pigment is known. However, in the conventional method, there are variations in the light-shielding performance depending on the wavelength, and when used for optical applications, defects may occur in images or videos. In addition, the inkjet ejection property is not sufficient, and regular maintenance of the apparatus is required, presenting problems for practical use.

[0007] An object of the present invention is to provide an inkjet ink and a light-shielding film that have high light-shielding properties in a wide wavelength range and are excellent in ejection stability and curability.

Means for Solving the Problems

[0008] [1] An active energy ray-curable inkjet ink containing a pigment, a polymerizable compound, and a photoinitiator, wherein the pigment contains carbon black and an inorganic pigment other than carbon black.

[0009] [2] The active energy ray-curable inkjet ink according to [1], wherein the inorganic pigment other than carbon black contains titanium black.

[0010] [3] When a coating film having a film thickness of  μm is formed, the absorbance at 455 nm (A 455 ), the absorbance at 555 nm (A 555 ), and the absorbance at  nm (A 655 ) satisfy the following formulas 1 to 3. The active energy ray-curable inkjet ink according to [1]. (Formula 1) 2 ≤ A 555 (Formula 2) 0.88 × A 555 ≤ A 455 ≤ 1.12 × A 555 (Formula 3) 0.88 × A 555 ≤ A 655 ≤ 1.12 × A 555

[0011] [4] The active energy ray curable inkjet ink according to [1], wherein the photopolymerization initiator comprises an acylphosphine oxide-based initiator and a thioxanthone-based initiator.

[0012] [5] A printed material obtained by printing an active energy ray curable inkjet ink described in any of [1] to [4] onto a substrate.

[0013] A method for manufacturing printed materials, comprising inkjet printing an active energy ray curable inkjet ink described in any of [1] to [4] onto a substrate. [Effects of the Invention]

[0014] According to the present invention, it is possible to provide an inkjet ink that has sufficient light-shielding properties for use in displays, electronic devices, etc., and that can form a light-shielding film by inkjet coating. [Modes for carrying out the invention]

[0015] The present invention will be described below with reference to preferred embodiments.

[0016] The present invention comprises a pigment, a polymerizable compound, and a photopolymerization initiator. The pigment includes carbon black and inorganic pigments other than carbon black, thereby improving light-shielding properties and suitability for inkjet coating. The main components of the present invention are described below.

[0017] <Pigments> The inkjet ink of the present invention contains carbon black and inorganic pigments other than carbon black as pigments to provide light-shielding properties.

[0018] Carbon black is a black pigment mainly composed of carbon and possesses very high coloring power. The carbon black content in the inkjet ink of this embodiment is preferably 0.5 to 5.0% by mass, and particularly preferably 1.0 to 3.0% by mass, of the total amount of inkjet ink. When the carbon black content is within the above range, the inkjet ink has excellent light-shielding properties, curability, and ejection stability.

[0019] The DBP oil absorption capacity of the carbon black that can be used in the inkjet ink of this embodiment is preferably 40 to 100 mL / 100 g, more preferably 40 to 80 mL / 100 g, and particularly preferably 40 to 65 mL / 100 g. Inkjet ink using carbon black having such a DBP oil absorption capacity exhibits excellent curability.

[0020] The specific surface area of ​​carbon black that can be used with the inkjet ink of this embodiment is 45 to 120 m². 2 It is preferable that the amount be / g, which is 50-95m 2 It is particularly preferable that the value be / g.

[0021] The carbon black contained in the inkjet ink of this embodiment preferably has a pH of 2 to 5, and particularly preferably 2 to 4. With carbon black having such a pH, the dispersion stability of the carbon black and the ejection stability of the inkjet ink are significantly improved.

[0022] The primary particle size of the carbon black is preferably 20 to 50 nm, more preferably 25 to 50 nm, and particularly preferably 30 to 50 nm. Carbon black having such a primary particle size has increased permeability of active energy rays and improved curability.

[0023] Besides carbon black, other inorganic pigments mainly include metal oxides. Examples include metal oxides of iron, copper, manganese, cobalt, and chromium. Titanium oxynitride, also known as titanium black, can also be suitably used.

[0024] The content of inorganic pigments other than carbon black is preferably 3 to 30% by mass, particularly preferably 5 to 20% by mass, and most preferably 8 to 15% by mass, based on the total amount of the inkjet ink. When the content of inorganic pigments other than carbon black is within the above range, an inkjet ink with excellent light-shielding properties, curability, and ejection stability is obtained.

[0025] By using titanium black as an inorganic pigment other than carbon black, it is possible to improve curability. The primary particle size of titanium black is not particularly limited, but 30 to 400 nm is preferred, 50 to 200 nm is more preferred, and 80 to 150 nm is most preferred.

[0026] Examples of commercially available titanium black paints include Titanium Black 13M, 13M-C, 13M-T, 12S, UF-8 (manufactured by Mitsubishi Materials), and Tilack D TM-A, TM-B, TM-S, TS-A, TS-M (manufactured by Akaho Chemicals).

[0027] The mixing ratio of carbon black to other inorganic pigments (carbon black:other inorganic pigments) is preferably 10:90 to 70:30, particularly preferably 20:80 to 60:40, and most preferably 30:70 to 50:50. This mixing ratio allows for a good balance of improved discharge properties and curing properties.

[0028] In this invention, in order to achieve uniform light shielding across the entire visible light region, the absorbance at 455 nm (A) when a 10 μm coating film is formed with the inkjet ink of the present invention is measured. 455 ), absorbance at 555nm (A 555 ), absorbance at 655nm (A 655 It is preferable that the following equations 1 to 3 are satisfied. (Formula 1)2≦A 555 (Formula 2)0.88×A 555 ≤ A 455 ≤ 1.12 × A 555 (Formula 3)0.88×A 555 ≤ A 655 ≤ 1.12 × A 555

[0029] Furthermore, it is more preferable to satisfy the following equations 1a to 3a, and particularly preferable to satisfy equations 1b to 3b.

[0030] (Formula 1a) 2.2≦A 555 (Formula 2a)0.92×A 555 ≤ A 455 ≤ 1.08 × A 555 (Formula 3a)0.92×A 555 ≤ A 655 ≤ 1.08 × A 555

[0031] (Formula 1b)2.4≦A 555 (Formula 2b)0.94×A 555 ≤ A 455 ≤ 1.06 × A 555 (Formula 3b)0.94×A 555 ≤ A 655 ≤ 1.06 × A 555

[0032] <Pigment-dispersed resin> In this invention, a pigment dispersion resin may be used as needed to stably disperse the pigment in the ink. A pigment dispersion resin is a resin that chemically adsorbs onto the pigment due to specific functional groups it possesses, and these pigment fine particles are incorporated into the ink to prevent pigment aggregation through steric repulsion and electrochemical repulsion.

[0033] The type of resin is not particularly limited as long as it has the above-mentioned functions, but examples include acrylic resin, (anhydrous) maleic acid resin, polyethyleneimine, polyallylamine, polydiallylamine, polyvinylimidazoline, and polyvinylpyrrolidone. In the present invention, pigment dispersion resins having basic functional groups can be suitably used. Examples of commercially available products include "Azisper-PB-821", "Azisper-PB-822", "Azisper-PB-824", and "Azisper-PB-881" from Ajinomoto Fine Techno Co., Ltd., and "DISPERBYK-162", "DISPERBYK-163", "DISPERBYK-168", "DISPERBYK-182", "DISPERBYK-184", "DISPERBYK-185", and "DISPERBYK-182" from Big Chemie Co., Ltd. Examples include "K-2013", "DISPERBYK-2155", "BYKJET-9150", "BYKJET-9151", "BYKJET-9152", Lubrizol's "Solspers 24000", "Solspers 32000", "Solspers 33000", "Solspers 35000", "Solspers 39000", "Solspers 86000", "Solspers J200", and "Solspers X300", and BASF's "EFKA PX4701", "EFKA PX4703", and "EFKA PX4733".

[0034] <Polymerizable compound> The present invention includes a polymerizable compound for fixing a light-shielding pigment onto a printing substrate. The polymerizable compound undergoes polymerization or crosslinking reactions due to radicals or cations generated from photopolymerization initiators, and has the function of curing the composition containing the polymerizable compound. Compounds having one polymerizable group are called monofunctional polymerizable compounds, and compounds having two or more are called polyfunctional polymerizable compounds, and both can be suitably used in the present invention. Polymerizable compounds are classified into monomers, which are the unit of polymerization, and oligomers, which are formed by the polymerization of multiple monomer units, and both can be suitably used in the present invention.

[0035] Polymerizable compounds that undergo polymerization reactions via radicals include those having polymerizable groups such as (meth)acryloyl groups, vinyl groups, allyl groups, and unsaturated carboxyl groups. Polymerizable compounds that undergo polymerization reactions via cations include those having polymerizable groups such as epoxy groups, oxetanyl groups, and vinyl groups. In this invention, any of these can be used, but the use of radical polymerizable compounds is preferred in terms of improving curability.

[0036] Examples of radical polymerizable monomers that can be used include the following: Examples of monofunctional radical polymerizable monomers include dicyclopentenyl (oxyethyl) (meth)acrylate, 2-methoxyethyl (meth)acrylate, methoxytriethylene glycol (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 2-(2-ethoxyethoxy)ethyl (meth)acrylate, methoxydipropylene glycol (meth)acrylate, dipropylene glycol (meth)acrylate, 2-ethylhexyl EO modified acrylate, β-carboxyethyl (meth)acrylate, trimethylolpropaneformal (meth)acrylate, isoamyl (meth)acrylate, cyclohexyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, isobolonyl (meth)acrylate, and norbornyl (meth)acrylate. Examples include dicyclopentanyl (meth)acrylate, isononyl (meth)acrylate, stearyl (meth)acrylate, n-octyl acrylate, isooctyl (meth)acrylate, lauryl (meth)acrylate, isodecyl (meth)acrylate, tridecyl (meth)acrylate, caprolactone (meth)acrylate, 1,4-cyclohexanedimethanol (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, acryloylmorpholine, N-acryloyloxyethylhexahydrophthalimide, N-vinyl-ε-caprolactam, N-vinyl-2-pyrrolidone, N-vinyl-2-oxazolidinone, and N-vinylmethyloxazolidinone. In particular, phenoxyethyl acrylate, tetrahydrofurfuryl acrylate, trimethylolpropane formal acrylate, and N-vinyl-ε-caprolactam are preferred from the standpoint of curing properties.

[0037] Examples of difunctional radical polymerizable monomers include 1,6-hexanediol di(meth)acrylate, ethoxylated (or propoxylated) 1,6-hexanediol di(meth)acrylate, 1,10-decanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 2,4-dimethyl-1,5-pentanediol di(meth)acrylate, 3-methyl-1,5-pentanediol di(meth)acrylate, butylethylpropanediol di(meth)acrylate, and ethoxylated cyclo Hexanemethanol di(meth)acrylate, polyethylene glycol di(meth)acrylate, ethylene glycol di(meth)acrylate, 2-ethyl-2-butylbutanediol di(meth)acrylate, hydroxypivalate neopentyl glycol di(meth)acrylate, EO-modified bisphenol A di(meth)acrylate, bisphenol F polyethoxy di(meth)acrylate, polypropylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 2-ethyl- 2-Butylpropanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, propoxylated ethoxylated bisphenol A di(meth)acrylate, propoxylated bisphenol A di(meth)acrylate, ethoxylated bisphenol A di(meth)acrylate, ethoxylated bisphenol F di(meth)acrylate, isocyanuric acid EO modified diacrylate, tricyclodecane di(meth)acrylate, dipropylene glycol di(meth)acrylate, tripropylene glycol di( Examples include meth)acrylate, PO-modified neopentyl glycol di(meth)acrylate, EO-modified neopentyl glycol di(meth)acrylate, dimethylol tricyclodecane di(meth)acrylate, cyclohexanedimethanol di(meth)acrylate, trimethylolpropane di(meth)acrylate, neopentyl glycol-modified trimethylolpropane di(meth)acrylate, dicyclopentanyl di(meth)acrylate, and 2-(2-vinyloxyethoxy)ethyl (meth)acrylate.Among these, dipropylene glycol diacrylate, 1,6-hexanediol diacrylate, and 2-(2-vinyloxyethoxy)ethyl acrylate are preferred from the viewpoint of curing properties.

[0038] Examples of trifunctional radical polymerizable monomers include trimethylolpropane tri(meth)acrylate, trimethylolethane tri(meth)acrylate, alkylene oxide-modified tri(meth)acrylate of trimethylolpropane (e.g., trimethylolpropane EO-modified triacrylate, trimethylolpropane PO-modified triacrylate, etc.), tetramethylolmethane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol tri(meth)acrylate, trimethylolpropane tri((meth) Examples include acryloyloxypropyl ether, alkylene oxide-modified isocyanurate tri(meth)acrylate, dipentaerythritol propionate tri(meth)acrylate, tri(meth)acryloyloxyethyl)isocyanurate, hydroxypivalaldehyde-modified dimethylolpropane tri(meth)acrylate, sorbitol tri(meth)acrylate, propoxylated trimethylolpropane tri(meth)acrylate, ethoxylated glycerin tri(meth)acrylate, and propoxylated glyceryl tri(meth)acrylate. Among these, trimethylolpropane triacrylate and trimethylolpropane EO-modified triacrylate are preferred from the viewpoint of curability.

[0039] Examples of tetrafunctional radical polymerizable monomers include pentaerythritol tetra(meth)acrylate, sorbitol tetra(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, dipentaerythritol propionate tetra(meth)acrylate, ethoxylated pentaerythritol tetra(meth)acrylate, and tetramethylolmethane tetra(meth)acrylate. Among these, pentaerythritol tetraacrylate is preferred.

[0040] Examples of pentafunctional radical polymerizable monomers include sorbitol penta(meth)acrylate and dipentaerythritol penta(meth)acrylate.

[0041] Examples of hexafunctional radical polymerizable monomers include dipentaerythritol hexa(meth)acrylate, sorbitol hexa(meth)acrylate, alkylene oxide-modified phosphazene hexa(meth)acrylate, and ε-captolactone-modified dipentaerythritol hexa(meth)acrylate. Among these, dipentaerythritol hexaacrylate is preferred.

[0042] <Oligomer> When using an oligomer as the polymerizable compound, the number of polymerizable groups contained in the oligomer is preferably 1 to 15 per molecule, more preferably 2 to 6, even more preferably 2 to 4, and particularly preferably 2, from the viewpoint of balancing flexibility and curability. Furthermore, the weight-average molecular weight of the oligomer is preferably 400 to 10,000, and more preferably 500 to 5,000.

[0043] Examples of radically polymerizable oligomers include urethane (meth)acrylate oligomers such as aliphatic urethane (meth)acrylate oligomers and aromatic urethane (meth)acrylate oligomers, acrylic ester (meth)acrylate oligomers, polyester (meth)acrylate oligomers, and epoxy (meth)acrylate oligomers.

[0044] The polymerizable compound content is preferably 30 to 90% by mass, and more preferably 50 to 80% by mass, of the total amount of the inkjet ink. When the polymerizable compound content is within the above range, the inkjet ink exhibits excellent curability and ejection stability.

[0045] <Photopolymerization initiator> The photopolymerization initiators that can be used in the present invention may be known photopolymerization initiators, and it is preferable to use, for example, molecular cleavage type or hydrogen abstraction type photopolymerization initiators. Furthermore, the photopolymerization initiators may be used alone or in combination of two or more types. Specifically, acylphosphine oxide initiators, benzophenone initiators, indan initiators, hydroxyacetophenone initiators, alkylaminoacetophenone initiators, oxime ester initiators, etc., can be used.

[0046] Furthermore, the term "photopolymerization initiator" in this application also includes materials generally referred to as sensitizers, which promote the generation of radicals in other photopolymerization initiators. Examples of such materials include aminobenzoate initiators, ketocoumarin initiators, and anthracene initiators.

[0047] Among these photopolymerization initiators, it is preferable to use one or more photopolymerization initiators selected from the group consisting of acylphosphine oxide initiators and thioxanthone initiators, in order to improve curability while maintaining high light-shielding properties, and it is particularly preferable to use at least an acylphosphine oxide initiator.

[0048] Furthermore, from the viewpoint of obtaining an inkjet ink that is particularly excellent in curability and the fineness of printed materials, and moreover, has good ejection stability, it is extremely preferable to use an acylphosphine oxide-based initiator and a thioxanthone-based initiator in combination as photopolymerization initiators, and it is even more preferable to use a bisacylphosphine oxide-based initiator and a thioxanthone-based initiator in combination.

[0049] <Acylphosphine oxide initiators> Specific examples of the acylphosphine oxide initiators mentioned above include diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide, ethoxyphenyl(2,4,6-trimethylbenzoyl)phosphine oxide, and phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, as well as polymers of these compounds. Examples of commercially available acylphosphine oxide initiators include "Omnirad TPO," "Omnirad TPO-L," "Omnirad TPO-H," "Omnirad 819," and "OMNIPOL TP" from IGM RESINS, and "Speedcure TPO," "Speedcure TPO-L," and "Speedcure BPO" from Lambson. Additionally, acylphosphine oxide initiators described in International Publication No. 2017 / 086224 and International Publication No. 2020 / 049378, and lithium phenyl(2,4,6-trimethylbenzoyl)phosphinate can also be used. In the inkjet ink of this embodiment, only one of the acylphosphine oxide-based initiators listed above may be used, or two or more may be used in combination.

[0050] When the inkjet ink of this embodiment contains an acylphosphine-based initiator, from the viewpoint of obtaining an inkjet ink with excellent curability and ejection properties, the amount of the initiator is preferably 4 to 15% by mass, and particularly preferably 6 to 12% by mass, of the total amount of the inkjet ink.

[0051] <Thioxanthone-based initiators> Specific examples of the thioxanthone-based initiators mentioned above include 2-isopropylthioxanthone, 4-isopropylthioxanthone, 2,4-diethylthioxanthone, 3-methoxythioxanthone, 2-carboxymethoxythioxanthone, 3-ethoxycarbonylmethoxythioxanthone, 3-butoxycarboxymethoxythioxanthone, 1,3-dimethyl-2-(2-ethylhexyloxy)thioxanthone, 2-[2,2-bis(ethoxycarbonyl)]ethylthioxanthone, 1-chloro-4-propoxythioxanthone, and polymers of these compounds. Furthermore, examples of commercially available thioxanthone initiators include "Omnirad ITX," "Omnirad DETX," and "OMNIPOL TX" from IGM Resins; "SPEEDCURE ITX," "SPEEDCURE 2-ITX," "SPEEDCURE DETX," "SPEEDCURE LTX," "SPEEDCURE CPTX," and "SPEEDCURE 7010" from Lambson; and "Genopol TX-2" from RAHN. Of these commercially available products, "OMNIPOL TX," "SPEEDCURE 7010," and "Genopol TX-2" are the aforementioned polymers. In the inkjet ink of this embodiment, only one of the thioxanthone-based initiators listed above may be used, or two or more may be used in combination.

[0052] When the inkjet ink of this embodiment contains a thioxanthone-based initiator, from the viewpoint of obtaining an inkjet ink with excellent curability and ejection properties, the amount of the initiator is preferably 0.5 to 8% by mass, and particularly preferably 1 to 5% by mass, of the total amount of the inkjet ink.

[0053] As described above, the inkjet ink of this embodiment preferably uses both an acylphosphine oxide-based initiator and a thioxanthone-based initiator. In this case, from the viewpoint of achieving excellent curability and fineness of printed materials, the content of the acylphosphine oxide-based initiator is preferably 1 to 25, and particularly preferably 2 to 12, when the content of the thioxanthone-based initiator is set to 1.

[0054] <Other photopolymerization initiators> The following are examples of photopolymerization initiators other than acylphosphine oxide-based initiators and thioxanthone-based initiators.

[0055] Examples of commercially available benzophenone initiators include "Omnirad BP," "Omnirad BMS," "Omnirad 4PBZ," "OMNIRAD EMK," and "Esacure 1001M" from IGM RESINS.

[0056] An example of a commercially available indan-based initiator is "SpeedCure XFs01" manufactured by LAMBSON.

[0057] Examples of commercially available hydroxyacetophenone initiators include "Omnirad 127," "Omnirad 184," "Omnirad 1173," "Omnirad 2959," and "Esacure KIP150" from IGM RESINS.

[0058] Examples of commercially available alkylaminoacetophenone initiators include "Omnirad 907," "Omnirad 369," and "Omnirad 379" manufactured by IGM Resins.

[0059] Examples of commercially available oxime ester initiators include BASF's "IRGACURE OXE01," "IRGACURE OXE02," and "IRGACURE OXE04."

[0060] Examples of commercially available aminobenzoate initiators include "Omnirad EDB," "Omnirad EHA," "Esacure A198," and "Omnipol ASA" from IGM Resins; "SPEEDCURE EDB," "SPEEDCURE EHA," "SPEEDCURE BEDB," and "SPEEDCURE 7040" from Lambson; and "GENOPOL AB-1" and "GENOPOL AB-2" from Rahn AG.

[0061] Examples of ketocoumarin initiators include "ESACURE 3644" manufactured by IGM RESINS.

[0062] Examples of commercially available anthracene-based initiators include "Anthracure UVS-581" manufactured by Kawasaki Chemical Industries, Ltd.

[0063] When the inkjet ink of this embodiment contains a photopolymerization initiator, the total amount of the photopolymerization initiator is preferably 3 to 20% by mass, more preferably 4 to 17% by mass, and particularly preferably 5 to 15% by mass, relative to the total amount of the inkjet ink. By keeping the total amount of the photopolymerization initiator within the above range, it is possible to achieve both curability and discharge stability.

[0064] <Other ingredients> In addition to the components described above, the inkjet ink of this embodiment may also contain surface modifiers, polymerization inhibitors, organic solvents, water, inert resins, and other additives.

[0065] <Surface modifier> The inkjet ink of this embodiment preferably contains a surface modifier for the purpose of improving wetting spread on the printing substrate, print quality including the fineness of the printed material, substrate adhesion, and ejection stability. Examples of surface modifiers that can be used include siloxane-based surface modifiers, fluorine-based surface modifiers, acetylene glycol-based surface modifiers, and acetylene monool-based surface modifiers. Among these, it is preferable to use a siloxane-based surface modifier from the viewpoint that it can improve wetting spread on the printing substrate, print quality including the fineness of the printed material, substrate adhesion, and ejection stability without worsening the dispersion stability of carbon black.

[0066] As the siloxane-based surface modifier mentioned above, for example, compounds having a dimethylsiloxane structure and / or modified versions thereof can be used. Among these, polyether-modified siloxane-based surface modifiers are particularly preferred. Specific examples of the polyether group include polyethylene oxide groups and polypropylene oxide groups. These may contain only one of these polyether groups in the molecule, or both.

[0067] Commercially available polyether-modified siloxane-based surface modifiers such as BYK(registered trademark)-378, 348, 349, 3420, 3760, BYK-UV3500, UV3510 from BIC Chemie, and TEGO(registered trademark) Glide 450, 440, 435, 432, 410, 406, 130, 110, 100 from EVONIK, are preferably used.

[0068] When using a siloxane-based surface modifier, its content is preferably 0.1 to 5.0% by mass, based on the total mass of the inkjet ink. Adjusting the content to 0.1% by mass or more improves the wettability and spreadability on the printing substrate, as well as the print quality, including the fineness of the printed material, and the adhesion. On the other hand, adjusting the content to 5.0% by mass or less makes it easier to ensure curability and ejection stability.

[0069] <Polymerization inhibitor> To improve the ejection stability of the inkjet ink, and further to improve the hue stability and suppress hardening wrinkles in printed materials, the inkjet ink of this embodiment may contain a polymerization inhibitor. Specific examples of such polymerization inhibitors include hindered phenol compounds, phenol compounds, hydroquinone compounds, phenothiazine compounds, phosphorus compounds, and nitrosophenylhydroxylamine compounds, which can be suitably used.

[0070] More specifically, examples of polymerization inhibitors that can be used in the inkjet ink of this embodiment include 4-methoxyphenol, tert-butylhydroquinone, 2,6-di-tert-butyl-4-methylphenol, pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], hydroquinone, methylhydroquinone, phenothiazine, dicumylphenothiazine, triphenylphosphine, and aluminum salts of N-nitrosophenylhydroxylamine.

[0071] The polymerization inhibitor content is preferably 0.01 to 2% by mass, more preferably 0.05 to 1% by mass, and particularly preferably 0.1 to 0.8% by mass, based on the total mass of the inkjet ink. By adjusting the content to the above range, it becomes easier to improve the ejection stability of the inkjet ink while maintaining curability.

[0072] <Organic solvents, water> In the inkjet ink of this embodiment, an organic solvent and / or water may be used to reduce the viscosity of the inkjet ink, improve its wetting and spreading properties and adhesion to the printing substrate, and ensure ejection stability. When an organic solvent and / or water is included, its content is preferably 0.1 to 70% by mass, more preferably 1 to 50% by mass, and particularly preferably 5 to 40% by mass, based on the total mass of the inkjet ink. Furthermore, from the viewpoint of ejection stability and wetting and spreading properties and adhesion to the printing substrate, when an organic solvent is used, it is preferable to use an organic solvent with a boiling point of 140 to 300°C.

[0073] Examples of organic solvents that can be used include alkylene glycol monoalkyl ether acetates, alkylene glycol diacetates, alkylene glycol monoalkyl ethers, alkylene glycol dialkyl ethers, alkanediols, lactams, lactones, other nitrogen-containing solvents, and other oxygen-containing solvents.

[0074] In particular, it is preferable to include at least one selected from the group consisting of alkylene glycol monoalkyl ethers, alkylene glycol dialkyl ethers, and alkylene glycol monoalkyl ether acetates. Tripropylene glycol monomethyl ether, dipropylene glycol monomethyl ether, propylene glycol monomethyl ether, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, tetraethylene glycol dialkyl ether, ethylene glycol monobutyl ether acetate, and diethylene glycol diethyl ether are especially preferred. In one embodiment, the organic solvent is preferably at least one selected from the group consisting of tetraethylene glycol dialkyl ether, ethylene glycol monobutyl ether acetate, and diethylene glycol diethyl ether.

[0075] <Inert resin> The inkjet ink of this embodiment may contain an inert resin for the purpose of providing adhesion to various printing substrates and adjusting the viscoelasticity of the ink to improve ejection stability. As the inert resin, (meth)acrylic resin, urethane resin, vinyl chloride-vinyl acetate copolymer resin, ketone resin, etc. can be used. In particular, from the viewpoint of improving both adhesion and ejection stability, it is preferable that the inert resin contains (meth)acrylic resin and / or ketone resin.

[0076] When the inkjet ink of this embodiment contains an inert resin, its content is preferably 0.1 to 10% by mass, more preferably 0.5 to 5% by mass, and particularly preferably 1 to 3% by mass, based on the total mass of the inkjet ink. By adjusting the above content within the above range, adhesion and ejection stability can be easily improved without worsening curability.

[0077] In this application, "inert resin" refers to a resin that does not participate in polymerization reactions, contributes to adhesion to the printing substrate, and has solubility in inkjet inks.

[0078] <Other additives> The inkjet ink of this embodiment may, if necessary, further contain additives such as ultraviolet absorbers and fade inhibitors in addition to the components described above. These components can be any conventionally known compounds.

[0079] <Physical properties of inkjet inks> In this embodiment, the inkjet ink preferably has a viscosity of 5 to 100 mPa·s at 25°C, more preferably 10 to 50 mPa·s, and most preferably 15 to 30 mPa·s, from the viewpoint of improving ejection stability. If the viscosity is 5 mPa·s or higher, the inkjet ink can be ejected well from the inkjet head. If it is 100 mPa·s or lower, the ejection accuracy will not decrease, and stable ejection can be continued. Furthermore, from the viewpoint of providing high-frequency suitability and enabling stable ejection even at high-speed printing, the viscosity is particularly preferably 10 to 50 mPa·s.

[0080] Furthermore, from the viewpoint of improving ejection stability, print resolution, and curability, the static surface tension of the inkjet ink at 25°C is preferably 20 to 45 mN / m, and particularly preferably 22 to 40 mN / m. The static surface tension used is the value measured by the plate method (Wilhelmi method). Specifically, for example, it can be measured at 25°C using an automatic surface tension meter "CBVP-Z" manufactured by Kyowa Interface Science Co., Ltd. and a platinum plate.

[0081] <Ink manufacturing method> The ink of the present invention can be manufactured by conventionally known methods. Specifically, first, a pigment, a polymerizable compound, and, if necessary, a pigment dispersion resin, polymerization inhibitor, etc., are mixed, and then the mixture is dispersed using a paint shaker, sand mill, roll mill, medialess disperser, etc., to prepare a pigment dispersion.

[0082] Next, the remaining polymerizable compound, a photopolymerization initiator, and other additives as needed are added to the obtained pigment dispersion to achieve the desired ink properties, and the mixture is thoroughly mixed. Then, coarse particles are filtered out using a filter or the like to obtain the ink of the present invention.

[0083] <Recording Method> An example of a recording method for manufacturing printed materials using the active energy ray curable inkjet ink of the present invention is a method that includes the steps of: ejecting the active energy ray curable inkjet ink from the nozzle of an inkjet head and applying it to a substrate (printing step); and irradiating the active energy ray curable inkjet ink applied to the substrate with active energy rays to cure the active energy ray curable inkjet ink (curing step).

[0084] <Printing process> As a method for printing with the ink of the present invention, a method is used in which droplets of the ink are ejected from an inkjet head and adhered to a printing substrate. The number of times the same ink droplet is adhered to a certain area on the substrate may be one or multiple times. An example of a printing process in which the adhesion is performed once is a method in which the substrate is transported while the inkjet head is fixed, and the ink is ejected from the inkjet head as it passes below the inkjet head (line head type one-pass printing process). An example of a printing process in which the adhesion is performed multiple times is a method in which the inkjet head is scanned in a direction perpendicular to the transport direction of the substrate, and ink is ejected multiple times to the same area on the substrate (shuttle head type multi-pass printing process).

[0085] <Curing process> There are no particular restrictions on the source of the active energy rays, and conventionally known sources can be used. Specifically, these include mercury lamps, xenon lamps, metal hydride lamps, UV-LEDs, ultraviolet laser diodes (UV-LDs), and other LEDs (light-emitting diodes), as well as gas and solid-state lasers.

[0086] When volatile components such as organic solvents or water are incorporated into the ink of the present invention, it is preferable to perform heat drying after applying the ink. This removes the organic solvents and water from the coating film and promotes curing.

[0087] <Base material> Examples of substrates used in the recording method described above include plastic substrates such as polypropylene (PP), polyethylene (PE), polyethylene terephthalate (PET), nylon, polystyrene, polycarbonate (PC), acrylic (PMMA, etc.), cycloolefin polymer (COP), and cycloolefin copolymer (COC); paper substrates such as art coated paper, semi-gloss coated paper, and cast coated paper; and metal substrates such as aluminum-metallized paper.

[0088] When the printed material of the present invention is used for optical applications, it is preferable to print on a transparent substrate, and polycarbonate (PC), acrylic (such as PMMA), cycloolefin polymer (COP), and cycloolefin copolymer (COC) can be suitably used.

[0089] <Printed material> The printed material of the present invention comprises a light-shielding film formed from the inkjet ink of the present invention on a substrate, and can be suitably used as an optical element. For example, it can be used as a light-shielding member for camera lenses, display panels, sensors, etc. [Examples]

[0090] The following are examples of the present invention, but the present invention is not limited to these examples. In the examples, "parts" and "%" refer to parts by mass and mass%, respectively.

[0091] [Example 1] <Ink preparation> As shown in Table 1, the pigment, pigment dispersion resin, polymerizable compound, and solvent were mixed and pre-dispersed in a disperser. Then, the final dispersion was carried out for 2 hours using a Dynomill packed with 0.5 mm diameter zirconia beads to obtain a pigment dispersion. To this dispersion, an initiator, surfactant, and polymerization inhibitor were added and stirred at 50°C for 1 hour. After this, coarse particles were removed using a 1 μm pore size filter to obtain the ink of Example 1.

[0092] <Measurement of absorbance of coating film> An inkjet coating apparatus (inkjet head, KM1024aSHE manufactured by Konica Minolta) equipped with a UV-LED irradiator (FirePower manufactured by Phoseon, peak emission wavelength 395 nm) was filled with ink, and a solid pattern was printed on a transparent PET film (Lumirror manufactured by Toray) to a film thickness of 10 μm. Further, UV irradiation was performed with a UV-LED irradiator so that the integrated light amount became 2000 mJ / cm 2 to obtain a coating film for evaluation. The absorbance of the coating film was measured with an ultraviolet-visible near-infrared spectrophotometer (UH5700 manufactured by Hitachi High-Tech), and the absorbance (A 455 ) at 455 nm, the absorbance (A 555 ) at 555 nm, and the absorbance (A 655 ) at 655 nm were obtained.

[0093] <OD value evaluation> The OD value of the coating film prepared by absorbance measurement was measured using a transmission densitometer (Ihac-T5 manufactured by Ihara Electronic Industry). If the OD value is 2 or more, it is practical as a light-shielding film.

[0094] <Suitability for curing evaluation> Under the same apparatus configuration and method as the inkjet coating conditions during absorbance measurement, the integrated light amount of UV irradiation was changed to confirm the integrated light amount required to cure the ink. The evaluation criteria are as follows, and a value of 2 or more is judged to be practical. 5: Cured with an integrated light amount of 500 mJ / cm 2 4: Cured with an integrated light amount of 1000 mJ / cm 3: Cured with an integrated light amount of 2000 mJ / cm 2 2: Cured with an integrated light amount of 4000 mJ / cm 1: Cured with an integrated light amount of 4000 mJ / cm 2 or not cured with an integrated light amount of 4000 mJ / cm 2: Cured with an integrated light amount of 4000 mJ / cm 2 1: Cured with an integrated light amount of 4000 mJ / cm or not cured with an integrated light amount of more than 4000 mJ / cm 2

[0095] <Discharge stability evaluation> The ink was filled using the same equipment configuration as for the inkjet coating conditions used for absorbance measurement, and the device was left to stand at 25°C for a certain period of time. Afterward, printing was performed to confirm whether it could print normally. The evaluation criteria are as follows, with a score of 2 or higher considered practical. 5: Printing is still possible after being left to stand for 2 hours. 4: Printing is still possible after 1 hour of standing. Printing is still possible after letting it sit for 3 hours and 30 minutes. Printing is still possible after letting it sit for 2:15 minutes. After 1:15 minutes of standing, normal printing is not possible.

[0096] <Hue Evaluation> The primary stimulus values ​​X, Y, and Z were calculated from the absorbance spectrum data obtained by absorbance measurement, and the CIE1931 chromaticity coordinate (x,y) was determined. Hue was determined from this chromaticity coordinate (x,y). The evaluation criteria are as follows, and a value of 3 or higher is preferable because it indicates that uniform light shielding is obtained. 5: 0.31 ≤ x ≤ 0.35, 0.35 ≤ y ≤ 0.39 3: 0.3 ≤ x ≤ 0.4, 0.3 ≤ y ≤ 0.4 1: x < 0.3 or 0.4 <x、y<0.3または0.4<y

[0097] [Examples 2-21 and Comparative Examples 1-6] Except for changing the ink composition as shown in Table 1, the ink was prepared and evaluated using the same procedure as in Example 1. However, in Examples 19-21, UV irradiation was performed after drying at 80°C for 5 minutes after printing during film preparation.

[0098] The details of each component in Table 1 are as follows: <Pigments> (Inorganic pigments) BL100: Titanium Industries' iron oxide "TAROX BL-100HP" (average primary particle size 300nm) TM3552: Composite oxide (Cu[Fe,Mn]O4) manufactured by Dainichi Seika Kogyo Co., Ltd. "Dipyroxide TM Black #3552" (average primary particle size 60 nm) 13M-T: Mitsubishi Materials Titanium Black "13M-T" SB350: Orion Engineered Carbons' carbon black "SpecialBlack350" (primary particle size 31nm) <Pigment-dispersed resin> SP32k: Lubrizol "Solspers 320000" <Polymerizable compound> PEA: Phenoxyethyl acrylate DPGDA: Dipropylene glycol diacrylate DPHA: Dipentaerythritol hexaacrylate <Solvent> DEDG: Diethylene glycol diethyl ether <Photopolymerization initiator> (Acylphosphine oxide initiators) TPO: IGM Resins' "Omnirad TPO N" Omni819: "Omnirad819" made by IGM Resins (Thioxanthone-based initiator) ITX: "SpeedCure 2-ITX" made by Arkema DETX: “SpeedCure DETX” made by Arkema (Alkylaminoacetophenone-based initiators) Omni369: “Omnirad369” made by IGM Resins <Surfactants> BYK333: BYK-333 manufactured by Big Chemie. <Polymerization inhibitor> BHT: 2,6-di-tert-butyl-4-methylphenol

[0099] [Table 1]

[0100] [Table 2]

[0101] The examples demonstrate that by including carbon black and inorganic pigments other than carbon black, a high OD value is achieved while maintaining good curability and discharge stability. In particular, improvements in curability and discharge stability were observed in the examples containing carbon black and titanium black.

[0102] Examples 15, 16, 18, and 20 showed improved curability by including both an acylphosphine oxide initiator and a thioxanthone initiator. Furthermore, Examples 18 and 20, which also used a bisacylphosphine oxide initiator, exhibited extremely high curability.

Claims

1. An active energy ray curable inkjet ink comprising a pigment, a polymerizable compound, and a photopolymerization initiator, wherein the pigment comprises carbon black and an inorganic pigment other than carbon black.

2. The activated energy ray curable inkjet ink according to claim 1, wherein the inorganic pigment other than carbon black includes titanium black.

3. Absorbance at 455 nm when a coating film with a thickness of 10 μm is formed (A ４５５ ), absorbance at 555 nm (A ５５５ ), absorbance at 655 nm (A ６５５ The active energy ray curable inkjet ink according to claim 1, wherein the following formulas 1 to 3 are satisfied. (Equation 1) 2≦A ５５５ (Equation 2) 0.88 × A ５５５ ≦ A ４５５ ≦ 1.12×A ５５５ (Equation 3) 0.88 × A ５５５ ≦ A ６５５ ≦ 1.12×A ５５５

4. The active energy ray curable inkjet ink according to claim 1, wherein the photopolymerization initiator comprises an acylphosphine oxide-based initiator and a thioxanthone-based initiator.

5. A printed article obtained by printing an active energy ray-curable inkjet ink according to any one of claims 1 to 4 onto a substrate.

6. A method for manufacturing a printed material, comprising inkjet printing an active energy ray curable inkjet ink according to any one of claims 1 to 4 onto a substrate.

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