Inkjet ink composition and recording method

Abstract

Provided is an inkjet ink composition and a recording method, which are excellent in storage stability, color development, transfer resistance, rub-off resistance, clogging recovery, and bubble discharge. The inkjet ink composition comprises: a pigment, which is carbon black derived from a biological oil; a binder resin; and a solvent, wherein the pigment is a self-dispersible pigment, the binder resin comprises a self-emulsifying resin, and the solvent comprises water, and the inkjet ink composition is a water-based ink.

Description

Technical Field

[0001] This invention relates to inkjet ink compositions and recording methods. Background Technology

[0002] Inkjet recording methods can achieve high-resolution image recording with relatively simple devices and have made rapid progress in various aspects. For example, Patent Document 1 discloses an aqueous inkjet ink composition with excellent environmental compatibility and storage stability, comprising a biologically derived pigment, a biologically derived dispersant, and a biologically derived organic solvent, wherein the organic solvent has a solubility parameter of 24.0 (cal / cm³) based on the Hansen method. 3 ) 1 / 2 The above compounds, which also contain hydroxyl groups.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent document 1: Japanese Patent Application Publication No. 2023-128719.

[0006] For water-based inkjet inks containing pigments, it is desirable to improve their clogging recovery, color development, and transfer inhibition. Summary of the Invention

[0007] The inkjet ink composition of the present invention comprises: a pigment, which is carbon black derived from bio-oil; a binder resin; and a solvent, wherein the pigment is a self-dispersing pigment, the binder resin comprises a self-emulsifying resin, and the solvent comprises water, and the inkjet ink composition is an aqueous ink.

[0008] The recording method of the present invention includes an adhesion step, wherein ink using the above-described inkjet ink composition is ejected from an inkjet head and adhered to a recording medium. Attached Figure Description

[0009] Figure 1 This is a diagram illustrating an example of a recording device used in the recording method of this embodiment.

[0010] Figure 2 Table 1 shows the monomer composition of the self-emulsifying resin used in the examples.

[0011] Figure 3 Table 2 shows the composition of each composition used in the examples and its evaluation results.

[0012] Figure 4 Table 3 shows the composition of each composition used in the examples and its evaluation results.

[0013] Figure 5Table 4 shows the composition of each composition used in the examples and their evaluation results.

[0014] Explanation of reference numerals in the attached figures

[0015] 10. Recording device; 11. Conveyor path; 12. Feed section; 14. Conveyor section; 16. Belt conveyor section; 18. Recording section; 20. Fd discharge section; 22. Fd mounting section; 24. Reversal path section; 26. Fu discharge section; 28. Fu mounting section; 30. Feed tray; 32. Feed roller; 34. Conveyor drive roller; 36. Conveyor driven roller; 38. First roller; 40. Second roller; 42. Circular belt; 42a. Upper section of the circular belt; 44. Support body; 46. Head support; 48. Inkjet head; 50. First branch; 52. Reversal path; 54. Second branch; 56. Discharge roller pair; 64. Discharge drive roller; 68. Drive shaft; 76. Mounting surface; 78. Protrusion; 80. First force-applying member; 82. Second force-applying member; 84, 86. Support shaft; P. Recording medium. Detailed Implementation

[0016] The following, as needed, will be referenced in the appendix. Figure 1 While this embodiment has been described in detail, the present invention is not limited thereto, and various modifications can be made without departing from its spirit. It should be noted that in the accompanying drawings, the same symbols are used to denote the same elements, and repeated descriptions are omitted. Furthermore, unless otherwise specified, the positional relationships such as up, down, left, and right are based on the positional relationships shown in the accompanying drawings. In addition, the scale of the accompanying drawings is not limited to the scale shown.

[0017] 1. Inkjet ink composition

[0018] The inkjet ink composition of this embodiment comprises: a pigment, which is carbon black derived from bio-oil; a binder resin; and a solvent, wherein the pigment is a self-dispersing pigment, the binder resin comprises a self-emulsifying resin, and the solvent comprises water, and the inkjet ink composition is a water-based ink.

[0019] By using colorants derived from natural sources, such as carbon black derived from bio-oil (hereinafter also referred to as "bio-oil CB"), in inks, environmentally friendly inks have been developed that reduce the components derived from petroleum and the CO2 emissions caused by these components. "CB" refers to carbon black.

[0020] For resin-dispersed pigments, such as carbon black, which are formed by dispersing pigments using dispersant resins, insufficient adhesion or adsorption between the dispersant resin and the pigment can lead to poor dispersion stability. Furthermore, there is a possibility that the dispersant resin may become free from the pigment during storage, or that the free dispersant resin may become foreign matter. Using self-dispersing pigments that do not require dispersant resins can prevent decreased storage stability and foreignization of the dispersant resin. However, when using self-dispersing pigments, sometimes the ink's abrasion resistance to the recording medium becomes insufficient, or the ink adhering to the medium is easily transferred elsewhere.

[0021] Therefore, in this embodiment, in addition to bio-oil CB as a self-dispersible pigment, a self-emulsifying resin is also used. Compared to petroleum-derived carbon black, bio-oil CB tends to contain more oxygen atoms as unburned components, making it easier to introduce more oxygen-containing functional groups through surface treatment. Therefore, bio-oil CB, as a self-dispersible pigment, exhibits particularly high dispersion stability and improved pigment surface wettability, resulting in an ink with exceptionally excellent storage stability, clogging recovery, and bubble removal properties. Furthermore, its reactivity with metal salts such as calcium salts contained in the recording medium is enhanced, thus making it an ink with excellent color development. Moreover, the self-emulsifying resin has a large number of hydrophilic functional groups on its surface, exhibiting high affinity for bio-oil CB as a self-dispersible pigment, which also has a large number of hydrophilic functional groups on its surface. Therefore, it becomes an ink with excellent rub resistance and resistance to transfer, i.e., excellent transfer resistance.

[0022] The following describes in detail the components that may be included in the ink composition of this embodiment and the manufacturing method.

[0023] 1.1. Pigments

[0024] The ink composition in this embodiment contains pigments as bio-oil CB. By using bio-oil CB derived from natural sources, it is possible to produce environmentally friendly inks that reduce petroleum-derived components and CO2 emissions caused by these components.

[0025] 1.1.1. Bio-oil CB

[0026] The pigment in this embodiment contains bio-oil CB. Bio-oil CB is CB derived from bio-oil. It is a substance produced by carbonizing bio-oil to form CB.

[0027] Bio-oil is not oil derived from underground resources such as petroleum, but rather refers to oil derived from existing organisms such as plants, animals, and microorganisms. It includes oil obtained by processing biological materials, oil extracted from or produced from organisms, etc.

[0028] Bio-oil is also referred to as biomass oil. Bio-oil CB is also called CB derived from biomass oil.

[0029] By using carbon black derived from biomass oils, the amount of petroleum-derived components in inks can be reduced. This results in lower carbon dioxide emissions compared to inks using petroleum-derived components, enabling the production of environmentally friendly inks.

[0030] Bio-oil CB is made by carbonizing bio-oil to produce carbon black. The manufacturing process, involving the combustion of liquids to carbonize them, is similar to that of petroleum-derived carbon black, making it relatively easy to produce. By purifying the liquid raw materials, impurities are also more easily reduced, thus inhibiting impurity adhesion and residue in the carbon black, resulting in improved storage stability.

[0031] There are no particular limitations on the manufacturing method of bio-oil CB; for example, well-known methods such as furnace method, tank method, and lamp method can be used. In addition, during the raw material production process of bio-oil or its modified products, in addition to conditions such as heating temperature and sample quantity, the structure and primary particles of carbon black can also be controlled by adding alkaline agents such as potassium hydroxide and sodium hydroxide.

[0032] Bio-oils used as raw materials for bio-oils (CB) can include animal fats, vegetable oils, and microbial oils. Examples of animal fats include, but are not limited to, tallow, horse oil, and fish oil. Examples of microbial oils include, but are not limited to, algae oil.

[0033] Even among bio-oils (CBs), vegetable oils (CBs) made from plant oils are preferred due to the following advantages: the plant oils used as raw materials are easier to obtain in large quantities and are relatively homogeneous; the plant oils used as raw materials are easy to process; and they are easy to preserve.

[0034] There are no particular limitations on the raw materials for vegetable oil CB, and examples include vegetable seed oils, tall oils, or wood tar, or modified products of these vegetable seed oils, tall oils, or wood tar, or their derivatives. It should be noted that modified products refer to products obtained by modifying vegetable oils within the range that achieves the effects of this embodiment.

[0035] The primary particle size of bio-oil CB is preferably below 80 nm. More preferably, it is 5–70 nm, 15–55 nm, 20–45 nm, or 25–35 nm. By keeping the primary particle size within the above range, there is a tendency to improve storage stability, transfer resistance, color development, clogging recovery, and bubble removal. It should be noted that the primary particle size of carbon black can be determined by observing the carbon black particles using an electron microscope and calculating it as the arithmetic mean diameter.

[0036] Primary particles are the smallest units of carbon black. They are mostly the smallest units produced during the carbonization process when carbon black is generated. Secondary particles are aggregates formed by the aggregation and cohesion of multiple primary particles. In ink compositions, carbon black is more often dispersed in the form of secondary particles.

[0037] The oil absorption capacity of the bio-oil CB is preferably 250 mL / 100g or less, or 30 mL / 100g or more. More preferably, it is 50–200 mL / 100g, 80–170 mL / 100g, 80–150 mL / 100g, or 90–130 mL / 100g. By keeping the oil absorption capacity of the DBP within the above range, there is a tendency to improve storage stability, transfer resistance, color development, clogging recovery, and bubble removal.

[0038] DBP oil absorption is a value expressed as the amount of dibutyl phthalate (DBP) absorbed by 100g of carbon black, which can be determined according to the test method specified in JIS K6221. Generally speaking, the more developed the secondary particle structure of the carbon black, the greater the DBP oil absorption.

[0039] The content of bio-oil CB relative to the total amount of the ink composition is preferably 0.1–15% by mass, 1–12% by mass, 2–9% by mass, and 3–7% by mass. By keeping the pigment content within the above range, there is a tendency to further improve storage stability, color development, clogging recovery, and bubble removal.

[0040] 1.1.2. Self-dispersing pigments

[0041] Pigments can be categorized by their dispersion method, such as resin-dispersed pigments that are dispersed through resins, and self-dispersing pigments that can disperse themselves even without a dispersant.

[0042] The resin used for dispersing resin-dispersed pigments is also a dispersant. For resin-dispersed pigments dispersed using a resin as a dispersant, insufficient adhesion or adsorption between the dispersant resin and the pigment can lead to poor dispersion stability, and there is a possibility that the dispersant resin may become free from the pigment during storage, or that the free dispersant resin may become foreign. The ink composition in this embodiment, by using a self-dispersing pigment, can prevent a decrease in storage stability and the foreignization of the dispersant resin. Furthermore, compared to petroleum-derived carbon black, bio-oils (CB) tend to contain more oxygen atoms as unburned components, making it easier to introduce more oxygen-containing functional groups through surface treatment. This tendency is particularly pronounced in vegetable oils (CB).

[0043] Therefore, bio-oil CBs, especially vegetable oil CBs, used to make self-dispersible pigments, exhibit exceptionally high dispersion stability and improved pigment surface wettability, resulting in inks with excellent storage stability, clogging recovery, and bubble removal properties. Furthermore, their particularly high reactivity with metal salts such as calcium salts contained in recording media makes them inks with excellent color development properties.

[0044] There are no particular limitations on the manufacturing method of self-dispersible pigments. For example, methods that introduce hydrophilic functional groups into the pigment surface by performing physical and / or chemical surface treatments can be cited. Examples of such physical treatments include vacuum plasma treatment. Additionally, examples of chemical treatments include oxidation treatments using oxidizing agents.

[0045] When bio-oil CB is used to make a self-dispersible pigment, hydrophilic functional groups are easily introduced into the pigment through the oxygen atoms contained in the bio-oil CB, which is therefore preferable. Since these functional groups are easily introduced into the pigment through the oxygen atoms contained in the bio-oil CB, they are hydrophilic functional groups containing oxygen atoms. The proportion of hydrophilic functional groups introduced can also be adjusted by adjusting the degree of oxidation treatment.

[0046] Alternatively, a method can be cited in which hydrophilic functional groups are introduced into the pigment surface by using a chemical reaction to combine a compound with hydrophilic functional groups. In this case, the oxygen atoms contained in the pigment also facilitate the chemical reaction with the compound with hydrophilic functional groups, making it easier to introduce the hydrophilic functional groups into the pigment, and is therefore preferred.

[0047] Alternatively, the above-mentioned compounds with hydrophilic functional groups can be reacted with the hydrophilic functional groups introduced into the pigment through the above-mentioned oxidation treatment through chemical reaction.

[0048] Examples of hydrophilic functional groups include ionic groups. Ionic groups include acidic groups and basic groups. There are no particular limitations on such ionic groups; examples include carboxyl groups, amino groups, sulfonyl groups, and phosphorus-containing acid groups.

[0049] The preferred groups are anionic groups such as carboxyl, sulfonyl, and phosphorus-containing acid groups.

[0050] Hydroxyl groups can be cited as hydrophilic functional groups, but the above-mentioned hydrophilic functional groups other than hydroxyl groups are preferred as hydrophilic functional groups used to make self-dispersing pigments, as they make the pigments more stable to disperse.

[0051] In this case, the self-dispersible pigment is preferably surface-treated by oxidation. Using such a self-dispersible pigment tends to improve storage stability, color development, clogging recovery, and bubble removal. Examples of oxidation treatments include: oxidation treatment using hypohalous acids or hypohalates, oxidation treatment using ozone, and oxidation treatment using persulfate or persulfate. Specific examples of oxidizing agents include, but are not limited to, sodium hypochlorite.

[0052] Due to the nature of the raw materials, bio-oils (CBs) contain complex impurities and sometimes have complex structures. This complexity of impurities and structures can sometimes lead to relatively poor storage and dispersion stability. This tendency is particularly pronounced in vegetable oils (CBs). Even under these circumstances, by preparing them as self-dispersible pigments, it is easy to introduce a large number of hydrophilic functional groups, resulting in excellent storage and dispersion stability, making them preferable.

[0053] In addition, for plant oil CB, the pigment contains a particularly large number of oxygen atoms, which makes it easy to introduce hydrophilic functional groups and easily exert the effects of the invention of this application, and is therefore preferred.

[0054] It should be noted that "structure" is a term that describes how carbon black particles aggregate, what shape they take, their configuration, the way the particles are connected, and their size, such as the state of secondary particles formed by the aggregation of primary particles.

[0055] 1.2. Adhesive Resin

[0056] The ink composition in this embodiment includes a self-emulsifying resin as a binder resin. Since the dissolution and dispersion of the self-emulsifying resin are reversible, it will not become foreign matter or a major cause of clogging even after the ink dries, thus improving the storage stability, clogging recovery, and bubble removal properties of the ink composition. Furthermore, the self-emulsifying resin has a large number of hydrophilic functional groups on its surface, exhibiting high affinity for bio-oil CB, a self-dispersing pigment that also has a large number of hydrophilic functional groups on its surface. Therefore, it becomes an ink with excellent abrasion resistance and transfer resistance.

[0057] 1.2.1. Self-emulsifying resin

[0058] For self-emulsifying resins, in inks with a high water concentration, they disperse through self-emulsification. However, in nozzles or similar environments, if water evaporates or the concentration of organic solvents increases, they will dissolve. Furthermore, if the water concentration increases again due to the supply of new ink, self-emulsification and redispersion can occur again.

[0059] There are no particular limitations on the monomers that constitute self-emulsifying resins; for example, hydrophobic monomers and hydrophilic monomers can be used. As hydrophobic monomers, there are no particular limitations. Examples include: methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, pentyl methacrylate, cyclohexyl methacrylate, 2-ethylhexyl methacrylate, octyl methacrylate, decyl methacrylate, lauryl methacrylate, stearyl methacrylate, isopropyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, isoamyl methacrylate, isooctyl methacrylate, isodecyl methacrylate, isododecyl methacrylate, isobornyl methacrylate, isostearyl methacrylate, dicyclopentyl methacrylate, and other alkyl methacrylates; styrene, α-methylstyrene, 2-methylstyrene, vinyltoluene, divinylbenzene, chlorostyrene, phenyl methacrylate, benzyl methacrylate, phenoxyethyl methacrylate, and other monomers containing aromatic groups.

[0060] As hydrophilic monomers, there are no particular limitations. Examples include: unsaturated carboxylic acid monomers such as acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, citracic acid, and 2-methacryloyloxymethyl succinate; unsaturated sulfonic acid monomers such as styrene sulfonic acid, 2-acrylamide-2-methylpropanesulfonic acid, and propyl(meth)acrylate; unsaturated phosphate monomers such as vinylphosphonic acid, vinyl phosphate, di(methacryloyloxyethyl) phosphate, diphenyl-2-acryloyloxyethyl phosphate, and diphenyl-2-methacryloyloxyethyl phosphate; cyclic trimethylolpropane methyl acetal (meth)acrylate, tetrahydrofurfuryl(meth)acrylate, and (2-methyl-2-ethyl-1,3-dioxolane-4-yl)acrylate. Ether-containing monomers such as esters; monomers containing unsaturated tertiary amines such as N,N-dimethylaminoethyl (meth)acrylate, N,N-dimethylaminopropyl (meth)acrylate, N,N-diethylaminoethyl (meth)acrylate, N,N-dimethylaminopropyl (meth)acrylamide, N,N-dimethylarylamine, vinylpyrrolidone, 2-vinylpyridine, 4-vinylpyridine, 2-methyl-6-vinylpyridine, and 5-ethyl-2-vinylpyridine; and monomers containing unsaturated ammonium salts such as N,N-dimethylaminoethyl (meth)acrylate quaternary ammonium compounds, N,N-diethylaminoethyl (meth)acrylate quaternary ammonium compounds, and N,N-dimethylaminopropyl (meth)acrylate quaternary ammonium compounds.

[0061] The self-emulsifying resin can be a homopolymer of the aforementioned hydrophilic monomers, hydrophobic monomers, etc., or it can be a copolymer. The copolymer can be a random copolymer or a block copolymer, but in this embodiment, the self-emulsifying resin is preferably a block copolymer. When the self-emulsifying resin is a block copolymer, by making each block have different hydrophilicity, the self-emulsifying resin can adopt a polymer micelle structure, thus further improving solubility and redispersibility. Therefore, there is a tendency for improved storage stability, clogging recovery, and bubble removal properties of the ink composition.

[0062] The block copolymer is not particularly limited; for example, it can be a diblock copolymer, a triblock copolymer, or have more than three blocks. Furthermore, the blocks can be composed of a single monomer or two or more monomers. It should be noted that in blocks containing two or more monomers, the monomers can be arranged randomly. A block copolymer is a copolymer in which the polymer chain is formed by multiple blocks, and the molecular chain contains two or more blocks. Diblock copolymers formed by two blocks are particularly preferred. In the case of two blocks, the two blocks are referred to as block A and block B. AB block copolymers formed by one block A and one block B are preferred. In this case, the ink composition exhibits superior storage stability, clogging recovery, etc., and is therefore preferred.

[0063] The self-emulsifying resin is preferably an acrylic block copolymer. Using acrylic block copolymers tends to improve storage stability, clogging recovery, and bubble removal. As an acrylic block copolymer, there are no particular limitations as long as it contains at least an acrylic monomer as a constituent component. The acrylic monomer is a monomer containing a (meth)acrylic acid group, such as (meth)acrylic acid, (meth)acrylate, or (meth)acrylamide.

[0064] The composition ratio of acrylic monomers to the components of the acrylic block copolymer is preferably 50% by mass or more, more preferably 70% by mass or more, further preferably 90% by mass or more, and particularly preferably 95% by mass or more. More preferably, it is 98% by mass or more, and can also be 100% by mass. Because there is a wide variety of acrylic monomers, when the composition ratio of acrylic monomers is within the above-mentioned range or above, it is easy to achieve the desired range for glass transition temperature, acid value, etc., resulting in a high degree of design freedom, and therefore it is preferred.

[0065] Self-emulsifying resin adhesives are preferably block copolymers formed from A blocks and B blocks with a higher acid value than the A blocks. Examples of such AB block copolymers include those with highly hydrophobic A blocks and highly hydrophilic B blocks. This allows the self-emulsifying resin adhesive to readily adopt a micellar structure with the hydrophobic blocks facing the center and the hydrophilic blocks facing the outside. Consequently, self-dispersion is easily achieved in environments with high water content, such as water. On the other hand, in environments with high organic content, a micellar structure is not adopted, and the adhesive readily dissolves in the solvent. This allows for easy modification of the dissolution and self-dispersion morphology depending on the environment.

[0066] Self-emulsifying resin adhesives are ideally soluble in compositions formed from organic solvents consisting solely of the organic solvents contained in the ink.

[0067] Thus, due to the presence of hydrophilic parts, it tends to exhibit improved redispersibility, clogging recovery, and storage stability in water-rich solvent environments. Furthermore, due to the presence of hydrophobic parts, it exhibits excellent solubility in organic solvents, thus tending to exhibit improved solubility, clogging recovery, and redispersibility in solvent environments with high organic solvent content.

[0068] In addition, the B block contains a high concentration of hydrophilic structures, which results in a high affinity for bio-oil CB with a large number of hydrophilic functional groups. Carbon black and binder resins are strongly fixed together, forming an ink coating with excellent abrasion resistance and transfer inhibition.

[0069] It should be noted that the acid value in this embodiment can be calculated based on the proportion of monomers with acidic groups in the block monomers.

[0070] In addition to monomers with acidic groups, the monomers constituting the B block may also include monomers without acidic groups, as needed. Furthermore, in addition to monomers without acidic groups, the monomers constituting the A block may also include monomers with acidic groups, within a range not exceeding the acid value of the B block.

[0071] Examples of monomers with acidic groups include unsaturated carboxylic acid monomers such as acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, citraconic acid, and 2-methacryloyloxymethyl succinate; unsaturated sulfonic acid monomers such as styrene sulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, and 3-sulfopropyl (meth)acrylate; and unsaturated phosphate monomers such as vinylphosphonic acid, vinyl phosphate, di(methacryloyloxyethyl) phosphate, diphenyl-2-acryloyloxyethyl phosphate, and diphenyl-2-methacryloyloxyethyl phosphate.

[0072] Furthermore, there are no particular limitations on monomers that do not have acidic groups; for example, other monomers such as hydrophobic monomers can be cited.

[0073] Relative to the total amount of monomers in the B-block, the content of monomers with acidic groups in the B-block is preferably 1-50% by mass, 5-40% by mass, 10-30% by mass, or 15-25% by mass. By keeping the content of monomers with acidic groups in the B-block within the above range, there is a tendency to further improve abrasion resistance, clogging recovery, and redispersibility.

[0074] In this embodiment, the block polymer formed by the A block and the B block with a higher acid value than the A block is preferably a block copolymer comprising an A block polymer having two or more hydrophobic monomers and a B block polymer having one or more hydrophobic monomers and one or more hydrophilic monomers. The hydrophobic monomers contained in the A block and the B block can be the same.

[0075] The glass transition temperature of the self-emulsifying resin adhesive is preferably 110°C or lower. Alternatively, it is preferably 5°C or higher, more preferably 10 to 100°C. Further preferably, it is 30°C or higher, more preferably 50°C or higher, and even more preferably 70°C or higher. Alternatively, it is preferably 80°C or lower, more preferably 60°C or lower, even more preferably 50°C or lower, even more preferably 30°C or lower, and particularly preferably 20°C or lower. When the glass transition temperature is above the above range, storage stability and bubble removal properties are superior, and therefore preferred. When the glass transition temperature is below the above range, scratch resistance and clogging recovery properties are superior, and therefore preferred.

[0076] The glass transition temperature is the overall glass transition temperature of a self-emulsifying resin adhesive, and in the case of block copolymers, it is a weighted average of the individual blocks. The glass transition temperature can be determined using the DSC method.

[0077] There are no particular limitations on the method for obtaining block copolymers; examples include free radical polymerization and living radical polymerization. Among these, living radical polymerization is preferred for obtaining a refined copolymer structure. Living radical polymerization is not particularly limited; examples include: the NMP method using nitro oxygen, the ATRP method utilizing the redox reaction of metal complexes, the RAFT method using dithiocarboxylic acid esters, methods utilizing cobalt catalysts, the TEP method using tellurium compounds, iodine transfer polymerization using iodine, and the RTCP method using iodides as initiators and organic compounds as catalysts.

[0078] As an initiator, there are no particular restrictions as long as it is a known initiator used in free radical polymerization. Examples include azo compounds such as azobis(isobutyronitrile) and 2,2'-azobis(4-methoxy-2,4-dimethylpentanonitrile); and peroxides such as benzoyl peroxide and dicumyl peroxide.

[0079] The content of the self-emulsifying resin is preferably 0.1 to 10% by mass, 0.5 to 5% by mass, and 1 to 3% by mass relative to the total amount of the ink composition. By keeping the content of the binder resin within the above range, there is a tendency to further improve storage stability, color development, transfer resistance, abrasion resistance, and bubble removal properties.

[0080] 1.3. Solvent

[0081] The ink composition in this embodiment contains a solvent. A solvent is a medium that disperses and dissolves pigments, adhesive resins, etc., and is a liquid component. The solvent contains at least water and may also contain organic solvents, etc. When simply referred to as a solvent, it means solvent.

[0082] 1.3.1. Organic solvents

[0083] The ink composition in this embodiment may contain an organic solvent as a solvent. The organic solvent preferably contains an octanol / water partition coefficient logP. ow Organic solvent A has a value of 0 to 1. By including organic solvent A in the ink composition, when the content of organic components is dominant during ink drying, the binder resin is more easily dissolved in the ink, tending to have improved storage stability and clogging recovery. Furthermore, during the ink drying process on the recording medium, the binder resin and the vegetable oil CB, which is a self-dispersing pigment, readily combine in organic solvent A, thus tending to have improved abrasion resistance. Depending on the needs, the ink composition in this embodiment may also contain logP. ow Organic solvent B has a value outside the range of 0 to 1. Organic solvent B is an organic solvent other than organic solvent A. The octanol / water partition coefficient logP is also included. ow The value is called the octanol / water partition coefficient, logP. ow Values, etc.

[0084] Octanol / water partition coefficient logP of organic solvent A ow The preferred values ​​are 0.1–1, 0.2–0.9, 0.3–0.8, 0.4–0.7, and 0.5–0.6. This is achieved by making logP... ow When the value is above 0, the solubility of the adhesive resin becomes higher, by increasing logP ow Values ​​below 1 indicate a tendency for better compatibility with water. Therefore, by making logP... owWhen the values ​​are within the above range, there is a tendency for the ink composition to exhibit improved storage stability, abrasion resistance, and clogging recovery.

[0085] In this embodiment, the octanol / water partition coefficient logP ow The value refers to the value defined in OECD Test Guideline 107. The octanol / water partition coefficient can be expressed as logP. ow logK ow etc. logP ow A higher value indicates higher hydrophobicity, logP ow The lower the value, the higher the hydrophilicity.

[0086] logP of the compound ow The value can be obtained through various methods, such as by measuring according to the method specified in JIS Z 7260-117. Alternatively, it can be calculated using Hansen Solubility Parameter Software (HSPIP).

[0087] There are no particular limitations on organic solvents A and B; examples include monohydric alcohols, polyhydric alcohols, ethers, ketones, and amides. Organic solvents can be used alone or in combination of two or more.

[0088] Examples of monohydric alcohols include: methanol, ethanol, n-propanol, isopropanol, n-butanol, 2-butanol, tert-butanol, isobutanol, n-pentanol, 2-pentanol, 3-pentanol, tert-pentanol, 2-phenoxyethanol, benzyl alcohol, phenoxypropanol, etc.

[0089] Polyols are organic solvents having two or more hydroxyl groups. Examples include diols with two hydroxyl groups and polyols with three or more hydroxyl groups. Glycerol is an example of a polyol with three or more hydroxyl groups.

[0090] Examples of diols include alkanediols and condensates of alkanediols formed by the condensation of intermolecular hydroxyl groups. In alkanediols, the alkane is replaced by two hydroxyl groups. Examples of condensates of alkanediols formed by the condensation of intermolecular hydroxyl groups include diols of alkane having 2 to 4 carbon atoms.

[0091] The alkanediols preferably have 2 or more carbon atoms, more preferably 4 or more, and more preferably 5 to 8. Additionally, 1,2-alkanediols are preferred.

[0092] Examples of diols include ethylene glycol, propylene glycol, 1,2-propanediol, 1,2-butanediol, 1,2-pentanediol, 1,2-hexanediol, 1,2-octanediol, 1,3-propanediol, 1,4-butanediol, and 1,6-hexanediol; and condensates of alkyl diols such as tetramethylenediol, hexamethylenediol, diethylene glycol, triethylene glycol, tetraethylenediol, polyethylene glycol, dipropylene glycol, tripropylene glycol, polypropylene glycol, and (poly)tetramethylenediol, which have a structure formed by the condensation of hydroxyl groups between molecules of alkyl diols.

[0093] As for ethers, there are no particular limitations; examples include alkyl ethers and glycol ethers. Examples of alkyl ethers include dimethyl ether, methyl ethyl ether, diethyl ether, isopropyl methyl ether, and isopropyl ethyl ether.

[0094] Examples of glycol ethers include: ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, tetraethylene glycol monoethyl ether, tetraethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol monopropyl ether, dipropylene glycol monobutyl ether, tripropylene glycol monomethyl ether, tripropylene glycol monoethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol monobutyl ether, tripropylene glycol monomethyl ether, tripropylene glycol monoethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol monobutyl ether, tripropylene glycol monomethyl ether, tripropylene glycol monoethyl ether, di ... Alkylene glycol monoalkyl ethers such as monobutyl ether; and alkylene glycol dialkyl ethers such as dimethyl ether, diethyl ether, dibutyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, diethylene glycol methyl ethyl ether, diethylene glycol methyl butyl ether, triethylene glycol dimethyl ether, triethylene glycol diethyl ether, triethylene glycol dibutyl ether, triethylene glycol methyl butyl ether, tetraethylene glycol dimethyl ether, tetraethylene glycol diethyl ether, tetraethylene glycol dibutyl ether, propylene glycol dimethyl ether, propylene glycol diethyl ether, dipropylene glycol dimethyl ether, dipropylene glycol diethyl ether, dipropylene glycol diethyl ether, and tripropylene glycol dimethyl ether.

[0095] Examples of ketones include acetone, methyl ethyl ketone, and diethyl ketone. Examples of amides include lactam compounds and other amides. Examples of lactam compounds include 2-pyrrolidone, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, and N-hydroxyethylpyrrolidone (HEP).

[0096] Organic solvent A is the octanol / water partition coefficient logP among the above-mentioned organic solvents. ow Solvents with a value of 0 to 1. Examples of such organic solvents A include: isopropyl methyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, 1,2-hexanediol methyl ethyl ketone, isopropanol, and methyl ethyl ketone.

[0097] The content of organic solvent A relative to the total amount of the ink composition is preferably 0.5–15% by mass, 3–12% by mass, 5–10% by mass, or 6–8% by mass. By keeping the content of organic solvent A within the above range, there is a tendency to further improve storage stability, abrasion resistance, and clogging recovery.

[0098] Organic solvent B can be any of the organic solvents mentioned above, but the octanol / water partition coefficient logP ow The value is less than 0.

[0099] The content of organic solvent B relative to the total amount of the ink composition is preferably 0.5–20% by mass, 1–15% by mass, 3–11% by mass, 5–9% by mass, or 6–8% by mass. By keeping the content of organic solvent B within the above range, there is a tendency to further improve storage stability, abrasion resistance, and clogging recovery.

[0100] When organic solvents A and B are included, the total content of organic solvents contained in the ink composition is preferably 0.5–30% by mass, 10–20% by mass, 11–18% by mass, 12–17% by mass, or 13–15% by mass, relative to the total amount of the ink composition. By keeping the content of organic solvents within the above range, there is a tendency to further improve storage stability, abrasion resistance, and clogging recovery.

[0101] 1.4. Moisturizers

[0102] The ink composition in this embodiment may contain a humectant. Examples of humectants include liquid humectants and solid humectants.

[0103] Liquid humectants are compounds that are liquid at room temperature. They can be organic solvents, but compounds with particularly excellent moisturizing properties are preferred. Examples include organic solvents with a standard boiling point exceeding 280°C, and in particular, polyols with a standard boiling point exceeding 280°C. Glycerin is an example. Room temperature is set at 25°C.

[0104] Solid humectants are solid at room temperature. As long as they are solid at room temperature and possess moisturizing properties, there are no particular limitations. Examples include: polyols such as erythritol, trimethylolpropane, di(trimethylol)propane, pentaerythritol, and dipentaerythritol; glucose, mannose, fructose, ribose, xylose, arabinose, galactose, aldonic acid, glucosyl alcohol (sorbitol), maltose, cellobiose, lactose, sucrose, trehalose, and maltotriose; sugars such as monosaccharides, disaccharides, oligosaccharides, and polysaccharides; derivatives of these sugars; and betaines such as trimethylglycine, triethylglycine, γ-butyryl betaine, homarine, trigonelline, carnitine, homoserine betaine, valine betaine, lysine betaine, ornithine betaine, alanine betaine, stachydrine, and glutamic acid betaine. Humectants can be used alone or in combination of two or more.

[0105] In this embodiment, the ink composition preferably includes betaine as a solid humectant. Betaine is a compound that has positive and negative charges at non-adjacent positions within the same molecule, with unbonded, dissociable hydrogen atoms on the positively charged atoms, enabling it to form an intramolecular salt, and is uncharged as a whole molecule. By including betaine, the inkjet ink composition's flight bend and non-ejection caused by drying at the inkjet nozzle can be better suppressed, and there is a tendency for improved clogging recovery and bubble removal.

[0106] The betaine content relative to the total amount of the ink composition is preferably 0.1–10% by mass, 2–8% by mass, 3–7% by mass, or 4–6% by mass. By keeping the betaine content within the above range, there is a tendency to further improve clogging recovery and bubble removal properties.

[0107] The content of the humectant relative to the total amount of the ink composition is preferably 1-30% by mass, 10-20% by mass, or 13-17% by mass. By keeping the content of the humectant within the above range, there is a tendency to further improve the clogging recovery and bubble removal properties.

[0108] 1.5. Surfactants

[0109] The ink composition in this embodiment may also contain a surfactant. There are no particular limitations on the surfactant; examples include silicone-based surfactants, acetylsyl glycol-based surfactants, and fluorinated surfactants. A single surfactant may be used, or two or more may be used in combination.

[0110] There are no particular limitations on acetylenol-based surfactants; examples include 2,4,7,9-tetramethyl-5-decyn-4,7-diol and its epoxide alkane adducts. Commercially available acetylenol-based surfactants include, for example, OLFINE E1010, EXP4200, EXP4300, SURFYNOL SE, SURFYNOL440, SURFYNOL 104, and SURFYNOL 465 (trade names manufactured by Nissin Chemical Industry Co., Ltd.).

[0111] As a fluorinated surfactant, there are no particular limitations. Examples include: perfluoroalkyl sulfonates, perfluoroalkyl carboxylates, perfluoroalkyl phosphates, perfluoroalkyl ethylene oxide adducts, perfluoroalkyl betaines, and perfluoroalkyl amine oxides.

[0112] As for silicone-based surfactants, there are no particular limitations; examples include polysiloxane compounds and polyether-modified silicones. Commercially available silicone-based surfactants include, for example, BYK-306, BYK-307, BYK-333, BYK-341, BYK-345, BYK-346, BYK-348, BYK-UV3500, BYK-UV3510, BYK-UV3530, and BYK-UV3570 (trade names manufactured by BYK Corporation).

[0113] The surfactant content is preferably 0.1–4% by mass, 0.3–3% by mass, 0.5–2.5% by mass, and 1–2% by mass relative to the total amount of the ink composition. By keeping the surfactant content within the above range, there is a tendency to further improve storage stability, clogging recovery, and bubble removal.

[0114] 1.6. pH adjuster

[0115] The inkjet ink composition in this embodiment may also include a pH adjuster. There are no particular limitations on the pH adjuster; examples include: inorganic acids such as sulfuric acid, hydrochloric acid, and nitric acid; inorganic bases such as lithium hydroxide, sodium hydroxide, potassium hydroxide, and ammonia; organic acids such as adipic acid, citric acid, and succinic acid; and organic bases such as triethanolamine, diethanolamine, monoethanolamine, triisopropanolamine, diisopropanolamine, and trihydroxymethylaminomethane. A single pH adjuster may be used, or two or more may be used in combination.

[0116] The pH adjuster content is preferably 0.1–3% by mass, 0.3–2% by mass, and 0.5–1.5% by mass relative to the total amount of the ink composition. By keeping the pH adjuster content within the above range, there is a tendency to further improve storage stability, abrasion resistance, clogging recovery, and bubble removal.

[0117] 1.7. Fulvic acid

[0118] The ink composition in this embodiment preferably contains fulvic acid. It is believed that fulvic acid can function as a dispersant for carbon black and adhesive resins, and tends to improve dispersibility and storage stability of the ink composition.

[0119] In addition, since carbon black is a self-dispersing pigment, it has a large number of hydrophilic functional groups, which increases its affinity for fulvic acid. Fulvic acid can easily adhere to carbon black, and its storage stability is further improved, making it a preferred choice.

[0120] In addition, carbon black derived from bio-oils sometimes suffers from reduced storage stability due to the complex composition or large size of impurities. However, since excellent storage stability can be obtained through fulvic acid, this invention is particularly useful.

[0121] Even among bio-oils (CB), vegetable oils (CB) tend to produce fulvic acid through oxidation, and are therefore preferred.

[0122] It is believed that by allowing fulvic acid to function as a surface coating material near the surface of carbon black, further agglomeration and coarsening of primary and secondary carbon black particles can be inhibited. Furthermore, it is believed that it can also inhibit the adhesion of impurities to the carbon black. Additionally, by further improving the wettability of the carbon black surface, microbubbles are less likely to accumulate in the carbon black pores, preventing printing nozzle and cleaning nozzle leakage; therefore, there is a tendency to further improve the bubble removal properties of the ink composition. Moreover, by further improving the affinity between carbon black and the binder resin, there is a tendency to further improve the transfer resistance and abrasion resistance of the ink composition. It should be noted that, in this embodiment, fulvic acid is not a resin dispersant as described above.

[0123] Fulvic acid is a general term for a group of acidic substances in decaying matter that do not precipitate due to acidity. It can be obtained by separation and purification from soil using acids and alkalis, or it can be obtained commercially. Additionally, it is generated during the oxidation treatment of carbon black as a self-dispersing process. The fulvic acid obtained in this way has high water solubility and low pH dependence, thus maintaining water solubility over a wide pH range and not easily becoming foreign even when the pH changes. That is, it can function usefully as a dispersing aid even when its state changes in the ink composition.

[0124] In this embodiment, fulvic acid can be prepared by mixing separately prepared substances to form a composition, or it can be used by concentrating or diluting fulvic acid separated from the treatment liquid generated as a byproduct during the oxidation treatment of carbon black. Alternatively, carbon black containing fulvic acid generated during the oxidation treatment can be used. Preferably, oxidized carbon black containing fulvic acid is used, and fulvic acid is further added separately to adjust the amount of fulvic acid to a predetermined range.

[0125] Fulvic acid preferably exhibits peaks at a fluorescence wavelength (EM) of 380–600 nm and an excitation wavelength (EX) of 180–320 nm in excitation-emission matrix analysis. In other words, it is preferable to have peaks within the range of excitation wavelengths (EX) corresponding to the aforementioned fluorescence wavelength (EM) range. Furthermore, it is preferable to have peaks at a fluorescence wavelength (EM) of 400–600 nm and an excitation wavelength (EX) of 200–300 nm in excitation-emission matrix analysis. Fulvic acid exhibiting peaks at both fluorescence and excitation wavelengths within the aforementioned ranges possesses a carbon skeleton similar to carbon black and exhibits high affinity for carbon black. Therefore, it tends to have improved storage stability, transfer resistance, abrasion resistance, clogging recovery, and bubble removal properties.

[0126] In this embodiment, the peak position of the fluorescence wavelength of fulvic acid in the excitation-emission matrix analysis method is preferably 400-550 nm, 400-500 nm, 420-480 nm, or 430-460 nm. By keeping the fluorescence wavelength of fulvic acid within the above range, there is a tendency to further improve storage stability, transfer resistance, abrasion resistance, clogging recovery, and bubble removal.

[0127] In this embodiment, the peak position of the excitation wavelength of fulvic acid in the excitation-emission matrix analysis method is preferably 200–320 nm, 200–300 nm, 220–280 nm, or 240–270 nm. By keeping the excitation wavelength of fulvic acid within the above range, there is a tendency to further improve storage stability, transfer resistance, abrasion resistance, clogging recovery, and bubble removal.

[0128] In the excitation-emission matrix analysis method, the number of peaks for the fluorescence wavelength and excitation wavelength of fulvic acid can each be more than one, or two to three. It should be noted that when fulvic acid has multiple peaks, it is preferable that at least one peak satisfies the above-mentioned wavelength region, and more preferably that all peaks satisfy the above-mentioned wavelength region.

[0129] The preferred mass ratio of fulvic acid to pigment is 0.0001–0.7, 0.001–0.5, 0.002–0.1, 0.003–0.05, or 0.005–0.02. By maintaining the mass ratio of fulvic acid to pigment within the above ranges, there is a tendency to further improve storage stability, transfer resistance, abrasion resistance, clogging recovery, and bubble removal properties.

[0130] The content of fulvic acid relative to the total amount of the ink composition is preferably 0.001 to 5% by mass, 0.01 to 1% by mass, 0.02 to 0.3% by mass, and 0.03 to 0.1% by mass. By keeping the content of fulvic acid within the above range, there is a tendency to further improve storage stability, transfer resistance, abrasion resistance, clogging recovery, and bubble removal.

[0131] 1.8. Water

[0132] The inkjet ink composition of this embodiment is an aqueous ink with water as the solvent. An aqueous inkjet ink composition refers to an inkjet ink composition that contains at least water as the main solvent component of the ink.

[0133] The water content relative to the total amount of the inkjet ink composition is preferably 40% by mass or more. More preferably, it is 40-99% by mass, 45-85% by mass, 50-70% by mass, 55-65% by mass, or 57-63% by mass. By setting the water content within the above range, there is a tendency to further improve storage stability, clogging recovery, and bubble removal.

[0134] 1.9. Other ingredients

[0135] The ink composition may contain components other than those mentioned above. Other components may include, as appropriate, various additives such as solvent aids, viscosity modifiers, antioxidants, preservatives, mildew inhibitors, and corrosion inhibitors.

[0136] 2. Recording Method

[0137] The recording method in this embodiment includes an adhesion step, in which the above-mentioned inkjet ink composition is ejected from the inkjet head using a predetermined inkjet head and adhered to the recording medium.

[0138] 3. Recording device

[0139] The recording apparatus in this embodiment includes the ink composition described above and an inkjet head having a nozzle that ejects the ink composition to a recording medium. More preferably, it further includes a supply flow path that allows the ink composition to flow and is connected to the inkjet head, and a filter unit disposed in the supply flow path of the inkjet head.

[0140] exist Figure 1An example of an inkjet recording apparatus that can be used in this embodiment is shown. Regarding the inkjet recording apparatus of this embodiment, refer to... Figure 1 Further details. Figure 1 In the XYZ coordinate system shown, the X direction represents the length direction of the recording medium, the Y direction represents the width direction of the recording medium in the transport path within the recording device, and the Z direction represents the height direction of the device.

[0141] As an example, the recording device 10 is a line inkjet printer capable of high-speed and high-density printing. The recording device 10 includes: a feed section 12 for holding recording media P such as paper, a transport section 14, a belt transport section 16, a recording section 18, an Fd (face down) discharge section 20 as an "discharge section", an Fd (face down) mounting section 22 as a "mounting section", a flipping path section 24 as a "flipping transport mechanism", a Fu (face up) discharge section 26, and a Fu (face up) mounting section 28.

[0142] The feed unit 12 is disposed at the lower part of the recording device 10. The feed unit 12 includes a feed tray 30 for holding the recording medium P and a feed roller 32 for feeding the recording medium P held in the feed tray 30 to the transport path 11.

[0143] The recording medium P, contained in the feed tray 30, is fed by the feed roller 32 along the transport path 11 to the transport section 14. The transport section 14 includes a transport drive roller 34 and a transport driven roller 36. The transport drive roller 34 is driven to rotate by a drive source (not shown). In the transport section 14, the recording medium P is held (niped) between the transport drive roller 34 and the transport driven roller 36 and is transported to the belt transport section 16 located downstream of the transport path 11.

[0144] The belt conveyor 16 includes: a first roller 38 located on the upstream side in the conveying path 11, a second roller 40 located on the downstream side, an annular belt 42 rotatably mounted on the first roller 38 and the second roller 40, and a support body 44 supporting the upper section 42a of the annular belt 42 between the first roller 38 and the second roller 40.

[0145] The annular belt 42 is driven by a first roller 38 or a second roller 40 (not shown), causing it to move from the +X direction to the -X direction in the upper section 42a. Therefore, the recording medium P conveyed from the conveying section 14 is further conveyed to the downstream side of the conveying path 11 in the belt conveying section 16.

[0146] The recording unit 18 includes a row-shaped inkjet head 48 and a head support 46 for holding the inkjet head 48. It should be noted that the recording unit 18 can be a serial recording unit in which the inkjet head is mounted on a carriage that reciprocates in the Y-axis direction. The inkjet head 48 is arranged opposite to the upper section 42a of the annular belt 42 supported by the support body 44. When the recording medium P is transported in the upper section 42a of the annular belt 42, the inkjet head 48 ejects ink onto the recording medium P to perform recording. Simultaneously with recording, the recording medium P is transported by the belt transport unit 16 to the downstream side of the transport path 11.

[0147] A first branch 50 is provided downstream of the transport path 11 of the conveyor section 16. The first branch 50 is configured to switch between the transport path 11, which transports the recording medium P to the Fd discharge section 20 or the Fu discharge section 26, and a flip path 52, which flips the recording surface of the recording medium P and transports the recording medium P to the recording section 18 again. It should be noted that during the transport process in the flip path 52, the recording surface of the recording medium P, which is switched and transported to the flip path 52 via the first branch 50, is flipped so that the side opposite to the original recording surface is opposite to the inkjet head 48 and is transported to the recording section 18 again.

[0148] A second branch 54 is further provided downstream of the first branch 50 along the transport path 11. The second branch 54 is configured to switch the transport direction of the recording medium P in such a way that the recording medium P is transported to the Fd discharge section 20 or to the Fu discharge section 26.

[0149] The recording medium P supplied to the Fd discharge section 20 in the second branch 54 is discharged from the Fd discharge section 20 and placed in the Fd mounting section 22. At this time, the recording surface of the recording medium P is mounted facing the Fd mounting section 22. Additionally, the recording medium P supplied to the Fu discharge section 26 in the second branch 54 is discharged from the Fu discharge section 26 and placed in the Fu mounting section 28. At this time, the recording surface of the recording medium P is mounted facing the side opposite to the Fu mounting section 28.

[0150] 4. Recording media

[0151] The recording medium used in this embodiment is not particularly limited, and examples include: absorbent recording medium, low-absorbent recording medium or non-absorbent recording medium, with absorbent recording medium being preferred.

[0152] Examples of absorbent recording media include ordinary paper such as electronic photo paper with high ink penetration, and inkjet paper with an ink-absorbing layer composed of silica or alumina particles, or an ink-absorbing layer composed of hydrophilic polymers such as polyvinyl alcohol or polyvinylpyrrolidone.

[0153] Examples of low-absorbency recording media include coated paper, plated paper, and cast-coated paper used in general offset printing, where ink penetration is relatively low.

[0154] Examples of non-absorbent recording media include: films and sheets made of plastics such as polyvinyl chloride, polyethylene, polypropylene, polyethylene terephthalate (PET), polycarbonate, polystyrene, and polyurethane; metal plates such as iron, silver, copper, and aluminum; or metal plates, plastic films, stainless steel, brass, and other alloy plates manufactured by vapor deposition of the aforementioned metals; and recording media obtained by bonding (coating) films made of plastics such as polyvinyl chloride, polyethylene, polypropylene, polyethylene terephthalate (PET), polycarbonate, polystyrene, and polyurethane onto a paper substrate.

[0155] 5. Records

[0156] The recording medium of this embodiment is obtained by attaching the above-described ink composition to a recording medium. The recording medium of this embodiment using the above-described ink composition can be recorded using inks with excellent storage stability, color development, transfer resistance, abrasion resistance, clogging recovery, and bubble removal properties.

[0157] Example

[0158] The present invention will now be described in more detail using examples and comparative examples. The present invention is not limited to the following examples.

[0159] exist Figures 3-5 Tables 2 to 4 show the composition of each ink composition of the examples and comparative examples, as well as their evaluation results.

[0160] 1. Preparation of inkjet ink composition

[0161] The inkjet ink compositions of each example were prepared by mixing and stirring in a manner that resulted in the compositions described in Tables 2-4. It should be noted that when fulvic acid was generated by oxidizing carbon black, the fulvic acid content, including the amount of fulvic acid contained in the carbon black, was adjusted to achieve the content described in Tables 2-4. Unless otherwise specified, the values ​​of each component shown in the examples in the tables represent mass percent. Furthermore, in the tables, each value represents the mass of the solid component (the solvent component is the amount of solvent content) of each component.

[0162] Details of the product ingredients used in Tables 2 to 4 are described below.

[0163] pigment: CB1~CB3, binchotan pigment, petroleum CB (refer to the preparation examples below) Adhesive resin: F1-5, Resin Dispersions (Refer to the preparation examples below) Fulvic acid: Fulvic acid (refer to the preparation example below) Organic solvents: BDG (diethylene glycol monobutyl ether, logP) ow The value is 0.56. BTG (triethylene glycol monobutyl ether, logP) ow The value is 0.44. 12HD (1,2-hexanediol, logP) ow The value is 0.57. TEG (triethylene glycol, logP) ow (Value: -1.75) PG (Propylene Glycol, LogP) ow The value is -0.92. 2P (2-pyrrolidone, logP) ow The value is -0.85. Moisturizer: Gly: Glycerin TMG: Trimethylglycine Surfactants: E1010 (acetylenic diol surfactant, manufactured by Nissin Chemical Industries, Ltd.) S104 (trade name "SURFYNOL 104", acetylenic diol surfactant, manufactured by Nissin Chemical Industry Co., Ltd.) pH adjuster: TEA (triethanolamine) water: Ion-exchanged water 1.1. Pigment Preparation Preparation of CB1 Cleaning process 25g of carbon black (PRINTEX Nature, manufactured by Orion Engineered Carbons Co., Ltd., vegetable oil carbon black) was stirred and washed with toluene to remove unburned components and other substances adhering to the surface of the carbon black.

[0164] Surface treatment process

[0165] For the carbon black after the cleaning process, add 5g of sodium hypochlorite to the water and perform ultrasonic treatment for surface treatment.

[0166] Dispersed processes

[0167] The carbon black dispersion after the surface treatment process was dispersed for 1 hour using a gyratory ball mill with 0.3 mm beads to obtain a slurry. Next, 20% by mass of sodium hypochlorite was added to the carbon black in the slurry, and the mixture was heated to 70°C for 30 minutes for surface treatment. The particle size was measured, and if the target particle size was not achieved, the above dispersion and surface treatment were repeated. It should be noted that a new hydrophobic surface is generated by dispersing the carbon black; therefore, the surface treatment reaction also occurs during the dispersion process.

[0168] Neutralization / purification process

[0169] Sodium hydroxide is added to the carbon black dispersion after the dispersion process to neutralize it to a pH of 8-9 suitable for ink. After the neutralization reaction, the dispersion is cooled to room temperature and subjected to solid-liquid separation using a centrifuge or similar device for desalination. The solid material is then recovered and dried at 100°C. This yields CB1 as a self-dispersible pigment.

[0170] Preparation of CB2

[0171] Carbon black (PRINTEX Nature, manufactured by Orion Engineered Carbons Co., Ltd.) and Joncryl 678 (styrene-acrylic resin, manufactured by BASF) as a dispersant were mixed in a mass ratio of 2:1 to obtain CB2.

[0172] Preparation of CB3

[0173] Carbon black (PRINTEX Nature, manufactured by Orion Engineered Carbons Co., Ltd.) and PEARLLEX NP (sodium lignosulfonate, trade name manufactured by Nippon Paper Co., Ltd.) as a dispersant were mixed in a mass ratio of 2:3 to obtain CB3.

[0174] Preparation of binchotan pigments

[0175] Binchotan (manufactured by KIRIYA Chemical Co., Ltd., made by carbonizing wood, not bio-oil black) was processed in the same way as CB1 to obtain binchotan pigment.

[0176] Preparation of petroleum CB

[0177] Petroleum-derived carbon black (trade name "Aqua-Black162", manufactured by Tokai Carbon Co., Ltd.) was processed in the same way as CB1 to obtain petroleum CB.

[0178] Preparation example of fulvic acid

[0179] 25g of carbon black (PRINTEX Nature, manufactured by Orion Engineered Carbons Co., Ltd., vegetable oil carbon black) was stirred and washed with toluene to remove unburned components and other substances adhering to the surface of the carbon black. After washing, 5g of sodium hypochlorite was added to water for oxidation treatment. Following treatment, the carbon black was removed by centrifugation, and the waste liquid was recovered. An alkaline aqueous solution was added to the waste liquid to separate the resulting insoluble matter (humic substances) from the liquid. An acidic aqueous solution was further added to the remaining liquid after removing the insoluble matter to separate the resulting insoluble matter. The remaining liquid was then concentrated and purified to obtain fulvic acid.

[0180] Excitation Emission Matrix Analysis (EEM)

[0181] The sample is diluted, and the excitation wavelength (Ex) is measured in three dimensions using the lateral reflection method under the following conditions. It should be noted that the surface reflection method can also be used when the concentration of the sample prepared for measurement is high.

[0182] Support: Liquid support (lateral metering system) or solid support (surface metering system)

[0183] Cell: Single-sided ground quartz cell (10×10mm square quartz cell, side metering) or double-sided ground quartz cell (20×10mm quartz cell, surface metering)

[0184] Measurement wavelength excitation (Ex): 200–700 nm

[0185] Measurement wavelength fluorescence (Em): 200–700 nm

[0186] Data interval excitation (Ex): 5.0nm

[0187] Data interval fluorescence (Em): 5.0 nm

[0188] Scan speed: 60,000 nm / min

[0189] Slit-width excitation (Ex): 5.0 nm

[0190] Slit-width fluorescence (Em): 5.0 nm

[0191] Sensitivity: Photomultiplier tube voltage 700V

[0192] Response time: 2ms

[0193] Automatic filter control: ON (Automatic high-order light cutoff)

[0194] When the fulvic acid obtained above was measured by excitation-emission matrix analysis, it had two peaks: one with an excitation wavelength of 260 nm and a fluorescence wavelength of 445 nm, and the other with an excitation wavelength of 265 nm and a fluorescence wavelength of 430 nm.

[0195] 1.2. Preparation of Adhesive Resin

[0196] Self-emulsifying resins F1 to F5 were obtained in the following order.

[0197] Preparation of F1

[0198] In a reaction vessel equipped with a stirrer, thermometer, reflux pipe, and nitrogen inlet pipe, the following were added as solvents: 236.3 parts by weight of diethylene glycol monobutyl ether (BDG), 2.3 parts by weight of 2-iodo-2-cyanopropane (CPI), 3.7 parts by weight of 2,2-azobis(4-methoxy-2,4-dimethylpentanonitrile) (trade name "V-70", manufactured by Fujifilm and Koh Genuine Pharmaceutical Co., Ltd.) (V-70), 0.1 parts by weight of N-iodosuccinimide (NIS), 68.7 parts by weight of tetrahydrofurfuryl methacrylate (THFMA), and 68.7 parts by weight of isobornyl methacrylate (IBXMA).

[0199] While the raw materials added to the reaction vessel were purged with nitrogen and stirred, polymerization was carried out at 45°C for 4 hours to synthesize a polymer (polymer block A). A portion of the reaction solution was sampled and measured, yielding a solids content of 37.4%, and the polymerization conversion calculated based on the solids content was approximately 100%. The polystyrene-converted number-average molecular weight (Mn) of polymer block A was determined by GPC using tetrahydrofuran (THF) as the developing solvent, resulting in a molecular weight (Mn) of 10000 and a dispersion (PDI = weight-average molecular weight (Mw) / number-average molecular weight (Mn)) of 1.2. In the following text, molecular weight was determined using this method. The glass transition temperature (Tg) of polymer block A was calculated using the Tg of the monomer homopolymer and the compositional blending ratio, and was 101.5°C. It was calculated based on a Tg of 60°C for the THFMA homopolymer and a Tg of 155°C for the IBXMA homopolymer. In the following text, Tg was determined using this calculation method.

[0200] After cooling the solution of polymer block A to 40°C, 2.7 parts by weight of V-70, 18.0 parts by weight of THFMA, 54.1 parts by weight of IBXMA, and 18.0 parts by weight of methacrylic acid (MAA) were added to the reaction vessel. Polymerization was carried out at 40°C for 4 hours to form polymer block B, yielding an AB diblock copolymer. The polymerization was confirmed to be essentially complete by determining the solids content and the amount of residual monomers based on gas chromatography. A sample of the reaction solution was taken and measured, revealing a solids content of approximately 50%, indicating a polymerization conversion of approximately 100%. The number-average molecular weight (Mn) of the obtained AB diblock copolymer was 17000, the PDI was 1.3, and the GPC peak of polymer block A shifted towards the higher molecular weight side, confirming it as an AB diblock copolymer. That is, the number-average molecular weight (Mn) of polymer block B was 7000. Furthermore, the acid value of polymer block B, calculated based on the aforementioned MAA content, is 130.3 mg KOH / g. The Tg of polymer block B is 143.3 °C. The Tg of the MAA homopolymer is calculated based on 228 °C. A portion of the polymer solution was precipitated in methanol and filtered, thoroughly washed with methanol, and dried to obtain a resin solid. The acid value was determined by titration with an ethanolic 0.1 mol / L potassium hydroxide solution, yielding a result of 51.5 mg KOH / g.

[0201] Next, at room temperature, a mixture of 14.0 parts by weight of 28% ammonia and 458.6 parts by weight of ion-exchanged water was added to neutralize and emulsify the mixture, yielding a self-emulsifying resin F1. It should be noted that, in the following text, the amount of water added was adjusted to achieve a polymer content of 25%. The solid content of F1 was 25.1%. Furthermore, after sufficient dilution with water, the number average particle size of the emulsion was measured using a dynamic light scattering particle size analyzer (particle size analyzer, trade name "nanoSAQRA", manufactured by Otsuka Electronics Co., Ltd.). The measured number average particle size was 75 nm. The pH was 8.9. Additionally, the viscosity was measured using an E-type viscometer at 25°C and was 3.6 Pa·s.

[0202] Preparation of F2~F5

[0203] Except for using the monomers specified in Table 1, the process was the same as for self-emulsifying resin F1 to obtain self-emulsifying resins F2 to F5. It should be noted that all units are parts by mass. Furthermore, the Tg of each self-emulsifying resin is summarized in Table 1. For F1 to F5, the acid value of polymer block B is higher than that of polymer block A. F1 to F5 are all dispersed in the ink by self-dispersion. F1 to F5 are all soluble in compositions of organic solvents formed solely from the organic solvents contained in the ink.

[0204] IBXMA (Isobornyl Methacrylate)

[0205] IBXA (Isobornyl Acrylate)

[0206] THFMA (Tetrahydrofurfuryl methacrylate)

[0207] STA (stearyl acrylate)

[0208] LA (Lauryl Acrylate)

[0209] OA (octyl acrylate)

[0210] MAA (Methacrylic Acid)

[0211] Preparation of resin dispersions

[0212] A non-self-emulsifying resin dispersion was obtained as described below. 900 g of deionized water and 3 g of sodium lauryl sulfate were added to a reaction vessel equipped with a stirrer, reflux condenser, dropping device, and thermometer. While purging with nitrogen under stirring, the temperature was raised to 70°C. Maintaining the internal temperature at 70°C, 4 g of potassium persulfate, acting as a polymerization initiator, was added and dissolved. An emulsion was prepared beforehand by adding 20 g of acrylamide, 300 g of styrene, 640 g of butyl acrylate, and 30 g of methacrylic acid to 450 g of deionized water and 3 g of sodium lauryl sulfate under stirring. This emulsion was continuously added dropwise to the reaction solution over 4 hours. After the addition was completed, aging was carried out for 3 hours. The resulting aqueous emulsion was cooled to room temperature, and deionized water and a 5% sodium hydroxide aqueous solution were added to adjust the solid content to 40% by weight and the pH to 8. The glass transition temperature of the resin particles in the resulting aqueous emulsion was -15°C.

[0213] 2. Evaluation Methods

[0214] 2.1. Storage stability

[0215] The ink composition was placed in an environment of 60°C for one week. Then, the change in the average particle size of the pigment particles in the ink after placement was calculated relative to the average particle size of the pigment particles in the ink before placement, and evaluated according to the following criteria. For the determination of the average particle size, the volume average particle size D50 of the ink was measured using an ELSZ-1000 (manufactured by Otsuka Electronics Co., Ltd.) by dynamic light scattering method.

[0216] Evaluation Criteria

[0217] A: The change rate is less than ±5%.

[0218] B: The change rate is greater than ±5% and less than ±10%.

[0219] C: The change rate is greater than ±10% and less than ±20%.

[0220] D: The change rate is ±20% or more.

[0221] 2.2. Color development (OD value)

[0222] The ink composition was installed on a modified Printer PX-M791FT (a product name manufactured by Seiko Epson Co., Ltd.) and printed at A4 size and a resolution of 720×720 dpi on Xerox P paper (copier paper manufactured by Fuji Xerox Co., Ltd., with a unit area weight of 64 g / m²). 2 Full-page printing was performed on paper (88 μm thick). The OD value of the recorded material was measured and evaluated according to the following evaluation criteria.

[0223] Evaluation Criteria

[0224] A: The OD value is 1.2 or higher.

[0225] B: OD value is above 1.0 and less than 1.2.

[0226] C: OD value is 0.8 or higher and less than 1.0.

[0227] D: OD value is less than 0.8.

[0228] 2.3. Transfer resistance

[0229] Using a modified Printer LX-10050 (a line inkjet printer, a product name manufactured by Seiko Epson), in an environment of 25°C and 50% humidity, with a print volume of 100%, Xerox P paper (Fuji Xerox copier paper, 64g / m²) was printed. 2 Full-page printing on paper (88μm thick). Evaluate the transfer marks that adhere at this time according to the following evaluation criteria.

[0230] Evaluation Criteria

[0231] A: When observed from a distance of 30cm, no transfer marks are visible.

[0232] B: When observed from a distance of 30cm, the transfer marks can be seen, but when observed from a distance of 50cm, the transfer marks cannot be seen.

[0233] C: Transfer marks can be seen when observed from a distance of 50cm, but not when observed from a distance of 80cm.

[0234] D: When observed from a distance of 80cm, transfer marks can be seen.

[0235] 2.4. Abrasion resistance

[0236] The various ink compositions were filled into a modified Printer PX-M791FT (manufactured by Seiko Epson Co., Ltd.), and Xerox P paper (copier paper manufactured by Fuji Xerox Co., Ltd., with a unit area weight of 64 g / m²) was used. 2 On a paper (88μm thick), the 26 letters of the English alphabet in size 20 font were recorded onto a recording medium. Immediately after recording, the recording medium was fixed on a horizontally set flat surface. After recording for 5 minutes, the text was wiped with a highlighter (OPTEX CARE) (a trade name manufactured by Zebra Corporation). Based on the ink penetration, the abrasion resistance was evaluated according to the following evaluation criteria.

[0237] Evaluation Criteria

[0238] A: Even after wiping three times, no color penetration occurred.

[0239] B: No color penetration occurred even after wiping twice, but color penetration occurred after wiping three times.

[0240] C: No color penetration occurred even after wiping once, but color penetration occurred after wiping twice.

[0241] D: Color penetration occurs after wiping once.

[0242] 2.5. Blockage recovery

[0243] Ink was filled into a modified Printer PX-M791FT (a product name manufactured by Seiko Epson Co., Ltd.), and a nozzle check was performed. After confirming that all nozzles were ejecting ink, the printhead was placed at 40°C for one week with the cap removed. After placement, the number of cleaning cycles required until all nozzles recovered was evaluated according to the following evaluation criteria.

[0244] Evaluation Criteria

[0245] A: Cleaning frequency is less than once.

[0246] B: Cleaning frequency is more than 2 times but less than 3 times.

[0247] C: The number of cleaning sessions is more than 4 but less than 5.

[0248] D: The cleaning was performed 5 times but all nozzles were not restored.

[0249] 2.6. Bubble discharge properties

[0250] Initial filling and cleaning were performed on a new, unused Printer PX-M791FT (trade name manufactured by Seiko Epson Co., Ltd.) using various ink compositions. The number of cleaning cycles until all nozzles were ejected was evaluated according to the following evaluation criteria. It should be noted that ink compositions with good bubble removal properties met the initial filling requirements.

[0251] Evaluation Criteria

[0252] A: All nozzles can be sprayed through initial filling and cleaning alone.

[0253] B: Nozzle leakage only occurs during the initial filling and cleaning process, and all nozzles spray out when the number of additional cleaning cycles is less than 1.

[0254] C: Nozzle leakage only occurs during the initial filling and cleaning process, and all nozzles spray out after up to 3 additional cleaning cycles.

[0255] D: Nozzle leakage occurred only during the initial filling and cleaning process, and the nozzles did not spray completely even after up to 3 additional cleaning cycles.

[0256] 3. Evaluation Results

[0257] According to Tables 2-4, the inkjet ink compositions of this embodiment, which contain self-dispersing pigments derived from bio-oils (CB) and self-emulsifying resins (binder resins), all exhibit excellent color development, transfer inhibition, and clogging recovery. Furthermore, they also tend to demonstrate excellent storage stability, abrasion resistance, and bubble removal properties.

[0258] In contrast, comparative examples of inkjet ink compositions not included in this embodiment all exhibited poor performance in any aspect of color development, transfer inhibition, or clogging recovery.

Claims

1. An inkjet ink composition comprising: Pigment, which is carbon black derived from bio-oil; Adhesive resins; and Solvent, The pigment is a self-dispersing pigment. The adhesive resin comprises a self-emulsifying resin. The solvent contains water. The inkjet ink composition is a water-based ink.

2. The inkjet ink composition according to claim 1, wherein, The DBP oil absorption of the pigment is 70 mL / 100g to 180 mL / 100g. The primary particle size of the pigment is 10 nm to 50 nm.

3. The inkjet ink composition according to claim 1, wherein, The pigment underwent surface treatment through oxidation.

4. The inkjet ink composition according to claim 1, wherein, It contains fulvic acid.

5. The inkjet ink composition according to claim 4, wherein, The fulvic acid exhibits a peak at a fluorescence wavelength (EM) of 400 nm to 600 nm and an excitation wavelength (EX) of 200 nm to 300 nm in the excitation-emission matrix analysis method.

6. The inkjet ink composition according to claim 1, wherein, The self-emulsifying resin is a block copolymer.

7. The inkjet ink composition according to claim 6, wherein, The self-emulsifying resin is a block copolymer formed from an acrylic resin.

8. The inkjet ink composition according to claim 1, wherein, The solvent comprises organic solvent A with an octanol / water partition coefficient of 0 to 1.

9. The inkjet ink composition according to claim 1, wherein, The inkjet ink composition also contains a humectant.

10. A recording method, comprising: The ink adhesion process involves ejecting the inkjet ink composition according to any one of claims 1 to 9 from the inkjet head and adhering it to the recording medium.

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