JP6202472B2 - Inkjet ink composition, recording method, and recording apparatus - Google Patents

Description

  The present invention relates to an inkjet ink composition, a recording method, and a recording apparatus.

  The ink jet recording method is capable of recording high-definition images with a relatively simple device, and has been rapidly developed in various fields. Among them, various studies have been made on ejection stability and the like. For example, Patent Document 1 discloses that an image or printed matter having high scratch resistance can be obtained even on a recording medium having excellent ejection stability, improved feathering resistance to plain paper, and hardly absorbing the ink composition. Possible inkjet ink compositions are described. Specifically, in an inkjet ink containing at least a pigment, water, a water-soluble solvent and polymer fine particles, the polymer fine particles have a shell structure composed of a core portion and a shell portion, and the shell portion is a predetermined single unit. An inkjet ink containing a monomer is disclosed.

JP 2008-260300 A

  The polymer fine particles used in Patent Document 1 are not designed in consideration of the recording head temperature during ink ejection during the printing process, the temperature of the recording medium, and the drying temperature. However, in an ink composition containing a resin that forms a film on a recording medium by heating, the resin may be welded in the recording head. In order to prevent this welding and improve the discharge stability, it is conceivable to improve the glass transition point (hereinafter also referred to as “Tg”) of the resin constituting the polymer fine particles. However, when the Tg of the resin is improved, the resin hardly melts when a film is formed on the recording medium by heating. Therefore, there is a problem that the adhesion between the resin and the recording medium is poor. On the other hand, if the Tg of the resin is lowered so as to improve the adhesion even at relatively low temperature heating, the resin is likely to be welded in the heated recording head, which in turn improves the discharge stability. There is a problem of being inferior.

  The present invention has been made to solve at least a part of the above-described problems, and is an inkjet ink composition excellent in ejection stability and adhesion, a recording method using the inkjet ink composition, and recording An object is to provide an apparatus.

  The present inventors diligently studied to solve the above problems. As a result, it was found that the above-mentioned problems can be solved by using predetermined polymer particles, and the present invention has been completed.

That is, the present invention is as follows.
[1]
A first step in which an inkjet ink composition is ejected from a recording head having a head temperature C (unit: ° C.) onto a recording medium and adhered; and the recording medium to which the inkjet ink composition is adhered A second step of drying at a drying temperature D (unit: ° C.), and an inkjet ink composition used in a recording method comprising:
Water and polymer particles,
The polymer particles include a core portion containing a resin having a glass transition temperature A (unit: ° C), and a shell portion containing a resin having a glass transition temperature B (unit: ° C) covering at least a part of the core portion. Have
The glass transition temperature A and the glass transition temperature B satisfy the following formula (1), and the glass transition temperature A and the glass transition temperature B are as follows in relation to the head temperature C and the drying temperature D: An ink-jet ink composition satisfying the formula (2).
30 <BA (1)
C <B <D (2)
[2]
The ink composition for inkjet according to [1], wherein the shell part includes a resin having a (meth) acrylate unit and a carboxylic acid monomer unit.
[3]
The inkjet ink composition according to [1] or [2], wherein the glass transition temperature A is 35 ° C. or lower.
[4]
4. The inkjet ink composition according to any one of [1] to [3], which is used in the recording method in which the recording medium is heated from the recording head side in the first step.
[5]
At least one of a fluorine-based surfactant and a silicone-based surfactant;
At least one of glycol ether and alkyl diol having 3 to 8 carbon atoms;
The inkjet ink composition according to any one of [1] to [4], further comprising:
[6]
The inkjet ink composition according to any one of [1] to [5] above, which is used in the recording method in which the drying temperature D is 45 to 130 ° C.
[7]
The inkjet according to any one of [1] to [6], wherein the recording medium has a surface temperature E (unit: ° C) of 30 to 70 ° C in the first step. Ink composition.
[8]
The ink composition for inkjet according to the preceding item [7], wherein the glass transition temperature B and the surface temperature E satisfy the following formula (3).
E <B (3)
[9]
A first step in which an inkjet ink composition is ejected from a recording head having a head temperature C (unit: ° C.) onto a recording medium and adhered; and the recording medium to which the inkjet ink composition is adhered A second step of drying at a drying temperature D (unit: ° C.),
The ink-jet ink composition includes water and polymer particles,
The polymer particles include a core portion containing a resin having a glass transition temperature A (unit: ° C), and a shell portion containing a resin having a glass transition temperature B (unit: ° C) formed on the surface of the core portion; Have
The recording method in which the glass transition temperature A, the glass transition temperature B, the head temperature C, and the drying temperature D satisfy the following formulas (1) and (2).
30 <BA (1)
C <B <D (2)
[10]
The recording method according to [9], wherein the glass transition temperature B and the surface temperature E satisfy the following formula (3).
E <B (3)
[11]
A recording head for discharging the inkjet ink composition according to any one of [1] to [8] above to a recording medium;
A head heating means for heating the recording head to a head temperature C (unit: ° C.);
Drying means for drying the recording medium to which the ink-jet ink composition is adhered at a drying temperature D (unit: ° C.);
A recording apparatus.

1 is a schematic cross-sectional view illustrating a configuration of a recording apparatus according to an embodiment. It is a flowchart of the recording method which concerns on this embodiment.

  Hereinafter, a mode for carrying out the present invention (hereinafter referred to as “the present embodiment”) will be described in detail with reference to the drawings as necessary. However, the present invention is not limited to this, Various modifications are possible without departing from the scope of the invention. In the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted. Further, positional relationships such as up, down, left and right are based on the positional relationships shown in the drawings unless otherwise specified. Further, the dimensional ratios in the drawings are not limited to the illustrated ratios. In the present specification, “(meth) acryl” means “acryl” and “methacryl” corresponding thereto, and “(meth) acrylate” means “acrylate” and “methacrylate” corresponding thereto. Further, the “core portion” and the “shell portion” need not be strictly in the structure and state. The resin constituting the core part and the resin constituting the shell part exist separately, and the resin constituting the core part only needs to be present so that the resin constituting the shell part covers a certain amount.

[Inkjet ink composition]
The ink-jet ink composition according to the present embodiment (hereinafter also simply referred to as “ink composition”) is obtained by transferring the ink-jet ink composition from a recording head having a head temperature C (unit: ° C.) to a recording medium. Ink jet for use in a recording method comprising: a first step of discharging and adhering; and a second step of drying the recording medium to which the ink jet ink composition is adhered at a drying temperature D (unit: ° C.). An ink composition comprising water and polymer particles, wherein the polymer particles cover a core part containing a resin having a glass transition temperature A (unit: ° C.) and at least a part of the core part. A shell portion containing a resin having a glass transition temperature B (unit: ° C.), the glass transition temperature A and the glass transition temperature B satisfy the following formula (1), and the glass transition temperature: (A ℃ and the glass transition temperature B satisfies the following formula (2) in relation to the head temperature C and the drying temperature D, the inkjet ink composition.
30 <BA (1)
C <B <D (2)

  The ink composition according to the present embodiment includes a first step in which the ink composition is ejected from a recording head having a head temperature C to a recording medium and adhered thereto; and the recording medium to which the ink composition is adhered. And a second step of drying at a drying temperature D. In such a recording method, the glass transition temperature A of the resin contained in the core portion of the polymer particles and the glass transition temperature B of the resin contained in the shell portion are expressed by the above formula ( By satisfying 1) and (2), both excellent ejection stability and adhesion can be achieved.

  That is, when the glass transition temperature B is higher than the glass transition temperature A by 30 ° C., the ink composition is difficult to be welded in the recording head, so that the ejection stability is improved. Further, since the glass transition temperature B is higher than the glass transition temperature A by 30 ° C., the abrasion resistance of the image recorded on the recording medium is improved. Further, since the glass transition temperature A is lower than the glass transition temperature B by 30 ° C., the core portion having a lower Tg is eluted after the shell portion is melted by heating after ejection, so that the ink for the recording medium is discharged. The adhesion of the composition is further improved. From this viewpoint, the difference (B−A) between the glass transition temperature B and the glass transition temperature A is preferably higher than 50 ° C., and more preferably higher than 70 ° C. On the other hand, B-A may be less than 130 ° C, less than 110 ° C, or less than 100 ° C. That is, B-A is preferably higher than 30 ° C. and lower than 130 ° C., more preferably higher than 50 ° C. and lower than 110 ° C., still more preferably higher than 70 ° C. and lower than 100 ° C.

  Further, by making the glass transition temperature B higher than the head temperature C, the shell portion is less likely to melt due to the temperature at the time of ink ejection, and the polymer particles are ejected from the recording head without collapsing the core-shell structure. Is possible. From this viewpoint, the difference (B−C) between the glass transition temperature B and the head temperature C is preferably 5 ° C. or higher, and more preferably 10 ° C. or higher. On the other hand, BC is preferably 60 ° C. or lower, and more preferably 50 ° C. or lower. That is, BC is preferably 5 to 60 ° C and more preferably 10 to 50 ° C.

  Furthermore, by making the drying temperature D higher than the glass transition temperature B, the resin contained in the shell portion is easily melted when the ink composition attached to the recording medium is dried. Accordingly, in combination with satisfying the above formula (1), the resin contained in the core part is eluted, and the resin contained in the shell part and the core part adheres to the recording medium. As a result, a film that adheres more firmly to the recording medium is formed. The drying temperature D is the surface temperature of the recording medium in the second step. The drying temperature D can be measured with a radiation thermometer. From this viewpoint, the difference (D−B) between the drying temperature D and the glass transition temperature B is preferably 5 ° C. or higher, and more preferably 10 ° C. or higher. On the other hand, D-B is preferably 50 ° C. or lower, and more preferably 40 ° C. or lower. That is, D-B is preferably 5 to 50 ° C, and more preferably 10 to 40 ° C.

  The ink composition according to the present embodiment is preferably used in a recording method in which the recording medium is heated from the recording head side in the first step. When the recording medium is heated from the recording head side, the recording head is heated when the recording medium is heated, and there is a problem that the resin easily melts in the head. In the case of an ink composition, since the shell portion Tg is higher than the recording head temperature, there is a tendency that the welding of the resin can be suppressed. Further, by heating the recording medium from the recording head side, the recording medium immediately after the ink composition can be efficiently heated even when the recording medium is thick.

  Furthermore, the ink composition according to this embodiment is preferably used in a recording method in which the drying temperature D in the second step is 45 to 130 ° C. The drying temperature D is more preferably 55 to 120 ° C, further preferably 70 to 110 ° C. Further, it is more preferable that the temperature is higher than the surface temperature E. When the drying temperature D is within the above range, in the ink composition attached to the recording medium, the shell portion of the polymer particles is sufficiently melted, and the adhesion of the ink composition to the recording medium is further improved and the drying property is improved. Therefore, high-speed printing tends to be possible. Further, since the drying temperature D is within the above range and the above formulas (1) and (2) are satisfied, the shell portion can be prevented from being melted when the ink composition is ejected. Can be maintained. When the drying temperature D is 45 to 130, high-speed printing of an image with high adhesion is possible while preventing thermal deformation of the recording medium.

  The ink composition according to this embodiment is preferably used in a recording method in which the surface temperature E (unit: ° C.) of the recording medium is 30 to 70 ° C. in the first step. The surface temperature E of the recording medium is preferably 30 to 70 ° C, more preferably 30 to 60 ° C, and further preferably 40 to 60 ° C. When the surface temperature E of the recording medium is within the above range and the above formulas (1) and (2) are satisfied, the melting of the shell portion immediately after landing of the ink on the recording medium is suppressed. Since volatile components such as moisture contained in the ink composition can be removed, bleeding resistance and high-speed printability tend to be further improved while maintaining ejection stability. When the surface temperature E of the recording medium is 30 to 60 ° C., there is a problem that the ink in the ink jet head is dried, but the core shell having high hydrophilicity is used in the ink composition according to this embodiment. There exists a tendency which can suppress the said malfunction by using resin. The surface temperature E may be determined by measuring the temperature of the ejection surface (nozzle plate) on which the nozzle group of the inkjet head is formed.

The glass transition temperature B preferably satisfies the following formula (3) in relation to the surface temperature E of the recording medium. When the glass transition temperature B satisfies the following formula (3) and the above formulas (1) and (2) are satisfied, moisture contained in the ink composition is suppressed while the shell portion is prevented from melting immediately after landing. Therefore, bleed resistance and high-speed printability tend to be further improved while maintaining ejection stability. From the same viewpoint as described above, the difference (B−E) between the glass transition temperature B and the surface temperature E of the recording medium is preferably 10 ° C. or more, and more preferably 15 ° C. or more. On the other hand, BE is preferably 50 ° C. or lower, and more preferably 40 ° C. or lower. That is, BE is preferably 10 to 50 ° C and more preferably 15 to 40 ° C.
E <B (3)

〔water〕
The ink composition according to this embodiment contains water. The water is not particularly limited, and pure water such as ion exchange water, ultrafiltration water, reverse osmosis water, distilled water, or ultrapure water can be used. By containing water, the organic solvent can be reduced, and as a result, an ink composition that is environmentally friendly can be obtained.

  The water content is preferably from 45 to 75 mass%, more preferably from 50 to 70 mass%, still more preferably from 55 to 65 mass%, based on the total mass (100 mass%) of the ink composition. When the water content is within the above range, the discharge stability and adhesion tend to be further improved.

(Polymer particles)
The ink composition according to the present embodiment includes polymer particles. The polymer particles are core-shell polymer particles having a core portion containing a resin having a glass transition temperature A and a shell portion containing a resin having a glass transition temperature B formed on the surface of the core portion. Moreover, the difference between the glass transition temperature A and the glass transition temperature B is 30 ° C. or more as shown by the above formula (1). By using such polymer particles, it is possible to suppress melting of the shell portion in the printing nozzle before discharge, and thus excellent discharge stability is achieved. Further, after discharge, after the shell portion is melted by heating, the core portion is eluted, and the adhesion of the ink composition to the recording medium and the abrasion resistance of the coating tend to be further improved.

(Core part)
The Tg (A) of the resin contained in the core part is preferably 35 ° C. or less, more preferably 20 ° C. or less, further preferably 5 ° C. or less, particularly preferably −5 ° C. or less. When the Tg (A) of the resin contained in the core part is 35 ° C. or lower, the core part can be easily eluted after the shell part is melted, so that the adhesion tends to be superior. Further, when the Tg (A) of the resin contained in the core part is −80 ° C. or higher, the storage stability of the ink composition tends to be excellent.

The resin contained in the core part and the shell part described later may be a homopolymer or a copolymer. When the resin contained in the core part and the shell part described later is a homopolymer, the Tg of the homopolymer described in various documents (for example, a polymer handbook) can be used. Moreover, when the resin contained in the core part and the shell part described later is a copolymer, the Tg of the copolymer is the Tg _n (unit: K) of various homopolymers and the mass fraction of the monomer ( W _n ) and the following FOX equation.
Where W _n ; mass fraction of each monomer
Tg _n ; Tg of the homopolymer of each monomer (unit: K)
Tg: Tg of copolymer (unit: K)

  Although it does not specifically limit as a homopolymer, For example, 2-ethylhexyl acrylate homopolymer (Tg: -70 degreeC), 2-ethylhexyl methacrylate homopolymer (Tg: -10 degreeC), 2-hydroxyethyl acrylate homopolymer (Tg) : -15 ° C), 2-hydroxyethyl methacrylate homopolymer (Tg: 55 ° C), 2-hydroxybutyl acrylate homopolymer (Tg: -7 ° C), 2-hydroxybutyl methacrylate homopolymer (Tg: 26 ° C), 2 -Methoxyethyl acrylate homopolymer (Tg: -50 ° C), 4-hydroxybutyl acrylate homopolymer (Tg: -80 ° C), iso-octyl methacrylate homopolymer (Tg: -45 ° C), iso-butyl acrylate homopolymer ( Tg: 43 ), Iso-butyl methacrylate homopolymer (Tg: 53 ° C.), iso-propyl acrylate homopolymer (Tg: −3 ° C.), iso-propyl methacrylate homopolymer (Tg: 81 ° C.), N, N-diethylaminoethyl methacrylate homo Polymer (Tg: 20 ° C.), N, N-dimethylaminoethyl acrylate homopolymer (Tg: 18 ° C.), N, N-dimethylaminoethyl methacrylate homopolymer (Tg: 18 ° C.), N, N-dimethylaminopropylacrylamide Homopolymer (Tg: 134 ° C), n-butyl acrylate homopolymer (Tg: -54 ° C), tert-butyl acrylate homopolymer (Tg: 43 ° C), tert-butyl methacrylate homopolymer (Tg: 20 ° C), acrylamide Homopoly -(Tg: 179 ° C), acrylic acid homopolymer (Tg: 106 ° C), acrylonitrile homopolymer (Tg: 125 ° C), isoamyl acrylate homopolymer (Tg: -45 ° C), isobutyl acrylate homopolymer (Tg: -26) ° C), isobutyl methacrylate homopolymer (Tg: 48 ° C), isobornyl acrylate homopolymer (Tg: 94 ° C), isobornyl methacrylate homopolymer (Tg: 155 ° C to 180 ° C), itaconic acid homopolymer (Tg) : 100 ° C), ethyl acrylate homopolymer (Tg: -22 ° C to -24 ° C), ethyl carbitol acrylate homopolymer (Tg: -67 ° C), ethyl methacrylate homopolymer (Tg: 65 ° C), ethoxyethyl acrylate homo Polymer (Tg: -50 ° C ), Ethoxyethyl methacrylate homopolymer (Tg: 15 ° C.), ethoxydiethylene glycol acrylate homopolymer (Tg: −70 ° C.), octyl acrylate homopolymer (Tg: −65 ° C.) iso-octyl acrylate homopolymer (Tg: −70 ° C.) ), Cyclohexyl acrylate homopolymer (Tg: 15 ° C. to 19 ° C.), cyclohexyl methacrylate homopolymer (Tg: 66 ° C. to 83 ° C.), dicyclopentanyl acrylate homopolymer (Tg: 120 ° C.), dicyclopentanyl methacrylate homo Polymer (Tg: 175 ° C), Styrene homopolymer (Tg: 100 ° C), Stearyl acrylate homopolymer (Tg: 35 ° C), Tertiary butyl acrylate homopolymer (Tg: 41 ° C), Tertiary rib Methacrylate homopolymer (Tg: 107 ° C), tetradecyl acrylate homopolymer (Tg: 24 ° C), tetradecyl methacrylate homopolymer (Tg: -72 ° C), tetrahydrofurfuryl acrylate homopolymer (Tg: -12 ° C), Tetrahydrofurfuryl methacrylate homopolymer (Tg: 60 ° C.), nonyl acrylate homopolymer (Tg: 58 ° C.), phenoxyethyl acrylate homopolymer (Tg: −22 ° C.), phenoxyethyl methacrylate homopolymer (Tg: 54 ° C.), butyl Acrylate homopolymer (Tg: -56 ° C), butyl methacrylate homopolymer (Tg: 20 ° C), propyl acrylate homopolymer (Tg: 3 ° C), propyl methacrylate homopolymer (Tg: 35 ° C), hex Decyl acrylate homopolymer (Tg: 35 ° C), hexadecyl methacrylate homopolymer (Tg: 15 ° C), hexyl acrylate homopolymer (Tg: -57 ° C), hexyl methacrylate homopolymer (Tg: -5 ° C, benzyl acrylate homopolymer) (Tg: 6 ° C), benzyl methacrylate homopolymer (Tg: 54 ° C), pentyl acrylate homopolymer (Tg: 22 ° C), pentyl methacrylate homopolymer (Tg: -5 ° C), maleic acid homopolymer (Tg: 130 ° C) ), Methacrylic acid homopolymer (Tg: 185 ° C.), carboxyethyl acrylate homopolymer (Tg: 37 ° C.), methyl acrylate homopolymer (Tg: 8 ° C.), methyl methacrylate homopolymer (Tg: 105 ° C.), methoxyethyl acetate Relate homopolymer (Tg: −50 ° C.), methoxy methacrylate homopolymer (Tg: −16 ° C.), lauryl acrylate homopolymer (Tg: −3 ° C. to 15 ° C.), lauryl methacrylate homopolymer (Tg: −65 ° C.), Examples thereof include vinyl acetate homopolymer (Tg: 32 ° C.). Tg is not limited to the above because it may vary depending on the homopolymer production method and stereoregularity.

  The Tg (A) of the resin contained in the core portion can be controlled by selecting the homopolymer when the resin is a homopolymer. Moreover, when resin is a copolymer, it can control by considering Tg of the said homopolymer, and the said FOX formula.

  Further, the resin contained in the core part is not particularly limited. For example, the resin has a hydrophilic (meth) acrylate monomer unit, a hydrophobic (meth) acrylate monomer unit having an alkyl group having 3 or more carbon atoms, and a cyclic structure. A polymer having at least one of a hydrophobic (meth) acrylate monomer unit, a (meth) acrylamide monomer unit or an N-substituted derivative thereof, an aromatic vinyl compound monomer unit, and a carboxylic acid monomer unit is preferable. Among these, a hydrophobic (meth) acrylate having an alkyl group having 3 or more carbon atoms and a polymer having an aromatic vinyl compound are preferable.

  The hydrophilic (meth) acrylate monomer is not particularly limited. For example, methyl (meth) acrylate, ethyl (meth) acrylate, α-hydroxymethyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, (poly) Examples include ethylene glycol (meth) acrylate, methoxy (poly) ethylene glycol (meth) acrylate, ethoxy (poly) ethylene glycol (meth) acrylate, and (poly) propylene glycol (meth) acrylate. Among these, methyl (meth) acrylate and ethyl (meth) acrylate are preferable. Here, “hydrophilic” means that the solubility in 100 mL of water (20 ° C.) is 0.3 g or more.

  Although it does not specifically limit as a hydrophobic (meth) acrylate monomer which has a C3 or more alkyl group, For example, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (Meth) acrylate, n-amyl (meth) acrylate, isoamyl (meth) acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, nonyl (meth) acrylate, decyl (meth) ) Acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, cetyl (meth) acrylate, neopentyl (meth) acrylate, behenyl (meth) acrylate, etc. (meth) acrylate having an alkyl group with 3 or more carbon atoms Over door, and the like. Among these, lauryl (meth) acrylate is preferable. Here, “hydrophobic” means that the solubility in 100 mL of water (20 ° C.) is less than 0.3 g.

  The hydrophobic (meth) acrylate monomer having a cyclic structure is not particularly limited, and examples thereof include cyclohexyl (meth) acrylate, dicyclopentanyl (meth) acrylate, dicyclopentenyl (meth) acrylate, and dicyclopentenyloxyethyl ( Examples include meth) acrylate, isobornyl (meth) acrylate, norbornyl (meth) acrylate, adamantyl (meth) acrylate, and tetrahydrofurfuryl (meth) acrylate.

  Although it does not specifically limit as a (meth) acrylamide monomer or its N-substituted derivative, For example, (meth) acrylamide, N-hydroxymethyl (meth) acrylamide, diacetone acrylamide, N, N-dimethylacrylic (meth) amide etc. (Meth) acrylamide or an N-substituted derivative thereof.

  The aromatic vinyl compound monomer is not particularly limited, and examples thereof include styrene, α-methylstyrene, p-methylstyrene, vinyltoluene, chlorostyrene, and divinylbenzene.

  Although it does not specifically limit as a carboxylic acid monomer, For example, (meth) acrylic acid, crotonic acid, maleic acid, fumaric acid, itaconic acid etc. are mentioned. Among these, (meth) acrylic acid is preferable. Here, the “carboxylic acid monomer unit” refers to a polymerizable monomer unit having a carboxyl group and a polymerizable unsaturated group.

  The said monomer may be used individually by 1 type, or may use 2 or more types together.

  Of all the repeating units constituting the resin contained in the core part, the content of the repeating unit derived from the hydrophobic monomer is preferably 80% by mass or more, and more preferably 90% by mass or more. Since the content of the repeating unit derived from the hydrophobic monomer is within the above range, a hydrophobic coating is formed on the surface of the image recorded on the recording medium by performing heat treatment or the like, so that the abrasion resistance is improved. It tends to improve.

  The resin contained in the core part may be used alone or in combination of two or more. When two or more kinds of resins are contained in the core portion, the glass transition temperature of the resin having the highest glass transition temperature is defined as the glass transition temperature A.

(Shell part)
The Tg (B) of the resin contained in the shell part is preferably 50 ° C. or higher, and more preferably 60 ° C. or higher. The Tg (B) of the resin contained in the shell part is preferably 120 ° C. or lower, more preferably 90 ° C. or lower. When the Tg (B) of the resin contained in the shell part is 120 ° C. or less, the shell part is likely to melt on the recording medium, and thus the adhesiveness tends to be excellent. Further, when the ink composition is heated in advance when the ink composition is discharged, the Tg (B) of the resin contained in the shell portion is 50 ° C. or higher, so that the core-shell structure is not collapsed. The coalesced particles can be ejected from the recording head, and the welding of the polymer particles in the printing nozzle can be further suppressed, so that the ejection stability tends to be superior.

  As the resin contained in the shell portion, a resin having a (meth) acrylate monomer unit and a carboxylic acid monomer unit is preferable. By using such a resin, a carboxyl group can be present on the surface of the shell portion. As a result, the dispersion stability of the polymer particles is further improved, and the viscosity of the ink composition is relatively low, so that the ejection stability tends to be further improved. The (meth) acrylate monomer unit is not particularly limited. For example, a hydrophilic (meth) acrylate monomer unit, a hydrophobic (meth) acrylate monomer unit having an alkyl group having 3 or more carbon atoms, or a hydrophobic structure having a cyclic structure. (Meth) acrylate monomer unit. Specific examples of the (meth) acrylate monomer unit and the carboxylic acid monomer unit are the same as those described above for the monomer unit constituting the resin contained in the core part. More than one species may be used in combination.

  Of all repeating units constituting the resin contained in the shell part, the content of repeating units derived from (meth) acrylic acid ester and unsaturated carboxylic acid is preferably 80% by mass or more, more preferably 90% by mass or more. 95 mass% or more is more preferable.

  Of all the repeating units constituting the resin contained in the shell part, the content of the repeating unit derived from the hydrophilic monomer is preferably 80% by mass or more, more preferably 90% by mass or more, and further preferably 95% by mass or more. . When the content of the repeating unit derived from the hydrophilic monomer is in the above range, a hydration layer is formed around the shell portion, so that the dispersion stability of the polymer particles in the ink composition tends to be improved. is there. Moreover, since it can suppress more effectively that a polymer particle adheres to a nozzle, it exists in the tendency for the discharge stability from the nozzle of a recording head to become more favorable.

  The resin contained in the shell part may be used alone or in combination of two or more. When two or more kinds of resins are contained in the shell portion, the glass transition temperature of the resin having the lowest glass transition temperature is defined as a glass transition temperature B.

  The particle diameter φ (unit: nm) of the polymer particles is preferably 30 nm to 500 nm, more preferably 30 nm to 200 nm, and further preferably 30 nm to 150 nm. When the particle diameter of the polymer particles is in the above range, the dispersion stability of the polymer particles in the ink composition tends to be further improved. The particle diameter (φ) of the polymer particles means a volume-based average particle diameter that can be determined by observation with a dynamic light scattering method or a transmission electron microscope.

  The ratio (c / s) between the mass (c) of the core part and the mass (s) of the shell part of the polymer particles is preferably 0.4 to 4.0, preferably 0.5 to 2.5. It is more preferable that it is and it is especially preferable that it is 0.6-2.0. Further, when the polymer particles satisfy the relationship of (c / s) /φ≧0.01, the balance between the mass of the core portion and the mass of the shell portion becomes good regardless of the size of the polymer particles. In addition, both the ejection stability of the ink composition and the rub resistance of the image recorded on the recording medium tend to be improved.

  Moreover, it is particularly preferable that the polymers constituting the core part and the shell part of the polymer particles are each non-crosslinked. By being non-crosslinked, the discharge stability tends to be further improved. The degree of crosslinking of the polymer can be quantified by measuring the polymer gel fraction (hereinafter also referred to as “THF gel fraction”) using tetrahydrofuran (THF). The THF gel fraction of the polymer particles is preferably 10% or less, and more preferably 5% or less. When the THF gel fraction of the polymer particles is within the above range, the abrasion resistance of the image recorded on the recording medium tends to be further improved.

The THF gel fraction can be measured, for example, as follows. About 10 g of core-shell type polymer particles are weighed into a Teflon (registered trademark) petri dish and dried at 120 ° C. for 1 hour to form a film. The obtained membrane is immersed in THF at 20 ° C. for 24 hours, filtered through a 100 mesh filter, and further dried at 20 ° C. for 24 hours. The THF gel fraction (%) can be obtained from the following formula. .
THF gel fraction (%) = (mass after re-drying / original mass) × 100

  The content of the polymer particles in the ink composition (in terms of solid content) is preferably 0.5% by mass or more and 20% by mass or less, and 0.6% by mass with respect to the total mass (100% by mass) of the ink composition. The content is more preferably 15% by mass or less, and further preferably 0.7% by mass or more and 10% by mass or less. When the content of the polymer particles is 0.5% by mass or more, it tends to be more excellent in abrasion resistance and adhesion. Moreover, it exists in the tendency which is more excellent in discharge stability because content of a polymer particle is 20 mass% or less.

  Here, the core-shell type polymer particles in the present specification only require that the resin that forms the core portion is localized in the core portion, and the resin that forms the shell portion is localized in the shell portion. It may be a polymer particle whose boundary with the part is not exactly clear.

(Method for synthesizing polymer particles)
The method for synthesizing the polymer particles is not particularly limited, but can be easily synthesized by, for example, a known emulsion polymerization method or an appropriate combination thereof. Specifically, a batch mixing polymerization method, a monomer dropping method, a pre-emulsion method, a seed emulsion polymerization method, a multistage emulsion polymerization method (two-stage emulsion polymerization method, etc.), a phase inversion emulsion polymerization method and the like can be mentioned.

  A polymerization method for synthesizing the core part first will be described. First, core particles are synthesized by an ordinary emulsion polymerization method using an aqueous medium. The conditions for the emulsion polymerization may be in accordance with known methods. For example, when the total amount of monomers used is 100 parts, the polymerization can usually be carried out using 100 to 500 parts of water (aqueous medium). . The polymerization temperature is preferably −10 to 100 ° C., more preferably −5 to 100 ° C., and further preferably 0 to 90 ° C. The polymerization time is preferably 0.1 to 30 hours, and more preferably 2 to 25 hours. Emulsion polymerization methods include batch method in which monomers are charged all at once, a method in which monomers are divided or continuously supplied, a method in which monomer pre-emulsions are divided or continuously added, or a combination of these methods in stages. Can be adopted. Moreover, the polymerization initiator, molecular weight regulator, emulsifier, etc. which are used for normal emulsion polymerization can be used 1 type, or 2 or more types as needed.

  The polymerization initiator is not particularly limited. For example, persulfates such as potassium persulfate and ammonium persulfate; diisopropyl peroxydicarbonate, benzoyl peroxide, lauroyl peroxide, tert-butylperoxy-2-ethylhexanoate Organic peroxides such as: azo compounds such as azobisisobutyronitrile, dimethyl-2,2′-azobisisobutyrate, 2-carbamoylazaisobutyronitrile; radical emulsifying compounds having a peroxide group The redox system which combined reducing agents, such as containing radical emulsifier, sodium hydrogensulfite, and ferrous sulfate, can be used. A polymerization initiator may be used individually by 1 type, or may use 2 or more types together.

  The molecular weight regulator is not particularly limited, but for example, n-hexyl mercaptan, n-octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, n-hexadecyl mercaptan, n-tetradecyl mercaptan, t-tetradecyl mercaptan, Mercaptans such as thioglycolic acid; xanthogen disulfides such as dimethylxanthogen disulfide, diethylxanthogen disulfide, diisopropylxanthogen disulfide; thiuram disulfides such as tetramethylthiuram disulfide, tetraethylthiuram disulfide, tetrabutylthiuram disulfide; chloroform, carbon tetrachloride, Halogenated hydrocarbons such as carbon tetrabromide and ethylene bromide; pentaphenylethane, α-methylstyrene dimer Hydrocarbons and the like; acrolein, methacrolein, allyl alcohol, 2-ethylhexyl thioglycolate, terpinolene, alpha-Terunepin, .gamma. Terunepin, dipentene, include 1,1-diphenylethylene. A molecular weight regulator may be used individually by 1 type, or may use 2 or more types together.

  Although it does not specifically limit as an emulsifier, For example, Anionic surfactants, such as alkyl sulfate ester salt and alkylbenzenesulfonate; Nonionic property, such as alkyl ester of polyethylene glycol, alkyl ether of polyethylene glycol, alkylphenyl ether of polyethylene glycol Surfactants; reactive emulsifiers containing hydrophilic groups, hydrophobic groups and radical reactive groups; polymer emulsifiers in which hydrophilic groups are introduced into polymers such as vinyl polymers and polyester polymers. . An emulsifier may be used individually by 1 type, or may use 2 or more types together. The hydrophilic group is an atomic group having a high affinity for water, and examples thereof include a nitro group, a hydroxyl group, an amino group, a carboxyl group, and a sulfonic acid group. A hydrophobic group is an atomic group having a lower affinity for water than a hydrophilic group. For example, a linear or branched alkyl group, alicyclic group, aromatic ring group, alkylsilyl group, A fluoroalkyl group etc. are mentioned.

  Next, the monomer for the shell portion is polymerized in the presence of the obtained core particles (core portion). Specifically, core-shell type polymer particles can be formed by seed polymerizing a monomer for the shell part in a state where the obtained core particles are used as seed particles. For example, the monomer for the shell portion or a pre-emulsion thereof may be added all at once, in a divided manner, or continuously in an aqueous medium in which the core particles are dispersed. It is preferable that the quantity of the core particle used at this time shall be 25-250 mass parts with respect to 100 mass parts of monomers for shell parts. In the case of using a polymerization initiator, a molecular weight regulator, an emulsifier and the like at the time of polymerization, the same ones as in the production of core particles can be used. Moreover, the conditions such as the polymerization time may be the same as in the production of the core particles.

  A polymerization method for synthesizing the shell portion first will be described. First, the shell part is synthesized. Specifically, a pre-emulsion solution containing the above-mentioned hydrophilic monomer is prepared using a reactive emulsifier, and the pre-emulsion solution is dropped into an aqueous medium together with a polymerization initiator to synthesize a shell portion. .

  Next, using the obtained shell part as a polymerization field, the core part is polymerized to synthesize polymer particles according to this embodiment. Specifically, a monomer mixture containing the above-mentioned hydrophobic monomer is dropped into an aqueous dispersion medium containing a shell part, and the core part is polymerized to form polymer particles. In addition, when making a shell part into a polymerization field, since it is not necessary to contain an emulsifier in a monomer mixture, it can be dripped as a monomer oil droplet.

  According to such a multi-stage emulsion polymerization method, since the shell part can be synthesized using a reactive emulsifier and the core part can be synthesized without using an emulsifier, the content of the emulsifier in the ink composition can be easily reduced to 0.01. It can be made into the mass% or less. In the ink composition, when the content of the emulsifier is 0.01% by mass or less, at the ink interface (the air-gas-liquid interface in the ink, the ink contact member such as the ink container, and the solid-liquid interface in the ink). Aggregation of the ink component is suppressed and storage stability is excellent, which is preferable. Further, in the ink composition, when the content of the emulsifier contained is 0.01% by mass or less, since the foaming property and the defoaming property are excellent, an ink container having an injection port capable of being filled with ink is preferably used. be able to. Here, the “ink container having an ink filling inlet” is an ink container having an inlet that can be attached or detached, and allows the user to easily inject the ink composition. On the other hand, it is easy to foam during injection. In addition, it is preferable that the opening area of the injection port is 20 mm 2 or more because the ink composition can be easily filled. Such an ink container is disclosed in, for example, Japanese Patent Application Laid-Open Nos. 2005-219483 and 2012-51309.

  Further, even when polymer particles are synthesized using a large amount of emulsifier, the content of the emulsifier contained in the ink composition is 0.01 mass by removing excess emulsifier after the synthesis of the polymer particles. % Or less.

  Finally, a core-shell polymer particle dispersion is obtained by neutralizing with a base such as sodium hydroxide, potassium hydroxide, ammonia, etc., adjusting the pH, and filtering as necessary.

[Color material]
The ink composition preferably contains a color material. Although it does not specifically limit as a coloring material, For example, a pigment or dye is mentioned.

  Although it does not specifically limit as an inorganic pigment, For example, carbon black (CI pigment black 7), such as furnace black, lamp black, acetylene black, channel black, iron oxide, and titanium oxide are mentioned.

  Examples of organic pigments include, but are not limited to, quinacridone pigments, quinacridone quinone pigments, dioxazine pigments, phthalocyanine pigments, anthrapyrimidine pigments, ansanthrone pigments, indanthrone pigments, flavanthrone pigments, Examples include perylene pigments, diketopyrrolopyrrole pigments, perinone pigments, quinophthalone pigments, anthraquinone pigments, thioindigo pigments, benzimidazolone pigments, isoindolinone pigments, azomethine pigments, and azo pigments. It is done.

  A pigment may be used individually by 1 type, or may use 2 or more types together.

  The content of the pigment is preferably 0.5 to 15% by mass, more preferably 1 to 10% by mass, and further preferably 1 to 5% by mass.

[Surfactant]
The ink composition preferably contains a surfactant. The surfactant is not particularly limited, and examples thereof include acetylene glycol surfactants, fluorine surfactants, and silicone surfactants. When the ink composition contains these surfactants, the wettability of the ink composition attached to the recording medium tends to be further improved.

  The acetylene glycol-based surfactant is not particularly limited, and examples thereof include 2,4,7,9-tetramethyl-5-decyne-4,7-diol and 2,4,7,9-tetramethyl-5- Selected from alkylene oxide adducts of decyne-4,7-diol and alkylene oxide adducts of 2,4-dimethyl-5-decyn-4-ol and 2,4-dimethyl-5-decyn-4-ol One or more are preferred. Although it does not specifically limit as a commercial item of a fluorochemical surfactant, For example, E series (A product made by Air Products Japan (Inc)) (Surfinol 465, Surfi, etc.), such as Olfine 104 series and Olfine E1010. Nord 61 (trade name, manufactured by Nissin Chemical Industry CO., Ltd.). One acetylene glycol surfactant may be used alone, or two or more acetylene glycol surfactants may be used in combination.

  The fluorosurfactant is not particularly limited. For example, perfluoroalkyl sulfonate, perfluoroalkyl carboxylate, perfluoroalkyl phosphate, perfluoroalkyl ethylene oxide adduct, perfluoroalkyl betaine, perfluoroalkyl betaine, A fluoroalkylamine oxide compound is mentioned. Although it does not specifically limit as a commercial item of a fluorochemical surfactant, For example, S-144, S-145 (made by Asahi Glass Co., Ltd.); FC-170C, FC-430, Fluorard-FC4430 (made by Sumitomo 3M Co., Ltd.) FSO, FSO-100, FSN, FSN-100, FS-300 (manufactured by Dupont); FT-250, 251 (manufactured by Neos). A fluorine-type surfactant may be used individually by 1 type, and may use 2 or more types together.

  Examples of silicone surfactants include polysiloxane compounds and polyether-modified organosiloxanes. Although it does not specifically limit as a commercial item of a silicone type surfactant, Specifically, BYK-306, BYK-307, BYK-333, BYK-341, BYK-345, BYK-346, BYK-347, BYK-348, BYK-349 (above trade name, manufactured by Big Chemie Japan Co., Ltd.), KF-351A, KF-352A, KF-353, KF-354L, KF-355A, KF-615A, KF- 945, KF-640, KF-642, KF-643, KF-6020, X-22-4515, KF-6011, KF-6012, KF-6015, KF-6017 (all trade names, manufactured by Shin-Etsu Chemical Co., Ltd.) Etc.

  The content of the surfactant in the ink composition is preferably 0.1 to 5% by mass and more preferably 0.1 to 3% by mass with respect to the total mass (100% by mass) of the ink composition. When the content of the surfactant is within the above range, the wettability of the ink composition attached to the recording medium tends to be further improved.

(Penetration agent)
The ink composition preferably further contains a penetrant. The ink composition quickly penetrates into the recording medium, so that a recorded matter with less image blur can be obtained.

  Such penetrants are not particularly limited, but preferred examples include polyhydric alcohol alkyl ethers (glycol ethers) and C3-C8 alkyl diols. Although it does not specifically limit as glycol ether, For example, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monomethyl ether acetate, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol Monopropyl ether, diethylene glycol monobutyl ether, diethylene glycol mono-t-butyl ether, triethylene glycol monobutyl ether, 1-methyl-1-methoxybutanol, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, B propylene glycol monobutyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol monopropyl ether, propylene glycol monobutyl ether, and dipropylene glycol monobutyl ether.

  The alkyl diol having 3 to 8 carbon atoms is not particularly limited, and examples thereof include 1,2-pentanediol and 1,2-hexanediol, 1,2-propanediol, 1,3-propanediol, , 4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 3-methyl-1,5-pentanediol, 2-ethyl-1 , 3-hexanediol.

  One penetrant may be used alone, or two or more penetrants may be used in combination.

  The content of the penetrant in the ink composition is preferably 0.1 to 20% by mass, and more preferably 0.5 to 10% by mass with respect to the total mass (100% by mass) of the ink composition. When the content is 0.1% by mass or more, the degree of penetration of the ink composition into the recording medium can be increased. On the other hand, when the content is 20% by mass or less, bleeding can be prevented from occurring in the image, and the improvement in the viscosity of the ink composition tends to be further suppressed.

[Cyclic amide compound]
The ink composition preferably further contains a cyclic amide compound. Since the ink composition contains a cyclic amide compound, the stability of the polymer particles is further improved, and the precipitation of foreign matters in the ink composition can be effectively prevented, so that the storage stability, particularly storage stability at high temperatures is achieved. There is a tendency to be more excellent in nature.

  In addition, since the cyclic amide compound also has a moisture retention performance, the polymer particles and other components can be prevented from aggregating and solidifying due to the evaporation of moisture during storage of the ink composition. As a result, clogging in the vicinity of the nozzles of the head during ink jet recording is prevented, and the ejection stability of the ink composition tends to be more excellent.

  The cyclic amide compound is not particularly limited, and examples thereof include 2-pyrrolidone, N-methyl-2-pyrrolidone, and N-ethyl-2-pyrrolidone. Among these, 2-pyrrolidone is preferable. A cyclic amide compound may be used individually by 1 type, and may use 2 or more types together.

  The content of the cyclic amide compound in the ink composition is preferably 0.5 to 5% by mass and more preferably 1 to 3% by mass with respect to the total mass (100% by mass) of the ink composition. When the content is within the above range, the long-term storage stability and ejection stability of the ink composition, and the rub resistance of the recorded matter due to the excellent adhesion of the ink composition tend to be more excellent. It is in.

[Other ingredients]
In order to maintain good storage stability and ejection stability from the head, the ink composition has a solvent, a humectant, a dissolution aid, a viscosity for improving clogging or preventing deterioration of the ink composition. Add various additives such as regulators, pH regulators, antioxidants, preservatives, antifungal agents, corrosion inhibitors, and chelating agents to capture metal ions that affect dispersion as appropriate You can also.

〔surface tension〕
The surface tension of the ink composition at 25 ° C. is preferably 20 to 50 mPa · s, and more preferably 20 to 40 mPa · s. When the surface tension is within the above range, the ejection stability tends to be good. The surface tension can be measured using a surface tension meter.

〔viscosity〕
The viscosity of the ink composition at 25 ° C. is preferably 20 mPa · s or less, and more preferably 10 mPa · s or less. When the viscosity is within the above range, the ejection stability tends to be good. The viscosity can be measured using a viscometer.

[Recording medium]
The recording medium is not particularly limited, and examples thereof include an absorptive recording medium, a low-absorbing recording medium, and a non-absorbing recording medium.

  The absorbent recording medium is not particularly limited, but is used for, for example, plain paper such as electrophotographic paper having high penetrability of the ink composition, inkjet paper, and general offset printing having relatively low penetrability of the ink composition. Art paper, coated paper, cast paper, and the like. Although it does not specifically limit as inkjet paper, Specifically, it was comprised from hydrophilic polymers, such as an ink absorption layer comprised from the silica particle and the alumina particle, or polyvinyl alcohol (PVA) and polyvinylpyrrolidone (PVP). Examples of the paper include an ink absorbing layer.

  The low-absorbency recording medium is not particularly limited, and examples thereof include coated paper having a coating layer for receiving the oil-based ink composition on the surface. The coated paper is not particularly limited, and examples thereof include printing paper such as art paper, coated paper, and matte paper.

  The non-absorbable recording medium is not particularly limited. For example, films and plates of plastics such as polyvinyl chloride, polyethylene, polypropylene, and polyethylene terephthalate (PET), and metals such as iron, silver, copper, and aluminum are used. Examples thereof include a plate, a metal plate produced by vapor deposition of these various metals, a plastic film, a plate made of an alloy such as stainless steel or brass.

Here, the “low-absorbing recording medium” and the “non-absorbing recording medium” refer to recording media whose water absorption from the start of contact to 30 msec in the Bristow method is 10 mL / m ² or less. . This Bristow method is the most popular method for measuring the amount of liquid absorbed in a short time, and is also adopted by the Japan Paper Pulp Technology Association (JAPAN TAPPI). For details of the test method, refer to Standard No. of “JAPAN TAPPI Paper Pulp Test Method 2000”. 51 "Paper and paperboard-Liquid absorbency test method-Bristow method".

  Further, the non-absorbent recording medium or the low-absorbing recording medium can be classified by the wettability of the recording surface with respect to water. For example, a 0.5 μL water droplet is dropped on the recording surface of the recording medium, and the contact angle reduction rate (comparison of the contact angle at 0.5 milliseconds after the landing and the contact angle at 5 seconds) is measured. The medium can be characterized. More specifically, as a property of the recording medium, the non-absorbing property of the “non-absorbing recording medium” indicates that the above-described reduction rate is less than 1%, and the low absorption of the “low-absorbing recording medium”. The property indicates that the decrease rate is 1% or more and less than 5%. Moreover, absorptivity means that said reduction rate is 5% or more. In addition, a contact angle can be measured using portable contact angle meter PCA-1 (made by Kyowa Interface Science Co., Ltd.) etc.

[Recording device]
The recording apparatus according to this embodiment includes a recording head for discharging the ink composition to a recording medium, a head heating unit for heating the recording head to a head temperature C, and the inkjet ink composition. Drying means for drying the attached recording medium at a drying temperature D. This recording apparatus may further include the ink-jet ink composition described above.

  FIG. 1 is a schematic sectional view of a recording apparatus according to this embodiment. As shown in FIG. 1, the recording apparatus 1 includes a recording head 2, an IR heater 3, a platen heater 4, a curing heater 5, a cooling fan 6, a preheater 7, and a ventilation fan 8. ing.

  The recording head 2 ejects an ink composition onto a recording medium. As the recording head 2, a conventionally known method can be used, and a head that ejects droplets by utilizing vibration of a piezoelectric element, that is, a head that forms ink droplets by mechanical deformation of an electrostrictive element can be used.

  The head heating means heats the recording head 2 to the head temperature C. The head heating means is not particularly limited. For example, the recording head 2 is heated via a means for directly heating the recording head 2 with warm air or an IR heater 3 or a recording medium heated with the platen heater 4. Means are mentioned. By heating the recording head 2, the ink composition in the recording head 2 has a reduced viscosity and can be ejected satisfactorily. Further, since the glass transition temperature B and the head temperature C satisfy the above formula (2), the shell portion of the polymer particles is difficult to melt in the recording head 2 and the polymer particles are welded in the recording head 2. This can be suppressed.

  When the IR heater 3 is used, the recording medium can be heated from the recording head 2 side. Thereby, the recording head 2 is also easily heated at the same time, but the temperature can be raised without being affected by the thickness of the recording medium as compared with the case where the recording head 2 is heated from the back surface of the recording medium. If the platen heater 4 is used, the recording medium can be heated from the side opposite to the recording head 2 side. Thereby, the recording head 2 is relatively hardly heated.

  The recording apparatus 1 preferably further includes a recording medium heating unit that heats the recording medium so that the surface temperature E is 30 to 60 ° C. when the ink composition is discharged onto the recording medium. The recording medium heating means is not particularly limited, and examples thereof include an IR heater 3 and a platen heater 4. By having the recording medium heating means, the ink composition adhering to the recording medium can be dried more quickly, and bleeding can be further suppressed.

  The drying means heats the recording medium to which the ink-jet ink composition is adhered to the drying temperature D and dries it. Although it does not specifically limit as a drying means, For example, means, such as the curing heater 5, a warm air mechanism (not shown), and a thermostat (not shown), are mentioned. When the drying means heats the recording medium on which the image is recorded, moisture contained in the ink composition is evaporated and scattered more quickly, and a film is formed by the polymer particles contained in the ink composition. Is done. In this manner, the dried ink is firmly fixed (adhered) on the recording medium, and a high-quality image excellent in abrasion resistance can be obtained in a short time.

  The above-mentioned “heating the recording medium” means increasing the temperature of the recording medium to a desired temperature, and is not limited to directly heating the recording medium.

  The recording apparatus 1 may have a cooling fan 6. After drying, the ink composition on the recording medium is cooled by the cooling fan 6 so that a film can be formed on the recording medium with good adhesion.

  The recording apparatus 1 may include a preheater 7 that preheats (preheats) the recording medium before the ink composition is ejected onto the recording medium. By preheating the recording medium before discharging the ink composition, a tendency to be able to form a high-quality image with little bleeding on the recording medium, particularly a non-absorbing and low-absorbing recording medium. It is in. The preheating temperature is preferably 80 to 120 ° C.

  Further, the recording apparatus 1 may include a ventilation fan 8 so that the ink composition attached to the recording medium is dried more efficiently.

〔Recording method〕
In the recording method according to the present embodiment, the ink composition is ejected from the recording head having the head temperature C onto the recording medium and adhered, and the recording medium to which the ink composition is adhered is dried. A second step of drying at a temperature D. The ink composition includes water and polymer particles, and the polymer particles include a core portion including a resin having a glass transition temperature A, and the core portion. And a shell portion containing a resin having a glass transition temperature B formed on the surface thereof, and the glass transition temperature A, the glass transition temperature B, the head temperature C, and the drying temperature D are expressed by the above formulas (1) and ( It satisfies 2). Hereinafter, a recording method using the above-described recording apparatus 1 of the present embodiment will be described.

[First step]
FIG. 2 shows a flowchart of the recording method according to the present embodiment. As shown in FIG. 2, the recording method according to this embodiment includes a first step and a second step. Of these, the first step is a step in which the ink composition described above is ejected from the recording head 2 at the head temperature C to the recording medium and adhered. As a result, the ink composition in the recording head 2 has a reduced viscosity and can be discharged well. Further, since the glass transition temperature B and the head temperature C satisfy the above formula (2), the shell portion of the polymer particles in the ink composition does not melt in the recording head 2, and the polymer is contained in the recording head 2. It is possible to suppress the welding of the particles, and this improves the discharge stability. The head temperature C is set lower than the glass transition temperature B, and the difference (B−C) between the glass transition temperature B and the head temperature C is preferably 5 ° C. or higher, and more preferably 10 ° C. or higher. On the other hand, BC is preferably 60 ° C. or lower, and more preferably 50 ° C. or lower. That is, BC is preferably 5 to 60 ° C and more preferably 10 to 50 ° C.

  In addition, the ink composition similar to the above can be used.

  In the first step, the recording medium is preferably heated from the recording head 2 side. When the recording medium is thick, the recording medium is heated from the recording head 2 side using the IR heater 3 or the like, and heated from the opposite side of the recording medium to the ink adhesion surface using the platen heater 4 or the like. Compared with the case where it does, it is easy to dry an ink composition more rapidly.

  The surface temperature E of the recording medium in the first step is preferably 30 to 60 ° C, more preferably 40 to 66 ° C. When the surface temperature E of the recording medium is within the above range, the viscosity of the ink is suppressed and the ejection stability tends to be excellent. The surface temperature E of the recording medium can be controlled using at least one of the IR heater 3 and the platen heater 4.

  The surface temperature E of the recording medium is lower than the glass transition temperature B, and the difference (B−E) between the glass transition temperature B and the surface temperature E of the recording medium is preferably 10 ° C. or more, and 15 ° C. or more. Is more preferable. On the other hand, BE is preferably 50 ° C. or lower, and more preferably 40 ° C. or lower. That is, BE is preferably 10 to 50 ° C and more preferably 15 to 40 ° C. Thereby, only the volatile matter of the ink composition on the recording medium can be volatilized more selectively without melting the shell of the polymer particles in the ink composition adhering to the recording medium.

[Second step]
The second step is a step of drying the recording medium to which the ink composition is adhered at the drying temperature D. The drying temperature D is higher than the glass transition temperature B, and the difference (D−B) between the drying temperature D and the glass transition temperature B is preferably 5 ° C. or higher, and more preferably 10 ° C. or higher. On the other hand, D-B is preferably 50 ° C. or lower, and more preferably 40 ° C. or lower. That is, D-B is preferably 5 to 50 ° C, and more preferably 10 to 40 ° C. When the drying temperature D is higher than the glass transition temperature B, the shell part of the polymer particles in the ink composition adhering to the recording medium is melted together with satisfying the above formula (1). The core part elutes and adheres onto the recording medium.

  After the second step, the ink composition on the recording medium is cooled by the cooling fan 6 so that a film can be formed on the recording medium with good adhesion.

  The drying temperature D in the second step is preferably used for a recording method having a temperature of 45 to 130 ° C. The drying temperature D is more preferably 55 to 120 ° C, further preferably 70 to 110 ° C. When the drying temperature D is within the above range, the drying rate tends to be fast while suppressing deformation of the substrate.

  Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples. The present invention is not limited in any way by the following examples.

[Material for ink composition]
The main materials for the ink compositions used in the following examples and comparative examples are as follows.
[Color material]
C. I. Pigment Blue 15: 3
(Penetration agent)
1,2-hexanediol (humectant)
1,2-propanediol (cyclic amide compound)
2-pyrrolidone [surfactant]
BYK348 (silicone surfactant, manufactured by Big Chemie Japan)
(Polymer particles)
Polymer particles 1 (produced according to Production Example 1)
Polymer particle 2 (produced according to Production Example 2)
Polymer particles 3 (produced according to Production Example 3)
Polymer particles 4 (produced according to Production Example 4)
Polymer particles 5 (produced according to Production Example 5)

[Production Example 1: Polymer particles 1]
To a reaction vessel equipped with a dropping device, a thermometer, a water-cooled reflux condenser, and a stirrer, 100 parts of ion exchange water and 0.2 part of potassium persulfate as a polymerization initiator are added, and 7 parts of ion exchange water. A monomer solution containing 0.05 part of sodium lauryl sulfate, 12 parts of styrene, 18 parts of n-butyl acrylate and 0.02 part of t-dodecyl mercaptan was added dropwise and stirred at 70 ° C. in a nitrogen atmosphere with stirring. Core particles were prepared. Thereafter, 2 parts of 10% ammonium persulfate solution was added and stirred, and further 30 parts of ion exchange water, 0.2 part of potassium lauryl sulfate, 42.5 parts of methyl methacrylate, 22.5 parts of butyl methacrylate, 25 parts of lauryl methacrylate, A reaction solution consisting of 10 parts of acrylic acid and 0.5 part of t-dodecyl mercaptan was added while stirring at 70 ° C., followed by polymerization reaction, neutralized with sodium hydroxide and adjusted to pH 8 to 8.5. A core-shell type polymer particle aqueous dispersion was prepared by filtration through a 3 μm filter.

[Production Example 2: Polymer particles 2]
To a reaction vessel equipped with a dropping device, a thermometer, a water-cooled reflux condenser, and a stirrer, 100 parts of ion exchange water and 0.2 part of potassium persulfate as a polymerization initiator are added, and 7 parts of ion exchange water. A monomer solution containing 0.05 part of sodium lauryl sulfate, 12 parts of styrene, 18 parts of n-butyl acrylate and 0.02 part of t-dodecyl mercaptan was added dropwise and stirred at 70 ° C. with stirring to react with the core. Particles were made. Thereafter, 2 parts of 10% ammonium persulfate solution was added and stirred. Further, 30 parts of ion exchange water, 0.2 part of potassium lauryl sulfate, 65 parts of methyl methacrylate, 25 parts of lauryl methacrylate, 10 parts of acrylic acid, t-dodecyl mercaptan A reaction solution consisting of 0.5 parts was added at 70 ° C. with stirring, followed by polymerization reaction, neutralized with sodium hydroxide, adjusted to pH 8 to 8.5 and filtered through a 0.3 μm filter. A core-shell polymer particle aqueous dispersion was prepared.

[Production Example 3: Polymer particles 3]
To a reaction vessel equipped with a dropping device, a thermometer, a water-cooled reflux condenser, and a stirrer, 100 parts of ion exchange water and 0.2 part of potassium persulfate as a polymerization initiator are added, and 7 parts of ion exchange water. A monomer solution containing 0.05 part of sodium lauryl sulfate, 12 parts of styrene, 18 parts of n-butyl acrylate and 0.02 part of t-dodecyl mercaptan was added dropwise and stirred at 70 ° C. with stirring to react with the core. Particles were made. Thereafter, 2 parts of 10% ammonium persulfate solution was added and stirred, and further 30 parts of ion exchange water, 0.2 part of potassium lauryl sulfate, 80 parts of methyl methacrylate, 10 parts of lauryl methacrylate, 10 parts of acrylic acid, t-dodecyl mercaptan A reaction solution consisting of 0.5 parts was added at 70 ° C. with stirring, followed by polymerization reaction, neutralized with sodium hydroxide, adjusted to pH 8 to 8.5 and filtered through a 0.3 μm filter. A core-shell polymer particle aqueous dispersion was prepared.

[Production Example 4: Polymer particles 4]
To a reaction vessel equipped with a dropping device, a thermometer, a water-cooled reflux condenser, and a stirrer, 100 parts of ion exchange water and 0.2 part of potassium persulfate as a polymerization initiator are added, and 7 parts of ion exchange water. A monomer solution containing 0.05 part of sodium lauryl sulfate, 32 parts of styrene, 40 parts of n-butyl acrylate and 0.02 part of t-dodecyl mercaptan was added dropwise and stirred at 70 ° C. in a nitrogen atmosphere to react with the core. Particles were made. Thereafter, 2 parts of 10% ammonium persulfate solution was added and stirred, and further 30 parts of ion exchange water, 0.2 part of potassium lauryl sulfate, 80 parts of methyl methacrylate, 10 parts of lauryl methacrylate, 10 parts of acrylic acid, t-dodecyl mercaptan A reaction solution consisting of 0.5 parts was added at 70 ° C. with stirring, followed by polymerization reaction, neutralized with sodium hydroxide, adjusted to pH 8 to 8.5 and filtered through a 0.3 μm filter. A core-shell polymer particle aqueous dispersion was prepared.

[Production Example 5: Polymer particles 5]
To a reaction vessel equipped with a dropping device, a thermometer, a water-cooled reflux condenser, and a stirrer, 100 parts of ion exchange water and 0.2 part of potassium persulfate as a polymerization initiator are added, and 40 parts of ion exchange water. , A reaction solution containing 0.2 parts of potassium lauryl sulfate, 104 parts of methyl methacrylate, 13 parts of lauryl methacrylate, 13 parts of acrylic acid, and 0.5 part of t-dodecyl mercaptan was added while stirring at 70 ° C. in a nitrogen atmosphere. After the polymerization reaction, the mixture was neutralized with sodium hydroxide, adjusted to pH 8 to 8.5, and filtered through a 0.3 μm filter to prepare an aqueous dispersion of core-shell polymer particles.

[Production Example 6: Polymer particles 6]
To a reaction vessel equipped with a dropping device, a thermometer, a water-cooled reflux condenser, and a stirrer, 100 parts of ion exchange water and 0.2 part of potassium persulfate as a polymerization initiator are added, and 7 parts of ion exchange water. A monomer solution containing 0.05 part of sodium lauryl sulfate, 32 parts of styrene, 40 parts of n-butyl acrylate and 0.02 part of t-dodecyl mercaptan was added dropwise and stirred at 70 ° C. in a nitrogen atmosphere to react with the core. Particles were made. Thereafter, 2 parts of a 10% ammonium persulfate solution was added and stirred, and further 30 parts of ion exchange water, 0.2 part of potassium lauryl sulfate, 44.8 parts of methyl methacrylate, 25 parts of stearyl acrylate, 22.5 of 2-ethylhexyl acrylate The reaction solution containing 7.7 parts of acrylic acid, 7.7 parts of acrylic acid and 0.5 part of t-dodecyl mercaptan was added while stirring at 70 ° C. in a nitrogen atmosphere, and then neutralized with sodium hydroxide to pH 8-8. The core-shell polymer particle aqueous dispersion was prepared by adjusting to 5 and filtering with a 0.3 μm filter.

MMA: Methyl methacrylate BMA: Butyl methacrylate LMA: Lauryl methacrylate AA: Acrylic acid BA: Butyl acrylate St: Styrene

[Preparation of ink composition]
Each material was mixed with the composition (mass%) shown in Table 3 below and stirred sufficiently to obtain each ink composition. In addition, a pigment and polymer particle show solid content.

[Evaluation]
(Discharge stability)
A part of the printer Stylus Pro 9900 (manufactured by Seiko Epson Corporation) was modified to provide a printer capable of adjusting the heating of the recording medium during ink jet recording. Using this printer, each ink composition is ejected from the nozzle of the recording head, a solid pattern is formed on a vinyl coated paper JT5829R (manufactured by Mactac), which is a recording medium, dried by a curing means, and cooled by a cooling fan Then, the dried ink composition was cooled. After 10 hours of continuous printing, the ejection stability was evaluated as follows. In addition, maintenance was performed every time recording was performed for 2 hours. Table 2 shows recording conditions (modes).

  The printer Stylus Pro 9900 (manufactured by Seiko Epson Corporation) has a platen heater and an IR heater as recording medium heating means, and a head heating means includes a nozzle plate, an ink chamber, and a flow path. It has a temperature-controllable heater, a platen heater and an IR heater as curing means, and a platen heater as a preheater.

(Evaluation)
A: Non-ejection or ejection disturbance occurs slightly during ejection, but returns during ejection, and there is almost no problem B: Non-ejection or ejection disturbance occurs during ejection, but does not return during ejection, but maintenance C: State that returns to the normal state due to the discharge C: Non-discharge or discharge disturbance occurs slightly during discharge, does not return during discharge, and does not return due to maintenance

[Adhesion]
Using a printer Stylus Pro 9900 (manufactured by Seiko Epson Corporation), each ink composition was ejected from the nozzles of the recording head, and the solids were printed on a vinyl chloride coated paper JT5829R (manufactured by Mactac) as a recording medium. A pattern was formed, dried with a curing heater, and the dried ink composition was cooled with a cooling fan. A JIS standard crosscut test was performed on the obtained recorded matter, and the adhesion of the ink composition was evaluated as follows.

(Evaluation)
A: State in which no separation is observed in all 25 lattices B: State in which separation is observed in less than 3 out of 25 lattices C: Separation is observed in 3 or more out of 25 lattices State

[High-speed printability]
Using a printer Stylus Pro 9900 (manufactured by Seiko Epson Corporation), each ink composition was ejected from the nozzles of the recording head, and the solids were printed on a vinyl chloride coated paper JT5829R (manufactured by Mactac) as a recording medium. A pattern was formed, dried with a curing heater, and the dried ink composition was cooled with a cooling fan. The recording resolution was 720 × 720 dpi, and the mass per ink droplet (ink mass) was 21 ng. The coating amount was varied from 7.5 to 11 mg per square inch, and a solid pattern having a duty of 70 to 100% was obtained. Aggregation unevenness in the Duty 70 to 100% portion of the obtained recorded matter was visually confirmed and evaluated as follows.

(Evaluation)
A: State in which aggregation unevenness cannot be visually confirmed B: State in which aggregation unevenness is visually confirmed with a part of ink mass C: State in which aggregation unevenness is confirmed regardless of ink mass

  DESCRIPTION OF SYMBOLS 1 ... Recording device, 2 ... Recording head, 3 ... IR heater, 4 ... Platen heater, 5 ... Curing heater, 6 ... Cooling fan, 7 ... Pre-heater, 8 ... Ventilation fan.

Claims (11)

A first step in which an inkjet ink composition is ejected from a recording head having a head temperature C (unit: ° C.) onto a recording medium and adhered; and the recording medium to which the inkjet ink composition is adhered A second step of drying at a drying temperature D (unit: ° C.), and an inkjet ink composition used in a recording method comprising:
Water and polymer particles,
The polymer particles include a core portion containing a resin having a glass transition temperature A (unit: ° C), and a shell portion containing a resin having a glass transition temperature B (unit: ° C) covering at least a part of the core portion. Have
The glass transition temperature A and the glass transition temperature B satisfy the following formula (1), and the glass transition temperature A and the glass transition temperature B are as follows in relation to the head temperature C and the drying temperature D: An ink-jet ink composition satisfying the formula (2).
30 <BA (1)
C <B <D (2)   The ink composition for inkjet according to claim 1, wherein the shell part includes a resin having a (meth) acrylate unit and a carboxylic acid monomer unit.   The inkjet ink composition according to claim 1 or 2, wherein the glass transition temperature A is 35 ° C or lower.   The ink composition for inkjet according to any one of claims 1 to 3, which is used in the recording method in which the recording medium is heated from the recording head side in the first step. At least one of a fluorine-based surfactant and a silicone-based surfactant;
At least one of glycol ether and alkyl diol having 3 to 8 carbon atoms;
The ink composition for inkjet according to any one of claims 1 to 4, further comprising:   The ink composition for inkjet according to any one of claims 1 to 5, which is used in the recording method in which the drying temperature D is 45 to 130 ° C.   The ink composition for inkjet according to any one of claims 1 to 6, which is used in the recording method in which the surface temperature E (unit: ° C) of the recording medium is 30 to 70 ° C in the first step. object. The ink composition for inkjet according to claim 7, wherein the glass transition temperature B and the surface temperature E satisfy the following formula (3).
E <B (3) A first step in which an inkjet ink composition is ejected from a recording head having a head temperature C (unit: ° C.) onto a recording medium and adhered; and the recording medium to which the inkjet ink composition is adhered A second step of drying at a drying temperature D (unit: ° C.),
The ink-jet ink composition includes water and polymer particles,
The polymer particles include a core portion containing a resin having a glass transition temperature A (unit: ° C), and a shell portion containing a resin having a glass transition temperature B (unit: ° C) formed on the surface of the core portion; Have
The recording method in which the glass transition temperature A, the glass transition temperature B, the head temperature C, and the drying temperature D satisfy the following formulas (1) and (2).
30 <BA (1)
C <B <D (2) The recording method according to claim 9, wherein the glass transition temperature B and the surface temperature E satisfy the following formula (3).
E <B (3) A recording head for discharging the ink-jet ink composition according to claim 1 to a recording medium;
A head heating means for heating the recording head to a head temperature C (unit: ° C.);
Drying means for drying the recording medium to which the ink-jet ink composition is adhered at a drying temperature D (unit: ° C.);
A recording apparatus.