JP2013064082A - Inkjet recording inkset and recording method using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inkjet recording ink that can impart scratch resistance close to that of an off-set recorded matter subjected to varnishing treatment in a printed paper; and to provide an inkjet recording method.SOLUTION: An inkjet recording inkset contains a color ink and a clear ink. The color ink contains a first polyurethane resin and a first polymer particle. The clear ink contains a second polyurethane resin and a second polymer particle. The mass ratio of the second polyurethane resin to the first polyurethane resin is 2 to 4. The mass ratio of the second polymer particle to the first polymer particle is 1 to 3.

Description

  The present invention relates to an ink set for inkjet recording and a recording method using the same.

  The ink jet recording method is a printing method in which printing is performed by causing ink droplets to fly and adhere to a recording medium such as paper. Due to recent advances in inkjet recording technology, inkjet recording methods have been used in the field of high-definition printing that has been realized only by silver salt photography and offset printing. Along with that, high gloss recording media comparable to photographic paper and art paper used in the field of silver salt photography and offset printing, so-called special paper, is used for inkjet recording, and glossiness equivalent to silver salt photography. Ink for ink jet recording that can realize an image having the above has been developed. Ink-jet recording inks have been developed that can achieve image quality comparable to that of silver halide photographs even when plain paper is used.

  For example, in order to realize a high-quality image, it has been proposed to perform recording by attaching a clear ink not containing a colorant to a recording medium together with a color ink. For example, Patent Document 1 proposes forming an image with color ink containing a colorant and attaching clear ink onto the image.

  By the way, with recent spread of image forming technology from digital data, desktop publishing (DTP) is becoming widespread, especially in the printing field. Even when printing is performed by DTP, a color proofing proof is produced in advance in order to confirm glossiness and color feeling with an actual recorded matter. An inkjet recording method is applied to the output of this proof, and in DTP, color reproduction and stability reproduction of a recorded matter are required. Therefore, a dedicated paper for inkjet recording is usually used as a recording medium. It is used.

  The dedicated paper for ink-jet recording is prepared so that the gloss and color feel are the same as the output actually printed on the printing paper. As described above, the material of the special paper is appropriately adjusted according to the type of the printing paper, but producing the special paper corresponding to all of the various printing papers causes an increase in manufacturing cost. Thus, in color proofing applications, there is a desire to perform ink jet recording on printed paper rather than dedicated paper. In addition, if the final calibration sample can be obtained by performing inkjet recording directly on the main printing paper without using dedicated paper, it is considered that the cost for calibration can be greatly reduced. Synthetic paper, which is widely used in the printing field and is formed into a film by mixing an inorganic filler or the like with polyethylene resin or polyester resin, has recently attracted attention as an environmentally friendly material that is excellent in recyclability.

  The main printing paper is a coated paper provided with a coating layer for receiving oil-based ink on its surface, but has a feature that the ink absorption capability of the coating layer is poor. For this reason, when water-based pigment ink generally used for ink jet recording is used, the permeability of the ink into the recording medium (printing paper) is low, and blurring and uneven aggregation may occur in the image.

  For example, Patent Document 2 discloses that a polysiloxane compound is used as a surfactant and an alkanediol such as 1,2-hexanediol is added as a solubilizer to improve bleeding. A pigment-based ink that has excellent gloss for special paper is disclosed.

  Patent Document 3 discloses that a colorant, water, a slightly water-soluble alkanediol, a water-soluble 1, A color ink containing 2-alkanediol, dialkylene glycol, and a surfactant has been proposed. Patent Document 4 describes at least a water-insoluble alkanediol, a water-soluble alcohol, water, and polymer fine particles, which are excellent in fixability and capable of obtaining a high-quality recorded product free from printed spots. Clear inks that contain and do not contain colorants have been proposed. However, it can be said that there is still a demand for an ink having excellent fixability in various recording media, particularly non-water-absorbing or low-water-absorbing recording media such as synthetic paper and printing paper.

JP 2003-335058 A JP 2005-194500 A JP 2009-209338 A JP 2009-297924 A

  However, since the color ink described in Patent Document 3 includes a colorant, the ink film strength is low, and the resin content imparting fixability is small, so that the abrasion resistance is weak. For this reason, the clear ink described in Patent Document 4 to which a fixing resin and a slipping agent are added can provide improved abrasion resistance even on the printing paper. However, with the fixability and slipperiness of the color ink and the clear ink, although the rubbing on the surface of the recorded material is almost inconspicuous, there is a problem that the ink on the surface of the recorded material is transferred to the non-printing surface.

  Further, when a number of recorded materials having images formed on the surface are stacked, the recorded materials rub against each other so that the ink component on the first recorded material is applied to the second recorded material in contact therewith. There is a case to transfer. Even if the above-mentioned problem does not occur, when cutting a plurality of recorded materials or punching holes, a high pressure is applied to the plurality of recorded materials, so that an ink component is formed on the cut surface or the punch hole surface. There is a new problem of transferring.

  The inventors of the present invention have excellent fixability on various recording media, in particular, non-water-absorbing or low-water-absorbing recording media such as synthetic paper and printing paper, with a specific ink set. It is to obtain a suppressed recorded matter. Means for solving the problems are as follows.

  (Application Example 1) An ink set for inkjet recording including a color ink and a clear ink, wherein the color ink includes a first polyurethane resin and a first polymer fine particle, and the clear ink is The second polyurethane resin and the second polymer fine particles, and the mass ratio of the second polyurethane resin to the first polyurethane resin is 2 to 4, and the first polymer fine particles are An ink set for inkjet recording, wherein the mass ratio of the second polymer fine particles is 1 to 3.

  (Application example 2) The total mass of the first and second polyurethane resins is 4.5 to 13.5, and the total mass of the first and second polymer fine particles is 3 to 6. The ink set for inkjet recording described in Example 1.

  (Application Example 3) The ink set for inkjet recording according to Application Example 1 or 2, wherein at least one of the first or second polymer fine particles is polyolefin.

  Application Example 4 The ink set for inkjet recording according to any one of Application Examples 1 to 3, wherein Tg of at least one of the first and second urethane resins is 50 ° C. or less.

  (Application example 5) The ink set for inkjet recording according to any one of application examples 1 to 4, wherein the color ink and the clear ink further contain an alkanediol having 7 or more carbon atoms.

  Application Example 6 The color ink and the clear ink further contain an alcohol having 6 or less carbon atoms, and the alcohol having 6 or less carbon atoms is at least one selected from the group consisting of alkanediol, alkanetriol, and alkylene glycol. The ink set for inkjet recording according to any one of Application Examples 1 to 5, which is a seed.

  (Application example 7) The ink set for inkjet recording according to any one of application examples 1 to 6, wherein the color ink and the clear ink further contain a polyorganosiloxane surfactant.

  (Application example 8) A recording method using the ink set according to any one of application examples 1 to 7, wherein after the color ink is attached to a recording medium, the clear ink is attached to the recording medium. ,Recording method.

  According to the present invention, it is possible to obtain a recorded matter that is excellent in fixability and excellent in glossiness and color developability even in various recording media, particularly non-water-absorbing or low-water-absorbing recording media such as synthetic paper and printing paper. It is also excellent in printing stability after elapse.

It is sectional drawing which shows typically the coating film of the recorded image immediately after discharge drying formed by making clear ink containing polyolefin wax adhere to a recording surface. It is sectional drawing which shows typically the coating film of the recording image after giving an abrasion factor to the coating-film surface of FIG.

  An ink jet recording ink set according to an embodiment of the present invention and a recording method using the same will be described.

<Definition>
In the present specification, the alkanediol may be either a straight chain or a branched chain.

  Water-soluble means that the solubility in water at 20 ° C. (the amount of solute with respect to 100 g of water) is 10.0 g or more, and poorly water-soluble means the solubility in water (100 g of water). It means that the amount of solute relative to 1.0 g is less than 1.0 g.

In the present specification, the “non-water-absorbing or low water-absorbing recording medium” refers to a recording medium that does not have a water-based ink receiving layer or has a poor water-based ink receiving layer. More quantitatively, a non-water-absorbing or low-water-absorbing recording medium is a recording medium whose recording surface has a water absorption of 10 mL / m ² or less from the start of contact to 30 msec 1/2 in the Bristow method. Indicates. 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".

<Ink set>
The ink set for ink jet recording (also referred to as ink set) according to the present embodiment is an ink set for ink jet recording including a color ink and a clear ink, and the color ink includes a first urethane resin and a first urethane resin. The clear ink contains a second urethane resin and a second polymer fine particle, and the mass ratio of the second urethane to the first urethane resin is 1 to 3 and an ink set for inkjet recording in which the mass ratio of the second polymer fine particles to the first polymer fine particles is 2 to 4 (hereinafter, “color ink and clear ink” are simply referred to as “ink set”). In some cases, color ink or clear ink may be simply referred to as “ink”). By using such an ink set, a recorded matter having excellent fixability can be obtained even in various recording media, particularly non-water-absorbing or low-water-absorbing recording media such as synthetic paper and printing paper.

  The fixability of the ink is caused by the frictional force on the surface of the recorded image and the adhesion between the medium and the ink. According to the ink set of the present embodiment, the first and second polymer fine particles reduce the frictional force on the surface of the recorded image (that is, the slipperiness is great), and further, the first and second Polyurethane resin enhances the adhesion between media and ink.

  Furthermore, according to the ink set of the present embodiment, the mass ratio of the second urethane to the first urethane resin is 1 to 3, and the mass ratio of the second polymer microparticles to the first polymer microparticles. 2 to 4, it is possible to suppress undesired transfer when cutting a plurality of recorded materials or punching holes.

(Polymer fine particles)
The ink set according to the present embodiment includes polymer fine particles. The first polymer fine particles contained in the color ink and the second polymer fine particles contained in the clear ink may be the same polymer fine particles or different polymer fine particles.

  Although the polymer fine particles are not particularly limited, for example, a polyolefin wax is preferable.

  The polyolefin wax preferably has a particle size larger than the dry film thickness of a film formed by depositing ink onto the recording surface. By adhering to the recording surface as particles protruding from the ink film, it is considered that the polyolefin wax particles are crushed by themselves when pressure is applied to the recording surface, and the slip of the outermost surface of the ink film can be improved. That is, when the clear ink adheres to the recording medium and dries, the polyolefin wax particles 1 protrude from the ink coating film 2 as shown in FIG. In this state, when the recorded image is affected by an external factor that causes wear, the protruding portion of the polyolefin wax particles 1 spreads on the film surface as shown in FIG. It is considered that this spread wax makes the recorded image less susceptible to wear and develops abrasion resistance.

  The particle diameter of the polyolefin wax is preferably 76 nm to 800 nm, particularly 150 nm or more, and particularly preferably 150 nm to 250 nm, from the viewpoints of fixability and printing stability after the passage. The particle size of the polyolefin wax means a particle diameter (average value) measured by a microtrack method.

  The polyolefin wax tends to remain as particles in a film fixed to the recording surface of the ink, and its melting point or ring-and-ball method softening point (JIS K 2207) is preferably 110 ° C. or higher, particularly preferably 110 to 150 ° C. .

  The polyolefin wax preferably has a penetration hardness (JIS K 2207) of 1 or more, more preferably 2 to 5.

  The polyolefin wax is not particularly limited as long as the state of particles having a predetermined particle diameter can be maintained in a film (a coating film such as a recording image) formed when ink is deposited on a recording surface. For example, a wax produced from an olefin such as ethylene, propylene, butylene or a derivative thereof and a copolymer thereof, specifically, a polyethylene wax, a polypropylene wax, a polybutylene wax or the like may be used alone or in combination.

As shown in FIG. 1, the polyolefin wax according to the present embodiment can be present in the ink film on the recording medium without forming a film. This is probably because the minimum film-forming temperature (MFT) has not been reached even after receiving a plasticizing effect such as the temperature during recording, the temperature during drying, and the solvent.
The preferred range of the minimum film-forming temperature (MFT) of the polyolefin wax according to the present embodiment is not limited by the above reason, but is preferably 20 ° C. or higher, more preferably 60 ° C. or higher. As such a polyolefin wax, it is also possible to use a commercially available one. Specific examples thereof include “Chemical Pearl W4005” (polyethylene wax, particle size 200 nm to 800 nm, ring and ball softening point 110 ° C., Chemipearl series such as a penetration degree hardness of 3 and a solid content of 40%, manufactured by Mitsui Chemicals, Inc. can be suitably used. Further, AQUACER 515 (polyethylene wax, particle size 100 to 200 nm, melting point 130 ° C., manufactured by Big Chemie Japan Co., Ltd. having a solid content of 30%) and the like can also be suitably used. In addition, polyolefin wax described in JP-A-2003-201436 can also be suitably used.

  According to the ink set of the present embodiment, the mass ratio of the second polymer particles to the first polymer particles is 1 to 3. By setting it within the above range, an image having excellent fixability can be formed.

  The content (solid content) of the polymer fine particles is not particularly limited as long as the above range is satisfied, and is, for example, 0.2 to 5.0 mass% with respect to the total mass of each ink. The preferred content is 1.0 to 4.0% by mass for the first polymer particles and 1.0 to 6.0% by mass for the second polymer particles. More preferable content is 1.5 to 3.0 mass% for the first polymer fine particles, and 1.5 to 4.5 mass% for the second polymer fine particles. By setting it within the above range, an image having excellent fixability can be formed.

(Polyurethane resin)
The ink set according to the present embodiment includes a polyurethane resin. The first polyurethane resin contained in the color ink and the second polyurethane resin contained in the clear ink may be the same polyurethane resin or different polyurethane resins.

  In the present embodiment, a polycarbonate-based or polyether-based anionic polyurethane resin is used as the polyurethane resin. A known method can be applied to the synthesis of the polyurethane resin having such a structure. For example, it can be obtained by reacting a compound having two or more isocyanate groups with a compound having two or more active hydrogen groups. Can do. The compound having two or more active hydrogen groups is a polyether polyol or a polycarbonate polyol.

  The compound having two or more isocyanate groups is not particularly limited, and examples thereof include chain aliphatic isocyanates such as tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate, dodecamethylene diisocyanate, trimethylhexamethylene diisocyanate, and lysine diisocyanate, 1,3-cyclohexylene diisocyanate, 1,4-cyclohexylene diisocyanate, hydrogenated xylylene diisocyanate, isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, 3,3'-dimethyl-4,4'-dicyclohexylmethane diisocyanate, etc. Aliphatic isocyanate having a cyclic structure of 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, m-phenylene dii Cyanate, p-phenylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 2,2'-diphenylmethane diisocyanate, 3,3'-dimethyl-4,4'-biphenylene diisocyanate, 3,3 ' -Dimethoxy-4,4'-biphenylene diisocyanate, 3,3'-dichloro-4,4'-biphenylene diisocyanate, 1,5-naphthalene diisocyanate, 1,5-tetrahydronaphthalene diisocyanate, xylylene diisocyanate, tetramethylxylylene diisocyanate Aromatic isocyanates such as One of these may be used alone, or two or more thereof may be used in combination.

  As the polyether polyol, a cyclic ether compound such as ethylene oxide, propylene oxide, butylene oxide, styrene oxide, tetrahydrofuran, or epichlorohydrin may be used alone or 2 by using a compound having an active hydrogen atom as a catalyst. A polymer obtained by, for example, mixing ring-opening polymerization by mixing more than one species. Specific examples include polyethylene glycol, polypropylene glycol, and polytetramethylene glycol. These may be used alone or in combination of two or more.

  Examples of the polycarbonate polyol include 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, diethylene glycol, polyethylene glycol, polypropylene glycol, or diols such as polytetramethylene glycol, phosgene, Examples thereof include a reaction product with a dialkyl carbonate such as dimethyl carbonate or a cyclic carbonate such as ethylene carbonate. These may be used alone or in combination of two or more.

  In order to make the polyurethane resin anionic, for example, a monomer having a carboxyl group or a sulfone group may be introduced. Examples of such monomers include monohydroxycarboxylic acids such as lactic acid; dihydroxycarboxylic acids such as α, α-dimethylolacetic acid, α, α-dimethylolpropionic acid, α, α-dimethylolbutyric acid, and 3,4-diaminobutanesulfone. Examples include acids and diaminosulfonic acids such as 3,6-diamino-2-toluenesulfonic acid.

  Generally, as a property of the polyurethane resin, the main chains of the polyurethane resin are loosely bonded by hydrogen bonds, so that a flexible and tough film structure can be formed. By using the polyurethane resin, in order to form a flexible film structure while spreading on the recording medium while maintaining fluidity at a temperature (10 ° C. to 40 ° C.) at which normal inkjet printing is performed, Friction improves. In addition, since a medium generally used for printing (for example, an inkjet recording sheet “OHP sheet” manufactured by Seiko Epson Corporation) is often positively charged, anionic urethane is used as an ink fixing resin. Thus, adhesion is improved by electrostatic interaction. In addition, since the polyether-based or polycarbonate-based polyurethane resin easily forms a highly flexible film as compared with a polyester-based polyurethane resin or the like, the abrasion resistance is improved. In addition, polyether-based or polycarbonate-based polyurethane resins are preferable for use in water-based inks because they have the property of not easily deteriorating against water.

  The glass transition temperature (Tg) of the polyurethane resin is preferably 50 ° C. or lower, more preferably 0 ° C. or lower, and particularly preferably −10 ° C. or lower. Although the detailed reason is not clear, in order to form an image while a polyurethane resin having a glass transition temperature of 50 ° C. or lower spreads on the recording medium, the metal compound as a color material is more firmly fixed on the recording medium. be able to. Thereby, an image having excellent abrasion resistance can be obtained. In particular, by setting the glass transition temperature of the polyurethane resin to 0 ° C. or less, intermittent printing characteristics can be remarkably improved and nozzle omission during ink jet recording can be suppressed.

  The ink of this embodiment using a polycarbonate-based or polyether-based anionic polyurethane resin as the polyurethane resin is formed into a film on the surface as it dries, and has a highly flexible film compared to a urethane resin such as polyester. Can be formed.

  As the polyurethane resin in the present embodiment, any of an emulsion type dispersed in a solvent and a solution type existing in a dissolved state in the solvent may be used. The emulsion type can be classified into a forced emulsification type and a self-emulsification type depending on the emulsification method, and any type can be used in this embodiment, but the self-emulsification type is preferred. Since the self-emulsification type dispersion is superior to the forced emulsification type in terms of film forming property and water resistance, it forms a water-resistant film on the surface.

  Examples of the polyurethane resin used in this embodiment include forced emulsification type polyurethane emulsions such as “Takelac (registered trademark) W-6061” (manufactured by Mitsui Chemicals), “Resamine D (registered trademark) D-1060” (large Nissei Kasei Co., Ltd.), “Takelac W-6021” (manufactured by Mitsui Chemicals), “WBR-016U” (polyether manufactured by Taisei Fine Chemical Co., Ltd., Tg = 20 ° C.) and the like. .

  When the above emulsion type is applied as the polyurethane resin, the average particle size of the polyurethane resin is preferably 50 to 200 nm, more preferably 60 to 200 nm. When the average particle diameter of the polyurethane resin is in the above range, the polyurethane resin particles can be uniformly dispersed in the ink.

  According to the ink set of the present embodiment, the mass ratio of the second polyurethane resin to the first polyurethane resin is 2 to 4. By setting it within the above range, an image having excellent fixability can be formed.

  The content (solid content) of the polyurethane resin is not particularly limited as long as the above relationship is satisfied, and is, for example, 1.0 to 10% by mass with respect to the total mass of each ink. The preferred content is 1.0 to 5.0% by mass for the first polyurethane resin and 2 to 10% by mass for the second polyurethane resin. More preferable content is 1.5 to 4.5 mass% for the first polyurethane resin, and 3 to 9 mass% for the second polyurethane resin. By setting it within the above range, an image having excellent fixability can be formed.

  The content mass ratio of the polyurethane resin to the polymer fine particles is not particularly limited as long as the effect of the present embodiment is exhibited. In the color ink, for example, the mass ratio of the first polyurethane resin to the first polymer fine particles is preferably 0.5 to 3.0, and more preferably 1.0 to 2.0. In the clear ink, for example, the mass ratio of the second polyurethane resin to the second polymer fine particles is preferably 0.5 to 5.0, and more preferably 2.0 to 4.0. By setting it within the above range, an image having excellent fixability can be formed.

(Slightly water-soluble alkanediol)
The ink according to the present embodiment contains poorly water-soluble alkanediol.

  According to a preferred aspect of this embodiment, the poorly water-soluble alkanediol is a one-terminal alkanediol. Moreover, according to the preferable aspect of this embodiment, the slightly water-soluble alkanediol is preferably an alkanediol having 7 or more carbon atoms, more preferably an alkanediol having 7 to 10 carbon atoms. More preferably, it is a poorly water-soluble 1,2-alkanediol and can suppress beading more effectively. Examples of the slightly water-soluble 1,2-alkanediol include 1,2-heptanediol, 1,2-octanediol, 5-methyl-1,2-hexanediol, and 4-methyl-1,2-hexanediol. Or 4,4-dimethyl-1,2-pentanediol. Among these, 1,2-octanediol is more preferable.

  The slightly water-soluble alkanediol is preferably contained in an amount of 1.0 to 4.0% by mass, more preferably 2.0 to 4.0% by mass, based on the entire ink. In view of preventing printing unevenness in a recording medium having low ink absorbency such as printing paper, that the content of the hardly water-soluble alkanediol in the ink is within the above range, and is not particularly lower than the lower limit. To preferred. On the other hand, when the upper limit is not exceeded, it is possible to prevent the slightly water-soluble alkanediol from being completely dissolved in the ink.

(Water-soluble alcohol)
The ink according to the present embodiment includes a specific water-soluble alcohol. The specific water-soluble alcohol according to the present embodiment is used as a solubilizing agent for dissolving the hardly water-soluble alkanediol. The solubilizer is, for example, 10 g of a mixture composed of 10% by mass of 1.2-octanediol and 90% by mass of pure water in an incompatible state such as aggregation or two-phase separation at 20 ° C. In addition, 10 g or less of the water-soluble alcohol can be converted into a transparent solution or a colloidal dispersion state by post-addition. Therefore, even if it is a water-soluble alcohol, glycerol does not correspond, for example.

  Although it does not specifically limit as said water-soluble alcohol as long as there exists an effect of this embodiment, C6 or less alkanediol, alkanetriol, and alkylene glycol are mentioned. Specific examples include 1,2,6-hexanetriol, 3-methyl-1,5-pentanetriol, 3-methyl-1,3-butanediol, 3-methyl-1,5-pentanediol, and dipropylene glycol. , 1,2-hexanediol, and one or more selected from the group consisting of 4-methyl-1,2-pentanediol.

  The water-soluble alcohol is preferably contained in an amount of 4.0 to 20.0% by mass, more preferably 7.0 to 12.0% by mass, and still more preferably 4.0 to 0.02% by mass with respect to the entire ink. 10.0% by mass. It is preferable that the content of the water-soluble alcohol in the ink is within the above range, and that it is not particularly lower than the lower limit from the viewpoint of dissolving the slightly water-soluble alkanediol in the ink. On the other hand, it is preferable that the upper limit is not exceeded from the viewpoint of the initial viscosity of the ink. Further, in various recording media, particularly non-water-absorbing or low-water-absorbing recording media such as synthetic paper and printing paper, the fixability is further improved. An excellent recorded material can be obtained.

  The content ratio of the slightly water-soluble alkanediol to the water-soluble alcohol is preferably 1: 1 to 1:20, more preferably 1: 1 to 1: 6. By setting it within this range, the slightly water-soluble alkanediol can be stably dissolved in the ink, and the ejection stability is improved. On the other hand, when the ratio of the water-soluble alcohol is in the above range, it is preferable that the upper limit is not particularly exceeded from the viewpoint of coexistence of the reduction of the initial ink viscosity and the reduction of the aggregation spots. In addition, it is preferable that the ratio of the water-soluble alcohol is within the above range, and that it is not particularly less than the lower limit from the viewpoint of stably dissolving the hardly water-soluble alkanediol in the ink, and the viscosity change during the course It is also preferable from the viewpoint of suppression and maintenance of storage stability.

(Surfactant)
The ink according to this embodiment preferably further contains a surfactant. Glossy recording media such as photographic paper, where glossiness is more important by using a surfactant, compared to a recording medium coated with a resin for receiving ink on the surface. Can be realized. In particular, even when a recording medium having a coating layer for receiving oil-based ink is provided on the surface receiving layer, such as printing paper, bleeding between colors (bleeding) can be prevented. At the same time, it is possible to prevent whitening due to reflected light of light generated with an increase in the amount of ink attached. In addition, when adding the surfactant to the ink of this embodiment, it is preferable to pay attention so that the dynamic surface tension is 26 mN / m or less. The dynamic surface tension can be measured using, for example, a bubble pressure dynamic surface tension meter BP2 (manufactured by KRUS).

  As the surfactant used in the present embodiment, an organopolysiloxane-based surfactant can be suitably used, and when forming a recorded image, the wettability to the surface of the recording medium is increased to increase the ink permeability. Can do. When an organopolysiloxane-based surfactant is used, it contains two types of alcohol solvents as described above, so that the solubility of the surfactant in the ink is improved and the generation of insoluble matters can be suppressed. It is possible to realize an ink having more excellent ejection stability.

  Commercially available surfactants such as those described above may be used. For example, Olfin PD-501 (manufactured by Nissin Chemical Industry Co., Ltd.), Olphine PD-570 (manufactured by Nissin Chemical Industry Co., Ltd.), BYK. -347 (made by Big Chemie Co., Ltd.), BYK-348 (made by Big Chemie Co., Ltd.), etc. can be used.

  In addition, as the organopolysiloxane surfactant, one or more compounds represented by the following formula (I) are included, or in the compound of the following formula (I), R represents a hydrogen atom or methyl A represents an integer of 2 to 11, m represents an integer of 2 to 50, and n preferably includes one or more compounds which are integers of 1 to 5, or In the compound of the following formula (I), R is a hydrogen atom or a methyl group, a is an integer of 2 to 13, m is an integer of 2 to 50, and n is an integer of 1 to 5 or More preferably, it comprises two or more compounds.

（式中、Ｒは水素原子またはメチル基を表し、ａは２〜１３の整数を表し、ｍは２〜７０の整数を表し、ｎは１〜８の整数を表す。）

(In the formula, R represents a hydrogen atom or a methyl group, a represents an integer of 2 to 13, m represents an integer of 2 to 70, and n represents an integer of 1 to 8.)

  In the compound of the above formula (I), R is a hydrogen atom or a methyl group, a is an integer of 2 to 13, m is an integer of 2 to 50, and n is an integer of 1 to 8. More preferably, it comprises one or more compounds. Alternatively, in the compound of the above formula (I), R is a methyl group, a is an integer of 6 to 18, m is 0 to 4, and n is 1 or 2, one or two or more compounds Or R is a methyl group, a is an integer of 6 to 18, m is 0, and n is 1 or 2 or more compounds. It is more preferable. By using such a specific organopolysiloxane surfactant, unevenness of ink aggregation is further improved even when printing on a printing paper as a recording medium.

  In the compound of the above formula (I), a is an integer of 2 to 5, m is an integer of 20 to 40, n is an integer of 2 to 4, and a is an integer of 7 to 11. M is an integer of 30 to 50, n is an integer of 3 to 5, a is an integer of 9 to 13, m is an integer of 2 to 4, and n is an integer of 1 to 2 It is more preferable to use a certain compound or a compound in which a is an integer of 6 to 10, m is an integer of 10 to 20, and n is an integer of 4 to 8. By using such a compound, the unevenness of ink aggregation can be further improved.

  In the compound of the above formula (I), R is a hydrogen atom, a is an integer of 2 to 5, m is an integer of 20 to 40, and n is an integer of 2 to 4, Alternatively, it is more preferable to use a compound in which a is an integer of 7 to 11, m is an integer of 30 to 50, and n is an integer of 3 to 5. By using such a compound, it is possible to further improve the uneven aggregation and bleeding of the ink.

  In the compound of the above formula (I), R is a methyl group, a is an integer of 9 to 13, m is an integer of 2 to 4, and n is an integer of 1 to 2, Alternatively, it is more preferable to use a compound in which a is an integer of 6 to 10, m is an integer of 10 to 20, and n is an integer of 4 to 8. By using such a compound, it is possible to further improve the uneven aggregation and bleeding of the ink.

  Furthermore, in the compound of the above formula (I), it is more preferable to use a compound in which R is a methyl group, a is an integer of 6 to 12, m is 0, and n is 1. By using such a compound, it is possible to further improve the uneven aggregation and bleeding of the ink.

  Moreover, in the compound of the said formula (I), R is a hydrogen atom, a is an integer of 7-11, m is an integer of 30-50, n is an integer of 3-5, , R is a methyl group, a is an integer of 9 to 13, m is an integer of 2 to 4, n is an integer of 1 to 2, R is a methyl group, and a is 6 It is most preferable to use a mixture of a compound having an integer of 10 to 10, m being an integer of 10 to 20, and n being an integer of 4 to 8. By using such a compound, it is possible to further improve the uneven aggregation and bleeding of the ink.

  Furthermore, in the above formula (I), R is a hydrogen atom, a is an integer of 7 to 11, m is an integer of 30 to 50, and n is an integer of 3 to 5, A compound in which R is a methyl group, a is an integer of 9 to 13, m is an integer of 2 to 4, n is an integer of 1 to 2, R is a methyl group, and a is 6 to It is most preferable to use a mixture of a compound having an integer of 18, m is 0, and n is 1. By using such a compound, it is possible to further improve the uneven aggregation and bleeding of the ink.

  The polyorganosiloxane surfactant is not particularly limited, but 20% by mass of glycerin, 10% by mass of 1,2-hexanediol, 0.1% by mass of the polyorganosiloxane surfactant, and water. In the case where the ink contains 69.9% by mass, it is preferable to use an ink whose 1 Hz dynamic surface tension is 26 mN / m or less. The dynamic surface tension can be measured using, for example, a bubble pressure dynamic surface tension meter BP2 (manufactured by KRUS).

  The surfactant is preferably contained in the ink according to the present embodiment in an amount of 0.01 to 1.0% by mass, more preferably 0.05 to 0.50% by mass. In addition, when the surfactant in which R is a methyl group and the surfactant in which R is a hydrogen atom are used in combination, when ink droplets adhere to the recording medium, the blurring of the dot shape is suppressed. Therefore, it is more preferable. In particular, in the case of using the surfactant in which R is a methyl group, the content may be larger than in the case of using the surfactant in which R is H, from the viewpoint of ink aggregation spots. preferable.

  Furthermore, it is more preferable that the content of the surfactant in which R is H is increased with respect to the surfactant in which R is a methyl group. By doing in this way, ink aggregation spots and bleeding can be improved even in printing main paper such as cast-coated paper, which is easy to repel ink and has a low permeation rate.

  The ink according to the present embodiment may further contain other surfactants, specifically, acetylene glycol surfactants, anionic surfactants, nonionic surfactants, amphoteric surfactants, and the like.

  Among these, acetylene glycol surfactants include, for example, 2,4,7,9-tetramethyl-5-decyne-4,7-diol, 3,6-dimethyl-4-octyne-3,6- Diol, or 3,5-dimethyl-1-hexyn-3ol, 2,4-dimethyl-5-hexyn-3-ol and the like can be mentioned. Commercially available acetylene glycol surfactants can also be used. For example, Olphine E1010, STG, Y (trade name, manufactured by Nissin Chemical Co., Ltd.), Surfynol 61, 104, 82, 465, 485 or TG (Trade name, manufactured by Air Products and Chemicals Inc.).

(Water, other ingredients)
The ink according to the present embodiment contains the above-described specific alcohol solvent and other various additives, and contains water as a solvent. It is preferable to use pure water or ultrapure water such as ion exchange water, ultrafiltration water, reverse osmosis water, or distilled water. In particular, water obtained by sterilizing these waters by ultraviolet irradiation or addition of hydrogen peroxide is preferable because generation of mold and bacteria is prevented for a long period of time.

  In addition, the ink according to the present embodiment preferably contains a penetrating solvent in addition to the above components.

  In the present specification, the penetrating solvent means a penetrating solvent used in ordinary ink jet recording ink, and examples thereof include glycol ethers.

  Specific examples of glycol ethers include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol mono-iso-propyl ether, ethylene glycol mono-n-butyl ether, ethylene glycol mono-iso-butyl ether, ethylene glycol mono-tert -Butyl ether, ethylene glycol monomethyl ether acetate, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono-n-propyl ether, diethylene glycol mono-iso-propyl ether, diethylene glycol mono-n-butyl ether, diethylene glycol mono-tert-butyl ether, triethylene Glycol mono-n-bu Ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol mono-n-propyl ether, propylene glycol mono-iso-propyl ether, propylene glycol mono-n-butyl ether, propylene glycol mono-tert-butyl ether, dipropylene glycol Monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol mono-n-propyl ether, dipropylene glycol-iso-propyl ether, dipropylene glycol mono-n-butyl ether, dipropylene glycol mono-tert-butyl ether, 1-methyl -1-methoxybutanol and the like, and one or a mixture of two or more thereof. It can be used.

  Among the glycol ethers, alkyl ethers of polyhydric alcohols are preferable, and ethylene glycol monoethyl ether, ethylene glycol mono-n-butyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono-n-butyl ether, triethylene glycol are particularly preferable. Monomethyl ether, triethylene glycol monoethyl ether or triethylene glycol mono-n-butyl ether is preferred. More preferred is triethylene glycol mono-n-butyl ether.

  Although the addition amount of the osmotic solvent may be appropriately determined, it is preferably about 0.1 to 30% by mass, more preferably about 1 to 20% by mass.

  The ink according to the present embodiment may contain a recording medium solubilizer in addition to the above components.

  As the recording medium solubilizer, pyrrolidones such as N-methyl-2-pyrrolidone can be preferably used. The addition amount of the recording medium solubilizer may be appropriately determined, but is preferably about 0.1 to 30% by mass, more preferably about 1 to 20% by mass.

  Further, it is preferable that the ink according to the present embodiment does not substantially contain a wetting agent. The wetting agent has a function to prevent the ink from drying and solidifying in an inkjet nozzle or the like, so when the ink is dropped on synthetic paper having a low ink absorption performance of the film, the ink does not dry and high-speed printing is performed. May cause problems. In addition, when ink containing a wetting agent is used, the next ink adheres to the recording medium in a state where unabsorbed ink exists on the surface of the recording medium, so that aggregation spots may occur.

  Therefore, in the present embodiment, when using such a recording medium with low ink absorption performance, it is preferable that the wetting agent is not substantially contained. Even when the ink is dried and solidified in the inkjet nozzle, the solidified ink can be redissolved by applying a solution containing a wetting agent.

  In particular, when applied to synthetic paper or the like having low ink absorbability, it is preferable that the wetting agent in a liquid state at 20 ° C. is not substantially contained.

  In the present specification, the wetting agent means a wetting agent used in ordinary ink jet recording inks. Specifically, glycerin, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, 1,3-propane. Water-soluble alkane diols having 3 to 5 carbon atoms such as diol, 3-methyl-1,3-butanediol, 1,3-butanediol, 1,2-pentanediol, trimethylolpropane, trimethylolmethane, Such as methylolethane. Among these, glycerin is preferable from the viewpoint of the influence on the 10 Hz surface tension. Further, “substantially free” means that the addition amount of these wetting agents is less than 1% by mass with respect to the ink. In addition, although it is clear for those skilled in the art that a part of the above-described penetrating solvent also acts as a wetting agent, in the present specification, the above-described penetrating solvent is not included in the wetting agent. .

  The ink according to the present embodiment further includes an anti-clogging agent for nozzles, an antiseptic, an antifungal agent, an antioxidant, a conductivity adjusting agent, a pH adjusting agent, a viscosity adjusting agent, a surface tension adjusting agent, an oxygen absorber, and the like. can do.

(Pigment)
The color ink according to the ink set of the present embodiment includes a pigment. The pigment is not particularly limited, and can be appropriately selected according to color inks such as cyan ink, magenta ink, yellow ink, and black ink.

  Examples of the pigment contained in the cyan ink include C.I. I. Pigment Blue 1, 2, 3, 15: 3, 15: 4, 15:34, 16, 22, 60; I. Bat Blue 4, 60 etc. are mentioned, and one or more of these are used. Of these, C.I. I. Pigment Blue 15: 3 and / or 15: 4 are preferably used, especially C.I. I. By using CI Pigment Blue 15: 3, it is possible to realize an image with a better hue.

  Examples of pigments contained in magenta ink include C.I. I. Pigment Red 5, 7, 12, 48 (Ca), 48 (Mn), 57 (Ca), 57: 1, 112, 122, 123, 168, 184, 202, 209; I. Pigment violet 19 and the like, and one or more of these may be used. Of these, C.I. I. Pigment red 122, 202, 209, and C.I. I. It is preferable to use one or more selected from the group consisting of CI Pigment Violet 19. In particular, γ-type C.I. I. Pigment violet 19 and C.I. I. By using a solid solution of Pigment Red 202 as a pigment, an image with a better hue can be realized.

  Examples of the pigment contained in the yellow ink include C.I. I. Pigment Yellow 1, 2, 3, 12, 14, 16, 17, 73, 74, 75, 83, 93, 95, 97, 98, 109, 110, 114, 128, 129, 138, 139, 147, 150, 151, 154, 155, 180, 185 and the like, and one or more of these are used. Of these, C.I. I. It is preferable to use one or more selected from the group consisting of CI Pigment Yellow 74, 110, 128, 129, and 147. In particular, C.I. I. By using a mixture of Pigment Yellow 74 and 129, an image with a better hue can be realized.

  Examples of the pigment contained in the black ink include lamp black (CI pigment black 6), acetylene black, furnace black (CI pigment black 7), channel black (CI pigment black 7), Carbons such as carbon black (CI pigment black 7), inorganic pigments such as iron oxide pigments; organic pigments such as aniline black (CI pigment black 1), etc. Carbon black is preferably used. Specifically, as carbon black, # 2650, # 2600, # 2300, # 2200, # 1000, # 980, # 970, # 966, # 960, # 950, # 900, # 850, MCF-88, # 55, # 52, # 47, # 45, # 45L, # 44, # 33, # 32, # 30 (above, manufactured by Mitsubishi Chemical Corporation), SpecialBlaek4A, 550, Printex95, 90, 85, 80, 75 , 45, 40 (above, manufactured by Degussa), Regal660, RmogulL, monarch1400, 1300, 1100, 800, 900 (above, manufactured by Cabot), Raven7000, 5750, 5250, 3500, 3500, 2500 ULTRA, 2000, 1500, 1255 , 1200, 1190 ULTRA, 1170, 1100 ULTRA, Raven5000UIII (above, manufactured by Columbian) and the like. Of these, C.I. I. Pigment black 6 and / or C.I. I. By using CI Pigment Black 7, it is possible to realize an image with a better hue.

  The pigment solid content concentration of the color ink according to the ink set of the present embodiment is not particularly limited, but is preferably 1 to 10% by mass from the viewpoint of ensuring color developability in a recorded image.

  The color ink according to the ink set of the present embodiment can include a dispersant for dispersing the pigment. Although a dispersing agent is not specifically limited, For example, a copolymer resin can be mentioned preferably. These copolymer resins are adsorbed on the pigment to improve dispersibility.

  Specific examples of the hydrophobic monomer in the copolymer resin include, for example, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, n-propyl acrylate, n-propyl methacrylate, iso-propyl acrylate, iso-propyl methacrylate, n- Butyl acrylate, n-butyl methacrylate, sec-butyl acrylate, sec-butyl methacrylate, tert-butyl acrylate, tert-butyl methacrylate, n-hexyl acrylate, n-hexyl methacrylate, n-octyl acrylate, n-octyl methacrylate, iso- Octyl acrylate, iso-octyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, Sil acrylate, decyl methacrylate, lauryl acrylate, lauryl methacrylate, stearyl acrylate, stearyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, 2-dimethylaminoethyl acrylate, 2 -Dimethylaminoethyl methacrylate, 2-diethylaminoethyl acrylate, 2-diethylaminoethyl methacrylate, glycidyl acrylate, glycidyl methacrylate, allyl acrylate, allyl methacrylate, cyclohexyl acrylate, cyclohexyl methacrylate, phenyl acrylate, phenyl methacrylate, nonyl phenyl acrylate, noni Phenyl methacrylate, benzyl acrylate, benzyl methacrylate, dicyclopentenyl acrylate, dicyclopentenyl methacrylate, bornyl acrylate, bornyl methacrylate, 1,3-butanediol diacrylate, 1,3-butanediol dimethacrylate, 1,4-butane Diol diacrylate, 1,4-butanediol dimethacrylate, ethylene glycol diacrylate, ethylene glycol dimethacrylate, diethylene glycol diacrylate, diethylene glycol dimethacrylate, triethylene glycol diacrylate, triethylene glycol dimethacrylate, tetraethylene glycol diacrylate, tetra Ethylene glycol dimethacrylate, polyethylene glycol di Acrylate, polyethylene glycol dimethacrylate, neopentyl glycol diacrylate, 1,6-hexanediol diacrylate, 1,6-hexanediol dimethacrylate, dipropylene glycol diacrylate, dipropylene glycol dimethacrylate, trimethylolpropane triacrylate, trimethylol Mention may be made of methylolpropane trimethacrylate, glycerol acrylate, glycerol methacrylate, styrene, methylstyrene, vinyltoluene and the like. You may use these individually or in mixture of 2 or more types.

  Specific examples of the hydrophilic monomer include acrylic acid, methacrylic acid, maleic acid, itaconic acid and the like.

  The copolymer resin of the hydrophobic monomer and the hydrophilic monomer is styrene from the viewpoint of achieving both color image glossiness, bronzing prevention, and ink storage stability and forming a color image having further glossiness. -(Meth) acrylic acid copolymer resin, styrene-methylstyrene- (meth) acrylic acid copolymer resin, or styrene-maleic acid copolymer resin, (meth) acrylic acid- (meth) acrylic acid ester copolymer resin, or It is preferably at least one of styrene- (meth) acrylic acid- (meth) acrylic ester copolymer resin.

  The copolymer resin may be a resin (styrene-acrylic acid resin) containing a polymer obtained by reacting styrene with acrylic acid or an ester of acrylic acid. Alternatively, the copolymer resin may be an acrylic acid-based water-soluble resin. Alternatively, a salt such as sodium, potassium, or ammonium may be used.

  The content of these copolymer resins is based on 100 parts by mass of the pigment from the viewpoint of achieving a color image having glossiness, prevention of bronzing, and storage stability of the ink and forming a color image having further excellent glossiness. The amount is preferably 10 to 50 parts by mass, and more preferably 10 to 35 parts by mass.

  A surfactant may be used as the dispersant. Such surfactants include fatty acid salts, higher alkyl dicarboxylates, higher alcohol sulfates, higher alkyl sulfonates, condensates of higher fatty acids and amino acids, sulfosuccinate esters, naphthenates, liquid fats. Anionic surfactants such as oil sulfate esters and alkyl allyl sulfonates; Cationic surfactants such as fatty acid amine salts, quaternary ammonium salts, sulfonium salts and phosphoniums; polyoxyethylene alkyl ethers and polyoxyethylene alkyls Nonionic surfactants such as esters, sorbitan alkyl esters, polyoxyethylene sorbitan alkyl esters and the like can be mentioned. It goes without saying that the above-described surfactant is also added to the ink so as to function as a surfactant.

(Inkjet recording method)
The inkjet recording method according to the present embodiment performs printing by using at least the above clear ink and the above color ink as an ink set, ejecting ink droplets, and attaching the droplets to a recording medium. Can do.

  Hereinafter, as an aspect of the ink jet recording method of the present embodiment, a case where the color ink is a cyan ink, a magenta ink, a yellow ink, and a black ink will be described as an example.

  The order of attachment of the ink droplets to the recording medium is that the yellow ink, magenta ink, cyan ink, or black ink droplet is adhered to the recording medium, and then the clear ink droplet is adhered to the recording medium. Conversely, after the droplets of clear ink are attached to the recording medium, any one of the droplets of yellow ink, magenta ink, cyan ink, or black ink may be attached to the recording medium. Further, the droplets of any one of yellow ink, magenta ink, cyan ink, and black ink and the clear ink droplet may be attached to the recording medium substantially simultaneously.

  Among these attachment orders, either a yellow ink, a magenta ink, a cyan ink, or a black ink droplet is attached to the recording medium, and then a clear ink droplet is attached to the recording medium, or the yellow ink The droplets of any one of magenta ink, cyan ink, or black ink and the clear ink droplet are preferably attached to the recording medium substantially simultaneously. More preferably, it is preferable that a droplet of any one of yellow ink, magenta ink, cyan ink, or black ink is attached to the recording medium, and then a clear ink droplet is attached to the recording medium. Here, “substantially simultaneous” means printing in the same drive from different nozzle rows in the same head of the printer.

  In the recording method according to the present embodiment, it is preferable to use synthetic paper or main printing paper as a recording medium, and in particular, art paper, high-quality paper used for POD (print on demand) and dedicated paper for laser printers, Even when printed at a low resolution, a high-quality image without white streaks or roughness can be realized. Examples of the high-quality paper for POD use include Ricoh Business Coat Gloss 100 (manufactured by Ricoh Co., Ltd.). Examples of the dedicated paper for the laser printer include LPCCTA4 (manufactured by Seiko Epson Corporation).

  EXAMPLES Hereinafter, although an Example is described in detail, this invention is not limited by these Examples.

<Ink>
Each ink set was prepared by mixing each component according to the composition of following Table 1 and Table 2, and filtering with a 10 micrometer membrane filter (Examples 1-6, Comparative Examples 1-6). The numerical values in Table 1 and Table 2 below represent the content (% by mass) in the ink.

The composition components in Tables 1 and 2 are as follows.
The styrene-acrylic resin is a copolymer having a molecular weight of 1600 and an acid value of 150.
As AQUACER 515, polyethylene wax having a particle size of 100 to 200 nm, a melting point of 130 ° C., and a solid content of 30% was used.
The sulfonate resin was prepared as described below.
As Chemipearl W4005, a product made by Mitsui Chemicals Co., Ltd. having a polyethylene wax, a particle size of 200 nm to 800 nm, a ring and ball method softening point of 110 ° C., a penetration method hardness of 3 and a solid content of 40% was used.
Resamine D-1060 was a self-emulsifying polyurethane emulsion, manufactured by Dainichi Seika Co., Ltd., having a solid content of 40%.
Orphine E1010 was manufactured by Nissin Chemical Industry Co., Ltd.

  The surfactant X in the table is an organopolysiloxane surfactant, and in the above formula (I), R is a hydrogen atom, a is an integer of 7 to 11, and m is 30 to 30. It is a surfactant composed of a compound having an integer of 50 and n being an integer of 3 to 5.

  Surfactant Y is an organopolysiloxane surfactant. In the above formula (I), R is a methyl group, a is an integer of 9 to 13, and m is an integer of 2 to 4. And n is a surfactant comprising a compound having an integer of 1 to 2.

  Surfactant Z is an organopolysiloxane surfactant. In the above formula (I), R is a methyl group, a is an integer of 6 to 18, m is 0, n Is a surfactant composed of a compound wherein

(Preparation of sulfonate resin)
The following components were charged into a 2 liter beaker and stirred at 100 rpm for 10 minutes to obtain a monomer emulsion.
Ethylenically unsaturated monomer: 348 g (58 parts) of methyl methacrylate
240 g (40 parts) of butyl acrylate
Acrylic acid 12g (2 parts)
Reactive emulsifier: 15% aqueous solution of Aqualon KH-10 30g
(Daiichi Kogyo Seiyaku Co., Ltd., containing sulfate ester group and polyoxyethylene group)
Chain transfer agent: 6 g of 2-ethylhexyl thioglycolate
Water: 450g

  Next, 520 g of water and 90 g of a 15% aqueous solution of the same reactive emulsifier as above are charged into a 2 L separable flask, heated to 60 ° C. while stirring at 180 rpm, charged with 2 g of ammonium persulfate and heated to 70 ° C. did.

  In this reactive emulsifier aqueous solution, the monomer emulsion obtained above was sequentially added for 3 hours while maintaining the polymerization temperature of 75 ° C. to carry out emulsion polymerization. Thereafter, the polymerization solution was heated to 80 ° C. and aged for 1 hour, and then cooled. Subsequently, 10% ammonia aqueous solution was added to the polymerization solution for neutralization, and the pH was adjusted to 7.3.

When the average particle diameter film-forming temperature and the weight average molecular weight (Mw) of the obtained sulfonic acid ester resin were measured, the average particle diameter was 50 nm, the film-forming temperature was 15 ° C., and Mw = 45,000. there were. The average particle diameter was measured using Photo PAR-III (manufactured by Otsuka Electronics Co., Ltd.), and the film forming temperature was measured using a film forming temperature tester (manufactured by Rigaku Corporation). The weight average molecular weight was measured using a GPC apparatus (SC8010 (GPC), manufactured by Tosoh Corporation) using standard polystyrene as a calibration curve. The measurement conditions were as follows.
・ Eluent: Tetrahydrofuran ・ Column: G4000HXL (manufactured by Tosoh Corporation)
・ Flow rate: 1000 μL / min ・ Column temperature: 40 ° C.

<Evaluation>
1. Ink fixability (rub resistance)
Two ink cartridges of an inkjet printer (PX-G930, manufactured by Seiko Epson Corporation) are filled with cyan ink (Examples 1 to 6, Comparative Examples 1 to 6), and the leftmost column (to the paper discharge side of the printer ( The yellow ink cartridge is mounted on a commercial product) and the right adjacent column (magenta ink cartridge mounted position on a commercial product). The clear ink (Examples 1 to 6 and Comparative Examples 1 to 6) is filled in two ink cartridges, and the third row from the left toward the paper discharge side of the printer (in the commercial product, the cyan ink cartridge is installed). Position) and the right next row (in the commercial product, mat black ink cartridge mounting position).

1-1. Continuous printing 3.6 mg / inch ² with a resolution of 720 x 720 dpi and a dot weight of 7 ng using cyan ink on OK Top Coat Plus (made by Oji Paper) or Ulite (made by Nippon Paper Industries). Within 1 minute, the solid ink was continuously coated on the cyan solid recording material by overcoating the clear ink with a resolution of 720 × 720 dpi, 1.0 mg / inch ² with a dot weight of 3 ng and at room temperature. Allowed to dry. The test was intermittently carried out with a load of 500 g × 10 times using a Gakushin type friction fastness tester (AB-301 COLOR FASTNESS RUBING TESTER, manufactured by TESTER SANGYO, LTD.) While being allowed to dry at room temperature. An image of the tester friction paper (OK Topcoat Plus) was captured with a scanner, the image was binarized with Photoshop (registered trademark), and the transfer area ratio was calculated.

1-2. Simultaneous printing Cyan ink and clear ink were simultaneously printed at a resolution of 720 × 720 dpi and a dot weight of 7 ng on OK Top Coat Plus (manufactured by Oji Paper) or Ulite (manufactured by Nippon Paper Industries). At this time, a recording image file is created so that the ink adhesion amount of cyan ink is 3.6 mg / inch ² and the ink adhesion amount of clear ink is 1.0 mg / inch ² , and is adjusted according to the head driving. Printed at the same time. Thereafter, the test was intermittently carried out with a load of 500 g × 10 times using a Gakushin type friction fastness tester (manufactured by AB-301 COLOR FASTNESS RUBING TESTER, TESTER SANGYO., LTD) while being allowed to stand and dry at room temperature. An image was taken with a scanner for the friction paper (OK Topcoat Plus) of the test machine, and the image was binarized with Photoshop to calculate the transfer area ratio.

Using the constant transfer area ratio obtained in the above “1-1. Continuous printing” and “1-2. Simultaneous printing”, ink fixability was evaluated according to the following evaluation criteria.
Evaluation criteria S: Transfer area ratio to friction paper is less than 30%.
A: The transfer area ratio to the friction paper is 30% or more and less than 50%.
B: The transfer area ratio to the friction paper is 50% or more and less than 80%.
C: Transfer area ratio to friction paper is 80% or more and less than 95%.
D: The transfer area ratio to the friction paper is 95% or more.

  The evaluation results are shown in Tables 3 and 4 below. In Table 4, “Continuous printing” “Clear ink present” represents the case where the clear ink of Example 2 was adhered within 1 minute of the cyan ink adhesion of Example 2, and “Simultaneous printing” in Table 4 “Clear ink present” represents the case where the cyan ink of Example 2 was adhered simultaneously with the attachment of the cyan ink of Example 2, and “Clear ink absent” in Table 4 represents that only the cyan ink of Example 2 was adhered. Represents the case.

2. Ink fixability (punch punching)
Two ink cartridges of an inkjet printer (PX-G930, manufactured by Seiko Epson Corporation) are filled with cyan ink (any one of Examples 1 to 6 and Comparative Examples 1 to 6), and leftmost toward the paper discharge side of the printer. (The yellow ink cartridge mounting position in the commercial product) and the right adjacent column (the magenta ink cartridge mounting position in the commercial product). Also, the clear ink (any one of Examples 1 to 6 and Comparative Examples 1 to 6) is filled in two ink cartridges, and the third column from the left toward the paper discharge side of the printer (in the commercial product, cyan) Ink cartridge mounting position) and the right adjacent column (in the commercial product, mat black ink cartridge mounting position).

2-1. Continuous printing Using a cyan ink on one side of OK Top Coat Plus (Oji Paper) or Ulite (Nippon Paper), which is the main printing paper, 3.6 mg / dot at a resolution of 720 x 720 dpi and a dot weight of 7 ng Inch ² was printed solid, and within 1 minute, on the cyan solid pattern, after clear ink was overcoated at 1.0 mg / inch ² with a resolution of 720 × 720 dpi, a dot weight of 3 ng, It was left at room temperature for 2 hours. The above operation was performed 30 times, 30 recorded materials were created, and the images of each recorded material were overlapped so that they did not contact each other (the surface with the recorded image and the surface without the recorded image were in contact with each other) Were used as evaluation samples.

  Punch of the above-mentioned evaluation sample using an office drilling machine (2-hole type, size of binding hole; diameter 5.5 to 6.5 mm) stipulated in Japanese Industrial Standards (JIS; Japan Industrial Standards) JIS S 6041 A drilling test was performed with a load of 15.0 kg. After the test, the transfer area ratio of the 15th recorded image to the 16th non-printed surface (surface without the recorded image) was evaluated. The transfer area ratio was calculated by taking an image with a scanner and binarizing the image with Photoshop.

2-2. Simultaneous printing Cyan ink and clear ink were simultaneously printed at a resolution of 720 × 720 dpi and a dot weight of 7 ng on OK Top Coat Plus (manufactured by Oji Paper) or Ulite (manufactured by Nippon Paper Industries). At this time, a recording image file is created so that the ink adhesion amount of cyan ink is 3.6 mg / inch ² and the ink adhesion amount of clear ink is 1.0 mg / inch ² , and is adjusted according to the head driving. After printing at the same time, it was left at room temperature for 2 hours. The above operation was performed 30 times, 30 recorded materials were created, and the images of each recorded material were overlapped so that they did not contact each other (the surface with the recorded image and the surface without the recorded image were in contact with each other) Were used as evaluation samples.

  Punch of the above-mentioned evaluation sample using an office drilling machine (2-hole type, size of binding hole; diameter 5.5 to 6.5 mm) stipulated in Japanese Industrial Standards (JIS; Japan Industrial Standards) JIS S 6041 A drilling test was performed with a load of 15.0 kg. After the test, the transfer area ratio of the 15th recorded image to the 16th non-printed surface (surface without the recorded image) was evaluated. The transfer area ratio was calculated by taking an image with a scanner and binarizing the image with Photoshop.

Using the transfer area ratios obtained in the above “2-1. Continuous printing” and “2-2. Simultaneous printing”, the ink fixability was evaluated according to the following evaluation criteria.
Evaluation criteria S: Transfer area ratio to non-printing surface is less than 30%.
A: The transfer area ratio to the non-printing surface is 30% or more and less than 50%.
B: The transfer area ratio to the non-printing surface is 50% or more and less than 80%.
C: The transfer area ratio to the non-printing surface is 80% or more and less than 95%.
D: The transfer area ratio to the non-printing surface is 95% or more.

  The evaluation results are shown in Table 5 below.

3. Ink fixability (recording method)
Two ink cartridges of an inkjet printer (PX-G930, manufactured by Seiko Epson) are filled with the cyan ink of Comparative Example 6, and the leftmost column toward the paper discharge side of the printer (in the commercial product, the yellow ink cartridge mounting position) ) And the right adjacent column (in the commercial product, the mounting position of the magenta ink cartridge). Further, the clear ink of Comparative Example 6 is filled in two ink cartridges, and the third column from the left (cyan ink cartridge mounting position in a commercial product) toward the printer discharge side, and the column on the right side thereof (A commercially available product has a matte black ink cartridge mounting position).

3-1. Continuous printing First, using a cyan ink on OK Top Coat Plus (made by Oji Paper) or Ulite (made by Nippon Paper Industries), which is the main printing paper, a resolution of 720 × 720 dpi, a dot weight of 7 ng, 3.6 mg / Inch ^{2 is used} for solid printing, and within 1 minute, the clear ink is applied onto the cyan solid pattern at a resolution of 720 × 720 dpi, 1.0 mg / inch ^{2 to} 2.5 mg / inch with a dot weight of ³ ng. after ² overcoat, it was allowed to stand at room temperature for 2 hours. The above operation was performed 30 times, 30 recorded materials were created, and the images of each recorded material were overlapped so that they did not contact each other (the surface with the recorded image and the surface without the recorded image were in contact with each other) Were used as evaluation samples.

  Punch of the above-mentioned evaluation sample using an office drilling machine (2-hole type, size of binding hole; diameter 5.5 to 6.5 mm) stipulated in Japanese Industrial Standards (JIS; Japan Industrial Standards) JIS S 6041 A drilling test was performed with a load of 15.0 kg. After the test, the transfer area ratio of the 15th recorded image to the 16th non-printed surface (surface without the recorded image) was evaluated. The transfer area ratio was calculated by taking an image with a scanner and binarizing the image with Photoshop.

3-2. Simultaneous printing Cyan ink and clear ink were simultaneously printed at a resolution of 720 × 720 dpi and a dot weight of 7 ng on OK Top Coat Plus (manufactured by Oji Paper) or Ulite (manufactured by Nippon Paper Industries). In this case, the ink adhesion quantity of cyan ink is 3.6 mg / inch ^2, the ink deposition amount of clear ink, creating a recorded image file to be 1.0mg / inch ² ~2.5mg / inch ² Then, after printing at the same time as the head drive, it was left at room temperature for 2 hours. The above operation was performed 30 times, 30 recorded materials were created, and the images of each recorded material were overlapped so that they did not contact each other (the surface with the recorded image and the surface without the recorded image were in contact with each other) Were used as evaluation samples.

  Punch of the above-mentioned evaluation sample using an office drilling machine (2-hole type, size of binding hole; diameter 5.5 to 6.5 mm) stipulated in Japanese Industrial Standards (JIS; Japan Industrial Standards) JIS S 6041 A drilling test was performed with a load of 15.0 kg. After the test, the transfer area ratio of the 15th recorded image to the 16th non-printed surface (surface without the recorded image) was evaluated. The transfer area ratio was calculated by taking an image with a scanner and binarizing the image with Photoshop.

Using the transfer area ratio obtained in “3-1. Continuous printing” and “3-2. Simultaneous printing”, the ink fixability was evaluated according to the following evaluation criteria.
Evaluation criteria S: Transfer area ratio to non-printing surface is less than 30%.
A: The transfer area ratio to the non-printing surface is 30% or more and less than 50%.
B: The transfer area ratio to the non-printing surface is 50% or more and less than 80%.
C: The transfer area ratio to the non-printing surface is 80% or more and less than 95%.
D: The transfer area ratio to the non-printing surface is 95% or more.

  The evaluation results are shown in Table 6 below. For the evaluation, the cyan ink and the clear ink of Comparative Example 6 were used. Note that “clear ink application amount” in Table 6 is “0” represents a case where clear ink is not attached.

  For example, the present invention includes substantially the same configuration (for example, a configuration having the same function, method, and result, or a configuration having the same purpose and effect) as the configuration described in the embodiment. In addition, the invention includes a configuration in which a non-essential part of the configuration described in the embodiment is replaced. In addition, the present invention includes a configuration that achieves the same effect as the configuration described in the embodiment or a configuration that can achieve the same object. In addition, the invention includes a configuration in which a known technique is added to the configuration described in the embodiment.

Claims (8)

An ink set for ink-jet recording comprising a color ink and a clear ink,
The color ink includes a first polyurethane resin and first polymer fine particles,
The clear ink includes a second polyurethane resin and second polymer fine particles, and
The mass ratio of the second polyurethane resin to the first polyurethane resin is 2-4,
An ink set for inkjet recording, wherein a mass ratio of the second polymer particles to the first polymer particles is 1 to 3. The total mass of the first and second polyurethane resins is 4.5 to 13.5;
The ink set for inkjet recording according to claim 1, wherein a total mass of the first and second polymer fine particles is 3 to 6.   The ink set for inkjet recording according to claim 1 or 2, wherein at least one of the first or second polymer fine particles is a polyolefin.   The ink set for inkjet recording according to any one of claims 1 to 3, wherein Tg of at least one of the first and second urethane resins is 50 ° C or lower.   The ink set for inkjet recording according to any one of claims 1 to 4, wherein the color ink and the clear ink further contain an alkanediol having 7 or more carbon atoms. The color ink and the clear ink further contain an alcohol having 6 or less carbon atoms,
The ink set for inkjet recording according to any one of claims 1 to 5, wherein the alcohol having 6 or less carbon atoms is at least one selected from the group consisting of alkanediol, alkanetriol, and alkylene glycol.   The ink set for ink jet recording according to any one of claims 1 to 6, wherein the color ink and the clear ink further contain a polyorganosiloxane surfactant. A recording method using the ink set according to claim 1,
A recording method, wherein the clear ink is adhered to the recording medium after the color ink is adhered to the recording medium.

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