JP2016196551A - Ink and inkjet recording method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink which gives a recorded matter with suppressed density unevenness when printed at a high density, and an inkjet method using the ink.SOLUTION: The ink contains a coloring material, water, a resin emulsion, an organic solvent containing 2-pyrrolidones and diols, and a silicone-based surfactant. The boiling points of the diols are 200-230°C inclusive. The ink contains, based on the total amount of the ink, 10 mass% or less of the diols, 2.0 mass% or more of the silicone-based surfactant, and 5.0 mass% or more of the resin emulsion in terms of solid content. The SP value of the silicone-based surfactant is less than 13.SELECTED DRAWING: None

Description

  The present invention relates to an ink and an inkjet recording method.

  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 obtaining a more stable and high-quality recorded matter.

  For example, Patent Document 1 discloses that an intermediate image in which density unevenness is suppressed by uniformly applying a liquid composition onto an intermediate transfer member and that the intermediate image has high transferability when high-speed recording is performed. For the purpose of providing an intermediate transfer type image recording method, a liquid composition applying step for applying a liquid composition containing a reactive agent for precipitating or aggregating a coloring material contained in an ink to an intermediate transfer member, and the liquid An image recording method comprising: an intermediate image recording step of recording an intermediate image by applying ink to at least a part of a region to which the composition is applied; and a transfer step of transferring the intermediate image to a recording medium, The contact angle of water on the surface of the intermediate transfer member is 40 degrees or more, the pH of the liquid composition is 6.0 or less, and the liquid composition contains a polyether siloxane compound having a specific structure. Image recording method is disclosed which is characterized in that.

JP 2013-144437 A

  In the conventional ink as described in Patent Document 1, the surface tension of the ink is reduced by including the surfactant. However, in order to dissolve the surfactant uniformly, an organic solvent having a high boiling point is used. Contains a large amount. However, an ink containing a large amount of an organic solvent having a high boiling point provides a recorded matter in which unevenness in density is sufficiently suppressed when printing at a high density due to insufficient drying of the ink after landing. It becomes difficult.

  Accordingly, the present invention has been made to solve at least a part of the above-described problems, and provides an ink and an ink jet method using the ink that provide a recorded matter in which unevenness of shading is suppressed when printed at a high density. The purpose is to provide.

  As a result of intensive studies to solve the above-described problems of the prior art, the present inventors have found that an organic material containing a coloring material, water, a predetermined amount of resin emulsion, 2-pyrrolidones, and a predetermined range of diols. Printed matter in which density unevenness is suppressed when printing is performed at a high density by using an ink containing a solvent and a specific silicone surfactant in a predetermined range and having a boiling point of the diol within a specific range. The present invention has been completed.

That is, the present invention is as follows.
[1]
An ink comprising a coloring material, water, a resin emulsion, an organic solvent containing 2-pyrrolidones and diols, and a silicone surfactant,
The boiling point of the diols is 200 ° C. or higher and 230 ° C. or lower,
The ink contains 10% by mass or less of the diol, 2.0% by mass or more of the silicone surfactant, and 5.0% by mass of the resin emulsion in terms of solid content with respect to the total amount of the ink. % Or more,
The ink whose SP value of the said silicone type surfactant is less than 13.
[2]
The ink according to [1], wherein the organic solvent contains 5.0 to 15% by mass of the 2-pyrrolidone with respect to the total amount of the organic solvent.
[3]
The ink according to [1] or [2], wherein the organic solvent contains 3.0% by mass or more and 10% by mass or less of the diol with respect to a total amount of the organic solvent.
[4]
The ink according to any one of [1] to [3], further comprising a wax emulsion.
[5]
The ink according to any one of [1] to [4], wherein the surface tension is 23 mN / m or less.
[6]
An ink jet recording method comprising: an ejecting step of ejecting the ink according to any one of [1] to [5] onto a non-absorbable recording medium having a temperature of 40 ° C. or higher using an ejection head.
[7]
The inkjet recording method according to [6], wherein the ejection step is a ejection step of ejecting the ink with a number of printing passes of 8 or less.

  Hereinafter, a mode for carrying out the present invention (hereinafter referred to as “the present embodiment”) will be described in detail. The following embodiments are examples for explaining the present invention, and are not intended to limit the present invention to the following contents. The present invention can be appropriately modified within the scope of the gist.

〔ink〕
The ink according to the present embodiment includes a color material, water, a resin emulsion, an organic solvent containing 2-pyrrolidones and diols, and a silicone surfactant. In addition, the ink contains 10% by mass or less of diol, 2.0% by mass or more of a silicone-based surfactant, and 5.0% by mass of a resin emulsion in terms of solid content with respect to the total amount of the ink. Including above. Furthermore, the boiling point of the diols is 200 ° C. or higher and 230 ° C. or lower, and the SP value of the silicone surfactant is less than 13.

  The surface tension of the ink of this embodiment is preferably 23 mN / m or less, more preferably 18 mN / m or more and 23 mN / m or less, and further preferably 20 mN / m or more and 23 mN / m or less. When the surface tension is 18 mN / m or more, the recording stability tends to be excellent. Further, when the surface tension is 23 mN / m or less, there is a tendency to obtain a recorded matter in which density unevenness is further suppressed when printing at a high density. In order to prepare an ink having a surface tension in the above range, for example, the content of the surfactant may be adjusted. The surface tension is measured by the method described in Examples described later.

  The ink set of the present embodiment is an ink set in which two or more inks having different types of color materials are combined. The inks of each color constituting the ink set are the inks of the present embodiment, and it is preferable that all the inks are the inks of the present embodiment. In color printing using two or more colors of the ink of the present embodiment, even in the case of high-density printing in which the total ink amount is larger than that of single-color printing, it is possible to suppress uneven density, and secondary colors or more There is a tendency for the print image quality to improve.

<Color material>
The ink of this embodiment includes a color material. Although it does not specifically limit as a coloring material, For example, dye and a pigment are mentioned. Of these, pigments are preferred. Although it does not specifically limit as a pigment, For example, the following are mentioned.

  Although it does not specifically limit as a black pigment, For example, it is No. 2300, no. 900, MCF88, No. 33, no. 40, no. 45, no. 52, MA7, MA8, MA100, no. 2200B, etc. (Mitsubishi Chemical Corporation), Raven 5750, Raven 5250, Raven 5000, Raven 3500, Raven 1255, Raven 700, etc. (above, Columbia Carbon, Carbon 1 Rubbi 400, Carbon Co. Rega1 330R, Rega1 660R, Mogul L, Monarch 700, Monarch 800, Monarch 880, Monarch 900, Monarch 1000, Monarch 1100, Monarch 1300, Monarch 1400, etc. (Cabot Corp. CA Kol. , Color B lack FW2, Color Black FW2V, Color Black FW18, Color Black FW200, Color B1ack S150, Color Black S160, Color Black S170, Printex 35, Printex U, Printex V, Printex 140U, Special Black 6, Special Black 5, Special Black 4A , Special Black 4 (manufactured by Degussa). Moreover, carbon black (CI pigment black 7), such as furnace black, lamp black, acetylene black, and channel black, and iron oxide are also mentioned.

  Although it does not specifically limit as a yellow pigment, For example, C.I. I. Pigment Yellow 1, 2, 3, 4, 5, 6, 7, 10, 11, 12, 13, 14, 16, 17, 24, 34, 35, 37, 53, 55, 65, 73, 74, 75, 81, 83, 93, 94, 95, 97, 98, 99, 108, 109, 110, 113, 114, 117, 120, 124, 128, 129, 133, 138, 139, 147, 151, 153, 154, 155, 167, 172, 180.

  Although it does not specifically limit as a magenta pigment, For example, C.I. I. Pigment Red 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 14, 15, 16, 17, 18, 19, 21, 22, 23, 30, 31, 32, 37, 38, 40, 41, 42, 48 (Ca), 48 (Mn), 57 (Ca), 57: 1, 88, 112, 114, 122, 123, 144, 146, 149, 150, 166, 168 170, 171, 175, 176, 177, 178, 179, 184, 185, 187, 202, 209, 219, 224, 245, or C.I. I. Pigment violet 19, 23, 32, 33, 36, 38, 43, 50.

  Although it does not specifically limit as a cyan pigment, For example, C.I. I. Pigment Blue 1, 2, 3, 15, 15: 1, 15: 2, 15: 3, 15:34, 15: 4, 16, 18, 22, 25, 60, 65, 66, C.I. I. Bat Blue 4, 60.

  In addition, the pigment used in color inks other than magenta, cyan, and yellow is not particularly limited. I. Pigment green 7,10, C.I. I. Pigment brown 3, 5, 25, 26, C.I. I. Pigment orange 1, 2, 5, 7, 13, 14, 15, 16, 24, 34, 36, 38, 40, 43, 63.

  The pigment content is preferably 0.1% by mass or more and 10% by mass or less, more preferably 0.2% by mass or more and 5.0% by mass or less, with respect to the total amount of ink (100% by mass). .

<Pigment dispersant>
Various methods can be applied to the above pigment in order to make it more stably dispersed and held in the ink. Examples of the method include a method of dispersing using a water-soluble resin and a method of dispersing using a surfactant. The water-soluble resin pigment dispersant is not particularly limited, and examples thereof include polyvinyl alcohols, polyvinyl pyrrolidones, acrylonitriles, vinyl acetate-acrylate copolymer, acrylate polymer, styrene- (meth). Acrylic acid ester copolymer, styrene-methacrylic acid ester-acrylic acid ester copolymer, styrene-α-methylstyrene-acrylic acid ester copolymer, styrene-α-methylstyrene-acrylic acid ester copolymer, styrene- Maleic acid ester copolymer, styrene-maleic anhydride copolymer, vinyl naphthalene-acrylic acid ester copolymer, vinyl naphthalene-maleic acid ester copolymer, vinyl acetate-maleic acid ester copolymer, vinyl acetate-croton Acid ester copolymer The As the form of the copolymer, any form of a random copolymer, a block copolymer, an alternating copolymer, and a graft copolymer can be used.

  Commercially available products may be used as the water-soluble resin pigment dispersant described above. Specifically, Joncryl 67 (weight average molecular weight: 12500, acid value: 213), Joncryl 678 (weight average molecular weight: 8,500, acid value: 215), Joncryl 586 (weight average molecular weight: 4) , 600, acid value: 108), joncryl 611 (weight average molecular weight: 8,100, acid value: 53), joncryl 680 (weight average molecular weight: 4,900, acid value: 215), joncryl 682 (weight) Average molecular weight: 1,700, acid value: 238), Joncryl 683 (weight average molecular weight: 8,000, acid value: 160), Joncryl 690 (weight average molecular weight: 16,500, acid value: 240) (above Trade name, manufactured by BASF Japan Ltd.).

  The surfactant-based pigment dispersant is not particularly limited, and examples thereof include alkane sulfonate, α-olefin sulfonate, alkylbenzene sulfonate, alkyl naphthalene sulfonate, acylmethyl taurate, and dialkyl sulfone. Anionic interfaces such as oxalate, alkyl sulfate, sulfated olefin, polyoxyethylene alkyl ether sulfate, alkyl phosphate, polyoxyethylene alkyl ether phosphate, monoglycerite phosphate Activators: Amphoteric surfactants such as alkyl pyridium salts, alkyl amino acid salts, alkyl dimethyl betaines; polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers, polyoxyethylene alkyl esters, polio Shi ethylene alkyl amides, glycerol alkyl esters, nonionic surfactants such as sorbitan alkyl esters.

  The content of the water-soluble resin pigment dispersant and the surfactant pigment dispersant is preferably 10 parts by mass or more and 150 parts by mass or less, more preferably 25 parts by mass or more and 100 parts by mass with respect to 100 parts by mass of the pigment. Or less. When the content of the water-soluble resin pigment dispersant and the surfactant pigment dispersant is within the above range, the dispersion stability of the pigment tends to be further improved.

  The method for dispersing the pigment is not particularly limited. For example, the pigment, water and the water-soluble resin pigment dispersant are mixed using a disperser; the pigment, water and the surfactant pigment dispersant are dispersed. The method of mixing using a machine is mentioned. When mixing, a water-soluble organic solvent and a neutralizing agent may be added as necessary. The disperser is not particularly limited, and examples thereof include a ball mill, a sand mill, an attritor, a roll mill, an agitator mill, a Henschel mixer, a colloid mill, an ultrasonic homogenizer, a jet mill, and an ang mill.

<Water>
The ink contains water. Water is a main medium of ink and is a component that evaporates and scatters when dried. The water is preferably water from which ionic impurities such as pure water such as ion exchange water, ultrafiltration water, reverse osmosis water, distilled water or ultrapure water are removed as much as possible. Further, when water sterilized by ultraviolet irradiation or addition of hydrogen peroxide is used, it is preferable because generation of mold and bacteria can be prevented when the ink is stored for a long time.

<Resin emulsion>
The ink of this embodiment contains a resin emulsion. Further, the ink contains 5.0% by mass or more of the resin emulsion in terms of solid content with respect to the total amount (100% by mass) of the ink. By including the resin emulsion, the effect of making the ink sufficiently fixed on the recording medium by forming the resin film and improving the abrasion resistance of the recorded matter is exhibited. Due to the effects described above, a recorded matter recorded using an ink containing a resin emulsion is excellent in adhesion and abrasion resistance on a non-ink-absorbing or low-absorbing recording medium.

  The glass transition temperature (Tg) of the resin emulsion is preferably 50 ° C. or higher and 150 ° C. or lower, more preferably 60 ° C. or higher and 120 ° C. or lower, and further preferably 70 ° C. or higher and 100 ° C. or lower. Due to the Tg being within the above range, recording of the resin emulsion particles in the ink is prevented from being associated with each other in the ink storage portion, the ink supply portion, and the ink discharge head inside the printer. On the other hand, after the ink after landing is heated and dried to about 100 ° C., the particles of the resin emulsion in the ink are bound to each other, which causes the printed matter to have abrasion resistance. It tends to be excellent. Tg can be measured by differential scanning calorimetry (DSC).

  The resin emulsion is not particularly limited. For example, (meth) acrylic acid, (meth) acrylic ester, acrylonitrile, cyanoacrylate, acrylamide, olefin, styrene, vinyl acetate, vinyl chloride, vinyl alcohol, vinyl ether, vinyl pyrrolidone, Examples thereof include homopolymers or copolymers of vinyl pyridine, vinyl carbazole, vinyl imidazole, and vinylidene chloride, fluororesins, and natural resins. Further, the copolymer may be in any form of a random copolymer, a block copolymer, an alternating copolymer, and a graft copolymer.

  The resin emulsion may be a commercially available product or may be prepared using an emulsion polymerization method or the like as follows. As a method for obtaining the resin in the ink in an emulsion state, the above-described water-soluble resin monomer is emulsion-polymerized in water containing a polymerization catalyst and an emulsifier. The polymerization initiator, the emulsifier, and the molecular weight modifier used in the emulsion polymerization can be used according to a conventionally known method.

  The average particle size of the resin emulsion is preferably in the range of 5.0 nm to 400 nm, more preferably in the range of 20 nm to 300 nm, in order to further improve the storage stability and recording stability of the ink.

  A resin emulsion may be used individually by 1 type, and may be used in combination of 2 or more type.

  The content of the resin emulsion (in terms of solid content) is 5.0% by mass or more, preferably 5.0% by mass or more and 15% by mass or less, more preferably based on the total amount of ink (100% by mass). Is 5.0 mass% or more and 10 mass% or less. When the content of the resin emulsion is 5.0% by mass or more, a recorded matter in which density unevenness is suppressed when printing at a high density is obtained. This factor is inferred as follows (however, the factor is not limited to this). That is, when an ink having a resin emulsion content of 5.0% by mass or more is used, after the ink is ejected toward the recording medium and landed on the recording medium, the viscosity rises due to water evaporation of the ink. Due to the abrupt occurrence of ink, the fluidity of the ink immediately after landing on the recording medium is reduced. For this reason, uneven density is less likely to occur due to the suppression of unnecessary movement of ink after landing. Further, when the content of the resin emulsion is 15% by mass or less, the recording stability tends to be further improved.

<Wax emulsion>
The ink of this embodiment may further contain a wax emulsion. Although it does not specifically limit as a wax emulsion, For example, a paraffin wax emulsion and a polyethylene wax emulsion are mentioned.

  In the present specification, the “wax emulsion” means a product in which solid wax particles are dispersed in water mainly using a surfactant.

  By including a paraffin wax emulsion in the ink according to the present exemplary embodiment, slip performance is imparted to the recorded matter, and thus the ink tends to have excellent abrasion resistance. In addition, since paraffin wax has water repellency, it tends to be able to improve the water resistance of the recorded matter.

  The “paraffin wax” in the present specification means a so-called petroleum wax, which is mainly composed of a linear paraffinic hydrocarbon (normal paraffin) having about 20 to 30 carbon atoms and a small amount of iso (iso). -It means a mixture of hydrocarbons containing paraffin and having a weight average molecular weight of about 300 to 500.

  When the ink in the present embodiment contains paraffin wax in an emulsion state, the viscosity of the ink can be easily adjusted to an appropriate range in the ink jet recording method, and the storage stability and recording stability of the ink are further improved. Tend to be able to.

  The melting point of the paraffin wax emulsion is preferably 110 ° C. or lower in order to further strengthen the ink film after landing and to further improve the abrasion resistance of the image. On the other hand, the lower limit of the melting point of the paraffin wax emulsion is preferably 60 ° C. or higher in order to prevent the recording surface from being dried and sticky. Further, the melting point is more preferably 70 ° C. or higher and 95 ° C. or lower in order to further improve the recording stability of the ink.

  The average particle diameter of the paraffin wax emulsion is preferably in the range of 5 nm or more and 400 nm or less, more preferably 50 nm or more in order to obtain a stable emulsion state and further improve the storage stability and ejection stability of the ink. The range is 200 nm or less. A commercially available product may be used as it is as the paraffin wax emulsion. Examples of the commercially available products include, but are not limited to, AQUACER 537, AQUACER 539 (trade names, manufactured by BYK).

  The content (in terms of solid content) of the paraffin wax emulsion is preferably 0.1% by mass or more and 3.0% by mass or less, and 0.3% by mass or more and 3.0% by mass with respect to the total amount of ink (100% by mass). % Or less is more preferable, and 0.3 mass% or more and 1.5 mass% or less are still more preferable. When the content is within the above range, an image having excellent abrasion resistance, blocking resistance, and water resistance can be formed on a non-ink-absorbing or low-absorbing recording medium, and There is a tendency that the ink can be excellent in prevention of clogging.

  By including a polyethylene wax emulsion in the ink of the present embodiment, the ink has a tendency to be more excellent in abrasion resistance.

  For example, a polyethylene wax emulsion is produced by polymerizing ethylene, or by producing polyethylene for general molding by reducing the molecular weight by thermal decomposition. The polyethylene wax is oxidized to add a carboxyl group or a hydroxyl group, and further emulsified using a surfactant to obtain a polyethylene wax emulsion in the form of an aqueous wax emulsion having excellent stability.

  A commercially available product may be used as it is as the polyethylene wax emulsion. The commercially available product is not limited to the following, but, for example, Nopcoat PEM17 (trade name, Sannopco (manufactured by SANNOPCCO LIMITED)), Chemipearl W4005 (trade name, Mitsui Chemicals (manufactured by Mitsui Chemicals, Inc.), AQUACER 515, AQUACER 593 (Trade name, manufactured by BYK).

  The average particle diameter of the polyethylene wax emulsion is preferably in the range of 5.0 nm to 400 nm, more preferably in the range of 50 nm to 200 nm, in order to further improve the storage stability and ejection stability of the ink.

  The content of the polyethylene wax emulsion (in terms of solid content) is preferably 0.1% by mass or more and 3.0% by mass or less, and preferably 0.3% by mass or more and 3.0% by mass with respect to the total amount of ink (100% by mass). % Or less is more preferable, and 0.3 mass% or more and 1.5 mass% or less are still more preferable. When the content is in the above range, the ink can be solidified and fixed satisfactorily even on a non-ink-absorbing or low-absorbing recording medium, and the storage stability and recording stability of the ink are improved. It tends to be even better.

  The preferable content range of each of the paraffin wax emulsion and the polyethylene wax emulsion is as described above. In addition, the total content (in terms of solid content) of the paraffin wax emulsion and the polyethylene wax emulsion contained in the ink is 0.4% by mass or more and 1% independently of the total amount (100% by mass) of the ink. The range of 6 mass% or less is preferable.

  The ink in the present embodiment may contain a wax other than the paraffin wax emulsion and the polyethylene wax emulsion (hereinafter referred to as “other wax”). The wax has a function of imparting slip performance to the surface of the formed recorded matter and improving the abrasion resistance. The wax is preferably contained in the ink in an emulsion state. Since the wax in the ink exists in an emulsion state, the viscosity of the ink can be easily adjusted to an appropriate range in the ink jet recording method, and the storage stability and ejection stability of the ink can be further improved. There is a tendency.

  Examples of other waxes include, but are not limited to, polyolefin waxes (excluding the above-described polyethylene wax), and polypropylene waxes are particularly preferable. As other waxes, commercially available products may be used as they are.

  The average particle diameter of other waxes is preferably 5.0 nm or more and 400 nm or less, and more preferably 50 nm or more and 200 nm or less in order to further improve the storage stability and ejection stability of the ink.

<Organic solvent>
The ink of this embodiment contains an organic solvent containing 2-pyrrolidones and diols, and the organic solvent is preferably a water-soluble organic solvent. The boiling point of diols contained in the organic solvent is 200 ° C. or higher and 230 ° C. or lower. Further, the ink contains 10% by mass or less of diol with respect to the total amount (100% by mass) of the ink. Since the ink contains an organic solvent containing 2-pyrrolidones, the resin emulsion can be more uniformly dissolved in the stage where the ink after landing is heated and dried to about 100 ° C., and the particles of the resin emulsion are bound together. Due to wearing, the printed material is more excellent in abrasion resistance.

  Although it does not specifically limit as 2-pyrrolidones, For example, 2-pyrrolidone and N-methyl-2-pyrrolidone are mentioned. Of these, 2-pyrrolidone is preferred.

  2-pyrrolidone may be used individually by 1 type, or may use 2 or more types together.

  The content of 2-pyrrolidones is preferably 0.5% by mass or more and 15% by mass or less, and more preferably 2.0% by mass or more and 10% by mass or less, with respect to the total amount of ink.

  The diol is not particularly limited as long as it is a compound having two hydroxyl groups. For example, ethylene glycol (boiling point 197 ° C.), diethylene glycol, triethylene glycol, propylene glycol (1,2-propanediol, boiling point 188 ° C.), Dipropylene glycol (boiling point 230 ° C.), 1,3-propylene glycol (1,3-propanediol, boiling point 214 ° C.), isobutylene glycol (2-methyl-1,2-propanediol, boiling point 176 ° C.), 1,2 -Butanediol (boiling point 193 ° C), 1,3-butanediol (boiling point 207 ° C), 1,4-butanediol (boiling point 228 ° C), 2-butene-1,4-diol (boiling point 235 ° C), 1, 2-pentanediol (boiling point 104 ° C.), 1,5-pentanediol (boiling point 242 ° C.), -Methyl-2,4-pentanediol (boiling point 198 ° C), 1,2-hexanediol (boiling point 223 ° C), 1,6-hexanediol (boiling point 253 ° C), 2-ethyl-1,3-hexanediol ( Boiling point 244 ° C.), 1,7-heptanediol (boiling point 258 ° C.), 1,8-octanediol (boiling point 171 ° C. (20 mmHg)). The ink of this embodiment contains at least one diol having a boiling point of 200 ° C. or higher and 230 ° C. or lower (hereinafter referred to as “specific diols”) among the diols described above. All the diols contained are preferably specific diols. Among the specific diols, 1,3-propanediol, 1,3-butanediol, and 1,2-hexanediol are preferable. By using specific diols, uneven density is further suppressed.

  By including the organic solvent containing the specific diol, the ink according to the present embodiment can provide a recorded matter in which uneven density is suppressed when printing is performed at a high density. This factor is inferred as follows (however, the factor is not limited to this). That is, by setting the content of the resin emulsion in the ink to 5.0% by mass or more, the fluidity of the ink after landing on the recording medium is reduced. However, since the conventional ink does not use diols (specific diols) having a boiling point in a predetermined range, the fluidity required at the time of storing or discharging the ink cannot be ensured. It is difficult to make the content of the resin emulsion substantially 5.0% by mass or more. On the other hand, the ink of the present embodiment can ensure the fluidity of the ink even when the content of the resin emulsion is increased by using specific diols, and the density unevenness when printed at a high density. Is suppressed.

  Diols may be used alone or in combination of two or more.

  Content of specific diols is 10 mass% or less with respect to the total amount (100 mass%) of ink, Preferably it is 1.0 mass% or more and 10 mass% or less, More preferably, it is 3.0 mass%. It is above 8.0 mass%. When the content of the specific diol is 10% by mass or less, a recorded matter in which density unevenness is suppressed when printing at a high density is obtained. It is surmised that this factor can maintain the effect of the resin emulsion that suppresses the fluidity of the ink after landing on the recording medium when the content of the specific diol is 10% by mass or less. (However, the factor is not limited to this.) Further, when the content of the specific diol is 1.0% by mass or more, the recording stability is further improved due to the difficulty of binding the resin emulsion particles in the ink before ejection. There is a tendency.

  The organic solvent of this embodiment may contain other organic solvents other than the above-mentioned 2-pyrrolidones and diols. Examples of other organic solvents include, but are not limited to, diethylene glycol mono-n-propyl ether, ethylene glycol mono-iso-propyl ether, diethylene glycol mono-iso-propyl ether, ethylene glycol mono-n-butyl ether, ethylene glycol mono -T-butyl ether, diethylene glycol mono-n-butyl ether, triethylene glycol monobutyl ether, diethylene glycol mono-t-butyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol mono-t-butyl ether, propylene glycol mono-n- Propyl ether, propylene glycol mono-iso-propyl ether, propylene glycol Mono-n-butyl ether, dipropylene glycol mono-n-butyl ether, dipropylene glycol mono-n-propyl ether, dipropylene glycol mono-iso-propyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, diethylene glycol ethyl methyl ether , Diethylene glycol butyl methyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, dipropylene glycol dimethyl ether, dipropylene glycol diethyl ether, tripropylene glycol dimethyl ether, methanol, ethanol, n-propyl alcohol, iso-propyl alcohol, n- Alcohols or glycols such as butanol, 2-butanol, tert-butanol, iso-butanol, n-pentanol, 2-pentanol, 3-pentanol, and tert-pentanol, N, N-dimethylformamide, N , N-dimethylacetamide, 2-oxazolidone, 1,3-dimethyl-2-imidazolidinone, dimethyl sulfoxide, sulfolane, and 1,1,3,3-tetramethylurea.

  Said organic solvent may be used individually by 1 type, or may use 2 or more types together.

<Silicone surfactant>
The ink of this embodiment contains a silicone-based surfactant. The ink contains 2.0% by mass or more of a silicone-based surfactant with respect to the total amount (100% by mass) of the ink. Furthermore, the SP value of the silicone-based surfactant is less than 13. Hereinafter, a silicone-based surfactant having an SP of less than 13 is also referred to as a specific silicone-based surfactant.

  Although it does not specifically limit as a silicone type surfactant, For example, a polysiloxane type compound and a polyether modified organosiloxane are mentioned. 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, BYK-3455 (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 (above trade names, manufactured by Shin-Etsu Chemical Co., Ltd.) Can be mentioned.

  The SP value (solubility parameter) of the silicone-based surfactant is less than 13, preferably 9 or more and 12 or less, more preferably 10 or more and 12 or less. When the SP value of the silicone-based surfactant is less than 13, a recorded matter in which density unevenness is suppressed when printing at a high density can be obtained. This factor is inferred as follows (however, the factor is not limited to this). That is, by setting the content of the resin emulsion in the ink to 5.0% by mass or more, the fluidity of the ink after landing on the recording medium is reduced. However, since the conventional ink does not use a silicone-based surfactant (specific silicone-based surfactant) having an SP value in a predetermined range, the surface of the ink droplet immediately after the silicone-based surfactant has landed on the recording medium. Is not sufficiently oriented. For this reason, the movement of the ink droplets that have landed on the recording medium occurs more quickly than the drop in fluidity of the ink droplets, so that the density unevenness of the printed matter tends to occur. On the other hand, the ink of this embodiment is oriented to the ink droplet surface immediately after the silicone surfactant has landed on the recording medium by using a specific silicone surfactant, and the content of the resin emulsion is 5. If it is 0% by mass or more, the movement of the ink droplets can be suppressed until the fluidity of the ink droplets is lowered, and uneven density when printed at a high density is suppressed. The SP value is measured by the method described in Examples described later.

  The content of the specific silicone surfactant is 2.0% by mass or more, preferably 2.0% by mass or more and 5.0% by mass or less, more preferably based on the total amount of ink (100% by mass). Is 2.0 mass% or more and 3.0 mass% or less. When the content of the specific silicone surfactant is 2.0% by mass or more, it is possible to obtain a recorded matter in which uneven density is suppressed when printing at a high density. This factor is inferred as follows (however, the factor is not limited to this). In the ink containing diols, the specific silicone surfactant is uniformly dissolved. However, immediately after the ink has landed on the recording medium, and when the gas-liquid interface or the interface between the recording medium and the recorded material becomes wide, the specific silicone surfactant moves to and arranges on these interfaces. . The specific silicone surfactant arranged at the interface reduces the contact angle between the ink after landing and the recording medium, and repels ink droplets after landing. In addition, since the content of the specific silicone surfactant is 2.0% by mass or more and the content of the resin emulsion is 5.0% by mass or more, immediately after landing on the recording medium. It is presumed that the phenomenon of unevenness in density is suppressed due to the fact that the ink droplets are spread and are relatively easily fixed before all of the plurality of inks are dried. Furthermore, when the content of the specific silicone surfactant is 5.0% by mass or less, the drying property of the ink is improved and the abrasion resistance tends to be further improved.

  The silicone-based surfactant of the present embodiment may include other surfactants other than the above-described silicone-based surfactant. Although it does not specifically limit as other surfactant, For example, a fluorine-type surfactant is mentioned.

[Inkjet recording method]
The ink jet recording method according to the present embodiment includes a discharge step of discharging the ink according to the present embodiment onto a recording medium using a discharge head. The ejection step is preferably an ejection step for ejecting the ink of the present embodiment onto a non-absorbable recording medium having a temperature of 40 ° C. or higher. Hereinafter, the ink jet recording method of the present embodiment will be described using a specific example of an ink jet recording apparatus that can be used in the ink jet recording method. The inkjet recording apparatus to be described later is not particularly limited as long as recording is performed by the inkjet recording method using the above-described ink, and an apparatus having the same configuration as the conventional one can be used.

[Discharge process]
The ejection step is a step of ejecting the ink onto a recording medium using an ejection head. In the ejection step, when a non-absorbable recording medium is used, the temperature is preferably 40 ° C. or higher, more preferably 45 ° C. or higher and 60 ° C. or lower. Due to the fact that the temperature of the non-absorbent recording medium in the ejection process is within the above range, the drying of the ink ejected onto the recording medium is promoted, thereby suppressing the uneven density of the recorded matter. There is a tendency. This is because the liquid component in the recorded material immediately after the ink landed on the non-absorbent recording medium and before the ink after landing flows on the surface of the non-absorbable recording medium. It is inferred to evaporate (however, the factor is not limited to this). Also, when an absorbent recording medium is used, high temperature recording tends to be possible by setting the temperature within the above range. In order to bring the temperature of the recording medium into the above range, the recording medium may be heated by a known method, for example, a method of heating the conveyance belt of the recording medium. The temperature can be measured using a commercially available thermography apparatus. As a specific example of the thermography apparatus, there is an infrared thermography apparatus H2640 / H2630 [trade name] (manufactured by NEC Avio Infrared Technologies Co., Ltd.).

  A serial printer in which the inkjet recording apparatus is a serial inkjet recording apparatus performs main scanning (pass) in which ink is ejected while the head moves in the main scanning direction intersecting the sub-scanning direction of the recording medium. Recording is performed with more than one pass (multi-pass), and if it is eight passes or less, printing can be performed at high speed.

  The ink jet recording method of the present embodiment may have the same steps as the conventionally known ink jet recording method, except that the method includes the above-described steps.

<Recording medium>
A recorded matter is obtained by ejecting ink onto a recording medium using the ink jet recording method of the present embodiment. Examples of the recording medium include an absorptive recording medium (absorbing recording medium), a low-absorbing recording medium (lower recording medium), or a non-absorbing recording medium (non-absorbing medium). Recording medium). The ink jet recording method of the present embodiment is various from a low-absorbing recording medium and a non-absorbing recording medium in which penetration of water-soluble ink is difficult to an absorbing recording medium in which penetration of water-soluble ink is easy. The present invention can be widely applied to recording media having excellent absorption performance.

  Although it does not specifically limit as an absorptive recording medium, For example, plain paper, such as electrophotographic paper with high ink permeability, inkjet paper (the ink absorption layer comprised from the silica particle or the alumina particle, or polyvinyl alcohol (PVA) ) Or art paper, coated paper, cast used for general offset printing, which has a relatively low ink permeability, from an ink-absorbing layer composed of a hydrophilic polymer such as polyvinylpyrrolidone (PVP) Paper is an example.

As a low-absorbency recording medium, for example, a paper whose surface is coated with a coating material to enhance aesthetics and smoothness, and classified as a coated paper for printing in the “Production Dynamic Statistics Classification” of the Ministry of Economy, Trade and Industry. Can be mentioned. Examples of the paint include those prepared by mixing a white pigment such as clay (kaolin) or calcium carbonate and an adhesive (binder) such as starch. It is preferably about 10 to 40 g / m ² as coated amount of the coating material. Specific examples of the low-absorbency recording medium include printing paper such as art paper, coated paper, matte paper, and cast paper.

  Further, the non-absorbable recording medium is not particularly limited. For example, a plastic film that does not have an ink absorbing layer, a substrate such as paper coated with plastic, or a plastic film adhered thereto. And the like. Examples of the plastic here include polyvinyl chloride (PVC), polyethylene terephthalate, polycarbonate, polystyrene, polyurethane, polyethylene, polypropylene, and polyacryl.

Here, the “low-absorbing recording medium” or “non-absorbing recording medium” refers to a recording medium having a water absorption of 10 mL / m ² or less from the start of contact to 30 msec in the Bristow method. . In the Bristow method of a low-absorbency or non-absorbent recording medium, the amount of water absorbed from the start of contact until 30 msec is preferably 0 to 10 mL / m ² , more preferably 0 mL / m ² or more to 7.0 mL. / m ² or more, and more preferably not more than 0 mL / m ² or more 5.0 mL / m ^2. 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 1.0%. Low absorptivity indicates that the above-mentioned decrease rate is 1.0% or more and less than 5.0%. Moreover, absorptivity means that said reduction rate is 5.0% 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.

  Hereinafter, the present embodiment will be described more specifically with reference to examples and comparative examples. However, the present embodiment is not limited to the following examples and comparative examples as long as the gist thereof is not exceeded.

  The main materials included in the ink sets used in the following examples and comparative examples are as follows.

[Color material]
For yellow (Y) ink: C.I. I. Pigment Yellow 155
For magenta (M) ink: C.I. I. Pigment Red 122
For cyan (C) ink: C.I. I. Pigment Blue 15: 3
For black (K) ink: C.I. I. Pigment Black 7
(Water-soluble resin dispersant)
Styrene-acrylic acid water-soluble resin [emulsion]
Resin emulsion (styrene-acrylic acid resin, Tg 85 ° C)
Wax emulsion (product name AQUACER 515, manufactured by Big Chemie Japan)
〔solvent〕
2-pyrrolidone propylene glycol (bp. (Boiling point, the same applies below): 188 ° C.)
1,2-butanediol (bp .: 191 ° C.)
1,2-hexanediol (bp .: 224 ° C.)
1,3-propanediol (bp .: 217 ° C.)
1,3-butanediol (bp .: 208 ° C.)
[Surfactant]
Silicone-based surfactant 1 (SP value 11.6, manufactured by BYK Japan, product name BYK-3455)
Silicone-based surfactant 2 (SP value 13.1, manufactured by Big Chemie Japan, product name BYK-349)
Fluorine-based surfactant (SP value 13.2, manufactured by BYK Japan, product name BYK-3440)

[Preparation of ink set]
In the compositions shown in Tables 1 and 2, the aqueous ink composition used in this example used a pigment dispersion in which the pigment was previously dispersed with a water-soluble resin dispersant. The pigment dispersion is first dissolved in ion-exchanged water in which an aqueous ammonia solution is dissolved by adding a styrene-acrylic acid copolymer (Tg: 85 ° C.) as a water-soluble resin dispersant in Tables 1 and 2 below. The pigments shown in Tables 1 and 2 below were added thereto for dispersion treatment. For each ink, the above pigment dispersion and other materials shown in Tables 1 and 2 below are placed in a container and stirred and mixed with a magnetic stirrer for 2 hours, and then filtered through a membrane filter having a pore size of 5 μm to produce dust, coarse particles, etc. It was prepared by removing impurities. Further, the inks of the respective colors constituting the ink set have the same composition except for the kind of the color material. In Tables 1 and 2 below, the numerical unit is mass%, and the total is 100.0 mass%.

(Physical property 1) SP value of surfactant The SP value of the surfactant was measured by cloud point titration. The cloud point titration is performed by the following K. W. SUH, J. et al. M.M. Calculation was performed according to the CORBETT equation (Journal of Applied Polymer Science, 12, 2359, 1968).
SP = (√Vml · δH + √Vmh · δD) / (√Vml + √Vmh)

Specifically, it measured as follows. While dissolving 0.5 g of the surfactant as a sample in 10 mL of acetone, n-hexane was added, the titration amount H (mL) at the cloud point was read, and deionized water was similarly added to the acetone solution. The titration amount D (mL) at the turbidity point was read and applied to the following formula to calculate Vml, Vmh, δH, and δD. The molecular weight (mol / mL) of each solvent is acetone: 74.4, n-hexane: 130.3, deionized water: 18, and the SP value of each solvent is acetone: 9.75, n- Hexane: 7.24, deionized water: 23.43. The results are shown in Tables 1 and 2.
Vml = 74.4 × 30.3 / ((1−VH) × 130.3 + VH × 74.4)
Vmh = 74.4 × 18 / ((1−VD) × 18 + VD × 74.4)
VH = H / (10 + H)
VD = D / (10 + D)
δH = 9.75 × 10 / (10 + H) + 7.24 × H / (10 + H)
δD = 9.75 × 10 / (10 + D) + 23.43 × D / (10 + D)

(Physical property 2) Surface tension of ink The surface tension of the obtained cyan ink of each ink set was measured. Using an automatic surface tension meter CBVP-Z (trade name, manufactured by Kyowa Interface Science Co., Ltd.), the surface tension when the platinum plate was wetted with ink in an environment of 25 ° C. was measured. The results are shown in Tables 1 and 2.

[Recording method]
As an ink jet recording type printer, an ink jet printer PX-G930 (trade name, manufactured by Seiko Epson Corporation), two cartridges per color are connected, the nozzle resolution per color is set to 360 dpi, and the temperature of the recording medium guide is set. We used the one that had been modified in a certain way, such as attaching a heater that can be adjusted.

(Evaluation 1) Density unevenness White PVC film (LLSPEX113, manufactured by Sakurai Co., Ltd.) which is a recording medium in which each ink set prepared above was heated to 55 ° C. by the inkjet recording method using the PX-G930 modified machine. In addition, the recording density of 720 × 720 dpi per color, the number of printing passes is 4, two colors of ink are used, and the total ink amount of two colors per unit area is 2 mg / inch ² to 1 mg / inch the secondary color is varied in ^two increments were recorded. Each recorded matter was heat-dried at 100 ° C. for 2 minutes to obtain each recorded matter having the following evaluation. The presence / absence of uneven density in each ink amount was visually observed and judged according to the following evaluation criteria.
◎: 2 color total ink amount of maximum uneven density does not occur 16 mg / inch ² or more ○: 2 color total ink amount of maximum uneven density does not occur 15 mg / inch ² or more ~16mg / inch less than ² △: uneven density maximum 2 colors total amount of ink 14 mg / inch ² or more to 15 mg / inch ² below. × There does not occur: the two colors total ink amount of maximum uneven density does not occur 14 mg / inch ² below evaluation results in tables 1 and 2 Show.

(Evaluation 2) Printing stability Printing stability was determined by continuously printing each ink set prepared above on a recording medium heated to 55 ° C. by an ink jet recording method using the above-described PX-G930 remodeling machine. / Judged by whether or not bending occurs. The evaluation criteria are shown below.
A: 3 pages or more of character strings are recorded on the entire A4 size, and nozzle missing / bent is not printed. ○: 2 pages of character strings are printed on the entire A4 size, no nozzle is missing / bent. No nozzle missing on the third page / first Bent in part △: 2 pages of character string printed on the entire A4 size, no nozzle omission / no bending, No nozzle missing on the 3rd page / curving occurrence ×: Printing character string on the entire A4 size, 2 pages Table 1 and 2 show the evaluation results of nozzle missing or bending within the end of the eye.

(Evaluation 3) Abrasion resistance A white PVC film (LLSPEX113, manufactured by Sakurai Co., Ltd.) which is a recording medium in which each ink set prepared above was heated to 55 ° C. by an ink jet recording method using the PX-G930 modified machine. ), Recording density of 720 x 720 dpi per color, printing pass number 4, recording ink amount per unit area at 9 mg / inch ² and drying by heating at 100 ° C for 2 minutes to obtain each recorded matter It was. Each of the obtained recorded materials was allowed to stand at 20 ° C. for 16 hours, and then loaded with a load of 500 g and a friction frequency of 50 times using a Gakushin type friction fastness tester “AB-301” (product name, manufactured by Tester Sangyo Co., Ltd.). Under the conditions, the friction piece attached with the white cotton cloth for friction and the recorded material were rubbed together, and the surface state of the image was visually observed and judged according to the following evaluation criteria. Tables 1 and 2 show the evaluation results as abrasion resistance.
○: Scratch / exfoliation where the ground is exposed after 50 times of rubbing Δ: Scratch / peeling occurs when 40-50 times of rubbing occurs to expose the base, and no scratch / exfoliation where the base is exposed after rubbing less than 40 times ×: Exfoliation occurs after rubbing less than 40 times, and the base is exposed

  By comparing the Examples and Comparative Examples shown in Tables 1 and 2, according to the ink according to the present invention, a printed matter in which density unevenness was suppressed when printed at a high density was obtained, and further printed at a high density. It has been found that sometimes the maximum ink amount is large, and excellent printing stability and scratch resistance can be obtained.

Claims (7)

An ink comprising a coloring material, water, a resin emulsion, an organic solvent containing 2-pyrrolidones and diols, and a silicone surfactant,
The boiling point of the diols is 200 ° C. or higher and 230 ° C. or lower,
The ink contains 10% by mass or less of the diol, 2.0% by mass or more of the silicone surfactant, and 5.0% by mass of the resin emulsion in terms of solid content with respect to the total amount of the ink. % Or more,
The ink whose SP value of the said silicone type surfactant is less than 13.   The ink according to claim 1, wherein the organic solvent contains 5.0% by mass to 15% by mass of the 2-pyrrolidones with respect to the total amount of the organic solvent.   The ink according to claim 1, wherein the organic solvent contains 3.0% by mass or more and 10% by mass or less of the diol with respect to the total amount of the organic solvent.   The ink according to any one of claims 1 to 3, further comprising a wax emulsion.   The ink according to any one of claims 1 to 4, wherein the surface tension is 23 mN / m or less.   An ink jet recording method, comprising: an ejecting step of ejecting the ink according to claim 1 to a non-absorbable recording medium having a temperature of 40 ° C. or higher using an ejecting head.   The inkjet recording method according to claim 6, wherein the discharging step is a discharging step of discharging the ink with a number of printing passes of 8 or less.