JP2022113704A - Recording method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink set that can prevent bleeding among inks and less likely causes clogging when a plurality of inks are recorded on a non-absorptive recording medium or a low-absorptive recording medium in a superimposed manner.

SOLUTION: The ink set includes a reaction liquid containing a coagulant, a first ink containing a color material, and a second ink containing a color material and is used for recording on a non-absorptive recording medium or a low-absorptive recording medium. The ink set is used for imparting the reaction liquid, the first ink, and the second ink to the recording medium in a superimposed manner in the described order.

SELECTED DRAWING: None

COPYRIGHT: (C)2022,JPO&INPIT

Description

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

The ink jet recording method is capable of recording high-definition images with a relatively simple apparatus, and is rapidly developing in various fields. For example, in Patent Document 1, for the purpose of image formation such as the formation of a white image having ink jetting characteristics and high hiding power when forming a white image using an inkjet recording method, It is disclosed that recording is performed on an OHP sheet using an ink composition containing titanium dioxide sol and a reaction liquid containing magnesium sulfate.

Japanese Patent Application Laid-Open No. 2002-103783

However, when recording is performed on a non-absorbent recording medium or a low-absorbing recording medium using the inkjet recording method described in Patent Document 1, when a color image is recorded using color inks on a white image, , there is a problem that the color ink bleeds.

Moreover, in order to suppress bleeding, a method of heating the recording medium instead of using the reaction liquid is also conceivable. However, if the recording medium is heated without using a reaction liquid, high heating energy is required, which causes clogging.

SUMMARY OF THE INVENTION The present invention has been made to solve at least part of the above-described problems. To provide an ink set capable of preventing bleeding between inks and hardly clogging.

The present inventors have made intensive studies to solve the above problems. As a result, they found that an ink set containing a predetermined pretreatment liquid separately from a plurality of inks for a non-absorbent recording medium or a low-absorbent recording medium could solve the above problems. I completed the present invention.

That is, the present invention is as follows.
[1]
It comprises a reaction liquid containing a coagulant, a first ink containing a coloring material, and a second ink containing a coloring material, and is used for recording on a non-absorbent recording medium or a low-absorbing recording medium. ,
The reaction liquid, the first ink, and the second ink are applied to the recording medium in this order, and used.
ink set.
[2]
At least one of the first ink and the second ink is a color ink containing a color coloring material or a black ink containing a black coloring material.
The ink set described in [1] above.
[3]
The other of the first ink and the second ink is a white ink containing a white colorant or a metallic ink containing a metallic colorant.
The ink set described in [2] above.
[4]
The ink set according to any one of [1] to [3] above, wherein the aggregating agent contains at least one selected from the group consisting of polyvalent metal salts and organic acids.
[5]
A ratio (colorant : polyvalent metal salt) is 1000: 1 to 31000: 1,
The ink set described in [4] above.
[6]
The ratio of the number of moles (unit: mol) of the organic acid contained in the reaction liquid to the total mass (unit: g) contained in the coloring materials of the first ink and the second ink (coloring material: organic acid ) is between 800:1 and 5500:1;
The ink set according to [4] or [5] above.
[7]
wherein the first ink is a white ink containing a white colorant or a metallic ink containing a metallic colorant;
wherein the second ink is a color ink containing a color coloring material or a black ink containing a black coloring material;
The ink set according to any one of [1] to [6] above.
[8]
The reaction solution has a surface tension of 55 mN/N or less at 25°C.
The ink set according to any one of [1] to [7] above.
[9]
The reaction liquid further contains at least one selected from the group consisting of a component that serves as an ink-receiving layer applied next to the reaction liquid, and a cationic resin.
The ink set according to any one of [1] to [8] above.
[10]
At least one kind (unit: g) selected from the group consisting of the component that will become the receiving layer and the cationic resin, which are contained in the reaction liquid, and the coloring material (unit: g) contained in the first ink (colorant: at least one selected from the group) is 7:1 to 70:1, the ink set according to [9] above.
[11]
A recording method using the ink set according to any one of [1] to [10] above,
a reaction liquid applying step of applying a reaction liquid contained in the ink set to a non-absorbent recording medium or a low-absorbent recording medium;
a first step of applying a first ink contained in the ink set to the region to which the reaction liquid has been applied;
a second step of applying a second ink included in the ink set to the region to which the first ink has been applied;
A recording method.
[12]
volatilization of volatile components contained in the reaction liquid and the first ink on the non-absorbent recording medium or the low-absorbent recording medium after the first step and before the second step; The amount is 95% by mass or less with respect to 100% by mass of the total mass of volatile components contained in the reaction liquid and the first ink before application.
The recording method described in [11] above.
[13]
The number of moles (unit: mol) of the polyvalent metal salt contained in the reaction liquid per unit area of the non-absorbent recording medium or the low-absorbent recording medium, the first ink and the second ink The ratio (coloring material: polyvalent metal salt) to the total mass (unit: g) of the coloring material contained in is 1000: 1 to 31000: 1,
The recording method according to [11] or [12] above.
[14]
The number of moles (unit: mol) of the organic acid contained in the reaction liquid per unit area of the non-absorbent recording medium or the low-absorbent recording medium, and the number of moles contained in the first ink and the second ink The ratio (coloring material: organic acid) to the total mass (unit: g) of the coloring material is 800: 1 to 5500: 1,
The recording method according to any one of [1] to [13] above.
[15]
From the components contained in the reaction liquid that will serve as receiving layers for the first ink and the second ink per unit area of the non-absorbent recording medium or the low-absorbent recording medium, and a cationic resin The ratio of the mass (unit: g) of at least one selected from the group to the mass (unit: g) of the colorant contained in the first ink (colorant: at least one selected from the group) is 7:1 to 70:1
The recording method according to any one of [11] to [14] above.

1 is a side view showing an outline of an entire example of an inkjet recording apparatus that can be used in this embodiment; FIG.

Embodiments for carrying out the present invention (hereinafter referred to as "present embodiments") will be described in detail below with reference to the drawings as necessary, but the present invention is not limited to these. Various modifications are possible without departing from the gist of the invention. In the drawings, the same elements are denoted by the same reference numerals, and overlapping descriptions are omitted. Moreover, the positional relationship such as up, down, left and right is based on the positional relationship shown in the drawings unless otherwise specified. Furthermore, the dimensional ratios of the drawings are not limited to the illustrated ratios.

[Ink set]
An ink set according to this embodiment includes a reaction liquid containing a flocculant, a first ink containing a coloring material, and a second ink containing a coloring material, and It is used for recording on a medium (hereinafter collectively referred to as a "recording medium"), and the reaction liquid and the first ink are applied onto the non-absorbent recording medium or the low-absorbent recording medium. , and the second ink are applied in this order. In addition, hereinafter, the first ink and the second ink are collectively referred to simply as "ink".

[Reaction solution]
The reaction liquid contains a flocculating agent. By using such a reaction liquid, it is possible to obtain high-quality recorded matter without heating the recording medium, and to suppress clogging of the nozzles caused by drying of the nozzles due to heating of the recording medium. be able to. Specifically, by containing the aggregating agent, the pigment contained in the first ink and the pigment contained in the second ink can be agglomerated without heating, thereby preventing bleeding of the second ink. Therefore, it is possible to prevent solid unevenness of the first ink, and to obtain a good-quality recorded matter.

(coagulant)
The flocculant is not particularly limited, but preferably contains, for example, at least one selected from the group consisting of polyvalent metal salts and organic acids.

(Polyvalent metal salt)
Although the polyvalent metal salt is not particularly limited, for example, a polyvalent metal salt of an inorganic acid or a polyvalent metal salt of an organic acid is preferable. Examples of such polyvalent metal salts include, but are not limited to, alkaline earth metals of group 2 of the periodic table (e.g., magnesium, calcium), transition metals of group 3 of the periodic table (e.g., lanthanum). , earth metals of group 13 of the periodic table (eg aluminum), lanthanides (eg neodymium). Suitable salts of these polyvalent metals are carboxylates (formic acid, acetic acid, benzoate, etc.), sulfates, nitrates, chlorides, and thiocyanates. Among them, preferably calcium or magnesium salts of carboxylic acids (formic acid, acetic acid, benzoate, etc.), calcium or magnesium salts of sulfuric acid, calcium or magnesium salts of nitric acid, calcium chloride, magnesium chloride, and thiocyanic acid. Calcium or magnesium salts may be mentioned. The polyvalent metal and the salt that constitute the polyvalent metal salt may be a combination of any of them, or may be a hydrate. In addition, polyvalent metal salt may be used individually by 1 type, and may use 2 or more types together.

The content of the polyvalent metal salt is preferably 0.5 to 5% by mass, more preferably 0.5 to 4% by mass, and even more preferably 1 to 4% by mass with respect to 100% by mass of the total mass of the reaction solution. . When the content of the polyvalent metal salt is within the above range, the resulting recorded matter tends to be more excellent in bleeding resistance.

(organic acid)
Examples of organic acids include, but are not limited to, phosphoric acid, oxalic acid, malonic acid, succinic acid, citric acid, and acetic acid. Among these, monovalent or divalent or higher carboxylic acids are preferred. By including such a carboxylic acid, the resulting recorded matter tends to be more excellent in bleeding resistance. In addition, an organic acid may be used individually by 1 type, and may use 2 or more types together. Also, the organic acid may be in the form of a salt. Examples of the organic acid salt include, but are not particularly limited to, salts of the above organic acids (not overlapping with the above polyvalent metal salts). Examples of the salt of the organic acid include, but are not particularly limited to, sodium acetate.
In addition, organic acid salt may be used individually by 1 type, and may use 2 or more types together.

The content of the organic acid is preferably 1 to 15% by mass, more preferably 1 to 14% by mass, even more preferably 1 to 7% by mass, relative to 100% by mass of the total mass of the reaction solution. When the content of the organic acid is within the above range, the resulting recorded matter tends to be more excellent in bleeding resistance.

The reaction liquid further contains at least one selected from the group consisting of a component that serves as a receiving layer for at least one of the first ink and the second ink (hereinafter simply referred to as "receiving layer component") and a cationic resin. preferably included.

(Component that serves as a receiving layer for at least one of the first ink and the second ink)
By including the receiving layer component in the reaction liquid, the resulting recorded matter tends to be more excellent in bleeding resistance and color development. The receptor layer component is not particularly limited, but examples thereof include fine particles that are solid in liquid, including inorganic fine particles and fine resin particles that are solid in liquid. Examples of such particles include cationic particles, nonionic particles and anionic particles. Among these, it is preferable to use a material in which gaps remain between the fine particles in a state in which a coating film is formed by adhering to the recording medium. The “gap” refers to a gap in the dried coating film of the reaction liquid. When the reaction liquid is applied to the recording medium to form a coating film, gaps are formed in the coating film by the component that will become the receiving layer, and at least the ink applied next to the reaction liquid is absorbed in the gaps, causing bleeding. is more preferable in that it is more suppressed. The component that serves as a receiving layer is usually a component that serves as a receiving layer for at least the first ink, and may also serve as a receiving layer for the second ink that is applied subsequently.

Since the particles are cationic, they have the effect of forming a layer for receiving the first ink and the second ink and imparting cohesion. Examples of cationic particles include, but are not limited to, Snowtech ST-AK (trade name, manufactured by Nissan Chemical Industries, Ltd.).

The anionic or nonionic particles form a layer that receives the first ink or the second ink. Examples of anionic particles or nonionic particles include, but are not limited to, anionic colloidal silica. Commercially available products include, for example, Snowtex ZL (trade name, manufactured by Nissan Chemical Industries, Ltd.).

The content of the receiving layer components is preferably 0.1 to 10% by mass, more preferably 0.1 to 6% by mass, based on 100% by mass of the total mass of the reaction solution. When the content of the receiving layer component is within the above range, the resulting recorded matter tends to be more excellent in bleeding resistance and color development. The receiving layer components may be used singly or in combination of two or more.

(cationic resin)
By containing the cationic resin in the reaction liquid, the resulting recorded matter tends to be more excellent in bleeding resistance and color development. Examples of the cationic resin include, but are not particularly limited to, a resin that is soluble in the reaction liquid and a resin that exhibits a dispersed state in a liquid such as a resin emulsion. The cationic resin interacts relatively weakly with the pigments contained in the first ink and the second ink compared to the aggregating agent described above, so it works more as an auxiliary agent for the aggregating agent than the aggregating agent. A resin that is soluble in the reaction solution is preferred because of its excellent interaction.

The resin soluble in the reaction solution is not particularly limited, but examples thereof include amine-based resins such as polyallylamine and polyallylamine derivatives.

Examples of resin emulsions include, but are not limited to, polyolefin resins, urethane resins, acrylic resins, and polyester resins. Examples thereof include resin emulsions that can be contained in the inks described later, and preferable commercial products include, for example, Arrowbase CD-1200 (manufactured by Unitika, trade name, polyolefin resin).

The content of the cationic resin is preferably 0.1 to 10% by mass, more preferably 0.1 to 6% by mass, relative to 100% by mass of the total mass of the reaction solution. When the content of the cationic resin is within the above range, the resulting recorded matter tends to be more excellent in bleeding resistance and color developability. The cationic resin may be used alone or in combination of two or more.

In addition to the above, the reaction liquid can contain a solvent, a surfactant, and the like.

〔solvent〕
Preferably, the reaction liquid in the present embodiment further contains a solvent. Although the solvent is not particularly limited, for example, an organic solvent or water can be used.

Examples of water include pure water such as ion-exchanged water, ultrafiltrated water, reverse osmosis water, and distilled water, and water from which ionic impurities are removed as much as possible, such as ultrapure water. In addition, the use of water sterilized by ultraviolet irradiation, addition of hydrogen peroxide, or the like can prevent the generation of mold and bacteria during long-term storage of the reaction solution. This tends to further improve the storage stability.

The content of water is preferably 80 to 95 parts by mass, more preferably 85 to 95 parts by mass, with respect to 100 parts by mass of the reaction liquid. When the water content is within the above range, the viscosity tends to be lower.

As the organic solvent, a volatile water-soluble organic solvent is more preferable. The organic solvent is not particularly limited, but specific examples include glycerin, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, 1,3-propanediol, 1,2-butanediol, 1,2 - pentanediol, 1,2-hexanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 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-butanol, 2-butanol, tert-butanol, iso-butanol, n-pentanol, 2 -Pentanol, 3-pentanol, and alcohols or glycols such as tert-pentanol, N,N-dimethylformamide, N,N-dimethylacetamide, 2-pyrrolidone, N-methyl-2-pyrrolidone, 2- oxazolidone, 1,3-dimethyl-2-imidazolidinone, dimethylsulfoxide, Sulfolane, and 1,1,3,3-tetramethylurea.

An organic solvent may be used individually by 1 type, and may be used in combination of 2 or more type. The content of the organic solvent is not particularly limited, and can be appropriately determined as necessary. Among these, it is preferable to use one or more selected from the group consisting of 1,2-hexanediol, triethylene glycol monobutyl ether, and dipropylene glycol monopropyl ether.

The content of the organic solvent is preferably 1 to 10% by mass with respect to 100% by mass of the total mass of the reaction solution.

[Surfactant]
The reaction liquid used in this embodiment preferably contains a surfactant. The surfactant is not particularly limited, but preferably at least one selected from the group consisting of acetylene glycol-based surfactants and polysiloxane-based surfactants.

Among these, polysiloxane-based surfactants are more preferable because they have a higher solubility in the reaction liquid and are more difficult to generate foreign substances in the reaction liquid.

The above acetylene glycol-based surfactants are not particularly limited, but examples include 2,4,7,9-tetramethyl-5-decyne-4,7-diol and 2,4,7,9-tetramethyl- selected from alkylene oxide adducts of 5-decyne-4,7-diol and alkylene oxide adducts of 2,4-dimethyl-5-decyn-4-ol and 2,4-dimethyl-5-decyn-4-ol are preferably one or more. These include E series such as Olfin 104 series and Olfin E1010 (trade name manufactured by Air Products Japan, Inc.), Olfin PD-002W, Surfynol 465 and Surfynol 61 (Nissin Chemical Industry Co., Ltd.). Chemical Industry Co., Ltd. (trade name), etc. are commercially available.

The polysiloxane-based surfactant is not particularly limited, and examples thereof include BYK-347 and BYK-348 (trade names manufactured by BYK Japan KK).

The content of the surfactant is preferably 0.1 to 3% by mass with respect to 100% by mass of the total mass of the reaction solution.

The surface tension of the reaction solution is preferably 55 mN/N or less, more preferably 40 mN/N or less at 25°C. When the surface tension is within the above range, the reaction liquid can be applied uniformly when recording is performed on the recording medium. The lower limit of the surface tension of the reaction solution is not particularly limited, but is preferably 1 mN/N or more at 25°C. The surface tension can be measured by the method described in Examples.

[First ink]
The first ink contains a coloring material. The content of the coloring material in the first ink is preferably 15 to 2% by mass, more preferably 13 to 3% by mass, relative to 100% by mass of the total mass of the first ink. When the content of the coloring material is within the above range, the resulting recorded matter tends to be more excellent in bleeding resistance and color development.

[Second ink]
The second ink contains a coloring material. The content of the coloring material in the second ink is preferably 15 to 2% by mass, more preferably 13 to 3% by mass, with respect to 100% by mass of the total mass of the second ink. When the content of the coloring material is within the above range, the resulting recorded matter tends to be more excellent in bleeding resistance and color development.

[Color material]
Coloring materials that can be contained in the first ink and the second ink are described below. Note that each of the first ink and the second ink may contain one type of coloring material alone or may contain two or more types of coloring materials.
Moreover, the coloring material may be a dye, and is preferably a pigment.

Examples of the black colorant used for the black ink include carbon black, which is not particularly limited. 2300, No. 900, MCF88, no. 33, No. 40, No. 45, No. 52, MA7, MA8, MA100, No. 2200B, etc. (manufactured by Mitsubishi Chemical Corporation), Raven 5750, Raven 5250, Raven 5000, Raven 3500, Raven 1255, Raven 700, etc. (manufactured by Carbon Columbia, R1), 400Rega Regal 330R, Regal 660R, Mogul L, Monarch 700, Monarch 800, Monarch 880, Monarch 900, Monarch 1000, Monarch 1100, Monarch 1300, Monarch 1400, etc. (manufactured by Cabot Corporation (CABOT JAPAN), Wcolcol K.K.) 、Ｃｏｌｏｒ Ｂｌａｃｋ 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).

The coloring material used for the white ink is not particularly limited, but examples include C.I. I. Pigment White 6, 18, 21 can be mentioned. Other pigments used in white ink include sulfates of alkaline earth metals such as barium sulfate, carbonates of alkaline earth metals such as calcium carbonate, silicas such as finely powdered silicic acid and synthetic silicates, metal compounds such as calcium silicate, alumina, alumina hydrate, titanium dioxide, and zinc oxide; and talc and clay.

The coloring material used for the yellow ink is not particularly limited, but 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, 167, 172, 180.

Coloring materials used for magenta ink are not particularly limited, but examples include 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.

The coloring material used for the cyan ink is not particularly limited, but 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.

Coloring materials other than magenta, cyan, and yellow include, but are not particularly limited to, C.I. 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.

Metallic pigments can be used as metallic colorants used in metallic inks, and fine metal particles can be used, and examples of metals include aluminum, aluminum alloys, and silver. A metallic ink is an ink in which a pattern formed by being applied to a recording medium has a feeling of metallic luster, and a metallic pigment is a pigment that expresses a feeling of metallic luster.

At least one of the first ink and the second ink is preferably a color ink containing a color colorant or a black ink containing a black colorant. Also, one of the first ink and the second ink is a color ink containing a color colorant or a black ink containing a black colorant, and the other of the first ink and the second ink is a white ink containing a white colorant. It is more preferable to have With such an ink set, when recording is made on a non-absorbent recording medium or a low-absorbing recording medium, it is possible to obtain color development properties on recording media other than white. For example, transparent, colored, and metallic media are preferably used.

Preferably, the first ink is a white ink containing a white colorant, and the second ink is a color ink containing a color colorant or a black ink containing a black colorant. With such an ink set, when recording is made on a non-absorbent recording medium or a low-absorbing recording medium, it is possible to obtain color development properties on recording media other than white. For example, transparent, colored, and metallic media are preferably used.

The ratio A between the number of moles (unit: mol) of the flocculant contained in the reaction liquid and the total mass (unit: g) of the coloring materials contained in the first ink and the second ink is 100:1 to 5000:1. is preferred, and 500:1 to 4000:1 is more preferred. When the ratio A is 100:1 or more, it is possible to prevent precipitation of the reaction liquid, cloudiness, stickiness, and generation of odor due to the reaction liquid. Further, when the ratio A is 5000:1 or less, bleeding during ink superimposition can be suppressed.

The ratio B between the number of moles (unit: mol) of the polyvalent metal salt contained in the reaction liquid and the total mass (unit: g) of the coloring materials contained in the first ink and the second ink is 300:1 to 5000. :1 is preferred, and 500:1 to 5000:1 is more preferred. When the ratio B is 300:1 or more, it is possible to prevent precipitation of polyvalent metal salts, cloudiness, stickiness and odor caused by polyvalent metal salts. Further, when the ratio B is 5000:1 or less, it is possible to suppress bleeding during ink superimposition.

The ratio C between the number of moles (unit: mol) of the organic acid contained in the reaction liquid and the total mass (unit: g) contained in the coloring materials of the first ink and the second ink is 100:1 to 800:1. is preferred, and 100:1 to 700:1 is more preferred. When the ratio C is 100:1 or more, it is possible to prevent precipitation of organic acid, white turbidity, stickiness and odor caused by organic acid. Further, when the ratio C is 800:1 or less, bleeding during ink superimposition can be suppressed.

The mass (unit: g) of at least one selected from the group consisting of receiving layer components and cationic resins contained in the reaction liquid and the mass (unit: g) of the coloring material contained in the first ink The ratio D is preferably 1:1 to 10:1, more preferably 1:1 to 5:1. When the ratio D is 1:1 or more (the former), the bleeding suppression function of the flocculant is more assisted, so bleeding tends to be suppressed more. In addition, when the ratio D is 10:1 or less (the former), the storage stability of the reaction liquid and the clogging reliability in the case of ink-jet coating tend to be excellent.

As is clear from Table 2, the above ratios are: Ratio A is the ratio (coloring material: flocculant), Ratio B is the ratio (coloring material: polyvalent metal salt), and Ratio C is the ratio (coloring material: organic acid ), the ratio D is a ratio (colorant: at least one selected from the above group), and the ratios A to C are those in a unit mass of the reaction liquid, a unit mass of the first ink, and a unit mass of the second ink. and the ratio D is for unit mass of reaction liquid and unit mass of first ink.

When a pigment is used as the colorant, the pigment may be used as a pigment dispersion obtained by dispersing it in water using a dispersant, or as a self-dispersion type surface in which a hydrophilic group is introduced into the pigment particle surface using a chemical reaction. It is preferably added to the ink as a pigment dispersion obtained by dispersing the treated pigment in water or by dispersing the polymer-coated pigment in water.

The dispersant is not particularly limited, but examples thereof include polymer dispersants (glue, gelatin, casein, proteins such as albumin, natural gums such as gum arabic and gum tragacanth, glucosides such as saponin, alginic acid and propylene glycol ester, alginic acid Triethanolamine, alginic acid fermented product of ammonium alginate methylcellulose, carboxymethylcellulose, cellulose derivative of ethylhydroxycellulose, polyvinyl alcohols, polypyrrolidones, polyacrylic acid, acrylic acid-acrylonitrile copolymer, potassium acrylate-acrylonitrile copolymer Polymers, vinyl acetate-acrylic acid ester copolymers, acrylic acid-acrylic acid ester copolymer acrylic resins, styrene-acrylic acid copolymers, styrene-methacrylic acid copolymers, styrene-methacrylic acid-acrylic acid Ester copolymer, styrene-acrylic resin of styrene-m-methylstyrene-acrylic acid copolymer, styrene-maleic acid copolymer, styrene-maleic anhydride copolymer, vinylnaphthalene-acrylic acid copolymer, acetic acid Vinyl-ethylene copolymers, vinyl acetate-fatty acid vinyl ethylene copolymers, vinyl acetate-maleic acid ester copolymers, vinyl acetate-croton copolymers, vinyl acetate-based copolymers of vinyl acetate-acrylic acid copolymers and salts thereof) and surfactants (various anionic surfactants, nonionic surfactants, amphoteric surfactants) can be used.

The self-dispersion type surface-treated pigment introduced with a hydrophilic group can be dispersed or dissolved in water without a dispersant by surface treatment such that a carboxyl group and its salt are directly bonded to the surface of the pigment. is. Specifically, it can be obtained by grafting a functional group or a molecule containing a functional group onto the surface of the pigment by a physical treatment of vacuum plasma or a chemical treatment using an oxidizing agent such as sodium hypochlorite or ozone. can be done. A single pigment particle may be grafted with a single functional group or a plurality of functional groups. The type and degree of the functional group to be grafted may be appropriately determined in consideration of dispersion stability in the ink, color density, and drying property on the front surface of the inkjet head.

In addition, the pigment coated with the polymer is not particularly limited. For example, after dispersing the pigment using a dispersant having a polymerizable group, a monomer (copolymerizable monomer) that can be and a photoradical polymerization initiator, and emulsion polymerization in water. Among these polymers, monomers and oligomers having at least one selected from the group consisting of acryloyl groups, methacryloyl groups, vinyl groups, and allyl groups as double bonds are prepared according to known polymerization methods using photoradical polymerization initiators. A polymerized one is preferably usable. A general method can be used for the above emulsion polymerization, and polymerization proceeds by free radicals generated by thermal decomposition of a water-soluble photoradical polymerization initiator in the presence of an emulsifier.

The pigments and dispersants that constitute the pigment dispersion may be used singly or in combination of two or more.

[Resin emulsion]
When the ink used in this embodiment contains a pigment as a coloring material, it preferably further contains a resin emulsion. By using the resin emulsion, as the ink dries, the resins in the resin emulsion and the resin and the pigment fuse with each other to fix the pigment to the recording medium. The abrasion resistance and adhesion can be further improved. Among resin emulsions, urethane resin emulsions and acrylic resin emulsions are preferred, and urethane resin emulsions are more preferred. As a result, the fixability of the ink is excellent, so that the recorded matter has excellent abrasion resistance and adhesion.

When the resin emulsion is contained in the ink, the resin emulsion forms a resin film on the recording medium, thereby sufficiently fixing the ink on the recording medium and improving the abrasion resistance of the recorded matter. . Therefore, the resin emulsion preferably contains a thermoplastic resin. In particular, urethane resin emulsions have a high degree of freedom in design, so that desired film physical properties can be easily obtained.

Anionic resin emulsions are also preferred. The resin contained in the anionic resin emulsion is not particularly limited. Examples include homopolymers or copolymers of vinyl alcohol, vinyl ether, vinylpyrrolidone, vinylpyridine, vinylcarbazole, vinylimidazole, and vinylidene chloride, fluororesins, and natural resins. Among them, at least one selected from the group consisting of (meth)acrylic resins and styrene-(meth)acrylic acid copolymer resins is preferable, and it is selected from the group consisting of acrylic resins and styrene-acrylic acid copolymer resins. At least one type is more preferred, and a styrene-acrylic acid copolymer-based resin is even more preferred. The above copolymer may be in any form of a random copolymer, a block copolymer, an alternating copolymer, and a graft copolymer.

As the resin emulsion, those obtained by known materials and production methods may be used, or commercially available products may be used. The commercial product is not particularly limited, but for example, Movinyl 966A (trade name, acrylic resin emulsion manufactured by Nippon Synthetic Chemical Industry Co., Ltd.), Microgel E-1002, Microgel E- 5002 (trade name, manufactured by Nippon Paint Co., Ltd.), Boncoat 4001, Boncoat 5454 (trade name, manufactured by DIC), SAE1014 (trade name, manufactured by Zeon Corporation), Saibinol SK-200 (trade name, manufactured by SAIDEN CHEMICAL INDUSTRY CO., LTD.), Joncryl 7100, Joncryl 390, Joncryl 711, Joncryl 511, Joncryl 7001, Joncryl 632, Joncryl 741, Jongkril 450, Jongkril 840, Jongkril 62J, Jongkril 74J, Jongkril HRC-1645J, Jongkril 734, Jongkril 852, Jongkril 7600, Jongkril 775, Jongkril 537J, Jongkril 1535, Jongkril PDX-7630A, Joncryl 352J, Joncryl 352D, Joncryl PDX-7145, Joncryl 538J, Joncryl 7640, Joncryl 7641, Joncryl 631, Joncryl 790, Joncryl 780, Joncryl 7610 (all trade names, BASF), NK Binder R-5HN (trade name, acrylic resin emulsion, solid content 44%, manufactured by Shin-Nakamura Chemical Co., Ltd.). Among these, Movinyl 966A, which is an acrylic resin emulsion, is preferable because it sufficiently satisfies the preferable physical properties of the resin emulsion described above.

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

The resin content of the resin emulsion is preferably 3 to 15% by mass, more preferably 7 to 14% by mass, and even more preferably 8 to 13% by mass with respect to 100% by mass of the total mass of each ink. Within the above range, the adhesion and abrasion resistance of the recorded matter tend to be better, and the long-term storage stability of the ink is excellent, and in particular, the viscosity of the ink tends to be low. It is in.

〔solvent〕
The ink in this embodiment preferably further contains a solvent. Although the solvent is not particularly limited, for example, an organic solvent or water can be used.

Examples of water include pure water such as ion-exchanged water, ultrafiltrated water, reverse osmosis water, and distilled water, and water from which ionic impurities are removed as much as possible, such as ultrapure water. In addition, the use of water that has been sterilized by ultraviolet irradiation or the addition of hydrogen peroxide can prevent the formation of mold and bacteria when the ink is stored for a long period of time. This tends to further improve the storage stability.

As the organic solvent, a volatile water-soluble organic solvent is more preferable. The organic solvent is not particularly limited, but specific examples include glycerin, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, 1,3-propanediol, 1,2-butanediol, 1,2 - pentanediol, 1,2-hexanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 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-butanol, 2-butanol, tert-butanol, iso-butanol, n-pentanol, 2 -Pentanol, 3-pentanol, and alcohols or glycols such as tert-pentanol, N,N-dimethylformamide, N,N-dimethylacetamide, 2-pyrrolidone, N-methyl-2-pyrrolidone, 2- oxazolidone, 1,3-dimethyl-2-imidazolidinone, dimethylsulfoxide, Sulfolane, and 1,1,3,3-tetramethylurea.

An organic solvent may be used individually by 1 type, and may be used in combination of 2 or more type. The content of the organic solvent is not particularly limited, and can be appropriately determined as necessary. Among these, it is preferable to use one or more selected from the group consisting of 1,2-hexanediol, triethylene glycol monobutyl ether, and dipropylene glycol monopropyl ether.

[Surfactant]
The ink used in this embodiment preferably contains a surfactant. The surfactant is not particularly limited, but preferably at least one selected from the group consisting of acetylene glycol-based surfactants and polysiloxane-based surfactants. By including these surfactants in the ink, the drying property of the ink adhering to the recording medium is further improved, and high-speed recording becomes possible.

Among these, the polysiloxane-based surfactant is more preferable because it has a higher solubility in the ink and is more difficult to generate foreign matter in the ink.

The above acetylene glycol-based surfactants are not particularly limited, but examples include 2,4,7,9-tetramethyl-5-decyne-4,7-diol and 2,4,7,9-tetramethyl- selected from alkylene oxide adducts of 5-decyne-4,7-diol and alkylene oxide adducts of 2,4-dimethyl-5-decyn-4-ol and 2,4-dimethyl-5-decyn-4-ol are preferably one or more. These include E series such as Olfin 104 series and Olfin E1010 (trade name manufactured by Air Products Japan, Inc.), Olfin PD-002W, Surfynol 465 and Surfynol 61 (Nissin Chemical Industry Co., Ltd.). Chemical Industry Co., Ltd. (trade name), etc. are commercially available.

The polysiloxane-based surfactant is not particularly limited, and examples thereof include BYK-347 and BYK-348 (trade names manufactured by BYK Japan KK).

[Moisturizer]
The ink used in this embodiment preferably further contains a humectant (wetting agent). As the moisturizing agent, any one that is generally used for inkjet ink can be used without particular limitation. The boiling point of the moisturizing agent is preferably 180°C or higher, more preferably 200°C or higher. When the boiling point is within the above range, it is possible to impart good water retention and wettability to the ink.

Specific examples of high-boiling humectants include, but are not limited to, ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, pentamethylene glycol, trimethylene glycol, 2-butene-1,4-diol, and 2-ethyl-1. ,3-hexanediol, 2-methyl-2,4-pentanediol, tripropylene glycol, polyethylene glycol having a number average molecular weight of 2000 or less, 1,3-propylene glycol, isopropylene glycol, isobutylene glycol, glycerin, mesoerythritol, and Pentaerythritol is mentioned.

Moisturizers may be used singly or in combination of two or more. Since the ink contains a humectant with a high boiling point, it is possible to obtain an ink that can maintain fluidity and redispersibility for a long time even when the pigment ink is left in an open state in contact with air. Furthermore, such an ink is less likely to cause clogging of the nozzles during printing using the printing apparatus or at the time of re-starting after the printing is interrupted, so that the ejection stability of the ink is excellent.

[Other ingredients]
The ink used in the present embodiment contains a dissolution aid, a viscosity modifier, a pH Various additives such as modifiers, antioxidants, preservatives, anti-mold agents, corrosion inhibitors, and chelating agents to trap metal ions that affect dispersion may also be added as appropriate. From the viewpoint of safety, it is preferable that the ink used in this embodiment is a water-based ink that contains the most water among the volatile components.

[Recording medium]
The ink set according to this embodiment is used for recording on a non-absorbent recording medium or a low-absorbing recording medium. Absorbent recording media are inferior in water resistance and abrasion resistance, and in the case of absorbent recording media having an ink-receiving layer on the surface, the cost may be high. A recording medium or a low-absorbent recording medium is superior in terms of water resistance, abrasion resistance, and low cost compared to an absorbent recording medium having an ink-receiving layer on its surface. The more non-absorbing the recording medium, the more likely it is to bleed, making it difficult to achieve both bleeding and printing speed. be.

Here, the term “low-absorbent recording medium” or “non-absorbent 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. . The Bristow method is the most popular method for measuring liquid absorption in a short period of time, and is also adopted by the Japan Pulp and Paper Institute (JAPAN TAPPI). For details of the test method, refer to Standard No. 2000 of "JAPAN TAPPI Paper Pulp Test Method 2000". 51 "Paper and paperboard--Liquid absorbency test method--Bristow method".

Non-absorbent recording media or low-absorbent recording media can also be classified according to the wettability of the recording surface to water. For example, 0.5 μL of water droplets are dropped on the recording surface of the recording medium, and the rate of decrease in contact angle (comparison between the contact angle at 0.5 milliseconds after impact and the contact angle at 5 seconds after impact) is measured. A medium can be characterized. More specifically, as the property of the recording medium, the non-absorbent property of the "non-absorbent recording medium" refers to the above-mentioned decrease rate of less than 1%, and the low absorption of the "low-absorbent recording medium" The property indicates that the rate of decrease is 1% or more and less than 5%. In addition, absorbability means that the rate of decrease is 5% or more. The contact angle can be measured using a portable contact angle meter PCA-1 (manufactured by Kyowa Interface Science Co., Ltd.) or the like.

Examples of low-absorbency recording media include, but are not limited to, coated paper having a coating layer for receiving oil ink on the surface. Specifically, it is a paper whose surface is coated with paint to enhance beauty and smoothness, and is classified as coated paper for printing according to the Ministry of Economy, Trade and Industry's "Current Production Statistics Classification". Paints include those made by mixing a white pigment, which is an inorganic compound such as clay (kaolin) or calcium carbonate, and an adhesive (binder) such as starch. The amount of coating applied is preferably about 10 to 40 g/m ² . Coated paper is not particularly limited, but includes recording paper such as art paper, coated paper, and matte paper.

Examples of non-absorbent recording media include, but are not limited to, plastic films that do not have an ink-absorbing layer, substrates such as paper coated with plastic, and plastic films adhered. etc. The plastics mentioned here include polyvinyl chloride, polyethylene terephthalate, polycarbonate, polystyrene, polyurethane, polyethylene, polypropylene, polyacryl, and the like.

In addition to the above recording media, non-ink-absorbing or low-ink-absorbing recording media such as plates of metals such as iron, silver, copper, and aluminum, and glass can also be used.

〔Recording method〕
The recording method according to the present embodiment includes a reaction liquid applying step of applying a reaction liquid onto a non-absorbent recording medium or a low-absorbent recording medium using the above-described ink set, and applying the first ink onto the reaction liquid. and a second step of applying the second ink over the first ink.

FIG. 1 is a side view schematically showing an example of an inkjet recording apparatus 1 that can be used in this embodiment. As shown in FIG. 1 , the inkjet recording apparatus 1 includes a recording medium feeding section 10 , a conveying section 20 , a recording section 30 , a drying device 90 , and a discharge section 70 . The inkjet recording apparatus 1 may also include a preheater (not shown) so that the recording medium F may be heated from the beginning.

Among them, the drying device 90 has a first drying section 40 for drying the recording medium and a second drying section 50 for drying the recorded matter obtained by the recording method according to the present embodiment.

Further, the feeding section 10 is provided so as to be able to feed the recording medium F to the conveying section 20 . Specifically, the feeding unit 10 has a roll medium holder 11, and the roll medium holder 11 holds the recording medium F. As shown in FIG. By rotating the recording medium F, the recording medium F can be fed to the transport section 20 on the downstream side in the feeding direction Y. As shown in FIG. Note that the recording medium F is not limited to a roll shape.

Further, the transport section 20 is provided so as to transport the recording medium F sent from the feeding section 10 to the recording section 30 . Specifically, the conveying section 20 has a first feed roller 21 and is configured to be able to further convey the fed recording medium F to the recording section 30 on the downstream side in the feeding direction Y. As shown in FIG.

Further, the recording unit 30 is provided so as to apply a reaction liquid to the recording medium F sent from the conveying unit 20 and eject ink for recording. Specifically, the recording unit 30 includes a head 31 that performs the reaction liquid application process, a head 32 that performs the first process, a recording head 33 that performs the second process, and a platen 34 as a medium support section. . The method of applying the reaction liquid and ink is not limited to inkjet, and in particular, the reaction liquid may be applied by roller coating, spray coating, or the like. Ink jetting is preferable in that the application position and application amount can be applied to the required area with high accuracy.

Among these, the platen 34 is provided so as to support the recording medium F from the back side. Further, the platen 34 is provided with a first drying section 40 that dries the reaction liquid applied to the recording medium F and the ink ejected onto the recording medium F. As shown in FIG. Further, a second feed roller 43 is provided downstream of the platen 34 in the feed direction Y. As shown in FIG. The second feed roller 43 is configured to feed the recorded recording medium F to the second drying section 50 downstream in the feed direction Y. As shown in FIG.

The second drying section 50 is configured to further dry the reaction liquid applied to the recording medium F and the ink ejected onto the recording medium F. As shown in FIG. Further, a third feed roller 65 is provided near the exit 64 of the second drying section 50 . The third feed roller 65 is arranged so as to come into contact with the back surface of the recording medium F, and is configured to be able to feed the recording medium F to the discharge section 70 downstream in the feeding direction Y.

Further, the discharge section 70 is provided so as to further feed the recording medium F sent from the second drying section 50 to the downstream side in the feeding direction Y and discharge it to the outside of the inkjet recording apparatus 1 . Specifically, the discharge section 70 has a fourth feed roller 71 , a fifth feed roller 72 , a sixth feed roller 73 , a seventh feed roller 74 and a take-up roller 75 . Among them, the fourth feed roller 71 and the fifth feed roller 72 are arranged so as to be in contact with the surface of the recording medium F. As shown in FIG. Also, the sixth feed roller 73 and the seventh feed roller 74 are arranged to form a roller pair. The recording medium F ejected by the sixth feed roller 73 and the seventh feed roller 74 is provided so as to be taken up by the take-up roller 75 .

[Reaction liquid application step]
The reaction liquid applying step is a step of applying the reaction liquid onto a non-absorbent recording medium or a low-absorbent recording medium. Application means is not particularly limited, but roller coating, spray coating, and inkjet coating can be used, for example. A step of drying at least part of the reaction liquid applied to the recording medium during or after the reaction liquid application step may be further provided.

The amount of the reaction liquid applied to the recording medium is preferably 1 to 10 mg/inch ² , more preferably 1 to 5 mg/inch ² . When the amount of the reaction liquid to be applied is within the above range, the resulting recorded matter tends to be more excellent in bleeding resistance.

The amount of the aggregating agent to be applied to the recording medium is preferably 0.5×10 ⁻⁴ to 15×10 ⁻⁴ mmol/inch ² (50 to 1500 nmol/inch ² ), more preferably 0.65×10 ⁻⁴ mmol/inch. ² or more is more preferable, 1×10 ⁻⁴ mmol/inch ² or more is more preferable, 1.5×10 ⁻⁴ mmol/inch ² or more is still more preferable, and 2×10 ⁻⁴ mmol/inch ² or more is still more preferable. , 3×10 ⁻⁴ mmol/inch ² or more is particularly preferred. The amount to be applied is more preferably 10.8×10 ⁻⁴ mmol/inch ² or less, still more preferably 10×10 ⁻⁴ mmol/inch ² or less, and particularly preferably 5×10 ⁻⁴ mmol/inch ² or less. When the amount of the aggregating agent to be applied is within the above range, the image quality of the recorded matter is further improved, and the values of the ratios F to H described below can be easily obtained, which is preferable. The application amount of the reaction liquid or the aggregating agent is the application amount of the reaction liquid or the aggregating agent per unit area in the region where the first ink and the second ink are applied in an overlapping manner.

[First step]
The first step is a step of applying the first ink from above the reaction liquid. At this time, since the reaction liquid and the first ink directly react, the first ink can quickly coagulate, and the reaction liquid does not have to be completely dried. Since the reaction liquid does not have to be completely dried and the reaction liquid does not have to be dried, application of the first ink can be started early, and high speed printing can be achieved. The method may further include a step of drying at least part of the reaction liquid and the first ink applied to the recording medium during or after the first step.

The amount of the first ink applied in the first step is preferably 2-20 mg/inch ² , more preferably 15-5 mg/inch ² . When the amount of the first ink to be applied is within the above range, the resulting recorded matter tends to be more excellent in bleeding resistance, clogging reliability, and stickiness.

[Second step]
The second step is a step of applying the second ink over the first ink. At this time, the reaction liquid and the first ink may not be completely dried. By applying the second ink in a state in which the first ink is not completely dried, the reaction liquid and the second ink can react even from above the first ink. Even if the liquid and the first ink are not completely dried, the second ink can be applied while suppressing bleeding, and a high recording speed can be achieved. Before the second step, there may be a step of drying at least a part of the reaction liquid and the first ink applied to the recording medium, and the step may be a step of partially drying, not completely drying. is preferred. Further, the method may have a step of drying the second ink applied to the recording medium during or after the second step.

The amount of the second ink applied in the second step is preferably 2-20 mg/inch ² , more preferably 15-5 mg/inch ² . When the amount of the first ink to be applied is within the above range, the resulting recorded matter tends to be more excellent in bleeding resistance, clogging reliability, and stickiness.

In the first step and the second step, the total applied amount (total mass) of the coloring material contained in the first ink and the second ink per unit area in the region where the first ink and the second ink are applied in an overlapped manner is 0.5 to 3 mg/inch ² is preferable, 1 mg/inch ² or more is preferable, 1.5 mg/inch ² or more is more preferable, and 2.5 mg/inch ² or less is more preferable.

Further, in the first step, the total applied amount of the coloring material contained in the first ink per unit area in the region where the first ink and the second ink are applied in an overlapped manner is 0.1 to 2.5 mg/inch ² . is preferred, 0.2 mg/inch ² or more is more preferred, 0.5 mg/inch ² or more is even more preferred, 1 mg/inch ² or more is particularly preferred, and 2 mg/inch ² or less is more preferred. When each application amount is within the above range, the image quality of the recorded matter is more excellent, and the values of the ratios E to H, which will be described later, can be easily obtained.
The application amount of each coloring material in the first step and the second step, the total application amount of the coloring material, the application amount of the coagulant in the reaction liquid application step, and the ratio E to ratio H described later are the first ink and the second ink. It is preferable that the area where the total amount of coloring material applied is the largest in the area to which is repeatedly applied, in that the image quality of the recorded matter can be further improved.

In the first step and the second step, the first ink or the second ink can be ejected from the nozzles of the line head or the serial head by the ink jet method and deposited on the recording medium. In the line method using a line head, the head is fixed and the recording medium is moved along the sub-scanning direction (longitudinal direction of the recording medium, transport direction). An image can be recorded on a recording medium by ejecting ink droplets. In the serial method using a serial head, the head is moved in the main scanning direction (horizontal direction and width direction of the recording medium), and ink droplets are ejected from the nozzle openings of the head in conjunction with this movement. Thus, an image can be recorded on the recording medium.

In the second step, at the time of applying the second ink, the volatilization amount of the volatile components contained in the reaction liquid and the first ink applied to the non-absorbent recording medium or low-absorbent recording medium is It is preferably 95% by mass or less, more preferably 85% by mass or less, and even more preferably 80% by mass or less with respect to 100% by mass of the total mass of volatile components contained in the reaction liquid and the first ink. Further, from the viewpoint of excellent clogging reliability and excellent recording speed, the content is further preferably 60% by mass or less, even more preferably 50% by mass or less, and even more preferably 30% by mass or less.
On the other hand, it is preferably 5% by mass or more, more preferably 10% by mass or more, particularly preferably 50% by mass or more, and even more preferably 60% by mass or more, from the viewpoint of better suppression of bleeding. Here, the "reaction liquid before application" means the reaction liquid before application of the reaction liquid of the reaction liquid applied to the recording medium in the reaction liquid application step, and "before application ... the first ink". The first ink means the first ink to be applied to the recording medium in the first step, before the first ink is applied. When the volatilization amount of the volatile component is 95% by mass or less, the reaction liquid and the second ink can efficiently react with each other, so that the recording speed can be increased. The volatilization amount of volatile components can be obtained by the method described in Examples.

The number of moles (unit: mol) of the aggregating agent contained in the reaction liquid per unit area in the area of the non-absorbent recording medium or low-absorbent recording medium where the first ink and the second ink are applied in layers. and the total mass (unit: g) of the coloring materials contained in the first ink and the second ink is preferably 800:1 to 31000:1, more preferably 800:1 to 16000:1, and 1600 :1 to 5100:1 is more preferred. When the ratio E is 800:1 or more, it is possible to prevent precipitation of the reaction liquid, cloudiness, stickiness, and generation of odor due to the reaction liquid. When the ratio E is 31000:1 or less, bleeding during ink superimposition can be suppressed. Note that the ratio E can be controlled by the amounts of the first ink, the second ink, and the reaction liquid applied.

The number of moles (unit: mol) of the polyvalent metal salt contained in the reaction liquid per unit area of the above region of the non-absorbent recording medium or the low-absorbent recording medium, and the number of moles contained in the first ink and the second ink The ratio F to the total mass (unit: g) of the colorant used is preferably 1000:1 to 31000:1, more preferably 1000:1 to 15000:1, even more preferably 1000:1 to 5100:1. When the ratio F is 1000:1 or more, it is possible to prevent precipitation of polyvalent metal salts, cloudiness, stickiness and odor caused by polyvalent metal salts. When the ratio F is 31000:1 or less, bleeding during ink superimposition can be suppressed. Note that the ratio F can be controlled by the amounts of the first ink, the second ink, and the reaction liquid applied.

The number of moles (unit: mol) of the organic acid contained in the reaction liquid per unit area of the above region of the non-absorbent recording medium or low-absorbent recording medium, and the colors contained in the first ink and the second ink The ratio G to the total mass (unit: g) of the material is preferably 800:1 to 5500:1, more preferably 800:1 to 1700:1, even more preferably 1000:1 to 1700:1. When the ratio G is 800:1 or more, it is possible to prevent precipitation of organic acids, white turbidity, stickiness and odor caused by organic acids. When the ratio G is 5500:1 or less, bleeding during ink superimposition can be suppressed. Note that the ratio G can be controlled by the amounts of the first ink, the second ink, and the reaction liquid applied.

At least one mass (unit :g) and the mass (unit: g) of the coloring material contained in the first ink is preferably 7:1 to 70:1, more preferably 7:1 to 50:1. When the ratio H is 7:1 or more (the former), there is a tendency to be even more excellent in suppressing bleeding. When the ratio H is 70:1 or less (the former), the reaction liquid tends to be applied more efficiently. Note that the ratio H can be controlled by the amounts of the first ink and the reaction liquid applied.

As is clear from Tables 3 to 5, each of the above ratios is the ratio E is the ratio (coloring material: flocculant), the ratio F is the ratio (coloring material: polyvalent metal salt), and the ratio G is the ratio (coloring material: organic acid), and the ratio H is the ratio (colorant: at least one selected from the above group).

In the recording method according to this embodiment, the surface temperature of the recording medium in the first step and/or the second step is preferably 10° C. or higher and 65° C. or lower. In addition, the temperature is more preferably 50° C. or lower, and even more preferably 40° C. or lower, in terms of better clogging reliability. On the other hand, the temperature is more preferably 20° C. or higher, further preferably 40° C. or higher, and particularly preferably 50° C. or higher, from the viewpoint of better recording speed. When the surface temperature of the recording medium is within the above range, it tends to be particularly excellent in clogging reliability and recording speed.

Hereinafter, the present invention will be described more specifically using examples and comparative examples. The present invention is by no means limited by the following examples.

[Materials for reaction liquid and ink]
Main materials for reaction liquids and inks used in the following examples and comparative examples are as follows.
[Pigment]
Titanium dioxide: Metal oxide NanoTek (R) Slurry manufactured by C.I. Kasei Co., Ltd. Cyan pigment: C.I. I. pigment blue 15:3
[Polyvalent metal salt]
Magnesium sulfate heptahydrate (molecular weight 246.47 g/mol)
Calcium acetate monohydrate (molecular weight 176.18 g/mol)
Calcium nitrate tetrahydrate (molecular weight 164.09 g/mol)
[Organic acid]
Succinic acid (molecular weight 118.09 g/mol)
[Surfactant]
BYK348 (silicone-based surfactant, manufactured by BYK-Chemie Japan)
[Resin emulsion]
Joncryl 62J (acrylic styrene resin, manufactured by BASF)
[Receptive layer component]
Anionic colloidal silica (“Snowtex ZL” manufactured by Nissan Chemical Industries, Ltd.)
[Cationic resin]
Cationic resin emulsion ("Arrowbase CD-1200" manufactured by Unitika)
〔Organic solvent〕
1,2 hexanediol [humectant]
Propylene glycol

[Preparation of reaction liquid and ink]
Each material was mixed in the composition (% by mass) shown in Table 1 below and sufficiently stirred to obtain a reaction liquid, a first ink, and a second ink, respectively.

[Method for measuring surface tension]
The surface tension of the reaction liquid was measured by the Wilhelmy method at a liquid temperature of 25° C. using a surface tension meter (manufactured by Kyowa Interface Science Co., Ltd., surface tension meter CBVP-Z, etc.).

[Preparation of ink set]
The resulting reaction liquid, first ink, and second ink were combined as shown in Table 2 to obtain ink sets.

[Examples 1 to 18, Comparative Examples 1 to 5]
A modified PX-G930 (manufactured by Epson Corporation) was used. The modified point is that a heater is attached to the platen so that the recording medium can be heated. The nozzle pitch is 180 dpi. The ink set prepared above was ejected from each head by an inkjet method under the recording conditions shown in Tables 1 to 3 in the order of the reaction liquid, the first ink, and the second ink, and PET made by Toray, which is a non-absorbent recording medium, was used. A solid pattern was attached on a film “Lumirror S10” (trade name, thickness 100 μm) or NP coated paper (manufactured by Lintec), which is a low-absorbent recording medium.
At this time, pattern 1 in which only the reaction liquid was applied, pattern 2 in which only the reaction liquid and the first ink were applied in layers, and pattern 3 in which the reaction liquid, the first ink, and the second ink were applied in layers were formed. Patterns 2 and 3 were formed simultaneously so as to be in contact with each other.

Specifically, in the case of forming pattern 3, the temperature of the recording medium is adjusted in advance with a heater so that it reaches the temperature shown in Tables 3 to 5, and then the reaction liquid is applied and the pattern (sub pattern) made of the reaction liquid is applied. pattern) is formed, then the first ink is applied onto the sub-pattern made of the reaction liquid to form a sub-pattern made of the first ink, and then the sub-pattern made of the first ink is made of the second ink. Pattern 3 was formed by forming a sub-pattern. The temperature of the recording medium was adjusted with a platen heater so that the temperatures shown in Tables 3 to 5 were maintained even during the application of the reaction liquid, the first ink, and the second ink. After the first step and before the start of the second step (at the start), the contents of the volatile components of the reaction liquid and the first ink on the recording medium were adjusted to the values in Tables 3 to 5, and the second step was performed. did the process. The recording resolution was set to 720×720 dpi, and the amounts of reaction liquid and ink per dot were adjusted so as to achieve the amount shown in the table.

[Volatilization amount of volatile components of the reaction liquid before the second step and the first ink]
After the first step and before the second step (when the recording medium is conveyed to the position facing the second ink head), the volatilization amount of the volatile components of the reaction liquid and the first ink in the pattern 3 is obtained by the following formula. Calculated by Here, Af is the total applied amount (mg) of the reaction liquid and the first ink applied to the recording medium in layers. Ae is the total residual amount of the reaction liquid and the first ink on the recording medium after the reaction liquid and the first ink have been dried (volatilized) to a state sufficient to use the recorded matter. Furthermore, A is the total mass of the reaction liquid and the first ink on the recording medium immediately before the second step.
Volatile amount % of volatile components = ((Af-A) / (Af-Ae)) × 100

Af can be obtained as the application amount of the reaction liquid and the first ink in the pattern 3 from the ejection data of the printer and the mass per dot. A can be obtained by measuring the mass of the recording medium at the time when the application of the second ink is started and the mass of the recording medium before the reaction liquid application process, and taking the difference. When measuring the volatilization amount of the volatile component, it is convenient to use a recording medium prepared for measurement. Measurements were made with an electronic balance. At the time of measurement, the relationship between the drying time and the amount of volatilization when the reaction liquid and the first ink are applied and then heated and dried on a platen is obtained. When printing with a printing apparatus, the time from the application of the reaction liquid and the first ink to the application of the second ink is set to any time in the relationship between the drying time and the volatilization amount obtained above. It is possible to obtain the desired amount of volatilization.

[evaluation]
[Bleeding during superposition recording of the first ink and the second ink]
Recorded matter was obtained by changing the amount of the second ink applied in pattern 3 from 30% to 200%, with the value shown in Tables 3 to 5 as 100%. Bleeding during superimposition recording of the first ink and the second ink was evaluated by the following evaluation criteria by visually observing the portion where pattern 3 and pattern 2 of the obtained recorded matter were in contact. Note that "200%" is a value that assumes the maximum total application amount of a plurality of color inks when secondary colors or higher colors are printed using a plurality of color inks. If it is A or AA in the following evaluation criteria, it can be said that a recorded matter in which bleeding is suppressed can be obtained even when a plurality of color inks are used.
(Evaluation criteria)
AA: There is no color mixture even when the applied amount of the second ink is 200%.
A: Color mixture does not occur if the applied amount of the second ink is up to 100%.
B: Color mixture does not occur if the applied amount of the second ink is up to 50%.
C: Color mixture occurs even when the applied amount of the second ink is 30%.

[Precipitation of Reaction Liquid on Recording Medium]
Precipitation of the reaction solution on the recording medium was evaluated by visually observing the pattern 1 according to the following evaluation criteria.
(Evaluation criteria)
A: No precipitation is observed.
B: Precipitation is observed, but cloudiness is not observed.
C: Precipitation is observed and cloudiness is observed.

[Clouding of image area]
The opacity of the ink-applied portion (image portion) was evaluated by visually observing Pattern 3 according to the following evaluation criteria.
(Evaluation criteria)
A: No white turbidity is observed.
B: Cloudiness is recognized.

[Solid unevenness of the first ink on the recording medium]
The solid unevenness of the first ink on the recording medium was evaluated according to the following evaluation criteria by visually observing Pattern 2.
(Evaluation criteria)
A: No uneven aggregation is observed in the first ink.
B: Slight aggregation unevenness is observed in the first ink.
C: Significant uneven aggregation is observed in the first ink.

[Odor of recorded matter]
The odor of the recorded matter was evaluated by sensory evaluation of pattern 3 according to the following evaluation criteria.
(Evaluation criteria)
A: No odor.
B: There is a slight odor.
C: Very strong odor.

[Stickiness of recorded materials]
The tackiness of the recorded matter was evaluated by the following evaluation criteria by superimposing the printed surfaces of Pattern 3 on each other.
(Evaluation criteria)
A: There is no sticking even if the printed surfaces of the two sheets are placed on top of each other and allowed to stand for one day. (no stickiness)
B: When two sheets were left on top of each other for one day and one sheet was lifted, the two sheets stuck to each other, but fell off within 1 minute. (Slightly sticky,)
C: Two sheets were left on top of each other for one day, and when one sheet was lifted, the two sheets stuck to each other, but did not come off even after 1 minute or more. (It is sticky.)

[Recording speed]
The recording speed was evaluated according to the following evaluation criteria based on the recording speed at which Pattern 3 was obtained.
(Evaluation criteria)
A: Recording is possible on one sheet of A4 size recording medium in less than 30 seconds.
B: Recording is possible on one A4 size recording medium in 30 seconds to 1 minute.
C: Recording can be performed on one sheet of A4 size recording medium for more than 3 minutes.

[Clogging reliability]
The clogging reliability was evaluated according to the following evaluation criteria by visually observing the nozzles after pattern 3 was recorded on 50 A4 size recording media.
(Evaluation criteria)
A: Neither nozzle missing nor nozzle bending occurs even after recording on 50 recording media.
B: When 50 recording media are recorded, no nozzle missing occurs, but nozzle bending occurs.
C: After recording 50 sheets on the recording medium, nozzle missing and nozzle bending occur.

A comparison between Examples and Comparative Examples 1 to 3 revealed that the ink set in which the reaction liquid did not contain a flocculant was inferior in the effect of suppressing the bleeding of the second ink. Further, by comparing Example and Comparative Example 4, it was found that heating the recording medium to 70° C. improved the effect of suppressing bleeding of the second ink when the reaction liquid did not contain an aggregating agent. It was found that the clogging reliability was inferior.

From Examples 1 to 4, it was found that bleeding was suppressed as the amount of polyvalent metal salt used increased. In addition, it was found that precipitation of the reaction liquid on the recording medium and cloudiness of the recorded matter are suppressed as the amount of the polyvalent metal salt used is reduced. Moreover, from Examples 5 to 11, it was shown that the same tendency was observed even when other polyvalent metal salts and organic acids were used.

Further, from Examples 12 and 13, it was found that bleeding was further suppressed by using a receiving layer component and a cationic resin. In addition, from the comparison between Example 14, other examples, and comparative examples 2 and 4, it was found that the lower the heat assist temperature, the better the clogging reliability. Further, from Examples 2 and 14 to 16, it was found that bleeding tends to be suppressed when the volatilization amount of the volatile component is high, but bleeding is suppressed when the volatilization amount is not too high.
It is presumed that this is because if the volatilization amount is too high, the coagulant contained in the reaction liquid cannot be sufficiently mixed up to the top of the first ink, making it difficult for the second ink and the coagulant to react. . In addition, it was found that the lower the volatilization amount, the better both the recording speed and the clogging reliability.

From Example 17, it was shown that the effect of the present invention can be obtained even if the colors and whites of the first ink and the second ink are reversed. Moreover, from Examples 9 and 18, it was shown that the effect of the present invention can be obtained even with other recording media. When a low-absorbent recording medium was used, bleeding tended to be more excellent. It has been found that the present invention is more useful when used for recording media. Furthermore, by comparing Example 19 with other examples, it was found that the higher the surfactant content of the reaction liquid and the lower the surface tension, the more bleeding, precipitation of the reaction liquid on the recording medium, and It was found that white turbidity was suppressed.

In the above example, recording was performed using a serial printer, but recording can also be performed using a line printer as shown in FIG. In this case, the time from the application of the reaction liquid and the first ink by the reaction liquid application head and the first ink application head to the application of the second ink after being transported to a position facing the second ink head. It is possible to control the volatilization amount of the recording medium by adjusting the transportation speed of the recording medium.

Claims (15)

It comprises a reaction liquid containing a coagulant, a first ink containing a coloring material, and a second ink containing a coloring material, and is used for recording on a non-absorbent recording medium or a low-absorbing recording medium. ,
The reaction liquid, the first ink, and the second ink are applied to the recording medium in this order, and used.
ink set. At least one of the first ink and the second ink is a color ink containing a color coloring material or a black ink containing a black coloring material.
The ink set according to claim 1. The other of the first ink and the second ink is a white ink containing a white colorant or a metallic ink containing a metallic colorant.
The ink set according to claim 2. The ink set according to any one of claims 1 to 3, wherein the aggregating agent contains at least one selected from the group consisting of polyvalent metal salts and organic acids. A ratio (colorant : polyvalent metal salt) is 1000: 1 to 31000: 1,
The ink set according to claim 4. The ratio of the number of moles (unit: mol) of the organic acid contained in the reaction liquid to the total mass (unit: g) contained in the coloring materials of the first ink and the second ink (coloring material: organic acid ) is between 800:1 and 5500:1;
The ink set according to claim 4 or 5. wherein the first ink is a white ink containing a white colorant or a metallic ink containing a metallic colorant;
wherein the second ink is a color ink containing a color coloring material or a black ink containing a black coloring material;
The ink set according to any one of claims 1 to 6. The reaction solution has a surface tension of 55 mN/N or less at 25°C.
The ink set according to any one of claims 1 to 7. The reaction liquid further contains at least one selected from the group consisting of a component that serves as an ink-receiving layer applied next to the reaction liquid, and a cationic resin.
The ink set according to any one of claims 1 to 8. At least one kind (unit: g) selected from the group consisting of the component that will become the receiving layer and the cationic resin, which are contained in the reaction liquid, and the coloring material (unit: g) contained in the first ink 10. The ink set according to claim 9, wherein the mass ratio of (colorant: at least one selected from the group) to the colorant is 7:1 to 70:1. A recording method using the ink set according to any one of claims 1 to 10,
a reaction liquid applying step of applying a reaction liquid contained in the ink set to a non-absorbent recording medium or a low-absorbent recording medium;
a first step of applying a first ink contained in the ink set to the region to which the reaction liquid has been applied;
a second step of applying a second ink included in the ink set to the region to which the first ink has been applied;
A recording method. volatilization of volatile components contained in the reaction liquid and the first ink on the non-absorbent recording medium or the low-absorbent recording medium after the first step and before the second step; The amount is 95% by mass or less with respect to 100% by mass of the total mass of volatile components contained in the reaction liquid and the first ink before application.
12. The recording method according to claim 11. The number of moles (unit: mol) of the polyvalent metal salt contained in the reaction liquid per unit area of the non-absorbent recording medium or the low-absorbent recording medium, the first ink and the second ink The ratio (coloring material: polyvalent metal salt) to the total mass (unit: g) of the coloring material contained in is 1000: 1 to 31000: 1,
13. The recording method according to claim 11 or 12. The number of moles (unit: mol) of the organic acid contained in the reaction liquid per unit area of the non-absorbent recording medium or the low-absorbent recording medium, and the number of moles contained in the first ink and the second ink The ratio (coloring material: organic acid) to the total mass (unit: g) of the coloring material is 800: 1 to 5500: 1,
The recording method according to any one of claims 11 to 13. From the components contained in the reaction liquid that will serve as receiving layers for the first ink and the second ink per unit area of the non-absorbent recording medium or the low-absorbent recording medium, and a cationic resin The ratio of the mass (unit: g) of at least one selected from the group to the mass (unit: g) of the colorant contained in the first ink (colorant: at least one selected from the group) is 7:1 to 70:1
The recording method according to any one of claims 11 to 14.

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