JP7416122B2 - Recording method - Google Patents

Description

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

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

Japanese Patent Application Publication No. 2002-103783

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

Furthermore, in order to suppress bleeding, a method of heating the recording medium instead of using a reaction liquid may also be considered. However, heating a recording medium without using a reaction liquid requires high heating energy and causes clogging.

The present invention has been made to solve at least a part of the above-mentioned problems, and when a plurality of inks are overlapped and recorded on a non-absorbent recording medium or a low-absorbent recording medium, To provide an ink set that can prevent bleeding between inks and is less likely to be clogged.

The present inventors have made extensive studies to solve the above problems. As a result, they discovered that the above problems can be solved with an ink set that includes a predetermined pretreatment liquid separately from a plurality of inks for non-absorbent recording media or low-absorbency recording media, The present invention has been completed.

That is, the present invention is as follows.
[1]
It comprises a reaction liquid containing a flocculant, a first ink containing a coloring material, and a second ink containing a coloring material, and is used for recording on a non-absorbing 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 the preceding item [1].
[3]
The other of the first ink and the second ink is a white ink containing a white coloring material or a metallic ink containing a metallic coloring material.
The ink set described in the preceding item [2].
[4]
The ink set according to any one of [1] to [3] above, wherein the flocculant contains at least one selected from the group consisting of polyvalent metal salts and organic acids.
[5]
The ratio of the number of moles (unit: mol) of the polyvalent metal salt contained in the reaction solution to the total mass (unit: g) of the coloring material contained in the first ink and the second ink (coloring material : polyvalent metal salt) is 1000:1 to 31000:1,
The ink set described in the preceding item [4].
[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 material of the first ink and the second ink (coloring material: organic acid ) is 800:1 to 5500:1,
The ink set described in the preceding item [4] or [5].
[7]
The first ink is a white ink containing a white coloring material or a metallic ink containing a metallic coloring material,
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 any one of the preceding items [1] to [6].
[8]
The surface tension of the reaction solution is 55 mN/N or less at 25°C.
The ink set described in any one of the preceding items [1] to [7].
[9]
The reaction liquid further contains at least one member selected from the group consisting of a component that becomes an ink receiving layer applied next to the reaction liquid, and a cationic resin.
The ink set described in any one of the preceding items [1] to [8].
[10]
At least one member (unit: g) selected from the group consisting of the component forming the receiving layer and the cationic resin contained in the reaction liquid, and the coloring material (unit: g) contained in the first ink. The ink set according to the preceding item [9], wherein the mass ratio of the coloring material to the ink set (coloring material: at least one selected from the group) is from 7:1 to 70:1.
[11]
A recording method using the ink set described in any one of the preceding items [1] to [10], comprising:
a reaction liquid applying step of applying a reaction liquid contained in the ink set to a non-absorbent recording medium or a low-absorbency recording medium;
a first step of applying a first ink included in the ink set to the area to which the reaction liquid has been applied;
a second step of applying a second ink included in the ink set to the area to which the first ink has been applied;
A recording method that has.
[12]
Volatization of volatile components contained in the reaction liquid and the first ink on the non-absorbent recording medium or the low-absorbency 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 the preceding paragraph [11].
[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, and 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 described in the preceding paragraph [11] or [12].
[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 organic acids contained in the first ink and the second ink. The ratio (coloring material: organic acid) to the total mass of the coloring material (unit: g) is 800:1 to 5500:1.
The recording method described in any one of the preceding paragraphs [1] to [13].
[15]
Components contained in the reaction liquid and forming a receiving layer for the first ink and the second ink, and a cationic resin per unit area of the non-absorbent recording medium or the low-absorbent recording medium. The ratio of the mass (unit: g) of at least one selected from the group consisting of the mass (unit: g) of the coloring material contained in the first ink (coloring material: at least one selected from the group) is 7:1 to 70:1,
The recording method described in any one of the preceding paragraphs [11] to [14].

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

Hereinafter, a mode for carrying out the present invention (hereinafter referred to as "the present embodiment") will be described in detail with reference to the drawings as necessary, but the present invention is not limited thereto. Various modifications are possible without departing from the gist. In addition, in the drawings, the same elements are given the same reference numerals, and overlapping explanations will be omitted. In addition, the positional relationships such as top, bottom, left, and right are based on the positional relationships shown in the drawings, unless otherwise specified. Furthermore, the dimensional ratios in the drawings are not limited to the illustrated ratios.

[Ink set]
The ink set according to the present embodiment includes a reaction liquid containing an aggregating agent, a first ink containing a coloring material, and a second ink containing a coloring material, and includes a non-absorbing recording medium or a low-absorbing recording medium. It is used for recording on a medium (hereinafter also collectively referred to as "recording medium"), and the reaction liquid and the first ink are placed on the non-absorbent recording medium or the low-absorbent recording medium. , and the second ink are applied overlappingly in this order. Note that hereinafter, the first ink and the second ink are also simply referred to as "ink."

[Reaction solution]
The reaction solution contains a flocculant. By using such a reaction liquid, high-quality recorded matter can be obtained without heating the recording medium, and nozzle clogging caused by drying of the nozzle due to heating of the recording medium can be suppressed. be able to. Specifically, by including an 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. This makes it possible to prevent unevenness of the first ink, and to obtain high-quality recorded matter.

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

(Polyvalent metal salt)
The polyvalent metal salt is not particularly limited, but for example, a polyvalent metal salt of an inorganic acid or a polyvalent metal salt of an organic acid is preferable. Such polyvalent metal salts are not particularly limited, but include, for example, alkaline earth metals in Group 2 of the periodic table (e.g., magnesium, calcium), transition metals in Group 3 of the periodic table (e.g., lanthanum). , earth metals of group 13 of the periodic table (for example, aluminum), and lanthanides (for example, neodymium). Preferred salts of these polyvalent metals include carboxylates (formic acid, acetic acid, benzoate, etc.), sulfates, nitrates, chlorides, and thiocyanates. Among these, preferred are calcium salts or magnesium salts of carboxylic acids (such as formic acid, acetic acid, benzoate, etc.), calcium salts or magnesium salts of sulfuric acid, calcium salts or magnesium salts of nitric acid, calcium chloride, magnesium chloride, and thiocyanic acid. Mention may be made of calcium salts or magnesium salts. The polyvalent metal and salt constituting the polyvalent metal salt may be a combination of any of them, or may be a hydrate. Note that the polyvalent metal salts may be used alone or in combination of two or more.

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, based on 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 material tends to have better 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 more carboxylic acids are preferred. By including such a carboxylic acid, the resulting recorded material tends to have better bleeding resistance. In addition, one type of organic acid may be used alone or two or more types may be used in combination. Further, 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-mentioned organic acids (however, they do not overlap with the above-mentioned polyvalent metal salts). The salt of the above-mentioned organic acid is not particularly limited, but includes, for example, sodium acetate.
In addition, one type of organic acid salt may be used alone or two or more types may be used in combination.

The content of the organic acid is preferably 1 to 15% by mass, more preferably 1 to 14% by mass, and even more preferably 1 to 7% by mass, based on 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 have better bleeding resistance.

The reaction liquid further contains at least one component selected from the group consisting of a component that becomes a receptor layer for at least one of the first ink and the second ink (hereinafter also simply referred to as "receptor layer component"), and a cationic resin. It is preferable to include.

(Component that becomes the receiving layer of at least one of the first ink and the second ink)
When the reaction solution contains the receptor layer component, the resulting recorded matter tends to have better bleed resistance and color development. The receptor layer component is not particularly limited, but includes, for example, fine particles that are solid in liquid, including fine inorganic particles and fine resin particles that are solid in liquid. Examples of such particles include cationic particles, nonionic particles, and anionic particles. Among these, preferred are those that leave gaps between the fine particles when they are adhered to the recording medium to form a coating film. "Gap" refers to the void in the dry state of the coating film of the reaction solution. When the reaction liquid is applied to the recording medium to form a coating film, gaps are created in the coating film due to the components that will become the receiving layer, and at least the ink applied after the reaction liquid is absorbed into the gaps, causing bleed. is even more preferable in that it is more suppressed. The component that becomes the receiving layer is usually a component that becomes the receiving layer for at least the first ink, and may also serve as the receiving layer for the second ink that is applied next.

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

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

The content of the receiving layer component 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 receptor layer components is within the above range, the resulting recorded material tends to have better bleed resistance and color development. The receiving layer components may be used alone or in combination of two or more.

(Cationic resin)
When the reaction solution contains a cationic resin, the resulting recorded matter tends to have better bleed resistance and color development. Examples of the cationic resin include, but are not particularly limited to, resins that are soluble in the reaction liquid and resins that are dispersed in liquids such as resin emulsions. Since the cationic resin has a relatively weak interaction with the pigment contained in the first ink and the second ink compared to the above-mentioned flocculant, it functions more as an auxiliary agent for the flocculant than the flocculant. Resins that are soluble in the reaction solution are preferred because of their excellent interaction.

Examples of the resin soluble in the reaction solution include, but are not limited to, amine resins, such as polyallylamine and polyallylamine derivatives.

Examples of the resin emulsion include, but are not limited to, polyolefin resins, urethane resins, acrylic resins, and polyester resins. For example, a resin emulsion that can be included in the ink described below is mentioned, and a preferred example of a commercially available product is Arrowbase CD-1200 (trade name, manufactured by Unitika, polyolefin resin).

The content of the cationic resin 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 cationic resin is within the above range, the resulting recorded material tends to have better bleed resistance and color development. The cationic resins may be used alone or in combination of two or more.

In addition to the above, the reaction solution may contain a solvent, a surfactant, and the like.

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

Examples of the water include pure water such as ion-exchanged water, ultrafiltrated water, reverse osmosis water, and distilled water, and water from which ionic impurities have been removed as much as possible, such as ultrapure water. Furthermore, if water is sterilized by ultraviolet irradiation or addition of hydrogen peroxide, the growth of mold and bacteria can be prevented when the reaction solution is stored for a long period of time. This tends to further improve storage stability.

The content of water is preferably 80 to 95 parts by weight, more preferably 85 to 95 parts by weight, based on 100 parts by weight of the reaction solution. 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 specifically includes 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 mono-butyl 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 -Alcohols or glycols such as pentanol, 3-pentanol, and tert-pentanol, N,N-dimethylformamide, N,N-dimethylacetamide, 2-pyrrolidone, N-methyl-2-pyrrolidone, 2- Mention may be made of oxazolidone, 1,3-dimethyl-2-imidazolidinone, dimethylsulfoxide, sulfolane, and 1,1,3,3-tetramethylurea.

The organic solvents may be used alone or in combination of two or more. 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 based on 100% by mass of the total mass of the reaction solution.

[Surfactant]
The reaction solution 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 surfactants and polysiloxane surfactants.

Among these, polysiloxane-based surfactants are more preferred because their solubility in the reaction liquid is increased and foreign matter is less likely to be generated in the reaction liquid.

The above acetylene glycol surfactants are not particularly limited, but include, for example, 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 One or more of these are preferred. These include the E series (trade names manufactured by Air Products Japan, Inc.) such as Olfin 104 series and Olfin E1010, Olfin PD-002W, Surfynol 465 and Surfynol 61 (Nissin Chemical Industry Co., Ltd.). It is available as a commercial product such as (trade name) manufactured by Chemical Industry CO., Ltd.).

Further, the polysiloxane 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 above-mentioned surfactant is preferably 0.1 to 3% by mass based on 100% by mass of the total mass of the reaction solution.

The surface tension of the reaction solution at 25° C. is preferably 55 mN/N or less, more preferably 40 mN/N or less. When the surface tension is within the above range, the reaction liquid can be uniformly applied when recording on a recording medium. Further, 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. Note that surface tension can be measured by the method described in Examples.

[First ink]
The first ink includes 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, based on 100% by mass of the first ink. When the content of the coloring material is within the above range, the resulting recorded material tends to have better bleed resistance and color development.

[Second ink]
The second ink includes 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, based on 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 material tends to have better bleed resistance and color development.

[Color material]
The coloring material that can be included in the first ink and the second ink will be described below. Note that each of the first ink and the second ink may contain only one type of coloring material, or may contain two or more types of coloring materials.
Further, the coloring material may be a dye and is preferably a pigment.

Examples of the black coloring material used in the black ink include carbon black, and are not particularly limited. For example, No. 2300, No. 900, MCF88, No. 33, No. 40, No. 45, No. 52, MA7, MA8, MA100, No. 2200B, etc. (all manufactured by Mitsubishi Chemical Corporation), Raven 5750, Raven 5250, Raven 5000, Raven 3500, Raven 1255, Raven 700, etc. (all manufactured by Columbia Carbon) bon Columbia), Rega1 400R, Rega1 330R, Rega1 660R, Mogul L, Monarch 700, Monarch 800, Monarch 880, Monarch 900, Monarch 1000, Monarch 1100, Monarch 1300, Monarch h 1400 etc. (manufactured by CABOT JAPAN KK), Color Black FW1 , Color Black FW2, Color Black FW2V, Color Black FW18, Color Black FW200, Color B1ack S150, Color Black S160, Color Black S170, Pri ntex 35, Printex U, Printex V, Printex 140U, Special Black 6, Special Black 5, Special Examples include Black 4A and Special Black 4 (manufactured by Degussa).

The coloring material used for the white ink is not particularly limited, but for example, C.I. I. Pigment White 6, 18, and 21 are listed. Other pigments used in white ink include alkaline earth metal sulfates such as barium sulfate, alkaline earth metal carbonates such as calcium carbonate, silicas such as finely divided silicic acid and synthetic silicates, Examples include metal compounds such as calcium silicate, alumina, alumina hydrate, titanium dioxide, and zinc oxide, as well as talc and clay.

The coloring material used in 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, and 180.

The coloring material used for magenta ink is not particularly limited, but 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. Pigment Violet 19, 23, 32, 33, 36, 38, 43, and 50.

The coloring material used in 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. Bat Blue 4 and 60 are examples.

Further, coloring materials other than magenta, cyan, and yellow are not particularly limited, but for example, C.I. I. Pigment Green 7,10, C. I. Pigment Brown 3, 5, 25, 26, C. I. Pigment Orange 1, 2, 5, 7, 13, 14, 15, 16, 24, 34, 36, 38, 40, 43, 63.

Metallic coloring materials used in metallic ink include metallic pigments, metal fine particles can be used, and metals include aluminum, aluminum alloys, silver, and the like. Metallic ink is an ink that is applied to a recording medium to form a pattern that has a metallic luster, and a metallic pigment is a pigment that exhibits a metallic luster.

It is preferable that 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. Further, 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, and the other of the first ink and the second ink is a white ink containing a white coloring material. It is more preferable that there be. By using such an ink set, when recording on a non-absorptive recording medium or a low-absorptive recording medium, it is possible to obtain color development on a recording medium other than white. For example, transparent, colored, metallic media, etc. are preferably used.

It is preferable that the first ink is a white ink containing a white coloring material, and the second ink is a color ink containing a coloring material or a black ink containing a black coloring material. By using such an ink set, when recording on a non-absorptive recording medium or a low-absorptive recording medium, it is possible to obtain color development on a recording medium other than white. For example, transparent, colored, metallic media, etc. are preferably used.

The ratio A between the number of moles of the flocculant (unit: mol) contained in the reaction liquid and the total mass (unit: g) of the coloring material contained in the first ink and the second ink is 100:1 to 5000:1. is preferable, and 500:1 to 4000:1 is more preferable. When the ratio A is 100:1 or more, precipitation of the reaction solution, cloudiness caused by the reaction solution, stickiness, and generation of odor can be prevented. Further, by setting the ratio A to 5000:1 or less, bleeding during ink overlapping can be suppressed.

The ratio B between the number of moles (unit: mol) of the polyvalent metal salt contained in the reaction solution and the total mass (unit: g) of the coloring material contained in the first ink and the second ink is 300:1 to 5000. :1 is preferable, and 500:1 to 5000:1 is more preferable. When the ratio B is 300:1 or more, it is possible to prevent precipitation of polyvalent metal salts, cloudiness caused by polyvalent metal salts, stickiness, and generation of odor. Further, by setting the ratio B to 5000:1 or less, bleeding during ink overlapping can be suppressed.

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 material of the first ink and the second ink is 100:1 to 800:1. is preferable, and 100:1 to 700:1 is more preferable. When the ratio C is 100:1 or more, precipitation of organic acids, cloudiness caused by organic acids, stickiness, and generation of odor can be prevented. Furthermore, by setting the ratio C to 800:1 or less, bleeding during ink overlapping can be suppressed.

The mass (unit: g) of at least one type selected from the group consisting of receptor 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 suppressing function of the flocculant is further assisted, so that bleeding tends to be further suppressed. Furthermore, when the ratio D is 10:1 or less (the former), the storage stability of the reaction solution and the reliability against clogging when coating by inkjet tend to be better.

As is clear from Table 2, 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 the ratio (coloring material: at least one selected from the above group), and the ratios A to C are the ratios between 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 using pigments as the above-mentioned coloring materials, the pigments can be used as a pigment dispersion obtained by dispersing it in water with a dispersant, or as a self-dispersion type surface in which hydrophilic groups are introduced into the surface of the pigment particles using a chemical reaction. It is preferably added to the ink as a pigment dispersion obtained by dispersing a treated pigment in water or a pigment coated with a polymer in water.

The above-mentioned dispersants are not particularly limited, but include, for example, polymeric dispersants (glue, gelatin, casein, proteins such as albumin, natural gums such as gum arabic and gum tragacanth, glucosides of saponin, alginic acid and propylene glycol ester, alginic acid Triethanolamine, alginate fermented product of ammonium alginate, methylcellulose, carboxymethylcellulose, cellulose derivatives of ethyl hydroxycellulose, polyvinyl alcohols, polypyrrolidones, polyacrylic acid, acrylic acid-acrylonitrile copolymer, potassium acrylate-acrylonitrile copolymer Polymer, vinyl acetate-acrylic ester copolymer, acrylic resin of acrylic acid-acrylic ester copolymer, styrene-acrylic acid copolymer, styrene-methacrylic acid copolymer, 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 copolymer, vinyl acetate-fatty acid vinyl ethylene copolymer, vinyl acetate-maleate ester copolymer, vinyl acetate-croton copolymer, vinyl acetate-based copolymer of vinyl acetate-acrylic acid copolymer and their salts) and surfactants (various anionic surfactants, nonionic surfactants, and amphoteric surfactants) can be used.

The above-mentioned self-dispersing surface-treated pigments with hydrophilic groups introduced are those that can be dispersed or dissolved in water without a dispersant by surface treatment such that carboxyl groups and their salts are directly bonded to the surface of the pigment. It is. Specifically, it can be obtained by grafting functional groups or molecules containing functional groups onto the surface of pigments through physical treatment using vacuum plasma or chemical treatment using oxidizing agents such as sodium hypochlorite or ozone. I can do it. A single pigment particle may be grafted with a single functional group or a plurality of functional groups may be grafted onto one pigment particle. The type and degree of the grafted functional group may be determined as appropriate while taking into consideration dispersion stability in the ink, color density, and drying property in front of the inkjet head.

The pigment coated with the above polymer is not particularly limited, but for example, after dispersing the pigment using a dispersant having a polymerizable group, a monomer (copolymerizable monomer) that can be copolymerized with the dispersant is used. It can be obtained by carrying out emulsion polymerization in water using and a photoradical polymerization initiator. Among these polymers, monomers and oligomers having at least one kind selected from the group consisting of acryloyl group, methacryloyl group, vinyl group, and allyl group as a double bond are prepared according to a known polymerization method using a photoradical polymerization initiator. Polymerized ones can be suitably used. The above-mentioned emulsion polymerization can be carried out using a general method, and the polymerization proceeds by free radicals generated by thermal decomposition of a water-soluble photoradical polymerization initiator in the presence of an emulsifier.

The pigment and dispersant constituting the pigment dispersion may be used alone or in combination of two or more.

[Resin emulsion]
When the ink used in this embodiment contains a pigment as a coloring material, it is preferable that the ink further contains a resin emulsion. By using the resin emulsion, as the ink dries, the resins in the resin emulsion and the resin and pigment fuse to each other, fixing the pigment to the recording medium, so that the image portion of the recorded material is fixed. Abrasion resistance and adhesion can be further improved. Among the resin emulsions, urethane resin emulsions and acrylic resin emulsions are preferred, and urethane resin emulsions are more preferred. As a result, the fixing properties of the ink are excellent, and thus both the abrasion resistance and adhesion of the recorded material are excellent.

When a resin emulsion is included in the ink, the resin emulsion forms a resin film on the recording medium, so that the ink is sufficiently fixed on the recording medium and the recorded material has excellent scratch resistance. . Therefore, it is preferable that the resin emulsion contains a thermoplastic resin. In particular, since urethane resin emulsions have a high degree of freedom in design, it is easy to obtain desired film properties.

Anionic resin emulsions are also preferred. The resin contained in the anionic resin emulsion is not particularly limited, but includes, for example, (meth)acrylic acid, (meth)acrylic ester, acrylonitrile, cyanoacrylate, acrylamide, olefin, styrene, vinyl acetate, vinyl chloride, Examples include homopolymers or copolymers of vinyl alcohol, vinyl ether, vinylpyrrolidone, vinylpyridine, vinylcarbazole, vinylimidazole, and vinylidene chloride, fluororesins, and natural resins. Among these, at least one selected from the group consisting of (meth)acrylic resins and styrene-(meth)acrylic acid copolymer-based resins is preferred, and at least one selected from the group consisting of acrylic resins and styrene-(meth)acrylic acid copolymer-based resins. At least one kind is more preferred, and styrene-acrylic acid copolymer resin is even more preferred. Note that the above copolymer may be in any form among random copolymers, block copolymers, alternating copolymers, and graft copolymers.

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

One type of resin emulsion may be used alone, or two or more types may be used in combination.

The resin content of the resin emulsion is preferably 3 to 15% by weight, more preferably 7 to 14% by weight, and even more preferably 8 to 13% by weight, based on 100% by weight of the total weight of each ink. By being within the above range, the adhesion and abrasion resistance of recorded materials tend to be better, and the ink tends to have excellent long-term storage stability, and in particular, the ink tends to have a lower viscosity. It is in.

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

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

As the organic solvent, a volatile water-soluble organic solvent is more preferable. The organic solvent is not particularly limited, but specifically includes 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 mono-butyl 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 -Alcohols or glycols such as pentanol, 3-pentanol, and tert-pentanol, N,N-dimethylformamide, N,N-dimethylacetamide, 2-pyrrolidone, N-methyl-2-pyrrolidone, 2- Mention may be made of oxazolidone, 1,3-dimethyl-2-imidazolidinone, dimethylsulfoxide, sulfolane, and 1,1,3,3-tetramethylurea.

The organic solvents may be used alone or in combination of two or more. 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 surfactants and polysiloxane surfactants. When the ink contains these surfactants, the drying properties of the ink attached to the recording medium are improved, and high-speed recording becomes possible.

Among these, polysiloxane surfactants are more preferable because they have a high solubility in the ink and are less likely to generate foreign matter in the ink.

The above acetylene glycol surfactants are not particularly limited, but include, for example, 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 One or more of these are preferred. These include the E series (trade names manufactured by Air Products Japan, Inc.) such as Olfin 104 series and Olfin E1010, Olfin PD-002W, Surfynol 465 and Surfynol 61 (Nissin Chemical Industry Co., Ltd.). It is available as a commercial product such as (trade name) manufactured by Chemical Industry CO., Ltd.).

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

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

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

The humectants may be used alone or in combination of two or more. By containing the humectant with a high boiling point in the ink, it is possible to obtain an ink that can maintain fluidity and redispersibility for a long time even if the pigment ink is left exposed to air in an open state. Furthermore, such ink is less likely to cause nozzle clogging during printing using a printing apparatus or when restarting after interruption, resulting in excellent ink ejection stability.

[Other ingredients]
In order to maintain good storage stability and ejection stability from the head, to improve clogging, or to prevent ink deterioration, the ink used in this embodiment contains solubilizers, viscosity modifiers, pH Various additives can also be added as appropriate, such as regulators, antioxidants, preservatives, fungicides, corrosion inhibitors, and chelating agents to capture metal ions that affect dispersion. From the viewpoint of safety, it is preferable that the ink used in this embodiment be a water-based ink that contains the largest amount of water among volatile components.

[Recording medium]
The ink set according to this embodiment is used for recording on a non-absorptive recording medium or a low-absorptive recording medium. Absorbent recording media have poor water resistance and abrasion resistance, and absorbent recording media with an ink-receiving layer on the surface can be expensive, whereas non-absorbent recording media have poor water resistance and abrasion resistance. Recording media or low-absorption recording media are superior in terms of water resistance, abrasion resistance, and lower cost than absorbent recording media configured with an ink-receiving layer on the surface. The more non-absorbent the recording medium, the more likely it is that bleeding will occur, and the more difficult it will be to achieve both the occurrence of bleeding and printing speed. Therefore, it is advantageous to use the ink set according to this embodiment, and a non-absorbent recording medium is even more advantageous. be.

Here, "low absorption recording medium" or "non-absorption recording medium" refers to a recording medium in which the amount of water absorbed within 30 msec from the start of contact is 10 mL/m ² or less in the Bristow method. . 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 and Pulp Technology Association (JAPAN TAPPI). Details of the test method can be found in the standard No. of "JAPAN TAPPI Paper and Pulp Test Method 2000 Edition". 51 "Paper and Paperboard - Liquid Absorption Test Methods - Bristow Method".

Furthermore, non-absorbent recording media and low-absorbent recording media can also be classified according to the wettability of the recording surface to water. For example, by dropping a 0.5 μL water drop onto the recording surface of the recording medium and measuring the rate of decrease in contact angle (comparison of the contact angle at 0.5 milliseconds and the contact angle at 5 seconds after impact), The medium can be characterized. More specifically, regarding the properties of the recording medium, the non-absorbency of a "non-absorbent recording medium" refers to the above-mentioned decrease rate of less than 1%, and the low absorption of a "low-absorbency recording medium" The above-mentioned reduction rate is 1% or more and less than 5%. Moreover, absorbency refers to the above-mentioned decrease rate of 5% or more. Note that the contact angle can be measured using a portable contact angle meter PCA-1 (manufactured by Kyowa Interface Science Co., Ltd.).

The low-absorbency recording medium is not particularly limited, but includes, for example, coated paper provided with a coating layer on the surface for receiving oil-based ink. Specifically, paper that has its surface coated with paint to enhance its aesthetic appearance and smoothness is classified as coated paper for printing under the Ministry of Economy, Trade and Industry's ``Production Statistics Classification''. Paints include those made by mixing white pigments, which are inorganic compounds such as clay (kaolin) and calcium carbonate, with adhesives (binder) such as starch. The coating amount of the paint is preferably about 10 to 40 g/m ² . The coated paper is not particularly limited, but includes, for example, recording papers such as art paper, coated paper, and matte paper.

Non-absorptive recording media are not particularly limited, but include, for example, plastic films that do not have an ink absorption layer, those that are coated with plastic on a base material such as paper, or those that have a plastic film adhered to them. etc. Examples of the plastic here include polyvinyl chloride, polyethylene terephthalate, polycarbonate, polystyrene, polyurethane, polyethylene, polypropylene, polyacrylic, and the like.

Furthermore, in addition to the above-mentioned recording media, non-ink-absorbing or low-ink-absorbing recording media such as plates made 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 absorbency recording medium using the above ink set, and a step of applying a reaction liquid onto a non-absorbent recording medium or a low-absorbency recording medium, and applying a first ink from above the reaction liquid. and a second step of applying a 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 conveyance 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.

Of these, the drying device 90 includes a first drying section 40 that performs a drying process of a recording medium, and a second drying section 50 that dries a 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 transport section 20. Specifically, the feeding section 10 has a roll medium holder 11, and the roll medium holder 11 holds the recording medium F. By rotating the recording medium F, the recording medium F can be fed to the conveying section 20 on the downstream side in the feeding direction Y. Note that the recording medium F is not limited to a roll shape.

Further, the conveying section 20 is provided so as to be able to convey the recording medium F sent from the feeding section 10 to the recording section 30. Specifically, the conveyance section 20 includes a first conveyance roller 21 and is configured to be able to convey the conveyed recording medium F further to the recording section 30 on the downstream side in the conveyance direction Y.

Further, the recording section 30 is provided so as to be able to apply a reaction liquid to the recording medium F sent from the transport section 20 and perform recording by discharging ink. Specifically, the recording section 30 includes a head 31 that performs a reaction liquid application step, a head 32 that performs a first step, a recording head 33 that performs a second step, and a platen 34 as a medium support section. . Note that the method for 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. Inkjet is preferable because it can apply the ink to the required area with high precision in the application position and amount.

Among these, the platen 34 is provided so as to be able 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. Furthermore, a second feed roller 43 is provided downstream of the platen 34 in the feed direction Y. The second feed roller 43 is configured to be able to send the recorded recording medium F to the second drying section 50 on the downstream side in the feed direction Y.

Further, 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. Furthermore, a third feed roller 65 is provided near the outlet 64 of the second drying section 50. The third feed roller 65 is arranged so as to be in contact with the back surface of the recording medium F, and is configured to be able to send the recording medium F to the discharge section 70 on the downstream side in the feeding direction Y.

Furthermore, the discharge section 70 is provided so that the recording medium F sent from the second drying section 50 can be further sent downstream in the feeding direction Y and discharged to the outside of the inkjet recording apparatus 1 . Specifically, the discharge section 70 includes 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 . Of these, 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. Further, the sixth feed roller 73 and the seventh feed roller 74 are arranged to form a roller pair. The recording medium F discharged by the sixth feed roller 73 and the seventh feed roller 74 is provided to be wound up by a take-up roller 75.

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

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 applied is within the above range, the resulting recorded material tends to have better bleed resistance.

The amount of aggregating agent applied to the recording medium is preferably 0.5×10 ^-4 to 15×10 ^-4 mmol/inch ² (50 to 1500 nmol/inch ² ), and 0.65×10 ^-4 mmol/inch ² or more is more preferable, 1×10 ⁻⁴ mmol/inch ² or more is even more preferable, 1.5×10 ⁻⁴ mmol/inch ² or more is even more preferable, and 2×10 ⁻⁴ mmol/inch ² or more is even more preferable. , 3×10 ⁻⁴ mmol/inch ² or more is particularly preferable. Further, the applied amount is more preferably 10.8×10 ⁻⁴ mmol/inch ² or less, further preferably 10×10 ⁻⁴ mmol/inch ² or less, and particularly preferably 5×10 ⁻⁴ mmol/inch ^{2 or} less. It is preferable that the amount of the aggregating agent applied is in the above range because the image quality of the recorded matter is even better and the values of ratio F to ratio H described later can be easily set. The applied amount of the reaction liquid or flocculant is the applied amount of the reaction liquid or flocculant per unit area in the area 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 react directly, the first ink can be rapidly aggregated, and the reaction liquid does not need to be completely dried. The reaction liquid does not need to be completely dry, and since the reaction liquid does not need to be dry, application of the first ink can be started early, and a high recording speed can be achieved. Note that the method may further include a step of drying at least a portion 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 to 20 mg/inch ² , more preferably 15 to 5 mg/inch ² . When the applied amount of the first ink is within the above range, the resulting recorded material tends to have better 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 do not need to be completely dried. By applying the second ink before the first ink is completely dry, the reaction liquid and the second ink can react even on top of the first ink. Even if the liquid and the first ink are not completely dry, the second ink can be applied while suppressing bleeding, and the recording speed can be increased. Before the second step, there may be a step of drying at least a portion of the reaction liquid and the first ink applied to the recording medium, and the step is not to dry completely but to partially dry. is preferred. Furthermore, the method may include 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 to 20 mg/inch ² , more preferably 15 to 5 mg/inch ² . When the applied amount of the first ink is within the above range, the resulting recorded material tends to have better 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 area where the first ink and the second ink are applied in an overlapping manner is: It is preferably 0.5 to 3 mg/inch ² , preferably 1 mg/inch ² or more, more preferably 1.5 mg/inch ² or more, and even more preferably 2.5 mg/inch ² or less.

In addition, in the first step, the total amount of the coloring material contained in the first ink applied per unit area in the area where the first ink and the second ink are applied in an overlapping manner is 0.1 to 2.5 mg/inch ² It is preferably 0.2 mg/inch ² or more, more preferably 0.5 mg/inch ² or more, particularly preferably 1 mg/inch ² or more, and more preferably 2 mg/inch ² or less. It is preferable that each application amount is as described above, since the image quality of the recorded product is even better and it is easy to set the values of ratio E to ratio H described later.
The amount of each coloring material applied in the first and second steps, the total amount of coloring material applied, the amount of flocculant applied in the reaction liquid application step, and the ratio E to ratio H described below are the same for the first ink and the second ink. It is preferable to set the coloring material to the area where the total amount of coloring material applied is the largest among the areas where the coloring material is applied in an overlapping manner, since the image quality of the recorded product can be further improved.

In the first step and the second step, the first ink or the second ink can be ejected from a nozzle of a line head or a serial head by an inkjet 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 (vertical direction of the recording medium, conveyance direction), and in conjunction with this movement, the nozzle opening of the head is An image can be recorded on a recording medium by ejecting ink droplets. In addition, in the serial method using a serial head, the head is moved along the main scanning direction (lateral direction, width direction of the recording medium), and ink droplets are ejected from the nozzle openings of the head in conjunction with this movement. Accordingly, an image can be recorded on the recording medium.

In the second step, at the time when the second ink is applied, the amount of volatile components contained in the reaction liquid and the first ink applied to the non-absorbent recording medium or the low-absorbent recording medium is the same as that before application. It is preferably 95% by mass or less, more preferably 85% by mass or less, even more preferably 80% by mass or less, based on 100% by mass of the total mass of volatile components contained in the reaction liquid and the first ink. In addition, in terms of excellent clogging reliability and excellent recording speed, it is even more 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, in terms of even better suppression of bleeding, the content 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. Here, the "reaction liquid before application" means the reaction liquid before application of the reaction liquid to be applied to the recording medium in the reaction liquid application step, and the "first ink before application" means the first ink before the first ink is applied to the recording medium in the first step. When the amount of volatile components is 95% by mass or less, the reaction liquid and the second ink can react efficiently, so that a higher recording speed can be achieved. Note that the amount of volatile components evaporated can be determined by the method described in Examples.

The number of moles (unit: mol) of the flocculant contained in the reaction liquid per unit area in the area of the non-absorbent recording medium or the low-absorbent recording medium to which the first ink and the second ink are applied in an overlapping manner. The ratio E of the total mass (unit: g) of the coloring material 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 31000:1. :1 to 5100:1 is more preferable. When the ratio E is 800:1 or more, precipitation of the reaction solution, cloudiness caused by the reaction solution, stickiness, and generation of odor can be prevented. When the ratio E is 31000:1 or less, bleeding during ink overlapping can be suppressed. Note that the ratio E can be controlled by the applied amounts of the first ink, the second ink, and the reaction liquid.

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 (unit: mol) of the polyvalent metal salt contained in the first ink and the second ink. The ratio F to the total mass (unit: g) of the coloring material is preferably 1000:1 to 31000:1, more preferably 1000:1 to 15000:1, and 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 caused by polyvalent metal salts, stickiness, and generation of odor. When the ratio F is 31000:1 or less, bleeding during ink overlapping can be suppressed. Note that the ratio F can be controlled by the applied amounts of the first ink, the second ink, and the reaction liquid.

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-absorptive recording medium or the low-absorptive recording medium, and the color contained in the first ink and the second ink. The ratio G to the total mass of the material (unit: g) is preferably 800:1 to 5500:1, more preferably 800:1 to 1700:1, and 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, cloudiness caused by organic acids, stickiness, and generation of odor. When the ratio G is 5500:1 or less, bleeding during ink overlapping can be suppressed. Note that the ratio G can be controlled by the applied amounts of the first ink, the second ink, and the reaction liquid.

The mass (unit: :g) and the mass (unit: g) of the coloring material contained in the first ink, the ratio H 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), it tends to be even more excellent in suppressing bleeding. When the ratio H is 70:1 or less (the former), the application efficiency of the reaction liquid tends to be more excellent. Note that the ratio H can be controlled by the applied amounts of the first ink and the reaction liquid.

As is clear from Tables 3 to 5, 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 (coloring material: at least one selected from the above group).

In the recording method according to the present embodiment, the surface temperature of the recording medium in the first step and/or the second step is preferably 10° C. or more and 65° C. or less. 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, in terms of better recording speed, the temperature is more preferably 20°C or higher, even more preferably 40°C or higher, and particularly preferably 50°C or higher. When the surface temperature of the recording medium is within the above range, clogging reliability and recording speed tend to be particularly excellent.

Hereinafter, the present invention will be explained in more detail using Examples and Comparative Examples. The present invention is not limited in any way by the following examples.

[Materials for reaction liquid and ink]
The main materials for the reaction liquid and ink used in the Examples and Comparative Examples below are as follows.
[Pigment]
Titanium dioxide: Metal oxide NanoTek (R) Slurry manufactured by CI Kasei Co., Ltd. Cyan pigment: C.I. I. pigment blue 15:3
[Polyvalent metal salt]
Magnesium sulfate heptahydrate (molecular weight 246.47g/mol)
Calcium acetate monohydrate (molecular weight 176.18g/mol)
Calcium nitrate tetrahydrate (molecular weight 164.09g/mol)
[Organic acid]
Succinic acid (molecular weight 118.09g/mol)
[Surfactant]
BYK348 (silicone surfactant, manufactured by BYK Chemie Japan)
[Resin emulsion]
Jonkryl 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 solution and ink]
Each material was mixed in the composition (mass %) shown in Table 1 below and sufficiently stirred to obtain a reaction liquid, a first ink, and a second ink, respectively.

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

[Preparation of ink set]
The obtained 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) was used. The modification was that a heater was attached to the platen, making it possible to heat the recording medium. The nozzle pitch is 180 dpi. The ink set prepared above was discharged from each head in the order of the reaction liquid, first ink, and second ink by an inkjet method under the recording conditions shown in Tables 1 to 3, and the reaction liquid, first ink, and second ink were ejected in this order from each head under the recording conditions shown in Tables 1 to 3. A solid pattern was adhered to a film "Lumirror S10" (trade name, thickness 100 μm) or NP coated paper (manufactured by Lintec), which is a low absorption recording medium.
At this time, a pattern 1 in which only the reaction liquid was applied, a pattern 2 in which only the reaction liquid and the first ink were applied in an overlapping manner, and a pattern 3 in which the reaction liquid, the first ink, and the second ink were applied in an overlapping manner were formed, respectively. Note that 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 to the temperature shown in Tables 3 to 5, and then the reaction liquid is applied to form a pattern (substrate) made of the reaction liquid. Then, a first ink is applied on a sub-pattern made of the reaction liquid to form a sub-pattern made of the first ink, and then a sub-pattern made of the second ink is formed on the sub-pattern made of the first ink. Pattern 3 was formed by forming sub-patterns. The temperature of the recording medium was adjusted using a platen heater so as to maintain the temperature shown in Tables 3 to 5 even during the application of the reaction liquid, first ink, and second ink. In addition, 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 are adjusted to the values shown in Tables 3 to 5, and the second step is carried out the process. The recording resolution was set to 720 x 720 dpi, and the amount of reaction liquid and ink per dot were adjusted so that the amount applied was as shown in the table.

[Amount of volatile components in the reaction solution and first ink before the second step]
The volatilization amount of the volatile components of the reaction liquid and the first ink in pattern 3 after the first step and before the second step (at the time when the recording medium is conveyed to the position facing the second ink head) is calculated by the following formula: Calculated by. Here, Af is the total amount (mg) of the reaction liquid and the first ink that are applied to the recording medium in an overlapping manner. Further, Ae is the total amount of residue of the reaction liquid and first ink on the recording medium in a state where 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 first ink on the recording medium immediately before the second step.
Volatilization amount % of volatile components = ((Af-A)/(Af-Ae)) x 100

Af can be determined as the amount of applied reaction liquid and first ink in pattern 3 from the printer's ejection data and the mass per dot. A can be determined by measuring the mass of the recording medium at the time of starting application of the second ink and the mass of the recording medium before the reaction liquid application step and taking the difference. When measuring the amount of volatile components evaporated, it is convenient to use a recording medium prepared for the measurement. The measurement was performed using an electronic balance. In the measurement, the relationship between the drying time and the amount of volatilization is determined when the reaction liquid and the first ink are applied and then dried by heating at a predetermined time using a platen. When recording with a recording device, the time from applying the reaction liquid and the first ink to applying the second ink is set to one of the times in the relationship between the drying time and the amount of volatilization determined above. This allows the desired amount of volatilization to be achieved.

[evaluation]
[Bleed during overlapping recording of first ink and second ink]
Recorded articles were obtained by varying the amount of second ink applied in Pattern 3 between 30 and 200%, with the values listed in Tables 3 to 5 being 100%. Bleeding during overlapping recording of the first ink and the second ink was evaluated by visually observing the contact portion of pattern 3 and pattern 2 of the resulting recorded material, and using the following evaluation criteria. Note that "200%" is a value assuming the maximum amount of the total amount of ink of multiple colors when recording colors of secondary colors or higher using multiple color inks. If it is A or AA in the following evaluation criteria, it can be said that a recorded matter with suppressed bleeding can be obtained even when a plurality of color inks are used.
(Evaluation criteria)
AA: There is no color mixing even when the amount of second ink applied is 200%.
A: If the amount of second ink applied is up to 100%, there will be no color mixing.
B: No color mixing occurs if the amount of second ink applied is up to 50%.
C: Color mixing occurs even when the amount of second ink applied is 30%.

[Precipitation of reaction liquid on recording medium]
The precipitation of the reaction liquid on the recording medium was evaluated by visually observing Pattern 1 using the following evaluation criteria.
(Evaluation criteria)
A: No precipitation observed.
B: Precipitation is observed, but no clouding is observed.
C: Precipitation is observed and cloudiness is observed.

[Cloudy in the image area]
The cloudiness of the ink-applied area (image area) was evaluated by visually observing Pattern 3 using the following evaluation criteria.
(Evaluation criteria)
A: No cloudiness is observed.
B: Cloudiness is observed.

[Solid spots of first ink on recording medium]
The unevenness of the first ink on the recording medium was evaluated by visually observing Pattern 2 using the following evaluation criteria.
(Evaluation criteria)
A: No agglomeration unevenness was observed in the first ink.
B: Some agglomeration unevenness is observed in the first ink.
C: Considerable agglomeration unevenness is observed in the first ink.

[Odor of recorded materials]
The odor of the recorded material was evaluated using the following evaluation criteria in a sensory evaluation of Pattern 3.
(Evaluation criteria)
A: There is no odor.
B: Slight odor.
C: There is a strong odor.

[Stickiness of recorded materials]
The stickiness of the recorded material was evaluated using the following evaluation criteria by overlapping the printed surfaces of Pattern 3.
(Evaluation criteria)
A: There is no sticking even if you leave two sheets with the printed sides stacked on top of each other for a day. (No stickiness)
B: Two sheets are left with their printed sides stacked on top of each other for a day, and when one sheet is lifted, the two sheets stick together, but fall off within 1 minute. (It is slightly sticky.)
C: Two sheets are left with their printed surfaces stacked on top of each other for a day, and when one sheet is lifted, the two sheets stick together, but they do 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: It is possible to record on one A4 size recording medium in less than 30 seconds.
B: Can record on one A4 size recording medium in 30 seconds to 1 minute.
C: It is possible to record on one A4 size recording medium for more than 3 minutes.

[Clogging reliability]
The clogging reliability was evaluated using the following evaluation criteria by visually observing the nozzles after pattern 3 was recorded on 50 A4 size recording media.
(Evaluation criteria)
A: Even after recording 50 sheets on the recording medium, no nozzle omission or nozzle bending occurs.
B: When 50 sheets of paper are recorded on a recording medium, nozzle omission does not occur, but nozzle bending occurs.
C: After recording 50 sheets on the recording medium, nozzle omission and nozzle bending occur.

By comparing the Examples and Comparative Examples 1 to 3, it was found 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. Furthermore, a comparison between Example and Comparative Example 4 revealed 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 a flocculant. It was found that reliability was poor due to clogging.

From Examples 1 to 4, it was found that bleeding was suppressed as the amount of polyvalent metal salt used increased. It was also found that the smaller the amount of polyvalent metal salt used, the more the precipitation of the reaction liquid on the recording medium and the cloudiness of the recorded matter were suppressed. Further, Examples 5 to 11 showed that a similar tendency exists even when other polyvalent metal salts or organic acids are used.

Furthermore, it was found from Examples 12 and 13 that bleeding was further suppressed by using a component serving as a receptor layer or a cationic resin. In addition, by comparing 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. In addition, from Examples 2 and 14 to 16, it was found that when the amount of volatile components evaporated is high, bleeding tends to be suppressed, but when the amount of volatile components is not too high, bleed is suppressed.
We speculate that this is because if the amount of volatilization is too high, the flocculant contained in the reaction liquid cannot be sufficiently mixed onto the first ink, making it difficult for the second ink to react with the flocculant. . It was also found that the lower the amount of volatilization, the better both recording speed and clogging reliability.

Example 17 showed that the effect of the present invention was obtained even when the colors and whites of the first ink and the second ink were reversed. In addition, Examples 9 and 18 showed that the effects of the present invention can be achieved even with other recording media. When a low-absorption recording medium was used, bleeding tended to be better. On the other hand, a non-absorbent recording medium had better water resistance and abrasion resistance. It has been found that the present invention is even more useful when used in recording media. Furthermore, by comparing Example 19 with other Examples, it was found that the higher the surfactant content and the lower the surface tension of the reaction solution, the more likely it was that bleeding, precipitation of the reaction solution on the recording medium, and recorded matter would be reduced. It was found that cloudiness was suppressed.

Note that in the above example, recording was performed using a serial printer, but it is also possible to perform recording using a line printer as shown in FIG. In this case, the time elapses from when the reaction liquid and the first ink are applied by the reaction liquid applying head and the first ink applying head to when the reaction liquid and the first ink are applied to the position facing the second ink head and the second ink is applied. The amount of volatilization of the recording medium can be controlled by adjusting the recording medium conveyance speed.

Claims (15)

a reaction liquid applying step of applying a reaction liquid containing a flocculant to a recording medium;
a first step of overlappingly applying a first ink containing a coloring material to the area to which the reaction liquid has been applied;
a second step of overlappingly applying a second ink containing a coloring material to the area to which the first ink has been applied;
Equipped with
The recording medium is a non-absorbent recording medium or a low-absorbing recording medium, and is a transparent recording medium,
The first ink is a color ink containing a color coloring material or a black ink containing a black coloring material,
the second ink is a white ink containing a white coloring material,
The reaction solution contains a polysiloxane surfactant,
The flocculant contains a polyvalent metal salt that is either a magnesium or calcium salt,
The reaction liquid applying step, the first step, and the second step are performed by an inkjet method,
A recording method , wherein a recorded matter obtained by recording is a recorded matter used when viewed from the back side of the recording surface of the recording medium . Volatization of volatile components contained in the reaction liquid and the first ink on the non-absorbent recording medium or the low-absorbency recording medium after the first step and before the second step The amount is 10 to 95% by mass 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 according to claim 1. The content of the white coloring material in the second ink is 2 to 15% by mass based on the total mass of the ink.
The recording method according to claim 2. The content of the polyvalent metal salt in the flocculant is 0.5 to 5% by mass based on the total mass of the reaction solution ,
The recording method according to any one of claims 1 to 3. The ratio of the number of moles (unit: mol) of the polyvalent metal salt contained in the reaction solution to the total mass (unit: g) of the coloring material contained in the first ink and the second ink (coloring material : polyvalent metal salt) is 1000:1 to 31000:1,
The recording method according to claim 1 . the reaction solution contains an organic acid as a flocculant,
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 material of the first ink and the second ink (coloring material: organic acid ) is 800:1 to 5500:1,
The recording method according to claim 1 or 5. In the first step, the surface temperature of the recording medium is 40° C. or less,
The recording method according to any one of claims 1 to 6. The surface tension of the reaction solution is 55 mN/N or less at 25°C.
The recording method according to any one of claims 1 to 7. The reaction liquid further contains at least one member 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 recording method according to any one of claims 1 to 8. At least one member (unit: g) selected from the group consisting of the component forming the receiving layer and the cationic resin contained in the reaction liquid, and a coloring material (unit: g) contained in the first ink. and the mass ratio (coloring material: at least one selected from the group) is 7:1 to 70:1,
The recording method according to claim 9. The first step and the second step are performed by an inkjet method using a line head or a serial head .
The recording method according to any one of claims 1 to 10. Volatization of volatile components contained in the reaction liquid and the first ink on the non-absorbent recording medium or the low-absorbency 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 according to any one of claims 1 to 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, and 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 any one of claims 1 to 12. the reaction solution contains an organic acid as a flocculant,
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 (unit: mol) of the organic acid contained in the first ink and the second ink. The ratio (coloring material: organic acid) to the total mass of the coloring material (unit: g) is 800:1 to 5500:1.
The recording method according to any one of claims 1 to 13. Components included in the reaction liquid and forming a receiving layer for the first ink and the second ink, and a cationic resin per unit area of the non-absorbent recording medium or the low-absorbent recording medium. The ratio of the mass (unit: g) of at least one selected from the group consisting of the mass (unit: g) of the coloring material contained in the first ink (coloring material: at least one selected from the group) is 7:1 to 70:1,
The recording method according to any one of claims 1 to 14.

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