Ink set, inkjet recording method, and recording device

Abstract

A problem addressed by the present invention is to provide an ink set and an inkjet recording method capable of suppressing color bleeding and achieving a wide color gamut. Also, to provide a recording device capable of reducing drying load while maintaining high quality.　In an ink set composed of a treatment liquid and an aqueous pigment ink containing two or more pigment dispersions X, the aqueous pigment ink contains at least two or more pigment dispersions X containing a pigment dispersion A and a pigment dispersion B. The absolute value of the difference between the maximum absorption wavelengths of the pigment dispersion A and the pigment dispersion B is 50 nm or more, and the aggregability of all the pigment dispersions contained in the mixture of the treatment liquid and the aqueous pigment ink and the aggregability of all the pigment dispersions themselves are set within specific ranges.

Description

Ink set, inkjet recording method and recording apparatus

[0001] The present invention relates to an ink set, an inkjet recording method, and a recording apparatus.

[0002] In recent years, there has been a demand for further improvements in quality in packaging technology, and higher quality is also required when printing directly onto a recording medium using label-less printing, etc., and more advanced printing technology is required.

[0003] For example, Patent Document 1 discloses a two-liquid ink set including two ink compositions and a reaction liquid that aggregates the ink. Patent Document 2 discloses a cyan ink containing a copper phthalocyanine pigment and a yellow pigment. However, these technologies leave room for improvement.

[0004] JP 2004-107453 A JP 2015-067717 A

[0005] Here, for example, to print on a recording medium on a packaging machine, a printer must be installed on the packaging machine, which limits the space available for the recording head position and drying space, etc. On the other hand, there is a high demand for spot colors such as corporate colors, and even in such cases, higher quality and a wider variety of color expression are required.

[0006] Furthermore, when printing onto a recording medium using conventional printing technology using YMC process colors, the amount of ink applied becomes too large, resulting in a trade-off between drying performance and productivity, and the drying device must be made larger to compensate for this. Furthermore, the increased number of recording heads also increases the size of the printing device, creating the problem of it being impossible to install it on a packaging machine. Another problem is that it is not possible to handle a wide color gamut.

[0007] Therefore, there is a demand for a technology that addresses the above-mentioned problems by using inks that have been pre-mixed in order to accurately represent colors that cannot be reproduced using YMC process colors in printing, i.e., special color inks.

[0008] In addition to the above-mentioned problems, when printing on a packaging machine, high-speed printing that matches the takt time of the packaging machine is required. However, with conventional inks, problems such as color bleeding on absorbent substrates and beading on non-absorbent substrates occur, making it difficult to obtain high-quality printed materials. To address this issue, a technology using ink and a reaction liquid has been disclosed.

[0009] For example, the technology disclosed in Patent Document 1 uses a two-liquid ink set consisting of two ink compositions and a reaction liquid that aggregates the inks during image formation, and the reactivity of the two inks with respect to the reaction liquid is made uniform.

[0010] Specifically, an ink set is used in which the difference between the maximum and minimum particle diameters of the pigments in multiple mixed solutions, each of which is prepared by mixing a 1000-fold diluted aqueous solution of an anionic dispersed pigment and a reaction solution with each of the above ink compositions at a mass ratio of 1:1, is set to 100 nm or less. This allows for a consistent color balance in the printed image, thereby maximizing color development. However, the above-mentioned patent document 1 fails to address the aggregation properties of the pigment dispersion contained in the ink before the two inks are mixed, and there is still room for improvement.

[0011] The technology disclosed in Patent Document 2 uses a cyan ink containing a copper phthalocyanine pigment. To address the problems of bronzing and a narrow green color gamut with this cyan ink, the color gamut is improved by mixing a yellow pigment into the cyan ink. However, Patent Document 2 does not mention color bleeding that occurs when a reaction liquid that aggregates the ink is used during image formation, and so there is still room for improvement.

[0012] The present invention has been made in consideration of the above problems and circumstances, and aims to provide an ink set and inkjet recording method that can suppress color bleeding and achieve a wide color gamut, as well as a recording apparatus that can suppress drying load while maintaining high quality.

[0013] The present inventors have discovered that the above-mentioned problems can be solved by adjusting the aggregation properties of the treatment liquid and each pigment dispersion to the same level in advance in an ink set composed of a treatment liquid and an aqueous pigment ink containing at least two or more types of pigment dispersion, and have arrived at the present invention.

[0014] 1. An ink set comprising a treatment liquid and an aqueous pigment ink, wherein the aqueous pigment ink contains at least two or more pigment dispersions X including pigment dispersion A and pigment dispersion B, and is an ink that aggregates when mixed with the treatment liquid, wherein the absolute value of the difference in maximum absorption maximum wavelength between pigment dispersion A and pigment dispersion B is 50 nm or more, and the aggregation index G defined by the following formula (I) of all pigment dispersions X contained in the mixed liquid of the treatment liquid and the aqueous pigment ink is Ｘ is less than 0.7, and Ｘ =X ａｆｔ / X ｂｅｆ (In the above formula (I), X ｂｅｆ represents the absorbance at the maximum absorption wavelength of pigment dispersion X in a 1:1 mixture of aqueous pigment ink and pure water. ａｆｔ represents the absorbance at the maximum absorption maximum wavelength derived from pigment dispersion X in the supernatant liquid after centrifuging a 1:1 mixture of an aqueous pigment ink and a 5-fold diluted aqueous solution of the treatment liquid.) The aggregation index G Ｘ the absolute value of the difference between the above is 0.4 or less.

[0015] 2. The aggregation index of pigment dispersions A and B defined by the formula (I) is expressed as G Ａ and G Ｂ When the above G Ａ and the G Ｂ satisfies all of the following formulas (1), (2), and (3): Formula (1): 0≦G Ａ <0.5 Formula (2): 0≦G Ｂ <0.5 Formula (3): |G Ａ -G Ｂ |≦0.2 (In the above formulas (1), (2) and (3), G Ａ= A ａｆｔ / A ｂｅｆ , G Ｂ =B ａｆｔ / B ｂｅｆ 2. The ink set according to claim 1,

[0016] 3. The ink set described in item 1, wherein the treatment liquid and the aqueous pigment ink are capable of being ejected by inkjet.

[0017] 4. The ink set described in item 1, wherein the aqueous pigment ink contains any one of a yellow pigment dispersion, a cyan pigment dispersion, and a magenta pigment dispersion.

[0018] 5. The ink set described in item 1, wherein the aqueous pigment ink contains at least two or more pigment dispersions X selected from a yellow pigment dispersion, a cyan pigment dispersion, and a magenta pigment dispersion.

[0019] 6. The ink set described in item 1, wherein the treatment liquid contains at least one of a polyvalent metal salt, an acid, or a cationic polymer.

[0020] 7. The ink set according to item 1, wherein the aqueous pigment ink contains a fixing resin.

[0021] 8. The ink set described in item 1, wherein the absolute value of the difference in particle size between the pigment dispersion A and the pigment dispersion B is less than 80 nm.

[0022] 9. An inkjet recording method using the ink set described in item 1, wherein the ink set includes an achromatic ink, and the aqueous pigment inks of two or more colors are not superimposed on the recording medium.

[0023] 10. An inkjet recording method using the ink set described in item 1, characterized in that an image is recorded by mixing and preparing the ink set in a flow path of a recording device.

[0024] 11. Aggregation index G between all pigment dispersions ＸA recording apparatus characterized in that a pigment dispersion having an absolute value of the difference between the two is 0.4 or less is mixed in an arbitrary ratio in a flow path and recording is performed.

[0025] The above-mentioned means of the present invention provide an ink set and an inkjet recording method that can suppress color bleeding and achieve a wide color gamut. It is also possible to provide a recording apparatus that can suppress drying load while maintaining high quality. The mechanism by which the effects of the present invention are manifested or acted upon is not clear, but is speculated as follows.

[0026] The ink set of the present invention is an ink set composed of a treatment liquid and an aqueous pigment ink, and contains at least two or more pigment dispersions with different hues in the ink. The pigment dispersions with different hues in the ink are mixed to form a particular color.

[0027] When forming a special color, for example, green ink is formed by mixing a yellow pigment and a cyan pigment, or red ink is formed by mixing a yellow pigment and a magenta pigment.

[0028] In such cases, the present invention is characterized by the use of an ink set consisting of a treatment liquid and an aqueous pigment ink containing at least two or more pigment dispersions, and by adjusting the aggregation properties of the treatment liquid and each pigment dispersion to the same level in advance, color bleeding is suppressed and a wide color gamut is achieved.

[0029] As a result of extensive research, the present inventors have found that it is possible to achieve high levels of suppression of color bleeding and a wide color gamut during image formation not only by simply aligning the coagulation properties to the same level, but also by aligning the coagulation properties of the treatment liquid and the ink between pigment dispersions using an index known as the coagulation index.

[0030] For example, in the technology disclosed in the aforementioned Patent Document 1, with regard to the reactivity between a reaction liquid and two types of ink, the difference between the maximum and minimum particle diameters of the pigments in a plurality of mixed solutions obtained by mixing a 1000-fold diluted aqueous solution of the reaction liquid with each of the above ink compositions at a mass ratio of 1:1 is set to 100 nm or less. However, with inks that contain two types of pigment dispersions in a single ink, such as the inks that make up the ink set of the present invention, it has been difficult to achieve a wide color gamut while obtaining a high color bleeding suppression effect, even when adjusted as described above.

[0031] The above-mentioned difficulties are presumed to be due to differences in the landing timing of the reaction liquid and the ink that constitute the ink set. In the technology described in Patent Document 1, the ink set is made of two or more ink compositions and a reaction liquid, so the landing timing of the reaction liquid, one ink composition, and the other ink composition differs. Furthermore, there are cases where one ink composition and the other ink composition pile up on the reaction liquid.

[0032] In contrast, in the ink set of the present invention, which is composed of the treatment liquid and the ink, the ink is of one type, so the multiple pigment dispersions contained in the ink react with the treatment liquid simultaneously. Ｘ It has been found that it is effective to use the formula below to set this within a certain range.

[0033] The aggregation index G of each pigment dispersion contained in the ink constituting the ink set of the present invention Ｘ is less than 0.7, and the aggregation index G Ｘ By making the absolute value of the difference between the two values ​​0.4 or less, each pigment dispersion reacts uniformly with the treatment liquid and aggregates uniformly, which is thought to suppress color bleeding during image formation and widen the color gamut.

[0034] If the aggregation index Gx is greater than 0.7, the aggregation force is insufficient, resulting in color bleeding and mottle in solid areas. If the absolute value of the difference in aggregation index Gx of each pigment dispersion exceeds 0.4, color bleeding occurs only in specific colors, resulting in poor image quality such as color bleeding at the outlines of thin lines.

[0035] It is presumed that color bleeding can be suppressed and the color gamut can be expanded by appropriately controlling the aggregation properties of each pigment dispersant using a wide variety of methods, such as the type of pigment, the type of pigment dispersant, the blending ratio of pigment and pigment dispersant, the type of neutralizing base in the pigment dispersant, the pigment dispersion method, the type of aggregating agent in the treatment liquid, and the constituent materials in the ink.

[0036] Furthermore, it is presumed that color bleeding that occurs when a processing liquid is used during image formation, as in the technology disclosed in Patent Document 2, can also be improved by making the aggregation properties of each pigment dispersion uniform using the method described in the present invention.

[0037] An example of a graph showing absorbance versus light absorption wavelength before and after mixing of a pigment dispersion with a treatment liquid. An example of a graph showing absorbance versus light absorption wavelength of an aqueous pigment ink and a pigment dispersion. An example of a graph showing absorbance versus light absorption wavelength of an aqueous pigment ink and a pigment dispersion in a supernatant liquid after mixing with a treatment liquid. An example of a mixing device that mixes components that make up an ink set. An example of the configuration of a recording device equipped with a mixing device. An example of an image recording method in a print test. An example of an image recording method in a two-color print test. An example of an image recording method in a treatment liquid application print test.

[0038] However, advantages and features provided by one or more embodiments of the present invention will be more fully understood from the following detailed description and the accompanying drawings, which are for illustrative purposes only and are not intended to define the limits of the invention.

[0039] The ink set of the present invention is an ink set composed of a treatment liquid and an aqueous pigment ink, wherein the aqueous pigment ink contains at least two or more pigment dispersions X including pigment dispersion A and pigment dispersion B, and is an ink that aggregates when mixed with the treatment liquid, wherein the absolute value of the difference in maximum absorption maximum wavelength between pigment dispersion A and pigment dispersion B is 50 nm or more, and the aggregation index G defined by the following formula (I) of all pigment dispersions X contained in the mixed liquid of the treatment liquid and the aqueous pigment ink is Ｘ is less than 0.7, and Ｘ =X ａｆｔ / X ｂｅｆ (In the above formula (I), X ｂｅｆrepresents the absorbance at the maximum absorption wavelength of pigment dispersion X in a 1:1 mixture of aqueous pigment ink and pure water. ａｆｔ represents the absorbance at the maximum absorption maximum wavelength derived from pigment dispersion X in the supernatant liquid after centrifuging a 1:1 mixture of an aqueous pigment ink and a 5-fold diluted aqueous solution of the treatment liquid.) The aggregation index G Ｘ The absolute value of the difference between the above and the above formula (1) is 0.4 or less. This feature is a technical feature common to or corresponding to each of the following embodiments (aspects).

[0040] In one embodiment of the present invention, the aggregation index of pigment dispersions A and B defined by the above formula (I) is Ａ and G Ｂ When the above G Ａ and the G Ｂ However, it is preferable to satisfy all of the above formulas (1), (2), and (3) from the viewpoints of suppressing color bleeding, improving the color gamut, and reducing the drying load.

[0041] From the viewpoint of controlling aggregation and color gamut expression, it is preferable that the treatment liquid and the aqueous pigment ink can be ejected by inkjet.

[0042] From the viewpoint of suppressing color bleeding and improving the color gamut, it is preferable that the aqueous pigment ink contains any one of a yellow pigment dispersion, a cyan pigment dispersion, and a magenta pigment dispersion.

[0043] From the viewpoint of suppressing color bleeding and improving the color gamut, it is more preferable that the aqueous pigment ink contains at least two or more pigment dispersions X selected from a yellow pigment dispersion, a cyan pigment dispersion, and a magenta pigment dispersion.

[0044] From the viewpoint of controlling aggregability, it is preferable that the treatment liquid contains at least one of a polyvalent metal salt, an acid, or a cationic polymer.

[0045] From the viewpoint of controlling aggregation, it is preferable that the aqueous pigment ink contains a fixing resin.

[0046] From the viewpoint of controlling aggregation, it is preferable that the absolute value of the difference in particle size between the pigment dispersion A and the pigment dispersion B is less than 80 nm.

[0047] The inkjet recording method of the present invention is an inkjet recording method that can suitably use the ink set of the present invention. The ink set is characterized in that it contains an achromatic ink, and that two or more colors of the aqueous pigment inks are not superimposed on the recording medium. This makes it possible to reduce the amount of ink applied and the drying load.

[0048] In the ink jet recording method of the present invention, it is preferable from the viewpoint of controlling cohesion that an image is recorded by mixing and preparing the ink set in the flow path of the recording device.

[0049] The recording device of the present invention is Ｘ The ink jet recording method is characterized by having a means for mixing pigment dispersions having an absolute value of the difference between the values ​​of α and β being 0.4 or less in an arbitrary ratio in a flow path for recording. This allows for efficient mixing of pigment dispersions having similar levels of aggregation, thereby enabling the formation of images with a wide color gamut and no color bleeding.

[0050] The present invention, its components, and embodiments and modes for carrying out the present invention will be described in detail below. In this application, the symbol "to" is used to mean that the numerical values ​​before and after it are included as the lower limit and upper limit.

[0051] [Two-component ink set] 1. Overview The ink set of the present invention is an ink set composed of a treatment liquid and an aqueous pigment ink, wherein the aqueous pigment ink contains at least two or more pigment dispersions X including pigment dispersion A and pigment dispersion B, and is an ink that aggregates when mixed with the treatment liquid, wherein the absolute value of the difference in maximum absorption maximum wavelength between pigment dispersion A and pigment dispersion B is 50 nm or more, and the aggregation index G defined by the following formula (I) of all pigment dispersions X contained in the mixed liquid of the treatment liquid and the aqueous pigment ink is Ｘ is less than 0.7, and Ｘ =X ａｆｔ / X ｂｅｆ (In the above formula (I), X ｂｅｆrepresents the absorbance at the maximum absorption wavelength of pigment dispersion X in a 1:1 mixture of aqueous pigment ink and pure water. ａｆｔ represents the absorbance at the maximum absorption maximum wavelength derived from pigment dispersion X in the supernatant liquid after centrifuging a 1:1 mixture of an aqueous pigment ink and a 5-fold diluted aqueous solution of the treatment liquid.) The aggregation index G Ｘ The absolute value of the difference between the two is 0.4 or less.

[0052] Pigment Dispersion X may contain Pigment Dispersion A and / or Pigment Dispersion B. It also includes pigment dispersions other than Pigment Dispersion A and Pigment Dispersion B.

[0053] As mentioned above, a feature of the present invention is that the aggregation properties of the pigment dispersions contained in one ink composition are made the same as those of the other ink composition, which makes the reaction mechanisms of the two ink compositions with the treatment liquid when they are mixed together comparable, thereby suppressing color bleeding and achieving a wide color gamut.

[0054] (1.1) Absorbance at Light Absorption Wavelength In spectroscopy, absorbance is a dimensionless quantity that indicates the degree to which the intensity of light is weakened when it passes through an object. The absorbance of ink can be calculated, for example, by measuring appropriately diluted ink with a spectrophotometer and multiplying the measured value by the dilution factor.

[0055] Here, the absorbance in an ink set made up of a treatment liquid and a water-based pigment ink will be described.

[0056] It is assumed that the aqueous pigment ink contains pigment dispersions A, B, and C, and is an ink that aggregates when mixed with the treatment liquid.

[0057] FIG. 1 is an example of a graph showing absorbance versus light absorption wavelength before and after a pigment dispersion is mixed with a treatment liquid. Ａ "," "D Ｂ " and "D Ｃ " represents the absorbance at each light absorption wavelength of pigment dispersions A, B, and C, and "PD Ａ ", "PD Ｂ " and "PD Ｃ" represents the absorbance of the mixed liquid of the treatment liquid and pigment dispersions A, B and C at each light absorption wavelength.

[0058] As can be seen from FIG. 1, the absorbance of the pigment dispersion at the absorption wavelength of light decreases due to aggregation and precipitation caused by mixing with the treatment liquid.

[0059] (Absorbance in the mixed solution: X ｂｅｆ The absorbance in a 1:1 mixture of an aqueous pigment ink and pure water can also be considered as the absorbance of the aqueous pigment ink before the reaction. In this specification, if the pigment dispersion contained in the aqueous pigment ink constituting the ink set according to the present invention is designated as X, the absorbance at the maximum absorption maximum wavelength derived from the pigment dispersion X in the 1:1 mixture of the aqueous pigment ink and pure water is "X ｂｅｆ " is defined as:

[0060] Here, the absorbance of a mixed liquid when the pigment dispersions contained in the aqueous pigment inks constituting the ink set according to the present invention are pigment dispersions A and B will be described.

[0061] The absorbance at the maximum absorption wavelength of pigment dispersion A in a 1:1 mixture of aqueous pigment ink and pure water is "A ｂｅｆ " and the absorbance at the maximum absorption wavelength of pigment dispersion B in the same mixture is "B ｂｅｆ "

[0062] In this case, FIG. 2 is an example of a graph showing the absorbance of an aqueous pigment ink and a pigment dispersion against the light absorption wavelength. In FIG. 2, an example is shown in which pigment dispersions A and B are used as the pigment dispersion. In FIG. 2, "L ｉｎｋ " represents the absorbance of the aqueous pigment ink at each light absorption wavelength, and "D Ａ " and "D Ｂ " represents the absorbance of pigment dispersions A and B at each light absorption wavelength.

[0063] As can be seen from FIG. ｂｅｆ and B ｂｅｆ is a value obtained by subtracting the absorbance from one of the pigment dispersions as a base.

[0064] (Absorbance in the supernatant: X ａｆｔ The absorbance attributable to the pigment dispersion in the supernatant liquid obtained after centrifuging a 1:1 mixture of an aqueous pigment ink and a 5-fold diluted aqueous solution of the treatment liquid can also be considered as the absorbance of the unreacted components of the aqueous pigment ink. In this specification, the absorbance at the maximum absorption maximum wavelength attributable to pigment dispersion X in the supernatant liquid obtained after centrifuging a 1:1 mixture of an aqueous pigment ink and a 5-fold diluted aqueous solution of the treatment liquid is referred to as "X ａｆｔ " is defined as:

[0065] Here, the absorbance of the supernatant liquid after centrifuging the mixed liquid when the pigment dispersions contained in the aqueous pigment ink constituting the ink set according to the present invention are pigment dispersion A and pigment dispersion B will be described.

[0066] The absorbance at the maximum absorption wavelength of pigment dispersion A in the supernatant after centrifuging a 1:1 mixture of the aqueous pigment ink and a 5-fold diluted aqueous solution of the treatment liquid was determined as "A ａｆｔ ", and the absorbance at the maximum absorption wavelength derived from pigment dispersion B is "B ａｆｔ In this case, FIG. 3 is an example of a graph showing the absorbance of the aqueous pigment ink and pigment dispersion in the supernatant liquid after mixing with the treatment liquid against the light absorption wavelength.

[0067] In FIG. Ｌ " represents the absorbance at the absorption wavelength of the aqueous pigment ink in the supernatant liquid after centrifuging a 1:1 mixture of the aqueous pigment ink and a 5-fold diluted aqueous solution of the treatment liquid.

[0068] "U Ａ " or "U Ｂ " represents the absorbance at the absorption wavelength derived from pigment dispersion A or B in the supernatant after centrifuging a 1:1 mixture of an aqueous pigment ink and a 5-fold diluted aqueous solution of the treatment liquid.

[0069] As can be seen from FIG. ａｆｔ and B ａｆｔ is a value obtained by subtracting the absorbance from one of the pigment dispersions as a base.

[0070] (1.2) Cohesion Index In this specification, the cohesion index G defined by the above formula (I) Ｘ is an index showing the reactivity between the treatment liquid and the pigment dispersion. Ｘ When the absolute value of the difference is 0.4 or less, it can be said that the aggregation properties of the pigment dispersions are similar.

[0071] X in formula (I) ａｆｔ represents the absorbance at the maximum absorption wavelength of pigment dispersion X in the supernatant after centrifuging a 1:1 mixture of an aqueous pigment ink and a 5-fold diluted aqueous solution of the treatment liquid, and ａｆｔ can also be said to be the absorbance at the maximum absorption wavelength originating from pigment dispersion X contained in the unreacted components of the water-based pigment ink.

[0072] In formula (I), X ｂｅｆ represents the absorbance at the maximum absorption wavelength of the pigment dispersion X in a 1:1 mixture of the aqueous pigment ink and pure water. Ｘ is an index showing "the reactivity between the treatment liquid and the aqueous pigment ink", that is, "aggregation property".

[0073] The aggregation index of pigment dispersions A and B defined by the formula (I) is expressed as G Ａ and G Ｂ When the above G Ａ and the G Ｂ satisfies all of the following formulas (1), (2), and (3): Formula (1): 0≦G Ａ <0.5 Formula (2): 0≦G Ｂ <0.5 Formula (3): |G Ａ -G Ｂ |≦0.2 (In the above formulas (1), (2) and (3), G Ａ = A ａｆｔ / A ｂｅｆ , G Ｂ =B ａｆｔ / B ｂｅｆ ) is preferable from the viewpoints of suppressing color bleeding, improving color gamut, and reducing drying load.

[0074] 2. Water-based pigment ink (2.1) Overview The water-based pigment ink constituting the two-component ink set of the present invention is characterized in that the water-based pigment ink aggregates when it is mixed with the treatment liquid constituting the two-component ink set. Furthermore, it is preferable that the water-based pigment ink be ejectable by inkjet printing from the viewpoints of controlling aggregation and color gamut expression.

[0075] (2.2) Pigment Dispersion The aqueous pigment ink according to the present invention contains a pigment dispersion, which is obtained by adding a pigment dispersant to a pigment.

[0076] The aggregation properties of each pigment dispersion can be appropriately controlled by a wide variety of methods, such as the pigment type, pigment dispersant type, blending ratio of pigment and pigment dispersant, neutralization base type of the pigment dispersant, pigment dispersion method, aggregating agent type in the treatment liquid, and constituent materials in the ink, which will be described later.

[0077] The aqueous pigment ink according to the present invention contains two or more pigment dispersions X including pigment dispersion A and pigment dispersion B, and the absolute value of the difference in maximum absorption maximum wavelength between pigment dispersion A and pigment dispersion B is 50 nm or more.

[0078] All pigment dispersions contained in the mixed liquid of the treatment liquid and the aqueous pigment ink have an aggregation index defined by the following formula (I) of less than 0.7. Formula (I): G Ｘ =X ａｆｔ / X ｂｅｆ

[0079] The absolute value of the difference in aggregation index between all pigment dispersions is in the range of 0.4 or less.

[0080] From the viewpoints of suppressing color bleeding and improving color gamut, it is preferable that the aqueous pigment ink contains any one of a yellow pigment dispersion, a cyan pigment dispersion, and a magenta pigment dispersion, and it is more preferable that the aqueous pigment ink contains at least two or more pigment dispersions selected from any one of these pigment dispersions.

[0081] From the viewpoint of controlling aggregation, it is preferable that the absolute value of the difference in particle size between the pigment dispersion A and the pigment dispersion B is less than 80 nm.

[0082] (2.3) Components The aqueous pigment ink according to the present invention contains a pigment and a pigment dispersant. The aqueous pigment ink preferably contains a fixing resin, a water-soluble solvent, a surfactant, a wax, and water. Furthermore, the aqueous pigment ink may contain other known additives, etc., as appropriate.

[0083] (Pigment) The pigment contained in the ink according to the present invention is preferably an anionic dispersed pigment, such as a self-dispersed pigment having anionic groups on its surface, a pigment dispersed using an anionic polymer dispersant, or a pigment dispersed while its surface is coated with an anionic resin. In particular, it is preferable to use a pigment dispersed using an anionic polymer dispersant, as it has excellent dispersibility and reacts appropriately with the treatment liquid to form pinning.

[0084] As the pigment, any conventionally known pigment can be used without any particular limitation, and for example, inorganic pigments such as titanium oxide, insoluble pigments, and organic pigments such as lake pigments can be preferably used.

[0085] Titanium oxide has three crystalline forms: anatase, rutile, and brookite, but the most commonly used can be broadly classified into anatase and rutile. While not particularly limited, rutile is preferred, as it has a high refractive index and high hiding power. Specific examples include the TR series from Fuji Titanium Industry Co., Ltd., the JR series from Teika Corporation, and Typepaque from Ishihara Sangyo Kaisha, Ltd.

[0086] The insoluble pigment is not particularly limited, but preferred examples include azo, azomethine, methine, diphenylmethane, triphenylmethane, quinacridone, anthraquinone, perylene, indigo, quinophthalone, isoindolinone, isoindoline, azine, oxazine, thiazine, dioxazine, thiazole, phthalocyanine, and diketopyrrolopyrrole.

[0087] Specific examples of organic pigments that can be preferably used include pigments for magenta or red, pigments for orange or yellow, pigments for green or cyan, and pigments for black.

[0088] Examples of pigments for magenta or red include C.I. Pigment Red 2, C.I. Pigment Red 3, C.I. Pigment Red 5, C.I. Pigment Red 6, C.I. Pigment Red 7, C.I. Pigment Red 15, C.I. Pigment Red 16, C.I. Pigment Red 48:1, C.I. Pigment Red 53:1, C.I. Pigment Red 57:1, C.I. Pigment Red 122, C.I. Pigment Red 123, C.I. Pigment Red 139, C.I. Pigment Red 1144, C.I. Pigment Red 149, C.I. Pigment Red 166, C.I. Pigment Red 177, C.I. Examples of the pigment include C.I. Pigment Red 178, C.I. Pigment Red 202, C.I. Pigment Red 222, C.I. Pigment Violet 19, and mixed crystals thereof.

[0089] Examples of orange or yellow pigments include C.I. Pigment Orange 31, C.I. Pigment Orange 43, C.I. Pigment Yellow 12, C.I. Pigment Yellow 13, C.I. Pigment Yellow 14, C.I. Pigment Yellow 15, C.I. Pigment Yellow 15:3, C.I. Pigment Yellow 17, C.I. Pigment Yellow 74, C.I. Pigment Yellow 93, C.I. Pigment Yellow 128, C.I. Pigment Yellow 94, C.I. Pigment Yellow 138, and C.I. Pigment Yellow 1155. In particular, C.I. Pigment Yellow 1155 is preferred in terms of the balance between color tone and lightfastness.

[0090] Examples of pigments for green or cyan include C.I. Pigment Blue 15, C.I. Pigment Blue 15:2, C.I. Pigment Blue 15:3, C.I. Pigment Blue 16, C.I. Pigment Blue 60, and C.I. Pigment Green 7.

[0091] Examples of black pigments include C.I. Pigment Black 1, C.I. Pigment Black 6, and C.I. Pigment Black 7.

[0092] (Pigment Dispersant) The ink according to the present invention preferably contains a pigment dispersant for dispersing the pigment. The pigment dispersant is not particularly limited, but is preferably a polymer dispersant having an anionic group, and one having a molecular weight in the range of 5,000 to 200,000 can be suitably used.

[0093] Examples of polymer dispersants include block copolymers and random copolymers having a structure derived from two or more monomers selected from styrene, styrene derivatives, vinylnaphthalene derivatives, acrylic acid, acrylic acid derivatives, maleic acid, maleic acid derivatives, itaconic acid, itaconic acid derivatives, fumaric acid, and fumaric acid derivatives, as well as salts thereof, polyoxyalkylenes, and polyoxyalkylene alkyl ethers.

[0094] The polymer dispersant preferably has an acryloyl group, and is preferably added after being neutralized with a neutralizing base.

[0095] The neutralizing base is not particularly limited, but is preferably an organic base such as ammonia, monoethanolamine, diethanolamine, triethanolamine, morpholine, etc. In particular, when the pigment is titanium oxide, the titanium oxide is preferably dispersed in a polymer dispersant having an acryloyl group.

[0096] The amount of polymer dispersant added is preferably within a range of 10 to 100% by mass, more preferably within a range of 10 to 40% by mass, based on the pigment.

[0097] The pigment is particularly preferably in the form of a so-called capsule pigment, which is a pigment coated with the polymer dispersant. As a method for coating a pigment with a polymer dispersant, various known methods can be used, and preferred examples thereof include a phase inversion emulsification method, an acid precipitation method, a method in which a pigment is dispersed in a polymerizable surfactant, a monomer is supplied thereto, and coating is performed while polymerizing, and a method in which the pigment dispersion is crosslinked with an epoxy crosslinking agent or the like.

[0098] A particularly preferred method is to dissolve the water-insoluble resin in an organic solvent such as methyl ethyl ketone, partially or completely neutralize the acidic groups in the resin with a base, then add the pigment and ion-exchanged water, disperse the pigment, remove the organic solvent, and add water as needed to prepare the dispersion.

[0099] The average particle size of the pigment particles in the ink in a dispersed state is preferably within a range of 40 to 300 nm. In particular, the average particle size is preferably within a range of 50 to 150 nm. This improves the dispersion stability of the pigment and the storage stability of the ink.

[0100] The particle size of the pigment can be measured by a commercially available particle size measuring device using a dynamic light scattering method, an electrophoresis method, etc. In particular, measurement by the dynamic light scattering method is simple and can measure the particle size range with high accuracy.

[0101] The pigment can be dispersed in a dispersing machine together with a dispersant and other additives required for various desired purposes.

[0102] As the dispersing machine, a conventionally known ball mill, sand mill, line mill, high-pressure homogenizer, etc. can be used.

[0103] Among these, dispersing the pigment using a sand mill is preferred because it results in a sharp particle size distribution. The material of the beads used for sand mill dispersion is not particularly limited, but is preferably zirconia or zircon from the viewpoint of preventing the generation of bead fragments and contamination with ionic components. Furthermore, the diameter of the beads is preferably within the range of 0.1 to 3 mm.

[0104] The content of the pigment in the ink is not particularly limited, but for titanium oxide, the content is preferably in the range of 7 to 18% by mass, and for organic pigments, the content is preferably in the range of 0.5 to 7% by mass.

[0105] (Fixing Resin) The aqueous pigment ink preferably contains a fixing resin from the viewpoint of controlling aggregation. Examples of resins contained in the ink according to the present invention include polyester resins, polyurethane resins, acrylic resins, composite resins thereof, and polyolefin resins. It is preferable that the aqueous pigment ink contains water-insoluble resin particles from the viewpoint of achieving both adhesion and storage stability.

[0106] The above-mentioned "water-insoluble resin microparticles" are those that are inherently water-insoluble, but have a form in which the resin disperses in an aqueous medium as microparticles. They are also water-insoluble resin microparticles that are forcibly emulsified using an emulsifier or the like and dispersed in water, or water-insoluble resin microparticles that are self-emulsifiable by introducing hydrophilic functional groups into the molecule, thereby forming a stable aqueous dispersion without using an emulsifier or a dispersion stabilizer. These resin microparticles are usually used in a state of being emulsified and dispersed in water or a water / alcohol mixed solvent.

[0107] Each resin will be described below. [Polyester Resin] A polyester resin having a polyester skeleton as water-insoluble resin particles can be obtained using a polyhydric alcohol component and a polycarboxylic acid component such as a polycarboxylic acid, a polycarboxylic acid anhydride, or a polycarboxylic acid ester.

[0108] <<Polyhydric Alcohol Component>> Examples of the polyhydric alcohol component include dihydric alcohols (diols). Examples of dihydric alcohols include alkylene glycols having 2 to 36 carbon atoms, alkylene ether glycols having 4 to 36 carbon atoms, alicyclic diols having 6 to 36 carbon atoms, and alkylene oxide adducts of the alicyclic diols having 2 to 4 carbon atoms. Other examples include bisphenols. These may be used alone or in combination of two or more.

[0109] Examples of alkylene glycols having 2 to 36 carbon atoms include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butylene glycol, and 1,6-hexanediol.

[0110] Examples of alkylene ether glycols having 4 to 36 carbon atoms include diethylene glycol, triethylene glycol, dipropylene glycol, polyethylene glycol, polypropylene glycol, and polybutylene glycol.

[0111] Examples of the alicyclic diol having 6 to 36 carbon atoms include 1,4-cyclohexanedimethanol and hydrogenated bisphenol A.

[0112] Examples of the alkylene oxide adducts (addition mole number in the range of 1 to 30) having 2 to 4 carbon atoms of the alicyclic diol include ethylene oxide adducts, propylene oxide adducts, and butylene oxide adducts.

[0113] Hereinafter, "ethylene oxide" will be abbreviated as "EO", "propylene oxide" as "PO", and "butylene oxide" as "BO".

[0114] Examples of bisphenols include alkylene oxide (EO, PO, BO, etc.) adducts (number of moles added ranges from 2 to 30) having 2 to 4 carbon atoms of bisphenol A, bisphenol F, bisphenol S, etc. These may be used alone or in combination of two or more.

[0115] <<Polycarboxylic Acid Component>> Examples of the polycarboxylic acid component include dicarboxylic acids. Examples of dicarboxylic acids include alkane dicarboxylic acids having 4 to 36 carbon atoms, alkenyl succinic acids, alicyclic dicarboxylic acids having 4 to 36 carbon atoms, alkene dicarboxylic acids having 4 to 36 carbon atoms, and aromatic dicarboxylic acids having 8 to 36 carbon atoms. These may be used alone or in combination of two or more.

[0116] Examples of alkanedicarboxylic acids having 4 to 36 carbon atoms include succinic acid, avidinic acid, and sebacic acid.

[0117] Examples of alkenyl succinic acids include dodecenyl succinic acid.

[0118] Examples of the alicyclic dicarboxylic acid having 4 to 36 carbon atoms include dimer acid (dimerized linoleic acid).

[0119] Examples of alkene dicarboxylic acids having 4 to 36 carbon atoms include maleic acid, fumaric acid, citraconic acid, and mesaconic acid.

[0120] Examples of aromatic dicarboxylic acids having 8 to 36 carbon atoms include phthalic acid, isophthalic acid, terephthalic acid, and derivatives thereof, and naphthalenedicarboxylic acid.

[0121] Others The number average molecular weight of the polyester resin is preferably in the range of 1,000 to 50,000, and more preferably in the range of 2,000 to 20,000.

[0122] As the polyester resin, commercially available products may be used. Examples of commercially available water-dispersible polyester resins include Vylonal MD-1100, MD-1200, MD-1245, MD-1480, MD-1500, and MD-2000 manufactured by Toyobo Co., Ltd., Plascoat Z-221, Z-446, Z-561, Z-880, and Z-3310 manufactured by Goo Chemical Co., Ltd., and PES Resin A-520, A-613D, A-615GE, A-640, A-645GH, A-647GEX, A-110F, and A-160P manufactured by Takamatsu Oil & Fat Co., Ltd.

[0123] Among the commercially available polyester resins, commercially available resins having a glass transition temperature of 40 to 90° C. are particularly preferred. Examples include Vylonal MD-1100, MD-1200, MD-1245, MD-1500, and MD-2000 manufactured by Toyobo Co., Ltd., Plascoat Z-221, Z-446, and Z-561 manufactured by Goo Chemical Co., Ltd., and PES Resin A-520, A-613D, A-615GE, A-640, A-645GH, and A-647GEX manufactured by Takamatsu Oil & Fat Co., Ltd. These may be used alone or in combination of two or more.

[0124] [Urethane Resin] As the urethane resin for the water-insoluble resin particles, those having a hydrophilic group can be used.

[0125] The urethane resin is preferably an aqueous dispersion of a self-emulsifying urethane having a water-soluble functional group dispersed in its molecule, or an aqueous dispersion of a forced-emulsifying urethane emulsified under strong mechanical shear force in combination with a surfactant. The urethane resin in the aqueous dispersion can be obtained by reacting a polyol with an organic polyisocyanate and a hydrophilic group-containing compound.

[0126] Examples of polyols that can be used to prepare the aqueous dispersion of the urethane resin include polyester polyols, polyether polyols, polycarbonate polyols, and polyolefin polyols.

[0127] Examples of polyester polyols include condensates of low molecular weight polyols and polycarboxylic acids.

[0128] Examples of low molecular weight polyols include ethylene glycol, diethylene glycol, triethylene glycol, 1,2- and 1,3-propylene glycol, neopentyl glycol, 1,3- and 1,4-butanediol, 3-methylpentanediol, hexamethylene glycol, 1,8-octanediol, 2-methyl-1,3-propanediol, bisphenol A, hydrogenated bisphenol A, trimethylolpropane, and cyclohexanedimethanol.

[0129] Examples of the condensation products with polycarboxylic acids include succinic acid, glutaric acid, adipic acid, sebacic acid, phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, tetrahydrofuran acid, endomethinetetrahydrofuran acid, and hexahydrophthalic acid.

[0130] Examples of polyether polyols include polyethylene glycol, polypropylene glycol, polyethylene polytetramethylene glycol, polypropylene polytetramethylene glycol, and polytetramethylene glycol.

[0131] Polycarbonate polyols can be obtained by reacting a carbonic acid derivative such as diphenyl carbonate, dimethyl carbonate, or phosgene with a diol, such as ethylene glycol, diethylene glycol, triethylene glycol, 1,2- and 1,3-propylene glycol, neopentyl glycol, 1,3- and 1,4-butanediol, 3-methylpentanediol, hexamethylene glycol, 1,8-octanediol, 2-methyl-1,3-propanediol, bisphenol A, hydrogenated bisphenol A, trimethylolpropane, and cyclohexanedimethanol.

[0132] Examples of organic polyisocyanates that can be used to prepare the aqueous dispersion of the urethane resin include aromatic isocyanates, aliphatic isocyanates, and alicyclic isocyanates. These may be used alone or in combination of two or more.

[0133] Examples of aromatic isocyanates include tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), polymeric MDI, xylylene diisocyanate (XDI), and tetramethylxylylene diisocyanate (TMXDI).

[0134] An example of the aliphatic isocyanate is hexamethylene diisocyanate (HMDI).

[0135] Examples of alicyclic isocyanates include isophorone diisocyanate (IPDI) and 4,4'-dicyclohexylmethane diisocyanate (hydrogenated MDI, H12MDI).

[0136] Examples of hydrophilic group-containing compounds that can be used to prepare aqueous dispersions of urethane resins include carboxylic acid-containing compounds and their derivatives such as sodium salts, potassium salts, and amine salts, as well as sulfonic acid-containing compounds and their derivatives such as sodium salts, potassium salts, and amine salts.

[0137] Examples of the carboxylic acid-containing compound include 2,2-dimethylolpropionic acid, 2,2-dimethylolbutanoic acid, 2,2-dimethylolbutyric acid, 2,2-dimethylolvaleric acid, glycine, etc. Examples of the sulfonic acid-containing compound include taurine (aminoethylsulfonic acid), ethoxypolyethylene glycol sulfonic acid, etc.

[0138] The urethane resin can be obtained by a known method. For example, a urethane prepolymer can be obtained by mixing the above-mentioned polyol, organic polyisocyanate, and hydrophilic group-containing compound and reacting them at 30 to 130°C for 30 minutes to 50 hours.

[0139] The urethane prepolymer is polymerized by extending the chain with a chain extender to form a urethane resin having a hydrophilic group. The chain extender is preferably water and / or an amine compound. By using water or an amine compound as the chain extender, the chain can react with free isocyanate in a short time, thereby efficiently extending the isocyanate-terminated prepolymer.

[0140] Examples of amine compounds used as chain extenders include aliphatic polyamines, aromatic polyamines, and polyhydrazino compounds. Examples of aliphatic polyamines include ethylenediamine and triethylenediamine. Examples of aromatic polyamines include metaxylenediamine and toluylenediamine. Examples of polyhydrazino compounds include hydrazine and adipic acid dihydrazide.

[0141] The amine compound may contain, together with the polyamine, a monovalent amine such as dibutylamine or methyl ethyl ketoxime as a reaction terminator to the extent that the polymerization is not significantly inhibited.

[0142] In the synthesis of the urethane prepolymer, a solvent that is inert to isocyanates and capable of dissolving the urethane prepolymer may be used. Examples of such solvents include dioxane, methyl ethyl ketone, dimethylformamide, tetrahydrofuran, N-methyl-2-pyrrolidone, toluene, and propylene glycol monomethyl ether acetate. These hydrophilic organic solvents used in the reaction step are preferably finally removed.

[0143] In the synthesis of the urethane prepolymer, a catalyst such as an amine catalyst, a tin-based catalyst, or a titanium-based catalyst may be added to accelerate the reaction.

[0144] Examples of the amine catalyst include triethylamine, N-ethylmorpholine, and triethyldiamine. Examples of the tin catalyst include dibutyltin dilaurate, dioctyltin dilaurate, and tin octoate. Examples of the titanium catalyst include tetrabutyl titanate.

[0145] The number average molecular weight of the urethane resin is preferably increased as much as possible by introducing a branched structure or an internal crosslinked structure, and is preferably within the range of 50,000 to 10,000,000.

[0146] By setting the molecular weight within the above range, the urethane resin becomes less soluble in solvents, thereby obtaining a coating film with excellent weather resistance and water resistance. The number average molecular weight (Mn) is a value measured by gel permeation chromatography (GPC).

[0147] For example, it can be determined from a calibration curve prepared using a polystyrene standard sample using a Shimadzu Corporation "RID-6A" (column: Tosoh Corporation "TSK-GEL", solvent: tetrahydrofuran (THF), column temperature: 40°C).

[0148] Commercially available urethane resins having a glass transition temperature in the range of 40 to 90°C include, for example, Neorez R-967, R-600, and R-9671 manufactured by Kusumoto Chemicals Co., Ltd., Evaphanol HA-560 manufactured by Nicca Chemical Co., Ltd., and SF870 manufactured by Daiichi Kogyo Seiyaku Co., Ltd.

[0149] [Acrylic Resin] The acrylic resin as the water-insoluble resin particles can be obtained by using an acrylic acid ester component, a methacrylic acid ester component, or a copolymer with a styrene component or the like.

[0150] Examples of the acrylic acid ester component and the methacrylic acid ester component include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, cyclohexyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, isobornyl (meth)acrylate, benzyl (meth)acrylate, and (meth)acrylic acid. 2-hydroxybutyl (meth)acrylate, benzyl (meth)acrylate, glycidyl (meth)acrylate, (meth)acrylic acid, (di)ethylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, glycerin di(meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, and acrylamide.

[0151] Examples of the styrene component include styrene, 4-methylstyrene, 4-hydroxystyrene, 4-acetoxystyrene, 4-acetylstyrene, and styrenesulfonic acid. These components may be used alone or in combination of two or more.

[0152] The number average molecular weight (Mn) of the acrylic resin is preferably in the range of 1,000 to 50,000, and more preferably in the range of 2,000 to 20,000.

[0153] When the number average molecular weight (Mn) of the acrylic resin is 1,000 or more, the cohesive force of the coating film is strong and the adhesion is improved, and when it is 50,000 or less, the solubility in organic solvents is good and the particle size of the emulsion dispersion is promoted to be miniaturized.

[0154] The number average molecular weight (Mn) is a value measured by gel permeation chromatography (GPC). For example, it can be determined from a calibration curve prepared using a polystyrene standard sample using a Shimadzu Corporation "RID-6A" column (column: Tosoh Corporation "TSK-GEL" column, solvent: tetrahydrofuran (THF) and column temperature: 40°C).

[0155] Commercially available acrylic resins having a glass transition temperature of 40 to 90°C include, for example, acrylic emulsions such as Movinyl 6899D, 6969D, and 6800 manufactured by Japan Coating Resins Co., Ltd., and acrylic emulsions such as TOCRYL W-7146, W-7147, W-7148, W-7149, and W-7150 manufactured by Toyochem Co., Ltd.

[0156] [Composite Resin Particles] The composite resin particles that can be contained in the ink are preferably composite resin particles in which an acrylic resin is emulsified in a urethane resin, i.e., composite resin particles having an inner layer made of an acrylic resin and a surface layer made of a urethane resin.

[0157] Here, the urethane resin is present at the interface between the acrylic resin as the water-insoluble resin particles and the water as the continuous phase, and functions as a water-insoluble resin particle layer different from the resin that protects the water-insoluble resin particles.

[0158] By emulsifying the acrylic resin with the urethane resin in this way to form composite resin microparticles, the physical properties of the image (coating film) can be improved, and the storage stability of the composite resin microparticles can also be improved, compared to when the acrylic resin and the urethane resin are emulsified and mixed separately.

[0159] In the composite resin microparticles obtained by emulsifying the acrylic resin in the urethane resin, the mass ratio (U / A) of the urethane resin (U) to the acrylic resin (A) is preferably 40 / 60 to 95 / 5. When the proportion of the urethane resin (U) is within the above range, compatibility with dispersants and solvent resistance are improved. Furthermore, when the proportion of the acrylic resin (A) is within the above range, adhesion to acrylic films is excellent. In the above proportions, the mass ratio (U / A) of the urethane resin (U) to the acrylic resin (A) is preferably 40 / 60 to 80 / 20.

[0160] The total resin concentration of the acrylic resin and the urethane resin in the composite resin particles is not particularly limited, but is preferably 5.0% by mass or more, and more preferably in the range of 10.0 to 70.0% by mass. When the resin concentration is within this range, the fixation of the ink to the substrate is good.

[0161] In addition, when emulsifying the acrylic resin with the urethane resin, a surfactant acting as an emulsifier can be used together with the urethane resin. The addition of an emulsifier can improve the storage stability of the composite resin particles.

[0162] Anionic surfactants and / or nonionic surfactants can be used as the emulsifier. It is preferable to use either the anionic surfactant or the nonionic surfactant, and more preferably to use both. The total amount of the anionic surfactant and the nonionic surfactant is preferably within the range of 1.0 to 20.0 parts by mass per 100 parts by mass of the total resin. Furthermore, by setting the total amount of the anionic surfactant and the nonionic surfactant to 20.0 parts by mass or less, water resistance and solvent resistance can be improved.

[0163] The blending mass ratio (X / Y) of the anionic surfactant (X) to the nonionic surfactant (Y) is preferably 100 / 0 to 50 / 50. By setting the blending amount of the anionic surfactant within this range, emulsifiability and storage stability can be further improved.

[0164] Examples of anionic surfactants that can be used for emulsification include alkyl sulfates, polyoxyethylene alkyl ether sulfates, sulfosuccinates, alpha-olefin sulfonates, N-acylamino acid salts, carboxylates, and phosphates. Of these, sulfosuccinates or alpha-olefin sulfonates are preferred.

[0165] The type of salt is not particularly limited, but examples include metal salts such as sodium salts, potassium salts, and magnesium salts, and triethanolamine salts.

[0166] Examples of nonionic surfactants that can be used for emulsification include polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers, polyoxyethylene alkylamine ethers, polyoxyethylene fatty acid esters, sorbitan fatty acid esters, and sucrose fatty acid esters. Among these, polyoxyethylene alkyl ethers or polyoxyethylene alkyl phenyl ethers are preferred.

[0167] The average particle size of the composite resin particles is not particularly limited, but is preferably within the range of 10 to 500 nm, more preferably within the range of 10 to 300 nm, and even more preferably within the range of 10 to 200 nm.

[0168] The average particle size can be measured using a commercially available particle size measuring device that uses dynamic light scattering, electrophoresis, or the like, but measurement using dynamic light scattering is simple and allows the particle size range to be measured with high accuracy.

[0169] By using composite resin particles in which an acrylic resin is emulsified in a urethane resin, it is possible to improve the fixability of an image (coating film) to an absorbent or non-absorbent substrate.

[0170] [Polyolefin Resin] Examples of polyolefin resins that can be used include polyethylene, polypropylene, ethylene-propylene copolymers, and random copolymers of ethylene and / or propylene with other comonomers. Examples of other comonomers include 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, and 1-nonene, each of which has two or more carbon atoms, and α-olefin comonomers having two to six carbon atoms. Alternatively, block copolymers can be used, and examples of such block copolymers include ethylene-propylene-butene copolymers.

[0171] It is also possible to use copolymers of two or more of the above other comonomers, and mixtures of two or more of the above polymers.

[0172] Commercially available polyolefin resins may be used. Examples of commercially available polyolefin resins include Arrowbase SB-1200 (manufactured by Unitika Ltd., "Arrowbase" is a registered trademark of the company), Auroren 150A, Auroren AE-301 (manufactured by Nippon Paper Industries Co., Ltd., "Auroren" is a registered trademark of the company), Superchlor E-415 (manufactured by Nippon Paper Industries Co., Ltd., "Superchlor" is a registered trademark of the company), and Hardlen Na-1001 (manufactured by Toyobo Co., Ltd., "Hardlen" is a registered trademark of the company).

[0173] The polyolefin resin is preferably an acid-modified polyolefin resin, in view of excellent character reproducibility in a two-liquid ink-jet recording method.

[0174] Acid-modified polyolefin resins are resins obtained by modifying polyolefin resins such as polyethylene and polypropylene with unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, maleic anhydride, fumaric acid, itaconic acid, etc. Among these acid-modified polyolefin resins, it is preferable to use polyolefin resins modified with maleic anhydride.

[0175] The content of the fixing resin in the ink is preferably 1 to 20% by mass, and more preferably 3 to 15% by mass, from the viewpoint of achieving both fixing properties and storage stability.

[0176] (Water-Soluble Solvent) The water-soluble solvent contained in the ink according to the present invention is preferably a water-soluble solvent having a boiling point in the range of 150 to 250°C.

[0177] Examples of such water-soluble solvents include alcohols, polyhydric alcohols, amines, amides, glycol ethers, and 1,2-alkanediols having 4 or more carbon atoms, and examples thereof include those exemplified in the treatment liquid.

[0178] The ink may contain one or a combination of two or more selected from the above-mentioned water-soluble solvents.

[0179] The content of the water-soluble solvent in the ink is not particularly limited, but is preferably in the range of 10 to 60% by mass.

[0180] (Surfactant) By including a surfactant in the ink according to the present invention, it is possible to improve the ink ejection stability and control the spread (dot diameter) of droplets that have landed on a recording medium.

[0181] The surfactant is not particularly limited, but when an anionic compound is contained in other constituents of the ink, the ionicity of the surfactant is preferably anionic, nonionic, or betaine type.

[0182] In the present invention, fluorine-based or silicone-based surfactants having a high static surface tension reducing ability, anionic surfactants such as dioctyl sulfosuccinate having a high dynamic surface tension reducing ability, and nonionic surfactants such as relatively low molecular weight polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, acetylene glycols, Pluronic surfactants (Pluronic is a registered trademark), and sorbitan derivatives are preferably used. It is also preferable to use a fluorine-based or silicone-based surfactant in combination with a surfactant having a high dynamic surface tension reducing ability.

[0183] By adding a silicone-based or fluorine-based surfactant as the surfactant, it is possible to further suppress ink mixing (beading) on ​​recording media made of various hydrophobic resins such as vinyl chloride sheets, and recording media with low ink absorption capacity such as printing paper, thereby obtaining high-quality printed images.

[0184] The silicone surfactant is preferably a polyether-modified silicone. For example, siloxanes having alkylene oxide groups on the side chain and / or both ends of the polydimethylsiloxane chain can be used. Specific examples include BYK-331, BYK-333, BYK-345, BYK-3450, BYK-3451, BYK-34155, BYK-346, BYK-347, BYK-348, and BYK-349 manufactured by BYK-Chemie, and TEGOWet KL245, TEGOWet 250, TEGOWet 260, TEGOWet 270, and TEGOWet 2 manufactured by Evonik. and KF-351A, KF-352A, KF-353, KF-354L, KF-3155A, KF-615A, KF-640, KF-642, KF-643, KF-6144, KF-945, KF-6011, KF-6012, KF-6015, KF-6017, KF-6020, KF-6204, and X-22-4515 manufactured by Shin-Etsu Chemical Co., Ltd.

[0185] As the polyether-modified silicone, trisiloxane having alkylene oxide groups at the side chain and / or both ends of the polydimethylsiloxane chain is particularly preferred. Use of trisiloxane can effectively reduce the dynamic surface tension of the treatment liquid, thereby producing an image with good adhesion to the substrate.

[0186] Examples of the trisiloxane include BYK-3450 and BYK-3451 manufactured by BYK Japan, and TEGOWET-KL245, TEGOWET-250, and TEGOWET-260 manufactured by Evonik.

[0187] The content of the polyether-modified silicone is preferably in the range of 0.5 to 2% by mass, and more preferably in the range of 0.5 to 1.5% by mass, relative to 100% by mass of the total mass of the treatment liquid.

[0188] The fluorine-based surfactants mentioned above refer to surfactants in which part or all of the hydrogen atoms bonded to the carbon atoms of the hydrophobic groups of ordinary surfactants have been substituted with fluorine. Among these, surfactants having a perfluoroalkyl group in the molecule are preferred.

[0189] The content of the surfactant in the ink is not particularly limited, but may be any amount that does not impair the storage stability of the ink, and is preferably in the range of 0.1 to 5.0% by mass, and more preferably in the range of 0.1 to 2.0% by mass.

[0190] (Water) The water contained in the ink according to the present invention is not particularly limited, and may be ion-exchanged water, distilled water, or pure water.

[0191] (Wax) The wax contained in the ink according to the present invention is preferably a polyolefin wax. When the ink contains a polyolefin wax, the water resistance and abrasion resistance of the resulting recorded matter are improved.

[0192] The polyolefin wax is not particularly limited, and examples thereof include waxes produced from olefins such as ethylene, propylene, and butylene, or derivatives thereof, and copolymers thereof, specifically polyethylene-based waxes, polypropylene-based waxes, and polybutylene-based waxes. Among these, polyethylene-based waxes are preferred from the viewpoint of more effectively reducing the occurrence of cracks in images. The polyolefin waxes can be used alone or in combination of two or more.

[0193] The polyolefin wax is preferably used in the form of a polyolefin wax emulsion in which solid wax particles are dispersed in water using the above-mentioned surfactant.

[0194] An example of a polyolefin wax emulsion is a method for producing a polyethylene wax emulsion. Polyethylene wax is produced by polymerizing ethylene, synthesizing it from hydrocarbon compounds, or by thermally decomposing polyethylene for general molding to reduce its molecular weight. This polyethylene wax is then oxidized to add carboxyl or hydroxyl groups. A surfactant is then used to emulsify the wax, resulting in a highly stable aqueous wax emulsion.

[0195] Commercially available polyolefin waxes include the Chemipearl series, such as "Chemipearl W4005" (manufactured by Mitsui Chemicals, Inc., polyethylene wax, particle size 200 to 800 nm, ring and ball softening point 110°C, needle penetration hardness 3, solids content 40%). Other examples include the AQUACER series, such as AQUACER 513 (polyethylene wax, particle size 100 to 200 nm, melting point 130°C, solids content 30%), AQUACER 497, AQUACER 513, and AQUACER 517 (all manufactured by BYK Additives & Instruments); the Hitec series, such as Hitec E-7025P, Hitec E-2213, Hitec E-9460, Hitec E-9015, Hitec E-4A, Hitec E-5403P, and Hitec E-8237 (all manufactured by Toho Chemical Industry Co., Ltd.); and Nopcoat PEM-17 (manufactured by San Nopco Ltd., polyethylene emulsion, particle size 40 nm). These are commercially available in the form of aqueous emulsions in which polyolefin wax is dispersed in water by conventional methods. Therefore, it can be added directly to the ink in the form of an aqueous emulsion.

[0196] (Other Known Additives, etc.) In addition to the additives described above, various known additives may be appropriately selected and used in the ink used in the present invention, as needed, depending on the purpose of improving ejection stability, compatibility with print heads and ink cartridges, storage stability, image storage stability, and other performances.

[0197] Examples of known additives include polysaccharides, viscosity modifiers, resistivity modifiers, film-forming agents, ultraviolet absorbers, antioxidants, anti-fading agents, anti-fungal agents, and anti-rust agents. Specific examples thereof include oil droplet fine particles such as liquid paraffin, dioctyl phthalate, tricresyl phosphate, and silicone oil; ultraviolet absorbers described in JP-A-57-74193, JP-A-57-87988, and JP-A-62-261476; anti-fading agents described in JP-A-57-74192, JP-A-57-87989, JP-A-60-72785, JP-A-61-146591, JP-A-1-95091, and JP-A-3-13376; and fluorescent brightening agents described in JP-A-59-42993, JP-A-59-52689, JP-A-62-280069, JP-A-61-242871, and JP-A-4-219266.

[0198] (2.5) Viscosity The ink used in the present invention having the above constitution preferably has a viscosity of 1 to 40 mPa·s at 25° C., more preferably 2 to 10 mPa·s.

[0199] 3. Treatment Liquid The treatment liquid according to the present invention contains at least an aggregating agent, and by aggregating or thickening the ink when an image is recorded on a substrate by inkjet printing, can have the function of accelerating ink image formation, improving the physical properties of the treatment liquid layer and the ink layer, and improving image quality.

[0200] From the viewpoint of controlling aggregation and color gamut expression, it is preferable that the treatment liquid according to the present invention be capable of being ejected by inkjet.

[0201] The treatment liquid according to the present invention may contain other components such as a flocculant, a water-soluble solvent, a surfactant, and water, as appropriate, within the range that does not impair the effects of the present invention.

[0202] (Aggregating Agent) The treatment liquid according to the present invention contains a material that generates aggregates when it comes into contact with ink, i.e., an aggregating agent, which is a polyvalent metal salt. The aggregating agent enhances interaction with the ink, thereby enabling the ink dots to be more firmly fixed.

[0203] [Polyvalent Metal Salt] The treatment liquid according to the present invention contains a material that causes agglomerates when it comes into contact with ink, i.e., an aggregating agent that is a polyvalent metal salt, which enhances the interaction with the ink and enables the ink dots to be more firmly fixed.

[0204] The polyvalent metal salt can aggregate anionic components (usually coloring materials or pigments, etc., which will be described later) in the ink by salting out.

[0205] The polyvalent metal salt may be a salt of a metal having a valence of two or more. The type of metal (cation) constituting the polyvalent metal salt is not particularly limited. For example, Ca ２＋ , Cu ２＋ , Ni ２＋ , Mg ２＋ , Zn ２＋ , Ba ２＋ divalent metal ions such as Al ３＋ , Fe ３＋ , Cr ３＋ , Y ３＋ trivalent metal ions such as Zr ４＋ and the like.

[0206] The type of salt constituting the polyvalent metal salt is not particularly limited, but known salts such as carbonates, sulfates, nitrates, hydrochlorides, organic carboxylates, organic sulfonates, borates, phosphates, hydrobroms, hydroiodides, and thiocyanates can be used.

[0207] Examples of the organic carboxylate include acetic acid, oxalic acid, lactic acid, fumaric acid, citric acid, salicylic acid, and benzoic acid.

[0208] Particularly preferred examples of polyvalent metal salts include calcium chloride, magnesium chloride, calcium nitrate, magnesium nitrate, magnesium acetate, calcium acetate, magnesium lactate, calcium pantothenate, and other calcium or magnesium salts of carboxylic acids.

[0209] The content of the polyvalent metal salt is preferably in the range of 0.5 to 20% by mass, and more preferably in the range of 1 to 10% by mass, relative to 100% by mass of the total mass of the treatment liquid, which is preferable from the viewpoint of effectively aggregating the anionic components in the ink and achieving a balance between image quality and hot water resistance.

[0210] [Organic Acid] In addition to the polyvalent metal salt, the treatment liquid according to the present invention may further contain an organic acid as an aggregating agent, which can aggregate anionic components in the ink by changing the pH.

[0211] Furthermore, the use of an organic acid makes it easier to maintain the storage stability of the treatment liquid, and makes it less likely that blocking will occur after the treatment liquid has been applied and dried. From the above perspectives, preferred organic acids to be contained in the flocculant include formic acid, acetic acid, propionic acid, isobutyric acid, oxalic acid, fumaric acid, malic acid, citric acid, malonic acid, succinic acid, maleic acid, benzoic acid, 2-pyrrolidone-5-carboxylic acid, lactic acid, acrylic acid and derivatives thereof, methacrylic acid and derivatives thereof, acrylamide and derivatives thereof, and other compounds having a carboxy group, sulfonic acid derivatives, and phosphoric acid and derivatives thereof.

[0212] It is preferable to use an organic acid that is not completely neutralized with a base. Neutralization with a base means that the acidic group of the acid is ionic bonded to another positively charged element or compound (e.g., an inorganic compound such as a metal). Furthermore, not completely neutralized means that among the acidic groups possessed by the organic acid, there are acidic groups that do not form the ionic bond.

[0213] Furthermore, the use of an organic acid makes it easier to maintain the storage stability of the treatment solution, and makes it less likely that blocking will occur after the treatment solution is applied and dried. From the above perspective, preferred organic acids include formic acid, acetic acid, propionic acid, and benzoic acid.

[0214] When an organic acid is contained, the content of the organic acid is preferably in the range of 0.1 to 10% by mass, and more preferably in the range of 1 to 3% by mass, relative to 100% by mass of the total mass of the treatment liquid.

[0215] [Inorganic Acid] In addition to the polyvalent metal salt, the treatment liquid according to the present invention may further contain an inorganic acid as a flocculating agent. The inorganic acid can flocculate the anionic components in the ink by changing the pH.

[0216] The inorganic acid is capable of aggregating pigments that may be contained in the ink, which will be described later. Examples of the inorganic acid include hydrochloric acid, nitric acid, sulfuric acid, and sulfamic acid.

[0217] Alternatively, a soluble cationic polymer may be used as the flocculant. Examples of the soluble cationic polymer include polyallylamine, polyvinylamine, polyethyleneimine, and polydiallyldimethylammonium chloride.

[0218] Examples of commercially available dissolving cationic polymers include KHE100L and FPA100L manufactured by Senka Corporation, and PAS-92A, PAS-M-1A, and PAS-21CL manufactured by Nittobo Medical Co., Ltd.

[0219] When an inorganic acid is added, the content of the inorganic acid is preferably in the range of 0.1 to 10% by mass, and more preferably in the range of 1 to 3% by mass, relative to 100% by mass of the total mass of the treatment liquid.

[0220] The content of the polyvalent metal salt or organic acid in the aqueous solution can be measured by a known method. For example, if the polyvalent metal salt is an inorganic acid, the content can be measured by ICP emission analysis, and if the polyvalent metal salt is an organic acid, the content can be measured by high performance liquid chromatography (HPLC).

[0221] When an organic acid is used, the amount of the organic acid applied is preferably an amount that adjusts the pH of the treatment liquid to a neutralization equivalent or less of the anionic components contained in the ink.

[0222] (Water-Soluble Solvent) The water-soluble solvent contained in the treatment liquid according to the present invention is preferably a water-soluble solvent having a boiling point in the range of 150 to 250°C.

[0223] Examples of water-soluble solvents having a boiling point in the range of 150 to 250° C. include alcohols, polyhydric alcohols, amines, amides, glycol ethers, and 1,2-alkanediols having 4 or more carbon atoms.

[0224] In addition, the SP value is 24 (J / cm ３ ) １／２ It is preferable to use a water-soluble solvent having an SP value of 24 (J / cm ３ ) １／２ The use of such a water-soluble solvent lowers the cloud point of the treatment liquid, which allows the treatment liquid to be heated to a temperature equal to or higher than its cloud point during the ink drying process, thereby producing an image with particularly good adhesion to non-absorbent substrates.

[0225] In the present invention, the SP value is referred to as the solubility parameter. The SP value in the present invention is a value calculated by the Fedors method. It is determined from the molar heat of vaporization of the water-soluble solvent and the molar volume of the water-soluble solvent at 25°C. Although the unit of the SP value is generally cal, when converting to the SI unit system, (cal / cm ３ ) １／２ = 2.046 x 10 ３ (J / m ３ ) １／２ In the following description, the unit of the SP value may be omitted, but the SP value is expressed as (J / cm ３ ) １／２ It is a value expressed in units of .

[0226] The SP value is 24 (J / cm ３ ) １／２ Examples of the water-soluble solvent having the above properties and a boiling point of 150° C. to 250° C. include polyhydric alcohols having 2 to 8 carbon atoms and polyalkylene glycols.

[0227] Examples of polyhydric alcohols having 2 to 8 carbon atoms include 1,2-ethanediol (SP value: 30.3, boiling point: 197°C), 1,2-propanediol (SP value: 28.0, boiling point: 188°C), 1,3-propanediol (SP value: 32.9, boiling point: 213°C), 1,2-butanediol (SP value: 26.1, boiling point: 192°C), 1,3-butanediol (SP value: 30.3, boiling point: 207°C), 1,4-butanediol (SP value: 30.7, boiling point: 230°C), and 2,3-butanediol (SP value: 2 9.9, boiling point: 177°C), 2-methyl-1,3-propanediol (SP value: 30.3, boiling point: 214°C), 1,2-pentanediol (SP value: 25.0, boiling point: 210°C), 1,5-pentanediol (SP value: 29.0, boiling point: 242°C), 1,2-hexanediol (SP value: 24.1, boiling point: 223°C), 1,6-hexanediol (SP value: 27.7, boiling point: 249°C), 2-methylpentane-2,4-diol (SP value: 26.8, boiling point: 197°C), and the like.

[0228] Examples of polyalkylene glycols include diethylene glycol (SP value: 30.6, boiling point: 2144°C) and dipropylene glycol (SP value: 27.2, boiling point: 230°C).

[0229] The treatment liquid may contain one or a combination of two or more selected from these water-soluble solvents.

[0230] It is sufficient that the ink contains at least one water-soluble solvent having a boiling point within the range of 150 to 250°C, and the ink may also contain alcohols other than those mentioned above, polyhydric alcohols, amines, amides, glycol ethers, and 1,2-alkanediols having 4 or more carbon atoms.

[0231] Examples of solvents other than water-soluble solvents having a boiling point in the range of 150 to 250°C include glycerin (SP value: 33.5, boiling point: 290°C), trimethylolpropane (SP value: 32.5, boiling point: 295°C), triethylene glycol (SP value: 27.8, boiling point: 287°C), and tetraethylene glycol (SP value: 26.1, boiling point: 275°C).

[0232] The total content of the water-soluble solvent is preferably in the range of 5 to 40% by mass, and more preferably in the range of 10 to 40% by mass, relative to 100% by mass of the total mass of the treatment liquid.

[0233] (Surfactant) The surfactant contained in the treatment liquid according to the present invention can improve the ejection stability of the treatment liquid from the nozzle and can control the spread of droplets that have landed on a recording medium (increase in dot diameter). There are no limitations on the surfactant that can be used in the treatment liquid according to the present invention, and those exemplified for the ink above can be used.

[0234] The content of the surfactant in the treatment liquid is not particularly limited, but is preferably in the range of 0.1 to 5.0 mass % of the total mass of the treatment liquid, and more preferably in the range of 0.1 to 2.0 mass %.

[0235] (Water) The treatment liquid according to the present invention may contain water, and there are no particular limitations on the type of water that can be used. For example, ion-exchanged water, distilled water, or pure water can be used.

[0236] (Other Components) The treatment liquid may contain other components such as a crosslinking agent, an antifungal agent, a bactericide, etc., as appropriate, within the scope of not impairing the effects of the present invention.

[0237] Further, for example, ultraviolet absorbers described in JP-A Nos. 57-74193, 57-87988 and 62-261476, anti-fading agents described in JP-A Nos. 57-74192, 57-87989, 60-72785, 61-146591, JP-A Nos. 1-95091 and 3-13376, anions, It is also possible to contain various known additives such as various cationic or nonionic surfactants, fluorescent brightening agents described in JP-A Nos. 59-42993, 59-52689, 62-280069, 61-242871, and JP-A No. 4-219266, antifoaming agents, lubricants such as diethylene glycol, preservatives, thickeners, antistatic agents, etc.

[0238] [Inkjet Recording Method] 4. Overview The inkjet recording method of the present invention is an inkjet recording method that can suitably use the ink set of the present invention, and is characterized in that the ink set includes an achromatic ink, and the aqueous pigment inks of two or more colors are not superimposed on a recording medium.

[0239] This makes it possible to reduce the amount of ink applied when forming an image on a recording medium, thereby reducing the drying load. From the viewpoint of controlling cohesion, it is also preferable to record an image by mixing and preparing the ink set of the present invention within the flow path of a recording device.

[0240] First, not overlapping two or more colors of ink leads to a reduction in the amount of ink applied during image formation. Also, when forming an image on a recording medium, for example, if you want to express green as the color of the image, you usually overlap yellow ink and cyan ink on the recording medium to express green.

[0241] However, when green is expressed in this way, the amount of ink used to form an image using yellow and cyan inks is twice as much as the amount of ink used to form an image using only green ink, which increases the drying load.

[0242] In contrast to this, in the ink set of the present invention, the aggregation properties of the pigment dispersions contained in the two color inks, such as the yellow ink and cyan ink, are adjusted to the same degree in advance.

[0243] This allows green to be expressed on the recording medium in the desired color gamut without color bleeding, eliminating the need to overlap two or more colors of ink on the recording medium to express green, thereby reducing the amount of ink applied and the drying load.

[0244] Generally, inks are classified into chromatic inks, achromatic inks, and clear inks. To clarify the definition of the achromatic inks described above in this specification, the types of inks will be defined below.

[0245] "Chromatic ink" basically refers to inks that have three attributes: hue, lightness, and saturation, such as yellow ink, magenta ink, and cyan ink.

[0246] "Achromatic ink" basically refers to toner that has no hue or saturation, but only brightness, such as black ink, white ink, and gray ink.

[0247] "Clear ink" refers to ink in which the layer formed by the clear ink transmits light in almost all or part of the visible light range.The clear ink layer allows you to see through to the other side, creating a transparent state.

[0248] (Substrate) The substrate (recording medium) used in the inkjet recording method of the present invention is not particularly limited, and examples thereof include plain paper ranging from thin paper to thick paper, high-quality paper, coated printing paper such as art paper or coated paper, water-soluble paper, commercially available Japanese paper or postcard paper, plastic film, cloth, leather, etc., but a non-absorbent substrate made of a non-absorbent material is preferred.

[0249] In the present invention, the term "non-absorbent recording substrate (medium)" refers to a recording medium having a water absorption rate of 10 mL / m2 or less within 30 msec from the start of contact in the Bristow method. ２ This refers to a recording substrate (medium) that is:

[0250] Details of the test method are described, for example, in Standard No. 51 "Paper and Paperboard - Liquid Absorbency Test Method - Bristow Method" of "JAPAN TAPPI Paper and Pulp Test Methods 2000 Edition."

[0251] The non-absorbable substrate may be a known plastic film, such as a polyester film such as polyethylene terephthalate, a polyamide film such as polyethylene film, polypropylene film, or nylon, or a biodegradable film such as a polystyrene film, polyvinyl chloride film, polycarbonate film, polyacrylonitrile film, or polylactic acid film.

[0252] In addition, films coated on one or both sides with polyvinylidene chloride are preferred to impart gas barrier properties, moisture resistance, aroma retention, etc. Films with vapor-deposited metal oxides are also preferred. The non-absorbent film may be either an unstretched film or a stretched film.

[0253] In the case of a plastic film, the thickness of the substrate is preferably in the range of 10 to 120 μm, more preferably 12 to 60 μm.

[0254] In addition, metal substrates such as tinplate for three-piece cans and tin-free steel plates (TFS plates, thickness 0.1 to 0.6 μm) are also preferably used as non-absorbent substrates. For example, they can be suitably used as packaging materials for canned foods, which are provided with a thermosetting resin coating layer.

[0255] The following materials are commonly used as packaging materials for canned foods to block air, moisture, and light and seal the food inside: epoxy-phenolic paint or polyester laminating agent is used on the food side, and polyester or acrylic thermosetting paint is used on the outside.

[0256] 5. Recording Process The inkjet recording method of the present invention uses an ink set containing a treatment liquid and an aqueous pigment ink, and forms an image by applying each of the treatment liquid and the aqueous pigment ink to the surface of a recording medium by droplet ejection means and allowing them to coalesce. Thus, the inkjet recording method of the present invention is a so-called two-liquid recording method.

[0257] According to this recording method, for example, a single inkjet printer can be used to continuously and efficiently apply the treatment liquid to the surface of a substrate (recording medium) and print with the aqueous pigment ink. Furthermore, the treatment liquid and the ink can be unified on the substrate, reducing the variation in dot diameter between substrates. As a result, it becomes possible to print characters, patterns, and the like with excellent image quality.

[0258] Specifically, the treatment liquid is first applied to a substrate, and then the ink is applied to the area where the treatment liquid has been applied while the treatment liquid is still wet, without going through a heat drying step. That is, the inkjet recording method comprises a treatment liquid application step of applying the treatment liquid to the recording area of ​​the substrate, and an ink application step of applying the ink, while the treatment liquid is still wet, to the area where the treatment liquid has been applied by an inkjet recording method.

[0259] In addition to the above steps, the inkjet recording method of the present invention preferably includes an ink heating and drying step of heating and drying the treatment liquid and ink applied to the substrate after the ink application step to form an image (image layer).

[0260] In the ink application step, it is preferable to apply ink to the area to which the treatment liquid has been applied when the drying rate of the treatment liquid is 30% or less. It is also preferable to carry out the ink application step within 10 seconds after the treatment liquid application step. It is particularly preferable to carry out the ink application step within 0.1 to 5 seconds after the treatment liquid application step when the drying rate of the treatment liquid is in the range of 1 to 10%.

[0261] Each step of the inkjet recording method will be described below. (5.1) Treatment liquid application step In the treatment liquid application step, the treatment liquid described above is applied onto a recording medium, which is a substrate. The method for applying the treatment liquid onto the recording medium is preferably an inkjet method.

[0262] When the substrate used is a metal substrate or the like, it is preferable to place the metal substrate on a conveyor belt and apply the treatment liquid layer while conveying the belt. It is also preferable to use a flatbed type printer that fixes the substrate to form the treatment liquid layer. In the treatment liquid application step, the amount of treatment liquid applied (also referred to as the "application amount") per unit area on which an image is formed is 5.0 g / m or less. ２ It is particularly preferable that the density is 0.3 to 5.0 g / m or less. ２ This allows high character reproducibility to be achieved in a two-liquid ink jet recording method.

[0263] (5.2) Ink Application Step The ink application step is a step in which the inks of the ink set described above are applied by an inkjet method simultaneously with or immediately after the application of the treatment liquid onto the recording medium, which is the substrate. In particular, it is preferable to apply the ink to the region to which the treatment liquid has been applied after the treatment liquid application step, when the drying rate of the treatment liquid is 30% or less. Furthermore, it is preferable to apply the ink to the region to which the treatment liquid has been applied within 10 seconds after the treatment liquid has been applied to the substrate.

[0264] The drying rate of the treatment liquid is defined by the following formula: (Drying rate of treatment liquid)=1-((mass (g) of treatment liquid after drying) / (mass (g) of treatment liquid before drying)

[0265] By applying ink when the drying rate of the treatment liquid is 30% or less, the ink and treatment liquid are united and mixed. Furthermore, by applying ink within 10 seconds after applying the treatment liquid to the substrate, it is possible to suppress the penetration of the treatment liquid into absorbent substrates and the repelling of the treatment liquid on non-absorbent substrates, thereby achieving higher image quality.

[0266] As described above, examples of a method for keeping the drying rate of the treatment liquid at 30% or less include adjusting the time between the application of the treatment liquid and the application of the ink, and appropriately adjusting the temperature of the recording medium.

[0267] Furthermore, in the ink application step, it is preferable to adjust the amount of ink droplets so that the amount of ink applied (also referred to as the "application amount") per unit area is within a range of 2 to 25 times the amount of treatment liquid applied, in order to achieve higher image quality, and a more preferable range for the application amount is within a range of 2.5 to 3.5 times.

[0268] The inkjet method is not particularly limited, and a printer equipped with an inkjet head loaded with ink can be used. Specifically, ink is ejected as droplets from the nozzles of the inkjet head based on a digital signal, and these droplets land on the treatment liquid layer of the substrate to perform printing.

[0269] The inkjet head may be either an on-demand type or a continuous type. On-demand type inkjet heads include electro-mechanical conversion type inkjet heads, including single-cavity type, double-cavity type, bender type, piston type, shear mode type, and shared wall type inkjet heads. Other examples include electro-thermal conversion type inkjet heads, including thermal inkjet type and bubble jet type inkjet heads ("Bubble Jet" is a registered trademark of Canon Inc.).

[0270] Of the above ink jet heads, ink jet heads using a piezoelectric element as the electromechanical conversion element used in the electromechanical conversion system (also called piezo type ink jet heads) are preferred.

[0271] The inkjet printer may be of either a scan type or a single pass type, and in the case of a single pass type, it is preferable to use a line head type inkjet head.

[0272] A line head type inkjet head is an inkjet head whose length is equal to or greater than the width of the printing range. As a line head type inkjet head, a single head whose length is equal to or greater than the width of the printing range may be used. Alternatively, a plurality of heads may be combined to form a head whose length is equal to or greater than the width of the printing range. Furthermore, a plurality of heads may be arranged side by side with their nozzles arranged in a staggered pattern to increase the overall resolution of the heads.

[0273] The conveying speed of the recording medium, which is the substrate, can be set within a range of, for example, 1 to 120 m / min. The faster the conveying speed, the faster the image formation speed. Note that even at a very high linear speed of 50 to 120 m / min, which is applicable to single-pass inkjet image formation methods, high-resolution images with high ink fixation can be obtained.

[0274] (5.3) Ink Heat Drying Process In the ink heat drying process, the ink applied to the recording medium, which is the substrate, i.e., the area where the ink is applied, is heated, thereby drying the ink and the treatment liquid.

[0275] In the ink heating and drying step, the heating temperature of the area where the ink has been applied is preferably within the range of 60 to 200° C. The heating time of the ink is adjusted appropriately according to the type of recording medium and the amount of ink applied.

[0276] By heating the ink-applied area in this manner, the solvent components of the treatment liquid and ink, such as water and water-soluble solvents, are removed. Simultaneously with this removal, particularly in the case of metal substrates, the polyvalent metal salt is dried at a temperature equal to or higher than its thermal decomposition temperature, thereby thermally decomposing it. This also improves the abrasion resistance of the image and adhesion to the substrate.

[0277] Heat drying may be performed using a non-contact heating drying device such as a drying oven or a hot air blower. Alternatively, heat drying may be performed using a contact heating drying device such as a hot plate or a heated roller. The drying temperature can be obtained by measuring any one of the following over the entire drying period of the treatment liquid: (a) when a non-contact heating drying device such as a drying oven or a hot air blower is used, the ambient temperature such as the furnace temperature or the hot air temperature; (b) when a contact heating drying device such as a hot plate or a heated roller is used, the temperature of the contact heating section; or (c) the surface temperature of the surface to be dried. It is more preferable to measure the surface temperature of the surface to be dried (c) as the measurement location.

[0278] The thickness of the image layer obtained as described above is preferably in the range of 0.3 to 3.0 μm, and more preferably in the range of 0.3 to 2.0 μm. When the thickness of the image layer is 0.3 μm or more, the adhesion and abrasion resistance of the image are easily improved. When the thickness of the image layer is 3.0 μm or less, the deformation stress applied to the image layer can be reduced, so the adhesion of the image layer is less likely to be impaired.

[0279] [Inkjet Recording Apparatus] As a recording apparatus that can be used in the present invention, a method of printing ink containing two or more pigment dispersions and a treatment liquid using a normal inkjet printing apparatus can be used. Ｘ It is also possible to use a means for recording by mixing pigment dispersions in which the absolute value of the difference between the values ​​of the dispersions is 0.4 or less in any ratio in the flow path. This allows pigment dispersions with similar levels of aggregation to be mixed efficiently, making it possible to form images with a wide color gamut and no color bleeding.

[0280] The means for mixing pigment dispersions in a desired ratio within a flow path for recording can be, for example, a recording device equipped with a mixer. Figure 4 shows an example of a mixer for mixing the components that make up an ink set. Below, each component of the mixer for mixing the components that make up the ink set of the present invention will be listed using Figure 4.

[0281] 4, there are no particular limitations on the components A and B, and for example, either or both of the components A and B may be pigment dispersions. Furthermore, both the components A and B may contain multiple types of pigment dispersions, or only one of the components may contain multiple types of pigment dispersions.

[0282] The mixing device 10 is composed of a storage tank 11 for storing the component A, a liquid supply flow path 12 for the component A, a liquid supply pump 13 for the component A, a storage tank 14 for the component B, a liquid supply pump 15 for the component B, a mixing unit 16, a liquid supply flow path 17, and a recording head 18. The components A and B are mixed in the mixing unit 16.

[0283] Fig. 5 shows an example of the configuration of a recording apparatus equipped with the mixing apparatus of Fig. 4. The recording apparatus 100 is composed of a storage tank 101 for storing component A, a liquid supply flow path 102 for component A, a liquid supply pump 103 for component A, a storage tank 104 for component B, a liquid supply pump 105 for component B, a static mixer 107 as a mixing unit, an electromagnetic valve 108, a sub-tank 109, a float sensor 110, a negative pressure generating pump 111, a liquid supply flow path 112, and a recording head 113.

[0284] (Adjustment of Mixing Ratio of Component A and Component B) The mixing ratio of component A and component B is appropriately adjusted by adjusting the liquid feed rates of the liquid feed pumps 103 and 105 .

[0285] A float sensor 110 is built into the subtank 109, and when the ink in the subtank falls below a certain amount, the sensor is activated and the liquid feed pumps 103 and 105 are activated to feed a certain ratio of liquid. The fed components A and B are mixed as they pass through a static mixer 107 to become a uniform ink.

[0286] (Print Head) During printing, the ink in the subtank 109 is sent to the print head 113 by the pumping capacity of the print head 113 itself. The subtank 109 has a built-in negative pressure control pump 111, which manages the ink in the print head 113 at a constant negative pressure so that it can be ejected stably.

[0287] As the print head 113, for example, a head manufactured by Konica Minolta with a resolution of 360 npi is used.

[0288] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these. In the examples, the terms "parts" and "%" are used, but unless otherwise specified, they represent "parts by mass" or "% by mass."

[0289] [1] Preparation of pigment dispersion: Example 1 [1-1] Preparation of pigment dispersion Y1 A mixed liquid was premixed by adding the following materials [1] in the following amounts: <Materials [1]> Yellow pigment "3GP-CT" 15.0% by mass Pigment dispersant: "Joncryl 819" 4.5% by mass Propylene glycol 20.0% by mass Antifungal agent "Proxel GXL(S)" 0.1% by mass Ion-exchanged water (Remainder: amount to make the total amount 100% by mass)

[0290] The yellow pigment "3GP-CT" in the material [1] is "Toner Yellow 3GP-CT" manufactured by Clariant. The pigment dispersant "Joncryl 819" is a pigment dispersant obtained by neutralizing "Joncryl 819" manufactured by BASF with dimethylaminoethanol to a neutralization rate of 80%.

[0291] Thereafter, the mixture was dispersed using a bead mill filled with 0.3 mm zirconia beads at a volume ratio of 50%, to prepare pigment dispersion Y1 having a pigment content of 15 mass %.

[0292] (Maximum absorption maximum wavelength and average particle diameter of pigment particles of pigment dispersion Y1) Pigment dispersion Y1 was diluted 15,000 times with pure water, and the absorption spectrum was measured using a spectrophotometer (V-1550 manufactured by JASCO Corporation). The maximum absorption maximum wavelength was calculated to be 411 nm. In addition, the average particle diameter D of the pigment particles contained in this pigment dispersion was measured using a multi-analyte nanoparticle diameter measurement system "nanoSAQLA" manufactured by Otsuka Electronics Co., Ltd. ５０ was measured and found to be 155 nm.

[0293] [1-2] Preparation of Pigment Dispersions Y2 to Y4, C1 to C3, M1 to M3, R1, and K1 Pigment dispersions Y2 to Y4, C1 to C3, M1 to M3, R1, and K1 were prepared in the same manner as in the preparation of Pigment Dispersion Y1, except that the pigments and pigment dispersants were changed as shown in Tables I and II.

[0294] (Maximum absorption maximum wavelength and average particle diameter of pigment particles of other pigment dispersions) The maximum absorption maximum wavelength of pigment dispersions Y2 to Y4, C1 to C3, M1 to M3, R1 and K1 were calculated and the average particle diameter of pigment particles was measured in the same manner as for pigment dispersion Y1.

[0295] The combination of product names and company names of the pigments and pigment dispersants used in the preparation of each pigment dispersion is shown in Table I. The neutralization base, neutralization rate, and concentration of the pigment dispersants used in the preparation of each pigment dispersion, as well as the maximum absorption wavelength and average particle size of the pigment particles, are shown in Table II.

[0296]

[0297]

[0298] [2] Preparation of aqueous pigment ink: Example 2 [2-1] Preparation of ink 1 The following material [2] was added in the amounts shown below with stirring, and the resulting mixture was filtered through a 1 μm filter to prepare ink 1. Note that no substantial change in composition was observed in ink 1 before and after filtration. <Material [2]> Pigment dispersion Y1 16.7% by mass (2.5% by mass as solid content) Pigment dispersion C1 16.7% by mass (2.5% by mass as solid content) Resin particle dispersion (5.0% by mass as solid content) Water-soluble solvent (PG: propylene glycol) 25% by mass Water-soluble solvent (DPG: dipropylene glycol) 5% by mass Surfactant "Olfine E1010" (Nissin Chemical Industry Co., Ltd.) 1% by mass Surfactant "KF351A" (Shin-Etsu Silicones Co., Ltd.) 0.2% by mass Antifungal agent "Proxel GXL(S)" (Lonza) 0.1% by mass Ion-exchanged water (Remainder: amount that makes the total amount 100% by mass)

[0299] The resin particle dispersion in the material [2] is "Vylonal MD-2000" manufactured by Toyobo Co., Ltd. The amount of the resin particle dispersion added was specifically adjusted so that the resin particles (solid content) in the ink was 5% by mass.

[0300] [2-2] Preparation of Inks 2 to 19 Inks 2 to 19 were prepared in the same manner as in the preparation of Ink 1, except that the blending amounts of the pigment dispersion, resin fine particle dispersion, water-soluble solvent, surfactant, antifungal agent, and water were changed as shown in Tables III and IV below.

[0301] In Tables III and IV, the pigment dispersions are classified into three types, A, B, and C, but this is provided merely for the sake of convenience in order to simplify and describe the parameters in each pigment dispersion classification.

[0302] The numerical values ​​of the amounts of each parameter in Tables III and IV represent mass %. The abbreviations for the resin particle dispersion, water-soluble solvent, and surfactant are as follows. <Resin particle dispersion> MD-2000: Polyester resin "Vylonal MD-2000" (manufactured by Toyobo Co., Ltd.) AE-301: Special modified polyolefin resin "Auroren AE-301" (manufactured by Nippon Paper Industries Co., Ltd.) <Water-soluble solvent> PG: Propylene glycol EG: Ethylene glycol DPG: Dipropylene glycol <Surfactant> E1010: Acetylene glycol-based surfactant "Olfine E1010" (manufactured by Nissin Chemical Industry Co., Ltd.) KF-351A: Silicone-modified surfactant "KF-351A" (manufactured by Shin-Etsu Silicones Co., Ltd.) TEGOWET: Silicone-based surfactant "TEGOWET-250" (manufactured by Evonik)

[0303]

[0304]

[0305] [2-3] Maximum absorption maximum wavelength and average particle size of the pigment dispersion contained in each ink The maximum absorption maximum wavelength and average particle size of the pigment dispersion contained in each prepared ink were the same as those in Table II in Example 1, and the absolute value of the difference between these values ​​was calculated. The calculated values ​​are shown in Tables V and VI.

[0306] |λ in Tables V and VI Ａ－Ｂ | means the absolute value of the difference between the maximum absorption maximum wavelength of a pigment dispersion classified into pigment dispersion class A and the maximum absorption maximum wavelength of a pigment dispersion classified into pigment dispersion class B.

[0307] |λ Ｂ－Ｃ | means the absolute value of the difference between the maximum absorption maximum wavelength of a pigment dispersion classified into pigment dispersion class B and the maximum absorption maximum wavelength of a pigment dispersion classified into pigment dispersion class C.

[0308] |λ Ｃ－Ａ | means the absolute value of the value obtained by subtracting the maximum absorption maximum wavelength of a pigment dispersion classified into pigment dispersion class A from the maximum absorption maximum wavelength of a pigment dispersion classified into pigment dispersion class C.

[0309] |D in Tables V and VI ５０Ａ－５０Ｂ | is the average particle diameter D of the pigment dispersion classified into pigment dispersion class A ５０Ａ Average particle diameter D of pigment dispersions classified into pigment dispersion category B ５０Ｂ means the absolute value of the value minus .

[0310] |D ５０Ｂ－５０Ｃ | is the average particle diameter D of the pigment dispersion classified into the pigment dispersion class B ５０Ｂ Average particle diameter D of pigment dispersions classified into pigment dispersion classification C ５０Ｃ means the absolute value of the value minus .

[0311] |D ５０Ｃ－５０Ａ | is the average particle diameter D of the pigment dispersion classified into the pigment dispersion classification C ５０Ｃ The average particle diameter D of the pigment dispersion classified into the pigment dispersion classification A is ５０Ａ means the absolute value of the value minus .

[0312]

[0313]

[0314] [3] Preparation of treatment liquid: Example 3 [3-1] Preparation of treatment liquid 1 The following materials [3] were added in the amounts shown below with stirring, and the resulting mixture was filtered through a 1 μm filter to prepare treatment liquid 1. <Materials [3]> Flocculant (calcium acetate hydrate) 3 mass% Water-soluble solvent (PG: propylene glycol) 14 mass% Water-soluble solvent (PG: propylene glycol) 14 mass% Water-soluble solvent (1,3-BDO: 1,3-butanediol) 10 mass% Surfactant (polyether-modified silicone) 1 mass% Antifungal agent "Proxel GXL(S)" (manufactured by Lonza) 0.1 mass% Ion-exchanged water (Remainder: amount that makes the total amount 100 mass%)

[0315] The surfactant (polyether-modified silicone) in the above material [3] is "BYK3450" manufactured by BYK-Chemie.

[0316] [3-2] Preparation of Treatment Liquids 2 and 3 Treatment liquids 2 and 3 were prepared in the same manner as in the preparation of Treatment Liquid 1, except that the amounts of the flocculant, water-soluble solvent, surfactant, antifungal agent, and water were changed as shown in Table VII below.

[0317]

[0318] The numerical values ​​of the amounts of each parameter in Table VII represent mass %. The abbreviations for the flocculant, water-soluble solvent, and surfactant are as follows: <Flocculant> Unisense KHE100L: Aqueous solution of dimethylamine-ammonia-epichlorohydrin condensate (manufactured by Senka Corporation) <Water-soluble solvent> DPG: Diethylene glycol PG: Propylene glycol 1,3-BDO: 1,3-butanediol <Surfactant> TEGOWET: Silicone surfactant "TEGOWET-250" (manufactured by Evonik) BYK-3450: Polyether-modified silicone "BYK-3450" (manufactured by BYK-Chemie)

[0319] [4] Printing Test 1: Example 4 (Method of Producing Image Recorded Material) Ink sets 1 to 45 were prepared by combining the prepared inks 1 to 15 and treatment liquids 1 to 3, respectively. The combinations are shown in Tables VIII and IX. Using the ink sets with the combinations shown in Tables VIII and IX, printing test 1 was carried out in the following manner, and image recorded materials were produced.

[0320] A single-pass printer (see FIG. 6) equipped with two independently driven inkjet heads (360 npi, ejection volume of 6 pL, 14 pL, or 28 pL, 1024 nozzles) manufactured by Konica Minolta was prepared.

[0321] Next, the head H ＰＬ Each processing liquid is filled in the head H ｉｎｋ Each ink was filled in the ink tank.

[0322] Subsequently, printing was performed on the recording medium using each ink set at a resolution of 360 × 720 dpi in single-pass mode, with the processing liquid always recorded first. As the recording media, two types were prepared: a polypropylene substrate (#20FOR, manufactured by Futamura Chemical Co., Ltd., thickness 20 μm) and coated paper (OK Top Coat, manufactured by Oji Paper Co., Ltd.).

[0323] The carriage conveyance speed was set to 300 mm / sec, and a configuration was adopted where no drying process was provided between the time of discharging and recording the processing liquid onto the recording medium and the time of discharging and recording the ink.

[0324] For the recording of the processing liquid, the liquid volume was set to 6 pL and the printing rate to 30%, and for the recording of the ink, the liquid volume was set to 28 pL and the printing rate to 100%.

[0325] The printed recording medium was put into a dryer set at 90°C and heated and dried for 5 minutes to produce an image recording.

[0326] [4-1] Evaluation of the smudging of missing characters An image recording was produced by the method of printing test 1 described above. At this time, missing characters of Chinese characters "口, 四, 日, 回, 因, 困, 固, 国, 目, 図, 國" were printed in MS Mincho font of 5 points and 7 points, and the printed character images were observed visually by 6 experts in image inspection from a distance of 15 cm, and the character quality was evaluated according to the following evaluation criteria. "AA" and "A" were regarded as having no practical problems, and "B" was evaluated as having practical problems.

[0327] (Evaluation criteria) AA: All of the missing characters of 5 points are clearly recorded down to the details. A: Only some of the missing characters of 5 points can be read, but all of the missing characters of 7 points are readable. B: There are characters that cannot be read not only among the missing characters of 5 points but also among the missing characters of 7 points.

[0328] [4-2] Evaluation of bleeding of thin lines An image recording was produced by the method of printing test 1 described above. At this time, thin lines with a width of 3 pixels were recorded, and the bleeding of the thin lines was observed visually by 6 experts in image inspection from a distance of 15 cm, and evaluation was performed according to the following evaluation criteria. "AA" and "A" were regarded as having no practical problems, and "B" was evaluated as having practical problems.

[0329] (Evaluation Criteria) AA: Fine lines are printed thin and straight. A: Fine lines are bulged in places and printed slightly distorted. B: Lines are significantly blurred and thick and distorted. Or color bleeding is observed.

[0330] [4-3] Evaluation of Mottling in Solid Areas Image recordings were made using the method of Printing Test 1 described above. A 5 cm x 5 cm solid image was recorded, and mottling in the solid areas was visually observed from a distance of 15 cm by six image inspection experts and evaluated according to the following evaluation criteria. "AA" and "A" were considered acceptable for practical use, and "B" was considered problematic for practical use.

[0331] (Evaluation criteria) AA: No density unevenness is observed in the image when observed from a distance of 15 cm. A: Density unevenness is observed in part of the image when observed from a distance of 15 cm, but density unevenness is not observed from a distance of 30 cm. B: Density unevenness is observed in the image when observed from a distance of 30 cm.

[0332] [4-4] Aggregation Index The aggregation index G of all pigment dispersions X contained in the mixed liquid of the treatment liquid and the ink Ｘ is defined by the following formula (I): Formula (I): G Ｘ =X ａｆｔ / X ｂｅｆ (In the above formula (I), X ｂｅｆ represents the absorbance at the maximum absorption wavelength of pigment dispersion X in a 1:1 mixture of aqueous pigment ink and pure water. ａｆｔ represents the absorbance at the maximum absorption maximum wavelength derived from pigment dispersion X in the supernatant after centrifuging a 1:1 mixture of an aqueous pigment ink and a 5-fold diluted aqueous solution of the treatment liquid.)

[0333] (X ｂｅｆ Using the inks in ink sets 1 to 45, 0.5 g of ink and 0.5 g of pure water were mixed in a sample tube to prepare a mixed liquid for each of ink sets 1 to 45, in which the ink and pure water were mixed in a 1:1 ratio.

[0334] After each of the obtained mixed solutions was appropriately diluted, the absorption spectrum was measured using a spectrophotometer (V-1550 manufactured by JASCO Corporation) and the absorbance spectrum was calculated by multiplying by the dilution factor. From each of the measured absorbance spectra, the absorbance A at the maximum absorption maximum wavelength derived from Class A of the pigment dispersions in Ink Sets 1 to 45 was calculated. ｂｅｆ and absorbance B at the maximum absorption wavelength derived from pigment dispersion classification B ｂｅｆ It was read as follows.

[0335] At that time, A ｂｅｆ and B ｂｅｆ When reading the absorbance, the absorbance from one of the pigment dispersions was subtracted as a base, as explained above with reference to FIG.

[0336] For example, absorbance B at the maximum absorption wavelength of pigment dispersion class B ｂｅｆ When reading the absorbance of one pigment dispersion, the absorbance of the other pigment dispersion is subtracted as a base. This will be specifically described.

[0337] First, in FIG. 2, when ink 1 is an aqueous pigment ink, pigment dispersion Y1 of pigment dispersion class A contained in ink 1 is pigment dispersion A in FIG.

[0338] 2. The pigment dispersion C1 of the pigment dispersion class B contained in the ink 1 corresponds to the pigment dispersion B in FIG.

[0339] At this time, the absorbance B at the maximum absorption maximum wavelength of the pigment dispersion C1 derived from the pigment dispersion class B is calculated by subtracting the absorbance of the pigment dispersion C1 from the absorbance of the aqueous pigment ink. ｂｅｆ Read as.

[0340] Absorbance A at maximum absorption wavelength derived from pigment dispersion class A ｂｅｆ Similarly, when reading the absorbance of the pigment dispersion Y1, the value obtained by subtracting the absorbance of the pigment dispersion Y1 from the absorbance of the aqueous pigment ink is used as the absorbance A at the maximum absorption maximum wavelength of the pigment dispersion of Class A. ｂｅｆ Read as.

[0341] In ink sets 43 to 45, which contain ink 15 containing three pigment dispersions as a component, the absorbance of the set of pigment dispersions whose maximum absorption maximum wavelength is closest to that of ink 15 was read. That is, the absorbance B at the maximum absorption maximum wavelength derived from pigment dispersion class B was ｂｅｆ and absorbance C at the maximum absorption maximum wavelength derived from pigment dispersion classification C ｂｅｆ It was read as follows.

[0342] (X ａｆｔ 1 g of the prepared treatment liquid was diluted 5 times with pure water to prepare 5-fold diluted aqueous solutions of treatment liquids 1 to 3. Hereinafter, the "5-fold diluted aqueous solutions of the treatment liquid" may also be simply referred to as "5-fold diluted treatment liquid."

[0343] Thereafter, 0.5 g of each prepared ink and 0.5 g of the 5-fold diluted treatment liquid were mixed in a sample tube to prepare a 1:1 mixture of the ink and the 5-fold diluted treatment liquid. The combinations of each ink and the treatment liquid used to prepare the 5-fold diluted treatment liquid were the combinations of ink sets 1 to 45 listed in Tables VIII and IX.

[0344] Thereafter, the mixture was centrifuged for 5 minutes at a centrifugal acceleration of 500 G using a centrifuge (CF16RX, manufactured by Hitachi Koki Co., Ltd.). Next, 0.1 g of the supernatant was taken and appropriately diluted 50 to 300 times with pure water.

[0345] For each of the ink sets 1 to 45, the mixture of ink and 5-fold diluted treatment solution was centrifuged, and the supernatant diluted solution was subjected to absorption spectrum measurement using a spectrophotometer (V-1550 manufactured by JASCO Corporation). The absorbance spectrum was then calculated by multiplying by the dilution factor.

[0346] Thereafter, from the absorbance spectrum of the diluted supernatant, the absorbance A at the maximum absorption maximum wavelength of the pigment dispersion of Class A was obtained. ａｆｔ and absorbance B at the maximum absorption wavelength derived from pigment dispersion classification B ａｆｔ It was read as follows.

[0347] At that time, A ａｆｔ and B ａｆｔ When reading the absorbance, the absorbance from one of the pigment dispersions was subtracted as a base, as explained above with reference to FIG.

[0348] For example, the absorbance B at the maximum absorption maximum wavelength of the pigment dispersion of Class B in the supernatant after centrifuging a 1:1 mixture of ink and a 5-fold diluted treatment liquid ａｆｔ When reading the absorbance of one pigment dispersion, the absorbance of the other pigment dispersion is subtracted as a base. This will be specifically described.

[0349] In ink set 1, the combination of ink and treatment liquid is ink 1 and treatment liquid 1.

[0350] In Figure 3, it is assumed that the mixed solution of ink 1 and a 5-fold diluted aqueous solution of treatment liquid 1 contains a mixed solution of pigment dispersion Y1 of pigment dispersion class A and the treatment liquid, and a mixed solution of pigment dispersion C1 of pigment dispersion class B and the treatment liquid.

[0351] Hereinafter, the "mixed liquid of pigment dispersion Y1 of pigment dispersion class A and a treatment liquid" will also be simply referred to as "mixed liquid AY1." Also, the "mixed liquid of pigment dispersion C1 of pigment dispersion class B and a treatment liquid" will also be simply referred to as "mixed liquid BC1."

[0352] At this time, the absorbance of the mixed solution BC1 subtracted from the absorbance of the mixed solution of ink 1 and a 5-fold diluted aqueous solution of treatment liquid 1 is the absorbance B at the maximum absorption maximum wavelength derived from the pigment dispersion class B. ａｆｔ Read as.

[0353] Absorbance A at maximum absorption wavelength derived from pigment dispersion class A ａｆｔ Similarly, when reading the absorbance of the mixed solution AY1, subtract the absorbance of the mixed solution AY1 from the absorbance of the mixed solution of ink 1 and a 5-fold diluted aqueous solution of treatment liquid 1, and obtain the absorbance A at the maximum absorption maximum wavelength derived from the pigment dispersion class A. ａｆｔ Read as.

[0354] In ink sets 43 to 45, which contain ink 15 containing three pigment dispersions as a component, the absorbance of the set of pigment dispersions whose maximum absorption maximum wavelength is closest to that of ink 15 was read. That is, the absorbance B at the maximum absorption maximum wavelength derived from pigment dispersion class B was ａｆｔ and absorbance C at the maximum absorption maximum wavelength derived from pigment dispersion classification C ａｆｔ It was read as follows.

[0355] [4-5] Cohesion index G Ｘ Calculation of the calculated X ｂｅｆ and X ａｆｔ Using the above, the cohesion index G is calculated using the following formula: Ｘ was calculated. Ｘ =X ａｆｔ / X ｂｅｆ

[0356] Tables VIII and IX show the aggregation index G derived from Class A of pigment dispersions in ink sets 1 to 45. Ａ , aggregation index G from pigment dispersion classification B Ｂ , and the aggregation index G from the pigment dispersion classification C Ｃ The absolute values ​​of the differences in the cohesiveness indices are also shown.

[0357]

[0358]

[0359] [5] Two-color printing test: Example 5 (Method of producing image recording material) A two-color printing test was carried out in the following manner using the two-color ink set shown in Table X. The two-color ink set was composed of α ink, β ink, and treatment liquid.

[0360] Furthermore, Table X lists two types of ink, α ink and β ink, but this is provided simply for convenience to simplify the description of each parameter for each ink classification. The abbreviations in Table X are as follows:

[0361] G Ａα G: aggregation index of class A of pigment dispersion contained in α ink Ｂα : Aggregation index of class B of pigment dispersion contained in α ink |G Ａα -G Ｂα |: G Ａα and G Ｂα Absolute value of the difference between Ａβ G: aggregation index of class A of pigment dispersion contained in β ink Ｂβ : Aggregation index of the pigment dispersion of the class B contained in the β ink |G Ａβ -G Ｂβ|: G Ａβ and G Ｂβ Absolute value of the difference between

[0362] A single-pass printer (see FIG. 7 ) equipped with three independently driven inkjet heads manufactured by Konica Minolta (360 npi, ejection volume of 6 pL, 14 pL, or 28 pL, 1024 nozzles) was prepared, and the head to be printed first was filled with each treatment liquid, and the head to be printed second was filled with the α ink and the β ink separately.

[0363] Thereafter, printing was carried out on a recording medium using each ink set in single pass mode at a resolution of 360 x 720 dpi, always with the treatment liquid printed first. Two types of recording media were prepared: a polypropylene base (#20FOR, manufactured by Futamura Chemical Co., Ltd., thickness 20 μm) and coated paper (OK Topcoat, manufactured by Oji Paper Co., Ltd.).

[0364] The carriage transport speed was set to 300 mm / sec, and a drying process was not performed between the time when the treatment liquid was ejected onto the recording medium and recording, and the time when the ink was ejected and recording.

[0365] The recording of the treatment liquid was set to a liquid volume of 6 pL and a printing rate of 30%, and the recording of the ink was set to a liquid volume of 28 pL and a printing rate of 100%.

[0366] The printed recording medium was placed in a dryer set at 90° C. and dried by heating for 5 minutes to obtain an image recording.

[0367] [Evaluation of Intercolor Bleeding] An image recording was prepared using the two-color printing test method described above. A two-color image was recorded in a 5 cm x 5 cm area, with 1 cm x 5 cm rectangular solid images arranged alternately adjacent to each other. Intercolor bleed was visually observed from a distance of 15 cm by six image inspection experts and evaluated according to the following evaluation criteria. "AA" and "A" were evaluated as acceptable for practical use, and "B" was evaluated as problematic for practical use. The image was configured so that the two colors did not overlap, and the treatment liquid was applied evenly over the entire 5 cm x 5 cm area.

[0368] AA: No color bleeding is observed between two adjacent colors. A: Some color mixing is observed at the boundary between two adjacent colors. B: The colors at the boundary between two adjacent colors are mixed, and the boundary is not clear.

[0369]

[0370] [6] Treatment liquid application printing test: Example 6 (Method of producing image recorded matter) Ink sets were prepared by combining the prepared inks 1 to 3 and 9 with inks 25 to 27 and treatment liquids 1 to 3. The combinations are shown in Table XI. Using the ink sets with the combinations in Table XI, a printing test was carried out in the following manner, and image recorded matters were produced.

[0371] A single-pass printer (see FIG. 8) equipped with one independently driven inkjet head (360 npi, ejection volume of 6 pL, 14 pL, or 28 pL, 1024 nozzles) manufactured by Konica Minolta was prepared.

[0372] Head H ｉｎｋ Each ink was filled in the ink tank. Then, each treatment liquid was applied to a designated recording medium using a bar coater (number No. 5, wet film thickness 10 μm).

[0373] Thereafter, printing was carried out on recording media using each ink set in single-pass mode at a resolution of 360 x 720 dpi. Two types of recording media were prepared: a polypropylene substrate (#20FOR, manufactured by Futamura Chemical Co., Ltd., thickness 20 μm) and coated paper (OK Topcoat, manufactured by Oji Paper Co., Ltd.).

[0374] The carriage transport speed was set to 300 mm / sec.

[0375] The ink recording was set at a liquid volume of 28 pL and a printing rate of 100%.

[0376] The printed recording medium was placed in a dryer set at 90° C. and dried by heating for 5 minutes to prepare an image recording material.

[0377] [Evaluation] An image recording was prepared by the method described above in Printing Test 1. At this time, evaluation of crushing of outline characters, bleeding of thin lines, and mottling of solid areas were carried out using the same evaluation methods and criteria as in Printing Test 1. The cohesion index was also calculated in the same manner.

[0378]

[0379] [7] Printing test using a specific mixing device and recording device: Example 7 (Method for producing an image recording material) A recording device as shown in FIG. 5, which is an example of the configuration of a recording device equipped with the mixing device shown in FIG. 4, was used for the printing test.

[0380] The component A was classified as α ink, and the component B was classified as β ink. Prepared ink 17 or 18 was used as the α ink, and prepared ink 19 was used as the β ink.

[0381] Ink sets were prepared by combining the α ink, the β ink, and treatment liquid 1. The combinations are shown in Tables XII and XIII. A printing test was carried out using the ink sets with the combinations shown in Tables XII and XIII in the following manner.

[0382] A single-pass printer (see FIG. 6) equipped with two independently driven inkjet heads (360 npi, ejection volume of 6 pL, 14 pL, or 28 pL, 1024 nozzles) manufactured by Konica Minolta was prepared.

[0383] Head H in FIG. ｉｎｋ The recording head 113 of the recording device equipped with the mixing device was connected to the liquid supply flow path 112 (see FIG. 5).

[0384] The α ink was filled in the storage tank 101 storing the A component in FIG. 5, and the β ink was filled in the storage tank 102 storing the B component in FIG.

[0385] The α ink and β ink were then mixed in an arbitrary ratio in the device shown in Figure 5, and printing was performed on a recording medium in single-pass mode at a resolution of 360 x 720 dpi, always with the treatment liquid printed first. Two types of recording media were prepared: a polypropylene base (#20FOR, manufactured by Futamura Chemical Co., Ltd., thickness 20 μm) and coated paper (OK Topcoat, manufactured by Oji Paper Co., Ltd.).

[0386] The carriage transport speed was set to 300 mm / sec, and a drying process was not performed between the time when the treatment liquid was ejected onto the recording medium and recording, and the time when the ink was ejected and recording.

[0387] The recording of the treatment liquid was set to a liquid volume of 6 pL and a printing rate of 30%, and the recording of the ink was set to a liquid volume of 28 pL and a printing rate of 100%.

[0388] The printed recording medium was placed in a dryer set at 90° C. and dried by heating for 5 minutes to obtain an image recording.

[0389] [Cohesion index G Ｘ After mixing in the device, the ink was extracted from the flow path, and the cohesiveness index was calculated by the method described in Printing Test 1. The results are shown in Tables XII and XIII.

[0390]

[0391]

[0392] [8] Overall Review As is clear from the above, it is clear that the present invention is superior to the comparative examples. It is also clear that the ink set of the present invention can suppress color bleeding and achieve a wide color gamut. Furthermore, it is clear that the inkjet recording method and inkjet recording apparatus of the present invention can suppress the drying load while maintaining high quality.

[0393] [9] Others As described above, the embodiments of the present invention have been described in detail and illustrated, but the descriptions in the above embodiments are examples of ink sets, inkjet recording methods, and inkjet recording apparatuses created for the purpose of illustration and illustration only, and the present invention is not limited to these. Furthermore, the materials constituting the ink set, inkjet recording method, and inkjet recording apparatus, the details of the recording method, the configuration and operation of each apparatus, etc. can be appropriately changed within the scope of the present invention without departing from the spirit of the present invention.

[0394] The scope of the present invention should be interpreted by the terms of the appended claims.

[0395] The present invention aims to provide an ink set and inkjet recording method that can suppress color bleeding and achieve a wide color gamut, and a recording apparatus that can suppress drying load while maintaining high quality.

[0396] REFERENCE SIGNS LIST 1 Stage 2 Conveying guide 10 Mixing device 11 Storage tank for component A 12 Liquid supply flow path for component A 13 Liquid supply pump for component A 14 Storage tank for component B 15 Liquid supply pump for component B 16 Mixing unit 17 Liquid supply flow path 18 Recording head 100 Recording device 101 Storage tank for component A 102 Liquid supply flow path for component A 103 Liquid supply pump for component A 104 Storage tank for component B 105 Liquid supply pump for component B 107 Static mixer as mixing unit 108 Solenoid valve 109 Sub-tank 110 Float sensor 111 Negative pressure control pump 112 Liquid supply flow path 18, 113 Recording head D Ａ D: absorbance of pigment dispersion A at each light absorption wavelength Ｂ D: absorbance of pigment dispersion B at each light absorption wavelength Ｃ PD: absorbance of pigment dispersion C at each light absorption wavelength Ａ PD: absorbance at each light absorption wavelength of the mixed liquid of the treatment liquid and pigment dispersion A Ｂ PD: absorbance at each light absorption wavelength of the mixed solution of the treatment liquid and pigment dispersion B Ｃ : absorbance at each light absorption wavelength of the mixed liquid of the treatment liquid and pigment dispersion C ｉｎｋ: absorbance of aqueous pigment ink at each light absorption wavelength U Ｌ The absorbance U of the supernatant liquid obtained after centrifuging a 1:1 mixture of the aqueous pigment ink and a 5-fold diluted aqueous solution of the treatment liquid is measured at the absorption wavelength of the aqueous pigment ink. Ａ Absorbance U at the absorption wavelength derived from pigment dispersion A in the supernatant after centrifuging a 1:1 mixture of an aqueous pigment ink and a 5-fold diluted aqueous solution of the treatment liquid Ｂ Absorbance H at the absorption wavelength of pigment dispersion B in the supernatant after centrifuging a 1:1 mixture of an aqueous pigment ink and a 5-fold diluted aqueous solution of the treatment liquid ＰＬ Head H for filling the treatment liquid ｉｎｋ Head H for filling ink α Head for filling α ink H β Head for filling β ink

Claims

1. An ink set composed of a processing liquid and an aqueous pigment ink, wherein the aqueous pigment ink contains at least two or more pigment dispersions X including a pigment dispersion A and a pigment dispersion B, and is an ink that aggregates by mixing with the processing liquid, the absolute value of the difference in the maximum absorption peak wavelength between the pigment dispersion A and the pigment dispersion B is 50 nm or more, and the aggregation index G of all the pigment dispersions X contained in the mixed liquid of the processing liquid and the aqueous pigment ink is defined by the following formula (I): Ｘ is less than 0.7, Formula (I): G Ｘ = X ａｆｔ / X ｂｅｆ (In the above formula (I), X ｂｅｆ represents the absorbance at the maximum absorption peak wavelength derived from the pigment dispersion X in a 1:1 mixed solution of the aqueous pigment ink and pure water. X ａｆｔ represents the absorbance at the maximum absorption peak wavelength derived from the pigment dispersion X in the supernatant after centrifuging a 1:1 mixed solution of the aqueous pigment ink and a 5-fold diluted aqueous solution of the processing liquid.) The absolute value of the difference in the aggregation index G Ｘ between all the pigment dispersions is 0.4 or less. An ink set characterized by this.

2. Let the aggregation indices of the pigment dispersions A and B defined by the formula (I) be G Ａ and G Ｂ respectively. When the above G Ａ and the above G Ｂ satisfy all of the following formulas (1), (2), and (3): Formula (1): 0 ≦ G Ａ < 0.5 Formula (2): 0 ≦ G Ｂ < 0.5 Formula (3): |G Ａ − G Ｂ | ≦ 0.2 (In the above formulas (1), (2), and (3), G Ａ = A ａｆｔ / A ｂｅｆ , G Ｂ = B ａｆｔ / B ｂｅｆ ), the ink set according to claim 1 is characterized by this.

3. The ink set according to claim 1, wherein the treatment liquid and the aqueous pigment ink are ejectable by an inkjet.

4. The ink set according to claim 1, wherein the aqueous pigment ink contains any one of a yellow pigment dispersion, a cyan pigment dispersion, and a magenta pigment dispersion.

5. The ink set according to claim 1, wherein the aqueous pigment ink contains two or more kinds of pigment dispersions X selected from at least any one of a yellow pigment dispersion, a cyan pigment dispersion, and a magenta pigment dispersion.

6. The ink set according to claim 1, wherein the treatment liquid contains at least any one of a polyvalent metal salt, an acid, or a cationic polymer.

7. The ink set according to claim 1, wherein the aqueous pigment ink contains a fixing resin.

8. The ink set according to claim 1, wherein the absolute value of the difference in particle diameter between the pigment dispersion A and the pigment dispersion B is less than 80 nm.

9. An inkjet recording method using the ink set according to claim 1, wherein the ink set includes an achromatic ink, and the aqueous pigment ink is not overlaid with two or more colors on a recording medium.

10. An inkjet recording method using the ink set according to claim 1, wherein an image is recorded by mixing and adjusting the ink set in a flow path of a recording apparatus.

11. Cohesion index G between all pigment dispersions Ｘ A recording apparatus, characterized by having means for mixing pigment dispersions having an absolute value of the difference in the cohesion index G between any two pigment dispersions of 0.4 or less in an arbitrary ratio within a flow path and recording the mixture.

Images