JP2008213178A - Recording medium for water-based ink and judging method of ink absorption characteristic thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a matte type inkjet recording medium which has an optimum printing suitability in the case of printing with either dye ink or pigment ink. <P>SOLUTION: The recording medium for water-based ink has an ink accepting layer including an alumina-containing porous layer on the surface of a paper substrate and is used for recording with the water-based ink containing an ink coloring material. The medium is so prepared that it satisfies formulas 0<V2<V1 and 0<V2<V3 regarding an absorption rate, on the occasion when distilled water dripped on the surface of the ink accepting layer is absorbed at a first absorption stage (V1) within 1 second immediately after dripping, a second absorption stage (V2) in 2 seconds or more and a third absorption stage (V3), and that an absorption quantity qa at an inflection point (a) from the first absorption stage to the second is 1.3 to less than 2.0 μL, while the absorption quantity qb at the inflection point b from the second absorption stage to the third is 2.0 to less than 2.5 μL. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a water-based ink recording medium having a paper support and an ink-receiving layer, and a method for determining the ink absorption characteristics thereof, and in particular, a mat-type water-based material having a relatively low glossiness suitable for ink jet recording. The present invention relates to an ink recording medium.

  In recent years, water-based ink prints that make hard copies at high speed are also performed by offset printing and letterpress printing, and the characteristics of the recording medium are becoming important for recording water-based inks. In particular, with the advancement of the technology of ink jet printers, which are representative of water-based ink printing, it has become possible to obtain clear images and excellent print quality. Along with this, in order to further improve the printing quality, a recording medium having higher characteristics has been required, and various recording media have been developed.

  On the other hand, the use of water-based ink jet printers has expanded and is also used for advertising such as posters. In such an application, it is necessary to maintain a clear image not only in recording characteristics such as high image quality and high recording density but also in long-term posting and long-term storage. Conventional water-based dye inks with excellent color developability are used as inks for ink jet printers. However, water-based dye inks generally tend to fade due to light, etc., so that the sharpness is lost over time, resulting in long-term posting. It was not suitable for storage. In order to solve such problems, printers and plotters using water-based pigment inks having excellent light resistance are increasing.

  However, in the case of the water-based pigment ink, the ink characteristics are different from those of the water-based dye ink due to the fact that the pigment of the water-based pigment ink is particulate. For this reason, a dedicated water-based ink recording medium is provided for each ink, and there is almost no recording medium that can achieve both. The present invention is as follows.

  In general, the recording medium for pigment ink is designed to increase the ink absorbency, and in the case of dye ink, it corresponds by the selection of the ink fixing agent instead of lowering the ink absorbency than that for the pigment ink. Designed. Thus, since water-based dye ink and water-based pigment ink have conflicting characteristics, if the ink and the recording medium are used in an incorrect combination, the result is only a recorded matter in which the quality such as image density and blurring is impaired. Not obtained. For example, when printing is performed on a conventional water-based ink recording medium for dye ink using pigment ink, the pigment ink is not absorbed, and there is a phenomenon that unevenness or cracking occurs in the printed portion, which is a practical problem. Has occurred.

  On the other hand, water-based ink recording media are roughly classified into a gloss type having a high glossiness, a mat type having a low glossiness, and a plain paper type having a texture almost similar to high-quality paper. The gloss type recording medium includes a type using a resin-coated paper used as a support for silver salt photographic printing paper and a type using paper. In any case, the coating layer can be formed with a pigment having a narrow fine particle size distribution and ensuring transparency, and both absorbency and glossiness are achieved. Among these recording media, when recording on a gloss type recording medium, the ink-receiving layer is formed using a fine pigment on the recording medium, so the ink absorption is slow, so the recording speed is reduced to the printer recording speed. This suppresses the occurrence of ink bleeding. This means that, as a result, the printing speed becomes slow, so that the capability of the printer cannot be fully exhibited.

  In particular, mat type recording media are designed mainly for ink absorptivity, so pigments with a much larger particle size are used in the coating liquid for forming the ink receiving layer compared to the gloss type. As a result, glossiness is suppressed. As a further improvement of this excellent ink absorbability, the surface of the paper support is subjected to a surface treatment that enhances solvent passage characteristics to promote a rapid liquid flow at the boundary between the ink receiving layer and the paper support. There are also things. In any case, since the mat type recording medium has a large pigment particle diameter, the ink absorption is faster than the gloss type, and the recording speed in the printer can be set faster. In recent years, with the spread of digital cameras and the like, when full-color images are recorded not only on gloss type but also on mat type recording media, the amount of ink per unit area increases compared to monochrome images. Ink absorption characteristics have been desired. When trying to meet this requirement, there arises a problem of causing the color and blur of each color.

As described above, a recording medium suitable for both water-based dye inks and water-based pigment inks having different absorption characteristics is not provided. In contrast, a plurality of ink receiving layers as described in Patent Document 1 and Patent Document 2 are provided. It is also conceivable to employ a recording medium that has been formed to improve recording suitability. However, it does not provide a recording medium for water-based ink that can be sufficiently adapted to the absorption characteristics of both dye ink and pigment ink.
JP-A-62-152779 JP-A-63-39373

  The present invention verifies the conventional recording medium for water-based ink, elucidates the reason why a suitable image cannot be obtained, and quantitatively or qualitatively determines the relationship between the paper support and the ink-receiving layer, which is difficult to elucidate. It is an object of the present invention to provide a water-based ink recording medium capable of forming a desired image without producing many samples. Further, the present invention is a water-based ink recording medium having optimum printability for both water-based dye ink and water-based pigment ink, which could not be achieved by the prior art, and printability by the water-based ink. An object of the present invention is to provide a method for making a determination without performing printing.

  Specifically, the first object of the present invention is to provide a novel aqueous ink recording medium that can ensure the color development and density uniformity of a “solid image” with either aqueous dye ink or aqueous pigment ink. . A second object of the present invention is to provide an easy-to-understand determination criterion that can determine an ink absorption characteristic that should be provided in a novel water-based ink recording medium that has not been conventionally used.

  A third object of the present invention is to provide a recording medium for water-based ink having specific liquid absorption characteristics necessary for desired image formation.

  A fourth object of the present invention is to provide a recording medium for water-based ink that can form a clear image even if the basis weight of the paper support is increased.

  A fifth object of the present invention is to provide a mat type water-based ink recording medium capable of forming an image having a depth feeling (depth) which has not been obtained conventionally.

  The present invention aims to solve at least one of these problems, but as will be apparent from the following description, the present invention also contributes to the solution of another problem.

  In order to solve the above-mentioned problems, the present inventors have investigated the relationship between the conventional paper support, the ink receiving layer, the boundary region between the paper support and the ink receiving layer and the ink absorption characteristics by making full use of an optical electron microscope or the like. Existence was examined. However, it has been difficult to qualify the relationship qualitatively or quantitatively. Accordingly, the inventors of the present invention have focused on the fact that the main component of the water-based ink is pure water as a method for clearly expressing the conventional recording medium characteristics, and the pure water alone has any behavior with respect to the recording medium. It was decided to consider whether it would be absorbed. In actual ink jet recording, ink droplets in the range of 2 picoliters to 8 picoliters are used, but the absorption of 1 microliter of pure water was measured, but the absorption was too early to be elucidated. . From there, many experiments were conducted and research was conducted. As a result, absorption characteristics of 4 microliters, which can distinguish the characteristics of conventional recording media, were obtained.

  The results of measuring the absorption characteristics of the recording surface of a conventional water-based ink recording medium are shown in FIG. 1 (J, K, L, and M show the absorption characteristics of a conventional water-based ink recording medium, and the horizontal axis indicates the amount of absorption. The vertical axis indicates the time after dropping). As can be seen from FIG. 1 and the comparative example, the conventional recording media indicated by the symbols J and K have a long period of time when there is almost no liquid absorbency, so that the ink that is substantially overflowing disturbs the image. Is correlated. The mechanism of such a phenomenon is considered to be related to the layer structure on the paper support. First, the water-based ink recording medium of the present invention is formed in a three-layer structure having a high-density boundary region newly provided with a filter function at the boundary region between the paper support and the ink receiving layer. On the other hand, the conventional recording media indicated by symbols J and K have a two-layer structure in which the paper support and the ink receiving layer are simply joined, and have a filter function due to the interface of the ink receiving layer. Since it is too strong, it is estimated that such an absorption characteristic is exhibited.

  Further, the recording medium of the code M is correlated with the result that the print density is greatly reduced because the absorption characteristic is performed in a very short time. As a mechanism, since the binder component in the ink receiving layer is small, there is almost no boundary region having a filter function due to the interface, and in reality, it is a two-layer configuration of the paper support and the ink receiving layer. Is dominant, and it is assumed that such absorption characteristics are exhibited.

  The recording medium with the code L is between these, and has improved characteristics as compared with the recording media with the codes K and J, but is correlated with the result that the dot spread is small and the density is not sufficient. The mechanism by which such a correlation is obtained is considered to be related to a substantial layer structure on the paper support. That is, by drying the ink receiving layer with a small amount of the binder component at a low temperature for a long time, the binder component penetrates the entire paper support, and the boundary area having a filter function at the interface between the ink receiving layer and the paper support is low. Formed in density. Therefore, although it is actually a two-layer structure, it is presumed that such a absorption characteristic is exhibited because the one-layer structure is dominant.

  Thus, the determination condition of the present invention is quantitatively and / or qualitatively significant for the characteristics of conventional recording media. From this knowledge, the present invention further solves the problems of the present invention, pursues the conditions of a recording medium that can achieve the object of the present invention, and has completed the present invention.

The determination method of the present invention is for a water-based ink having a paper support and an ink receiving layer provided on the surface of the paper support and containing alumina, an adhesive, and a reactive substance of an ink coloring material. This is a method for determining absorption characteristics by setting the following criteria for a recording medium.
(1) A droplet obtained by dropping 4 μl of distilled water on the surface of the ink receiving layer (distilled water droplet) is absorbed in the following three absorption stages.
A first absorption stage that absorbs at a first absorption rate V1 (μl / sec) within 1 second immediately after dropping.
A second absorption stage that absorbs at a second absorption rate V2 (μl / sec) after the first absorption stage.
A third absorption stage in which absorption is performed at the third absorption rate V3 (μl / sec) after the second absorption stage.
(2) The inflection point that transitions from the first absorption stage V1 to the second absorption stage V2 is a, the inflection point that transitions from the second absorption stage V2 to the third absorption stage V3 is b, and the third absorption stage V3 Let c be the final point.
(3) The amount of absorption at each point is qa, qb, qc, and the time at each point is ta, tb, tc.

  Here, the absorption speeds V1, V2, and V3 described in the present invention connect inflection points and end points, and correspond to approximate straight lines at respective stages derived from measured values. The inflection point of the present invention indicates a change point at which the absorption rate V1 changes to the absorption rate V2, and a change point at which the absorption rate V2 changes from the absorption rate V3. When the change from V1 to V2 or V2 to V3 has a gently changing inflection region, for example, from the intersection of extending the approximate straight line of V1 and V2, perpendicular to the approximate curve of the inflection region Indicates the lowered intersection.

  In general, a paper support having a high degree of sizing is to be used in order to suppress the blurring of the paper support that is likely to occur when a paint is applied. On the contrary, the present inventors have tried to use a paper support having a low degree of sizing, and moreover, it is common to use a neutral paper having a low color change in the pH of the paper support. Attempts to use acidic paper were also made. In any case, in order to obtain excellent quality, each layer of the ink receiving layer or the base material alone was considered important, and research was conducted focusing on the properties of each single body. It has been found that the influence of each single element is not dominant, but the “filtering action” in the boundary region of the interface between the ink receiving layer and the paper support is dominant.

  2 and 3 show the absorption characteristics of a conventional water-based ink recording medium and the water-based ink recording medium of the present invention. A, B, C, D, E, F, G, H, I in FIG. 2 and N, O, P, Q, R, S, T, U, V, and W in FIG. 3 are for the water-based ink of the present invention. The absorption characteristics of the recording medium are shown. As is apparent from FIGS. 1, 2, and 3, the absorption characteristics of the aqueous ink recording medium of the present invention are clearly different from those of the conventional aqueous ink recording medium. Even when comparing actual printed matter, it is confirmed that the printed matter on the recording medium of the present invention has the best print quality, and there is a correlation between the absorption characteristics of FIGS. Was found. In addition, as a result of measuring the absorption characteristics with distilled water having a droplet volume of 1 μl to 7 μl, it was found that the difference in the absorption characteristics was the clearest with 4 μl.

  Thus, in order to investigate the properties including all of the ink receiving layer and the paper support, further studies were conducted. As a result, it has been found that the absorption speed of the recording medium for water-based ink needs to satisfy a specific condition, and the present invention relates to a method for determining the ink absorption characteristics of the recording medium for water-based ink and the recording medium for water-based ink shown below. It came to.

The present invention is as follows.
(1) A water-based ink recording medium in which an ink-receiving layer having a porous layer containing alumina is provided on the surface of a paper support and is recorded using a water-based ink containing the ink color material, A first absorption stage in which a droplet of 4 μl of distilled water dropped on the surface of the ink receiving layer is absorbed at a first absorption rate V1 (μl / sec) within 1 second immediately after the dropping, and after the first absorption stage, A second absorption stage that absorbs at 2 absorption speeds V2 (μl / sec) for at least 2 seconds and a third absorption stage after the second absorption stage and at a third absorption speed V3 (μl / sec). The absorption stage absorbs 4 μl of distilled water droplets, and the absorption of the droplets from the first absorption stage to the third absorption stage has the formula:
0 <V2 <V1
0 <V2 <V3
And the second absorption rate V2 (μl / sec) is greater than 0.01 (μl / sec) and less than 0.32 (μl / sec),
The inflection point that transitions from the first absorption stage to the second absorption stage is a, the inflection point that transitions from the second absorption stage to the third absorption stage is b, and the final point of the third absorption stage Is c, the amount of absorption at each inflection point is qa, qb, qc, and the time to each inflection point or final point is ta, tb, tc,
Absorption amount qa at the inflection point a is 1.3 μl or more and less than 2.0 μl, and the absorption amount qb at the second inflection point b is 2.0 μl or more and less than 2.5 μl. recoding media.
(2) The water-based ink recording medium according to (1), wherein the inflection point a occurs within 0.5 seconds immediately after dropping.
(3) The water-based ink recording medium according to (1), wherein an absorption amount (qb−qa) in the second absorption stage is 0.3 μl or more and 1.4 μl or less.
(4) The water-based ink recording medium according to (1), wherein an absorption amount (qb−qa) in the second absorption stage is 0.5 μl or more and 1.0 μl or less.
(5) The water-based ink recording medium according to (1), wherein an absorption amount qa at the inflection point a is 1.5 μl or more.
(6) The water-based ink according to (5), wherein the water-based ink recording medium has a basis weight of 180 g / m ² or more and 300 g / m ² or less, and the inflection point b occurs within 8 seconds immediately after the dropping. Recording media.
(7) The water-based ink recording medium according to any one of (1) to (6), wherein the paper support has a Steecht sizing degree of 5 seconds to 50 seconds.
(8) The pH _{B of the} ink receiving layer is represented by the formula:
5 <pH _B ≦ 7
The water-based ink recording medium according to any one of (1) to (6), wherein:
(9) The pH _{A of the} paper support and the pH _{B of the} ink receiving layer are represented by the formula:
1 <(pH _B −pH _A ) <4
The water-based ink recording medium according to (8), wherein:
(10) The second absorption speed V2 (μl / sec) is a speed greater than 0.05 (μl / sec) and smaller than 0.23 (μl / sec). 6) The water-based ink recording medium according to any one of 6).
(11) The second absorption rate V2 (μl / sec) is a rate greater than 0.12 (μl / sec) and less than 0.23 (μl / sec). 6) The water-based ink recording medium according to any one of 6).

(12) A water-based ink recording medium having a paper support having a Steecht sizing degree of 5 seconds to 50 seconds, and an ink receiving layer containing alumina and an adhesive on the surface of the paper support,
A first absorption stage in which a droplet of 4 μl of distilled water dropped on the surface of the ink receiving layer is absorbed at a first absorption speed V1 (μl / sec) within 1 second immediately after the dropping, and after the first absorption stage A second absorption stage absorbing at a second absorption rate V2 (μl / sec) for at least 2 seconds and a third absorption rate V3 (μl after the second absorption stage and occurring within 8 seconds immediately after the dropping. / Sec) absorbs the 4 μl droplets by the third absorption stage, and absorption of the droplets from the first absorption stage to the third absorption stage is expressed by the formula:
0 <V2 <V3 <V1
And the second absorption rate V2 (μl / sec) is greater than 0.01 (μl / sec) and less than 0.32 (μl / sec),
The inflection point that transitions from the first absorption stage to the second absorption stage is a, the inflection point that transitions from the second absorption stage to the third absorption stage is b, and the final point of the third absorption stage Is the amount of absorption at each inflection point or final point, qa, qb, qc, and the time to each inflection point or final point is ta, tb, tc,
The water system is characterized in that the absorption amount qa at the inflection point a is 1.5 μl or more and 2.0 μl or less, and the absorption amount (qb−qa) in the second absorption stage is 0.3 μl or more and 1.0 μl or less. Ink recording medium.
(13) The pH _{B of the} ink receiving layer is represented by the formula:
5 <pH _B ≦ 7
The pH _{A of the} paper support and the pH _{B of the} ink receiving layer are expressed by the formula:
1 <(pH _B −pH _A ) <4
The basis weight of the paper support and the ink receiving layer is in the range of 180 g / m ² or more and 300 g / m ² or less, and the recording medium for water-based ink according to (12).
(14) The second absorption speed V2 (μl / sec) is a speed greater than 0.12 (μl / sec) and smaller than 0.23 (μl / sec) (12) or ( A recording medium for water-based ink as described in 13).

(15) A water-based ink recording medium having an ink receiving layer having a porous layer containing alumina on the surface and recorded using a water-based ink containing an anionic coloring material,
A first absorption stage in which a droplet of 4 μl of distilled water dropped on the surface of the ink receiving layer is absorbed at a first absorption speed V1 (μl / sec) within 1 second immediately after the dropping, and after the first absorption stage A second absorption stage of absorbing at a second absorption speed V2 (μl / sec) for 2 seconds or more, and a third absorption after the second absorption stage and absorbing at a third absorption speed V3 (μl / sec) Absorbs 4 μl of distilled water droplets according to the step, and the absorption of the droplets from the first absorption step to the third absorption step is:
0 <V2 <V1
0 <V2 <V3
And the second absorption rate V2 (μl / sec) is greater than 0.01 (μl / sec) and less than 0.32 (μl / sec),
The inflection point for transition from the first absorption stage to the second absorption stage is a, the inflection point for transition from the second absorption stage to the third absorption stage is b, and the final point of the third absorption stage V3 Is c, the amount of absorption at each inflection point is qa, qb, qc, and the time to each inflection point or final point is ta, tb, tc,
The absorption amount qa at the inflection point a is 1.3 μl or more and 2.0 μl or less, and the absorption amount (qb−qa) of the second absorption stage is 0.3 μl or more and 1.0 μl or less. A recording medium for water-based ink.
(16) The second absorption rate V2 (μl / sec) is a rate greater than 0.05 (μl / sec) and less than 0.23 (μl / sec). Recording medium for water-based ink.
(17) The recording medium for water-based ink according to (16), wherein the paper support has a Steecht sizing degree of 5 seconds to 50 seconds.

(18) A water-based ink recording medium having a paper support and an ink receiving layer provided on the surface of the paper support and containing alumina and an adhesive.
A first absorption stage in which a droplet of 4 μl of distilled water dropped on the surface of the ink receiving layer is absorbed at a first absorption speed V1 (μl / sec) within 1 second immediately after the dropping, and after the first absorption stage A second absorption stage that absorbs at a second absorption rate V2 (μl / sec) for at least 2 seconds, and after the second absorption stage, the absorption is performed at a third absorption rate V3 (μl / sec). The absorption of the droplets from the first absorption stage to the third absorption stage is expressed by the formula:
0 <V2 <V1
0 <V2 <V3
And the second absorption rate V2 (μl / sec) is greater than 0.01 (μl / sec) and less than 0.32 (μl / sec),
The inflection point that transitions from the first absorption stage to the second absorption stage is a, the inflection point that transitions from the second absorption stage to the third absorption stage is b, and the final point of the third absorption stage Is c, the amount of absorption at each point is qa, qb, qc, and the time to each inflection point or final point is ta, tb, tc,
The absorption amount qa at the inflection point a is 1.3 μl or more and less than 2.0 μl, the absorption amount qb at the inflection point b is more than the absorption amount qa of the first absorption stage and less than 2.5 μl, and The water-based ink recording medium, wherein an absorption amount (qb−qa) in the second absorption stage is 0.3 μl or more and 1.4 μl or less.
(19) The water-based ink recording medium as described in (18), wherein an absorption amount (qb-qa) in the second absorption stage is 0.38 μl or more and 1.0 μl or less.

(20) The water-based ink recording medium according to (19), wherein the absorption qa at the inflection point a is 1.5 μl or more.
(21) The recording medium for water-based ink according to (18), wherein the second absorption stage occurs within 2.0 seconds or more and 13.5 seconds immediately after the dropping of the droplets.
(22) The aqueous ink recording medium according to (21), wherein a time tc of the third absorption stage is within 14.1 seconds from immediately after the dropping of the droplet.
(23) The second absorption stage occurs within 6.1 seconds immediately after the dropping of the droplet, and the final time tc of the third absorption stage occurs within 8 seconds ( 20) A recording medium for water-based inks.
(24) The second absorption stage occurs after 9.5 seconds immediately after the dropping of the droplet, and the time tc of the final point of the third absorption stage occurs within 14.5 seconds. The recording medium for water-based ink according to (19).
(25) The second absorption speed V2 (μl / sec) is a speed greater than 0.05 (μl / sec) and smaller than 0.23 (μl / sec). 24. The recording medium for water-based ink according to any one of 24).

(26) The second absorption rate V2 (μl / sec) is greater than 0.12 (μl / sec) and smaller than 0.23 (μl / sec). Recording medium for water-based ink.
(27) The second absorption rate V2 (μl / sec) is a rate larger than 0.05 (μl / sec) and smaller than 0.09 (μl / sec). Recording medium for water-based ink.

(28) A method for determining ink absorption characteristics of a water-based ink recording medium having a paper support and an ink receiving layer containing alumina and an adhesive on the surface of the paper support,
A first absorption stage for absorbing a droplet obtained by dropping 4 μl of distilled water on the surface of the ink-receiving layer of the water-based ink recording medium at a first absorption speed V1 (μl / sec) within 1 second immediately after the dropping; A second absorption stage that absorbs at a second absorption speed V2 (μl / sec) after one absorption stage for at least 2 seconds, and a third absorption speed V3 (μl / sec) after the second absorption stage. Being absorbed by a third absorption stage that absorbs at
The second absorption rate V2 (μl / sec) is greater than 0.01 (μl / sec) and smaller than 0.32 (μl / sec);
An inflection point a that transitions from the first absorption stage to the second absorption stage, an inflection point b that transitions from the second absorption stage to the third absorption stage, and a final point c of the third absorption stage are measured. When the amount of absorption at each point is qa, qb, qc, and the time until each inflection point or final point is ta, tb, tc,
The amount of absorption qa in the first absorption stage is 1 μl or more and less than 2.0 μl;
The absorption qb of the second absorption stage is greater than the absorption qa of the first absorption stage and less than 2.5 μl;
A method of determining ink absorption characteristics of a recording medium for water-based ink, comprising determining whether the amount of absorption (qb-qa) in the second absorption stage is 0.3 μl or more and 1.4 μl or less. .
(29) The second absorption rate V2 (μl / sec) is greater than 0.05 (μl / sec) and smaller than 0.23 (μl / sec). (28) Ink absorption characteristics determination method for a water-based ink recording medium.
(30) The basis weight of the paper support and the ink receiving layer is within a range of 180 g / m ² or more and 300 g / m ² or less, and the second absorption rate V2 (μl / sec) is 0.12 ( (28) The method for determining ink absorption characteristics of a water-based ink recording medium according to (28), wherein the speed is greater than [mu] l / sec) and less than 0.23 [[mu] l / sec).

  In the recording medium of the present invention, it is preferable that the conditions of the claims of the present application are obtained as a whole. However, even if one point that slightly deviates from the conditions of the present invention is scattered due to unexpected factors such as dust, the effect of the invention in which the present invention is implemented can be substantially obtained as a whole. Are included in the present invention. Even in the long type such as cut paper or roll paper, it is preferable to fall within the scope of the present invention in all parts, but if the present invention is substantially applied to the main area, It is included in the invention.

  The present invention achieves a filter function capable of optimizing a substantially liquid permeation state mainly in the boundary region between the ink receiving layer and the paper support mainly by having the second absorption stage. That is, a predetermined amount of liquid that has penetrated into the ink receiving layer is said to be association or aggregation of the coloring materials while being moved moderately according to the provisions of the claims of the present invention (for example, the speed V2 of the second absorption stage). The greatest feature lies in the presence of the second absorption stage, which corresponds to providing an effect. The predetermined amount is one factor that influences the image density, and in the present invention, it is an amount of 1.3 μl or more (preferably 1.5 μl or more) and 2 μl or less of the 4 μl of distilled water. .

This second absorption stage exhibits an excellent effect in improving image density and suppressing bleeding. At the inflection point of the final region at this stage, it seems that an effect equivalent to forming an optimal color material fixing state in the ink receiving layer is brought about. Then, at the inflection point, the third absorption stage where the rapid absorption to the paper support is started, so that unnecessary solvent and moisture can be diffused, and a substantial solid-liquid separation function is exhibited. It seems to have been. Therefore, the present invention provides a new filter function at the boundary area between the ink receiving layer and the paper support, not at the boundary surface as if the two layers of the paper support and the ink receiving layer were simply joined. It is clear that this is an excellent invention. In any case, according to the present invention, it is possible to obtain the desired performance by providing the second absorption stage that can absorb water-based ink reasonably. That is, it is possible to minimize blurring regardless of whether water-based dye ink or water-based pigment ink is used for printing over a wide range where the basis weight of the water-based ink recording medium is 130 g / m ² or more and 300 g / m ² or less. it can. As a result, a clear image was obtained with high density and excellent uniformity. Further, if the present invention is applied to a mat type, it becomes possible to print a deeper image. Other effects of the present invention can be understood from the following description.

"About the first invention"
In the first invention of the present invention described in (1) above, the absorption rate from the first absorption stage to the third absorption stage is a value determined by the following method.

Using a microabsorption tester (DAT) manufactured by Fibro, 4 μl (microliter) of distilled water (23 ° C.) was added with a microsyringe to an aqueous ink recording medium adjusted to an environment of 23 ° C. and 50% RH. It is dropped on the surface of the ink receiving layer. The outline of the dropped distilled water droplet is photographed with a video camera, the volume of the droplet is obtained by analyzing the photographed image, and the absorption amount and the absorption time are obtained from the change with time of the volume.
The volume calculation is given by the formula: H = height, B = droplet diameter.
V (volume) = πH (0.75 B ² + H ² ) ÷ 6
This is the value obtained in. Moreover, since the volume change of the droplet is large immediately after the dropping, it is preferable to shorten the measurement interval such as an interval of 0.02 seconds.

  In addition, distilled water (23 ° C.) was used as a standard solution in the evaluation of the present invention because the composition of the ink differs from printer to printer of each company, or from printer to printer of the same company. In addition, a drop of several pl (picoliter), which is often applied in recent printers, cannot be evaluated sufficiently because absorption is instantaneous. Further, printing of photographic images and the like on a mat type water-based ink recording medium is performed with a plurality of colors (for example, six colors) and at a faster speed than the gloss type printing, so the amount of ink is increased. Yes. In the present invention, the evaluation of the absorbency at the surface of the ink receiving layer, the inside of the ink receiving layer, the boundary between the ink receiving layer and the paper support, and the paper support coincides with the change in the absorption rate when dropping 4 μl. It was found and evaluated.

  For the absorption speeds V1, V2, and V3, for example, as shown in FIG. At that time, the inclination becomes the absorption rate. Although the absorption rate may change at every plotted interval, in the present invention, large changes in the absorption rate are V1, V2, and V3, respectively. That is, in V1, V2, and V3, the absorption rate may slightly increase or decrease. The present invention determines the separation function of a color material (ink color material) and a solvent in ink during recording by obtaining a large change in absorption speed.

  This will be further described with reference to FIG. 2. A conventional water-based ink recording medium shows values such as J, K, L, and M. In both cases, absorption of 0 <V2 <V1 and 0 <V2 <V3 is shown. In general, the recording medium K that is commercially available as a mat type water-based ink recording medium has a long V2 period of 16.6 seconds, and does not readily absorb. Further, the recording medium L that is generally marketed as a mat type water-based ink recording medium has an absorption amount qa of 1.07 μl in the first absorption stage, and an absorption amount of 1.44 μl in the subsequent second absorption stage. Is performed in less than 5 seconds. Furthermore, the recording medium M commercially available for pigment ink has a V2 period as short as 0.6 seconds, and the absorption ends instantaneously.

  The inventors have investigated absorption characteristics having excellent recording suitability for both pigment inks and dye inks. As a result, the recording media having the absorption characteristics of codes A to I and recording media of codes N to W are excellent. Was found. In particular, a recording medium having absorption characteristics satisfying 0 <V2 <V1 and 0 <V2 <V3 is preferable.

  The first absorption stage is absorption at the first absorption rate (V1) within 1 second immediately after the dropping, and is mainly due to absorption on the surface of the ink receiving layer, and has the highest absorption rate among the three stages. . By increasing this speed, it is possible to separate the ink coloring material and the solvent in the surface of the ink receiving layer or in the ink receiving layer. In particular, in the case of pigment ink, by separating the color material and the solvent at an early stage, aggregation of the color material is promoted, and high-density recording can be obtained. Also, a dye ink is preferable because the solvent is quickly separated from the dye and bleeding can be prevented. If the absorption rate at this stage is slower than at other stages, ink bleeding occurs on the surface of the ink receiving layer.

  If the amount of ink absorbed in the first absorption stage is too large, the amount of ink contributing to the effect in the second absorption stage and the third absorption stage is insufficient. On the other hand, if the ink absorption amount in the first absorption stage is too small, the amount of ink contributing to the effect in the second absorption stage and the third absorption stage becomes excessive. Therefore, the amount of absorption qa in the first absorption stage is optimally more than 1.3 μl and less than 2.0 μl. When the amount is small, the solid image uniformity decreases, and when the amount is large, the image density decreases.

  The second absorption stage is the second absorption rate (V2) after the first absorption stage. Part of the liquid that has penetrated into the ink receiving layer is due to absorption from the surface of the paper support to the start of penetration into the paper support. It is optimal to have this stage for at least 2 seconds. If the time is less than 2 seconds, the ink does not spread in or on the surface of the ink receiving layer, resulting in insufficiently spread dots, density unevenness, and solid image uniformity. In particular, in order to achieve excellent dot spread, it is preferable that the ink absorption amount (qb−qa) at this stage is 0.3 μl or more and the absorption quantity of the first stage or less. If it is less than 0.3 μl, the spread of the dots is insufficient, and if the amount of absorption in the first absorption stage is exceeded, the absorption to the paper support becomes larger than the spread of the dots, resulting in density unevenness. It tends to be easier. In particular, when the ink absorption amount (qb−qa) at the second absorption speed V2 is 0.5 μl or more, a good effect is obtained.

  The third absorption stage is by absorption into the paper support. Optimally, the third absorption stage occurs within 8 seconds immediately after the addition. If the third absorption stage is not reached even after 8 seconds, since the ink is held on the surface of the ink receiving layer for a long time, aggregation of the coloring material occurs in the droplets, and the recording density decreases.

  The first invention defines the absorption characteristics of the water-based ink recording medium, and the method for producing the water-based ink recording medium is not particularly limited.

  In FIG. 2, a water-based ink recording medium is manufactured using different coating liquids that form the same ink-receiving layer, and a symbol A using a paper support having a Steecht sizing degree of 15 seconds is denoted by 50 seconds. Compare with B using a paper support. If it does so, the time of a 2nd absorption stage will become shorter with the code | symbol A (15-second paper support body). When different ink-receiving layer coating liquids are used on the same paper support, the average particle diameter of alumina is almost the same, but it contains fine components compared to code C using alumina with few fine components. The second absorption stage is shorter when the code A using alumina is used.

  It is generally known that the ink receiving layer has a high absorption rate and the paper support has a low absorption rate. Furthermore, it is also known that the absorption rate is faster when the value of the steecht size is smaller. Perhaps the absorption characteristic of the first invention is a phenomenon that occurs when alumina is used, as in the prior art. It is considered that the function of controlling the absorption characteristics is given to the boundary portion between the paper support and the ink receiving layer in the present invention. This is because when the ink receiving layer is formed on the paper support, the adhesive component penetrates into the gap formed by the pulp-pulp or pulp-filler in the vicinity of the surface of the paper support, and the alumina component fills. This is thought to be due to such actions as It is considered that the penetration of the adhesive component can lengthen the time of the second absorption stage, and filling the alumina triggers absorption into the paper support, and shifts to the third absorption stage.

  Code C using alumina with a small amount of fine components takes longer time for the second absorption stage than code A using alumina containing fine components. This is considered to be sufficient.

The absorption rate in the first absorption stage can be adjusted by using alumina as in the prior art, but can be adjusted by controlling the alumina content.
The absorption rate in the second absorption stage can be adjusted by changing the binder content in the boundary region at the interface between the ink receiving layer and the paper support. Specifically, it is necessary to contain a relatively large amount of the ink receiving layer component (binder), and this can be achieved by increasing the binder ratio in the ink receiving layer. Moreover, it can adjust by changing drying conditions.
The absorption speed in the third absorption stage can be adjusted to be faster by reducing the degree of sizing of the paper support.

  Moreover, it is preferable that the succinity degree of the paper support is 5 or more and 50 seconds or less.

Furthermore, since the coloring mechanism on the recording medium differs between the case where the coloring material is a dye and the case of a pigment,
5 <pH _B ≦ 7
It is preferable that both the dye ink and the pigment ink have excellent color developability.

In particular, the relationship between the pH _{A of the} paper support and the pH _B of the ink receiving layer is 1 <(pH _B −pH _A ) <4.
If the above condition is satisfied, the above-mentioned condition that the color developability tends to be excellent can be satisfied by the production conditions of the paper support, the preparation of the ink receiving layer coating liquid, and the like.

  Incidentally, the mat type water-based ink recording medium has low glossiness, and the 75% glossiness value of about 15% or less is mainly used in the market. However, the present invention is limited to this glossiness value. Is not to be done.

"About various materials"
The water-based ink recording medium having the ink absorption characteristics as described above can be produced by combining selection of a paper support, selection of components of the ink receiving layer, selection of a method for forming the ink receiving layer, and the like.

(About paper support)
Examples of the pulp used as the main component of the paper support include chemical pulps such as LBKP and NBKP, mechanical pulps such as GP and TMP, and recycled recycled paper. Two or more of these may be mixed. In this, it is preferable to mix | blend LBKP as a main component of a pulp component. Moreover, it is preferable to use chlorine free pulps, such as ECF pulp and TCF pulp. The beating degree is not particularly limited, but beating is preferably performed so that the freeness is 300 to 500 ml (CSF: JIS-P-8121). When the beating degree is advanced, cockling tends to deteriorate when printing is performed, but there is a tendency for uneven dyeing to occur, and when the beating degree is low, smoothness tends not to be obtained.

  In addition to the above pulp, a filler may be blended in the paper support. The filler is blended for the purpose of adjusting the air permeability of the paper support, imparting opacity, and adjusting ink absorbency. As the filler, for example, clay, kaolin, calcined kaolin, talc, calcium carbonate, magnesium carbonate, aluminum hydroxide, calcium hydroxide, silica, titanium oxide and the like can be used as appropriate. Of these, calcium carbonate is preferred because it provides a paper support with high whiteness.

  The filler is preferably 1 part by mass or more and 35 parts by mass or less with respect to 100 parts by mass of the total pulp. If the amount of filler is small, not only the whiteness decreases but also the ink absorbability tends to decrease, and if too large, the paper stiffness (rigidity) decreases and the paper strength tends to decrease.

  The paper support used in the recording medium for water-based inks of the present invention includes rosin-based sizing agents, alkenyl succinic anhydride, alkyl ketene dimers, internal sizing agents such as petroleum resin-based sizing agents, rosin-based, petroleum resin-based, oxidation Synthesis comprising two or more copolymers such as starch, acetylated starch, starch such as hydroxyethylated starch and derivatives thereof, polyvinyl alcohol and derivatives thereof, styrene, alkyd, polyamide, acrylic, olefin, maleic acid, vinyl acetate, etc. The Steecht sizing degree is adjusted by using a resin sizing agent or a surface sizing agent such as a synthetic resin emulsion system or a wax system.

  The degree of sizing of the paper support is measured according to JIS P 8122 and is preferably in the range of 5 seconds to 50 seconds. When the sizing degree is less than 5 seconds, the component in the paint of the ink receiving layer penetrates into the paper support, or the binder component in the paint penetrates into the substrate, so that the surface of the coating film The strength is weakened. For this reason, even if the ink receiving layer of the present invention is formed, the effect of improving the color developability of both the dye ink and the pigment ink cannot be obtained. If the Steecht sizing degree exceeds 50 seconds, the water resistance of the printed part decreases.

The papermaking method is not particularly limited, and the papermaking method can be produced using a known papermaking machine such as a long net papermaking machine, a circular netting papermaking machine, or a twin wire type papermaking machine. Depending on the pH of the papermaking raw material, it is divided into acidic paper and neutral paper, both of which can be used. In addition, it is preferable to show specific pH _A, and it is preferable to use acidic paper.

In addition, starch, polyvinyl alcohol, cationic resin, or the like can be coated and impregnated on the surface by a size press or the like to adjust surface smoothness, improve strength, printability, and writing ability. Furthermore, in order to improve the smoothness of the paper support, it is possible to perform a smoothing treatment with a calendar or the like. The pH _A can also be adjusted by applying a pH adjusting substance. Preferably, the basis weight of the paper support is 130 g / m ² or more and 300 g / m ² or less.

(Ink receiving layer)
The ink receiving layer contains at least alumina and an adhesive, and may contain inorganic pigments other than alumina as other components. In that case, the content of alumina is preferably 50% by weight or more based on the total inorganic pigment in the ink receiving layer. As other inorganic pigments, for example, clay, kaolin, calcined kaolin, talc, calcium carbonate, magnesium carbonate, calcium hydroxide, amorphous silica, titanium oxide and the like can be used as appropriate.

  Alumina has a positive charge on the pigment surface compared to other pigments, and dye inks used in ordinary ink jets have negative charges. It is preferable as a pigment because it has excellent ink absorbability. The alumina here includes aluminum oxide typified by α-alumina and γ-alumina, and alumina hydrate typified by boehmite. Among these, γ-alumina is preferably used from the viewpoint of adjusting the particle size of the particles. The production method of γ-alumina is not particularly limited. The γ-alumina may be produced by any method of firing alumina hydrate and thermally decomposing aluminum salt. A calcined product of alumina hydrate is preferable because it is suitable for both aqueous ink recording media for pigment inks and aqueous ink recording media for dye inks.

  The average particle diameter of the secondary particles of the pigment containing alumina used for the ink receiving layer is not particularly limited as long as the ink receiving layer of the aqueous ink recording medium satisfying the absorption characteristics of the present invention can be formed. . Especially, the thing of 10 micrometers or less is preferable, and 4 micrometers or more and 8 micrometers or less are more preferable. When the average particle diameter of the secondary particles exceeds 10 μm, the image sharpness decreases and the surface roughness decreases in both the ink jet recording medium for dye ink and the aqueous ink recording medium for pigment ink. It tends to cause a problem that it is noticeable and printing unevenness is likely to occur. When the average particle diameter is less than 4 μm, the absorbability of the dye ink tends to be lowered when this is used for an aqueous ink recording medium for dye ink. Further, when the thickness is further reduced, the light-transmitting property of the ink receiving layer becomes higher, so that the light resistance of recording with the dye ink tends to be lowered, and the coating strength tends to be lowered. Further, even when used in a water-based ink recording medium for pigment ink, the fixability of the pigment ink tends to decrease.

  In the present invention, the average particle diameter of the pigment containing alumina is based on the Coulter counter method and represents the volume average particle diameter measured using a sample obtained by ultrasonically dispersing silica in distilled water for 30 seconds. It is.

  The pigment containing alumina having a secondary average particle size as described above has a broad particle size distribution (as a guideline, a range of 1 μm to 9 μm), and can enter between pulp fibers on the surface of the paper support. It is particularly preferable to include a fine particle size. Normally, the binder or cationic resin component in the ink receiving layer penetrates the surface of the paper support at the boundary between the ink receiving layer and the paper support of the formed aqueous ink recording medium. Is coated. Also, the absorption rate of the paper support alone is much higher than that of the ink receiving layer. In such a paper support, the absorption speed becomes very slow, the ink solvent cannot be easily absorbed by the paper support, and often does not show the absorption speed as in the present invention. The absorption speed of the paper support is increased by allowing fine silica to enter the gap formed between the pulp fibers on the surface of the paper support at the boundary between the ink receiving layer of the formed aqueous ink recording medium and the paper support. Thus, it is considered that an effect of assisting the absorption of the ink solvent of the paper support occurs. This action has the effect of suppressing the excessive spread of the landed ink droplets. When the absorption rate to the paper support is slow, the ink droplets spread excessively, and the recording density tends to be lowered and blurring tends to occur.

  The adhesive used in the ink receiving layer is not particularly limited, and proteins such as casein, soybean protein, and synthetic protein; various starches such as starch and oxidized starch; polyvinyl alcohol and derivatives thereof; carboxymethylcellulose, Cellulose derivatives such as methyl cellulose; Conjugated diene resins such as styrene-butadiene resin and methyl methacrylate-butadiene copolymer; Acrylic polymer that is a polymer or copolymer such as acrylic acid, methacrylic acid, acrylic ester, and methacrylic ester Resins; Vinyl-based resins such as ethylene-vinyl acetate copolymers, and the like, and conventionally known adhesives that are generally used for recording media. These may use only 1 type and may use 2 or more types of adhesives together.

  Among these adhesives, polyvinyl alcohol is preferable because of its good adhesion to pigments. Polyvinyl alcohol derivatives such as silanol-modified polyvinyl alcohol and cationized polyvinyl alcohol can also be used as appropriate.

  The mixing ratio of the alumina and the adhesive is 30 to 70 parts by mass, preferably 40 to 60 parts by mass with respect to 100 parts by mass of silica. If the amount of the adhesive is large, the permeation rate decreases.If the amount is small, the amount of adhesive in the boundary region between the paper support and the ink receiving layer is insufficient, and the absorption characteristics cannot be adjusted. The layer strength tends to be weak.

  The ink receiving layer further includes a cationic ink fixing agent, a thickening agent, an antifoaming agent, a wetting agent, a surfactant, a coloring agent, an antistatic agent, a light fastness auxiliary agent, which are used in general coated paper production, Various auxiliary agents such as ultraviolet absorbers, antioxidants, and preservatives are added as appropriate.

The coating amount of the ink receiving layer is not particularly limited, but is preferably 10 g / m ² or more and 20 g / m ² or less. When the coating amount is less than the above lower limit, the sharpness of the image tends to be lowered, and when the coating amount is larger than the upper limit, the coating film strength and the sharpness of the image are liable to be lowered from another viewpoint. Note that a plurality of ink receiving layers may be laminated, and in this case, the ink receiving layer composition may be different between the layers.

  The ink receiving layer can be formed by various known coating apparatuses such as a blade coater, an air knife coater, a roll coater, a bar coater, a gravure coater, a rod blade coater, a lip coater, a curtain coater, and a die coater.

  The drying condition of the ink receiving layer is adjusted by the concentration of the ink receiving layer coating solution, etc., but the behavior of the absorption speed varies depending on the drying condition. The treatment is preferably performed under as strong a drying condition as possible, but excessive drying tends to reduce the color developability. After coating, finishing treatment may be performed using a calendar such as a machine calendar, a super calendar, or a soft calendar. However, such treatment also crushes voids on the surface of the ink receiving layer, so that the absorption speed is regulated. It is optimal to adjust so that it does not go out of range.

“About the second and fourth inventions”
The method for measuring the absorption rate in the second invention of the present invention described in (12) is the same as that in the first invention. In the second invention, it is preferable that the relationship of V1, V2, and V3 satisfies 0 <V2 <V3 <V1. The amount of absorption qa in the first absorption stage V1 is 1.5 μl or more and 2.0 μl or less. Further, the amount of absorption (qb−qa) in the second absorption stage V2 is defined as 0.3 μl or more and 1.0 μl or less. By exhibiting such absorption characteristics, it is possible to promote solid-liquid separation and sufficiently maintain the spread of ink. In the second stage of absorption in the second invention, it is important that the liquid is moderately absorbed in the second stage. This progresses and executes a reliable response to the portion of the ink color material to be fixed. Means that.

  In the third invention of the present invention described in the above (15), the method for measuring the absorption rate is the same as that of the first invention. In the third invention, it is preferable that the relationship of V1, V2, and V3 satisfies 0 <V2 <V1 and 0 <V2 <V3. The amount of absorption qa in the first absorption stage V1 is set to 1.0 μl or more and 2.0 μl or less. Further, the amount of absorption (qb−qa) in the second absorption stage V2 is defined as 0.3 μl or more and 1.0 μl or less. By exhibiting such absorption characteristics, it is possible to promote solid-liquid separation and sufficiently maintain the spread of ink.

  The absorption of the second stage in the third aspect of the present invention is that the liquid is moderately absorbed in the second stage when it is assumed that the third stage of the present invention occurs within a period of 1 second to 8 seconds immediately after the dropping. is important. This means that a reliable response to the portion where the color material of the ink is to be fixed proceeds and is executed. As a numerical value, the amount of absorption (qb-qa) during the period is preferably in the range of 0.3 μl or more and 1.0 μl or less, and preferably in the range of 0.5 μl or more and 1.4 μl or less. Practically, a range of 0.3 μl (or 0.5 μl) to 1.0 μl is preferable.

  In the fourth invention of the present invention described in (18) above, the method for measuring the absorption rate is the same as in the first invention. In the fourth aspect of the invention, the amount of absorption qa in the first absorption stage V1 is set to an absorption amount of 1 μl or more and less than 2.0 μl. Further, the absorption amount qb in the second absorption stage V2 is set to be larger than the absorption quantity qa in the first absorption stage and less than 2.5 μl. The amount of absorption (qb−qa) in the second absorption stage is defined as 0.3 μl or more and 1.4 μl or less. By exhibiting such absorption characteristics, it is possible to promote solid-liquid separation and sufficiently maintain the spread of ink.

  In the second stage of absorption in the fourth invention, it is important that the liquid is moderately absorbed in the second stage. This means that a reliable response to the portion where the color material of the ink is to be fixed proceeds and is executed. As a numerical value, it is desirable that the amount of absorption (qb-qa) in the period is 0.3 μl or more and 1.4 μl or less, and preferably 0.5 μl or more and 1.4 μl or less. That is good. Practically, a range of 0.3 μl (or 0.5 μl) to 1.0 μl is preferable.

  In the second invention to the fourth invention, the invention focuses on the absorption behavior of the ink, except that it is a water-based ink recording medium having a porous layer containing alumina and using a water-based ink containing an anionic coloring material. There is no particular limitation. Known supports, inorganic pigments, cationic compounds, binders and the like can be used as appropriate. The porous layer mainly serves as an ink receiving layer.

  Further, the pH of the porous layer is greater than 5 and 7 or less. The porous layer is provided with a pulp layer as an ink absorbing layer in the lower layer, and the pH of the pulp layer is preferably smaller than the pH of the porous layer, and the paper support has a squeecht size of 5 seconds or more and 50 seconds. Seconds or less are preferred.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples. Moreover, unless otherwise indicated, the part and% in an example are solid content except water, and show a mass part and mass%, respectively.

  The sticky sizing degree of the paper support obtained in each Example and Comparative Example, the print density of the water-based ink recording medium, and the print water resistance were evaluated by the following methods.

In the evaluation, printing on a water-based ink recording medium was performed by the following two printers.
(1) Commercially available pigment ink inkjet printer (trade name: ImagePROGRAF W6200, manufactured by CANON, print mode: thick coated paper / clean).
(2) Commercially available dye ink inkjet printer (trade name: PIXUS ip8600, print mode: matte photo paper / clean) manufactured by CANON.

[Stick human sizing degree]
The stiffness of the paper support was measured according to JIS P8122.

[Print density]
An image (“high-definition color digital standard image XYZ / JIS-SCID”, identification symbol: S6, image name: color chart) issued by the Japanese Standards Association was used. This image was printed with two models, ImagePROGRAF W6200 (using pigment ink) and PIXUS ip8600 (dye ink). Printing density of the highest color tone portion of black and magenta was measured with RD-914 manufactured by GuretagMacbeth.

[Smear]
The blurring of the printing at the border between black and red in two types of ImagePROGRAF W6200 and PIXUS ip8600 was visually evaluated.
Evaluation criteria:
(Double-circle): The blur of printing is not recognized at all and it is an excellent level.
○: There is a slight blur of printing, but it is a level that does not cause a problem in practice.
Δ: Slightly blurring of printing and slightly problematic in practical use.
X: The level at which printing blur is remarkable and becomes a serious problem in practical use.

[Image uniformity]
Two types of black print parts, ImagePROGRAF W6200 and PIXUS ip8600, were visually observed and evaluated according to the following evaluation criteria.
Evaluation criteria:
A: Excellent solid uniformity, deep image, high quality.
○: Solid uniformity and good quality.
Δ: Solid uniformity is slightly bad.
X: Bad.

[PH of paper]
The paper surface pH of the paper support and the water-based ink recording medium was measured. The pH of the paper is J. TAPPI paper pulp test method, no. It is measured by the 6-A method.

<Example 1>
[Paper Support I]
10 parts of calcined kaolin is added to 100 parts of hardwood bleached kraft pulp (freeness 400 ml, CSF: JIS-P-8121), 1.0 part of cationic starch, 0.7 part of rosin sizing agent, 2.0 parts of sulfuric acid band It was added and mixed thoroughly to obtain a papermaking raw material. This paper-making raw material is made into a paper using a long mesh multi-cylinder paper machine, dried to a moisture content of 10%, applied with a 7% aqueous solution of oxidized starch at a size press of 4 g / m ² on both sides, dried, and dried. Paper support I having a basis weight of 190 g / m ² and a Steecht size of 15 seconds was produced by drying to 0%.

[Preparation of ink receiving layer coating solution]
As a pigment, alumina hydrate (manufactured by SASOL, trade name: DISPERAL HP14) was heated and fired at 500 ° C. for 1 hour. When the heat-fired powder was measured by an X-ray diffraction measurement method, it was confirmed that the powder had undergone crystal transition to γ-type alumina. The alumina was treated with a ball mill so that the number of weight average secondary particle diameter of 6.4 μm and weight secondary particle diameter of 2 μm or less was 52% of the total amount of alumina. A coating liquid was prepared by mixing and dispersing 100 parts of the treated alumina, 40 parts of PVA (trade name: PVA117, manufactured by Kuraray Co., Ltd.), 2 parts of nitric acid and water as an adhesive.

[Preparation of recording medium for water-based ink]
Apply the ink receiving layer coating liquid on one side of the paper support I so that the coating amount is 12 g / m ² , dry it, and set the time to start drying to 5 seconds. The basis weight of the produced water-based ink recording medium was 202 g / m ² . Each of the above evaluations was performed on the obtained aqueous ink recording medium. The results are shown in Table 1.

<Example 2>
The externally added sizing agent of the paper support I of Example 1 was changed to oxidized starch: PVA: styrene-acrylic resin = 4: 0.5: 0.5 (5% solution), and the Steecht sizing degree was 50. A water-based ink recording medium was produced in the same manner as in Example 1 except that the time was changed to seconds.

<Example 3>
The pigment in the ink-receiving layer coating liquid of Example 1 is a ball mill so that the number of particles having a weight average secondary particle diameter of 6.9 μm and a weight secondary particle diameter of 2 μm or less is 23% of the total amount of alumina. It was changed to alumina obtained after pulverization and classification. Otherwise, a water-based ink recording medium was produced in the same manner as in Example 1.

<Example 4>
A water-based ink recording medium was produced in the same manner as in Example 1 except that the basis weight of the paper support I in Example 1 was changed to 220 g / m ² . The basis weight of the aqueous ink recording medium was 232 g / m ² .

<Example 5>
A water-based ink recording medium was prepared in the same manner as in Example 1 except that the time until the drying of the water-based ink recording medium preparation of Example 1 was started was changed to 10 seconds.
<Example 6>
A water-based ink recording medium was prepared in the same manner as in Example 1 except that the time until the drying of the water-based ink recording medium preparation of Example 1 was started was changed to 15 seconds.
<Example 7>
A water-based ink recording medium was prepared in the same manner as in Example 1 except that the time until the drying of the water-based ink recording medium preparation of Example 1 was started was changed to 20 seconds.
<Example 8>
A water-based ink recording medium was prepared in the same manner as in Example 1 except that the time until the drying of the water-based ink recording medium preparation of Example 1 was started was changed to 25 seconds.
<Example 9>
A water-based ink recording medium was prepared in the same manner as in Example 1 except that the time until the drying of the water-based ink recording medium preparation of Example 1 was started was changed to 30 seconds.
<Example 10>
50 parts of alumina hydrate particles (manufactured by Daimei Chemical Co., Ltd., product name: C20) and 50 parts of wet-process silica (manufactured by Tosoh Silica Co., Ltd., product name: Nipgel AY603) were mixed. The obtained mixture was treated with a ball mill so that the number of the weight average secondary particle diameter of 5.5 μm and the weight secondary particle diameter of 2 μm or less was 60% of the total amount of the pigment. A water-based ink recording medium was produced in the same manner as in Example 1 except that this pigment was used in place of the pigment of Example 1.

<Comparative Example 1>
[Paper Support II]
A mixture of light calcium carbonate and kaolin 75:25 was added to 100 parts of hardwood bleached kraft pulp (freeness 400 ml, CSF: JIS-P-8121). Furthermore, 1.0 part of cationic starch, 0.04 part of alkenyl succinic anhydride-based neutral sizing agent and 0.5 part of sulfuric acid band were added and mixed thoroughly to obtain a papermaking raw material. This paper raw material was paper-made using a long mesh multi-cylinder paper machine, and the water content was dried to 10%. Further, a 7% solution in which oxidized starch, PVA, and styrene-acrylic resin were mixed at a ratio of 5.2: 1.3: 0.6 was applied with a size press at a rate of 4 g / m ² on both sides, dried, and moisture was added. Paper support B having a basis weight of 190 g / m ² was produced by drying to 0%. The Steecht sizing degree was 300 seconds.

[Preparation of recording medium for water-based ink]
A water-based ink recording medium was prepared in the same manner as in Example 1 except that the paper support I in Example 1 was changed to the paper support II.
<Comparative example 2>
A commercially available recording medium for mat type water-based ink (manufactured by CANON, trade name: thick mouth coated paper). <Comparative Example 3>
A commercially available recording medium for mat type water-based ink (manufactured by EPSON, trade name: photo matte paper / pigment type).
<Comparative Example 4>
A commercially available recording medium for mat type water-based ink (manufactured by EPSON, trade name: PM matte paper).

  Each of the above-mentioned evaluations was performed on these water-based ink recording media. The evaluation results are shown in Table 2. Table 1 and FIG. 2 show the relationship between the absorption speed, the absorption time, and the absorption amount at each absorption stage of the recording medium.

  When the solid print portions of the examples and the comparative examples were observed, both the pigment ink and the dye ink were clear in the examples 1 to 9 and the comparative example 1 with no gloss unevenness, but the comparative examples 1 to 4 were Uneven gloss occurred and the image was unclear. Further, the ink receiving layers of the recording media of Examples 1 to 9 and Comparative Examples 1 to 4 were removed using a razor, and the presence of silica in the boundary area between the paper support and the ink receiving layer was determined using an SEM. And observed. As a result, in Examples 1 to 9, the presence of alumina particles on the paper support side and the ink receiving layer side was confirmed with the interface boundary region between the ink receiving layer and the paper support interposed therebetween.

  As can be seen from these Examples and Comparative Examples, the absorption speed V2 in the second stage of Examples 1 to 9 is 0.12 μl / second or more and 0.23 μl / second or less. Then, it can be understood that the absorption rate V2 in the second absorption stage is faster than the absorption rate 0.01 μl / second for the symbols J and K, and slower than 0.32 μl / second for L. In addition, when the amount of absorption qa in the first absorption stage is 1.6 μl or more, the amount of absorption is relatively large. Therefore, the time of the second absorption stage (tb−ta) is 2 seconds or more, but is relatively short. You can see that it is time. Further, the absorption amount (qb−qa) in the second absorption stage of these examples is 0.39 μl or more and 0.86 μl or less, and is less than half compared with the absorption quantity qa in the first absorption stage. There are many cases. In terms of ink absorption, a relatively large amount of ink absorption is absorbed in a short period of time in the first stage, but the absorbed ink performs proper stagnation and movement with almost no bleeding, It is presumed that the balance that can ensure the improvement of the print density and the image clarity is secured. This is clear from the resulting image. More specifically, in this example, the time tb of the second absorption stage is within 2.5 seconds to 6.1 seconds immediately after the dropping, and the time (tb−ta) of the second absorption stage is 2.2 seconds or more and 5.8 seconds or less.

The previous examples are disclosed as effective examples for so-called thick letters in which the total basis weight of the paper support and the ink receiving layer is 180 g / m ² or more and 300 g / m ² or more. On the other hand, an embodiment showing that the present invention is effective for a recording medium having a normal thickness will be described in addition to the following. In the following examples, the paper support was specifically reduced in thickness. However, the technical idea of the present invention does not depend on the thickness or basis weight, and satisfies the constituent requirements in each claim. It has been confirmed that the effects of each claim can be obtained. Typical examples are shown below.

[Paper Support III]
Similarly to the paper support I, 10 parts of calcined kaolin was added to 100 parts of hardwood bleached kraft pulp (400 ml freeness, CSF: JIS-P-8121). Furthermore, 1.0 part of cationic starch, 0.7 part of rosin sizing agent and 2.0 parts of sulfuric acid band were added and mixed well to obtain a papermaking raw material. This paper raw material was paper-made using a long mesh multi-cylinder paper machine, and the water content was dried to 10%. Furthermore, a paper support III having a basis weight of 150 g / m ² and a Steecht size of 10 seconds was applied by applying a 7% aqueous solution of oxidized starch with a size press at 4 g / m ² on both sides and drying. Manufactured.

<Example 10>
A water-based ink recording medium was produced in the same manner as in Example 1 except that the paper support III was changed to Example 1. The basis weight of the aqueous ink recording medium was 162 g / m ² .
<Example 11>
A water-based ink recording medium was prepared in the same manner as in Example 1 except that the paper support III was changed to Example 1 and the time until drying was started was changed to 10 seconds.
<Example 12>
A water-based ink recording medium was produced in the same manner as in Example 1 except that the paper support III was changed to Example 1 and the time until drying was started was changed to 3 seconds.
<Example 13>
The recording medium for water-based ink was changed to the paper support III of Example 1, the time until the drying was started was changed to 3 seconds, and the temperature of the drying was changed to 160 ° C. in the same manner as in Example 1. A medium was made.
<Example 14>
A water-based ink recording medium was produced in the same manner as in Example 1, except that the paper support III was changed to Example 1 and the drying was changed to 160 ° C.

[Paper Support IV]
Similarly to the paper support I, 10 parts of calcined kaolin was added to 100 parts of hardwood bleached kraft pulp (400 ml freeness, CSF: JIS-P-8121). Furthermore, 1.0 part of cationic starch, 0.7 part of rosin sizing agent and 2.0 parts of sulfuric acid band were added and mixed well to obtain a papermaking raw material. This paper raw material is made into a paper using a long mesh multi-cylinder paper machine, dried to a moisture content of 10%, coated with a 7% aqueous solution of oxidized starch at a rate of 4 g / m ² on both sides, dried, Paper support III having a basis weight of 127 g / m ² and a Steecht size of 9 seconds was produced by drying to 0%.
<Example 15>
A water-based ink recording medium was produced in the same manner as in Example 1 except that the paper support IV was changed to that in Example 1. The basis weight of the aqueous ink recording medium was 139 g / m ² .
<Example 16>
A water-based ink recording medium was produced in the same manner as in Example 1, except that the paper support IV was changed to Example 1 and the time until drying was started was changed to 10 seconds.
<Example 17>
A water-based ink recording medium was produced in the same manner as in Example 1, except that the paper support IV was changed to 3 and the time until the drying was started was changed to 3 seconds.
<Example 18>
A change to the paper support IV of Example 1, the time until the start of drying was changed to 3 seconds, and the drying was performed in the same manner as in Example 1 except that the temperature was changed to 160 ° C. A medium was made.
<Example 19>
A water-based ink recording medium was produced in the same manner as in Example 1 except that the paper support IV was changed to Example 1 and the drying was changed to 160 ° C.

  Each of the above-mentioned evaluations was performed on these water-based ink recording media. The evaluation results are shown in Table 3. Table 4 and FIG. 3 show the relationship between the absorption speed, the absorption time, and the absorption amount at each absorption stage of the recording medium.

As can be seen from the examples, when the qa (1.3 μl or more) in the first absorption stage in the present invention is less than 1.60 μl, the amount of absorption in the first absorption stage is relatively small. Therefore, it can be understood that the color material fixing corresponding to the image density is performed by gently absorbing the absorption amount (qb−qa) in a relatively long time in the second absorption stage. Specifically, the occurrence of tb, which is the start time of the third absorption stage, is 9.5 seconds or more, and the absorption rate V2 of the second absorption stage is preferably 0.01 μl / second or more and smaller than 0.12 μl / second. . In N, O, P, Q, R, S, T, U, V, and W, the tb of the second absorption stage is 9.6 to 13.5 seconds, and the absorption speed V2 is 0.06 μl. / Second or more and 0.10 μl / second or less. This condition is a more effective condition for the present invention. In particular, this range shows that the present invention is effective for a so-called normal thickness recording medium having a basis weight of 130 g / m ² or more and less than 180 g / m ² .

  As can be seen from these tables, in the embodiment of the present invention, the absorption rate V2 of the second absorption stage is faster than the absorption rate of J and K of 0.01 μl / second, and faster than the absorption rate of L of 0.32 μl / second. I understand that it is slow. Specifically, from the table, A, B, C, D, E, F, G, H, and I of the examples of the present invention are 12 to 17 times faster than the absorption rates of J and K, and L The absorption speed is about 1/2 times slower. In N, O, P, Q, R, S, T, U, V, and W, the absorption speed of the second absorption stage is 5 to 8 times faster than the absorption speed of J and K. , L is about 1/6 to 1/4 times slower. In other words, the “moderate” speed we say is between 0.05 μl / second and 0.17 μl / second. This condition is a more effective condition for the present invention.

As described above, a first absorption stage for absorbing a droplet of 4 μl of distilled water dropped on the surface of the ink receiving layer at a first absorption rate V1 (μl / sec) within 1 second immediately after the dropping, A second absorption stage that absorbs at a second absorption speed V2 (μl / sec) after one absorption stage for at least 2 seconds, and a third absorption speed V3 (μl / sec) after the second absorption stage. And the absorption of the liquid droplets from the first absorption stage to the third absorption stage is expressed by the formula:
0 <V2 <V1
0 <V2 <V3
And an inflection point that shifts from the first absorption stage to the second absorption stage is defined as a (inflection point a), and the inflection point that shifts from the second absorption stage to the third absorption stage. Is b (inflection point b), the final point of the third absorption stage is c (final point c), the amount of absorption at each point is qa, qb, qc, and the time to each inflection point or final point Is ta, tb, tc, the absorption amount qa at the inflection point a is 1 μl or more and less than 2.0 μl, and the absorption amount qb at the inflection point b is larger than the absorption amount qa at the first absorption stage. When the amount of absorption (qb-qa) is less than 2.5 μl and the absorption amount (qb−qa) in the second absorption stage is 0.3 μl or more and 1.4 μl or less, the effect of the present invention can be obtained regardless of the thickness and basis weight. can get. More specifically, the second support stage occurs after 9.5 seconds immediately after the dropping of the droplets, and the time tc of the final point of the third absorption stage occurs within 14.5 seconds. It was found that the effect of the present invention can be sufficiently obtained even in a system in which the thickness of the film is reduced.

It is explanatory drawing which measured the characteristic of the conventional recording medium based on the determination method of this invention. It is explanatory drawing explaining the absorption characteristic graph of the recording medium of the Example of this invention. It is explanatory drawing explaining the absorption characteristic graph of the recording medium of the other Example of this invention.

Explanation of symbols

A: Absorption speed of the aqueous ink recording medium obtained in Example 1 B: Absorption speed of the aqueous ink recording medium obtained in Example 2 C: Absorption of the aqueous ink recording medium obtained in Example 3 Speed D: Absorption speed of the aqueous ink recording medium obtained in Example 4 E: Absorption speed of the aqueous ink recording medium obtained in Example 5 F: Absorption speed of the aqueous ink recording medium obtained in Example 6 Absorption speed G: Absorption speed of aqueous ink recording medium obtained in Example 7 H: Absorption speed of aqueous ink recording medium obtained in Example 8 I: Recording medium for aqueous ink obtained in Example 9 Absorption speed J: Water-based ink recording medium obtained in Example 10 Absorption speed K: Water-based ink recording medium obtained in Comparative Example 1 Absorption speed L: Water-based ink recording obtained in Comparative Example 2 Absorption speed M of medium: recording medium for water-based ink obtained in Comparative Example 3 Absorption speed N: Absorption speed of the water-based ink recording medium obtained in Comparative Example 4 O: Absorption speed of the water-based ink recording medium obtained in Example 11 P: Water-based ink recording obtained in Example 12 Absorption speed of medium Q: Absorption speed of recording medium for water-based ink obtained in Example 13 R: Absorption speed of recording medium for water-based ink obtained in Example 14 S: For water-based ink obtained in Example 15 Absorption speed T of recording medium: Absorption speed of recording medium for water-based ink obtained in Example 16 U: Absorption speed of recording medium for water-based ink obtained in Example 17 V: Water-based ink obtained in Example 18 Absorption speed of recording medium for water W: Absorption speed of recording medium for water-based ink obtained in Example 19 X: Absorption speed of recording medium for water-based ink obtained in Example 20

Claims (30)

An ink-receiving layer having a porous layer containing alumina is provided on the surface of a paper support, and is a recording medium for water-based ink recorded using a water-based ink containing the ink coloring material, wherein the ink-receiving layer A first absorption stage in which a droplet having 4 μl of distilled water dropped on the surface is absorbed at a first absorption speed V1 (μl / sec) within 1 second immediately after the dropping, and a second absorption speed after the first absorption stage. A second absorption stage that absorbs at V2 (μl / sec) for at least 2 seconds, and a third absorption stage that absorbs at a third absorption rate V3 (μl / sec) after the second absorption stage, To absorb the 4 μl of distilled water droplets, and the absorption of the droplets from the first absorption stage to the third absorption stage is represented by the formula:
0 <V2 <V1
0 <V2 <V3
And the second absorption rate V2 (μl / sec) is greater than 0.01 (μl / sec) and less than 0.32 (μl / sec),
The inflection point that transitions from the first absorption stage to the second absorption stage is a, the inflection point that transitions from the second absorption stage to the third absorption stage is b, and the final point of the third absorption stage Is c, the amount of absorption at each inflection point is qa, qb, qc, and the time to each inflection point or final point is ta, tb, tc,
The water-based ink is characterized in that the absorption amount qa at the inflection point a is 1.3 μl or more and less than 2.0 μl, and the absorption amount qb at the second inflection point b is 2.0 μl or more and less than 2.5 μl. Recording media.   The water-based ink recording medium according to claim 1, wherein the inflection point a occurs within 0.5 seconds immediately after dropping.   The water-based ink recording medium according to claim 1, wherein an absorption amount (qb−qa) in the second absorption stage is 0.3 μl or more and 1.4 μl or less.   The water-based ink recording medium according to claim 1, wherein an absorption amount (qb−qa) in the second absorption stage is 0.5 μl or more and 1.0 μl or less.   The water-based ink recording medium according to claim 1, wherein the amount of absorption qa at the inflection point a is 1.5 μl or more. 6. The water-based ink recording according to claim 5, wherein the water-based ink recording medium has a basis weight of 180 g / m ² or more and 300 g / m ² or less, and the inflection point b occurs within 8 seconds immediately after dropping. Medium.   The aqueous ink recording medium according to any one of claims 1 to 6, wherein the paper support has a Steecht sizing degree of 5 seconds or more and 50 seconds or less. The pH _{B of the} ink receiving layer is represented by the formula:
5 <pH _B ≦ 7
The water-based ink recording medium according to any one of claims 1 to 6, wherein: The pH _{A of the} paper support and the pH _{B of the} ink receiving layer are expressed by the formula:
1 <(pH _B −pH _A ) <4
The water-based ink recording medium according to claim 8, wherein:   The second absorption rate V2 (μl / sec) is a rate greater than 0.05 (μl / sec) and less than 0.23 (μl / sec). The recording medium for water-based ink according to any one of the above.   7. The second absorption rate V2 (μl / sec) is a rate greater than 0.12 (μl / sec) and less than 0.23 (μl / sec). The recording medium for water-based ink according to any one of the above. A water-based ink recording medium comprising a paper support having a Steecht sizing degree of 5 seconds or more and 50 seconds or less, and an ink receiving layer containing alumina and an adhesive on the surface of the paper support;
A first absorption stage in which a droplet of 4 μl of distilled water dropped on the surface of the ink receiving layer is absorbed at a first absorption speed V1 (μl / sec) within 1 second immediately after the dropping, and after the first absorption stage A second absorption stage absorbing at a second absorption rate V2 (μl / sec) for at least 2 seconds and a third absorption rate V3 (μl after the second absorption stage and occurring within 8 seconds immediately after the dropping. / Sec) absorbs the 4 μl droplets by the third absorption stage, and absorption of the droplets from the first absorption stage to the third absorption stage is expressed by the formula:
0 <V2 <V3 <V1
And the second absorption rate V2 (μl / sec) is greater than 0.01 (μl / sec) and less than 0.32 (μl / sec),
The inflection point that transitions from the first absorption stage to the second absorption stage is a, the inflection point that transitions from the second absorption stage to the third absorption stage is b, and the final point of the third absorption stage Is the amount of absorption at each inflection point or final point, qa, qb, qc, and the time to each inflection point or final point is ta, tb, tc,
The absorption qa at the inflection point a is 1.5 μl or more and 2.0 μl or less,
The water-based ink recording medium, wherein an absorption amount (qb-qa) in the second absorption stage is 0.3 μl or more and 1.0 μl or less. The pH _{B of the} ink receiving layer is represented by the formula:
5 <pH _B ≦ 7
The pH _{A of the} paper support and the pH _{B of the} ink receiving layer are expressed by the formula:
1 <(pH _B −pH _A ) <4
The basis weight of the paper support and the ink receiving layer is within a range of 180 g / m ² or more and 300 g / m ² or less, and the recording medium for water-based ink according to claim 12.   15. The second absorption rate V2 (μl / sec) is a rate greater than 0.12 (μl / sec) and less than 0.23 (μl / sec). A recording medium for water-based ink. A water-based ink recording medium having an ink receiving layer having a porous layer containing alumina on the surface and recorded using a water-based ink containing an anionic coloring material,
A first absorption stage in which a droplet of 4 μl of distilled water dropped on the surface of the ink receiving layer is absorbed at a first absorption speed V1 (μl / sec) within 1 second immediately after the dropping, and after the first absorption stage A second absorption stage of absorbing at a second absorption speed V2 (μl / sec) for 2 seconds or more, and a third absorption after the second absorption stage and absorbing at a third absorption speed V3 (μl / sec) Absorbs 4 μl of distilled water droplets according to the step, and the absorption of the droplets from the first absorption step to the third absorption step is:
0 <V2 <V1
0 <V2 <V3
And the second absorption rate V2 (μl / sec) is greater than 0.01 (μl / sec) and less than 0.32 (μl / sec),
The inflection point for transition from the first absorption stage to the second absorption stage is a, the inflection point for transition from the second absorption stage to the third absorption stage is b, and the final point of the third absorption stage V3 Is c, the amount of absorption at each inflection point is qa, qb, qc, and the time to each inflection point or final point is ta, tb, tc,
The absorption amount qa at the inflection point a is 1.3 μl or more and 2.0 μl or less, and the absorption amount (qb−qa) according to the second absorption stage is 0.3 μl or more and 1.0 μl or less. A water-based ink recording medium.   16. The water-based ink according to claim 15, wherein the second absorption speed V2 (μl / sec) is a speed greater than 0.05 (μl / sec) and smaller than 0.23 (μl / sec). Recording media.   17. The water-based ink recording medium according to claim 16, wherein the paper support has a Steecht sizing degree of 5 seconds or more and 50 seconds or less. A water-based ink recording medium comprising a paper support and an ink receiving layer provided on the surface of the paper support and containing alumina and an adhesive;
A first absorption stage in which a droplet of 4 μl of distilled water dropped on the surface of the ink receiving layer is absorbed at a first absorption speed V1 (μl / sec) within 1 second immediately after the dropping, and after the first absorption stage A second absorption stage that absorbs at a second absorption rate V2 (μl / sec) for at least 2 seconds, and after the second absorption stage, the absorption is performed at a third absorption rate V3 (μl / sec). The absorption of the droplets from the first absorption stage to the third absorption stage is expressed by the formula:
0 <V2 <V1
0 <V2 <V3
And the second absorption rate V2 (μl / sec) is greater than 0.01 (μl / sec) and less than 0.32 (μl / sec),
The inflection point that transitions from the first absorption stage to the second absorption stage is a, the inflection point that transitions from the second absorption stage to the third absorption stage is b, and the final point of the third absorption stage Is c, the amount of absorption at each point is qa, qb, qc, and the time to each inflection point or final point is ta, tb, tc,
The absorption amount qa at the inflection point a is 1.3 μl or more and less than 2.0 μl, the absorption amount qb at the inflection point b is more than the absorption amount qa of the first absorption stage and less than 2.5 μl, and The water-based ink recording medium, wherein an absorption amount (qb-qa) in the second absorption stage is 0.3 μl or more and 1.4 μl or less.   19. The water-based ink recording medium according to claim 18, wherein an absorption amount (qb-qa) in the second absorption stage is 0.38 μl or more and 1.0 μl or less.   20. The water-based ink recording medium according to claim 19, wherein the amount of absorption qa at the inflection point a is 1.5 μl or more.   19. The water-based ink recording medium according to claim 18, wherein the second absorption stage occurs within 2.0 seconds or more and 13.5 seconds immediately after the dropping of the droplets.   The water-based ink recording medium according to claim 21, wherein the time tc of the third absorption stage is within 14.1 seconds from immediately after the dropping of the droplet.   21. The method according to claim 20, wherein the second absorption stage occurs within 6.1 seconds immediately after the dropping of the droplet, and the final time tc of the third absorption stage occurs within 8 seconds. The recording medium for water-based ink as described.   The second absorption stage occurs after 9.5 seconds immediately after the dropping of the droplet, and the time tc of the final point of the third absorption stage occurs within 14.5 seconds. 19. A recording medium for water-based ink according to item 19.   25. The second absorption rate V2 (μl / sec) is a rate greater than 0.05 (μl / sec) and less than 0.23 (μl / sec). The recording medium for water-based ink according to any one of the above.   24. The water-based ink according to claim 23, wherein the second absorption speed V2 (μl / sec) is greater than 0.12 (μl / sec) and smaller than 0.23 (μl / sec). Recording media.   25. The water-based ink according to claim 24, wherein the second absorption speed V2 (μl / sec) is greater than 0.05 (μl / sec) and smaller than 0.09 (μl / sec). Recording media. A method for determining the ink absorption characteristics of a water-based ink recording medium having a paper support and an ink receiving layer containing alumina and an adhesive on the surface of the paper support,
A first absorption stage for absorbing a droplet obtained by dropping 4 μl of distilled water on the surface of the ink-receiving layer of the water-based ink recording medium at a first absorption speed V1 (μl / sec) within 1 second immediately after the dropping; A second absorption stage that absorbs at a second absorption speed V2 (μl / sec) after one absorption stage for at least 2 seconds, and a third absorption speed V3 (μl / sec) after the second absorption stage. Being absorbed by a third absorption stage that absorbs at
The second absorption rate V2 (μl / sec) is greater than 0.01 (μl / sec) and smaller than 0.32 (μl / sec);
An inflection point a that transitions from the first absorption stage to the second absorption stage, an inflection point b that transitions from the second absorption stage to the third absorption stage, and a final point c of the third absorption stage are measured. When the amount of absorption at each point is qa, qb, qc, and the time until each inflection point or final point is ta, tb, tc,
The amount of absorption qa in the first absorption stage is 1 μl or more and less than 2.0 μl;
The absorption qb of the second absorption stage is greater than the absorption qa of the first absorption stage and less than 2.5 μl;
Determining the ink absorption characteristics of the water-based ink recording medium, comprising determining whether the amount of absorption (qb-qa) in the second absorption stage is 0.3 μl or more and 1.4 μl or less. Method.   29. The water-based ink according to claim 28, wherein the second absorption speed V2 (μl / sec) is a speed greater than 0.05 (μl / sec) and smaller than 0.23 (μl / sec). For determining ink absorption characteristics of recording medium for printing. The basis weight of the paper support and the ink receiving layer is within a range of 180 g / m ² or more and 300 g / m ² or less, and the second absorption speed V2 (μl / sec) is 0.12 (μl / sec). 29. The method for determining ink absorption characteristics of a water-based ink recording medium according to claim 28, wherein the speed is greater than (sec) and less than 0.23 (μl / sec).

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