JP4722793B2 - Method for determining ink absorption characteristics of recording medium for water-based ink - Google Patents

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. Conventionally, water-based dye inks that are excellent in color developability are used as inks for ink jet printers, but in general, water-based dye inks tend to fade due to light, etc. 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, it is said that the ink absorption is faster than the gloss type and the recording speed in the printer can be set faster. Along with the widespread use, when full-color images are recorded not only on the gloss type but also on mat type recording media, the amount of ink per unit area increases as compared to a single color image. However, if you try to meet this requirement, there will be a problem that the color and blur of each color will be brought about.

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. Although it is conceivable to employ a recording medium that has been formed to enhance recording suitability, it does not provide a water-based ink recording medium 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 problem 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 included in a novel water-based ink recording medium that has not existed before.
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. Although the existence was examined, it was 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 Table 1 as J, K, L, and M. FIG. 1 (J, K, L, and M are conventional water-based ink recording media. The vertical axis indicates the amount of absorption, and the horizontal axis indicates the time after dropping. As can be seen from FIG. 1, since the conventional recording media indicated by the symbols J and K have a long period in which there is almost no liquid absorbency, the result is that the ink that has substantially overflowed disturbs the image. Are correlated. As a mechanism of such a phenomenon, the water-based ink recording medium of the present invention has a three-layer structure having a high-density boundary region newly provided with a filter function in the boundary region between the paper support and the ink receiving layer. However, the conventional recording medium indicated by symbols J and K has a two-layer structure in which the paper support and the ink receiving layer are simply joined together, and is a filter formed by the interface of the ink receiving layer. Since the function is too strong, it is assumed that such absorption characteristics are 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. As a mechanism, an ink receiving layer having a small binder component is dried at a low temperature for a long time, so that the binder component penetrates the entire paper support and has a filter function at the interface between the ink receiving layer and the paper support. Is formed at a low density, so it is actually a two-layer structure, but it is presumed that such absorption characteristics are 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 a water-based ink having a paper support, an ink receiving layer containing an amorphous silica provided on the surface of the paper support, an adhesive, and a reactive substance with an ink coloring material. A first absorption stage for absorbing a droplet obtained by dropping 4 μl of distilled water onto the surface of the ink receiving layer at a first absorption rate V1 (μl / sec) within 1 second immediately after the dropping; After the first absorption stage, absorption is performed at the second absorption speed V2 (μl / sec), and after the second absorption stage, absorption is performed at the third absorption speed V3 (μl / sec). An inflection point that is absorbed by the third absorption stage and is a transition point from the first absorption stage V1 to the second absorption stage V2, and a transition point from the second absorption stage V2 to the third absorption stage V3. The point is b, the final point of the third absorption stage V3 is c, and the amount of absorption at each point qa, a qb, qc, ta time points, tb, a method of determining the absorption properties of the water-based ink recording media when the 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, or a change point at which the absorption rate V2 changes to the absorption rate V3, and changes from V1 to V2 and from V2 to V3. When the change has a gradually changing inflection region, for example, it indicates an intersection point perpendicular to the approximate curve of the inflection region from the intersection point obtained by extending the approximate straight line of V1 and V2.

In general, in order to suppress the blurring of the paper support, which is likely to occur when applying paint, etc., it is supposed to use a paper support with a high degree of sizing. Attempts to use a low-stiffness paper support, and neutral paper with a low color change of the paper support is generally used, whereas acid paper is used. Also tried.
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 the 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, and I in FIG. 2 are graphs of the measurement results shown in Table 1 below, and N, O, P, Q, R, and N in FIG. S, T, U, V, and W are graphs of the measurement results shown in Table 3 below, and all indicate the absorption characteristics of the recording medium for water-based ink of the present invention.

As is clear from Tables 1, 2, 3, 4 and FIGS. 1, 2, and 3, the water-based ink recording medium of the present invention has an absorption characteristic clearly different from that of conventional water-based ink recording media. Even if the actual printed matter is compared, it is confirmed that the printed product on the recording medium of the present invention has the best print quality, and the absorption characteristics and actual images shown in FIGS. And found that there is a correlation.
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.
As described above, as a result of further intensive studies to investigate the properties including all of the ink receiving layer and the paper support, it was found that the absorption speed of the water-based ink recording medium must satisfy a specific condition. The present invention has been reached with respect to a method for determining the ink absorption characteristics of the water-based ink recording medium and the water-based ink recording medium described below.

The present invention relates to an invention for a method for determining ink absorption characteristics of a water-based ink recording medium selected from the following inventions .
(1) An ink receiving layer having a porous layer containing a reactive substance with an inorganic pigment and an ink coloring material is provided on the surface of the paper support, and recording is performed using an aqueous ink containing the ink coloring material. A first absorption stage, which is a recording medium for water-based ink, that absorbs a droplet of 4 μl of distilled water dropped on the surface of the ink receiving layer at a first absorption speed V1 (μl / sec) within 1 second immediately after the dropping. A second absorption stage for at least 2 seconds or more after absorption at the second absorption speed V2 (μl / sec) after the first absorption stage, and a third absorption speed V3 (after the second absorption stage). The 4 μl of distilled water droplets are absorbed by the third absorption stage that performs absorption at μl / sec), and the absorption of the liquid droplets from the first absorption stage to the third absorption stage is expressed by the equation 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 expressed 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 expressed 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 paper support having a Steecht sizing degree of 5 seconds to 50 seconds, and an ink receiving layer containing a reactive substance of amorphous silica, an adhesive, and an ink coloring material on the surface of the paper support. A water-based ink recording medium,
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), the 4 μl droplet is absorbed by the third absorption stage, and the absorption of the liquid droplets from the first absorption stage to the third absorption stage is expressed by the equation 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 ink receiving layer has a pH _B of 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 thickness of the ink receiving layer is 25 μm or more and 35 μm or less, and the basis weight of the paper support and the ink receiving layer is within the range of 180 g / m ² or more and 300 g / m ² or less. 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 recording for water-based ink having an ink receiving layer having a porous layer containing a reactive substance with an inorganic pigment and an ink coloring material on the surface, and recording using a water-based ink containing an anionic coloring material A medium,
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 depending on the stage, and the absorption of the droplets from the first absorption stage to the third absorption stage is expressed by the equation 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 comprising: a paper support; and an ink receiving layer containing a reactive substance of amorphous silica, an adhesive, and an ink color material provided 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 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 equation 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) Ink absorption characteristics of a water-based ink recording medium having a paper support and an ink receiving layer containing a reactive substance of amorphous silica, an adhesive, and an ink color material on the surface of the paper support are determined. A method,
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).

  The recording medium of the present invention preferably has the conditions described in each claim as a whole. However, the recording medium is slightly different from the conditions of the present invention due to unexpected factors such as dust. Even if is scattered, it is included in the present invention as long as the effect of implementing the present invention is substantially obtained as a whole. 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 substantial liquid permeation state mainly at the second absorption stage in the boundary region between the ink receiving layer and the paper support, which has not been heretofore known. That is, a predetermined amount of liquid penetrating the ink receiving layer (in the present invention, 1.3 μl or more and 2 μl or less, preferably 1.5 μl or more in the above 4 μl of distilled water due to one factor affecting the image density). In the range satisfying the requirements defined in the claims of the present invention (for example, the speed V2 of the second absorption stage, etc.) The presence of the corresponding second absorption stage has the greatest feature. 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. And, at this inflection point, it is possible to diffuse the solvent and water which are no longer needed by starting the third absorption stage in which the rapid absorption to the paper support is performed, and the substantial solid-liquid separation function. Seems to have been demonstrated. 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, since the second absorption stage capable of absorbing water-based ink moderately is provided, the basis weight of the water-based ink recording medium is in a wide range from 130 g / m ^{2 to} 300 g / m ^2. When printing was performed with either water-based dye ink or water-based pigment ink, the blur was minimized and 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 speed from the first absorption stage to the third absorption stage is such that the recording medium for water-based ink placed in an environment of 23 ° C. and 50% RH for 24 hours is Fibro. Using a dynamic absorption tester (DAT) manufactured by the company, 4 μl (microliter) of distilled water (23 ° C.) from the height of about 1 cm to the surface of the ink receiving layer with a microsyringe in an environment of 23 ° C. and 50% RH. ) Dropping one drop, taking a picture of the outline of the dropped drop with a video camera, analyzing the shot image, obtaining the volume of the drop, and using the values obtained for the amount of absorption and the absorption time from the change in volume over time is there.
The volume calculation is given by the equation: 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, dripping of several pl (picoliter), which is often applied in recent printers, cannot be evaluated sufficiently because the absorption is instantaneous, and photographic images on a mat type water-based ink recording medium can be used. Since printing is performed with ink of a plurality of colors (for example, six colors) and at a faster speed than the gloss type printing, the amount of ink is increased. 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. In the present invention, the separation function of the colorant and the solvent in the ink at the time of recording is determined by obtaining a large change in the absorption speed.

  Further description will be made based on FIGS. 2 and 3. The 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. If the amount of ink absorption is too small, the second absorption is performed. Since the amount of ink that contributes to the effects in the stage and the third absorption stage becomes excessive, it is optimal that the absorption amount qa in the first absorption stage is 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.

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. Compared with the code B using the paper support, the code A (15-second paper support) has a shorter time for the second absorption stage. When different ink-receiving layer coating liquids are used on the same paper support, the average particle diameter of amorphous silica is almost the same, but it contains fine components when compared to code C using silica with few fine components. The second absorption stage is shorter when the code A using silica 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 sizing degree is smaller. Probably, the absorption characteristic of 1st invention is a phenomenon generate | occur | produced by using an amorphous silica like the prior art. In the present invention, when the ink receiving layer is formed on the paper support, the boundary portion penetrates the adhesive component into the gap formed by the pulp-pulp or pulp-filler that is present near the surface of the paper support. In addition, 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 by the action of filling the amorphous silica component. Due to the penetration of the adhesive component, the time of the second absorption stage can be lengthened, and by filling the amorphous silica, it is considered that the absorption to the inside of the paper support is triggered and the process proceeds to the third absorption stage. .
The reason why the second absorption stage is longer in the code C using the silica having less fine components than in the code A using the silica containing the fine components is that there is no trigger for absorption inside the paper support. This is considered to be sufficient.

The absorption rate in the first absorption stage can be adjusted by using amorphous silica as in the prior art, but can be adjusted by controlling the content of amorphous silica.
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 is different between the case where the coloring material is a dye and the case where the pigment is a pigment, pH _B indicating the pH of the ink receiving layer is
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 pH _A indicating the pH of the paper support and pH _B of the ink receiving layer is 1 <(pH _B −pH _A ) <4.
If satisfied, the color developability tends to be excellent.
It is possible to satisfy the above conditions by the production conditions of the paper support, the preparation of the ink receiving layer coating liquid, and the like.

The thickness of the ink receiving layer is not particularly limited, but is particularly preferably 25 μm or more and 35 μm or less. Incidentally, when the thickness of the ink receiving layer is 25 μm or more, it is preferable because the amount of ink absorbed by a printer that draws a color balance with six or more colors of ink can be secured. However, if the thickness is larger than 35 μm, the recording density with dye ink decreases. From another point of view, the coating strength decreases.
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 Because the strength is weak, even if the ink receiving layer of the present invention is formed, the effect of improving the color developability cannot be obtained for both the dye ink and the pigment ink. 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 an inorganic pigment, an adhesive, and a substance reactive with the ink coloring material, such as a cationic ink fixing agent.
As the inorganic pigment, for example, clay, kaolin, calcined kaolin, talc, calcium carbonate, magnesium carbonate, aluminum hydroxide, calcium hydroxide, amorphous silica, titanium oxide and the like can be used as appropriate.
Among these, amorphous silica is preferable as an inorganic pigment because it is excellent in color developability and ink absorbability compared to other pigments. The method for producing amorphous silica is not particularly limited, and may be produced by any method of electric arc method, dry method, and wet method (precipitation method, gel method), but wet method silica is used for pigment ink. This is preferable because it is suitable for both water-based ink recording media and water-based ink recording media for dye inks.

The average particle diameter of the secondary particles of the amorphous silica is not particularly limited as long as it can form the ink receiving layer of the water-based ink recording medium satisfying the absorption characteristics of the present invention. It is preferably 4 μm or more and 8 μm or less. When the average particle diameter of the secondary particles of the amorphous silica exceeds 10 μm, the sharpness of the image is reduced in both the inkjet recording medium for the dye ink and the aqueous ink recording medium for the pigment ink. There is a tendency that the roughness is conspicuous 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 addition, in this invention, the average particle diameter of a silica 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.

  The amorphous silica having a secondary average particle diameter as described above has a broad particle size distribution (as a guideline, a range of 1 μm or more and 9 μm or less), and can enter between pulp fibers on the surface of the paper support. It is particularly preferable that the particle diameter is included. 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. In addition, 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 its derivatives; carboxymethylcellulose, Cellulose derivatives such as methyl cellulose; Conjugated diene resins such as styrene-butadiene resin and methyl methacrylate-butadiene copolymer; Polymers or copolymers such as acrylic acid, methacrylic acid, acrylic acid ester, and methacrylic acid ester. Resins; Vinyl-based resins such as ethylene-vinyl acetate copolymers, and the like, and conventionally known hydrophilic adhesives 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 blending ratio of the silica 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.

On the other hand, the reactive substance with the ink color material used in the ink receiving layer is not particularly limited, and a cationic ink fixing agent is particularly preferable. Examples of the cationic ink fixing agent include (1) polyalkylene polyamines such as polyethylene polyamine and polypropylene polyamine or derivatives thereof, and (2) acrylic heavy compounds having secondary amino groups, tertiary amino groups, and quaternary ammonium groups. (3) Polyvinylamine, polyvinylamidine, 5-membered ring amidines, (4) Dicyan cationic resin represented by dicyandiamide-formalin copolymer, (5) Polyamine represented by dicyandiamide-polyethyleneamine copolymer system cationic resin, (6) dimethylamine - epichlorohydrin copolymer, (7) diallyldimethylammonium -SO ₂ copolymer, (8) diallylamine salt -SO ₂ copolymer, (9) dimethyldiallylammonium chloride polymer, (10) Heavy weight of allylamine salt (11) Homopolymer or copolymer of vinylbenzyltriallyl ammonium salt, (12) Dialkylaminoethyl (meth) acrylate quaternary salt copolymer, (13) Acrylamide-diallylamine salt copolymer, (14) ) Examples include commercially available products such as aluminum salts such as polyaluminum chloride and polyaluminum acetate, which are used alone or in combination.

  Even in these cationic ink fixing agents, it is preferable to use an acrylamide-diallylamine copolymer and a diallyldimethylammonium chloride polymer in combination. It is preferable to use an acrylamide-diallylamine copolymer and a diallyldimethylammonium chloride polymer in combination because of excellent color developability when recorded with pigment ink, color developability when recorded with dye ink, and storage stability. The improvement in color developability is thought to be because the coloring material in the ink can be fixed in the ink receiving layer without aggregating.

  The blending amount of the cationic ink fixing agent is preferably 5 parts by mass or more and 60 parts by mass or less, more preferably 20 parts by mass or more and 50 parts by mass or less with respect to 100 parts by mass of the pigment. When the amount of the ink fixing agent is less than 5 parts by mass, the sharpness of the image tends to be lowered, and when it exceeds 60 parts by mass, the appearance after coating tends to be lowered.

  For the ink-receiving layer, thickeners, antifoaming agents, wetting agents, surfactants, colorants, antistatic agents, light fastness aids, UV absorbers, antioxidants used in general coated paper production Various auxiliary agents such as preservatives and preservatives are appropriately added. The porous layer is a layer in which pores on the particle surface of the inorganic pigment, or gaps or voids between the particles exist even if it contains a water-soluble adhesive.

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 in the previous period 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.
Also in the third aspect of the invention, it is important that the absorption of the liquid in the second stage is moderately absorbed in the second stage. This means that the ink color material progresses and executes a reliable response to the portion to be fixed. As a numerical value, the absorption amount (qb−qa) during the period is preferably in the range of 0.3 μl or more and 1.0 μl or less, preferably in the range of 0.5 μl or more and 1.4 μl or less. Is within. 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 1.3 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.
Also in the fourth aspect of the invention, it is important that the absorption of the liquid in the second stage is moderately absorbed in the second stage. This means that the ink color material progresses and executes a reliable response to the portion to be fixed. As a numerical value, it is desired that the amount of absorption (qb-qa) during the period is 0.3 μl or more and 1.4 μl or less, preferably 0.5 μl or more and 1.4 μl. It is preferable to be within the following range. 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 ink, and uses a water-based ink containing an anionic coloring material, and a porous layer containing a reactive substance of an inorganic pigment and an ink coloring material. There is no particular limitation other than the water-based ink recording medium. 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.
Moreover, the pH of the porous layer is greater than 5 and 7 or less, and the porous layer includes a pulp layer as an ink absorption layer in the lower layer, and the pH of the pulp layer is higher than the pH of the porous layer. It is preferable that the paper support has a small sizing degree of 5 to 50 seconds.

  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 using a commercially available pigment ink inkjet printer (CANON, trademark: ImagePROGRAF W6200, print mode: thick-coated paper / clean), and a commercially available dye ink inkjet. A printer (trade name: PIXUS ip8600, printing mode: matte photo paper / clean) manufactured by CANON Co., Ltd. was used.

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

[Print density]
Images ("High-definition color digital standard image XYZ / JIS-SCID", identification symbol: S6, image name: color chart) issued by the Japanese Standards Association, ImagePROGRAF W6200 (using pigment ink) and PIXUS ip8600 (dye ink) The print density was measured using RD-914 manufactured by Guretag Macbeth for the highest color tone portions of black and magenta.

[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 does not cause any practical problems.
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.

<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 Add and mix thoroughly to make a papermaking raw material, make paper using a long mesh multi-cylinder paper machine, dry the water to 10%, and apply a 7% aqueous solution of oxidized starch at 4 g / m ² on both sides with a size press The paper support I having a basis weight of 190 g / m ² and a Steecht size of 15 seconds was produced by drying to a moisture content of 5.0%.

[Preparation of ink receiving layer coating solution]
Wet silica (trade name: Nipgel AY603, manufactured by Tosoh Silica Co., Ltd.) is used as a pigment, and the number of weight secondary particle size of 6.6 μm and weight average secondary particle size of 2 μm or less is 47% of the total amount of silica. 100 parts of silica treated as above, 35 parts of silyl-modified PVA (trade name: R-1130, manufactured by Kuraray Co., Ltd.), 5 parts of PVA (product name: PVA135, manufactured by Kuraray Co., Ltd.), styrene-acrylic copolymer 10 parts of a combined resin, 20 parts of an acrylamide-diallylamine copolymer (manufactured by Sumitomo Chemical Co., Ltd., trade name: SR1001), 10 parts of diallyldimethylammonium chloride (manufactured by Senka Corporation, trade name: CP101) as an ink fixing agent, and water A coating liquid was prepared by mixing and dispersing.

[Preparation of recording medium for water-based ink]
Applying the ink receiving layer coating liquid on one side of the paper support I so that the coating amount is 12 g / m ² , drying, and setting 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 evaluation results are shown in Table 2. In addition, the relationship between the absorption speed, the absorption time, and the absorption amount at each absorption stage of the recording medium is shown as “A” in Table 1 and FIG.

<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.
Each of the above evaluations was performed on the obtained aqueous ink recording medium. The evaluation results are shown in Table 2. In addition, the relationship between the absorption speed, the absorption time, and the absorption amount at each absorption stage of the recording medium is shown as “B” in Table 1 and FIG.

<Example 3>
The pigment in the ink-receiving layer coating liquid of Example 1 was wet-process silica, and the number of weight average secondary particle diameter of 7.0 μm and weight average secondary particle diameter of 2 μm or less was 20% of the total amount of silica. A water-based ink recording medium was prepared in the same manner as in Example 1 except that the silica was obtained by pulverization using a sand mill and classification.
Each of the above evaluations was performed on the obtained aqueous ink recording medium. The evaluation results are shown in Table 2. In addition, the relationship between the absorption speed, the absorption time, and the absorption amount at each absorption stage of the recording medium is shown as C in Table 1 and FIG.

<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 water-based ink recording medium was 232 g / ^{m 2.} The results are shown in Table 1.
Each of the above evaluations was performed on the obtained aqueous ink recording medium. The evaluation results are shown in Table 2. Further, the relationship between the absorption speed, the absorption time, and the absorption amount at each absorption stage of the recording medium is shown as a symbol D in Table 1 and FIG.

<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.
Each of the above evaluations was performed on the obtained aqueous ink recording medium. The evaluation results are shown in Table 2. Further, the relationship between the absorption speed, the absorption time, and the absorption amount at each absorption stage of the recording medium is shown as a symbol E in Table 1 and FIG.

<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.
Each of the above evaluations was performed on the obtained aqueous ink recording medium. The evaluation results are shown in Table 2. In addition, the relationship between the absorption speed, the absorption time, and the absorption amount at each absorption stage of the recording medium is shown as “F” in Table 1 and FIG.

<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.
Each of the above evaluations was performed on the obtained aqueous ink recording medium. The evaluation results are shown in Table 2. Further, the relationship between the absorption speed, the absorption time, and the absorption amount at each absorption stage of the recording medium is shown as “G” in Table 1 and FIG.

<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.
Each of the above evaluations was performed on the obtained aqueous ink recording medium. The evaluation results are shown in Table 2. Further, the relationship between the absorption speed, the absorption time, and the absorption amount at each absorption stage of the recording medium is shown as “H” in Table 1 and FIG.

<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.
Each of the above evaluations was performed on the obtained aqueous ink recording medium. The evaluation results are shown in Table 2. Further, the relationship between the absorption speed, the absorption time, and the absorption amount at each absorption stage of the recording medium is shown as a symbol I in Table 1 and FIG.

<Comparative Example 1>
[Paper Support II]
A mixture of light calcium carbonate and kaolin in a ratio of 75:25 is added to 100 parts of hardwood bleached kraft pulp (400 ml of freeness, CSF: JIS-P-8121), 1.0 part of cationic starch, alkenyl succinic anhydride system Add 0.04 part of neutral sizing agent and 0.5 part of sulfuric acid band, mix well to make papermaking raw material, dry the water to 10% using a long mesh multi-cylinder paper machine, and oxidize with size press A 7% solution in which starch, PVA, and styrene-acrylic resin were mixed at a ratio of 5.2: 1.3: 0.6 was applied to 4 g / m ² on both sides, dried, and dried to a moisture content of 5.0%. A paper support II having a basis weight of 190 g / m ² was produced. The Steecht sizing degree was 300 seconds.

[Preparation of recording medium for water-based ink]
A water-based ink recording medium was produced in the same manner as in Example 1 except that the paper support I in Example 1 was changed to the paper support II.
Each of the above evaluations was performed on the obtained aqueous ink recording medium. The evaluation results are shown in Table 2. In addition, the relationship between the absorption speed, the absorption time, and the absorption amount at each absorption stage of the recording medium is shown as a symbol J in Table 1 and FIG.

<Comparative Example 2>
A commercially available recording medium for mat type water-based ink (manufactured by CANON, trade name: thick mouth coated paper).
Each of the above evaluations was performed on this aqueous ink recording medium. The evaluation results are shown in Table 2. Further, the relationship between the absorption speed, the absorption time, and the absorption amount at each absorption stage of the recording medium is shown as a symbol K in Table 1 and FIG.

<Comparative Example 3>
A commercially available recording medium for mat type water-based ink (manufactured by EPSON, trade name: photo matte paper / pigment type). The evaluation results are shown in Table 3 and indicated as L in FIG.
Each of the above evaluations was performed on this aqueous ink recording medium. The evaluation results are shown in Table 2. Further, the relationship between the absorption speed, the absorption time, and the absorption amount at each absorption stage of the recording medium is shown as a symbol L in Table 1 and FIG.

<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 evaluations was performed on this aqueous ink recording medium. The evaluation results are shown in Table 2. Further, the relationship between the absorption speed, the absorption time, and the absorption amount at each absorption stage of the recording medium is shown as a symbol M in Table 1 and FIG.

  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. In addition, 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 detected using an SEM. When observed, Examples 1 to 9 confirmed the presence of silica particles on the paper support side and the ink receiving layer side 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, and the absorption speed V2 of the second absorption stage. Can be understood to be faster than the absorption rate of 0.01 μl / second for codes 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 0.80 μl or less, and is less than half compared with the absorption quantity qa in the first absorption stage. ing. 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 2.3 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 example showing that the present invention is effective for a recording medium having a normal thickness will be described below. 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 the constituent requirements in each claim are as follows. It has been confirmed that the effects of the claims can be obtained if they are satisfied. Typical examples are shown below.

[Paper Support III]
Similarly to 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, rosin sizing agent 0. 7 parts and 2.0 parts of sulfuric acid band are added and mixed thoroughly to make a papermaking raw material. Papermaking is carried out using a long mesh multi-cylinder papermaking machine, the water content is dried to 10%, and 7% of the oxidized starch is obtained with a size press. The aqueous solution was applied at 4 g / m ² on both sides, dried, and dried to a moisture content of 5.0% to produce a paper support III having a basis weight of 150 g / m ² and a Steecht size of 10 seconds.

<Example 10>
A water-based ink recording medium was produced in the same manner as in Example 1 except that the paper support I in Example 1 was changed to the paper support III. The basis weight of the aqueous ink recording medium was 162 g / m ² .
Each of the above evaluations was performed on the obtained aqueous ink recording medium. The evaluation results are shown in Table 4. Further, the relationship between the absorption speed, the absorption time, and the absorption amount at each absorption stage of the recording medium is shown as N in Table 3 and FIG.

<Example 11>
A water-based ink recording medium was prepared in the same manner as in Example 1 except that the paper support I of Example 1 was changed to the paper support III and the time until drying was started was changed to 10 seconds.
Each of the above evaluations was performed on the obtained aqueous ink recording medium. The evaluation results are shown in Table 4. Further, the relationship between the absorption speed, the absorption time, and the absorption amount at each absorption stage of the recording medium is shown as a symbol O in Table 3 and FIG.

<Example 12>
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 III and the time until the drying was started was changed to 3 seconds.
Each of the above evaluations was performed on the obtained aqueous ink recording medium. The evaluation results are shown in Table 4. In addition, the relationship between the absorption speed, the absorption time, and the absorption amount at each absorption stage of the recording medium is shown as P in Table 3 and FIG.

<Example 13>
The paper support I in Example 1 was changed to the paper support III, the time until the drying was started was changed to 3 seconds, and the drying was changed to 160 ° C. A water-based ink recording medium was prepared.
Each of the above evaluations was performed on the obtained aqueous ink recording medium. The evaluation results are shown in Table 4. Further, the relationship between the absorption speed, the absorption time, and the absorption amount at each absorption stage of the recording medium is shown as a symbol Q in Table 3 and FIG.

<Example 14>
A water-based ink recording medium was prepared in the same manner as in Example 1 except that the paper support I of Example 1 was changed to the paper support III and the drying temperature was changed to 160 ° C.
Each of the above evaluations was performed on the obtained aqueous ink recording medium. The evaluation results are shown in Table 4. Further, the relationship between the absorption speed, the absorption time, and the absorption amount at each absorption stage of the recording medium is shown as a symbol R in Table 23 and FIG.

<Example 15>
[Paper Support IV]
Similarly to the 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 parts and 2.0 parts of sulfuric acid band are added and mixed thoroughly to make a papermaking raw material. Papermaking is carried out using a long mesh multi-cylinder papermaking machine, the water content is dried to 10%, and 7% of the oxidized starch is obtained with a size press. The aqueous solution was applied at 4 g / m ² on both sides, dried, and dried to a moisture content of 5.0%, thereby producing a paper support IV having a basis weight of 127 g / m ² and a Steecht size of 9 seconds.
A water-based ink recording medium was produced in the same manner as in Example 1 except that the paper support I in Example 1 was changed to the paper support IV. The basis weight of the aqueous ink recording medium was 139 g / m ² .
Each of the above evaluations was performed on the obtained aqueous ink recording medium. The evaluation results are shown in Table 4. In addition, the relationship between the absorption speed, the absorption time, and the absorption amount at each absorption stage of the recording medium is shown as “S” in Table 3 and FIG.

<Example 16>
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 IV and the time until the drying was started was changed to 10 seconds.
Each of the above evaluations was performed on the obtained aqueous ink recording medium. The evaluation results are shown in Table 4. Further, the relationship between the absorption speed, the absorption time, and the absorption amount at each absorption stage of the recording medium is shown as a symbol T in Table 3 and FIG.

<Example 17>
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 IV and the time until the drying was started was changed to 3 seconds.
Each of the above evaluations was performed on the obtained aqueous ink recording medium. The evaluation results are shown in Table 4. Further, the relationship between the absorption speed, the absorption time, and the absorption amount at each absorption stage of the recording medium is shown as a symbol U in Table 3 and FIG.

<Example 18>
The paper support I of Example 1 was changed to the paper support IV, the time until the drying was started was changed to 3 seconds, and the drying was changed to 160 ° C., and the same procedure as in Example 1 was performed. A water-based ink recording medium was prepared.
Each of the above evaluations was performed on the obtained aqueous ink recording medium. The evaluation results are shown in Table 4. Further, the relationship between the absorption speed, the absorption time, and the absorption amount at each absorption stage of the recording medium is shown as a symbol V in Table 3 and FIG.

<Example 19>
A water-based ink recording medium was prepared in the same manner as in Example 1 except that the paper support I of Example 1 was changed to the paper support IV and the temperature of drying was changed to 160 ° C.
Each of the above evaluations was performed on the obtained aqueous ink recording medium. The evaluation results are shown in Table 4. Further, the relationship between the absorption speed, the absorption time, and the absorption amount at each absorption stage of the recording medium is shown as a symbol W in Table 3 and FIG.

As can be seen from the examples, when the qa (1.3 μl or more) of the first absorption stage in the present invention is less than 1.60 μl, the absorption amount of the first absorption stage is relatively small. 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 at the 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, tb of the second absorption stage is 9.6 seconds or more and 13.5 seconds or less, and the absorption speed V2 is 0.05 μl. / Second or more and 0.09 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 Tables 1 to 4, in the examples of the present invention, the absorption rate V2 of the second absorption stage is faster than the absorption rate of 0.01 μl / second for J and K, and the absorption rate of L is 0. It can be seen that it is slower than 32 μl / sec. Specifically, from the table, A, B, C, D, E, F, G, H, and I of Examples of the present invention are 12 to 17 times faster than J and K absorption rates. , L is about 1/2 times slower than the absorption rate, and N, O, P, Q, R, S, T, U, V, W are absorbed in the second absorption stage. Is 5 to 8 times faster than the absorption rate of J and K, and about 1/6 to 1/4 times slower for L. That is, the “moderate” speed that we say is a speed of 0.05 μl / second or more and 0.23 μl / second or less. 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 equation 0 <V2 <V1.
0 <V2 <V3
While satisfying the relationship
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 When 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 without being influenced by the thickness or basis weight.
More specifically, the second absorption stage occurs after 9.5 seconds immediately after the dropping of the droplet, and the final point time tc of the third absorption stage occurs within 14.5 seconds, thereby supporting the paper. It has been found that the effect of the present invention can be sufficiently obtained even in a system in which the thickness of the body 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 Comparative Example 1 Absorption speed K: Water-based ink recording medium obtained in Comparative Example 2 Absorption speed L: Water-based ink recording obtained in Comparative Example 3 Absorption speed M of medium: recording medium for water-based ink obtained in Comparative Example 4 Absorption speed N: Absorption speed of water-based ink recording medium obtained in Example 10 O: Absorption speed of water-based ink recording medium obtained in Example 11 P: Water-based ink recording medium obtained in Example 12 Absorption speed Q: Water-based ink recording medium obtained in Example 13 Absorption speed R: Water-based ink recording medium obtained in Example 14 Absorption speed S: Water-based ink recording obtained in Example 15 Absorption speed T of 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: For water-based ink obtained in Example 18 Absorption speed W of recording medium: Absorption speed of recording medium for water-based ink obtained in Example 19

Claims (3)

This is a method for determining the ink absorption characteristics of an aqueous ink recording medium having a paper support and an ink receiving layer containing a reactive substance of amorphous silica, an adhesive, and an ink coloring material on the surface of the paper support. And
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. And
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.
When
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;
Absorption amount (qb-qa) in the second absorption stage is 0.3 μl or more and 1.4 μl or less.
A method for determining ink absorption characteristics of a recording medium for water-based inks. 2. The water-based ink according to claim 1, wherein the second absorption speed V2 (μl / sec) is a speed greater than 0.05 (μl / sec) and smaller than 0.23 (μl / sec). A method for determining ink absorption characteristics of a recording medium. The basis weight of the paper support and the ink receiving layer is 180 g / m ² 300 g / m ² Within the following range, the second absorption rate V2 (μl / sec) is greater than 0.12 (μl / sec) and smaller than 0.23 (μl / sec). The method for determining ink absorption characteristics of a water-based ink recording medium according to claim 1.

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