JPH07232473A - Medium to be recorded, ink jet recording method using medium and dispersion of alumina hydrate - Google Patents

Abstract

PURPOSE:To absorb efficiently a dye and a solvent of an ink component and provide a medium to be recorded of good coloring properties and quick drying properties and an ink jet recording method using the medium by making an alumina hydrate with two maximums or more in the pore radius distribution. CONSTITUTION:An alumina hydrate is contained as a pigment in a medium to be recorded and two maximums or more are provided in the pore radius distribution of an ink receptive layer. Printing of good coloring and quick drying can be resumed by using the above-said medium to be recorded and absorbing efficiently a dye and a solvent forming an ink component. Also an ink receptive layer 2 composed mainly of the alumina hydrate and a binder is formed as a single layer on a base 1. As the alumina hydrate is provided with positive charge, the ink dye is fixed in a good manner to form an image of good coloring, and also the alumina hydrate is preferred most as a material for the ink receptive layer, since problems like the browning of black ink, light fastness and others generated in the conventional process of using a silica compound are not generated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording medium suitable for recording using an aqueous ink and an inkjet recording method using the same, and particularly to a high image density, a clear color tone, a high resolution and an ink. To a recording medium having excellent absorption capacity, an inkjet recording method using the same, and an alumina hydrate dispersion liquid particularly suitable for producing the recording medium.

[0002]

2. Description of the Related Art In recent years, an ink jet recording system is one in which minute droplets of ink are ejected by various operating principles and adhered to a recording medium such as paper to record images, characters, etc. It has characteristics such as high speed and low noise, easy multi-coloring, great flexibility in recording pattern, and no need for development and fixing. It has rapidly spread in various applications such as information equipment as various image recording devices. There is. Furthermore, images formed by the multi-color inkjet method can obtain prints comparable to those of the multi-color printing by the plate making method and the printing by the color-photographic method. Since it is cheaper than multicolor printing and printing, it is being widely applied to the field of full color image recording. Although the recording apparatus and recording method have been improved along with the improvement of recording characteristics such as high-speed recording, high-definition recording, and full-color recording, it seems that high-quality characteristics are also required for the recording medium. Has become.

Conventionally, various forms of recording media have been proposed. For example, Japanese Unexamined Patent Publication No. 52-53012 discloses an inkjet paper in which a low-sized base paper is impregnated with a surface-treatment coating material. JP-A-53-4911
In U.S. Pat. No. 3,200,043, a urea-formalin resin powder internally added
An ink jet paper in which a water-soluble polymer is impregnated in a paper is disclosed. JP-A-55-5830 discloses an ink jet recording paper having a support surface provided with an ink-absorptive coating layer, and JP-A-55-51583 discloses amorphous as a pigment in a coating layer. An example using silica is disclosed, and JP-A-55-146786 discloses an example using a water-soluble polymer coating layer.

US Pat. Nos. 4,879,166 and 5
104730, JP-A-2-276670, and JP-A-4
In Japanese Patent Laid-Open Nos. 37576 and 5-32037, recording sheets having a layer using alumina hydrate having a boehmite structure are proposed.

Further US Pat. No. 4,374,804
No. 5,104,730, JP-A-58-110287, and JP-A-4-37576, it is also possible to form an ink receiving layer having a multilayer structure by using a silica or alumina material. ing.

However, the conventional recording medium has the following problems.

1) US Pat. No. 5,104,730,
In JP-A-2-276670, JP-A-2-276671, and JP-A-3-275378, the average pore diameter is 10
A recording medium having a narrow pore size distribution of ~ 30Å is disclosed. With this pore size distribution, the adsorption of the dye is good, but the absorption of the solvent is insufficient, and beading occurs. The term "beading" as used herein means that when the next ink dot is applied adjacently to the previous ink dot before the previously applied ink dot is fixed on the recording medium, the ink dot moves in the lateral direction. This is a phenomenon in which the particles move irregularly and, as a result, agglomeration occurs between adjacent dots, resulting in uneven image density.

2) In the case of printing a color image, the amount of ink is large, so that the printed ink does not completely absorb in the pores and overflows to the surface of the ink receiving layer, causing bleeding and degrading the printing quality. Will end up.

3) In high-speed printing, fast drying property is required, but since the surface is not dry when printing is performed due to insufficient absorption speed, the output image may be damaged by contact.

4) US Pat. No. 5,104,730,
JP-A-2-276670, JP-A-2-276667, and JP-A-3-275378 disclose recording media having an extremely narrow pore size distribution. However, JP-A-4-267180 and JP-A-5-16517.
As disclosed in Japanese Patent Laid-Open Publication No. JP-A No. 2004-242, since each ink dye (cyan, magenta, yellow, and black) and the ink solvent are selectively adsorbed in the pores of a specific diameter, the printing is changed when the ink composition changes. It will blur.

5) Since the viscosity of the dispersion liquid of the pigment or the like increases with time and the coating cannot be performed, there is a problem that the solid content concentration of the liquid cannot be increased. As a countermeasure,
Japanese Unexamined Patent Publication No. 4-67986 discloses a method of lowering the polymerization degree of a binder polymer. However, there are problems such as cracking and water resistance reduction of the ink receiving layer, and sufficient improvement has not been made.

6) There is a problem that the solid content concentration cannot be increased because the viscosity of the dispersion liquid is high. JP-A-4-6798
As a countermeasure, Japanese Patent Publication No. 5 discloses a method of adding an acid such as a monocarboxylic acid as a dispersant. However, manufacturing problems such as irritating odor and corrosion occur.

7) US Pat. Nos. 4,780,356 and 4 to improve ink absorbency and image resolution.
No. 374804, No. 5104730, Japanese Patent Publication No. 3-72
460, JP-A-55-11829, 58.
-110287 gazette, the same 62-270378 gazette,
Japanese Patent Application Laid-Open No. 4-37576 discloses a method in which the ink receiving layer has a two-layer or multi-layer structure. But,
In addition to coating and drying the ink-receiving layer twice, the number of steps increases, and because the physical properties of each layer are different, changes over time, appearance defects such as cracks in the ink-receiving layer, and printing There is also a problem that each layer is separated and peeled off.

8) Japanese Patent Laid-Open No. 3-281384 discloses that
Disclosed is an alumina hydrate forming a bundle-like aggregate having an aspect ratio of 3 or less and oriented in a certain direction, and a method of forming an ink receiving layer using the alumina hydrate. However, since the alumina hydrate particles are oriented and densely packed, the gap between the alumina hydrate particles in the ink receiving layer is likely to be narrowed. Therefore, it is biased toward the smaller pore size,
Moreover, the pore size distribution tends to be narrowed. As a result, there is a problem that beading occurs as in the above case.

[0015]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above problems. The purpose of the present invention is to efficiently absorb a dye and a solvent, which are ink components, and An object of the present invention is to provide a recording medium that is good and can be dried quickly, and an inkjet recording method using the recording medium.

The present invention also provides a pigment dispersion suitable for producing the recording medium.

[0017]

[Means and Actions for Solving the Problems]
The following is achieved by the present invention.

That is, the present invention is a recording medium characterized by containing an alumina hydrate having two or more maximums in the pore radius distribution.

According to the present invention, in a recording medium having an ink receiving layer containing a pigment and a binder provided on a substrate, alumina hydrate is contained as a pigment, and the ink receiving layer has two pore radius distributions. The recording medium is characterized by having the above-mentioned maximums.

Further, the present invention is a recording medium characterized in that an alumina hydrate having two or more maximums in the pore radius distribution is internally added to the fibrous substance.

Further, in the present invention, an alumina hydrate containing 0.1 to 1.0% by weight of nitrate radicals and having two or more maximums in the pore radius distribution is added to ion-exchanged water in a solid content concentration of 15% by weight.
Viscosity when dispersed at 20 ° C., shear rate of 7.9 sec ⁻¹ , is not more than 75 CPS, and nitrate radical is 0.1-0.1%.
Alumina hydrate containing 1.0% by weight and having two or more maximums in the pore radius distribution is added to ion-exchanged water to have a solid concentration of 2
When dispersed at 0% by weight, the viscosity is 20 ° C, shear rate 1
It is 100 CPS or less as measured at 0.2 sec ⁻¹ , or an alumina hydrate containing 0.1 to 1.0% by weight of nitrate radicals and having two or more maximums in the pore radius distribution is ionized. The viscosity when dispersed in exchanged water at a solid content concentration of 25% by weight is 500C when measured at 20 ° C and a shear rate of 10.2 sec- ^1.
It is a dispersion liquid of alumina hydrate characterized by being PS or less.

Furthermore, the present invention is characterized in that the above-mentioned recording medium is used as a recording medium in an ink jet recording method in which droplets of ink are ejected from fine holes to be applied to the recording medium for printing. And an inkjet recording method.

By using the recording medium of the present invention, the dye and the solvent, which are the components of the ink, are efficiently absorbed, so that it is possible to realize printing with good color development and quick drying. .

The recording medium of the present invention is a recording medium containing at least an alumina hydrate having the characteristics described above in the pore radius distribution as an essential component. 1, the ink receiving layer formed mainly from the alumina hydrate and the binder is formed as a single layer on the substrate as shown in FIG. It is the configured configuration. Alumina hydrate has a positive charge, so that it can fix ink dyes well and give images with good color development. In addition, brown ink of black ink, light resistance, etc. This is the most preferable material for the ink receiving layer because it does not have the problem of (1).

As the alumina hydrate used in the recording medium of the present invention, amorphous alumina hydrate is preferable as determined by X-ray diffraction analysis.

Alumina hydrate is defined by the following general formula.

Al ₂ O _3-n (OH) _2n · mH ₂ O In the formula, n represents any one of integers of 0, 1, 2 or 3, and m is 0-10, preferably 0-5. Represents the value of. Since mH ₂ O represents a detachable aqueous phase that often does not participate in the formation of crystal lattices, m can also take non-integer values. Also, when calcining a material of this kind, m can reach a value of zero.

Alumina hydrate can be produced by a known method such as hydrolysis of aluminum alkoxide and hydrolysis of sodium aluminate. Rosek et al. (C
collectCzech Chem Commun, 5
6, 1253-1262, 1991) report that the porous structure of hydrated alumina is affected by precipitation temperature, solution pH, aging time and surfactant.

For example, Kodansha, Catalyst Course, Volume 5, Engineering, Catalyst Design (1985), page 123, describes that alumina hydrate generally has one maximum pore size distribution. There is. Kobayashi (front, 15 volumes, 282,
(1977), the maximum pore size distribution of alumina hydrate is 1
It is reported that it is one. Rosek et al. (Coll
ect Czech. Chem. Commun. 5
6 (6), 1263-1269, 1991) is 30
It has been reported that aluminum hydroxide precipitated at a pH of 7 to 8 at a relatively low temperature of ˜50 ° C. exhibits a bimodal pore structure having maxima in the large pore region and the medium pore region.

The shape of the alumina hydrate used in the present invention is
Preferably, it is flat and has an average aspect ratio of 3 to 10, and a flat surface has an aspect ratio of 0.6 to 1.0. The definition of the aspect ratio can be obtained by the method described in Japanese Patent Publication No. 5-16015. The aspect ratio is represented by the ratio of "diameter" to "thickness" of the particles. Here, the “diameter” means the diameter of a circle having an area equal to the projected area of the particles when observing the alumina hydrate with a microscope or an electron microscope. The aspect ratio is the ratio between the diameter showing the minimum value and the diameter showing the maximum value of the flat plate surface when observed in the same manner as the aspect ratio. When the average aspect ratio is smaller than the above range, the pore size distribution range of the ink receiving layer becomes narrow, and when it is large, it becomes difficult to manufacture the alumina hydrate with the same particle size. If the average aspect ratio is smaller than the above range, the pore size distribution becomes narrow as well. Among the alumina hydrates, pseudo-boehmite is described in literature (Rocek J., et al,
Applied Catalysis, Vol. 74, 29-
36, 1991), it is generally known that there are ciliated and non-ciliated shapes.

According to the knowledge of the present inventor, even in the case of hydrated alumina, the tabular shape has better dispersibility than the hair bundle (ciliate shape), and when the ink receiving layer is formed, the drawing of FIG. Since the orientation of the alumina hydrate particles becomes random as shown in the substitute photograph, the pore size distribution becomes wider, which is more preferable.

It should be noted that, on page 402 of the Paper Processing Manual, it is described that the aluminum hydroxide particles have a hexagonal flat plate shape. In addition, Heidilite (trade name, manufactured by Showa Denko),
Aluminum hydroxide such as HYDRAL (trade name, manufactured by ALCOA) is known. Furthermore, JP-A-2-27667
No. 0 discloses a hair-like bundle of alumina sol having an aspect ratio of 2 to 10, and JP-A-3-285814 discloses a plate-like boehmite sol having an aspect ratio of 2 to 10. However, each of the above documents does not show any relation between the shape of the alumina hydrate and the pore structure or dispersibility in the particles as described later.

The BET surface area of the alumina hydrate, the pore size distribution of the alumina hydrate and the ink receiving layer containing the alumina hydrate, the pore volume as described below, and the isothermal adsorption / desorption curve are nitrogen adsorption. It can be determined simultaneously by the desorption method. The BET specific surface area of the alumina hydrate used in the present invention is preferably in the range of 70 to 300 m ² / g. BE
When the T specific surface area is smaller than the lower limit of the above range, it becomes impossible to sufficiently adsorb and fix the dye in the ink to the larger pore size distribution, and when it is larger than the upper limit of the range, the pigment is well dispersed. There is a possibility that the coating cannot be performed and the pore size distribution cannot be controlled.

The method for producing the alumina hydrate used in the present invention is not particularly limited, but preferably a method capable of producing an amorphous alumina hydrate, for example, the Bayer method or alum thermal decomposition. Any method such as a method can be adopted.

In the present invention, a particularly preferable method for producing an amorphous alumina hydrate is a method of obtaining an alumina hydrate by adding an acid to a long-chain aluminum alkoxide and hydrolyzing it. Can be mentioned.
Here, the long-chain aluminum alkoxide is, for example, an alkoxide having 5 or more carbon atoms and further having 12 to 12 carbon atoms.
It is preferable to use the alkoxide of No. 22 because it facilitates the removal of the alcohol content and the shape control of the alumina hydrate as described below. The above method has an advantage that impurities such as various ions are less likely to be mixed in, as compared with the method of producing alumina hydrogel or cationic alumina. Further, since long-chain aluminum alkoxide is easy to remove alcohol after hydrolysis, there is also an advantage that dealcoholation of alumina hydrate can be completed as compared with the case of using short-chain alkoxide such as aluminum isopropoxide. is there. Further, in the method using the above long-chain aluminum alkoxide, the alumina hydrate particles obtained by hydrolysis are likely to have a flat plate shape, and the particle shape can be easily controlled. In this method, it is preferable to set the pH of the solution at the start of hydrolysis to 6 or less in order to obtain an amorphous alumina hydrate. Here, when the pH becomes 8 or more,
The finally obtained alumina hydrate becomes crystalline.

The alumina hydrate obtained by the above method undergoes a hydrothermal synthesis step to grow particles (ripening step). By adjusting the conditions of the step, the pore shape of the alumina hydrate particles can be controlled within a specific range. When the aging time is appropriately set, primary particles of alumina hydrate having a relatively uniform particle diameter grow, and the pores forming the pores are aligned and the pore diameter distribution is narrowed.
If the aging time is made longer than this condition, an alumina hydrate having a bimodal pore size distribution can be obtained. The sol obtained here can be used as a dispersion as it is, as disclosed in JP-A-2-276670. However, in the present invention, the sol is once dried by a method such as spray drying to obtain a powder. It is preferable to prepare a dispersion after the state. In this case, the dispersibility of the alumina hydrate in water is further improved.

The alumina hydrate obtained by this method has two or more maximums in the pore radius distribution. The pore structure is mainly formed by the gaps between the alumina hydrate primary particles. The reason for having two or more maximums is that the alumina hydrate used in the present invention is tabular and the primary particles in the dry powder are oriented in random directions. It is considered that this is due to the generation of a gap in the portion overlapped in the direction and a gap in the end face and the portion overlapped with the main plane or the end face. As described above, two or more maximums of the pore radius distribution are caused by the gaps between the primary particles, and at least one of the pore diameters having the maximum is the minor axis or major axis diameter of the main plane of the primary particle. At least one of the pore diameters having the other maximums is about several times larger than the diameter of the minor axis or the major axis of the principal plane. As described above, the alumina hydrate of the present invention has two or more maximums in the pore radius distribution. Such an alumina hydrate is dispersed up to the primary particles in the coating dispersion liquid, but the pore radius distribution having two or more maximums can be obtained by dispersing the alumina hydrate and coating it on the substrate. Even if the ink receiving layer is formed through the drying process, it is maintained. The reason for this is as shown in the drawing-substitute photograph of FIG.
The primary particles are oriented in random directions respectively, and as in the case of hydrated alumina, the gap between the portions where the primary particles overlap with each other in the principal plane direction of the flat plate via the binder, and the end face and the principal plane or the end face are It is presumed that two or more local maxima of the pore radius distribution due to the generation of the voids in the portions overlapped with each other through the binder are maintained also in the ink receiving layer.

JP-A-58-110287 discloses a recording sheet having a peak pore size of 0.05 μm or less and 0.2 to 10 μm. However, while the former peak is due to the gap between the primary particles, the latter peak is
The present invention is different from the present invention in which primary particles are formed by agglomeration between secondary or tertiary or higher-order particles and two or more maximums are generated from the interstices between primary particles. Therefore,
The peak position of the pore size is completely different.

In the above-described embodiment of the recording medium of the present invention, a coating liquid (alumina hydrate dispersion liquid) in which the above-mentioned alumina hydrate as a pigment and a binder are mixed on a substrate.
To form an ink receiving layer. The physical properties of the ink receiving layer are not determined only by the alumina hydrate used,
Type and mixing amount of binder, concentration of coating liquid, viscosity, dispersion state, coating device, coating head, coating amount, air volume of dry air,
Since it varies depending on various manufacturing conditions such as temperature and blowing direction, it is necessary to control the manufacturing conditions within an optimum range in order to obtain the characteristics of the ink receiving layer according to the present invention.

In the recording medium of the present invention, the pore radius distribution of the ink receiving layer also has two or more maximums. The solvent component in the ink is absorbed by the relatively large pores, and the dye in the ink is adsorbed by the relatively small pores. One of the maximum values is preferably a pore radius of 100 Å or less, more preferably 10 to 60 Å. The other maximum is preferably within the range of 100 to 200Å in the pore radius. If the former maximum is larger than the upper limit of the above range, the adsorption and fixation of the dye in the ink will be poor and the image will bleed and beading will occur.
When the maximum value of the latter is smaller than the lower limit of the above range, the absorption of the solvent component in the ink is poor and the drying of the ink is poor, and the surface of the ink receiving layer does not dry when printed out from the apparatus and the maximum value of the latter is reduced. Is larger than the upper limit of the above range, cracks are likely to occur in the ink receiving layer.

In the present invention, the pore radius distribution of hydrated alumina also has two or more maximums. Similar to the ink receiving layer, one of the relatively small maximums of such a pore size distribution is preferably a pore radius of 100 Å or less, and more preferably 10 or less.
It is ~ 60Å. A relatively large maximum has a pore radius of 100-
A range of 200Å is preferred. The pore structure of the ink receiving layer is formed by the primary alumina hydrate as described above, but since this pore structure has already formed its property in the alumina hydrate, the pore radius distribution When the maximum value of is outside the above range, the pore radius distribution of the ink receiving layer cannot be within the above specified range.

The total pore volume of the ink receiving layer is 0.1 to 10.
The range of 1.0 cc / g is preferable. A more preferable range is 0.4 to 0.6 cc / g. If the pore volume of the ink receiving layer is larger than the above range, the ink receiving layer will be cracked and powder will fall off, and if it is smaller than the above range, ink absorption will be poor. Further, the pore volume of the ink receiving layer is preferably 8 cc / m ² or more. Below the above range, particularly when multicolor printing is performed, the ink overflows from the ink receiving layer, and bleeding occurs in the image. Pore radius 100
The pore volume of the pores having a maximum value of Å or less is preferably 0.1 to 10%, more preferably 1 to 5% of the total pore volume.

Here, the pore volume of pores having a pore radius of 100 Å or less is a range of pores showing a maximum value in the pore radius distribution up to a half radius. The width of the volume. If the pore volume of the pores having a maximum value within the pore radius of 100 Å or less of the ink receiving layer is smaller than the above range, the adsorption of dye in the ink becomes poor. Becomes worse. The total pore volume of the hydrated alumina is also 0.4 to 1.0 cc / g, and more preferably 0.4 to 0.6 cc / g. The volume of pores having a maximum value of 100 Å or less is preferably 0.1 to 10% of the total pore volume. A more preferable range is 1 to 5%. Since the pore volume of the ink receiving layer depends on the pore volume of the alumina hydrate, outside the above range, the pore volume of the ink receiving layer cannot be within the specified range.

In the recording medium having the ink receiving layer on the substrate of the present invention, 90% of the maximum adsorbed gas amount determined by the isothermal nitrogen adsorption / desorption curve of the ink receiving layer derived by the nitrogen adsorption / desorption method Relative pressure difference between adsorption and desorption (Δ)
P) is preferably 0.2 or less. A more preferable range is 0.15 or less, and a further preferable range is 0.10.
It is the following. The relative pressure difference (ΔP) is McBain
(J. Am. Chem. Soc., 57, 699, 1
935), it can be used as a measure of the possibility that ink fountain-shaped pores are present. The smaller the relative pressure difference (ΔP), the closer the pores are to the straight pipe, and the larger the pores, the ink vase shape. If the relative pressure difference (ΔP) is out of the above range, the dryness of the ink after printing is deteriorated. still,
In JP-A-60-245588, the shape of the pores of the alumina xerogel used in the ink receiving layer is preferably a uniform and linear shape with a small labyrinth degree, an ink bottle shape with a narrow inlet, and a constricted portion in the middle. It is described that the gourd shape, the serpentine shape, etc., which are present, are not preferable from the viewpoint of absorption rate, but no specific measuring method for the actual physical property values is shown.

In the recording medium of the present invention, the recording medium having the ink receiving layer containing the alumina hydrate was determined from the isothermal nitrogen adsorption / desorption curve of the alumina hydrate derived by the nitrogen adsorption / desorption method. , The maximum amount of adsorbed gas is 90
The relative pressure difference (ΔP) between adsorption and desorption at an adsorbed gas amount of
It is preferably 0.2 or less. A more preferable range is 0.15 or less, and a still more preferable range is 0.10 or less. Outside this range, the relative pressure difference (ΔP) obtained from the isothermal nitrogen adsorption / desorption curve of the ink receiving layer cannot be within the specified range.

The number of hydroxyl groups on the surface of the alumina hydrate used in the recording medium of the present invention is preferably 10 ²⁰ / g or more. If it is less than this value, the solid content concentration of the dispersion obtained by dispersing the alumina hydrate in water cannot be increased. The number of hydroxyl groups in the alumina hydrate can be determined by titration with a triethylaluminum solution.

The surface potential of the hydrated alumina can be determined by a zeta potential meter. Japanese Patent Laid-Open No. 60-2329
Japanese Patent Publication No. 90 discloses that the alumina compound has a positive charge and the value of the zeta potential in the examples, but the specific measuring method and conditions are not described. The value of the zeta potential is the cell of the measuring device, the electrode structure, the applied voltage, the solid content concentration, the pH of the dispersion liquid,
Since it depends on the dispersant and additives used, the absolute values cannot be directly compared unless the measurement conditions and equipment are standardized.

The alumina hydrate used in the present invention is an aqueous dispersion of 0.1% by weight and has a zeta potential of 15 mV or more at pH 6 without addition of a dispersant and additives. preferable. When the zeta potential is within this range, the alumina hydrate can be easily dispersed in the dispersion liquid to the level of primary particles. When the zeta potential is less than 15 mV, aggregates or precipitates are generated as the solid content concentration increases, or when the binder dispersion and alumina hydrate are mixed, the particles partially aggregate to form a large lump. To form. Therefore, particularly in a recording medium having an ink receiving layer, the pore size of the ink receiving layer is significantly increased, the strength of the ink receiving layer is reduced, powder is removed, and the dye fixability during printing is improved. It may get worse.

Alumina hydrate is generally stable in a low pH range, so it is known that an acid is added to lower the pH of the dispersion in order to improve the dispersibility.
The addition of an acid is not preferable because it causes an irritating odor or corrosion and limits the type of binder used. Also,
The known method of adding a dispersant is not preferable because the liquid is repelled when the dispersion is applied. On the other hand, when the pH range becomes higher, the primary particles may be aggregated and the particle size may be increased depending on the type of the alumina hydrate, resulting in an apparently high zeta potential. The zeta potential of the alumina hydrate specified in the present invention is, of course, measured in the state where such particles do not aggregate, but in order to check the presence or absence of the aggregation state of such particles, the dispersed particles It is effective to measure the particle size of. A known method can be adopted as a method for measuring the particle diameter. However, it is necessary to confirm that the particle size in the dispersion liquid of pH 6 in which the zeta potential is measured has almost the same value as the particle size in the dispersion liquid of pH 4 which is said to stably disperse the particles. .

In the present invention, it is preferable that the specific alumina hydrate as described above has a nitrate radical of 0.1 to 1.0.
The viscosity of a dispersion liquid containing a solid content of 15% by weight in ion-exchanged water has a dispersion temperature of 20 ° C.,
75 CPS or less when measured at a shear rate of 7.9 sec ^-1 ,
It is particularly preferably 30 CPS or less. Further, preferably, the viscosity of the dispersion liquid obtained by dispersing the same alumina hydrate containing 0.1 to 1.0% by weight of nitrate radical in ion-exchanged water at a solid concentration of 20% by weight is the dispersion liquid temperature. It is 100 CPS or less when measured at 20 ° C. and a shear rate of 10.2 sec ⁻¹ ,
It is particularly preferably 80 CPS or less. Furthermore, the viscosity of a dispersion obtained by dispersing the same alumina hydrate containing 0.1 to 1.0% by weight of nitrate radicals in ion-exchanged water at a solid concentration of 25% by weight has a dispersion temperature of 20 ° C. , Shear rate 10.
It is preferably 500 CPS or less, and particularly preferably 460 CPS or less, measured at 2 seconds- ¹ . In each of the above-mentioned cases, when the viscosity exceeds the upper limit of the range, it is necessary to reduce the solid content concentration of the dispersion, which is not preferable in terms of mass productivity.

The viscosity of the dispersion of the alumina hydrate can be measured by using a rotational viscometer such as a B type viscometer.

As a result of comparing and examining the conventional example using the above-mentioned pseudo-beamite and the present invention, the differences are as follows.

1) In the above-mentioned conventional example, the pore size distribution is 45% of the total pore volume in the range of ± 10Å of the average pore radius.
Alternatively, only the range in which the pore volume is 55% and the width of the pore size distribution is narrow is disclosed. On the other hand, the present inventor has found that an alumina hydrate having two maximums in the pore size distribution and an ink receiving layer using the alumina hydrate are effective. By having these two maxima, the functional separation of the pores is performed, the solvent component in the ink is absorbed by the pores with a relatively large diameter, and the dye component in the ink is adsorbed by the pores with a relatively small diameter. It has been found that by doing so, a recording medium with good color development can be obtained in which the ink dries quickly even when printing is performed with multiple colors at high speed.

2) In the above-mentioned conventional example, regarding the pore diameter and the pore volume, the total pore volume of the pore radius of 10 to 40 Å is 0.2 to 1.0 cc / g, and the total pore volume of 40 to 100 Å is 0. 1
~ 0.4cc / g, 100cc ~ 1000Å 0.1cc
/ G. On the other hand, the present inventor has set the relationship between the pore volume per unit area of the ink receiving layer and the isothermal nitrogen adsorption / desorption curve within the range described in the present specification, thereby adsorbing and drying the ink after printing. Have been found to be significantly improved.

3) In the above-mentioned conventional example, a pseudo-baemite sol and a method for producing an ink receiving layer using the same are described. Further, the shape of pseudo-boehmite and the solid content concentration of the dispersion are described. On the other hand, the present inventor has found that tabular alumina hydrate is used. Such a plate-like amorphous alumina hydrate can be produced preferably by hydrolyzing a long-chain aluminum alkoxide, so that an alumina hydrate having a small amount of ions or raw material alcohol mixed therein can be easily obtained. You can In this step, the alumina hydrate is likely to be tabular grains and the shape can be easily controlled. The dispersibility is extremely higher than that of conventionally known alumina hydrate having a hairy bundle. Furthermore, by not using a sol to directly prepare a dispersion (particularly a coating dispersion), it is possible to easily obtain a low-viscosity dispersion having a high solid content concentration by using alumina hydrate once dried and powderized. Can be obtained.

In the recording medium of the present invention, the binder that can be used in combination with the alumina hydrate can be freely selected from water-soluble polymers. For example, polyvinyl alcohol or a modified product thereof (cation-modified, anion-modified, silanol-modified),
Cellulose such as starch or a modified product thereof (oxidation, etherification), gelatin or a modified product thereof, casein or a modified product thereof, carboxymethyl cellulose, gum arabic, hydroxyethyl cellulose, hydroxypropylmethyl cellulose and the like. -Derivatives, SBR latex, NBR latex, conjugated diene-based copolymer latex such as methyl methacrylate-butadiene copolymer, functional group-modified polymer latex, vinyl-based copolymer such as ethylene vinyl acetate copolymer Latex, polyvinylpyrrolidone, maleic anhydride or a copolymer thereof, an acrylic acid ester copolymer and the like are preferable. These binders can be used alone or in combination of two or more. The mixing ratio of the alumina hydrate and the binder can be arbitrarily selected from the range of 1: 1 to 30: 1. More preferable range is 5: 1 to 2
It is 5: 1. When the amount of the binder is less than the above range, the mechanical strength of the ink receiving layer is insufficient, and cracking and powder drop occur. When the amount of the binder is more than the above range, the pore volume is small and the ink absorption is small. become worse.

Alumina hydrate, a binder, if necessary, a dispersant, a thickener, a pH adjusting agent, a lubricant, a fluidity modifier, a surfactant, an antifoaming agent, a water resistance agent, a foam suppressing agent. ,Release agent,
A foaming agent, a penetrating agent, a coloring dye, a fluorescent whitening agent, an ultraviolet absorber, an antioxidant, an antiseptic agent and an antifungal agent can be added as required.

The waterproofing agent can be freely selected from known materials such as halogenated quaternary ammonium salts and quaternary ammonium salt polymers.

As the base material of the recording medium of the present invention, paper such as appropriately sized paper, non-sized paper, resin coated paper using polyethylene and the like, sheet-like thermoplastic film, etc. Materials and fabrics can be used. In the case of a thermoplastic film, polyester, polystyrene, polyvinyl chloride, polymethylmethacrylate, cellulose acetate,
It is also possible to use a transparent film such as polyethylene or polycarbonate, or an opaque sheet filled with a pigment or finely foamed.

The dispersion of alumina hydrate, which is preferably used for producing the recording medium of the present invention, can be prepared as follows. The above-mentioned powdery alumina hydrate is added to ion-exchanged water to prepare a liquid having a predetermined solid content concentration. Then, a mechanical shearing force or ultrasonic waves is applied to the dispersion liquid as needed to control the particle size of the alumina hydrate. Thereafter, a separately prepared binder dispersion is added, and if necessary, treatments such as dispersion, heating, and defoaming are performed to obtain a final dispersion for coating.

In the recording medium having the ink receiving layer of the present invention, the method for forming the ink receiving layer on the substrate is as follows. A method of coating and drying on the surface can be used. As a coating method, generally used are a blade coater, an air knife coater, a roll coater, a brush coater, a curtain coater, a bar coater, and a gravure. A coating technique using a coater, a spray device or the like can be adopted. The coating amount of the dispersion liquid is 0.5 to 60 g / m ^{2 in} terms of dry solid content, more preferably 5 to 45 g / m ² .
m ² . If necessary, the surface smoothness of the ink receiving layer can be improved by using a calendar roll or the like after coating.

The recording medium of the type in which the alumina hydrate of the present invention is internally added is an alumina hydrate (dispersion thereof).
Can be produced by an internal addition method in which is added to the slurry containing the fibrous substance in the papermaking process. In this way,
If necessary, a paper strength improver, a yield improver, and a coloring agent may be added and used. As a yield improver,
It can be selected or used in combination with a cationic retention aid such as cationized starch and dicyandiamide formalin condensate or an anionic retention aid such as anionic polyacrylic amide and anionic colloidal silica.

The ink used for recording on the recording medium of the present invention mainly contains a coloring material (dye or pigment), a water-soluble organic solvent and water. As the dye, for example, a direct dye, an acid dye, a basic dye, a reactive dye, a water-soluble dye represented by an edible dye is preferable, and in combination with the recording medium, fixability, color developability, vividness, Any material may be used as long as it gives an image satisfying the required performance such as stability, light resistance and the like.

The water-soluble dye is generally used by dissolving it in water or a solvent consisting of water and an organic solvent, and these solvent components are preferably a mixture of water and various water-soluble organic solvents. Is used, but it is preferable to adjust the water content in the ink to be in the range of 20 to 90% by weight, preferably 60 to 90% by weight.

Examples of the water-soluble organic solvent include methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol.
, Sec-butyl alcohol, tert-butyl alcohol, isobutyl alcohol and the like, alkyl alcohols having 1 to 4 carbon atoms, amides such as dimethylformamide and dimethylacetamide, acetone, diacetone alcohol Such as ketones or ketone alcohols, tetrahydrofuran, dioxane and other ethers, polyethylene glycol, polypropylene glycol and other polyalkylene glycols, ethylene glycol, propylene glycol, 1, 2 , 6-hexanetrio-
, Thiodiglycol, hexylene glycol, diethylene glycol, and other alkylene groups having an alkylene group containing 2 to 6 carbon atoms, glycerin, ethylene glycol methyl ether, diethylene glyco-mertyl ether, Examples thereof include lower alkyl ethers of polyvalent alcohols such as diethylene glycol ethyl ether, triethylene glycol monomethyl ether and triethylene glycol monoethyl ether.

Among many of these water-soluble organic solvents,
Preferred are polyhydric alcohols such as diethylene glycol, and lower alkyl ethers of polyhydric alcohols such as triethylene glycol monomethyl ether and triethylene glycol monoethyl ether. Polyvalent alcohols are
It is particularly preferable because it has a great effect as a lubricant for preventing a decrease in nozzle clogging due to evaporation of water in the ink and precipitation of a water-soluble dye.

A solubilizer may be added to the ink. Typical solubilizers are nitrogen-containing heterocyclic ketones, and their purpose is to dramatically improve the solubility of the water-soluble dye in a solvent. For example, N-methyl-2-pyrrolidone and 1,3-dimethyl-2-imidazolidinone are preferably used. To further improve the properties, a viscosity modifier, a surfactant, a surface tension modifier, p
Additives such as an H adjuster and a specific resistance adjuster can also be added.

An ink jet recording method is preferable as a method for recording by applying the above-mentioned ink to the recording medium. In this recording method, the ink is effectively separated from the nozzle to apply the ink to the recording medium. Any method may be used as long as it can be obtained. In particular, according to the method described in JP-A-54-59936, an ink-jet system in which ink subjected to the action of thermal energy causes a rapid volume change, and the action force resulting from this state change causes ink to be ejected from a nozzle Can be used effectively.

[0069]

EXAMPLES The present invention will be described in more detail below with reference to examples, but the present invention is not limited thereto. The physical properties according to the present invention were measured as follows. 1) BET specific surface area, pore size distribution, pore volume, isothermal desorption curve characteristics A recording medium having an ink receiving layer formed on an alumina hydrate or PET film is sufficiently heated and degassed, and then nitrogen adsorption / desorption is performed. It measured using the separation method. (Manufactured by Cantachrome,
Auto Solve 1) The BET specific surface area was calculated by the method of Brunauer et al. (J. Am. Chem. Soc., Volume 60, 3
09, 1938) The method of Barrett et al. Was used for the calculation of pore radius and pore volume. (J. Am. Chem. Soc., Vol. 73,
373, 1951) ・ From the isothermal nitrogen adsorption / desorption curve, 90% of the maximum adsorption gas amount
The relative pressure difference (ΔP) between adsorption and desorption with the amount of adsorbed gas was determined. 2) X-ray diffraction image It was performed using an X-ray diffraction device (manufactured by Rigaku Denki Co., Ltd.). 3) Shape observation of alumina hydrate (aspect ratio, aspect ratio, particle shape) Alumina hydrate was dispersed in ion-exchanged water and dropped on a collodion membrane to prepare a measurement sample. This sample was observed with a transmission electron microscope (H-500 manufactured by Hitachi Ltd.). 4) Number of hydroxyl groups 1 g of alumina hydrate was weighed and titrated with triethylaluminum. 5) Zeta potential Alumina hydrate was dispersed in ion-exchanged water so that the solid content concentration was 0.1% by weight, and then the pH of the dispersion was adjusted to 6 using nitric acid and measured. . (Bi-ZETA plus manufactured by Brookhaven Co., liquid temperature 20 ° C., using acrylic cell) 6) Solution viscosity An aqueous dispersion having a solid content concentration of 15% by weight of alumina hydrate is prepared and at a temperature of 20 ° C. VI made by TOKIMEC
The shear rate was measured at 7.9 sec ^-1 using a SCOMETER. In addition, an aqueous dispersion having a solid content concentration of 20% by weight of alumina hydrate was prepared, and the TOK was prepared at a temperature of 20 ° C.
The measurement was performed at a shear rate of 10.2 sec ^-1 using a VISCOMETER manufactured by IMEC. 7) Nitrate radical The nitrate radical was extracted from the alumina hydrate with hot water, measured by ion chromatography (Hitachi, L-3720), and expressed as a weight percentage in the alumina hydrate. 8) Printing characteristics Using an inkjet printer equipped with an inkjet head provided with 128 nozzles for 4 colors of Y, M, C, and Bk at a nozzle interval of 16 nozzles per 1 mm, using an ink having the following composition, Inkjet recording was performed to evaluate the ink drying property (absorption property), image density, bleeding, and beading.

(1) Ink Dryness The dry state of the ink on the surface of the recording medium after solid printing of the Y, M, C and Bk inks in a single color or multiple colors was examined by touching the recording portion with a finger. Ink amount for monochrome printing is 1
It was set to 00%. When the ink amount is 300%, the ink does not adhere to the finger ⊚, when the ink amount is 200% the ink does not adhere to the finger ∘, when the ink amount is 100%, the ink does not adhere to the finger Δ, the ink is 100% Is attached to your finger
And (2) Image Density The image density of the image solidly printed with the Bk ink was evaluated using a Macbeth reflection densitometer RD-918. (3) Bleeding and beading The bleeding and beading on the surface of the recording medium after solid printing of the Y, M, C, and Bk inks in a single color or multiple colors were visually evaluated. The ink amount in monochromatic printing was set to 100%. If the ink amount does not occur at 300%, it is ⊚, if it does not occur at the ink amount of 200%, ○, the ink amount is 100.
% If not occurred, x if 100% occurred
And

Ink composition Dye 5 parts Diethylene glycol 10 parts Polyethylene glycol 10 parts Water 75 parts Dye Y: C.I. I. Direct Yellow-86 M: C.I. I. Acid Red 35 C: C.I. I. Direct Bull-199 Bk: C.I. I. Hood Black 2

Examples 1 to 4 Aluminum dodoxide was prepared by the method described in US Pat. No. 4,242,271. Then, the aluminum alkoxide was hydrolyzed by the method described in US Pat. No. 4,202,870 to produce an alumina slurry. Water was added to this alumina slurry until the solid content of alumina hydrate reached 7.9%. Alumina slurry
Had a pH of 9.5. The pH was adjusted by adding a 3.9% nitric acid solution. Colloidal sols were obtained under the respective aging conditions shown in Table 1. This colloidal sol was spray-dried at 75 ° C. to obtain an alumina hydrate. This alumina hydrate was amorphous as shown in the X-ray diffraction image of FIG. In addition, a drawing-substitute photograph of Fig. 3 (electron micrograph: magnification of 30,000)
It had a flat plate shape as shown in FIG. The physical properties of the hydrated alumina were measured by the methods described above. The results are shown in Table 2 and FIG.
And shown in FIG.

Polyvinyl alcohol (Gosenol NH18 manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) was dissolved and dispersed in ion-exchanged water to obtain a 10% by weight solution. Examples 1 to 4
The above alumina hydrate was dispersed in ion-exchanged water in the same manner to obtain a 15% by weight dispersion liquid. The above-mentioned alumina hydrate and polyvinyl alcohol solution were weighed in amounts such that the polyvinyl alcohol solid content and the alumina hydrate solid content became 1:10 by weight mixing ratio, and they were mixed and stirred to mix. A dispersion was obtained. The mixed dispersion liquid was applied to PET having a thickness of 100 μm.
It was die-coated on a film (Lumira manufactured by Toray Industries, Inc.) to obtain a receptive layer having a thickness of 30 μm. The drawing-substitute photograph (electron micrograph: magnification: 50,000 times) of FIG. 4 is an observation of a cross section of the ink receiving layer, in which the tabular alumina hydrates are randomly arranged in the ink receiving layer. The physical properties of the ink receiving layer were measured by the methods described above. The measurement results are shown in Table 3.

Examples 5 to 8 The alumina hydrate dispersion prepared in Examples 1 to 4 and the polyvinyl alcohol dispersion were mixed with alumina hydrate solids and the same polyvinyl alcohol solid as in Example 1. The respective amounts were adjusted such that the weight became 15: 1 by weight, and mixed and stirred to obtain a mixed dispersion. 20 g / m ² air of the above-mentioned mixed dispersion on a high-quality paper (Shirahoi 157, manufactured by Daishowa Paper Manufacturing Co., Ltd.)
An ink receiving layer was obtained by knife coating. The physical properties of the ink receiving layer were measured by the methods described above. The measurement results are shown in Table 4.

Examples 9 to 12 Freeness (C.S.F.) 370 m as raw material pulp
80 parts of hardwood bleached kraft pulp (LBKP) and 410 ml of softwood kraft pulp (NBKP) 2
0 part was used, and 35 wt% of the alumina hydrate prepared in Examples 1 to 4 as a filler was used as a filler, and a cationized starch (CATOF, manufactured by Oji National Co., Ltd.) was used as a yield improver. Was added internally to the pulp solids in an amount of 0.3% by weight, and further 0.05% by weight of a polyacrylic amide-based retention aid (Pall Flock FR-X manufactured by Seikou Kagaku Kogyo Co., Ltd.) was added immediately before papermaking. , TAPP
Paper was made to a basis weight of 70 g / m ² using an I standard sheet former. Next, oxidized starch with a concentration of 2% (made by Nippon Shokuhin Co.,
MS3800) solution was attached by a size press device to obtain a recording medium. The measurement results are shown in Table 5.

Comparative Example 1 According to the method described in Example 1 of JP-A-4-4181, an alumina sol (manufactured by Catalysis Kasei Co., AS-
2) and polyvinyl alcohol (Kuraray, PVA11)
A recording medium was prepared using 7). The zeta potential of the alumina sol was measured by the above method. Further, the alumina sol was concentrated to a solid content concentration of 15% and the viscosity was measured. The physical property values are shown in Table 6.

Comparative Example 2 According to the method described in Example 4 of JP-A-4-4181, alumina sol (manufactured by Catalysis Chemicals Co., AS-
A recording medium was prepared using 3) and the same polyvinyl alcohol as in Comparative Example 1. The physical property values are shown in Table 6.

Comparative Example 3 According to the method described in Example 1 of JP-A-3-143678, an alumina sol (manufactured by Nissan Chemical Co., Ltd., 10
0) and the same polyvinyl alcohol as in Comparative Example 1 were used to prepare a recording medium. The physical property values are shown in Table 6.

Comparative Example 4 An alumina sol was prepared according to the method described in Example 1 of JP-A-5-32037. A recording medium was prepared using the alumina sol and the same polyvinyl alcohol as in Comparative Example 1. The physical property values are shown in Table 6.

[0080]

[Table 1]

[0081]

[Table 2]

[0082]

[Table 3]

[0083]

[Table 4]

[0084]

[Table 5]

[0085]

[Table 6]

[0086]

【The invention's effect】

1) Since the same pigment or ink receiving layer has two or more maximum pore size distributions, the functional separation of the pores can be performed.

2) Since the dye in the ink can be efficiently absorbed by the pores having a relatively small diameter, it is possible to obtain an image having a sufficient resolution and a sufficient density of color development.

3) Since the solvent components in the ink can be absorbed quickly by the pores having a relatively large diameter, an image with good resolution can be obtained without beading, bleeding, or ink overflow.

4) The absence of hysteresis facilitates the removal of the solvent component in the ink, improves the drying property of the ink, and prevents bleeding and show-through.

5) Since the dispersibility is good, the viscosity can be lowered even in a dispersion having a high solid content concentration.

6) Since the dispersibility is good even in the neutral region where the pH is around 7, the amount of acid added to the dispersion can be reduced.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an embodiment of a recording medium of the present invention.

FIG. 2 is a diagram showing an X-ray diffraction image of alumina hydrate used in the present invention.

FIG. 3 is a drawing-substituting photograph showing the shape of alumina hydrate used in the present invention.

FIG. 4 is a drawing-substituting photograph showing the arrangement of alumina hydrate in the ink receiving layer as seen from the cross section of the ink receiving layer according to the present invention.

FIG. 5 is a diagram showing a pore size distribution of an alumina hydrate of Example 1 of the present invention.

FIG. 6 is a diagram showing an isothermal adsorption curve of hydrated alumina of Example 1 of the present invention.

[Explanation of symbols]

 1 substrate 2 ink receiving layer

[Procedure amendment]

[Submission date] August 1, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Figure 3

[Correction method] Change

[Correction content]

FIG. 3 is a drawing-substituting photograph showing a particle structure of an alumina hydrate used in the present invention.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] Fig. 4

[Correction method] Change

[Correction content]

FIG. 4 is a drawing-substituting photograph showing a particle structure of alumina hydrate in an ink receiving layer as seen from a cross section of the ink receiving layer according to the present invention.

Claims (24)

[Claims] 1. A recording medium comprising an alumina hydrate having two or more maximums in a pore radius distribution. 2. A recording medium having an ink receiving layer containing a pigment and a binder provided on a substrate, wherein the ink receiving layer contains alumina hydrate as a pigment, and the ink receiving layer has two or more maximums in the pore radius distribution. A recording medium having. 3. A recording medium characterized in that an alumina hydrate having two or more maximums in the pore radius distribution is internally added to a fibrous substance. 4. The recording medium according to claim 1, wherein the maximum of the radius distribution of pores of the alumina hydrate is 100 Å or less and in the range of 100 to 200 Å. 5. The recording medium according to claim 2, wherein the maximum of the pore radius distribution of the ink receiving layer is 100 Å or less and in the range of 100 to 200 Å. 6. Alumina hydrate having a pore volume of 0.4 to
The recording medium according to claim 1, which has a density of 0.6 cc / g. 7. The ink receiving layer has a pore volume of 0.4 to 0.
The recording medium according to claim 2, which is 6 cc / g. 8. The pore volume of the pores having a maximum value of 100 Å or less of the alumina hydrate is 0.1 to 1 of the total pore volume.
The recording medium according to claim 1, 3 or 4, which is 0%. 9. The pore volume of the pores having a maximum value of 100 Å or less in the ink receiving layer is 0.1 to 10 of the total pore volume.
%, And the recording medium according to claim 2 or 5. 10. The total pore volume of the ink receiving layer is 8 c.
The recording medium according to claim ^2, which has a c / m ² or more. 11. The relative pressure difference (ΔP) between adsorption and desorption at an adsorbed gas amount of 90% of the maximum adsorbed gas amount obtained from an isothermal nitrogen adsorption / desorption curve of the alumina hydrate is 0.2 or less. The recording medium according to any one of claims 1, 3, 4, and 8. 12. A relative pressure difference (ΔP) between adsorption and desorption at an adsorbed gas amount of 90% of the maximum adsorbed gas amount obtained from an isothermal nitrogen adsorption / desorption curve of the ink receiving layer is 0.2 or less. The recording medium according to claim 2, 5, or 9. 13. The recording medium according to claim 1, wherein the alumina hydrate is an amorphous compound. 14. The recording medium according to claim 13, wherein the alumina hydrate is a tabular alumina hydrate having an average aspect ratio of 3 to 10. 15. The recording medium according to claim 14, wherein the tabular alumina hydrate has a BET specific surface area of 70 to 300 m ² / g. 16. The recording medium according to claim 14, wherein an average aspect ratio of the flat plate surface of the flat alumina hydrate is 0.6 to 1.0. 17. The number of hydroxyl groups of the alumina hydrate is 10
^The recording medium according to claim 1, wherein the recording medium is ²⁰ pieces / g or more. 18. A hydrate of the alumina hydrate at pH 6
The recording medium according to claim 1, wherein the target potential is 15 mV or higher. 19. An alumina hydrate containing 0.1 to 1.0% by weight of nitrate radicals and having two or more maximum pore size distributions is dispersed in ion-exchanged water at a solid concentration of 15% by weight, The viscosity is 75 when measured at a temperature of 20 ° C and a shear rate of 7.9 sec- ^1.
A dispersion liquid of hydrated alumina, which is CPS or less. 20. An alumina hydrate containing 0.1 to 1.0% by weight of nitrate radicals and having two or more maximums in the pore size distribution is dispersed in ion-exchanged water at a solid concentration of 20% by weight, The viscosity is ¹ when measured at a temperature of 20 ° C and a shear rate of 10.2 sec ^- 1.
Dispersion liquid of hydrated alumina, which is not more than 00 CPS. 21. An alumina hydrate containing 0.1 to 1.0% by weight of nitrate radicals and having two or more maximum pore size distributions is dispersed in ion-exchanged water at a solid concentration of 25% by weight. The viscosity is 5 when measured at a temperature of 20 ° C and a shear rate of 10.2 sec- ^1.
Dispersion liquid of hydrated alumina, which is not more than 00 CPS. 22. The dispersion according to claim 19, which is a dispersion of a pigment for producing a recording medium. 23. A droplet of ink is ejected from a fine hole,
An inkjet recording method for applying a print to a recording medium, wherein the recording medium according to claim 1 is used as the recording medium. 24. The ink jet recording method according to claim 23, wherein thermal energy is applied to the ink to eject ink droplets.