JP2006289864A - Inkjet medium to be recorded - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet medium to be recorded which is excellent in image fastness (lightfastness, gas-resistance, and water-resistance or the like) and capable of achieving high ink absorption performance and excellent image quality. <P>SOLUTION: The inkjet medium to be recorded has an ink receiving layer at least on one face on a support. The ink receiving layer contains pigments, a binder resin, and a water-soluble aluminum-based compound. The concentration of sulfate ions included in the water-soluble aluminum-based compound is 0.51-2.70 mass%. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention provides an ink jet recording medium suitable for recording using water-based ink. In particular, the present invention relates to an ink jet recording medium having long-term image storage stability and excellent image characteristics.

  In recent years, with the rapid development of the information technology (IT) industry, various information processing systems have been developed, and a recording method and a recording apparatus suitable for each information processing system have been developed and put into practical use. Among such recording methods, the inkjet recording method is advantageous in that it can be recorded on various recording materials, the hardware (equipment) is relatively inexpensive, is compact, and is excellent in low noise. It has been widely used not only in offices but also in so-called home use. In addition, with the recent increase in resolution of inkjet printers, it has become possible to obtain a high-quality recorded product comparable to a so-called silver salt photograph, and various properties have been improved for inkjet recording media. The properties required for recent inkjet recording media include glossy, surface smoothness, photographic paper-like texture similar to silver salt photography, etc. High image fastness (light resistance, gas resistance, water resistance, etc.) of the image after printing is required.

  The glossy photographic paper for obtaining a high-quality recorded image similar to a photograph so far has (1) an ink receiving layer containing fine inorganic pigment particles and a water-soluble resin and having a high porosity on the support. Inkjet recording medium (see Patent Documents 1 and 2), (2) As a thing that pays attention to both water resistance and light resistance due to a cationic polymer, for example, (meth) acrylate and / or (meth) acrylamide type cation moiety and Inkjet recording media using a cationic polymer having both a vinylbenzylammonium salt-based cationic moiety (see Patent Documents 3 to 4), (3) Focusing on polyaluminum chloride compounds as ink fixing agents, and recording images over time Ink jet recording media with improved bleeding and water resistance (see Patent Documents 5 to 8) have been proposed. In Patent Document 7, by setting the sulfate ion concentration contained in polyaluminum chloride to 0.5% by mass or less, bleeding and water resistance of a recorded image can be improved, but at the same time, light resistance and gas resistance are improved. Can not achieve.

As described above, various studies have been made so far, and it is particularly excellent in image fastness (light resistance, gas resistance, water resistance, etc.), and can achieve high ink absorption performance and good image quality. At present, such an ink jet recording medium has not been fully developed.
JP 10-119423 A Japanese Patent Laid-Open No. 10-217601 JP 11-348409 A JP 2003-305943 A Japanese Patent Laid-Open No. Sho 61-16884 JP 2001-113817 A JP 2004-202964 A Japanese Patent No. 3371365

  The problems to be solved by the present invention are as follows. That is, it is a problem to achieve improvement in light resistance and gas resistance while satisfying the bleeding and water resistance of recorded images over time.

  Accordingly, an object of the present invention is to provide an ink jet recording medium that is excellent in image fastness (light resistance, gas resistance, water resistance) and can achieve high ink absorption performance and good image quality (bleed over time). The purpose is to do.

  The inventor of the present application has made extensive studies in order to solve the above-mentioned problems. As a result, the ink-receiving layer constituting the ink jet recording medium contains a water-soluble aluminum compound containing a specific amount of sulfate ions. It has been found that the above problems can be solved by synergistically expressing the aggregation effect with the dye by the aluminum compound and the salting out effect by the sulfate ion, and the present invention has been completed.

The inkjet recording medium according to the present invention is an inkjet recording medium having an ink receiving layer on at least one side of a support.
<1> The ink receiving layer contains a pigment, a binder resin, and a water-soluble aluminum compound, and a concentration of sulfate ions contained in the water-soluble aluminum compound is 0.51% by mass to 2.70% by mass. It is characterized by. (Claim 1)
<2> At least one of the water-soluble aluminum compounds is polyaluminum chloride. (Claim 2)
<3> The basicity of the polyaluminum chloride is 40.0% to 79.9%. (Claim 3)
<4> the content in the ink receiving layer of the water-soluble aluminum compound, characterized in that it is a ^{0.02g / m 2 ~1.50g / m 2} . (Claim 4)

  According to the present invention, an ink receiving layer is formed using a water-soluble aluminum compound having a sulfate ion concentration of 0.51% by mass to 2.70% by mass contained in the water-soluble aluminum compound. By synergistically expressing the agglomeration effect of the dye by the water-soluble aluminum compound and the salting-out effect by the sulfate ion, the image fastness (light resistance, ozone resistance, water resistance, etc.) is excellent and good. It is possible to provide an ink jet recording medium having ink absorptivity and capable of forming a high-resolution and high-density image.

  Hereinafter, an inkjet recording medium which is excellent in image fastness (light resistance, gas resistance, water resistance, etc.), which is the object of the present invention, and which can achieve high ink absorption performance and good image quality is described below. This will be described in detail.

A. Water-soluble aluminum-based compound The ink-receiving layer of the present invention contains a water-soluble aluminum-based compound together with a pigment in order to improve blurring of recorded images over time and water resistance. The water-soluble aluminum compound is distributed over the thickness direction and the surface direction of the ink receiving layer. When a polyvalent metal such as a water-soluble aluminum compound is present in the ink receiving layer at a predetermined content, the dye in the ink is often anionic. Aggregation occurs between them, and aging blur under high temperature and high humidity conditions is improved. Further, it is difficult to redissolve the dye molecule group in such an aggregated state in the ink receiving layer of the ink jet recording medium, and it is difficult to redissolve easily by simply contacting water with the ink receiving layer. For these reasons, the present inventors consider that the water resistance is improved.

  However, in order to improve the storage stability (light resistance, gas resistance, etc.) of the image area, the aggregation effect as a polyvalent metal originally possessed by this water-soluble aluminum compound is not sufficient, and in the ink receiving layer It is possible to improve the storage stability (light resistance, gas resistance, etc.) of the image area by adding sulfate ions to the salt to express the salting out effect of the sulfate ions.

  However, simply forming an ink receiving layer by combining a water-soluble aluminum-based compound and sulfate ions limits the effect of improving image fastness and image quality. Accordingly, the present inventors have conducted various studies on the characteristics of the water-soluble aluminum-based compound, and in order to obtain excellent image fastness (light resistance, gas resistance, water resistance, etc.) and image quality, It was found that a water-soluble aluminum-based compound containing a specific concentration of sulfate ions may be contained in the present invention, and the present invention has been completed.

  The light resistance, gas resistance, and water resistance are improved in this way because of the synergistic effect of the aggregation (association) effect between the water-soluble aluminum compound and the dye and the salting-out effect of sulfate ions. It is thought that it was because of. As a result, it is difficult to redissolve easily by simply contacting water with the ink receiving layer, and at the same time, the oxidation site of the dye is stabilized.

  In addition, it is considered that the stability of the water-soluble aluminum compound itself (and the dye aggregation characteristics and reactivity resulting therefrom) change by including a predetermined concentration of sulfate ion in the water-soluble aluminum compound. In the present invention, the selective range is a sulfate ion concentration range in which the aggregation characteristics of the water-soluble aluminum compound are sufficiently exhibited and a sulfate ion concentration range in which the salting-out effect of sulfate ions is sufficiently demonstrated synergistically. Is.

  The concentration of sulfate ion contained in the water-soluble aluminum-based compound needs to be 0.51% by mass to 2.70% by mass. The sulfate ion concentration here indicates the solid content concentration in the aqueous solution of the water-soluble aluminum-based compound. When the sulfate ion concentration is less than 0.51% by mass, the water resistance is sufficiently exhibited, but the light resistance and gas resistance are insufficient. In addition, in the case of less than 0.51% by mass, it is extremely difficult for the water-soluble aluminum-based compound to exist in a solution state in the coating solution, and from the viewpoint of solution stability, it is 0.51% by mass or more. It is necessary to be. Further, when the amount exceeds 2.70% by mass, the aggregation of the dye contained in the ink is promoted too much, so that a bronze phenomenon may occur particularly in cyan and magenta. In addition, the dye in the ink agglomerates near the surface of the recording medium, which may affect not only the bronze but also the ink absorbency, resulting in poor absorption such as beading. It is because it is not preferable. When the sulfate ion concentration is within these ranges, a recording medium having excellent light resistance, gas resistance and quality can be obtained due to the synergistic effect of the water-soluble aluminum compound and sulfate ion.

  Specific examples of the water-soluble aluminum compound include aluminum sulfite, aluminum thiosulfate, polyaluminum chloride, aluminum nitrate nonahydrate, aluminum chloride hexahydrate and the like. These can be used alone or in combination of two or more.

  The water-soluble aluminum compound of the present invention is particularly preferably a basic polyaluminum hydroxide compound (polyaluminum chloride) from the viewpoint of improving water resistance, weather resistance and aging blur.

  However, a basic polyaluminum hydroxide compound (polyaluminum chloride), which is a water-soluble aluminum compound commercially available so far, exists in the form of an aqueous solution, and the sulfate ion concentration in the aqueous solution is around 3.0% by mass. The concentration was high, and the same effect as in the present invention could not be obtained.

  This sulfate ion originates from being contained as a raw material or a stabilizer in the production of a basic polyaluminum hydroxide compound (polyaluminum chloride), which remains in the water-soluble aluminum-based compound. Is. Therefore, the water-soluble aluminum compound used in the present invention must be produced in a state in which sulfate ions remain in a predetermined preferable concentration range. For example, other substitutes may be used as raw materials or stabilizers. A predetermined amount of sulfate ions may be separated by performing membrane separation, chromatographic separation, or the like on the aqueous solution containing a water-soluble aluminum compound containing high-concentration sulfate ions produced by the above production method.

  Among the water-soluble aluminum compounds used in the present invention, the basicity of a basic polyaluminum hydroxide compound (polyaluminum chloride) which is a particularly preferred form is preferably 40.0% to 79.9%. A more preferable basic polyaluminum hydroxide compound has a basicity range of 45.0% to 65.0%. If it is less than 40.0%, the water resistance and image preservability (light resistance, gas resistance, etc.) may be deteriorated. On the other hand, if it exceeds 79.9%, it is not preferable because it is easily insoluble in water and unstable in water, and the ink absorbability is remarkably lowered.

The mechanism for causing such a difference depending on the basicity of the basic polyaluminum hydroxide compound is considered as follows. The basic polyaluminum hydroxide compound (polyaluminum chloride) includes [Al ₂ (OH) _n Cl _6-n ] _m (formula 1), [Al (OH) ₃ ] _n AlCl ₃ (formula 2), Al _n ( OH) _m Cl _(3n-m) 0 <m <3n (Formula 3) is known to be represented by three general formulas: [Al ₆ (OH) ₁₅ ] ³⁺ , [Al ₈ (OH ) ₂₀ ] ⁴⁺ , [Al ₁₃ (OH) ₃₄ ] ⁵⁺ , [Al ₂₁ (OH) ₆₀ ] ³⁺ It is clear that the higher the molecular weight, the higher the polynuclear condensed ion. Higher molecular weight basic polyaluminum hydroxide (polyaluminum chloride) having a higher basicity is considered to have a higher cation influence and a higher ability to aggregate dyes more efficiently. However, it is not preferable that the basicity becomes too high. Some basic polyaluminum hydroxide compounds (polyaluminum chloride) commercially available so far have a basicity of 80.0% or more. However, these cause the dye in the ink to agglomerate near the surface of the recording medium, which may affect not only bronze but also ink absorbency, resulting in poor absorption such as beading. This is not preferable.

  In addition, in the case of a basic polyaluminum hydroxide compound having a low molecular weight and a low basicity, the ability to agglomerate the dye is lowered and the water resistance is inferior. (Light resistance, gas resistance, etc.) may also be deteriorated.

  In the case of using the basic polyaluminum hydroxide compound as described above, the weight average molecular weight is preferably 500 or more, particularly preferably about 1000 to 100,000. The above basic poly water-soluble aluminum compounds can be used in combination of two or more, or in combination with other types of water-soluble aluminum compounds.

Further, in the present invention, the amount contained in the ink-receiving layer of the water-soluble aluminum compound (solids) is preferably from ^{0.02g / m 2 ~1.50g / m 2} , 0.02g / m 2 ~0 0.5 g / m ² is more preferable. When the content is less than 0.02 g / m ² , the improvement effect such as aging blur may be insufficient. On the other hand, when the content exceeds 1.50 g / m ² , There is a concern that the ink absorbability is lowered.

Here, in the present specification, the sulfate ion concentration is measured by measuring the mass of an aqueous solution sample (coating solution) of a water-soluble aluminum compound, removing moisture at a temperature of 100 ° C., and then at a temperature of 1450 ° C. The sample was burned and determined quantitatively from the infrared absorption spectrum of SO ₄ (absorption wave number: 1100 ± 50 cm ⁻¹ ). As the measuring device, a sulfur analyzer manufactured by HORIBA, Ltd. “ "EMIA-120 type" is used.

  In addition, the basicity of said water-soluble aluminum compound is measured by the measuring method prescribed | regulated by JIS specification JISK1475-1996. As a method for synthesizing a basic polyaluminum hydroxide compound (basic aluminum chloride), there are a mixed acid method and an autoclave method, which can be synthesized using at least one of these two methods. In the mixed acid method, it is possible to adjust the basicity of basic aluminum chloride synthesized depending on the reaction conditions of a mixed acid of aluminum hydroxide and hydrochloric acid or sulfuric acid as a raw material. In the autoclave method, aluminum hydroxide as a raw material is dissolved in hydrochloric acid using an autoclave to produce a basic aluminum chloride solution having a basicity of about 45%, and then a small amount of an alkaline agent (sodium carbonate, calcium carbonate, etc.) Therefore, it is possible to adjust the basicity of basic aluminum chloride by controlling these reaction conditions.

B. Inkjet recording medium Next, an inkjet recording medium having an ink receiving layer containing an image fading inhibitor as described above will be described in detail.

  The ink receiving layer is formed of a pigment and a binder in addition to the water-soluble aluminum compound.

(Pigment)
As the pigment, alumina hydrate can be contained as a main component, particularly in terms of dye fixing property, transparency, printing density, color developability, and glossiness, but the following pigments can also be used. Alumina hydrate is distinguished from the water-soluble aluminum-based compound in that it is insoluble in water. Examples of inorganic pigments include light calcium carbonate, heavy calcium carbonate, magnesium carbonate, kaolin, aluminum silicate, diatomaceous earth, calcium silicate, magnesium silicate, synthetic amorphous silica, colloidal silica, alumina, magnesium hydroxide, and other organic pigments. Examples thereof include styrene plastic pigments, acrylic plastic pigments, polyethylene particles, microcapsule particles, urea resin particles, and melamine resin particles. One kind selected from these, or two or more kinds selected as necessary can be used in combination.

A particularly suitable recording medium according to the present invention is preferably a recording medium having an ink receiving layer mainly composed of a pigment having an average particle diameter of 1 μm or less as the above-mentioned pigment. Particularly preferable examples of the pigment include silica or aluminum oxide fine particles. The reason why it is particularly effective in aluminum oxide fine particles and silica is considered as follows. That is, it has been found that the color material adsorbed on the aluminum oxide fine particles and silica is susceptible to fading of the color material by gases such as NO _x , SO _x , and ozone, but these pigments are easy to attract the gas, This is because gas is present in the vicinity of and the colorant is likely to fade. A preferable silica fine particle is a silica fine particle typified by colloidal silica. Colloidal silica itself is also available from the market, and particularly preferable examples include those described in Japanese Patent Nos. 2803134 and 2881847. Preferable examples of the aluminum oxide fine particles include alumina hydrate fine particles. As the alumina hydrate, for example, one represented by the following general formula (1) can be suitably used.

Al ₂ O _3-n (OH) _2n · mH ₂ O (1)
(In the above formula, n represents any of 0, 1, 2, or 3, and m represents a value in the range of 0 to 10, preferably 0 to 5. However, m and n are not 0 at the same time. MH ₂ O often represents a detachable aqueous phase that does not participate in the formation of the crystal lattice, so m can be an integer or non-integer value. When heated, m can reach a value of 0).

  Alumina hydrate is generally produced by hydrolysis of aluminum alkoxide or sodium aluminate as described in US Pat. Nos. 4,242,271 and 4,202,870. By a known method such as a method of performing decomposition, or a method of neutralizing by adding an aqueous solution of aluminum sulfate, aluminum chloride or the like to an aqueous solution of sodium aluminate or the like, as described in JP-B-57-447605. Can be manufactured. Preferred alumina hydrates in the present invention are alumina hydrates showing a boehmite structure or an amorphous state by analysis by X-ray diffraction, and in particular, JP-A-7-232473 and JP-A-8-132731. And alumina hydrates described in JP-A-9-66664, JP-A-9-76628, and the like. The shape of the alumina hydrate may be any of a flat plate shape, a fiber shape, a needle shape, a spherical shape, a rod shape, and the like.

  In order to give glossiness to the surface of an inkjet recording medium, when the casting process is performed with the ink-receiving layer wet by the rewet method, it is necessary to use a plate-like alumina hydrate having a low orientation tendency. preferable. Since the plate-like alumina hydrate has a good water absorbability, the re-wetting liquid easily penetrates, so that the ink receiving layer swells and the alumina hydrate particles are easily rearranged. Therefore, high glossiness can be obtained. Moreover, since the rewetting liquid penetrates efficiently, the production efficiency at the time of casting is also increased.

(binder)
In the present invention, it is preferable to use polyvinyl alcohol as the binder. In addition, modified polyvinyl alcohol, starch or modified product thereof, gelatin or modified product thereof, casein or modified product thereof, gum arabic, carboxymethylcellulose, hydroxyethylcellulose, hydroxypropylmethylcellulose and other cellulose derivatives, SBR latex, NBR latex , Conjugated diene copolymer latex such as methyl methacrylate-butadiene copolymer, functional group modified polymer latex, vinyl copolymer latex such as ethylene vinyl acetate copolymer, polyvinyl pyrrolidone, maleic anhydride or copolymer thereof It is also possible to use a conventionally known binder such as a coalescence or an acrylic ester copolymer. These binders can be used alone or in combination of two or more.

  In the present invention, as the binder used in forming the ink receiving layer, it is also preferable to use a conventionally known binder in combination with the polyvinyl alcohol.

  The mixing ratio of the pigment of the ink jet recording medium used in the present invention and the binder is preferably in the range of 1: 1 to 100: 1. By setting the amount of the binder in the above range, it is possible to maintain a pore volume suitable for application of the image fading inhibitor to the ink receiving layer. The preferable content of the pigment fine particles in the ink receiving layer is 50% by mass or more, more preferably 70% by mass or more, still more preferably 80% by mass or more, and 99% by mass or less based on the solid content. Most preferred.

(Crosslinking agent)
Incorporation of at least one selected from the group consisting of boric acid and borate as a crosslinking agent in the ink receiving layer forming material formed as described above is extremely difficult in forming the ink receiving layer. It is valid. Examples of boric acid that can be used in this case include not only orthoboric acid (H ₃ BO ₃ ) but also metaboric acid and hypoboric acid. The borate is preferably a water-soluble salt of boric acid. Specifically, for example, sodium salt of boric acid (Na ₂ B ₄ O ₇ · 10H ₂ O, NaBO ₂ · 4H ₂ O etc.), potassium salt _{(K 2 B 4 O 7 ·} 5H 2 O, alkali metal salts such KBO _2, etc.), an ammonium salt of boric acid _{(NH 4 B 4 O 9 ·} 3H 2 O, NH 4 BO 2 , etc.) And alkaline earth metal salts such as magnesium salt and calcium salt of boric acid.

  It is preferable to use orthoboric acid from the viewpoint of the temporal stability of the coating solution and the effect of suppressing the occurrence of cracks. Further, the amount used is preferably in the range of 100: 1 to 100: 15 by weight as boric acid solid content with respect to the binder in the ink receiving layer.

  Even within this range, cracks may occur depending on the manufacturing conditions and the use amount needs to be selected. On the other hand, exceeding the above range is not preferable because the temporal stability of the coating solution is lowered. That is, in the case of production, since the coating liquid is used for a long time, if the content of boric acid is large, the viscosity of the coating liquid increases during that time, and the generation of a gelled product occurs. It is necessary to frequently change the coating liquid and clean the coater head, and the productivity is significantly reduced. Furthermore, when the above range is exceeded, for the same reason as the first and second surface treatments described later, in the casting step, a point-like surface (cast surface) defect is likely to occur, and a uniform and good glossy surface is obtained. There may not be.

  The ink receiving layer formed as described above preferably has the pore properties satisfying the following conditions in order to achieve the purpose and effect such as high ink absorbability and high fixability.

First, the pore volume of the ink receiving layer is preferably in the range of 0.1 to 1.0 cm ³ / g. That is, when the pore volume is less than the above range, sufficient ink absorption performance cannot be obtained, resulting in an ink receiving layer with poor ink absorption, and in some cases, ink overflows and bleeding occurs in the image. There is a fear. On the other hand, when it exceeds the above range, there is a tendency that cracks and powder fall off easily occur in the ink receiving layer. The BET specific surface area of the ink receiving layer is preferably ^{20 to} 450 m ² / g. If it is less than the above range, sufficient gloss may not be obtained, and haze increases (transparency decreases), so the image appears to be “white haze”. There is a fear. Furthermore, this case is not preferable because there is a possibility that the adsorptivity of the dye in the ink may be lowered. On the other hand, exceeding the above range is not preferable because cracks are likely to occur in the ink receiving layer. The values of the pore volume and the BET specific surface area are obtained by a nitrogen adsorption / desorption method.

(Other additives)
Other additives can be used in the ink receiving layer, for example, a dispersant, a thickener, a pH adjuster, a lubricant, a fluidity modifier, a surfactant, an antifoaming agent, if necessary. Examples include a release agent, a fluorescent brightening agent, an ultraviolet absorber, and an antioxidant, and the image fading inhibitor of the present invention can be preferably used.

(Coating amount)
Further, when the ink receiving layer of the present invention is formed, the thickness of the ink receiving layer has a higher degree of freedom than the conventional one, that is, it can be made thicker than the conventional one. Considering high ink absorbability, the dry coating amount is preferably 30 g / m ² or more, and the upper limit is more preferably 50 g / m ² . If it is less than 30 g / m ² , the ink absorption is sufficient especially when used in a printer in which a plurality of light-color inks are added in addition to black ink in addition to the three colors of cyan, magenta, and yellow. Sex cannot be obtained. That is, ink overflow may occur and bleeding may occur, or the ink dye may diffuse to the support and the print density may decrease. On the other hand, when it exceeds 50 g / m ² , it may occur that the generation of cracks cannot be completely suppressed. Furthermore, if it is 30 g / m ² or more, an ink-receiving layer exhibiting sufficient ink absorbency even in a high-temperature and high-humidity environment can be obtained. Further, when the dry coating amount is 50 g / m ² or less, uneven coating of the ink receiving layer is further less likely to occur, and an ink receiving layer having a stable thickness can be produced.

(Support)
The ink receiving layer as described above is formed on one side or both sides of the support. Support materials include chemical pulps such as LBKP and NBKP, mechanical pulps such as GP, PGW, RMP, TMP, CTMP, CMP, and CGP, wood pulp such as waste paper pulp such as DIP, and synthetic fiber pulps such as polyethylene fiber. As a main component, pigments, sizing agents, fixing agents, yield improvers, paper strength enhancers, and other additives usually used in papermaking are mixed as needed to make a long net paper machine, A base paper produced by various machines such as a net paper machine and a twin-wire paper machine, a base paper provided with a size press or an anchor coat layer with starch, polyvinyl alcohol, etc. on the base paper, and a coat layer provided thereon Coated paper such as art paper, coated paper and cast coated paper is also included. In order to improve the smoothness of the surface of the support in order to obtain good recording characteristics and glossiness as an inkjet recording paper, the machine may be provided with an ink receiving layer as it is on such base paper and coated paper. A calendar device such as a calendar, a TG calendar, or a soft calendar may be used in the previous stage of coating the ink receiving layer. Further, as the support, a polyolefin resin layer may be provided on the base paper, a synthetic resin such as polyethylene, polypropylene, polyester, nylon, rayon, polyurethane, etc., a film material of a mixture thereof, or the synthetic resin as a fiber. Also included are sheets that have been molded.

(solvent)
As a method for adding the water-soluble aluminum-based compound of the present invention to the ink receiving layer, the following addition methods 1 and 2 can be used, but when overcoating as the second coating liquid (when addition method 2 is used). As the solvent, water or a mixed solvent of water and an organic solvent can be used.

  Examples of organic solvents that can be used in this case include methanol, ethanol, n-propanol, i-propanol, methylolpropane, diethylene glycol, triethylene glycol, glycerin, ethylene glycol, propylene glycol, and 3,6-dithione-1,8. Preferred are those having good compatibility with alcohols such as octanediol and methoxypropanol, ketones such as acetone and methyl ethyl ketone, and water such as tetrahydrofuran, acetonitrile and pyrrolidone. These can be used alone or in combination of two or more.

  Moreover, the addition amount of the said solvent with respect to a water-soluble aluminum type compound is 1: 1-1: 100 by weight ratio, and 1: 5-1: 50 is more preferable.

(Production method)
There are the following two methods for adding the water-soluble aluminum compound to the ink receiving layer. The manufacturing method in the case of each addition method is described below.

<Method 1 of adding water-soluble aluminum compound>
A method of applying a coating liquid containing a pigment, a binder, and a water-soluble aluminum compound to form an ink receiving layer on a support, followed by drying and solidifying. The concentration of each component in the coating liquid is determined in the ink receiving layer. Is set according to the required amount. The coating amount of the coating solution is preferably ^{30.0~50.0g / m 2, 30.0~40.0g / m} 2 is more preferable.

<Method 2 for adding water-soluble aluminum compound>
A method in which a first coating liquid containing a pigment and a binder for forming an ink receiving layer is applied to a support, dried and solidified, and then a second coating liquid containing a water-soluble aluminum compound is applied thereon and dried. It is. First, a first coating solution containing a pigment and a binder resin and a second coating solution containing a water-soluble aluminum-based compound containing sulfate ions having a concentration of 0.51% by mass to 2.70% by mass are prepared. Here, the concentration of each component in the first coating liquid is set according to the required amount in the ink receiving layer.

Subsequently, the first coating liquid and then the second coating liquid are coated on the support. The coating amount of the first coating liquid is preferably ^{30.0~50.0g / m 2, 30.0~40.0g / m} 2 is more preferable. The coating amount of the second coating liquid is preferably from ^{0.02g / m 2 ~1.50g / m 2} , 0.02g / m 2 ~0.5g / m 2 is more preferable.

  From the appearance of the inkjet recording medium after finishing, the coating method of these coating liquids is preferably a non-contact coating method with respect to the ink receiving layer surface, and examples include a die coater, an air knife coater, and a spray. It is not particularly limited, and a contact-type coating method such as a roll coater, a bar coater, or a gravure coater can also be used.

  After forming the ink receiving layer as described above, a glossy surface can be formed on the surface of the ink receiving layer by a casting method. The manufacturing method will be described. The casting method is a method in which an ink receiving layer in a wet state or a plastic state is pressure-bonded to a heated mirror-like drum (cast drum) surface, dried in the pressure-bonded state, and the mirror surface is ink-coated. This is a method of copying on the surface of the receiving layer, and there are three typical methods, namely, a direct method, a rewet method (indirect method), and a coagulation method.

  Any of these casting methods can be used. However, as described above, in the present invention, it is preferable to use alumina hydrate in the ink receiving layer of the recording medium for inkjet. Since high glossiness is obtained by using the rewet cast method, it is more preferable.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited to these Examples.

(Production Example 1 of inkjet recording medium)
First, a support was produced as follows. 0.60 parts by mass of cationized starch in a pulp slurry consisting of 80 parts by weight of hardwood bleached kraft pulp (LBPK) with a freeness of 450 ml CSF (Canadian Standard Freeness) and 20 parts by weight of softwood bleached kraft pulp (NBPK) with a freeness of 480 ml CSF Parts by weight, 10 parts by weight of heavy calcium carbonate, 15 parts by weight of light calcium carbonate, 0.10 parts by weight of alkyl ketene dimer, 0.03 parts by weight of cationic polyacrylamide, and 0.40 parts by weight of sulfuric acid band. After the adjustment, the paper was made with a long web paper, subjected to a three-stage wet press, and dried with a multi-cylinder dryer. After that, impregnated with an oxidized starch aqueous solution to a solid content of 1.0 g / m ² with a size press machine, dried and machine calendered, basis weight 155 g / m ² , Steecht size 100 seconds, A support having an air permeability of 50 seconds, a Beck smoothness of 30 seconds, and a Gurley stiffness of 11.0 mN was obtained.

Next, an undercoat layer was formed on the support obtained above as follows. First, as a coating liquid used for forming the undercoat layer, 100 parts by mass of kaolin (Ultra White 90, manufactured by Engelhard) / zinc oxide / aluminum hydroxide having a weight ratio of 65/10/25, and commercially available 7 parts by mass of a commercially available styrene-butadiene latex was added to a slurry having a solid content of 70% by mass comprising 0.1 part by mass of a polyacrylic acid-based dispersant and adjusted so as to have a solid content of 60% by mass. To obtain a composition. Next, this composition was coated on both sides of the support with a blade coater so that the dry coating amount was 15 g / m ² and dried. After that, machine calender finishing (linear pressure 150 kgf / cm), basis weight 185 g / m ² , Steecht size degree 300 seconds, air permeability 3,000 seconds, Beck smoothness 200 seconds, Gurley stiffness 11.5 mN undercoat A layered support was obtained. The whiteness of the support with the undercoat layer was measured for each of the five A4 size samples cut and obtained as an average value. As a result, it was L: 95, a ^* : 0, b ^* :-2 (determined as the hue of JIS Z 8729).

  Next, the ink-receiving layer was formed by applying the first coating liquid, but after application of the tetraborate aqueous solution, that is, as soon as the coating liquid was impregnated in the undercoat layer, the ink was directly applied on the undercoat layer. A receiving layer was formed. In this case, the first coating liquid and the coating method used for forming the ink receiving layer are as follows.

Sodium aluminate was added to a 4% by mass solution of aluminum chloride to adjust the pH to 4. Then, it heated up to 90 degreeC, stirring, and stirred for a while. Thereafter, sodium aluminate was added again to adjust the pH to 10, and the aging reaction was carried out for 40 hours while maintaining the temperature. Then, it returned to room temperature and adjusted pH to 7-8. The dispersion was desalted and then peptized with acetic acid to obtain a colloidal sol. The colloidal sol of alumina hydrate was concentrated to obtain a 17% by mass solution. Polyvinyl alcohol PVA117 (trade name: manufactured by Kuraray Co., Ltd.) was dissolved in pure water to obtain a 9% by mass solution. The colloidal sol of alumina hydrate and the polyvinyl alcohol solution were mixed and stirred so that the alumina hydrate solid content and the polyvinyl alcohol solid content were 10: 1 by weight to obtain a dispersion. This was coated at 30 m / min with a die coater so that the dry coating amount was 35 g / m ² . Then, it was dried at 170 ° C. to form an ink receiving layer, and then a rewetting cast process using hot water was performed on the surface of the ink receiving layer using a rewetting cast coater to obtain a recording medium 1. From the BET measurement, the average pore radius of the recording medium 1 at this time was 8.5 nm, and the pore volume was 0.65 ml / g.

Example 1
After applying 5% aqueous solution (second coating solution) of polyaluminum chloride (basicity: 40.0%, sulfate ion concentration: 0.51% by mass) to the ink receiving layer provided as described above with a roll coater, The excess was scraped off with a Mayer bar, and the coating amount was 0.02 g / m ² as a solid content, that is, applied at 60 m / min so as to be 0.1% by mass with respect to the total solid content of the ink receiving layer. And after drying at 110 degreeC within 5 second after coating and obtaining the target recording medium 2 for inkjet, the following evaluation was performed.

(Example 2)
After applying 5% aqueous solution (second coating solution) of polyaluminum chloride (basicity: 40.0%, sulfate ion concentration: 0.51% by mass) to the ink receiving layer provided as described above with a roll coater, The excess was scraped off with a Mayer bar, and the coating amount was 1.00 g / m ² as a solid content, that is, applied at 60 m / min so as to be 1.0 mass% with respect to the total solid content of the ink receiving layer. And after drying at 110 degreeC within 5 second after coating and obtaining the target recording medium 3 for inkjet, the following evaluation was performed.

(Example 3)
After applying 5% aqueous solution (second coating solution) of polyaluminum chloride (basicity: 40.0%, sulfate ion concentration: 0.51% by mass) to the ink receiving layer provided as described above with a roll coater, The excess was scraped off with a Mayer bar, and the coating amount was 1.50 g / m ² as a solid content, that is, applied at 60 m / min so as to be 3.0% by mass with respect to the total solid content of the ink receiving layer. And after drying at 110 degreeC within 5 second after coating and obtaining the target recording medium 4 for inkjet, the following evaluation was performed.

Example 4
After applying 5% aqueous solution (second coating solution) of polyaluminum chloride (basicity: 79.9%, sulfate ion concentration: 2.70% by mass) to the ink receiving layer provided as described above with a roll coater, The excess was scraped off with a Mayer bar, and the coating amount was 0.02 g / m ² as a solid content, that is, applied at 60 m / min so as to be 0.1% by mass with respect to the total solid content of the ink receiving layer. And after drying at 110 degreeC within 5 second after coating and obtaining the target recording medium 5 for inkjet, the following evaluation was performed.

(Example 5)
After applying 5% aqueous solution (second coating solution) of polyaluminum chloride (basicity: 79.9%, sulfate ion concentration: 2.70% by mass) to the ink receiving layer provided as described above with a roll coater, The excess was scraped off with a Mayer bar, and the coating amount was 1.00 g / m ² as a solid content, that is, applied at 60 m / min so as to be 1.0 mass% with respect to the total solid content of the ink receiving layer. And after drying at 110 degreeC within 5 second after coating and obtaining the target recording medium 6 for inkjet, the following evaluation was performed.

(Example 6)
After applying 5% aqueous solution (second coating solution) of polyaluminum chloride (basicity: 79.9%, sulfate ion concentration: 2.70% by mass) to the ink receiving layer provided as described above with a roll coater, The excess was scraped off with a Mayer bar, and the coating amount was 1.50 g / m ² as a solid content, that is, applied at 60 m / min so as to be 3.0% by mass with respect to the total solid content of the ink receiving layer. And after drying at 110 degreeC within 5 second after coating and obtaining the target recording medium 7 for inkjet, the following evaluation was performed.

(Examples 7 to 9)
After applying 5% aqueous solution (second coating solution) of polyaluminum chloride (basicity: 51.0%, sulfate ion concentration: 1.03% by mass) to the ink receiving layer provided as described above with a roll coater, 0.02 g / m ² coating amount scraping the excess Meyer bar as solids (example 7), 1.00g / m ² (example 8), 1.50g / m ² (example 9), i.e. 60 m / min so as to be 0.1% by mass (Example 7), 1.0% by mass (Example 8), and 3.0% by mass (Example 9), respectively, based on the total solid content of the ink receiving layer. Coated with. And after drying at 110 degreeC within 5 second after coating and obtaining the target recording media 8-10 for inkjet, the following evaluation was performed.

(Examples 10 to 12)
After applying a 5% aqueous solution (second coating solution) of polyaluminum chloride (basicity: 62.0%, sulfate ion concentration: 1.57% by mass) to the ink receiving layer provided as described above with a roll coater, 0.02 g / m ² coating amount scraping the excess Meyer bar as solids (example 10), 1.00g / m ² (example 11), 1.50g / m ² (example 12), i.e. 60 m / min so as to be 0.1% by mass (Example 10), 1.0% by mass (Example 11), and 3.0% by mass (Example 12), respectively, based on the total solid content of the ink receiving layer. Coated with. And after drying at 110 degreeC within 5 second after coating and obtaining the target recording media 11-13 for inkjet, the following evaluation was performed.

(Examples 13 to 15)
After applying a 5% aqueous solution (second coating solution) of polyaluminum chloride (basicity: 70.9%, sulfate ion concentration: 2.06% by mass) to the ink receiving layer provided as described above with a roll coater, 0.02 g / m ² coating amount scraping the excess Meyer bar as solids (example 13), 1.00g / m ² (example 14), 1.50g / m ² (example 15), i.e. 60 m / min so as to be 0.1% by mass (Example 13), 1.0% by mass (Example 14), and 3.0% by mass (Example 15), respectively, based on the total solid content of the ink receiving layer. Coated with. And after drying at 110 degreeC within 5 second after coating and obtaining the target recording media 14-16 for inkjet, the following evaluation was performed.

(Example 2 of recording medium for inkjet recording)
(Example 16)
First, a support was produced as follows. 0.60 parts by mass of cationized starch in a pulp slurry consisting of 80 parts by weight of hardwood bleached kraft pulp (LBPK) with a freeness of 450 ml CSF (Canadian Standard Freeness) and 20 parts by weight of softwood bleached kraft pulp (NBPK) with a freeness of 480 ml CSF Parts by weight, 10 parts by weight of heavy calcium carbonate, 15 parts by weight of light calcium carbonate, 0.10 parts by weight of alkyl ketene dimer, 0.03 parts by weight of cationic polyacrylamide, and 0.40 parts by weight of sulfuric acid band. After the adjustment, the paper was made with a long web paper, subjected to a three-stage wet press, and dried with a multi-cylinder dryer. After that, impregnated with an oxidized starch aqueous solution to a solid content of 1.0 g / m ² with a size press machine, dried and machine calendered, basis weight 155 g / m ² , Steecht size 100 seconds, A support having an air permeability of 50 seconds, a Beck smoothness of 30 seconds, and a Gurley stiffness of 11.0 mN was obtained.

Next, an undercoat layer was formed on the support obtained above as follows. First, as a coating liquid used for forming the undercoat layer, 100 parts by mass of kaolin (Ultra White 90, manufactured by Engelhard) / zinc oxide / aluminum hydroxide having a weight ratio of 65/10/25, and commercially available 7 parts by mass of a commercially available styrene-butadiene latex was added to a slurry having a solid content of 70% by mass comprising 0.1 part by mass of a polyacrylic acid-based dispersant and adjusted so as to have a solid content of 60% by mass. To obtain a composition. Next, this composition was coated on both sides of the support with a blade coater so that the dry coating amount was 15 g / m ² and dried. After that, machine calender finishing (linear pressure 150 kgf / cm), basis weight 185 g / m ² , Steecht size degree 300 seconds, air permeability 3,000 seconds, Beck smoothness 200 seconds, Gurley stiffness 11.5 mN undercoat A layered support was obtained. The whiteness of the support with the undercoat layer was measured for each of the five A4 size samples cut and obtained as an average value. As a result, it was L: 95, a ^* : 0, b ^* :-2 (determined as the hue of JIS Z 8729).

  Next, the ink receiving layer was formed by applying the coating solution once, but after the application of the tetraborate aqueous solution, that is, immediately after the coating solution was impregnated in the undercoat layer, the ink receiving layer was directly applied on the undercoat layer. An ink receiving layer was formed. The coating liquid and coating method used for forming the ink receiving layer at that time are as follows.

Sodium aluminate was added to a 4% by mass solution of aluminum chloride to adjust the pH to 4. Then, it heated up to 90 degreeC, stirring, and stirred for a while. Thereafter, sodium aluminate was added again to adjust the pH to 10, and the aging reaction was carried out for 40 hours while maintaining the temperature. Then, it returned to room temperature and adjusted pH to 7-8. The dispersion was desalted and then peptized with acetic acid to obtain a colloidal sol. The colloidal sol of alumina hydrate was concentrated to obtain a 17% by mass solution. Polyvinyl alcohol PVA117 (trade name: manufactured by Kuraray Co., Ltd.) was dissolved in pure water to obtain a 9% by mass solution. The colloidal sol of alumina hydrate and the polyvinyl alcohol solution were mixed and stirred so that the alumina hydrate solid content and the polyvinyl alcohol solid content were 10: 1 by weight to obtain a dispersion. A polyaluminum chloride aqueous solution (basicity: 51.0%, sulfate ion concentration: 1.03% by mass) is added to the dispersion immediately before the die coater so that the dry coating amount is 35 g / m ^2. Coating was performed at 30 m / min. The polyaluminum chloride aqueous solution was added so that the alumina hydrate solid content and the polyaluminum chloride solid content at this time were 100: 0.06 in weight ratio. Thereafter, the ink receiving layer is formed by drying at 170 ° C., and the surface of the ink receiving layer is subjected to a rewetting casting process using hot water using a rewetting cast coater to obtain the recording medium 21, and then the following recording medium 21 is obtained. Evaluation was performed. From the BET measurement, the average pore radius of the recording medium 21 at this time was 8.7 nm, and the pore volume was 0.68 ml / g.

(Example 17)
The addition ratio of the polyaluminum chloride aqueous solution in Example 16 was the same as that in Example 16 except that the alumina hydrate solid content and the polyaluminum chloride solid content were added in a weight ratio of 100: 3.2. A recording medium was created. Thereby, the recording medium 22 was obtained, and the following evaluation was performed using this.

(Example 18)
The addition ratio of the polyaluminum chloride aqueous solution in Example 16 was the same as that in Example 16 except that the alumina hydrate solid content and the polyaluminum chloride solid content were added in a weight ratio of 100: 4.9. A recording medium was created. Thereby, the recording medium 23 was obtained, and the following evaluation was performed using this.

(Comparative Example 1)
The following evaluation was performed using the recording medium 1 as it was.

(Comparative Example 2)
After applying a 5% aqueous solution of polyaluminum chloride (basicity: 62.0%, sulfate ion concentration: 3.10% by mass) to the ink receiving layer provided as described above with a roll coater, scrape off the excess with a Mayer bar. The coating amount was 60 m / min so that the coating amount was 2.00 g / m ² as a solid content, that is, 3.0% by mass with respect to the total solid content of the ink receiving layer. And after drying at 110 degreeC within 5 second after coating and obtaining the target recording medium 17 for inkjet, the following evaluation was performed.

(Comparative Example 3)
After applying a 5% aqueous solution of polyaluminum chloride (basicity: 39.9%, sulfate ion concentration: 2.71% by mass) to the ink receiving layer provided as described above with a roll coater, scrape off the excess with a Mayer bar. The coating amount was 60 m / min so that the coating amount was 2.00 g / m ² as a solid content, that is, 3.0% by mass with respect to the total solid content of the ink receiving layer. And after drying at 110 degreeC within 5 second after coating and obtaining the target recording medium 18 for inkjet, the following evaluation was performed.

(Comparative Example 4)
After applying a 5% aqueous solution of polyaluminum chloride (basicity: 80.0%, sulfate ion concentration: 0.40% by mass) to the ink receiving layer provided as described above with a roll coater, scrape off excess with a Mayer bar. The coating amount was 60 m / min so that the coating amount was 2.00 g / m ² as a solid content, that is, 3.0% by mass with respect to the total solid content of the ink receiving layer. And after drying at 110 degreeC within 5 second after coating and obtaining the target recording medium 19 for inkjet, the following evaluation was performed.

(Comparative Example 5)
After applying a 5% aqueous solution of polyaluminum chloride (basicity: 80.0%, sulfate ion concentration: 0.30% by mass) to the ink receiving layer provided as described above with a roll coater, scrape off excess with a Mayer bar. The coating amount was 60 m / min so that the coating amount was 2.00 g / m ² as a solid content, that is, 3.0% by mass with respect to the total solid content of the ink receiving layer. And after drying at 110 degreeC within 5 second after coating and obtaining the target recording medium 20 for inkjet, the following evaluation was performed.

(Evaluation methods)
A) Image storability of recorded matter <Preparation of recorded matter>
The inkjet recording medium 1 produced in Examples 1 to 18 and Comparative Examples 1 to 5 described above using a photo printer (trade name: PIXUS 950i, ink: BCI-6, manufactured by Canon) using an inkjet method. On the recording surface of ˜23, black, cyan, magenta, and yellow single color patches were printed with images having an image density (OD) of approximately 1.0, thereby producing recorded matter. The recorded material produced as described above was used for the following tests.

<Light resistance test>
A fluorescent lamp exposure test was performed on the recorded matter using a fluorescent lamp tester (trade name: FT-1 manufactured by Suga Test Instruments Co., Ltd.).
Test condition Fluorescent light intensity: 75000 Lux
Test time: 520 hours Temperature and humidity conditions in the test layer: 24 ° C., 50% RH
Method for evaluating fluorescent lamp resistance;
The image density of the recorded matter before and after the test was measured using a spectrophotometer / Spectrino (manufactured by Gretag Macbeth Co.), the residual density rate was obtained from the following formula, and judged based on the criteria described below. The results are shown in Tables 1 and 2.

Density remaining rate (%) = image density after test / image density before test × 100
Judgment criteria A: Magenta density residual rate of 85% or more.
○: Magenta concentration remaining rate of 80% or more and less than 85%.
Δ: Residual rate of magenta concentration is 75% or more and less than 80%.
X: The magenta density residual rate is less than 75%.

<Gas resistance test>
An ozone exposure test was performed using an ozone test apparatus (trade name: ozone weatherometer, manufactured by Suga Test Instruments Co., Ltd.).
Test conditions;
Exposure gas composition: Ozone 3ppm
Test time: 2 hours Temperature and humidity conditions in the test layer: 40 ° C., 60% RH
Gas resistance evaluation method;
The recorded matter before and after the test was measured using a spectrophotometer / spectrino (manufactured by Gretag Macbeth Co.), ΔE was obtained from the following formula, and judged based on the criteria described below. The results are shown in Tables 1 and 2.
Delta] E = {(pre-test L values - after test L value) ² + (pre-test a ^* value - test after a ^* value) ² + (pre-test b ^* value - post-test b ^* value) ^{2} 1/2}
Judgment criteria O: Black, cyan, magenta, yellow single color patches having the largest color difference ΔE from the initial image with a value of less than 5.
Δ: Black, cyan, magenta, and yellow single color patches with the largest color difference ΔE from the initial image having a value of 5 or more and less than 10.
X: One of the black, cyan, magenta, and yellow single color patches having the largest color difference ΔE from the initial image is 10 or more.

B) Image density (OD)
The inkjet recording medium 1 produced in Examples 1 to 18 and Comparative Examples 1 to 5 described above using a photo printer (trade name: PIXUS 950i, ink: BCI-6, manufactured by Canon) using an inkjet method. A solid print of process black was performed on the recording surfaces of ˜23 to produce recorded matter. After printing, it was allowed to stand for 24 hours, and the image density (OD) was measured using a spectrophotometer / spectrino (manufactured by Gretag Macbeth). The results of evaluation based on the following criteria are shown in Tables 1 and 2.
Criteria A: Image density (OD) is 2.2 or more B: Image density (OD) is 2.0 or more and less than 2.2 C: Image density (OD) is less than 2.0.

C) Water resistance For the ink jets produced in Examples 1 to 18 and Comparative Examples 1 to 5 described above using a photo printer (trade name: PIXUS 950i, ink: BCI-6, manufactured by Canon) using an ink jet method. Solid prints of cyan, magenta, yellow, and black single color patches were performed on the recording surfaces of the recording media 1 to 23 to produce recorded matter. After standing for 3 hours, it was immersed in water for 1 minute, and the flow of the image ink was visually observed and evaluated according to the following criteria. The results are shown in Tables 1 and 2.
Criteria A: Ink dye did not flow at all.
B: A level in which the ink dye slightly flows but has almost no influence on the color density.
C: Although a part of the ink dye flowed and the color density became thin, there was no problem in practical use.
D: A level at which most of the ink dye flows and becomes a problem in actual use.

D) Discoloration over time Using a photo printer (trade name: PIXUS 950i, ink: BCI-6, manufactured by Canon) using an ink jet method, the ink jets produced in Examples 1 to 18 and Comparative Examples 1 to 5 described above. A grid-like linear pattern (line width: 0.28 mm) in which magenta ink and black ink are arranged next to each other is printed on the recording surfaces of recording media 1 to 23, and a spectrophotometer / spectrino (manufactured by Gretag Macbeth) Was used to measure the image density (OD). Next, after being left for 3 hours after printing, it was stored in a constant temperature and humidity chamber at a temperature of 30 ° C. and a humidity of 80% RH for one week, and then the image density (OD) was measured again to obtain the difference in density (ΔOD) between the two. Based on the following criteria. The smaller the value of the concentration difference (ΔOD), the more the occurrence of aging blur is suppressed. The results are shown in Tables 1 and 2.
Criteria A: ΔOD was less than 0.25.
B: ΔOD was 0.25 or more and less than 0.4.
C: ΔOD was 0.4 or more.

E) Ink absorbability Ink jets produced in Examples 1 to 18 and Comparative Examples 1 to 5 using a photo printer (trade name: PIXUS 950i, ink: BCI-6, manufactured by Canon) using an ink jet method. On the recording surfaces of the recording media 1 to 23 for recording, 8 intermediate gradations from single cyan to magenta were printed to produce recorded matter. The image quality was comprehensively determined visually for each halftone patch of the recorded matter on which the image was printed. Judgment criteria are as described below. The results are shown in Tables 1 and 2.
Judgment criteria A: The uniformity of light and shade in the patch is particularly excellent.
B: Almost no shade is found in the patch, and the uniformity is excellent.
C: There is a little shading in the patch.
D: Light and shade in the patch is recognized, but there is no particular problem in actual use. E: A level causing problem in actual use.

F) Bronze Using the inkjet printer (trade name: PIXUS 90i, ink: BCI-6, manufactured by Canon), the inkjet covers prepared in Examples 1 to 18 and Comparative Examples 1 to 5 above. Solid prints of cyan, magenta, yellow, and black single-color patches were performed on the recording surfaces of the recording media 1 to 23 to produce recorded matter. After leaving for 3 hours, the presence or absence of bronzing of the image ink and its extent were visually observed and evaluated according to the following criteria. The results are shown in Tables 1 and 2.
Criteria A: Bronze is not uniformly generated in the solid patch.
B: Although the portion where the bronze is generated minutely is confirmed, it is not the level which becomes a problem in practical use.
C: The occurrence of bronze is clearly confirmed, and is a level that causes a problem in practical use.

表１、２の結果より、インク受容層にポリ塩化アルミニウムを含んでいるインクジェット用被記録媒体であって、該ポリ塩化アルミニウムが含む硫酸イオン濃度が０．５１〜２．７０質量％であるものを含有する本発明のインクジェット用被記録媒体（実施例１〜１８）は、画像堅牢性（耐光性、耐ガス性、耐水性）が格別に改善され、画像濃度が高く、インク吸収性、ブロンズ等の画像品位に優れ、高温高湿下における経時ニジミが抑制されていることが判明した。一方、硫酸イオン濃度が上記の範囲外のポリ塩化アルミニウムを用いた比較例のインクジェット用被記録媒体（比較例２〜５）は、上記いずれの特性も劣っていた。

From the results shown in Tables 1 and 2, an inkjet recording medium containing polyaluminum chloride in the ink receiving layer, and the sulfate ion concentration contained in the polyaluminum chloride is 0.51 to 2.70% by mass. Inkjet recording media (Examples 1 to 18) of the present invention, which contain the above, are remarkably improved in image fastness (light resistance, gas resistance, water resistance), high image density, ink absorption, and bronze. It was found that the image quality such as the above was excellent, and the aging blur at high temperature and high humidity was suppressed. On the other hand, the ink jet recording media (Comparative Examples 2 to 5) of Comparative Examples using polyaluminum chloride having a sulfate ion concentration outside the above range were inferior in any of the above characteristics.

Claims (4)

In an inkjet recording medium having an ink receiving layer on at least one side of a support,
The ink-receiving layer contains a pigment, a binder resin, and a water-soluble aluminum compound, and the concentration of sulfate ions contained in the water-soluble aluminum compound is 0.51% by mass to 2.70% by mass. An inkjet recording medium.   2. The ink jet recording medium according to claim 1, wherein at least one of the water-soluble aluminum compounds is polyaluminum chloride.   The ink jet recording medium according to claim 2, wherein the basicity of the polyaluminum chloride is 40.0% to 79.9%. Amount contained in the ink receiving layer of the water-soluble aluminum compound, characterized in that a ^{0.02g / m 2 ~1.50g / m 2} , according to any one of claims 1 to 3 Inkjet recording medium.