JP2006142645A - Inkjet recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recording medium, in which the absorption of ink is favorable and a highly dense image recording is possible and, at the same time, the resistance to bleeding with time and resistance to water are improved. <P>SOLUTION: The ink accepting layer of the inkjet recording medium includes at least one kind selected from the group consisting of a boron compound, a copper compound, an aluminum compound, a titanium compound, a zirconium compound and an iron compound and a cationic polymer, which has a 1,2- or 1,3-diol structure and an I/O value of not more than 2.5. The preferable cationic polymer has general formula (1), wherein A is a unit derived from a cationic vinyl monomer having a quaternary ammonium group, B is a unit derived from a vinyl monomer having an I/O value≤0.5, R is H or CH<SB>3</SB>, Z is a bivalent combining group, l=20-80 mol%, m=10-70 mol%, n=5-10 mol% (l+m+n=100) and p=1 or 2. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an inkjet recording medium, and more specifically, suitable for inkjet recording of robust images using liquid ink such as water-based ink and oil-based ink, or solid ink that is melted and liquefied at room temperature solid to be used for printing. The present invention relates to an ink jet recording medium.

  In recent years, various information processing systems have been developed along with the rapid development of the information industry, and recording methods and apparatuses suitable for the information processing systems have been put into practical use. Among the recording methods, the inkjet recording method is capable of recording on various recording materials, the hardware (device) is relatively inexpensive, compact, excellent in quietness, etc. It has been widely used in so-called home use.

  In addition, with the recent increase in resolution of inkjet printers, so-called photographic-like high-quality recorded matter can be obtained, and various recording materials have been developed. From the viewpoint of commercial value as a recording material, it has excellent ink absorptivity and a high-density image is obtained, and the image storability after recording is good, that is, the image fades or blurs after long-term storage. It is required that the quality does not deteriorate.

  Various ink jet recording sheets provided with an ink receiving layer having a three-dimensional structure having a high porosity formed from inorganic pigment fine particles and a water-soluble resin have been disclosed as those having enhanced ink absorption (for example, Patent Documents 1 to 3), high-density and high-resolution image recording has become possible. However, there is a problem in terms of so-called bleeding over time and water resistance, in which the ink solvent diffuses in the layer together with the dye during storage for a long period of time after recording.

  As one of means for preventing bleeding with time and improving water resistance, inorganic mordants such as cationic polymers and polyvalent metal salts are known as mordants for fixing anionic ink dyes. For example, a technique of forming a layer using a cationic polymer having a quaternary ammonium base together with inorganic fine particles such as silica and a water-soluble resin such as PVA to improve ink bleeding and water resistance during storage after recording. Is disclosed (for example, see Patent Documents 4 to 6). In addition, there is a layer in which boric acid or the like is further used as a water-soluble resin curing agent in this composition, and a water-soluble resin such as PVA is crosslinked and cured by the action of boric acid or the like (see, for example, Patent Document 7). As described above, it is known that blurring of an image can be improved by using a cationic polymer in combination, but the image density obtained with this configuration is still insufficient.

  Further, a technique using a polymer capable of chelating boric acid with N and OH in the molecule in the presence of boric acid or the like has been proposed (see, for example, Patent Document 8). However, this is for the purpose of improving the surface shape and increasing the density, and since no cationic groups (such as ammonium groups) are introduced into the polymer molecule, no improvement in image bleeding can be expected.

  In addition to the above, cationic PVA may be used as the cationic polymer having a 1,3-diol structure (see, for example, Patent Documents 9 to 10), or the inorganic / organic ratio (I / O) in the copolymerization component of the polymer. There is also a disclosure relating to a technique in which (value) is 0.5 or more (see, for example, Patent Document 11). However, in the former, the amount of cationic groups introduced is small and highly polar because of its constitution, it is insufficient as an effect to improve image bleeding, and as in the latter, bleeding is improved by simply increasing the polarity of the polymer. The effect cannot be obtained sufficiently.

Japanese Patent Laid-Open No. 10-203006 Japanese Patent Laid-Open No. 10-217601 JP-A-11-20306 JP 2002-172850 A JP 2002-192830 A JP 2002-274013 A JP-A-12-212235 JP 2004-168058 A JP-A-60-245585 Japanese Examined Patent Publication No. 6-41226 Japanese Patent Laid-Open No. 10-217601

  As described above, although various studies have been made on techniques for improving image bleeding due to aging and moisture over a long period of time, it is still insufficient under the present situation where high quality images like a photograph are required. Tolerance has not been ensured, and establishment of a technique capable of improving the prevention of bleeding with time and water resistance to a higher degree is demanded.

  The present invention has been made in view of the above, and provides an ink jet recording medium that is excellent in ink absorption and capable of high-density image recording, and that is particularly excellent in anti-bleeding and water resistance of a recorded image. The purpose is to achieve the purpose.

Specific means for achieving the above object are as follows.
<1> In an inkjet recording medium having an ink receiving layer on a support, the ink receiving layer is at least one selected from the group consisting of boron compounds, Cu compounds, Al compounds, Ti compounds, Zr compounds, and Fe compounds. And a cationic polymer having a 1,2- or 1,3-diol structure and an inorganic / organic ratio (I / O value) of 2.5 or less. It is a medium.

  <2> The inkjet recording medium according to <1>, wherein the cationic polymer has a cation equivalent of 1 meq / g or more.

  <3> The inkjet recording medium according to <1> or <2>, wherein the cationic polymer is a polymer represented by the following general formula (1).

  In the general formula (1), A represents a structural unit derived from a cationic vinyl monomer having a quaternary ammonium group, and B is derived from a vinyl monomer having an I / O value of 0.5 or less. Represents a structural unit. R represents a hydrogen atom or a methyl group, and Z represents a divalent linking group. l represents 20 to 80 mol%, m represents 10 to 70 mol%, n represents 5 to 10 mol%, and l + m + n = 100 is satisfied. p represents 1 or 2.

  <4> The inkjet recording medium according to <3>, wherein the structural unit represented by A is at least one of the following formulas (2) and (3).

In the above formula, R ⁰ represents a hydrogen atom or a methyl group, and R ¹ , R ² , R ³ , R ⁵ , R ⁶ , and R ⁷ are each independently an alkyl group or aralkyl group having 1 to 18 carbon atoms. Represents an aryl group, and R ⁴ represents an alkylene group, an aralkylene group, or an arylene group. Y represents a divalent linking group. X ⁻ represents a counter anion.

  According to the present invention, it is possible to provide an ink jet recording medium that is excellent in ink absorption and capable of high-density image recording, and that is particularly excellent in bleeding with time and water resistance of a recorded image.

The inkjet recording medium of the present invention includes a cationic polymer that acts and chelates with a boron compound, a Cu compound, an Al compound, a Ti compound, a Zr compound, or an Fe compound, and the cationic polymer and the boron compound, the Cu compound, A cross-linked structure can be formed with an Al compound, Ti compound, Zr compound, or Fe compound.
Hereinafter, the ink jet recording medium of the present invention will be described in detail.

  The ink jet recording medium of the present invention has at least one ink receiving layer, and the ink receiving layer includes a boron compound, a Cu compound, an Al compound, a Ti compound, a Zr compound, and an Fe compound (hereinafter referred to as “the present invention”). At least one selected from the group consisting of “crosslinking component” and a 1,2- or 1,3-diol structure, and an inorganic / organic ratio (I / O value) of 2.5. At least a cationic polymer (hereinafter also referred to as “cationic polymer according to the present invention”), preferably further containing fine particles and a water-soluble resin, and cross-linking the water-soluble resin as necessary. A crosslinking agent, a mordant and other components can be further used.

-Boron compounds, Cu compounds, Al compounds, Ti compounds, Zr compounds, and Fe compounds-
The ink receiving layer according to the present invention contains at least one selected from the group consisting of a boron compound, a Cu compound, an Al compound, a Ti compound, a Zr compound, and an Fe compound (crosslinking component according to the present invention). The crosslinking component according to the present invention acts on a 1,2- or 1,3-diol portion of the cationic polymer according to the present invention described later to undergo a crosslinking reaction, thereby forming a higher-order crosslinked body in the layer. By doing so, it is possible to more effectively prevent image bleeding (bleeding over time) that occurs with time after recording, and to secure higher water resistance. Further, as will be described later, the crosslinking component according to the present invention is a compound that also functions as a crosslinking agent for the water-soluble resin. In particular, when the water-soluble resin is used in combination with the cationic polymer according to the present invention, the water-soluble resin is used. In addition to crosslinking and curing, the cationic polymer according to the present invention is also cured by forming a crosslinked structure, so that the bleeding resistance with time and the water resistance can be further improved.

Examples of the boron compound include borax, boric acid, borates (for example, orthoborate, InBO ₃ , ScBO ₃ , YBO ₃ , LaBO ₃ , Mg ₃ (BO ₃ ) ₂ , Co ₃ (BO ₃ ) ₂ , two Borate (eg, Mg ₂ B ₂ O ₅ , Co ₂ B ₂ O ₅ ), metaborate (eg, LiBO ₂ , Ca (BO ₂ ) ₂ , NaBO ₂ , KBO ₂ ), tetraborate (eg, Na _{2 B 4 O 7 · 10H 2} O), five borate _{(e.g., KB 5 O 8 · 4H 2} O, Ca 2 B 6 O 11 · 7H 2 O, CsB 5 O 5), and the like.
Of these, borax, boric acid, and borate are preferable, and boric acid is particularly preferable in that a crosslinking reaction can be promptly caused.

  Examples of the Cu compound include cupric chloride, ammonium copper (II) chloride dihydrate, and copper sulfate. Examples of the Al compound include aluminum sulfate, aluminum alum, aluminum sulfite, and thiosulfuric acid. Examples thereof include aluminum, polyaluminum chloride, aluminum nitrate nonahydrate, aluminum chloride hexahydrate, and basic polyaluminum hydroxide. Examples of the Ti compound include titanium tetrachloride, tetraisopropyl titanate, titanium acetyl. Examples include acetonate, titanium lactate, and titanium triethanolamate. Examples of the Zr compound include zirconium acetate, ammonium zirconium carbonate, ammonium zirconium nitrate, potassium zirconium carbonate, zirconium ammonium citrate, zirconium stearate, zirconium octylate, zirconium acetylacetonate, zirconyl sulfate, zirconyl nitrate, oxy Examples of the Fe compound include ferrous bromide, ferrous chloride, ferric chloride, ferrous sulfate, and ferric sulfate.

  Of these, Zr compounds, Al compounds, and Ti compounds are particularly preferable, and zirconium acetate, ammonium zirconium carbonate, aluminum alum, polyaluminum chloride, and titanium lactate are particularly preferable.

  The content of the crosslinking component according to the present invention in the ink receiving layer is preferably 1 to 100% by mass, and more preferably 5 to 50% by mass with respect to the mass of the cationic polymer according to the present invention described later. By setting the content in the above range, it is possible to effectively form a crosslinked structure, effectively suppress bleeding over time of an image after recording, and form a highly water-resistant image. it can.

-Cationic polymer-
The ink receiving layer according to the present invention has a 1,2- or 1,3-diol structure and has an inorganic / organic ratio represented by an organic conceptual diagram, that is, an I / O value of 2.5 or less. It contains at least one kind of certain cationic polymer (cationic polymer according to the present invention). The cationic polymer according to the present invention has a diol structure in the molecule, and this diol is cross-linked with the cross-linking component according to the present invention so that the inside of the layer is an ester (for example, borate ester). Therefore, it is possible to fix the ink (coloring material) after recording, to prevent image bleeding (bleeding with time) generated with time, and to ensure higher water resistance. Moreover, since it has a low polarity with an I / O value of 2.5 or less, it is particularly effective for improving bleeding resistance over time.

  The cationic polymer according to the present invention can be appropriately selected from polymers having a 1,2- or 1,3-diol structure and a cationic group. Preferred polymers include 1,2- or 1 In addition to the 1,3-diol structure, there may be mentioned a cationic polymer having a primary to tertiary amino group or a salt thereof or a quaternary ammonium base.

  In the present invention, the I / O value is set to 2.5 or less, but 0.8 to 2.3 is preferable and 1.0 to 2 is preferable in that the effect of the present invention can be more effectively achieved. 0.0 is particularly preferred. When the I / O value is in the above range, the image blur after recording can be effectively suppressed while suppressing the low polarity and the water solubility of the cationic resin from being too high.

  Here, the I / O value is a parameter that represents a measure of the hydrophilicity / lipophilicity of a compound or substituent. A detailed explanation can be found in “Organic Conceptual Diagram” (Yoshio Koda, Sankyo Publishing, 1984). is there. I represents inorganic property, and O represents organic property. The greater the I / O value, the greater the inorganic property, that is, the higher the polarity and the greater the hydrophilicity.

  In addition, the cation equivalent of the cationic polymer is preferably 1 meq / g or more from the viewpoint of effectively improving bleeding resistance and water resistance. In view of more effective effects of the present invention, 2.0 meq / g or more is more preferable, and the upper limit is preferably 5 meq / g. If the cation equivalent is less than 1 meq / g, the ratio of the mordanting site for mordanting the ink may be relatively small, so that the immobilization of the coloring matter may be insufficient. It greatly contributes to immobilization and can effectively prevent bleeding with time and improve water resistance. In addition, the dispersibility of the coating solution does not deteriorate due to the excessive cation equivalent.

  Here, the cation equivalent is an equivalent (mmol) of a cationic group (for example, a total of amino group, ammonium group and the like) contained per 1 g of the polymer, and is expressed by meq / g.

  In the above, the cationic polymer has an inorganic / organic ratio (I / O value) in an organic conceptual diagram of 2.5 or less (more preferably 0.8 to 2.3), and a cation equivalent of 1 meq / It is preferable to select the ratio of the structure and the copolymerization component so as to be g or more (more preferably 2.0 to 5.0 meq / g).

As the cationic polymer according to the present invention, a polymer represented by the following general formula (1) is particularly preferable.

  In the general formula (1), A represents a structural unit derived from a cationic vinyl monomer having a quaternary ammonium group. By adding this A to the polymer structure, it is polymerized and cured by itself, and since it contains a quaternary ammonium group (high cation equivalent), it acts greatly on the ink and is effective in improving bleeding resistance and water resistance. .

  Examples of the cationic vinyl monomer constituting the structural unit represented by A include (meth) acrylic acid alkyl ester [methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate. Isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, hexyl (meth) acrylate, octyl (meth) acrylate, (meth) (Meth) acrylic acid C [carbon number] 1-C18 alkyl ester, etc.] such as 2-ethylhexyl acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, etc., (meth) acrylic acid cycloalkyl ester [( Meth) acrylic acid cyclohexyl etc.], (meth) acrylic acid aryl ester [(meth) acrylic acid Phenyl, etc.], aralkyl esters [benzyl (meth) acrylate], substituted (meth) acrylic acid alkyl esters [such as 2-hydroxyethyl (meth) acrylate], aromatic vinyls [styrene, vinyltoluene, α-methyl Styrene, etc.], vinyl esters [vinyl acetate, vinyl propionate, vinyl versatate, etc.], allyl esters [allyl acetate, etc.], halogen-containing monomers [vinylidene chloride, vinyl chloride, etc.], vinyl cyanide [(meta ) Acrylonitrile etc.], olefins [ethylene, propylene etc.], etc.

In the general formula (1), B represents a structural unit derived from a vinyl monomer having an I / O value of 0.5 or less. Since the I / O value is low, the polarity is small, and it is effective in improving aging resistance and water resistance.
Examples of the vinyl monomer constituting the structural unit represented by B include styrene, vinyl toluene, t-butyl methacrylate, hexyl methacrylate, cyclohexyl methacrylate, 2-ethylhexyl (meth) acrylate, (meta ) Benzyl acrylate and the like are preferred, and styrene or vinyltoluene is particularly preferred.

In the general formula (1), R represents a hydrogen atom or a methyl group, and Z represents a divalent linking group.
Specific examples of Z include —O— and —NR′—, and R ′ includes a hydrogen atom or an alkyl group (for example, a methyl group, an ethyl group, an n-propyl group, an n-butyl group, n-hexyl group, etc.).

In said general formula (1), l represents 20-80 mol%, Preferably it is 25-75, Most preferably, it is 30-70. Moreover, m represents 10-70 mol%, Preferably it is 20-70, Most preferably, it is 30-70. n represents 5-10 mol%, Preferably it is 5-8, Most preferably, it is 5-7. In the above, the sum of l + m + n is 100.
P represents 1 or 2, and is preferably 1.

  Among the cationic polymers represented by the general formula (1), the structural unit represented by A is preferably a structural unit represented by the following formula (2) and / or formula (3). A may be composed of only formula (2), may be composed only of formula (3), or may be a unit composed of both formula (2) and formula (3).

In the above formulas (2) and (3), R ⁰ represents a hydrogen atom or a methyl group. In Formula (2) or Formula (3), R ¹ , R ² , R ³ , R ⁵ , R ⁶ , and R ⁷ are each independently an alkyl group having 1 to 18 carbon atoms, an aralkyl group, or an aryl group. Represents.

The alkyl group having 1 to 18 carbon atoms represented by R ¹ , R ² , R ³ , R ⁵ , R ⁶ , or R ⁷ may be unsubstituted or have a substituent, for example, methyl Group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, t-butyl group, n-hexyl group, cyclohexyl group, 2-ethylhexyl group, n-octyl group, n-nonyl group, n Examples include -decyl group, n-dodecyl group, n-octadecyl group, hydroxyethyl group, 1-hydroxypropyl group and the like. Preferably, it is a C1-C8 alkyl group, and a methyl group, an ethyl group, n-propyl group, isopropyl group, n-butyl group, n-hexyl group, and 2-hydroxyethyl group are especially suitable.

The aralkyl group represented by R ¹ , R ² , R ³ , R ⁵ , R ⁶ , or R ⁷ may be unsubstituted or substituted, and examples thereof include a benzyl group, a phenylethyl group, A vinylbenzyl group, a hydroxyphenylmethyl group, etc. are mentioned.

The aryl group represented by R ¹ , R ² , R ³ , R ⁵ , R ⁶ , or R ⁷ may be unsubstituted or substituted. For example, a phenyl group, an alkylphenyl group ( For example, methylphenyl group, ethylphenyl group, n-propylphenyl group, n-butylphenyl group), naphthyl group, chlorophenyl group, dichlorophenyl group, trichlorophenyl group, bromophenyl group, hydroxyphenyl group, methoxyphenyl group, acetoxy A phenyl group, a cyanophenyl group, etc. are mentioned.

Of the above, R ¹ , R ² , R ³ , R ⁵ , R ⁶ , or R ⁷ is particularly preferably a benzyl group, a phenylethyl group, a phenyl group, or a naphthyl group.

In the formula (2), R ⁴ represents an alkylene group, an aralkylene group, or an arylene group, and Y represents a divalent linking group.
The alkylene group represented by R ⁴ may be unsubstituted or substituted, and is preferably an alkylene group having 1 to 8 carbon atoms. For example, a methylene group, an ethylene group, a trimethylene group, 2-hydroxypropylene Group, hexamethylene group and the like. The aralkylene group represented by R ⁴ may be unsubstituted or substituted, and is preferably an aralkylene group having 7 to 8 carbon atoms, such as a benzylidene group, which is represented by R ^4. The arylene group may be unsubstituted or substituted, and is preferably an arylene group having 6 to 10 carbon atoms, such as a phenylene group.

  The divalent linking group represented by Y has the same meaning as Z in the general formula (1), and includes, for example, —O— and —NR′—, and R ′ represents a hydrogen atom or an alkyl group. Represents a group (for example, methyl group, ethyl group, n-propyl group, n-butyl group, n-hexyl group, etc.).

In the formula (2) and formula (3), X ⁻ represents a counter anion. Specific examples include halogen ions (Cl ⁻ , Br ⁻ , I ⁻ ), sulfonate ions, alkyl sulfonate ions, aryl sulfonate ions, alkyl carboxylate ions, aryl carboxylate ions, and the like.

  The molecular weight of the cationic polymer represented by the general formula (1) is preferably about 1,000 to 500,000, and more preferably 2,000 to 100,000, as a weight average molecular weight. By adjusting the molecular weight within the above range, a high degree of water resistance can be obtained, and image bleeding over time can be effectively suppressed, and handling defects associated with excessive molecular weight do not occur. .

  The cationic polymer represented by the general formula (1) is preferably water-soluble or soluble in water-miscible organic solvent, and used as a form of water-dispersible latex. It is also possible.

  Hereinafter, preferable examples (polymers P-1 to P-5) of the cationic polymer represented by the general formula (1) are listed. However, the present invention is not limited to these.

Next, a method for synthesizing the cationic polymer according to the present invention will be described using the polymers P-1 to P-3 as examples.
(Synthesis example 1): Synthesis of polymer P-1 2- (methacryloyloxy) ethyltrimethylammonium chloride (41.5 parts), styrene (8.75 parts), and glycerol methacrylate (2.64 parts) are dissolved in ethanol (123 parts). This was heated to 70 ° C. under a nitrogen stream, and 0.082 part of 2,2′-azobis (2-amidinopropane) dihydrochloride (V-50, manufactured by Wako Pure Chemical Industries, Ltd.) was added, And stirred with heating. Two hours later, 0.082 part of V-65 was further added thereto, and the mixture was heated and stirred at 70 ° C. for 4 hours.
Thereafter, the obtained reaction solution was poured into 2000 parts of ethyl acetate with stirring, and the resulting viscous solid was dried to obtain the polymer P-1 having the above structure (I / O value = 1.88, cation equivalent 3.78 meq). / G) 49.8 parts of a white solid was obtained.

(Synthesis Example 2): Synthesis of Polymer P-2 41.5 parts of 2- (methacryloyloxy) ethyltrimethylammonium chloride used in Synthesis Example 1 was changed to 26.0 parts, and 8.75 parts of styrene was 24.6 parts. The polymer P-2 having the above structure (I / O value = 1.08, cation equivalent 2.32 meq) in the same manner as in Synthesis Example 1, except that 2.64 parts of glycerol methacrylate was changed to 3.34 parts. / G) 47.3 parts of a white solid was obtained.

(Synthesis Example 3): Synthesis of Polymer P-3 Except for replacing 41.5 parts of 2- (methacryloyloxy) ethyltrimethylammonium chloride used in Synthesis Example 1 with 42.4 parts of trimethylvinylbenzylammonium chloride. In the same manner as in Synthesis Example 1, 46.2 parts of a white solid of the polymer P-3 having the structure described above (I / O value = 1.39, cation equivalent 3.72 meq / g) was obtained.

  The above polymers P-4 to P-5 can also be synthesized by an approximate method. The polymer P-4 has an I / O value = 1.05 and a cation equivalent of 1.75 meq / g, and the polymer P-5 has an I / O value = 1.38, a cation equivalent of 3.73 meq / g. g.

The content of the ink receiving layer of the cationic polymer according to the present invention, preferably 0.1-2 g / m ^2, more preferably 0.2 to 1.5 g / m ^2. By setting the content in the above range, it is possible to effectively form a crosslinked structure, effectively suppress bleeding over time of an image after recording, and form a highly water-resistant image. In addition, the content of the ink is not so high that the ink absorbability is not lowered.

-Fine particles-
The ink receiving layer according to the present invention can contain at least one kind of fine particles.
The ink receiving layer of the ink jet recording medium has a porous structure by containing fine particles, thereby improving the ink absorption performance. In particular, when the solid content of the fine particles in the ink receiving layer is 50% by mass or more, more preferably more than 60% by mass, it becomes possible to form a more favorable porous structure, and sufficient ink absorptivity. This is preferable because an ink jet recording medium having the above can be obtained. Here, the solid content in the ink receiving layer of fine particles is a content calculated based on components other than water in the composition constituting the ink receiving layer.
The fine particles used in the present invention are preferably inorganic fine particles, but organic fine particles can also be used as long as the effects of the present invention are not impaired.

  Preferred examples of the organic fine particles include polymer fine particles obtained by emulsion polymerization, microemulsion polymerization, soap-free polymerization, seed polymerization, dispersion polymerization, suspension polymerization, and the like. Specifically, polyethylene, polypropylene, Examples include polystyrene, polyacrylate, polyamide, silicon resin, phenol resin, natural polymer powder, latex or emulsion polymer fine particles, and the like.

Examples of the inorganic fine particles include silica fine particles, colloidal silica, titanium dioxide, barium sulfate, calcium silicate, zeolite, kaolinite, halloysite, mica, talc, calcium carbonate, magnesium carbonate, calcium sulfate, pseudoboehmite, zinc oxide, water. Examples thereof include zinc oxide, alumina, aluminum silicate, calcium silicate, magnesium silicate, zirconium oxide, zirconium hydroxide, cerium oxide, lanthanum oxide, and yttrium oxide. Among these, silica fine particles, colloidal silica, alumina fine particles, or pseudoboehmite are preferable from the viewpoint of forming a good porous structure. The fine particles may be used as primary particles or in a state where secondary particles are formed. The average primary particle size of these fine particles is preferably 2 μm or less, and more preferably 200 nm or less.
Furthermore, silica fine particles having an average primary particle size of 20 nm or less, colloidal silica having an average primary particle size of 30 nm or less, alumina fine particles having an average primary particle size of 20 nm or less, or pseudoboehmite having an average pore radius of 2 to 15 nm is more preferable. In particular, silica fine particles, alumina fine particles, or pseudoboehmite each having the above-mentioned diameters are preferable.

  Silica fine particles are generally roughly classified into wet method particles and dry method (gas phase method) particles according to the production method. In the wet method, a method in which activated silica is produced by acid decomposition of a silicate, which is appropriately polymerized and coagulated and precipitated to obtain hydrous silica is the mainstream. On the other hand, the gas phase method is a method by high-temperature gas phase hydrolysis of silicon halide (flame hydrolysis method), a method in which silica sand and coke are heated and reduced by an arc in an electric furnace and oxidized with air. The method of obtaining anhydrous silica by the (arc method) is the mainstream, and “gas phase method silica” means anhydrous silica fine particles obtained by the gas phase method. As the silica fine particles used in the present invention, gas phase method silica fine particles are particularly preferable.

Vapor phase silica is different from hydrous silica in terms of the density of silanol groups on the surface, the presence or absence of vacancies, etc., and exhibits different properties, but is suitable for forming a three-dimensional structure with a high porosity. The reason for this is not clear, but in the case of hydrous silica, the density of silanol groups on the surface of the fine particles is large at 5 to 8 / nm ² , and the silica fine particles tend to aggregate closely (aggregate). In the case of the method silica, the density of silanol groups on the surface of the fine particles is 2 to 3 / nm ² , so that it is sparse soft agglomeration (flocculate), resulting in a structure with a high porosity. Is done.

  Since the vapor phase silica has a particularly large specific surface area, the ink absorbency and retention efficiency are high, and since the refractive index is low, transparency can be imparted to the receiving layer by dispersing to an appropriate particle size. It is characterized by high color density and good color development. The transparency of the ink-receiving layer is not only for applications that require transparency, such as OHP, but also for high color density and good color development gloss even when applied to recording sheets such as photo glossy paper. Is important.

  The average primary particle size of the vapor phase silica is preferably 30 nm or less, more preferably 20 nm or less, particularly preferably 10 nm or less, and most preferably 3 to 10 nm. Vapor phase silica is easy to adhere to each other by hydrogen bonds with silanol groups, so it can form a structure with a large porosity when the average primary particle size is 30 nm or less, effectively improving ink absorption characteristics. Can be made.

The content of the fine particles in the ink receiving layer is preferably 10 to 90% by mass and more preferably 20 to 80% by mass with respect to the total solid mass of the layer.
Silica fine particles may be used in combination with other fine particles described above. When other fine particles and vapor phase method silica are used in combination, the content of vapor phase method silica in all the fine particles is preferably 30% by mass or more, and more preferably 50% by mass or more.

As the inorganic fine particles, alumina fine particles, alumina hydrate, a mixture or a composite thereof are also preferable. Of these, alumina hydrate is preferable because it absorbs and fixes ink well, and pseudoboehmite (Al ₂ O ₃ .nH ₂ O) is particularly preferable. Alumina hydrates can be used in various forms, but it is preferable to use sol boehmite as a raw material because a smooth layer can be easily obtained.

About the pore structure of pseudo boehmite, the average pore radius is preferably 1 to 30 nm, and more preferably 2 to 15 nm. The pore volume is preferably 0.3 to 2.0 cc / g, more preferably 0.5 to 1.5 cc / g. Here, the pore radius and the pore volume are measured by a nitrogen adsorption / desorption method, and can be measured by, for example, a gas adsorption / desorption analyzer (for example, trade name “Omni Soap 369” manufactured by Coulter).
Among alumina fine particles, vapor-phase method alumina fine particles are preferable because of their large specific surface area. The average primary particle diameter of the vapor phase process alumina is preferably 30 nm or less, and more preferably 20 nm or less.

  When the above-mentioned fine particles are used in an ink jet recording medium, for example, JP-A-10-81064, JP-A-10-119423, JP-A-10-157277, JP-A-10-217601, JP-A-11-348409, JP-A-2001-138621. No. 2000-43401 No. 2000-2111235 No. 2000-309157 No. 2001-96897 No. 2001-138627 No. 11-91242 No. 8-2087 No. 8-2090 No. 8-2091, 8-2093, 8-174992, 11-192777, JP-A-2001-301314, and the like can also be preferably used.

-Water-soluble resin-
The ink receiving layer according to the present invention can contain at least one water-soluble resin.
Examples of the water-soluble resin include a polyvinyl alcohol resin that is a resin having a hydroxy group as a hydrophilic structural unit [polyvinyl alcohol (PVA), acetoacetyl-modified polyvinyl alcohol, cation-modified polyvinyl alcohol, anion-modified polyvinyl alcohol, silanol-modified polyvinyl. Alcohol, polyvinyl acetal, etc.], cellulose resins [methyl cellulose (MC), ethyl cellulose (EC), hydroxyethyl cellulose (HEC), carboxymethyl cellulose (CMC), hydroxypropyl cellulose (HPC), hydroxyethyl methyl cellulose, hydroxypropyl methyl cellulose, etc.], Chitins, chitosans, starches, resins with ether bonds [polyethylene oxide (PEO), polyp Pyrene oxide (PPO), polyethylene glycol (PEG), poly ether (PVE)], and resins having carbamoyl groups [polyacrylamide (PAAM), polyvinyl pyrrolidone (PVP), polyacrylic acid hydrazide, etc.] and the like.
Moreover, the polyacrylic acid salt which has a carboxyl group as a dissociable group, maleic acid resin, alginate, gelatins, etc. can be mentioned.

Among these, polyvinyl alcohol resin is particularly preferable. Examples of polyvinyl alcohol include Japanese Patent Publication No. 4-52786, Japanese Patent Publication No. 5-67432, Japanese Patent Publication No. 7-29479, Japanese Patent No. 2537827, Japanese Patent Publication No. 7-57553, Japanese Patent No. 2502998, Japanese Patent No. 3053231, JP 63-176173, JP 2604367, JP 7-276787, JP 9-207425, JP 11-58941, JP 2000-135858, JP 2001-205924, JP 2001-287444, JP-A-62-278080, JP-A-9-39373, JP-A-2750433, JP-A-2000-158801, JP-A-2001-213045, JP-A-2001-328345, JP-A-8- No. 324105, JP-A-11-348417, etc. It is.
Examples of water-soluble resins other than polyvinyl alcohol resins include compounds described in “0011” to “0014” of JP-A No. 11-165461.

These water-soluble resins may be used alone or in combination of two or more.
The content of the water-soluble resin in the ink receiving layer is preferably 9 to 40% by mass and more preferably 12 to 33% by mass with respect to the total solid content of the ink receiving layer.

The water-soluble resin and fine particles described above, which mainly constitute the ink receiving layer of the present invention, may be a single material or a mixed system of a plurality of materials.
From the viewpoint of maintaining transparency, the type of water-soluble resin combined with fine particles, particularly silica fine particles, is important. When the gas phase method silica is used, the water-soluble resin is preferably a polyvinyl alcohol resin, more preferably a polyvinyl alcohol resin having a saponification degree of 70 to 100%, and a saponification degree of 80 to 99.5%. The polyvinyl alcohol resin is particularly preferable.

The polyvinyl alcohol-based resin has a hydroxyl group in its structural unit, and since this hydroxyl group and the surface silanol group of the silica fine particle form a hydrogen bond, a three-dimensional network having a secondary particle of the silica fine particle as a network chain unit. It becomes easy to form a structure. By forming this three-dimensional network structure, it is considered that an ink receiving layer having a porous structure with a high porosity and sufficient strength is formed.
In ink jet recording, the porous ink receiving layer obtained as described above can absorb ink rapidly by a capillary phenomenon, and can form dots with good roundness without ink bleeding.

  In addition, other water-soluble resins may be used in combination with the polyvinyl alcohol resin. When other water-soluble resin and polyvinyl alcohol resin are used in combination, the content of the polyvinyl alcohol resin is preferably 50% by mass or more, and more preferably 70% by mass or more in the total water-soluble resin.

<Content ratio of fine particles to water-soluble resin>
The mass content ratio [PB ratio (x / y)] between the fine particles (x) and the water-soluble resin (y) greatly affects the film structure and film strength of the ink receiving layer. That is, as the mass content ratio [PB ratio] increases, the porosity, pore volume, and surface area (per unit mass) increase, but the density and strength tend to decrease.

  As the PB ratio (x / y) of the ink receiving layer according to the present invention, it is possible to prevent a decrease in film strength and cracking during drying caused by the PB ratio being too large, and the PB ratio is too small. From the viewpoint of preventing the ink absorbability from being lowered due to the void being easily blocked by the resin and decreasing the void ratio, 1.5 to 10 is preferable.

  Since stress may be applied to the recording medium when passing through the conveyance system of the ink jet printer, the ink receiving layer needs to have sufficient film strength. Further, when cutting into a sheet shape, the ink receiving layer needs to have sufficient film strength in order to prevent cracking or peeling of the ink receiving layer. Considering these cases, the PB ratio (x / y) is more preferably 5 or less, and more preferably 2 or more from the viewpoint of ensuring high-speed ink absorbability in an ink jet printer. .

For example, a coating solution in which vapor phase method silica fine particles having an average primary particle size of 20 nm or less and a water-soluble resin are completely dispersed in an aqueous solution at a PB ratio (x / y) of 2 to 5 is applied on a support. When the applied coating layer is dried, a three-dimensional network structure is formed in which secondary particles of silica fine particles are network chains, the average pore diameter is 30 nm or less, the porosity is 50 to 80%, the pore specific volume Can be easily formed with a translucent porous film having a specific surface area of 100 m ² / g or more.

-Other components-
In the ink jet recording medium of the present invention, the ink receiving layer can be constituted by further using a crosslinking agent, a mordant, various additives and the like in addition to the above-described constituent components.
<Crosslinking agent>
In the ink-receiving layer according to the present invention, the layer containing the crosslinking component and the cationic polymer according to the present invention, the fine particles, and the water-soluble resin (for example, coating layer) is further water-soluble in addition to the crosslinking component according to the present invention. A cross-linking agent for cross-linking the functional resin may be used in combination to cause a cross-linking reaction between the cross-linking agent and the water-soluble resin, thereby obtaining a more highly cured porous layer.

Although the crosslinking component (boron compound etc.) according to the present invention described above contributes to the crosslinking of the above water-soluble resin, particularly polyvinyl alcohol resin, the following compounds can be used as other crosslinking agents.
For example, aldehyde compounds such as formaldehyde, glyoxal and glutaraldehyde; ketone compounds such as diacetyl and cyclopentanedione; bis (2-chloroethylurea) -2-hydroxy-4,6-dichloro-1,3,5- Active halogen compounds such as triazine and 2,4-dichloro-6-S-triazine sodium salt; divinylsulfonic acid, 1,3-vinylsulfonyl-2-propanol, N, N′-ethylenebis (vinylsulfonylacetamide) ), Active vinyl compounds such as 1,3,5-triacryloyl-hexahydro-S-triazine; N-methylol compounds such as dimethylolurea and methyloldimethylhydantoin; melamine resins (for example, methylolmelamine, alkylated methylolmelamine) ;Epoxy resin;

Isocyanate compounds such as 1,6-hexamethylene diisocyanate; aziridine compounds described in US Pat. Nos. 3,017,280 and 2,983611; carboximide compounds described in US Pat. No. 3,100,704; glycerol triglycidyl Epoxy compounds such as ether; Ethyleneimino compounds such as 1,6-hexamethylene-N, N′-bisethyleneurea; Halogenated carboxaldehyde compounds such as mucochloric acid and mucophenoxycyclolic acid; 2,3-dihydroxy Dioxane compounds such as dioxane; metal compounds such as chromium alum, potash alum, chromium acetate other than Cu compounds, Al compounds, Ti compounds, Zr compounds, and Fe compounds, polyamine compounds such as tetraethylenepentamine, adipine Acid dich Hydrazide compounds such Hydrazide, small molecule or polymer having two or more oxazoline groups, and the like.

Crosslinking and curing using a crosslinking agent can be performed, for example, as follows. That is,
Coating in which the ink receiving layer contains the above-described crosslinking component according to the present invention, a crosslinking agent other than the crosslinking component, a cationic polymer, fine particles (for example, vapor phase method silica fine particles), a water-soluble resin (for example, polyvinyl alcohol), and the like. In the case of a layer obtained by crosslinking and curing a coating layer coated with a liquid (hereinafter also referred to as “first liquid”), the crosslinking and curing is performed by the first liquid and / or the following basic solution (hereinafter referred to as “second liquid”). And a cross-linking component according to the present invention and a cross-linking agent other than the cross-linking component are added and (1) the first liquid is applied at the same time, or (2) the application is applied by applying the first liquid. It is preferably performed by applying the second liquid adjusted to pH 7.1 or higher to the coating layer at any time during the drying of the layer and before the coating layer exhibits reduced-rate drying. it can.

The crosslinking agent may be contained in either the first liquid or the second liquid, and may be contained in both the first liquid and the second liquid. Moreover, you may use a crosslinking agent in combination of 2 or more types besides using individually by 1 type.
The mass of the crosslinking agent in the case of containing the crosslinking agent is a range in which the total amount of the crosslinking component and the crosslinking agent according to the present invention described above is 0.5 to 50% by mass with respect to the mass of the water-soluble resin. Is preferable, and the range of 1 to 25% by mass is more preferable.

<mordant>
It is also preferable that the ink receiving layer according to the present invention contains a so-called mordant other than the cationic polymer according to the present invention described above for the purpose of further improving the water resistance and aging resistance of the image. . When this mordant is further present in the ink receiving layer, it interacts with the liquid ink containing the applied anionic dye as a coloring material to stabilize the coloring material, and further improve water resistance and bleeding over time. Contributes to improvement.

  Preferable examples of the mordant include organic mordants such as cationic polymers (cationic mordants) and inorganic mordants such as water-soluble metal compounds. The organic mordant and the inorganic mordant may be used in combination with the organic mordant and the inorganic mordant in addition to being used alone.

As the cationic mordant, a polymer mordant containing a primary to tertiary amino group or a quaternary ammonium base as a cationic group and not containing a 1,2- or 1,3-diol structure is generally used. is there. On the other hand, in the present invention, a cationic non-polymer mordant can also be used.
Examples of the polymer mordant include a homopolymer of a monomer having a primary to tertiary amino group and a salt thereof, or a quaternary ammonium base (mordant monomer), and the mordant monomer and other monomers (hereinafter, What is obtained as a copolymer or condensation polymer with “non-mordant monomer”). These polymer mordants can be used in any form of water-soluble polymer or water-dispersible latex particles.

  Examples of the monomer (mordanting monomer) include trimethyl-p-vinylbenzylammonium chloride, trimethyl-m-vinylbenzylammonium chloride, triethyl-p-vinylbenzylammonium chloride, triethyl-m-vinylbenzylammonium chloride, N , N-dimethyl-N-ethyl-Np-vinylbenzylammonium chloride, N, N-diethyl-N-methyl-Np-vinylbenzylammonium chloride, N, N-dimethyl-Nn-propyl-N -P-vinylbenzylammonium chloride, N, N-dimethyl-Nn-octyl-Np-vinylbenzylammonium chloride, N, N-dimethyl-N-benzyl-Np-vinylbenzylammonium chloride, N, N-die Ru-N-benzyl-Np-vinylbenzylammonium chloride, N, N-dimethyl-N- (4-methyl) benzyl-Np-vinylbenzylammonium chloride, N, N-dimethyl-N-phenyl-N -P-vinylbenzylammonium chloride;

Trimethyl-p-vinylbenzylammonium bromide, trimethyl-m-vinylbenzylammonium bromide, trimethyl-p-vinylbenzylammonium sulfonate, trimethyl-m-vinylbenzylammonium sulfonate, trimethyl-p-vinylbenzylammonium acetate, trimethyl-m-vinyl Benzylammonium acetate, N, N, N-triethyl-N-2- (4-vinylphenyl) ethylammonium chloride, N, N, N-triethyl-N-2- (3-vinylphenyl) ethylammonium chloride, N, N-diethyl-N-methyl-N-2- (4-vinylphenyl) ethylammonium chloride, N, N-diethyl-N-methyl-N-2- (4-vinylphenyl) ethylammonium chloride Tate;

N, N-dimethylaminoethyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate, N, N-diethylaminopropyl (meth) acrylate, N, N- Methyl chloride, ethyl chloride, methyl bromide of dimethylaminoethyl (meth) acrylamide, N, N-diethylaminoethyl (meth) acrylamide, N, N-dimethylaminopropyl (meth) acrylamide, N, N-diethylaminopropyl (meth) acrylamide , Quaternized products of ethyl bromide, methyl iodide or ethyl iodide, or sulfonates, alkyl sulfonates, acetates or alkyl carboxylates substituted for their anions.

  Specifically, for example, monomethyl diallyl ammonium chloride, trimethyl-2- (methacryloyloxy) ethylammonium chloride, triethyl-2- (methacryloyloxy) ethylammonium chloride, trimethyl-2- (acryloyloxy) ethylammonium chloride, triethyl- 2- (acryloyloxy) ethylammonium chloride, trimethyl-3- (methacryloyloxy) propylammonium chloride, triethyl-3- (methacryloyloxy) propylammonium chloride, trimethyl-2- (methacryloylamino) ethylammonium chloride, triethyl-2- (Methacryloylamino) ethylammonium chloride, trimethyl-2- (acryloylamino) ethyl Ammonium chloride, triethyl-2- (acryloylamino) ethylammonium chloride, trimethyl-3- (methacryloylamino) propylammonium chloride, triethyl-3- (methacryloylamino) propylammonium chloride, trimethyl-3- (acryloylamino) propylammonium chloride Triethyl-3- (acryloylamino) propylammonium chloride;

N, N-dimethyl-N-ethyl-2- (methacryloyloxy) ethylammonium chloride, N, N-diethyl-N-methyl-2- (methacryloyloxy) ethylammonium chloride, N, N-dimethyl-N-ethyl- 3- (acryloylamino) propylammonium chloride, trimethyl-2- (methacryloyloxy) ethylammonium bromide, trimethyl-3- (acryloylamino) propylammonium bromide, trimethyl-2- (methacryloyloxy) ethylammonium sulfonate, trimethyl-3- And (acryloylamino) propylammonium acetate.
Other examples of the copolymerizable monomer include N-vinylimidazole and N-vinyl-2-methylimidazole.

  The non-mordant monomer does not contain a basic or cationic moiety such as a primary to tertiary amino group and a salt thereof, or a quaternary ammonium base, and does not show an interaction with a dye in an inkjet ink. Or the monomer which interaction is substantially small is said.

  Examples of the non-mordant monomer include (meth) acrylic acid alkyl ester; (meth) acrylic acid cycloalkyl ester such as cyclohexyl (meth) acrylate; (meth) acrylic acid aryl ester such as phenyl (meth) acrylate; Aralkyl esters such as (meth) benzyl acrylate; Aromatic vinyls such as styrene, vinyl toluene and α-methylstyrene; Vinyl esters such as vinyl acetate, vinyl propionate and vinyl versatic acid; Allyl esters such as allyl acetate Halogen-containing monomers such as vinylidene chloride and vinyl chloride; vinyl cyanide such as (meth) acrylonitrile; olefins such as ethylene and propylene; and the like.

The (meth) acrylic acid alkyl ester is preferably a (meth) acrylic acid alkyl ester having 1 to 18 carbon atoms in the alkyl moiety, such as methyl (meth) acrylate, ethyl (meth) acrylate, (meth) Propyl acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, hexyl (meth) acrylate, octyl (meth) acrylate, Examples include 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, and the like.
Of these, methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate, and hydroxyethyl methacrylate are preferable.
The non-mordant monomers can also be used singly or in combination of two or more.

Further, as the polymer mordant, polydiallyldimethylammonium chloride, polymethacryloyloxyethyl-β-hydroxyethyldimethylammonium chloride, polyethyleneimine, polyallylamine and derivatives thereof, polyamide-polyamine resin, cationized starch, dicyandiamide formalin condensate, dimethyl Addition of 2-hydroxypropylammonium salt polymer, polyamidine, polyvinylamine, dicyandiamide-formalin polycondensate, dicyanamide-cachinic resin represented by dicyanamide-diethylenetriamine polycondensate, polyamine-type katine resin, epichlorohydrin-dimethylamine addition polymer, dimethyldiallylammonium phosphorus chloride -SO ₂ copolymers, diallylamine salt -SO ₂ copolymer, etc. It can be mentioned.

Examples of the inorganic mordant include polyvalent water-soluble metal salts and hydrophobic metal salts. Specific examples include magnesium, calcium, scandium, vanadium, manganese, nickel, zinc, gallium, germanium, strontium, yttrium, molybdenum, indium, barium, lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, dysproprosium. , A metal salt selected from erbium, ytterbium, hafnium, tungsten, and bismuth, or a complex thereof.
In addition to these, salts of aluminum, titanium, iron, copper, and zirconium and complexes thereof can also be mentioned. Examples of inorganic mordants include Cu compounds, Al compounds, and the like mentioned as the crosslinking component according to the present invention described above. Ti compounds, Zr compounds, and Fe compounds may be used.

  Specific examples include calcium acetate, calcium chloride, calcium formate, calcium sulfate, barium acetate, barium sulfate, barium phosphate, manganese chloride, manganese acetate, manganese formate dihydrate, manganese ammonium sulfate hexahydrate, cobalt chloride , Cobalt thiocyanate, cobalt sulfate, nickel sulfate hexahydrate, nickel chloride hexahydrate, nickel acetate tetrahydrate, nickel ammonium sulfate hexahydrate, nickel amidosulfate tetrahydrate, zinc phenolsulfonate, Zinc bromide, zinc chloride, zinc nitrate hexahydrate, zinc sulfate, chromium acetate, chromium sulfate, magnesium sulfate, magnesium chloride hexahydrate, magnesium citrate nonahydrate, sodium phosphotungstate, sodium tungsten citrate 12 tungstophosphoric acid n hydrate, 12 tungsto Acid 26 hydrate, molybdenum chloride, 12 molybdophosphoric acid n hydrate, gallium nitrate, germanium nitrate, strontium nitrate, yttrium acetate, yttrium chloride, yttrium nitrate, indium nitrate, lanthanum nitrate, lanthanum chloride, lanthanum acetate, benzoic acid Lanthanum acid, cerium chloride, cerium sulfate, cerium octylate, praseodymium nitrate, neodymium nitrate, samarium nitrate, europium nitrate, gadolinium nitrate, dysprosium nitrate, erbium nitrate, ytterbium nitrate, hafnium chloride, bismuth nitrate, etc. Examples of the cross-linking component (Cu compound, Al compound, Ti compound, Zr compound, and Fe compound) according to the above are exemplified.

The content of the ink receiving layer of the mordant is preferably ^{0.01~5g / m 2, 0.1~3g / m} 2 is more preferable.

<Other ingredients>
In the ink jet recording medium of the present invention, various known additives such as acids, ultraviolet absorbers, antioxidants, fluorescent brighteners, monomers, polymerization initiators, and polymerization prohibitions may be used as necessary in addition to the above components. Agents, anti-bleeding agents, preservatives, viscosity stabilizers, antifoaming agents, surfactants, antistatic agents, matting agents, anti-curling agents, water-proofing agents, and the like.
Details of the various additives are described in paragraph numbers [0080] to [0096] of JP-A No. 2004-167784.

-Support-
The ink jet recording medium of the present invention comprises a support and is formed by forming at least one ink receiving layer on the support.
As the support, any of a transparent support made of a transparent material such as plastic and an opaque support made of an opaque material such as paper can be used. In particular, in order to take advantage of the transparency of the ink receiving layer, it is preferable to use a transparent support or a highly glossy opaque support. Further, a read-only optical disk such as a CD-ROM or DVD-ROM, a write-once optical disk such as a CD-R or DVD-R, or a rewritable optical disk can be used as a support, and an ink receiving layer can be provided on both sides of the label. .

The material that can be used for the transparent support is preferably a material that is transparent and can withstand radiant heat when used in an OHP or a backlight display. Examples of the material include polyesters such as polyethylene terephthalate (PET); polysulfone, polyphenylene oxide, polyimide, polycarbonate, polyamide and the like. Of these, polyesters are preferable, and polyethylene terephthalate is particularly preferable.
Although there is no restriction | limiting in particular as thickness of the said transparent support body, 50-200 micrometers is preferable at the point which is easy to handle.

  As the highly glossy opaque support, one having a glossiness of 40% or more on the surface on which the ink receiving layer is provided is preferable. The glossiness is a value determined according to the method described in JIS P-8142 (75-degree specular gloss test method for paper and paperboard). Specifically, the following supports are mentioned.

  For example, high gloss paper support such as art paper, coated paper, cast coated paper, baryta paper used for silver salt photographic support, etc .; polyesters such as polyethylene terephthalate (PET), nitrocellulose, cellulose acetate , Cellulose esters such as cellulose acetate butyrate, and plastic films such as polysulfone, polyphenylene oxide, polyimide, polycarbonate, and polyamide are made opaque by adding a white pigment or the like (surface calendering may be applied). Glossy film; or a support in which a polyolefin coating layer containing or not containing a white pigment is provided on the surface of a highly glossy film containing the various paper supports, the transparent support or the white pigment. Etc. A white pigment-containing foamed polyester film (for example, foamed PET containing polyolefin fine particles and forming voids by stretching) can also be suitably exemplified. Furthermore, resin-coated paper used for silver salt photographic printing paper is also suitable.

Although there is no restriction | limiting in particular also about the thickness of the said opaque support body, 50-300 micrometers is preferable at the point of handleability.
Further, the surface of the support may be subjected to corona discharge treatment, glow discharge treatment, flame treatment, ultraviolet irradiation treatment, etc. in order to improve wettability and adhesion.

Next, the base paper used for the resin-coated paper will be described in detail.
As the base paper, wood pulp is used as a main raw material, and paper is made using synthetic pulp such as polypropylene or synthetic fiber such as nylon or polyester in addition to wood pulp as necessary. As the wood pulp, any of LBKP, LBSP, NBKP, NBSP, LDP, NDP, LUKP, NUKP can be used, but it is preferable to use more LBKP, NBSP, LBSP, NDP, LDP with a lot of short fibers. preferable. However, the ratio of LBSP and / or LDP is preferably 10% by mass or more and 70% by mass or less.
The pulp is preferably a chemical pulp (sulfate pulp or sulfite pulp) with few impurities, and a pulp having a whiteness improved by bleaching is also useful.

  In the base paper, sizing agents such as higher fatty acids and alkyl ketene dimers, white pigments such as calcium carbonate, talc and titanium oxide, paper strength enhancing agents such as starch, polyacrylamide and polyvinyl alcohol, fluorescent whitening agents, polyethylene glycols A water retaining agent such as a dispersant, a softening agent such as a quaternary ammonium, and the like can be appropriately added.

  The freeness of the pulp used for papermaking is preferably 200 to 500 ml as defined by CSF, and the fiber length after beating is a 24 mesh residual mass% and a 42 mesh residual as defined in JIS P-8207. 30 to 70% of the sum with the mass% of is preferable. In addition, it is preferable that the mass% of 4 mesh remainder is 20 mass% or less.

The basis weight of the base paper is preferably 30 to 250 g, and particularly preferably 50 to 200 g. The thickness of the base paper is preferably 40 to 250 μm. The base paper can be given a high smoothness by calendering at the paper making stage or after paper making. The density of the base paper is generally 0.7 to 1.2 g / m ² (JIS P-8118). Furthermore, the base paper stiffness is preferably 20 to 200 g under the conditions specified in JIS P-8143.

  A surface sizing agent may be applied to the surface of the base paper. As the surface sizing agent, a sizing agent similar to the size that can be added to the base paper can be used. The pH of the base paper is preferably 5 to 9 when measured by a hot water extraction method defined in JIS P-8113.

  The polyethylene covering the front and back surfaces of the base paper is mainly low-density polyethylene (LDPE) and / or high-density polyethylene (HDPE), but some other LLDPE, polypropylene, etc. can also be used.

  In particular, the polyethylene layer on the side on which the ink receiving layer is formed is obtained by adding rutile or anatase type titanium oxide, fluorescent whitening agent, ultramarine blue to polyethylene, as is widely done in photographic paper. What improved transparency, whiteness, and hue is preferable. Here, as content of titanium oxide, about 3-20 mass% is preferable with respect to polyethylene, and 4-13 mass% is more preferable. Although the thickness of a polyethylene layer does not have limitation in particular, 10-50 micrometers is suitable for both front and back layers. Further, an undercoat layer can be provided on the polyethylene layer in order to provide adhesion to the ink receiving layer. As the undercoat layer, aqueous polyester, gelatin and PVA are preferable. Moreover, as thickness of this undercoat layer, 0.01-5 micrometers is preferable.

  Polyethylene-coated paper can be used as glossy paper, or when it is coated by melt-extruding polyethylene onto the surface of the base paper, a matte or silky surface that can be obtained with ordinary photographic printing paper by performing a so-called molding process. Can also be used.

  A back coat layer can also be provided on the support, and examples of components that can be added to the back coat layer include a white pigment, an aqueous binder, and other components. Details of components that can be added to the backcoat layer are described in paragraphs [0112] to [0113] of JP-A No. 2004-167784.

-Production of inkjet recording media-
The ink jet recording medium of the present invention has at least one ink receiving layer, and the ink receiving layer includes, for example, the aforementioned crosslinking component and cationic polymer according to the present invention, fine particles, water-soluble resin, and crosslinking. A step of applying a first liquid (ink receiving layer coating liquid) containing an agent to form a coating layer on a support (coating process), and (1) applying the first liquid to the coating layer At the same time, (2) during the drying of the coating layer formed by applying the first liquid and before the coating layer exhibits reduced-rate drying, the second liquid (pH 7.1 or higher) It can be suitably formed by a method (Wet-on-Wet method << WOW method >>) comprising a step (curing step) of applying a basic solution) and crosslinking and curing the coating layer. The coating layer coated on the support in the coating step is crosslinked by a chelate of the crosslinking component according to the present invention in the layer and the cationic polymer, and further the water-soluble resin is crosslinked in the curing step, whereby the coating layer is formed. A highly cross-linked and cured ink receiving layer is formed.
The crosslinking component and the cationic polymer according to the present invention described above are desirably contained in the first liquid, and the crosslinking agent for crosslinking the water-soluble resin is contained in at least one of the first liquid and the second liquid. do it.

  The above-mentioned cross-linking curing (curing step) by the WOW method is preferable from the viewpoint of ink absorbability of the ink receiving layer and prevention of film cracking. In addition, when a large amount of mordant is present on the surface of the ink receiving layer, the applied ink (coloring material) is sufficiently mordanted, color density, bleeding with time, gloss on the image area, water resistance of characters and images after recording, and ozone resistance. It is preferable at the point which can improve property. About a mordant, you may make it partly contain in the layer initially provided in a support body, In that case, the mordant provided later may be the same or different.

In the present invention, the ink receiving layer containing the above-described crosslinking component (for example, boric acid) according to the present invention, the cationic polymer according to the present invention, fine particles (for example, vapor phase silica), and a water-soluble resin (for example, polyvinyl alcohol). The coating liquid for coating (first liquid) can be prepared, for example, as follows. That is,
Gas phase method silica (fine particles), boric acid (crosslinking component according to the present invention) and the cationic polymer according to the present invention are added to water (for example, 10 to 20% by mass of silica in water), and a high-speed rotating wet colloid mill (For example, Claremix, manufactured by M Technique Co., Ltd.), for example, under high-speed rotation conditions of 10,000 rpm (preferably 5000 to 20000 rpm), for example, for 20 minutes (preferably 10 to 30 minutes). An aqueous dispersion of polyvinyl alcohol (PVA) is then added to this (for example, so that the amount of PVA is about 1/3 of the mass of vapor phase silica), and dispersion is performed under the same rotational conditions as above. Can be prepared. At this time, in order to impart stability to the ink receiving layer coating solution, it is preferable to adjust the pH to about 9.2 with ammonia water or the like, or to use a dispersant. The obtained coating solution for the ink receiving layer is in a uniform sol state, and this is coated on a support by the coating method shown below and dried to form a porous ink receiving layer having a three-dimensional network structure. Can be formed.

  As described above, the preparation of the aqueous dispersion composed of the vapor phase silica, boric acid and the cationic polymer according to the present invention is carried out by preparing the vapor phase silica aqueous dispersion in advance, and adding this aqueous dispersion to the boric acid and the present invention. You may make it add to the dispersion | distribution aqueous solution which disperse | distributed the cationic polymer concerned, and may make it add a dispersion | distribution aqueous solution to a gaseous-phase-method silica water dispersion conversely, or may mix simultaneously. Good. Moreover, you may add to dispersion | distribution aqueous solution as mentioned above using the gaseous phase method silica instead of a gaseous phase method silica aqueous dispersion.

  After mixing the above-mentioned gas phase method silica and the like, the aqueous dispersion having an average particle diameter of 50 to 300 nm can be obtained by finely granulating the mixture using a disperser. As the disperser, various conventionally known dispersers such as a high-speed rotating disperser, a medium stirring disperser (such as a ball mill and a sand mill), an ultrasonic disperser, a colloid mill disperser, and a high pressure disperser can be used. A medium stirring type disperser, a colloid mill disperser, or a high-pressure disperser is preferable in that the formed fine particles are efficiently dispersed.

  In each step, water, an organic solvent, or a mixed solvent thereof can be used as a solvent. Examples of the organic solvent include alcohols such as methanol, ethanol, n-propanol, i-propanol and methoxypropanol, ketones such as acetone and methyl ethyl ketone, tetrahydrofuran, acetonitrile, ethyl acetate and toluene.

  The ink receiving layer coating solution is applied by a known coating method using, for example, an extrusion die coater, an air doctor coater, a bread coater, a rod coater, a knife coater, a squeeze coater, a reverse roll coater, a bar coater, or the like. Can do.

  In the curing step, the second liquid (basic solution) can be applied after the application of the ink receiving layer coating liquid (first liquid), but the application is performed before the coating layer exhibits reduced-rate drying. Is preferably performed. That is, after the application of the first liquid, the second liquid is preferably introduced while the coating layer exhibits constant rate drying.

  In the curing step, “before the coating layer comes to show reduced-rate drying” usually refers to a process for several minutes immediately after the application of the coating liquid for the ink-receiving layer. It shows the phenomenon of “constant rate drying” in which the content of the solvent (dispersion medium) decreases in proportion to time. About the time which shows this "constant rate drying", it describes in chemical engineering handbook (pages 707-712, Maruzen Co., Ltd. issue, October 25, 1980), for example.

  As described above, after the ink-receiving layer coating solution is applied, the coating layer is dried until the coating layer exhibits reduced-rate drying. This drying is generally performed at 40 to 180 ° C. for 0.5 to 10 minutes (preferably 0.5 to 5 minutes). The drying time naturally varies depending on the coating amount, but usually the above range is appropriate.

  As a method of giving before the coating layer shows reduced-rate drying, (1) a method of further applying the second liquid on the coating layer, (2) a method of spraying by a method such as spraying, (3 ) A method of immersing the support on which the coating layer is formed in the second liquid.

  In the above method (1), the second liquid is applied by, for example, curtain flow coater, extrusion die coater, air doctor coater, bread coater, rod coater, knife coater, squeeze coater, reverse roll coater, bar A known coating method such as a coater can be used. However, it is preferable to use a method in which the coater does not directly contact an already formed coating layer, such as an extrusion die coater, a curtain flow coater, a bar coater or the like.

  After application of the second liquid, it is generally heated at 40 to 180 ° C. for 0.5 to 30 minutes to be dried and cured. Especially, it is preferable to heat at 40-150 degreeC for 1 to 20 minutes.

  The coating process and the curing process can be performed simultaneously. That is, the second liquid (basic solution) can be preferably applied at the same time as the first liquid (ink receiving layer coating liquid) is applied. In such a case, the first liquid and the second liquid are added to the second liquid (basic solution). An ink receiving layer can be formed by simultaneously applying (multilayer coating) on a support so that one liquid is in contact with the support, followed by drying and curing.

  The simultaneous coating (multilayer coating) can be performed by a coating method using, for example, an extrusion die coater or a curtain flow coater. After the simultaneous application, the formed application layer is dried. In this case, the drying is generally performed by heating the application layer at 15 to 150 ° C. for 0.5 to 10 minutes, preferably 40 to 100. It is carried out by heating at a temperature of 0.5 to 5 minutes.

  When the simultaneous coating (multilayer coating) is performed by, for example, an extrusion die coater, the two types of coating liquid discharged simultaneously are in the vicinity of the discharge port of the extrusion die coater, that is, before moving onto the support. In that state, it is coated on the support in multiple layers. Since the two-layer coating liquid layered before coating is likely to cause a cross-linking reaction at the interface between the two liquids when transferred to the support, the two liquids to be ejected are mixed in the vicinity of the discharge port of the extrusion die coater. As a result, thickening is likely to occur, which may hinder the application operation. Therefore, at the time of simultaneous application as described above, it is preferable to apply the simultaneous triple layer application with the barrier liquid (intermediate liquid) interposed between the two liquids together with the application of the first liquid and the second liquid.

  The barrier layer solution can be selected without particular limitation. For example, an aqueous solution containing a trace amount of water-soluble resin, water, or the like can be given. The water-soluble resin is used in consideration of applicability for the purpose of a thickener and the like. For example, cellulose resin (for example, hydroxypropylmethylcellulose, methylcellulose, hydroxyethylmethylcellulose) And polymers such as polyvinylpyrrolidone and gelatin. The barrier layer liquid may contain a mordant.

  After forming the ink receiving layer on the support, the ink receiving layer is subjected to, for example, supercalendering, gloss calendering, etc., and calendering through the roll nip under heat and pressure, so that surface smoothness, glossiness, It is possible to improve transparency and coating strength. However, the calendar process may cause a decrease in the porosity (that is, the ink absorbability may be decreased), so it is necessary to set the conditions under which the decrease in the porosity is small.

  As roll temperature in the case of performing a calendar process, 30-150 degreeC is preferable and 40-100 degreeC is more preferable. Moreover, as a linear pressure between rolls at the time of a calendar process, 50-400 kg / cm is preferable and 100-200 kg / cm is more preferable.

In the case of inkjet recording, the thickness of the ink receiving layer needs to have an absorption capacity sufficient to absorb all of the droplets, and therefore needs to be determined in relation to the porosity in the layer. For example, if the ink amount is 8 nL / mm ² and the porosity is 60%, a film having a layer thickness of about 15 μm or more is required. Considering this point, in the case of ink jet recording, the layer thickness of the ink receiving layer is preferably 10 to 50 μm.

The pore diameter of the ink receiving layer is preferably 0.005 to 0.030 μm, more preferably 0.01 to 0.025 μm in terms of median diameter.
The porosity and the median diameter of the pores can be measured using a mercury porosimeter (trade name: Bore Sizer 9320-PC2, manufactured by Shimadzu Corporation).

  The ink receiving layer is preferably excellent in transparency. As a guide, the haze value when the ink receiving layer is formed on a transparent film is preferably 30% or less, and 20% or less. It is more preferable. The haze value can be measured with a haze meter (HGM-2DP: manufactured by Suga Test Instruments Co., Ltd.).

  A polymer fine particle dispersion may be added to a constituent layer (for example, an ink receiving layer or a back layer) of the ink jet recording medium of the present invention. This polymer fine particle dispersion is used for the purpose of improving film properties such as dimensional stabilization, curling prevention, adhesion prevention, and film cracking prevention. The polymer fine particle dispersion is described in JP-A Nos. 62-245258, 62-1316648, and 62-110066. When a polymer fine particle dispersion having a low glass transition temperature (40 ° C. or lower) is added to the mordant-containing layer, cracking and curling of the layer can be prevented. Further, even when a polymer fine particle dispersion having a high glass transition temperature is added to the back layer, curling can be prevented.

  The ink jet recording medium of the present invention is disclosed in JP-A-10-81064, JP-A-10-119423, JP-A-10-157277, JP-A-10-217601, JP-A-11-348409, JP-A-2001-138621, 2000. No. 43401, No. 2000-21235, No. 2000-309157, No. 2001-96897, No. 2001-138627, JP-A-11-91242, No. 8-2087, No. 8-2090, No. 8- It can also be produced by the methods described in Japanese Patent Nos. 2091 and 8-2093.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist thereof. In this example, an ink jet recording sheet is prepared as an example of the ink jet recording medium of the present invention, and “part” is based on mass unless otherwise specified.

Example 1
-Production of support-
Wood pulp composed of 100 parts of LBKP is beaten to 300 ml Canadian freeness with a double disc refiner, 0.5 parts of epoxidized behenamide, 1.0 part of anionic polyacrylamide, 0.1 part of polyamide polyamine epichlorohydrin, 0.5 part of cationic polyacrylamide All parts were added at an absolutely dry mass ratio with respect to the pulp, and weighed with a long net paper machine to produce a base paper of 170 g / m ² .

In order to adjust the surface size of the obtained base paper, a solution obtained by adding 0.04% of a fluorescent whitening agent (Whitetex BB, manufactured by Sumitomo Chemical Co., Ltd.) to a 4% aqueous solution of polyvinyl alcohol was completely dried on the base paper. After impregnation so as to be 0.5 g / m ^{2 in} terms of conversion and drying, a calender treatment was further performed to obtain a base paper adjusted to a density of 1.05 g / cc.

After the corona discharge treatment was performed on the wire surface side (back side) of the obtained base paper, high-density polyethylene was coated to a thickness of 19 μm using a melt extruder to form a resin layer composed of a mat surface. (Hereinafter, the resin layer side is referred to as “back surface”). After the corona discharge treatment is further applied to the surface of the resin layer on the back side, aluminum oxide (antistatic agent; alumina sol 100, manufactured by Nissan Chemical Industries, Ltd.) and silicon dioxide (Snowtex O, Nissan Chemical Industries, Ltd.) )) Was dispersed in water at a mass ratio of 1: 2 so that the dry mass was 0.2 g / m ² .

  Further, after the corona discharge treatment is performed on the felt surface side (front side) where the resin layer is not provided, anatase-type titanium dioxide 10%, a trace amount of ultramarine blue, and a fluorescent brightening agent 0.01 using a melt extruder % (Polyethylene) and MFR (melt flow rate) 3.8 low density polyethylene is extruded to a thickness of 29 μm to form a high gloss thermoplastic layer on the surface of the base paper (hereinafter referred to as this The highly glossy surface is referred to as the “front surface”) and used as a support.

Example 1
-Preparation of coating solution for ink receiving layer-
(A) Vapor phase silica fine particles, (b) ion-exchanged water, and (c) Charol DC-902P in the following composition are mixed and dispersed using KD-P [manufactured by Shinmaru Enterprises Co., Ltd.] Then, (d) zirconium acetate, (e) boric acid aqueous solution, (f) polyvinyl alcohol, (g) surfactant, and (h) the above-mentioned Synthesis Example 1 were further added to this dispersion. A solution containing the polymer P-1 and (i) ion-exchanged water was added to prepare a coating solution for an ink receiving layer. At this time, the mass ratio of the silica fine particles to the water-soluble resin [PB ratio = (a) / (f)] is 4.5, and the pH of the coating liquid for the ink receiving layer after the preparation is 3.5 and is acidic. Indicated.

<Composition of coating liquid for ink receiving layer>
(a) Leolosil QS-30 (average primary particle diameter 7 nm) ... 10.0 parts [manufactured by Tokuyama Corporation; vapor phase method silica fine particles (inorganic fine particles)]
(b) Ion exchange water: 51.6 parts
(c) Charol DC-902P (51% aqueous solution) 1.0 part [manufactured by Nittobo Co., Ltd .; dispersant]
(d) Zirconium acetate (25% aqueous solution) ... 0.3 part
(e) 5% aqueous solution of boric acid (crosslinking agent) 8.0 parts
(f) 8% aqueous solution of polyvinyl alcohol (water-soluble resin) 27.8 parts [PVA-235 (saponification degree 88%, polymerization degree 3500), manufactured by Kuraray Co., Ltd.]
(g) 10% aqueous solution of Emulgen 109P (HLB value 13.6) ... 0.1 part [manufactured by Kao Corporation; surfactant]
(h) Polymer P-1 (25% aqueous solution) 2.5 parts [cationic polymer according to the present invention obtained in Synthesis Example 1 described above]
(i) Ion exchange water ... 23.1 parts

−Preparation of inkjet recording medium−
The front surface of the support obtained above was subjected to corona discharge treatment, and then the ink receiving layer coating solution was applied to the front surface at an application amount of 200 ml / m ² using an extrusion die coater. The coating layer was dried at 80 ° C. (wind speed of 3 to 8 m / sec) with a dryer until the solid content concentration of the coating layer became 20%. At this time, the coating layer showed constant rate drying. Immediately thereafter, this was immersed in a mordant solution having the following composition for 30 seconds to deposit 20 g / m ² on the surface of the coating layer, and further dried at 80 ° C. for 10 minutes. Thus, an ink jet recording sheet (1) of the present invention provided with an ink receiving layer having a dry layer thickness of 32 μm was produced.

<Composition of mordant solution>
(a) Boric acid (crosslinking agent) ... 0.65 part
(b) Zircozol AC-7 (28% aqueous solution) ... 6.5 parts [Daiichi Rare Element Chemical Industries, Ltd .; zirconium ammonium carbonate]
(c) Ammonium carbonate: 6.0 parts
(d) Ion exchange water ... 83.8 parts
(e) Megafac F-1405 (10% aqueous solution) 0.2 part [Dainippon Ink & Chemicals, Inc .; fluorinated surfactant]

(Examples 2-3)
In Example 1, the polymer P-1 used for the preparation of the coating liquid for the ink receiving layer was replaced with the polymer P-2 or the polymer P-3 obtained in the synthesis examples 2 to 3 described above (according to the present invention). Inkjet recording sheets (2) to (3) of the present invention were produced in the same manner as in Example 1 except that the cationic polymer was replaced.

(Examples 4 to 6)
In each of Examples 1 to 3, Examples 1 to 3 except that 0.6 parts of a polyaluminum chloride 40% aqueous solution (Al ₂ (OH) ₅ Cl) was further added to the composition of the ink receiving layer coating solution. In the same manner as above, inkjet recording sheets (4) to (6) of the present invention were produced.

(Comparative Examples 1-3)
In Example 1, the same amount of the following polymer P-10 [Comparative Example 1] or cation-modified polyvinyl alcohol (trade name: PVA C-118) was used for preparing the ink receiving layer coating solution. Kuraray Co., Ltd .; cation-modified PVA) Comparative ink jet recording sheets (7) to 7 in the same manner as in Example 1 except that [Comparative Example 2] was used instead of or not added [Comparative Example 3]. (9) was produced. The polymer P-10 was synthesized as follows.

<Synthesis of Polymer P-10>
In the synthesis example 1 described above, a polymer P-10 having the following structure (I / O value = 1) was prepared in the same manner as in synthesis example 1 except that 2.64 parts of glycerol methacrylate was replaced with 2.14 parts of hydroxyethyl methacrylate. A white solid having 1.87 and a cation equivalent of 3.83 meq / g was obtained.

(Evaluation)
The following evaluation was performed for each of the inkjet recording sheets (1) to (6) of the present invention obtained above and the comparative inkjet recording sheets (7) to (9). The evaluation results are shown in Table 1 below.

1. Ink absorbability Using an inkjet printer PM-950C (manufactured by Seiko Epson Corporation), Y (yellow), M (magenta), C (cyan), K (black) on the ink receiving layer of each inkjet recording sheet, Immediately after printing a solid image of B (blue), G (green), and R (red) (after about 10 seconds), the paper is pressed onto each image to transfer the ink onto the paper. Was visually observed and evaluated according to the following evaluation criteria. If the transfer of ink onto the paper is not observed, it indicates that the ink absorption rate is good.
[Evaluation criteria]
A: No transfer of ink onto the paper was observed.
B: Partial transfer of ink onto paper was observed.
C: Ink transfer onto paper was considerably recognized.

2. Image density Using an inkjet printer PM-950C (manufactured by Seiko Epson Corporation), a solid black image was printed on the ink receiving layer of each inkjet recording sheet, and the reflection density D in the image area after leaving for 3 hours was measured. It was measured with a reflection densitometer X-rite 938 (manufactured by X-rite) and evaluated according to the following evaluation criteria.
[Evaluation criteria]
A: D> 2.1
B: 2.1 ≧ D ≧ 1.8
C: 1.8> D

3. Using a water-resistant inkjet printer PM-950C (manufactured by Seiko Epson Corporation), Y (yellow), M (magenta), C (cyan), K (black), B on the ink receiving layer of each inkjet recording sheet (Blue), G (Green), and R (Red) solid images were printed, allowed to stand for 3 hours, then immersed in water for 1 hour, and the degree of ink spilling into water was observed visually to evaluate the following. Evaluation was made according to criteria.
[Evaluation criteria]
A: No outflow of ink (dye) was observed.
B: The outflow part of the ink (dye) was recognized and the color density fell.
C: Ink (dye) was almost completely discharged.

4). Bleeding over time Using an inkjet printer PM-950C (manufactured by Seiko Epson Corporation), a magenta ink and a black ink are adjacent to each other on each inkjet recording sheet (line width 0.28 nm). ) And the visual density (OD ^fresh ) was measured with X-rite 310TR (manufactured by X-rite). After the measurement, each inkjet recording sheet on which a linear pattern is printed is put in a clear file, stored in a constant temperature and humidity chamber at 35 ° C. and a relative humidity of 80% for 3 days, and then again the visual density (OD ^thermo). ) Was measured. And density | concentration change rate (DELTA) D (= OD ^thermo -OD ^fresh / OD ^fresh * 100;%) was computed from the obtained density | concentration measurement value, and it evaluated according to the following evaluation criteria as a parameter | index which evaluates a bleeding with time. The smaller the density change rate, the less (good) the bleeding with time.
[Evaluation criteria]
A: ΔD <20%
B: 20% ≦ ΔD <35%
C: 35% ≦ ΔD <50%
D: 50% ≦ ΔD

As shown in Table 1, in Examples 1 to 6 (inkjet recording sheets (1) to (6) of the present invention) using chelation of a cationic polymer having a diol structure, the ink absorbability is excellent and the concentration is high. In addition, the printed image was less likely to bleed over time and was excellent in water resistance. In particular, in Examples 4 to 6 [inkjet recording sheets (4) to (6)] in which polyaluminum chloride was further added, it was possible to more effectively prevent bleeding of images over time.
On the other hand, in Comparative Examples 1 and 2 each using a cationic polymer having no diol structure or a cation-modified PVA having a low cation equivalent and a high polarity, the effect of preventing bleeding in particular is insufficient. In Comparative Example 3 in which the cationic polymer was not added, both the prevention of bleeding over time and the water resistance were greatly inferior.

Claims (4)

In an inkjet recording medium having an ink receiving layer on a support,
The ink receiving layer has at least one selected from the group consisting of boron compounds, Cu compounds, Al compounds, Ti compounds, Zr compounds, and Fe compounds, and a 1,2- or 1,3-diol structure; An ink jet recording medium comprising: a cationic polymer having an inorganic / organic ratio (I / O value) of 2.5 or less.   The inkjet recording medium according to claim 1, wherein the cationic equivalent of the cationic polymer is 1 meq / g or more. The inkjet recording medium according to claim 1, wherein the cationic polymer is a polymer represented by the following general formula (1).

[In the formula, A represents a structural unit derived from a cationic vinyl monomer having a quaternary ammonium group, and B represents a structural unit derived from a vinyl monomer having an I / O value of 0.5 or less. . R represents a hydrogen atom or a methyl group, and Z represents a divalent linking group. l represents 20 to 80 mol%, m represents 10 to 70 mol%, n represents 5 to 10 mol%, and l + m + n = 100 is satisfied. p represents 1 or 2. ] The inkjet recording medium according to claim 3, wherein the structural unit represented by A is at least one of the following formulas (2) and (3).

[Wherein, R ⁰ represents a hydrogen atom or a methyl group, and R ¹ , R ² , R ³ , R ⁵ , R ⁶ , and R ⁷ are each independently an alkyl group or aralkyl group having 1 to 18 carbon atoms. Represents an aryl group, and R ⁴ represents an alkylene group, an aralkylene group, or an arylene group. Y represents a divalent linking group. X ⁻ represents a counter anion. ]