JP2005131866A - Medium for inkjet recording and its production method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a medium for inkjet recording which has an excellent ink absorbency and is free from bleeding over time. <P>SOLUTION: The medium for inkjet recording has an ink receiving layer on a support. The medium is characterized in that the ink receiving layer is a polymer having the lower limit critical solution temperature in (A) fine particles, (B) a mordant and (C) water, and includes a co-polymer containing a unit having a group to develop temperature sensitivity and a unit having a hydroxyl group. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to liquid inks such as water-based inks (using dyes or pigments as coloring materials) and oil-based inks, solid inks that are solid at room temperature, and are melt-liquefied and used for printing. More particularly, the present invention relates to an ink jet recording sheet that has excellent ink receiving performance and suppresses blurring of an image portion over time, and a method for manufacturing the same.

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

  In addition, with the recent increase in resolution of inkjet printers, various recording materials have been developed, such as so-called photographic-like high-quality recorded matter. From the viewpoint of providing commercial value as a recording material, it has excellent ink absorbability and good image storage stability after recording, that is, the image may be faded or deteriorated by long-term storage. Not required.

An ink jet recording sheet provided with an ink receiving layer having a high porosity and a three-dimensional structure formed from inorganic pigment fine particles and a water-soluble resin is disclosed as an ink absorption enhancement (for example, Patent Document 1). -3), it is said that a high-resolution image can be formed.
A polymer having a negative temperature coefficient of solubility in water, which is hydrophilic and dissolves in water at a temperature below the lower critical solution temperature (LCST), but becomes hydrophobic and precipitates above that temperature. Inkjet recording media using the above are disclosed (see Patent Documents 4 to 7).
If this polymer is coated on a support at a temperature lower than the lower critical eutectic temperature (LCST) and raised to the temperature or higher during drying, gelation occurs instantaneously, so that the drying time is shortened and the formation of the porous film is reduced. An ink jet recording medium that is easy and excellent in ink absorbability can be obtained.

However, an ink jet recording medium using such a polymer may cause blurring over time when stored for a long time in a high temperature and high humidity environment.
Japanese Patent Laid-Open No. 10-203006 Japanese Patent Laid-Open No. 10-217601 JP-A-11-20306 JP-A-8-244334 JP-A-9-254533 JP 2001-180105 A JP 2003-103904 A

  Accordingly, an object of the present invention is to provide an ink jet recording medium having excellent ink absorptivity and suppressing aging blur and a method for producing the same.

In view of such circumstances, the present inventor has conducted extensive research and found that the following ink jet recording medium is excellent in ink absorbability and excellent in aging, and thus completed the present invention.
That is, the present invention provides the following.

  <1> In an inkjet recording medium having an ink receiving layer on a support, the ink receiving layer is a polymer having a lower critical eutectic temperature in A) fine particles, B) mordant, and C) water, and is temperature sensitive. An inkjet recording medium comprising a copolymer having a unit having a group exhibiting properties and a unit having a hydroxyl group.

  <2> C) The inkjet recording medium according to <1>, wherein the copolymer has a lower critical eutectic temperature of 20 to 60 ° C.

<3> The inkjet recording medium according to <1> or <2>, wherein the copolymer (C) is a copolymer containing an N-substituted (meth) acrylamide unit and a unit having a hydroxyl group.
<4> The inkjet recording medium according to <1> or <2>, wherein the C) copolymer has a structural unit represented by the following general formula (1).

[Wherein, R represents a hydrogen atom or a methyl group, and R ¹ and R ² each independently represent a hydrogen atom or an alkyl group having 1 to 12 carbon atoms which may have a substituent, or R ¹ and R ² may be linked to each other to form a cyclic structure. Q represents a unit having a hydroxyl group. m and n represent mol% of the repeating unit, and 10 ≦ m ≦ 90 and 10 ≦ n ≦ 90. ]

  <5> C) The ink jet recording medium according to <1> or <2>, wherein the copolymer is a block or graft copolymer.

  <6> A) The ink receiving layer coating solution according to any one of <1> to <5>, wherein the fine particles are one or more selected from silica fine particles, colloidal silica, alumina fine particles, and pseudoboehmite. .

  <7> B) The ink jet recording medium according to any one of <1> to <6>, wherein the mordant is a cationic resin and / or a water-soluble polyvalent metal salt.

  <8> On the support, A) fine particles, B) mordant, and C) a polymer having a lower critical solution temperature in water, including a unit having a group exhibiting temperature sensitivity and a unit having a hydroxyl group. An ink jet recording medium comprising: a coating solution containing a polymer applied at a temperature lower than the lower critical eutectic temperature of the copolymer, and heat-dried at a temperature 5 ° C. or more higher than the lower critical eutectic temperature. Production method.

  The ink jet recording medium of the present invention is excellent in ink absorbability and has little aging blur.

The ink jet recording medium of the present invention is an ink jet recording medium having an ink receiving layer on a support, wherein the ink receiving layer has a lower critical eutectic temperature in A) fine particles, B) mordant, and C) water. It is a combination, and includes a copolymer including a unit having a group exhibiting temperature sensitivity and a unit having a hydroxyl group.
The ink jet recording medium of the present invention may further contain other components as necessary.
Hereinafter, the ink jet recording medium will be described in detail.

(Polymer having a lower critical eutectic temperature in water and comprising a unit having a group exhibiting temperature sensitivity and a unit having a hydroxyl group)
In the present invention, the ink receiving layer is a polymer having a lower critical solution temperature in water, and includes a copolymer having a unit having a temperature-sensitive group and a unit having a hydroxyl group (hereinafter referred to as “the present polymer”). Contain).
This polymer is a polymer having a negative solubility temperature coefficient in water, and is hydrophilic and soluble in water at a temperature lower than the lower critical solution temperature (LCST), but becomes hydrophobic and precipitates at a temperature higher than that temperature. However, this change is reversible. The polymer preferably has a lower critical co-melting temperature at 10 to 90 ° C. in water, more preferably 20 to 60 ° C., and more preferably 30 to 50 ° C. Those having a temperature are preferred.

The lower critical co-melting temperature is determined by the turbidity method (for example, J. Macromol. Sci., Chem. A2, Vol. 1141, page 1968) Light scattering method (for example, J. Chem. Phys. Vol. 81, page 6379) 1984), calorimetric analysis (eg, J. Phys. Chem. 94, 4352, 1990), nuclear magnetic resonance (eg, J. Polym. Sci., Polym. Phys, 29). 963, 1991), fluorescence analysis (for example, Macromolecules 23, 233, 1990), and infrared spectroscopy (for example, Polym. J. 31, 21, 21, 1999). Year). In the polymer of the present invention, any measurement method may be used, but the turbidity method is the most commonly used measurement method and is preferable. For example, the polymer to be tested is dissolved in distilled water so as to be 1% by weight, and 2 mL of this solution is placed in a 5 mL test tube. The temperature of the test tube is raised from 25 ° C. to 80 ° C. at a rate of 1 ° C. per minute in a water bath, and the temperature at which turbidity is first observed visually can be measured as the lower critical eutectic temperature.

  This polymer is a copolymer obtained by polymerizing a monomer that exhibits temperature sensitivity after polymerization and a monomer containing a monomer having a hydroxyl group. Examples include vinyl ether and N-substituted (meth) acrylamide.

As this polymer, a polymer having a unit represented by the following general formula (1) is preferable.

[Wherein, R represents a hydrogen atom or a methyl group, and R ¹ and R ² each independently represent a hydrogen atom or an alkyl group having 1 to 12 carbon atoms which may have a substituent, or R ¹ and R ² may be linked to each other to form a cyclic structure. Q represents a unit having a hydroxyl group. m and n represent mol% of the repeating unit, and 10 ≦ m ≦ 90 and 10 ≦ n ≦ 90. ]

In the general formula (1), specific examples of R ¹ and R ² include hydrogen, methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, sec-butyl group, t-butyl group, pentyl. Group, hexyl group, heptyl group, n-octyl group, 2-ethylhexyl group, t-octyl group, nonyl group, decyl group, dodecyl group, cyclopropyl group, hydroxyethyl group, 2-methoxyethyl group, 3-methoxypropyl Group, 3-ethoxypropyl group, or a pyrrolidine ring or piperidine ring formed by connecting these groups to each other. Of these, preferred are hydrogen, methyl group, ethyl group, n-propyl group, and isopropyl group.
m and n represent mol% of each repeating unit, and 10 ≦ m ≦ 90 and 10 ≦ n ≦ 90. Preferred ranges of m and n are 20 ≦ m ≦ 80 mol% and 20 ≦ n ≦ 80 mol%. If m is less than 10 mol%, LCST may increase and ink absorbency may decrease. If n is less than 10 mol%, film cracking may occur.

  Q represents a unit given from a monomer having a hydroxyl group. Specific examples of the monomer that gives Q include vinyl alcohol, 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, glycerol mono (meth) acrylate, 2 -Methacryloyloxyethyl-D-glucopyranoside, 2-methacryloyloxyethyl-D-mannopyranoside, 2-methacryloyloxyethyl-D-galactopyranoside, p-hydroxymethylstyrene, and the like.

In addition to the above, the present polymer is preferably a block or graft copolymer. Thereby, since the binding with the inorganic fine particles is improved, an ink jet recording medium having good ink absorbability can be provided. In particular, a block or graft copolymer of vinyl alcohol and N-substituted acrylamide is preferable.
When the present polymer is a block or graft copolymer, the N-substituted (meth) acrylamide unit is preferably 1 to 90% by weight, particularly preferably 5 to 80% by weight.

This polymer is a copolymer obtained by polymerizing at least a monomer exhibiting thermosensitive behavior after polymerization and a monomer having a hydroxyl group, and further contains a vinyl monomer copolymerizable with these units. May be. Examples of such monomers include alkyl (meth) acrylate [eg, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, (meth) acrylic. N-butyl acid, isobutyl (meth) acrylate, t-butyl (meth) acrylate, hexyl (meth) acrylate, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate , (Meth) acrylic acid C1-18 alkyl esters such as stearyl (meth) acrylate], (meth) acrylic acid cycloalkyl esters [(meth) acrylic acid cyclohexyl etc.], (meth) acrylic acid aryl esters [(meta ) Phenyl acrylate, etc.], aralkyl esters [(meth) acrylic acid Benzyl etc.], substituted (meth) acrylic acid alkyl esters, (meth) acrylamides [eg (meth) acrylamide, dimethyl (meth) acrylamide etc.], aromatic vinyls [styrene, vinyltoluene, α-methylstyrene 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 [(meth) acrylonitrile, etc. ], Olefins [ethylene, propylene, etc.] and the like.
These monomers may be used alone or as a copolymerizable two or more monomers.

This polymer can be easily synthesized by radical polymerization. A method for obtaining a thermosensitive polymer by radical polymerization is described in detail, for example, in JP-A No. 2000-212144.
The content of the ink receiving layer of this polymer is preferably in the 1 to 10 g / m ^2, particularly preferably a 2 to 6 g / m ^2.
Specific examples of this polymer are shown below.

In the present invention, in addition to the present polymer, other water-soluble resins may be used as long as the effects of the present invention are not impaired. As such a water-soluble resin, for example, a polyvinyl alcohol resin (polyvinyl alcohol (PVA), acetoacetyl-modified polyvinyl alcohol, cation-modified polyvinyl alcohol, anion-modified polyvinyl alcohol, which is a resin having a hydroxy group as a hydrophilic structural unit, Silanol-modified polyvinyl alcohol, polyvinyl acetal, etc.], cellulosic 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, starch, resins having an ether bond [polyethylene oxide (PEO) , Polypropylene 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 the 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, and Japanese Patent No. 3053231. JP-A-63-176173, JP-A-2604367, JP-A-7-276787, JP-A-9-207425, JP-A-11-58941, JP-A-2000-135858, JP-A-2001-205924, JP 2001-287444, JP 62-278080, JP 9-39373, JP 2750433, JP 2000-18801, JP 2001-213045, JP 2001-328345, JP 8 -324105, JP-A-11-348417, etc. It is below.
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.

(Fine particles)
The ink receiving layer of the ink jet recording medium of the present invention further contains 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 absorbability. 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.

  Examples of preferable 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.
Further, 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, and pseudoboehmite 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 above wet method, a method is mainly used in which activated silica is produced by acid decomposition of a silicate, and this is appropriately polymerized and agglomerated and precipitated to obtain hydrous silica. 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.

The gas phase method 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 fine particle surface is high at 5 to 8 / nm ² , and the silica fine particles tend to aggregate (aggregate) easily. 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.

  The above-mentioned vapor phase silica has a particularly large specific surface area, so the ink absorption and retention efficiency is high, and the refractive index is low. Therefore, if the dispersion is made to an appropriate particle size, transparency can be imparted to the receiving layer. It is characterized by high color density and good color development. The transparency of the receiving layer is not only for applications that require transparency such as OHP, but also in terms of obtaining 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 diameter 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. Since the vapor phase silica is easily adhered to each other by hydrogen bonding with a silanol group, a structure having a large porosity can be formed when the average primary particle diameter is 30 nm or less, and ink absorption characteristics are effectively improved. Can be improved.

  Silica fine particles may be used in combination with the other fine particles described above. When the other fine particles and the vapor phase silica are used in combination, the content of the vapor phase 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 used in the present invention, 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 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 size of the vapor phase alumina is preferably 30 nm or less, and more preferably 20 nm or less.

  When the above-mentioned fine particles are used in an inkjet 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-2001-2001. 138621, 2000-43401, 2000-21235, 2000-309157, 2001-96897, 2001-138627, JP-A-11-91242, 8-2087, 8-2090 No. 8-2091, No. 8-2093, No. 8-174992, No. 11-192777, JP-A No. 2001-301314, etc. can be preferably used.

  The polymer and the fine particles, 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.

This polymer has a hydroxyl group in its structural unit. Since this hydroxyl group and the surface silanol group of the silica fine particle form a hydrogen bond, a three-dimensional network structure in which the secondary particle of the silica fine particle is a network chain unit is formed. It becomes easy to form. By forming this three-dimensional network structure, it is considered that a porous ink receiving layer having 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.

  The polymer may be used in combination with the other water-soluble resin. When the other water-soluble resin and the present polymer are used in combination, the content of the present polymer is preferably 20% by mass or more, and more preferably 50% by mass or more in the total 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) such as the present polymer 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.

  The ink receiving layer coating liquid of the present invention prevents the decrease in film strength and cracking during drying caused by the PB ratio being too large as the mass content ratio [PB ratio (x / y)] In addition, when the PB ratio is too small, the gap is easily blocked by the resin, and from the viewpoint of preventing the ink absorbency from being lowered due to the decrease in the porosity, 1.5 to 10 is preferable.

  Since stress may be applied to the recording sheet when passing through the conveyance system of the inkjet 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 mass ratio (x / y) is more preferably 5 or less, while it is more preferably 2 or more from the viewpoint of ensuring high-speed ink absorbency in an inkjet printer.

For example, a gas phase method silica fine particle having an average primary particle size of 20 nm or less and the present polymer are coated on a support with a coating solution in which the polymer is completely dispersed in an aqueous solution at a mass ratio (x / y) of 2 to 5, When the coating layer is dried, a three-dimensional network structure is formed in which the secondary particles of silica fine particles are network chains, the average pore diameter is 30 nm or less, the porosity is 50 to 80%, and the pore specific volume is 0.00. A translucent porous film having a specific surface area of 5 ml / g or more and a specific surface area of 100 m ² / g or more can be easily formed.

(mordant)
In the present invention, in order to further improve the water resistance and aging resistance of the formed image, a mordant is contained in the ink receiving layer.
As such a mordant, a cationic polymer (cationic mordant) or an inorganic mordant is preferable as an organic mordant, and the liquid ink having an anionic dye as a coloring material can be obtained by making the mordant present in the ink receiving layer. It can interact with each other to stabilize the coloring material and improve water resistance and aging resistance. The organic mordant and the inorganic mordant may be used alone or in combination with the organic mordant and the inorganic mordant.

As the cationic mordant, a polymer mordant having a primary to tertiary amino group or a quaternary ammonium base as a cationic group is generally used. 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), the mordant monomer and other monomers (hereinafter, What is obtained as a copolymer or condensation polymer with “non-mordant monomer”). Moreover, these polymer mordants can be used in any form of a water-soluble polymer or water-dispersible latex particles.

  Examples of the monomer (mordant 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- Dimethylaminoethyl (meth) acrylamide, N, N-diethylaminoethyl (meth) acrylamide, N, N-dimethylaminopropyl (meth) acrylamide, N, N-diethylaminopropyl (meth) acrylamide, and salts thereof (for example, hydrochloride) Nitrate, acetate, lactate, methanesulfonate, p-toluenesulfonate, etc.);

  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) ethylammonium chloride, triethyl-2- (acryloylamino) Tylammonium 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.
In addition, as mordant monomers, N-vinylimidazole, N-vinyl-2-methylimidazole, 2-vinylpyridine, 4-vinylpyridine, 4-vinyl-N-methyl-pyridinium chloride, 4-vinyl-N-ethyl-pyridinium Examples thereof include bromide, dimethyl diallylammonium chloride, monomethyl diallylammonium chloride, and the like.
These mordant monomers can be used singly or in combination of two or more copolymerizable monomers.

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 alkyl (meth) acrylate [for example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, (meth) acrylate n -Butyl, isobutyl (meth) acrylate, t-butyl (meth) acrylate, hexyl (meth) acrylate, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, (meth) acrylic acid (Meth) acrylic acid C1-18 alkyl ester such as lauryl, stearyl (meth) acrylate], (meth) acrylic acid cycloalkyl ester [(meth) acrylic acid cyclohexyl etc.], (meth) acrylic acid aryl Esters [phenyl (meth) acrylate, etc.], aralkyl esters [(meth) Benzyl crylate, etc.], substituted (meth) acrylic acid alkyl esters [eg 2-hydroxyethyl (meth) acrylate, methoxymethyl (meth) acrylate, allyl (meth) acrylate, etc.], (meth) acrylamides [For example, (meth) acrylamide, dimethyl (meth) acrylamide, N-ethyl (meth) acrylamide, N-isopropyl (meth) acrylamide, etc.], aromatic vinyl [styrene, vinyl toluene, α-methylstyrene, etc.], vinyl Esters [vinyl acetate, vinyl propionate, vinyl versatate, etc.], allyl esters [eg, allyl acetate], halogen-containing monomers [vinylidene chloride, vinyl chloride, etc.], vinyl cyanide [(meth) acrylonitrile, etc.], Olefin [ethylene, propylene Etc.].
These non-mordant monomers can also be used singly or in combination of two or more.

  Further, as the polymer mordant, polyethyleneimine (and derivatives thereof), polyvinylamine (and derivatives thereof), polyallylamine (and derivatives thereof), polyamidine, cationic polysaccharides (cationized starch, chitosan), dicyan cationic resin ( Examples thereof include dicyandiamide-formalin polycondensate), polyamine cationic resin (dicyandiamide-diethylenetriamine polycondensate), epichlorohydrin-dimethylamine addition polymer, dimethyldiallylammonium chloride-sulfur dioxide copolymer, and the like.

  As the organic mordant in the present invention, a polymer having a quaternary ammonium base is preferable, and a (meth) acrylate polymer, a vinylbenzylammonium polymer having a quaternary ammonium base having a weight average molecular weight of 1,000 to 100,000, or A diallylammonium-based polymer is particularly preferable.

An inorganic mordant can also be used as the mordant of the present invention, and examples of the inorganic mordant include polyvalent water-soluble metal salts and hydrophobic metal salt compounds.
Specific examples of the inorganic mordant include, for example, magnesium, aluminum, calcium, scandium, titanium, vanadium, manganese, iron, nickel, copper, zinc, gallium, germanium, strontium, yttrium, zirconium, molybdenum, indium, barium, lanthanum, Examples thereof include salts or complexes of metals selected from cerium, praseodymium, neodymium, samarium, europium, gadolinium, dysproprosium, erbium, ytterbium, hafnium, tungsten, and bismuth.

  Specifically, for example, 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, chloride chloride Dicopper, ammonium copper (II) chloride dihydrate, copper sulfate, cobalt chloride, cobalt thiocyanate, cobalt sulfate, nickel sulfate hexahydrate, nickel chloride hexahydrate, nickel acetate tetrahydrate, nickel sulfate Ammonium hexahydrate, nickel amidosulfate tetrahydrate, aluminum sulfate, aluminum alum, basic polyaluminum hydroxide, aluminum sulfite, aluminum thiosulfate, polyaluminum chloride, aluminum nitrate nonahydrate, aluminum chloride hexahydrate Products, ferrous bromide, ferrous chloride, ferric chloride, Ferrous acid, ferric sulfate, zinc phenolsulfonate, zinc bromide, zinc chloride, zinc nitrate hexahydrate, zinc sulfate, titanium tetrachloride, tetraisopropyl titanate, titanium acetylacetonate, titanium lactate, zirconium acetyl Acetonate, zirconyl acetate, zirconyl sulfate, ammonium zirconium carbonate, zirconyl stearate, zirconyl octylate, zirconyl nitrate, zirconium oxychloride, zirconium zirconium chloride, chromium acetate, chromium sulfate, magnesium sulfate, magnesium chloride hexahydrate, citric acid Magnesium nonahydrate, sodium phosphotungstate, sodium tungsten citrate, 12 tungstophosphoric acid n hydrate, 12 tungstosilicic 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, lanthanum benzoate, cerium chloride, cerium sulfate, cerium octylate, praseodymium nitrate, neodymium nitrate, nitric acid Examples include samarium, europium nitrate, gadolinium nitrate, dysprosium nitrate, erbium nitrate, ytterbium nitrate, hafnium chloride, and bismuth nitrate.

The inorganic mordant of the present invention is preferably a water-soluble polyvalent metal salt, more preferably an aluminum-containing inclusion, a titanium-containing compound, or a zirconium-containing inclusion, and further, basic polyaluminum hydroxide, polychlorinated Particularly preferred are aluminum, aluminum acetate, aluminum lactate, titanium lactate, zirconyl acetate, ammonium zirconium carbonate and zirconium oxychloride.
In the present invention, the mordant amount contained in the ink receiving layer is preferably from ^{0.01g / m 2 ~10g / m 2} , 0.1g / m 2 ~5g / m 2 is more preferable.

(Crosslinking agent)
In the present invention, the porous layer contains a crosslinking agent capable of crosslinking the present polymer and / or the water-soluble resin used in combination, and is cured by a crosslinking reaction between the crosslinking agent and the polymer and / or the water-soluble resin used in combination. The aspect which is.

Boron compounds are preferred for crosslinking the above water-soluble resins, particularly polyvinyl alcohol resins. 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), can be mentioned five borate _{(e.g., KB 5 O 8 · 4H 2} O, Ca 2 B 6 O 11 · 7H 2 O, CsB 5 O 5) or the like. Among them, Of these, borax, boric acid, and borate are preferable, and boric acid is particularly preferable in that a crosslinking reaction can be promptly caused.

The following compounds other than the boron compound can also be used as a crosslinking agent for the water-soluble resin.
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 2,983,611; 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-containing compounds such as titanium lactate, aluminum sulfate, chromium alum, potash alum, zirconyl acetate, chromium acetate, polyamine compounds such as tetraethylenepentamine, hydrazide compounds such as adipic acid dihydrazide, A low molecule or polymer containing two or more oxazoline groups.
The above crosslinking agents may be used singly or in combination of two or more.

In the crosslinking and curing, a crosslinking agent is added to a coating solution containing fine particles, a water-soluble resin, etc. (hereinafter sometimes referred to as “coating solution A”) and / or the following basic solution, and (1) the coating solution And (2) at any time during the drying of the coating layer formed by coating the coating solution and before the coating layer exhibits reduced-rate drying. The above basic solution (hereinafter sometimes referred to as “coating liquid B”) is preferably applied to the coating layer. The application of the cross-linking agent is preferably performed as described below when a boron compound is taken as an example. That is, when the ink receiving layer is a layer obtained by crosslinking and curing a coating layer coated with a coating solution (coating solution A) containing a water-soluble resin containing fine particles and polyvinyl alcohol, crosslinking curing is performed by (1) the coating described above. (2) When the coating layer formed by coating the coating solution is being dried and before the coating layer exhibits reduced-rate drying, a basic pH of 7 or higher This is performed by applying a solution (coating liquid B) to the coating layer. The boron compound as a cross-linking agent may be contained in either the coating solution A or the coating solution B, and may be contained in both the coating solution A and the coating solution B.
1-50 mass% is preferable with respect to water-soluble resin, and, as for the usage-amount of a crosslinking agent, 5-40 mass% is more preferable.

(Other ingredients)
If necessary, the coating liquid of the present invention may further contain various known additives such as ultraviolet absorbers, antioxidants, fluorescent brighteners, monomers, polymerization initiators, polymerization inhibitors, anti-bleeding agents, and antiseptics. , A viscosity stabilizer, an antifoaming agent, a surfactant, an antistatic agent, a matting agent, an anti-curling agent, a water-proofing agent, and the like.

In the present invention, it is preferable that the ink receiving layer coating liquid contains a storage stability improving agent such as an ultraviolet absorbent, an antioxidant, and a bleeding inhibitor.
As these ultraviolet absorbers, antioxidants, and bleeding inhibitors, alkylated phenol compounds, alkylthiomethylphenol compounds, hydroquinone compounds, alkylated hydroquinone compounds, tocopherol compounds, thiodiphenyl ether compounds, compounds having two or more thioether bonds, Bisphenol compounds, O-, N- and S-benzyl compounds, hydroxybenzyl compounds, triazine compounds, phosphonate compounds, acylaminophenol compounds, ester compounds, amide compounds, ascorbic acid, amine antioxidants, 2- (2-hydroxy Phenyl) benzotriazole compound, 2-hydroxybenzophenone compound, acrylate, water-soluble or hydrophobic metal salt, organometallic compound, metal complex, 2- (2-hydroxyphenyl) 1,3 5, -triazine compound, metal deactivator, phosphite compound, phosphonite compound, hydroxyamine compound, nitrone compound, peroxide scavenger, polyamide stabilizer, polyether compound, basic auxiliary stabilizer, nucleating agent, benzofuranone compound , Indolinone compounds, phosphine compounds, polyamine compounds, thiourea compounds, urea compounds, hydrazide compounds, amidine compounds, sugar compounds, hydroxybenzoic acid compounds, dihydroxybenzoic acid compounds, trihydroxybenzoic acid compounds, and the like.

  Among these, alkylated phenol compounds, compounds having two or more thioether bonds, bisphenol compounds, ascorbic acid, amine-based antioxidants, water-soluble or hydrophobic metal salts, organometallic compounds, metal complexes, hydroxyamine compounds Polyamine compounds, thiourea compounds, hydrazide compounds, hydroxybenzoic acid compounds, dihydroxybenzoic acid compounds, trihydroxybenzoic acid compounds and the like are preferable.

  Specific examples of the compound include Japanese Patent Application Nos. 2002-13005, 10-182621, 2001-260519, 4-34953, 4-34513, and 11-170686. No. 4-34512, EP 1138509, JP-A-60-67190, JP-A-7-276808, JP-A-2001-94829, JP-A-47-10537, JP-A-58-111942, and JP-A-58-212844. 59-19945, 59-46646, 59-109055, 63-53544, JP 36-10466, 42-26187, 48-30492, 48-31255, 48-41572, 48-54965, 50-10726, U.S. Pat.Nos. 2,719,086, 3, 707,375, 3,754,919, 4,220,711,

  Japanese Patent Publication Nos. 45-4699, 54-5324, European Published Patent Nos. 223739, 309401, 309402, 3105301, 310552, 457416, German Published Patent No. 3435443, Kaisho 54-48535, 60-107384, 60-107383, 60-125470, 60-125471, 60-125472, 60-287485, 60-287486, 60-287487, 60-287488, 61-160287, 61-18854, 61-2111079, 62-146678, 62-146680, 62-146679, 62- No. 282885, No. 62-262047, No. 63-051174, Nos. 63-89877, 63-88380 same issue, same 66-88381 JP, same 63-113536 issue,

  63-163351, 63-203372, 63-224989, 63-251282, 63-267594, 63-182484, JP-A-1-239282, JP-A-2-262654, 2-71262, 3-121449, 4-291865, 4-291684, 5-611166, 5-119449, 5-188687, 5-188686, 5 No. 110490, No. 5-110437, No. 5-170361, No. 48-43295, No. 48-33212, US Pat. Nos. 4,814,262, No. 4,980,275, and the like. .

The other components may be used alone or in combination of two or more. These other components may be added after being water-solubilized, dispersed, polymer-dispersed, emulsified or oil-dropped, or may be encapsulated in microcapsules. In the coating solution of the present invention, the amount of the other components added is preferably 0.01 to 10 g / m ² .

  Further, for the purpose of improving the dispersibility of the inorganic fine particles, the inorganic surface may be treated with a silane coupling agent. Examples of the silane coupling agent include an organic functional group (for example, vinyl group, amino group (primary to tertiary amino group, quaternary ammonium base), epoxy group, mercapto, in addition to the site for coupling treatment. A group having a group, a chloro group, an alkyl group, a phenyl group, an ester group or the like).

In the present invention, the coating solution for the ink receiving layer preferably contains a surfactant. As the surfactant, any of cationic, anionic, nonionic, amphoteric, fluorine and silicon surfactants can be used.
Examples of the nonionic surfactant include polyoxyalkylene alkyl ethers and polyoxyalkylene alkyl phenyl ethers (for example, diethylene glycol monoethyl ether, diethylene glycol diethyl ether, polyoxyethylene lauryl ether, polyoxyethylene stearyl ether, polyoxyethylene Ethylene nonylphenyl ether), oxyethylene / oxypropylene block copolymer, sorbitan fatty acid esters (for example, sorbitan monolaurate, sorbitan monooleate, sorbitan trioleate, etc.), polyoxyethylene sorbitan fatty acid esters (for example, polyoxyethylene) Sorbitan monolaurate, polyoxyethylene sorbitan monooleate, polyoxyethylene sorbitan Lyolate, etc.), polyoxyethylene sorbitol fatty acid esters (eg, polyoxyethylene sorbitol tetraoleate), glycerin fatty acid esters (eg, glycerol monooleate), polyoxyethylene glycerin fatty acid esters (polyoxymonostearate) Ethylene glycerol, monooleic acid polyoxyethylene glycerin, etc.), polyoxyethylene fatty acid esters (polyethylene glycol monolaurate, polyethylene glycol monooleate, etc.), polyoxyethylene alkylamine, acetylene glycols (eg, 2, 4, 7) , 9-tetramethyl-5-decyne-4,7-diol, and ethylene oxide adducts, propylene oxide adducts, and the like of the diols), and polyoxy Ruki alkylene alkyl ethers are preferable. These nonionic surfactants may be used alone or in combination of two or more.

  Examples of the amphoteric surfactant include amino acid type, carboxyammonium betaine type, sulfoammonium betaine type, ammonium sulfate betaine type, imidazolium betaine type and the like. For example, US Pat. No. 3,843,368, JP, JP-A-59-49535, JP-A-63-236546, JP-A-5-303205, JP-A-8-262742, JP-A-10-282619, JP-A-2514194, JP-A-2759597, JP-A-2000-351269, etc. Can be used preferably. Of the amphoteric surfactants, the amino acid type, carboxyammonium betaine type, and sulfoneammonium betaine type are preferable. The amphoteric surfactants may be used alone or in combination of two or more.

Examples of the anionic surfactant include fatty acid salts (for example, sodium stearate, potassium oleate), alkyl sulfate esters (for example, sodium lauryl sulfate, triethanolamine lauryl sulfate), and sulfonates (for example, sodium dodecylbenzenesulfonate). Alkyl sulfosuccinate (for example, sodium dioctyl sulfosuccinate), alkyl diphenyl ether disulfonate, alkyl phosphate, and the like.
Examples of the cationic surfactant include alkylamine salts, quaternary ammonium salts, pyridinium salts, imidazolium salts, and the like.

Examples of the fluorosurfactant include compounds derived from an intermediate having a perfluoroalkyl group using a method such as electrolytic fluorination, telomerization, or oligomerization.
Examples thereof include perfluoroalkyl sulfonates, perfluoroalkyl carboxylates, perfluoroalkyl ethylene oxide adducts, perfluoroalkyl trialkyl ammonium salts, perfluoroalkyl group-containing oligomers, and perfluoroalkyl phosphate esters.

  As the silicon-based surfactant, silicon oil modified with an organic group is preferable, and a structure in which a side chain of a siloxane structure is modified with an organic group, a structure in which both ends are modified, and a structure in which one end is modified can be taken. Examples of the organic group modification include amino modification, polyether modification, epoxy modification, carboxyl modification, carbinol modification, alkyl modification, aralkyl modification, phenol modification, and fluorine modification.

  In the present invention, the content of the surfactant is preferably 0.001 to 2.0%, more preferably 0.01 to 1.0% with respect to the coating solution for the ink receiving layer. Further, when coating is performed using two or more liquids as the ink receiving layer coating liquid, it is preferable to add a surfactant to each coating liquid.

In the present invention, the ink receiving layer coating solution preferably contains a high-boiling organic solvent for preventing curling. The high-boiling organic solvent is an organic compound having a boiling point of 150 ° C. or higher at normal pressure, and is a water-soluble or hydrophobic compound. These may be liquid or solid at room temperature, and may be low molecules or polymers.
Specifically, aromatic carboxylic acid esters (for example, dibutyl phthalate, diphenyl phthalate, phenyl benzoate, etc.), aliphatic carboxylic acid esters (for example, dioctyl adipate, dibutyl sebacate, methyl stearate, dibutyl maleate) , Dibutyl fumarate, triethyl acetyl citrate, etc.), phosphate esters (eg, trioctyl phosphate, tricresyl phosphate, etc.), epoxies (eg, epoxidized soybean oil, epoxidized fatty acid methyl, etc.), alcohols (eg, stearyl) Alcohol, ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, glycerol, diethylene glycol monobutyl ether (DEGMBE), triethylene glycol monobutyl ether, glycerol Methyl ether, 1,2,3-butanetriol, 1,2,4-butanetriol, 1,2,4-pentanetriol, 1,2,6-hexanetriol, thiodiglycol, triethanolamine, polyethylene glycol, etc. ), Vegetable oils (eg, soybean oil, sunflower oil, etc.) and higher aliphatic carboxylic acids (eg, linoleic acid, oleic acid, etc.).
The content of the high-boiling organic solvent in the ink-receiving layer coating solution is preferably 0.05 to 1% by mass, particularly preferably 0.1 to 0.6% by mass.

<Support>
As the support used in the ink jet recording medium of the present invention, either a transparent support made of a transparent material such as plastic or an opaque support made of an opaque material such as paper can be used. In order to make use 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 CD-ROM or DVD-ROM, a write-once optical disk such as CD-R or DVD-R, or a rewritable optical disk may be used as a support, and an ink receiving layer may be provided on the label surface side. it can.

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.

  The surface of the support may be subjected to corona discharge treatment, glow discharge treatment, flame treatment, ultraviolet irradiation treatment or the like in order to improve wettability and adhesion.

Next, the base paper used for the resin-coated paper will be described in detail.
The base paper is made from wood pulp as a main raw material and, if necessary, paper using synthetic pulp such as polypropylene or synthetic fibers such as nylon or polyester in addition to wood pulp. As the wood pulp, any of LBKP, LBSP, NBKP, NBSP, LDP, NDP, LUKP, and NUKP can be used, but more LBKP, NBSP, LBSP, NDP, and LDP with a larger amount of short fibers are used. 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 that forms the ink receiving layer is added with rutile or anatase type titanium oxide, fluorescent whitening agent, ultramarine, and polyethylene, as is widely done in photographic paper. Those having improved whiteness and hue are preferred. Here, as a titanium oxide content, 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 melt-extruded onto the surface of the base paper and coated, the matte surface or silky surface that can be obtained with ordinary photographic printing paper by so-called molding Can also be used.

A back coat layer can 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.
Examples of white pigments contained in the backcoat layer include light calcium carbonate, heavy calcium carbonate, kaolin, talc, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, zinc sulfide, zinc carbonate, satin white, and aluminum silicate. , Diatomaceous earth, calcium silicate, magnesium silicate, synthetic amorphous silica, colloidal silica, colloidal alumina, pseudoboehmite, aluminum hydroxide, alumina, lithopone, zeolite, hydrous halloysite, magnesium carbonate, magnesium hydroxide, white inorganic pigment, styrene And organic pigments such as polyethylene plastic pigments, acrylic plastic pigments, polyethylene, microcapsules, urea resins, and melamine resins.

Examples of the aqueous binder used in the backcoat layer include styrene / maleate copolymer, styrene / acrylate copolymer, polyvinyl alcohol, silanol-modified polyvinyl alcohol, starch, cationized starch, casein, gelatin, carboxy Examples thereof include water-soluble polymers such as methyl cellulose, hydroxyethyl cellulose, and polyvinyl pyrrolidone, and water-dispersible polymers such as styrene butadiene latex and acrylic emulsion.
Examples of other components contained in the backcoat layer include an antifoaming agent, an antifoaming agent, a dye, a fluorescent brightening agent, a preservative, and a water-proofing agent.

(Preparation of inkjet recording medium)
The ink receiving layer of the ink jet recording medium of the present invention is preferably formed, for example, by applying a coating solution containing the present polymer, fine particles, mordant and the like on the surface of the support and heating and drying.

In the present invention, the ink receiving layer coating solution can be prepared, for example, as follows. That is,
Vapor phase silica fine particles and a dispersant are added to water (for example, silica fine particles in water are 10 to 20% by mass), and a high-speed rotating wet colloid mill (for example, “Clairemix” manufactured by M Technique Co., Ltd.) For example, at a high speed of 10,000 rpm (preferably 5000 to 20000 rpm), for example, for 20 minutes (preferably 10 to 30 minutes) and then dispersed, and then a crosslinking agent (boron compound) and the polymer aqueous solution (for example, And the dispersion is carried out under the same rotation conditions as described above. The obtained coating liquid is in a uniform sol state, and a porous ink-receiving layer having a three-dimensional network structure can be formed by coating this on a support by the following coating method and drying it.

In addition, the preparation of the aqueous dispersion composed of the above-mentioned vapor phase method silica and a dispersant may be carried out by preparing a vapor phase method silica aqueous dispersion in advance and adding the aqueous dispersion to the aqueous dispersant solution. The aqueous solution may be added to the vapor phase silica aqueous dispersion, or may be mixed simultaneously. Further, instead of vapor phase silica aqueous dispersion, powder vapor phase silica may be used and added to the aqueous dispersant as described above.
After mixing said vapor phase silica and a dispersing agent, the mixed liquid is refined using a disperser, whereby an aqueous dispersion having an average particle diameter of 50 to 300 nm can be obtained. As a disperser used for obtaining the aqueous dispersion, various types of conventionally known dispersers such as a high-speed rotating disperser, a medium stirring disperser (ball mill, sand mill, etc.), an ultrasonic disperser, a colloid mill disperser, and a high pressure disperser Although a disperser can be used, a stirrer-type disperser, a colloid mill disperser, or a high-pressure disperser is preferable from the viewpoint that the formed fine particles are efficiently dispersed.

  Moreover, water, an organic solvent, or these mixed solvents can be used as a solvent in each process. Examples of the organic solvent that can be used for this coating 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. It is done.

In addition, a chaotic polymer can be used as the dispersant. Examples of the chaotic polymer include the aforementioned mordants. It is also preferable to use a silane coupling agent as the dispersant.
The amount of the dispersant added to the fine particles is preferably 0.1% to 30%, more preferably 1% to 10%.

The ink receiving layer coating solution can be applied by a known coating method such as an extrusion die coater, an air doctor coater, a bread coater, a rod coater, a knife coater, a squeeze coater, a reverse roll coater, or a bar coater. .
The coating solution is preferably applied at a temperature lower than the lower critical eutectic temperature of the polymer, and is heat-dried at a temperature of 5 ° C. or higher, particularly 10 ° C. or higher from the lower critical eutectic temperature.

The ink receiving layer of the ink jet recording medium of the present invention is formed, for example, by applying a coating liquid A containing at least fine particles and a water-soluble resin on the surface of a support, and (1) simultaneously with the coating and (2) the coating. A method in which the coating layer to which the coating solution B is applied is crosslinked and cured after the coating solution B having a pH of 7 or more is applied to the coating layer in the middle of drying and before the coating layer exhibits a reduced rate of drying. It may be. Here, the coating solution A is a coating solution containing the present polymer, fine particles, mordant and the like.
Providing an ink receiving layer that has been crosslinked and cured in this manner is preferable from the viewpoints of ink absorptivity and prevention of film cracking.

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

  As described above, after the coating solution A is applied, the coating layer is dried until the coating layer exhibits a reduced rate of drying. This drying is generally performed at 40 to 180 ° C. for 0.5 to 10 minutes (preferably, 0 .5-5 minutes). The drying time naturally varies depending on the coating amount, but the above range is usually appropriate.

  As a method of giving before the said 1st application layer comes to show a decreasing rate drying rate, (1) The method of further apply | coating the coating liquid B on an application layer, (2) Spraying by methods, such as spraying And (3) a method of immersing the support on which the coating layer is formed in the coating solution B, and the like.

  In the method (1), examples of the coating method for coating the coating liquid B include a curtain flow coater, an extrusion die coater, an air doctor coater, a bread coater, a rod coater, a knife coater, a squeeze coater, a reverse roll coater, and a 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 the already formed first coating layer, such as an extrusion die coater, a curtain flow coater, a bar coater or the like.

  When the coating liquid B is applied simultaneously with the application of the ink receiving layer coating liquid (coating liquid A), the coating liquid A and the coating liquid B are placed on the support so that the coating liquid A is in contact with the support. The ink receiving layer can be formed by simultaneously coating (multilayer coating) and then 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.

  When the above simultaneous coating (multilayer coating) is performed by, for example, an extrusion die coater, the two types of coating liquid discharged at the same time are close to the discharge port of the extrusion die coater, that is, before moving onto the support. A multilayer is formed, and in that state, the multilayer is applied on the support. 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, when applying simultaneously as described above, it is preferable to apply the coating solution A and the coating solution B together with the barrier layer solution (intermediate layer solution) interposed between the two solutions.

  The barrier layer solution can be selected without particular limitation. For example, an aqueous solution containing a trace amount of water-soluble resin, water, and 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, a cellulose resin (for example, hydroxypropylmethylcellulose, methylcellulose, hydroxyethylmethylcellulose) And polymers such as polyvinylpyrrolidone and gelatin. The barrier layer solution may contain the above mordant.

  After application of the coating solution, the coating layer is dried. This drying is performed at a lower critical eutectic temperature of 5 ° C. to 180 ° C. for 0.5 to 30 minutes, and drying and curing are performed. . Especially, it is preferable to heat for 1 to 20 minutes at 5 degreeC high temperature -150 degreeC of the lower critical solution temperature of this polymer.

  After forming the ink receiving layer on the support, surface smoothness, glossiness, transparency, and coating strength can be obtained by calendering through the roll nip under heat and pressure using, for example, super calender, gloss calender, etc. It is possible to improve. However, the calendar process may cause a decrease in the porosity (that is, the ink absorptivity may be decreased), so it is necessary to set 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 ink jet 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 pore median diameter can be measured using a mercury porosimeter (trade name “Bore Sizer 9320-PC2” manufactured by Shimadzu Corporation).

In addition, 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 support is preferably 30% or less, More preferably, it is 20% or less.
The haze value can be measured using a haze meter (HGM-2DP: 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. If a polymer fine particle dispersion having a low glass transition temperature (40 ° C. or lower) is added to the layer containing the mordant, 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.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited to these Examples. In the examples, “parts” and “%” indicate “parts by mass” and “% by mass” unless otherwise specified, and “degree of polymerization” indicates “degree of mass average polymerization”.

Synthesis example 1
9.0 parts of polyvinyl alcohol having a terminal SH group (“PVA M-115” manufactured by Kuraray Co., Ltd., saponification degree: 97 to 98%) is dissolved by heating in 81 parts of deionized water and adjusted to pH 3 with hydrochloric acid. To this, 1.0 part of N-isopropylacrylamide and 9 parts of water are added and stirred at 25 ° C. under a nitrogen stream.
To this, 0.060 parts of potassium bromate was added and stirred at 25 ° C. for 6 hours to obtain thermosensitive polymer 1. The lower critical solution temperature of polymer 1 was 34 ° C. (distilled water, turbidity method).

Synthesis example 2
A thermosensitive polymer 2 was obtained in the same manner as in Synthesis Example 1 except that 1.0 part of N-isopropylacrylamide in Synthesis Example 1 was changed to 0.5 part. The lower critical solution temperature of polymer 2 was 35 ° C. (distilled water, turbidity method).

Synthesis example 3
A thermosensitive polymer 3 was obtained in the same manner as in Synthesis Example 1 except that 1.0 part of N-isopropylacrylamide in Synthesis Example 1 was changed to 1.0 part of N, N-diethylacrylamide. The lower critical eutectic temperature of the polymer 3 was 34 ° C. (distilled water, turbidity method).

(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 base paper, 0.04% of a fluorescent whitening agent (“Whiteex BB” manufactured by Sumitomo Chemical Co., Ltd.) is added to a 4% aqueous solution of polyvinyl alcohol, and this is 0 in terms of absolute dry mass. The base paper was impregnated to a density of 0.5 g / m 2, dried, and then subjected to a calendering process 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 (back surface) 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 surface is referred to as “back surface”). The resin layer on the back side is further subjected to corona discharge treatment, and thereafter, as an antistatic agent, aluminum oxide (“Alumina sol 100” manufactured by Nissan Chemical Industries, Ltd.) and silicon dioxide (“Nissan Chemical Industry Co., Ltd.” “ A dispersion obtained by dispersing SNOWTEX O ”) in water at a mass ratio of 1: 2 was applied so that the dry mass was 0.2 g / m 2.

  Furthermore, after the corona discharge treatment is applied to the felt surface (surface) side where the resin layer is not provided, anatase-type titanium dioxide 10%, a trace amount of ultramarine blue, and a fluorescent whitening agent 0.01% (vs. polyethylene) A low-density polyethylene containing MFR (melt flow rate) 3.8 is extruded using a melt extruder to a thickness of 29 μm, and a high gloss thermoplastic resin layer is formed on the surface side of the base paper. (Hereinafter, this high-gloss surface is referred to as a “front side”), which was used as a support.

[Example 1]
(Preparation of coating liquid A for ink receiving layer)
(1) Gas phase method silica fine particles and (2) ion-exchanged water and (3) “Charol DC-902P” in the following composition are mixed, and KD-P (manufactured by Shinmaru Enterprises Co., Ltd.) is used. After the dispersion, a solution containing the following (4) polyaluminum chloride, (5) zirconyl acetate, (6) boric acid water, (7) polymer 1, (8) surfactant, (9) ion-exchanged water. In addition, an ink receiving layer coating solution A was prepared.
The mass ratio of the silica fine particles to the water-soluble resin (PB ratio = (1) :( 7)) was 4.5, and the pH of the ink-receiving layer coating liquid A was 3.5, indicating acidity.

<Composition of ink receiving layer coating liquid A>
(1) Gas phase method silica fine particles (inorganic fine particles) 10.0 parts (“Leosil QS-30” manufactured by Tokuyama Corporation, average primary particle size 7 nm)
(2) Ion-exchanged water 51.6 parts (3) “Charol DC-902P” (51% aqueous solution) 1.0 part (dispersant, manufactured by Nittobo Co., Ltd.)
(4) Polyaluminum chloride (40% aqueous solution, basic structural formula: Al ₂ (OH) ₅ Cl) 0.6 part (5) Zirconyl acetate (25% aqueous solution) 0.3 part (6) Borate water (5% Aqueous solution, crosslinking agent) 8.0 parts (7) Polymer 1 (8% aqueous solution) 27.8 parts (8) Surfactant (Olfin PD-101, manufactured by Nissin Chemical Industry Co., Ltd.) 0.1 part ( 9) 24.3 parts of ion-exchanged water

(Preparation of inkjet recording sheet)
After the corona discharge treatment is applied to the front surface of the support, the ink receiving layer coating liquid A obtained above is applied to the front surface of the support at an application amount of 200 ml / m 2 using an extrusion die coater. (Coating process), and dried for 15 minutes at 80 ° C. (wind speed 3 to 8 m / sec) with a hot air dryer (drying process). This produced the inkjet recording sheet (1) of the present invention provided with an ink receiving layer having a dry film thickness of 33 μm.

[Examples 2-3]
The ink jet recording sheet (2) and (2) of the present invention were all used in the same manner as in Example 1 except that the polymer 1 was changed to polymers 2 and 3 in <Composition of Ink Receptive Layer Coating Liquid A> in Example 1. 3) was produced.

[Example 4]
(Preparation of inkjet recording sheet)
After the corona discharge treatment is applied to the front surface of the support, the ink receiving layer coating liquid A is applied to the front surface of the support at an application amount of 200 ml / m ² using an extrusion die coater (application step). ), And dried with a hot air dryer at 80 ° C. (wind speed 3 to 8 m / sec) until the solid content concentration of the coating layer reached 20%. This coating layer exhibited a constant rate of drying during this period. Immediately thereafter, it was immersed in coating solution B having the following composition for 30 seconds to deposit 20 g / m ² on the coating layer, and further dried at 80 ° C. for 10 minutes (drying step). This produced the inkjet recording sheet (4) of the present invention provided with an ink receiving layer having a dry film thickness of 32 μm.

<Composition of coating liquid B>
(1) Boric acid (crosslinking agent) 0.65 parts (2) Ammonium zirconium carbonate 6.5 parts ("Zircozol AC-7" manufactured by Daiichi Rare Element Chemical Co., Ltd., 28% aqueous solution)
(3) Ammonium carbonate 6.0 parts (4) Ion-exchanged water 83.8 parts (5) Surfactant (Megafac F-1405, manufactured by Dainippon Ink & Chemicals) 0.2 part

[Comparative Example 1]
Example 1 except that Polymer 1 was changed to polyvinyl alcohol ("PVA235" manufactured by Kuraray Co., Ltd., saponification degree 88%, polymerization degree 3500) in <Composition of Ink Receptive Layer Coating Liquid A> in Example 1. A comparative inkjet recording sheet (5) was prepared in the same manner as described above.

[Comparative Example 2]
A comparative inkjet recording sheet (6) was prepared in the same manner as in Example 1 except that the polymer 1 was changed to poly (N-isopropylacrylamide) in the <composition of the ink receiving layer coating solution A> in Example 1. Produced.

[Comparative Example 3]
Example 4 except that the polymer 1 was changed to polyvinyl alcohol (“PVA235” manufactured by Kuraray Co., Ltd., saponification degree 88%, polymerization degree 3500) in <Composition of Ink Receptive Layer Coating Liquid A> in Example 4. A comparative inkjet recording sheet (7) was prepared in the same manner as described above.

(Evaluation test)
The following evaluation tests were performed on each of the inkjet recording sheets (1) to (4) of the present invention obtained above and the comparative inkjet recording sheets (5) to (7). The test results are shown in Table 1 below.

<Occurrence of cracks>
The presence or absence of cracks generated on the surface of the A4 size inkjet recording sheet and the size thereof were visually observed and evaluated according to the following criteria.
The case where the crack was not recognized on the surface was evaluated as A, the case where the crack of 1-5 places was recognized as B, and the case where the crack of 6 places or more was recognized as C.

<curl>
The inkjet recording sheet is cut into A6 size, left on a flat test plate for 1 hour in an environment of 10 ° C. and 20% relative humidity, and the height of the inkjet recording sheet from the four square test plates is measured. The average value was taken as the curl value.
A curl value of less than 2 mm was evaluated as A, a case of 2 to 6 mm was evaluated as B, and a case of 6 mm or more was evaluated as C.

<Ink absorbability>
Using an inkjet printer ("PM-900C" manufactured by Seiko Epson Corporation), Y (yellow), M (magenta), C (cyan), K (black), B ( A solid image of blue), G (green), and R (red) is printed, and immediately after that (after about 10 seconds), the paper is pressed against the image to visually transfer the ink onto the paper. Observed and evaluated according to the following criteria.
A when the transfer of ink onto the paper is not recognized at all, A when the transfer of the ink onto the paper is partially recognized as B, and the transfer of the ink onto the paper is recognized to be a level that has a practical problem. Evaluated as C.

<Print density>
Using an inkjet printer (“PM-900C” manufactured by Seiko Epson Corporation), a solid black image is printed on each inkjet recording sheet, and after standing for 3 hours, the reflection density of the printed surface is measured by reflection density measurement. It was measured with a meter (“Xrite 938” manufactured by Xrite).
The case where the reflection density was 2.1 or higher was evaluated as A, the case where the reflection density was 1.8 to 2.1 was evaluated as B, and the case where less than 1.8 was evaluated as C.

<Burning over time>
Lattice-like linear pattern (line width 0.28 nm) in which magenta ink and black ink are adjacent to each other on each inkjet recording sheet using an inkjet printer ("PM-900C" manufactured by Seiko Epson Corporation) And measured the visual density (ODfresh) with X-Light 310TR (manufactured by X-Light Co., Ltd.) After the measurement, each printed ink-jet recording sheet was placed in a clear file and kept at a constant temperature and humidity of 35 ° C. and a relative humidity of 80%. After storing in the tank for 3 days, the visual density (ODthermo) was measured again, and the density change rate (ODthermo / ODfresh × 100) was calculated.A density change rate was less than 120% A, 120-150% B, 150% or more was evaluated as C. The smaller the density change rate, the smaller (good) the aging blur.

From the results of Table 1 above, the inkjet recording sheets of the present invention (Examples 1 to 4) are free from cracks and curls, have excellent ink absorption speed and image area density, and suppress blurring under high temperature and high humidity conditions. As a result, the recording sheet was found to be excellent in image stability.
On the other hand, a comparative inkjet recording sheet that did not use this copolymer could not satisfy all of these performances.

  According to the present invention, it is possible to provide an ink jet recording sheet having good ink absorptivity, excellent image density, and little aging over time even when stored in a high temperature and high humidity environment for a long time.

Claims (8)

  In an inkjet recording medium having an ink receiving layer on a support, the ink receiving layer is a polymer having a lower critical eutectic temperature in A) fine particles, B) mordant, and C) water, and exhibits temperature sensitivity. An ink jet recording medium comprising: a unit having a group having a functional group; and a copolymer comprising a unit having a hydroxyl group.   2. The ink jet recording medium according to claim 1, wherein the copolymer has a lower critical solution temperature of 20 to 60 ° C.   3. The ink jet recording medium according to claim 1, wherein the copolymer is a copolymer containing an N-substituted (meth) acrylamide unit and a unit having a hydroxyl group. 3. The ink jet recording medium according to claim 1, wherein the copolymer has a structural unit represented by the following general formula (1).

[Wherein, R represents a hydrogen atom or a methyl group, and R ¹ and R ² each independently represent a hydrogen atom or an alkyl group having 1 to 12 carbon atoms which may have a substituent, or R ¹ and R ² may be linked to each other to form a cyclic structure. Q represents a unit having a hydroxyl group. m and n represent mol% of the repeating unit, and 10 ≦ m ≦ 90 and 10 ≦ n ≦ 90. ]   3. The ink jet recording medium according to claim 1, wherein the copolymer is a block or graft copolymer.   The inkjet recording medium according to any one of claims 1 to 5, wherein A) the fine particles are one or more selected from silica fine particles, colloidal silica, alumina fine particles, and pseudoboehmite.   B) The mordant is a cationic resin and / or a water-soluble polyvalent metal salt. The ink jet recording medium according to any one of claims 1 to 6.   On a support, A) a fine particle, B) a mordant, and C) a polymer having a lower critical solution temperature in water, comprising a unit having a group exhibiting temperature sensitivity and a unit having a hydroxyl group. A method for producing an ink jet recording medium, comprising: coating a coating solution containing the copolymer at a temperature lower than the lower critical eutectic temperature of the copolymer and drying by heating at a temperature higher than the lower critical eutectic temperature by 5 ° C. or more.