JP2008194970A - Inkjet recording material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recording material featuring a compatibility between good ink absorption and high glossiness and also satisfies pigment ink aptitude and excels in casting. <P>SOLUTION: The inkjet recording material has a base material and at least one layer of coating stratum formed on this base material, contains cationic silica and chitosan at least in the topmost layer of the recording material, and is characterized by undergoing pressure-weld processing by the heated mirror plane drum while the topmost layer is in a wet condition. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an ink jet recording material that has both good ink absorbability and high glossiness, satisfies pigment ink suitability, and is excellent in cast suitability.

  Inkjet recording, which forms images by ejecting ink droplets from fine nozzles and depositing them on the surface of the recording medium, has low noise during recording, is easy to form full-color images, and is fast It is widely used in terminal printers, facsimiles, plotters, form printing, and the like due to reasons such as recording capability and lower recording costs than other printing devices.

  In recent years, inkjet printers have been improved in definition and speed, and the spread to general home users has been increasing for the purpose of outputting captured images using a digital camera or the like.

  Among them, the ink jet recording body is required to have ink absorbability corresponding to the speeding up of the ink jet printer. Further, in order to bring the quality of a recorded image obtained by outputting a photographed image close to the quality of a silver salt photograph, the glossiness of the surface of the ink jet recording body is required, and high image quality such as coloring property and depth of the recorded image is required. Furthermore, with the advent of pigment ink jet printers having good image storage stability, the ability to record pigment inks on high gloss ink jet recording materials is also required.

In response to the demands on these ink jet recording materials, the following proposals have been made in order to satisfy not only the conventional ink absorptivity and glossiness, but also the glossiness and suitability for pigment inks at the same time.
For example, in an ink jet recording body in which a base material, a coating layer, and an outermost layer are sequentially provided, there is a proposal of imparting pigment ink suitability to the outermost layer using cationic colloidal silica (see Patent Document 1).
Further, using colloidal particles having a porous structure made of amorphous silica / alumina having an average particle diameter of 200 nm or less on the outermost layer, the outermost layer is brought into pressure contact with a heated mirror drum surface (so-called casting method), A recording body has been proposed that not only enhances gloss but also has excellent ink absorbability (see Patent Document 2). Furthermore, by including fine pigments and synthetic polymer latex as main components in the outermost layer, an ink jet recording body is proposed in which not only the gloss is improved but also the strength of the coating film is increased (Patent Documents 3 to 4). reference).
On the other hand, there is an example in which chitosan, which is a kind of polysaccharide, is contained in an ink receiving layer, and a recording material excellent in printing density, indoor discoloration resistance, cracking, and water resistance is proposed. For example, a recording medium containing a cationic pigment having a BET specific surface area of 50 to 170 m ² / g and chitosan and / or a chitosan salt in the ink receiving layer on the substrate surface (see Patent Document 5), or an alumina hydrate in the ink receiving layer A recording body containing a product and chitosan has been proposed (see Patent Document 6).

In the proposals of Patent Documents 1 and 3, although satisfactory scratch resistance and pigment ink suitability on the surface of an ink jet recording body can be obtained, glossiness and density of a recorded image are not sufficient.
Further, Patent Document 2 is excellent in glossiness and suitability for pigment ink, but because the pigment is porous, the coating film strength is weak and the color developability of the recorded image is not sufficient.
The proposal of Patent Document 4 is excellent in gloss, pigment ink suitability, and print density, but the mirror drum surface is easily soiled and cast suitability is low.
Further, in the proposals of Patent Documents 5 and 6, although excellent in indoor discoloration resistance, water resistance, and print density, the suitability of pigment ink is not sufficient, and the glossiness is also low.
Japanese Patent Laid-Open No. 2004-11459 Japanese Unexamined Patent Publication No. 7-117335 Japanese Patent Laid-Open No. 7-101142 JP 2005-41232 A JP-A-5-169789 JP-A-9-109545

  An object of the present invention is to provide an ink jet recording material that has both good ink absorbability and high glossiness, satisfies pigment ink suitability, and is excellent in cast suitability.

In order to impart pigment ink suitability, it is necessary to improve scratch resistance. For this purpose, it is desirable to make the outermost layer cationic, but aluminum oxide, magnesium oxide, magnesium hydroxide, etc. are used as the cationic pigment. As a result, the print density is greatly reduced.
In addition, when the outermost coating liquid becomes cationic, the mirror drum is much more easily soiled and castability tends to be lower than when it is anionic.

On the other hand, chitosan that is water-soluble in the acidic region and insoluble in the neutral region evaporates with the heat during casting, and forms a coating layer while the chitosan is insolubilized. In addition to improvement, a binder effect is also produced, so that the amount of binder added can be reduced as compared with the current situation.
When the outermost layer contains chitosan together with cationic silica and the coating liquid of the outermost layer is wet, it is pressure-bonded with a heated mirror drum, so that the peelability from the cast drum is improved. The outermost surface can be uniformly peeled from the drum, there are few surface streaks and spots, and gloss and print quality are good. Further, since there is no drum contamination due to poor peeling, the productivity is extremely good.

  As a result of repeated studies, the inventors of the present invention include a cationic silica and chitosan in the outermost layer of the ink jet recording material, and press-bonding the heated mirror drum while the outermost coating liquid is in a wet state. Thus, the inventors have found that these problems can be solved, and have completed the present invention.

The present invention includes the following embodiments.
[1] An ink jet recording body comprising a base material and at least one coating layer formed on the base material, wherein at least the outermost layer of the recording material contains cationic silica and chitosan, An ink jet recording material, wherein the ink jet recording material is subjected to pressure-bonding treatment with a heated mirror drum while the surface layer is in a wet state.
[2] The inkjet recording material according to [1], wherein the cationic silica contains 70 to 100% by mass of cationic colloidal silica having an average primary particle size of 10 to 100 nm.
[3] The cationic silica contains 70 to 100% by mass of a cationic gas phase method silica having an average primary particle diameter of 7 to 20 nm and an average secondary particle diameter of 700 nm or less. ] The inkjet recording body as described in above.
[4] The inkjet recording material according to [1] to [3], wherein the chitosan is blended in an amount of 0.5 to 30 parts by mass with respect to 100 parts by mass of the cationic silica.
[5] The inkjet recording material according to [1] to [4], wherein the chitosan has a molecular weight of 10,000 to 500,000.

[Layer structure]
The present invention is an inkjet recording body having a base material and at least one coating layer formed on the base material, and at least the outermost layer of the recording body contains cationic silica and chitosan, It is an ink jet recording material that is pressure-bonded to a heated mirror drum while the outermost layer is in a wet state.
The coating layer may be only the outermost layer, but it is preferable that one or more coating layers are provided between the substrate and the outermost layer because ink absorbability is improved.
In the present invention, a layer similar to the above may be provided on the opposite side of the surface of the substrate on which the recording layer is provided. In this case, the effect of the present invention can be exhibited on both sides of the ink jet recording body.

<Base material>
There are no particular restrictions on the type, shape, dimensions, etc. of the base material, and it can be used as a permeable support or a non-permeable support. A gas-permeable support is preferred for obtaining.

(Air-permeable support)
Examples of the air-permeable support include paper substrates such as high-quality paper, medium-quality paper, coated paper, art paper, cast-coated paper, foil paper, craft paper, baryta paper, impregnated paper, vapor-deposited paper, and water-soluble paper. Can be used. Moreover, resin sheets, woven fabrics, nonwoven fabrics, and the like having air permeability can be used.

The paper base is composed of wood pulp as a main component and containing a filler as necessary.
As the wood pulp, various chemical pulps, mechanical pulps, regenerated pulps and the like can be used. These pulps can control paper strength, papermaking aptitude, etc. by adjusting the beating degree with a beating machine. The beating degree (freeness) of the pulp is not particularly limited, but it is desirable to increase the beating degree in order to improve smoothness. However, when recording on paper, paper blurring caused by moisture in the ink and blurring of the recorded image occur. In many cases, better results are obtained when the degree of beating is not advanced. Therefore, the beating degree is generally 250 to 550 ml (CSF: JIS-P-8121), and preferably 300 to 500 ml.
Moreover, chlorine free pulps, such as ECF and TCF pulp, can be used preferably.

The filler is blended for the purpose of imparting opacity and adjusting ink absorbability, and porous pigments such as silica, calcined kaolin and zeolite, calcium carbonate, clay, talc, kaolin and titanium oxide can be used. Among these, calcium carbonate is particularly preferable because it has a high whiteness.
1-20 mass% is preferable and, as for the content rate (ash content) of the filler in a paper base material, 3-15 mass% is more preferable. With this content rate, smoothness, air permeability, and paper strength are balanced, and as a result, an ink jet recording body excellent in glossiness is easily obtained.

A sizing agent, a fixing agent, a paper strength enhancer, a cationizing agent, a yield improving agent, a dye, a fluorescent brightening agent, and the like can be added to the paper base as an auxiliary agent.
Furthermore, in the size press process of the paper machine, pigments, starch, polyvinyl alcohols, cationic resins, anionic resins and the like can be applied and impregnated to adjust the surface strength, sizing degree, and the like.
The Steecht sizing degree (as 100 g / m ² paper) is preferably 1 to 200 seconds, and more preferably 4 to 120 seconds. When the Steecht sizing degree is 1 second or longer, operational problems such as wrinkling at the time of coating are improved, and when the Steecht sizing degree is 200 seconds or less, ink absorbency is improved. The curl after printing is good.
Although the basic weight of a base material is not specifically limited, 20-400 g / m < ² > is preferable.

The air permeability (JIS-P-8117) of the air-permeable support is preferably 20 to 500 seconds and more preferably 35 to 300 seconds in the case of paper having a basis weight of 170 g / m ² . When the air permeability is 20 seconds or more, blurring of the surface of the ink jet recording body is suppressed, and the apparent glossiness tends to be improved. On the other hand, when it is 500 seconds or less, sticking to the drum at the time of pressure contact with the mirror drum is improved, and the outermost layer is sufficiently dried, and high surface gloss tends to be easily obtained.

(Non-permeable support)
When an air-impermeable support is used, the ink solvent does not penetrate into the base material, which is effective in preventing cockling. In the case of using a non-air-permeable support, a pressure-bonding process is performed with a heated mirror drum using a nip cast method described later. However, the nip cast method has less glossiness because it has less time to stick to the mirror drum compared to the pressure bonding method of the air-permeable support to the mirror drum using the wet cast method, rewet cast method, gelled cast method, etc. described later. There is a risk of lowering.
Examples of the non-permeable support include films such as polyethylene, polypropylene, soft polyvinyl chloride, hard polyvinyl chloride, and polyester (including synthetic paper), metal foils, high-quality paper, and art paper. , Coated paper, cast coated paper, foil paper, kraft paper, impregnated paper, vapor-deposited paper, water-soluble paper, etc. and resin-coated paper in which a thermoplastic resin such as polyolefin is laminated on non-woven fabric, paper or non-woven fabric in films The laminated sheet etc. which bonded etc. are illustrated. Among these, so-called synthetic paper typified by YUPO (manufactured by YUPO Corporation) obtained by stretching polypropylene and applying special processing, and resin-coated paper obtained by laminating a paper base material with a polyolefin resin (preferably polyethylene resin) are preferable. A paper substrate having an air permeability exceeding 500 seconds can also be used.

  Synthetic paper is usually obtained by extruding a polypropylene resin containing an inorganic pigment such as calcium carbonate and biaxially stretching to form voids inside. Among them, a laminated sheet composed of a plurality of layers is preferable, and the use of a synthetic paper having a skin layer without unevenness is particularly preferable on the surface on which the recording layer is formed. Various layers such as an anchor layer, a primer layer, and an antistatic layer may be formed on the surface of the synthetic paper in order to improve coating suitability or chargeability.

As the resin-coated paper, among them, a support in which a polyethylene resin kneaded with titanium oxide is coated on the paper surface is particularly preferable because the finished appearance is almost the same as that of photographic printing paper.
The thickness of the polyethylene resin layer is preferably 3 to 50 μm, more preferably 5 to 30 μm. When the thickness of the polyethylene resin layer is less than 3 μm, defects are not suppressed during resin coating, thickness control is difficult, and smoothness is difficult to obtain. On the other hand, if it is thicker than 50 μm, the smoothness is saturated and no further quality can be expected.

The paper base material used for the resin-coated paper is manufactured using wood pulp as a main material.
As the wood pulp, various chemical pulps, mechanical pulps, regenerated pulps and the like can be used as appropriate. These pulps can control paper strength, smoothness, papermaking suitability, and the like by adjusting the beating degree with a beater. The beating degree is not particularly limited, but generally 250 to 550 ml (CSF: JIS-P-8121) is preferable.
Further, chlorine-free pulp such as ECF and TCF pulp can be preferably used, and a pigment can be added as necessary. As the pigment, talc, calcium carbonate, clay, kaolin, calcined kaolin, silica, zeolite and the like are preferably used. The addition amount of the pigment is preferably 1 to 20% by mass with respect to the wood pulp. Opacity and smoothness can be increased by adding a pigment, and the paper strength is not reduced by setting the added amount of the pigment to 20% by mass or less.

<Outermost layer>
The outermost layer in the present invention contains cationic silica and chitosan, and an ink jet recording body is manufactured by applying a pressure-bonding treatment (so-called casting method) with a mirror drum while the outermost layer coating liquid is in a wet state.
By using cationic silica as the outermost layer, not only the dye ink but also the pigment ink can be quickly fixed, and the pigment is very excellent in scratching property.
In addition, by including chitosan in the outermost layer at the same time, drum contamination, which is a problem when cationic silica is used in the outermost layer, is not caused, and the releasability is improved. High gloss is imparted to the body surface.
When the silica used for the outermost layer is cationic colloidal silica, the pigment is densely arranged, so that it has a very high gloss, but a binder must be added to form a layer without cracks. However, since chitosan has a binder effect in addition to the improvement in releasability, the amount of other binders can be reduced, and deterioration of ink absorbency accompanying an increase in the amount of binder added can be prevented.
When using cationic silica forming secondary particles, the pigment itself has a porous structure, so the original absorption is high, but a large amount of binder is added to form a layer without cracks. Must. Also in this case, the amount of binder can be reduced by the binder effect of chitosan, and the ink absorptive effect can be improved.
In addition to these cationic silicas, other cationic pigments can be mixed in the outermost layer as long as the paint does not aggregate.
In order to obtain a glossy recording material, the number of pigments to be used is preferably as small as possible, and the cationic silicas having the same specific surface area and the same particle size are more preferable.
Further, in order to further improve the peeling of the outermost layer from the pressed mirror surface from the cast drum, a release agent such as stearamide, polyethylene wax, ammonium oleate or the like is included in the outermost layer coating solution. Or may be applied to a mirror drum. Among these, it is particularly preferable to use a cationic release agent. Although the addition amount of the release agent in the outermost layer coating liquid is not particularly limited, it is generally preferably 0.5 to 10 parts by mass with respect to 100 parts by mass of the pigment.

(Cationic silica)
The cationic silica in the present invention is obtained by cationizing anionic silica by various methods. Examples of the anionic silica include precipitated silica, gel silica, mesoporous silica, gas phase silica, and colloidal silica. Among them, gas phase silica or colloidal silica provides high gloss and print density. Therefore, it is preferably used.
Among the cationic silicas, the cationic gas phase method silica and the cationic colloidal silica that are preferably used will be described in detail later.

The method of cationization of the cationic silica used in the present invention is not particularly limited, but a method of coating the surface of silica with alumina by reacting a compound of polyvalent metal ions such as aluminum ions may be used. Alternatively, a silane coupling agent having an ammonium group may be added to the surface of the silica to be modified to cationic silica.
Alternatively, cationic silica may be obtained by dispersing composite particles obtained by mixing anionic silica and a cationic compound in an aqueous medium.

(Cationic compound)
Examples of the cationic compound mixed with the anionic silica include the following.
1) Polyalkylene polyamines such as polyethylene polyamine and polypropylene polyamine, and derivatives thereof 2) Acrylic resin having secondary amino group, tertiary amino group, and / or quaternary ammonium group 3) Polyvinylamine Polyvinylamidines, 5-membered cyclic amidines 4) Dicyan cationic resins such as dicyandiamide-formalin polycondensates 5) Polyamine cationic resins such as dicyandiamide-diethylenetriamine polycondensates 6) Epoxychlorohydrin-dimethylamine addition polymerization things 7) dimethyldiallylammonium chloride -SO ₂ copolymer 8) diallylamine -SO ₂ copolymer 9) dimethyldiallylammonium chloride polymer 10) polymer of allyl amine salt 11) dialkylamino ethyl (Meth) acrylate quaternary ammonium salt polymer 12) Acrylamide-diallylamine salt copolymer 13) Polyaluminum salts such as polyaluminum chloride, polyaluminum acetate, and polyaluminum lactate Among these, 1) 5-membered ring amidines, 2) It is preferable to use aluminum salts such as polyaluminum chloride, polyaluminum acetate, and polyaluminum lactate.
In addition, it is preferable that it is 1-30 mass parts with respect to 100 mass parts of anionic colloidal silica (solid content), and, as for the compounding quantity of a cationic compound, it is more preferable that it is 2-15 mass parts.

Examples of the dispersion method include homomixers, pressure homogenizers, ultrasonic homogenizers, microfluidizers, optimizers, nanomizers, high-speed rotary mills, roller mills, container drive media mills, media agitation mills, jet mills, sand grinders, Claire mixes, etc. Is used.
In order to make the composite particles of a cationic compound and colloidal silica close to a monodisperse state, it cannot be sufficiently dispersed by a general dispersion method, and it is necessary to apply a stronger mechanical force. In particular, the pressure dispersion method is effective.

The pressure dispersion method is a method in which a slurry-like mixture of raw material particles is continuously passed through an orifice at a high pressure and pulverized under high pressure.
The treatment pressure was 19.6 × 10 ^{6 to} 343.2 × 10 ⁶ Pa (200 to 3500 kgf /
cm ² ), preferably 49.0 × 10 ^{6 to} 245.3 × 10 ⁶ Pa (500 to 2500 kgf / cm ² ), and 98.1 × 10 ^{6 to} 196.2 × 10 ⁶ Pa (1000 More preferably, it is ˜2000 kgf / cm ² ).
Thereby, it is possible to obtain cationic colloidal silica close to a monodispersed state.
Further, it is preferable that the slurry-like mixture passed through the orifice under high pressure is further subjected to a dispersion or pulverization method by causing it to collide against each other.
In the method of facing collision, the dispersion liquid is guided to the inlet side of the facing collision dispersion pulverization apparatus while being pressurized. Next, the introduced dispersion is branched into two passages in the apparatus. Furthermore, the flow velocity is accelerated by narrowing the flow path with an orifice, and the two dispersion liquid streams are caused to collide with each other so that the particles are pulverized by mutual collision.
As a material constituting the portion that accelerates or collides the dispersion liquid in the apparatus, diamond is preferably used for reasons such as suppression of wear.
As the high-pressure pulverizer, a pressure homogenizer, an ultrasonic homogenizer, a microfluidizer, and a nanomizer are used. Among them, a microfluidizer and a nanomizer are particularly preferably used as a high-speed collision type homogenizer.

  The average primary particle size of the cationic colloidal silica is preferably 10 to 100 nm, and more preferably 20 to 50 nm. If it is smaller than 10 nm, the absorptivity deteriorates, and if it is larger than 100 nm, the print density may be lowered. The colloidal silica has a spherical shape and a bead-like shape. When a spherical shape is used, the gloss becomes high. Further, the non-spherical colloidal silica connected in a bead shape is superior in terms of ink absorptivity, and can be appropriately selected according to the purpose. Further, colloidal silica having different shapes can be used in combination.

The average primary particle size of the cationic vapor phase silica is preferably 7 to 20 nm, more preferably 8 to 15 nm. By setting the average primary particle size within this range, high glossiness can be obtained and the color development of the recorded image is also excellent.
If the average primary particles are too small, the ink absorbability is inhibited, and if the average primary particles are too large, the printing density is lowered, which is not preferable.

Here, the average primary particle diameter is an average of measured values observed with an electron microscope (TEM). When the dispersed particle is a monodisperse, the particle diameter R of the single particle is directly measured. When the particle is a secondary dispersion, the single particle cannot be directly measured. The particle diameter R of the single particle is measured assuming the outer shape of the particle. At this time, in principle, a position where the single particles do not overlap each other is selected, and the particle diameter R of the single particles is measured.
In this way, the particle diameter R of 100 single particles was measured and averaged to obtain the average primary particle diameter.

In the case of colloidal silica, secondary particles are not formed, and only the primary particles are dispersed, but in the case of gas phase method silica, secondary particles in which primary particles are aggregated are present in the coating liquid. To do.
The average secondary particle diameter of the vapor phase method silica is preferably 10 to 700 nm, and more preferably 500 nm or less. If the average secondary particle diameter is larger than 700 nm, the print density may be lowered.
The content of the cationic colloidal silica or the cationic vapor phase silica that is the cationic silica is preferably 70 to 100% by mass, and more preferably 80 to 100% by mass.
When the content of the cationic colloidal silica or the cationic gas phase method silica is less than 70% by mass, it is difficult to impart high glossiness.

<Measurement method of average secondary particle size>
The average secondary particle size was measured by preparing 200 g of an aqueous dispersion having a pigment concentration of 3% by mass, subjecting this to a homomixer and stirring and dispersing at 1000 rpm for 30 minutes. It is used for electron microscope (SEM and TEM) observation, taking an electron microscope photograph of 10,000 to 400,000 times, and measuring and averaging the diameters of particles existing in an area of 5 cm × 5 cm square in the photograph. (See "Handbook of fine particles", Asakura Shoten, p52, 1991).

(Chitosan)
The chitosan according to the present invention is obtained by deacetylating chitin. Chitin can be dissolved in a solvent only by a special system such as N, N-dimethylacetamide / LiCl system, but water solubility is improved by deacetylation of chitin. The deacetylation can be changed by appropriately adjusting the alkali concentration used in the treatment, the treatment temperature, the treatment time, and the like. To dissolve in water in the presence of an acid, the degree of deacetylation is 65. % Or more.
Chitin refers to β-1,4-poly (N-acetyl-D-glucosamine) that forms the exoskeleton of crustaceans such as shrimp and coral and insects, and is naturally bound to proteins. Biosynthesized in form. Chitin can be obtained by removing ash, protein, and the like from an exoskeleton of a living body by acid treatment such as hydrochloric acid and alkali treatment such as sodium hydroxide.
The chitosan in the present invention is dissolved in water in the presence of an acid. Examples of acids used to dissolve chitosan include organic acids such as formic acid, acetic acid, lactic acid, malonic acid, malic acid, tartaric acid, citric acid, and adipic acid, and inorganic acids such as hydrochloric acid, nitric acid, and phosphoric acid. Organic acids such as lactic acid, citric acid and acetic acid are preferably used.
Since chitosan dissolves in the acid and exhibits cationic properties, even when mixed with cationic silica, it can exhibit excellent releasability and binder effect without agglomeration.
In addition, chitosan, which is water-soluble in the acidic region and insoluble in the neutral region, improves the castability because the acid evaporates due to the heat during casting and forms a coating layer while the chitosan is insolubilized. In addition, since the binder effect is also produced, the current amount of added binder can be reduced.
In the present invention, chitosan dissolves with stirring with the above acid, but chitosan generally dissolves more easily as the liquid temperature is higher and the acid concentration is higher, but in the case of the present invention, if the acid concentration is too high, printing Since the color of the ink may change later, it is not preferable. The amount of the acid used for dissolving chitosan in the present invention is 5 to 300 parts by mass, more preferably 10 to 100 parts by mass with respect to 100 parts by mass of the chitosan solid content.
Further, the temperature at the time of dissolving chitosan is not particularly restricted because it has almost no adverse effect on chitosan, but is preferably about 30 to 80 ° C, and more preferably about 40 to 60 ° C. Once chitosan is dissolved, the solubility does not change even when the liquid temperature falls.
The molecular weight of chitosan is not particularly limited, but if the molecular weight is too low, the binder effect may be reduced, and if it is too high, the gloss tends to decrease. Therefore, the molecular weight is preferably about 10,000 to 500,000, preferably 50,000 to 400,000 is more preferable.
This molecular weight can be obtained by GPC measurement.
Here, the molecular weight measurement obtained by GPC measurement can be performed by an apparatus such as SC-8010 (manufactured by Tosoh Corp.). Specifically, THF (tetrahydrofuran) is used as the solvent and eluent of the sample, For example, when the flow rate of THF is 1.0 ml / min, a THF solution of a sample is put into a measuring device, the detection time of the sample taken from the column is obtained, and a calibration curve of polystyrene that is a standard sample (with known molecular weight) Calculate the molecular weight of the sample.

As for the preferable compounding ratio of chitosan and cationic silica, 0.5-30 mass parts is preferable with respect to 100 mass parts of cationic silica, and 1-15 mass parts is more preferable. If the amount of chitosan is less than 0.1 parts by mass, the effect of improving the releasability in cast finishing may be reduced, and if it is more than 30 parts by mass, the ink absorbability may be impaired.

(binder)
In the outermost layer in the present invention, a binder can be blended as necessary for reasons such as improving the coating strength. Although it does not specifically limit as a binder, For example, hydrophilic resin, hydrophobic resin, etc. are mentioned.
Examples of the hydrophilic resin include polysaccharides such as polyvinyl alcohol, polyvinyl pyrrolidone, casein, chitosan, and starch, gelatin, synthetic proteins, and cellulose derivatives such as carboxymethyl cellulose and methyl cellulose.
Examples of the hydrophobic resin include water-insoluble synthetic resin latex (emulsion type, solvent type) and the like.
Among these, a hydrophilic resin is preferably used for the reason that the transparency of the coating film is good and the color developability of the recorded image is excellent. These binders may be used alone or in combination of two or more.

Moreover, about the said water-insoluble synthetic resin latex, it can be used in the range which does not impair the effect of this invention from the reason of the coating-film intensity | strength of an outermost layer, and a glossiness improving. In the present invention, since the outermost layer contains cationic silica as a main component, the water-insoluble synthetic resin latex used is preferably nonionic or cationic.
The type of the water-insoluble synthetic resin latex is not particularly limited. For example, an acrylic resin emulsion, a urethane resin emulsion, a styrene resin emulsion, a styrene-acrylate copolymer resin emulsion, or a styrene-butadiene. Copolymer-based resin emulsion, methyl methacrylate-butadiene copolymer resin emulsion, acrylic ester and methacrylic ester polymer and / or copolymer resin emulsion, ethylene-vinyl acetate copolymer Examples thereof include emulsions of combined resins, and emulsions of functional group-modified polymer resins obtained by modifying these polymers or copolymers with monomers containing functional groups such as carboxyl groups.
Among these, emulsion-type latexes can be preferably used because of particularly good dispersion stability of the paint, and acrylic resin emulsions, urethane resin emulsions, and styrene because of their good coating strength. An emulsion of a resin can be more preferably used.

Examples of the water-insoluble synthetic resin latex exhibiting cationic properties include those that have been cationically modified, such as cationic organic particles described in JP-A No. 2003-211821.
In order to further increase the glossiness and the color density of the recorded image, the average particle size of the resin-containing particles in the emulsion is preferably 5 nm to 70 nm, and more preferably 10 to 50 nm.

The binder content may be added in a range that does not impair the ink absorbency, but when cationic colloidal silica is used as the cationic silica, 1 to 10 mass with respect to 100 mass% of silica (solid content). % Is preferable, and 2 to 5% by mass is more preferable. Moreover, when using a cationic gas phase method silica as cationic silica, 5-40 weight% is preferable with respect to 100 weight% of silica (solid content), and 10-30 weight% is further more preferable.
When the blending amount of the binder is small, the coating film strength is insufficient, and when the blending amount is too large, the ink absorbability may be inhibited.

<Formation of outermost layer>
In the present invention, the outermost layer contains cationic silica and chitosan and is formed in pressure contact with a mirror drum. In this case, the outermost layer is formed differently between the case where a permeable support is used and the case where a non-permeable support is used.

  When an air-permeable support is used as the base material, after applying the outermost layer coating liquid, it is pressed against a heated mirror drum (for example, cast drum) while in a wet state, dried, and then mirror drum By further peeling, surface finishing can be performed by a so-called casting method in which the mirror surface of the drum is copied onto the surface of the outermost layer.

As the casting method, a wet casting method, a rewet casting method, a gelled casting method, or the like conventionally known in the field of coated paper for printing can be applied.
Also, immediately before the coating layer is pressed against the mirror drum, the outermost layer coating liquid is applied between the coating layer surface on the press roll and the mirror drum, and the mirror surface finish is performed by immediately pressing and drying (hereinafter referred to as the surface coating). Nip casting method finishing). The recording material obtained by this method is a preferable method because gloss and image quality comparable to a silver salt photograph can be obtained.

  In addition, in order to obtain an ink jet recording material having extremely high gloss by casting the outermost layer, the air permeability (JIS-P) of the support (base material excluding the outermost layer and the entire coating layer) on which the outermost layer is formed. −8117) is preferably 3500 seconds or less, more preferably 2000 seconds or less, and even more preferably 1500 seconds or less.

  In order to prevent cracking and increase the drying efficiency, the surface temperature of the heated mirror surface is preferably controlled to 70 to 120 ° C.

When a non-permeable support is used for the base material, if a casting method is used that dries on a mirror drum similar to the permeable support, steam accumulates between the base material and the drum, and gloss cannot be obtained. .
Therefore, while the outermost layer is in a wet state, the outermost layer coating solution is applied between the coating layer surface on the press roll and the mirror drum at the nip portion between the mirror drum and the press roll, and is brought into pressure contact with the mirror drum. Thus, the mirror surface is neatly copied onto the coating layer, immediately peeled off from the mirror drum, and then dried by a dryer or the like to obtain gloss.
Also in this case, the surface temperature of the heated mirror surface is preferably controlled to 70 to 120 ° C. Moreover, in order to make it easy to peel off the outermost layer from the pressed mirror surface, a release agent may be contained in the coating liquid, or may be applied to the mirror surface.

Dry the solid coating amount of the outermost layer, if the pigment of the outermost layer is cationic colloidal silica, and more that is preferably 0.2-5 g / ^{m 2,} it is 0.5 to 2 g / ^{m 2} preferable. When the coating amount is less than 0.2 g / m ² , the coating film becomes excessively thin, the gloss is lowered, and interference color due to light tends to occur. On the other hand, if the coating amount is more than 5 g / m ² , the ink absorption rate may decrease, which is not preferable.
Also, if the pigment of the outermost surface layer of cationic fumed silica is preferably 1 to 15 g / ^{m 2,} and more preferably 2 to 10 g / ^{m 2.} If the coating amount is less than 1 g / m ² , the coating film may be excessively thin and the gloss may be lowered. If the coating amount is more than 15 g / m ² , the coating film may be cracked, which is not preferable.

<First coating layer>
The coating layer in the present invention may be one outermost layer, but one or more layers may be provided between the substrate and the outermost layer.
The coating layer adjacent to at least the outermost layer in the present invention (hereinafter sometimes referred to as the first coating layer) preferably contains a specific dry silica fine dispersion. The first coating layer cannot be absorbed by the outermost layer, and quickly fixes the colorant in the ink that has passed through the first coating layer to obtain a uniform image (dot roundness) with high color development (high print density). This is a layer having both functions of forming a highly smooth and highly film-forming layer in which high gloss is easily obtained when the outermost layer is provided.

In order to realize the image quality of a photograph, the transparency of the coating layer on which the colorant in the ink is fixed is important. If the coating layer is transparent, the colorant fixed in the coating layer can be seen from the outside, so that the image has a depth (depth) and an image closer to a silver salt photograph can be obtained.
However, since a coating layer having high transparency is generally difficult to absorb ink, in order to obtain a preferable coating layer in the present invention, it is important to satisfy both film formability and ink absorbability. It becomes a point. In order to realize this, it is not sufficient to simply reduce the pigment contained in the coating layer.

  Therefore, it is effective to eliminate pores larger than the wavelength of light in the coating layer to which the ink is fixed, that is, to set the peak in the pore distribution of the coating layer of the present invention to 0.1 μm or less. In order to set the peak in the pore distribution to 0.1 μm or less, a coating layer can be provided while suppressing cracking of the coating film by a specific pigment and a coating method described later.

(Pigment for coating layer)
The pigment contained in the coating layer is not particularly limited, and examples thereof include silica, alumina, and alumina hydrate. These may be used alone or in combination of two or more.
In particular, after adding alkali to dry silica, mesoporous silica, and colloidally dispersed silica seed solution, a feed solution consisting of at least one selected from an aqueous solution of active silicic acid and alkoxysilane is added to the seed solution little by little. Secondary silica dispersion obtained by growing silica fine particles, alumina, alumina hydrate, and the like are preferably used.

Furthermore, among these, the dry silica fine dispersion is preferably used because the film-forming property of the coating layer and the image density after printing are good, and among them, the average primary particle diameter is 3 to 40 nm. Those having a particle size of 700 nm or less are more preferably used. Among them, a plurality of primary particles having an average primary particle diameter of 7 to 13 nm are used in order to easily fix colorants such as dyes and pigments in the ink and to increase the ink absorption rate, the color density of the recorded image, and the glossiness. It is more preferable to use pigment particles having an average secondary particle diameter of 10 to 200 nm formed by aggregation of particles.
The dry silica fine dispersion having this specific particle size is preferably contained in at least the coating layer adjacent to the outermost layer, in order to increase the transparency of the coating layer, and the pore diameter distribution curve of the coating layer It is preferable to control the peak at substantially 0.1 μm or less.

When a silica pigment is used as the pigment, it can also be used as cationic silica. This cationic silica can be prepared, for example, as follows.
(1) Disperse dry silica fine particles in water and, if necessary, pulverize them to reduce the average particle size to a desired value, add a cationic compound to this dispersion, and add silica-cation compound aggregates. And is subjected to pulverization to adjust the average particle size to 10 to 700 nm.
(2) Alkylene oxide polymer (for example, ethylene oxide-propylene oxide copolymer), inorganic acid aqueous solution (for example, hydrochloric acid aqueous solution), 1,3,5-trimethylbenzene, using silane compound, for example, tetraethoxysilane as a template The resulting composite is collected by filtration and dried to prepare a silica-template composite powder. This powder is fired to prepare mesoporous silica. This mesoporous silica is dispersed in water and subjected to pulverization to adjust the average particle diameter of the mesoporous silica to a desired value. A cationic compound is added to this dispersion to form a mesoporous silica-cationic compound aggregate, which is then pulverized to adjust its average particle size to 10 to 700 nm.
(3) A sodium silicate solution is diluted with water, and this aqueous solution is treated with a hydrogen-type cation exchange resin to prepare an aqueous active silicate solution. A part of the activated silicic acid aqueous solution is added to distilled water heated to 100 ° C. to prepare a seed solution containing silica fine particles. The seed solution is stabilized with ammonia water, heated to 100 ° C., the remaining active silicic acid aqueous solution is added, and the mixture is heated to reflux at 100 ° C. to prepare a silica fine particle dispersion. The silica fine particle dispersion prepared to an appropriate concentration is mixed with a cationic compound, and the resulting silica-cationic compound aggregate dispersion is subjected to a pulverization treatment, whereby the average particle diameter of the aggregate particles is 10 to 700 nm. Adjust to.
Among the methods (1) to (3), (1) is preferably used.

As described above, silica-cationic compound aggregate particles obtained by mixing and aggregating silica and a cationic compound are preferably used after being pulverized so that the average particle diameter is 700 nm or less.
In this case, the cationic compound may be the same as the cationic compound used for the cationization of the silica used for the outermost layer, and in particular, the fixability and dispersibility of the dye and pigment in the ink are improved. It is preferable to use 1) 5-membered ring amidines and 2) aluminum salts such as polyaluminum chloride, polyaluminum acetate, and polyaluminum lactate.

The pigment particles having an average particle diameter of 700 nm or less here can be produced by, for example, a method of applying a strong force by mechanical means, that is, a so-called breaking down method (a method of subdividing a bulk material).
The mechanical means include an ultrasonic homogenizer, a pressure homogenizer, a liquid collision homogenizer, a high-speed rotary mill, a roller mill, a container drive medium mill, a medium agitation mill, a jet mill, a mortar, and a disintegrator A device for grinding and kneading the pulverized product with a bowl-shaped stirring bar), a sand grinder, a nanomizer and the like. In order to reduce the particle size, classification and pulverization can be repeated.

(Binder for coating layer)
The binder used for the coating layer is appropriately selected and used depending on the type of the coating layer forming method described later.

<Second coating layer>
In the present invention, the second coating layer is provided between the substrate and the first coating layer for the purpose of improving the unevenness and smoothness of the substrate, absorbing the ink solvent, and improving the surface gloss. A plurality of coating layers may be provided such as a third coating layer. Hereinafter, these layers are referred to as a second coating layer.

The main purpose of the second coating layer is to quickly separate the solvent in the ink from the first coating layer. On the other hand, the purpose of providing the first coating layer is to quickly fix the colorant in the ink and obtain a high color (high printing density) and a uniform image (dot roundness). Therefore, when the second coating layer quickly separates the solvent, the first coating layer can quickly fix the colorant in the ink.
Due to the functions of the second coating layer and the first coating layer, the ink jet recording material of the present invention has a high ink absorption speed and a very excellent image uniformity by quickly separating the solvent. In addition, a pigment, a binder, etc. can be suitably mix | blended with a 2nd coating layer.

(Pigment for second coating layer)
Examples of the pigment include various publicly known pigments in the general coated paper field. For example, after adding alkali to gas phase method silica, mesoporous silica, wet method silica, colloidally dispersed silica seed solution, the seed is added. A secondary silica dispersion obtained by growing silica fine particles by adding a small amount of a feed liquid consisting of at least one selected from an active silicic acid aqueous solution and alkoxysilane to the liquid (described in JP-A-2001-354408), Colloidal silica, alumina, alumina hydrate, calcined kaolin, kaolin, clay, calcined clay, zinc oxide, tin oxide, magnesium sulfate, aluminum hydroxide, calcium carbonate, satin white, aluminum silicate, titanium dioxide, smectite, zeolite, silicic acid Magnesium, magnesium carbonate, magnesium oxide Diatomaceous earth, styrene-based plastic pigments, urea resin-based plastic pigments and the like are used. Above all, the cost is low, the selection range is very wide, the post-measuring method can be applied, the drying can be efficiently dried by high temperature and high air flow, and the second coating layer can be manufactured at low cost. Furthermore, since the change in the capillary force of the pores due to the moisture change of the coating film is small, kaolin, calcined kaolin, calcium carbonate, titanium oxide, wet silica are used for the reason that almost no curling occurs due to environmental changes. Preferably used. Furthermore, it is more preferable to use kaolin that is a plate-like pigment, calcined kaolin, or titanium oxide that is a cubic pigment because a coating layer having high smoothness can be obtained. These pigments may be used alone or in combination of two or more.

In order to obtain good ink absorbability and surface gloss, the pigment of the second coating layer preferably has at least one peak in the pore diameter distribution curve in the range of 0.1 to 10 μm, more preferably 0.8. It is in the range of 1 to 2 μm. If it is smaller than 0.1 μm, the solvent separation effect is lowered, and it is difficult to obtain good ink absorbability, and if it is larger than 10 μm, the smoothness of the recording material may be inferior. A pigment having an average primary particle diameter of 3 to 40 nm and a primary particle having an average primary particle diameter of 5 to 25 nm is preferred. A pigment having a particle size of 1.0 to 2.5 μm is more preferable.
The average particle diameter of the pigment in the second coating layer is preferably 2 to 50 times that of the first coating layer, and preferably 5 to 10 times, since the balance between crack control and ink absorbability is good. It is more preferable.

(Binder for second coating layer)
The binder is not particularly limited, and examples thereof include water-soluble resin binders such as polyvinyl alcohol and water-insoluble synthetic resin latexes. Among these, emulsion type latex is preferably used as a main component, and acrylic emulsion type latex and urethane emulsion type latex are more preferable. By using the polymer latex, the coating film strength is improved, and the coating film hardly becomes brittle due to the influence of the polyvinyl alcohol crosslinking agent contained in the first coating layer. Moreover, there is no problem even if other water-soluble resin binder is contained in order to adjust ink absorbency, paint viscosity, and the like.
The ratio of the pigment to the binder is preferably 10 to 50 parts by mass of the binder with respect to 100 parts by mass of the pigment from the viewpoint of the balance between ink absorbency and coating film strength.

  In addition, each coating layer of the present invention includes a dispersant, a thickener, an antifoaming agent, a colorant, and a fluorescent brightening agent used in general coated paper production in addition to a pigment, a binder, and a cationic compound. In addition, various auxiliary agents such as antistatic agents and preservatives may be appropriately contained.

<Back layer>
In the present invention, a back surface layer is provided on the back surface, which is the other surface side of the base material not provided with the outermost layer, in order to improve the texture of the photograph, the curling prevention of the ink jet recording material, and the transportability. May be. Although it does not specifically limit in a back surface layer, A pigment and binder type | system | group (for example, colloidal silica and acrylic emulsion type binders), an organic emulsion type (for example, acrylic type emulsion type binders), hydrophilicity and hydrophobicity And an adhesive system (for example, a coating film of polyvinyl alcohol), a laminate (for example, polyethylene, etc.) and the like. Among them, a laminate made of polyethylene is most preferably provided because the texture of the photograph is improved.

  Furthermore, a coating layer having the same configuration as the front surface is provided on the back surface, an ink jet recording body or another recording body is bonded to form a double-sided recording body, an adhesive layer is formed on the back surface to form a label, It is possible to apply known means such as bonding to the surface of an IC card to form a card.

[Method for producing inkjet recording material]
The method for producing the ink jet recording material will be described in detail below.

<Formation of coating layer>
In order to form the coating layer, for example, at the same time as applying the coating layer coating liquid containing a pigment and a binder, or during the drying of the coating layer coated with the coating layer coating liquid, Before the coating liquid layer exhibits a decreasing rate of drying, it is effective to produce it by forming a film by thickening or crosslinking the coating liquid.
Specifically, the methods listed in the following (A) to (C) can be exemplified and can be appropriately adopted, but are not limited to these methods.
In addition, the formation method of a coating layer here is not restricted to the 1st coating layer adjacent to the outermost layer.

For example,
(A) It contains a hydrophilic resin that forms a hydrogel by electron beam irradiation, and immediately after coating or in the middle of drying of the coated coating layer, the coating layer is reduced at a reduced rate. Before showing, the method of thickening the coating liquid layer by irradiation with an electron beam (forms a hydrogel),
(B) The coating layer is a coating solution containing a binder, immediately after coating or during the drying of the coated coating layer, before the coating layer exhibits a reduced drying rate. And a method of thickening and crosslinking the coating with a compound having a crosslinking property with the binder,
(C) For example, a thermosensitive polymer compound as a binder (showing hydrophilicity in a temperature range below a certain temperature (temperature sensitive point) described in JP-A-2003-40916), and hydrophobic in a temperature range higher than the temperature sensitive point A method of increasing the viscosity of the coating liquid layer by reducing the temperature of the coating liquid layer immediately after coating,
Etc. can be illustrated.

When forming a coating layer by the method of said (A) and (B), the well-known binder used for inkjet recording bodies can be used as a binder.
Examples thereof include water-soluble resins such as cellulose derivatives such as polyvinyl alcohol, polyvinyl pyrrolidone, casein, soybean protein, synthetic proteins, starch, carboxymethyl cellulose, and methyl cellulose. Among these, polyvinyl alcohol having particularly high adhesion to the pigment is preferably used.
Furthermore, in order to improve the balance between film formability and ink absorbability, it is preferable to use polyvinyl alcohol having a degree of polymerization of 2000 or more, and more preferably polyvinyl alcohol having a degree of polymerization of 3500 to 5000. Further, in order to improve ink absorbency, two or more kinds of binder materials (for example, a mixture of two or more water-soluble resins, a mixture of one or more water-soluble resins and one or more latexes) are used. May be.

  Various known crosslinking agents and gelling agents can be used as the compound having crosslinkability with the binder. Examples of the compound having a crosslinking property to polyvinyl alcohol include aldehyde-based crosslinking agents such as glyoxal, epoxy-based crosslinking agents such as ethylene glycol diglycidyl ether, vinyl-based crosslinking agents such as bisvinylsulfonylmethyl ether, boric acid and borax. Examples include boron-containing compounds, glycidyl compounds, zirconium compounds, aluminum compounds, chromium compounds and the like. Among these, a boron-containing compound is particularly preferable because thickening or gelation occurs quickly.

The boron-containing compound is an oxygen acid having a boron atom as a central atom and a salt thereof. Specific examples include orthoboric acid, metaboric acid, hypoboric acid, tetraboric acid, pentaboric acid, and sodium salts, potassium salts, and ammonium salts thereof. Among these, orthoboric acid and disodium tetraborate are preferably used because they have an effect of appropriately thickening the paint.
Although content of a boron compound is based also on the polymerization degree of a boron compound and polyvinyl alcohol, it is preferable to contain 0.01-2.0 g / m < ² > on the single side | surface of a base material. When the content is 2.0 g / m ² or less, the crosslinking density with the hydrophilic binder does not become too high, and the coating strength can be improved. On the other hand, when the content is 0.01 g / m ² or more, the crosslinking with the hydrophilic binder is strengthened, the gelation of the paint is promoted, and the coating film is hardly cracked.

  The coating layer is prepared by, for example, applying or impregnating a crosslinking agent in advance to the coating layer and applying a coating layer coating liquid, or by blending a crosslinking agent in the coating layer coating liquid. It is manufactured by a method such as a method of applying, or a method of applying a crosslinking agent after applying a coating liquid for a coating layer. Among them, it is preferable to apply a crosslinking agent in advance because thickening or gelation can be caused uniformly.

  The dry solid content mass ratio of the pigment and the binder in the coating layer is preferably 2 to 50 parts by mass with respect to 100 parts by mass of the pigment. Especially, since the balance of ink absorptivity and coating-film intensity | strength becomes further better, it is more preferable that it is 5-30 mass parts, and it is further more preferable that it is 10-25 mass parts. When the amount of the binder is 50 parts by mass or less, the ink absorption speed can be controlled to suppress the occurrence of beading (spotted density unevenness in the solid print part), and the amount of the binder is 2 parts by mass or more. The strength of the coating film can be imparted.

The dry solid coating amount of the coating layer, without limitation, is preferably generally is 1 to 40 g / ^{m 2,} more preferably 3 to 30 g / ^{m 2.} When the coating amount is 1 g / m ² or more, the ink absorbency in a high-definition and high-speed printer is sufficient, and when the coating amount is 40 g / m ² or less, the coating film is less likely to crack. Become.

Examples of the coating apparatus for forming the coating layer include various coating apparatuses such as a blade coater, an air knife coater, a roll coater, a bar coater, a gravure coater, a rod blade coater, a lip coater, a curtain coater, and a die coater.
Moreover, a 2nd coating layer, a 1st coating layer, or a some 2nd coating layer can also be simultaneously coated using a slide bead coater etc. When two or more coating layers are applied, it is preferable to use a method in which the upper layer is applied onto the lower layer while the lower layer is not dried, that is, a wet-on-wet method.
Moreover, as a method of performing electron beam irradiation, (1) coating, electron beam irradiation, and drying are repeated, (2) coating and drying the next layer after electron beam irradiation, and (3) multilayers simultaneously There are methods such as coating and electron beam irradiation.

(ink)
The ink for ink jet recording on the ink jet recording material of the present invention includes a dye for forming an image and a liquid medium for dissolving or dispersing the dye as essential components, and if necessary, various dispersants and interfaces. It is prepared by adding an activator, a viscosity adjuster, a specific resistance adjuster, a pH adjuster, an antifungal agent, a dispersion stabilizer or the like.
Examples of the dye or pigment used in the ink include conventionally known dyes, such as direct dyes, acid dyes, basic dyes, reactive dyes, food dyes, disperse dyes, oil dyes, and various colored pigments. it can.
The contents of the dye and the pigment in the ink are set according to the type of the solvent component of the ink, the characteristics required for the ink, and the like. Also in the case of the ink used for this invention, it can set to 0.1-20 mass% which is content of the dye and pigment in the conventional ink.

  Examples of the ink solvent include water and various water-soluble organic solvents. Examples of the organic solvent include alkyl alcohols having 1 to 4 carbon atoms such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, and isobutyl alcohol; ketones or ketones such as acetone and diacetone alcohol; Alcohols; polyalkylene glycols such as polyethylene glycol and polypropylene glycol; alkylene glycols having 2 to 6 alkylene groups such as ethylene glycol, propylene glycol, butylene glycol, triethylene glycol, thiodiglycol, hexylene glycol and diethylene glycol Amides such as dimethylformamide; ethers such as tetrahydrofuran; glycerin, ethylene glycol methyl ether, diethylene glycol Rumechiru (ethyl) ether, lower alkyl ethers of polyhydric alcohols such as triethylene glycol monomethyl ether, and the like.

  Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. Moreover, unless otherwise indicated, the part and% in an example are solid content except water, and show a mass part and mass%, respectively.

[Paper base]
100 parts by weight of wood pulp (LBKP; freeness 400 ml CSF), 5 parts by weight of calcined kaolin (trade name: Ancilex), 0.05 parts by weight of a commercially available sizing agent, 1.5 parts by weight of a sulfuric acid band, 0. A paper base material consisting of 5 parts by mass and 0.75 parts by mass of starch was used, and a paper substrate having a basis weight of 180 g / m ² was produced by a long net paper machine.

[Resin-coated paper base]
After performing corona discharge treatment on both sides of the paper base, the following polyolefin resin composition 1 mixed and dispersed with a Banbury mixer so that the coating amount is 27 g / m ² on the felt side of the paper base, Moreover, the polyolefin resin composition 2 was apply | coated to the wire surface side of a paper base material with the melt extruder (melting temperature of 320 degreeC) which each has a T-type die so that a coating amount may be 30 g / m < ² >. Subsequently, the felt surface side of the paper base material was cooled and solidified with a mirror cooling roll, and the wire surface side of the paper base material was cooled and solidified with a rough cooling roll.
A resin-coated paper base material having a smoothness (Oken type, J.TAPPI No. 5) of 6000 seconds and an opacity (JIS P 8138) of 93% was produced.

(Polyolefin resin composition 1)
35 parts by mass of long-chain low-density polyethylene resin (density 0.926 g / cm ³ , melt index 20 g / 10 min), 50 parts by mass of low-density polyethylene resin (density 0.919 g / cm ³ , melt index 2 g / 10 min) , 15 parts by mass of anatase-type titanium dioxide (Ishihara Sangyo Co., Ltd., trade name: A-220), 0.1 parts by mass of zinc stearate, 0.03 parts by mass of antioxidant (manufactured by Ciba Geigy, trade name: Irganox 1010), Ultramarine (Daiichi Kasei Co., Ltd., trade name: Aoguchi Ultramarine No. 2000) 0.09 parts by mass, fluorescent whitening agent (Ciba Geigy, trade name: UVITEX OB) 0.3 parts by mass.

(Polyolefin resin composition 2)
High-density polyethylene resin (density 0.954 g / cm ³ , melt index 20 g / 10 minutes) 65 parts by mass, low-density polyethylene resin (density 0.924 g / cm ³ , melt index 4 g / 10 minutes) 35 parts by mass.

[Cationic silica fine particles A]
Gas phase method silica having an average particle size of 1.0 μm (manufactured by Nippon Aerosil Co., Ltd., trade name: Aerosil A300, average primary particle size of about 8 nm) is dispersed by a homomixer and then flowed at high speed until the average particle size reaches 50 nm. The mixture was pulverized and dispersed with a collision type homogenizer to prepare an aqueous dispersion of 10% by mass silica.
10 parts by mass of a cationic compound having a 5-membered ring amidine structure (product name: SC-700, molecular weight 300,000) having a 5-membered ring amidine structure is added to 100 parts by mass of the 10% by mass aqueous dispersion, and a high-speed flow collision type homogenizer is added. And a 10% by mass aqueous dispersion of a silica-cationic compound having an average particle size of 0.10 μm was prepared.

(Example 1)
[Coating fluid A]
18 parts by mass of polyvinyl alcohol (manufactured by Kuraray Co., Ltd., trade name: PVA-235, polymerization degree 3500, saponification degree 88.5%) as a binder is mixed with 100 parts by mass of the cationic silica fine particles A, and an aqueous dispersion ( (Silica concentration 10% by mass) was prepared.
[Coating fluid B]
100 parts by weight of cationic colloidal silica having an average primary particle size of 30 nm (Grace, trade name: SJ4000C), 10 masses of chitosan (Kuraray, trade name: OTS, average molecular weight: 100,000) as a binder and release agent Parts were mixed in water to prepare an aqueous dispersion (silica concentration: 10% by mass).

[Preparation of inkjet recording material]
After coating the coating liquid A on one side of a paper substrate (manufactured by Oji Paper Co., Ltd., marshmallow 209 g / m ² ) so that the coating amount is 20 g / m ² , immediately under a nitrogen gas environment An electron beam with an accelerating voltage of 175 kV and an irradiation dose of 50 kGy was irradiated by an electron beam irradiation apparatus (Electro Curtain manufactured by ESI). The coated surface after irradiation was a jelly-like solid, and was hydrogelled. Subsequently, the hydrogelled coating liquid layer was dried to form a first coating layer.
Furthermore, after coating the coating liquid B on this first coating layer so that the coating amount becomes 2 g / m ² , it is immediately pressed against a mirror drum having a surface temperature of 90 ° C., dried and peeled off. Thus, an ink jet recording material was produced.

(Example 2)
An ink jet recording material was prepared in the same manner as in Example 1 except that the following coating liquid C was used instead of the outermost layer coating liquid B in Example 1.
[Coating fluid C]
Cationic colloidal silica having an average primary particle size of 40 nm (produced by Grace, trade name: SJ4001), 100 parts by weight of emulsion type urethane resin latex (average particle size: 10 nm) as a binder, and chitosan (Kuraray) as a release agent. An aqueous dispersion (silica concentration: 5% by mass) was prepared by mixing 5 parts by mass, manufactured by the company, trade name: OTS, average molecular weight: 100,000) in water.

(Example 3)
In Example 2, an ink jet recording material was produced in the same manner as in Example 2 except that the following coating liquid D was used instead of the outermost layer coating liquid C. The coating amount of the outermost layer was 5 g / m ² .
[Coating fluid D]
Cationic silica fine particles A (average primary particle size 8 nm, average secondary particle size 100 nm) 100 parts by weight, emulsion type urethane resin latex (average particle size: 10 nm) 20 parts by weight as binder, chitosan (Kuraray) as binder and release agent Product name: OTS, average molecular weight: 100,000) 10 parts by weight, cationic release agent (cation-modified polyethylene wax emulsion) 3 parts by weight mixed in water to obtain an aqueous dispersion (silica concentration 15% by weight) Was prepared.

Example 4
After coating the coating liquid E on one surface side of a paper substrate (manufactured by Oji Paper Co., Ltd., marshmallow 209 g / m ² ) so that the coating amount becomes 10 g / m ² , the same as in Example 1 The paint was hydrogelated by irradiation with an electron beam. Immediately pressed onto a mirror drum with a surface temperature of 90 ° C., dried and peeled off to produce an ink jet recording material.
[Coating fluid E]
The chitosan (product name: OTS, average molecular weight: 100,000) of the coating liquid D was changed to chitosan (manufactured by Dainichi Seika Co., Ltd., product name: Daichitosan, average molecular weight: 400,000). It adjusted similarly to the coating liquid D.

(Example 5)
The paper base was changed to the above resin-coated paper base, and after pressing and peeling onto a mirror drum having a surface temperature of 90 ° C. in the same manner as in Example 1, it was dried for 5 minutes in a hot air dryer at 120 ° C. A recording body was produced.

(Example 6)
A second coating layer is previously provided on the paper substrate using the following coating solution F, and a 3% by mass aqueous borax solution is applied to the second coating layer to a dry coating amount of 1.5 g / m ² . It was applied as follows. On top of that, the first coating layer A is applied so that the coating amount (solid content) is 20 g / m ^2. The first coating layer was formed by applying and drying the layer coating.
Next, after coating the coating liquid B on the first coating layer so that the coating amount (solid content) is 2 g / m ² , the surface temperature is 90 ° C. while in a wet state. The ink-jet recording material was produced by pressing against a mirror drum, drying and peeling.
[Coating fluid F]
50 parts by weight of kaolin (manufactured by Engelhard, Inc., trade name: URTLA WHITE 90, average particle diameter 0.7 μm) and titanium oxide (trade name: R-21, average particle diameter 0.5 μm, rutile type, manufactured by Sakai Chemical Co., Ltd.) 30 parts by mass of acrylic resin latex (trade name: JK-7000, manufactured by Meisei Chemical Co., Ltd.) was added to parts by mass to prepare a coating solution F having a solid content concentration of 20% by mass. The coating solution was applied to the paper substrate of Example 1 so as to be 10 g / m ² and dried to obtain a second coating layer.

(Example 7)
The paper substrate (manufactured by Oji Paper Co., Ltd., marshmallow 209 g / ^{m 2)} on one side of, the amount of applying the second coating layer coating solution G was applied so as to 10 g / ^{m 2.} On top of that, the wet-on-wet method (the first coating layer A while the second coating layer is not dried) is applied so that the coating amount A (solid content) of the first coating layer coating liquid A is 20 g / m ² . The first and second coating layers were formed by applying and drying the coating layer paint).
Next, after coating the coating liquid B on the first coating layer so that the coating amount (solid content) is 2 g / m ² , the surface temperature is 90 ° C. while in a wet state. The ink-jet recording material was produced by pressing against a mirror drum, drying and peeling.
[Coating fluid G]
50 parts by weight of kaolin (manufactured by Engelhard, Inc., trade name: URTLA WHITE 90, average particle diameter 0.7 μm) and titanium oxide (trade name: R-21, average particle diameter 0.5 μm, rutile type, manufactured by Sakai Chemical Co., Ltd.) 30 parts by mass of acrylic resin latex (trade name: JK-7000, manufactured by Meisei Chemical Co., Ltd.) and 13 parts by weight of borax were added to parts by mass to prepare a coating liquid G having a solid content concentration of 20% by mass.

(Example 8)
Inkjet recording was carried out in the same manner as in Example 1 except that 10 parts by mass of chitosan (trade name: OTS, average molecular weight: 100,000) of coating liquid B of Example 1 was changed to 0.3 parts by mass. The body was made.

Example 9
An ink jet recording material was prepared in the same manner as in Example 1 except that 10 parts by mass of chitosan (product name: OTS, average molecular weight: 100,000) of coating liquid B of Example 1 was changed to 35 parts by mass. Produced.

(Example 10)
An ink jet recording material was produced in the same manner as in Example 1 except that chitosan (product name: OTS, average molecular weight: 100,000) of coating liquid B of Example 1 was changed to chitosan having a molecular weight of 5000. .

(Comparative Example 1)
The outermost layer was coated on the first coating layer with a bar so as to be ² g / m ² , dried for 5 minutes with a 120 ° C. hot air dryer, and cast-treated in the same manner as in Example 1. An ink jet recording material was prepared.

(Comparative Example 2)
An ink jet recording material was produced in the same manner as in Example 1 except that chitosan was not added to the outermost layer coating material of Example 1.

(Comparative Example 3)
An ink jet recording material was prepared in the same manner as in Example 2 except that the colloidal silica of Example 1 was changed to acidic anionic colloidal silica (manufactured by Nissan Chemical Co., Ltd., trade name: ST-OL, average primary particle size 40 nm). Produced.

<Evaluation method>
The ink absorbability of the ink jet recording material, the color developability of the recorded image, the glossiness, the pigment ink suitability, and the cast suitability were evaluated by the following methods, and the results are shown in Table 1.
The evaluation of the color developability of the recorded image was performed by measuring the color density of the recorded image.

For the ink jet printer, EPSON, trademark: PM-G820, printing mode: EPSON photographic paper, high-definition mode were used.
In addition, only in the case of evaluating the suitability of the pigment ink, a trademark: PX-G900, printing mode: EPSON photographic paper, and clean mode were used.

"Ink absorbability (beading)"
Green ink was solid-printed on the ink jet recording medium, and whether or not there were spots in the solid-printed image was visually observed and evaluated in the following three stages.
Print spots are a phenomenon that occurs when the ink that has been struck first is not completely absorbed by the coating layer of the ink jet recording body, and the next ink comes and overlaps the surface, and the ink absorption speed is slow. Then, it will appear prominently.
A: No printed spots are seen.
○: A slight level of printed spots is observed, but there is no practical problem.
X: There are many printing spots and there are practical problems.

“Color development of printed images (print density)”
The ink jet recording medium was solid-printed with black ink, and the color density was measured with a Macbeth reflection densitometer (model: Gretag Macbeth RD-19, manufactured by Macbeth). Only when measuring the color density, the printing mode was set to EPSON photo paper, clean mode, and no color correction.

"Glossiness"
An ISO-400 image ("high-definition color digital standard image data ISO / JIS-SCID", p13, image name: fruit basket) is printed on an inkjet recording medium, and the image is inclined with respect to the surface of the recording medium. The visual angle was evaluated from the angle, and the evaluation was made in the following four stages.
A: There is a glossiness similar to that of a silver salt photograph.
○: High glossiness, but inferior to silver salt photography.
X: There is not much glossiness like a printing paper.

“Pigment ink suitability”
Immediately after printing with black pigment ink on the ink jet recording material, the printed portion was immediately rubbed with gauze, and the fixability of the pigment ink was evaluated in the following three stages.
A: The printed part is not affected at all.
○: The pigment ink is slightly attached to the gauze, but there is no practical problem.
X: The printed part is wiped off with gauze, and there is a problem in practical use.

"Cast aptitude"
After the ink jet recording body was peeled from the mirror drum, it was evaluated according to the following criteria whether or not the pigment on the surface layer of the ink jet recording body remained on the mirror surface.
A: None at all.
○: Slightly seen.
X: Dirt is seen and there is an operational (practical) problem.

Claims (5)

An inkjet recording medium having a base material and at least one coating layer formed on the base material, wherein at least the outermost layer of the recording material contains cationic silica and chitosan, and the outermost layer is wet An ink jet recording material that has been pressure-bonded with a heated mirror drum while in a state. 2. The ink jet recording material according to claim 1, wherein the cationic silica contains 70 to 100 mass% of cationic colloidal silica having an average primary particle diameter of 10 to 100 nm. The cationic silica contains 70 to 100% by mass of a cationic gas phase method silica having an average primary particle diameter of 7 to 20 nm and an average secondary particle diameter of 700 nm or less. The inkjet recording body as described. The inkjet recording material according to claim 1, wherein the chitosan is blended in an amount of 0.5 to 30 parts by mass with respect to 100 parts by mass of the cationic silica. The ink jet recording material according to claim 1, wherein the chitosan has a molecular weight of 10,000 to 500,000.