JP5921419B2 - Inkjet recording paper - Google Patents

Description

  The present invention relates to an ink jet recording paper having good ink absorptivity and image sharpness not only for dye ink but also for pigment ink.

  The ink jet recording system is a system in which ink droplets are ejected and deposited on recording paper to form dots and recording is performed. In recent years, recording with high print quality has become possible due to technological advances in ink jet printers, inks, and recording media. If ordinary plain paper has a certain size or more, it can be expected to have a certain level of print quality with little bleeding, but if higher print quality is required, ink suitable for ink jet printer ink on the medium A dedicated medium having a receiving layer provided on various substrates is used. These ink-jet recording media include paper and / or film as a support, a medium having a pigment coating layer mainly composed of a pigment and a binder (void-type medium), or a resin coating that does not contain a pigment. A medium (swelling medium) provided with a layer on the surface is often used.

  The ink jet recording medium is further classified into a matte medium and a glossy medium from the surface state. The latter glossy medium is used when image quality closer to silver halide photography is required. As a general method for producing a glossy medium, there are a method of forming an ink receiving layer by a cast coating method and imparting gloss to the surface, and a method of forming an ink receiving layer on a photographic paper substrate.

  When the latter substrate for photographic paper is generally called RC paper (resin-coated paper), a polyethylene film layer is formed on the paper substrate, and therefore when an ink receiving layer is formed on the surface thereof, Since the film surface is smooth, the surface of the ink receiving layer is also smooth, and a glossy surface is easily formed. However, the total cost is that it is necessary to increase the coating amount of the ink receiving layer in order to increase the ink absorbency, and since the base material itself is more expensive than paper, it is necessary to use the former cast coating method for glossy media. Compared to higher prices. In addition, when it is discarded, there is a problem that it cannot be recycled because it is a composite material. From an ecological point of view, gloss media manufactured by the cast coating method, which can be recycled on a paper basis, has an advantage. is there.

  On the other hand, as ink for inkjet printers, not only dye inks using dye colorants, which have been the mainstream in the past, but also pigment inks in which colored pigments with excellent storage stability such as water resistance and light resistance are used are used. It has become. These pigment inks have an average particle diameter of about 50 to 100 nm and 5 to 10 times the size of the dye molecule, so that the absorption speed is inevitably different. Therefore, it is necessary to design a coating layer in order to truly improve the color of the pigment ink.

  As a conventional technique, there is a proposal of an ink jet paper in which the color development is improved by defining the surface zeta potential of the ink jet recording paper that is mainly recorded with pigment ink (see, for example, Patent Document 1). In addition, there is a proposal of an ink jet recording paper that improves the color developability by defining the smoothness of the ink receiving layer for the ink jet recording paper that performs recording with pigment ink (see, for example, Patent Document 2).

Japanese Patent Laid-Open No. 2003-21833 JP 2001-96907 A

  However, in the case of the technique described in Patent Document 1, the medium is not a void type but a so-called plain paper, and a photographic image is printed, and the ink-jet paper does not have a good color developability.

  Further, even in the case of the technique described in Patent Document 2, the color developability of the pigment ink is insufficient.

  Therefore, from the research results of the present inventors, it has been concluded that it is difficult for the proposed content to have good color development when a photographic image is printed with pigment ink.

  An object of the present invention is to provide an ink jet recording paper having good ink absorptivity and image sharpness not only for dye ink but also for pigment ink.

The ink jet recording paper according to the present invention is an ink jet recording paper in which an ink receiving layer containing a pigment and a binder is provided on at least one side of a substrate, and is determined by a BJH method from a nitrogen desorption isotherm of the ink receiving layer. In addition, the maximum value (peak) of the pore diameter distribution curve exists only in the range of 40 to 90 nm , and the pigment is vapor phase silica (A) having an average primary particle diameter of 5 to 12 nm and an average primary particle diameter of 15 to 25 nm gas phase method silica (B), wherein the mass ratio A: B of the gas phase method silica (A) and the gas phase method silica (B) is in the range of 20:80 to 80:20. .

In the ink jet recording paper according to the present invention, the total pore volume of the ink receiving layer determined by the BJH method from the nitrogen desorption isotherm of the ink receiving layer is preferably 10 to 35 cm ³ / m ² . It becomes possible to further improve the color developability of the pigment ink.

  The present invention can provide a recording medium excellent in color developability of not only a dye ink but also a pigment ink.

  Next, the present invention will be described in detail with reference to embodiments, but the present invention is not construed as being limited to these descriptions. As long as the effect of the present invention is exhibited, the embodiment may be variously modified.

  The inkjet recording paper according to the present embodiment is the maximum of the pore diameter distribution curve obtained by the BJH method from the nitrogen desorption isotherm of the ink receiving layer in the ink jet recording paper provided with the ink receiving layer on at least one side of the substrate. The value (peak) exists only in the range of 40 to 90 nm. More preferably, it is in the range of more than 43 nm and less than 80 nm, and more preferably in the range of only 50 to 70 nm. Here, whether or not the maximum value (peak) is in the range of 40 to 90 nm is determined by whether or not the value at the top position of the peak is in the range of 40 to 90 nm. Therefore, the value at the bottom of the peak may be out of the range of 40 to 90 nm. The ink jet recording paper according to the present embodiment achieves both high ink absorption and high image clarity of pigment ink. When the maximum value (peak) is less than 40 nm, the absorptivity and image clarity of the pigment ink are inferior. When the maximum value (peak) is in a range exceeding 90 nm, the pigment ink is blurred white and image clarity is poor. In the present invention, if it is in the range of 40 to 90 nm, it may have two or more peaks, but it is preferably one peak. More preferably, it is a single peak (mono peak) and the half width of the peak is less than 50 nm. The half width of the peak is more preferably 45 nm or less. In a broad peak where the half width of the peak exceeds 50 nm, the image clarity of the dye ink deteriorates.

It is preferable that the total pore volume of the ink receiving layer determined by the BJH method from the nitrogen desorption isotherm of the ink receiving layer is 10 to 35 cm ³ / m ² . More preferably, it is 15-30 cm < ³ > / m < ² >. When the total pore volume is less than 10 cm ³ / m ² or more than 35 cm ³ / m ² , the image clarity of the pigment ink is inferior. In the present invention, the total pore volume is obtained by the following calculation (Equation 1) from the pore volume value obtained by the BJH method from the nitrogen desorption isotherm and the coating amount.
(Equation 1) Total pore volume (cm ³ / m ² ) = Pore volume value (cm ³ / g) × Coating amount (g / m ² )
Here, the total pore volume when the ink receiving layer is provided on both sides means a numerical value relating to the coating layer per one side. Here, the ink receiving layer may have two or more layers. Hereinafter, when there are two or more ink receiving layers, the outermost layer of the ink receiving layer may be simply referred to as the “outermost layer”. The ink receiving layer closest to the paper substrate is referred to as “undercoat layer”. When there are three or more ink receiving layers, a layer between the outermost layer and the undercoat layer is referred to as an “intermediate layer”.

  In the present embodiment, the method for measuring the pore diameter distribution of the ink receiving layer is a nitrogen adsorption method. The nitrogen adsorption method is a method in which nitrogen molecules having a known size or property are adsorbed on a solid surface, the amount of adsorbed gas molecules is measured, and pore diameter distribution and total pore volume are obtained. Unlike the mercury intrusion method, the nitrogen adsorption method can measure only a very small pore diameter (for example, 0.1 to 100 nm). Only the pore diameter can be measured easily. In the prior literature, there is an example in which the pore distribution and pore volume of the coating layer are regulated by the mercury intrusion method, but since the reproducibility in the region of 0.1 to 100 nm is doubtful, the numerical reliability It is thought that it is scarce. Therefore, in this invention, it measures using the nitrogen adsorption method about the measurement of pore distribution and pore volume. In this embodiment, the pore diameter distribution and the total pore volume were determined by the BJH method from the isothermal curve during nitrogen desorption. An example of a commercially available measuring device is the Tristar II 3020 series (manufactured by Shimadzu Corporation).

  Moreover, in this embodiment, the maximum value (pore diameter peak) of the pore diameter distribution curve can be adjusted by changing various conditions as long as the effect of the present invention is exhibited. The maximum value of the pore diameter distribution curve can be adjusted in the range of 40 to 90 nm using the type, particle diameter, and BET specific surface area of the pigment contained in the ink receiving layer as control factors. For example, the maximum value of the pore diameter distribution curve decreases as the BET specific surface area of the pigment (type that forms secondary particles) increases. In addition, the maximum value of the pore diameter distribution curve increases as the particle diameter of a pigment (a type that does not form secondary particles) such as colloidal silica increases. The types of pigment will be exemplified later. Further, in this embodiment, as a means for controlling the maximum value, the ink receiving layer mainly comprises secondary particle pigments having an average primary particle diameter of 5 to 40 nm and a binder, and the average It is preferable to contain two or more pigments having different primary particle sizes. The peak in the range of 40 to 90 nm can be made a preferable one (mono peak), and the maximum value is easy to control. Preferably, the secondary particle pigment (A) having an average primary particle size of 5 to 12 nm and the secondary particle pigment (B) having an average primary particle size of 15 to 25 nm are in a mass ratio of A: B = 20: 80 to 80:20. It is preferable to mix with. It is more preferable to mix at a mass ratio of A: B = 30: 70 to 70:30. Here, the average particle diameter of the secondary particle pigment is preferably 50 to 500 nm, and more preferably 60 to 300 nm. By using a pigment forming secondary particles, there is an advantage that the ink absorbability is easily increased. As will be described later, the secondary particle pigment is more preferably gas phase method silica. The average primary particle size can be determined with an electron microscope. The average secondary particle diameter can be determined by a dynamic light scattering method. Further, as a means for controlling the maximum value, the ink receiving layer may be mainly composed of a secondary particle pigment having an average primary particle diameter of 10 to 25 nm and a binder. The maximum value can be made to be in the range of 40 to 90 nm by using secondary particle pigments in the range of the average primary particle diameter narrowly limited to 10 to 25 nm, and one peak (monopeak) Can be.

  In the present embodiment, the pigment contained in the ink receiving layer includes gas phase method silica, spherical colloidal silica, non-spherical colloidal silica, synthetic amorphous silica, alumina modified silica, γ-alumina, θ-alumina, σ- Alumina and pseudo boehmite. These may be used alone or in combination of two or more as long as the effects of the present invention are not impaired.

  In the present embodiment, it is preferable that gas phase method silica is mainly used as the pigment of the ink receiving layer. Vapor phase method silica is also called dry method silica or fumed silica, and is generally produced by flame hydrolysis. Specifically, it is manufactured by gas phase hydrolysis of volatile silane compounds such as silicon tetrachloride in an oxyhydrogen flame, and conditions such as flame temperature, supply ratio of oxygen and hydrogen, supply of raw material silicon tetrachloride, etc. Obtained by changing.

The BET specific surface area of the vapor phase method silica is preferably 100 to 400 m ² / g. By setting the BET specific surface area within this range, it is easy to adjust the maximum value of the pore diameter distribution curve to a range of 40 to 90 nm. More preferably, it is 150-380 m < ² > / g, Most preferably, it is 180-350 m < ² > / g. When the BET specific surface area is less than 100 m ² / g, the image clarity of the pigment ink may be inferior. When the BET specific surface area exceeds 400 m ² / g, the viscosity of the coating solution may be too high, resulting in poor stability. Here, the BET specific surface area is a surface area per unit mass determined by the BET method. The BET method is a method for measuring the specific surface area of a powder by a gas phase adsorption method, and is a method for obtaining the total surface area, that is, the specific surface area of a 1 g sample from an adsorption isotherm. Usually, nitrogen gas is often used as the adsorbed gas, and the most frequently used method is to measure the amount of adsorption from the change in pressure or volume of the gas to be adsorbed. The most prominent expression for expressing the isotherm of multimolecular adsorption is the Brunauer, Emmett, and Teller equation, called the BET equation, which is widely used for determining the surface area. The adsorption amount is obtained based on the BET equation, and the surface area is obtained by multiplying the area occupied by one adsorbed molecule on the surface.

  Examples of the binder contained in the ink receiving layer include polyvinyl alcohol (including modified polyvinyl alcohols such as carboxyl-modified polyvinyl alcohol and silanol-modified polyvinyl alcohol), polyvinyl acetal, oxidized starch, etherified starch, carboxymethyl cellulose, Hydroxyethyl cellulose, casein, gelatin, soy protein, polyethyleneimide resin, polyvinylpyrrolidone resin, polyacrylic acid or copolymer thereof, maleic anhydride copolymer, acrylamide resin, acrylate resin, polyamide resin, Acrylic resin, styrene-acrylic resin, polyurethane resin, polyester resin, polyvinyl butyral resin, alkyd resin, epoxy resin, epichlorohydrin resin Acrylic polymer latex such as styrene-butadiene copolymer, methyl methacrylate-butadiene copolymer, acrylic acid ester, methacrylic acid ester polymer or copolymer, vinyl type such as ethylene-vinyl acetate copolymer Polymer latex, composite resin of colloidal silica and acrylic resin, composite resin of colloidal silica and styrene-acrylic resin. These may be used alone or in combination of two or more. Polyvinyl alcohol is preferably contained from the viewpoint of achieving both ink absorbability and excellent gloss. The amount of the binder used is determined in consideration of printability of the recording medium, strength of the ink receiving layer, surface glossiness, coating liquid properties, and the like. The content of the binder in the ink receiving layer is preferably in the range of 1 to 100 parts by weight with respect to 100 parts by weight of the pigment in the ink receiving layer. More preferably, it is 5 to 60 parts by mass with respect to 100 parts by mass of the pigment in the ink receiving layer, and further preferably 10 to 50 parts by mass with respect to 100 parts by mass of the pigment in the ink receiving layer. If it is less than 1 part by mass, the coating layer strength may decrease. If it exceeds 100 parts by mass, the ink absorbability may decrease.

  In the present invention, the ink receiving layer preferably contains a cationic polymer as an ink fixing agent. By containing a cationic polymer in the ink receiving layer, the water resistance of the ink can be improved. Cationic polymers used in the present invention include, for example, polyethyleneimine, epichlorohydrin-modified polyalkylamine, polyamine, polyamine polyamide epichlorohydrin, dimethylamine ammonia epichlorohydrin, polyvinylbenzyltrimethylammonium halide, polydiacryldimethylammonium halide, polydimethylaminoethyl methacrylate hydrochloride Salt, polyvinylpyridium halide, cationic polyacrylamide, cationic polystyrene copolymer, diallyldimethylammonium chloride polymer, diallyldimethylammonium chloride sulfur dioxide copolymer, diallyldimethylammonium chloride amide copolymer, dicyandiamide formalin polycondensate , Dicyandiamide diethylenetriamine polycondensate , Polyallylamine, polydiallylamine, polyallylamine hydrochloride, polyacrylamide resin, polyamide epoxy resin, melamine resin acid colloid, urea resin, cationic modified polyvinyl alcohol, amino acid type amphoteric surfactant, betaine type compound, polyamidine compound, Other quaternary ammonium salts and cation-modified polyurethane resins. These may be used alone or in combination of two or more. Examples of the method of adding the cationic polymer to the ink receiving layer include a method of adding it to the ink receiving layer forming coating material, and a case where the outermost layer of the ink receiving layer is dried by a cast coating method. A method of adding to the liquid or the rewetting liquid is also possible. When blended in the ink-receiving layer-forming coating material, it is preferable to add at the time of pigment dispersion from the viewpoint of maintaining the stability of the coating material and the uniformity of the pores. In addition, when the outermost layer of the ink receiving layer is dried by the cast coating method, both addition to the ink receiving layer forming coating and addition to the coagulating liquid or rewet liquid may be performed. . In the present embodiment, the content of the cationic polymer is preferably 0.05 to 20% by mass with respect to the dry mass of the ink receiving layer. If it is less than 0.05% by mass, the water resistance may be inferior. If it exceeds 20% by mass, the ink absorbability may deteriorate. Here, the dry weight of the ink receiving layer is the dry weight of the layer when the ink receiving layer is one layer, and the total of the dry weight of each layer when the ink receiving layer is two or more layers. It is the ratio of mass. The content of the cationic polymer is the ratio of the total mass of all the cationic polymers when two or more cationic polymers are used in combination. Further, when the ink receiving layer has two or more layers and the cationic polymer is blended in a plurality of layers, the ratio is the ratio of the total mass of all cationic polymers to the total mass of all ink receiving layers.

  Examples of the coating method of the coating liquid for forming the ink receiving layer of the present embodiment include an air knife coater, roll coater, reverse roll coater, bar coater, comma coater, blade coater, die coater, and simultaneous multilayer coater. There are known coating machines, but any one may be used.

The coating amount (absolute dry mass) of the ink receiving layer is preferably 5 to 40 g / m ² per side. More preferably, it is 10-35 g / m < ² >, More preferably, it is 15-30 g / m < ² >. If it is less than 5 g / m ² , the ink absorbability may be inferior. If it exceeds 40 g / m ² , the mechanical strength of the coated surface may be insufficient.

  In the ink jet recording paper according to this embodiment, when it is desired to produce a paper having a glossy ink receiving layer surface, so-called ink jet glossy paper, the outermost layer of the ink receiving layer is preferably formed by drying by a cast coating method. As the cast coating method, a wet method, a coagulation method, and a rewet method are known. In the present embodiment, the coagulation method or the rewet method is preferable, and the coagulation method is more preferable. The coagulation method is a method in which a coagulation liquid is applied and coagulated while the coating layer is in a wet state, and is pressed against a cast drum and dried. In the coagulation treatment, it is important to select a coagulant that effectively coagulates with the binder component of the ink receiving layer. In this embodiment, the binder is preferably polyvinyl alcohol. The coagulant is preferably a boron compound. More preferably, either or both of sodium borate and boric acid are used. As the polyvinyl alcohol, silanol-modified polyvinyl alcohol is preferably used. By containing silanol-modified polyvinyl alcohol, it is possible to reduce cracks in the coating layer and to improve the image clarity of the pigment ink. Moreover, it is preferable that the concentration of the coagulation liquid is high because the coagulation force is increased and the scratch resistance is further improved. The solid content concentration of the coagulation liquid is preferably 1% by mass or more. More preferably, it is 1.5 mass% or more. The upper limit of the concentration of the coagulating liquid is preferably 10% by mass from the viewpoint of workability and cost. The content of the coagulant is preferably 5% by mass or more based on the binder that can coagulate. When the amount is less than 5% by mass, the surface strength may decrease. The content of the coagulant is more preferably 10% by mass or more. The binder capable of coagulation is a binder in the outermost layer of the ink receiving layer. The content of the coagulant is preferably 100 parts by mass or less with respect to 100 parts by mass of the binder capable of coagulation. If it exceeds 100 parts by mass, the coagulant becomes excessive with respect to the binder, which is uneconomical. Although the solidification method has been described so far, in the present embodiment, the ink receiving layer may be dried by a rewetting method. The rewet method is a method in which the outermost layer of the ink receiving layer is coated and dried, and then the coated layer is wetted with a rewet liquid and pressed against the cast drum.

  When the outermost layer of the ink receiving layer is dried by the cast coating method, a glossy surface having high image clarity can be formed by adjusting the cast drum temperature, the pressure during pressure bonding, and the line speed. About these various conditions, it can optimize by calculating | requiring optimal conditions according to the installation to be used and a coating liquid.

  After the casting process, calendar processing such as machine calendar, soft calendar, super calendar, etc. may be performed, and for curling adjustment, water, curling agent etc. are coated on the back side, or humidification is performed to adjust curling. You can also.

  The ink receiving layer may be provided on one side of the substrate or on both sides. By providing on both sides, it can be used for double-sided printing. When provided on both sides, the composition of each side may be the same or different. However, the pore distribution and pore volume values defined in the present invention are the measurement results of the ink receiving layer per side.

  Any substrate can be used in the present invention. In addition, as described above, from the viewpoint of ecology, the ink jet recording paper based on recyclable paper is superior. Examples of the paper base material used in the present embodiment are high-quality paper, medium-quality paper, and white paperboard. Acid paper, neutral paper, and the like can also be used. In the present embodiment, it is desirable to use ECF (Elemental Chlorine Free) pulp or TCF (Total Chlorine Free) pulp with less environmental impact. In addition, as a filler to be included in the paper substrate, heavy calcium carbonate, light calcium carbonate, magnesium carbonate, titanium oxide, synthetic silica, alumina, talc, calcined kaolin clay, kaolin clay, bentonite, zeolite, aluminum hydroxide, Known fillers such as zinc oxide can be used.

  In addition to pulp and filler, various papermaking chemicals such as known paper strength agents, sulfuric acid bands, yield improvers, sizing agents, dyes, and fluorescent dyes may be appropriately used in the paper stock. The preparation method, blending method, and addition method of each papermaking chemical for each paper stock are not particularly limited as long as the effects of the present invention are not impaired. In addition, it is possible to make paper using a well-known paper machine such as a circular net paper machine, a long net paper machine, or a twin wire paper machine using a paper material. . Furthermore, it is also possible to mix waste paper with the paper base material as long as the effects of the present invention are not impaired.

  It is preferable to apply a known water-soluble polymer such as starch, polyvinyl alcohol, or polyacrylamide to the paper base material with a size press or the like in order to suppress excessive penetration of the coating liquid.

  Next, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples. In the examples, “parts” and “%” represent “parts by mass” and “mass%”, respectively, unless otherwise specified. The number of added parts is a value in terms of solid content.

Example 1
(Formation of paper substrate)
100 parts of hardwood bleached kraft pulp (Canadian standard freeness of 500 ml CSF), 1.0 part of cationic starch (Neotac # 40T, manufactured by Nippon Shokuhin Kako Co., Ltd.), 0.15 part of acidic rosin sizing agent, and liquid sulfuric acid band 0 .5 parts and talc (talc NTL: manufactured by Nihon Talc Co., Ltd.), the amount of which was adjusted so as to have an ash content of 8%, were blended to obtain a paper material. This stock was made using a long paper machine to obtain a paper web. Thereafter, oxidized starch (MS # 3800: manufactured by Nippon Food Chemical Co., Ltd.) as a sizing solution was applied on both sides of the paper substrate with a size press so that the dry coating amount was 1.0 g / m ² per side, and a cylinder dryer was used. Dried. Thereafter, surface treatment was performed using a steel calender under the conditions of a linear pressure of 40 kg / cm, 25 ° C., and 2 nips and 1 pass to produce high-quality paper (acidic paper) having a basis weight of 180 g / m ² and used as a paper substrate. .

(Formation of ink receiving layer)
Vapor phase method silica (Leoroceal QS-40, average primary particle size 7 nm, BET specific surface area 400 m ² / g: manufactured by Tokuyama) as a pigment, Vapor phase method silica (Leosea QS-09, average primary particle size 22 nm, BET) A specific surface area of 100 m ² / g: manufactured by Tokuyama Co., Ltd.) and 50 parts of cationic diallyldimethylammonium chloride polymer (Unisense CP-103: manufactured by Senka Co., Ltd.) were dispersed in water to obtain a slurry having a solid content concentration of 20%. . Next, with respect to 100 parts of the pigment, 15 parts of polyvinyl alcohol (PVA-235, saponification degree 87 mol%: manufactured by Kuraray Co., Ltd.) was blended and stirred with respect to 100 parts of the pigment, and the ink was received with a solid concentration of 18%. A layer coating solution was obtained. This ink receiving layer coating solution was applied to the surface of the paper substrate so that the dry coating amount was 25 g / m ² .

(Example 2)
In Example 1, as a pigment, gas phase method silica (Reosileal QS-102, average primary particle size 12 nm, BET specific surface area 200 m ² / g: manufactured by Tokuyama Corporation), gas phase method silica (Reoloseal QS-10, average primary) Inkjet recording paper was prepared under the same conditions as described in Example 1 except that the particle diameter was 15 nm and the BET specific surface area was 150 m ² / g (made by Tokuyama).

( Reference Example 3)
In Example 1, the same conditions as described in Example 1 except that 100 parts of gas phase method silica (Leosil QS-102, average primary particle size 12 nm, BET specific surface area 200 m ² / g: manufactured by Tokuyama Corporation) was used as the pigment. Inkjet recording paper was prepared.

( Reference Example 4)
In Example 1, the same conditions as described in Example 1 except that 100 parts of gas phase method silica (Leosil QS-09, average primary particle diameter 22 nm, BET specific surface area 100 m ² / g: manufactured by Tokuyama Corporation) was used as the pigment. Inkjet recording paper was prepared.

(Example 5)
In Example 1, as a pigment, gas phase method silica (Leorosil QS-102, average primary particle size 12 nm, BET specific surface area 200 m ² / g: manufactured by Tokuyama Corporation), gas phase method silica (Leolosil QS-09, average primary) Inkjet recording paper was prepared under the same conditions as described in Example 1 except that the particle diameter was 22 nm and the BET specific surface area was 100 m ² / g (manufactured by Tokuyama).

(Example 6)
In Example 1, as a pigment, gas phase method silica (Reolocyl QS-40, average primary particle diameter 7 nm, BET specific surface area 400 m ² / g: manufactured by Tokuyama Corporation), gas phase method silica (Reoloseal QS-09, average primary) Inkjet recording paper was prepared under the same conditions as described in Example 1 except that the particle diameter was 22 nm and the BET specific surface area was 100 m ² / g (produced by Tokuyama).

(Example 7)
In Example 1, as a pigment, gas phase method silica (Leoroceal QS-40, average primary particle diameter 7 nm, BET specific surface area 400 m ² / g: manufactured by Tokuyama Corporation), gas phase method silica (Reosileal QS-09, average primary) An ink jet recording paper was prepared under the same conditions as described in Example 1 except that the particle diameter was 22 nm and the BET specific surface area was 100 m ² / g (made by Tokuyama).

(Example 8)
An ink receiving layer coating solution similar to that in Example 1 was prepared. This coating solution was applied to the surface of the paper base so that the dry coating amount was 25 g / m ^2, and then boric acid as a coagulant was 1.0% and sodium borate was 1.0%. An aqueous solution containing the solution was further applied as a coagulation liquid (concentration of the coagulation liquid was 2.0%) so that the coating amount was 1.0 g / m ^2, and the coagulation treatment was performed. While it was wet, it was pressed against a cast drum having a surface temperature of 105 ° C. to produce a glossy inkjet recording paper.

(Comparative Example 1)
In Example 1, the same conditions as described in Example 1 except that 100 parts of gas phase process silica (Leolosil QS-40, average primary particle diameter of 7 nm, BET specific surface area of 400 m ² / g: manufactured by Tokuyama Corporation) was used as the pigment. Inkjet recording paper was prepared.

(Comparative Example 2)
Inkjet recording paper was prepared under the same conditions as described in Example 1, except that 100 parts of colloidal silica (Snowtex AK, average primary particle size 15 nm: manufactured by Nissan Chemical Industries, Ltd.) was used as the pigment in Example 1.

(Comparative Example 3)
Inkjet recording paper was prepared under the same conditions as described in Example 1, except that 100 parts of colloidal silica (Snowtex AK-L, average primary particle size 50 nm: manufactured by Nissan Chemical Industries, Ltd.) was used as the pigment in Example 1. .

(Comparative Example 4)
In Example 1, the same conditions as described in Example 1 were used except that the gel method synthetic silica (thyroid 74X5500, average secondary particle size 50 nm, BET specific surface area 350 m ² / g: manufactured by Grace) was used as the pigment. Inkjet recording paper was prepared.

(Comparative Example 5)
In Example 1, 50 parts of gel method synthetic silica (thyloid 74X5500, average secondary particle diameter 50 nm, BET specific surface area 350 m ² / g: manufactured by Grace) as a pigment, gas phase method silica (Rheolosil QS-09, average primary particles) Inkjet recording paper was prepared under the same conditions as described in Example 1 except that the diameter was 22 nm and the BET specific surface area was 100 m ² / g (made by Tokuyama).

  The obtained ink jet recording paper was subjected to the following test, and the results are shown in Table 1 (Example) and Table 2 (Comparative Example).

(1) Measurement of pore diameter distribution and total pore volume of ink receiving layer (maximum pore diameter of pore diameter distribution curve, total pore volume of ink receiving layer):
After the obtained ink jet recording paper is cut into a plurality of small pieces having a size of about 3 mm × 3 mm, about 1 g is vacuum degassed at 105 ° C. and 10 Pa or less for 12 hours, and then a pore distribution measuring device by nitrogen adsorption method The pore diameter distribution and the pore volume value were measured using Tristar II 3020 (manufactured by Shimadzu Corporation). The total pore volume of the present invention is determined by the following calculation (Equation 1).
(Equation 1) Total pore volume (cm ³ / m ² ) = Pore volume value (cm ³ / g) × Coating amount (g / m ² )
Here, the total pore volume when the ink receiving layer is provided on both sides means a numerical value relating to the coating layer per one side. In this measurement method, since the pores of the paper substrate are too large and are not substantially measured and can be ignored, the pore volume value obtained by the measurement is used as the total pore volume value of the ink receiving layer. . For the same reason, the pore diameter distribution obtained by measurement was used as the pore diameter distribution of the ink receiving layer.

  Based on the pore diameter distribution curve obtained by the BJH method from the nitrogen desorption isotherm of the ink receiving layer, the maximum (peak) pore diameter was determined as follows. The background line is drawn in the range of the pore diameter of 0 to 100 nm. Using the background line as a reference, the maximum value (peak) height (“height” corresponds to intensity) and the maximum value of the pore diameter distribution curve are measured. When there was one peak, the maximum value of the pore diameter distribution curve was read. If there are two or more peaks, select the maximum value (peak) having a height of 5% or more of the peak height of the maximum intensity, and read all the pore diameters of the selected maximum value (peak). It was. Note that when there are two peaks in the pore distribution curve, for example, the maximum value of one pore diameter distribution curve is 15 nm and the maximum value of the other pore diameter distribution curve is 23 nm, Table 1 and In Table 2, “15, 23” and the maximum value of each pore diameter distribution curve are also shown. Moreover, the half width was measured only when the peak was a single peak.

(2) Image clarity of dye ink:
ISO standard image (ISO / JIS-SCID high-definition color digital standard image data, image name: portrait, image identification number: N1) using a dye ink dedicated inkjet printer (PM-T960: manufactured by Seiko Epson Corporation) Then, printing was performed on the obtained ink jet recording paper. The printed image was visually evaluated.
A: The recorded image is very clear and clear in contrast, and can be used (practical level).
○: The recorded image is clear and the contrast is clear, so that it can be used (practical level).
Δ: The contrast of the recorded image is clear, but the print density is low and the image is not clear (impractical level).
X: The contrast of the recorded image is not clear, the print density is extremely low, and the sharpness is extremely poor (practical level).

(3) Absorption of dye ink:
Using a dye ink dedicated ink jet printer (PM-T960: manufactured by Seiko Epson Corporation), using each ink of CMYK, solid (100% density) and characters of each ink of CMYK, and RGB (Red-Green-Blue) Solid (100% density) and letters were printed on the glossy paper for void type ink jet recording. The boundary of each color of the solid portion and the degree of blurring of the characters were evaluated visually.
(Double-circle): The boundary is clear, there is no blur, and the character is clear and can be used practically (practical level).
○: The blurring of the boundary is not conspicuous, the characters are clear, and can be used (practical level).
(Triangle | delta): The blur of a boundary is conspicuous, a character is unclear, and there is a problem in practical use (practical use impossible level).
X: The blurring of the boundary is severe, and the characters cannot be identified, which is impractical (impractical level).

(4) Image clarity of pigment ink:
Using an ISO standard image (ISO / JIS-SCID high-definition color digital standard image data, image name: portrait, image identification number: N1) using an inkjet printer dedicated to pigment ink (PX-G5300: manufactured by Seiko Epson Corporation) It printed on the obtained inkjet recording paper. The printed image was visually evaluated.
A: The recorded image is very clear and clear in contrast, and can be used (practical level).
○: The recorded image is clear and the contrast is clear, so that it can be used (practical level).
Δ: The contrast of the recorded image is clear, but the print density is low and the image is not clear (impractical level).
X: The contrast of the recorded image is not clear, the print density is extremely low, and the sharpness is extremely poor (practical level).

(5) Absorption of pigment ink:
Using an inkjet printer dedicated to pigment ink (PX-G5300: manufactured by Seiko Epson Corporation), using each CMYK ink, solid (100% density) and characters of each CMYK ink, and RGB (Red-Green-Blue) Solid (100% density) and letters were printed on the glossy paper for void type ink jet recording. The boundary of each color of the solid part and the degree of blurring of the characters were visually evaluated as follows.
(Double-circle): The boundary is clear, there is no blur, and the character is clear and can be used practically (practical level).
○: The blurring of the boundary is not conspicuous, the characters are clear, and can be used (practical level).
(Triangle | delta): The blur of a boundary is conspicuous, a character is unclear, and there is a problem in practical use (practical use impossible level).
X: The blurring of the boundary is severe, and the characters cannot be identified, which is impractical (impractical level).

As is apparent from Table 1, Examples 1-2 and 5-8 are superior in pigment ink absorption and image sharpness compared to Comparative Examples 1-5.

  In Comparative Examples 1 to 5, since the maximum value (peak) of the pore diameter distribution curve obtained by the BJH method from the nitrogen desorption isotherm of the ink receiving layer was outside the range of 40 to 90 nm, the image clarity of the pigment ink Inferior to

Claims (2)

In an inkjet recording paper having an ink receiving layer containing a pigment and a binder on at least one side of a substrate, the maximum value of the pore diameter distribution curve obtained by the BJH method from the nitrogen desorption isotherm of the ink receiving layer (Peak) exists only in the range of 40 to 90 nm , and the pigment is vapor phase silica (A) having an average primary particle size of 5 to 12 nm and gas phase method silica (B) having an average primary particle size of 15 to 25 nm. An ink jet recording paper, wherein the mass ratio A: B of the vapor phase silica (A) and the vapor phase silica (B) is in the range of 20:80 to 80:20 . 2. The ink jet recording sheet according to claim 1, wherein the total pore volume of the ink receiving layer determined by a BJH method from a nitrogen desorption isotherm of the ink receiving layer is 10 to 35 cm ³ / m ² .