JP2008023947A - Ink jet recording paper and its manufacturing process - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To manufacture ink jet recording paper having both high glossiness and high ink absorbency in high productivity. <P>SOLUTION: In the ink jet recording paper having a lower coating layer and an upper coating layer which contain pigments, respectively, in this order on at least one side surface of a base sheet containing wood pulp as a main ingredient, the lower coating layer contains 50 wt.% or more of the pigment (A) having an aspect ratio of 10-70 in the entire pigment in the lower coating layer, the pigment (A) contains a grain size distribution in which the particles of 0.4 μm or more to 4.2 μm or less is 60% or more of the entirety by the integrated value of a volume reference in a laser diffraction type grain size distribution measurement, and further the lower coating layer is made by coating the coating liquid for the lower coating layer by a blade coater. The upper coating layer is made by coating the coating liquid for the upper coating layer by a curtain coater. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an ink jet recording paper excellent in gloss and ink absorbability, and a method for producing the same.

  The ink jet recording system has been rapidly spread in recent years because it is easy to make full color and the printing noise is low. In this method, fine droplets of ink are ejected from a nozzle toward a recording medium at high speed, and images and characters are recorded, and the ink contains a large amount of solvent. Therefore, it is necessary for the recording medium to absorb ink promptly. In recent years, with the widespread use of computers and digital cameras, image quality (high color development, resolution, color reproducibility, and high glossiness) close to that of silver halide photography has been demanded. So-called coated paper type ink jet recording media have been developed.

As a means for producing an ink jet recording medium having good ink absorbability, it is known to increase the specific surface area of the pigment used in the ink receiving layer. Therefore, pigments such as synthetic amorphous silica, in which small primary particles such as synthetic silica are aggregated, that is, large specific surface area and particle diameter of several μm or more are widely used in the ink receiving layer. However, the ink jet recording paper using these pigments is a so-called mat type having almost no gloss.
Further, in recent years, an ink jet recording medium provided with two or more ink receiving layers has been proposed in order to obtain a high ink absorbability that is difficult to obtain with a single-layer coated product. However, off-line application of two or more ink-receiving layers is not only disadvantageous in terms of operability, but solvent components (binders, etc.) in the ink-receiving layer coating solution applied to the uppermost layer penetrate into the lower layer. Since the gap is filled, the effect of improving the ink absorbability is small, and further, the distribution of the binder in the surface direction and the thickness direction of the ink receiving layer becomes non-uniform, resulting in a decrease in image quality. Further, when the ink absorption is increased by increasing the coating amount, problems such as a decrease in the adhesiveness of the ink receiving layer and powder falling off easily occur.

On the other hand, a method of forming a coating liquid film composed of a plurality of layers of coating liquid described in Patent Document 1 and coating using a slide curtain coater, or two or more types of coating described in Patent Document 2 A method is disclosed in which a liquid is applied using a couple curtain coater, which is a method of sequentially applying liquid from separate slits, and then dried at once. However, since curtain coating is contour coating, it is good when applied to a highly smooth support such as a film. However, when the support is paper, the surface shape is non-uniform, so smoothness Thus, it is impossible to obtain a coated surface with a high glossiness.
On the other hand, as a method for producing a highly glossy ink jet recording medium, for example, a method of applying gloss to a mirror drum described in Patent Document 3 (casting method), an alumina or a colloid described in Patent Document 4 There has been proposed a method of coating a material having high glossiness such as silica with a blade coater or the like. However, since the casting method has a high drying load, there is a problem that the production speed is slow, that is, the production efficiency is low. In addition, the coating by the blade coater is not a contour coating, so the ink receiving layer cannot be uniformly formed and printed. There is a problem that the ink receiving layer becomes dense due to causing unevenness and pressing the coating liquid under pressure, resulting in poor ink absorbability.

JP 2001-113226 A JP 2005-270954 A JP-A-62-95285 JP 2001-232934 A

  The present invention has been made in view of the above circumstances, and an object of the present invention is to produce an inkjet recording sheet having both high gloss and high ink absorbency with high productivity.

As a result of intensive studies on the above problems, the present inventors have determined that a pigment having a very uniform particle size distribution and an aspect ratio of 10 to 70 is added to a base paper mainly composed of wood pulp by 100 wt. By using an undercoat layer coating solution containing 50 parts by weight or more per part, coating this with a blade coater, and then applying a topcoat layer coating solution containing a pigment with a curtain coater. The inventors have found that this can be solved, and have completed the present invention.
That is, the present invention is an inkjet recording paper having an undercoat layer and a topcoat layer each containing a pigment in this order on at least one side of a base paper mainly composed of wood pulp, and the undercoat layer has an aspect ratio of 10 The pigment (A) of ˜70 is contained in the total amount of the face in the undercoat layer in an amount of 50% by weight or more, and the pigment (A) is a particle having a particle size of 0.4 μm or more and 4.2 μm or less in laser diffraction particle size distribution measurement. Has a particle size distribution that is 60% or more of the total volume-based integrated value. Further, the undercoat layer is formed by applying a coating solution for an undercoat layer with a blade coater, and the overcoat layer is applied for a topcoat layer. An ink jet recording paper, wherein the liquid is coated with a curtain coater.

  Further, the topcoat layer preferably contains vapor phase alumina as a pigment from the viewpoint of glossiness and ink absorbability. Moreover, it is preferable that the 75-degree specular glossiness of the surface of the topcoat layer is 40% or more.

  Further, the present invention is a method for producing an ink jet recording paper having an undercoat layer containing a pigment and an overcoat layer in this order on at least one side of a base paper mainly composed of wood pulp, the undercoat layer having an aspect ratio The pigment (A) having an A of 10 to 70 is contained in an amount of 50% by weight or more in the total amount of the face in the undercoat layer, and the pigment (A) is 0.4 μm or more and 4.2 μm or less in the laser diffraction particle size distribution measurement. The particles have a particle size distribution that is 60% or more of the total volume-based integrated value. Furthermore, after the undercoat layer coating liquid is applied on at least one side of the base paper with a blade coater, the formed undercoat layer is This is a method for producing an ink jet recording paper in which an overcoat layer coating solution is applied with a curtain coater while it is not dried, and an overcoat layer is provided on the undercoat layer.

  The ink jet recording paper of the present invention and the ink jet recording paper manufactured using the manufacturing method of the present invention have high gloss and high ink absorbability, and are excellent in productivity.

Details of the present invention will be described below.
The present invention performs so-called wet-on-wet coating by coating the undercoat layer on-line without applying a drying step after coating the undercoat layer. The undercoat layer is a blade coater and the topcoat layer is a curtain coater. It is characterized by coating with. When the topcoat layer is applied through a drying process after the undercoat layer is applied, the solvent components (auxiliaries such as a binder and a water resistance agent) and fine pigments in the topcoat layer penetrate into the undercoat layer. For this reason, the gap in the undercoat layer is filled or the binder distribution becomes non-uniform, so that the ink absorbability and the ink-jet suitability such as print density and water resistance are lowered. On the other hand, if the undercoat layer is in an undried state, it is possible to minimize the penetration of the components of the overcoat layer coating liquid into the undercoat layer.
Furthermore, in the wet-on-wet coating, the pigment component of the overcoat layer coating liquid is less likely to penetrate into the undercoat layer, so that the smoothness of the overcoat layer tends to be higher than that with the drying step in between, Glossiness is also considered to be high.

  When providing the undercoat layer, it is preferable to use a blade coater. The blade coater can be classified into paddle type, flooded nip type, fountain type, short dwell type, etc. according to the application method of the coating liquid, and it can be classified into vent blade, bevel blade, bar blade, etc. according to the blade blade. Any of these can be used as appropriate. By coating with a blade coater, the pigment is oriented parallel to the coated surface and the coated surface becomes smooth, so that the smoothness and gloss of the finally obtained ink jet recording paper are improved.

When providing the topcoat layer, it is particularly preferable to use a curtain coater and apply the coating while the undercoat layer is undried. Use of a coating method such as a blade coater or an air knife coater that contacts the base paper when measuring the coating amount is not preferable because the topcoat layer can only be applied after the undercoat layer is dried. When a curtain coater, which is a coating method that does not contact the base paper when the coating amount is measured as in the present invention, coating can be performed even when the undercoat layer is wet.
Curtain coater coating used in the present invention is a method of applying a coating liquid in a non-contact manner by allowing the coating liquid to flow down and falling freely, and known methods such as a slide curtain method, a couple curtain method, and a twin curtain method. A thing can be adopted and is not particularly limited. Moreover, the number of top coat layers is not particularly limited as long as the drying step is not interposed. Various conditions such as coating solution concentration, coating speed, curtain film width, drop angle and the like are appropriately adjusted.

The undercoat layer and the overcoat layer in the present invention contain a pigment, a binder, and other additives and have ink absorbability.
The pigment contained in the undercoat layer has an aspect ratio of 10 to 70, and in the laser diffraction particle size distribution measurement, particles of 0.4 μm or more and 4.2 μm or less are 60% or more of the total in terms of volume-based integrated values. The pigment (A) having a particle size distribution is contained. Specific examples of the pigment (A) include kaolin, clay, delaminated clay, talc, mica group, aluminum hydroxide, synthetic amorphous silica, colloidal silica, gas phase method silica, alumina, alumina hydrate (alumina sol , Colloidal alumina, pseudoboehmite, etc.), calcium silicate, aluminum silicate, magnesium silicate, magnesium carbonate, light calcium carbonate, heavy calcium carbonate, calcium sulfate, titanium dioxide, zinc oxide, zinc carbonate, aluminum hydroxide, plastic pigment, etc. Among them, it is preferable to use a flat pigment (kaolin, clay, talc, mica group, etc.). For the particle size distribution, a sample slurry is dropped and mixed into pure water to obtain a uniform dispersion, and a value measured with a laser particle size measuring device (device used: Mastersizer S type manufactured by Malvern) is used. The aspect ratio is the ratio of the major axis to the minor axis of the pigment particle (the ratio of the major axis to the pigment particle thickness in the case of a flat pigment). In the present invention, the aspect ratio is determined by observing the pigment particle by observation with an electron microscope or the like. Observe and calculate using the major and minor axis values measured visually.

The above-mentioned pigment having the particle size distribution of the present invention has a sharp particle size distribution as compared with general pigments, has a uniform particle size, has a low packing density of pigment particles, and forms a porous and bulky coating layer. . A porous coating layer is excellent in ink absorbency because the average void diameter is larger than that of a dense coating layer of the pigment. In addition, since such a pigment is excellent in the covering property of the base paper, the surface smoothness is high, and when the overcoat layer is provided, the gloss development effect is large. The sharper the particle size distribution of the pigment (A), the easier it is to obtain the above effect. In laser diffraction particle size distribution measurement, particles of 0.4 μm or more and 4.2 μm or less are contained by 65% or more of the total volume-based integrated value. It is preferable to have a particle size distribution.
In place of the pigment (A) having the above particle size distribution, when a pigment containing less than 60% of particles falling in the range of 0.4 to 4.2 μm and containing many particles having a particle size smaller than this range is used, Although the glossiness of white paper is increased, the ink absorbability is reduced because the coating layer is dense. In addition, when a pigment containing less than 60% of particles in the range of 0.4 to 4.2 μm and containing many particles having a particle size larger than this range is used, the smoothness deteriorates, so When provided, the gloss desired by the present invention cannot be obtained.

Further, in the present invention, generally known pigments other than the pigment (A) having the above particle size distribution, such as kaolin, clay, delaminated clay, talc, mica group, aluminum hydroxide, synthetic amorphous silica , Colloidal silica, vapor phase silica, alumina, alumina hydrate (alumina sol, colloidal alumina, pseudoboehmite, etc.), calcium silicate, aluminum silicate, magnesium silicate, magnesium carbonate, light calcium carbonate, heavy calcium carbonate, calcium sulfate, One or more kinds of titanium dioxide, zinc oxide, zinc carbonate, aluminum hydroxide, plastic pigment, etc. can be mixed and used together with the pigment (A). The pigment used in combination with the pigment (A) is preferably used in combination with an average particle size (measured with the laser particle size measuring instrument) of 4.2 μm or less.
However, it is necessary to contain 50% by weight or more of the pigment (A) with respect to the total amount of the undercoat layer. When the amount of the pigment (A) is less than 50% by weight, the pigment particles are densely packed and a porous and bulky coating layer is not formed, so that the glossiness and ink absorbability desired by the present invention cannot be obtained.

  In the present invention, the greater the aspect ratio of the pigment (A), the better the surface smoothness. Pigments with an aspect ratio of less than 5 are inferior in smoothness because the ratio of orientation parallel to the coating surface is reduced, while those with an aspect ratio of more than 70 are costly and difficult to obtain industrially. Therefore, the ink absorbability is inferior. In terms of the balance between glossiness and ink absorbability, the aspect ratio is more preferably 10-40.

In the present invention, the pigment contained in the overcoat layer is synthetic amorphous silica, colloidal silica, vapor phase silica, alumina, alumina hydrate (alumina sol, colloidal alumina, pseudoboehmite, etc.), aluminum silicate, magnesium silicate, carbonic acid. Magnesium, light calcium carbonate, heavy calcium carbonate, kaolin, talc, calcium sulfate, titanium dioxide, zinc oxide, zinc carbonate, calcium silicate, aluminum hydroxide, plastic pigment, etc. It is preferable to use method silica, gas phase method alumina, and colloidal silica, and gas phase method alumina is more preferable in terms of gloss. A method for producing vapor phase alumina is widely known, and for example, it can be produced by a method including a step of hydrolyzing vapor of aluminum chloride in a hydrogen or oxygen flame. The alumina particles thus produced have a relatively low degree of aggregation or are very nearly monodispersed in a shape close to a true sphere, and are therefore suitable for ink jet recording media that require transparency.
The vapor-phase process alumina used for the overcoating layer of the present invention may be in the form of primary particles or secondary aggregated particles. The preferred form of alumina in the present invention is the form of secondary agglomerated particles. The primary particle diameter is preferably 3 nm to 50 nm, and the diameter of secondary aggregated particles is preferably 120 nm to 200 nm. The overcoat layer containing such an aggregate has a sufficient ink absorption capacity and moderate glossiness. When the primary particle diameter is less than 3 nm, the gap between the primary particles is remarkably reduced, the ability to absorb the solvent and ink in the ink is lowered, and a desired clear image cannot be obtained. On the other hand, when the primary particle diameter is larger than 50 nm, the aggregated secondary particle diameter is increased, the desired glossiness cannot be obtained, and the transparency of the overcoat layer is decreased, which causes a decrease in image quality.

  Examples of the binder used in the undercoat layer coating solution and the overcoat layer coating solution include polyvinyl alcohol and modified products thereof, starches such as oxidized starch and etherified starch, SB latex, NB latex, acrylic latex, and ethylene vinyl acetate. One kind or two or more kinds can be appropriately selected from known binders such as latex, casein, gelatin, carboxymethylcellulose, polyurethane, vinyl acetate resin, and unsaturated polyester resin. The number of blending parts is preferably 3 to 60 parts by weight, particularly 5 to 30 parts by weight, based on 100 parts by weight of the pigment. If the number of blended parts of the binder is small, the surface strength is insufficient, and if it is too large, the ink absorbability is insufficient.

  In the present invention, a cationic water-soluble resin can also be contained in the undercoat layer and / or the overcoat layer as a dye fixing agent. Examples of the cationic water-soluble resin used in the present invention include secondary amines, tertiary amines, and quaternary ammonium salts such as polyethyleneimine salts, dimethylamine epihalohydrin condensates, polyvinylamine salts, polyallylamine salts, and polydimethylaminoethyl. Examples thereof include methacrylate quaternary salts, polydiallyldimethylammonium salts, diallylamine acrylamide copolymer salts, and quaternary ammonium salts of polystyrene. Among them, a dimethylamine epihalohydrin condensate having excellent printing quality for both dye ink and pigment ink and particularly high printing density and water resistance is preferable. Two or more of these cationic resins can be used in combination.

The surface tension of the coating liquid is preferably equal to or higher in the undercoat layer than in the overcoat layer. When the surface tension of the undercoat layer coating liquid is lower, a phenomenon occurs in which the coating film of the overcoat layer repels on the coating film of the undercoat layer, resulting in a decrease in surface properties. Anionic surfactants such as carboxylate, sulfonate, sulfate ester, phosphate ester salt, ether type, ether ester type, ester type, nitrogen-containing type, etc. to adjust the surface tension of the coating liquid Any amount of amphoteric surfactants such as nonionic surfactants, betaines, aminocarboxylates, and imidazoline derivatives can be mixed in the coating solution.
Furthermore, if necessary, pigment dispersants, thickeners, sizing agents, antifoaming agents, antifoaming agents, mold release agents, foaming agents, colored dyes, colored pigments, fluorescent dyes, preservatives, water resistance agents, pH adjustments An auxiliary agent such as an agent can be added as appropriate.

In the present invention, the coating amounts of the undercoat layer and the overcoat layer are preferably 5 to ²⁰ g / m ² and ² to 20 g / m ² , respectively. When the coating amount of the undercoat layer is 5 g / m ² or less, the base paper cannot be completely coated. When the coating amount of the top coat layer is 2 g / m ² or less, the undercoat layer is completely coated. Cannot be obtained, and the glossiness is inferior. Moreover, when there is much coating amount, the drying load in the drying process after coating will increase, and productivity will fall with the fall of a coating speed. In addition, when drying at a high load, the binder in the coating liquid moves to the surface of the coating layer together with the solvent to evaporate, reducing the amount of voids on the surface, and the ink absorbability deteriorates. Causes dirt and other problems. Furthermore, the problem of powder falling also arises because the coating layer strength decreases.
In the present invention, a back coat layer may be provided on the back surface of the base paper. Furthermore, after forming the overcoat layer, it is possible to perform surface treatment with a calendar apparatus such as a machine calendar, a super calendar, or a soft calendar.

Wood pulp used for the base paper includes chemical pulp (coniferous bleached or unbleached kraft pulp, hardwood bleached or unbleached kraft pulp, etc.), mechanical pulp (ground pulp, thermomechanical pulp, chemical thermomechanical pulp, etc.) Black pulp and the like can be used alone or mixed at an arbitrary ratio.
The paper making method of the base paper is not particularly limited, and a known method can be used. The pH during papermaking may be any of acidic, neutral and alkaline. Moreover, since inclusion of a filler in the base paper tends to improve the opacity of the paper, it is preferable to include a filler in the paper. As the filler, known fillers such as hydrated silicic acid, white carbon, talc, kaolin, clay, calcium carbonate, titanium oxide, synthetic resin filler and the like can be used. Further, the base paper may contain auxiliary agents such as a sulfuric acid band, a sizing agent, a paper strength enhancer, a yield improver, a colorant, a dye, an antifoaming agent, a pH adjuster, and a bulking agent as necessary. The basis weight of the base paper is not particularly limited.

Examples of the present invention will be specifically described below, but the present invention is not limited to these embodiments. In the examples, “parts” and “%” all represent “parts by weight” and “% by weight”.

<Example 1>
[Preparation of base paper]
10% calcium carbonate, 0.5% cationized starch, 0.05% alkyl ketene dimer and 1% sulfuric acid band are added to 100% pulp slurry consisting of hardwood bleached kraft pulp (freeness 350ml). A paper web was formed with a paper machine, a three-stage wet press was performed, and after drying, machine calendering was performed to obtain a base paper having a basis weight of 90 g / m ² .

[Preparation of coating liquid 1 for undercoat layer]
Kaolin A (trade name: Capim DG, volume-based particle size distribution: particle size 0.4 to 4.2 μm 73%, aspect ratio 11) as 100 parts as pigment, 0% polyacrylic acid soda as dispersant .2 parts were added and dispersed with a serie mixer to prepare a pigment slurry having a solid content of 60%. To this slurry, 3 parts of oxidized starch (trade name: MS-3600, manufactured by Nippon Food Processing Co., Ltd.), 5 parts of latex (trade name: PA-0226, manufactured by Nippon A & L Co., Ltd.) and diluted water are added to form a solid content of 55%. A working solution was prepared.

[Preparation of topcoat layer coating solution 1]
Gas phase method alumina (trade name: CAB-O-SPERSE PG-003) 100 parts as a pigment, 15 parts polyvinyl alcohol (trade name: PVA-217, manufactured by Kuraray Co., Ltd.) as a binder, and cation as a dye fixing agent 10 parts of a functional resin (manufactured by Nippon Kasei Co., Ltd., trade name: KA-1000, dimethylamine / ethylenediamine / epichlorohydrin copolymer) and diluted water were added and mixed by stirring to prepare a coating solution having a solid content concentration of 27%.

[Preparation of inkjet recording paper]
The undercoat coating solution 1 is applied onto the base paper using a bar blade coater so that the coating amount becomes 7 g / m ^2, and the overcoat layer coating solution 1 is applied to the curtain coater without interposing a drying step. Was applied so that the coating amount was 15 g / m ² . This was dried until the moisture content became 4.8%, and then surface-treated with a soft calendar to produce an ink jet recording paper.

<Example 2>
100 parts of kaolin B (manufactured by Rio Capim, trade name: Capim NP, volume-based particle size distribution: particle size 0.4 to 4.2 μm 66%, aspect ratio 24) as a pigment for the undercoat layer coating solution 1 An ink jet recording paper was prepared in the same manner as in Example 1 except that.

<Example 3>
[Preparation of undercoat layer coating solution 2]
70 parts of kaolin A as a pigment, 30 parts of synthetic amorphous silica A (manufactured by Tosoh Silica Co., Ltd., trade name: nip gel AY-200, average secondary particle size 3.2 μm measured by laser diffraction method), hydrophilic As an adhesive, 30 parts of polyvinyl alcohol (trade name: PVA-117, manufactured by Kuraray Co., Ltd.), 4 parts of ethylene vinyl acetate copolymer (trade name: AM-3150, manufactured by Showa Kogyo Co., Ltd.), dilution water were added and mixed with stirring. A coating solution having a solid content concentration of 27% was prepared.

[Preparation of inkjet recording paper]
An ink jet recording paper was prepared in the same manner as in Example 1 except that the undercoat layer coating solution 2 was used for the undercoat layer.

<Example 4>
An ink jet recording paper was prepared in the same manner as in Example 1 except that colloidal silica (manufactured by Nissan Chemical Industries, Ltd., trade name: Snowtex OUP) was used as the pigment of the coating liquid 1 for the topcoat layer.

<Example 5>
An ink jet recording paper was prepared in the same manner as in Example 1 except that gas phase method silica (manufactured by Nippon Aerosil Co., Ltd., trade name: Aerosil 50) was used as the pigment of the coating liquid 1 for the topcoat layer.

<Example 6>
An ink jet recording paper was prepared in the same manner as in Example 1 except that the undercoat layer was applied and then the overcoat layer was applied through a drying process.

<Example 7>
An ink jet recording paper was prepared in the same manner as in Example 3 except that the undercoat layer was applied and then the overcoat layer was applied through a drying process.

<Example 8>
An ink jet recording paper was prepared in the same manner as in Example 5 except that after the undercoat layer was applied, a topcoat layer was applied through a drying process.

<Comparative Example 1>
As a pigment for the coating liquid 1 for the undercoat layer, 100 parts of Kaolin C (manufactured by Imeris Co., Ltd., trade name: KCS, volume-based particle size distribution: particle size 0.4 to 4.2 μm 54%, aspect ratio 14) was used. An ink jet recording paper was prepared in the same manner as in Example 6 except for the above.

<Comparative example 2>
100 parts of kaolin D (made by Imeris Co., Ltd., trade name: DB plate, volume-based particle size distribution: particle size 0.4 to 4.2 μm 58%, aspect ratio 13) are used as the pigment of the coating solution 1 for the undercoat layer. An ink jet recording paper was prepared in the same manner as in Example 6 except that.

<Comparative Example 3>
As a pigment of the coating liquid 1 for the undercoat layer, spindle-shaped light calcium carbonate (Okutama Kogyo Co., Ltd., trade name: TP-121, volume-based particle size distribution: particle size 0.4 to 4.2 μm, 76%, aspect ratio 5 ) Was used in the same manner as in Example 6 except that 100 parts were used.

<Comparative Example 4>
An ink jet recording paper was prepared in the same manner as in Example 6 except that 30 parts of kaolin A and 70 parts of synthetic amorphous silica A were used as the pigment of the undercoat layer coating liquid 2.

<Comparative Example 5>
An ink jet recording paper was prepared in the same manner as in Example 1 except that the undercoat layer was applied using a curtain coater.

<Comparative Example 6>
An ink jet recording paper was prepared in the same manner as in Example 3 except that the undercoat layer was coated using a curtain coater.

<Comparative Example 7>
An ink jet recording paper was prepared in the same manner as in Example 4 except that the undercoat layer was coated using a curtain coater.

<Comparative Example 8>
An ink jet recording paper was prepared in the same manner as in Example 5 except that the undercoat layer was coated using a curtain coater.

<Comparative Example 9>
An ink jet recording paper was prepared in the same manner as in Example 1 except that the undercoat layer was applied, followed by a drying process, and the overcoat layer was applied using a bar blade coater.

<Comparative Example 10>
An ink jet recording paper was prepared in the same manner as in Example 3 except that the undercoat layer was applied, followed by a drying process, and the topcoat layer was applied using a bar blade coater.

<Comparative Example 11>
An ink jet recording paper was prepared in the same manner as in Example 4 except that after the undercoat layer was applied, a drying step was performed, and the topcoat layer was applied using a bar blade coater.

<Comparative Example 12>
An ink jet recording paper was prepared in the same manner as in Example 5 except that after the undercoat layer was applied, a drying step was performed, and the topcoat layer was applied using a bar blade coater.

<Comparative Example 13>
An ink jet recording paper was prepared in the same manner as in Example 1 except that the undercoat layer 1 was applied using the curtain coater so that the coating amount was 15 g / m ² without providing the undercoat layer.

[aspect ratio]
For 100 particles observed with an electron microscope, the ratio of major axis to minor axis (major axis / minor axis) was calculated, and the average value was obtained. The aspect ratio of kaolin was determined from the ratio of major axis to thickness (major axis / thickness).
[Particle size distribution]
The sample slurry was dropped and mixed in pure water to obtain a uniform dispersion, and the measurement was performed with a laser particle size measuring instrument (equipment used: Mastersizer S type manufactured by Malvern). The measurement was performed when the obscuration value was 15.

[Evaluation methods]
The glossiness and ink absorbency were evaluated by the methods shown below. It can be preferably used when the evaluation is Δ or more.
<Glossiness>
According to JIS-P-8142, the 75 ° specular gloss of the coated paper was measured.
○: 75 ° specular gloss is 60% or more.
○ ': 75 ° specular gloss is 50% or more and less than 60%.
Δ: 75 ° specular gloss is 40% or more and less than 50%.
X: 75 ° specular gloss is less than 40%.
<Ink absorbability>
Using Microsoft spreadsheet software “Excel”, create a solid image of the red and green solid images next to each other and print it using an inkjet printer (trade name: PM-G730, manufactured by Seiko Epson Corporation). did. The color boundary blur was visually evaluated.
○: No bleed at the boundary part ○ ': Little bleed at the boundary part △: Some bleed at the boundary part x: Significant bleed at the boundary part

  Tables 1 to 3 show the results of evaluating the ink jet recording paper obtained in Examples and Comparative Examples by the above method.

As is clear from Table 1, the inkjet papers of the present inventions of Examples 1 to 8 were highly evaluated for glossiness and ink absorbency. As in Examples 6 to 8, those having a drying step between layers had a slightly inferior ink absorptivity, but were practically satisfactory.
On the other hand, as in Comparative Examples 1 to 4, a pigment having a particle size distribution in which 60% or more of the undercoat layer is contained in a range of 0.4 to 4.2 μm on a volume basis and an aspect ratio of 10 to 70 is used. Those not used in more than one part were inferior in glossiness because the smoothness of the undercoat layer was lowered. Furthermore, since the undercoat layer coated with a curtain coater as in Comparative Examples 5 to 8 is contour coating, the smoothness of the undercoat layer is low, so the ink absorbency is excellent, but the glossiness Was inferior. In addition, as in Comparative Examples 9 to 12, those having a top coat layer coated with a blade coater had deteriorated ink absorbability. Further, in the case where no undercoat layer was provided as in Comparative Example 13, the smoothness of the base paper was low, and the coating liquid penetrated into the base paper, and therefore the glossiness was inferior.

Claims (4)

An ink jet recording paper having an undercoat layer and a topcoat layer each containing a pigment in this order on at least one side of a base paper mainly composed of wood pulp, the undercoat layer having an aspect ratio of 10 to 70 50% by weight or more of (A) is contained in the total amount of the face in the undercoat layer, and the pigment (A) has a volume-based integration of particles of 0.4 μm to 4.2 μm in the laser diffraction particle size distribution measurement. The undercoat layer has a particle size distribution that is 60% or more of the total value, and the undercoat layer is formed by coating the undercoat layer coating solution with a blade coater, and the overcoat layer is coated with the overcoat layer coating solution with a curtain coater. An ink jet recording paper, characterized by being coated. The inkjet recording paper according to claim 1, wherein the overcoat layer contains vapor phase alumina as a pigment. An inkjet recording paper having a 75-degree specular gloss on the surface of the topcoat layer of 40% or more. A method for producing an ink jet recording paper having an undercoat layer and a topcoat layer each containing a pigment in this order on at least one side of a base paper comprising wood pulp as a main component, wherein the undercoat layer has an aspect ratio of 10 to 70 A pigment (A) is contained in an amount of 50% by weight or more in the total amount of the face in the undercoat layer, and the pigment (A) has a particle size of 0.4 μm or more and 4.2 μm or less based on volume in laser diffraction particle size distribution measurement. In addition, the undercoat layer coating liquid is applied to at least one surface of the base paper with a blade coater, and the formed undercoat layer is not dried. A method for producing an inkjet recording paper, wherein a topcoat layer coating liquid is applied with a curtain coater, and an overcoat layer is provided on the undercoat layer.