JP2016175399A - Printing paper for rotary industrial inkjet printers and printed matter manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a printing paper for a rotary type industrial inkjet printer having printability for an offset printer, excellent in color concentration uniformity, striking-through inhibition property and dot reproducibility for the rotary type industrial inkjet printer using an aqueous pigment ink.SOLUTION: The problem is solved by a printing paper for a rotary type industrial inkjet printer having a base paper, and one or more coated layer containing a pigment, a binder and a water soluble multivalent cation salt on at least one surface of the base paper, where at least one kind of the pigment is kaolin having an average particle diameter of 0.20 μm to 1.50 μm inclusive, the content of the kaolin in the coated layer is 50 pts.mass or more based on 100 pts.mass of the pigment, the content of the water soluble multivalent cation salt in the coated layer is 1.0 pts.mass to 6.0 pts.mass inclusive based on 100 pts.mass of the pigment, and a surface resistance rate of a coated layer surface side having the coated layer under environment of 23°C and 50% RH required according to JIS K 6911:2006 of 2.0×10Ω to 5.0×10Ω inclusive.SELECTED DRAWING: None

Description

  The present invention relates to a printing paper for an industrial inkjet printer used in a rotary industrial inkjet printer, and a printed matter manufacturing method using the printing paper for an industrial inkjet printer.

  2. Description of the Related Art A rotary industrial inkjet printer that uses an inkjet recording system is known as an industrial or commercial printer for producing a large number of commercial prints and newspapers (see, for example, Patent Document 1). Rotary industrial inkjet printers are sold under the names such as TruepressJet from Dainippon Screen Manufacturing, MJP series from Miyakoshi, Prosper and VERSAMARK from Kodak, InkjetWebPress from HP, and JetLeader from Tokyo Machine Works, Ltd. ing.

  Such a rotary industrial inkjet printer, although depending on printing conditions, has a color printing speed that is several tens of times faster than ordinary household and SOHO inkjet printers and large inkjet printers. 60 m / min or more. In particular, newspaper printing is faster, and a rotary industrial inkjet printer for newspaper printing uses a printing speed of more than 100 m / min and 150 to 200 m / min. For this reason, rotary industrial inkjet printers are distinguished from general household and SOHO inkjet printers and large-format inkjet printers.

  A rotary industrial inkjet printer can handle variable information and can be adapted for on-demand printing. In many cases, a printing company employs a form in which fixed information is printed by a conventional printing machine such as an offset rotary printing press, and variable information is printed by a rotary industrial inkjet printing press. In particular, conventional rotary presses often use offset rotary presses in terms of print image quality and manufacturing costs.

  Therefore, it is necessary to have printability for both printing by a conventional printing press such as a rotary offset printing press and printing by a rotary industrial inkjet printing press. Without these printing aptitudes, it is impossible to produce a printed matter having a sufficient image quality as a product by these printing machines.

As a coated paper for ink-jet printing that has high gloss on white paper and has excellent ink absorption, ink fixability, and coating layer strength, and can produce high-quality printed matter using an ink-jet commercial printing machine, In a coated paper for inkjet printing having a coating layer containing a pigment and a binder on at least one surface, the pigment contains 70% by mass or more of acicular light calcium carbonate, and the binder comprises a latex binder and starch. The ratio of the mass of the latex binder to the mass of the starch (the mass of the latex binder / the mass ratio of the starch) is 0.3 to 25, and the mass of the pigment of the coating layer and the binder Inkjet printing coated papers having a ratio to the mass of (pigment mass / binder mass ratio) of 3 to 30 are known (for example, special References 2).
Inkjet-compatible newsprint for offset printing, which is suitable for printing on an offset newspaper rotary press and excellent in ink-jet printing, mainly contains waste paper pulp as raw material pulp, white carbon as filler, and contains a sizing agent. Ink-jet newsprint for ink-jet offset printing made with no sizing and sized with a surface sizing agent, wherein (a) the fiber composition of the disaggregated pulp is 15% by mass or less; (b) the length of the disaggregated pulp Average fiber length is 0.7 to 1.0 mm; (c) Length average fiber length distribution of disaggregated pulp is 20% or less of 1.2 mm or more pulp; (d) A surface treatment agent containing a surface sizing agent and a binder. Coated, water absorption time 50 to 170 seconds; (e) Shape by ink jet printing determined by a specific measurement method Inkjet corresponding offset printing newsprint number of 100 to 200 is known (e.g., see Patent Document 3).

JP 2012-111123 A Japanese Patent Laying-Open No. 2015-013459 JP 2011-161720 A

  Roughly, there are water-based dye inks and water-based pigment inks in inks used in industrial inkjet printing presses, but water-based pigment inks are used from the viewpoints of storage stability such as light resistance and color density. Often done.

  In aqueous pigment inks, when the printing speed increases, if the ink absorbability of the printing paper varies partially, the color density of the printed portion may become non-uniform. This is due to the principle of inkjet, which ejects ink droplets from fine nozzles, and the ink used in industrial inkjet printers has a lower colorant content concentration than the ink of conventional printers such as offset printers. Because. In addition, in the case of water-based pigment ink, if the ink absorbability of the printing paper becomes insufficient as the printing speed increases, the dot reproducibility may decrease in the printed portion. When the dot reproducibility decreases, the image quality deteriorates. This is because the paper conveyance speed increases in proportion to the high printing speed, and ink droplets adhering to the surface of the printing paper flow when they land on the paper surface. That is, dots formed by ink droplets that have landed on the surface of the paper have a distorted shape, or the outline of the dots become unclear, causing a reduction in image quality.

  Colorization is progressing not only in the commercial printing field but also in the newspaper printing field, and the demand for image quality is increasing. Newspaper paper is susceptible to ink breakthrough due to its low basis weight. The reason for this is that the ink used for industrial inkjet printers has a lower color material content concentration than the ink of conventional printers such as offset printers. In the case of paper having a small basis weight such as newspaper paper, if the ink absorptivity is increased, the ink see-through phenomenon tends to occur. “Ink breakthrough” is a phenomenon in which ink reaches the deep part of the paper without stopping on the printing side, and the printed image is visually recognized from the opposite side. In commercial printing, duplex printing is often performed, and the phenomenon of ink breakthrough impairs the value as a product.

  The ink-jet printing coated paper described in Patent Document 2 and the ink-jet-compatible offset printing newsprint described in Patent Document 3 are about the uniformity of color density in the printed portion, dot reproducibility, and suppression of ink back-through. Needs further improvement.

An object of the present invention is to provide a printing paper for a rotary industrial inkjet printer having the following performance.
1. Have printability for an offset printer (offset printability).
2. Excellent color density uniformity in the printed area of a rotary industrial inkjet printer using aqueous pigment ink (color density uniformity).
3. Excellent anti-through-through control of ink for rotary industrial inkjet printers that use water-based pigment ink (back-through suppression).
4). Excellent dot reproducibility for a rotary industrial inkjet printer using water-based pigment ink (dot reproducibility).
Another object of the present invention is to provide a printed matter production method using a rotary industrial inkjet printer capable of producing a printed matter excellent in color density uniformity, strikethrough suppression, and dot reproducibility in a printed portion. That is.

As a result of intensive studies conducted by the inventor in view of the above, the object of the present invention is achieved by the following.
(1) It has a base paper and at least one coating layer containing a pigment, a binder and a water-soluble polyvalent cation salt on at least one surface of the base paper, and at least one of the pigments has an average particle size of 0 A kaolin of 20 μm or more and 1.50 μm or less, and the content of the kaolin in the coating layer is 50 parts by mass or more with respect to 100 parts by mass of the pigment in the coating layer, and the water-soluble polyvalent cation salt The content in the coating layer of 23 ° C. is 1.0 part by mass or more and 6.0 parts by mass or less with respect to 100 parts by mass of the pigment in the coating layer, and is determined in accordance with JIS K 6911: 2006. For rotary industrial inkjet printers having a surface resistivity of 2.0 × 10 ¹⁰ Ω to 5.0 × 10 ¹² Ω on the side of the coating layer having the coating layer in an environment of 50% RH Printing paper.

  (2) A step of obtaining a printing paper for an industrial inkjet printer as described in (1) above, a step of obtaining a printed matter by printing on the printing paper with a rotary industrial inkjet printer using an aqueous pigment ink, A printed matter manufacturing method comprising:

According to the present invention, a rotary printing industry that has printability for an offset printing press, and excellent color density uniformity, back-through suppression, and dot reproducibility for an industrial rotary printing press using a water-based pigment ink. Printing paper for inkjet printers can be provided. In addition, according to the present invention, there is provided a printed matter production method using a rotary industrial inkjet printer capable of producing a printed matter excellent in color density uniformity, strikethrough suppression, and dot reproducibility in a printed portion. Can do.
The effect of the present invention depends on the coating layer containing a specific kaolin, binder and water-soluble polyvalent cation salt as a pigment, and setting the surface resistivity on the coating layer side of the printing paper in a specific region. It can be obtained by a synergistic effect.

  Hereinafter, the printing paper for industrial inkjet printers of the rotary type according to the present invention (hereinafter simply referred to as “printing paper”) will be described in detail. As used herein, “inkjet printing” refers to printing using a rotary industrial inkjet printer.

  For example, when printing fixed information on national articles and variable information such as articles and advertisements by region in newspapers, gravure printing press, offset printing press, letterpress printing press, flexographic printing press for part or all of the fixed information It is preferable to print using a conventional printing machine. In particular, an offset rotary printing press is preferable in terms of printing image quality and manufacturing cost. A conventional printer may be before or after printing using a rotary industrial inkjet printer.

  The gravure printing machine is a type of printing machine that transfers ink to a printing medium through a roll-shaped plate cylinder in which an image is engraved. The offset printing machine is an indirect printing type printing machine in which ink is once transferred to a blanket and then transferred again to a printing medium. The letterpress printing machine is a letterpress type printing machine that performs printing by applying pressure so that the ink applied to the letterpress is pressed against the printing medium. A flexographic printing machine is a letterpress type printing machine that uses a flexible and elastic resin plate.

  Base paper is chemical pulp such as LBKP (Leaf Bleached Kraft Pulp), NBKP (Needle Bleached Kraft Pulp), GP (Groundwood Pulp), PGW (Pressure Ground Wood pulp), RMP (Refiner Mechanical Pulp), TMP (ThermoMechanical Pulp), CTMP (ChemiThermoMechanical Pulp), CMP (ChemiMechanical Pulp), mechanical pulp such as CGP (ChemiGroundwood Pulp), and at least one cellulose pulp selected from waste paper pulp such as DIP (DeInked Pulp), filler, and if necessary Paper made from paper containing various additives such as a sizing agent, fixing agent, retention agent, and cationizing agent by a conventionally known method such as acidic papermaking, neutral papermaking, and alkaline papermaking.

  In the present invention, conventionally known pigments can be used as fillers. Examples of pigments include light calcium carbonate, heavy calcium carbonate, kaolin, talc, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, zinc sulfide, zinc carbonate, satin white, aluminum silicate, diatomaceous earth, alumina, lithopone, zeolite And inorganic pigments such as magnesium carbonate and magnesium hydroxide. Furthermore, organic pigments, such as a styrene plastic pigment, an acrylic plastic pigment, polyethylene, a microcapsule, a urea resin, a melamine resin, can be mentioned. Moreover, multiple types can be used together from these.

  For base paper, other additives include pigment dispersants, thickeners, fluidity improvers, antifoaming agents, antifoaming agents, mold release agents, foaming agents, penetrating agents, colored dyes, colored pigments, fluorescent whitening agents UV absorbers, antioxidants, antiseptics, antibacterial agents, water resistance agents, paper strength enhancers, and the like can be appropriately contained within a range that does not impair the desired effects of the present invention.

The printing paper of the present invention has at least one coating layer containing a pigment, a binder, and a water-soluble polyvalent cation salt on at least one surface of the base paper.
At least one of the pigments is kaolin having an average particle diameter of 0.20 μm to 1.50 μm. The content of the kaolin in the coating layer is 50 parts by mass or more with respect to 100 parts by mass of the pigment in the coating layer. When the pigment in the coating layer deviates from the above conditions, the printing paper can obtain offset printing suitability, or color density uniformity or dot reproducibility for a rotary industrial inkjet printer using aqueous pigment ink. Can not.

  Kaolin is an industrially refined and processed kaolin ore produced in nature, and is produced through processes such as grinding, washing, iron removal, and classification. Highly workable materials such as delaminated kaolin made thin by applying shear to improve aspect ratio, engineered kaolin adjusted to sharpen particle size distribution, and calcined kaolin with enhanced cohesiveness Is also included.

  In the present invention, the average particle size is the average particle size of single particles in the case of single particles, and the average particle size of aggregated particles when forming aggregated particles such as secondary particles. The average particle diameter of kaolin can be determined from the state of printing paper. As a method for this, for example, an electron micrograph of the surface of a printing paper is taken using a scanning electron microscope with an element analysis function such as an energy dispersive X-ray spectrometer, and the photographed particles are regarded as a sphere having an approximate area. Thus, the average particle size is calculated by calculating the particle size and measuring particles from 100 particles present in the photographed image.

  The average particle diameter can also be determined by measurement using a laser diffraction / scattering method or a dynamic light scattering method. In this case, the average particle diameter is an average particle diameter based on a particle size distribution measurement based on a volume using a laser diffraction / scattering method or a dynamic light scattering method. The average particle size can be calculated from the obtained particle size distribution. For example, the average particle size can be calculated by measuring the particle size distribution using a laser diffraction / scattering particle size distribution analyzer Microtrac MT3300EXII manufactured by Nikkiso Co., Ltd.

  The coating layer can contain a conventionally known pigment in the papermaking field in addition to the kaolin. Examples of conventionally known pigments include clay, heavy calcium carbonate, light calcium carbonate, talc, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, zinc sulfide, zinc carbonate, satin white, aluminum silicate, diatomaceous earth, calcium silicate. And inorganic pigments such as magnesium silicate, synthetic amorphous silica, colloidal silica, aluminum hydroxide, alumina, lithopone, zeolite, magnesium carbonate, and magnesium hydroxide. Furthermore, organic pigments such as styrene plastic pigment, acrylic plastic pigment, styrene-acrylic plastic pigment, polyethylene, microcapsule, urea resin, melamine resin and the like can be mentioned.

The binder is a conventionally known binder in the papermaking field. For example, various kinds of acrylic acid polymers such as sodium polyacrylate and polyacrylamide, polyvinyl acetate, styrene-butadiene copolymer, and ethylene vinyl acetate are used. Mention may be made of copolymers, polyvinyl alcohol, modified polyvinyl alcohol, formalin resins such as polyethylene oxide, urea or melamine, and water-soluble compounds such as polyethyleneimine, polyamide polyamine, epichlorohydrin. Furthermore, the binder includes starch purified from natural plants, hydroxyethylated starch, oxidized starch, etherified starch, phosphate esterified starch, enzyme-modified starch, cold water soluble starch obtained by flash drying them, dextrin, mannan, chitosan And natural polysaccharides such as arabinogalactan, glycogen, inulin, pectin, hyaluronic acid, carboxymethylcellulose, hydroxyethylcellulose and the like, and modified products thereof. Furthermore, examples of the binder include natural proteins such as casein, gelatin, soybean protein, and collagen, and modified products thereof, and synthetic polymers and oligomers such as polylactic acid and peptides. The binder can be used alone or in combination of two or more selected from these. The binder can be used after cation modification.
The content of the binder in the coating layer is preferably 3 parts by mass or more and 30 parts by mass or less, and more preferably 5 parts by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the pigment in the coating layer. This is because if the binder content is within the above range, the ink absorbability of the printing paper becomes better.

  The water-soluble polyvalent cation salt is a water-soluble salt containing a metal polyvalent cation. A preferred polyvalent cation salt is a salt that contains a polyvalent metal cation and can be dissolved in water at 20 ° C. in an amount of 1% by mass or more. Examples of polyvalent cations of metals include divalent cations such as magnesium, calcium, strontium, barium, nickel, zinc, copper, iron, cobalt, tin and manganese; trivalent cations such as aluminum, iron and chromium Or tetravalent cations such as titanium and zirconium; and complex ions thereof. The anion that forms a salt with the metal polyvalent cation may be either an inorganic acid or an organic acid, and is not particularly limited. Examples of inorganic acids include hydrochloric acid, nitric acid, phosphoric acid, sulfuric acid, boric acid, hydrofluoric acid, and the like. Examples of the organic acid include formic acid, acetic acid, lactic acid, citric acid, oxalic acid, succinic acid, and organic sulfonic acid.

  In the present invention, the water-soluble polyvalent cation salt is preferably a calcium salt such as calcium chloride, calcium formate, calcium nitrate, or calcium acetate. The reason for this is that the strikethrough suppression is further obtained. From the viewpoint of chemical cost, calcium chloride or calcium nitrate is preferable.

  The content of the water-soluble polyvalent cation salt in the coating layer is 1.0 part by mass or more and 6.0 parts by mass or less with respect to 100 parts by mass of the pigment in the coating layer. The content is preferably 1.5 parts by mass or more and 5.0 parts by mass or less from the viewpoint of the balance between the breakthrough suppression and the dot reproducibility. If the content of the water-soluble polyvalent cation salt in the coating layer is out of the above range, the printing paper cannot obtain color density uniformity, show-through suppression or dot reproducibility.

  In addition to the pigment, binder and water-soluble polyvalent cation salt, the coating layer may be a pigment dispersant, a thickener, an antifoaming agent, an antifoaming agent, a foaming agent, a release agent, a penetrating agent, if necessary. It may contain various conventionally known auxiliaries that are usually used in the papermaking field, such as wetting agents, thermal gelling agents, printing suitability improvers, dye fixing agents, lubricants, dyes, fluorescent whitening agents or water resistance agents. it can.

The coating layer can be obtained by coating and drying a coating layer coating solution. Examples of the method for applying the coating layer coating liquid include various blade coaters such as a rod blade coater, air knife coater, roll coater, bar coater, curtain coater, short dwell coater, and film transfer coater. However, it is not limited to these. Preferred are various blade coaters or film transfer coaters suitable for high-speed productivity, and particularly preferred is a film transfer coater.
Examples of the drying method include various drying apparatuses such as a straight tunnel dryer, an arch dryer, an air loop dryer, a hot air dryer such as a sine curve air float dryer, an infrared heating dryer, a dryer using a microwave, and the like. Can be, but is not limited to.

The coating amount of the coating layer is 3.0 g / m ² per side from the viewpoint of compatibility between printing suitability for conventional printing presses such as offset rotary printing presses and ink absorbability for rotary industrial inkjet printing presses. The range of 10.0 g / m ² or less is preferable, and the range of 4.0 g / m ² or more and 8.0 g / m ² or less is more preferable. In the present invention, the coating amount refers to the coating amount of dry solid content per one side. When the coating layer has two or more layers on one side of the base paper, the coating amount means the total of these.

The surface resistivity of the printing paper is a value of the surface resistivity on the coating layer surface side having the coating layer of the present invention in an environment of 23 ° C. and 50% RH measured in accordance with JIS K 6911. The surface resistivity of the printing paper of the present invention is 2.0 × 10 ¹⁰ Ω or more and 5.0 × 10 ¹² Ω or less. If the surface resistivity of the printing paper is out of the above range, the printing paper cannot obtain color density uniformity and / or dot reproducibility. The reason for this is unknown, but is presumed as follows. Inkjet water-based pigment inks are normally charged for stable dispersion, so that the printing paper has a specific surface resistivity in inkjet printing, which affects ink drop absorption, resulting in color density uniformity and Dot reproducibility is obtained.

  The surface resistivity can be adjusted by a conventionally known method in the papermaking field. For example, a method for adjusting the type and content of the binder contained in the coating layer, a method for adjusting the type and content of the water-soluble polyvalent cation salt contained in the coating layer, and the content in the coating layer Examples thereof include a method for adjusting the water content and a method for adjusting the water content. Further, the surface resistivity can be adjusted somewhat depending on the base paper, for example, a method for adjusting the type and content of the sizing agent internally added to the base paper and a method for adjusting the water content of the base paper. Can do. The sizing agent internally added to the base paper is, for example, rosin sizing agent for acidic paper, alkenyl succinic anhydride, alkyl ketene dimer, neutral rosin sizing agent or cationic styrene-acrylic for neutral paper. A sizing agent can be mentioned.

  The printing paper can be subjected to a calendering process after making the base paper or after providing a coating layer.

The basis weight of the printing paper is preferably 40 g / m ² or more. In addition, the basis weight of newsprint is preferably 55 g / m ² or less. This is because if the basis weight is within the range, the effect of suppressing the breakthrough appears.

  The printing paper of the present invention is used in a rotary industrial inkjet printer. A preferred rotary industrial inkjet printer is a rotary industrial inkjet printer with a printing speed exceeding 100 m / min.

Printed matter manufacturing method The printed matter producing method of the present invention includes a step of obtaining the above-mentioned printing paper and a step of printing on the printing paper by a rotary industrial inkjet printer to obtain a printed matter. According to the method for producing a printed matter of the present invention, a printed matter having excellent color density uniformity, back-through suppression, and dot reproducibility can be produced in a printed portion. The printing paper and the rotary industrial inkjet printer are the same as the above-described printing paper for the rotary industrial inkjet printer and the rotary industrial inkjet printer, and redundant description is omitted.

  The step of obtaining the printing paper includes manufacturing the printing paper or obtaining the manufactured printing paper.

  In the process of obtaining printed matter by printing on printing paper with a rotary industrial inkjet printer, the rotary industrial inkjet printer preferably uses a water-based pigment ink from the viewpoint of the weather resistance of the obtained printed matter. .

  In the step of printing on printing paper with a rotary industrial inkjet printer to obtain a printed matter, the printing speed is preferably more than 100 m / min.

  In the printed matter manufacturing method of the present invention, a printing press selected from a gravure printing press, an offset printing press, a letterpress printing press, a flexographic printing press, and the like, before and / or after the step of printing with a rotary industrial inkjet printing press. The method may further include a step of printing on the printing paper. Thereby, fixed information and variable information can be handled in a printing process, and the obtained printed matter can also have sufficient image quality as a product. Among the printing presses, an offset printing press is preferable in terms of manufacturing cost and print quality.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples as long as the gist thereof is not exceeded. In addition, “parts by mass” and “mass%” shown in the examples indicate dry solids equivalents or values of substantial components unless otherwise specified. Moreover, the coating amount indicates a dry solid content conversion amount.

<Measurement of average particle size of kaolin>
The surface of the printing paper is photographed with a scanning electron microscope (JSM-6490LA, manufactured by JEOL Ltd.), and the particle diameter is calculated from the photographed image by regarding the photographed kaolin particles as a sphere having an approximate area, The average particle size was calculated by measuring the particle size from 100 kaolin particles present in the photographed image. The average particle diameter is shown in Table 1.

  For each example and each comparative example, printing paper was prepared according to the following procedure.

<Preparation of paper stock>
The paper stock was prepared according to the following contents.
LBKP (freeness 400 mlcsf) 100 parts by weight Sizing agent (alkyl ketene dimer system) The number of blending parts is listed in Table 1. Filler (light calcium carbonate) 20 parts by weight Amphoteric starch 0.08 parts by weight Sulfuric acid band 0.08 parts by weight

<Preparation of coating layer coating solution>
The coating layer coating solution was prepared according to the following contents.
Kaolin The average particle size and the number of parts are listed in Table 1. Other pigment types and the number of parts are listed in Table 1. Phosphate esterized starch The number of parts is listed in Table 1 Ethylene-vinyl acetate copolymer The number of parts is listed in Table 1 Water-soluble cation salt The kind and the number of blending parts were blended as described above in Table 1, mixed and dispersed with water, and adjusted to a concentration of 40% by mass.

<Preparation of printing paper>
The above-mentioned stock was made with a long paper machine to obtain a base paper. Subsequently, using the film transfer coater equipped on the on-machine coater, the above coating layer coating solution was applied and dried on both sides so that the coating amount per side was 7 g / m ² . After drying, a calendar process was performed to obtain a printing paper having a basis weight of 49 g / m ² . The calendering was performed using a device composed of an elastic roll and a metal roll, and the nip linear pressure was set at a linear pressure of 50 kN / m within a range in which a thickness profile in the width direction was appropriately obtained. The temperature of the metal roll was 40 ° C.

Other pigments abbreviated in Table 1 are as follows.
A: Heavy calcium carbonate (WH-90, manufactured by Hyogo Clay Company)
B: Light calcium carbonate (TP123, manufactured by Okutama Kogyo Co., Ltd.)
C: Synthetic silica (Nipgel AZ-204, manufactured by Tosoh Silica)

The compounds selected from the water-soluble cation salts shown in abbreviations in Table 1 are as follows.
a: calcium chloride b: calcium nitrate c: magnesium sulfate d: sodium chloride

  About the obtained printing paper of each Example and each comparative example, it evaluated by the following method about each item.

<Surface resistivity>
The surface resistivity is 4329A type insulation resistance meter (HIGH RESISTANCE METER) and 16008A type electrode (RESITIVITY CELL) manufactured by Yokogawa Hewlett-Packard Company. The measurement was performed under the following environmental conditions with a charge voltage of 100 V and a charge time of 30 seconds.

<Evaluation of suitability for offset printing>
An offset rotary printing press (Lithopia BT-2-600 type) manufactured by Mitsubishi Heavy Industries, Ltd., printing speed: 150 m / min, ink used: Dainippon Ink, Web World Terrace N, black, indigo, red, yellow ) Was printed at 6000 m, and the occurrence of blanket piling after printing and the state of the print sample were determined by visual evaluation. In the present invention, if the evaluation is 3 to 5, the printing paper has an offset printability.
5: Extremely good.
4: Good.
3: Range in which there is no practical problem.
2: Defect.
1: Extremely bad.

<Evaluation of color density uniformity>
An evaluation image was printed at 6000 m at 105 m / min with an aqueous pigment ink using an inkjet printer Jet Leader 1500 manufactured by Tokyo Kikai Seisakusho. Black, cyan, magenta, yellow solid colors and other three-color inks other than black, a total of seven colors (red, green, blue) in a solid pattern of 3 colors x 3 cm square with no gaps in a horizontal row Printing was done by recording side by side. The color density uniformity of each solid color portion of the printed portion was determined by visual evaluation. In the present invention, if the evaluation is 3 to 5, the printing paper is excellent in color density uniformity.
5: The color density is uniform.
4: The density is slightly non-uniform depending on the color.
3: The color density is slightly uneven.
2: The color density is partially uneven.
1: The color density is non-uniform throughout the printed portion.

<Evaluation of penetration-through inhibition>
An evaluation image was printed at 6000 m at 105 m / min using an inkjet printer Jet Leader 1500 manufactured by Tokyo Machine Works. Printing was performed by a method of recording a black solid print pattern in 10 cm × 10 cm square. The whiteness is measured from the opposite side of the black solid printing portion using the whiteness measurement method defined in JIS P 8148: 2001. “Whiteness of white portion without printing (optical%)” — “Black solid” The degree of whiteness (optical%) of the printed part was calculated, and the penetration of ink on the printing paper was evaluated. The whiteness was measured by using a PF-10 made by Nippon Denshoku Co., Ltd. and placing a sample on a standard plate under the conditions of UV cut. In the present invention, if the evaluation is 3 to 5, the printing paper is excellent in the see-through suppression.
5: Less than 10 optical%.
4: 10 optical% or more and less than 13 optical%.
3: 13 optical% or more and less than 16 optical%.
2: 16 optical% or more and less than 19 optical%.
1: 19% optical or more.

<Evaluation of dot reproducibility>
An evaluation image using standard image data (image name: N5A) published by the Japanese Standards Association was printed at 6000 m at 105 m / min using an inkjet printer Jet Leader 1500 manufactured by Tokyo Machine Works. The printed image was observed with a microscope, and the degree to which the landed dot shape collapsed from a perfect circle and the sharpness of the dot outline were determined by visual evaluation. In the present invention, if the evaluation is 3 to 5, the printing paper is excellent in dot reproducibility.
5: True circle and clear.
4: Almost perfect circle and clear.
3: Slightly lost from the perfect circle and slightly lacking in clarity. However, there is no practical problem.
2: Disrupted somewhat from the perfect circle and somewhat lacking in clarity.
1: It breaks from a perfect circle and lacks clarity.

  Table 2 shows the evaluation results of each example and each comparative example.

  From Table 2, the printing paper of each example corresponding to the present invention has offset printing suitability, color density uniformity for a rotary industrial inkjet printer using an aqueous pigment ink, and strikethrough suppression, and It can be seen that the dot reproducibility is excellent.

  On the other hand, it can be seen from Table 2 that the effects of the present invention cannot be obtained in each comparative example that does not satisfy the conditions of the present invention.

Claims (2)

A base paper and at least one coating layer containing a pigment, a binder, and a water-soluble polyvalent cation salt on at least one side of the base paper, and at least one of the pigments has an average particle size of 0.20 μm or more 1. It is kaolin of 50 μm or less, the content of the kaolin in the coating layer is 50 parts by mass or more with respect to 100 parts by mass of the pigment in the coating layer, and the coating of the water-soluble polyvalent cation salt The content in the layer is 1.0 part by mass or more and 6.0 parts by mass or less with respect to 100 parts by mass of the pigment in the coating layer, and is 23 ° C. and 50% determined in accordance with JIS K 6911: 2006. Printing paper for rotary industrial inkjet printers having a surface resistivity of 2.0 × 10 ¹⁰ Ω or more and 5.0 × 10 ¹² Ω or less on the side of the coating layer having the coating layer in an RH environment.   A printed matter manufacturing method comprising: a step of obtaining a printing paper for an industrial inkjet printer according to claim 1; and a step of obtaining a printed matter by printing on the printing paper with a rotary industrial inkjet printer using a water-based pigment ink. Method.