JP2011132647A - Pigment-coated paper for printing and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide pigment-coated paper for gloss ink-based printing, excellent in offset printing suitability, also having printing suitability with a high speed ink jet printer using a water-based pigment ink, and suitable for hybrid printing. <P>SOLUTION: The pigment-coated paper for printing, in which at least one pigment-coated layer is disposed on at least one side of base paper is characterized in that the most surface layer of the pigment-coated layer is a layer obtained by coating a dried coating layer comprising 100 pts.mass of a pigment, ≥50 pts.mass of light calcium carbonate having an average particle diameter (short diameter) of ≤0.8 μm, and a latex binder and casein as a binder, with the aqueous solution of a water-soluble polybasic metal salt, and then drying the coated layer. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a pigment-coated paper for printing. More specifically, the present invention relates to a pigment-coated paper for gloss printing suitable for hybrid printing, which is excellent in offset printing suitability and has print suitability by a high-speed ink jet printer using aqueous pigment ink.

Offset printing has become the mainstream of printed matter manufacturing methods because high-speed and large-volume printing is possible. On the other hand, with the development of inkjet recording technology in recent years, variable data such as coupons, lucky numbers, barcodes, QR codes, etc. are additionally printed with a monochrome inkjet printer on a printed matter obtained by preprinting fixed data by a full color offset printing method. The number of cases where hybrid printing is performed is increasing.
As an example, in the packaging field, for example, in a food box, after fixed data is offset printed on a coated paperboard (so-called coated ball) during the campaign period, the serial number and QR code are additionally printed, and box making is performed. In some cases.

  In the physical distribution field, mail services are growing greatly on the back of inexpensive delivery charges. Usually, mail is printed with an address and barcode on the envelope surface, and shipment and receipt confirmation are performed by reading the barcode. An envelope using non-coated paper can be directly recorded by inkjet, but an envelope using pigment-coated paper is used to obtain a higher-quality offset print image. In this case, a method is adopted in which a label on which necessary data such as an address and a barcode is printed is attached to the envelope surface on which the offset print image is printed. This requires not only the label itself, but also a release paper that protects the pressure-sensitive adhesive surface, and a sticking operation also occurs. If ink jet recording can be performed directly on an envelope based on pigment coated paper, it is advantageous from the viewpoint of cost, resource saving, energy saving, and working time.

In these applications, it may be exposed to high-temperature and high-humidity environments depending on the weather, or it may come into contact with moisture such as rain, so it may be unreliable in recording with water-based dye ink. It is rare.
Further, in these applications, when passing through an automatic sorting apparatus such as a box making process or a post office, contact with a member and an ink jet printing portion are rubbed, and therefore, improvement in scratch resistance is desired.

As the pigment-coated paper for printing used in offset printing, there are usually those described in JP-A-7-189179 (Patent Document 1). The coated paper is usually coated with a coating layer coating solution containing pigments, binders, etc. at least 10 g / m ² per side of the base paper using various coaters, and then calendered to smooth the surface. Manufactured. Since these general coated papers mainly focus on printing process suitability, they have a pigment coating layer strength that does not generate picking or blistering in offset printing, but have poor ink-jet ink absorbability.

  As a printing paper suitable for both offset printing and inkjet printing, a method of providing a layer containing a pigment mainly composed of silica on a base paper (Japanese Patent Laid-Open No. 2002-127487, Patent Document 2) has been proposed. By using silica in the pigment coating layer, the ink-jet ink absorbability is improved, but since it does not cause picking during offset printing, it is necessary to use a large amount of binder components, so the gloss of the pigment coated paper surface is reduced. In addition, the texture of gloss printing paper cannot be obtained, and the use of silica increases the manufacturing cost and greatly exceeds the cost of general gloss printing paper, so it is not accepted by the market. .

  In addition, a cationic resin having a specific structure is coated on the base paper in advance, and a pigment coating layer mainly composed of light calcium carbonate is provided, and a specific surface by the Bristow method (J. TAPPI No. 51-87) on the surface is provided. There has been proposed a coated paper for printing (Japanese Patent Application Laid-Open No. 2004-84141, Patent Document 3) in which the amount of ink transfer in the absorption time is defined. However, even with this method, the surface of the pigment-coated paper cannot obtain a high glossiness, and the texture of the gloss printing paper cannot be obtained.

Further, at least two coating layers are provided on the base paper, the base paper adjacent layer contains a pigment having a specific shape, and the surface layer contains thermoplastic organic fine particles having a specific glass transition temperature. Prevents cracks during offset printing and electrophotographic recording by generating cracks on the surface and improving the air permeability of the coating layer, and is also used as inkjet paper (Japanese Patent Laid-Open No. 2005-36379, Patent Documents) 4) has also been proposed. However, since the viscosity of inkjet ink is much lower than the viscosity of offset printing ink and the heat melting viscosity of electrophotographic toner, if there are many cracks on the paper surface, the ink bleeds along the cracks. A feathering phenomenon occurs and satisfactory print image quality cannot be obtained.
Furthermore, the coated paper for pressure-sensitive adhesive sheets in which the Oken-type smoothness on the surface of the pigment coating layer, the steecht sizing degree of the base paper, the density of the pigment coated paper, etc. are specified in a specific range (Japanese Patent Application Laid-Open No. 2009-228171). No. 5, Patent Document 5) has been proposed. However, in this case as well, although satisfactory printability by monochrome ink jet can be obtained with the aqueous dye ink, the fixability (abrasion resistance) of the aqueous pigment ink is poor. Accordingly, the present situation is that a pigment-coated paper for printing having surface strength capable of offset printing, printability by aqueous pigment inkjet, and high surface gloss has not been obtained.

JP-A-7-189179 (first item) Japanese Patent Laid-Open No. 2002-127487 (first item) JP 2004-84141 A (Section 6) Japanese Patent Laying-Open No. 2005-36379 (first item) JP 2009-228171 A (first item)

  An object of the present invention is to provide a gloss-based pigment-coated paper suitable for hybrid printing which is excellent in offset printing suitability and also has print suitability by a high-speed ink jet printer using a water-based pigment ink. It is an object to provide a pigment-coated paper with excellent wet pick strength during printing.

  As a result of diligent research to solve the above-mentioned problems, the present inventor used specific light calcium carbonate as the outermost layer of the pigment coating layer, blended casein as a binder, and further an aqueous solution of a water-soluble polyvalent metal salt. It has been found that the problem can be solved by forming a layer treated with 1. The present invention is as follows.

(1) In a pigment coated paper for printing in which at least one pigment coated layer is provided on at least one surface on a base paper, the outermost layer of the pigment coated layer has an average particle diameter ( An aqueous solution of a water-soluble polyvalent metal salt is applied to a dried coating layer containing 50 parts by weight or more of light calcium carbonate having a minor axis) of 0.8 μm or less and containing a latex binder and casein as binders, A pigment coated paper for printing, characterized in that it is a dried layer.
(2) The pigment-coated paper for printing according to (1), wherein the latex binder is a styrene / butadiene copolymer latex.
(3) The print-coated paper for printing according to (1) or (2), wherein casein is contained in an amount of 1 to 10 parts by mass with respect to 100 parts by mass of the pigment.
(4) The pigment-coated paper for printing according to any one of (1) to (3), wherein the water-soluble polyvalent metal salt is calcium formate.
(5) The pigment-coated paper for printing according to any one of (1) to (4), wherein the outermost layer contains 3 to 15 parts by mass of a hollow plastic pigment with respect to 100 parts by mass of the pigment.
(6) The pigment for printing according to any one of (1) to (5), wherein the pigment coating layer has an inner coating layer containing light calcium carbonate as a main component between the base paper and the outermost layer. It is coated paper.
(7) In a method for producing a pigment-coated paper for printing in which at least one pigment-coated layer is provided on at least one surface of a base paper, the outermost layer of the pigment-coated layer is an average of 100 parts by mass of pigment. A coating solution containing 50 parts by weight or more of light calcium carbonate having a particle size (minor axis) of 0.8 μm or less and a latex binder and casein as a binder is applied and dried, and then an aqueous solution of a water-soluble polyvalent metal salt. Is a method for producing a pigment-coated paper for printing, which is characterized by coating and drying.

  According to the present invention, it is possible to obtain a pigment-coated paper for gloss printing suitable for hybrid printing, which is excellent in offset printing suitability, particularly excellent in wet pick strength, and also has print suitability by a high-speed inkjet printer using an aqueous pigment ink.

  The present invention will be described in detail below. The printing pigment-coated paper of the present invention is a printing pigment-coated paper in which at least one pigment coating layer is provided on at least one surface of a base paper. The outermost layer of the pigment coating layer is a pigment 100. In a mass part, the dried coating layer containing 50 parts by mass or more of light calcium carbonate having an average particle size (minor axis) of 0.8 μm or less, and containing a latex binder and casein as a binder, It is characterized by being a layer coated with an aqueous solution of a metal salt and dried.

  The outermost layer of the pigment coating layer only needs to be coated with an aqueous solution of a water-soluble polyvalent metal salt, and may be a single layer or a plurality of layers. The formation of a plurality of layers is preferable because the kind of pigment in each layer, the binder ratio, and the like can be changed. However, since the manufacturing cost increases, it is preferable to limit the number to two to three pigment coating layers.

  The light calcium carbonate used as the main component in the outermost layer is not particularly limited as long as the average particle diameter (minor axis) is 0.8 μm or less. As the shape of the light calcium carbonate, for example, a columnar shape or a spindle shape is preferable. When the average particle diameter (minor axis) exceeds 0.8 μm, the glossiness of white paper is lowered, and further, the ink gloss after offset printing is lowered, and the texture of the printed matter is impaired. Furthermore, the pigment particles of the aqueous pigment ink may sink into the gaps between the pigment particles, and the print density may be reduced. The main component here means containing 50 parts by mass or more of light calcium carbonate in 100 parts by mass of the pigment, preferably 70 parts by mass or more, and more preferably 80 parts by mass or more. In addition, although the value described in the catalog of the product to use is employ | adopted for an average particle diameter (short axis), when there is no description, the value measured with the Digimatic caliper from a SEM photograph (magnification x10,000) is used. Adopt it.

  In the outermost layer, a pigment other than a specific light calcium carbonate can be used in combination. Specific examples thereof include, for example, kaolin, heavy calcium carbonate, agglomerated calcium carbonate, light calcium carbonate having an average particle diameter (short axis) exceeding 0.8 μm, talc, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, Made of mineral materials such as alumina, magnesium carbonate, magnesium oxide, silica, particulate silica, colloidal silica, magnesium aluminosilicate, particulate calcium silicate, particulate magnesium carbonate, white carbon, satin white, bentonite, zeolite, sericite, smectite Pigments, polystyrene resins, styrene / acrylic copolymer resins, urea resins, melamine resins, acrylic resins, vinylidene chloride resins, benzoguanamine resins, and organic pigments made of these micro hollow particles or through-hole organic materials It is below.

  Of these, kaolin is excellent in offset printability but may hinder the fixing of the aqueous pigment ink. Therefore, kaolin is preferably used in an amount of 30 parts or less with respect to 100 parts by mass of the pigment. Further, it is preferable to use 3 to 15 parts by mass of an organic pigment (also referred to as a hollow plastic pigment) made of fine hollow particles or a through-hole type organic material in 100 parts by mass of the pigment. When it is used in an amount of 3 parts by mass or more, a gloss improvement effect is exhibited, and by reducing the blending to 15 parts by mass or less, a decrease in surface strength is prevented and both offset printing suitability is achieved.

As the binder used in the outermost layer, a latex binder and casein are used in combination.
Latex binders include diisobutylene / maleic anhydride copolymer salt, styrene / maleic anhydride copolymer salt, ethylene / acrylic acid copolymer salt, styrene / acrylic acid copolymer salt, urea resin, melamine resin, Amide resin, styrene / acrylic copolymer latex, polyurethane latex, styrene, acrylic acid, methacrylic acid, acrylic ester, methacrylic ester, acrylamide, methacrylamide, methyl vinyl ether and other vinyl polymers and copolymers, Examples thereof include synthetic rubber latex such as methyl methacrylate / butadiene resin, polyurethane resin, polyester resin, polyamide resin, olefin / maleic anhydride resin, melamine resin, and the like. Among them, the styrene / butadiene copolymer latex is preferably used as an essential component since the surface strength of the pigment-coated paper for printing is easily obtained and the decrease after gloss is small.

  The latex binder may be blended in an amount of about 4 to 30 parts by mass with respect to 100 parts by mass of the pigment, and 8 to 20 parts by mass is a more preferable range. Incidentally, when the content is less than 4 parts by mass, sufficient surface strength cannot be obtained, and there is a possibility that offset printing may be hindered. When it exceeds 30 parts by mass, the ink-jet ink solvent permeability may be reduced. .

  Casein has the effect of improving the surface strength particularly when wet without causing a reduction in glossiness due to the reaction with the water-soluble polyvalent metal salt applied in the post-treatment. As addition amount of casein, 1-10 mass parts is preferable with respect to 100 mass parts of outermost layer pigments. When the addition amount is less than 1 part by mass, a remarkable addition effect cannot be obtained, and when the addition amount exceeds 10 parts by mass, the ink-jet ink solvent permeability may be lowered.

  Moreover, starch, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, gum arabic, etc. can also be used together in the outermost layer.

  When providing a plurality of pigment coating layers, the inner coating layer provided between the outermost layer and the base paper is not particularly limited to pigments and binders. As the pigment, the pigments exemplified in the outermost layer can be appropriately used, but those having a specific average particle size used in the outermost layer can be preferably used. In particular, the inner coating layer preferably contains 50 parts by mass or more of the light calcium carbonate with respect to 100 parts by mass of the pigment, more preferably 60 parts by mass or more, and most preferably 70 parts by mass or more. Incidentally, when the light calcium carbonate content is less than 50 parts by mass, there is a possibility that sufficient solvent absorbability of the inkjet ink cannot be obtained.

  As the pigment, the binder exemplified in the outermost layer can be used as appropriate, but the use of a latex binder is preferred. The latex binder is preferably contained in an amount of about 8 to 15 parts by mass with respect to 100 parts by mass of the pigment. In particular, when the latex binder is a styrene / butadiene copolymer latex, by setting the content to 8 parts by mass or more, it is possible to obtain sufficient surface strength to prevent troubles in offset printing suitability, and 15 parts by mass. By making it below, it can prevent that the solvent absorptivity of an inkjet ink falls. In addition, a binder other than the styrene / butadiene copolymer can be used in combination, and as a specific example, it can be appropriately selected from those used in the outermost layer.

  In each coating layer, various auxiliary agents such as surfactants, pH regulators, viscosity modifiers, softeners, gloss imparting agents, waxes, dispersants, flow modifiers, stabilizers, antistatic agents , A crosslinking agent, a sizing agent, a fluorescent brightening agent, a colorant, an ultraviolet absorber, an antifoaming agent, a water-resistant agent, a plasticizer, a lubricant, an antiseptic, and a fragrance are appropriately included as necessary. May be.

As for the coating amount of the outermost layer of this invention, 6-30 g / m < ² > is preferable. When the coating amount is less than 6 g / m ² , there is a possibility that the glossiness cannot be optimized because sufficient coating cannot be performed. In addition, when it is more than 30 g / m ² , the operability is lowered, such as the drying property at the time of coating is deteriorated, the manufacturing cost is increased, and when processing into a box or an envelope in the packaging field or the logistics field, There is also a possibility that the outermost layer may be lost at the folded portion or the folded portion. A more preferable coating amount is 6 to 18 g / m ² , and a particularly preferable coating amount is 6 to 12 g / m ² .

As for the coating amount of the said inner side coating layer of this invention, 3-30 g / m < ² > is preferable. In particular, in the case of the inner coating layer in contact with the base paper, if the coating amount is less than 3 g / m ² , it is difficult to fill the unevenness of the base paper, and there is a possibility that glossiness may be lowered. When the amount is more than 30 g / m ² , the operability is lowered such as poor drying during coating, and the production cost is increased. In addition, when processing into a box or envelope in the packaging field or the logistics field, There is also a possibility that the inner coating layer may be lost in the folded portion or the folded portion. A more preferable coating amount is 3 to 15 g / m ² , and a particularly preferable coating amount is 6 to 12 g / m ² . In the case having an inner coating layer, can also reduce the coverage of the outermost layer, 3~27g / ^{m 2} approximately, is preferably 3 to 20 g / ^{m 2,} more preferably 4 to 15 g / ^{m 2} .

  The coating method for forming the pigment coating layer is generally a conventional coating apparatus such as a blade coater, air knife coater, roll coater, reverse roll coater, bar coater, curtain coater, slot die coater, gravure coater, or Chanplex. Coating devices such as coaters, brush coaters, two rolls, metering blade type size press coaters, bill blade coaters, short dwell coaters, gate roll coaters and the like can be used as appropriate. Among these, blade coaters that can apply high-concentration coating liquids at high speeds suppress the penetration of the binder resin of the coating layer into the base paper, so the amount of the binder resin used makes it possible to absorb ink jet ink and surface strength. These layers are preferably used because they are easy to obtain, and because excellent surface properties are obtained and high glossiness is easily obtained.

In the present invention, by applying an aqueous solution of a water-soluble polyvalent metal salt on the outermost layer of a pigment coating layer formed by applying and drying on a base paper, good offset printability and water-based pigment inkjet ink The solvent passage is obtained.
Specific examples of such polyvalent metal salts include formic acid, acetic acid, citric acid, tartaric acid, lactic acid, malonic acid, maleic acid, glycolic acid, malic acid, acrylic acid, hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid and other calcium, zinc , Magnesium and aluminum salts. Among these, zinc sulfate and calcium formate can improve the wet strength and provide excellent offset printing suitability, so that the amount of binder used can be reduced and water pigment ink-jet ink absorbability is easily obtained. Furthermore, calcium formate is preferably used because it imparts water pigment inkjet ink solvent permeability.

The application amount of the polyvalent metal salt is not particularly limited, but is, for example, about 0.001 to ² g / m ² , more preferably 0.02 to 0.5 g / m ² . In order to obtain a remarkable coating effect, it is necessary to apply 0.001 g / m ² or more, and by setting it to ² g / m ² or less, it is possible to prevent the pigment ink fixability from being lowered.
As a method for applying the polyvalent metal salt, the same application apparatus as that for the coating layer is used. Furthermore, it can be used as a rewetting liquid for a cast coater, and nip coating using a calendar is also possible in the smoothing process.

  The pigment-coated paper having the pigment coating layer is excellent in offset printing suitability and excellent in printability by a high-speed ink jet printer using an aqueous pigment ink. In addition, because it has excellent scratch resistance of the ink-jet printing part required when passing through the box making process in the package field and the automatic sorting device such as the post office in the logistic field, it can be used for boxes and envelopes in the package field and the logistic field. It is a pigment-coated paper suitable for applications. In addition, since the strength of the coating layer is superior to conventional printing paper using silica as the main component in the coating layer (for example, Patent Document 2), it is suitable for processing boxes and envelopes in the packaging and logistics fields. Is also a suitable pigment coated paper.

  The pigment coating layer may be provided on one side of the base paper or may be formed on both sides. The base paper will be described below.

  About the pulp which comprises the base paper in this invention, in the range which does not impair the effect of this invention, there is no limitation in the manufacturing method, a kind, etc. in particular. For example, chemical pulp such as KP, mechanical pulp such as SGP, RGP, BCTMP and CTMP, waste paper pulp such as deinked pulp, and non-wood pulp such as kenaf, bamboo, straw, hemp, etc. Organic synthetic fibers such as polyamide fibers and polyester fibers, recycled fibers such as polynosic fibers, and inorganic fibers such as glass fibers, ceramic fibers, and carbon fibers can also be used in combination. In addition, it is preferable to use chlorine free pulp, such as ECF pulp and TCF pulp, as the pulp used for the base paper.

  The beating degree of the pulp constituting the base paper is not particularly limited, but is preferably adjusted in the range of 300 to 550 cc (CSF), for example. When the beating degree exceeds 550 cc, the entanglement and adhesive strength of the fibers are insufficient, so that satisfactory internal strength cannot be obtained, and blisters may occur during offset printing. On the other hand, if it is less than 300 cc, the effect of improving the adhesion due to the entanglement of the fibers is saturated, and conversely, the printing strength may be reduced due to the influence of the single fiber strength reduction. More preferably, it is 350-520cc.

  In the base paper, a binder, a dry paper strength enhancer, and a wet paper strength enhancer can be used in combination as long as the effects of the present invention are not impaired. Examples of the binder include water-soluble polymers such as various starches, polyvinyl alcohol, and carboxymethyl cellulose. Examples of the dry paper strength enhancer include anionic, cationic, or amphoteric polyacrylamide resins. Examples of the wet paper strength enhancer include polyamide resins, melamine / formaldehyde resins, urea / formaldehyde resins, polyamide / polyamine / epichlorohydrin resins, and polyethyleneimine resins.

  In the present invention, the sizing degree of the base paper is not particularly limited, but is generally adjusted to a Steecht sizing degree of about 100 seconds or less. As a method for adjusting the sizing degree, the internal sizing agent contained in the raw material and the surface sizing agent applied by a size press coating machine are adjusted to a predetermined sizing degree, either singly or in combination. As internal sizing agents, sizing agents such as rosin sizing agents, synthetic sizing agents, petroleum resin sizing agents, alkyl ketene dimers, and alkenyl succinic anhydride neutral sizing agents can be used. A suitable sizing agent and fixing agent are used in combination. Examples of the surface sizing agent include styrene / maleic acid copolymer, styrene / acrylic acid copolymer, styrene / methacrylic acid copolymer, etc. in addition to those used in the above-mentioned internal sizes. It is not something.

  Moreover, a filler may be blended in the base paper as necessary. As the filler, various pigments generally used for fine paper can be used, such as kaolin, calcined kaolin, calcium carbonate, calcium sulfate, barium sulfate, titanium dioxide, talc, zinc oxide, alumina, magnesium carbonate, magnesium oxide, Mineral pigments such as silica, white carbon, bentonite, zeolite, sericite and smectite, as well as fine hollow particles, solid particles and polystyrene resins, urea resins, melamine resins, acrylic resins and vinylidene chloride resins Examples thereof include organic pigments such as through-hole particles.

  In addition to the pulp fiber and filler, various anionic, nonionic, and cationic properties that have been used in the past are included in the stock when the base paper is made, as long as the desired effects of the present invention are not impaired. Alternatively, various papermaking internal additives such as amphoteric yield improver and freeness improver can be appropriately selected and used as necessary. Furthermore, internal additives for papermaking such as dyes, fluorescent brighteners, pH adjusters, antifoaming agents, pitch control agents, slime control agents and the like can be added as necessary.

  There is no particular limitation on the paper making method of the base paper. For example, an acidic paper making method in which the paper making pH is around 4.5, an alkaline filler such as calcium carbonate is contained as a main component, and the paper making pH is from about 6 to about the paper making pH. All paper making methods such as neutral paper making method with 9 weak alkalinity can be applied, and long paper machine, twin wire paper machine, round net paper machine, Yankee paper machine etc. are used as appropriate can do.

Even when the base paper used in the present invention is a paperboard, the constituted pulp is not particularly limited. For example, one or two or more of bleached or unbleached chemical pulp, mechanical pulp, deinked or undeinked pulp waste paper pulp, and the like are used as appropriate. In addition, a sizing agent, a paper strength agent, a chemical stabilizer, a filtering agent, a filler, a dye, and the like can be appropriately added to the base paper as necessary. The base weight of the base paper is usually about 150 to 650 g / m ² .
In the case of paperboard base paper, it is possible to use the above filler.
As a paper machine for obtaining a paperboard base paper, a paper machine such as a long net paper machine, a short net paper machine, a circular net paper machine, an on-top former or a gap former can be used. The base paper is made by combining them. When the base paper is a paperboard, it is excellent in strength, so that it becomes a pigment-coated paperboard for printing particularly suitable for applications such as boxes and envelopes used in the packaging field and the logistics field.

  The pigment-coated paper for printing of the present invention is one in which each pigment-coated layer is provided and then subjected to a smoothing treatment to develop surface gloss. As a smoothing processing method, a normal smoothing processing device such as a super calendar, a gloss calendar, a soft calendar, or the like is used. The smoothing process may be appropriately performed on-machine or off-machine, and the form of the pressure device, the number of pressure nips, heating, and the like are appropriately adjusted according to a normal smoothing device. As various physical properties of the pigment coated paper for printing after the smoothing treatment, the white paper glossiness (JIS-P8142) at 75 degrees on the surface is not particularly limited. This is preferable because a printed matter with high ink gloss can be obtained.

Moreover, although it does not specifically limit about the density as a pigment coated paper for printing, It is preferable that it is 0.95-1.15 g / cm < ³ >. If the density is less than 0.95 g / cm ³ , sufficient printing strength may not be obtained, and if it exceeds 1.15 g / cm ³ , the ink-jet ink absorption capacity cannot be secured, so Ink absorbability may not be obtained. However, the density when using paperboard as the base paper is preferably about 0.75 to 1.00.

  In the present invention, the method for producing a hybrid printed material is not particularly limited. For example, the fixed information can be created by printing the variable information with an inkjet printer after printing it with an offset printer, but it can also be offset printed after the variable information is printed with the inkjet printer first. Both of them can be online or offline, and the paper form can be created by either plain or winding. When used in the packaging field or the physical distribution field, hybrid printing may be performed before box making or bag making, or variable information may be printed by an ink jet printer after box printing or bag making.

  Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited thereto. In the examples, “parts” and “%” are parts by mass and mass% unless otherwise specified.

Example 1
[Manufacture of base paper]
A pulp slurry of 90 parts by weight of LBKP (CSF freeness 450 ml) and 10 parts by weight of NBKP (CSF freeness 450 ml), alkenyl succinic anhydride (trade name: Fibran 81, manufactured by National Starch Co., Ltd.) 0.05 mass as an internal sizing agent Part, 0.2 part by mass of polyacrylamide resin (trade name: PS194-7, manufactured by Arakawa Chemical Industries) and 0.6 part by mass of sulfuric acid band are added as a paper strength enhancer, and these mixtures are diluted with white water. A paper stock having a pH of 5.3 and a solid content concentration of 1.1% was prepared. This stock is subjected to a papermaking machine to make a paper, and the obtained wet paper has 0.2 parts of a styrene / maleic acid copolymer (trade name: Polymeralon 385, manufactured by Arakawa Chemical Industries), oxidized starch ( A size press liquid containing 5.5% concentration of product name: Ace A (manufactured by Oji Cornstarch Co., Ltd.) is applied with a size press apparatus so that the applied amount is 2 g / m ² in terms of dry mass, dried, and further A smoothing process was performed using a machine calendar to obtain a base paper having a basis weight of 94 g / m ² .

[Preparation of coating solution for inner coating layer]
Spindle-like light calcium carbonate 63% dispersion (trade name: Tamapearl TP221GS, average particle size (minor axis) 0.3 μm, manufactured by Okutama Kogyo Co., Ltd.) 159 parts by mass, oxidized starch (trade name: Ace A, manufactured by Oji Cornstarch) ) And 20 parts by weight of a 20% aqueous solution of styrene / butadiene copolymer latex (trade name: T-2531H, manufactured by JSR) 24 parts by weight were added and stirred. A 50% coating solution was prepared.

[Dissolution of casein]
Water, 10 parts by mass of urea, and 100 parts by mass of New Zealand casein are mixed and stirred, and the temperature rise is started. Next, 7.7 parts by mass of 25% ammonia solution was added, the temperature was raised to 60 ° C., held for 20 minutes, and then cooled to obtain a 10% casein aqueous solution.
[Preparation of coating solution for outermost layer]
Water, 63% dispersion of spindle-shaped light calcium carbonate in 36 parts by mass of the 10% aqueous solution of casein obtained above (trade name: Tamapearl TP221GS, average particle size (minor axis) 0.3 μm, manufactured by Okutama Kogyo Co., Ltd.) 159 Mass parts and 37 parts by mass of a 50% dispersion of styrene / butadiene copolymer latex (trade name: T-2531H, manufactured by JSR) were added and stirred to prepare a coating solution having a solid content concentration of 50%.

[Formation of inner coating layer]
The inner coating layer coating solution was applied to both sides of the base paper using a blade coater so that the dry coating amount per side was 7 g / m ² to form an inner coating layer.
[Formation of outermost layer]
The outermost layer coating solution is applied onto the inner coating layer formed on both sides of the base paper using a blade coater so that the dry coating amount per side is 10 g / m ^2. Formed.
[Application of polyvalent metal salt aqueous solution]
After applying a 4% aqueous solution of calcium formate onto the outermost layer formed on both sides of the base paper so as to adhere 0.12 g / m ² per side using a roll coater, linear pressure is applied using a super calender. Smoothing treatment was performed under the conditions of 60 kg / cm and 2 nips, and a pigment-coated paper for printing having a basis weight of 128 g / m ² was obtained.

Example 2
In the preparation of the coating solution for the outermost layer in Example 1, 159 parts by mass of a spindle-shaped light calcium carbonate 63% dispersion (trade name: Tama Pearl TP221GS, average particle size (short axis) 0.3 μm, manufactured by Okutama Kogyo Co., Ltd.) Example 1 except that 167 parts by mass of a columnar light calcium carbonate 60% dispersion (trade name: Tama Pearl TP-123CS, average particle diameter (short diameter) 0.44 μm, manufactured by Okutama Kogyo Co., Ltd.) was used instead of Similarly, a pigment-coated paper for printing having a basis weight of 128 g / m ² was obtained.

Example 3
In the preparation of the coating solution for the outermost layer in Example 1, 159 parts by mass of a spindle-shaped light calcium carbonate 63% dispersion (trade name: Tama Pearl TP221GS, average particle size (short axis) 0.3 μm, manufactured by Okutama Kogyo Co., Ltd.) Example 1 with the exception that 161 parts by mass of a 62% dispersion of columnar light calcium carbonate (trade name: Tamapearl TP-123HG, average particle diameter (short diameter) 0.2 μm, manufactured by Okutama Kogyo Co., Ltd.) was used instead of Similarly, a pigment-coated paper for printing having a basis weight of 128 g / m ² was obtained.

Example 4
In the preparation of the coating solution for the outermost layer in Example 1, 159 parts by mass of a spindle-shaped light calcium carbonate 63% dispersion (trade name: Tama Pearl TP221GS, average particle size (short axis) 0.3 μm, manufactured by Okutama Kogyo Co., Ltd.) Example 1 except that 154 parts by mass of a 65% dispersion of spindle-shaped light calcium carbonate (trade name: YCC-FD, average particle diameter (short diameter) 0.6 μm, manufactured by Yabashi Kogyo Co., Ltd.) is used instead of Similarly, a pigment-coated paper for printing having a basis weight of 128 g / m ² was obtained.

Example 5
In the preparation of the outermost layer coating liquid of Example 1, the same procedure as in Example 1 was conducted, except that 20 parts by mass of a 26% dispersion of a hollow plastic pigment (trade name: AE-852, manufactured by JSR) was added. Thus, a pigment-coated paper for printing having a basis weight of 128 g / m ² was obtained.

Example 6
In the application of the polyvalent metal salt aqueous solution in Example 1, a 4% aqueous solution of zinc sulfate was used in place of the 4% aqueous solution of calcium formate, and the coating was performed so as to adhere to 0.12 g / m ^2. In the same manner as in No. 1, a pigment-coated paper for printing having a basis weight of 128 g / m ² was obtained.

Example 7
In the application of the polyvalent metal salt aqueous solution of Example 1, the concentration of the calcium formate aqueous solution was reduced from 4% to 1%, and it was applied in the same manner as in Example 1 except that it was applied so as to adhere 0.03 g / m ^2. A pigment-coated paper for printing with an amount of 128 g / m ² was obtained.

Example 8
In the application of the polyvalent metal salt aqueous solution of Example 1, the basis weight was the same as in Example 1 except that the concentration of the calcium formate aqueous solution was increased from 4% to 10% and applied so as to adhere 0.3 g / m ^2. A pigment-coated paper for printing with an amount of 128 g / m ² was obtained.

Example 9
In the production of the pigment-coated paper for printing of Example 1, the example was used except that non-coated paperboard (trade name: Collaboration Fine-W, manufactured by Oji Specialty Paper Co., Ltd.) having a basis weight of 350 g / m ² was used as the base paper. In the same manner as in No. 1, a pigment-coated board for printing having a basis weight of 384 g / m ² was obtained.

Comparative Example 1
In the preparation of the coating solution for the outermost layer in Example 1, the amount of spindle light calcium carbonate 63% dispersion (trade name: Tamapearl TP221GS, average particle size (short axis) 0.3 μm, manufactured by Okutama Kogyo Co., Ltd.) Was reduced from 159 parts by weight to 48 parts by weight, and a basis weight of 128 g was obtained in the same manner as in Example 1 except that 100 parts by weight of a kaolin (trade name: Ultra White 90, manufactured by BASF Japan) was used at 100 parts by weight. A pigment-coated paper for printing of / m ² was obtained.

Comparative Example 2
In the preparation of the coating solution for the outermost layer in Example 1, 159 parts by mass of a spindle-shaped light calcium carbonate 63% dispersion (trade name: Tama Pearl TP221GS, average particle size (short axis) 0.3 μm, manufactured by Okutama Kogyo Co., Ltd.) A pigment-coated paper for printing having a basis weight of 128 g / m ² was obtained in the same manner as in Example 1 except that 159 parts by mass of a 63% dispersion of light calcium carbonate having an average particle size of 1.7 μm was used instead of.
Comparative Example 3
In the preparation of the coating solution for the outermost layer in Example 1, instead of 36 parts by mass of a 10% aqueous solution of casein, phosphate-modified starch (trade name: Coating Starch PN-700S, manufactured by Sanwa Starch Kogyo Co., Ltd.) A pigment-coated paper for printing having a basis weight of 128 g / m ² was obtained in the same manner as in Example 1 except that 18 parts by mass of a 20% aqueous solution was used.

Comparative Example 4
In the production of the printing pigment-coated paper of Example 1, a printing pigment-coated paper having a basis weight of 128 g / m ² was obtained in the same manner as in Example 1 except that the polyvalent metal salt was not applied.

  The following evaluation was performed on the obtained pigment-coated paper for printing, and the results are shown in Table 1.

"Evaluation methods"
[Measurement of surface gloss of coating layer]
The surface gloss of the obtained pigment-coated paper was measured at an incident angle of 75 degrees according to JIS P8142 using a gloss meter (described in JIS-Z8741).

[Evaluation of offset printability on the coating layer surface]
(Dry pick strength)
Using a RI printing machine (RI-1, manufactured by Ishikawajima Industrial Machinery Co., Ltd.), solid printing is performed using a test ink (SD50 Red BT-13 for Best One Paper Test, manufactured by T & K TOKA), and the printed surface is picked. The degree of was visually determined. 5 is the best in the 5-level evaluation, 1 is the worst level, and 3 is the allowable limit.

(Wet pick strength)
In the dry pick strength test method, wet pick strength was evaluated in the same manner as in the dry pick strength test method, except that water was adhered to the surface of each coated pigment-coated paper with a water adhesion roll before printing.

[Evaluation of ink-jet printability on coating layer surface]
(Evaluation of ink absorbency)
(1) The obtained pigment coated paper is set in an oil absorption meter automatic type (JIS P-8130, manufactured by Kumagaya Riki Kogyo Co., Ltd.).
(2) A cellophane tape is affixed to the upper part of the set test piece, and 5 μl of aqueous pigment inkjet ink (black ink for True Press Jet 520 from Dainippon Screen Co., Ltd.) is put on the cellophane tape using a microsyringe.
(3) After passing the metal roller over the ink, the time until the glossiness of the stretched ink surface disappeared was visually judged to evaluate the ink jet ink absorption speed.
In general, it was determined that what dried within 5 seconds had suitability for an actual printer.

(Evaluation of initial fixability)
In the same manner as the evaluation of the ink absorptivity, an inkjet ink was applied on the obtained pigment-coated paper, and immediately after rubbing with a finger, the initial fixability was evaluated based on the ratio to the optical density difference from the non-rubbed portion.

(Evaluation of scratch resistance)
In the same manner as the ink absorption evaluation described above, an inkjet ink was applied on the obtained pigment-coated paper, left for one day in an environment of 23 ° C. and 50% RH, and rubbed with a finger. The scratch resistance was evaluated based on the ratio of

  As Table 1 clearly shows, the print-coated paper for printing according to the present invention has a dry pick strength and a wet pick strength of 5 and has extremely excellent strength and has an offset printability. Yes. Also, a pigment-coated paper for printing having high suitability for water-based pigment inkjet ink and excellent suitability as hybrid printing paper was obtained (Examples 1 to 9). However, when the outermost layer formulation deviates from the provisions of the present invention and when the polyvalent metal salt was not applied on the outermost layer, a pigment-coated paper suitable for hybrid printing was not obtained (Comparative Examples 1 to 4).

  The present invention provides a gloss-coated pigment-coated paper suitable for hybrid printing, which has excellent offset printing suitability and high-speed inkjet printer recording suitability using aqueous pigment inks. It is extremely useful in practice in the logistics field.

Claims (7)

In a pigment coated paper for printing in which at least one pigment coated layer is provided on at least one surface of a base paper, the outermost layer of the pigment coated layer has an average particle diameter (short diameter) in 100 parts by mass of pigment. Was coated with an aqueous solution of a water-soluble polyvalent metal salt on a dried coating layer containing at least 50 parts by weight of light calcium carbonate of 0.8 μm or less and containing a latex binder and casein as binders. A pigment-coated paper for printing, characterized in that it is a layer. 2. The pigment-coated paper for printing according to claim 1, wherein the latex binder is a styrene / butadiene copolymer latex. The printing pigment-coated paper according to claim 1 or 2, wherein the casein is contained in an amount of 1 to 10 parts by mass with respect to 100 parts by mass of the pigment. The water-soluble polyvalent metal salt is calcium formate, The pigment-coated paper for printing according to any one of claims 1 to 3. The pigment coated paper for printing according to any one of claims 1 to 4, wherein the outermost layer contains 3 to 15 parts by mass of a hollow plastic pigment with respect to 100 parts by mass of the pigment. The pigment-coated paper for printing according to any one of claims 1 to 5, wherein the pigment-coated layer has an inner coating layer containing light calcium carbonate as a main component between the base paper and the outermost layer. In the method for producing a pigment coated paper for printing, in which at least one pigment coated layer is provided on at least one surface of the base paper, the outermost layer of the pigment coated layer has an average particle diameter ( After coating and drying a coating solution containing 50 parts by weight or more of light calcium carbonate having a minor axis) of 0.8 μm or less and containing a latex binder and casein as a binder, an aqueous solution of a water-soluble polyvalent metal salt is applied, A method for producing a pigment-coated paper for printing, which comprises drying.