JPWO2018163795A1 - Coated paper - Google Patents

Abstract

An object of the present invention is to provide a bulky coated paper excellent in printability. By adding starch granules to the pigment coating layer according to the present invention, a bulky coated printing paper having excellent printability can be produced.

Description

  The present invention relates to coated paper. In particular, the present invention relates to a coated paper containing starch granules in a pigment coated layer.

  2. Description of the Related Art Coated paper for printing is widely used in commercial fields such as flyers, catalogs, brochures, and direct mails for the purpose of advertising and promotion. In particular, in recent years, both printing and processing have become more and more complex, and the demands for printing paper have become more severe in environments such as on-demand printing and high-speed machines.

  Coated paper is used for various uses such as books, posters, and wrapping paper, and in any of the uses, the tendency to reduce the weight is remarkable. Weight reduction of paper is required both from the viewpoint of cost reduction such as material cost, warehouse storage cost, transportation cost, etc., and also from the viewpoint of ensuring the ease of transportation of consumers against lightweight media such as e-books and smartphones in recent years. Quality. In the world of coated paper for printing, in order to achieve both the need for weight reduction and the sense of quality of paper, expectation is being raised for a bulky technology for reducing the weight while maintaining the paper thickness.

As a technique for increasing the bulk of a coated paper for printing (a technique for reducing the density), an attempt to increase the bulk of a pigment-coated layer has been studied in addition to an attempt to increase the bulk of a base paper. As a technique for making base paper bulky, for example, Patent Literature 1 describes that paper is made bulky by adding a nonionic surfactant. Patent Document 2 discloses a method in which a bulk base paper containing mechanical pulp (density: 0.70 g / cm ³ or less) is coated with a coating liquid containing 10 to 50 parts by weight of starch per 100 parts by weight of a pigment. It has been proposed to produce a bulky coated paper for printing by coating by a transfer method. Further, Patent Document 3 discloses a bulky printing coating by coating a low-density base paper (density: 0.50 to 0.75 g / cm ³ or less) with a coating layer containing a pigment having a large particle diameter. It has been proposed to make paper.

JP-A-11-200283 JP 2011-026752 A JP 2005-248379 A

  The technique of blending a surfactant described in Patent Literature 1 to reduce the density of a base paper has a problem in that the strength of the base paper, particularly the interlayer strength of the base paper, decreases. Further, in the technique of blending mechanical pulp according to Patent Document 2 to lower the density of the base paper, the stiffness of the base paper is increased, the cushioning property of the paper at the time of printing is reduced, and the printability may be reduced. Further, when a pigment having a large particle diameter is used in a pigment coating layer as in Patent Document 3, the pigment having a large particle diameter easily falls off the coating layer, and the pigment particles have no cushioning property. There have been problems such as insufficient strength and poor print appearance.

  Japanese Patent Application Laid-Open No. 2007-303048 proposes that silicone-processed special starch particles are further applied on a pigment coating layer in order to reduce ink rubbing of the matte coated paper for printing. Have been. However, when a surface layer containing coarse starch particles is further applied on the pigment coating layer, the starch particles are exposed on the surface of the coated paper, and defects (holes) appear on the surface of the coated paper due to the separation of the starch particles. ) May be possible. In this method, it is necessary to separately apply a surface layer containing starch particles, and it is necessary to use special starch particles that have been subjected to silicone processing, and thus there are problems in terms of operation and cost.

  In view of such a situation, an object of the present invention is to provide a bulky coated paper excellent in printability.

As a result of intensive studies on the above-described problems, the present inventors have found that a bulky printing-coated paper can be obtained by including starch particles in the pigment coating layer of the printing-coated paper, and have completed the present invention. . The present invention includes, but is not limited to, the following embodiments.
(1) Coated printing paper having a base paper and a pigment coated layer containing starch granules and a white pigment.
(2) The coated paper according to (1), wherein the average particle size of the starch granules is 8 to 25 μm.
(3) The coated paper according to (1) or (2), wherein the weight ratio of the starch particles to the total of the starch particles and the white pigment constituting the pigment coating layer is 0.5 to 10%.
(4) The coated paper according to any one of (1) to (3), wherein the coated paper has a plurality of pigment coated layers, and the starch particles are present at least in an outermost coated layer. .
(5) The coated paper according to (4), wherein the weight ratio of the starch granules to the total of the starch granules and the white pigment constituting the outermost coating layer is 0.5 to 10%.
(6) Based on JAPAN TAPPI paper pulp test method No. 47, when a white paper sample of a coated paper is vaporized and dyed using an iodine solution (quantitative method), the dyed starch particles having a diameter of 2 to 50 μm are obtained. The coated paper according to any one of (1) to (5), wherein the number is 1 to 300 pieces / 1 mm ² .

  According to the present invention, a bulky coated paper for printing can be produced by adding unsteamed starch granules to the pigment coated layer.

FIG. 1 is a graph showing the particle size distribution of starch particles used in Examples. FIG. 2 is a photograph when the number of starch particles on the surface of the coated paper according to Sample 1-5 was measured. FIG. 3 is a graph showing the particle size distribution of starch particles on the surface of the coated paper according to Sample 1-5. FIG. 4 is a photograph of a section including starch particles of the coated paper according to Sample 1-5, which was observed with an electron microscope.

  In the present invention, starch granules are used for the pigment coating layer. Generally, starch is heated in the presence of water and used as a binder in a base paper or a coating layer using a starch which has been subjected to a steaming step of gelatinizing the starch granules as a binder.In the present invention, the granular starch is coated with a pigment. Used for construction work. Examples of the granular starch include starch that has not been steamed, starch that has been granulated after steaming, and the like. ADVANTAGE OF THE INVENTION According to this invention, while being able to reduce the coating layer of the coating paper for printing, the printability of the coating paper can be improved.

  The coated paper of the present invention is not particularly limited as long as it is a coated paper in which a pigment coating layer containing a white pigment is provided on base paper, and is used for offset printing, gravure printing, letterpress printing, inkjet printing, and the like. Not only coated paper, but also white paperboard having a pigment coating layer on paperboard base paper may be used. The coated paper of the present invention has one or more pigment coated layers on the base paper, but may have two or more pigment coated layers. The number of pigment coating layers is not particularly limited, but is preferably three or less in consideration of paper weight reduction. The coated paper of the present invention may have a pigment coated layer on only one side of the base paper, or may have a pigment coated layer on both sides of the base paper. The base paper may or may not be coated with a pigment-free coating liquid (size press liquid).

The coating amount of the coated paper in the present invention can be appropriately selected according to the application, but is generally ² to ²⁰ g / m ² in solid content per one side, and may be 4 to 19 g / m ² , It may be 6 to 18 g / m ² or 8 to 17 g / m ² .

  The pigment (white pigment) used in the coating layer of the present invention is not particularly limited, and those conventionally used for coated paper can be used. For example, kaolin, clay, engineered kaolin, delaminate Inorganic pigments such as Ted clay, heavy calcium carbonate, light calcium carbonate, talc, titanium dioxide, barium sulfate, calcium sulfate, zinc oxide, silicic acid, silicate, colloidal silica, satin white, etc. and solid, hollow, or core shell Organic pigments such as molds can be used alone or as a mixture of two or more as needed. Further, as a kind of the pigment, it is preferable to contain kaolin or clay from the viewpoint of reducing paper smoothness and ink rubbing. From the viewpoint of the degree of drying of the ink at the time of printing, heavy calcium carbonate and light calcium carbonate are preferable, and from the viewpoint of improving the opacity, light calcium carbonate having a uniform particle diameter and shape is particularly preferable. This is because the bulky coating layer structure scatters light efficiently.

  When using calcium carbonate for the coating layer, the content of light calcium carbonate or heavy calcium carbonate, or a combination of both, is preferably 50 parts by mass or more, more preferably 70 parts by mass or more, per 100 parts by mass of the pigment, and is preferably 80 parts by mass or more. It is more preferably at least part by mass. Further, from the viewpoint of forming a uniform coating layer on the base paper and the drying property during printing, the average particle diameter of the coating pigment is 0.2 to 5 μm as measured by a laser diffraction type particle size distribution analyzer. Preferably, it is 0.2 to 3 μm.

  In the present invention, any commonly used coater may be used. Either an on-machine coater or an off-machine coater may be used. For an on-machine coater, roll coaters such as size press coaters, gate roll coaters, rod metaling size press coaters, bill blade coaters, blade metaling size press coaters, short dwell blades Coaters such as a coater and a jet fountain blade coater can be used. The coating speed is not particularly limited, but is preferably, for example, 150 to 2000 m / min, and more preferably 400 to 1500 m / min. In the present technology, 150 to 1800 m / min is preferable for a blade coater and 150 to 2000 m / min for a size press coater.

  In the present invention, the method of drying the wet coating layer is not limited, and various methods such as a steam superheating cylinder, a heated hot air dryer, a gas heater dryer, an electric heater dryer, and an infrared heater dryer may be used alone or in combination. it can.

Starch Granules In the present invention, granular starch is used in the pigment coating layer. Generally, starch is broken down by steaming, but in the present invention, unsteamed granular starch (starch granules) or starch granules formed after steaming is used. Starch refers to a mixture consisting of amylose and amylopectin, and the mixing ratio generally varies depending on the plant that is the raw material of starch. As the starch, various processed starches and dextrins can be suitably used.

  In the present invention, the average particle diameter of the starch particles, the median diameter (d50) measured by a laser diffraction particle size distribution analyzer such as Mastersizer S manufactured by Malvern Co. is preferably 8 to 25 μm, more preferably 10 to 20 μm, 12-17 μm is more preferred. Here, the median diameter is a diameter that, when the powder is divided into two from a certain particle diameter, the larger side and the smaller side have the same amount, and in the present invention, the median diameter on a volume basis is used. Can be. Further, the distribution range of the particle diameter can be measured, for example, by laser diffraction. Preferably, 90% of the starch particles are distributed to 50 μm or less, more preferably 2 to 50 μm, and still more preferably. Are distributed between 5 and 30 μm, most preferably between 5 and 25 μm.

  The starch of the present invention is not particularly limited as long as it is granular starch granules, and the method of modification, variety of raw materials, and the like are also free. Examples of the modified starch, modified starch, and processed starch include oxidized starch, hydroxyesterified starch (HES), phosphate ester starch, esterified starch, and dextrin. Preferred raw materials for the starch used in the present invention include corn, potato, tapioca and the like.

  In a preferred embodiment, the blending amount of the starch granules in the present invention is 0.5 to 10% with respect to the total of the white pigment and the starch granules constituting one layer of the pigment coating layer, but is more preferably 8% or less. It may be 5% or less. When two or more pigment coating layers are provided, the starch granules of the present invention may be contained in any of the layers. However, in order to exert the effect of the present invention greatly, the outermost pigment coating furthest from the base paper is required. It is preferable to include it in the engineered layer. When starch particles are contained in the outermost coating layer, the problem of ink rubbing that occurs when superimposed coated papers immediately after printing can be greatly reduced. Even when it is contained in a layer other than the outermost pigment coating layer, a bulky coated paper can be obtained.

Adhesive In the present invention, an adhesive conventionally used for coated paper can be used. Examples of the adhesive used for the pigment coating layer include various copolymers such as styrene / butadiene, styrene / acryl, ethylene / vinyl acetate, butadiene / methyl methacrylate, and vinyl acetate / butyl acrylate, and polyvinyl alcohol. , Maleic anhydride copolymer, acrylic acid / methyl methacrylate copolymer and other synthetic adhesives; proteins such as casein, soybean protein, and synthetic protein; oxidized starch, positive starch, urea phosphorylated starch, hydroxy Etherified starch such as ethyl etherified starch; starches such as dextrin; cellulose derivatives such as carboxymethyl cellulose, hydroxyethyl cellulose and hydroxymethyl cellulose. One or more adhesives can be appropriately selected and used. In the present invention, it is preferable to use a starch-based polymer compound and latex in combination as an adhesive. The combined use can provide the advantages of both a starch compound and a latex.

  In the present invention, the content of the adhesive in the pigment coating layer is preferably 5 parts by weight or more and 20 parts by weight or less based on 100 parts by weight of the pigment. When latex is used, its content is preferably from 1 to 15 parts by mass, more preferably from 1 to 10 parts by mass, based on 100 parts by mass of the pigment. When the amount is more than 15 parts by mass, the printing surface strength is excellent, but the cost is high and further effects cannot be expected. When a starch-based polymer is used as an adhesive, the amount is preferably from 1 part by weight to 15 parts by weight, more preferably from 1 part by weight to 10 parts by weight. When two or more pigment coating layers are provided, the innermost pigment coating layer near the base paper preferably has a higher latex content than the starch-based polymer, and the outermost pigment coating furthest from the base paper. The layer preferably contains more starch-based polymer than latex.

  In the present invention, the method for preparing the coating liquid is not particularly limited, and can be appropriately adjusted depending on the type of the coater. Although not limited thereto, the solid content concentration of the coating liquid is preferably 40 to 75% by weight, more preferably 50 to 72% by weight, and may be 60 to 69% by weight. The viscosity of the coating liquid is preferably from 300 to 2000 mPa · s, more preferably from 500 to 1500 mPa · s, as measured by a B-type viscometer according to JIS K 7117-1.

  In the present invention, if necessary, various assistants, such as dispersants, thickeners, water retention agents, defoaming agents, water-proofing agents, coloring agents, and fluorescent whitening agents, which are blended with ordinary pigments for coated paper. Agents can be used as appropriate.

Base paper The coated paper of the present invention has a base paper layer. Base paper can be manufactured by a known method. For example, base paper can be manufactured by making papermaking raw material (paper stock) in a wire part and then subjecting it to a press part and a predryer part. The base paper used in the present invention may be a single-layer paper or a multi-layer paper, but in the case of producing a white paperboard, it is preferable to use a multilayer paper. The method for producing the base paper of the present invention is not particularly limited, and can be a known method using a known raw material. The base paper used in the present invention is not particularly limited, and generally used high-quality paper, medium-quality paper, paperboard, paper-change, machine-coated paper, art paper, cast-coated paper, synthetic paper, resin-coated paper, plastic film, and the like. Can be used without exception.

  As the pulp raw material used for the base paper of the present invention, chemical pulp can be used. As the chemical pulp, bleached hardwood kraft pulp (LBKP) and softwood bleached kraft pulp (NBKP) can be suitably used. In addition to chemical pulp, various types of pulp can be used according to the purpose. For example, deinked pulp (DIP), ground wood pulp (GP), refined ground wood pulp (RGP), thermomechanical pulp (TMP), chemithermo Examples include mechanical pulp (CTMP), chemical ground pulp (CGP), and semi-chemical pulp (SCP). As the deinked pulp, there can be used selected waste paper such as high quality paper, medium quality paper, lower grade paper, newsprint, flyers, magazines, etc., and deinked pulp made from unselected waste paper mixed with these.

  In the present invention, known fillers can be arbitrarily used as fillers for base paper, for example, heavy calcium carbonate, light calcium carbonate, clay, silica, light calcium carbonate-silica composite, kaolin, calcined kaolin, delamikaolin, white Amorphous manufactured by mineralization of carbon, talc, magnesium carbonate, barium carbonate, barium sulfate, aluminum hydroxide, calcium hydroxide, magnesium hydroxide, zinc hydroxide, zinc oxide, titanium oxide and sodium silicate An inorganic filler such as silica and an organic filler such as a urea-formalin resin, a melamine resin, a polystyrene resin and a phenol resin can be used alone or in combination. Among these, heavy calcium carbonate and light calcium carbonate, which are typical fillers in neutral papermaking and alkali papermaking, are preferably used for improving opacity. The filler ratio in paper is not particularly limited, but is preferably 1 to 40% by solid mass, more preferably 5 to 35% by mass, and even more preferably 10 to 30% by mass.

  In the present invention, known papermaking additives can be used. For example, a papermaking internal additive such as a sulfuric acid band or various anionic, cationic, nonionic or amphoteric retention improvers, drainage improvers, various paper strength enhancers or internal sizing agents may be used as required. Can be used. Examples of the dry paper strength improver include polyacrylamide and cationized starch, and examples of the wet paper strength improver include polyamidoamine epichlorohydrin. In order to obtain a higher bulking effect, a bulking agent may be added to the base paper. These chemicals are added within a range that does not affect formation or operability. Examples of the neutral sizing agent include alkyl ketene dimer, alkenyl succinic anhydride, and neutral rosin sizing agent. Further, a dye, a fluorescent brightener, a pH adjuster, a defoaming agent, a pitch control agent, a slime control agent and the like can be added as required.

  The papermaking method of the base paper in the present invention is not particularly limited, and a fourdrinier including a top wire, an on-top former, a gap former, a round net, a fourdrinier and a round net together. It can be carried out using a paperboard machine, a Yankee dryer machine, or the like, and may be a single-layer or multi-layer machine. The pH during papermaking may be acidic, neutral or alkaline, but is preferably neutral or alkaline. The papermaking speed is not particularly limited.

The basis weight of the base paper of the present invention is not particularly limited, and can be appropriately selected depending on the use. For example, the basis weight of the base paper, if the general coated paper for printing can be a ^{25~160g / m 2, 35~150g / m} 2, may be a 45~140g / ^{m 2,} coated white paperboard If so, it may be 200 g / m ² or more.

The base paper used for the coated paper of the present invention may have a clear (transparent) coating layer on one side or both sides. By applying the clear coating on the base paper, the surface strength and smoothness of the base paper can be improved, and the coatability at the time of pigment coating can be improved. In the present invention, the above-mentioned adhesive can be used as a binder in the clear coating layer. The amount of the clear coating is preferably 0.1~4.0g / ^{m 2} in terms of solid per side content, and more preferably 0.5 to 2.5 g / ^{m 2.}

  In the present invention, the clear coating means, for example, various types of starch such as starch and oxidized starch using a coater (coating machine) such as a size press, a gate roll coater, a pre-metalling size press, a curtain coater, and a spray coater. Means that a coating solution (surface treatment solution) containing a water-soluble polymer such as polyacrylamide or polyvinyl alcohol as a main component is applied to a base paper (size press).

  In the present invention, it is preferable to perform a pre-calendering process on the base paper before coating by an online soft calendar, an online chilled calendar, or the like, and to smooth the base paper in advance in order to uniform the coating layer after coating. . In this case, the processing linear pressure is preferably 30 to 100 kN / m, and more preferably 50 to 100 kN / m. The moisture content of the base paper during the pre-calendering process is also important, and the moisture content is preferably 3 to 5%.

Coated paper surface In the present invention, the coated paper produced as described above may be subjected to a surface treatment as necessary, but it is difficult to obtain the bulky effect of the present invention, and it is preferable not to perform a calender treatment. . When performing a smoothing process, a normal smoothing device such as a super calender, a gloss calender, a soft calender, a heat calender, a shoe calender, or the like can be used. The smoothing device is appropriately used in an on-machine or an off-machine, and the form of the pressure device, the number of pressure nips, heating, and the like are appropriately adjusted. However, calendering at a low pressure is preferable.

  The coated paper of the present invention can correspond to various printing methods, such as coated paper for offset printing, coated paper for letterpress printing, coated paper for gravure printing, inkjet paper, dry electrophotographic paper, and wet-type electronic paper. It can be used for photo paper.

As described above, in the coated paper according to the present invention, starch particles are used in the pigment coating layer. However, if coarse starch particles are excessively exposed on the coated paper surface, the starch particles may fall off. It will be easier. According to JAPAN TAPPI paper pulp test method No. 47, when a white paper sample of coated paper is vaporized and dyed using an iodine solution (quantitative method), the number of dyed starch particles having a diameter of 2 to 50 μm is as follows: 1 to 300 pieces / 1 mm ² is preferred, 2 to 200 pieces / 1 mm ² is more preferred, 3 to 150 pieces / 1 mm ² is still more preferred, and 4 to 100 pieces / 1 mm ² is still more preferred, and 5 to 50 pieces / 1 mm 2 ^It may be ² .

  Hereinafter, the present invention will be described in more detail with reference to specific experimental examples, but the present invention is not limited to the following experimental examples. In addition, unless otherwise specified, in this specification, numerical ranges are described as including their endpoints, and “parts” and “%” indicate “parts by weight” and “% by weight”, respectively.

Evaluation method (1) Paper quality / basis weight: Measured according to JIS P 8124.
-Paper thickness / density: Measured according to JIS P8118.
-Ash content: Measured according to ISO1762-1974.

(2) Blank paper gloss (%)
It was measured based on JIS-P8142.

(3) Print gloss (%)
Using an offset sheet-fed ink (NEX-M, manufactured by Toyo Ink) with an offset sheet-fed printing press (4 colors) manufactured by Roland Co., the printing density of the solid portion was 1.60 at a printing speed of 8000 sheets / hr, Printing was performed in the order of indigo red (CMY) so that red 1.50 and yellow 1.10. The glossiness of the indigo red (CMY) solid printed portion of the obtained printed matter was measured based on JIS P-8142.

(4) Gloss difference (point)
The value obtained by subtracting the blank glossiness from the print glossiness is defined as the gloss difference. If the gloss difference is 20 points or more, the difference in gloss between the printed portion and the blank portion is sufficiently obtained, and the printed material is easily visible. .
Gloss difference = print gloss (%)-blank gloss (%)

(5) Printing surface impression Using a sheet-fed offset printing press (4 colors) manufactured by Roland Co., Ltd., using an offset sheet-fed ink (NEX-M manufactured by Toyo Ink), and a printing speed of 8000 sheets / hr, the solid ink density of the solid portion. Was printed so as to be 1.80, and then the print surface feeling of the solid printing portion was evaluated on a three-point scale. The evaluation criteria were as follows, and were evaluated visually.
-3 (O): No unevenness is observed in the printed part.
2 (△): Slight unevenness is observed in the printed portion, but there is no practical problem.
1 (x): Many unevenness is seen in the printed part.

(6) Ink rubbing Offset sheet-fed printing press (4 colors) manufactured by Roland Co., Ltd., using an offset sheet-fed ink (NEX-M manufactured by Toyo Ink), and a printing speed of 8000 sheets / hr. Printing was performed so that the ink became 1.80. Next, the ink was humidified for 24 hours based on JIS P8111, rubbed once with a Gakushin type friction fastness tester under a load of 500 gf so that the black solid printing portion was fitted to the blank paper portion, and transferred to the blank paper portion. Was visually evaluated in five stages as ink rubbing.
* 5: There is no transfer of ink at all.
* 4: There is almost no transfer of ink.
* 3: There is slight ink transfer, but there is no practical problem.
* 2: Transfer of ink is large.
* 1: Very much ink transfer.

(7) Number of Starch Particles on Coated Paper Surface An iodine solution (quantitative method) was prepared based on JAPAN TAPPI paper pulp test method No. 47, and a white paper sample was vaporized and dyed. Then, a digital microscope (VHX- manufactured by Keyence Corporation) was used. The number of dyed starch granules having a diameter of 2 to 50 μm in a range of 1.5 mm × 2.1 mm was measured using 900. Four places were measured at a magnification of 200 times, The average number was calculated.

(8) Average particle size and particle size distribution of starch particles The average particle size (d50) and particle size distribution of starch particles were measured by laser diffraction. Specifically, starch particles were analyzed using Mastersizer S manufactured by Malvern.

Raw materials for coated paper (base paper)
-Chemical pulp: NBK's LBKP (hardwood bleached kraft pulp)
・ Light calcium carbonate: Nippon Paper internal filler

(Pigment)
-Heavy calcium carbonate: FMT97 manufactured by Pima Tech (average particle diameter d50 measured by laser diffraction method = 0.64 μm, proportion of particles having a particle diameter of 2 μm or less measured by laser diffraction method: 97%)
Light calcium carbonate: Nippon Paper Coating Pigment (average particle diameter d50 measured by laser diffraction method = 0.92 µm, ratio of particles having a particle size of 2 µm or less measured by laser diffraction method: 89%)
Kaolin: KCS manufactured by Imerys (average particle diameter d50 = 4.05 μm measured by laser diffraction method)
-Starch particles: Y-3P manufactured by Japan Cornstarch (unmodified corn starch, average particle diameter d50 measured by laser diffraction method: about 15 µm)
FIG. 1 shows the particle size distribution of the starch particles measured using a Mastersizer S (laser diffraction type particle size distribution analyzer) manufactured by Malvern.

(binder)
・ Styrene / butadiene copolymer latex: PB1537 manufactured by A & L (average particle diameter 110 nm, glass transition temperature 10 ° C.)
-Styrene-butadiene copolymer latex: A & L PB9501 (average particle diameter 80 nm, glass transition temperature -12 ° C)
-Oxidized starch: SK200 (corn starch) manufactured by Japan Corn Starch

Experiment 1: Production of coated paper (two-layer coating)
On base paper having a basis weight of 75 g / ^{m 2,} the pigment coating layer dry coating amount per side is 6.5 g / ^{m 2} (under layer), dry coating amount per one side 10.5 g / pigment coating layer is m ² (the top layer: Saisotonurikoso) was produced coated printing paper having a (samples 1-1 to 1-7, basis weight: about 109 g ^{/ m} 2).

(Base paper)
Fine paper having a basis weight of 98 g / m ² and a density of 0.73 g / cm ³ was used as a base paper. The pulp formulation was 100% chemical pulp (LBKP 100% by weight) and contained 13% by weight of light calcium carbonate as a filler.

(Under coating)
Using heavy calcium carbonate as a pigment, 100 parts by weight (solid content) of the pigment, 7 parts by weight of a styrene-butadiene copolymer latex (PB1537 manufactured by A & L) and an oxidized starch (manufactured by Nippon Cornstarch) as an adhesive SK200) was added, and water was further added to obtain an undercoating liquid having a solid content concentration of 66% by weight.

On the base paper, an under pigment coating liquid is coated on both sides with a blade coater at a coating speed of 650 m / min so that a dry coating amount per one side is 6.5 g / m ^2, and then dried to form an under coating. An engineering layer was provided on the base paper.

(Top coating)
Heavy calcium carbonate slurry and starch particles (Y-3P, manufactured by Nippon Cornstarch Co., Ltd., not steamed) were used as coating pigments in the amounts shown in the following table, and styrene was used as an adhesive for 100 parts by weight (solid content) of the pigment. 4 parts by weight of a butadiene copolymer latex (PB9501 manufactured by A & L) and 6 parts by weight of oxidized starch (SK200 manufactured by Nippon Cornstarch) are added, and water is further added to form a top coating having a solid content of 66% by weight. A pigment coating liquid was obtained.

On the undercoated base paper, a pigment coating solution for top coating is coated on both sides with a blade coater so that the dry coating amount per side is 10.5 g / m ^2, and then dried and coated for printing. Man-made paper was obtained (samples 1-1 to 1-6).

  In addition, Sample 1-7 was manufactured as a coated paper in which starch particles were blended in the under layer. Specifically, the same as Sample 1-6 except that the coating used for the under coating was 90 parts by weight of heavy calcium carbonate and 10 parts by weight of starch particles (Y-3P, manufactured by Nippon Corn Starch Co., Ltd., not steamed). To produce a coated paper for printing.

  Further, except that the heavy calcium carbonate used for the under layer and the top layer was replaced with light calcium carbonate, and starch particles (Y-3P manufactured by Nippon Cornstarch, uncooked) were used for the under layer in the composition shown in the following table. Coated paper for printing was manufactured in the same manner as 1-1 (Samples 1-8 to 1-9).

Experiment 2: Production of coated paper (single-layer coating)
On base paper having a basis weight of 75 g / m ^2, the pigment coating layer dry coating weight per one side is 15 g / m ² to both surfaces coated to produce a coated printing paper (sample 2-1 2-2, basis weight: about 105 g / m ² ).

  As a pigment, 53.5 parts by weight (solid content) of heavy calcium carbonate slurry, 45 parts by weight (solid content) of kaolin, and 1.5 parts by weight of uncooked starch particles were used. 4 parts by weight of a styrene-butadiene copolymer latex (PB9501 manufactured by A & L) and 6 parts by weight of oxidized starch (SK200 manufactured by Nippon Cornstarch Co., Ltd.) were added thereto, and water was further added thereto to obtain a pigment coating having a solid content of 66% by weight. A working liquid was obtained.

This pigment coating liquid was coated on both sides of the base paper of Experiment 1 with a blade coater so that the dry coating amount per side was 15.0 g / m ^2, and then dried to obtain a coated paper for printing. (Sample 2-1).

  In addition, a coated paper for printing was obtained in the same manner as in Sample 2-1 except that uncooked starch particles were not used and heavy calcium carbonate was used in an amount of 55 parts by weight (Sample 2-2: Comparative Example). .

  Further, coated papers for printing were produced in the same manner as in Samples 2-1 and 2-2, except that heavy calcium carbonate was replaced with light calcium carbonate (samples 2-3 to 2-4).

  As is clear from the table, a low-density coated paper for printing could be obtained by adding unsteamed starch granules to the pigment coated layer. Since the specific gravity of starch particles is smaller than that of inorganic pigments, the density of the pigment coating layer is reduced by blending the starch particles, and when the starch particles are blended in the outermost coating layer, the starch particles increase the paper thickness. Therefore, it is considered that the density of the coated paper was reduced.

  In addition, the coated paper for printing of the present invention showed little ink rubbing after printing and excellent coating suitability. The starch particles present near the surface of the coated paper increase the unevenness of the coated paper surface, reduce the contact area between the superposed coated papers, and reduce the ink rubbing due to the cushioning properties of the starch particles. Conceivable.

2 to 4 show the results of analyzing the coated paper according to Sample 1-5. FIG. 2 shows a surface photograph when the surface of the coated paper according to Sample 1-5 is analyzed. The number of starch granules having a diameter of 2 to 50 μm is 11 per 1.5 mm × 2.1 mm (per 1 mm ^2). It was about 3.5). In addition, as is apparent from the cross-sectional photograph shown in FIG. 4, the presence of the starch particles in the pigment coating layer allows the coated paper according to the present invention to prevent the starch particles from being excessively exposed, such as during printing. In this case, a pigment coating layer from which the starch particles hardly fall off was obtained.

Claims (6)

  Coated printing paper comprising a base paper and a pigment coated layer containing starch granules and a white pigment.   The coated paper according to claim 1, wherein the average particle size of the starch granules is 8 to 25 m.   3. The coated paper according to claim 1, wherein a weight ratio of the starch particles to the total of the starch particles and the white pigment constituting the pigment coating layer is 0.5 to 10%. 4.   The coated paper according to any one of claims 1 to 3, wherein the coated paper has a plurality of pigment coated layers, and the starch particles are present at least in an outermost coated layer.   The coated paper according to claim 4, wherein the weight ratio of the starch granules to the total of the starch granules and the white pigment constituting the outermost coating layer is 0.5 to 10%. According to JAPAN TAPPI paper pulp test method No. 47, when a white paper sample of coated paper is vaporized and dyed using an iodine solution (quantitative method), the number of dyed starch particles having a diameter of 2 to 50 μm is as follows: 1 to 300 pieces / 1 mm ^2, coated paper according to claim 1.