JP5809580B2 - Coated paper for printing - Google Patents

Description

  The present invention relates to a double-sided printing coated paper used in an offset printing machine. In particular, double-sided printing that reduces gloss ghost (a phenomenon in which a pattern corresponding to an image of a preprinted printing surface appears on a postprinted printing surface), which has been a problem in offset printing using a sheet of paper. It relates to coated paper.

  Offset printing is currently the main printing method for printing commercial printed materials such as flyers, brochures, and catalogs, and printed publications such as books and magazines. There are two types of offset printing machines, called a sheet-fed machine for printing a sheet and a so-called off-wheel machine for printing a wound paper.

  There is also a type called a double-sided machine that uses an oxidation polymerization type ink as an ink used in a sheet-fed machine and prints both sides of the paper in the same process. However, in general, one side of a sheet is printed, and after printing, after the ink on the printing surface is dried, the sheet is reversed and the opposite side is printed. When the ink on the opposite side is dried, post-processing operations such as cutting and bookbinding are performed to produce a product.

  There is a gloss ghost as a printing trouble peculiar to double-sided printing on a sheet-fed machine. Gross ghost is a phenomenon in which a pattern corresponding to an image of a preprinted print surface appears on a postprinted print surface. The ink on the preprinted printing surface overlaps and touches the ink on the postprinted printing surface, which affects the drying of the postprinted ink. As a result, the image portion of the preprinted printing surface in the image portion of the postprinted printing surface Is a phenomenon in which a difference in gloss occurs in a portion in contact with the image, and a pattern appears on the image portion of the printed surface after post-printing (see, for example, Non-Patent Document 1). Gross ghost significantly deteriorates the aesthetics of the printed matter, resulting in a decrease in commercial value.

  As a conventional method for reducing the gloss ghost, a method of adjusting by a printing operation on the printing press side is employed (see, for example, Non-Patent Documents 1 and 2). For example, it is a method of promoting the drying of ink on the preprinted printing surface so as not to affect the drying of the printed surface after postprinting. In this method, when the preprinted printing surface has reached the state where ink is set, a work called “air blowing” is performed to introduce fresh air between the sheets, and oxidative polymerization of oil components in the ink is performed. Accelerates ink drying by promoting. In addition, a “tempering” operation may be performed when the post-printed printing surface has reached an ink-set state. The ink set state is the stage where the ink does not adhere to the finger even if the finger touches the surface of the printing surface, but the ink is removed when rubbed strongly. The state where the state has not reached the dry and hardened state.

  Further, as a conventional method for making the gross ghost inconspicuous, a technique of “solid surface preprinting” is known (for example, see Non-Patent Documents 1 and 2). “Solid surface printing” is an image that has a large solid area or dark area, or an image that has many solid areas or dark areas, taking into account the images printed on the front and back of the paper. In this method, the surface to be printed is printed first.

  However, the response by the printing operation on the printing press increases the amount of work for the printing operator, and it is not possible to know whether you can prevent the gross ghost even if these measures are taken. There is. When a gross ghost occurs, a loss due to reprinting or discounting or a delay in delivery time may occur, which greatly reduces the productivity of the printing company. From the above, a paper response is required for reducing the gloss ghost, but there is still no method that can fully satisfy the paper response.

Tokyo Paper Cooperative, [online], Q & A / Printing Bean Knowledge / Frequently Trouble with Sheet-fed Printing / Gross Ghost, [Search January 30, 2012], Internet <URL: http://www.tykk.com /tykk/q_and_a/mame/maiyo/index.html> Yoshiyuki Terui, “Offset Printing Book Succession of Printing Knowledge and Technology”, Printing Publishing Research Institute, Inc., published on September 20, 2007, p. 153

  Common printing coated papers are classified into matte paper, dull paper, and gloss paper from the one with the lower gloss level of white paper. However, from the viewpoint of visibility and sharpness, there is often a demand for coated paper for printing that has a high printing gloss even with matte paper. In addition, glossy paper and low-gloss coated paper for printing are markedly impaired in merchantability. In order to perform continuous printing, the picking strength (hereinafter referred to as “surface strength”) of the surface of the coated paper for printing is required to be strong.

  Gross ghost affects the drying of the ink on the printed surface after the ink is printed on the printed surface that has been preprinted after double-sided printing. This is a phenomenon in which a difference in gloss occurs at a position where it overlaps and comes into contact with the image portion of the preprinted printing surface, so that it is necessary to quickly dry the ink on the paper side. However, generally, when ink drying is fast, the printing gloss is almost always lowered, and it is also required that the printing gloss is not lowered. In addition, a large amount of coated coated paper is usually printed continuously. During continuous printing, when the surface strength of the coated paper for printing is weak, dust picked from the surface of the coated paper may adhere to the plate cylinder or blanket cylinder of the printing press, and the print quality may be deteriorated. Therefore, the plate cylinder and the blanket cylinder are frequently cleaned, and it is required from the viewpoint of printing workability that the surface strength of the coated paper for printing is not reduced. Further, the coated coated paper is also required to be free from gloss ghosts even if pre-printing is started from any side.

  An object of the present invention is to provide a coated paper for printing that can suppress gloss ghost, which is a printing trouble peculiar to double-sided printing with a sheet-fed machine for offset printing, and does not reduce printing gloss and surface strength. .

  As a result of intensive studies in order to solve the above-mentioned problems, the inventor of the present invention applied a printing paper having at least two coating layers containing a pigment on both sides of the base paper. The coating layer adjacent to the outermost coating layer on each side contains calcium carbonate, and in the volume-based particle size distribution of the calcium carbonate, the frequency of the particle size of 1.0 μm or more is 3% by volume or less, and the particle size is 0.2 μm or less. Is more than 15% by volume, the calcium carbonate content is 80% by mass or more based on the total pigment solid content of the coating layer adjacent to the outermost coating layer, and is the highest on each of both surfaces on the base paper. The coating layer adjacent to the surface coating layer and the outermost coating layer is a coated paper for printing containing a latex having a glass transition temperature of −20 ° C. or more and less than 20 ° C., so that printing gloss and surface strength are not reduced. Found that it can suppress gross ghosts .

  A preferred embodiment of the present invention is a double-sided printing coated paper for a sheet-fed offset printing machine in which at least two coating layers containing a pigment are coated on both sides of a base paper, The coating layer adjacent to the surface coating layer contains calcium carbonate, and in the volume-based particle size distribution of the calcium carbonate, the frequency of the particle size of 1.0 μm or more is 3% by volume or less, and the frequency of the particle size of 0.2 μm or less is 15 The content of the calcium carbonate is 80% by mass or more based on the total pigment solid content of the coating layer adjacent to the outermost coating layer, and the outermost coating layer on each side of the base paper. The coating layer adjacent to the outermost coating layer contains a latex having a glass transition temperature of −20 ° C. or higher and lower than 20 ° C.

  ADVANTAGE OF THE INVENTION According to this invention, the coated paper for printing which can suppress the gloss ghost which is a printing trouble peculiar when performing double-sided printing with the sheet | seat machine of offset printing, and does not reduce printing gloss and surface strength can be provided.

  Hereinafter, the coated paper for printing of the present invention will be described in detail.

  The present invention is a printing coated paper in which at least two coating layers containing a pigment are coated on both sides of a base paper, and the coating layer adjacent to each outermost coating layer on both sides of the base paper is Containing calcium carbonate, and in the volume-based particle size distribution of the calcium carbonate, the frequency of the particle size of 1.0 μm or more is 3% by volume or less, and the frequency of the particle size of 0.2 μm or less is more than 15% by volume. An amount of 80% by mass or more based on the total pigment solid content of the coating layer adjacent to the outermost coating layer, and each outermost coating layer on the base paper and the coating layer adjacent to the outermost coating layer Is a coated paper for printing containing a latex having a glass transition temperature of -20 ° C or higher and lower than 20 ° C. Thereby, the gloss ghost which is a printing trouble peculiar to double-sided printing with a sheet-fed offset printing machine can be suppressed, and printing gloss and surface strength are not reduced.

  In the present invention, the outermost coating layer refers to a coating layer located on the outermost side with respect to the base paper. The coating layer adjacent to the outermost coating layer refers to a coating layer that is in contact with the outermost coating layer and located on the base paper side. Since the coating paper for printing of the present invention is formed by coating a coating layer on both sides of the base paper, the outermost coating layer and the coating layer adjacent to the outermost coating layer are formed on both sides of the base paper. Each exists.

  In the present invention, at least one of the coating layers adjacent to the outermost coating layer is calcium carbonate as a pigment. The calcium carbonate contained in the coating layer adjacent to the outermost coating layer has a volume standard particle size distribution in which the frequency of the particle size of 1.0 μm or more is 3% by volume or less and the frequency of the particle size of 0.2 μm or less is more than 15% by volume. It is. The content of calcium carbonate contained in the coating layer adjacent to the outermost coating layer is 80% by mass or more based on the total pigment solid content in the coating layer adjacent to the outermost coating layer. When calcium carbonate has the above-mentioned particle size distribution characteristics and is in the above-mentioned range of content, it is possible to suppress the occurrence of gloss ghost without lowering the printing gloss and surface strength in combination with the later-described latex.

  In the volume-based particle size distribution of calcium carbonate contained in the coating layer adjacent to the outermost coating layer, the frequency with a particle size of 1.0 μm or more is more than 3% by volume, or the frequency with a particle size of 0.2 μm or less is 15% by volume or less. If it is, the gross ghost cannot be suppressed. In addition, when the content of calcium carbonate contained in the coating layer adjacent to the outermost coating layer is less than 80% by mass with respect to the total pigment solid content in the coating layer adjacent to the outermost coating layer In addition, the gross ghost cannot be suppressed.

  In the present invention, the volume-based particle size distribution of calcium carbonate can be adjusted by crushing and sieving. The pulverization method is roughly classified into a dry pulverization method and a wet pulverization method. The dry pulverization method is suitable for use as pulverization up to an average particle diameter of several μm or coarse pulverization before wet pulverization. Representative examples of the dry pulverization apparatus include a jaw crusher, a hammer crusher, a cone crusher, a roller mill, a pin mill, a ball mill, and a jet mill. The wet pulverization method is suitable for finer pulverization than dry pulverization. The pulverization chamber in which a stirring disk or a rotor with a pin is provided is filled with beads for pulverization, and the stirring disk and the rotor with a pin are rotated at high speed. The slurry of material is passed through while being allowed to pass. Typical examples of the wet pulverization apparatus include products such as Imex, Ashizawa Finetech, Mitsui Mining, Hosokawa Micron, etc., and there are vertical and horizontal types. The wet pulverization method is suitable as a method for finally adjusting the particle size distribution of the calcium carbonate used in the present invention. The sieving can be performed with a mesh.

  When pulverization is advanced in the wet pulverization method, the frequency of particle diameters of 1.0 μm or more is relatively decreased, the frequency of particle diameters of 1.0 μm or more is 3% by volume or less, and the frequency of particle diameters of 0.2 μm or less is increased. Thus, the frequency of the particle diameter of 0.2 μm or less exceeds 15% by volume. By sieving during the pulverization, the calcium carbonate having the volume-based particle size distribution of the present invention can be obtained.

  In addition, the shape and material of the pulverization chamber of the wet pulverizer, the shape of the beads for pulverization, the material and filling rate, the shape of the stirring member, the material and rotation speed, the type and amount of the dispersing agent should be selected appropriately. be able to.

  As the material for the grinding beads, alumina beads, zirconia beads, zirconia / silica ceramic beads and the like are excellent in terms of high specific gravity, high hardness and high durability, and high performance glass beads can also be used. As the size of the bead particles, those having a diameter in the range of 0.1 mm to 5.0 mm are preferably used. In some cases, it is efficient to use coarse beads for relatively coarse calcium carbonate, and fine beads to make them finer.

  Dispersant adsorbs on the surface of calcium carbonate, promotes the wetting of calcium carbonate, inhibits aggregation and sedimentation of calcium carbonate by charge repulsion and steric hindrance of polymer structure, and stabilizes the calcium carbonate slurry There is. Typical examples include polyacrylic acid alkali salts, condensed phosphates, polyvinyl alcohol and the like. As the wet pulverization proceeds, it is necessary to adsorb a new dispersant on the newly appearing calcium carbonate surface, and therefore, the dispersant may be added excessively in advance or may be added during the wet pulverization.

  The calcium carbonate used for the coating layer in the present invention is preferably heavy calcium carbonate obtained by pulverizing naturally produced limestone ore. Light calcium carbonate obtained by chemically reacting calcium hydroxide can be further pulverized, or a biological material such as a shell containing a sufficient calcium carbonate component can be pulverized.

  In the present invention, the particle size distribution of calcium carbonate is a particle size distribution obtained by a particle size distribution measuring apparatus using a laser diffraction / scattering method. In general, the particle size distribution is expressed in% of the frequency within a specific particle size range of an aggregate of particles such as slurry and powder. The frequency criterion includes a volume criterion or a number criterion, and the particle size distribution according to the present invention is a volume criterion. In the laser diffraction / scattering method, the particle size distribution is obtained by detecting and calculating a signal corresponding to the volume distribution using the characteristics of the scattered light depending on the size of the particle when the particle is irradiated with a laser as the measurement principle. A typical measurement apparatus includes an apparatus manufactured by Nikkiso Co., Ltd. (Microtrac. Inc).

  The volume-based particle size distribution of calcium carbonate in the present invention is measured by a laser diffraction / scattering particle size distribution measuring device after first diluting and dispersing a sample collected from a calcium carbonate slurry with a dropper or the like with distilled water or ion-exchanged water. An appropriate amount is dropped into the cell for measurement. From the volume-based particle size distribution obtained from the measuring device, the frequency of the particle size of 1.0 μm or more and the particle size of 0.2 μm or less can be obtained.

  In the present invention, the glass transition temperature can be determined by measuring with a differential scanning calorimeter such as EXSTAR 6000 (manufactured by Seiko Denshi), DSC220C (manufactured by Seiko Denshi Kogyo), DSC-7 (manufactured by PerkinElmer). The intersection of the baseline and the endothermic peak slope is defined as the glass transition temperature.

  In the present invention, latex is a liquid dispersion of a resin and can be produced from a polymerizable monomer by using a known production method such as an emulsion polymerization method. For example, (meth) acrylic ester resin, styrene-acrylonitrile resin, vinyl acetate resin, ethylene-vinyl acetate resin, ethylene-vinyl acetate-vinyl chloride resin, styrene- (meth) acrylic ester resin, styrene-butadiene resin, acrylonitrile -Synthetic resins such as butadiene resins, ethylene-vinyl chloride resins, isoprene resins, chloroprene resins, polyester resins, polyurethane resins, urea resins, alkyd resins, and polymers obtained by combining these resins in a graft or block manner, and natural Examples thereof include liquid dispersions such as rubber. In the present invention, for example, a vinyl acetate resin refers to a resinous polymer mainly composed of vinyl acetate, and this includes not only a homopolymer but also one or more other types mainly composed of vinyl acetate. Those obtained by copolymerizing monomers are also included. The latex of the outermost coating layer is preferably a styrene-butadiene resin latex in terms of layer strength. Furthermore, the latex of the coating layer adjacent to the outermost coating layer is also preferably a styrene-butadiene resin latex.

  The glass transition temperature of the latex is, for example, a monomer having a high glass transition temperature as a homopolymer such as styrene, methyl methacrylate, propylene, or acrylic acid, and a low glass transition temperature as a homopolymer such as ethylene, butadiene, or vinyl chloride. A monomer can be adjusted by combining the addition amount at the time of superposition | polymerization. The particle size of the latex can be controlled by adjusting the micelle size formed by the emulsifier of emulsion polymerization and the amount of radical chain transfer agent added.

  In the present invention, the latex contained in the outermost coating layer and the coating layer adjacent to the outermost coating layer has a glass transition temperature of −20 ° C. or higher and lower than 20 ° C. When the glass transition temperature of the latex in the outermost coating layer and in the coating layer adjacent to the outermost coating layer is out of this range, the printing gloss or surface strength of the coated paper for printing is lowered. In some cases, a gross ghost is also generated.

  In the present invention, the outermost coating layer and the coating layer adjacent to the outermost coating layer contain latex, the glass transition temperature of the latex is in the above range, and the coating layer adjacent to the outermost coating layer Contains calcium carbonate, and the calcium carbonate is in the particle size distribution characteristic and the content range described above, it is possible to obtain a coated paper for printing that can suppress the gloss ghost and does not reduce the printing gloss and the surface strength.

  In the coating layer on the post-printed side, the outermost coating layer according to the present invention and the coating layer adjacent to the outermost coating layer can suppress the gloss ghost and do not reduce the printing gloss and surface strength. It becomes coated paper for printing. However, in the case of a printing coated paper in which the post-printing surface is always limited, the workability at the printing site is significantly reduced. Accordingly, in the present invention, the outermost coating layer and the coating layer adjacent to the outermost coating layer are preferably provided on both sides of the base paper. Further, since gross ghost is remarkably generated in sheet-fed offset printing, as a preferable aspect of the present invention, the coated paper for printing of the present invention is for a sheet-fed offset printing machine in which double-sided printing is performed by a sheet-fed offset printing machine. It is preferable to use it as a double-sided printing coated paper.

  In the present invention, the base paper includes chemical pulps such as LBKP and NBKP, mechanical pulps such as GP, PGW, RMP, TMP, CTMP, and CGP, and various pulps such as waste paper pulp, and light calcium carbonate and heavy calcium carbonate Paper made by blending various fillers such as talc, clay, kaolin, etc., sizing agents, fixing agents, retention agents, paper strength enhancers, etc., as required, acidic, neutral, alkaline Paper can be made with either of these.

  In the present invention, the base paper may or may not be subjected to a size press treatment with a sizing liquid. The sizing liquid may contain a known surface sizing agent such as starch or polyvinyl alcohol.

  In the present invention, a paper machine known in the paper industry such as a long paper machine, a twin wire paper machine, a combination paper machine, a circular paper machine, and a Yankee paper machine can be appropriately used as a paper machine in the base paper making method.

  The ISO whiteness of the base paper is not limited at all, but the whiteness is preferably 84% or more.

  In the present invention, one or more other coating layers can be provided between the coating layer adjacent to the outermost coating layer and the base paper.

  In the present invention, the pigment contained in the outermost coating layer or other coating layer (excluding the coating layer adjacent to the outermost coating layer) is not particularly limited, and is a conventionally known pigment. Can be used. For example, various kaolins, clays, talc, calcium carbonate, satin white, lithopone, titanium dioxide, zinc oxide, silica, colloidal silica, alumina, alumina hydroxide, plastic pigments, etc., commonly used as pigments on coated paper for printing Can be used as appropriate, and a plurality of types can be used in combination.

  In the present invention, the method for coating the outermost coating layer is not particularly limited. For example, various systems such as a film transfer coater such as a gate roll and a shim sizer, an air knife coater, a rod coater, a blade coater, and a direct fountain coater can be used as appropriate. A blade coater or an air knife coater is preferable.

  In the present invention, the pigment contained in the coating layer adjacent to the outermost coating layer is not particularly limited except calcium carbonate according to the present invention, and conventionally known pigments can be used in combination. Examples thereof include various kaolins, clays, talc, satin white, lithopone, titanium dioxide, zinc oxide, silica, colloidal silica, alumina, alumina hydroxide, and plastic pigments. Those generally used as pigments in the coated paper for printing may be used in combination as appropriate.

In the present invention, the method for coating a coating layer adjacent to the outermost coating layer or other coating layers (excluding the outermost coating layer) is not particularly limited. For example, various systems such as a film transfer coater such as a gate roll and a shim sizer, an air knife coater, a rod coater, a blade coater, and a direct fountain coater can be used as appropriate. A blade coater is preferable. The coating solid content mass per one side of the coating layer adjacent to the outermost coating layer or other coating layer (excluding the outermost coating layer) is preferably 5 g / m ² or more and 17 g / m ² or less. . The coating solid content mass per one side of the coating layer adjacent to the outermost coating layer may be the same or different on each of the both surfaces as long as it is within the above range. If it is this range, the influence of the unevenness | corrugation on the surface of a base paper can be reduced, and smoothness can be improved.

  In the present invention, the outermost coating layer or the coating layer adjacent to the outermost coating layer can use a conventionally known binder in addition to latex. Examples of binders that can be used in the present invention include ordinary starches, oxidized starches, phosphate esterified starches, enzyme-modified starches and starches such as cold water soluble starches obtained by flash drying them, polyvinyl alcohol, polyacrylic acid Water-soluble synthetic compounds such as sodium, polyethylene oxide, polyacrylamide, urea or melamine-formalin resin, polyethyleneimine, polyamidepolyamine-epichlorohydrin, natural products such as wax, casein, and soy protein, and those that are cationized. . This may be used alone or in combination with latex. Moreover, you may use multiple types together from these.

  The other coating layer can be appropriately selected from the above latex or the above-mentioned conventionally known binder as a binder.

  In the present invention, each coating layer may be blended with various auxiliaries and additives generally used in producing coated paper. For example, examples of the thickener include water-soluble polymers such as carboxymethyl cellulose, sodium alginate, methyl cellulose, and hydroxyethyl cellulose, and silicates. Furthermore, if necessary, the coating layer may be a dispersant, a pH adjuster, a lubricant, an antifoaming agent, a water resistant agent, a surfactant, a foam inhibitor, a release agent, a foaming agent, a penetrating agent, a coloring dye, a fluorescent dye. You may mix | blend a whitening agent, a ultraviolet absorber, antioxidant, antiseptic | preservative, antibacterial agent, etc.

  The printing coated paper in the present invention can be treated with a super calendar or a soft calendar at each stage where the base paper and the respective coating layers are provided. In particular, it is preferable to calender the outermost coating layer after coating and drying.

  The coated paper for printing of the present invention is suitable for offset printing, and is suitable for coated paper used for duplex printing with a sheet-fed offset printing machine. Moreover, the coated paper for printing of this invention can use at least one printing surface or the partial area | region of one printing surface for various printing systems, such as the printing by an inkjet system, or the printing by an electrophotographic system.

  Examples The present invention will be described more specifically with reference to the following examples, but is not limited to these examples. All parts by mass described in the formulation are values of the solid content or the amount of substantial components.

  The printing coated paper of each example and each comparative example was produced according to the following contents.

<Preparation of base paper>
As a base paper, a 1% by mass pulp slurry was prepared with the following composition, and a base paper for coating having a basis weight of 76 g / m ² was made with a long net paper machine.
(Base paper combination)
ECF bleached LBKP (freeness 440 mlcsf) 70 parts by weight ECF bleached NBKP (freeness 490 mlcsf) 30 parts by weight light calcium carbonate 6.0 parts by weight commercial cationized starch 1.0 part by weight commercial cationic polyacrylamide Yield improver 0.030 parts by mass

<Preparation of calcium carbonate>
As calcium carbonate, commercially available natural limestone is coarsely pulverized to an average particle size of about 30 μm with a jaw crusher, hammer crusher, or roller mill, and water and a commercially available polyacrylic acid alkali salt type dispersant are added to this and stirred. A pre-dispersed slurry having a solid content of about 75% by mass was used. This pre-dispersed slurry was further pulverized by using a wet pulverizer manufactured by Ashizawa Finetech Co., Ltd. (horizontal and cylindrical pulverization chamber dimensions: diameter of about 0.5 m, length of about 1.3 m). The beads were made of zirconia having a diameter of about 1 mm, the filling rate was 83% by volume, and the flow rate was about 15 liters / minute. In the pulverization treatment, the following calcium carbonates A to I were prepared by changing the number of passes and sieving with a mesh while measuring the volume-based particle size distribution. The volume-based particle size distribution was measured by Nikkiso Microtrack 9320-X100, and each frequency was calculated.

Calcium carbonate A:
Frequency 0% by volume of particle diameter 1.0 μm or more / Frequency 39% by volume of particle diameter 0.2 μm or less
Calcium carbonate B:
Frequency 1% by volume of particle diameter 1.0 μm or more / Frequency 32% by volume of particle diameter 0.2 μm or less
Calcium carbonate C:
Frequency 3% by volume of particle diameter 1.0 μm or more / Frequency 21% by volume of particle diameter 0.2 μm or less
Calcium carbonate D:
Frequency 3% by volume of particle size 1.0 μm or more / Frequency 16% by volume of particle size 0.2 μm or less
Calcium carbonate E:
Frequency 3% by volume of particle diameter 1.0 μm or more / Frequency 14% by volume of particle diameter 0.2 μm or less
Calcium carbonate F:
Frequency 5% by volume of particle size 1.0 μm or more / frequency 17% by volume of particle size 0.2 μm or less
Calcium carbonate G:
Frequency 20% by volume of particle size 1.0 μm or more / Frequency 17% by volume of particle size 0.2 μm or less
Calcium carbonate H:
Frequency 20% by volume of particle size 1.0 μm or more / frequency 10% by volume of particle size 0.2 μm or less
Calcium carbonate I:
50% by volume with a particle size of 1.0 μm or more / 0% by volume with a particle size of 0.2 μm or less

<Preparation of coating solution for coating layer adjacent to outermost coating layer>
The number of calcium carbonate is listed in Table 1. Kaolin (primary kaolin: average particle size 1.3 μm) The number of blended is listed in Table 1. Styrene-butadiene latex (glass transition temperature is listed in Table 1) 9.0 parts by weight Polyvinyl Alcohol (complete saponification, degree of polymerization 400) 3.0 parts by weight Calcium stearate lubricant 0.4 part by weight Printability improver (water-soluble modified polyamine resin) 0.3 part by weight

  Blended in the above-mentioned solid part by mass, adjusted with sodium hydroxide so as to have a pH of 9.8, and adjusted for water with a B-type viscosity of about 500 to 2000 mPa · s for blade coating It was set as the coating liquid for coating layers adjacent to a construction layer.

<Preparation of coating liquid for outermost coating layer>
Kaolin (primary kaolin: average particle size 1.3 μm) 60 parts by mass Hollow pigment (commercially available polystyrene organic hollow pigment: average particle size 1 μm, hollow ratio 50% by volume)
9.5 parts by mass Calcium carbonate (heavy calcium carbonate: average particle size 0.8 μm) 30.5 parts by mass Styrene-butadiene latex (glass transition temperature is listed in Table 1) 14 parts by mass Polyvinyl alcohol (completely saponified, Polymerization degree 400) 1.2 parts by mass Calcium stearate lubricant 0.4 parts by mass Printability improver (water-soluble modified polyamine resin) 0.4 parts by mass Fluorescent dye 0.5 parts by mass Blue pigment 0.05 parts by mass Synthetic antifoaming agent 0.2 parts by mass

  Blended with the above solid content by mass part, adjusted with sodium hydroxide so as to have a pH of 9.8, and adjusted with water so that the B-type viscosity is about 10 to 30 mPa · s for air knife coating. It was set as the coating liquid for construction layers.

<Preparation of coated paper for printing>
The coating paper for printing of each Example and Comparative Examples 1-10 was manufactured as follows.
Apply the coating liquid of the coating layer adjacent to the outermost coating layer on both sides of the base paper produced as described above using a blade coater type coating device, and dry it to the outermost coating. A coated paper provided with a coating layer adjacent to the layer was obtained. The coating solid content mass per side was 10.0 g / m ² . Apply the coating solution of the outermost coating layer on both sides of the coating layer adjacent to the outermost coating layer of the obtained coated paper using an air knife coater type coating device, and dry. The outermost coating layer was provided. The coating solid content mass per side was 6.0 g / m ² . The obtained coated paper was finished off-line with a soft calendar device to produce a coated paper for printing.

The coated paper for printing of Comparative Examples 11 and 12 was produced as follows.
Apply the coating liquid of the coating layer adjacent to the outermost coating layer on both sides of the base paper produced as described above using a blade coater type coating device, and dry it to the outermost coating. A coated paper provided with a coating layer adjacent to the layer was obtained. The coating solid content mass per one side was 16.0 g / m ² . Without providing the outermost coating layer on the obtained outer coated paper, it was finished off-line with a soft calender device to produce a coated paper for printing.

  Evaluation of the coated paper for printing was performed by the following method.

<Evaluation of gross ghost>
Using a sheet-fed machine (Diamond 3H-4 manufactured by Mitsubishi Heavy Industries, Ltd.), four-color printing was performed using a lithographic offset process ink. As images to be printed, letters, figures, and photographic images were printed for preprinting, and sheets were stacked as they were. After 24 hours, a solid image and a flat screen image having a large area for printing were printed on the opposite side, and the sheets were stacked as they were. After 24 hours, the gross ghost attributed to the pre-printed image on the solid image and the flat mesh image of the post-printing was visually evaluated in the following six stages. Evaluation criteria are shown below. In the present invention, four or more are the objects of the invention.
6: No gross ghost is recognized.
5: Gloss ghost is slightly observed by oblique observation.
4: Gross ghost is observed by oblique observation.
3: A gross ghost is slightly observed in the solid image.
2: Gross ghost is observed in the solid image.
1: Gross ghost is more clearly recognized.

<Evaluation of printing gloss>
Using an RI printing machine (Meiji Seisakusho Co., Ltd.), 0.3 ml of sheet-fed offset process ink magenta ink (manufactured by DIC, Space Color Fusion GST) was kneaded with a roller, and solid printing was performed on the test piece. In accordance with JIS Z8741 method 3, printing gloss was evaluated at an angle of 60 ° -60 ° reflectivity. Evaluation criteria are shown below. In the present invention, four or more are the objects of the invention.
5: Print gloss is 51.0% or more.
4: The print gloss is 44.0% or more and less than 51.0%.
3: The print gloss is 37.0% or more and less than 44.0%.
2: The printing gloss is 30.0% or more and less than 37.0%.
1: Print gloss is less than 30.0%.

<Evaluation of surface strength>
Using an RI printing machine (manufactured by Meisei Seisakusho Co., Ltd.), printing was performed with black ink having a tack value of 20. In addition, printing was performed with black ink having a tack value of 20 immediately after the print sample was moistened with a water supply roll. The degree of picking on both printed surfaces was evaluated in the following four stages, and in the case of different evaluations, priority was given to the inferior one. Evaluation criteria are shown below. In the present invention, three or more are the objects of the invention.
4: Picking cannot be determined.
3: Picking can be distinguished slightly.
2: Picking can be determined.
1: Picking can be clearly identified.

  Table 1 shows the evaluation results of Examples 1 to 12 and Comparative Examples 1 to 12.

  In Examples 1 to 12 corresponding to the present invention, it is understood that the gloss ghost is suppressed and neither the printing gloss nor the printing durability is deteriorated. On the other hand, in Comparative Example 11 and Comparative Example 12, which are single layers, gloss ghosts are suppressed regardless of whether the glass transition temperature is within the range of the present invention or outside the range of the present invention, but printing gloss and printing durability are improved. I can't satisfy both. Even in the case of two layers, Comparative Example 1 in which the calcium carbonate according to the present invention is less than 80% by mass with respect to the total pigment solid content of the coating layer adjacent to the outermost coating layer is insufficient in terms of gross ghost. And the glass transition temperature of latex contained in Comparative Examples 2 to 6 in which the frequency of calcium carbonate does not correspond to the present invention in the volume-based particle size distribution and the outermost coating layer or the coating layer adjacent to the outermost coating layer However, Comparative Examples 7 to 10, which do not correspond to the range according to the present invention, cannot satisfy all of the effects according to the present invention.

Claims (1)

  In a double-sided printing coated paper for a sheet-fed offset printing machine in which at least two coating layers containing a pigment are coated on both sides of a base paper, the coating layer adjacent to the outermost coating layer on each side of the base paper Contains calcium carbonate, and in the volume-based particle size distribution of the calcium carbonate, the frequency of the particle size of 1.0 μm or more is 3% by volume or less, and the frequency of the particle size of 0.2 μm or less is more than 15% by volume. The content is 80% by mass or more based on the total pigment solid content of the coating layer adjacent to the outermost coating layer, and the coating adjacent to the outermost coating layer and the outermost coating layer on both sides of the base paper. A double-sided coated coated paper for sheet-fed offset printing machines, wherein the working layer contains a latex having a glass transition temperature of -20 ° C or higher and lower than 20 ° C.