Coated paper for printing

Abstract

A pigment coating layer is provided on at least one side of the base paper, Coated printing paper, the outermost pigment coating layer of which contains calcium carbonate having an average particle size (D50) of more than 0.50 μm and not more than 0.80 μm, and the white paper gloss (75°) is 60% or more.

Description

[Technical Field]

[0001] This invention relates to a coated paper for printing that has high white gloss and high strength. [Background technology]

[0002] Coated paper is broadly classified into glossy coated paper and matte coated paper. Among glossy coated papers, high-gloss coated paper includes art paper and super art paper, which were traditionally used for high-quality printing, as well as coated paper used for catalogs and brochures. These papers have a glossy finish with high white paper gloss and high print gloss. Matte coated paper, on the other hand, has lower white paper gloss and print gloss than high-gloss coated paper, and includes dull-finish coated paper and matte-finish coated paper.

[0003] Generally, high-gloss coated paper achieves its glossiness by using large quantities of flat pigments such as kaolin or clay, or by using plastic pigments with good gloss-producing properties. The main surface of flat pigments such as kaolin or clay is acidic, and the sides are basic (Non-Patent Literature 1), and adhesives such as latex commonly used in coated paper contain acidic groups. Therefore, the main surface of kaolin or clay is acidic, resulting in low affinity with adhesives such as latex. On the other hand, the sides of kaolin or clay are basic, resulting in high affinity with adhesives, but the small surface area prevents sufficient bonding area from being achieved, leading to the problem of low strength development efficiency.

[0004] Kaolin or clay is a pigment with yellow to brown hues, and coated paper that uses a lot of it tends to have a strong yellow tint, so high-gloss coated paper tends to have a yellowish hue. * a * b * b in the colorimetric system * As shown, paper with a strong yellowish tint is b * The value tends to be high. When printed on paper with a strong yellow tint, the overall yellow tint of the printed material becomes stronger, resulting in a tendency for the color reproduction of the printed material to be inferior.

[0005] Plastic pigments are extremely expensive materials, making them difficult to use in general-purpose glossy coated paper such as flyers. Furthermore, there is a growing trend to avoid using plastic pigments, which are organic pigments, due to environmental concerns.

[0006] In addition, a technique has been proposed for high-gloss coated paper that uses very fine calcium carbonate with an average particle size of 0.50 μm or less to improve gloss (Patent Document 2). However, calcium carbonate with excessively fine particle size also increases the specific surface area, which increases the binder requirement and may result in a decrease in paper strength. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2007-231457 [Patent Document 2] Japanese Patent Application Publication No. 7-229091 [Non-patent literature]

[0008] [Non-Patent Document 1] Journal of the Japan Pulp and Paper Technology Association, Vol. 62 (2008), No. 6, pp. 694-699 [Overview of the project] [Problems that the invention aims to solve]

[0009] The objective of this invention is to provide a coated paper for printing that has high white gloss and high strength. [Means for solving the problem]

[0010] In view of the above problems, the inventors conducted extensive research and found that a printed coated paper having a pigment coating layer containing specific fine calcium carbonate particles solves the above problems. That is, the above problems are solved by the present invention as described below. [1] The base paper has a pigment coating layer on at least one side, The calcium carbonate contained in the outermost pigment coating layer has an average particle diameter (D50) greater than 0.50 μm and less than or equal to 0.80 μm, A coated paper for printing with a white paper glossiness (75°) of 60% or more. [2] The coated paper for printing according to [1], wherein 40 parts by weight or more of the calcium carbonate is contained in 100 parts by weight of the pigment in the outermost pigment coating layer. [3] The coated paper for printing according to [1] or [2], wherein the average particle diameter (D50) of the calcium carbonate is 0.55 to 0.75 μm. [4] The coated paper for printing according to any one of [1] to [3], wherein the printing glossiness of the blue-red printing part is 70% or more. [5] The coated paper for printing according to [2], wherein 75 parts by weight or more of the calcium carbonate is contained in 100 parts by weight of the pigment in the outermost pigment coating layer. [6] The coated paper for printing according to any one of [1] to [5], which has a plurality of pigment coating layers and the coating amount of the outermost pigment coating layer is larger than the coating amount of the innermost pigment coating layer. [7] The coated paper for printing according to any one of [1] to [6], wherein the coating amount of the outermost coating layer is 7 g / m 2 or more. [Effect of the Invention]

[0011] According to the present invention, a coated paper for printing having high white paper glossiness and high strength can be provided. [Mode for Carrying Out the Invention] <00​​​​​​​Printable coated paper is paper for printing that has a pigment coating layer provided on a base paper. The pigment coating layer is a layer mainly composed of white pigment. The printable coated paper of the present invention contains calcium carbonate in the outermost pigment coating layer having an average particle size (D50) greater than 0.50 μm and 0.80 μm or less. The printable coated paper of the present invention can be subjected to commercial printing such as offset printing, gravure printing, and on-demand printing (laser method, inkjet method, electrophotographic method) on the paper surface, and its uses include, but are not limited to, books, magazines, posters, envelopes, and calendars.

[0014] (1) Pigment coating layer 1) Pigments The pigment coating layer contains calcium carbonate particles with an average particle size (D50) greater than 0.50 μm and less than or equal to 0.80 μm (hereinafter also referred to as "first calcium carbonate"). D50 is the 50% volume average particle size. Laser diffraction method The particle size distribution and D50 of the pigment can be measured using a Malvern Mastersizer 3000 or similar instrument. The upper limit of the D50 of calcium carbonate is preferably 0.75 μm or less, and more preferably 0.70 μm or less. From the viewpoint of the specific surface area of ​​the pigment and the amount of binder required, the lower limit is preferably 0.55 μm or more. Within the above D50 range, the coating layer becomes denser, resulting in high gloss. Furthermore, compared to using pigments smaller than 0.50 μm, the amount of binder required is lower, thus enabling the production of printed coated paper with excellent strength.

[0015] If the pigment coating layer is present on both sides of the base paper, it is sufficient that the outermost pigment coating layer on at least one side contains the first calcium carbonate.

[0016] The lower limit of the amount of first calcium carbonate blended in the outermost pigment coating layer is preferably 40 parts by weight or more, more preferably 75 parts by weight or more, and even more preferably 80 parts by weight or more, per 100 parts by weight of pigment in the pigment coating layer. The entire amount may be first calcium carbonate. The first calcium carbonate is preferably heavy calcium carbonate or light calcium carbonate produced in the causticization process of the pulp manufacturing process (caustic light calcium carbonate, see Japanese Patent No. 5274077).

[0017] As the white pigment other than the first calcium carbonate in the pigment coating layer, pigments commonly used in the field can be used. Examples include inorganic pigments such as kaolin, clay, engineered kaolin, delaminated clay, heavy calcium carbonate, light calcium carbonate, talc, titanium dioxide, barium sulfate, calcium sulfate, zinc oxide, silicic acid, silicates, colloidal silica, and satin white, as well as organic pigments such as solid, hollow, or core-shell types. Multiple types of these pigments may be used in combination.

[0018] As a white pigment other than the first calcium carbonate, it is preferable to use heavy calcium carbonate or light calcium carbonate (hereinafter also referred to as "second calcium carbonate") with a D50 of more than 0.80 μm. Calcium carbonate has excellent bonding properties with adhesives (binders) and improves whiteness, thus achieving high strength, whiteness, and printability. The total amount of the first and second calcium carbonates in 100 parts by weight of pigment in the outermost pigment coating layer is preferably 90 parts by weight or more, and more preferably 100 parts by weight. When there are two or more pigment coating layers, the total amount of the first and second calcium carbonates in the pigment coating layers other than the outermost coating layer is not limited, but is preferably within the above range. The second calcium carbonate is preferably heavy calcium carbonate or caustic light calcium carbonate.

[0019] 2) Adhesive The pigment coating layer contains an adhesive (binder) as a matrix. The adhesive is not limited, and known adhesives can be used. Examples include latexes such as styrene-butadiene copolymers, styrene-acrylic copolymers, ethylene-vinyl acetate copolymers, butadiene-methyl methacrylate copolymers, vinyl acetate-butyl acrylate copolymers, maleic anhydride copolymers, and acrylic acid-methyl methacrylate copolymers; polyvinyl alcohols such as fully saponified polyvinyl alcohol, partially saponified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, and acetoacetyl-modified polyvinyl alcohol; proteins such as casein, soy protein, and synthetic protein; starches such as oxidized starch, positive starch, urea phosphate esterified starch, hydroxyethyl etherified starch, and dextrin; and cellulose derivatives such as carboxymethylcellulose, hydroxyethylcellulose, and hydroxymethylcellulose. Multiple types of these can be used in combination.

[0020] From the viewpoint of printability and coating suitability, the amount of adhesive is preferably 5 to 30 parts by weight, and more preferably 8 to 25 parts by weight, per 100 parts by weight of pigment in the total pigment coating layer. The upper limit is more preferably 20 parts by weight or less, and most preferably 17 parts by weight or less. If the total amount of adhesive exceeds 30 parts by weight, the viscosity of the pigment coating liquid increases, making operational problems more likely during coating. Furthermore, in this case, there is a tendency for the drying properties of the ink to decrease. On the other hand, if the total amount of adhesive is less than 5 parts by weight, it becomes difficult to obtain sufficient surface strength.

[0021] The coated paper for printing of the present invention preferably contains 10 to 80% by weight of latex in all adhesives, and more preferably contains 15 to 70% by weight of latex. Latex is an adhesive in the form of an emulsion. Styrene-butadiene latex is preferred as the latex. As described above, calcium carbonate has good affinity with adhesives having acidic groups such as latex compared to kaolin or clay. Therefore, by using latex in the coated paper for printing of the present invention, a coated paper for printing excellent in strength expression can be obtained. The coated paper for printing of the present invention has a pigment coating layer. When it has two or more pigment coating layers, the layer closest to the base paper preferably contains 10 to 80% by weight of latex in all adhesives, and the layer far from the base paper preferably contains 30 to 60% by weight of latex. As other adhesives, it is particularly preferable to use starches, and the amount thereof is preferably 30 to 90% by weight in all adhesives in the layer closest to the base paper, and preferably 40 to 70% by weight in the layer far from the base paper.

[0022] 3) Other additives The pigment coating layer may contain various auxiliaries usually blended in pigments for coated papers, such as dispersants, thickeners, water retention agents, defoamers, water resistance agents, dyes, coloring pigments, etc., if necessary.

[0023] 4) Coating amount The coating amount of the pigment coating layer is preferably 7 g / m² or more in terms of solid content per side, more preferably 10 g / m² or more, and even more preferably 15 g / m² or more. If the coating amount is less than 7 g / m², the unevenness on the surface of the paper base material cannot be sufficiently covered, so the receptivity of printing ink may be significantly reduced, and sufficient white paper glossiness may not be obtained. On the other hand, the coating amount of the pigment coating layer is preferably 50 g / m² or less, more preferably 40 g / m² or less, and even more preferably 35 g / m² or less. The coating amount is the total value of all pigment coating layers per side. When there are two or more pigment coating layers, the coating amount of the innermost pigment coating layer (the pigment coating layer adjacent to the base paper) is 2 to 15 g / m² 2 or more, 2 more preferably 10 g / m 2 or more, and 2 even more preferably 15 g / m 2 or more. If the coating amount is less than 7 g / m 2 ², the unevenness on the surface of the paper base material cannot be sufficiently covered, so the receptivity of printing ink may be significantly reduced, and sufficient white paper glossiness may not be obtained. On the other hand, the coating amount of the pigment coating layer is preferably 50 g / m 2 ² or less, more preferably 40 g / m2 Preferably, and more preferably, 5 to 12 g / m 2 Furthermore, the coating amount of the outermost pigment coating layer is 7 g / m². 2 The above is preferable, 8 g / m 2 The above is more preferable. 2 The following is preferable: 15 g / m 2 The following is more preferable: Since the gloss development is greatly influenced by the outermost coating layer, it is preferable that the amount of the outermost coating layer is greater than the amount of the innermost pigment coating layer.

[0024] (2) Base paper 1) Pulp Any known pulp can be used as the base paper. Known pulps include chemical pulp, wood pulp (GP), refined wood pulp (RGP), thermomechanical pulp (TMP), chemothermetic pulp (CTMP), chemigland pulp (CGP), semi-chemical pulp (SCP), and recycled paper pulp. In the present invention, it is preferable to use chemical pulp. Chemical pulp can be produced by the kraft pulp method or the sulfite pulp method, and both can be used in the present invention, but chemical pulp produced by the kraft method is preferable in terms of production cost. From the viewpoint of whiteness and other factors, the chemical pulp content in the raw pulp is preferably 60% by weight or more, more preferably 80% by weight or more, even more preferably 90% by weight or more, and particularly preferably 95% by weight or more.

[0025] 2) Filler Known fillers may be used in the base paper. Known fillers include inorganic fillers such as heavy calcium carbonate, light calcium carbonate, clay, silica, light calcium carbonate-silica composite, kaolin, calcined kaolin, delaminated kaolin, white carbon, talc, magnesium carbonate, barium carbonate, barium sulfate, aluminum hydroxide, calcium hydroxide, magnesium hydroxide, zinc hydroxide, zinc oxide, titanium dioxide, and amorphous silica produced by neutralization of sodium silicate with mineral acids, as well as organic fillers such as urea-formaldehyde resin, melamine resin, polystyrene resin, and phenolic resin. Among these, heavy calcium carbonate and light calcium carbonate, which are typical fillers in neutral papermaking and alkali papermaking, are preferably used to improve opacity. The calcium carbonate used as a filler may be the first calcium carbonate or the second calcium carbonate mentioned above, but light calcium carbonate is preferred. The filler ratio in the paper is not particularly limited, but 1 to 40% by weight is preferred, and 10 to 35% by weight is more preferred. Considering the strength of the base paper, the amount is more preferably 10 to 20% by weight.

[0026] 3) Others Known papermaking additives can also be used. For example, aluminum sulfate, various anionic, cationic, nonionic, or amphoteric yield improvers, water drainage improvers, various paper strength enhancers, and internal sizing agents can be used as needed. Examples of dry paper strength improvers include polyacrylamide and cationized starch, while examples of wet paper strength improvers include polyamidoamine epichlorohydrin. These chemicals are added within a range that does not affect the form or operability. Examples of internal sizing agents include alkyl ketene dimers, alkenyl succinic anhydride, and rosin sizing agents. Furthermore, dyes, pigments, fluorescent whitening agents, pH adjusters, defoamers, pitch control agents, slime control agents, etc., can also be added as needed.

[0027] 4) Basis weight of the base paper The basis weight of the base paper for the coated printing paper of the present invention is 40-160 g / m². 2 Preferably, 45-150 g / m² 2More preferably, 50-140 g / m 2 That is even more preferable.

[0028] 5) Clear coating layer The printed coated paper of the present invention may have a clear (transparent) coating layer on one or both sides of the base paper described above. By applying a clear coating to the base paper, the surface strength and smoothness of the base paper can be improved, and the coating suitability when applying pigment coating can be improved. The amount of clear coating is 0.1 to 3.0 g / m² of solid content per side. 2 Preferably, 0.2 to 2.0 g / m 2 More preferably, and even more preferably, 0.5 to 2.0 g / m 2 That is the case.

[0029] In the present invention, clear coating refers to the process of applying a coating liquid (surface treatment liquid) mainly composed of starches such as starch, oxidized starch, and various modified starches (automodified, cationically modified, etc.), polyacrylamide, and polyvinyl alcohol, onto a base paper using a coater (coating machine) such as a 2-roll pound size press, gate roll coater, pre-metalling size press, curtain coater, or spray coater, by sizing (size pressing). It is also possible to coat the clear coating liquid with a sizing agent. In the present invention, it is preferable to coat with starch.

[0030] 2. Manufacturing method The printed coated paper of the present invention can be manufactured by known methods, but it is preferable to manufacture it by coating a base paper with a pigment coating solution containing a pigment and an adhesive.

[0031] (1) Preparation of the base paper The raw materials used for the base paper in the present invention have already been described. The base paper is manufactured using known papermaking methods. For example, it can be manufactured using a wire mesh paper machine including a top wire, an on-top former, a gap former, a round wire mesh paper machine, a paperboard paper machine that uses both a wire mesh paper machine and a round wire mesh paper machine, a Yankee dryer machine, etc. The pH during papermaking may be acidic, neutral, or alkaline, but neutral or alkaline is preferred. The papermaking speed is also not particularly limited. The base paper used in the present invention may be single-layer or multi-layer, but single-layer base paper is preferably used.

[0032] (2) Smoothing treatment of the base paper Before applying the pigment coating solution to the resulting base paper, it is preferable to smooth the base paper using various calendering devices. Commonly used calendering devices such as supercalenders and soft calenders can be used as appropriate. Calendering conditions, such as the temperature of the rigid rolls, calendering pressure, nip count, roll speed, and paper moisture content before calendering, are appropriately selected according to the required quality. Calendering the base paper improves its smoothness and thus its suitability for pigment coating.

[0033] (3) Preparation of pigment coating solution The pigment coating solution can be prepared by dispersing or dissolving pigments, adhesives, and optionally additives in water. The composition of each component is adjusted so that the aforementioned pigment coating layer can be formed. When performing blade coating, the solid content concentration of the pigment coating solution is preferably 40-70% by weight, more preferably 60-70% by weight. The viscosity of the pigment coating solution is preferably in the range of 500-5000 mPa·s, measured at 60 rpm at room temperature. When performing coating with a roll coater, the solid content of the pigment coating solution is preferably 30-60% by weight, more preferably 40-60% by weight. If the solid content is too low, backflow may occur in blade coating; if it is too high, the blade load will increase, leading to increased blade wear; and in roll coaters, boiling may occur, affecting operability.

[0034] (4) Coating method The coating method is not limited, and known coating methods such as roll coaters and blade coaters can be used. The coating speed is also not particularly limited, but 400 to 1800 m / min is preferred for blade coaters, and 400 to 2000 m / min is preferred for roll coaters. In the present invention, the pigment coating layer may be coated with a single-layer blade coater, coated with a roll coater and then coated with a blade coater, or coated with a blade coater and then coated with a blade coater. However, it is preferable to use a blade coater for coating the outermost coating layer because it can improve the smoothness of the surface.

[0035] The printed coated paper of the present invention has a pigment coating layer on at least one side, and may have two or more pigment coating layers. When there are two or more pigment coating layers, the fiber coverage is improved and the smoothness is also increased. If there are three or more layers, the amount of coating can be increased and the quality of the coated paper will be improved, but from the viewpoint of cost and operability, it is preferable to have one or two layers. As described above, a clear coating layer may be provided on the base paper, and then a pigment coating layer may be provided on top of that.

[0036] (5) Other processes The method for drying the wet coating layer is not limited, and for example, a steam heating cylinder, a heated hot air dryer, a gas heater dryer, an electric heater dryer, an infrared heater dryer, etc., can be used.

[0037] The coated paper for printing of the present invention may be surface-treated after being manufactured as described above, and calendering is preferred to obtain high gloss. When calendering is performed, commonly used calendering devices such as supercalenders and soft calenders can be used as appropriate. Calendering conditions such as the temperature of the rigid roll, calendering pressure, number of nips, roll speed, and moisture content of the paper before calendering are appropriately selected according to the required quality, but hot soft nip calendering is more preferable for the coated paper for printing of the present invention. The preferred conditions for this treatment are a linear pressure of 140 to 300 kN / m, a temperature of 70 to 300°C, and 5 nips or more. The processing speed is approximately 200 to 800 m / min.

[0038] 3.Paper quality (1) Glossiness of white paper White paper gloss is an index indicating the degree of gloss on white paper, and in this invention, it is the specular gloss at an angle of 75° to the normal of the paper surface, measured according to JIS-P8142. The coated printing paper of this invention is a high-gloss coated printing paper with high white paper gloss. The white paper gloss of the coated printing paper of this invention is 60% or more, preferably 65% ​​or more, and more preferably 70% or more. There is no upper limit to the white paper gloss, but it is 100% or less.

[0039] (2) Print gloss Print gloss is an indicator of the degree of gloss of a printed material after printing, and in this invention, it is measured by the method described below. The print gloss (CM) of the blue-red printed area is preferably 70 or higher, and preferably 75% or higher. [Examples]

[0040] The present invention will be specifically described below with reference to examples, but the present invention is not limited thereto. Parts by weight and weight percent are values ​​on a solid content basis.

[0041] <Evaluation Method> (1)Basic weight Measurements were taken in accordance with JIS P 8124. (2) ISO whiteness: Measured in accordance with JIS P8148 using a color difference meter CMS-35SPX manufactured by Murakami Color Co., Ltd., under conditions including ultraviolet light. (3) Glossiness of white paper Measurements were taken in accordance with JIS-P8142. (4) Print gloss Using a Roland offset sheet-fed printing press (4 colors) and offset sheet-fed inks (NEX-M, manufactured by Toyo Ink Co., Ltd.), printing was performed at a printing speed of 8000 sheets / hr, with the ink density of solid areas being cyan 1.60 and sorrel 1.50, in the order of cyan-sinus-red (CM). The gloss of the solid cyan-sinus-red (CM) printed areas of the resulting printed materials was measured according to JIS P-8142. (5)Print surface strength Using an RI-I type printing press (manufactured by Akira Seisakusho), printing was performed using printing ink (NEX-Y manufactured by Toyo Ink). After printing, the print marks on the rubber roll were manually transferred to transfer paper, and the degree of picking was visually evaluated. The evaluation criteria were as follows: A = rarely occurs, B = occurs

[0042] <Material> The following was used. (1) Heavy calcium carbonate Manufactured by Fimatec Co., Ltd., Product name: FMT97, D50 = 0.88 μm Manufactured by Fimatec Co., Ltd., Product name: FMT75, D50 = 1.65 μm Manufactured by Fimatec Co., Ltd., Product name: Curvital 90, D50 = 1.22 μm Manufactured by Fimatec Co., Ltd., Product name: FMT100YF, D50 = 0.59 μm Manufactured by Fimatec Co., Ltd., Product name: FMT100, D50 = 0.65 μm Manufactured by Imerys Minerals Japan Co., Ltd., Product name: Curvital 97, D50 = 0.88 μm (2) Clay Kamin HydraGloss D50 = 0.22 μm Made by Imerys Minerals Japan, Premier, D50 = 2.055 μm (3) Adhesives Styrene-butadiene copolymer latex starch: Dynacoat 68NB (manufactured by GSL Japan Co., Ltd.) Biolatex (manufactured by Ecosynthetix) (4) Dye Purple dye (manufactured by Mikuni Pigment Co., Ltd.) Blue dye (manufactured by Mikuni Pigment Co., Ltd.) Black dye (manufactured by Mikuni Pigment Co., Ltd.) Fluorescent dye: canwhite (manufactured by Kanazia Japan Co., Ltd.)

[0043] <Series 3> [Example 1] This paper uses 100% chemical pulp by weight and contains 13.5% by weight of light calcium carbonate as filler, with a basis weight of 75 g / m². 2 I prepared the original paper.

[0044] 100 parts by weight of heavy calcium carbonate (manufactured by Fimatec Co., Ltd., product name: FMT97, D50=0.88μm) was used as the pigment. To this, 3 parts by weight of styrene-butadiene copolymer latex and 6 parts by weight of oxidized starch were added as adhesives, and water was added to obtain a primer pigment coating solution with a solid content of 65% by weight.

[0045] Using 100 parts by weight of fine-grained heavy calcium carbonate (manufactured by Fimatec Co., Ltd., product name: 100YF, D50=0.59μm), 7.7 parts by weight of styrene-butadiene copolymer latex as an adhesive, 1.3 parts of starch-based binder "Biolatex" (indicated as BLx in the table), and the dyes as shown in Table 1, water was added to obtain a topcoat pigment coating solution with a solid content of 66% by weight.

[0046] On the aforementioned base paper, the undercoat pigment coating liquid was applied with a blade coater, with a dry coating amount of 9.5 g / m² per side. 2 The coating was applied to both sides and dried. Furthermore, a topcoat pigment solution was applied using a blade coater, with a dry coating amount of 8.5 g / m² per side. 2The paper was coated on both sides, nipped using a resin roll and a metal roll, and calendered under the temperature and nip pressure conditions shown in Table 1 to obtain coated paper for printing. This coated paper was evaluated using the method described above.

[0047] [Example 2] Printable coated paper was manufactured and evaluated in the same manner as in Example 1, except that the amount of latex in the undercoat coating solution was changed.

[0048] [Comparative Examples 1 and 2] Printing coated paper was manufactured and evaluated in the same manner as in Example 1, except that the coating solution shown in Table 1 was used.

[0049] <Series 1> [Examples 3 and 4] This paper uses 100% chemical pulp by weight and contains 13.5% by weight of light calcium carbonate as filler, with a basis weight of 69 g / m². 2 I prepared the original paper. A primer pigment coating solution with a solid content of 65% by weight was obtained using the pigments and adhesives shown in Table 1. A topcoat pigment coating solution with a solid content of 65% by weight was obtained using the pigments and adhesives shown in Table 1. Using these materials, coated paper for printing was manufactured and evaluated in the same manner as in Example 1.

[0050] [Comparative Examples 3 and 4] Printable coated paper was manufactured and evaluated in the same manner as in Example 3, except that the topcoat liquid was changed as shown in Table 1.

[0051] <Series 2> [Examples 5-8] Made using 100% chemical pulp by weight, containing 13.5% by weight of light calcium carbonate as filler, and pressed to a starch size, resulting in a basis weight of 75 g / m². 2 I prepared the original paper. Using the pigments and adhesives shown in Table 1, a pigment coating solution with a solid content of 65% by weight was obtained. Using these materials, a printed coated paper having a single pigment coating layer was manufactured and evaluated in the same manner as in Example 1.

[0052] [Comparative Example 5] Printing coated paper was manufactured and evaluated in the same manner as in Example 5, except that the coating solution was changed as shown in Table 1.

[0053] [Table 1-1]

[0054] [Table 1-2]

[0055] [Table 1-3]

[0056] Examples 3 and 4 of Series 1 showed that using calcium carbonate with a D50 of 0.80 μm or less improved the printed surface strength compared to Comparative Example 4, which incorporated clay, suggesting the possibility of reducing the amount of binder used. Furthermore, Examples 3 and 4 achieved high gloss even under the same calendering conditions as Comparative Example 3, which used calcium carbonate with a larger average particle size.

[0057] Series 2 relates to single-coated printed paper. In Examples 5-8, which incorporated calcium carbonate with a D50 of 0.80 μm or less, a higher gloss was obtained compared to Comparative Example 5, which used calcium carbonate with a larger average particle size, similar to Series 1 (double coating). In Example 8, although the amount of starch binder was reduced by 1 part by weight compared to Example 5, the print surface strength remained at a level that did not cause problems for printing, and no significant difference was observed between the two.

[0058] From Series 3 onwards, it has become clear that by using calcium carbonate with a D50 of 0.80 μm or less, it is possible to improve strength while maintaining equivalent white paper gloss compared to cases using clay or kaolin, and to obtain a printed coated paper with equivalent strength even with a reduced amount of adhesive. Therefore, it is clear that the printed coated paper of the present invention has high white paper gloss and excellent strength.

Claims

1. A method for manufacturing coated paper for printing, wherein the base paper has a pigment coating layer on at least one side, the white paper gloss (75°) is 60% or more, and the print gloss of the blue and red printed area is 70% or more, The process includes providing an outermost coating layer containing, as a first calcium carbonate, heavy calcium carbonate or caustic light calcium carbonate having an average particle size (D50) greater than 0.50 μm and less than or equal to 0.80 μm, and as a second calcium carbonate, heavy calcium carbonate or caustic light calcium carbonate with a D50 greater than 0.80 μm. Manufacturing method.

2. The manufacturing method according to claim 1, comprising the step of providing the outermost pigment coating layer containing 40 parts by weight or more of the first calcium carbonate in 100 parts by weight of the pigment.

3. The manufacturing method according to claim 1 or 2, wherein the average particle size (D50) of the first calcium carbonate is 0.55 to 0.75 μm.

4. The manufacturing method according to claim 2, comprising the step of providing an outermost coating layer containing 75 parts by weight or more of the first calcium carbonate in 100 parts by weight of pigment.

5. A manufacturing method according to any one of claims 1 to 4, comprising the step of providing multiple pigment coating layers, wherein the amount of the outermost pigment coating layer is greater than the amount of the innermost pigment coating layer.

6. The amount of the outermost pigment coating layer is 7 g / m ２ The manufacturing method according to any one of claims 1 to 5.

Images