Gravure printing coated paper for packaging container

Abstract

To provide gravure printing coated paper having high rupture strength sufficient for use as a packaging container and excellent gravure printability.SOLUTION: Gravure printing coated paper has a pigment coating layer including a pigment and a binder at least on one side of base paper, wherein the base paper includes, as a raw material pulp, 30 wt.% or over of a conifer kraft pulp (NKP) in the whole raw material pulp, the pigment coating layer includes, as the pigment, 60 wt.% or over of a clay in the pigment, having an aspect ratio of under 10 and an average particle diameter (D50) of under 1.0 μm under, and a coating amount of the pigment coating layer per one side is 11 g / m2 or over as solid content.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a coated paper for gravure printing that combines excellent burst strength and printability. [Background technology]

[0002] Gravure printing is an intaglio printing method in which ink is transferred to the recessed areas of a plate under pressure, and because it has excellent gradation reproduction, it is widely used in the commercial printing field for magazines, catalogs, pamphlets, etc. that contain illustrations such as photographs. In particular, there is a demand for gravure printing paper used in the commercial printing field that is low-cost and has excellent printability in order to reduce the cost of the paper itself.

[0003] Gravure printing is an intaglio printing method, so it uses a harder plate than offset printing. This makes it difficult for the plate surface to completely adhere to the paper during gravure printing, which can result in speckles, where halftone dots do not transfer properly. If there is a lot of this speckle, it will result in a decrease in print quality. To suppress the occurrence of speckles, it is important to increase the adhesion between the gravure printing plate surface and the paper.

[0004] In order to improve adhesion between the gravure printing plate and the paper, it is effective to increase the smoothness and elasticity of the paper, and methods that have been proposed include increasing the amount of hardwood kraft pulp (LKP) in the pulp composition of the base paper to increase smoothness, and adding mechanical pulp (MP) to increase elasticity. On the other hand, when printed coated paper is used for applications such as packaging paper, it is effective to increase the burst strength, and a method has been proposed to increase the amount of softwood kraft pulp (NKP) in the pulp composition of the base paper. In particular, when printed coated paper is used for packaging containers for cigarettes, chocolates, etc., the container dimensions are small and the folds must be sharp to enhance the aesthetic appeal of the container, so there is a demand for increasing the burst strength to prevent the container from breaking at the folds.

[0005] In addition, as a method for improving the smoothness of the coated paper surface from the viewpoint of paint formulation, it has been proposed to incorporate layered silicate mineral pigments with a high aspect ratio (delaminated clay, talc, etc.) into the coating layer formation material (Patent Document 1). However, when a large amount of pigments with a high aspect ratio are incorporated into the coating layer composition, the viscosity of the coating solution increases, making handling during preparation difficult and likely to cause coating defects such as streaks and scratches. For this reason, the current situation is that the solid content concentration of the paint for forming the coating layer cannot be made too high, and as a result of applying a paint with a high moisture content, it is necessary to ensure a long drying time for the paper, which is not suitable for high-speed operation. In addition, pigments such as delaminated clay and talc with a high aspect ratio are suitable for applications with low white paper gloss, such as matte coated paper (Patent Document 2), but when the amount incorporated is increased, the gloss expression deteriorates, so it has been difficult to use them for glossy coated paper that requires white paper gloss.

[0006] Also, a method is known in which calcined clay is used in combination with other pigments to prevent speckles and improve opacity. However, calcined clay has poor fluidity, which increases the viscosity of the coating liquid, which is likely to cause coating defects such as streaks and scratches, and deteriorates the workability of the coating process. For this reason, even when calcined clay is used, the solid viscosity of the paint cannot be made very high, and as a result, it is necessary to maintain a long drying time after coating, which limits high-speed operation.

[0007] Furthermore, a method is known in which organic pigments such as plastic pigments are used to impart high white paper gloss, anti-speckle effect, opacity, etc. (Patent Document 3). Pigments are more expensive than inorganic pigments, which increases costs, and coating solutions containing organic pigments tend to increase in viscosity under high shear stress, which can easily cause coating defects such as streaks and scratches. For this reason, the current situation is that the solids concentration of the paint cannot be made too high, which results in the need to maintain a long drying time after coating, which is unsuitable for high-speed operation. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] JP 2002-088679 A [Patent Document 2] JP 2000-199198 A [Patent Document 3] Japanese Patent Application Publication No. 1-20396 Summary of the Invention [Problem to be solved by the invention]

[0009] In view of the above, there has been a demand for the development of a coated paper for gravure printing which has a burst strength high enough for use in packaging containers and the like and which is excellent in suitability for gravure printing.

[0010] In view of the above circumstances, an object of the present invention is to provide a gravure-printing coated paper for use in packaging containers, which has high bursting strength and excellent suitability for gravure printing. [Means for solving the problem]

[0011] As a result of intensive research into the above-mentioned problems, the present inventors have discovered a coated paper for gravure printing having a pigment coating layer containing a pigment and an adhesive on at least one side of a base paper, the base paper containing softwood kraft pulp (NKP) as a raw pulp in an amount of 30% by weight or more of the total raw pulp, the pigment coating layer containing clay as a pigment having an aspect ratio of less than 10 and an average particle size (D50) of less than 1.0 μm in an amount of 60% by weight or more of the total pigment, and the coating weight of the pigment coating layer being 11 g / m2 in terms of solid content per side. 2 We have found a coated paper for gravure printing characterized by the above.

[0012] The present invention includes, but is not limited to, the following inventions.

[0013] (1) A coated paper for gravure printing to be used for packaging containers, the coated paper for gravure printing having a pigment coating layer containing a pigment and an adhesive on at least one side of a base paper, the base paper containing softwood kraft pulp (NKP) as a raw pulp in an amount of 30% by weight or more of the total raw pulp, the pigment coating layer containing clay as a pigment having an aspect ratio of less than 10 and an average particle size (D50) of less than 1.0 μm in an amount of 60% by weight or more of the total pigment, and the coating weight of the pigment coating layer being 11 g / m2 in terms of solid content per side. 2 The coated paper for gravure printing as described above.

[0014] (2) The coated paper for gravure printing according to (1), wherein the base paper contains softwood kraft pulp (NKP) as raw pulp in an amount of 70% by weight or less of the total raw pulp.

[0015] (3) The coating weight of the pigment coating layer is 15 g / m2 in solids per side. 2 is less than or equal to (1 ) or (2). (4) The coated paper for gravure printing according to any one of (1) to (3), wherein the pigment coating layer contains precipitated calcium carbonate as a pigment. (5) The coated paper for gravure printing according to any one of (1) to (4), wherein the adhesive comprises a copolymer latex. (6) A coated paper for gravure printing according to any one of (1) to (5), wherein the adhesive comprises a styrene-butadiene copolymer latex. (7) The coated paper for gravure printing according to any one of (1) to (6), wherein the pigment coating layer contains 1 to 20 parts by weight of an adhesive in terms of solid content per 100 parts by weight of the pigment. (8) The coated paper for gravure printing according to any one of (1) to (7), wherein the base paper contains 1 to 40% by weight of a filler in terms of solid content. (9) Basis weight: 45 to 75 g / m 2 The coated paper for gravure printing according to any one of (1) to (8), (10) The coated paper for gravure printing according to any one of (1) to (9), wherein the 75 degree specular gloss of the surface of the pigment coating layer measured in accordance with JIS P 8142:2005 is 70% or more. (11) The coated paper for gravure printing according to any one of (1) to (10), wherein the smoothness of the surface of the pigment coating layer is 1.1 μm or less, as measured according to JIS P 8151:2004 using a hard backing and a clamp pressure of 2000 kPa. Effect of the Invention

[0016] According to the present invention, it is possible to obtain a coated paper for gravure printing having high burst strength and excellent suitability for gravure printing. In particular, the coated paper according to the present invention has sufficient burst strength for use in packaging containers and the like, and has excellent suitability for gravure printing. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] The present invention relates to a coated paper for gravure printing for use in packaging containers. The coated paper for gravure printing according to the present invention has a burst strength sufficient for use in packaging containers, and in a preferred embodiment has a burst strength of 135 kPa or more. <Papermaking> The base paper used in the present invention is made by beating a pulp raw material such as chemical pulp, mechanical pulp, or deinked pulp into a pulp slurry, to which fillers normally used in papermaking processes, such as talc, kaolin, heavy calcium carbonate, light calcium carbonate, and titanium dioxide, are added as necessary, and further, auxiliary agents, such as paper strength agents, sizing agents, defoaming agents, and colorants, are added (internal addition), and then the paper is made.

[0018] The pulp raw material for the base paper of the present invention contains softwood kraft pulp (NKP) at 30% by weight or more of the total raw pulp. By containing 30% by weight or more of NKP, which has long and thick fibers, in the total raw pulp, high burst strength can be achieved. On the other hand, if the NKP content is high, the smoothness of the base paper decreases and the suitability for gravure printing tends to decrease, so it is preferable that the NKP content be 70% by weight or less of the total raw pulp.

[0019] In the present invention, there is no limitation on the type of pulp raw material other than NKP, and various pulps can be used depending on the application. For example, chemical pulp such as hardwood kraft pulp (LKP), groundwood pulp (GP), refiner groundwood pulp (RGP), thermomechanical pulp (TM), etc. P), Chemi-Thermomechanical Pulp (CTMP), Chemi-Grand Pulp (CGP), Semi-Chemical Pulps commonly used as pulp raw materials for printing paper, such as mechanical pulp such as Calpulp (SCP), deinked pulp (DIP) made from sorted waste paper such as fine paper, medium quality paper, low quality paper, newspapers, flyers, magazines, etc., or unsorted waste paper that is a mixture of these, can be used alone or in combination as appropriate.

[0020] As the filler for the base paper of the present invention, any known filler can be used as necessary, for example, heavy calcium carbonate, light calcium carbonate, clay, silica, light calcium carbonate-silica composite, kaolin, calcined kaolin, delaminated kaolin, talc, etc. can be used alone or in combination. The filler content in the paper is preferably 1 to 40% by solids weight, more preferably 10 to 35% by solids weight.

[0021] As the auxiliary agents used in the papermaking of the base paper of the present invention, any known agent can be used as necessary. For example, paper strength agents such as dry strength agents and wet strength agents, sizing agents such as rosin-based sizing agents, synthetic sizing agents, petroleum resin-based sizing agents, and neutral sizing agents, retention agents, and drainage improvers. , coagulants, aluminum sulfate, dyes, pH control agents, defoamers, pitch control agents, UV protection agents, anti-fading agents, slime control agents, etc. can be used alone or in combination.

[0022] There are no particular limitations on the papermaking machine used for making the base paper of the present invention, and common papermaking machines can be used, such as Fourdrinier machines including on-top formers, gap formers, etc., cylinder machines, paperboard machines using both, Yankee dryer machines, etc. There are also no particular limitations on the papermaking conditions, and any of acidic papermaking, neutral papermaking, and alkaline papermaking can be used.

[0023] The base paper of the present invention may be clear-coated with adhesives such as starch and polyvinyl alcohol, and, if necessary, surface sizing agents, water retention agents, thickeners, lubricants, etc., using a gate roll coater, a size press, a premetering size press, etc.

[0024] In the present invention, when drying the base paper, it is possible to use ordinary devices such as a steam heater, a gas heater, an infrared heater, an electric heater, a hot air heater, a microwave, a cylinder dryer, etc. There are also no particular limitations on the drying conditions, and they can be appropriately set within the range of ordinary operation.

[0025] In the present invention, it is preferable to pre-calender the base paper before applying the pigment coating layer using an online soft calendar, online chilled calendar or the like to smooth the base paper in advance, since this makes the pigment coating layer uniform and makes it easier to obtain a gravure printing coated paper with excellent suitability for gravure printing. When the base paper is subjected to a pre-calendering treatment, the calendering line pressure is preferably 10 to 100 kN / m. In addition, the moisture content of the base paper when the pre-calendering treatment is performed is preferably 3.0 to 5.0%. If the moisture content of the base paper is less than 3.0%, the effect of the pre-calendering treatment may not be fully obtained. If the moisture content of the base paper is more than 5.0%, the base paper may be easily crushed, and the opacity and stiffness may decrease.

[0026] In the present invention, the basis weight of the base paper is not particularly limited, but is usually 30 to 400 g / m 2 Approximately, preferably 40 to 250 g / m 2 More preferably, it is about 40 to 60 g / m 2 It is.

[0027] <Coating> In the present invention, the pigment coating layer contains 60% by weight or more of clay having an aspect ratio of less than 10 and an average particle size (D50) of 1.0 μm or less, based on 100 parts by weight of the pigment constituting the pigment coating layer. By using such a pigment, it is possible to obtain excellent gravure printing characteristics while maintaining high operability. Here, the aspect ratio in the present invention indicates the shape of a particle represented by the particle diameter / thickness, and the pigment particle sample was magnified and observed under an electron microscope, and the diameter and thickness of 10 to 20 randomly selected particle samples were measured, and the average value of this ratio was adopted. The average particle size (D50) is the average particle size at 50% volume, and is measured by a laser diffraction method, and can be measured by a Mastersizer 3000 manufactured by Malvern, etc.

[0028] In the present invention, there is no limitation on the type of other pigment that constitutes the pigment coating layer, and one or more of inorganic pigments such as kaolin, clay, 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, which have traditionally been used for coated paper, and organic pigments such as plastic pigments can be used in combination.

[0029] In the present invention, it is preferable to use a copolymer latex as the adhesive used in the pigment coating layer. The copolymer latex may be a natural resin latex or a synthetic resin latex. Any of the above may be used. Examples of synthetic resin latexes include various polymer and copolymer latexes such as vinyl polymer latex, styrene-butadiene copolymer latex, styrene-acrylic copolymer latex, ethylene-vinyl acetate copolymer latex, butadiene-methyl methacrylate copolymer latex, vinyl acetate-butyl acrylate copolymer latex, maleic anhydride copolymer latex, and acrylic acid-methyl methacrylate copolymer latex, and these can be used alone or in combination of two or more. In the present invention, the copolymer latex is preferably used in an amount of 1 to 20 parts by weight, more preferably 3 to 15 parts by weight, in terms of solid content, per 100 parts by weight of the pigment constituting the pigment coating layer.

[0030] In the present invention, other adhesives that can be used in the pigment coating layer include, for example, proteins such as casein, soy protein, and synthetic protein; polyvinyl alcohols; oxidized starch, cationic starch, urea phosphate esterified starch, etherified starch such as hydroxyethyl ether starch, starches such as dextrin; and cellulose derivatives such as carboxymethyl cellulose, hydroxyethyl cellulose, and hydroxymethyl cellulose. One or more of these adhesives that have traditionally been used for coated paper can be used in combination.

[0031] As additives to be blended as necessary in the pigment coating layer of the present invention, various auxiliary agents conventionally used in coated paper, such as dispersants, thickeners, water retention agents, defoamers, waterproofing agents, colorants, etc., can be appropriately used.

[0032] In the present invention, the method for preparing the coating liquid for the pigment coating layer is not particularly limited, but from the viewpoint of coating suitability, the solid content concentration of the coating liquid for the pigment coating layer is preferably about 50 to 68% by weight.

[0033] In the present invention, when providing a pigment coating layer, various coating devices such as a blade coater, a bar coater, a roll coater, an air knife coater, a reverse roll coater, a curtain coater, a size press coater, and a gate roll coater can be used, and coating can be performed on one or both sides of the base paper. Among these coating devices, it is preferable to use a blade coater, which is a leveling coating method, in the present invention. In particular, the use of a short dwell time application type blade coater is preferable because it increases the smoothness of the pigment coating layer and makes it easier to obtain a gravure printing coated paper with excellent gravure printability.

[0034] The coated paper for gravure printing of the present invention has a coating weight of the pigment coating layer of 11 g / m2 in terms of solid content per side. 2 The coating weight of the pigment coating layer is 11 g / m2 in solids per side. 2 If it is less than this, the coverage of the base paper with the pigment coating layer will be insufficient, resulting in poor suitability for gravure printing. In addition, the coating weight of the pigment coating layer is 15 g / m2 in solids per side.2 A thickness of 100 μm or less is preferable because it provides a good balance between gravure printability and runnability. One pigment coating layer may be provided on one side of the base paper, or two or more layers may be provided. When two or more pigment coating layers are provided on one side of the base paper, the total coating amount of the two or more pigment coating layers must be 11 g / m2 in solids per side. 2 That's all.

[0035] In the present invention, when drying the pigment coating layer, a typical device such as a steam heater, a gas heater, an infrared heater, an electric heater, a hot air heater, a microwave, a cylinder dryer, etc. The drying conditions are not particularly limited and can be appropriately set within the range of typical operation.

[0036] The coated paper for gravure printing of the present invention can be applied to various known and used finishing equipment, such as a Super Curren It is preferable to perform the smoothing treatment using a calender, gloss calendar, soft calendar, matte calendar, etc., because this increases the smoothness of the pigment coating layer and makes it easier to obtain gravure printing coated paper with excellent gravure printability. The conditions for the smoothing treatment can be appropriately set within the normal operating range, but it is preferable to set the calender line pressure to 50 to 400 kN / m.

[0037] The basis weight of the coated paper for gravure printing of the present invention is usually 40 to 400 g / m 2 Approximately, preferably 45 to 250 g / m 2 In particular, the basis weight of coated paper for gravure printing is 45 to 75 g / m 2 This is preferable when used for packaging containers for cigarettes, chocolates, etc., because it is possible to prevent damage to the container from the folded portion even if the folded portion is sharp in order to improve the aesthetic appearance of the container.

[0038] The coated paper for gravure printing of the present invention preferably has a 75 degree specular gloss of the pigment coating layer surface measured in accordance with JIS P 8142:2005 of 70% or more. From the viewpoint of suitability for gravure printing, it is preferable that the smoothness of the pigment coating layer surface is 1.1 μm or less when measured according to JIS P 8151:2004 using a hard backing and a clamp pressure of 2000 kPa. EXAMPLES

[0039] The present invention will be described in more detail below with reference to examples of the present invention, but the present invention is not limited thereto. In this specification, unless otherwise specified, parts and % represent parts by weight and % by weight, respectively, and numerical ranges are described as including their endpoints.

[0040] [Example 1] A pulp slurry containing 34 parts of softwood kraft pulp (NKP), 55 parts of hardwood kraft pulp (LKP), and 11 parts of groundwood pulp (GP) was prepared, and 10 parts of precipitated calcium carbonate was added as a filler. 0.5 parts of an internal strength agent, and 0.2 parts of a neutral rosin sizing agent were added to prepare a paper stock.

[0041] Next, this paper stock was used to make paper on a fourdrinier paper machine, with a basis weight of 50 g / m 2 We obtained the original paper.

[0042] Next, 100 parts of pigment containing 73 parts of clay 1 (manufactured by KaMin, product name: Hydralax, aspect ratio: 4.4, average particle size (D50): 0.66 μm) and 27 parts of causticized precipitated calcium carbonate were mixed with 10 parts of styrene-butadiene copolymer latex as an adhesive and 0.5 parts of fluorescent dye to prepare coating solution 1 for the pigment coating layer with a solids concentration of 65%.

[0043] Next, the coating solution 1 for the pigment coating layer was applied to one side of the base paper at a solid content of 12 g / m 2 The coating was applied using a blade coater with a short dwell time application method so that the coating was applied to the substrate, and then dried by a conventional method.

[0044] The paper was then smoothed using a two-stage, two-stack soft calendar to obtain a coated paper for gravure printing.

[0045] [Example 2] A pulp slurry containing 39 parts of softwood kraft pulp (NKP), 50 parts of hardwood kraft pulp (LKP), and 11 parts of groundwood pulp (GP) was prepared, to which 10 parts of light calcium carbonate was added as a filler, and a paper stock was prepared by adding 0.5 parts of an internal strength agent and 0.2 parts of a neutral rosin sizing agent. Next, a paper with a basis weight of 50 g / m was made using this paper stock on a papermaking machine. 2 We obtained the original paper.

[0046] Next, 100 parts of pigment containing 100 parts of clay 2 (manufactured by KaMin, product name: Hydragloss, aspect ratio: 4.3, average particle size (D50): 0.85 μm) was mixed with 7 parts of styrene-butadiene copolymer latex as an adhesive and 0.5 parts of fluorescent dye to prepare coating solution 2 for the pigment coating layer with a solid content concentration of 65%.

[0047] Next, the coating solution 2 for the pigment coating layer was applied to one side of the base paper at a solid content of 12 g / m 2 The coating was applied using a blade coater with a short dwell time application method so that the coating was applied to the substrate, and then dried by a conventional method.

[0048] The paper was then smoothed using a two-stage, two-stack soft calendar to obtain a coated paper for gravure printing.

[0049] [Comparative Example 1] A coated paper for gravure printing was obtained in the same manner as in Example 1, except that a pulp slurry containing 25 parts of softwood kraft pulp (NKP), 44 parts of hardwood kraft pulp (LKP), and 11 parts of groundwood pulp (GP) was prepared and used for the base paper of Example 1.

[0050] [Comparative Example 2] A coated paper for gravure printing was obtained in the same manner as in Example 1, except that 100 parts of a pigment containing 50 parts of clay 1 (manufactured by KaMin, product name: Hydralax, aspect ratio: 4.4, average particle size (D50): 0.66 μm) and 50 parts of causticized precipitated calcium carbonate was used for coating solution 1 for the pigment coating layer in Example 1.

[0051] [Comparative Example 3] Coating solution 2 for the pigment coating layer of Example 2 was applied at a solid content of 10 g / m 2 A coated paper for gravure printing was obtained in the same manner as in Example 2, except that the coating was performed so that the following composition was applied:

[0052] [Comparative Example 4] For the coating solution 2 for the pigment coating layer in Example 2, 100 parts of a pigment containing 100 parts of Clay 3 (manufactured by Imerys, product name: Contour Extreme, aspect ratio: 33.0, average particle size (D50): 1.96 μm) was used, and the solid content per one side was 10 g / m 2 A coated paper for gravure printing was obtained in the same manner as in Example 2, except that the coating was performed so that the following composition was applied:

[0053] [Reference example 1] For the pigment coating layer coating solution 2 in Example 2, 100 parts of a pigment containing 100 parts of Clay 3 (manufactured by Imerys, product name: Contour Extreme, aspect ratio: 33.0, average particle size (D50): 1.96 μm) was used to prepare a pigment coating layer coating solution 3 having a solid content concentration of 67%, and the coating solution was applied at a solid content of 12 g / m2 per side. 2 However, coating was impossible and no coated paper for gravure printing was obtained.

[0054] <Evaluation method> The tests were carried out based on the evaluation methods shown below.

[0055] (1)Basic weight Measurements were taken based on JIS P 8124:2011.

[0056] (2) Paper thickness and density Measurements were taken based on JIS P 8118:2014.

[0057] (3) Paper gloss The 75 degree specular gloss of the pigment coating layer surface was measured based on JIS P 8142:2005.

[0058] (4) Whiteness Based on JIS P 8148:2001, measurements were taken under conditions including ultraviolet light using a color difference meter CMS-35SPX manufactured by Murakami Shikisai Co., Ltd.

[0059] (5) Bursting strength Measurements were performed based on JIS P8112:2008, and the evaluation criteria were as follows: ○: Burst strength is 135kPa or more ×: Burst strength is less than 135 kPa

[0060] (6) PPS roughness The smoothness of the pigment coating layer surface was measured using a hard backing and a clamp pressure of 2000 kPa in accordance with JIS P 8151:2004.

[0061] (7) Gravure printing suitability Using a printing tester (IGT, product name: IGT AIC2-5 printing tester) equipped with a Heliotest accessory, printing was performed at a printing speed of 1.0 m / sec and a printing pressure of 50 kgf / cm, and the distance from the start of printing to the 20th missing dot in the variable halftone screen area was measured. The longer the distance to the 20th missing dot, the better the suitability for gravure printing. The evaluation criteria were as follows. ○: The distance from the start of printing to the 20th missing dot is 40 mm or more ×: The distance from the start of printing to the 20th missing dot is less than 40 mm.

[0062] [Table 1]

[0063] The evaluation results are shown in Table 1. As is clear from Table 1, the base paper contains 30% by weight or more of softwood kraft pulp (NKP) as the raw pulp, and 60% by weight of the total pigment is clay with an aspect ratio of less than 10 and an average particle size (D50) of less than 1.0 μm. or more, with a coating weight of 11 g / m2 (solids) per side 2 It was confirmed that the coated paper for gravure printing of the present invention having the above-described pigment coating layer has high burst strength and excellent suitability for gravure printing. On the other hand, the coated paper for gravure printing of Comparative Example 1, in which the base paper contained less than 30% by weight of softwood kraft pulp (NKP) as the raw pulp, had poor burst strength. Also, the coated paper for gravure printing of Comparative Example 2, in which the pigment coating layer contained less than 60% by weight of clay with an aspect ratio of less than 10 and an average particle size (D50) of less than 1.0 μm as the pigment, had a coating weight of 11 g / m2 in solids per side, and the coating weight of the pigment coating layer was 11 g / m2 in solids per side. 2 The coated papers for gravure printing of Comparative Examples 3 and 4, which had a hardness of less than 100%, were inferior in suitability for gravure printing.

Claims

1. A coated paper for gravure printing for use in packaging containers, comprising: This coated paper for gravure printing has a pigment coating layer containing a pigment and an adhesive on at least one side of a base paper, the base paper contains softwood kraft pulp (NKP) as a raw pulp in an amount of 30% by weight or more of the total raw pulp, the pigment coating layer contains clay as a pigment having an aspect ratio of less than 10 and an average particle size (D50) of less than 1.0 μm in an amount of 60% by weight or more of the total pigment, and the coating weight of the pigment coating layer is 11 g / m2 in terms of solid content per side. ２ The coated paper for gravure printing as described above.

2. 2. The coated paper for gravure printing according to claim 1, wherein the base paper contains, as raw pulp, 70% by weight or less of softwood kraft pulp (NKP) based on the total raw pulp.

3. The coating amount of the pigment coating layer is 15 g / m2 in solid content per side. ２ 3. The coated paper for gravure printing according to claim 1, wherein:

4. 4. The coated paper for gravure printing according to claim 1, wherein the pigment coating layer contains precipitated calcium carbonate as a pigment.

5. The coated paper for gravure printing according to any one of claims 1 to 4, wherein the adhesive comprises a copolymer latex.

6. The coated paper for gravure printing according to any one of claims 1 to 5, wherein the adhesive comprises a styrene-butadiene copolymer latex.

7. 7. The coated paper for gravure printing according to claim 1, wherein the pigment coating layer contains 1 to 20 parts by weight of adhesive in terms of solid content per 100 parts by weight of the pigment.

8. 8. The coated paper for gravure printing according to claim 1, wherein the base paper contains 1 to 40% by weight of a filler in terms of solid content.

9. Basis weight: 45 to 75 g / m ２ The coated paper for gravure printing according to any one of claims 1 to 8,

10. The coated paper for gravure printing according to any one of claims 1 to 9, wherein the 75 degree specular gloss of the pigment coating layer surface measured in accordance with JIS P 8142:2005 is 70% or more.

11. The coated paper for gravure printing according to any one of claims 1 to 10, wherein the smoothness of the surface of the pigment coating layer is 1.1 µm or less, as measured according to JIS P 8151:2004 using a hard backing and a clamp pressure of 2000 kPa.

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