JP2015074860A - Method of producing coated white paperboard - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of producing a coated white paperboard which is excellent in ink setting properties in off-set printing, piling resistance and operability while retaining gravure printability.SOLUTION: A method of producing a coated white paperboard provided with two or more coating layers including a top coat serving as the outermost layer and an undercoat layer closer to base paper than the top coat layer on the surface of base paper and includes a step of forming a top coat layer by using a coating liquid for the top coat layer containing pigments including 5-15 mass% of heavy calcium carbonate and an adhesive and a step of forming an undercoat layer by using a coating liquid for the undercoat layer having a concentration of solid contents of 50-70% and a B type viscosity of 400 mPa s or lower.

Description

  The present invention relates to a method for producing coated white paperboard.

  Conventional coated white paperboard usually has two coated layers containing pigment and adhesive as the main components on one side of the base paper of the whiteboard made by combining, sheet-fed flat offset printing and gravure Printability is required for both printing, but poor smoothness due to poor whiteboard paper formation due to the composition, resulting in adhesion of the coating layer to the plate during gravure printing (cushioning), etc. For this reason, it did not necessarily have good gravure printability. Further, if the coating layer has smoothness and cushioning properties in order to solve these problems, generally, when offset printing is performed, printing troubles such as piling often occur. In this regard, for example, in the field of general printing paper such as art paper and coated paper, there is a complete distinction between offset printing and gravure printing. When each paper is printed by a different printing method, printing as described above is performed. Trouble occurs. In particular, between paper for offset printing and gravure printing, in order to improve the anti-piling property, increasing the amount of adhesive to increase the printing strength decreases the ink drying property (ink setting property) during printing. Or optical properties such as whiteness and concealment properties are degraded.

  The coated white paperboard used for processing paper containers is different from general printing coated papers for printing and publishing applications, and is required to have paper container processing suitability in addition to printability. As surface processing for surface cosmetics and surface protection, varnishing, press coating processing, film laminating processing, etc., and further as box making processing, punching processing, ruled line processing, gluing processing, etc. are performed, so the above printing In addition to suitability, these various types of post-processing suitability are also required for coated white paperboard.

  As for surface processing of coated white paperboard, there are various surface processing methods such as varnishing, press coating and film laminating as mentioned above. Of these, coater for varnish and UV drying equipment are installed after the printing machine. Inline varnish (UV varnish) processing is used because paper containers can be produced more efficiently by continuously varnishing the coated white paperboard after printing as it is, and it is economically superior. Increasing cases. However, for coated white paperboard, which also requires offset printing suitability, it is necessary to improve the absorption capacity of the coating layer in order to improve offset printing suitability such as ink drying properties and water absorbability. Since the varnish developed on the surface of the coated white paperboard is absorbed, it becomes impossible to form a varnish layer having a sufficient thickness, and this reduces the expression of varnish gloss, resulting in the desired cosmetic effect and surface protection effect. There is a problem that cannot be obtained.

  In order to solve the above-mentioned problem, at least one pigment selected from calcined clay, structured kaolin and delaminated clay is used as an undercoat layer as a white paper board for offset / gravure printing, and the solid content is 30 to 70 per total pigment. A polymer latex containing 5% by weight of a polymer latex having a glass transition temperature of −50 to −5 ° C. as an adhesive and having a solid content of 5 to 25% by weight relative to the total pigment, and having a glass transition temperature of 0 as an adhesive for the overcoat There has been proposed a coated white paperboard containing 3 to 30% by weight of a polymer latex having a solid content relative to the pigment of 3 ° C. or higher (see Patent Document 1). However, when containing 30 to 70% by weight of calcined clay or the like like the above coated white paperboard, it causes an increase in the viscosity of the paint, so it is necessary to set the paint concentration low when coating with the coating device, As the coating concentration decreases, the coverage and smoothness of the coating layer decrease, and the missing dots for gravure printing may deteriorate. In addition, since a pigment that forms a bulky coating layer such as calcined clay or structured kaolin is used as in the above method, the absorbability of the coating layer increases, and the suitability for varnishing tends to decrease.

Further, as a coated paper for printing having excellent smoothness, a particle size (D ₇₅ ) corresponding to 75% by mass of a particle size distribution curve and a particle size (D ₂₅ ) corresponding to 25% by mass are applied to the top coating layer. The heavy calcium carbonate having a ratio of D ₇₅ / D ₂₅ in the range of 1.5 to 3.3 is contained in an amount corresponding to 10 to 90% by mass of the total pigment contained in the overcoat layer. (See Patent Document 2), the average particle size as a pigment in the undercoat coating layer is in the range of 1.0 to 3.5 μm, the particle size corresponding to 75% by mass of the particle size distribution curve (D ₇₅ ) and 25% by mass It is proposed to contain 50 parts by mass or more of light calcium carbonate in which D ₇₅ / D ₂₅ is in the range of 1.5 to 4.0, the ratio to the particle diameter (D ₂₅ ) corresponding to the above (see Patent Document 3). ing.

  However, since the smoothness of the surface by the calendar pressure treatment is limited due to the need to maintain the paper thickness with respect to the strength development of the paper container, compared to general gravure coated paper for printing and publishing applications, In coated white paperboard that tends not to exhibit smoothness, it is difficult to obtain sufficient gravure printing suitability only by improving smoothness expression with a pigment having a characteristic particle size distribution as in the above technique.

  Various proposals have been made to improve the quality of coated white paperboard as described above, but various aptitudes such as printing suitability, varnishing suitability, post-processing suitability in paper container processing, especially gravure printing suitability and offset printing suitability, Moreover, the present condition is that the result which fully satisfies varnish processing aptitude is not obtained.

JP 2002-363877 A JP 2004-003057 A JP 2009-221613 A

  The main object of the present invention is to provide a method for producing a coated white paperboard which is excellent in ink setting property and anti-piling property in offset printing while maintaining the gravure printability.

  As a result of intensive studies in view of the above-described conventional technology, the present inventors have solved the above-described problems. That is, the present invention relates to the following coated white paperboard.

  Item 1: A method for producing a coated white paperboard, wherein an outermost coating layer on the surface of a base paper and two or more coating layers including an undercoat layer closer to the base paper than the top coating layer are provided, A step of forming the topcoat layer using a coating solution for a topcoat layer containing a pigment containing 5 to 15% by mass of calcium and an adhesive, a solid content concentration of 50 to 70%, and a B-type viscosity of 400 mPa · s or less A method for producing a coated white paperboard comprising a step of forming the undercoat layer using an undercoat layer coating solution.

  Item 2: The step of forming the overcoat layer is a step of forming an overcoat layer by blade coating or air knife coating, and the step of forming the undercoat layer is a step of forming an undercoat layer by rod coating. 2. A method for producing a coated white paperboard according to 1.

Claim 3: wherein the ratio of the 75 particle size of the cumulative weight percent of the particle size distribution curve subbing layer as a pigment _{(D 75)} and 25 cumulative mass% particle size _{(D 25) (D 75 /} D 25) is 3.3 The manufacturing method of the coated white paperboard of claim | item 1 or 2 containing the latex whose glass transition temperature is -50--30 degreeC as the following heavy calcium carbonate and an adhesive agent.

  Item 4: Any one of Items 1 to 3, wherein the overcoat layer contains light calcium carbonate as a pigment, and a mass ratio of light calcium carbonate to heavy calcium carbonate in the overcoat layer is 5: 1 to 1: 1. The manufacturing method of the coated white paperboard as described in a term.

Item 5: Ratio (D ₇₅ / D) of 75 cumulative mass% particle diameter (D ₇₅ ) and 25 cumulative mass% particle diameter (D ₂₅ ) of the particle size distribution curve of heavy calcium carbonate contained in the overcoat layer ₂₅ ) The manufacturing method of the coated white paperboard of any one of claim | item 1 -4 whose term is larger than 3.3.

  Item 6: The method for producing a coated white paperboard according to any one of Items 1 to 5, wherein the overcoat layer contains a kaolin having an average particle diameter of 0.30 μm or less by a precipitation method as a pigment.

  Item 7: The above-described overcoat layer contains a polymer latex as an adhesive, and the polymer latex contained in the overcoat layer and / or the undercoat layer is composed of a polymer latex having an average particle diameter of more than 120 nm. The manufacturing method of the coated white paperboard of any one of these.

  The method for producing a coated white paperboard of the present invention provides a method for producing a coated white paperboard that is excellent in ink setting and piling resistance in offset printing while maintaining the gravure printing suitability, and also excellent in operability. Moreover, it is excellent also in varnish drawability.

  In the present invention, two or more coating layers laminated on the surface of the base paper are provided. The outermost topcoat layer (hereinafter also simply referred to as the topcoat layer) contains a pigment and an adhesive containing heavy calcium carbonate, and the content of heavy calcium carbonate is 5 to 15 of all pigments contained in the topcoat layer. % By mass. Thereby, it is possible to obtain an excellent ink setting property by containing an adhesive which is excellent in ink setting property but difficult to achieve both printing strength. If it is less than 5% by mass, the printing strength is lowered, and it is difficult to obtain the anti-pilling resistance in offset printing. On the other hand, if it exceeds 15 mass%, missing dots in gravure printing increase and lack suitability.

  Examples of the pigment that can be contained in the topcoat layer in the present invention include heavy calcium carbonate, light calcium carbonate, titanium dioxide, calcium sulfite, gypsum, barium sulfate, talc, kaolin, clay, calcined kaolin, white carbon, amorphous silica, Regeneration using deramikaolin, diatomaceous earth, magnesium carbonate, titanium dioxide, aluminum hydroxide, calcium hydroxide, magnesium hydroxide, zinc hydroxide, zinc oxide, magnesium oxide, bentonite, sericite, paper sludge, deinked floss In addition to inorganic pigments such as particles, organic pigments such as urea formalin resin fine particles and fine hollow particles can be used.

  Among these, heavy calcium carbonate is inexpensive and frequently used as a white pigment in addition to high whiteness. The finer the particle size, the more the white paper gloss and smoothness can be improved, but the required amount of adhesive increases and the print gloss is lowered. In the present invention, in coated white paperboard, which has poor formation due to sheeting and restrictions on smoothing treatment, a small amount of heavy calcium carbonate having a fine particle in the outermost coating layer which is the outermost layer of the coating layer and having a wide particle size distribution. By containing, while maintaining gloss and smoothness, the surface strength is increased and the effect of excellent printing strength is exhibited.

  The topcoat layer in the present invention further contains light calcium carbonate as a pigment, and the mass ratio of light calcium carbonate to heavy calcium carbonate is preferably 5: 1 to 1: 1. More preferably, it is in the range of 4.5: 1 to 1: 1. By setting the mass ratio of light calcium carbonate to 5 or less, the surface strength can be increased and the printing strength can be improved. On the other hand, whiteness and opacity can be improved by setting it to 1 or more. Further, the light calcium carbonate content ratio may be adjusted within the above range, and is not particularly limited. However, from the viewpoint of maintaining the high whiteness and fully exhibiting the effects of the present invention, all pigments contained in the overcoat layer Is preferably about 15 to 50% by mass, and more preferably about 15 to 45% by mass.

  The shape of the light calcium carbonate includes a needle shape, a column shape, a cubic shape, a spindle shape, and the like, and is not particularly limited in the present invention, but it may be a spindle shape from the viewpoint of further improving the ink setting property and UV varnish gloss. preferable. Although it does not specifically limit as a preparation method of spindle-shaped light calcium carbonate, The method described in Unexamined-Japanese-Patent No. 2011-225390 is mentioned. In particular, spindle-shaped light calcium carbonate having an average particle size of 0.4 μm or less is preferable from the viewpoint of improving ink setting properties and UV varnish gloss. The lower limit of the average particle diameter is preferably 0.2 μm or more from the viewpoint of improving particle stability and surface strength.

In the present invention, the particle size distribution curve measured by the sedimentation method (Cedigraph) of heavy calcium carbonate contained in the overcoat layer is 75 cumulative mass% particle diameter (D ₇₅ ) and 25 cumulative mass% particle diameter (D ₂₅ )) (D ₇₅ / D ₂₅ ) is preferably larger than 3.3. More preferably, it is 3.5 or more. Here, the value of D ₇₅ / D ₂₅ means that the smaller the particle size distribution is, the smaller the value is. In the present application, by increasing the particle size distribution of the heavy calcium carbonate so as not to have a relatively uniform particle size, the surface strength can be improved and the printing strength can be further increased. Further, it is possible to omit the step of pulverizing and classifying heavy calcium carbonate to narrow the particle size distribution, and to reduce the cost. The upper limit of the value of D ₇₅ / D ₂₅ is not particularly limited, but is preferably 5.5 or less, more preferably 5.0 or less, and even more preferably 4.5 or less from the viewpoint of not reducing smoothness.

  In the present invention, the overcoat layer preferably further contains kaolin as a pigment. In particular, kaolin having an average particle diameter of 0.30 μm or less is preferable. Thereby, ink setting property can be improved and workability | operativity can be improved. The lower limit of the average particle diameter is not particularly limited, but it is preferably 0.1 μm or more as a commercially available product without causing a problem of formation of secondary aggregates. The average particle diameter in the present invention is a particle diameter measured by a sedimentation method (Cedigraph) and having a cumulative mass of 50%.

  The content ratio of kaolin is not particularly limited, but is preferably 30 to 90% by mass in the total pigment of the overcoat layer. The lower limit is more preferably 35% by mass or more. Moreover, 75 mass% or less is more preferable, and, as for an upper limit, 65 mass% or less is still more preferable. By setting it to 30% by mass or more, ink setting properties and UV varnish gloss can be improved. On the other hand, whiteness can be improved by setting it as 90 mass% or less.

  The topcoat layer in the present invention contains an adhesive. The adhesive is not particularly limited, and examples thereof include various starches such as oxidized starch, cationized starch, and esterified starch, synthetic resin adhesives such as polyvinyl alcohol, proteins such as casein, soy protein, and synthetic protein, carboxy Water-soluble adhesives such as cellulose derivatives such as methylcellulose and methylcellulose, conjugated diene polymer latex such as styrene-butadiene copolymer, methylmethacrylate-butadiene copolymer, polymer of acrylate ester and / or methacrylate ester or Acrylic acid polymer latex such as copolymer, vinyl polymer latex such as ethylene-vinyl acetate copolymer, or these various polymer latexes modified with a functional group-containing monomer such as carboxy group. Or non-alkali soluble polymer latex And the like. These can be used singly or in combination of two or more.

  The overcoat layer in the present invention preferably contains a polymer latex having an average particle size of more than 120 nm as an adhesive. By increasing the particle size of the latex, the adhesive strength generally decreases, but in the present invention, the printing strength can be increased by heavy calcium carbonate, so that an appropriate void is formed in the coating layer by the latex having a large particle size. Thus, the ink setting property can be further enhanced. In addition, the cushioning property of the overcoat layer can be increased to improve the gravure printing suitability. The upper limit of the average particle diameter is not particularly limited, but is preferably 180 nm or less from the viewpoint of maintaining adhesive strength and improving suitability for varnish processing.

  About content of said polymer latex in top coat layer, in order to express cushioning property of a top coat layer, deformability, smoothness, ink drying property, surface strength, and varnish processing suitability, polymer latex is 100 masses of pigment. It is preferable to contain 5-20 mass parts with respect to a part. By setting it as 5 mass parts or more, the cushioning property of a topcoat layer, a deformability, surface strength, and varnish suitability can be improved. On the other hand, by setting it to 20 parts by mass or less, the smoothness and ink drying property of the topcoat layer can be improved.

  When latex and a water-soluble adhesive are used in combination in the topcoat layer, the content of the water-soluble adhesive is preferably 3 parts by mass or less with respect to 100 parts by mass of the total pigment contained in the topcoat layer. It is particularly preferable to do this. When the content of the water-soluble adhesive in the topcoat layer is 3 parts by mass or less with respect to the total pigment contained in the topcoat layer, the cushioning property and smoothness of the topcoat layer can be improved and the gravure printing suitability can be improved. In addition, localization of the water-soluble adhesive due to binder migration during coating to drying can be suppressed, and ink drying can be improved.

  The coating layer in the present invention has a multilayer structure comprising at least an outermost coating layer and an undercoat layer closer to the base paper than the top coating layer, and is formed on the surface of the base paper. The undercoat layer may be adjacent to the topcoat layer or may be adjacent to the surface of the base paper. Moreover, the coating layer may be formed in the back surface of the base paper if needed. In the present invention, from the viewpoint of improving smoothness, the undercoat layer is preferably adjacent to the topcoat layer and adjacent to the surface of the base paper.

The undercoat layer is a ratio (D ₇₅ / D) of 75 cumulative mass% particle diameter (D ₇₅ ) and 25 cumulative mass% particle diameter (D ₂₅ ) of a particle size distribution curve measured by a sedimentation method (Cedigraph) as a pigment. It is preferable to contain latex having a glass transition temperature in the range of −50 to −30 ° C. as heavy calcium carbonate with D ₂₅ ) of 3.3 or less and an adhesive. Smooth expression can be improved by the effect of a pigment having a relatively uniform particle diameter than that used for the topcoat layer. In addition, due to the effect of the adhesive having a low glass transition temperature, cushioning property is imparted to the undercoat layer and the undercoat layer can be easily deformed. Due to these synergistic effects, when the plate comes into contact with paper during gravure printing, the adhesion between the paper surface and the plate is improved and excellent gravure halftone reproducibility is exhibited. Moreover, it has the effect of improving coating layer strength (printing strength) and ink drying property (ink setting property) for offset printing suitability.

  With respect to the effect expression of the undercoat layer as described above in the present invention, the pigment used for the undercoat layer has a particle shape that hardly inhibits the cushioning properties and the deformability of the undercoat layer, and is wet or dry with respect to the raw pigment pigment. Of these, calcium carbonate having an irregular and block-like particle shape is particularly preferred from the viewpoint of the characteristics produced by pulverization and classification (particle size distribution adjustment). In addition, calcium carbonate is particularly preferable because it is the cheapest of the pigments used in the paper coating field. Pigments used in the paper coating field include kaolin and talc with strong flatness, light calcium carbonate with strong acicularity and columnarity, and satin white as pigments with unique shapes. Pigments with strong shape characteristics may hinder the cushioning properties and deformability of the undercoat layer. In addition, the pigment having strong shape characteristics as described above is expensive in terms of price.

  Regarding the particle diameter of all the pigments containing calcium carbonate used in the undercoat layer, the particle size distribution curve measured by the precipitation method is 50 as the particle diameter that hardly inhibits the cushioning property, deformability, and smoothness of the undercoat layer. The average particle diameter corresponding to the cumulative mass% is preferably in the range of 0.5 to 1.2 μm, and particularly preferably in the range of 0.5 to 0.8 μm. By setting the average particle diameter of all pigments in the undercoat layer to 1.2 μm or less, the surface smoothness of the undercoat layer is improved and the smoothness of the overcoat layer is affected. can get. Moreover, the ink drying property of offset printing can be improved. On the other hand, by setting the average particle size of all pigments in the undercoat layer to 0.5 μm or more, the coating layer strength can be increased and the offset printability can be improved.

Further, regarding the particle size distribution of the above calcium carbonate in the undercoat layer, from the viewpoint of containing a large amount of pigment particle diameter that effectively works for the formation of the coating layer and the expression of smoothness, the content of coarse particles and fine particles is small, and the average particle A type having a large particle diameter in the vicinity of the diameter (type having a narrow particle size distribution) is preferred. That is, in the present invention, the ratio (D ₇₅ / D) of the particle diameter (D ₇₅ ) corresponding to ₇₅ cumulative mass% and the particle diameter (D ₂₅ ) corresponding to 25 cumulative mass% of the particle size distribution curve measured by the sedimentation method. D ₂₅ ) is preferably 3.3 or less, and more preferably 3.1 or less.

In the undercoat layer of the present invention, the use of calcium carbonate having a narrow particle size distribution and a relatively uniform particle size allows the pigment particles to be efficiently and effectively not embedded in the voids between the particles. Since it affects the layer formation of the coating layer, it is possible to form a coating layer having higher coverage and smoothness than pigments having a wide particle size distribution. With the D _{75 /} D ₂₅ of calcium carbonate in the primer layer 3.3 or less, reduce fines, in that fines are sunk into the gap of the pulp fibers of the base paper, coating layer formed, smoothness expression There is no fear of not working effectively. Moreover, the coating layer strength in offset printing can be improved.

  The content of calcium carbonate in the undercoat layer is preferably 80% by mass or more of the total pigment contained in the undercoat layer as a ratio that does not easily inhibit the cushioning property, deformability, and smoothness of the undercoat layer. It is especially preferable that it is 100 mass%. By setting it to 80% by mass or more, the cushioning property, deformability and smoothness of the undercoat layer may be hindered due to the influence of the particle shape and particle size of other pigments blended in addition to this, and coating in offset printing There is no fear of deteriorating the layer strength.

  For pigments that can be used in combination with the above calcium carbonate in the undercoat layer, pigments other than the calcium carbonate defined in the present invention, such as ordinary clay, heavy calcium carbonate, light calcium carbonate, titanium dioxide, aluminum hydroxide, silica, Within the above specified range, one or more of publicly known pigments used in the general coated paper manufacturing field such as regenerated particles made from satin white, talc, paper sludge, and deinked floss are not impaired. And can be used as appropriate.

  The polymer latex used as the adhesive for the undercoat layer in the present invention preferably has a glass transition temperature in the range of −50 to −30 ° C. By setting the glass transition temperature to −50 ° C. or higher, the polymer latex becomes too soft, and there is no possibility that the coating layer strength in offset printing is deteriorated. On the other hand, by setting the temperature to −30 ° C. or lower, the cushioning property and deformability of the undercoat layer necessary for obtaining sufficient gravure printability can be obtained, and there is no fear of increasing missing dots.

  About the average particle diameter of the polymer latex used for the undercoat layer, in order to express the cushioning property, the deformability, the smoothness, the ink drying property and the coating layer strength of the undercoat layer, the average particle diameter is 100 to 300 nm. It is preferable to do. More preferably, it is larger than 120 nm and 180 nm or less. By setting the average particle diameter of the polymer latex of the undercoat layer to 100 nm or more, the cushioning property, deformability, smoothness, and ink drying property of the undercoat layer can be improved. On the other hand, the coating layer strength can be improved by setting the average particle diameter of the polymer latex of the undercoat layer to 300 nm or less.

  In the present invention, it is preferable that the overcoat layer contains a polymer latex as an adhesive, and the polymer latex contained in the overcoat layer and / or the undercoat layer is made of a polymer latex having an average particle diameter of more than 120 nm. Made of a polymer latex with a single average particle size, it has excellent balance of cushioning properties, deformability, smoothness, ink drying properties, and coating layer strength, and is effective for both gravure printing and offset printing. Can be improved.

  The polymer latex in the undercoat layer is not particularly limited as long as the glass transition point and the average particle diameter are within the above ranges, and can be appropriately selected from those that can be used for the overcoat layer, for example. These can be used alone or in combination of two or more.

  About content of said polymer latex in undercoat layer, in order to express the cushioning property of an undercoat layer, a deformability, smoothness, and coating layer intensity | strength, polymer latex is 100 mass parts of pigments in undercoat layer. It is preferable to contain 5-20 mass parts. By setting it as 5 mass parts or more, the cushioning property of a undercoat layer, a deformability, smoothness, and the coating layer intensity | strength can be improved. On the other hand, by setting it to 20 parts by mass or less, the smoothness and ink drying property of the undercoat layer can be improved.

  As an adhesive other than latex in the undercoat layer, one or more kinds of starches such as polyvinyl alcohol, oxidized starch, cationized starch, esterified starch and dextrin are impaired as a water-soluble adhesive. The content of the water-soluble adhesive at that time is preferably 4 parts by mass or less with respect to 100 parts by mass of the total pigment contained in the undercoat layer, and 0 mass by mass. It is particularly preferable to use parts. By setting the total amount of the water-soluble adhesive in the undercoat layer to 4 parts by mass or less, the cushioning property of the undercoat layer can be improved and the gravure printing suitability can be improved.

  The coating layer in the present invention can be formed, for example, by coating and drying using a coating liquid containing water as a dispersion medium. For example, the overcoat layer may be formed on the undercoat layer using a coating solution for an overcoat layer containing heavy calcium carbonate and an adhesive, and if necessary, light calcium carbonate, kaolin, specific latex, and the like. The undercoat layer may be formed on the base paper using an undercoat layer coating solution containing specific calcium carbonate and latex. In the coating liquid, if necessary, pH adjusters such as dispersants, caustic soda, ammonia water, antifoaming agents, preservatives, fluorescent dyes, mold release agents, dyes, water resistance agents, flow modifiers, color pigments, etc. Can be contained as appropriate.

  The solid content concentration of the undercoat layer coating solution and the overcoat layer coating solution in the present invention can be selected in the range of 10 to 75%.

  As a method of coating each coating liquid, a coating apparatus generally used for coated paper production can be used, for example, blade coater, rod coater, air knife coater, roll coater, reverse roll coater, bar coater, curtain coater. White paperboard by on-machine or off-machine method using coating equipment such as die slot coater, gravure coater, chanplex coater, 2 roll size press coater, gate roll size press coater, film metering size press coater It can be coated on the base paper constituting.

  As a coating method for the undercoat layer, it is possible to form a coating layer having a certain thickness (so-called contour coating) in a form that relatively follows the irregularities on the surface of the base paper. A coating system using a rod coater, an air knife coater, a curtain coater, etc. is preferable because a coating layer having a property can be easily obtained and high-concentration coating and high-speed coating are possible. Among these, coating with a rod coater is preferable from the viewpoint of obtaining a relatively high smooth coating surface.

  In the present invention, coating is performed using a coating solution for an undercoat layer having a solid content concentration of 50 to 70% and a B-type viscosity of 400 mPa · s or less. More preferably, the B-type viscosity is 300 mPa · s or less. By maintaining the solid content concentration and the B-type viscosity of the coating solution for the undercoat layer in the above ranges, the solid content concentration and the viscosity of the coating solution that tends to increase due to selective absorption as the coating progresses are usually The range can be stably maintained, and the operability can be remarkably improved. Moreover, the effect which was excellent in gravure printing aptitude with few missing dots can be obtained by maintaining high density and improving coverage. For this reason, the coating method by a rod coater can be employ | adopted suitably. The lower limit of the B-type viscosity is not particularly limited, but is preferably 50 mPa · s or more from the viewpoint of suppressing uneven swimming of the coating liquid. The B-type viscosity can be adjusted by adjusting the solid content concentration or by adding a water-soluble adhesive to the undercoat layer coating solution. In the present invention, the solid content concentration and the B-type viscosity can be suitably adjusted by including a specific calcium carbonate and latex in the undercoat layer coating solution.

  Furthermore, it is preferable that the coating liquid for undercoat layers contains polycarboxylic acid sodium salt as a dispersing agent. Thereby, the coating liquid before coating can suppress the thickening with time, and can stably keep the B-type viscosity within a preferable range. Although it does not specifically limit as content of a dispersing agent, The range of 0.01-0.3 part is preferable with respect to 100 mass parts of all the pigments.

  As the coating method of the topcoat layer, it is possible to form a coating layer having a relatively high smooth coating surface (so-called flat coating), which makes it easy to obtain high gravure printability and high Coating with a blade coater capable of high-density coating and high-speed coating, or coating with an air knife coater that has excellent white paper feel, no equipment wear, etc. during coating weighing, and can be operated stably for a long time Is preferred.

  In the present invention, the coating solution for the undercoat layer is applied with a rod coater, and the coating solution for the overcoat layer containing light spindle-shaped calcium carbonate and a polymer latex having an average particle diameter larger than 120 nm is applied with an air knife coater. This aspect is preferred as a method for producing coated white paperboard having excellent quality balance and excellent operability.

About the coating amount of each coating layer, it is preferable to adjust solid content concentration suitably according to a coating system so that it may become the range of 0.5-20 g / m < ² > by dry weight per single side | surface, and also undercoat The coating amount of the layer is 5 to 15 g / m ² as the dry weight per side, the coating amount of the top coat layer is 3 to 15 g / m ² as the dry weight per side, and the coating of the undercoat layer and the top coat layer It is more preferable to adjust the total amount to be in the range of 8 to 25 g / m ² as a dry weight per side.

By setting the coating amount of the undercoat layer to 5 g / m ² or more as the dry weight per side, the surface of the base paper can be sufficiently covered, and the desired smoothness in the present invention can be obtained, which is preferable. On the other hand, by setting it to 15 g / m ² or less, there is no possibility of causing a crack in the coating layer when a box is put in a ruled line during box making. In addition, with respect to the overcoat layer, by setting the dry weight per side to 3 g / m ² or more, the surface of the undercoat layer can be sufficiently covered, and there is no risk of causing ink transfer failure, and offset printing and gravure printing. Both can improve printability. On the other hand, by setting it to 15 g / m ² or less, similarly to the case of the undercoat layer, there is no possibility of causing a crack in the coating layer when forming a box with a ruled line during box making.

  In the present invention, a pigment coating layer is provided on the surface (back surface) opposite to the surface of the base paper coated with the undercoat layer and the topcoat layer for the purpose of improving printability, offset printing workability, and punching workability. Also good.

The white paperboard base paper in the present invention is made by combining two or more paper layers. That is, the base paper has a multilayer structure including at least a surface layer having a relatively high whiteness and a back layer having a relatively low whiteness. However, since the rice paper weight of white paperboard is often 200 g / m ² or more, a structure of three or more layers in which an intermediate layer is present between the surface layer and the back layer is usually used. It is composed of 4 layers or more of middle layer (1 layer or more) / back layer. However, the layer structure of the base paper is not limited to these. The overcoat layer and undercoat layer in the present invention are provided on the surface layer side.

  For the surface layer, pulp with high whiteness is usually used. For example, bleached chemical pulp obtained by kraft pulping, sulphite pulping, alkali pulping of conifers or hardwoods, or cotton pulp, linter pulp, waste paper pulp, and the like. Waste paper pulp includes pulps made from old paper such as upper white / card, special white / middle white / white Manila, imitation and color including Kent used paper, newspapers, magazines, cutting / medium anti-aged paper, etc. However, it is not limited as used paper used in the present invention. These waste papers may be used as they are after the disaggregation and dust removal treatments, but can be used as waste paper pulp after passing through the steps of deinking, bleaching, ink dispersion, washing, etc., if necessary.

  The base paper has a front and lower layer as necessary. The pulp used for the above-mentioned surface layer is used for the surface layer, unbleached chemical pulp obtained by kraft pulping, sulfite pulping, alkali pulping, etc., or GP (ground pulp). Mechanical pulp such as TMP (thermomechanical pulp) and waste paper pulp can be used. As the used paper pulp, pulp prepared from tea imitation, corrugated cardboard, backing paper / sheet certificate, balls, etc. can be used in addition to the used paper used for the surface layer. Usually, however, used paper that is lower in quality than the surface layer, that is, used paper containing a large amount of medium fiber is used. For example, deinked waste paper such as newspapers, magazines, white / middle white, and balls is generally used, but the present invention is not limited to using these.

  The base paper has a middle layer as required. All the pulp that can be used for the front layer, the front lower layer, and the back layer can be used for the middle layer. However, since the middle layer is a layer sandwiched at least between the front layer and the back layer, it is usually a base paper of white paperboard. In general, the lowest pulp is used among the paper layers constituting the sheet. For example, a newspaper, a magazine, a ticket, a medium quality antiquity, tea imitation, cardboard, a mount, a ground ticket, a ball, etc. are mentioned. These waste papers are generally used as they are after disaggregation and dust removal treatment, but may be used after passing through each process such as deinking, bleaching, ink dispersion, and washing, as necessary. However, the present invention is not limited to those using these raw materials.

  For the back layer, it is possible to use all the pulp used for the surface layer, front surface lower layer, middle layer, but usually newspapers, magazines, tickets, medium-sized antiko, tea imitation, corrugated cardboard, mount, land ticket, Waste paper such as balls is used as it is after disaggregation and dust removal treatment. Of course, after the disaggregation and dust removal treatment, steps such as deinking, bleaching, and ink dispersion can be arbitrarily added as necessary, but the present invention is limited to those using these treatments. It is not something.

  In the pulp slurry composition used for each layer from the surface layer to the back layer, a paper strength enhancer, a water resistance agent, a water repellent, a foamable microcapsule, a sizing agent, a dye, Yield improver, filler, pH adjuster, slime control agent, thickener, preservative, antifungal agent, antibacterial agent, flame retardant, antiseptic, rodenticide, insect repellent, moisturizer, freshness retainer, oxygen scavenger , Microcapsules, foaming agents, surfactants, electromagnetic shielding materials, antistatic agents, rust inhibitors, fragrances, deodorants and the like can be selected and blended. These can be used in combination.

  The base paper used for the white paperboard of the present invention can of course be obtained by hand-drawing, but is usually made by a multi-stage paper machine equipped with at least two wire parts. As a single wire type, there are a circular net type, a long net type, an inclined type, a twin wire type, and the like, and a wire part in which methods generally used for papermaking are combined in multiple stages is usually used. For example, there are a long mesh patterning, a short mesh patterning, a short mesh pattern combination, a long mesh pattern combination, and the like. Also, as a drying method, a method generally used for papermaking, for example, a Yankee dryer, a multi-cylinder dryer, etc., is used, but a multi-cylinder dryer is more preferable in view of the fact that white paperboard is generally thick. .

  In the present invention, before forming the undercoat layer, after forming the undercoat layer, or after completing the formation of the overcoat layer, smoothing is performed using a machine calendar, a soft calendar, a super calendar, or the like. Can be applied. From the viewpoint of improving smoothness, it is preferable after the overcoat layer is formed. As described above, the smoothness of the coated white paperboard is improved by applying the smoothing treatment to the coated whiteboard paper after coating, thereby improving the gravure printing suitability.

  The present invention will be described in more detail with reference to examples, but the present invention is not limited thereto. Unless otherwise specified, “part” and “%” in the examples indicate “part by mass” and “% by mass”, respectively.

(Average pigment particle size)
A 0.1% solution of sodium pyrophosphate is added to a single dispersion of each pigment to prepare a pigment diluted dispersion with a solid content concentration of about 4 to 8%, and further dispersed for 5 minutes with an ultrasonic cleaning device. The pigment particle size distribution was measured by sedimentation method using Cedigraph 5100 (manufactured by Micromeritics, USA) for the pigment diluted dispersion obtained in the above, and from the obtained pigment particle size distribution, 50 cumulative mass% of the particle size distribution curve was obtained. The corresponding particle diameter was defined as the average particle diameter (μm).

_{(D 75} particle size and _{D 25} particle size of the pigment, as well as the method for calculating the _D 75 _{/ D 25)}
A pigment particle size distribution by the precipitation method, 75% of the particle size distribution curve, respectively D ₇₅ particle size of the particle diameter corresponding to 25% of the total mass%, and a D ₂₅ particle size ([mu] m). Based on the D ₇₅ particle diameter and D ₂₅ particle diameter of the obtained pigment, the ratio (D ₇₅ / D ₂₅ ) between the D ₇₅ particle diameter and the D ₂₅ particle diameter was calculated.

(Latex particle size)
The Brownian motion of copolymer latex (emulsion particles) in water of each copolymer latex is observed by dynamic laser light scattering method, and the temporal fluctuation of the scattered light intensity (fluctuation of the number of photons in the scattered light) is accurately measured. We analyzed by the photon correlation method to obtain the diffusion coefficient by grasping with various time scales. (Unit of average particle size: nm)

(Glass transition temperature of latex)
Each copolymer latex was measured with a differential scanning calorimeter (DSC: manufactured by Seiko Instruments Inc.) for a dried film of the copolymer latex obtained by vacuum drying at 100 ° C. for 20 hours.

(B type viscosity)
The prepared coating liquid was measured with a B-type viscometer (model: BM, manufactured by Tokyo Keiki Co., Ltd.) at a liquid temperature of 35 ° C. and a rotation speed of 60 rpm.

Example 1
(Preparation of base paper)
Imitation / colored waste paper pulp containing Kent waste paper on the surface of the first layer on the surface of the base paper, deinked waste paper pulp on the bottom layer of the second layer, middle layer of the third layer, middle layer of the fourth layer , And the back layer of the fifth layer which is the back side, using undeinked waste paper pulp to make 5 layers, and then machine calendering, for coated white paperboard with a weight of 290 g / m ² A base paper was obtained.

(Preparation of coating solution for undercoat layer)
As a pigment, 100 parts of heavy calcium carbonate B (trade name: FMT90, manufactured by Pfematec Co., Ltd., average particle size 0.78 μm, D ₇₅ / D ₂₅ = 4.4) is used, and the solid content is obtained using a coreless disperser. A pigment dispersion having a concentration of 70% was prepared. Subsequently, 3 parts of oxidized starch (trade name: Oji Ace Y, manufactured by Oji Cornstarch Co., Ltd.), styrene-butadiene copolymer latex F (trade name: BA025) in terms of solid content with respect to 100 parts of pigment for this pigment dispersion. 14 parts by Asahi Kasei Chemicals, glass transition temperature -12 ° C., average particle size 80 nm) were finally added to obtain a coating solution for an undercoat layer having a solid content concentration of 50% and a B-type viscosity of 50 mPa · s. .

(Preparation of coating solution for topcoat layer)
As a pigment, 5 parts of heavy calcium carbonate A (trade name: FMT-OP, manufactured by Phimatech, average particle size 0.6 μm, D ₇₅ / D ₂₅ = 3.0), kaolin A (trade name: Ultra White 90) , BASF, average particle size 0.32 μm) 90 parts, and titanium dioxide (trade name: KA-100, manufactured by Korea Cosmo Chemical Co., Ltd.) 5 parts. 0.1 part of soda was added, and a pigment dispersion having a solid content concentration of 68% was prepared using a Coreless disperser. Next, for this pigment dispersion, 2 parts of oxidized starch (trade name: Ace Y, supra) and styrene-butadiene copolymer latex B (trade name: B1840, Asahi Kasei) in terms of solid content with respect to 100 parts of pigment. 16 parts by chemicals, average particle size 95 nm) were added, respectively, to finally obtain a coating solution for an overcoat layer having a solid content concentration of 42% and a B-type viscosity of 40 mPa · s.

(Preparation of coated white paperboard)
An undercoat layer is formed by coating and drying the undercoat layer coating liquid on the surface of the coated white paperboard base paper using a bar coater so that the dry weight per side is 10 g / m ^2. did. On the undercoat layer, a top coat layer was formed by coating and drying the above-mentioned overcoat layer coating solution using a bar coater so that the dry weight per side was 10 g / m ² . The base paper on which the undercoat layer and the overcoat layer were formed was subjected to a paper feeding process using a soft calender with a metal roll surface temperature of 200 ° C. and 2 nips to obtain a coated white paperboard.

Example 2
In the preparation of the coating liquid for the top coat layer of Example 1, the amount of heavy calcium carbonate A was changed to 10 parts instead of 5 parts, and the amount of kaolin A was changed to 85 parts instead of 90 parts. A coated white paperboard was obtained in the same manner.

Example 3
In the preparation of the coating solution for the top coat layer of Example 1, the amount of heavy calcium carbonate A was changed to 15 parts instead of 5 parts, and the amount of kaolin A was changed to 80 parts instead of 90 parts. A coated white paperboard was obtained in the same manner.

Example 4
In the production of the coated white paperboard of Example 3, the coating solution for the undercoat layer was set to a solid content concentration of 60% and the B-type viscosity was 380 mPa · s, and the coating was applied using a rod coater instead of the bar coater. A coated white paperboard was obtained in the same manner as in Example 3 except that the liquid was applied using an air knife coater instead of the bar coater.

Example 5
In the production of the coated white paperboard of Example 4, the coating solution for the topcoat layer had a solid content concentration of 60% and a B-type viscosity of 500 mPa · s, and was applied except that coating was performed using a blade coater instead of an air knife coater. In the same manner as in Example 4, a coated white paperboard was obtained.

Example 6
In the preparation of the coating solution for the undercoat layer of Example 4, heavy calcium carbonate A (trade name: FMT-OP, manufactured by PMMA Tech, average particle size 0.6 μ, D ₇₅ / D was used instead of heavy calcium carbonate B. ₂₅ = 3.0), instead of styrene-butadiene copolymer latex F, styrene-butadiene copolymer latex A (trade name: T2548A, manufactured by JSR, glass transition temperature -34 ° C., average particle diameter 140 nm) was used. A coated white paperboard was obtained in the same manner as in Example 4 except that the solid content concentration was 60% and the B-type viscosity was 200 mPa · s.

Example 7
In the preparation of the coating solution for the overcoat layer of Example 6, the amount of heavy calcium carbonate A was changed to 15 parts and 5 parts, the amount of kaolin A was changed to 80 parts, and light calcium carbonate A (trade name) : Tama Pearl TP221F, manufactured by Okutama Kogyo Co., Ltd., average particle size 0.41 μm, spindle-shaped particles) was added in the same manner as in Example 6 to obtain a coated white paperboard.

Example 8
In the preparation of the coating solution for the overcoat layer of Example 7, the amount of heavy calcium carbonate A was changed to 5 parts, 10 parts, the amount of light calcium carbonate A was changed to 50 parts, 30 parts, and the amount of kaolin A was changed to 30 parts. Coated white paperboard was obtained in the same manner as in Example 7 except that the amount was changed to 55 parts.

Example 9
In the preparation of the coating solution for the overcoat layer of Example 7, the amount of heavy calcium carbonate A was changed to 5 parts, 15 parts, the amount of light calcium carbonate A was changed to 50 parts, and the amount of kaolin A was changed to 30 parts. Coated white paperboard was obtained in the same manner as in Example 7 except that 65 parts was used instead of parts.

Example 10
Coating in the same manner as in Example 7 except that heavy calcium carbonate B (trade name: FMT90, supra) was used in place of heavy calcium carbonate A in the preparation of the coating solution for the overcoat layer of Example 7. White paperboard was obtained.

Example 11
In the preparation of the coating solution for the overcoat layer of Example 8, coating was carried out in the same manner as in Example 8, except that heavy calcium carbonate B (trade name: FMT90, supra) was used instead of heavy calcium carbonate A. White paperboard was obtained.

Example 12
Coating in the same manner as in Example 9 except that heavy calcium carbonate B (trade name: FMT90, supra) was used in place of heavy calcium carbonate A in the preparation of the coating solution for the topcoat layer of Example 9. White paperboard was obtained.

Example 13
In the preparation of the coating solution for the overcoat layer of Example 11, kaolin B (trade name: Hydra Gloss 90, manufactured by KAMIN, average particle size 0.22 μm) was used in place of kaolin A. Thus, a coated white paperboard was obtained.

Example 14
In the preparation of the coating solution for the overcoat layer of Example 13, styrene-butadiene copolymer latex D (trade name: T2831H, manufactured by JSR Corporation, average particle size 130 nm) was used in place of styrene-butadiene copolymer latex B. Except for the above, coated white paperboard was obtained in the same manner as in Example 13.

Example 15
In the preparation of the coating solution for the overcoat layer of Example 14, light calcium carbonate B (trade name: Tama Pearl TP221GS, manufactured by Okutama Kogyo Co., Ltd., average particle size 0.45 μm, spindle-shaped particles) was used instead of light calcium carbonate A. Except for the above, a coated white paperboard was obtained in the same manner as in Example 14.

Example 16
In the preparation of the coating solution for the topcoat layer of Example 14, light calcium carbonate C (trade name: Tama Pearl TP123CS, manufactured by Okutama Kogyo Co., Ltd., average particle size 0.45 μm, needle-like particles) was used instead of light calcium carbonate A. Except for the above, a coated white paperboard was obtained in the same manner as in Example 14.

Comparative Example 1
Example 14 In the preparation of the coating solution for the topcoat layer of Example 14, the amount of heavy calcium carbonate A was 3 parts instead of 10 parts, and the amount of light calcium carbonate was changed to 37 parts instead of 30 parts. In the same manner, a coated white paperboard was obtained.

Comparative Example 2
Example 14 In the preparation of the coating solution for the overcoat layer of Example 14, Example 14 was carried out except that the amount of heavy calcium carbonate A was changed to 10 parts and 18 parts, and the amount of light calcium carbonate was changed to 30 parts. In the same manner, a coated white paperboard was obtained.

Comparative Example 3
In the preparation of the undercoat layer coating solution of Example 14, the amount of oxidized starch was 6 parts instead of 3 parts,
Example 14 except that the coating liquid for the undercoat layer was applied so that the dry weight per side was 15 g / m ^{2 in} the production of coated white paperboard with a solid content concentration of 60% and a B-type viscosity of 600 mPa · s. In the same manner, a coated white paperboard was obtained.

Comparative Example 4
In the preparation of the coating liquid for the undercoat layer of Example 14, the amount of styrene-butadiene copolymer latex A was changed to 14 parts, 5 parts, the amount of oxidized starch was changed to 3 parts, and the solid content concentration was 30 parts. %, B-type viscosity of 50 mPa · s, in the production of coated white paperboard, except that the undercoat layer coating solution was applied so that the dry weight per side was 4 g / m ^2. Coated white paperboard was obtained.

  The coated white paper board thus obtained is conditioned for 6 hours under the conditions in accordance with JIS P8111. After that, the white paper quality is white paper gloss, smoothness and whiteness, and the offset printability is printing strength, printing glossiness, and ink drying properties. The following evaluations were performed on the missing dots as (ink setting properties), gravure printing suitability, and UV varnish glossiness as post-processing suitability (varnish suitability). The results were as shown in Table 1.

(Blank gloss)
The coated surface of the coated white paperboard was measured according to JIS P8142: 2005.

(PPS smoothness)
The coated surface of the coated white paperboard is measured according to JIS P8151: 2004 using a pressure-type smoothness meter (measuring device: L & W PPS tester, manufactured by Lorentzen & Wettre) to measure the smoothness when the pressure condition is 1960 kPa. did. The unit is μm, and the smaller the value, the better the smoothness.

(Whiteness)
The coated surface of the coated white paperboard was measured using a spectral whiteness meter SC-10WT (manufactured by Suga Test Instruments) in accordance with JIS P 8148: 2001.

(Offset printing suitability: printing glossiness)
Printing on the coated surface of white paperboard using an RI printing machine (Meiji Seisakusho) using 0.6 cc of printing ink (trade name: FUSION-G black, S type, manufactured by Dainippon Ink & Chemicals, Inc.) And 60 degree glossiness was measured using a gloss meter (GM-26D, manufactured by Murakami Color Research Laboratory).

(Offset printing suitability: printing strength)
Using a RI printing machine (manufactured by Meisei Seisakusho) on the coated surface of coated white paperboard, the degree of coating layer picking that occurs when printing using offset ink was visually observed and evaluated according to the following criteria: . The higher the printing strength is, the better the anti-piling resistance without picking.
A: Very good.
○: Good.
Δ: Slightly inferior
X: Inferior.

(Offset printing suitability: ink drying)
Using an RI printing suitability evaluation machine (Ming Seisakusho), apply 0.5cc ink for offset sheet-fed printing to the coated surface of the coated white paperboard and print it on the printed surface after 3 minutes of printing. The state of ink transfer (set-off) to high-quality paper after bonding with a constant pressure was evaluated according to the following criteria.
(Double-circle): It does not transcribe | transfer to white paper and ink drying property is very quick.
○: Almost no transfer to white paper, and ink drying is fast.
Δ: Slight transfer on white paper and slow ink drying, but practically acceptable level.
X: There is a lot of transfer of white paper, the ink drying property is slow, and the level is not practically acceptable.

(Applicability to gravure printing: missing dots)
The coated surface of the coated white paperboard was subjected to gravure printing using a printing bureau type gravure printing tester, and the degree of missing dots at 50% gradation halftone dots was visually observed and evaluated according to the following criteria.
A: There are almost no missing dots.
○: Several missing dots are recognized.
Δ: About a dozen missing dots are observed.
X: Many missing dots exceeding 20 are recognized.

(UV varnish gloss)
After adjusting the UV curable varnish (trade name: Dicure Clear UV1603, manufactured by DIC Graphics Co., Ltd.) to 10 seconds with Zahn Cup # 4, a coating device with a UV curing device (
The UV curable varnish was applied to the coated surface of coated white paperboard and UV cured and dried to perform varnish surface processing using a model: SG610UV, manufactured by Duplo. The glossiness of the varnished portion of the obtained coated white paperboard was measured using a gloss meter (GM-26D, manufactured by Murakami Color Research Laboratory) with an incident angle of 60 degrees.

Claims (7)

  A method for producing a coated white paperboard, comprising providing an outermost topcoat layer on the surface of a base paper and two or more coating layers including an undercoat layer closer to the base paper than the topcoat layer, comprising 5 heavy calcium carbonate A step of forming the overcoat layer using a coating liquid for an overcoat layer containing a pigment and an adhesive containing in a proportion of ˜15% by mass, an undercoat layer having a solid content concentration of 50 to 70% and a B-type viscosity of 400 mPa · s or less A method for producing a coated white paperboard comprising a step of forming the undercoat layer using a coating liquid.   The step of forming the overcoat layer is a step of forming an overcoat layer by blade coating or air knife coating, and the step of forming the undercoat layer is a step of forming an undercoat layer by rod coating. The manufacturing method of the coated white paperboard of description. The ratio of the 75 particle size of the cumulative weight percent of the particle size distribution curve subbing layer as a pigment and _{(D 75)} 25 as the particle size of the cumulative _{mass% (D 25) (D 75} / D 25) is 3.3 or less heavy The manufacturing method of the coated white paperboard of Claim 1 or 2 containing the polymer latex whose glass transition temperature is -50 to -30 degreeC as quality calcium carbonate and an adhesive agent.   The said topcoat layer contains a light calcium carbonate as a pigment, The mass ratio of the light calcium carbonate and the heavy calcium carbonate in the said topcoat layer is 5: 1 to 1: 1 in any one of Claims 1-3. The manufacturing method of the coated white paperboard of description. Wherein the ratio of the 75 particle size of the cumulative weight percent of the particle size distribution curve of heavy calcium carbonate contained in the overcoat layer _{(D 75)} and 25 cumulative mass% particle size _{(D 25) (D 75 /} D 25) is The manufacturing method of the coated white paperboard of any one of Claims 1-4 larger than 3.3.   The manufacturing method of the coated white paperboard of any one of Claims 1-5 in which the said topcoat layer contains the kaolin whose average particle diameter by a precipitation method is 0.30 micrometer or less as a pigment.   The said topcoat layer contains polymer latex as an adhesive agent, The polymer latex contained in topcoat layer and / or undercoat layer consists of polymer latex which has an average particle diameter larger than 120 nm, Any one of Claims 1-6 A method for producing a coated white paperboard according to claim 1.